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Sample records for chubut group cretaceous

  1. Un ejemplo excepcional de brechamiento (sismita? en el grupo Chubut, Patagonia An exceptional example of brecciation (seismite? in the Chubut Group, Patagonia

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    Edgardo Navarro

    2010-10-01

    Full Text Available Un brechamiento excepcional en unidades sedimentarias pelíticas del Grupo Chubut en la cercanía de la localidad de Telsen, provincia de Chubut, muestra que han sido afectadas por una etapa de telodiagénesis (diagénesis de exhumación. Presentan evidencias de deformación frágil relacionadas con mecanismos de sobrepresurización. Estos depósitos de edad aptiana, se disponen subhorizontales y constituyen asociaciones fluviales lateralmente extendidas. Un continuo de estructuras sedimentarias deformacionales se desarrollan enteramente sobre los depósitos pelíticos correspondientes a la asociación de facies de llanura de inundación. Cuatro intervalos fueron reconocidos de manera continua: 1 fracturado in situ, 2 brechado, 3 brechado fangosostenido y 4 homogeneizado. Conductos de escape potenciales de diversos tamaños, tienen desarrollo en el intervalo fangosostenido, que en ocasiones llegan a atravesar el intervalo superior homogéneo. El mecanismo de sobrepresurización, se habría visto favorecido por la presencia de cuerpos de areniscas conglomerádicas tobáceas confinantes (capa sello, que impidieron el escape de fluidos, permitiendo la licuefacción parcial a total y fluidización de la rocas sedimentarias de la llanura aluvial. Fallas normales reconocidas en el área, que afectan al Grupo Chubut, constituirían un elemento de juicio para establecer un origen sísmico a estas fábricas brechadas, cuya magnitud habría superado M>5 de la escala Mercalli modificada. La característica reológica frágil del material a partir del cual se originaron, convierte a estas estructuras en un ejemplo natural excepcional de brechamiento a partir de un mecanismo de sobrepresurización fosilizado.Sedimentary units of the Chubut Group in the proximity of the Telsen locality, in Chubut province affected by a telodiagenesis stage, display evidence of brittle deformation related to over-pressurizing mechanisms. These sub-planar deposits of Aptian age

  2. Procedencia de areniscas del Grupo Chubut en el área central de la Sierra de San Bernardo. Análisis preliminar Provenance of the Chubut Group Sandstones in the central area of the Sierra de San Bernardo. Preliminary analysis

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    M.A. Tunik

    2004-12-01

    Full Text Available Se llevaron a cabo análisis petrográficos de detalle que permitieron determinar las modas detríticas en areniscas del Grupo Chubut con el fin de inferir el marco tectónico del área de aporte de las mismas. Sobre la base de las muestras estudiadas, se observan características petrográficas distintivas entre areniscas de las Formaciones Matasiete, Castillo y Bajo Barreal. La presencia de trizas dentro de las areniscas de las Formaciones Castillo y Bajo Barreal sugeriría una depositación concomitante con volcanismo de arco activo. El ploteo de las modas detríticas en diagramas de discriminación de ambiente de procedencia mostró una diferenciación entre las unidades del Grupo Chubut. La Formación Matasiete presenta una procedencia de arco magmático no disectado, mientras que las muestras correspondientes a las Formaciones Castillo y Bajo Barreal sugieren una procedencia de arco magmático transicional o disectado. Esto último sumado a la presencia de trizas de caída directa podría explicarse por la migración del arco volcánico hacia el oeste y a la exposición de las raíces del arco volcánico del Cretácico inferior por deformación en la faja plegada concomitante con un volcanismo activo ubicado hacia el oeste de la zona de estudio.Petrographic studies were performed in order to characterize the detrital modes of the Chubut Group sandstones. Matasiete, Castillo and Bajo Barreal Formation showed distinctive petrographic characteristics. The presence of shards on the Castillo and Bajo Barreal Formations suggests that the deposition took place on an active volcanic setting. The detrital modes indicates derivation from three different environments among the Chubut Group. The Matasiete Formation shows a provenance from a non-dissected magmatic arc. Meanwhile, the detrital modes of the Castillo and Bajo Barreal Formations suggest derivation from a transitional to dissected arc. A westward migration of the volcanic arc and the

  3. Origin of channel systems in the Upper Cretaceous chalk group of the Paris Basin

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    Esmerode, E. V.; Surlyk, Finn

    2009-01-01

    The Upper Cretaceous Chalk Group of the Anglo-Paris Basin is known to show wedging beds and channel-like features which disrupt the quietly deposited pelagic chalk that covered most of NW Europe in the Late Cretaceous. Two-D reflection seismic data from the Brie region, SE of Paris, show...... is suggested due to the uninterrupted deep-marine chalk facies below and above both unconformities, and the unrealistically large sea-level drop of more than 200 m, which would be necessary for subaerial exposure of the central Paris Basin during the Campanian. The channels are oriented parallel to the margins...

  4. Tourism, Transnationality and Ethnolinguistic Vitality: The Welsh in the Chubut Province, Argentina

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    Johnson, Ian

    2010-01-01

    This article aims to develop the concept of ethnolinguistic vitality by adopting a qualitative approach to vitality rather than the statistical approach traditionally used. Ten small-size focus group style interviews were held with members of the Welsh-Argentinean community in the Chubut Province in the south of Argentina in order to explore…

  5. Diverse dinosaur-dominated ichnofaunas from the potomac group (Lower Cretaceous) Maryland

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    Stanford, R.; Lockley, M.; Weems, R.

    2007-01-01

    Until recently fossil footprints were virtually unknown from the Cretaceous of the eastern United States. The discovery of about 300 footprints in iron-rich siliciclastic facies of the Patuxent Formation (Potomac Group) of Aptian age is undoubtedly one of the most significant Early Cretaceous track discoveries since the Paluxy track discoveries in Texas in the 1930s. The Patuxent tracks include theropod, sauropod, ankylosaur and ornithopod dinosaur footprints, pterosaur tracks, and miscellaneous mammal and other vertebrate ichnites that collectively suggest a diversity of about 14 morphotypes. This is about twice the previous maximum estimate for any known Early Cretaceous vertebrate ichnofauna. Among the more distinctive forms are excellent examples of hypsilophodontid tracks and a surprisingly large mammal footprint. A remarkable feature of the Patuxent track assemblage is the high proportion of small tracks indicative of hatchlings, independently verified by the discovery of a hatchling-sized dinosaur. Such evidence suggests the proximity of nest sites. The preservation of such small tracks is very rare in the Cretaceous track record, and indeed throughout most of the Mesozoic. This unusual preservation not only provides us with a window into a diverse Early Cretaceous ecosystem, but it also suggests the potential of such facies to provide ichnological bonanzas. A remarkable feature of the assemblage is that it consists largely of reworked nodules and clasts that may have previously been reworked within the Patuxent Formation. Such unusual contexts of preservation should provide intriguing research opportunities for sedimentologists interested in the diagenesis and taphonomy of a unique track-bearing facies.

  6. A New Giant Titanosauria (Dinosauria: Sauropoda) from the Late Cretaceous Bauru Group, Brazil

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    2016-01-01

    Titanosaurian dinosaurs include some of the largest land-living animals that ever existed, and most were discovered in Cretaceous deposits of Argentina. Here we describe the first Brazilian gigantic titanosaur, Austroposeidon magnificus gen. et sp. nov., from the Late Cretaceous Presidente Prudente Formation (Bauru Group, Paraná Basin), São Paulo State, southeast Brazil. The size of this animal is estimated around 25 meters. It consists of a partial vertebral column composed by the last two cervical and the first dorsal vertebrae, all fairly complete and incomplete portions of at least one sacral and seven dorsal elements. The new species displays four autapomorphies: robust and tall centropostzygapophyseal laminae (cpol) in the last cervical vertebrae; last cervical vertebra bearing the posterior centrodiapophyseal lamina (pcdl) bifurcated; first dorsal vertebra with the anterior and posterior centrodiapophyseal laminae (acdl/pcdl) curved ventrolaterally, and the diapophysis reaching the dorsal margin of the centrum; posterior dorsal vertebra bearing forked spinoprezygapophyseal laminae (sprl). The phylogenetic analysis presented here reveals that Austroposeidon magnificus is the sister group of the Lognkosauria. CT scans reveal some new osteological internal features in the cervical vertebrae such as the intercalation of dense growth rings with camellae, reported for the first time in sauropods. The new taxon further shows that giant titanosaurs were also present in Brazil during the Late Cretaceous and provides new information about the evolution and internal osteological structures in the vertebrae of the Titanosauria clade. PMID:27706250

  7. Sedimentary Basin Analysis and Petroleum Potential of the Cretaceous Yuchon Group In Haenam Depression, SW Korea

    Institute of Scientific and Technical Information of China (English)

    Son Jin-Dam

    2000-01-01

    The Yuchon Group in the Late Cretaceous of Haenam and Mokpo area on the southwest coast of Korea peninsula can be divided into two Formations: (1) the intermediate volcanic Formation (Hwawon Formation), about 500m thick, (2)the acidic volcanic Formation (Hwangsan Formation), about 400m thick in ascending order.The former comprises intermediate volcaniclastics interlayered with volcanic rocks, and red mudrock and tuffaceous sandstone indicating fluvial deposits. The latter is subdivided into the upper part (Hwangsan Tuff Member) consisting of subaerial pyroclastics and intercalated rhyolites, and the lower part (Byeongonri Member) including subaqueous volcaniclastics, lake deltaic sandstone and gravelstone, lacustrine black shale and limestone and chert, and lake turbidite sandstone.The Late Cretaceous basin including Haenam subbasin in southwest Korea was largely formed of extensional nonmarine depressions (volcano- tectonic) bounded by NE- SW sinistral fault system.The thermal maturation based on geochemical and mineralogical studies for the black shales and tuffaceous sandstones reached the late stage of oil generation zone or gas generation stage. It seems that black shales and limestones are fairly good as source rock. The porosity of potential reservoir sandstone and tuff ranges from 5 % to 11%, but their permeability except the fractured rocks is very low ( <1md) because of fine pore throats reduced by diagenetic cementation of tuffaceous sandstones. Numerous potential traps might have been formed by the later folding and faulting along with lateral facies change and abundant mudrocks and volcaniclastics should make excellent seals.

  8. Magnetostratigraphy of the Lower Cretaceous Hekou and Liupanshan Group in NW China and its Implications for the Composite of the Cretaceous Normal Superchron (cns)

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    Dai, S.; Yan, N.; Luo, L.; Jenkyns, H. C.; Mac Niocaill, C.; Tang, Y.; Peng, D.; Wang, W.

    2015-12-01

    Are the short reversed-polarity subzones of the Cretaceous Normal Superchron (CNS) recorded in non-marine deposits? And, if so, how long did they last? These questions have been a matter of debate for some time. Lower Cretaceous terrestrial deposits in NW China, provide an opportunity to examine this problem. Here we present high-resolution magnetostratigraphic results for two Lower Cretaceous successions, the Liupanshan Group (Liupanshan Basin) and the Hekou Group (Longzhong Basin), NW China, and propose a minor revision for the CNS. The Liupanshan Group is a ~1300-m thick succession and comprises the alluvial-fluvial- lacustrine clastic sediments and carbonate rocks and gypsiferous mudstones. Samples from 457 levels were measured on the 2G cryogenic magnetometer after demagnetization. Six normal-polarity and five reversed-polarity magnetozones were obtained, which are correlated with the M3n to the M-'2r' of the GPTS of Gradstein (2012). The paleomagnetic data allow us to assign the Liupanshan Group to the interval from 131 Ma to 106 Ma (Barremian to Late Albian). The Hekou Group is 3700-m thick and consists of fluvial, lacustrine and deltaic sandstones, mudstones, conglomerates. 28 normal-polarity and 27 reversed-polarity magnetozones were observed from the thermal demagnetization for ~ 800 samples, and they can be reasonably correlated to the M15 thorough M-"2r" of GPTS of Gradstein (2012). This correlation yields an age control for the Hekou Group of 139-106 Ma (Valanginian- Albian). The different basal age of these two basins indicates that the Hekou Basin was initially developed prior to the Liupanshan Basin, but they stopped to develop almost at the same time. We found a short minus magnetozone in the upper part of the two groups, lying between M-'1r' and M-'2r' of the C34 of GPTS, equivalent to the reversed-polarity subzone (G2003) reported by Gilder et al. (2003) in a basalt from the Tuoyun Basin, NW China. Finally, we propose an alternative version for

  9. Environmental changes and shallow marine fossil bivalve assemblages of the Lower Cretaceous Miyako Group, NE Japan

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    Fujino, Shigehiro; Maeda, Haruyoshi

    2013-03-01

    We reconstructed the environmental changes recorded in the Lower Cretaceous Miyako Group via facies analysis and delineated the relationship between depositional facies and the occurrence of diverse marine invertebrate macrofossils. The Miyako Group consists of deposits from alluvial bay-head delta, bay-head delta front, central bay, and lower shoreface to inner shelf depositional settings. Fossil bivalve assemblages responded to shifts in these sedimentary environments. We defined three fossil bivalve assemblages from the central bay and lower shoreface to inner shelf deposits. The assemblages in the inner shelf and central bay deposits are clearly different, even though they occur within similar depositional facies. This contrast in assemblages results from environmental differences between closed and open settings; this interpretation is supported by the occurrence of stenohaline crinoids. We defined a fourth bivalve assemblage in a tsunami deposit intercalated within the bay-head delta front deposits. It consists of polygenic allochthonous shells, some that were derived from an estuarine environment or the shallow seafloor and others that were torn from small reefs.

  10. On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil

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    Diogenes A. Campos

    2011-03-01

    Full Text Available A new crocodyliform from the Upper Cretaceous (Campanian-Maastrichtian Presidente Prudente Formation of the Bauru Group is described based on two almost complete skulls and mandibles. The material comes from the "Tartaruguito" site, situated at an old railroad between the cities of Pirapozinho and Presidente Prudente, state of São Paulo, Brazil. The new species, Pepesuchus deiseae gen. et sp. nov., is classified in the clade Peirosauridae on the basis of three synapomorphies: the presence of five premaxillary teeth, the anterior two premaxillary alveoli nearly confluent, and the oval cross-section of the jugal along the lower temporal bar. The new taxon increases the outstanding crocodyliform diversity of the Bauru Group, particularly of the Peirosauridae, which might turn out to be one of the most representative clades of gondwanan mesoeucrocodylians.Um novo crocodilomorfo da Formação Presidente Prudente, Cretáceo Superior (Campaniano-Maastrichtiano do Grupo Bauru é descrito com base em dois exemplares, consistindo de crânio e mandíbulas quase completos. O material é procedente da localidade conhecida como "Tartaruguito", situada em um antigo ramal ferroviário que ligava as cidades de Pirapozinho e Presidente Prudente, Estado de São Paulo, Brasil. A nova espécie, denominada de Pepesuchus deiseae gen. et sp. nov., é classificada no clado Peirosauridae, com base em três sinapomorfias: presença de cinco dentes pré-maxilares, os dois primeiros alvéolos da pré-maxila quase confluentes e a secção transversal do jugal ao longo da barra temporal inferior oval. O novo táxon aumenta a marcante diversidade de crocodiliformes do Grupo Bauru e dos Peirosauridae, que poderá vir a ser um dos clados mais representativos de mesoeucrocodilianos gondwânicos.

  11. Provenance and U-Pb geochronology of the Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, and its tectonic significance

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    Jacques-Ayala, C.; Barth, A.P.; Wooden, J.L.; Jacobson, C.E.

    2009-01-01

    The Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, is a 2.8km thick clastic sedimentary sequence deposited in a continental basin closely related to volcanic activity. It consists of three formations: the Pozo Duro (oldest), the Anita, and the Escalante (youngest). Petrographic study, conglomerate pebble counts, and U-Pb geochronology of detrital zircons were performed to determine the source and age of this sequence, and to interpret its tectonic setting. In the sandstones of all three formations, the most abundant grains are those of volcanic composition (Q38F22L 40, Q35F19L46, and Q 31F22L47, respectively). The Pozo Duro Formation includes well-rounded quartz-arenite clast conglomerates, whereas conglomerates of the two upper units have clasts predominantly of andesitic and rhyolitic composition. The most likely source for these sediments was the Jurassic volcanic arc exposed in northern Sonora and southern Arizona. Zircons from five sandstone samples define two main age groups, Proterozoic and Mesozoic. The first ranges mostly from 1000 to 1800Ma, which suggests the influence of a cratonic source. This zircon suite is interpreted to be recycled and derived from the same source area as the quartz-rich sandstone clasts in the basal part of the section. Mesozoic zircons range from Triassic to Late Cretaceous, which confirms the proposed Late Cretaceous age for the sequence, and also corroborates Jurassic felsic source rocks. Another possible source was the Alisitos volcanic arc, exposed along the western margin of the Baja California Peninsula. Of regional significance is the great similarity between the El Chanate Group and the McCoy Mountains Formation of southeastern California and southwestern Arizona. Both are Cretaceous, were deposited in continental environments, and have similar zircon-age patterns. Also, both exhibit intense deformation and locally display penetrative foliation. These features strongly suggest that both units underwent

  12. Programa provincial de lectura del Chubut

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    Natalia Alejandra Alaniz

    2014-10-01

    Full Text Available En el marco del proyecto “Dispositivos pedagógicos en las dinámicas de lavida escolar en contexto de pobreza urbana” lo que se propuso investigar es la forma de implementación del Programa de Lectura de la provincia de Chubut. El mismo fue creado por Resolución Ministerial N° 1044/ 08, a partir de diversos trabajos que comenzaron en el año 2003 a través de la Ley de Educación 26. 026, y que posteriormente se incorporaron a nivel provincial mediante la Resolución N ° 174/12 para revalorizar las trayectorias escolares de cada niño/a. El programa consiste en poner el énfasis en el vínculo pedagógico mediante la adecuación de los espacios curriculares, de tal modo que se pueda lograr una articulación entre los diferentes niveles educativos, desde el nivel inicial al secundario. Articulando para ello recursos materiales y humanos que posibiliten el acompañamiento del proceso de enseñanza y aprendizaje de lectura.A partir de esto, el objetivo de este trabajo fue indagar cómo perciben los docentes de una escuela pública la implementación del Programa Provincial de Lectura, lo que implico utilizar metodologías y técnicas de investigación apropiadas para obtener las experiencias actuales en el territorio y en la cotidianidad de los propios actores escolares. Teniendo en consideración que el dispositivo pedagógico es una construcción histórica, que produce subjetividades, y por consiguiente formas de ver y entender el mundo.

  13. Sedimentary record of terminal Cretaceous accretions in Ecuador : the Yunguilla Group in the Cuenca area

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    Jaillard, Etienne; Bengtson, Peter; Ordoñez, Martha; Vaca, Wilmer; Dhondt, Annie,; Suárez, Johnny; Toro Álava, Jorge

    2008-01-01

    A reappraisal of the "Late Cretaceous Yunguilla Formation" of the Cuenca area enables the definition of four distinct formations, correlatable with those of southwestern Ecuador. A mid- to late-Campanian marine transgression (Jadan Formation) is overlain by quartz-rich conglomerates of fan-delta to turbiditic fan environment (Quimas Formation) of latest Campanian-earliest Maastrichtian age, which Lire interpreted as evidence of the accretion of a first oceanic terrane (San Juan). Disconformab...

  14. Sedimentary record of terminal Cretaceous accretions in Ecuador: The Yunguilla Group in the Cuenca area

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    Jaillard, Etienne; Bengtson, Peter; Ordoñez, Martha; Vaca, Wilmer; Dhondt, Annie; Suárez, Johnny; Toro, Jorge

    2008-03-01

    A reappraisal of the "Late Cretaceous Yunguilla Formation" of the Cuenca area enables the definition of four distinct formations, correlatable with those of southwestern Ecuador. A mid- to late-Campanian marine transgression (Jadán Formation) is overlain by quartz-rich conglomerates of fan-delta to turbiditic fan environment (Quimas Formation) of latest Campanian-earliest Maastrichtian age, which are interpreted as evidence of the accretion of a first oceanic terrane (San Juan). Disconformable, arkosic turbidites and cherts (Tabacay Formation) of early Maastrichtian age are thought to represent the erosion of the newly accreted oceanic terrane. A major unconformity of late Maastrichtian age, caused by the accretion of a second oceanic terrane (Guaranda), is followed by the deposition of quartz-rich micaceous shelf sandstones (Saquisilí Formation) of Paleocene age. A third accretion event (late Paleocene) is recorded in coastal Ecuador. Each accretion event correlates with the uplift and erosion of the Eastern Cordillera and with a sedimentary hiatus in the eastern areas. In Ecuador, accretion of oceanic terranes contributed to the build up of the Andes through tectonic underplating of low-density material, and the eastern areas did not behave as flexural foreland basins during late Cretaceous-Paleogene times.

  15. Nueva edad de la base del grupo Chubut en la mena uranífera Cerro Solo, provincia del Chubut

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    Nilda Marveggio

    2013-09-01

    Full Text Available En este trabajo se analizan las características litológicas de la roca hospedante de la mineralización de uranio del yacimiento Cerro Solo, que corresponde al miembro inferior de la Formación Los Adobes, unidad basal del Grupo Chubut en su sector norte. Se analiza la asociación de polen angiospérmico de allí recuperada, y en base a ese análisis, se establece una edad albiana temprana para la asociación polínica, que determina una edad más joven que la considerada hasta el momento para el inicio de la depositación de las sedimentitas del Grupo Chubut en el depocentro del yacimiento Cerro Solo.

  16. Timing and petroleum sources for the Lower Cretaceous Mannville Group oil sands of northern Alberta based on 4-D modeling

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    Higley, D.K.; Lewan, M.D.; Roberts, L.N.R.; Henry, M.

    2009-01-01

    The Lower Cretaceous Mannville Group oil sands of northern Alberta have an estimated 270.3 billion m3 (BCM) (1700 billion bbl) of in-place heavy oil and tar. Our study area includes oil sand accumulations and downdip areas that partially extend into the deformation zone in western Alberta. The oil sands are composed of highly biodegraded oil and tar, collectively referred to as bitumen, whose source remains controversial. This is addressed in our study with a four-dimensional (4-D) petroleum system model. The modeled primary trap for generated and migrated oil is subtle structures. A probable seal for the oil sands was a gradual updip removal of the lighter hydrocarbon fractions as migrated oil was progressively biodegraded. This is hypothetical because the modeling software did not include seals resulting from the biodegradation of oil. Although the 4-D model shows that source rocks ranging from the Devonian-Mississippian Exshaw Formation to the Lower Cretaceous Mannville Group coals and Ostracode-zone-contributed oil to Mannville Group reservoirs, source rocks in the Jurassic Fernie Group (Gordondale Member and Poker Chip A shale) were the initial and major contributors. Kinetics associated with the type IIS kerogen in Fernie Group source rocks resulted in the early generation and expulsion of oil, as early as 85 Ma and prior to the generation from the type II kerogen of deeper and older source rocks. The modeled 50% peak transformation to oil was reached about 75 Ma for the Gordondale Member and Poker Chip A shale near the west margin of the study area, and prior to onset about 65 Ma from other source rocks. This early petroleum generation from the Fernie Group source rocks resulted in large volumes of generated oil, and prior to the Laramide uplift and onset of erosion (???58 Ma), which curtailed oil generation from all source rocks. Oil generation from all source rocks ended by 40 Ma. Although the modeled study area did not include possible western

  17. Geología de la quebrada Honda, cuenca del lago La Plata, Chubut Geology of the Quebrada Honda, basin of Lago La Plata, Chubut

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    G.V. Depine

    2004-12-01

    Full Text Available La quebrada Honda, situada en el sur de la cuenca de los lagos La Plata y Fontana, en la provincia de Chubut, presenta una columna estratigráfica que comienza en el Jurásico superior con rocas calcoalcalinas de arco volcánico intermedias a ácidas de la Formación Lago La Plata. Las rocas sedimentarias que rellenan la cuenca de intraarco neocomiana corresponden al Grupo Coyhaique, dentro del cual se encuentran las Formaciones Tres Lagunas y Katterfeld, que se ubican dentro de un modelo paleoambiental como cortejo sedimentario de borde de plataforma, sucedido por un cortejo transgresivo, cuya edad es acotada al Hauteriviano inferior, debido al hallazgo de restos de Favrella americana en pelitas de la Formación Katterfeld. Vinculados con la extensión que da lugar a la cuenca se registran los cuerpos hipabisales calcoalcalinos básicos del Gabro Quebrada Honda y se los relaciona con un volcanismo de características más evolucionadas de la Formación Don Rueda, de edad neocomiana tardía. Si bien este magmatismo de arco volcánico es subaéreo, presenta indicios de interacción con cuerpos de agua por lo que corrobora la concomitancia de este evento con la sedimentación póstuma de Grupo Coyhaique. Se registra un evento de inversión tectónica que tendría una edad máxima de 80 Ma.The quebrada Honda is situated in the Lago La Plata-Fontana basin in Chubut. The stratigraphy of the area begins in the Upper Jurassic with the calc-alkaline intermediate to acidic Lago La Plata Formation rocks. The Neocomian Coyhaique Group, which includes the Tres Lagunas and Katterfeld Formations, is the sedimentary filling of the intraarc basin that was developed by that time. These units are included in a paleoenviromental model as a shelf-margin system tract followed by a transgressive system tract. The discovery of Favrella americana in the Katterfeld Formation constrains to the Early Hauterivian the age of these sequences. The hypabissal calc

  18. Geoquímica dela zona caolinizada de Mina Estrella Gaucha, provincia de Chubut Geochemistryof the kaolinized zone of Estrella Gaucha mine, Province of Chubut

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    Pedro J. Maiza

    2009-06-01

    Full Text Available Mina Estrella Gaucha es un yacimiento de caolínubicado a 70 km de la localidad de Alto Río Senguerr, provincia de Chubut,emplazado en areniscas tobáceas y conglomerádicas de la Formación Apeleg deedad cretácica inferior. La mineralogía de la zona estudiada es muy homogénea yestá constituida por dickita prácticamente pura con muy escasa cantidad dealunita y un contenido variable de cuarzo. A escala del yacimiento sedesarrolla una zonación en la que se distinguen cuatro zonas de alteración,distribuidas de techo a piso de la forma siguiente: 1 nivel superior silicificado;2 zona alunitizada; 3 zona caolinizada y 4 zona de sericita-clorita. Con elfin de determinar el origen del depósito se ha llevado a cabo un estudiomineralógico, de geoquímica de elementos mayores, menores y traza y de losisótopos estables de O y H de la zona caolinizada. Los análisis químicos deelementos mayoritarios confirman que se trata de caolín prácticamente puro. Elcontenido de elementos traza y las relaciones (P vs. S, Zr vs.Ti, Cr + Nb vs. Ti + Fe, y Ce + Y + La vs. Ba + Sr sugieren queel caolín se ha formado por alteración hidrotermal de las tobas volcánicas encajantes.La composición isotópica de los caolines muestran valores de δ18Oentre +5,1 y +8.8 ‰ y de D entre -82 y -89‰, compatibles con unorigen hidrotermal de los mismos.Estrella Gaucha mine is situated 70 km of Alto Río Senguerr(Province of Chubut.It is a kaolin deposit hosted by sandy and conglomeratic tuffs of the ApelegFormation (Lower Cretaceous. The mineralogy of the zone is very homogeneousand it is characterized by dickite almost pure, traces of alunite and quartz.There are four alteration zones. 1 silicification; 2 zone with alunite; 3 kaolinizedzone and 4 zone with sericite - chlorite. In order to know the origin of thedeposit a mineralogical, geochemical (major and trace elements and stableisotope study (O and H of the kaolinized zone was carried out. Trace elementcontent and

  19. Trajectory and contribution of geoscientists (1906-1961) to dinosaur research in the Bauru Group (Cretaceous) in the Triângulo Mineiro region of Brazil

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    Peyerl, Drielli; Candeiro, Carlos Roberto A.; Mendonça Figueirôa, Silvia Fernanda

    2015-08-01

    The present study discusses geological and paleontological research conducted by geoscientists in the Late Cretaceous Bauru Group, of the Triângulo Mineiro region, Brazil. This analysis based largely on historical documentary sources focuses on the pioneering work of geoscientists, who made numerous discoveries of dinosaur fossils. This work contributes to a chronological survey that has been compiled on the geological studies in the Bauru Group, and describes the importance of the paleontological discoveries made during the twentieth century.

  20. Analysis of sedimentary rocks from the Jurassic/Cretaceous boundary: INAA and RNAA of platinum group elements

    International Nuclear Information System (INIS)

    Within a geophysical and paleontological project aimed at a detailed and precise correlation of the Jurassic/Cretaceous (J/K) boundary interval in the Tethyan and Boreal region, detailed magnetostratigraphic and biostratigraphic profiles with a well-defined J/K boundary were selected from several sites for a detailed geochemical characterization. Instrumental neutron activation analysis (INAA) was employed in the characterization of a vertical profile around the assumed J/K boundary in the Boreal Realm situated on the Nordvik peninsula, North of Middle Siberia, Russia, for which a platinum group element (PGE) anomaly has been reported in literature. Multimode INAA included short-time and long-time modes of irradiation either with reactor-pile neutrons or with epithermal/fast neutrons (ENAA) under a Cd shielding. The analyses encompassed about 40 major and trace elements. A radiochemical separation procedure for PGE determination consisting in sample decomposition by alkaline-oxidative fusion, reduction of PGE, and precipitation of their sulfides was tested. Despite difficulties, elevated levels of Pt and Ir were determined in selected samples at ppb and sub-ppb levels, respectively

  1. Biostratigraphy and carbon isotope stratigraphy of uppermost Cretaceous-lower Cenozoic Muzzle Group in middle Clarence valley, New Zealand

    International Nuclear Information System (INIS)

    Muzzle Group strata exposed along southeast-flowing tributaries of the Clarence River valley, Marlborough, record hemipelagic-pelagic sedimentation across a high latitude (c. 55 degrees S), terrigenous sediment-starved, continental margin from latest Cretaceous to middle Eocene times. Studies of dinoflagellates, foraminifera, calcareous nannofossils, and radiolarians have been integrated with bulk carbonate δ13C profiles to establish the chronostratigraphy for two stratigraphic sections along Bluff and Muzzle Streams, middle Clarence valley. The two sections comprise similar successions. Uppermost Cretaceous (upper Haumurian) micritic limestone of Mead Hill Formation is overlain unconformably by Teredo Limestone, a c. 0.25 m thick bed of highly glauconitic, calcareous sandstone. This unit, the basal member of Amuri Limestone, is overlain conformably by c. 15 m thick Lower Limestone, micritic limestone that is glauconitic at base and progressively more marl-rich in its upper part. Lower Limestone grades up into Lower Marl, a poorly exposed, 40-70 m thick unit of alternating marl and micritic limestone beds. Biostratigraphy indicates that the base of Amuri Limestone is younger at Bluff Stream (earliest Eocene, early Waipawan) than at Muzzle Stream (late Paleocene, late Teurian). In the condensed (12 m) upper Paleocene-lower Eocene Amuri Limestone sequence at Muzzle Stream, a trend in δ13C from high (≥2.4 permille) to low (≤1 permille) values is consistent with global records across three major climate or carbon cycle perturbations: the late Paleocene carbon isotope maximum (PCIM, 59-56 Ma), the initial Eocene thermal maximum (IETM, 55.5 Ma), and the early Eocene climatic optimum (EECO, 53-50 Ma). Probably only the upper PCIM is preserved in the 4 m thick siliceous limestone interval overlying Teredo Limestone. The IETM is well-defined by a 1 permille negative δ13C excursion at the base of a 0.8 m thick marl-rich unit (Dee Marl), 5 m above the base of Lower

  2. New observations on Permocalculus gosaviensis SCHLAGINTWEIT, 1991 (calcareous alga from the Upper Cretaceous of the Northern Calcareous Alps (Gosau Group, Austria

    Directory of Open Access Journals (Sweden)

    Felix Schlagintweit

    2010-08-01

    Full Text Available New thin-sections from the Upper Cretaceous Gosau Group of Brandenberg, Tyrol, Austria, yielded well-preserved specimens of the calcareous alga Permocalculus gosaviensis Schlagintweit. Microfacies are foraminiferal-algal wackestones; stratigraphy is Upper Turonian (?Lower Coniacian. It is shown that the original description was based on oblique sections leading to the incorrect assumption of a piriform segment morphology. Instead, P. gosaviensis is a representative of Permocalculus of the group with constrictions/swellings along the segments (waxing-and-waning type. Permocalculus nikolapantici Radoičić from the Upper Turonian of Serbia is considered a junior synonym of Permocalculus gosaviensis Schlagintweit.

  3. Mineralogical data on angelaite, Cu2AgPbBiS4, from the Los Manantiales District, Chubut, Argentina

    DEFF Research Database (Denmark)

    Topa, D.; Paar, W.H.; Putz, H.;

    2010-01-01

    0.97Pb1.05Bi1.00S3.91. The ideal formula (on the basis of nine atoms) is Cu2AgPbBiS4, which requires Cu 16.31, Ag 13.84, Pb 26.58, Bi 26.81, S 16.45, total 100 wt.%. Angelaite is orthorhombic, with a 12.734(5), b 4.032(1), c 14.633(5) Å, V 751.8(5) Å3, space group Pnma and Z = 4. The calculated......Angelaite, ideally Cu2AgPbBiS4, occurs as a hypogene mineral in polymetallic ores at the Ángela groups of veins in the mining district of Los Manantiales, in the province of Chubut, Argentina. The new mineral species is predominantly associated with pyrite, sphalerite, chalcopyrite, hematite...

  4. Stratigraphic evolution of a long-lived submarine channel system in the Late Cretaceous Nanaimo Group, British Columbia, Canada

    Science.gov (United States)

    Bain, Heather A.; Hubbard, Stephen M.

    2016-05-01

    Submarine canyons and slope channel systems are important conveyers of sediment from uplifted catchments to oceanic sedimentary sinks. Long-lived conduits can be established through deep incision of submarine canyons, with bathymetric relief of hundreds of meters to greater than a kilometer in many instances. Alternatively, a combination of erosion of the continental slope and aggradation of levees can yield a broadly comparable stratigraphic product through evolution of channels with more subdued bathymetric relief. Despite differences in formative geomorphic elements on the paleo-seafloor, differentiating the stratigraphic architecture amongst these systems is challenging, particularly in outcrop datasets. Accurate stratigraphic interpretation has significant implications for understanding the frequency and magnitude of controlling processes such as mountain building and denudation or eustatic sea-level fluctuations. In this study, deep-water channel strata of the Late Cretaceous Nanaimo Group are examined at Hornby and Denman islands, British Columbia, Canada. Evidence for a long-lived submarine conduit records the history of sediment transfer at multiple temporal and spatial scales. The composite submarine channel system deposit is 19.5 km wide and 1500 m thick, which formed and filled over ~ 15 Ma. Facies scale analyses highlight conglomeratic channel fill juxtaposed against thin-bedded out-of-channel deposits. Erosional surfaces are commonly mantled by mass-transport deposits, which provide evidence for conduit wall reworking and maintenance. At a larger scale, a series of composite, conglomerate-prone channelform bodies are observed to stratigraphically stack in two distinct phases: (1) early persistence of laterally offset (migrated) channels; and (2) later vertically aligned and aggraded channels. This stratigraphic trend is comparable to composite, multi-phase degradational-aggradational submarine channel complexes observed globally. As such, we consider

  5. A new turtle from the Upper Cretaceous Bauru Group of Brazil, updated phylogeny and implications for age of the Santo Anastácio Formation

    Science.gov (United States)

    Menegazzo, Mirian Costa; Bertini, Reinaldo José; Manzini, Flávio Fernando

    2015-03-01

    A new Podocnemidinura specimen from the Upper Cretaceous Bauru Group (Paraná Basin) of southeastern Brazil was described. The Bauru Group provided an important portrait of the Brazilian Mesozoic terrestrial biota, which boasts a vertebrate fauna formed from fishes, frogs, lacertilians, crocodyliforms, dinosaurs and mammals; records of palynomorphs; and invertebrate fauna consisted of gastropods, bivalves, ostracods and conchostracans. Nevertheless, the age of these continental deposits is not precisely estimated, which prevents global correlations, and its fauna is argued to be endemic. The new specimen described is the first turtle from the Santo Anastácio Formation, and its morphological comparison with other South American forms provided a significant advancement in the understanding of the age of this unit (Late Cretaceous). This study permitted a revision of the turtle taxa of the Bauru Group. As a result, some taxa were considered synonym, including the new Santo Anastácio form. The specimen is still unnamed due to the absence of skull characters that preclude its accurate positioning within the Bauru Group skull-based taxa. In addition, the phylogenetic affinities of this taxon were analyzed into Podocnemidinura clade.

  6. Geophysical characterization of circular structures in Chubut and Mendoza (Argentina): Impact vs. Volcanism

    Science.gov (United States)

    Prezzi, C.; Orgeira, M. J.; Risso, C.; Acevedo, R.; Ponce, F.; Nullo, F.; Martinez, O.; Rabassa, J.; Margonari, L.; Corbella, H.

    2013-05-01

    This work focuses on two main objectives. One of them is to provide information to discern the genesis of the circular structures present in Bajada del Diablo (Chubut, Argentina) considered as impact craters, and the other one is to contribute to a better knowledge of the circular structures located in the volcanic fields of Llancanelo and Payunia (Mendoza, Argentina). Chubut circular structures have been attributed to the collision of an extraterrestrial body, possibly an asteroid. However, doubts persist about their genesis because of the lack of direct geological evidences. Since detailed geomorphological studies have ruled out an origin by wind deflation, the prevailing alternative hypothesis attributes these circular structures to a volcanic process. On the other hand, the study of the volcanic fields of Payunia and Llancanelo (Mendoza) will contribute to the knowledge of the mechanics of hydromagmatic processes in the area, and the origin of circular structures morphologically similar to those located in Chubut. In the Payunia volcanic field at least 27 cones with evidences of hydromagmatism, in a field of more than 800 pure magmatic cones, have been recognized. This study tries to determine if a relationship between the observed volcanic circular structures and participation of water during the eruption exists. Magnetic and gravity field surveys of the circular volcanic structures in Llancanelo and Payunia volcanic fields were performed in order to determine their relationship with the type of eruption. Electromagnetic, magnetic and gravity field surveys were also carried out in Chubut circular structures. The comparative analysis of geological and geophysical results obtained in the circular structures of Chubut and those obtained in the circular structures in the volcanic areas of Llancanelo and Payunia suggest an impact origin for the circular structures of Chubut.

  7. Shrimps from the Santana Group (Cretaceous: Albian: new species (Crustacea: Decapoda: Dendrobranchiata and new record (Crustacea: Decapoda: Caridea

    Directory of Open Access Journals (Sweden)

    ALLYSSON P. PINHEIRO

    2014-06-01

    Full Text Available The fossil shrimp Araripenaeus timidus n. gen. n. sp. is the first fossil Penaeoidea from Brazil. Here, we describe, illustrate and compare it with Paleomattea deliciosa, a fossil Sergestoidea (Dendrobranchiata previously described from the same region. The material of the early Cretaceous (Albian was collected in the town of Jardim, south of the state of Ceará, in the superior septarian concretion level of the Romualdo Formation. Additionally, a second specimen of Kellnerius jamacaruensis was found in the same site of the Araripe Basin.

  8. Shrimps from the Santana Group (Cretaceous: Albian): new species (Crustacea: Decapoda: Dendrobranchiata) and new record (Crustacea: Decapoda: Caridea).

    Science.gov (United States)

    Pinheiro, Allysson P; Saraiva, Antônio Áf; Santana, William

    2014-04-29

    The fossil shrimp Araripenaeus timidus n. gen. n. sp. is the first fossil Penaeoidea from Brazil. Here, we describe, illustrate and compare it with Paleomattea deliciosa, a fossil Sergestoidea (Dendrobranchiata) previously described from the same region. The material of the early Cretaceous (Albian) was collected in the town of Jardim, south of the state of Ceará, in the superior septarian concretion level of the Romualdo Formation. Additionally, a second specimen of Kellnerius jamacaruensis was found in the same site of the Araripe Basin.

  9. Indigenous identity and textiles: an economic policy strategies in the province of Chubut La identidad indígena y sus textiles: estrategias de una política económica en la provincia de Chubut

    Directory of Open Access Journals (Sweden)

    Patricia María Méndez

    2010-01-01

    Full Text Available From the conception of the identity of individuals and of the groups as an elaboration, arises that the current indigenous identity employed by the state in the province of Chubut is functional to a policy which aims to prevent the emigration of the few people in rural areas of the province. It affirms that such a strategy is not new and that in the past other versions of this identity have also been useful to legitimate power projects. Through ethnographic and historical work, we explore some physical and social characteristics of rural areas of that province, some provincial regulations of government agencies, and certain attributes, preterits and present, of the indigenous identity employed by the state and of one of its symbols, Mapuche tissues. Laterally it refers in what way this identity is considered by some identified.A partir de la concepción de la identidad de las personas y de los grupos como una elaboración, se plantea que la actual identidad indígena empleada por el Estado en la provincia de Chubut resulta funcional a una política que pretende evitar la emigración de los escasos pobladores de las zonas rurales de la provincia. Se afirma que tal estrategia no es novedosa y que en el pasado otras versiones de esa identidad también han resultado útiles a los proyectos del poder legítimo. Mediante un trabajo etnográfico e histórico, se analizan algunas características físicas y sociales de la zona rural de esa provincia, algunas normativas de organismos gubernamentales provinciales, y ciertos atributos pretéritos y actuales de la identidad indígena empleada por el Estado y de uno de sus símbolos, los tejidos mapuches. Lateralmente se refiere de qué manera esa identidad es considerada por algunos identificados.

  10. New occurrences of microvertebrate fossil accumulations in Bauru Group, Late Cretaceous of western São Paulo state, Brazil

    Science.gov (United States)

    Alveş, Y. M.; Bergqvist, L. P.; Brito, P. M.

    2016-08-01

    In this work, we present the results of several palaeontological expeditions to four Upper Cretaceous fossil microsites of the Adamantina and Presidente Prudente formations in western São Paulo State, Brazil. Despite the fragmentary condition of the fossils recovered, they represent an important record of vertebrate microremains. The material, recovered through screen washing, comprises teeth and scales of Lepisosteidae; two morphotypes of Halecostomi teeth with similarities to Characiformes and Amiiformes; a Teleostei tooth of molariform shape; fin spines of Siluriformes; teeth of possible Baurusuchidae, Notosuchia (probably Adamantinasuchus or Mariliasuchus), Neosuchia (probably Itasuchus or Goniopholis), and other Mesoeucrocodylia indet.; probable teeth of Abelisauroidea, other Theropoda indet., and a phalanx of Aves. The comparative microvertebrate fossil accumulation from western São Paulo State provides evidence that: 1) floodplain channels accumulate large concentrations of microremains; 2) coarse sandstone privileges enamel tissues like teeth and scales; 3) new vertebrate fossil records have been discovered in Florida Paulista, Alfredo Marcondes, and Alvares Machado outcrops.

  11. Cranial bones and atlas of titanosaurs (Dinosauria, Sauropoda) from Late Cretaceous (Bauru Group) of Uberaba, Minas Gerais State, Brazil

    Science.gov (United States)

    Martinelli, Agustín G.; Marinho, Thiago da Silva; Filippi, Leonardo S.; Ribeiro, Luiz Carlos Borges; Ferraz, Mara Lúcia da Fonseca; Cavellani, Camila Lourencini; Teixeira, Vicente de Paula Antunes

    2015-08-01

    Isolated left prefrontal, left squamosal and atlas of titanosaur dinosaurs are described and compared. They come from the Late Cretaceous Serra da Galga Member of the Marília Formation at the Serra do Veadinho region, Peirópolis (Uberaba County, Minas Gerais State, Brazil). Due to the sparse cranial elements of titanosaurs already known from Brazil, these specimens are noticeable to be presented. In addition, the atlas vertebra is described for the first time for Brazilian titanosaurs. The morphology of the cranial bones closely resembles lithostratian titanosaurs, such as Rapetosaurus, rather than basal titanosaurs. The atlas is similar to that of other titanosaurs, suggesting that the anatomy of this element seems to be more conservative than other vertebral elements, in which vertebral laminae play an important rule in titanosaur taxonomy.

  12. Jurassic tetrapods and flora of Cañadón Asfalto Formation in Cerro Cóndor area, Chubut Province Flora y tetrápodos del Jurásico de la Formación Cañadón Asfalto en el área de Cerro Cóndor, provincia de Chubut

    OpenAIRE

    Ignacio H. Escapa; Juliana Sterli; Diego Pol; Laura Nicoli

    2008-01-01

    The plant and tetrapod fossil record of the Cañadón Asfalto Formation (Middle to Late Jurassic) found in Cerro Cóndor area (Chubut Province) is summarized here. The flora is dominated by conifers (Araucariaceae, Cupressaceae sensu lato) but also includes ferns and equisetaleans. The tetrapod fauna is composed of dinosaur taxa described in the 70's as well as other remains recently described and other vertebrate groups such as amphibians, turtles, and mammals. The amphibian remains have been i...

  13. Platinum-group elements in the cores of potassium feldspar spherules from the Cretaceous-Tertiary boundary at Caravaca (Spain

    Directory of Open Access Journals (Sweden)

    Palomo, I.

    1994-04-01

    Full Text Available The abundant spherules present in the Cretaceous-Tertiary boundary layer at Caravaca are diagenetically transformed to potassium feldspar. Before our study no possible relicts of the precursor material had been reported. but in this paper we describe the presence of cores in these spherules that could represent a relict of the «unknown precursor». These cores are made up of C mixed with Si. Mg. AL Cr. Ca among other elements. Laser Ablation System analysis also reveals an enrichment in pe;E could suggest an extraterrestrial origin for this material. PI. Pd and Ir do not show a chondritic ratio: however. asevere modification of their concentration could be expected during the early diagenetic processes.Las esférulas existentes en la lámina de sedimento del tránsito Cretácico-Terciario de la sección de Caravaca han sido transformadas diagenéticamente a feldespato potásico. En este trabajo se describe la existencia de núcleos encontrados en el interior de las esférulas. los cuales' pueden representar relictos del material precursor. Dichos núcleos están constituidos por C. Si. Mg, AL Cr y Ca entre otros elementos. Se pone de relieve, por vez primera, su notable enriquecimiento en elementos del grupo del platino, cuyas relaciones no condríticas pueden ser debidas a la existencia de importantes modificaciones en su concentración inicial causadas por los procesos diagenéticos y por la existencia de materia orgánica.

  14. Chemical characteristics of Upper Cretaceous (Turonian) jet of the Gosau Group of Gams/Hieflau (Styria, Austria)

    Energy Technology Data Exchange (ETDEWEB)

    Bechtel, A.; Gratzer, R.; Sachsenhofer, R.F. [Institut fuer Geowissenschaften, Prospektion und Angewandte Sedimentologie, Montanuniversitaet Leoben, Peter-Tunner-Str. 5, A-8700 Leoben (Austria)

    2001-03-01

    Jet and coaly sediments within the Upper Cretaceous (Gosau) Schoenleiten Formation were collected from two outcrops near Gams/Hieflau (Styria, Austria). For comparison, additional jet and coal samples from different Gosau localities were included in the study. The identification of jet as bituminous driftwood (collotelinite) has been provided by microscopical examination of organic matter [Kollmann, H.A. and Sachsenhofer, R.F., Mitt. Ref. Geol. und Palaeont. Landesmuseum Joanneum SH 2 (1998) 223]. Rock-Eval analyses revealed enhanced HI and lower T{sub max} values of jet compared with the coals and coaly shales. The results reflect the higher contents of bituminous organic matter compared to vitrain-rich coals of similar maturity. In comparison with the coals and coaly shales, high amounts of liberated hydrocarbons (mg HC/g C{sub org}) are in contrast to generally lower yields of soluble organic matter during extraction with dichloromethane, indicating that portions of the hydrocarbons are liberated from lipids loosely bound to kerogen during pyrolysis. Further differences in n-alkane distribution patterns, odd over even predominance, pristane/phytane, and pristane/n-C{sub 17} ratios exist between jet, coals and coaly shales. The microbial origin of short-chain n-alkanes presumably resulted from the degradation of the predominant odd-numbered long-chain n-alkanes within the jet. The occurrence of biological markers (sesqui and diterpenoids) within the sediments (coaly shales), coals and jet samples indicates the origin of terrestrial organic matter from conifers. Biomarker composition of jet samples indicates enhanced aromatisation of sesqui and diterpenoids. These results correspond to enhanced aromatisation of steranes, as reflected by generally higher relative contents of triaromatic steroids in the jet. Because of comparable maturation (0.5-0.6% R{sub r}) of the coals, coaly shales and the jet samples, confirmed by the isomerisation of {alpha}{beta} C{sub 31

  15. Petrologic and isotopic data from the Cretaceous (Campanian) Blackhawk Formation and Star Point Sandstone (Mesaverde Group), Wasatch Plateau, Utah

    Science.gov (United States)

    Fishman, Neil S.; Turner, Christine E.; Peterson, Fred

    2013-01-01

    The presence of discrete minerals associated with coal—whether (1) detrital or authigenic constituents of the coals or in thin mudstone or siltstone units interbedded with coals, or (2) authigenic phases that formed along cleats—might influence its utilization as an energy resource. The build-up of sintered ash deposits on the surfaces of heat exchangers in coal-fired power plants, due to the alteration of minerals during combustion of the coal, can seriously affect the functioning of the boiler and enhance corrosion of combustion equipment. In particular, the presence of sodium in coals has been considered a key factor in the fouling of boilers; however, other elements (such as calcium or magnesium) and the amount of discrete minerals burned with coal can also play a significant role in the inefficiency of and damage to boilers. Previous studies of the quality of coals in the Cretaceous (Campanian) Blackhawk Formation of the Wasatch Plateau, Utah, revealed that the sodium content of the coals varied across the region. To better understand the origin and distribution of sodium in these coals, petrologic studies were undertaken within a sedimentological framework to evaluate the timing and geochemical constraints on the emplacement of sodium-bearing minerals, particularly analcime, which previously had been identified in coals in the Blackhawk Formation. Further, the study was broadened to include not just coals in the Blackhawk Formation from various localities across the Wasatch Plateau, but also sandstones interbedded with the coals as well as sandstones in the underlying Star Point Sandstone. The alteration history of the sandstones in both formations was considered a key component of this study because it records the nature and timing of fluids passing through them and the associated precipitation of sodium-bearing minerals; thus, the alteration history could place constraints on the distribution and timing of sodium mineralization in the interbedded or

  16. Depositional Environments of Late Danian Plant Localities: Chubut Provice, Patagonia, Argentina

    Science.gov (United States)

    Comer, E.; Slingerland, R. L.; Wilf, P.

    2010-12-01

    Diverse, well-preserved macroflora are observed within Cretaceous and Paleocene sediments of Chubut Province, Patagonia, Argentina. These macroflora are the most well preserved early Paleocene flora from Gondwana and add new insight into the diversity and environments of that epoch. Two major sites of fossil preservation, Palacio de los Loros and Parque Provincial Ormachea, sit near the top of the Late Danian (65.5-61.7 Ma) Salamanca Formation. Understanding the depositional history of the Salamanca is important in characterizing paleoenvironments in which these flora lived and relating these Patagonian macroflora to concurrent Paleocene flora within the Gondwanan supercontinent. During a two week field season, twenty stratigraphic sections were measured along the outcrop belt at Palacio de los Loros and Ormachea Park as well as two minor sites; Las Flores, and Rancho Grande. Photo mosaics, laser ranger data, and stratigraphic columns were merged with elevated geologic maps and imported into Fledermaus to generate a 3-D visualization of facies relationships. Rock samples were also collected and will be thin sectioned and analyzed for petrography and grain size. The Salamanca Fm. consists of 7 facies, listed here in stratigraphically ascending order: 1)Transgressive sands, 2)Wispy-bedded claystone, 3)Banco Verde, 4)White Cross bedded sandstone, 5)Accretion set siltstone, 6)Transitional silty claystone and 7)Banco Negro. Based on these facies, the Salamanca Fm. is interpreted as a marine-shelf to brackish, tide-dominated, estuarine deposit. The base of the Salamanca Fm. rests on an unconformity representing a marine flooding surface and lower sections of the Salamanca, facies 1 and 2, contain abundant glauconite and fossils indicative of a marine shelf environment. These facies give way upwards to bi-directional trough cross bedded sandstones interspersed with flaser bedded sandy siltstones (facies 3 and 4) indicating a less marine estuary with strong flow regimes

  17. Caracterización geológica del skarn "El Abuelo" Alto Río Senguerr, Chubut Geological characterization of "El Abuelo" skarn deposit, Alto Rio Senguerr, Chubut

    Directory of Open Access Journals (Sweden)

    M.E. Lanfranchini

    2004-12-01

    Full Text Available El skarn "El Abuelo" está situado en el extremo sudoccidental de la Provincia del Chubut, República Argentina. Se desarrolla en un ambiente tectónico de arco magmático, en corteza continental. Está emplazado en sedimentitas silicoclásticas con intercalaciones carbonáticas y se vincula a cuerpos intrusivos riodacíticos, conjunto atribuido al Cretácico inferior. En esta manifestación se reconocieron anomalías en elementos metalíferos (Fe, Cu, Pb, Zn, Ag que le confieren interés como guía para la exploración de recursos minerales en esta región. La presente contribución tiene por finalidad tipificar al skarn a través de una caracterización geológica y mineralógica. La asociación paragenética de minerales reconocidos permitió identificar dos episodios: uno metasomático y otro hidrotermal, ambos desarrollados en las sedimentitas (exoskarn. El primero fue originado por fluidos de derivación magmática, que provocaron la formación de minerales calcosilicáticos. Posteriormente la incorporación de agua en el sistema facilitó el desarrollo de minerales hidratados, retrogradando parcialmente al skarn, proceso que fue seguido por la depositación de hematita, magnetita y sulfuros, acompañados de sílice. La asociación de minerales calcosilicáticos, junto a la variación en la composición química de piroxenos y granates y la mineralización identificada, permiten tipificar al skarn "El Abuelo" como cálcico, con hierro como metal dominante."El Abuelo" skarn deposit is located in southwest Chubut province. It was formed in a magmatic arc tectonic environment, developed in continental crust. The skarn is hosted in low cretaceous silicoclastic sands interbedded with limestones, and it is related to small rhyodacitic sub-volcanic bodies. Anomalous contents of metals (Fe, Cu, Pb, Zn, Ag provide an interesting exploration guide. This paper is devoted to give a geological and a mineralogical characterization of the skarn, in order

  18. Corrales de piedra, campos abiertos y pampas de camaruco: Memorias de relacionalidad en la meseta central de Chubut Stone yards, open fields and sacred places: Memories of relatedness in the Chubut´s central plateau

    Directory of Open Access Journals (Sweden)

    Ana Ramos

    2008-12-01

    Full Text Available La "cuestión indígena" como política de estado en Argentina ha estado acompañada por la elaboración académica de mapas étnicos. Las definiciones hegemónicas de estas entidades han presupuesto generalmente algún elemento "esencial" como, por ejemplo, fenotipos, uso de una lengua, o la aglutinación en torno a linajes consanguíneos. A partir de las reformulaciones de las teorías del parentesco desde el modelo heurístico de las sociedades de casas y las teorías sobre la relacionalidad proponemos una aproximación a la memoria social como marco alternativo de interpretación histórica. Esta contempla las prácticas sociales del parentesco y la objetivación de la continuidad de los grupos de pertenencia en las políticas y lugares de la memoria -corrales de piedra, actividades productivas y pampas de camaruco- en la región de la "meseta" de Chubut. Dichas relaciones con el espacio físico cuestionan tanto las definiciones académicas tradicionales de parentesco y de cacicazgo como las clasificaciones étnicas-nacionales.The "Indigenous issue" as a state policy in Argentina has been accompanied by an academic production of ethnic maps. Hegemonic definitions of these entities used to presume some "essential" elements like the phenotype, the use of language or consanguineous lineage membership. Based on the reformulation of kinship theory, which came from the heuristic model of houses and relatedness theory, we propose an approach to social memory as an alternative framework for historical interpretation. This includes kinship social practices as well as the materialization of group membership's continuity in policies and places of memory -such as stone yards, productive activities, open fields and sacred places- in the Chubut central plateau. Finally, we argue that regarding a physical space, these relations question not only the ethnic-national classifications but also the traditional academic definitions of kinship and chieftaincy.

  19. Polen de las Mieles de la Patagonia Andina (Chubut-Argentina Pollen of honeys from the Andean Patagonia (Chubut-Argentina

    Directory of Open Access Journals (Sweden)

    Alicia Forcone

    2006-07-01

    Full Text Available Se describen e ilustran mediante fotomicrografías tomadas con MO y MEB, 30 tipos polínicos, determinados en las mieles producidas en la región andina de Chubut (Patagonia Argentina. Los tipos morfológicos descriptos pertenecen a las siguientes familias: Alstroemeriaceae, Apiaceae, Buddlejaceae, Caryophyllaceae, Caprifoliaceae, Celastraceae, Clusiaceae, Convolvulaceae, Ericaceae, Elaeocarpaceae, Fabaceae, Fagaceae, Lamiaceae, Papaveraceae, Polemoniaceae, Polygalaceae, Proteaceae, Ranunculaceae, Rosaceae, Saxifragaceae, Solanaceae, Thymelaceae y Verbenaceae. La mayoría de los tipos polínicos descriptos fueron hallados en las mieles como polen de menor importancia o traza con excepción de Aristotelia chilensis y Escallonia sp., que alcanzaron la categoría de polen dominante, y de Lomatia hirsuta, hallada como polen secundario.Thirty pollen types identified in the honeys from the Andean region of Chubut are described and illustrated by means of LM and SEM photomicrographs. Pollen types belong to the following families: Alstroemeriaceae, Apiaceae, Buddlejaceae, Caryophyllaceae, Caprifoliaceae, Celastraceae, Clusiaceae, Convolvulaceae, Ericaceae, Elaeocarpaceae, Fabaceae, Fagaceae, Lamiaceae, Papaveraceae, Polemoniaceae, Polygalaceae, Proteaceae, Ranunculaceae, Rosaceae, Saxifragaceae, Solanaceae, Thymelaceae, and Verbenaceae. Most pollen types described were found in the honeys as minor important pollen or traces, except Aristotelia chilensis, Escallonia sp., which reached the category of dominant pollen, and Lomatia hirsuta, which was found as secondary pollen.

  20. Distribution of palaeosols and deposits in the temporal evolution of a semiarid fluvial distributary system (Bauru Group, Upper Cretaceous, SE Brazil)

    Science.gov (United States)

    Basilici, Giorgio; Bo, Patrick Führ Dal'; de Oliveira, Emerson Ferreira

    2016-07-01

    The stratigraphic and sedimentological knowledge of the Bauru Group (Upper Cretaceous, SE Brazil) is still generally insufficient and controversial. A sedimentological and palaeopedological study allowed to interpret the south-eastern portion of the Bauru Group according to the model of a fluvial distributary system. This work has two objectives: (1) to include palaeosols in the interpretation of a fluvial distributary system and (2) to give detailed information on the sedimentological and stratigraphic features of the SE portion of the Bauru Group in order to support biostratigraphical, taphonomic and palaeoecological studies. In the south-eastern portion of the Bauru Group, three genetic stratigraphic units were described and interpreted, here informally called lower, intermediate and upper units. The lower unit is constituted of muddy sandstone salt flat deposits and sandstone sheet deltas deposits and is interpreted as a basinal part of a fluvial distributary system. The intermediate unit is formed of very fine to fine-grained sandstone-filled ribbon channel and sandy sheet-shaped beds, suggesting a distal or medial portion of a fluvial distributary system. The upper unit does not match with the present models of the fluvial distributary system because mostly constituted of moderately developed, well-drained, medium- to fine-grained sandstone palaeosols, which testify pauses of sedimentation to the order of 104 years. Preserved features of sedimentary structures suggest that the parent material was formed by occasional catastrophic unconfined flows. This unit may represent the most distal portion of a fluvial distributary system generated by retrogradation of the alluvial system due to aridification of the climate. The upper unit may be interpreted also as proximal portion of fluvial distributary system if considering the coarser-grained and the well-drained palaeosols. However, the absence of channel deposits makes this interpretation unconvincing.

  1. Lagoonal sedimentation and fluctuating salinities in the Vectis Formation (Wealden Group, Lower Cretaceous) of the Isle of Wight, southern England

    Science.gov (United States)

    Stewart, D. J.; Ruffell, A.; Wach, G.; Goldring, R.

    1991-06-01

    Sedimentation in the Shepherd's Chine Member of the Vectis Formation is characterised by a cyclicity of four principal facies on which a strong asymmetry has been imprinted by erosional events. The four lithofacies are: (1) very fine to fine sandstones; (2) heterolithic sand/silt and mudstones; (3) parallel-laminated (pinstripe) mudstones; and (4) black mudstones. The biota, principally associated with lithofacies 2 and 3 (as shelly partings and coquinas), can be grouped into five molluscan associations which range from freshwater to quasi-marine. These associations are poorly correlated with the lithofacies, but fluctuate within and between cycles. Salinity and storm frequency increase towards the top of the formation, heralding the main marine Aptian transgression. Lithofacies and biotas indicate deposition in a lagoon that was shallow and temporarily emergent. The cyclicity is thought to represent the more distal phases of the advance and retreat of deltaic sand bodies, derived from a westerly direction, into the lagoon. Major storm events broke the symmetry of the cycles. A deltaic facies, represented by the Barnes High Sandstone Member, is thought to be laterally linked, reworked deltaic sandstone lobes.

  2. Un ejemplo excepcional de brechamiento (sismita? en el grupo Chubut, Patagonia

    Directory of Open Access Journals (Sweden)

    Edgardo Navarro

    2010-10-01

    Full Text Available Un brechamiento excepcional en unidades sedimentarias pelíticas del Grupo Chubut en la cercanía de la localidad de Telsen, provincia de Chubut, muestra que han sido afectadas por una etapa de telodiagénesis (diagénesis de exhumación. Presentan evidencias de deformación frágil relacionadas con mecanismos de sobrepresurización. Estos depósitos de edad aptiana, se disponen subhorizontales y constituyen asociaciones fluviales lateralmente extendidas. Un continuo de estructuras sedimentarias deformacionales se desarrollan enteramente sobre los depósitos pelíticos correspondientes a la asociación de facies de llanura de inundación. Cuatro intervalos fueron reconocidos de manera continua: 1 fracturado in situ, 2 brechado, 3 brechado fangosostenido y 4 homogeneizado. Conductos de escape potenciales de diversos tamaños, tienen desarrollo en el intervalo fangosostenido, que en ocasiones llegan a atravesar el intervalo superior homogéneo. El mecanismo de sobrepresurización, se habría visto favorecido por la presencia de cuerpos de areniscas conglomerádicas tobáceas confinantes (capa sello, que impidieron el escape de fluidos, permitiendo la licuefacción parcial a total y fluidización de la rocas sedimentarias de la llanura aluvial. Fallas normales reconocidas en el área, que afectan al Grupo Chubut, constituirían un elemento de juicio para establecer un origen sísmico a estas fábricas brechadas, cuya magnitud habría superado M>5 de la escala Mercalli modificada. La característica reológica frágil del material a partir del cual se originaron, convierte a estas estructuras en un ejemplo natural excepcional de brechamiento a partir de un mecanismo de sobrepresurización fosilizado.

  3. Mortalidad en la población galesa de Gaiman, provincia de Chubut, Argentina

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    Caratini, Alicia Liliana

    2005-01-01

    Full Text Available El objetivo de este trabajo es analizar la evolución en el tiempo de las defunciones y de las causas de muerte por edad y sexo de la población galesa de Gaiman, provincia de Chubut, Argentina. Los datos fueron obtenidos de las Actas de Defunción del Archivo del Registro Civil de la ciudad de Rawson, Chubut. El período de estudio se extendió de 1892 a 1961 y para su descripción y análisis se lo dividió en decenios. Se registraron 2103 defunciones de las cuales 1039 (49% correspondieron a galeses y sus descendientes, lo cual representa un promedio de 14.6 muertes por año. Se detectó una sobremortalidad masculina (59%, esperable en una población colonizadora con predominio de varones. Se observó un incremento, en el tiempo, de la edad media de defunción, lo que indica mejoras en las condiciones socioeconómicas y de salud de la población. La mortalidad infantil y los natimortos representaron el 20% y el 11%, respectivamente, de las defunciones y se constató una transición desde una mortalidad provocada por enfermedades de naturaleza exógena a otra de causalidad endógena. Al compararse nuestros datos con los de la provincia de Chubut y el país, se comprobó, en todos los casos, un descenso de la mortalidad en el tiempo, aunque en Gaiman esa disminución fue más significativa, probablemente por la atención que la comunidad le dedicaba a la educación y a la salud.

  4. Estratigrafía y petrología del sector noreste de sierra de Apas. Provincia del Chubut Stratigraphy and petrology of the Northeastern sector of Sierra de Apas. Chubut Province

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    M. Remesal

    2004-12-01

    Full Text Available La sierra de Apas, ubicada entre las provincias de Rio Negro y Chubut, forma parte del magmatismo de intraplaca emplazado durante el Paleogeno-Neógeno en el norte de la Patagonia extrandina. En el sector noreste se ha definido una estratigrafía integrada por: traquitas oscuras, flujos piroclásticos, traquitas claras, domos riolíticos y basaltos porfíricos y afíricos. Las traquitas oscuras, son relativamente más antiguas, tienen bajo porcentaje de fenocristales, y clasifican como traquitas- benmoreítas. Las traquitas claras son porfíricas, y clasifican como comenditas. Su ubicación estratigráfica es confirmada por una edad K/Ar de 19 ± 2 Ma. Los flujos piroclásticos son predominantemente vítreos, cubren a las traquitas oscuras y tienen composiciones traquiandesíticas. La petrografía y geoquímica establecen una estrecha relación con las traquitas claras. El único cuerpo dómico en el área es el cerro Colorado, cuya composición corresponde a una riolita peralcalina ó comendita; una edad K/Ar de 24 ± 1 Ma establece por primera vez su relación temporal. La unidad efusiva más joven corresponde a lavas basálticas, agrupadas en afíricas y porfíricas. Se propone designar a las primeras como basaltos olivínicos transicionales en tanto que los basaltos porfíricos se subdividen en basaltos olivínicos alcalinos y hawaiitas. Los datos estratigráficos y geoquímicos sugieren que la asociación volcánica estudiada es el resultado de al menos dos etapas evolutivas. Una de ellas incluye los basaltos, traquitas claras, flujos claros y comenditas que muestran un patrón de cristalización fraccionada. Las traquitas oscuras, más viejas, corresponderían a otro estadio evolutivo.The volcanic building of Sierra de Apas (located on the limit between the Rio Negro and Chubut provinces is part of the Paleogene-Neogene intraplate magmatism of the northern Extrandean Patagonia. This contribution is focused on the northeastern of the Sierra

  5. Disparity of Early Cretaceous Lamniformes sharks

    OpenAIRE

    Söderblom, Fredrik

    2015-01-01

    The geological range of lamniform sharks stretches from present day species such as Carcharodon carcharias (great white shark) back to the at the moment oldest undoubted fossil finds during the Early Cretaceous. In this paper a geometric morphometric analysis was performed on images of Early Cretaceous lamniform teeth collected from published literature in order to examine the change in disparity (range of morphological variation within a group) throughout the time period. Due to limited avai...

  6. Determination of Quality Chemical Parameters of Honey from Chubut (Argentinean Patagonia Determinación de Parámetros Químicos de Calidad de las Mieles de Chubut (Patagonia Argentina

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    Pia Valeria Aloisi

    2010-12-01

    Full Text Available This study was intended to evaluate the quality chemical parameters of 62 Apis mellifera L. honey samples, from the Province of Chubut, Argentine. Samples were obtained from the three melliferous areas of this province: Andean region, lower Chubut River valley and plains of Senguerr River. The average values obtained for electrical conductivity (0.33 mS cm-1 and pH (4.17 indicate that the analyzed honeys came mainly from nectar. Electrical conductivity was higher in honeys from the Andean region than in honeys from the other two regions. Moisture (water content was low, with an average value of 14.67%. The hydroxymethylfurfural (HMF content was very low and ranged between 0.0 and 14.70 mg kg-1. Moisture, HMF and free acidity values show good maturity and absence of undesirable fermentation in all the samples. Diastase activity had a mean value of 13.50 units on the Gothe scale. Color parameter presented variations between honeys from different areas. The analytical values for the samples from the Andean region, the lower Chubut River valley and the plains of the Senguerr River respectively were: 67.73, 40.33 and 23.26 mm Pfund. Results obtained in this study, indicate that honeys produced in Chubut present excellent quality properties according to international standards.Este estudio se realizó para evaluar los parámetros químicos de calidad de 62 muestras de mieles de Apis mellifera L., provenientes de la Provincia de Chubut. Las muestras de mieles se obtuvieron de las tres regiones melíferas de esta provincia: la Región Andina, el valle inferior del Río Chubut y la llanura del Río Senguerr. Los valores promedio obtenidos para conductividad eléctrica (0,33 mS cm-1 y pH (4,17 indican que las mieles fueron principalmente de néctar. Los valores de conductividad eléctrica fueron mayores en las mieles de la Región Andina que en las mieles de las otras regiones. La humedad (contenido de agua fue baja, con un valor medio de 14,67%. El

  7. 兰州-民和盆地下白垩统河口群沉积特征及盆地分析%Sedimentology and basin analysis of the Early Cretaceous Hekou Group in Lanzhou-Minhe basin

    Institute of Scientific and Technical Information of China (English)

    陈军; 柳永清; 旷红伟; 刘燕学; 彭楠; 许欢; 董超; 刘海; 薛沛霖

    2013-01-01

    Lanzhou-Minhe basin is a typical intracontinental rift basin in northwest Gansu formed in the Early Cretaceous. The Hek-ou Group in Lanzhou-Minhe basin is characterized by purplish red clastic sediments with a variety of grain sizes. On the basis of previous researches, the authors conducted field sedimentary investigations and studies of sedimentary fades, provenance and palaeocurrent of the Hekou Group along different stratigraphic sections such as Hekou, Yanguoxia and Zhongpu. The results indicate that the Hekou Group experienced an evolution of sedimentary faices from alluvial fan through fan delta and lacustrine/fluvial facies to deltaic sedimentary facies. Provenance and palaeocurrents suggest that the uplifted Qilian Mountain around the basin was the main material source of sediments during the Early Cretaceous. It is also shown that the previous Datonghe Formation belonged to the Late Jurassic-Early Cretaceous period and the Heko Group was deposited since the earlier Early Cretaceous. In addition, dinosaur fossils and pollen assemblages in the Heko Group and their environmental implications were described as well. Finally, a reconstruction model for palaeogeography of Lanzhou-Minhe basin in the Early Cretaceous was established.%兰州-民和盆是早白量世时期中国西部典型的陆内断陷沉积盆地,该时期主要发育的河口群是一套红褐色碎屑岩地层.在前人研究的基础上,对河口、盐锅峡、兰州中铺等地河口群进行野外地质调查,以盆地分析方法为手段,从地层、沉积相、物源和古水流等方面对盆地内的河口群进行研究分析认为,河口群在沉积相序上经历了冲积扇相-扇三角洲相-湖相/河流相-三角洲相的演化过程.在对大通河组与河口群综合研究的基础上,认为大通河组的时代宜划归为晚侏罗世-早白垩世,且河口群地层包括了早白垩世早期的沉积.结合河口群砾石成分、砂岩组分和古水

  8. Lower Cretaceous aquifers

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set represents the extent of the Lower Cretaceous aquifers in the states of Montana, Wyoming, South Dakota, Kansas, Nebraska, Iowa, and Minnesota..

  9. Jurassic tetrapods and flora of Cañadón Asfalto Formation in Cerro Cóndor area, Chubut Province

    Directory of Open Access Journals (Sweden)

    Ignacio H. Escapa

    2008-12-01

    Full Text Available The plant and tetrapod fossil record of the Cañadón Asfalto Formation (Middle to Late Jurassic found in Cerro Cóndor area (Chubut Province is summarized here. The flora is dominated by conifers (Araucariaceae, Cupressaceae sensu lato but also includes ferns and equisetaleans. The tetrapod fauna is composed of dinosaur taxa described in the 70's as well as other remains recently described and other vertebrate groups such as amphibians, turtles, and mammals. The amphibian remains have been interpreted as representatives of a new species of Notobatrachus, considered one of the most basal members of the anuran lineage. Similarly, turtle remains have been recently recognized as a new species of basal turtle, bringing valuable information about the early evolution of this group. The dinosaur remains are largely dominated by saurischian taxa, represented by basal forms of Eusauropoda and Tetanurae. In addition, three different mammalian species have been identified and considered as early representatives of an endemic Gondwanan mammalian fauna. The fossil record of this formation represents the most completely known biota from the continental Middle to Late Jurassic of the Southern Hemisphere and one of the most complete of the entire world.

  10. Change in the meiofauna community structure of sandy beaches of the Nuevo Gulf (Chubut, Argentina

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    Carlos A. Harguinteguy

    2012-01-01

    Full Text Available The composition and distribution of the benthic meiofauna assemblages of the Nuevo Gulf (Chubut, Argentina are described in relation to abiotic variables. The meiofauna and sediment samples were collected in the intertidal zone of four sandy beaches with different anthropic disturbances in June 2005. The samples were obtained at 20 sampling sites using a 2.5 cm diameter core tube at a depth of 10 cm. A total of 13 meiofauna taxa were identified, with the meiofauna being primarily represented by nematodes, gastrotrichs, ciliates and polychaetes and the meiofauna abundances ranging from 1.5 × 10³ to 6.5 × 10³ ind. 10 cm‑2. Univariate (one-way ANOVA test and multivariate (ANOSIM/MDS test analyses showed clear dissimilarities in community structures between sites with anthropic effects and those in pristine condition, revealed by the significant differences were found between beaches near to and far way from a city with port activity. The meiofaunal assemblage varied in abundance and diversity, and these changes in the community structure may have been related to environmental gradients on the shore. The BIO‑ENV analysis showed that the redox potential discontinuity depth might be the main factor in the spatial distribution of organisms.

  11. Estratigrafía y petrología del sector noreste de sierra de Apas. Provincia del Chubut Stratigraphy and petrology of the Northeastern sector of Sierra de Apas. Chubut Province

    OpenAIRE

    M. Remesal; F.M. Salani; G.I. Massaferro; M.E. Cerredo

    2004-01-01

    La sierra de Apas, ubicada entre las provincias de Rio Negro y Chubut, forma parte del magmatismo de intraplaca emplazado durante el Paleogeno-Neógeno en el norte de la Patagonia extrandina. En el sector noreste se ha definido una estratigrafía integrada por: traquitas oscuras, flujos piroclásticos, traquitas claras, domos riolíticos y basaltos porfíricos y afíricos. Las traquitas oscuras, son relativamente más antiguas, tienen bajo porcentaje de fenocristales, y clasifican como traquitas- be...

  12. Estratigrafía y petrología del sector noreste de sierra de Apas. Provincia del Chubut

    OpenAIRE

    M. Remesal; F.M. Salani; G.I. Massaferro; M.E. Cerredo

    2004-01-01

    La sierra de Apas, ubicada entre las provincias de Rio Negro y Chubut, forma parte del magmatismo de intraplaca emplazado durante el Paleogeno-Neógeno en el norte de la Patagonia extrandina. En el sector noreste se ha definido una estratigrafía integrada por: traquitas oscuras, flujos piroclásticos, traquitas claras, domos riolíticos y basaltos porfíricos y afíricos. Las traquitas oscuras, son relativamente más antiguas, tienen bajo porcentaje de fenocristales, y clasifican como traquitas- be...

  13. Salud bucal y nutrición en cazadores-recolectores del nordeste del Chubut en el Holoceno

    OpenAIRE

    Novellino, Paula; Gómez Otero, Julieta

    2009-01-01

    Investigaciones arqueológicas llevadas a cabo en Patagonia centro-septentrional (costa atlántica y valle inferior del río Chubut) demostraron que el área fue utilizada desde por lo menos el Holoceno medio. Estudios de isótopos estables ( 13C y 15N) en muestras óseas humanas indican que los cazadores-recolectores que la ocuparon mantuvieron una dieta mixta que combinó el consumo de guanacos, plantas terrestres, moluscos y pinnípedos. No obstante esta tendencia general, se observó variabilidad ...

  14. Evolución geomorfológica y cronología relativa de los niveles aterrazados del área adyacente a la desembocadura del río Chubut al Atlántico (Provincia del Chubut Geomorphological evolution and relative chronology of terrace levels adjacent to the Chubut River mouth to the Atlantic (Chubut Province.

    Directory of Open Access Journals (Sweden)

    Emilio F González Díaz

    2011-12-01

    Full Text Available Se describe un antiguo abanico aluvial y su posterior evolución. Las acumulaciones del antiguo abanico aluvial han sido interpretadas como la continuidad septentrional de los rodados patagónicos de la meseta Montemayor, una propuesta que es rebatida. La base metodológica del reconocimiento del antiguo abanico aluvial y su distinción genética y temporal, la constituyó el análisis geomórfico y la evaluación altimétrica. Su asignación temporal es un problema aún no resuelto. La metodología condujo a diferenciar tres sistemas geomórficos o niveles, relacionados con sucesivos episodios de agradación y erosión, los que ocupan posiciones cada vez más inferiores, coincidiendo con el complejo paleodrenaje del antiguo abanico aluvial. Sus desarrollos sucesivos son vinculados con protoríos Chubut 1, 2, 3 propuestos y el correspondiente a un paleovalle Simpson. Pese a las limitaciones apuntadas, se propone que el modelo evolutivo del antiguo abanico aluvial responde a una estructura de corte y relleno, que avalaría una composición poliformacional del antiguo abanico aluvial y además la migración progresiva del paleodrenaje hacia el sur. Un análisis geomorfológico y altimétrico diferenció un nivel superior integrado por restos de tres planicies (Pa, Pm y Pb, un nivel medio con dos terrazas (T1 y T2 y un complejo nivel inferior de cinco terrazas (T3, T4, T5 T6 y T7. Evidencias relícticas de los paleodrenajes propuestos son los paleovalles Estancia Paz y Don Morgan-Saraza del nivel superior. La edad del antiguo abanico aluvial basada en la evolución geomórfica del área de estudio, es tentativamente asignada a un incierto lapso del Pleistoceno superior entre el interglacial Sangamon y fines de la última glaciación.An ancient alluvial fan and its subsequent evolution are described. Ancient alluvial fan accumulations have been interpreted as the northern continuation of the rodados patagónicos of the Montemayor Plateau, a proposal

  15. Monitorieo de DDI en el noreste de la provincia de Chubut (2004

    Directory of Open Access Journals (Sweden)

    G. S. Zarza

    2008-06-01

    Full Text Available Un total de 668 alumnos de escolaridad primaria, de ambos sexos, fue estudiado en este monitoreo de bocio endémico en dos ciudades del noreste de la provincia de Chubut: Puerto Madryn (493 niños y Trelew (175 niños. La edad de los escolares osciló entre 5 y 15 años. La palpación tiroidea fue hecha por el conjunto de los médicos participantes. Sin embargo, con la finalidad de aunar criterios con lo realizado previamente (1-18, se tomó como única referencia la palpación de H. N., que se llevó a cabo en la totalidad de los niños estudiados. La definición del grado de bocio fue similar a la utilizada en los otros relevamientos (1. Se determinó la yoduria en muestras casuales de orina emitidas por los niños una vez que fueron palpados (161 de Puerto Madryn y 139 de Trelew. Se midió el contenido de yodo en 467 muestras de sal de consumo hogareño de Puerto Madryn y en 161 de Trelew. El examen palpatorio de los niños reveló la existencia de bocio grado 1 solamente. La prevalencia de bocio encontrada fue de 3,9 % en Puerto Madryn y de 2,9 % en Trelew. Los niveles de yoduria alcanzaron, en Puerto Madryn, una media de 188±95,8(DS μg/L y una mediana de 171 μg/L, al tiempo que en Trelew la media fue de 245±102,3 μg/L y la mediana de 196 μg/L. El contenido de yodo de las sales que aportaron los alumnos, si bien varió según la marca de sal utilizada, tuvieron un nivel relativamente adecuado de yodo en aquellas de consumo masivo. De esta manera, observamos que en la localidad de Puerto Madryn el promedio de yodo en la sal, tomada en conjunto, fue de 32,0 ± 10,9 mg/Kg, mientras que para Trelew fue de 31,5 ± 8,5 mg/Kg. Al analizar las concentraciones de yodo <15 mg/Kg, observamos que fue del 9 % en Puerto Madryn y del 5 % en Trelew. Teniendo en cuenta la línea de corte del 10 % que fija el ICCIDD (19 como valor óptimo, podemos observar que la situación de ambas poblaciones es satisfactoria. Concluimos que en estas dos ciudades del

  16. Geología de la quebrada Honda, cuenca del lago La Plata, Chubut

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    G.V. Depine

    2004-12-01

    Full Text Available La quebrada Honda, situada en el sur de la cuenca de los lagos La Plata y Fontana, en la provincia de Chubut, presenta una columna estratigráfica que comienza en el Jurásico superior con rocas calcoalcalinas de arco volcánico intermedias a ácidas de la Formación Lago La Plata. Las rocas sedimentarias que rellenan la cuenca de intraarco neocomiana corresponden al Grupo Coyhaique, dentro del cual se encuentran las Formaciones Tres Lagunas y Katterfeld, que se ubican dentro de un modelo paleoambiental como cortejo sedimentario de borde de plataforma, sucedido por un cortejo transgresivo, cuya edad es acotada al Hauteriviano inferior, debido al hallazgo de restos de Favrella americana en pelitas de la Formación Katterfeld. Vinculados con la extensión que da lugar a la cuenca se registran los cuerpos hipabisales calcoalcalinos básicos del Gabro Quebrada Honda y se los relaciona con un volcanismo de características más evolucionadas de la Formación Don Rueda, de edad neocomiana tardía. Si bien este magmatismo de arco volcánico es subaéreo, presenta indicios de interacción con cuerpos de agua por lo que corrobora la concomitancia de este evento con la sedimentación póstuma de Grupo Coyhaique. Se registra un evento de inversión tectónica que tendría una edad máxima de 80 Ma.

  17. Un primitivo Notonychopidae (Litopterna del Paleoceno inferior de Punta Peligro, Chubut, Argentina

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    Morales, J.

    1997-12-01

    Full Text Available The discovery of a new ungulate species, Requisia vidmari gen. nov., nov. sp. in the lower Paleocene of Punta Peligro, Chubut (Argentine represents the earliest known record of Litopterna. The dental morphology of this new genus is very similar to that known for Notonychops powelli Soria, 1989, differing mainly by its more primitive M3, which is less elongated and less selenodont. Requisia vidmari, together with Wainka tshotshe Simpson, 1948, can be included in the family Notonychopidae, which appear to represent an ancestral grade in the evolution of Litopterna. Because cladogenesis of South American ungulates clearly took place prior to the Punta Peligro fauna and was apparently rapid, phylogenetic interpretation is difficult.Se comunica un nuevo ungulado con dentición pre-selenodonta del Paleoceno inferior, Peligrense, de Patagonia, Argentina. Su morfología dentaria es muy similar a la de Notonychops powelli Soria, 1989, pero con caracteres más primitivos. La morfología de las cúspides, el tipo de desgaste y los caracteres crescentiformes del M3 indican que Requisia vidmari gen. nov., sp. nov. presenta fuertes evidencias del desarrollo de caracteres selenodontos, por lo que se lo considera como el más primitivo representante del orden Litopterna. Requisia vidmari y probablemente Wainka tshotshe Simpson, 1948, son primitivos en relación a Notonychops, pero su similitud morfológica justificaría su inclusión en la misma familia Notonychopidae. Se considera que la radiación adaptativa de los ungulados paleocenos de América del Sur fue precoz, eventualmente rápida, lo que dificulta encontrar un modelo filogenético suficientemente explicativo.

  18. La identidad en la encrucijada: la comunidad galesa del Chubut y las conmemoraciones del Centenario y Bicentenario de la Revolución de Mayo

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    Geraldine Lublin

    2013-12-01

    Full Text Available El presente artículo se propone rastrear a grandes rasgos la relación ―especial‖ entre el estado nacional argentino y, a partir de 1958, la provincia de Chubut por una parte y los colonos galeses que se establecieron en Chubut desde 1865 y sus descendientes por otra, a través del análisis de la posición de la colectividad galesa del Chubut en dos momentos históricos destacados: el Centenario y el Bicentenario de la Revolución de Mayo (1810. Al corresponderse el perfil de los galeses con la idea de poblaciones "civilizadas" que las autoridades pretendían impulsar en desmedro de los legítimos pobladores originales, estas políticas dieron lugar a una fuerte identificación histórica de la Provincia de Chubut con la llamada "gesta galesa". Se generó asimismo una peculiar dinámica triangular de las relaciones estatales, cuya evolución a través del tiempo ha desembocado en la actual promoción de la identidad chubutense como el resultado de la fusión de las culturas de los tehuelches originarios y los colonos galeses.

  19. Live birth in Cretaceous marine lizards (mosasauroids).

    OpenAIRE

    Caldwell, M W; Lee, M S

    2001-01-01

    Although live-bearing (viviparity) has evolved around 100 times within reptiles, evidence of it is almost never preserved in the fossil record. Here, we report viviparity in mosasauroids, a group of Cretaceous marine lizards. This is the only known fossil record of live-bearing in squamates (lizards and snakes), and might represent the oldest occurrence of the trait in this diverse group; it is also the only known fossil record of viviparity in reptiles other than ichthyosaurs. An exceptional...

  20. Cretaceous eustasy revisited

    Science.gov (United States)

    Haq, Bilal U.

    2014-02-01

    Eustatic sea-level changes of the Cretaceous are reevaluated based on a synthesis of global stratigraphic data. A new terminology for local/regional or relative sea-level changes (eurybatic shifts) is proposed to distinguish them from global (eustatic) sea-level changes, with the observation that all measures of sea-level change in any given location are eurybatic, even when they include a strong global signal. Solid-earth factors that influence inherited regional topography and thus modify physical measures of amplitude of the sea-level rises and falls locally are reviewed. One of these factors, dynamic topography (surface expression of mass flow in the upper mantle on land- and seascapes), is considered most pertinent in altering local measures of amplitude of sea-level events on third-order time scales (0.5-3.0 Myr). Insights gained from these models have led to the reconciliation of variance between amplitude estimates of eurybatic shifts in any given region and global measures of eustatic changes. Global estimates of third-order events can only be guesstimated at best by averaging the eurybatic data from widely distributed time-synchronous events. Revised curves for both long-term and short-term sea-level variations are presented for the Cretaceous Period. The curve representing the long-term envelope shows that average sea levels throughout the Cretaceous remained higher than the present day mean sea level (75-250 m above PDMSL). Sea level reached a trough in mid Valanginian (~ 75 m above PDMSL), followed by two high points, the first in early Barremian (~ 160-170 m above PDMSL) and the second, the highest peak of the Cretaceous, in earliest Turonian (~ 240-250 m above PDMSL). The curve also displays two ~ 20 Myr-long periods of relatively high and stable sea levels (Aptian through early Albian and Coniacian through Campanian). The short-term curve identifies 58 third-order eustatic events in the Cretaceous, most have been documented in several basins, while

  1. Crecimiento y desarrollo de una población infanto juvenil de la provincia de Chubut

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    Torres, María Fernanda

    1999-01-01

    Full Text Available La diferenciación y adaptación ontogenética son temas centrales en antropología biológica por cuanto su modificación puede afectar la dinámica evolutiva poblacional. Numerosos factores estresantes actúan provocando variación en la expresión fenotípica y nuevas respuestas adaptativas. En el presente trabajo se determinó el crecimiento de niños de 5 a 14 años contrastando con estándares internacionales. La muestra se constituyó con 473 escolares de Río Mayo (Chubut, de ambos sexos. Se relevaron y calcularon variables corporales. Para la comparación con los estándares los datos fueron convertidos a escores z y contrastados además mediante pruebas de Wilcoxon. La estadística empleada consistió en análisis multifactorial de la varianza y pruebas de LSD. Si bien hubo crecimiento en todos los grupos etáreos analizados, los valores obtenidos difirieron significativamente de los correspondientes al estándar. En varones, a excepción del pliegue subescapular, que presentó escores z superiores al estándar las restantes variables se ubicaron entre 0 y -2 DS, siendo más afectadas las estaturas total y sentado y el área muscular. En mujeres, se observó una situación similar a excepción del área adiposa y la masa corporal, con valores mayores al estándar. Estos resultados evidencian la presencia de una desnutrición que abarca toda la franja etárea. La disminución de la talla y el aumento del tejido adiposo constituyen sin duda, respuestas adaptativas que permiten la supervivencia de los individuos frente a la injuria nutricional.

  2. Avulsion at a drift-dominated mesotidal estuary: The Chubut River outlet, Patagonia, Argentina

    Science.gov (United States)

    Isla, Federico; Espinosa, Marcela; Rubio, Belén; Escandell, Alejandra; Gerpe, Marcela; Miglioranza, Karina; Rey, Daniel; Vilas, Federico

    2015-10-01

    The Chubut River flows from the Andes to the Atlantic Ocean, and is interrupted by a single dam built at the middle valley. The lower valley is dominated by the aggradation of an alluvial plain induced by a complex of spits that enclosed the inlet in the last 5000 years. The river has reduced its flow because the blocking of the upper basin by terminal moraines during the Upper Pleistocene. At least the last two marine transgressions have flooded this estuary, and contributed to the aggradation during regressions. The area is of particular interest in regard to irrigation channels practiced since the XIX century. Today, the mean monthly flow is less than 10 m3/s although peaks of 95 m3/s have been recorded in Gaiman in July 2001. The dynamics of the estuary is dominated by waves (wave-dominated estuary) as tidal effects attenuate in less than 5 km. Three vibracores were collected within this floodplain: (a) at Gaiman, an area without any effect of the sea (35 km from the coast); (b) at Trelew, at the former avulsion plain of the river (18 km from the coast); and (c) at Playa Magagna, a saltmarsh located 0.4 km from the beach. At the Gaiman core (1.54 m long) fresh-water epiphytic diatoms dominate (Epithemia sorex, Cocconeis placentula, Ulnaria ulna) suggesting the aggradation of an alluvial plain. The Trelew core (2.19 m long) was collected from a deltaic plain. It was composed by fine sand with organic matter at the base that evolved into silty layers to the top. Several unconformities and laminae with heavy minerals were detected by their geochemical composition analysed by micro X-ray fluorescence (Itrax XRF core scanner). Fine-sand laminated layers were perfectly detected by their high content in S and Cl. On the other hand, mud layers presented lower content in Mg and Al with increments in Ca and V. The core from the marsh area (1.67 m long) was analysed in terms of the diatom evolution in order to detect Holocene sea-level and salinity effects. The sand flats

  3. Hemipelagic cephalopods from the Maastrichtian (late Cretaceous) Parras Basin at La Parra, Coahuila, Mexico, and their implications for the correlation of the lower Difunta Group

    Science.gov (United States)

    Ifrim, Christina; Stinnesbeck, Wolfgang; Garza, Rufino Rodríguez; Ventura, José Flores

    2010-04-01

    Few biostratigraphic data exist from the Parras and La Popa basins, mainly due to the absence of index fossils. This paper describes 19 ammonoid species from 15 genera and 1 nautilid from La Parra, southeastern Coahuila, Mexico. The assemblage consists of Tethyan [( Baculites ovatus, Brahmaites ( Anabrahmaites) vishnu, Fresvillia constricta, Hauericeras rembda, Pachydiscus ( P.) ex gr. neubergicus, Solenoceras reesidei, Tetragonites cf. superstes], cosmopolitan ( Anagaudryceras politissimum, Desmophyllites diphylloides, Diplomoceras cylindraceum, Gaudryceras kayei, Phyllopachyceras forbesianum, Pseudophyllites indra), and cold water taxa [ Fresvillia teres, Hypophylloceras ( Neophylloceras) surya, H. ( N.) hetonaiense, Pachydiscus ( P.) cf. egertoni]. Eutrephoceras sp. and Menuites juv. sp. were not determined to species level. A similar assemblage was recently described from the coeval Méndez Formation at Cerralvo, Nuevo León. Species endemic to North America, particularly the Western Interior Seaway, are absent at La Parra. The ammonoid assemblage and associated planktonic foraminifers allow for precise biostratigraphic assignation to the early Maastrichtian planktonic foraminiferal zone CF 5, and thus provide an important marker level for correlation of the lower Difunta Group. The new biostratigraphic data presented herein allow for the first time precise dating of the Cañon del Tule Formation of the Difunta Group. Their combination with existing sequence- and magnetostratigraphic data improve the correlation of the lower Difunta Group with time-equivalent lithostratigraphic units such as the Cárdenas Formation in Mexico. They also provide new insight into ammonoid migration patterns induced by sea-level changes. Baculites ovatus migrated into the La Popa Basin as a result of the sea-level highstand documented at La Parra.

  4. Brazilian continental cretaceous

    Science.gov (United States)

    Petri, Setembrino; Campanha, Vilma A.

    1981-04-01

    Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

  5. Movilidad Espacial, Ocupación y Empleo en el Valle Inferior del Río Chubut Spatial mobility, Occupation and Employment in the Inferior Valley of the River Chubut

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    M. Marcela Crovetto

    2011-12-01

    Full Text Available Desde una perspectiva que propone una serie de críticas a la tipología dicotómica de clasificación demográfica del espacio habitado, rural y urbano, se ha indagado sobre las formas que adquiere la movilidad espacial cotidiana en relación al empleo y a la ocupación en el Valle Inferior del Río Chubut -patagonia argentina-, atendiendo a una situación especial de movilidad espacial cotidiana como es la referida a la producción de cerezas en el Valle. Se utilizaron fuentes secundarias estadísticas, históricas y documentales en articulación con la construcción de datos primarios mediante relevamientos operados por distintas técnicas. Fundamentalmente se aplicó una encuesta a hogares (200 casos de barrios periféricos de las localidades involucradas en el Valle Inferior del Río Chubut El centro del ejercicio de la investigación estuvo en contraponer los resultados de una encuesta realizada en campo de acuerdo tanto a la clasificación clásica de la zona de residencia (rural o urbana como a una propuesta alternativa para la investigación. Así se evaluaron los matices escondidos dentro de las homogeneizantes ideas de rural y urbano, sintetizadas por la cantidad de habitantes -en Argentina con 2000 o más se considera un espacio urbano, con menos un espacio rural- observándose, especialmente, que muchas trayectorias cotidianas de actores sociales considerados clásicamente urbanos se acercaban mucho a las de los actores de las zonas rurales.From a perspective that proposes a number of criticisms of the dichotomous typology of demographic classification of living space, rural and urban, has inquired about the forms that everyday spatial mobility in relation to employment in the Valle Inferior del Río Chubut - Patagonia-Argentina, following a special situation of everyday spatial mobility as that concerning the production of cherries in the Valley. Were used statistics, historical and documentary in coordination with the construction

  6. Early Cretaceous Tectonism and Diatoms in Korea

    Institute of Scientific and Technical Information of China (English)

    Ki-Hong CHANG; Sun-Ok PARK

    2008-01-01

    The Early Cretaceous Sindong Group, a non-marine molasse, unconformably overlies the folded earliest Cretaceous Myogok Formation. The tectonism that folded the Jaseong Synthem including the Myogok and other formations is here called the Nakdong-Jaeryeonggang (N-J) tectonism. The Oknyeobong and Dabokni Formations are discussed to show that they belong to the Jaseong Synthem. The Dabokni Formation yielded fossil diatoms whose age has been referred as the "earliest Cretaceous" based on the geologically constrained age of the fossil-bearing deposit. The age of the N-J tectonism appears Barremian as it is between the Hauterivian Myogok Formation and the Aptian Sindong Group with the TPN (Trigonioides-Plicatounio-Nippononaia) fauna. The N-J tectonism, an orogeny, quite deformed pre-Aptian strata in Korea, but can hardly find its reported equivalent in NE China. A revised correlation table shows that the Jaseong- Sindong sequence corresponds to the Jehol Group of China. The Sindong-Hayang transition was characterized by basin migration and dextral rotation probably caused by the Tan-Lu fault system in a broad sense.

  7. Parasites in rodent coprolites from the historical archaeological site Alero Mazquiarán, Chubut Province, Argentina

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    Norma Haydée Sardella

    2009-02-01

    Full Text Available The aim of this study was to examine the parasitic remains that were found in rodent coprolites collected from the archaeological site Alero Mazquiarán (Chubut Province, 45º44'15"S, 70°25'9"W, which is assigned to the interface of the Araucanian and Tehuelche cultures, dated at 212 ± 35 years B.P. The faecal material from two unidentified rodent species (X-10 and X-11 was collected from one human pelvic cavity found in a multiple burial. The faecal samples were processed and examined using paleoparasitological procedures. The X-10 coprolites were positive for eggs of Monoecocestus sp. (Cestoda: Anoplocephalidae and the X-11 faeces were positive for Pterygodermatites sp. (Nematoda: Rictulariidae, Trichosomoides sp. (Nematoda: Trichosomoididae and Monoecocestus sp. In this study, we discuss parasitic life cycles, the zoonotic importance of parasites and the behaviour of the aboriginal people.

  8. Parasites in rodent coprolites from the historical archaeological site Alero Mazquiarán, Chubut Province, Argentina.

    Science.gov (United States)

    Haydée Sardella, Norma; Horacio Fugassa, Martín

    2009-02-01

    The aim of this study was to examine the parasitic remains that were found in rodent coprolites collected from the archaeological site Alero Mazquiarán (Chubut Province, 45 degrees 44'15''S, 70 degrees 25'9''W), which is assigned to the interface of the Araucanian and Tehuelche cultures, dated at 212 +/- 35 years B.P. The faecal material from two unidentified rodent species (X-10 and X-11) was collected from one human pelvic cavity found in a multiple burial. The faecal samples were processed and examined using paleoparasitological procedures. The X-10 coprolites were positive for eggs of Monoecocestus sp. (Cestoda: Anoplocephalidae) and the X-11 faeces were positive for Pterygodermatites sp. (Nematoda: Rictulariidae), Trichosomoides sp. (Nematoda: Trichosomoididae) and Monoecocestus sp. In this study, we discuss parasitic life cycles, the zoonotic importance of parasites and the behaviour of the aboriginal people.

  9. Simbirskiasaurus and Pervushovisaurus reassessed: implications for the taxonomy and cranial osteology of Cretaceous platypterygiine ichthyosaurs

    OpenAIRE

    Fischer, Valentin; Arkhangelsky, Maxim; Stenshin, Ilya; Uspensky, Gleb; Godefroit, Pascal

    2014-01-01

    The ichthyosaur fossil record is interspersed by several hiatuses, notably during the Cretaceous. This hampers our understanding of the evolution and extinction of this group of marine reptiles during the last 50 million years of its history. Several Cretaceous ichthyosaur taxa named in the past have subsequently been dismissed and referred to the highly inclusive taxon Platypterygius, a trend that has created the impression of low Cretaceous ichthyosaur diversity. Here, we describe the crani...

  10. Plantas Medicinales en el Parque Nacional los alerces, Chubut, Patagonia Argentina

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    Carolina Toledo

    2012-12-01

    Full Text Available El objetivo de este estudio fue identificar las plantas con valor medicinal empleadas por los antiguos pobladores del Parque Nacional Los Alerces y relacionarlas con la riqueza específica de plantas medicinales presentes en el área. Se entrevistaron 16 pobladores asentados en la Reserva Nacional que tenían conocimiento de las plantas medicinales, más allá de que hicieran uso o no de las mismas. Las entrevistas fueron semiestructuradas, completadas de manera escrita e individual por el entrevistador. Las mismas incluían diez preguntas que recopilaban información respecto a las especies usadas como medicina, modo de preparación y aplicación, frecuencia de uso, localización de las plantas en el ámbito del área protegida, forma de obtención de las especies, y el modo de adquisición de los conocimientos respecto a las plantas. Los pobladores mencionaron el uso de 42 especies con valor medicinal, distribuidas en 24 familias, de las cuales las mejor representadas fueron Lamiaceae (21,4% y Asteraceae (14,2%. En cuanto al origen de las plantas medicinales citadas por los pobladores, el 58, 5% correspondió a especies exóticas. Los usos más frecuentes fueron para trastornos del sistema digestivo, seguido en orden decreciente y en menor proporción para tratar afecciones respiratorias, cardiovasculares y de la piel. Al comparar la riqueza total de especies medicinales presentes en el Parque y las registradas a partir de las entrevistas, se observa que se hace uso de un 28,6% de lo disponible en el área.Medicinal plants in The Alerces National Park, Chubut, Argentinean Patagonia. The aim of this study was to identify the medicinal plants used by the old residents in The Alerces National Park and to relate this information with medicinal species richness in the area. An interview was employed with 16 local people settled in the National Reserve who had knowledge of medicinal plants, past or not to make use of them. The interviews were semi

  11. Jurassic tetrapods and flora of Cañadón Asfalto Formation in Cerro Cóndor area, Chubut Province Flora y tetrápodos del Jurásico de la Formación Cañadón Asfalto en el área de Cerro Cóndor, provincia de Chubut

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    Ignacio H. Escapa

    2008-12-01

    Full Text Available The plant and tetrapod fossil record of the Cañadón Asfalto Formation (Middle to Late Jurassic found in Cerro Cóndor area (Chubut Province is summarized here. The flora is dominated by conifers (Araucariaceae, Cupressaceae sensu lato but also includes ferns and equisetaleans. The tetrapod fauna is composed of dinosaur taxa described in the 70's as well as other remains recently described and other vertebrate groups such as amphibians, turtles, and mammals. The amphibian remains have been interpreted as representatives of a new species of Notobatrachus, considered one of the most basal members of the anuran lineage. Similarly, turtle remains have been recently recognized as a new species of basal turtle, bringing valuable information about the early evolution of this group. The dinosaur remains are largely dominated by saurischian taxa, represented by basal forms of Eusauropoda and Tetanurae. In addition, three different mammalian species have been identified and considered as early representatives of an endemic Gondwanan mammalian fauna. The fossil record of this formation represents the most completely known biota from the continental Middle to Late Jurassic of the Southern Hemisphere and one of the most complete of the entire world.Se resume brevemente el registro de plantas y tetrápodos fósiles de la Formación Cañadón Asfalto (Jurásico Medio a Superior en el área de Cerro Cóndor, provincia de Chubut. La flora está conformada por coníferas de las familias Araucariaceae y Cupressaceae sensu lato dominando la asociación, la cual se completa con helechos y equisetales en proporciones menores. La fauna de tetrápodos se compone por los clásicos dinosaurios descriptos en los 70`s, a los que se suman nuevos restos pertenecientes a este grupo, así como anfibios, tortugas y mamíferos coleccionados en la última década. Los restos de anfibios han sido interpretados como representantes de una nueva especie de Notobatrachus, considerado

  12. Cretaceous Crocodyliforms from the Sahara

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    Paul Sereno

    2009-11-01

    Full Text Available Diverse crocodyliforms have been discovered in recent years in Cretaceous rocks on southern landmasses formerly composing Gondwana.  We report here on six species from the Sahara with an array of trophic adaptations that significantly deepen our current understanding of African crocodyliform diversity during the Cretaceous period.  We describe two of these species (Anatosuchus minor, Araripesuchus wegeneri from nearly complete skulls and partial articulated skeletons from the Lower Cretaceous Elrhaz Formation (Aptian-Albian of Niger. The remaining four species (Araripesuchus rattoides sp. n., Kaprosuchus saharicus gen. n. sp. n., Laganosuchus thaumastos gen. n. sp. n., Laganosuchus maghrebensis gen. n. sp. n. come from contemporaneous Upper Cretaceous formations (Cenomanian in Niger and Morocco.

  13. Facies y ambientes del grupo Salta (cretácico-paleógeno en Tumbaya, Quebrada de Humahuaca, provincia de Jujuy Facies and environments of the Salta Group (Cretaceous-Paleogene in Tumbaya, Quebrada de Humahuaca, JujuyProvince

    Directory of Open Access Journals (Sweden)

    María Cristina Sánchez

    2010-11-01

    Full Text Available Los depósitos rojos del Grupo Salta (Cretácico-Paleógeno que afloran en la quebrada de Tumbaya, margen derecha de la quebrada de Humahuaca (provincia de Jujuy, se caracterizan por presentar facies distintas a las típicas de otros lugares de la cuenca. Son facies proximales de ambiente general árido a semiárido cuya acumulación avanzó sobre el extremo N-NO del alto constituido por la dorsal Salto-Jujeña. La relación de base y de techo del depósito es de discordancia erosiva con el Grupo Mesón (Cámbrico y angular con acumulaciones cuaternarias de bajada respectivamente. En el afloramiento están representadas las principales unidades del Grupo Salta tanto del synrift como del postrift. El reconocimiento y estudio de las facies permitió identificar y caracterizar de base a techo los Subgrupos Pirgua, Balbuena y Santa Bárbara, y las distintas formaciones de cada subgrupo. En el Subgrupo Pirgua (arenas eólicas no es posible diferenciar sus tres unidades formacionales, por lo tanto se lo menciona como Formación Pirgua. En el Subgrupo Balbuena se reconocen las Formaciones Lecho, que consta de facies fluviales de tipo mantos de crecida, y Yacoraite que muestra condiciones ambientales transicionales, continentales y marino litoral-sublitoral carbonático influenciado por mareas y tormentas. El Subgrupo Santa Bárbara está presente con sus Formaciones Mealla, Maíz Gordo y Lumbrera que representan una sucesión fluvial granodecreciente con desarrollo de paleosuelos múltiples; se reconocen mantos de crecida asociadas a planicies fangosas.The red deposits of Salta Group (Cretaceous-Paleogene which outcrops in the quebrada de Tumbaya, right margin of Quebrada de Humahuaca (province of Jujuy, they are characterized by facies that differs from the typical ones in their places of the Salta Group basin. They are proximal facies, characterized by arid and semi-arid conditions whose accumulation advanced on the N-NW side of the Salto-Jujuy high

  14. A New Thorny Lacewing (Insecta:Neuroptera:Rhachiberothidae) from the Early Cretaceous Amber of Lebanon

    Institute of Scientific and Technical Information of China (English)

    Julian F.PETRULEVI(C)IUS; Dany AZAR; André NEL

    2010-01-01

    A new genus and species of Rhachiberothidae,Raptorapax terribilissima gen.et sp.nov.from the Cretaceous amber of Lebanon is described.The new genus is assigned to the subfamily Paraberothinae.The new material confirms the great diversity of the group in the Cretaceous age and its decrease in diversity in recent times.

  15. 山东莱阳盆地早白垩世莱阳群的遗迹化石%A PRELIMINARY STUDY OF NONMARINE TRACE FOSSILS FROM THE LAIYANG GROUP (EARLY CRETACEOUS),LAIYANG BASIN, EASTERN CHINA

    Institute of Scientific and Technical Information of China (English)

    李日辉; 张光威

    2001-01-01

    山东莱阳早白垩世莱阳群自下而上分为瓦屋夼组、林寺山组、止风庄组、水南组、龙旺庄组和曲格庄组,为一套河湖相沉积,产有较丰富、分异度较高的非海相遗迹化石和兽脚类恐龙足迹化石。共鉴定出遗迹属11个,未定属1个,其中遗迹种9个,未定种2个。遗迹化石是:Cochlichnus anguines, Diplocraterion parallelum, Helminthoidichnites tenuis, Palaeophycus tubularis, Planolites montanus, Scolica sp., Scoyenia gracilis, Skolithos linearis, Taenidium cameronensis, Thalassinoides sp.;恐龙足迹化石是:Paragrallator yangi。这些化石按习性可分为4类,即:居住构造、爬行迹、觅食迹和牧食迹,其中又以前3种为主。遗迹化石在剖面上的分布不均匀,以上部的水南组、龙旺庄、曲格庄3个组最丰富。%Relatively abundant and diverse nonmarine trace fossils (including small theropod dinosaur footprints) were discovered from the Early Cretaceous Laiyang Group , Laiyang Basin, eastern China. The Laiyang Group, consisting of a sequence of fluvial-lacustrine strata with a thickness of 1,655 m, can be divided into six formations, which are, in ascending order, the Wawukuang, Linsishan, Zhifengzhuang, Shuinan, Longwanzhuang and Qugezhuang Formations.   Eleven ichnogenera, including ten invertebrate ones and a dinosaur ichnogenus, and a type of unknown arthropod crawling trace are described in the present paper. The 10 invertebrate inchnogenera are represented by Cochlichnus anguines, Diplocraterion parallelum, Helminthoidichnites tenuis, Palaeophycus tubularis, Planolites montanus, Scolica sp., Scoyenia gracilis, Skolithos linearis, Taenidium cameronensis, Thalassinoides sp.. The dinosaur track is Paragrallator yangi Li et Zhang.   Trace fossils are unevenly distributed across the section. The middle formation-the Shuinan Formation, and the upper two formations-the Longwangzhuang Formation and the Qugezhuang Formation

  16. El volcanismo del complejo Marifil en Arroyo Verde, vertiente suroriental del Macizo de Somún Cura, Chubut

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    Marcelo J Márquez

    2010-05-01

    Full Text Available Se describen en este trabajo las facies volcánicas pertenecientes al Complejo Marifil que afloran en la localidad de Arroyo Verde, vertiente suroriental del macizo de Somún Cura, provincia del Chubut. Se discriminan facies de ignimbritas riolíticas, brechas piroclásticas, domos y domos vítreos traquíticos y diques riolíticos. Las relaciones de campo indican que las ignimbritas fueron el primer evento eruptivo que se alternaron con esporádicas coladas de bloques y cenizas. Luego se produjo la intrusión de las facies dómicas y por último la de los diques riolíticos. Las facies descriptas tienen composiciones que varían entre riolitas y traquitas con altos contenidos de K, característicos de las rocas pertenecientes a este complejo. Teniendo en cuenta las características observadas se propone un mecanismo fisural de erupción en esta localidad.

  17. Palaeophytochemical Constituents of Cretaceous Ginkgo coriacea Florin Leaves

    Institute of Scientific and Technical Information of China (English)

    You-Xing Zhao; Cheng-Sen Li; Xiao-Dong Luo; Yu-Fei Wang; Jun Zhou

    2006-01-01

    Chemical investigation of the organic solvent extract of Cretaceous Ginkgo coriacea Florin leaves by liquid chromatography-mass spectroscopy (LC-MS) and gas chromatography-mass spectrometry (GC-MS), analogous to those from extant leaves of Ginkgo biloba L., led to the detection of a group of natural flavonoids and other volatiles. The similarity of the chemical constituents in these two species of Ginkgo suggest that the secondary metabolism of extant G. biloba is close to that of the Cretaceous species. The remaining natural products may be one explanation why the leaves of the Cretaceous G. coriacea have been preserved morphologically in fossilization. The detection of flavonoids suggests that the leaves of G. coriacea experienced a mild post-depositional environment during their fossilization. This appears to be the oldest occurrence of flavonoids in plant fossils.

  18. The Cretaceous System in China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper provides an outline of Cretaceous stratigraphy and paleogeography in China,which is based on rich data obtained from recent researches. Cretaceous deposits are widespread in China. Most strata are of nonmarine origin and marine sediments occur only in Tibet, western Tarim Basin of Xinjiang, Taiwan and limited localities of eastern Heilongjiang. All deposits are rich in fossils and well-constrained biostratigraphically. The stratigraphic successions of different regions are illustrated, and general stratigraphic division and correlation have been introduced. The marine deposits are described in the Tibetan Tethys, Kashi-Hotan Region of Xinjiang, eastern Heilongjiang,western Yunnan and Taiwan; the nonmarine deposits are outlined from northeast China, southeast China, southern interior China, southwest China, the Shaanxi-Gansu-Ningxia region, and northwestern China intermontane basins. The sedimentary facies and paleogeography are diversified.In Tibet the basin evolution is largely related to the subduction and collision of the Indian Plate against the Eurasian Continent, and shows a tectonic evolution in the Cretaceous. Foraminifera are a dominant biota in the Tibet Tethys. Nonmarine sediments include variegated and red beds, coal- or salt-bearing horizons, and volcanic rocks. These deposits contain diverse and abundant continental faunas and floras, as well as important coal and oil resources. The Cretaceous stratigraphy and paleogeography in China have presented a foundation for geological studies.

  19. El volcanismo del complejo Marifil en Arroyo Verde, vertiente suroriental del Macizo de Somún Cura, Chubut The volcanism of the Marifil Complex in Arroyo Verde, Southeastern slope of the Somun Cura Massif, Chubut

    Directory of Open Access Journals (Sweden)

    Marcelo J Márquez

    2010-05-01

    Full Text Available Se describen en este trabajo las facies volcánicas pertenecientes al Complejo Marifil que afloran en la localidad de Arroyo Verde, vertiente suroriental del macizo de Somún Cura, provincia del Chubut. Se discriminan facies de ignimbritas riolíticas, brechas piroclásticas, domos y domos vítreos traquíticos y diques riolíticos. Las relaciones de campo indican que las ignimbritas fueron el primer evento eruptivo que se alternaron con esporádicas coladas de bloques y cenizas. Luego se produjo la intrusión de las facies dómicas y por último la de los diques riolíticos. Las facies descriptas tienen composiciones que varían entre riolitas y traquitas con altos contenidos de K, característicos de las rocas pertenecientes a este complejo. Teniendo en cuenta las características observadas se propone un mecanismo fisural de erupción en esta localidad.Marifil Complex volcanic facies that crop out in the locality of Arroyo Verde, SE slope of Macizo de Somún Cura, are described here. Rhyolitic ignimbrite facies, pyroclastic breccias, traquitic domes and vitreous domes, and rhyolitic dikes are distinguished. Field relationships point out the ignimbrites as the first effusive event. Some sporadically block and ash flows are intercalated within the ignimbrites. These deposits were intruded by domes; the latest event is represented by the intrusion of the rhyolitic dykes. Chemical composition of these rocks varies between high K rhyolites and traquites, which correspond to typical characteristics of the Marifil Complex rocks. The observations allow proposing a fissural mechanism of eruption for these facies in this locality.

  20. Angelaíta en la paragénesis del distrito Los Manantiales, provincia del Chubut: Una nueva especie mineral Angelaite in the paragenesis of Los Manantiales district, Chubut, Argentina: a new mineral species

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    M.K. de Brodtkorb

    2004-12-01

    Full Text Available Angelaíta, Cu2AgPbBiS2 , una nueva especie mineral, fue localizada en la mina Ángela, mineralización de tipo IS del distrito Los Manantiales, Chubut, Argentina. La paragénesis incluye esfalerita, pirita, calcopirita, galena y en menor cantidad arsenopirita, betekhtinita, bornita, matildita, oro, plata, electrum, telurio, cervelleíta y hematita. La galena presenta numerosas inclusiones de angelaíta, aikinita, wittichenita y miharaíta. Esta paragénesis se presenta en vetas asociada a diferentes rocas volcánicas de la Formación Lonco Trapial de edad jurásica. La composición química de angelaíta fue obtenida con una microsonda electrónica. Se presenta en granos anhedrales de 10-100mm, es de color gris verdoso, moderadamente pleocroica y anisótropa.Angelaíte Cu2AgPbBiS2, a new mineral species, occurs in Mina Ángela, an IS type mineralization at the Los Manantiales district. The assemblage contains sphalerite, pyrite, chalcopyrite, galena with numerous inclusions of angelaíte, aikinite, miharaíte, and in smaller amounts arsenopyrite, betekhtinite, bornite, matildite, gold, silver, electrum, tellurium cervelleíte and hematite. Galena presents numerous inclusions of angelaíta, aikinita, wittichenita y miharaíta. This paragenesis occurs in veins associated with different volcanic rocks of the jurassic Lonco Trapial Formation. Angelaíte was observed as anhedral grains of 10-100mm, greenish grey in colour, moderately pleochroic and anisotropic.

  1. Los dueños del rebaño. Origen étnico y capacidad ovina en Chubut

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    Fernando Coronato

    2015-04-01

    Full Text Available Continuando la línea de investigación inaugurada por Elsa Barbería en “Los dueños de la tierra” en Santa Cruz, avanzamos sobre la distribución de las diferentes comunidades étnicas y su parte en el poblamiento patagónico a partir del análisis cartográfico diacrónico. Para el último período del proceso utilizamos la base de datos del catastro del Chubut (2006 para evaluar « la capacidad ganadera» (entendida como la acumulación de hectáreas y ovinos de cada comunidad étnica. Estas fueron asociadas a los grupos patronímicos identificados previamente, a saber: alemán, bóer, británico (inglés y escocés, español, francés, galés, italiano, mapuche, polaco, tehuelche y vasco. Las Sociedades Anónimas se consideraron como un grupo aparte. Del tratamiento estadístico de los datos se obtuvo la superficie media de las (más de 2000 propiedades, la talla media del rebaño y la cosecha de lana de cada grupo, detectándose diferencias significativas entre algunos de ellos. Las Sociedades Anónimas se despegan solitarias hacia los latifundios, mientras que en el extremo opuesto se ubican los grupos aborígenes, arrinconados en los minifundios y la subsistencia. Estos datos relativamente actuales muestran la continuidad de los procesos identificados en el análisis catastral de etapas previas del poblamiento que se remontan a más de un siglo.

  2. Caracterización geológica del skarn "El Abuelo" Alto Río Senguerr, Chubut

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    M.E. Lanfranchini

    2004-12-01

    Full Text Available El skarn "El Abuelo" está situado en el extremo sudoccidental de la Provincia del Chubut, República Argentina. Se desarrolla en un ambiente tectónico de arco magmático, en corteza continental. Está emplazado en sedimentitas silicoclásticas con intercalaciones carbonáticas y se vincula a cuerpos intrusivos riodacíticos, conjunto atribuido al Cretácico inferior. En esta manifestación se reconocieron anomalías en elementos metalíferos (Fe, Cu, Pb, Zn, Ag que le confieren interés como guía para la exploración de recursos minerales en esta región. La presente contribución tiene por finalidad tipificar al skarn a través de una caracterización geológica y mineralógica. La asociación paragenética de minerales reconocidos permitió identificar dos episodios: uno metasomático y otro hidrotermal, ambos desarrollados en las sedimentitas (exoskarn. El primero fue originado por fluidos de derivación magmática, que provocaron la formación de minerales calcosilicáticos. Posteriormente la incorporación de agua en el sistema facilitó el desarrollo de minerales hidratados, retrogradando parcialmente al skarn, proceso que fue seguido por la depositación de hematita, magnetita y sulfuros, acompañados de sílice. La asociación de minerales calcosilicáticos, junto a la variación en la composición química de piroxenos y granates y la mineralización identificada, permiten tipificar al skarn "El Abuelo" como cálcico, con hierro como metal dominante.

  3. Composición corporal de escolares pertenecientes a diferentes contextos socioeconómicos de Puerto Madryn, Chubut, Argentina

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    Dahinten, Silvia Lucrecia

    2007-01-01

    Full Text Available El desigual desarrollo del tejido muscular y de la distribución de tejido adiposo que tiene lugar durante el crecimiento humano presenta dimorfismo sexual (DS, en condiciones de vida saludables. Esta variación ha sido traducida en algoritmos utilizando la circunferencia y pliegues subcutáneos del brazo y se han elaborado ecuaciones para calcular áreas. El objetivo fue evaluar el DS observado en el crecimiento corporal de escolares de 6 a 14 años de hogares con diferente NBI -(NBI alto y (NBI bajo-. Se estudió transversalmente una muestra de 500 mujeres y 570 varones de la ciudad de Puerto Madryn, Chubut. Se relevaron: perímetro braquial y pliegues subcutáneos tricipital y subescapular y se calcularon las áreas adiposa (AAB y muscular (AMB. Se utilizaron pruebas de Wilcoxon, p= 0.05. El AAB de las mujeres fue a casi todas las edades superior a la de los varones (NBI bajo p=0.09; NBI alto p=0.02. A edades tempranas, el AMB mostró que los varones presentaron cifras similares a las mujeres. A partir de los 12 años, sin embargo, los varones comenzaron a incrementar la masa muscular. En las niñas este aumento se hizo mucho más lento (NBI alto p=0.01; NBI bajo p=0.03. La ausencia de DS en el NBI bajo, para los caracteres considerados, se relaciona con el aumento de tejido adiposo en los varones de este sector que muestra la adopción dentro de la comunidad, de dietas de alto contenido en grasas y carbohidratos acompañadas de altas tasas de obesidad.

  4. Jurassic-Cretaceous Herpetofaunas from the Jehol Associated Strata in NE China:Evolutionary and Ecological Implications

    Institute of Scientific and Technical Information of China (English)

    WANG Yuan; DONG Liping; Susan E.EVANS

    2010-01-01

    @@ Jurassic-Cretaceous herpetofaunas have recently been recovered from tuffinterbedded lacustrine strata in northeastern(NE)China.Most of them are from the Early Cretaceous Jehol Group(131-120 Ma),which has yielded a diverse and important fossil assemblage including insects,plants,fishes and tetrapods.

  5. Cretaceous stratigraphy of sierra de Beauvoir, Fuegian Andes, Argentina

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    Daniel R. Martinioni

    2013-03-01

    Full Text Available The Cretaceous stratigraphy north of Lago Fagnano, Tierra del Fuego, was poorly known until the last decade of the twentieth century. Stratigraphic, sedimentologic, and paleontological observations in sierra de Beauvoir and surroundings enabled the recognition of two main packages of dominant marine mudstone. 1 A more than 450 m thick package of slate, shale and mudstone, constituted by the revised Lower Cretaceous Beauvoir Formation. A type locality in the core of sierra de Beauvoir, with diagnostic Aptian-Albian fossils including inoceramids of the Inoceramus neocomiensis group and Aucellina sp., is proposed for this unit. 2 A more than 1,500 m thick, mudstone-dominated, but sandier upward, package consisting of at least three Upper Cretaceous units. Arroyo Castorera Formation (nom. nov. bears Turonian inoceramids of the I. hobetsensis group and I. cf. lamarcki. Río Rodríguez Formation (nom. nov. has Coniacian inoceramids, cf. Cremnoceramus sp. Policarpo Formation bears poorly preserved ammonites (Grossouvrites sp., Maorites sp., and Diplomoceras sp., together with diagnostic Maastrichtian dinocysts (Manumiella spp. complex, Operculodinium cf. azcaratei, some specimens of Fibrocysta-Exochosphaeridium complex, and Palaeocystodinium granulatum. Both packages were deposited in deep-marine environments and show, as a whole, a coarsening upward trend in the succession of Cretaceous rocks. Beauvoir Formation is part of the back-arc basin-fill of the former Rocas Verdes marginal basin. Arroyo Castorera Formation appears as a transition to the initiating Late Cretaceous Austral foreland basin evolution, clearly represented by turbiditic deposits of Río Rodríguez and Policarpo formations that were progressively accumulated in front of the rising Fuegian Andes.

  6. Evolución geomorfológica y cronología relativa de los niveles aterrazados del área adyacente a la desembocadura del río Chubut al Atlántico (Provincia del Chubut

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    Emilio F González Díaz

    2011-12-01

    Full Text Available Se describe un antiguo abanico aluvial y su posterior evolución. Las acumulaciones del antiguo abanico aluvial han sido interpretadas como la continuidad septentrional de los rodados patagónicos de la meseta Montemayor, una propuesta que es rebatida. La base metodológica del reconocimiento del antiguo abanico aluvial y su distinción genética y temporal, la constituyó el análisis geomórfico y la evaluación altimétrica. Su asignación temporal es un problema aún no resuelto. La metodología condujo a diferenciar tres sistemas geomórficos o niveles, relacionados con sucesivos episodios de agradación y erosión, los que ocupan posiciones cada vez más inferiores, coincidiendo con el complejo paleodrenaje del antiguo abanico aluvial. Sus desarrollos sucesivos son vinculados con protoríos Chubut 1, 2, 3 propuestos y el correspondiente a un paleovalle Simpson. Pese a las limitaciones apuntadas, se propone que el modelo evolutivo del antiguo abanico aluvial responde a una estructura de corte y relleno, que avalaría una composición poliformacional del antiguo abanico aluvial y además la migración progresiva del paleodrenaje hacia el sur. Un análisis geomorfológico y altimétrico diferenció un nivel superior integrado por restos de tres planicies (Pa, Pm y Pb, un nivel medio con dos terrazas (T1 y T2 y un complejo nivel inferior de cinco terrazas (T3, T4, T5 T6 y T7. Evidencias relícticas de los paleodrenajes propuestos son los paleovalles Estancia Paz y Don Morgan-Saraza del nivel superior. La edad del antiguo abanico aluvial basada en la evolución geomórfica del área de estudio, es tentativamente asignada a un incierto lapso del Pleistoceno superior entre el interglacial Sangamon y fines de la última glaciación.

  7. A Ceratopsian Dinosaur from the Lower Cretaceous of Western North America, and the Biogeography of Neoceratopsia.

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    Andrew A Farke

    Full Text Available The fossil record for neoceratopsian (horned dinosaurs in the Lower Cretaceous of North America primarily comprises isolated teeth and postcrania of limited taxonomic resolution, hampering previous efforts to reconstruct the early evolution of this group in North America. An associated cranium and lower jaw from the Cloverly Formation (?middle-late Albian, between 104 and 109 million years old of southern Montana is designated as the holotype for Aquilops americanus gen. et sp. nov. Aquilops americanus is distinguished by several autapomorphies, including a strongly hooked rostral bone with a midline boss and an elongate and sharply pointed antorbital fossa. The skull in the only known specimen is comparatively small, measuring 84 mm between the tips of the rostral and jugal. The taxon is interpreted as a basal neoceratopsian closely related to Early Cretaceous Asian taxa, such as Liaoceratops and Auroraceratops. Biogeographically, A. americanus probably originated via a dispersal from Asia into North America; the exact route of this dispersal is ambiguous, although a Beringian rather than European route seems more likely in light of the absence of ceratopsians in the Early Cretaceous of Europe. Other amniote clades show similar biogeographic patterns, supporting an intercontinental migratory event between Asia and North America during the late Early Cretaceous. The temporal and geographic distribution of Upper Cretaceous neoceratopsians (leptoceratopsids and ceratopsoids suggests at least intermittent connections between North America and Asia through the early Late Cretaceous, likely followed by an interval of isolation and finally reconnection during the latest Cretaceous.

  8. An abelisaurid from the Late Cretaceous of Egypt: implications for theropod biogeography.

    Science.gov (United States)

    Smith, Joshua B; Lamanna, Matthew C

    2006-05-01

    Recent paleogeographic scenarios postulate the isolation of continental Africa during the Late Cretaceous. The absence of abelisaurid theropods from Upper Cretaceous African strata was offered as support of hypothesized African isolation with the acknowledgement that the paucity of African abelisaurids may be mostly an issue of sampling. Here we report on a shed theropod tooth from the Upper Cretaceous (Maastrichtian, approximately 70 Ma) Duwi Formation of Egypt. The tooth was referred to the Malagasy abelisaurid "Megalosaurus" crenatissimus (=Majungasaurus crenatissimus) in 1921. A discriminant function analysis was run to test for morphological congruence between the Egyptian tooth and the dentitions of 24 theropod taxa. The analysis correctly classified 96.6% of the teeth in the sample and assigned the tooth to Majungasaurus. As current paleogeographic reconstructions posit Madagascar had attained its current position relative to Africa before the Late Cretaceous, it is unlikely that the Egyptian tooth actually pertains to Majungasaurus. Nevertheless, its classification as an abelisaurid supports its referral to the clade. This tooth thus constitutes defensible evidence of an abelisaurid from the post-Cenomanian Cretaceous of mainland Africa. Combined with recent discoveries of abelisaurids in Niger and Morocco, the result indicates that Abelisauridae was a diverse group in Africa during the Cretaceous, existing in multiple places for at least approximately 25 Ma and weakens support for hypotheses of an isolated Africa during the Late Cretaceous. PMID:16541232

  9. A new genus of alderflies (Megaloptera: Sialidae) in Upper Cretaceous Burmese amber

    OpenAIRE

    Huang, Diying; Azar, Dany; Michael S. Engel; Cai, Chenyang; Garrouste, Romain; Nel, André

    2016-01-01

    International audience A new genus and species of Mesozoic alderfly is described as Haplosialodes liui gen. et sp. nov., and from an adult male preserved in Cretaceous Burmese amber. The new genus is closely related to the genera Haplosialis Navás (Recent fauna of Madagascar), Indosialis Lestage (Recent fauna of Southeast Asia), and Eosialis Nel et al. (Eocene of France), suggesting a possible Early Cretaceous age for the clade that comprises these groups.

  10. A Tenebrionid beetle’s dataset (Coleoptera, Tenebrionidae from Peninsula Valdés (Chubut, Argentina

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    German Cheli

    2013-12-01

    Full Text Available The Natural Protected Area Peninsula Valdés, located in Northeastern Patagonia, is one of the largest conservation units of arid lands in Argentina. Although this area has been in the UNESCO World Heritage List since 1999, it has been continually exposed to sheep grazing and cattle farming for more than a century which have had a negative impact on the local environment. Our aim is to describe the first dataset of tenebrionid beetle species living in Peninsula Valdés and their relationship to sheep grazing. The dataset contains 118 records on 11 species and 198 adult individuals collected. Beetles were collected using pitfall traps in the two major environmental units of Peninsula Valdés, taking into account grazing intensities over a three year time frame from 2005–2007. The Data quality was enhanced following the best practices suggested in the literature during the digitalization and geo-referencing processes. Moreover, identification of specimens and current accurate spelling of scientific names were reviewed. Finally, post-validation processes using DarwinTest software were applied. Specimens have been deposited at Entomological Collection of the Centro Nacional Patagónico (CENPAT-CONICET. The dataset is part of the database of this collection and has been published on the internet through GBIF Integrated Publishing Toolkit (IPT (http://data.gbif.org/datasets/resource/14669/. Furthermore, it is the first dataset for tenebrionid beetles of arid Patagonia available in GBIF database, and it is the first one based on a previously designed and standardized sampling to assess the interaction between these beetles and grazing in the area. The main purposes of this dataset are to ensure accessibility to data associated with Tenebrionidae specimens from Peninsula Valdés (Chubut, Argentina, also to contribute to GBIF with primary data about Patagonian tenebrionids and finally, to promote the Entomological Collection of Centro Nacional Patag

  11. Estratigrafía y petrología del sector noreste de sierra de Apas. Provincia del Chubut

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    M. Remesal

    2004-12-01

    Full Text Available La sierra de Apas, ubicada entre las provincias de Rio Negro y Chubut, forma parte del magmatismo de intraplaca emplazado durante el Paleogeno-Neógeno en el norte de la Patagonia extrandina. En el sector noreste se ha definido una estratigrafía integrada por: traquitas oscuras, flujos piroclásticos, traquitas claras, domos riolíticos y basaltos porfíricos y afíricos. Las traquitas oscuras, son relativamente más antiguas, tienen bajo porcentaje de fenocristales, y clasifican como traquitas- benmoreítas. Las traquitas claras son porfíricas, y clasifican como comenditas. Su ubicación estratigráfica es confirmada por una edad K/Ar de 19 ± 2 Ma. Los flujos piroclásticos son predominantemente vítreos, cubren a las traquitas oscuras y tienen composiciones traquiandesíticas. La petrografía y geoquímica establecen una estrecha relación con las traquitas claras. El único cuerpo dómico en el área es el cerro Colorado, cuya composición corresponde a una riolita peralcalina ó comendita; una edad K/Ar de 24 ± 1 Ma establece por primera vez su relación temporal. La unidad efusiva más joven corresponde a lavas basálticas, agrupadas en afíricas y porfíricas. Se propone designar a las primeras como basaltos olivínicos transicionales en tanto que los basaltos porfíricos se subdividen en basaltos olivínicos alcalinos y hawaiitas. Los datos estratigráficos y geoquímicos sugieren que la asociación volcánica estudiada es el resultado de al menos dos etapas evolutivas. Una de ellas incluye los basaltos, traquitas claras, flujos claros y comenditas que muestran un patrón de cristalización fraccionada. Las traquitas oscuras, más viejas, corresponderían a otro estadio evolutivo.

  12. Paleosuelos en Cordones litorales de la formación Caleta Valdés, pleistoceno superior, noreste de Chubut

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    Pablo J Bouza

    2014-03-01

    Full Text Available El objetivo de este trabajo es evaluar los cambios climáticos y ecológicos registrados en los paleosuelos de la Formación Caleta Valdés (Pleistoceno superior y determinar las propiedades pedogenéticas que pueden ser utilizadas como indicadores paleopedológicos. El área de estudio se encuentra en el NE de la provincia del Chubut, en el ámbito de la Península Valdés. La estratigrafía superficial presenta tres unidades de sedimentación que fueron alternativamente edafizadas. El paleosuelo más antiguo (3Btkb-3Bkmb, formado en los depósitos gravosos de los cordones pleistocenos, presenta un mayor contenido de Fe pedogenético -presumiblemente hematita - un predominio de esmectitas y menores contenidos de δ13C y de δ18O, lo que indica una mayor proporción de plantas C3 y un clima estacionalmente contrastante de tipo mediterráneo (régimen xérico. Considerando que los cordones se habrían depositado en el MIS 5e, la formación del paleosuelo habría ocurrido durante el final de ese piso isotópico interglacial. Este paleosuelo habría sido erosionado y sepultado por episodios sedimentológicos, posiblemente asociados a los procesos periglaciares de los pisos isotópicos 4-2. Estos depósitos constituyeron -conjuntamente con adiciones eólicas- los materiales parentales de un nuevo suelo que evolucionó a la secuencia de horizontes 2Btb-2Btkb-2Bkb-2Ck durante un lapso de estabilidad ambiental. Este evento pedogenético probablemente esté asociado al lapso más húmedo y con marcada estacionalidad de las precipitaciones, ocurrido durante el Tardiglacial - Holoceno temprano, que fue seguido de un período de mayor sequía y aumento de temperaturas durante el Holoceno medio registrado en la región. El tercer evento pedogenético está representado por las secuencias de horizontes A-C.

  13. Efectos de la instalación de un gasoducto sobre algunas propiedades del suelo superficial y la cobertura vegetal en el NE de Chubut Gas-pipeline installation effects on superficial soil properties and vegetation cover in Northeastern Chubut

    Directory of Open Access Journals (Sweden)

    Esteban Kowaljow

    2008-07-01

    Full Text Available En este trabajo describimos el impacto del tendido de un gasoducto y de la reposición parcial del material removido, sobre algunas propiedades físicas y químicas del suelo y sobre la cobertura vegetal en tres sitios ecológicos del nordeste de Chubut. En cada sitio se identificaron 4 zonas diferentes: zona 1, faja desmontada y compactada por el tránsito de maquinaria pesada; zona 2, faja desmontada, con posterior reposición del suelo y la vegetación removidos; y otras dos zonas correspondientes a la estepa adyacente no disturbada: montículos asociados a arbustos y espacios entre montículos. Los mayores valores de densidad aparente se encontraron en los suelos de la zona 1 y en los del entremontículo (1,43 Mg m-3. La resistencia a la penetración fue significativamente mayor en las zonas 1 y 2, ambas zonas presentaron valores de resistencia a la penetración superiores a 1 MPa. La tasa de infiltración fue mucho mayor en el montículo (261 mm h-1 que en el resto de las zonas. La velocidad de infiltración de la zona 2 (85 mm h-1 fue mayor a la de la zona 1 (35 mm h-1 y el entremontículo (50 mm h-1. Los contenidos de carbono orgánico y nitrógeno de los suelos de las zonas 1 y 2 fueron similares a los del entremontículo y significativamente inferiores a los del montículo, excepto en la zona 2 de uno de los sitios ecológicos. La remoción de la vegetación y el suelo superficial, y el posterior tránsito de maquinaria pesada durante la instalación del gasoducto produjeron un fuerte impacto sobre las propiedades físicas del suelo. La mayor limitación de los suelos disturbados fue su baja capacidad para incorporar agua, derivada principalmente de su elevada compactación y baja porosidad, lo que explicaría en parte la lenta recuperación de la cobertura vegetal en la zona 1. En ninguno de los tres sitios estudiados, la reposición del material removido por la actividad del desmonte significó una medida de recuperación eficaz

  14. An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures.

    Science.gov (United States)

    Zheng, Xiao-Ting; You, Hai-Lu; Xu, Xing; Dong, Zhi-Ming

    2009-03-19

    Ornithischia is one of the two major groups of dinosaurs, with heterodontosauridae as one of its major clades. Heterodontosauridae is characterized by small, gracile bodies and a problematic phylogenetic position. Recent phylogenetic work indicates that it represents the most basal group of all well-known ornithischians. Previous heterodontosaurid records are mainly from the Early Jurassic period (205-190 million years ago) of Africa. Here we report a new heterodontosaurid, Tianyulong confuciusi gen. et sp. nov., from the Early Cretaceous period (144-99 million years ago) of western Liaoning Province, China. Tianyulong extends the geographical distribution of heterodontosaurids to Asia and confirms the clade's previously questionable temporal range extension into the Early Cretaceous period. More surprisingly, Tianyulong bears long, singular and unbranched filamentous integumentary (outer skin) structures. This represents the first confirmed report, to our knowledge, of filamentous integumentary structures in an ornithischian dinosaur.

  15. La depresión del "bajo" del diablo" (NE del Chubut: Una propuesta geomórfica acerca de su origen y su evolución

    Directory of Open Access Journals (Sweden)

    Emilio F González Díaz

    2013-06-01

    Full Text Available El Bajo del Diablo está situado en el NE de Chubut. Se analizan sus geoformas internas y marginales, proponiéndose su génesis por deflación y se presenta un esquema de su evolución, que está íntimamente influenciada por los cambios climáticos cuaternarios. Se carece de datos para establecer con precisión la temporalidad de los hechos. Un protorío Chubut generó un abanico aluvial local ó nivel superior durante el Interglacial Sangamon (± 120.000 años. Su degradación y el desarrollo del nivel medio (T1 y T2 por un prerío Chubut, causó la exposición de un sector del débil sustrato terciario, un núcleo marginado por las resistentes psefitas de los niveles. El establecimiento local de las frías, secas y ventosas condiciones de la Última Glaciación, condujo a una progresiva exhondación por deflación (asociada a meteorización del núcleo, proceso que culminó en una depresión poco profunda y de pendientes suaves (Pfannen. Un húmedo intervalo pluvial, facilitó la formación de un efímero lago en ella. Su progresiva reducción -expresada por cordones litorales en posiciones cada vez más bajas- estuvo motivada por un retorno a las frías y secas condiciones previas. La coetánea reactivación de la deflación, llevó a la consiguiente mayor profundización de la depresión. Durante este proceso, se produjo la exhumación del paleorelieve del basamento regional, compuesto por las volcanitas jurásicas de la Formación Marifil. Finalizado el período glaciario, el proceso fluvial y el de remoción en masa ampliaron más aun la depresión, que hoy aparece caracterizada por abruptas pendientes y mayor profundidad (Wannen. Dos perfiles expresan la relaciones entre las distintas geoformas reconocidas.

  16. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds

    OpenAIRE

    Zhang, Fucheng; Kearns, Stuart L.; Patrick J Orr; Benton, Michael J.; Zhou, Zhonghe; Johnson, Diane; Xu, Xing; Wang, Xiaolin

    2010-01-01

    Spectacular fossil remains from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of early birds and dinosaurs, and contributed to understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are ...

  17. Geography of end-Cretaceous marine bivalve extinctions

    Science.gov (United States)

    Raup, David M.; Jablonski, David

    1993-01-01

    Analysis of the end-Cretaceous mass extinction, based on 3514 occurrences of 340 genera of marine bivalves (Mollusca), suggests that extinction intensities were uniformly global; no latitudinal gradients or other geographic patterns are detected. Elevated extinction intensities in some tropical areas are entirely a result of the distribution of one extinct group of highly specialized bivalves, the rudists. When rudists are omitted, intensities at those localities are statistically indistinguishable from those of both the rudist-free tropics and extratropical localities.

  18. Geography of cretaceous extinctions: Data base development

    Science.gov (United States)

    Raup, D. M.

    1991-01-01

    Data bases built from the source literature are plagued by problems of data quality. Unless the data acquisition is done by experts, working slowly, the data base may contain so much garbage that true signals and patterns cannot be detected. On the other hand, high quality data bases develop so slowly that satisfactory statistical analysis may never be possible due to the small sample sizes. Results of a test are presented of the opposite strategy: rapid data acquisition by non-experts with minimal control on data quality. A published list of 186 species and genera of fossil invertibrates of the latest Cretaceous Age (Maestrichtian) were located through a random search of the paleobiological and geological literature. The geographic location for each faunal list was then transformed electronically to Maestrichtian latitude and longitude and the lists were further digested to identify the genera occurring in each ten-degree, latitude-longitude block. The geographical lists were clustered using the Otsuka similarity coefficient and a standard unweight-pair-group method. The resulting clusters are remarkably consistent geographically, indicating that a strong biogeographic signal is visible despite low-quality data. A further test evaluated the geographic pattern of end-Cretaceaous extinctions. All genera in the data base were compared with Sepkoski's compendium of time ranges of genera to determine which of the reported genera survived the Cretaceous mass extinction. In turn, extinction rates for the ten-degree, latitude-longitude blocks were mapped. The resulting distribution is readily interpretable as a robust pattern of the geography of the mass extinction. The study demonstrates that a low-quality data base, built rapidly, can provide a basis for meaningful analysis of past biotic events.

  19. Tyrant dinosaur evolution tracks the rise and fall of Late Cretaceous oceans.

    Directory of Open Access Journals (Sweden)

    Mark A Loewen

    Full Text Available The Late Cretaceous (∼95-66 million years ago western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah--including a new taxon which represents the geologically oldest member of the clade--to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.

  20. Patrimonio arqueológico, memoria y territorio. Procesos de autoctonización entre los mapuches de Lago Puelo, Chubut (Patagonia, Argentina

    Directory of Open Access Journals (Sweden)

    Carolina Crespo

    2011-01-01

    Full Text Available Este artículo analiza las disputas de sentido que se configuran en torno de la categoría de "autoctonía" en la localidad de Lago Puelo -Comarca Andina del Paralelo 42º, noroeste de Chubut, Patagonia, Argentina-, su articulación con determinados derechos y demandas de la población mapuche y el lugar que ocupa el patrimonio arqueológico en el proceso de autoctonización de esta población dentro de procesos hegemónicos cambiantes. Tal forma de categorización resulta central en las modalidades de construcción de identidades políticas de los pueblos indígenas, de configuración de sus demandas y de las políticas estatales de reconocimiento de derechos hacia estos pueblos.

  1. Angelaíta en la paragénesis del distrito Los Manantiales, provincia del Chubut: Una nueva especie mineral

    Directory of Open Access Journals (Sweden)

    M.K. de Brodtkorb

    2004-12-01

    Full Text Available Angelaíta, Cu2AgPbBiS2 , una nueva especie mineral, fue localizada en la mina Ángela, mineralización de tipo IS del distrito Los Manantiales, Chubut, Argentina. La paragénesis incluye esfalerita, pirita, calcopirita, galena y en menor cantidad arsenopirita, betekhtinita, bornita, matildita, oro, plata, electrum, telurio, cervelleíta y hematita. La galena presenta numerosas inclusiones de angelaíta, aikinita, wittichenita y miharaíta. Esta paragénesis se presenta en vetas asociada a diferentes rocas volcánicas de la Formación Lonco Trapial de edad jurásica. La composición química de angelaíta fue obtenida con una microsonda electrónica. Se presenta en granos anhedrales de 10-100mm, es de color gris verdoso, moderadamente pleocroica y anisótropa.

  2. Evaluation of the Cerro Solo nuclear ore, province of Chubut. Geological characteristics of the deposit and of the basin. Pt. 2

    International Nuclear Information System (INIS)

    The Cerro Solo uranium ore deposit, is located 420 km west from Trelew city, Chubut province, in the extra-andean. The geologic environment belongs to the northwest edge portion of the intracratonic San Jorge Gulf Basin. The uraniferous district is named Pichinanes Ridge district. The mineralization lies 25 to 130 m depth, and is hosted by Los Adobes formation aged Aptian-Albian, made up by conglomerates, sandstones, coarse-sandstones and less abundant siltstones and claystones. The Cerro Solo ore deposit that belongs to the sandstone type-uranium occurrences are lenticular or tabular shaped, associated with organic material and pyrite, generally roughly parallel to the bedding (Trend-Type). The uranium minerals are uraninite and coffinite associated with organic material and pyrite, and frequently hematite, goethite, calcite, siderite and barite are observed. (Author)

  3. Procedencia de areniscas del Grupo Chubut en el área central de la Sierra de San Bernardo. Análisis preliminar

    Directory of Open Access Journals (Sweden)

    M.A. Tunik

    2004-12-01

    Full Text Available Se llevaron a cabo análisis petrográficos de detalle que permitieron determinar las modas detríticas en areniscas del Grupo Chubut con el fin de inferir el marco tectónico del área de aporte de las mismas. Sobre la base de las muestras estudiadas, se observan características petrográficas distintivas entre areniscas de las Formaciones Matasiete, Castillo y Bajo Barreal. La presencia de trizas dentro de las areniscas de las Formaciones Castillo y Bajo Barreal sugeriría una depositación concomitante con volcanismo de arco activo. El ploteo de las modas detríticas en diagramas de discriminación de ambiente de procedencia mostró una diferenciación entre las unidades del Grupo Chubut. La Formación Matasiete presenta una procedencia de arco magmático no disectado, mientras que las muestras correspondientes a las Formaciones Castillo y Bajo Barreal sugieren una procedencia de arco magmático transicional o disectado. Esto último sumado a la presencia de trizas de caída directa podría explicarse por la migración del arco volcánico hacia el oeste y a la exposición de las raíces del arco volcánico del Cretácico inferior por deformación en la faja plegada concomitante con un volcanismo activo ubicado hacia el oeste de la zona de estudio.

  4. Monitoreo ambiental de aguas superficiales y subterráneas, consideración de áreas sensibles, distrito uranífero Pichiñán Este, departamento Paso de Indios, provincia del Chubut

    Directory of Open Access Journals (Sweden)

    Humberto O Nievas

    2013-09-01

    Full Text Available En el ámbito de los estudios ambientales los sitios de localización de pobladores son considerados como áreas sensibles frente a una posible explotación del recurso uranífero. Se analiza la hidroquímica de los alrededores del distrito uranífero Pichiñán Este, sector central de la provincia del Chubut, por medio de un monitoreo que, desde el 2007, se realiza aplicando la metodología de muestreo de la comunidad europea. Se caracteriza la calidad del agua considerando elementos mayoritarios, minoritarios y trazas, estableciendo de esta manera sus potenciales usos. Estos resultados son informados a los pobladores y a la autoridad de control ambiental de la provincia del Chubut. Aunque, en general, la calidad del agua en cada punto de muestreo se mantiene relativamente constante, se observan variaciones naturales en los contenidos químicos.

  5. Live birth in Cretaceous marine lizards (mosasauroids).

    Science.gov (United States)

    Caldwell, M W; Lee, M S

    2001-12-01

    Although live-bearing (viviparity) has evolved around 100 times within reptiles, evidence of it is almost never preserved in the fossil record. Here, we report viviparity in mosasauroids, a group of Cretaceous marine lizards. This is the only known fossil record of live-bearing in squamates (lizards and snakes), and might represent the oldest occurrence of the trait in this diverse group; it is also the only known fossil record of viviparity in reptiles other than ichthyosaurs. An exceptionally preserved gravid female of the aigialosaur Carsosaurus (a primitive mosasauroid) contains at least four advanced embryos distributed along the posterior two-thirds of the long trunk region (dorsal vertebrae 9-21). Their orientation suggests that they were born tail-first (the nostrils emerging last) to reduce the possibility of drowning, an adaptation shared with other highly aquatic amniotes such as cetaceans, sirenians and ichthyosaurs; the orientation of the embryos also suggests that they were not gut contents because swallowed prey are usually consumed head-first. One embryo is located within the pelvis, raising the possibility that the adult died during parturition. Viviparity in early medium-sized amphibious aigialosaurs may have freed them from the need to return to land to deposit eggs, and permitted the subsequent evolution of gigantic totally marine mosasaurs. PMID:11747556

  6. Cretaceous Onlap, Gulf of Mexico Basin [cretonlapg

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The maximum extent of Cretaceous onlap is generalized from Plate 3, Structure at the base and subcrop below Mesozoic marine section, Gulf of Mexico Basin (compiled...

  7. Review of the Upper Jurassic-Lower Cretaceous stratigraphy in Western Cameros basin, Northern Spain

    DEFF Research Database (Denmark)

    Vidal, Maria del Pilar Clemente

    2010-01-01

    The Upper Jurassic-Lower Cretaceous stratigraphy of the Cameros basin has been reviewed. In Western Cameros the stratigraphic sections are condensed but they have a parallel development with the basin depocentre and the same groups have been identified. The Tera Group consists of two formations: ...

  8. Middle Cretaceous dinosaur assemblages from northern Brazil and northern Africa and their implications for northern Gondwanan composition

    Science.gov (United States)

    Candeiro, Carlos Roberto A.

    2015-08-01

    Dinosaurs are one of the most dominant groups in Cretaceous reptilian faunas. A summary of their record in northern Brazil and northern Africa during the middle of the Cretaceous Period (Aptian-Cenomanian) is presented here. Dinosaurs are represented by 32 species (three ornithischians, six sauropods and 23 theropods) from Brazil, Egypt, Lybia, Morocco, Niger, Sudan and Tunisia. These dinosaur assemblages provide fundamental data about distribution and composition of sauropods and theropods in northern Gondwana during the middle of the Cretaceous Period and confirm these assemblages to be among the most important dinosaur faunas in the north Gondwana areas.

  9. SHRIMP U-Pb dating and geochemistry of the Cretaceous plutonic rocks in the Korean Peninsula: A new tectonic model of the Cretaceous Korean Peninsula

    Science.gov (United States)

    Kim, Sung Won; Kwon, Sanghoon; Park, Seung-Ik; Lee, Changyeol; Cho, Deung-Lyong; Lee, Hong-Jin; Ko, Kyoungtae; Kim, Sook Ju

    2016-10-01

    The Cretaceous tectonomagmatism of the Korean Peninsula was examined based on geochemical and geochronological data of the Cretaceous plutonic rocks, along with distribution of volcano-sedimentary nonmarine N- to NE-trending fault bounded sedimentary basins. We conducted sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb ages and whole-rock geochemical compositions of 21 Cretaceous plutonic rocks, together with previously published data, from the central to southern Korean Peninsula. Four age groups of plutonic rocks were identified: Group I (ca. 119-106 Ma) in the northern to central area, Group II (ca. 99-87 Ma) in the central southern area, Group III (ca. 85-82 Ma) in the central to southern area, and Group IV (ca. 76-67 Ma) in the southernmost area. These results indicate a sporadic trenchward-younging trend of the Cretaceous magmatism in the Korean Peninsula. The Group I, II, and III rocks are dominated by high-K calc-alkaline I-type rocks with rift-related A-type granitoids. In contrast, the Group IV rocks are high-K calc-alkaline I-type plutonic rocks with no A-type rocks. The geochemical signatures of the entire groups indicated LREEs (light rare earth elements) enrichments and negative Nb, Ta, and Ti anomalies, indicating normal arc magmatism. A new tectonic model of the Cretaceous Korean Peninsula was proposed based on temporal and spatial distribution of the Cretaceous plutons represented by four age groups; 1) magmatic quiescence throughout the Korean Peninsula from ca. 160 to 120 Ma, 2) intrusions of the I- and A-type granitoids in the northern and central Korean Peninsula (Group I plutonic rocks from ca. 120 to 100 Ma) resulted from the partial melting of the lower continental crust due to the rollback of the Izanagi plate expressed as the conversion from flat-lying subduction to normal subduction. The Gyeongsang nonmarine sedimentary rift basin in the Korean Peninsula and adakite magmatism preserved in the present-day Japanese Islands

  10. Late Cretaceous- Cenozoic history of deciduousness and the terminal Cretaceous event.

    Science.gov (United States)

    Wolfe, J.A.

    1987-01-01

    Deciduousness in mesic, broad-leaved plants occurred in disturbed, middle-latitude environments during the Late Cretaceous. Only in polar environments in the Late Cretaceous was the deciduous element dominant, although of low diversity. The terminal Cretaceous event resulted in wide-spread selection for plants of deciduous habit and diversification of deciduous taxa, thus leaving a lasting imprint on Northern Hemisphere vegetation. Various environmental factors have played important roles in subsequent diversification of mesic, broad-leaved deciduous taxa and in origination and decline of broad-leaved deciduous forests. Low diversity and rarity of mesic deciduous plants in the post-Cretaceous of the Southern Hemisphere indicate that the inferred 'impact winter' of the terminal Cretaceous event had little effect on Southern Hemisphere vegetation and climate. -Author

  11. Influencia de Especies Arbóreas Implantadas sobre Parámetros Biológicos y Bioquímicos en un Suelo Forestal de Chubut, Argentina Influence of Implanted tree Species on Biological and Biochemical Parameters in a Forest soil of Chubut, Argentina

    Directory of Open Access Journals (Sweden)

    Diana N Effron

    2012-01-01

    Full Text Available Se estudió la influencia de algunas especies forestales sobre propiedades biológicas y bioquímicas de un suelo, con el propósito de contribuir a establecer criterios que logren un desarrollo sustentable para un sistema forestal. El sitio de estudio es un suelo forestal de Chubut, en la Patagonia Argentina. Se tomaron muestras superficiales de suelo de tres parcelas con una especie dominante cada una: Roble (Quercus robur, Fresno (Fraxinus excelsior L. y Pino radiata (Pinus radiata D. Don.. En ellas se determinaron carbono de respiración, actividad deshidrogenasa, actividad fosfatasa ácida, número de bacterias totales y amilolíticas, actinomicetes y hongos totales, mientras que en las hojas se determinó fósforo. Los resultados mostraron diferencias importantes de estos parámetros para las diferentes especies estudiadas, diferencias que son explicadas por la composición química de las diferentes especies vegetales.The influence of some tree species on biological and biochemical properties of a forest soil was studied with the purpose of establishing criteria to achieve a sustainable development of a forest system. The study site is a forest soil of Chubut, in the Argentinean Patagonia. Surface soil samples were taken of three plots with a dominant species each one: Oak (Quercus robur, Ash (Fraxinus excelsior L. and Radiata Pine (Pinus radiata D. Don.. Microbial respiration, dehydrogenase and acid phosphatase activities, counts of aerobic and amylolytic bacteria, actinomyces and fungi were determined in soil samples, while phosphorous was determines in leaves. The results showed important differences of these parameters for the different species considered in the study, differences that are explained by the different chemical composition of the vegetal species.

  12. Dawsonite and other carbonate veins in the Cretaceous Izumi Group, SW Japan: a natural support for fracture self-sealing in mud-stone cap-rock in CGS?

    Energy Technology Data Exchange (ETDEWEB)

    Okuyama, Yasuko; Funatsu, Takahiro; Fujii, Takashi [Institute for Geo-Resources and environment, GSJ, AISI, 1-1-1 Higashi, Central 7, Tsukuba, ibaraki 305-8567 (Japan); Take, Shuji [Kishiwada Nature Club, c/o Kishiwada City Natural History Museum, Sakai-Machi 5-6, Kishiwada, Osaka 596-0072 (Japan)

    2013-07-01

    Dawsonite-bearing carbonate veins are abundant in a compact mud-stone layer of the lower part of the Izumi Group, SW Japan. The mode of occurrence of the veins probably indicates fracturing and mineral sealing associated with upwelling of CO{sub 2}-rich fluid evolved in the reservoir beneath. The carbonate veins studied here can be a natural support to fracturing and healing of mud-stone cap-rock in the CO{sub 2} geological storage. (authors)

  13. Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary.

    Science.gov (United States)

    Longrich, Nicholas R; Tokaryk, Tim; Field, Daniel J

    2011-09-13

    The effect of the Cretaceous-Paleogene (K-Pg) (formerly Cretaceous-Tertiary, K-T) mass extinction on avian evolution is debated, primarily because of the poor fossil record of Late Cretaceous birds. In particular, it remains unclear whether archaic birds became extinct gradually over the course of the Cretaceous or whether they remained diverse up to the end of the Cretaceous and perished in the K-Pg mass extinction. Here, we describe a diverse avifauna from the latest Maastrichtian of western North America, which provides definitive evidence for the persistence of a range of archaic birds to within 300,000 y of the K-Pg boundary. A total of 17 species are identified, including 7 species of archaic bird, representing Enantiornithes, Ichthyornithes, Hesperornithes, and an Apsaravis-like bird. None of these groups are known to survive into the Paleogene, and their persistence into the latest Maastrichtian therefore provides strong evidence for a mass extinction of archaic birds coinciding with the Chicxulub asteroid impact. Most of the birds described here represent advanced ornithurines, showing that a major radiation of Ornithurae preceded the end of the Cretaceous, but none can be definitively referred to the Neornithes. This avifauna is the most diverse known from the Late Cretaceous, and although size disparity is lower than in modern birds, the assemblage includes both smaller forms and some of the largest volant birds known from the Mesozoic, emphasizing the degree to which avian diversification had proceeded by the end of the age of dinosaurs. PMID:21914849

  14. Circulación, intercambio y uso de obsidianas en la costa de la provincia del Chubut (Patagonia argentina, durante el Holoceno tardío

    Directory of Open Access Journals (Sweden)

    Julieta Gómez Otero

    2005-12-01

    Full Text Available Se presentan los resultados de un nuevo análisis de elementos traza en 26 artefactos de 19 sitios arqueológicos de la costa de la provincia del Chubut. Dieciocho sitios son del sector norte, entre las desembocaduras del Arroyo Verde y del río Chubut y el último está situado al sur, en Cabo Dos Bahías. Seis diferentes tipos de obsidiana fueron identificados; tres de ellos de fuentes conocidas: los tipos T/SCI de la fuente de Telsen y SI de la fuente Sacanana, ambas del centro-norte de la provincia del Chubut y el tipo PDAI de la fuente de Pampa del Asador, en la provincia de Santa Cruz. Los tipos de fuente desconocida son: CC? anteriormente determinado en un sitio arqueológico de Cerro Castillo, margen suroeste de la Meseta de Somuncurá; el tipo T/SCII, en principio considerado como subtipo de la fuente de Telsen, pero según estos nuevos análisis pertenece a una fuente distinta; y un tipo nuevo, MSI, cuya fuente estaría en la Meseta de Somuncurá. La información aquí presentada indica que los seis diferentes tipos de obsidiana llegaron a la costa central de Patagonia desde centros de aprovisionamiento independientes y desde distancias variables entre 100 km y 800 km.The results of analyses of trace-elements in twenty-six samples of obsidian from 19 archaeological sites along the Atlantic coast, between Golfo San Matías Oeste (41°55´58.8´´S and Cabo Dos Bahías (44°54´77.9´´S are presented as a contribution to studies of sources and distribution of obsidian in archaeological sites in central Patagonia, specifically the province of Chubut, Argentina. Six different types of obsidian occur in this collection, three of which come from known obsidian sources. Four of the samples are chemically similar to obsidian type T/SCI, which is derived from near Sierra Negra (42°21'S - 66°36´W, northeast of the town of Telsen, and is located between 100 and 235 km linear distance west of the sites along the coast in which this obsidian

  15. Lower Cretaceous Dinosaur Tracks from Puebla, Mexico

    Directory of Open Access Journals (Sweden)

    Rubén A. Rodríguez-de la Rosa

    2012-01-01

    Full Text Available Dinosaur tracks have been identified near San Martín Atexcal, southern Puebla, Mexico, within the sedimentary sequence of the San Juan Raya Formation of Lower Cretaceous (Albian age. The tracksite, located in the bed of the Magdalena River, reveals six different ichnofossiliferous levels identified within a 9 m thick sedimentary sequence. The inferred environment is that of a tidal (marginal marine mudflat (Level I. Level I preserves three theropods trackways (?Allosauroidea, additionally, isolated tracks belonging to iguanodontids (Ornithopoda. Level II preserves faint iguanodontid tracks. Levels III to V preserve sauropod tracks. Younger level VI preserves, although morphologically different, a track belonging to Ornithopoda. The dinosaur tracks from San Martín Atexcal support the existence of continental facies within the San Juan Raya Formation; they represent the second record of dinosaur tracks from the Lower Cretaceous of Mexico and are part of an important but little documented record of Lower Cretaceous dinosaurs in Mexico.

  16. Stratigraphic correlation of the Late Cretaceous Simsima Formation United Arab Emirates and Akveren Formation, northwest Turkey

    Science.gov (United States)

    Abdelghany, O.; Abu Saima, M.; Ramazanoglu, S.; Arman, H.

    2015-11-01

    Latest Cretaceous (Campanian-Maastrichtian) microfossils are used to correlate the carbonate rocks of the Simsima Formation in the northeastern part of the Arabian Peninsula (Northern Oman Mountains, United Arab Emirates and Oman) with the Akveren Formation in Kandira (northwest Turkey, near Black Sea region). Both formations have characteristically rich planktonic foraminiferal and calcareous nannofossil faunal assemblages that permit the recognition of the Globotruncanella havanensis Zone and Quadrum sissinghii Zone CC22. The palaeontological data is used to build an appropriate palaeoenvironmental model for the latest Cretaceous Aruma Group in the Oman Mountains foreland basin. The study reveals that the Late Cretaceous formations of UAE and Turkey can be divided into an open marine carbonate shelf facies (planktonic foraminifera/calcareous nannofossil biomicrite) and a shallow-marine carbonate facies (rudistids, coralline algal foraminiferal biomicrite).

  17. Lower Cretaceous Xigaze ophiolites formed in the Gangdese forearc : Evidence from paleomagnetism, sediment provenance, and stratigraphy

    NARCIS (Netherlands)

    Huang, Wentao; van Hinsbergen, Douwe J J; Maffione, Marco; Orme, Devon A.; Dupont-Nivet, Guillaume; Guilmette, Carl; Ding, Lin; Guo, Zhaojie; Kapp, Paul

    2015-01-01

    The India-Asia suture zone of southern Tibet exposes Lower Cretaceous Xigaze ophiolites and radiolarian cherts, and time-equivalent Asian-derived clastic forearc sedimentary rocks (Xigaze Group). These ophiolites have been interpreted to have formed in the forearc of the north-dipping subduction zon

  18. Cretaceous metamorphism, magmatism and shearing in the Waipuna Valley, directly south of the Reefton Goldfield

    International Nuclear Information System (INIS)

    Rocks in the Waipuna Valley in Westland show that the area immediately south of the Reefton Goldfield has been dramatically affected by Cretaceous tectonism. The main lithology in the Waipuna Valley is metasedimentary Greenland Group that is here subdivided into four types (I, II, III and IV). Type I contains abundant detrital grains with a weak Palaeozoic greenschist facies overprint and is compositionally indistinguishable from unmineralised Greenland Group within the goldfield. Type II contains detrital grains, but also a weak amphibolite facies foliation or, where proximal to granitoid intrusions, a hornfelsic texture. Type III contains no detrital components and records polyphase recrystallisation. U-Th-Pb monazite dating indicates that metamorphism in the Type III rocks occurred, at least in part, at 108.1 ± 1.2 Ma. Type IV Greenland Group has partially melted. Zircon from granitoids intruding Greenland Group in the Waipuna Valley indicate Cretaceous (c. 111 Ma) emplacement. Greenland Group Types III and IV, and the granitic plutons, have been variably sheared with quartz textures indicating progressive cooling during deformation. A mylonite zone occurs just above outcrop of the Type IV rocks. Field and age relationships are interpreted to show that the Waipuna Valley exposes portions of an upper plate and lower plate to a Cretaceous ductile shear zone that is here named the Waipuna Shear Zone. The overall structure is similar to the nearby Cretaceous extensional Paparoa Metamorphic Core Complex. The Reefton Goldfield lies in the upper plate to the Waipuna Shear Zone, not far above the mylonite zone. Cretaceous metamorphism and shearing of Greenland Group could have aided formation and then transport of gold-bearing fluids into structurally higher rocks. (author).

  19. Late cretaceous aquatic plant world in Patagonia, Argentina.

    Directory of Open Access Journals (Sweden)

    N Rubén Cúneo

    Full Text Available In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla and a monocot (Araceae. Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae. Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form and the eudicot angiosperm Nelumbo (Nelumbonaceae are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae, ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America.

  20. Late cretaceous aquatic plant world in Patagonia, Argentina.

    Science.gov (United States)

    Cúneo, N Rubén; Gandolfo, María A; Zamaloa, María C; Hermsen, Elizabeth

    2014-01-01

    In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla) and a monocot (Araceae). Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae). Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form) and the eudicot angiosperm Nelumbo (Nelumbonaceae) are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae), ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America. PMID:25148081

  1. Analysis of admixture and genetic structure of two Native American groups of Southern Argentinean Patagonia.

    Science.gov (United States)

    Sala, Andrea; Corach, Daniel

    2014-03-01

    Argentinean Patagonia is inhabited by people that live principally in urban areas and by small isolated groups of individuals that belong to indigenous aboriginal groups; this territory exhibits the lowest population density of the country. Mapuche and Tehuelche (Mapudungun linguistic branch), are the only extant Native American groups that inhabit the Argentinean Patagonian provinces of Río Negro and Chubut. Fifteen autosomal STRs, 17 Y-STRs, mtDNA full length control region sequence and two sets of Y and mtDNA-coding region SNPs were analyzed in a set of 434 unrelated individuals. The sample set included two aboriginal groups, a group of individuals whose family name included Native American linguistic root and urban samples from Chubut, Río Negro and Buenos Aires provinces of Argentina. Specific Y Amerindian haplogroup Q1 was found in 87.5% in Mapuche and 58.82% in Tehuelche, while the Amerindian mtDNA haplogroups were present in all the aboriginal sample contributors investigated. Admixture analysis performed by means of autosomal and Y-STRs showed the highest degree of admixture in individuals carrying Mapuche surnames, followed by urban populations, and finally by isolated Native American populations as less degree of admixture. The study provided novel genetic information about the Mapuche and Tehuelche people and allowed us to establish a genetic correlation among individuals with Mapudungun surnames that demonstrates not only a linguistic but also a genetic relationship to the isolated aboriginal communities, representing a suitable proxy indicator for assessing genealogical background.

  2. Possible lattice organs in Cretaceous Thylacocephala

    NARCIS (Netherlands)

    Lange, Sven; Schram, Frederick R.

    2002-01-01

    Structures, reminiscent of the lattice organs in thecostracan crustaceans, are described from the carapace cuticle of Cretaceous thylacocephalans. The new lattice organ like structures occur in pairs along the dorsal midline. While these have a similar outline to true lattice organs, they seem to la

  3. Astronomical calibration of the Maastrichtian (Late Cretaceous)

    DEFF Research Database (Denmark)

    Husson, Dorothée; Galbrun, Bruno; Laskar, Jacques;

    2011-01-01

    Recent improvements to astronomical modeling of the Solar System have contributed to important refinements of the Cenozoic time scale through astronomical calibration of sedimentary series. We extend this astronomical calibration into the Cretaceous, on the base of the 405 ka orbital eccentricity...

  4. Cretaceous desert cycles, wind direction and hydrologic cycle variations in Ordos Basin:Evidence for Cretaceous climatic unequability

    Institute of Scientific and Technical Information of China (English)

    JIANG Xinsheng; PAN Zhongxi; XIE Yuan; LI Minghui

    2004-01-01

    Climatic state under greenhouse effect is a currently hot point. Whether greenhouse climate in geological history, especially in Cretaceous, was equable or not has aroused extensive discussion. By analysis on depositional cyclcity, wind direction change and hydrologic cycle variation of Cretaceous desert in the Ordos Basin of China, the unequability of Cretaceous climate is dealt. It is shown that Cretaceous climate was extremely cyclic, not only having long and mid term but also having strong seasonal even instantaneous changes. Therefore, it is suggested that Cretaceous climate was not equable.

  5. Cretaceous desert cycles, wind direction and hydrologic cycle variations in Ordos Basin: Evidence for Cretaceous climatic unequability

    Institute of Scientific and Technical Information of China (English)

    JIANG; Xinsheng; PAN; Zhongxi; XIE; Yuan; LI; Minghui

    2004-01-01

    Climatic state under greenhouse effect is a currently hot point. Whether greenhouse climate in geological history, especially in Cretaceous, was equable or not has aroused extensive discussion. By analysis on depositional cyclcity, wind direction change and hydrologic cycle variation of Cretaceous desert in the Ordos Basin of China, the unequability of Cretaceous climate is dealt. It is shown that Cretaceous climate was extremely cyclic, not only having long and mid term but also having strong seasonal even instantaneous changes. Therefore, it is suggested that Cretaceous climate was not equable.

  6. Sedimentary basin analysis and petroleum potential of the Cretaceous and Tertiary strata in Korea.

    Energy Technology Data Exchange (ETDEWEB)

    Son, Jin-Dam; Kwak, Young-Hoon; Bong, Pil-Yoon [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

    1999-12-01

    Since 1992 sedimentary basin analysis to assess petroleum potential of the Cretaceous and Tertiary strata in the Korean onshore and continental shelf have been carried out. The Cretaceous non-marine strata mainly occupy the Gyeongsang Basin in southeastern part of the Korean Peninsula and small basins such as Haenam and Gyeokpo depressions in western coastal areas. The Tertiary strata are mostly distributed in Domi, Cheju, Socotra subbasins, and Okinawa Trough in the South Continental Shelf, and Kunsan and Heuksan basins in the West. The basin evolution and petroleum potential for each basins are characterized as follow. The Cretaceous Gyeongsang sediments were deposited in three subbasins including Milyang, Euisung and Yongyang subbasins. The black shales in Nakdong and Jinju formations are interpreted to contain abundant organic matter during the deposition, thermal maturity reaching up to the zone of dry gas formation. Because porosity and permeability are too low, the sandstones can act as a tight gas reservoir rather than conventional oil and gas reservoir. The latest Cretaceous strata of Haenam and Kyeokpo depressions in western coastal area are correlated into the Yuchon Volcanic Group of the Gyeongsang Basin. Petroleum potential of the Early Cretaceous basin in the West Continental Shelf could be relatively high in terms of sedimentary basin filled with thick lacustrine sediments. The Kunsan basin in the West Continental Shelf originated in the Early Cretaceous time expanded during the Paleocene time followed by regional erosion at the end of Paleocene on which Neogene sediment have been accumulated. The Paleocene-Eocene sublacustrine shales may play an major role as a source and cap rocks. South Continental Shelf Basin is subdivided by Cheju subbasin in the center, Socotra Subbasin to the west, Domi Subbasin to the northeast and Okinawa Trough to the East. The potential hydrocarbon traps associated with anticline, titled fault blocks, fault, unconformity

  7. Análisis de la diversidad biológica y mestizaje en la ciudad de Puerto Madryn (Prov. de Chubut, Argentina

    Directory of Open Access Journals (Sweden)

    Parolín, María Laura

    2013-12-01

    Full Text Available En el marco del estudio de la composición genética de las poblaciones cosmopolitas de Argentina, se analizó una muestra poblacional de la localidad de Puerto Madryn (PM con la finalidad de evaluar su diversidad biológica mediante la utilización de marcadores biparentales y uniparentales y comparar los resultados con los obtenidos previamente por nuestro equipo de investigación en seis poblaciones cosmopolitas de distintas regiones de la Argentina, aunque poniendo el énfasis en las correspondientes a la Región Patagónica.Las muestras biológicas fueron tomadas con consentimiento informado a 82 dadores de sangre no emparentados que concurrieron al Banco de Sangre y al Hospital Subzonal de dicha localidad, a quienes también se les realizó una encuesta genealógica. A partir de los datos proporcionados por los marcadores autosómicos, se registró una contribución europea de 67.2%, amerindia de 29.4% y africana de 3.4%. A un origen amerindio fueron adscriptos el 59.9% y 8.7% de los linajes maternos y paternos, respectivamente, revelando un desigual aporte autóctono por género.El aporte europeo se vio representado principalmente por el Hg H (19.5% y se detectaron sólo dos linajes subsaharianos.En PM las migraciones desde el centro del país han generado un fuerte impacto, reflejado en la mayor contribución de marcadores europeos respecto de dos muestras estudiadas previamente en Chubut (Comodoro Rivadavia y Esquel. Estas diferencias al interior de una misma provincia nos advierten que no puede abordarse el análisis de la constitución genética de las poblaciones sin dar cuenta de las particularidades regionales.

  8. Small theropod teeth from the Late Cretaceous of the San Juan Basin, northwestern New Mexico and their implications for understanding latest Cretaceous dinosaur evolution.

    Science.gov (United States)

    Williamson, Thomas E; Brusatte, Stephen L

    2014-01-01

    Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian - Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately coeval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod diversity were lost

  9. Small theropod teeth from the Late Cretaceous of the San Juan Basin, northwestern New Mexico and their implications for understanding latest Cretaceous dinosaur evolution.

    Directory of Open Access Journals (Sweden)

    Thomas E Williamson

    Full Text Available Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian - Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately coeval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod

  10. Magnesioferrite from the Cretaceous-Tertiary boundary, Caravaca, Spain

    Science.gov (United States)

    Bohor, Bruce F.; Foord, Eugene E.; Ganapathy, Ramachandran

    1986-12-01

    The results of an analysis of samples separated from the Cretaceous-Tertiary (K-T) boundary clay at Caravaca, Spain are presented. Magnetically fractionated samples were irradiated with thermal neutrons, and the element concentrations were determined by gamma-ray counting. The magnetic mineral separated from the basal layer of the K-T boundary is a spinel-type phase having the composition of magnesioferrite, and is high (about 29 ppb) in iridium. This spinel-type phase and others of the spinel group found in K-T boundary clays have been proposed to represent unaltered remnants of ejecta deposited from an earth-girdling dust cloud formed from the impact of an asteroid or other large bolide at the end of the Cretaceous period. Major element composition (high Cr and Ni) and trace element ratios of the analyzed samples indicate either an extraterrestrial or mantle source for the magnesioferrite. On the basis of the crystal morphology and general compositon of the grains, rapid crystallization at high temperature is indicated, most likely directly from a vapor phase or emanating cloud and in an environment of moderate oxygen fugacity.

  11. The first Late Cretaceous (Maastrichtian dinosaur footprints from Transylvania (Romania

    Directory of Open Access Journals (Sweden)

    Matei Vremir

    2002-09-01

    Full Text Available An Uppermost Cretaceous (Maastrichtian site exposing dinosaur footprints is reported from the Sebes̡ area (Transylvanian Depression. This is the first dinoturbated layer discovered in our country, containing also numerous bones belonging to various dinosaurs. The track-site is located near Lancrăm village and provides only two quite well preserved footprints (one track. The medium sized (FL = 23,3 cm; FW = 17,8 cm; pace = 103 cm; ST = 200 cm plantigrad-tridactyle footprints belong to Ornithopedoidei, according to their morphology. An assignment to the Iguanodontichnus CASAMIQUELA & FASOLA, 1968 group seems to be appropriate (tentatively, associated to the “Rhabdodon” iguanodontian dinosaur. The importance of this discovery lies in the stratigraphical significance, confirming the Uppermost Cretaceous age of these dinosaur-bearing continental deposits exposed between Sebes̡ and Alba-Iulia (as well as the autochthon/ paraautochon status of some vertebrate assemblages identified there, which previously were considered Oligocene or even Miocene. Additional data regarding size, speed and locomotion of the Transylvanian Iguanodontian ”Rhabdodon” dinosaurs are added.

  12. El caso del Outburst Flood histórico de la laguna Derrumbe, Cholila, Chubut: Colapso de dique Morénico en la Cordillera Norpatagónica The historic outburst flood of the laguna Derrumbe, Cholila, Chubut: Fast glacier retreat and moraine dam failure in North Patagonian Cordillera

    Directory of Open Access Journals (Sweden)

    Bruno Colavitto

    2012-09-01

    Full Text Available La laguna Derrumbe es un cuerpo de agua ubicado en los Andes Norpatagónicos en la provincia de Chubut, Argentina. Está contenida en un circo glaciario y endicada por una morena frontal del glaciar homónimo. A través del reconocimiento de campo se pudo describir a esta laguna y a un importante depósito rocoso que se halla aguas abajo de la misma, interpretado como un depósito de outburst flood. Estos depósitos son generados por procesos de alta energía relacionados con la rotura de un dique natural, en este caso un dique morénico. El estudio realizado permitió concluir que la morena frontal del glaciar Derrumbe sufrió una rotura parcial en tiempos históricos, desatando así una inundación súbita aguas abajo de la laguna, a través del valle del río Tigre, en la localidad de Cholila. En este trabajo se analizaron las posibles causas que dieron lugar a la rotura, la cual probablemente sea producto del rápido retroceso que el glaciar experimentó durante la década del ´50 y principios del ´60. Retroceso comparable con el ocurrido en muchos de los cuerpos glaciares de los Andes Patagónicos durante el último siglo.The Laguna Derrumbe is a body of water located in the North Patagonian Andes, in Chubut province, Argentina. This lake is contained in a glacial cirque and dammed by the terminal moraine of the namesake glacier. Through field survey it was possible to describe this lake and an important rocky deposit downstream of it, which is interpreted as an outburst flood deposit. These deposits are generated by high-energy processes related to the failure of a natural dam, in this case a moraine dam. The study made allowed to conclude that the frontal moraine of the Derrumbe glacier suffered a partial rupture in historic times, unleashing a flash flood downstream to the lake, through the Tigre river valley in the town of Cholila. In this work the possible causes that led to the failure are discussed, concluding that the main cause

  13. Mammalian hairs in Early Cretaceous amber

    Science.gov (United States)

    Vullo, Romain; Girard, Vincent; Azar, Dany; Néraudeau, Didier

    2010-07-01

    Two mammalian hairs have been found in association with an empty puparium in a ˜100-million-year-old amber (Early Cretaceous) from France. Although hair is known to be an ancestral, ubiquitous feature in the crown Mammalia, the structure of Mesozoic hair has never been described. In contrast to fur and hair of some Jurassic and Cretaceous mammals preserved as carbonized filaments, the exceptional preservation of the fossils described here allows for the study of the cuticular structure. Results show the oldest direct evidence of hair with a modern scale pattern. This discovery implies that the morphology of hair cuticula may have remained unchanged throughout most of mammalian evolution. The association of these hairs with a possible fly puparium provides paleoecological information and indicates peculiar taphonomic conditions.

  14. History of the Cretaceous Osbourn spreading center

    OpenAIRE

    Downey, Nathan J.; Stock, Joann M.; Clayton, Robert W.; Cande, Steven C.

    2007-01-01

    The Osbourn Trough is a fossil spreading center that rifted apart the Manihiki and Hikurangi Plateaus during Cretaceous time. Previous models of the Osbourn spreading center are based on data collected near the trough axis, and therefore only constrain the history of the Osbourn spreading center during the last few Ma of spreading. Our data set includes multibeam data collected northward to the Manihiki Plateau, allowing us to examine seafloor morphology created during the entire active perio...

  15. Depositional features of the fan delta from lower Cretaceous Kezilesu Group in Yecheng sag, southwestern Tarim Basin%塔里木盆地西南部叶城凹陷下白垩统克孜勒苏群扇三角洲沉积特征及模式

    Institute of Scientific and Technical Information of China (English)

    厚刚福; 孙雄伟; 李昌; 刘群; 曾庆鲁; 熊冉; 曹全斌

    2012-01-01

    以野外露头、岩心观察为基础,结合录井、测井及粒度分析,认为叶城凹陷下白垩统克孜勒苏群发育进积型扇三角洲,划分出扇三角洲平原与扇三角洲前缘水下分流河道、分流间湾与河口坝.扇三角洲平原受重力流作用明显;扇三角洲前缘主要受牵引流作用,在盆地的短轴方向延伸范围较小,而在长轴方向延伸范围较大,与相邻扇三角洲前缘朵叶叠置连片.扇三角洲由山前向断陷湖盆进积,在盆地的短轴方向构成一侧为陡坡、另一侧为宽缓斜坡的单断式断陷盆地充填模式.这种沉积模式不仅控制了扇三角洲各亚相单元的发育特征,而且对微相类型与砂体分布有控制作用.%Based on field outcrop and core observation, combined with mud logging, logging and grain size analysis, the authors found that there are prograded fan delta sediments in lower Cretaceous Kezilesu Group of Yecheng sag, which can be divided into fan delta plain, fan delta frontier underwater distributary channel, mouth bar and interdistributary bay. Fan delta plain was obviously affected by gravity flow, whereas fan delta frontier was mainly affected by traction current. The latter extended limitedly in the direction of the short axis, and extended a considerable distance in superimposition association with adjacent fan delta frontier leaves in the direction of the long axis. Fan delta experienced progradation from the piedmont area to the faulted lake basin, forming mono-faulted fault basin filling model in the direction of the short axis, which was steep slope on one side, and wide and gentle slope on the other side. This sedimentary model controlled not only characteristics of each unit of the fan delta but also microfacies types and sand distribution.

  16. Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous-Palaeogene mass extinction.

    Science.gov (United States)

    Halliday, Thomas John Dixon; Upchurch, Paul; Goswami, Anjali

    2016-06-29

    The effect of the Cretaceous-Palaeogene (K-Pg) mass extinction on the evolution of many groups, including placental mammals, has been hotly debated. The fossil record suggests a sudden adaptive radiation of placentals immediately after the event, but several recent quantitative analyses have reconstructed no significant increase in either clade origination rates or rates of character evolution in the Palaeocene. Here we use stochastic methods to date a recent phylogenetic analysis of Cretaceous and Palaeocene mammals and show that Placentalia likely originated in the Late Cretaceous, but that most intraordinal diversification occurred during the earliest Palaeocene. This analysis reconstructs fewer than 10 placental mammal lineages crossing the K-Pg boundary. Moreover, we show that rates of morphological evolution in the 5 Myr interval immediately after the K-Pg mass extinction are three times higher than background rates during the Cretaceous. These results suggest that the K-Pg mass extinction had a marked impact on placental mammal diversification, supporting the view that an evolutionary radiation occurred as placental lineages invaded new ecological niches during the Early Palaeocene. PMID:27358361

  17. Climate and carbon-cycling in the Early Cretaceous

    OpenAIRE

    Littler, K

    2011-01-01

    The Cretaceous (~145–65 Ma) is widely regarded as a greenhouse period with warm, equable climates and elevated atmospheric CO2 relative to the modern. However, the earliest Cretaceous (Berriasian–Barremian; 145–125 Ma) is commonly characterised as a relatively colder “coolhouse” interval, typified by lower global temperatures than the mid-Cretaceous. Unfortunately, the lack of absolute sea surface temperature (SST) estimates prior to the Barremian has hampered efforts to defini...

  18. Upper Cretaceous to Pleistocene melilitic volcanic rocks of the Bohemian Massif: petrology and mineral chemistry

    Directory of Open Access Journals (Sweden)

    Skála Roman

    2015-06-01

    Full Text Available Upper Cretaceous to Pleistocene volcanic rocks of the Bohemian Massif represent the easternmost part of the Central European Volcanic Province. These alkaline volcanic series include rare melilitic rocks occurring as dykes, sills, scoria cones and flows. They occur in three volcanic periods: (i the Late Cretaceous to Paleocene period (80–59 Ma in northern Bohemia including adjacent territories of Saxony and Lusatia, (ii the Mid Eocene to Late Miocene (32.3–5.9 Ma period disseminated in the Ohře Rift, the Cheb–Domažlice Graben, Vogtland, and Silesia and (iii the Early to Late Pleistocene period (1.0–0.26 Ma in western Bohemia. Melilitic magmas of the Eocene to Miocene and Pleistocene periods show a primitive mantle source [(143Nd/144Ndt=0.51280–0.51287; (87Sr/86Srt=0.7034–0.7038] while those of the Upper Cretaceous to Paleocene period display a broad scatter of Sr–Nd ratios. The (143Nd/144Ndt ratios (0.51272–0.51282 of the Upper Cretaceous to Paleocene rocks suggest a partly heterogeneous mantle source, and their (87Sr/86Srt ratios (0.7033–0.7049 point to an additional late- to post-magmatic hydrothermal contribution. Major rock-forming minerals include forsterite, diopside, melilite, nepheline, sodalite group minerals, phlogopite, Cr- and Ti-bearing spinels. Crystallization pressures and temperatures of clinopyroxene vary widely between ~1 to 2 GPa and between 1000 to 1200 °C, respectively. Nepheline crystallized at about 500 to 770 °C. Geochemical and isotopic similarities of these rocks occurring from the Upper Cretaceous to Pleistocene suggest that they had similar mantle sources and similar processes of magma development by partial melting of a heterogeneous carbonatized mantle source.

  19. Evolution and palaeoenvironment of the Bauru Basin (Upper Cretaceous, Brazil)

    Science.gov (United States)

    Fernandes, Luiz Alberto; Magalhães Ribeiro, Claudia Maria

    2015-08-01

    The Bauru Basin was one of the great Cretaceous desert basins of the world, evolved in arid zone called Southern Hot Arid Belt. Its paleobiological record consists mainly of dinosaurs, crocodiles and turtles. The Bauru Basin is an extensive region of the South American continent that includes parts of the southeast and south of Brazil, covering an area of 370,000 km2. It is an interior continental basin that developed as a result of subsidence of the central-southern part of the South-American Platform during the Late Cretaceous (Coniacian-Maastrichtian). This sag basin is filled by a sandy siliciclastic sequence with a preserved maximum thickness of 480 m, deposited in semiarid to desert conditions. Its basement consists of volcanic rocks (mainly basalts) of the Lower Cretaceous (Hauterivian) Serra Geral basalt flows, of the Paraná-Etendeka Continental Flood Basalt Province. The sag basin was filled by an essentially siliciclastic psammitic sequence. In lithostratigraphic terms the sequence consists of the Caiuá and Bauru groups. The northern and northeastern edges of the basin provide a record of more proximal original deposits, such as associations of conglomeratic sand facies from alluvial fans, lakes, and intertwined distributary river systems. The progressive basin filling led to the burial of the basaltic substrate by extensive blanket sand sheets, associated with deposits of small dunes and small shallow lakes that retained mud (such as loess). Also in this intermediate context between the edges (more humid) and the interior (dry), wide sand sheet areas crossed by unconfined desert rivers (wadis) occurred. In the central axis of the elliptical basin a regional drainage system formed, flowing from northeast to southwest between the edges of the basin and the hot and dry inner periphery of the Caiuá desert (southwest). Life in the Bauru Basin flourished most in the areas with the greatest water availability, in which dinosaurs, crocodiles, turtles, fish

  20. Crocodyliform biogeography during the Cretaceous: evidence of Gondwanan vicariance from biogeographical analysis.

    Science.gov (United States)

    Turner, Alan H.

    2004-01-01

    Explanations of the distributions of terrestrial vertebrates during the Mesozoic are currently vigorously contested and debated in palaeobiogeography. Recent studies focusing on dinosaurs yield conflicting hypotheses. Dispersal, coupled with regional extinction or vicariance driven by continental break-up, have been cited as the main causal factors behind dinosaur distributions in the Mesozoic. To expand the scope of the debate and test for vicariance within another terrestrial group, I herein apply a cladistic biogeographical method to a large sample of Cretaceous crocodyliform taxa. A time-slicing methodology is employed and a refinement made to account for the divergence times of the analysed clades. The results provide statistically significant evidence that Gondwana fragmentation affected crocodyliform diversification during the Mid-Late Cretaceous. Detection of a vicariant pattern within crocodyliforms is important as it helps corroborate vicariance hypotheses in other fossil and extant groups as well as furthers the move towards more taxonomically diverse approaches to palaeobiogeographical research. PMID:15451689

  1. Bias correction for the orientation distribution of slump fold axes: Application to the Cretaceous Izumi basin

    OpenAIRE

    Koyama, Toshiyuki; Yamaji, Atsushi; Sato, Katsushi

    2012-01-01

    Linear structures perpendicular to an outcrop surface are easily discovered, but those parallel to the surface are not, giving rise to a biased orientation distribution of the structures. Here, we propose a bias correction method: Statistical inversion was conducted to unbias the distribution of the axes of mesoscale slump folds in the Cretaceous Izumi Group, Japan using the orientation distribution of outcrop surfaces. The observed axes showed a cluster in the SE quadrant. Their unbiased dis...

  2. Skin of the Cretaceous mosasaur Plotosaurus: implications for aquatic adaptations in giant marine reptiles

    OpenAIRE

    Lindgren, Johan; Alwmark, Carl; Caldwell, Michael W.; Anthony R Fiorillo

    2009-01-01

    The physical nature of water and the environment it presents to an organism have long been recognized as important constraints on aquatic adaptation and evolution. Little is known about the dermal cover of mosasauroids (a group of secondarily aquatic reptiles that occupied a wide array of predatory niches in the Cretaceous marine ecosystems 92–65 Myr ago), a lack of information that has hindered inferences about the nature and level of their aquatic adaptations. A newly discovered Plotosaurus...

  3. Comment on "Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification".

    Science.gov (United States)

    Bininda-Emonds, Olaf R P; Purvis, Andy

    2012-07-01

    Meredith et al. (Reports, 28 October 2011, p. 521) question three findings of our delayed-rise hypothesis for present-day mammals made with reference to the Cretaceous-Paleogene (KPg) boundary, based on their new time tree of the group. We show that their own data do not support their objections and that the macroevolutionary patterns from the respective phylogenies are not statistically different.

  4. NEW ABELISAURID MATERIAL FROM THE UPPER CRETACEOUS (CENOMANIAN OF MOROCCO

    Directory of Open Access Journals (Sweden)

    SIMONE D'ORAZI PORCHETTI

    2011-11-01

    Full Text Available Fragmentary cranial bones of dinosaur origin have been recently recovered from the Kem Kem beds (Upper Cretaceous, Cenomanian of Morocco. They include two incompletely preserved maxillary bones evidencing diagnostic features of abelisaurid theropods. These new finds provide further evidence of Abelisauridae in the Late Cretaceous of Morocco. 

  5. Genesis of Low-Resistivity Oil layers from Cretaceous System in Luxi Area and Its Geological Significance

    Institute of Scientific and Technical Information of China (English)

    朱国华

    2002-01-01

    Genesis of low-resistivity oil layers from cretaceous system in Luxi area was studied. The result shows that the resistivity of oil layers is lower than that of water layers from Tugulu Group(K1tg),Cretaceous in Luliang area,Zhungeer basin, resulting in a disaccordance with logging interpretation on oil layers,oil-water layers and water layers.The research on the petro-texture of reservoirs also shows that the watered clay pellicle (I/S, I, ch) is well developed in K1tg expands the section of conductive net and results in a low resistivity of oil layers.

  6. Geologic and biostratigraphic framework of the non-marine Cretaceous-Tertiary boundary interval in western North America

    Science.gov (United States)

    Nichols, D.J.

    1990-01-01

    Palynologically defined Cretaceous-Tertiary boundary sites in nonmarine rocks in western North America exhibit similar characteristics. All are marked by abrupt disappearance of the regional uppermost Cretaceous palynoflora at the level of an iridium anomaly; most also yeild shock-metamorphosed minerals. All are in coal-bearing, fluvial or paludal depositional settings, although the boundary horizon may be below, within, above, or at some stratigraphic distance from coal seams. At many sites the lowermost Tertiary beds contain assemblages overwhelmed by fern spores that, together with extinctions of some groups of angiosperms, are taken as evidence of regional devastation of terrestrial plant communities and subsequent recolonization by pioneer species. ?? 1990.

  7. Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back?

    Directory of Open Access Journals (Sweden)

    Maria Zammit

    2012-04-01

    Full Text Available Recent descriptions of new taxa and recognition of survivorship of Jurassic genera across the Jurassic–Cretaceous boundary bring the total number of Cretaceous ichthyosaur genera to eight. Taxa currently known from the Cretaceous include Ophthalmosaurus, Caypullisaurus, Aegirosaurus, Platypterygius, Maiaspondylus, Athabascasaurus, Sveltonectes, and Acamptonectes. This review summarizes the occurrence of all Cretaceous genera. A discussion of morphological diversity demonstrates the different, though overlapping, ecological niches occupied by the different taxa, while the comparison of phylogenetic hypotheses shows the problems inherent in understanding the evolutionary relationships between Cretaceous genera. The Late Jurassic radiation indicated in the competing phylogenetic hypotheses may correlate with the opening of the Atlantic Ocean or additional dispersal routes established by the breakup of Gondwana. Inclusion of the stratigraphically oldest Platypterygius species may aid in resolving these evolutionary relationships.

  8. Preliminary vitrinite and bitumen reflectance, total organic carbon, and pyrolysis data for samples from Upper and Lower Cretaceous strata, Maverick Basin, south Texas

    Science.gov (United States)

    Hackley, Paul C.; Dennen, Kristin O.; Gesserman, Rachel M.; Ridgley, Jennie L.

    2009-01-01

    The Lower Cretaceous Pearsall Formation, a regionally occurring limestone and shale interval of 500-600-ft maximum thickness (Rose, 1986), is being evaluated as part of an ongoing U.S. Geological Survey (USGS) assessment of undiscovered hydrocarbon resources in onshore Lower Cretaceous strata of the northern Gulf of Mexico. The purpose of this report is to release preliminary vitrinite and bitumen reflectance, total organic carbon, and pyrolysis data for Pearsall Formation, Glen Rose Formation, Hosston Formation, Austin Group, and Eagle Ford Group samples from the Maverick Basin in south Texas in order to aid in the characterization of these strata in this area. The preliminary nature of this report and the data contained herein reflect that the assessment and characterization of these samples is a work currently in progress. Pearsall Formation subdivisions are, in ascending stratigraphic order, the Pine Island Shale, James Limestone, and Bexar Shale Members (Loucks, 2002). The Lower Cretaceous Glen Rose Formation is also part of the USGS Lower Cretaceous assessment and produces oil in the Maverick Basin (Loucks and Kerans, 2003). The Hosston Formation was assessed by the USGS for undiscovered oil and gas resources in 2006 (Dyman and Condon, 2006), but not in south Texas. The Upper Cretaceous Austin Group is being assessed as part of the USGS assessment of undiscovered hydrocarbon resources in the Upper Cretaceous strata of the northern Gulf of Mexico and, along with the Upper Cretaceous Eagle Ford Group, is considered to be an important source rock in the Smackover-Austin-Eagleford Total Petroleum System (Condon and Dyman, 2006). Both the Austin Group and the Eagle Ford Group are present in the Maverick Basin in south Texas (Rose, 1986).

  9. Low ecological disparity in Early Cretaceous birds.

    Science.gov (United States)

    Mitchell, Jonathan S; Makovicky, Peter J

    2014-07-22

    Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (=pygostylians) from the Jehol Biota (≈125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem. PMID:24870044

  10. Cretaceous-Palaeogene experiments in Biogeochemical Resilience

    Science.gov (United States)

    Penman, D. E.; Henehan, M. J.; Hull, P. M.; Planavsky, N.; Schmidt, D. N.; Rae, J. W. B.; Thomas, E.; Huber, B. T.

    2015-12-01

    Human activity is altering biogeochemical cycles in the ocean. While ultimately anthropogenic forcings may be brought under control, it is still unclear whether tipping points may exist beyond which human-induced changes to biogeochemical cycles become irreversible. We use the Late Cretaceous and the Cretaceous-Palaeogene (K-Pg) boundary interval as an informative case study. Over this interval, two carbon cycle perturbations (gradual flood basalt volcanism and abrupt bolide impact) occurred within a short time window, allowing us to investigate the resilience of biogeochemical cycles to different pressures applied to the same initial boundary conditions on very different time scales. We demonstrate that relatively gradual emission of CO2 from the Deccan large igneous province was efficiently mitigated within the limits of existing biogeochemical processes. However, the rapid extinction of pelagic calcifying organisms at the K-Pg boundary due to the Chicxulub bolide impact had more profound effects, and caused lasting (> 1 million years) changes to biogeochemical cycles. By combining sedimentological observations with boron isotope-based pH reconstructions over these events, we document two potentially useful partial analogues for best and worst case scenarios for anthropogenic global change. We suggest that if current ocean acidification results in the mass extinction of marine pelagic calcifiers, we may cause profound changes to the Earth system that will persist for 100,000s to millions of years.

  11. Sedimentología y paleoambientes del Subgrupo Río Colorado (Cretácico Superior, Grupo Neuquén, en las bardas de la ciudad de Neuquén y alrededores Sedimentology and sedimentary paleoenvironments of Río Colorado Subgroup (Upper Cretaceous, Neuquén Group, in Neuquén city and surrounding areas

    Directory of Open Access Journals (Sweden)

    M.L. Sánchez

    2006-06-01

    Full Text Available En la ciudad de Neuquén y alrededores afloran depósitos del Cretácico superior asignados al Subgrupo Río Colorado. La presente contribución da a conocer los resultados del análisis sedimentológico y paleoambiental de las Formaciones Bajo de la Carpa (Santoniano y Anacleto (Campaniano inferior. Los estudios llevados a cabo permitieron definir cuatro litofacies conglomerádicas, nueve de areniscas y dos pelíticas, que fueron agrupadas en nueve asociaciones de litofacies, dos de ellas de origen eólico y siete fluviales. La Formación Bajo de la Carpa está representada en la base por un sistema fluvial efímero, y en el techo por depósitos de interacción fluvio- eólica. Los depósitos fluviales corresponden a flujos canalizados durante episodios de máxima descarga. Luego se identifica un campo de dunas transversales, afectado en el subambiente de interduna por corrientes fluviales efímeras, y dunas parabólicas producto de la removilización del sistema eólico infrayacente, asociadas con depósitos de flujos efímeros en manto. La extensión y geometría de los campos de dunas respondieron a variaciones climáticas de corto término, interferencia del sistema fluvial, oscilaciones del nivel freático, bajo suministro y/o disponibilidad de sedimentos y factores tectónicos. La Formación Anacleto presenta en su base sistemas fluviales de baja sinuosidad, alta energía y rápida agradación, controlados por un bajo espacio de acomodación y condiciones climáticas con marcada estacionalidad. Hacia el tope se identifica un sistema fluvial anastomosado que refleja variaciones climáticas y aumento de la tasa de subsidencia acompañada de un lento ascenso del nivel de base relacionado con la ingresión atlántica maastrichtiana.Upper Cretaceous deposits included in Río Colorado Subgroup crop out in Neuquén city and surrounding areas. This work shows the results of the sedimentogical and paleoenvironmental analysis of Bajo de la Carpa

  12. Newly combined 40Ar/39Ar and U-Pb ages of the Upper Cretaceous timescale from Hokkaido, Japan

    Science.gov (United States)

    Gaylor, J. R.; Heredia, B. D.; Quidelleur, X.; Takashima, R.; Nishi, H.; Mezger, K.

    2011-12-01

    The main targets for GTS next project (www.gtsnext.eu) are to develop highly refined geological time scales, including the Upper Cretaceous. The Cretaceous period is characterised by numerous global anoxic events in the marine realm, rich ammonitic fossil assemblages and specialised foraminifera. However, lack of age diagnostic macro and micro fossils in the North Pacific sections has made it difficult to link these with global sections such as the Western Interior Basin (North America). Using advances with terrestrial C-isotope and planktic foraminifera records within Central Hokkaido we are able to correlate these sections globally. The Cretaceous Yezo group in Central Hokkaido comprises deep marine mudstones and turbidite sandstones interbedded with acidic volcanic tuffs. Using various sections within the Yezo group, we radiometrically dated tuffs at the main stage boundaries in the Upper Cretaceous. The samples derive from the Kotanbetsu, Shumarinai, Tiomiuchi and the Hakkin river sections, spanning the time from the Albian-Cenomanian up until the Campanian-Santonian boundaries, and were dated using 40Ar/39Ar, K/Ar and U-Pb techniques. Recent age constraints in the Hokkaido counterparts (Kotanbetsu sections) show good coherence between radiometric chronometers on the various Upper Cretaceous stage boundaries. These additional ages together with our isotope ages from the different sections around the Hokkaido basin are well linked by the various faunal assemblages and C-isotope curves. The combined radio isotope ages contribute to previous attempts (such as those focused in the Western Interior Basin) supporting the synchronicity of events such as global oceanic anoxic events. Finally, the ages obtained here also compliment the previous C-isotope and planktic foraminifera records allowing for a more precise climatic history of the Northwest Pacific during the Cretaceous. The research within the GTSnext project is funded by the European Community's Seventh

  13. Estratigrafía del Grupo Neuquén, Cretácico Superior de la Cuenca Neuquina (Argentina: nueva propuesta de ordenamiento litoestratigráfico Stratigraphy of the Neuquén Group, Upper Cretaceous of the Neuquén Basin (Argentina: new proposal for lithostratigraphic ordaining

    Directory of Open Access Journals (Sweden)

    Alberto C. Garrido

    2010-12-01

    éano Atlántico y el comienzo de la depositación del Grupo Malargüe.The Neuquén Group conform a succession of non-marine deposits of fluvial, aeolian and shallow lacustrine origin, developed in the Neuquén Basin between the Lower Cenomanian and the Middle Campanian (Upper Cretaceous. This succession reaches 1,200 m of maximum thick, being bounded at the base and the top by the Patagonidican and Huantraiquican unconformities respectively. In this paper two new formations are proposed (Los Bastos and Sierra Barrosa Formations, nom. nov., and the subgroups were reconfigurated. Consequently, the Neuquén Group is composed lithostratigraphically by three subgroups and nine formations. The Río Limay Subgroup comprehend the Candeleros and Huincul Formations, representing low sinuosity channel deposits developed under tectonic and climatic subordinated control. The Río Neuquén Subgroup comprehend to the Cerro Lisandro, Portezuelo, Los Bastos, Sierra Barrosa and Plottier Formations, conforming a psamitic and pelitic interstratified succession of fluvial origin, mainly developed under climatic control. Finally, the Río Colorado Subgroup integrated by the Bajo de la Carpa and Anacleto Formations, comprehend fluvial deposits developed under a new dominant tectonic control. At the start of the deposition of the Neuquén Group, the Dorsal de Huincul worked as a structural high, generating toward the south of the Neuquén Basin one a small endorreic depocentre corresponding to the Picún Leufú Sub-basin, scheme that would have been keep up to ends of the deposit of the Candeleros Formation. During the rest of the deposit of this sequence, the drainage would have been kept without major modifications towards the pacific slope across a central collector flowing in sense N-NW. Towards the end of the deposit of the Neuquén Group takes place the inversion of the regional slope of the basin, making possible the ingression of the Atlantic Ocean and the beginning of the deposition of

  14. A New Genus and Species of Sapeornithidae from Lower Cretaceous in Western Liaoning, China

    Institute of Scientific and Technical Information of China (English)

    YUAN Chongxi

    2008-01-01

    Sapeornithidae is a basal pygostylian family of Early Cretaceous primitive birds, in which only one genus and species, Sapeornis chaoyangensis, was reported before. This paper deals with a new genus and species of this family, Didactylornis jii gen. et sp. nov., which was unearthed from the Early Cretaceous Jiufotang Formation in western Liaoning. According to our phylogenetic analyses, both Didactylornis gen. nov. and Sapeornis form a sister group, which is basal to the clade formed by Confuciusornis and all the more derived birds, and more closely related to the short-tailed pygostylian birds than to the long-tailed avialian birds. The early history of pygostylian birds is poorly documented except for the studies of Confuciusornis and Sapeornis. The discovery of Didactylornis jii gen. et sp. nov. adds the new material for the study on the early evolution of birds.

  15. Molecular and paleontological evidence for a post-Cretaceous origin of rodents.

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    Shaoyuan Wu

    Full Text Available The timing of the origin and diversification of rodents remains controversial, due to conflicting results from molecular clocks and paleontological data. The fossil record tends to support an early Cenozoic origin of crown-group rodents. In contrast, most molecular studies place the origin and initial diversification of crown-Rodentia deep in the Cretaceous, although some molecular analyses have recovered estimated divergence times that are more compatible with the fossil record. Here we attempt to resolve this conflict by carrying out a molecular clock investigation based on a nine-gene sequence dataset and a novel set of seven fossil constraints, including two new rodent records (the earliest known representatives of Cardiocraniinae and Dipodinae. Our results indicate that rodents originated around 61.7-62.4 Ma, shortly after the Cretaceous/Paleogene (K/Pg boundary, and diversified at the intraordinal level around 57.7-58.9 Ma. These estimates are broadly consistent with the paleontological record, but challenge previous molecular studies that place the origin and early diversification of rodents in the Cretaceous. This study demonstrates that, with reliable fossil constraints, the incompatibility between paleontological and molecular estimates of rodent divergence times can be eliminated using currently available tools and genetic markers. Similar conflicts between molecular and paleontological evidence bedevil attempts to establish the origination times of other placental groups. The example of the present study suggests that more reliable fossil calibration points may represent the key to resolving these controversies.

  16. New Mid-Cretaceous (latest Albian dinosaurs fromWinton, Queensland, Australia.

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    Scott A Hocknull

    Full Text Available BACKGROUND: Australia's dinosaurian fossil record is exceptionally poor compared to that of other similar-sized continents. Most taxa are known from fragmentary isolated remains with uncertain taxonomic and phylogenetic placement. A better understanding of the Australian dinosaurian record is crucial to understanding the global palaeobiogeography of dinosaurian groups, including groups previously considered to have had Gondwanan origins, such as the titanosaurs and carcharodontosaurids. METHODOLOGY/PRINCIPAL FINDINGS: We describe three new dinosaurs from the late Early Cretaceous (latest Albian Winton Formation of eastern Australia, including; Wintonotitan wattsi gen. et sp. nov., a basal titanosauriform; Diamantinasaurus matildae gen. et sp. nov., a derived lithostrotian titanosaur; and Australovenator wintonensis gen. et sp. nov., an allosauroid. We compare an isolated astragalus from the Early Cretaceous of southern Australia; formerly identified as Allosaurus sp., and conclude that it most-likely represents Australovenator sp. CONCLUSION/SIGNIFICANCE: The occurrence of Australovenator from the Aptian to latest Albian confirms the presence in Australia of allosauroids basal to the Carcharodontosauridae. These new taxa, along with the fragmentary remains of other taxa, indicate a diverse Early Cretaceous sauropod and theropod fauna in Australia, including plesiomorphic forms (e.g. Wintonotitan and Australovenator and more derived forms (e.g. Diamantinasaurus.

  17. Dental Disparity and Ecological Stability in Bird-like Dinosaurs prior to the End-Cretaceous Mass Extinction.

    Science.gov (United States)

    Larson, Derek W; Brown, Caleb M; Evans, David C

    2016-05-23

    The causes, rate, and selectivity of the end-Cretaceous mass extinction continue to be highly debated [1-5]. Extinction patterns in small, feathered maniraptoran dinosaurs (including birds) are important for understanding extant biodiversity and present an enigma considering the survival of crown group birds (Neornithes) and the extinction of their close kin across the end-Cretaceous boundary [6]. Because of the patchy Cretaceous fossil record of small maniraptorans [7-12], this important transition has not been closely examined in this group. Here, we test the hypothesis that morphological disparity in bird-like dinosaurs was decreasing leading up to the end-Cretaceous mass extinction, as has been hypothesized in some dinosaurs [13, 14]. To test this, we examined tooth morphology, an ecological indicator in fossil reptiles [15-19], from over 3,100 maniraptoran teeth from four groups (Troodontidae, Dromaeosauridae, Richardoestesia, and cf. Aves) across the last 18 million years of the Cretaceous. We demonstrate that tooth disparity, a proxy for variation in feeding ecology, shows no significant decline leading up to the extinction event within any of the groups. Tooth morphospace occupation also remains static over this time interval except for increased size during the early Maastrichtian. Our data provide strong support that extinction within this group occurred suddenly after a prolonged period of ecological stability. To explain this sudden extinction of toothed maniraptorans and the survival of Neornithes, we propose that diet may have been an extinction filter and suggest that granivory associated with an edentulous beak was a key ecological trait in the survival of some lineages. PMID:27112293

  18. Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America

    Science.gov (United States)

    Mitchell, Jonathan S.; Roopnarine, Peter D.; Angielczyk, Kenneth D.

    2012-11-01

    The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America.

  19. Stratigraphy, foraminiferal assemblages and paleoenvironments in the Late Cretaceous of the Upper Magdalena Valley, Colombia (part I)

    Science.gov (United States)

    Vergara, Luis S.

    1997-03-01

    The present work focuses on the Cretaceous record (Middle Albian-Maastrichtian) of the Upper Magdalena Valley (UMV), with a scope that covers facies and biofacies. The nomenclatural scheme previously stated for the Girardot-Guataqui area is here extended and proposed for all the basin, the following fomational units being characterized in detail. The Hondita Formation (Middle Albian-late Turonian), placed on top of the Caballos Formation, is separated from the Lomagorda Formation (late Turonian-early Santonian) by a chert interval within a succession of predominantly dark shales deposited in outer shelf environments. The Olini Group (early Santonian-late Campanian) presents two conspicuous chert units (Lidita Inferior and Superior) overlain by the Nivel de Lutitas y Arenas (early Maastrichtian). The sandstones of La Tabla and finally the mudstones of the Seca Formation (Maastrichtian) represent diverse littoral environments of the end of the Cretaceous. In the UMV, the Cretaceous system attains approximately 1350 m of thickness. Within the paleogeographic scenario, the drowning of the basin and of the adjacent Central Cordillera during most of the Late Cretaceous enabled upwelling currents and the development of widespread pelagic sediments. These sediments graded to shallower water deposits towards the south of the basin. In the Upper Cretaceous, four sequences of second order can be identified. The longer cycle begins at the base of the Hondita Formation and exhibits the maximum flooding in the Cenomanian condensed section of this unit. Following this cycle, three successive sudden sea level drops mark the boundaries of complete sequences, each comprising well developed lowstand, transgressive and highstand system tracts. After the last cycle was completed, the basin was uplifted and rocks of the Seca Formation were cannibalized by fluvial processes during the Tertiary. An angular unconformity that truncates this unit represents the uppermost sequence boundary of

  20. Chemotaxonomical aspects of lower Cretaceous amber from Reconcavo Basin, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Ricardo; Azevedo, Debora A., E-mail: ricardopereira@iq.ufrj.b, E-mail: debora@iq.ufrj.b [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica; Carvalho, Ismar S. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Geociencias; Fernandes, Antonio Carlos S. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Museu Nacional. Dept. de Geologia e Paleontologia

    2011-07-01

    The chemical composition of Lower Cretaceous amber samples from Reconcavo Basin (Salvador, Bahia) was performed by GC-MS to characterize possible botanical sources. The compounds identified were hydrocarbonic and polar diterpenoids, such as abietane, dehydroabietane, tetrahydroretene, dehydroabietol, dehydroabietic acid, ferruginol and sugiol. Other diterpenoid classes were not detected as well as triterpenoids. The composition of the extracts and chemosystematic data allows relating the samples to conifers of Podocarpaceae or Cheirolepidiaceae families due to detection of ferruginol, a specific biomarker to these families. The data concerning Cretaceous amber in the Reconcavo Basin provided information concerning the presence of a resinous flora in the Maracangalha Formation sediments during the Lower Cretaceous. (author)

  1. The Cretaceous Quiet Zone: How Quiet?

    Science.gov (United States)

    Gallet, Y.; Dyment, J.; Kitazawa, M.; Bouligand, C.; Hoise, E.; Kim, M.; Savary, J.; Royer, J.; Choi-Dyment, Y.; Gotab, B.

    2005-12-01

    Geomagnetic field intensity variations deduced from magnetostratigraphic data are mainly restricted to the past few million years. As a consequence, many important questions, such as the long-term evolution of the geomagnetic field intensity and the temporal distribution of excursions, remain unsolved yet. The possibility to recover these fluctuations over a long time interval from marine magnetic anomalies is therefore of particular interest. Within the period documented by these anomalies, the Cretaceous Normal Superchron (CNS) presents a major interest in geomagnetism as little is known on the characteristics of the geomagnetic field during this event, except that it apparently did not reverse for about 35 Myr. Cruise Magofond 3 of R/V Suroit (July-August 2005) was dedicated to the CNS, with a target area on the Cretaceous Quiet Zone off Western Africa, on the eastern flank of the Mid-Atlantic Ridge. Both sea-surface and deep tow magnetic anomaly profiles have been collected. Magnetic observatory data from M'Bour (Senegal) and Guimar (Canary Islands) have been regularly transmitted to the ship in order to check for any external magnetic field disturbance which may have affected the data. In addition, seismic reflection data were acquired to insure that the observed anomalies are not caused by the basement topography and, eventually, to estimate and correct such an effect. Altogether, these data brings new constraints on the variability of the geomagnetic field during the superchron. As a preliminary result, they show the occurrence of several consistent short-wavelength magnetic anomalies which may be linked either to short reversed polarity intervals or to excursions. In particular, the ISEA reversed polarity subchron at the beginning of the CNS seems to be present in most profiles. Other observed anomalies may also depict subchrons and would therefore challenge the concept of a non-reversing geodynamo during the exceptionally long CNS.

  2. Cretaceous choristoderan reptiles gave birth to live young

    Science.gov (United States)

    Ji, Qiang; Wu, Xiao-Chun; Cheng, Yen-Nien

    2010-04-01

    Viviparity (giving birth to live young) in fossil reptiles has been known only in a few marine groups: ichthyosaurs, pachypleurosaurs, and mosasaurs. Here, we report a pregnant specimen of the Early Cretaceous Hyphalosaurus baitaigouensis, a species of Choristodera, a diapsid group known from unequivocal fossil remains from the Middle Jurassic to the early Miocene (about 165 to 20 million years ago). This specimen provides the first evidence of viviparity in choristoderan reptiles and is also the sole record of viviparity in fossil reptiles which lived in freshwater ecosystems. This exquisitely preserved specimen contains up to 18 embryos arranged in pairs. Size comparison with small free-living individuals and the straight posture of the posterior-most pair suggest that those embryos were at term and had probably reached parturition. The posterior-most embryo on the left side has the head positioned toward the rear, contrary to normal position, suggesting a complication that may have contributed to the mother’s death. Viviparity would certainly have freed species of Hyphalosaurus from the need to return to land to deposit eggs; taking this advantage, they would have avoided intense competition with contemporaneous terrestrial carnivores such as dinosaurs.

  3. Detrital Zircon Geochronology of Cretaceous and Paleogene Strata Across the South-Central Alaskan Convergent Margin

    Science.gov (United States)

    Bradley, Dwight; Haeussler, Peter; O'Sullivan, Paul; Friedman, Rich; Till, Alison; Bradley, Dan; Trop, Jeff

    2009-01-01

    Ages of detrital zircons are reported from ten samples of Lower Cretaceous to Paleogene metasandstones and sandstones from the Chugach Mountains, Talkeetna Mountains, and western Alaska Range of south-central Alaska. Zircon ages are also reported from three igneous clasts from two conglomerates. The results bear on the regional geology, stratigraphy, tectonics, and mineral resource potential of the southern Alaska convergent margin. Chugach Mountains - The first detrital zircon data are reported here from the two main components of the Chugach accretionary complex - the inboard McHugh Complex and the outboard Valdez Group. Detrital zircons from sandstone and two conglomerate clasts of diorite were dated from the McHugh Complex near Anchorage. This now stands as the youngest known part of the McHugh Complex, with an inferred Turonian (Late Cretaceous) depositional age no older than 91-93 Ma. The zircon population has probability density peaks at 93 and 104 Ma and a smattering of Early Cretaceous and Jurassic grains, with nothing older than 191 Ma. The two diorite clasts yielded Jurassic U-Pb zircon ages of 179 and 181 Ma. Together, these findings suggest a Mesozoic arc as primary zircon source, the closest and most likely candidate being the Wrangellia composite terrane. The detrital zircon sample from the Valdez Group contains zircons as young as 69 and 77 Ma, consistent with the previously assigned Maastrichtian to Campanian (Late Cretaceous) depositional age. The zircon population has peaks at 78, 91, 148, and 163 Ma, minor peaks at 129, 177, 330, and 352 Ma, and no concordant zircons older than Devonian. A granite clast from a Valdez Group conglomerate yielded a Triassic U-Pb zircon age of 221 Ma. Like the McHugh Complex, the Valdez Group appears to have been derived almost entirely from Mesozoic arc sources, but a few Precambrian zircons are also present. Talkeetna Mountains - Detrital zircons ages were obtained from southernmost metasedimentary rocks of the

  4. Neurocranial osteology and neuroanatomy of a late Cretaceous titanosaurian sauropod from Spain (Ampelosaurus sp..

    Directory of Open Access Journals (Sweden)

    Fabien Knoll

    Full Text Available Titanosaurians were a flourishing group of sauropod dinosaurs during Cretaceous times. Fossils of titanosaurians have been found on all continents and their remains are abundant in a number of Late Cretaceous sites. Nonetheless, the cranial anatomy of titanosaurians is still very poorly known. The Spanish latest Cretaceous locality of "Lo Hueco" yielded a relatively well preserved, titanosaurian braincase, which shares a number of phylogenetically restricted characters with Ampelosaurus atacis from France such as a flat occipital region. However, it appears to differ from A. atacis in some traits such as the greater degree of dorsoventral compression and the presence of proatlas facets. The specimen is, therefore, provisionally identified as Ampelosaurus sp. It was CT scanned, and 3D renderings of the cranial endocast and inner-ear system were generated. Our investigation highlights that, although titanosaurs were derived sauropods with a successful evolutionary history, they present a remarkably modest level of paleoneurological organization. Compared with the condition in the basal titanosauriform Giraffatitan brancai, the labyrinth of Ampelosaurus sp. shows a reduced morphology. The latter feature is possibly related to a restricted range of head-turning movements.

  5. Neurocranial Osteology and Neuroanatomy of a Late Cretaceous Titanosaurian Sauropod from Spain (Ampelosaurus sp.)

    Science.gov (United States)

    Knoll, Fabien; Ridgely, Ryan C.; Ortega, Francisco; Sanz, Jose Luis; Witmer, Lawrence M.

    2013-01-01

    Titanosaurians were a flourishing group of sauropod dinosaurs during Cretaceous times. Fossils of titanosaurians have been found on all continents and their remains are abundant in a number of Late Cretaceous sites. Nonetheless, the cranial anatomy of titanosaurians is still very poorly known. The Spanish latest Cretaceous locality of “Lo Hueco” yielded a relatively well preserved, titanosaurian braincase, which shares a number of phylogenetically restricted characters with Ampelosaurus atacis from France such as a flat occipital region. However, it appears to differ from A. atacis in some traits such as the greater degree of dorsoventral compression and the presence of proatlas facets. The specimen is, therefore, provisionally identified as Ampelosaurus sp. It was CT scanned, and 3D renderings of the cranial endocast and inner-ear system were generated. Our investigation highlights that, although titanosaurs were derived sauropods with a successful evolutionary history, they present a remarkably modest level of paleoneurological organization. Compared with the condition in the basal titanosauriform Giraffatitan brancai, the labyrinth of Ampelosaurus sp. shows a reduced morphology. The latter feature is possibly related to a restricted range of head-turning movements. PMID:23355905

  6. Cretaceous/Paleogene floral turnover in Patagonia: drop in diversity, low extinction, and a Classopollis spike.

    Directory of Open Access Journals (Sweden)

    Viviana D Barreda

    Full Text Available Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.

  7. Letter. Late cretaceous seasonal ocean variability from the arctic

    OpenAIRE

    Davies, Andrew; Kemp, Alan E.S.; Pike, Jennifer

    2009-01-01

    The modern Arctic Ocean is regarded as barometer of global change and amplifier of global warming1 and therefore records of past Arctic change are of a premium for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the late Cretaceous, yet records from such times may yield important clues to its future behaviour given current global warming trends. Here we present the first seasonally resolved sedimentary record from the Cretaceous from...

  8. Evidence for global cooling in the Late Cretaceous

    OpenAIRE

    Linnert, C.; Robinson, S.A.; J.A. Lees; Bown, P.R.; I. Pérez-Rodríguez; Petrizzo, M.R.; F. Falzoni; Littler, K; Arz, J.A.; Russell, E. E.

    2014-01-01

    The Late Cretaceous ‘greenhouse’ world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the Campanian–Maastrichtian int...

  9. Palaeoenvironmental and climatic changes in Australia during the early Cretaceous

    OpenAIRE

    Oosting, Antje Margriet

    2004-01-01

    Biochronostratigraphy for the Tethyan and Boreal mid-Cretaceous (Barremian-Albian) is traditionally based on ammonites. Because of the lack of useful ammonites in the Australian mid-Cretaceous, and the existence of strong faunal and floral latitudinal contrasts, to date chronostratigraphic correlation between the different realms is not straightforward. In the present study dinoflagellate cyst events (first and last occurrences) combined with changes in organic-carbon-isotope (δ13Corg) strati...

  10. Corals from the Upper Cretaceous (Maastrichtian) Ocozocoautla Formation, Chiapas, Mexico

    OpenAIRE

    Filkorn, Harry F.; Javier Avendaño Gil; Marco A. Coutiño José; Francisco J. Vega Vera

    2005-01-01

    The coral species from the Upper Cretaceous (Maastrichtian) strata of the Ocozocoautla Formation in Chiapas, Mexico, are identified, described and illustrated for the first time. This coral fauna is composed of 12 species, nine of which are colonial, presumably zooxanthellate, reef-building forms. This is the first time that six of these species have been reported from Mexico. The majority (11) of these species are endemic to the Caribbean region and known only from the Late Cretaceous.

  11. The Cretaceous Tetori biota in Japan and its evolutionary significance for terrestrial ecosystems in Asia

    Science.gov (United States)

    Matsukawa, M.; Ito, M.; Nishida, N.; Koarai, K.; Lockley, M.G.; Nichols, D.J.

    2006-01-01

    Cretaceous nonmarine deposits are widely distributed on the Asian continent and include various kinds of zoo- and phyto-assemblages. The Tetori Group is one of the most important Mesozoic terrestrial deposits in East Asia, and for this reason its geology, stratigraphy, and biota have been studied intensively by our group for more than a decade. We present the main results herein. We confirm that formations as lithostratigraphic units are the best geological correlation tools for the Tetori Group and the best tools for a geological mapping of the group. Although subgroups have previously been used for correlation, proper designation and evaluation of subgroups is required if they are to be used effectively, and we show that previous geological correlation of the Tetori Group has been confused by inappropriate definition of these subgroups. We located fossil localities including reported zoo- and phyto-assemblages in the framework of formations correlated by our stratigraphy. The occurrence of zoo-assemblages was probably controlled by environments (i.e., most are in situ), but phyto-assemblages were mostly transported and rapidly buried by high-energy river systems. Although two distinct dinosaur faunas and four floras have been named for the zoo- and phyto-assemblages in the Tetori Group, in reality there is only one Tetori Dinosaur Fauna and one Tetori Flora, as proved by careful correlation. Two types of zoo-assemblages co-occur in the Tetori Group: vertebrate species whose ancestors flourished in the Jurassic (as found in China), and their descendants from the Late Cretaceous. As the latter modern type of assemblage is more abundant than the former, changeable environments at the continental margin probably accelerated evolution of more modern species. We can employ nonmarine molluscan species as geological correlation tools in some cases, i.e., when their taxon ranges are well-confirmed by independent evidence. However, because freshwater molluscan species and

  12. Late Cretaceous Volcaniclastics in NW Turkey

    Science.gov (United States)

    Boehm, Katharina; Wolfgring, Erik; Omer Yilmaz, Ismail; Tüysüz, Okan; Wagreich, Michael

    2015-04-01

    On the southwestern coast of the Black Sea, in the western Pontides Upper Cretaceous tuff layers are present. The tuffs are intercalated with limestones, marls and turbidites and were investigated with focus on their geochemistry, to get new insights to the arrangement of terranes and ocean basins at this time. In the region two Upper Cretaceous volcanic units can be distinguished, separated by distinct red pelagic limestone successions, belonging to the Unaz Formation. The lower volcanic unit is named Dereköy Formation and is Turonian to Santonian in age. It is thought to be deposited within extension structures, contemporaneously with rifting in the western Black Sea basin. The upper volcanic unit is called Cambu Formation. According to biostratigraphic data it is deposited throughout Campanian, when spreading in the western Black Sea basin started. Interpreted as submarine deposits, element mobility has to be taken into account when interpreting geochemical ICP-MS data of the volcaniclastics. Multiple discrimination diagrams with suitable proxies elucidate the type of volcanism and contribute to reconstruction of the tectonic setting. The classified rock types range from basaltic to rhyodacitic in both volcanic formations. Basically degree of differentiation and alkalinity are the parameters looked at, when determining rock types of the volcanic eruption. Further volcanic series are specified as calc-alkaline to shoshonitic. Moreover, a volcanic arc setting seems to be the most likely case, following several discrimination diagrams, as well as normalized multi-element plots. This tectonic setting can be discussed in connection with paleo-tectonic reconstructions. Most cited in literature nowadays are models favoring a northward subduction of the northern branch of Neotethys, creating an extensional setting north of the Pontides. This kind of back arc extension is interpreted as the reason of a southward drift of the Istanbul continental fragment from Eurasia

  13. Groundwater from Lower Cretaceous rocks in Kansas

    Science.gov (United States)

    Keene, Katherine M.; Bayne, Charles Knight

    1976-01-01

    Sandstones in Lower Cretaceous rocks contain supplies, of water that may be adequate to meet increasing present and future demands for supplemental municipal and domestic use in central and western Kansas. An estimated 70 to 80 million acre-feet (86,000 to 99,000 cubic hectometers) of water containing less than 1,000 milligrams per liter dissolved solids may be acceptable for use at the present (1976). An additional 10 to 15 million acre-feet (12,000 to 18,000 cubic hectometers) containing 1,000 to 3,000 milligrams per liter dissolved solids is estimated to be available for use in the future with appropriate desalinization. Lower Cretaceous rocks crop out from Washington County on the north to Comanche County on-the south. The rocks dip from a structural high in the southwest part of the State to structural lows in the northwest and north-central part. Depth below land surface increases generally northwestward to about 2,600 feet (790 meters); thickness of the rocks increases westward, nearly zero to about 850 feet (260 meters). The rocks consist chiefly of marine to nonmarine shale and silt- stone interbedded with coastal to deltaic sandstone. The interbedded sandstone, which composes about one-third of the rocks, consists of one or more lenses that thicken westward to about 400 feet (120 meters) in the central part of western Kansas. The yield of water to individual wells is related to areal extent, thickness, and interconnection of the sand lenses and to grain size and cementation of the sand. Large amounts of water may be pumped by wells where loosely cemented sand lenses are interconnected. Wells commonly yield adequate supplies for domestic and stock use; reported yields from municipal and irrigation wells range from about 100 to 2,000 gallons per minute (6 to 125 liters per second). Recharge to the Lower Cretaceous-rocks occurs in the area of outcrop and from hydraulically connected saturated Cenozoic rocks, especially in the southern part of the State

  14. 40Ar/39Ar dating of the Late Cretaceous

    International Nuclear Information System (INIS)

    . Finally, using advances with terrestrial carbon isotope and planktonic foraminifera records within central Hokkaido, Northwest Pacific, sections from the Cretaceous Yezo group were correlated to that of European and North American counterparts. Datable ash layers throughout the Kotanbetsu and Shumarinai section were analysed using both 40Ar/39Ar and U-Pb methods. We successfully dated two ash tuff layers falling either side of the Turonian - Coniacian boundary, yielding an age range for the boundary between 89.31 ± 0.11 Ma and 89.57 ± 0.11 Ma or a boundary age of 89.44 ± 0.24 Ma. Combining these U-Pb ages with recent published ages we are able to reduce the age limit once more and propose an age for the Turonian - Coniacian boundary as 89.62 ± 0.04 Ma. (author)

  15. Fleas (Siphonaptera) are Cretaceous, and evolved with Theria.

    Science.gov (United States)

    Zhu, Qiyun; Hastriter, Michael W; Whiting, Michael F; Dittmar, Katharina

    2015-09-01

    Fleas (order Siphonaptera) are highly-specialized, diverse blood-feeding ectoparasites of mammals and birds with an enigmatic evolutionary history and obscure origin. We here present a molecular phylogenetic study based on a comprehensive taxon sampling of 259 flea taxa, representing 16 of the 18 extant families of this order. A Bayesian phylogenetic tree with strong nodal support was recovered, consisting of seven sequentially derived lineages with Macropsyllidae as the earliest divergence, followed by Stephanocircidae. Divergence times of flea lineages were estimated based on fossil records and host specific associations to bats (Chiroptera), suggesting that the common ancestor of extant Siphonaptera diversified during the Cretaceous. However, most of the intraordinal divergence into extant lineages took place after the K-Pg boundary. Ancestral states of host association and biogeographical distribution were reconstructed, suggesting with high likelihood that fleas originated in the southern continents (Gondwana) and migrated from South America to their extant distributions in a relatively short time frame. Theria (placental mammals and marsupials) represent the most likely ancestral host group of extant Siphonaptera, with marsupials occupying a more important role than previously assumed. Major extant flea families evolved in connection to post K-Pg diversification of Placentalia. The association of fleas with monotremes and birds is likely due to later secondary host association. These results suggest caution in casually interpreting recently discovered Mesozoic fossil "dinosaur fleas" of Northeast Asia as part of what we currently consider Siphonaptera. PMID:25987528

  16. La extensa zona de deslizamientos de la escarpa oriental de la Pampa de Salamanca, Chubut, entre los 45°00´S y 45°45´S The extensive zone of slides on the eastern erosion scarp of Pampa de Salamanca, Chubut

    Directory of Open Access Journals (Sweden)

    E.F. González Díaz

    2004-12-01

    Full Text Available Durante la ejecución del mapa geomorfológico de la provincia del Chubut, se identificó entre las latitudes de los 45°00´S y 45°45´S y a lo largo de unos 70-75 km, una extensa faja de deslizamientos adyacente y prácticamente paralela a la escarpa oriental de la Pampa de Salamanca. Los deslizamientos, con marcado predominio de deslizamientos rotacionales, perturban el tramo superior de la secuencia sedimentaria terciaria. En los niveles arcillosos de la Formación Chenque (= Formación Patagonia, se localizarían las superficies de despegue o corte (shear para su ocurrencia. Diferencias entre sus rasgos morfológicos, tipológicos y el promotor sugerido permiten proponer cuatro zonas (I, II, III y IV de deslizamientos. La tipología aquí propuesta es provisoria, siendo sólo una base de futuras elaboraciones. Cronológicamente se diferenciaron dos conjuntos de deslizamientos: unos antiguos, más extensos y de mayor volumen, con marcadas evidencias de erosión y aquellos modernos, más reducidos, que con excelente conservación de su morfología primaria, son producto de posteriores removilizaciones acontecidas en sectores de los antiguos, que se expresan esencialmente bajo la forma de flujos (corrientes de tierra o earthflows y más ocasionalmente como deslizamientos rotacionales secundarios (slumps. Entre los de mayor edad, los de la zona I, son definidos como afines en general a un deslizamiento rotacional con una fase distal de flujo; ocasionalmente habrían superado los límites del actual acantilado marino. A pesar de esta primera apreciación, no se descarta su consideración como ejemplos de expansiones laterales (lateral spreads. Los de la zona II, son definidos como deslizamientos rotacionales múltiples retrogradantes. Aquellos de la zona III integran un conjunto de deslizamientos con un marcado control estructural (N50°E, en sus desprendimientos. La zona IV, compone una estrecha y continua faja adyacente a la Pampa de

  17. La materia orgánica particulada: comparación de métodos para su determinación y su valor como indicador de calidad de suelos del Chubut Particulate organic-matter: a comparison of methods for its determination and its role as an indicator of soil quality for some soils in the province of Chubut

    Directory of Open Access Journals (Sweden)

    Lina Sonia Videla

    2008-12-01

    Full Text Available La materia orgánica particulada (MOP es un componente dinámico del suelo, que responde selectiva y rápidamente a los cambios de manejo y distintos tipos de disturbios. El objetivo de este estudio fue comparar dos técnicas de determinación de MOP en distintos suelos y evaluar el potencial de esta variable como indicadora de calidad de los mismos. Se estudiaron tres sitios ecológicos de la provincia del Chubut con distinto manejo o afectados por distintos disturbios: Media Luna Clausura (ML C, Media Luna Pastoreo (ML P, Puerto Madryn bioperturbado (PM B, Puerto Madryn no bioperturbado (PM NB, Punta Ninfas no erosionado (PN NE y Punta Ninfas erosionado (PN E. En muestras de suelos extraídas de 0 a 5 cm (PM y PN y de 0 a 10 cm (ML de profundidad se determinó la materia orgánica total (MOT y la MOP por vía húmeda (MOPh (Método Walkley y Black y por ignición en mufla (MOPi a 430 °C. En los Molisoles de ML y en los Aridisoles de PM la MOPi fue mayor que la MOPh, mientras que para los Aridisoles de PN no se registraron diferencias significativas entre los dos métodos. Para los suelos con carbonatos (PM o con alofanos (ML, el método por ignición sobreestimó los contenidos de MOP. La MOT presentó una alta correlación con la MOPh y con la MOPi para todos los suelos en conjunto (r² = 0,89 y r² = 0,73, respectivamente. El suelo que presentó una mayor relación MOP/MOT fue PN NE. En contraste, el suelo PN E, mostró los valores más bajos para esta relación, lo que indicaría, por un lado, que la poca MO que contienen estos suelos está predominantemente asociada a la fracciónParticulate organic-matter (MOP is a dynamic soil component that quickly and selectively responds to management changes and to different disturbance regimes. We compared two techniques to determine the MOP content in different soils and assessed the potential of this variable as an indicator of soil quality. We studied the soils of three ecological sites located

  18. Estratigrafía, análisis de facies y paleoambientes de la formación cañadón asfalto en el depocentro jurásico cerro Cóndor, provincia del Chubut Stratigraphy, facies analysis and paleoenvironments of the Cañadón Asfalto Formation, Jurassic Cerro Cóndor depocenter, Chubut province

    Directory of Open Access Journals (Sweden)

    Nora Cabaleri

    2010-05-01

    Full Text Available El depocentro Cerro Cóndor representa la secuencia estratigráfica del Jurásico continental más completa de la cuenca de Cañadón Asfalto y de Sudamérica austral. Se sitúa en la Patagonia extraandina, en ambas márgenes del río Chubut medio. La sedimentación en esta cuenca pull apart, acompañada por efusiones de basalto olivínico, comenzó en el Jurásico Medio temprano. Predominan en la Formación Cañadón Asfalto los depósitos lacustres caracterizados por asociaciones de facies carbonáticas y siliciclásticas intercaladas con rocas lávicas en la base y depósitos piroclásticos hacia el techo de la unidad. Se describe el desarrollo de facies a lo largo de un corte norte-sur que abarca las secciones de estancia El Torito y de los cañadones Los Loros, Las Chacritas, Carrizal, Asfalto y Lahuincó. Las facies/microfacies carbonáticas están representadas por mudstones, wackestones,packstones, grainstones y calizas microbialíticas características de ambientes litorales, marginales y palustres. En la Formación Cañadón Asfalto se distinguen un miembro inferior (Las Chacritas, constituido por calizas, lutitas, areniscas y conglomerados, intercalados con basaltos olivínicos y por otro superior (Puesto Almada compuesto por tobas, tufitas, lutitas y areniscas. El primero es portador de una asociación palinológica de edad bajociano-bathoniana y el segundo de dinosaurios de edad tithoniana. Se describen detalladamente e ilustran las secciones estratigráficas de ambos miembros de la formación en sus localidades tipo, cañadón Las Chacritas y estancia el Torito y se reconstruyen los paleoambientes del depocentro desde el Aaleniano al Tithoniano. La edad del miembro Puesto Almada en su localidad tipo se obtuvo mediante una datación radimétrica (K/Ar de biotitas provenientes de una delgada capa de toba volcánica (147,1 ± 3,3 Ma, Tithoniano proveniente de la parte superior de la unidad.The Cerro Cóndor depocenter represents the

  19. Proxy data constraints on Cretaceous sea surface temperature evolution

    Science.gov (United States)

    O'Brien, Charlotte L.; Robinson, Stuart A.; O'Connor, Lauren K.; Pancost, Richard D.

    2015-04-01

    It is well established that greenhouse conditions prevailed during the Cretaceous. However, constraining the exact nature of the greenhouse gas forcing, climatic warming and climate sensitivity remains an ongoing topic of research. Proxy temperature data provide valuable observational constraints on Cretaceous climate. In particular, much of our understanding of Cretaceous climate warmth comes from marine temperature proxy data reconstructions derived using planktic foraminiferal oxygen isotope (δ18O) palaeothermometry and, more recently, the TEX86 proxy, based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids (GDGTs). Both of these proxies provide estimates of sea surface temperature (SST), however each technique is subject to a number of proxy-specific caveats. For example, δ18O values in planktic foraminifer may be compromised by preservation and/or diagenetic alteration, while the TEX86 proxy has undergone several temperature calibration re-evaluations and the exact mechanism that relates GDGT production to SST is not fully understood. Here we synthesise and reinterpret available TEX86- and δ18O-SST proxy data for the entire Cretaceous. For the TEX86 data, where possible we re-evaluate the fractional abundance of all individual GDGTs. By utilising fractional GDGT abundances we are also able to compute methane indices and branched and isoprenoid tetraether (BIT) indices, as well as apply both the TEX86H and TEX86L temperature calibrations. For each of the two SST proxy techniques, TEX86 and δ18O, we apply consistent temperature calibrations and place all data on a common timescale. Our new data-based SST synthesis allows us to examine long term temperature trends in the Cretaceous, including latitudinal temperature gradient variations, and evaluate global versus regional temperature patterns. Through considering both TEX86 and planktic foraminiferal δ18O data we critically compare the application of these two techniques

  20. Microspectroscopic evidence of cretaceous bone proteins.

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    Johan Lindgren

    Full Text Available Low concentrations of the structural protein collagen have recently been reported in dinosaur fossils based primarily on mass spectrometric analyses of whole bone extracts. However, direct spectroscopic characterization of isolated fibrous bone tissues, a crucial test of hypotheses of biomolecular preservation over deep time, has not been performed. Here, we demonstrate that endogenous proteinaceous molecules are retained in a humerus from a Late Cretaceous mosasaur (an extinct giant marine lizard. In situ immunofluorescence of demineralized bone extracts shows reactivity to antibodies raised against type I collagen, and amino acid analyses of soluble proteins extracted from the bone exhibit a composition indicative of structural proteins or their breakdown products. These data are corroborated by synchrotron radiation-based infrared microspectroscopic studies demonstrating that amino acid containing matter is located in bone matrix fibrils that express imprints of the characteristic 67 nm D-periodicity typical of collagen. Moreover, the fibrils differ significantly in spectral signature from those of potential modern bacterial contaminants, such as biofilms and collagen-like proteins. Thus, the preservation of primary soft tissues and biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.

  1. Paleointensity of the geomagnetic field in the Cretaceous (from Cretaceous rocks of Mongolia)

    Science.gov (United States)

    Shcherbakova, V. V.; Kovalenko, D. V.; Shcherbakov, V. P.; Zhidkov, G. V.

    2011-09-01

    A representative collection of Cretaceous rocks of Mongolia is used for the study of the magnetic properties of the rocks and for determination of the paleodirections and paleointensities H anc of the geomagnetic field. The characteristic NRM component in the samples is recognized in the temperature interval from 200 to 620-660°C. The values of H anc are determined by the Thellier-Coe method with observance of all present-day requirements regarding the reliability of such kind of results. Comparison of data in the literature on paleointensity in the Cretaceous superchron and in the Miocene supports the hypothesis of the inverse correlation between the average intensity of the paleofield and the frequency of geomagnetic reversals. The increase in the average intensities is accompanied by an appreciable increase in the variance of the virtual dipole moment (VDM). We suggest that the visible increase in the average VDM value in the superchron is due to the greater variability of VDM in this period compared to the Miocene.

  2. On a New Genus of Basal Neoceratopsian Dinosaur from the Early Cretaceous of Gansu Province, China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A new genus and species of basal neoceratopsian dinosaur, Auroraceratops rugosus, is reported based on material from the Early Cretaceous Xinminpu Group in the Gongpoquan Basin of Gansu Province, China. Auroraceratops is represented by a nearly complete skull and low jaws, and different greatly from all other neoceratopsians by its considerable breadth of the nasals, fungiform expansion of the dorsal end of the lacrimal, highly developed rugosity of the jugal, dentary and surangular, and inflated, striated premaxillary teeth. The finding of Auroraceratops adds diversity and helps elucidate the evolution of basal neoceratopsian dinosaurs.

  3. The Cretaceous Fossil Burmaculex antiquus Confirmed as the Earliest Known Lineage of Mosquitoes (Diptera: Culicidae).

    Science.gov (United States)

    Borkent, Art; Grimaldi, David A

    2016-01-01

    A second female of mid-Cretaceous Burmaculex antiquus Borkent & Grimaldi, preserved in 99 myo Burmese amber, and the oldest known member of the Culicidae, is described in detail. Although generally opaque and distorted, some character states are added or refined. The discovery of well-developed scales on the legs shows that this feature must now be considered a synapomorphy of both the fossil and all extant members of the family. Previously described synapomorphies and further interpretation here confirm the phylogenetic position of this fossil as the sister group to extant and all known fossil Culicidae. It is placed in the new subfamily Burmaculicinae.

  4. Structural extremes in a cretaceous dinosaur.

    Science.gov (United States)

    Sereno, Paul C; Wilson, Jeffrey A; Witmer, Lawrence M; Whitlock, John A; Maga, Abdoulaye; Ide, Oumarou; Rowe, Timothy A

    2007-11-21

    Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic.

  5. Structural extremes in a cretaceous dinosaur.

    Directory of Open Access Journals (Sweden)

    Paul C Sereno

    Full Text Available Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic.

  6. El caso del Outburst Flood histórico de la laguna Derrumbe, Cholila, Chubut: Colapso de dique Morénico en la Cordillera Norpatagónica

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    Bruno Colavitto

    2012-09-01

    Full Text Available La laguna Derrumbe es un cuerpo de agua ubicado en los Andes Norpatagónicos en la provincia de Chubut, Argentina. Está contenida en un circo glaciario y endicada por una morena frontal del glaciar homónimo. A través del reconocimiento de campo se pudo describir a esta laguna y a un importante depósito rocoso que se halla aguas abajo de la misma, interpretado como un depósito de outburst flood. Estos depósitos son generados por procesos de alta energía relacionados con la rotura de un dique natural, en este caso un dique morénico. El estudio realizado permitió concluir que la morena frontal del glaciar Derrumbe sufrió una rotura parcial en tiempos históricos, desatando así una inundación súbita aguas abajo de la laguna, a través del valle del río Tigre, en la localidad de Cholila. En este trabajo se analizaron las posibles causas que dieron lugar a la rotura, la cual probablemente sea producto del rápido retroceso que el glaciar experimentó durante la década del ´50 y principios del ´60. Retroceso comparable con el ocurrido en muchos de los cuerpos glaciares de los Andes Patagónicos durante el último siglo.

  7. High diversity in cretaceous ichthyosaurs from Europe prior to their extinction.

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    Valentin Fischer

    Full Text Available BACKGROUND: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic-Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and 'greensands' deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early-Late Cretaceous boundary. METHODOLOGY/PRINCIPAL FINDINGS: To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France; a revised taxonomic scheme is proposed. We recognize the following taxa in the 'greensands': the platypterygiines 'Platypterygius' sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa. CONCLUSION/SIGNIFICANCE: Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian

  8. Radioactivity and uranium content of some Cretaceous shales, central Great Plains

    Science.gov (United States)

    Tourtelot, Harry A.

    1955-01-01

    The Sharon Springs member of the Pierre shale of Cretaceous age, a hard black organic-rich shale similar to the Chattanooga shale, is radioactive throughout central and western South Dakota, most of Nebraska, northern Kansas, and northeastern Colorado. In the Missouri River valley, thin beds of the shale contain as much as 0.01 percent uranium. Beds as much as 20 feet thick or more have a radioactivity of about 0.01 percent equivalent uranium in southwestern Nebraska according to interpretation of gamma-ray well logs. The radioactivity and uranium content is highest in the Missouri River valley in South Dakota and in southwestern Nebraska where the shale rests disconformably on the underlying Niobrara formation of Cretaceous age. Near the Black Hills, and in the area to the north, the shale of the Sharon Springs member rests on a wedge of the Gammon ferruginous member of the Pierre, which is represented by a disonformity to the east and south, and the radioactivity of the shale is low although greater than that of over-lying strata. The shale also contains a suite of trace elements in which arsenic, boron, chromium, copper, molybdenum, nickel, selenium, and vanadium are conspicuous. Molybdenum and tin are less abundant in the Sharon Springs than in similar shales of Palezoic age and silver and selenium are more abundant. In the Great Plains region, the upper 30-50 feet of Cretaceous shales overlain unconformably by the White River group of Oligocene age has been altered to bright-colored material. This altered zone is chiefly the result of pre-Oligocene weathering although post-Oligocene ground water conditions also have affected the zone. The greatest radioactivity occurs in masses of unaltered shale measuring about 1 x 4 feet in cross section included in the lower part of the altered zone. Where the zone is developed on shale and marl of the Niobrara formation, parts of the included unaltered shale contains as much as 0.1 percent equivalent uranium and 0

  9. A first record of Cretaceous aphids (Hemiptera, Sternorrhyncha, Aphidomorpha) in Australia, from the Lower Cretaceous Koonwarra Fossil Bed, Victoria.

    Science.gov (United States)

    Martin, Sarah K; Skidmore, Luke I; Stilwell, Jeffrey D

    2016-01-01

    This paper describes the first species of aphid from the Lower Cretaceous Koonwarra Fossil Bed of the Gippsland Basin, southeastern Victoria, Australia. This aphid, herein named Koonwarraphis rotundafrons gen. & sp. nov., is assigned to the cosmopolitan Cretaceous superfamily Tajmyraphidoidea, which has been previously described from the Lebanese, Taimyrian, Canadian, Myanmar (Burmese), and Spanish ambers. Koonwarraphis rotundafrons is the first aphid recorded from the eastern Gondwanan landmass during the Cretaceous, and represents the only tajmyraphidoid preserved as a compression fossil, rather than as an amber inclusion. Due to the nature of the fossil's preservation, Koonwarraphis cannot be firmly placed in any of the described tajmyraphidoid families; however, all observable morphological features suggest that the genus is broadly typical of the superfamily and Cretaceous aphids in general. Koonwarraphis' shortened rostrum, a feature also seen in other tajmyraphidoids, suggests an association with the more herbaceous aspects of the Early Cretaceous Victorian flora. Considering the modern aphid preference for angiosperm plants, it is possible that this aphid was living upon the herbaceous early angiosperms recorded previously from the Koonwarra macrofloral assemblage. PMID:27395744

  10. More stable yet bimodal geodynamo during the Cretaceous superchron?

    Science.gov (United States)

    Lhuillier, Florian; Gilder, Stuart A.; Wack, Michael; He, Kuang; Petersen, Nikolai; Singer, Brad S.; Jicha, Brian R.; Schaen, Allen J.; Colon, Dylan

    2016-06-01

    We report palaeomagnetic and 40Ar/39Ar dating results from two sequences of basaltic lava flows deposited at the same locality in western China, yet separated in time by ~50 Myr: one set lies within the Cretaceous normal superchron at 112-115 Ma and a second at 59-70 Ma spanning the Cretaceous-Palaeogene boundary. We find that magnetic field directions during the superchron exhibit bimodal populations: one with inclinations representative of a dipolar field and another with shallow inclinations that could reflect a more complex, multipolar field. However, the time-dependent variability in field directions was 50% lower during the superchron than after, which implies greater field stability during the superchron. Our results suggest that episodes of less dipolar field behavior occurred within the Cretaceous superchron and raise the question whether a second, more multipolar, field state is more persistent than previously thought.

  11. Molecular fossils in Cretaceous condensate from western India

    Indian Academy of Sciences (India)

    Sharmila Bhattacharya; Suryendu Dutta; Ratul Dutta

    2014-07-01

    The present study reports the biomarker distribution of condensate belonging to the early Cretaceous time frame using gas chromatography-mass spectrometry (GC–MS). The early Cretaceous palaeoenvironment was inscribed into these molecular fossils which reflected the source and conditions of deposition of the condensate. The saturate fraction of the condensate is characterized by normal alkanes ranging from -C9 to -C29} (CPI-1.13), cycloalkanes and C14 and C15 sesquiterpanes. The aromatic fraction comprises of naphthalene, phenanthrene, their methylated derivatives and cyclohexylbenzenes. Isohexylalkylnaphthalenes, a product of rearrangement process of terpenoids, is detected in the condensate. Several aromatic sesquiterpenoids and diterpenoids have been recorded. Dihydro-ar-curcumene, cadalene and ionene form the assemblage of sesquiterpenoids which are indicative of higher plant input. Aromatic diterpenoid fraction comprises of simonellite and retene. These compounds are also indicative of higher plants, particularly conifer source which had been a predominant flora during the Cretaceous time.

  12. Molecular fossils in Cretaceous condensate from western India

    Science.gov (United States)

    Bhattacharya, Sharmila; Dutta, Suryendu; Dutta, Ratul

    2014-06-01

    The present study reports the biomarker distribution of condensate belonging to the early Cretaceous time frame using gas chromatography-mass spectrometry (GC-MS). The early Cretaceous palaeoenvironment was inscribed into these molecular fossils which reflected the source and conditions of deposition of the condensate. The saturate fraction of the condensate is characterized by normal alkanes ranging from n-C9 to n-C29 (CPI-1.13), cycloalkanes and C14 and C15 sesquiterpanes. The aromatic fraction comprises of naphthalene, phenanthrene, their methylated derivatives and cyclohexylbenzenes. Isohexylalkylnaphthalenes, a product of rearrangement process of terpenoids, is detected in the condensate. Several aromatic sesquiterpenoids and diterpenoids have been recorded. Dihydro- ar-curcumene, cadalene and ionene form the assemblage of sesquiterpenoids which are indicative of higher plant input. Aromatic diterpenoid fraction comprises of simonellite and retene. These compounds are also indicative of higher plants, particularly conifer source which had been a predominant flora during the Cretaceous time.

  13. New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs

    Science.gov (United States)

    Brusatte, Stephen L.; Averianov, Alexander; Sues, Hans-Dieter; Muir, Amy; Butler, Ian B.

    2016-03-01

    Tyrannosaurids-the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus-were the apex predators in continental ecosystems in Asia and North America during the latest Cretaceous (ca. 80-66 million years ago). Their colossal sizes and keen senses are considered key to their evolutionary and ecological success, but little is known about how these features developed as tyrannosaurids evolved from smaller basal tyrannosauroids that first appeared in the fossil record in the Middle Jurassic (ca. 170 million years ago). This is largely because of a frustrating 20+ million-year gap in the mid-Cretaceous fossil record, when tyrannosauroids transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known. We describe the first distinct tyrannosauroid species from this gap, based on a highly derived braincase and a variety of other skeletal elements from the Turonian (ca. 90-92 million years ago) of Uzbekistan. This taxon is phylogenetically intermediate between the oldest basal tyrannosauroids and the latest Cretaceous forms. It had yet to develop the giant size and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Cretaceous species. Tyrannosauroids apparently developed huge size rapidly during the latest Cretaceous, and their success in the top predator role may have been enabled by their brain and keen senses that first evolved at smaller body size.

  14. Cretaceous Oceanic Red Beds: Distribution, Lithostratigraphy and Paleoenvironments

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Cretaceous oceanic red beds (CORBs) represented by red shales and marls, were deposited during the Cretaceous and early Paleocene, predominantly in the Tethyan realm, in lower slope and abyssal basin environments. Detailed studies of CORBs are rare; therefore, we compiled CORBs data from deep sea ocean drilling cores and outcrops of Cretaceous rocks subaerially exposed in southern Europe, northwestern Germany, Asia and New Zealand. In the Tethyan realm, CORBs mainly consist of reddish or pink shales, limestones and marlstones. By contrast, marlstones and chalks are rare in deep-ocean drilling cores. Upper Cretaceous marine sediments in cores from the Atlantic Ocean are predominantly various shades of brown, reddish brown, yellowish brown and pale brown in color. A few red, pink, yellow and orange Cretaceous sediments are also present. The commonest age of CORBs is early Campanian to Maastrichtian, with the onset mostly of oxic deposition often after Oceanic Anoxic Events (OAEs), during the early Aptian, late Albian-early Turonian and Campanian.This suggests an indicated and previously not recognized relationship between OAEs, black shales deposition and CORBs. CORBs even though globally distributed, are most common in the North Atlantic and Tethyan realms, in low to mid latitudes of the northern hemisphere; in the South Atlantic and Indian Ocean in the mid to high latitudes of the southern hemisphere; and are less frequent in the central Pacific Ocean. Their widespread occurrence during the late Cretaceous might have been the result of establishing a connection for deep oceanic current circulation between the Pacific and the evolving connection between South and North Atlantic and changes in oceanic basins ventilation.

  15. Plant macrofossils of the upper Cretaceous Kaitangata coalfield, New Zealand

    Energy Technology Data Exchange (ETDEWEB)

    Pole, M.; Douglas, B. [University of Queensland, Brisbane, Qld. (Australia). Dept. of Botany

    1999-08-15

    Uppermost Cretaceous sediments from the Cretaceous Kaitangata Coal Mine and the Wangaloa coast (south of Dunedin, New Zealand) were investigated for dispersed plant macrofossils. The gymnosperms include two cycads (Macrozamia sp. and Pterostoma sp.), Ginkgo sp., three further possible ginkgophyte taxa, and ten conifer taxa. The conifers include two new conifer genera and species, Maikuku stephaniae and Ware riderensis, which are placed in the Taxodiaceae s.l. There are also 13 types of angiosperm cuticle. Sample heterogeneity as regards taxa present and their abundance suggests taxonomic heterogeneity in the original vegetation.

  16. Marine reptiles from the Late Cretaceous of northern Patagonia

    Science.gov (United States)

    Gasparini, Z.; Casadio, S.; Fernández, M.; Salgado, L.

    2001-04-01

    During the Campanian-Maastrichtian, Patagonia was flooded by the Atlantic and reduced to an archipelago. Several localities of northern Patagonia have yielded marine reptiles. Analysis of several assemblages suggests that the diversity and abundance of pelagic marine reptiles in northern Patagonia was higher by the end of the Cretaceous than previously thought. Several plesiosaurids, including Aristonectes parvidens and the polycotylid Sulcusuchus, and the first remains of mosasaurinae have been found. The Cretaceous marine reptile record from South America is scanty. Nevertheless, materials described here suggest that Tethyan and Weddelian forms converged in northern Patagonia, as seen with invertebrates.

  17. Marine carbon cycling following end Cretaceous extinction

    Science.gov (United States)

    Ridgwell, Andy; Thomas, Ellen; Alegret, Laia; Schmidt, Daniela

    2010-05-01

    Knowing how the transport of particulate organic carbon and associated nutrients into the ocean interior is controlled, is a prerequisite to reliable predictions of future changes in marine carbon cycling as the circulation and carbonate chemistry of the oceans are perturbed. Multiple mechanisms for particulate organic carbon transport have been proposed, most commonly based on sediment trap observations. Yet these observations primarily provide evidence for correlations between fluxes rather than being able to pin-point any particular mechanism. Despite this, global models tend to adopt one or other mechanism (e.g., ballasting) without independent justification. The geological record may help, as the evolution of pelagic ecosystems through the Phanerozoic has seen the emergence of animals (faecal pellets) and silicification and calcification of planktic organisms (ballasting), with evolutionary innovation fundamentally altering the nature of the oceanic biological pump. Moreover, catastrophic and transitory events, in which pelagic ecosystems were temporary disrupted, altering and biological pumping mechanisms, produced a tell-tale marine geochemical signature than may help elucidate the working of the biological pump. Here we focus on the bolide impact at the Cretaceous-Palaeogene boundary as it induced an enigmatic ‘collapse' in surface-to-deep carbon isotope (d13C) gradients, previously interpreted as representing a complete cessation of biological productivity and/or carbon pumping. Contemporaneous with this was a pronounced extinction of planktic calcifiers, resulting in an order of magnitude reduction in carbonate burial in deep-sea sediments. On face value, no (or little) carbonate ballasting and only a minor possible importance for dust together with ceased organic carbon transport to depth, is consistent with the existence of a dominant (carbonate) mineral ballasting mechanism prior to the event. However, a collapsed surface-to-deep d13C gradient does

  18. Double fossilization in eukaryotic microorganisms from Lower Cretaceous amber

    Directory of Open Access Journals (Sweden)

    Alonso Jesús

    2009-02-01

    Full Text Available Abstract Background Microfossils are not only useful for elucidating biological macro- and microevolution but also the biogeochemical history of our planet. Pyritization is the most important and extensive mode of preservation of animals and especially of plants. Entrapping in amber, a fossilized resin, is considered an alternative mode of biological preservation. For the first time, the internal organization of 114-million-year-old microfossils entrapped in Lower Cretaceous amber is described and analyzed, using adapted scanning electron microscopy in backscattered electron mode in association with energy dispersive X-ray spectroscopy microanalysis. Double fossilization of several protists included in diverse taxonomical groups and some vegetal debris is described and analyzed. Results In protists without an exoskeleton or shell (ciliates, naked amoebae, flagellates, determinate structures, including the nuclei, surface envelopes (cortex or cytoplasmic membrane and hyaloplasm are the main sites of pyritization. In protists with a biomineralized skeleton (diatoms, silicon was replaced by pyrite. Permineralization was the main mode of pyritization. Framboidal, subhedral and microcrystalline are the predominant pyrite textures detected in the cells. Abundant pyritized vegetal debris have also been found inside the amber nuggets and the surrounding sediments. This vegetal debris usually contained numerous pyrite framboids and very densely packed polycrystalline pyrite formations infilled with different elements of the secondary xylem. Conclusion Embedding in amber and pyritization are not always alternative modes of biological preservation during geological times, but double fossilization is possible under certain environmental conditions. Pyritization in protists shows a quite different pattern with regard to plants, due to the different composition and cellular architecture in these microorganisms and organisms. Anaerobic sulphate

  19. Secondarily flightless birds or Cretaceous non-avian theropods?

    Science.gov (United States)

    Kavanau, J Lee

    2010-02-01

    Recent studies by Varricchio et al. reveal that males cared for the eggs of troodontids and oviraptorids, so-called "non-avian theropods" of the Cretaceous, just as do those of most Paleognathic birds (ratites and tinamous) today. Further, the clutches of both groups have large relative volumes, and consist of many eggs of relatively large size. By comparison, clutch care by most extant birds is biparental and the clutches are of small relative volume, and consist of but few small eggs. Varricchio et al. propose that troodontids and oviraptorids were pre-avian and that paternal egg care preceded the origin of birds. On the contrary, unmentioned by them is that abundant paleontological evidence has led several workers to conclude that troodontids and oviraptorids were secondary flightless birds. This evidence ranges from bird-like bodies and bone designs, adapted for climbing, perching, gliding, and ultimately flight, to relatively large, highly developed brains, poor sense of smell, and their feeding habits. Because ratites also are secondarily flightless and tinamous are reluctant, clumsy fliers, the new evidence strengthens the view that troodontids and oviraptorids were secondarily flightless. Although secondary flightlessness apparently favors paternal care of clutches of large, abundant eggs, such care is not likely to have been primitive. There are a suite of previously unknown independent findings that point to the evolution of, first, maternal, followed by biparental egg care in earliest ancestors of birds. This follows from the discovery of remarkable relict avian reproductive behaviors preserved by virtue of the highly conservative nature of vertebrate brain evolution. These behaviors can be elicited readily by exposing breeding birds to appropriate conditions, both environmental and with respect to their eggs and chicks. They give significant new clues for a coherent theory of avian origin and early evolution. PMID:19800747

  20. Formation of the soft-sediment deformation structures and its constraints on dinosaur fossil burial of the Cretaceous in Zhucheng, Shandong province, East China

    Science.gov (United States)

    He, Bizhu; Qiao, Xiufu; Cai, Zhihui; Tian, Hongshui; Chen, Shuqing

    2013-04-01

    The triangular-shaped Zhucheng depression is located in the southwestern part of the Jiaolai basin, Jiaodong peninsula, East China. Various soft-sediment deformation structures are recognized in the southern Zhucheng depression, which have behaviour are plastic and/or brittle. Soft-sediment deformation structures mainly include undulate fold, mound and sag, diapir, convolute deformation and seismic-unconformity in the Lower Cretaceous, which are composed of fine-grained sediments in lacustrine environment, while load structure, ball and pillow structure, plunged sediment mixtures structure, fault-graded occurred in the Upper Cretaceous, which formed in a conglomeratic or coarse arenaceous alluvial fan and flood-plain setting. These soft-sediment deformation structures are proposed triggered by paleoearthquake. The deformed layers and undeformed layers developed in intervals, suggesting frequent seismic activities. In studied area, numerous giant hadrosaurid skeleton fossils have been found in the Upper Cretaceous Wangshi Group science 1958, and unusual and abundant dinosaur track fossils have been discovered in the Lower Cretaceous Yangzhuang Formation of Laiyang Group. The widespread identified soft-sediment deformation structures are proximately underlying or overlying these dinosaur fossil bearing strata. The depositional setting changed while multiple paleo-seismic events and tectonic activity happened. In the Early Cretaceous, after the occurrence of paleo-earthquakes and environmental changes, dinosaurs migrated and a lot of tracks with similar orientation on lacustrine offshore were preserved. In the Late Cretaceous, a large-scale dinosaur fossil layers and paleo-earthquake records occurred in intervals, indicating that the dinosaur fossils may be associated with large-scale debris flow and frequent earthquake events. Based on regional tectonic setting, distribution of soft-sediment deformation structures and predicted magnitude of paleo-earthquakes, the

  1. Sea level regulated tetrapod diversity dynamics through the Jurassic/Cretaceous interval

    Science.gov (United States)

    Tennant, Jonathan P.; Mannion, Philip D.; Upchurch, Paul

    2016-09-01

    Reconstructing deep time trends in biodiversity remains a central goal for palaeobiologists, but our understanding of the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) boundary, 145 million years ago, remains poorly understood, despite an apparent minor extinction and the radiation of numerous important clades. Here we apply a rigorous subsampling approach to a comprehensive tetrapod fossil occurrence data set to assess the group's macroevolutionary dynamics through the J/K transition. Although much of the signal is exclusively European, almost every higher tetrapod group was affected by a substantial decline across the boundary, culminating in the extinction of several important clades and the ecological release and radiation of numerous modern tetrapod groups. Variation in eustatic sea level was the primary driver of these patterns, controlling biodiversity through availability of shallow marine environments and via allopatric speciation on land.

  2. Sea level regulated tetrapod diversity dynamics through the Jurassic/Cretaceous interval.

    Science.gov (United States)

    Tennant, Jonathan P; Mannion, Philip D; Upchurch, Paul

    2016-01-01

    Reconstructing deep time trends in biodiversity remains a central goal for palaeobiologists, but our understanding of the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) boundary, 145 million years ago, remains poorly understood, despite an apparent minor extinction and the radiation of numerous important clades. Here we apply a rigorous subsampling approach to a comprehensive tetrapod fossil occurrence data set to assess the group's macroevolutionary dynamics through the J/K transition. Although much of the signal is exclusively European, almost every higher tetrapod group was affected by a substantial decline across the boundary, culminating in the extinction of several important clades and the ecological release and radiation of numerous modern tetrapod groups. Variation in eustatic sea level was the primary driver of these patterns, controlling biodiversity through availability of shallow marine environments and via allopatric speciation on land. PMID:27587285

  3. Cretaceous Oceanic Redbeds:Implications for Paleoclimatology and Paleoceanography

    Institute of Scientific and Technical Information of China (English)

    WANG Chengshan; HUANG Yongjian; HU Xiumian; LI Xianghui

    2004-01-01

    The Cretaceous is among the most unusual eras in the geological past. Geoscience communities have been having great concerns with geological phenomena within this period, for example carbonate platforms and black shales in the Early and Middle Cretaceous respectively, during the last decades. But few people have paid any attention to the set of pelagic redbeds lying on the black shales, not to mention the applications to paleoclimatology and paleoceanography. It is shown by the sedimentary records of redbeds, that they were deposited around the CCD, with both a higher content of iron and much lower concentrations of organic carbon, which implies conditions with a relatively high content of oxygen. Such redbeds occurred in the global oceans, mainly in the Tethyan realm, with different durations of deposition and a climax from the late Santonian to early Campanian. Global cooling and dramatic changes in ocean currents might help to increase the oxygen flux between the atmosphere and ocean, after the large scale organic carbon burial during the Middle Cretaceous, and therefore lead to the oxygenation of deep ocean and so the occurrence of late Cretaceous oceanic redbeds.

  4. The Cretaceous opening of the South Atlantic Ocean

    Science.gov (United States)

    Granot, Roi; Dyment, Jérôme

    2015-03-01

    The separation of South America from Africa during the Cretaceous is poorly understood due to the long period of stable polarity of the geomagnetic field, the Cretaceous Normal Superchron (CNS, lasted between ∼121 and 83.6 Myr ago). We present a new identification of magnetic anomalies located within the southern South Atlantic magnetic quiet zones that have arisen due to past variations in the strength of the dipolar geomagnetic field. Using these anomalies, together with fracture zone locations, we calculate the first set of magnetic anomalies-based finite rotation parameters for South America and Africa during that period. The kinematic solutions are generally consistent with fracture zone traces and magnetic anomalies outside the area used to construct them. The rotations indicate that seafloor spreading rates increased steadily throughout most of the Cretaceous and decreased sharply at around 80 Myr ago. A change in plate motion took place in the middle of the superchron, roughly 100 Myr ago, around the time of the final breakup (i.e., separation of continental-oceanic boundary in the Equatorial Atlantic). Prominent misfit between the calculated synthetic flowlines (older than Anomaly Q1) and the fracture zones straddling the African Plate in the central South Atlantic could only be explained by a combination of seafloor asymmetry and internal dextral motion (leading to the emergence of north-south flow of intermediate and deep-water which might have triggered the global cooling of bottom water and the end for the Cretaceous greenhouse period.

  5. Trace element and isotope geochemistry of Cretaceous-Tertiary boundary sediments: identification of extra-terrestrial and volcanic components

    Science.gov (United States)

    Margolis, S. V.; Doehne, E. F.

    1988-01-01

    Trace element and stable isotope analyses were performed on a series of sediment samples crossing the Cretaceous-Tertiary (K-T) boundary from critical sections at Aumaya and Sopelano, Spain. The aim is to possibly distinguish extraterrestrial vs. volcanic or authigenic concentration of platinum group and other elements in K-T boundary transitional sediments. These sediments also have been shown to contain evidence for step-wise extinction of several groups of marine invertebrates, associated with negative oxygen and carbon isotope excursions occurring during the last million years of the Cretaceous. These isotope excursions have been interpreted to indicate major changes in ocean thermal regime, circulation, and ecosystems that may be related to multiple events during latest Cretaceous time. Results to date on the petrographic and geochemical analyses of the Late Cretaceous and Early Paleocene sediments indicate that diagenesis has obviously affected the trace element geochemistry and stable isotope compositions at Zumaya. Mineralogical and geochemical analysis of K-T boundary sediments at Zumaya suggest that a substantial fraction of anomalous trace elements in the boundary marl are present in specific mineral phases. Platinum and nickel grains perhaps represent the first direct evidence of siderophile-rich minerals at the boundary. The presence of spinels and Ni-rich particles as inclusions in aluminosilicate spherules from Zumaya suggests an original, non-diagenetic origin for the spherules. Similar spherules from southern Spain (Caravaca), show a strong marine authigenic overprint. This research represents a new approach in trying to directly identify the sedimentary mineral components that are responsible for the trace element concentrations associated with the K-T boundary.

  6. Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton

    Energy Technology Data Exchange (ETDEWEB)

    van Houten, F.B.

    1980-06-01

    Nonmarine to paralic detrital deposits accumulated in six large basins between Algeria and the Arabo-Nubian shield during major regression in latest Jurassic and Early Cretaceous time. The Ghadames Sirte (north-central Libya), and Northern (Egypt) basins lay along the cratonic margin of northeastern Africa. The Murzuk, Kufra, and Southern (Egypt) basins lay in the south within the craton. Data for reconstructing distribution, facies, and thickness of relevant sequences are adequate for the three northern basins only. High detrital influx near the end of Jurassic time and in mid-Cretaceous time produced regressive nubian facies composed largely of low-sinuosity stream and fahdelta deposits. In the west and southwest the Ghadames, Murzuk, and Kufra basins were filled with a few hundred meters of detritus after long-continued earlier Mesozoic aggradation. In northern Egypt the regressive sequence succeeded earlier Mesozoic marine sedimentation; in the Sirte and Southern basins correlative deposits accumulated on Precambrian and Variscan terranes after earlier Mesozoic uplift and erosion. Waning of detrital influx into southern Tunisia and adjacent Libya in the west and into Israel in the east initiated an Albian to early Cenomanian transgression of Tethys. By late Cenomanian time it had flooded the entire cratonic margin, and spread southward into the Murzuk and Southern basins, as well as onto the Arabo-Nubian shield. Latest Jurassic-earliest Cretaceous, mid-Cretaceous, and Late Cretaceous transgressions across northeastern Africa recorded in these sequences may reflect worldwide eustatic sea-level rises. In contrast, renewed large supply of detritus during each regression and a comparable subsidence history of intracratonic and marginal basins imply regional tectonic control. 6 figures.

  7. Políticas de territorialización de indígenas en Chubut: Provincialización de las relaciones interétnicas a través del acceso a la tierra

    Directory of Open Access Journals (Sweden)

    Fabiana Nahuelquir

    2012-12-01

    Full Text Available En el presente artículo buscamos un doble objetivo. Por un lado, realizar una propuesta metodológica de lectura y análisis de presupuestos implícitos en los archivos estatales de tierras, construidos por el estado de la Provincia de Chubut. Por otro, nos abocamos al interior del discurso estatal a reconstruir las premisas que articularon las relaciones interétnicas entre el estado provincial y las familias indíge-nas, autoidentificadas como mapuche y mapuche-tehuelche. Tomamos como punto de partida con-ceptos como los de performance, contextualización y entextualización con la finalidad de (Bauman y Briggs, 2000 proponer una estrategia de análisis y reconstrucción de los marcos de referencia de los que partían los discursos estatales acerca del indígena y, al mismo tiempo, nos ocupamos de indagar cómo dichos marcos proveían de representaciones en curso a partir de las cuales se fijaba el sentido de las relaciones entre este grupo y el resto de la sociedad. El abordaje de las relaciones interétnicas entre el estado provincial y los indígenas requiere de un análisis desde una perspectiva histórica y multisituada. En consecuencia, cruzamos las sentencias de los archivos estatales con los posiciona-mientos de las narrativas indígenas y nos introducimos, entonces, en las particularidades de procesos conformación de comunidad provincial y de alterización de los indígenas al interior de las premisas que la primordializaban

  8. A gravid lizard from the Cretaceous of China and the early history of squamate viviparity

    Science.gov (United States)

    Wang, Yuan; Evans, Susan E.

    2011-09-01

    Although viviparity is most often associated with mammals, roughly one fifth of extant squamate reptiles give birth to live young. Phylogenetic analyses indicate that the trait evolved more than 100 times within Squamata, a frequency greater than that of all other vertebrate clades combined. However, there is debate as to the antiquity of the trait and, until now, the only direct fossil evidence of squamate viviparity was in Late Cretaceous mosasauroids, specialised marine lizards without modern equivalents. Here, we document viviparity in a specimen of a more generalised lizard, Yabeinosaurus, from the Early Cretaceous of China. The gravid female contains more than 15 young at a level of skeletal development corresponding to that of late embryos of living viviparous lizards. This specimen documents the first occurrence of viviparity in a fossil reptile that was largely terrestrial in life, and extends the temporal distribution of the trait in squamates by at least 30 Ma. As Yabeinosaurus occupies a relatively basal position within crown-group squamates, it suggests that the anatomical and physiological preconditions for viviparity arose early within Squamata.

  9. EVOLUTION. A four-legged snake from the Early Cretaceous of Gondwana.

    Science.gov (United States)

    Martill, David M; Tischlinger, Helmut; Longrich, Nicholas R

    2015-07-24

    Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana.

  10. Male spike strobiles with Gnetum affinity from the Early Cretaceous in western Liaoning, Northeast China

    Institute of Scientific and Technical Information of China (English)

    Shuang-Xing GUO; Jin-Geng SHA; Li-Zeng BIAN; Yin-Long QIU

    2009-01-01

    A fossil with Gnetum affinity was found in the Jianshangou Member (Barremian Age) of the Yixian Formation (Lower Cretaceous Epoch) of the Jehol Group in western Liaoning, northeastern China. The single fossil specimen is represented by both elongate-cylindrical male spike strobiles which borne within a nodal bract of cauliflorous branch. The spike strobiles have apparent nodes, invisible internodes, and numerous verticillate involucral collars. The microsporangiate units within involucral collars are not seen. The male spike strobiles with verticillate involucral collars occur exclusively in Gnetum; hence, the fossil strobiles are attributed to a new taxon, Khitania columnispicata gen. & sp. nov., being closely related to Gnetum. The general isotopic dating suggests an age of Barremian, ca. 125-122 million years (Myr) ago for the Jianshangou Member. The palaeoecological and palaeoclimatic inference based on the compositions of flora and fauna, and lithological characters of the fossil locality suggests that the fossil plants grew in a subtropical mesophytic forest and under a warmer climate. The remains of male spike strobiles are the first record of gnetalean macrofossil. It documents the evolution of the distinct gnetoid morphology and indicates a wider range of distribution of Gnetaceae in the Early Cretaceous than present day.

  11. Hadrosauroid Dinosaurs from the Late Cretaceous of the Sultanate of Oman.

    Directory of Open Access Journals (Sweden)

    Eric Buffetaut

    Full Text Available Fragmentary post-cranial remains (femora, tibia, vertebrae of ornithischian dinosaurs from the Late Cretaceous of the Sultanate of Oman are described and referred to hadrosauroids. The specimens come from the Al-Khod Conglomerate, of latest Campanian to Maastrichtian age, in the north-eastern part of the country. Although the fragmentary condition of the fossils precludes a precise identification, various characters, including the shape of the fourth trochanter of the femur and the morphology of its distal end, support an attribution to hadrosauroids. With the possible exception of a possible phalanx from Angola, this group of ornithopod dinosaurs, which apparently originated in Laurasia, was hitherto unreported from the Afro-Arabian plate. From a paleobiogeographical point of view, the presence of hadrosauroids in Oman in all likelihood is a result of trans-Tethys dispersal from Asia or Europe, probably by way of islands in the Tethys shown on all recent paleogeographical maps of that area. Whether hadrosauroids were widespread on the Afro-Arabian landmass in the latest Cretaceous, or where restricted to the « Oman island » shown on some paleogeographical maps, remains to be determined.

  12. Late Cretaceous-Early Palaeogene tectonic development of SE Asia

    Science.gov (United States)

    Morley, C. K.

    2012-10-01

    The Late Cretaceous-Early Palaeogene history of the continental core of SE Asia (Sundaland) marks the time prior to collision of India with Asia when SE Asia, from the Tethys in the west to the Palaeo-Pacific in the east, lay in the upper plate of subduction zones. In Myanmar and Sumatra, subduction was interrupted in the Aptian-Albian by a phase of arc accretion (Woyla and Mawgyi arcs) and in Java, eastern Borneo and Western Sulawesi by collision of continental fragments rifted from northern Australia. Subsequent resumption of subduction in the Myanmar-Thailand sector explains: 1) early creation of oceanic crust in the Andaman Sea in a supra-subduction zone setting ~ 95 Ma, 2) the belt of granite plutons of Late Cretaceous-Early Palaeogene age (starting ~ 88 Ma) in western Thailand and central Myanmar, and 3) amphibolite grade metamorphism between 70 and 80 Ma seen in gneissic outcrops in western and central Thailand, and 4) accretionary prism development in the Western Belt of Myanmar, until glancing collision with the NE corner of Greater India promoted ophiolite obduction, deformation and exhumation of marine sediments in the early Palaeogene. The Ranong strike-slip fault and other less well documented faults, were episodically active during the Late Cretaceous-Palaeogene time. N to NW directed subduction of the Palaeo-Pacific ocean below Southern China, Vietnam and Borneo created a major magmatic arc, associated with rift basins, metamorphic core complexes and strike-slip deformation which continued into the Late Cretaceous. The origin and timing of termination of subduction has recently been explained by collision of a large Luconia continental fragment either during the Late Cretaceous or Palaeogene. Evidence for such a collision is absent from the South China Sea well and seismic reflection record and here collision is discounted. Instead relocation of the subducting margin further west, possibly in response of back-arc extension (which created the Proto

  13. Tectonic evolution of the Sicilian Maghrebian Chain inferred from stratigraphic and petrographic evidences of Lower Cretaceous and Oligocene flysch

    Directory of Open Access Journals (Sweden)

    Puglisi Diego

    2014-08-01

    Full Text Available The occurrence of a Lower Cretaceous flysch group, cropping out from the Gibraltar Arc to the Balkans with a very similar structural setting and sedimentary provenance always linked to the dismantling of internal areas, suggests the existence of only one sedimentary basin (Alpine Tethys s.s., subdivided into many other minor oceanic areas. The Maghrebian Basin, mainly developed on thinned continental crust, was probably located in the westernmost sector of the Alpine Tethys. Cretaceous re-organization of the plates triggered one (or more tectonic phases, well recorded in almost all the sectors of the Alpine Tethys. However, the Maghrebian Basin seems to have been deformed by Late- or post-Cretaceous tectonics, connected with a “meso-Alpine” phase (pre-Oligocene, already hypothesized since the beginning of the nineties. Field geological evidence and recent biostratigraphic data also support this important meso- Alpine tectonic phase in the Sicilian segment of the Maghrebian Chain, indicated by the deformations of a Lower Cretaceous flysch sealed by Lower Oligocene turbidite deposits. This tectonic development is emphasized here because it was probably connected with the onset of rifting in the southern paleomargin of the European plate, the detaching of the so-called AlKaPeCa block (Auct.; i.e. Alboran + Kabylian + Calabria and Peloritani terranes and its fragmentation into several microplates. The subsequent early Oligocene drifting of these microplates led to the progressive closure of the Maghrebian Basin and the opening of new back-arc oceanic basins, strongly controlled by extensional processes, in the western Mediterranean (i.e. Gulf of Lion, Valencia Trough, Provençal Basin and Alboran Sea.

  14. A molecular genetic time scale demonstrates Cretaceous origins and multiple diversification rate shifts within the order Galliformes (Aves).

    Science.gov (United States)

    Stein, R Will; Brown, Joseph W; Mooers, Arne Ø

    2015-11-01

    The phylogeny of Galliformes (landfowl) has been studied extensively; however, the associated chronologies have been criticized recently due to misplaced or misidentified fossil calibrations. As a consequence, it is unclear whether any crown-group lineages arose in the Cretaceous and survived the Cretaceous-Paleogene (K-Pg; 65.5 Ma) mass extinction. Using Bayesian phylogenetic inference on an alignment spanning 14,539 bp of mitochondrial and nuclear DNA sequence data, four fossil calibrations, and a combination of uncorrelated lognormally distributed relaxed-clock and strict-clock models, we inferred a time-calibrated molecular phylogeny for 225 of the 291 extant Galliform taxa. These analyses suggest that crown Galliformes diversified in the Cretaceous and that three-stem lineages survived the K-Pg mass extinction. Ideally, characterizing the tempo and mode of diversification involves a taxonomically complete phylogenetic hypothesis. We used simple constraint structures to incorporate 66 data-deficient taxa and inferred the first taxon-complete phylogenetic hypothesis for the Galliformes. Diversification analyses conducted on 10,000 timetrees sampled from the posterior distribution of candidate trees show that the evolutionary history of the Galliformes is best explained by a rate-shift model including 1-3 clade-specific increases in diversification rate. We further show that the tempo and mode of diversification in the Galliformes conforms to a three-pulse model, with three-stem lineages arising in the Cretaceous and inter and intrafamilial diversification occurring after the K-Pg mass extinction, in the Paleocene-Eocene (65.5-33.9 Ma) or in association with the Eocene-Oligocene transition (33.9 Ma).

  15. Arctic black shale formation during Cretaceous Oceanic Anoxic Event 2

    DEFF Research Database (Denmark)

    Lenniger, Marc; Nøhr-Hansen, Henrik; Hills, Len V.;

    2014-01-01

    The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid-paleolatitudes are re......The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid...... caused massive organic-carbon burial on the Arctic shelf in general, with important implications for hydrocarbon source-rock distribution in the Arctic region....

  16. A gigantic feathered dinosaur from the lower cretaceous of China.

    Science.gov (United States)

    Xu, Xing; Wang, Kebai; Zhang, Ke; Ma, Qingyu; Xing, Lida; Sullivan, Corwin; Hu, Dongyu; Cheng, Shuqing; Wang, Shuo

    2012-04-04

    Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y. huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y. huali differed from tyrannosaurids in its growth strategy. Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.

  17. A long tailed bird from the Late Cretaceous of Zhejiang

    Institute of Scientific and Technical Information of China (English)

    蔡正全; 赵丽君

    1999-01-01

    A new fossil bird was discovered from the lower part of Upper Cretaceous of Linhai, Zhejiang. With a long tail comprising more than 20 caudal vertebrae, this new brid is morphologically similar to that of Archaeopteryx. Meanwhile, it is similar to Confuciusornis in lacking in teeth. The bird shows the following plesiomorphies besides a long tail: elements of the forelimbs are simple in structure; bones of the manus are separate from one another and two digits are free; abdominal ribs are present. And the new bird shows some apomorphies: The skull bones are lightly built with no teeth; the hindlimbs are better developed than the forelimbs, the articular condyle of the femur is pronouced; the sternum is broad and long; the phalanges and unguals are small, showing its ground-dwelling habit. The fossil bird, coming from the rock of the Late Cretaceous in shouthem China, is very significant to the study of the evolution and relationships of birds.

  18. Mummified precocial bird wings in mid-Cretaceous Burmese amber.

    Science.gov (United States)

    Xing, Lida; McKellar, Ryan C; Wang, Min; Bai, Ming; O'Connor, Jingmai K; Benton, Michael J; Zhang, Jianping; Wang, Yan; Tseng, Kuowei; Lockley, Martin G; Li, Gang; Zhang, Weiwei; Xu, Xing

    2016-01-01

    Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans. PMID:27352215

  19. Solid state 13C NMR analysis of Brazilian cretaceous ambers

    International Nuclear Information System (INIS)

    13C cross polarization with magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectra have been obtained for the first time to three Cretaceous amber samples from South America. The samples were dated to Lower Cretaceous and collected in sediments from the Amazonas, Araripe and Reconcavo basins, Brazil. All samples have very similar spectra, consistent with a common paleobotanical source. Some aspects of the spectra suggest a relationship between Brazilian ambers and Araucariaceae family, such as intense resonances at 38-39 ppm. All samples are constituted by polylabdane structure associated to Class Ib resins, constituted by polymers of labdanoid diterpenes. Finally, information concerning some structural changes during maturation, such as isomerization of Δ8(17) and Δ12(13) unsaturations, were obtained by 13C NMR analyses. The results concerning botanical affinities are in accordance with previous results obtained by gas chromatography-mass spectrometry (GC-MS). (author)

  20. Geology along southwest coast of Mexico - implications for Cretaceous Paleogeography

    Energy Technology Data Exchange (ETDEWEB)

    Campa, U.M.F.

    1986-04-01

    The coast of Mexico between Puerto Vallarta (lat. 21/sup 0/N) and the Bay of Tehuantepec (long. 94/sup 0/) rises steeply from the Middle America Trench to expose deeply eroded terranes of metamorphosed ophiolitic, basinal to terrigenous sedimentary, and arc volcanic rocks of Pennsylvanian to middle Cretaceous age, in part lying on older Paleozoic and Proterozoic rocks. Granitic intrusios are of Late Cretaceous to early Cenozoic age. The terranes are overlapped by volcanic rocks of middle Cenozoic age and locally, along the coast, by marine Miocene strata. It is particularly significant to paleogeographic reconstructions that there are no known marine coastal deposits of Late Cretaceous or early Cenozoic age. Eight tectono-stratigraphic units are currently recognized. The Colima terrane is a complete sequence of red colvaniclastic beds and limestones from Neocomian to Aptian (ammonites, rudistids). The Tumbiscatio terrane is comprised of lavas and radiolarian cherts, at least in part Triassic. The Huetamo terrane is formed of turbiditic, volcaniclastic, and calcareous sequences of Late Jurassic and Early Cretaceous age (ammonites), locally containing fragments of ophiolite. The fourth unit is comprised of ophiolite terranes. Guerrero terranes are gently metamorphosed lavas, tuffs, and sediments of Late Jurassic to Aptian-Albian age. The Mixteca terrane is comprised of terrigenous calcareous sequences of Pennsylvanian and Early Jurassic ages lying on early Paleozoic basement. The Oaxaca terrane is a Paleozoic sedimentary sequence overlying metamorphic precambrian basement, and the Xalapa terrane is formed of migmatitic, gneissic rocks of Jurassic(.) age. However, this preliminary breakdown does not convey the chaotic complexity of the region.

  1. Early Cretaceous Aucellina (bivalvia) from the Dajiashan area, northeastern China

    Science.gov (United States)

    Jiang, B. Y.; Huawei, Cai; Jingeng, Sha

    2004-07-01

    Aucellina is described systematically for the first time from the Dajiashan Formation of the Dajiashan area. Earlier, it had been identified as Otapiria. Based on the occurrence of Aucellina caucasica-Aucellina aptiensis-Aucellina acuminata assemblage, the age of the Dajiashan Formation is revised from Early Jurassic to Early Cretaceous and probably ranges from Late Barremian to Early Albian. In addition, the distribution of Aucellina, as well as the differentiation between Aucellina and Buchia, are discussed briefly in this paper.

  2. Late Cretaceous intraplate silicic volcanism in the Lake Chad region: incipient continental rift volcanism vs. Cameroon Line volcanism

    Science.gov (United States)

    Shellnutt, G.; Lee, T. Y.; Torng, P. K.; Yang, C. C.

    2015-12-01

    The crustal evolution of west-central Africa during the Cretaceous was directly related to plate motion associated with the opening of the central Atlantic Ocean. Late Cretaceous (~66 Ma) to recent magmatism related to the Cameroon Line stretches from Northern Cameroon (i.e. Golda Zuelva) to the Gulf of Guinea (i.e. Pagalu) and is considered to be due to mantle-crust interaction. The volcanic rocks at Hadjer el Khamis, west-central Chad, are considered to be amongst the oldest volcanic rocks of the Cameroon Line but their relationship is uncertain because they erupted during a period of a regional extension associated with the opening of the Late Cretaceous (~75 Ma) Termit basin. The silicic volcanic rocks can be divided into a peraluminous group and a peralkaline group with both rock types having similar chemical characteristics as within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma and indicates the rocks erupted ~10 million years before the next oldest eruption attributed to the Cameroon Line. The Sr isotopes (i.e. ISr = 0.7050 to 0.7143) show a wide range but the Nd isotopes (i.e. 143Nd/144Ndi = 0.51268 to 0.51271) are more uniform and indicate that the rocks were derived from a moderately depleted mantle source. Major and trace elemental modeling show that the silicic rocks likely formed by shallow fractionation of a mafic parental magma where the peraluminous rocks experienced crustal contamination and the peralkaline rocks did not. The silicic rocks are more isotopically similar to Late Cretaceous basalts in the Doba and Bongor basins (i.e. ISr = 0.7040 to 0.7060; 143Nd/144Ndi = 0.51267 to 0.51277) of southern Chad than to rocks of the Cameroon Line (i.e. ISr = 0.7026 to 0.7038; 143Nd/144Ndi = 0.51270 to 0.51300). Given the age and isotopic compositions, it is likely that the silicic volcanic rocks of the Lake Chad area are related to Late Cretaceous extensional tectonics rather than to Cameroon Line magmatism.

  3. Upper cretaceous magmatic suites of the Timok magmatic complex

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    Banješević Miodrag

    2010-01-01

    Full Text Available The Upper Cretaceous Timok Magmatic Complex (TMC developed on a continental crust composed of different types of Proterozoic to Lower Cretaceous rocks. The TMC consists of the magmatic suites: Timok andesite (AT - Turonian-Santonian, Metovnica epiclastite (EM - Coniacian-Campanian, Osnić basaltic andesite (AO and Ježevica andesite (AJ - Santonian-Campanian, Valja Strž plutonite (PVS - Campanian and Boljevac latite (LB. The sedimentary processes and volcanic activity of the TMC lasted nearly continuously throughout nearly the whole Late Cretaceous. The sedimentation lasted from the Albian to the Maastrichtian and the magmatism lasted for 10 million years, from the Upper Turonian to the Upper Campanian. The volcanic front migrated from East to West. The volcanic processes were characterized by the domination of extrusive volcanic facies, a great amount of volcanic material, a change in the depositional environment during the volcanic cycle, sharp facial transitions and a huge deposition of syn- and post-eruptive resedimented volcaniclastics.

  4. Geochemical characterization of Cretaceous sand-stones from the Southern Benue Trough, Nigeria

    Institute of Scientific and Technical Information of China (English)

    Odigi M.I.; Amajor L.C.

    2009-01-01

    Geochemical studies of sandstones from the three lithostratigraphic successions in the southern Benue Trough of Nigeria were undertaken for a geochemical characterization of the sandstones, and to assess their strati-graphic and source evolution.Major and trace elements data were obtained from outcrop sandstone samples. The SIO2/Al2O2, Fe2O3/K2O ra-tios and CaO contents have been used to characterize the Cretaceous sandstones into Al-rich and high and low Fe2O3/K2O ratio sandstones. Results indicate that there are geochemical features that display stratigraphic trends across the succession from the Asu River Group, Eze-Aku Group to the proto-Niger Delta succession which may imply a discontinuous evolution from different source terrains of Precambrian and Mesozoic ages that supplied the sediments. The Asu River Group sandstones have lower SiO2, Al2O3, Fe2O3 and higher MgO; the Eze-Aku sand-stones have higher TiO2, CaO, alkalis and lower MgO while the proto-Niger Delta sandstones have higher SiO2, Al2O3, Fe2O3 and lower alkalis and CaO. These discontinuities signify the influence of tectonic impulses that af-fected the southern Benue Trough during the Cretaceous time. Changes in ratios of TiO2/Al2O3, Fe2O3, Cr and Zr suggest an increasingly mafic contribution to the depositional basin with time. The chemical index of alteration in-creases with time, possibly suggesting that a more intense weathering regime in the hinterland developed with time.

  5. Earliest zygodactyl bird feet: evidence from Early Cretaceous roadrunner-like tracks

    Science.gov (United States)

    Lockley, Martin G.; Li, Rihui; Harris, Jerald D.; Matsukawa, Masaki; Liu, Mingwei

    2007-08-01

    Fossil footprints are important in understanding Cretaceous avian diversity because they constitute evidence of paleodiversity and paleoecology that is not always apparent from skeletal remains. Early Cretaceous bird tracks have demonstrated the existence of wading birds in East Asia, but some pedal morphotypes, such as zygodactyly, common in modern and earlier Cenozoic birds (Neornithes) were unknown in the Cretaceous. We, herein, discuss the implications of a recently reported, Early Cretaceous (120-110 million years old) trackway of a large, zygodactyl bird from China that predates skeletal evidence of this foot morphology by at least 50 million years and includes the only known fossil zygodactyl footprints. The tracks demonstrate the existence of a Cretaceous bird not currently represented in the body fossil record that occupied a roadrunner ( Geococcyx)-like niche, indicating a previously unknown degree of Cretaceous avian morphological and behavioral diversity that presaged later Cenozoic patterns.

  6. Cretaceous oceanic red beds (CORBs): Different time scales and models of origin

    Science.gov (United States)

    Hu, Xiumian; Scott, Robert W.; Cai, Yuanfeng; Wang, Chengshan; Melinte-Dobrinescu, Mihaela C.

    2012-12-01

    The Cretaceous oceanic red bed (CORB) is a newly opened window on global oceanic and climate changes during the Cretaceous greenhouse world. As a result of the International Geoscience Programmes 463, 494 and 555 (2002-2010), CORBs have been documented in many places by numerous publications. The principle goal of this paper is to summarize scientific advances on CORBs including chronostratigraphy, sedimentology, mineralogy, elemental and isotopic geochemistry, and their relationship to oceanic anoxic events (OAEs), palaeoclimate and palaeoceanography. We propose a new geochemical classification of the CORBs using CaO, Al2O3 and SiO2 values, which lithologically refer to marly, clayey, and cherty CORBs respectively. Detailed mineralogical studies indicate that hematite, goethite and Mn2 +-bearing calcite are the minerals imparting the red color of CORBs. Hematite clusters of several to tens of nanometers in the calcite structure are the main cause of the red coloring of limestones, and the Mn2 +-bearing calcite gives additional red color. Goethite was thought to form originally with hematite, and was subsequently transformed to hematite during late diagenesis. Chronostratigraphic data allow the distinction of two groups of CORBs by their durations. Short-term CORBs are generally less than 1 myr in duration, and seem to be on the scale of Milankovitch cycles. During the deposition of Cretaceous reddish intervals from ODP cores 1049 and 1050, low primary productivity and relatively high surface temperature resulted in low organic carbon flux into the sediments which reduced oxygen demand and produced oxidizing early diagenetic conditions. In such an oxic environment, iron oxides formed imparting the reddish color. The long-term CORBs' depositional events lasted longer than 4 myr, and may be a possible consequence of the OAEs. Enhanced amounts of organic carbon and pyrite burial during and after the OAEs would have resulted in a large and abrupt fall in atmospheric CO

  7. Late Cretaceous and Cenozoic exhumation history of the Malay Peninsula

    Science.gov (United States)

    François, Thomas; Daanen, Twan; Matenco, Liviu; Willingshofer, Ernst; van der Wal, Jorien

    2015-04-01

    The evolution of Peninsular Malaysia up to the collisional period in the Triassic is well described but the evolution since the collision between Indochina and the Sukhothai Arc in Triassic times is less well described in the literature. The processes affecting Peninsular Malaysia during the Jurassic up to current day times have to explain the emplacement multiple intrusions (the Stong Complex, and the Kemahang granite), the Jurassic/Cretaceous onland basins, the Cenozoic offshore basins, and the asymmetric extension, which caused the exhumation of Taku Schists dome. The orogenic period in Permo-Triassic times, which also formed the Bentong-Raub suture zone, resulted in thickening of the continental crust of current day Peninsular Malaysia due to the collision of the Indochina continental block and the Sukhothai Arc, and is related to the subduction of oceanic crust once present between these continental blocks. The Jurassic/Cretaceous is a period of extension, resulting in the onland Jurassic/Cretaceous basins, synchronous melting of the crust, resulting in the emplacement Stong Complex and the Kemahang granite and thinning of the continental crust on the scale of the Peninsular, followed by uplift of the Peninsular. Different models can explain these observations: continental root removal, oceanic slab detachment, or slab delamination. These models all describe the melting of the lower crust due to asthenospheric upwelling, resulting in uplift and subsequent extension either due to mantle convective movements or gravitational instabilities related to uplift. The Cenozoic period is dominated by extension and rapid exhumation in the area as documented by low temperature thermocrological ages The extension in this period is most likely related to the subduction, which resumed at 45 Ma, of the Australian plate beneath the Eurasian plate after it terminated in Cretaceous times due to the collision of an Australian microcontinental fragment with the Sunda margin in the

  8. Stratigraphy and palaeoclimate of Spitsbergen, Svalbard, during the Early Cretaceous

    Science.gov (United States)

    Vickers, Madeleine; Price, Gregory; Watkinson, Matthew; FitzPatrick, Meriel; Jerrett, Rhodri

    2016-04-01

    During the Early Cretaceous, Spitsbergen was located at a palaeolatitude of ~60°N. Abundant fossil wood derived from conifer forests, dinosaur trackways, enigmatic deposits such as glendonites, and stable isotope data from the Early Cretaceous formations of Spitsbergen suggest that the climate at that time was much more dynamic than the traditional view of "invariant greenhouse" conditions on Earth. The Early Cretaceous succession in central Spitsbergen comprises a regressive-transgressive mega-cycle. This is made up of the deep water to wave-dominated, Berriasian-Hauterivian Rurikfjellet Formation; the deltaic, Barremian Helvetiafjellet Formation; and the coastal to deep water, Aptian-Albian Carolinefjellet Formation. An erosion surface marks the base of the Helvetiafjellet Formation. Two regions with excellently exposed Early Cretaceous strata were chosen for study in this project: the Festningen section, on the north-western side of Isfjorden; and outcrops found along Adventdalen, near Longyearbyen, ~40km northeast of Festningen. We present the data collected in July 2015 from the Adventdalen area, and compare and correlate it with sedimentological and geochemical data collected from the Festningen succession in 2014. The Festningen section records a full sequence from the Berriasian to the Aptian, whereas the Longyearbyen sections record Aptian-Albian deposition. We use carbon isotope stratigraphy to constrain the Barremian-Aptian boundary in the previously only indirectly-dated Helvetiafjellet Formation, and to identify other major global climatic and carbon cycle perturbations in the Early Cretaceous. We are thus able to correlate this succession with other successions globally. We combine this δ13C(terrestrial) data with sedimentological and petrological data to elucidate the origins of enigmatic glendonites found in both regions. Glendonites are thought to be associated with cold-water (and therefore also cold-climate) conditions, although their mode of

  9. Vegetation-atmosphere interactions and their role in global warming during the latest Cretaceous

    OpenAIRE

    Upchurch, G. R.; Otto-Bliesner, B. L.; Scotese, C.

    1998-01-01

    Forest vegetation has the ability to warm Recent climate by its effects on albedo and atmospheric water vapour, but the role of vegetation in warming climates of the geologic past is poorly understood. This study evaluates the role of forest vegetation in maintaining warm climates of the Late Cretaceous by (1) reconstructing global palaeovegetation for the latest Cretaceous (Maastrichtian); (2) modelling latest Cretaceous climate under unvegetated conditions and different distributions of pal...

  10. Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards.

    Science.gov (United States)

    Daza, Juan D; Stanley, Edward L; Wagner, Philipp; Bauer, Aaron M; Grimaldi, David A

    2016-03-01

    Modern tropical forests harbor an enormous diversity of squamates, but fossilization in such environments is uncommon and little is known about tropical lizard assemblages of the Mesozoic. We report the oldest lizard assemblage preserved in amber, providing insight into the poorly preserved but potentially diverse mid-Cretaceous paleotropics. Twelve specimens from the Albian-Cenomanian boundary of Myanmar (99 Ma) preserve fine details of soft tissue and osteology, and high-resolution x-ray computed tomography permits detailed comparisons to extant and extinct lizards. The extraordinary preservation allows several specimens to be confidently assigned to groups including stem Gekkota and stem Chamaleonidae. Other taxa are assignable to crown clades on the basis of similar traits. The detailed preservation of osteological and soft tissue characters in these specimens may facilitate their precise phylogenetic placement, making them useful calibration points for molecular divergence time estimates and potential keys for resolving conflicts in higher-order squamate relationships. PMID:26973870

  11. A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians.

    Science.gov (United States)

    Azuma, Yoichi; Xu, Xing; Shibata, Masateru; Kawabe, Soichiro; Miyata, Kazunori; Imai, Takuya

    2016-02-23

    Our understanding of coelurosaurian evolution, particularly of bird origins, has been greatly improved, mainly due to numerous recently discovered fossils worldwide. Nearly all these discoveries are referable to the previously known coelurosaurian subgroups. Here, we report a new theropod, Fukuivenator paradoxus, gen. et sp. nov., based on a nearly complete specimen from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs. Computed-tomography data indicate that Fukuivenator possesses inner ears whose morphology is intermediate between those of birds and non-avian dinosaurs. Our phylogenetic analysis recovers Fukuivenator as a basally branching maniraptoran theropod, yet is unable to refer it to any known coelurosaurian subgroups. The discovery of Fukuivenator considerably increases the morphological disparity of coelurosaurian dinosaurs and highlights the high levels of homoplasy in coelurosaurian evolution.

  12. Evidence of Egg Diversity in Squamate Evolution from Cretaceous Anguimorph Embryos.

    Directory of Open Access Journals (Sweden)

    Vincent Fernandez

    Full Text Available Lizards are remarkable amongst amniotes, for they display a unique mosaic of reproduction modes ranging from egg-laying to live-bearing. Within this patchwork, geckoes are believed to represent the only group to ever have produced fully calcified rigid-shelled eggs, contrasting with the ubiquitous parchment shelled-eggs observed in other lineages. However, this hypothesis relies only on observations of modern taxa and fossilised gecko-like eggshells which have never been found in association with any embryonic or parental remains. We report here the first attested fossil eggs of lizards from the Early Cretaceous of Thailand, combining hard eggshells with exquisitely preserved embryos of anguimoph (e.g. Komodo dragons, mosasaurs. These fossils shed light on an apparently rare reproduction strategy of squamates, demonstrate that the evolution of rigid-shelled eggs are not an exclusive specialization of geckoes, and suggest a high plasticity in the reproductive organs mineralizing eggshells.

  13. Geología y geoquímica de los cuerpos básicos alcalinos al sur de los lagos Musters y Colhué Huapí, cuenca del golfo San Sorge, Chubut

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    Nilda D Menegatti

    2014-12-01

    Full Text Available En la región de los lagos Colhué Huapí y Musters, situada en la sierra de San Bernardo en el centro sur de la provincia del Chubut, afloran cuerpos ígneos básicos de carácter alcalino con estructuras de stocks, sills, lopolitos y diques, con edades comprendidas entre el Eoceno y Pleistoceno. En este trabajo, se presentan los resultados obtenidos del estudio efectuado en los cerros Negro, Cresta-Puricelli, Guacho, Solo, San Bernardo, Cresta-Trompete y Los Leones-Tumba del Indio, todos ellos localizados al sur de la localidad de Sarmiento. La litología identificada corresponde a gabro, monzogabro nefelínico, sienita nefelínica, basalto y basanita, siendo el gabro la variedad predominante. De acuerdo a la forma, el tamaño, los gradientes texturales y la presencia de zeolitas que presentan los cuerpos intrusivos, se considera que éstos se emplazaron en niveles corticales altos (<1 km. La mayoría de las rocas analizadas son básicas con un porcentaje de SiO2 entre 44 y 48 %, y se caracterizan por el alto contenido en Fe2O3 (10,66-14,67 %, TiO2 (1,23-3,37 % y álcalis (3,35-5,91 %. Los diagramas normalizados tienen el diseño típico de basaltos alcalinos de intraplaca, compatibles con una fuente de tipo OIB enriquecida en elementos incompatibles, con residuo granatífero en la fuente y ausencia de contaminación con la placa subducida o cortical. La pendiente pronunciada de la curva normalizada de REE (La/Yb = 10,2-22,4 señala relativamente bajos grados de fusión parcial. A partir del análisis estructural se plantea un ambiente extensional para el emplazamiento de estos cuerpos que es coherente con lo que indican las características geoquímicas.

  14. Estratigrafía, análisis de facies y paleoambientes de la formación cañadón asfalto en el depocentro jurásico cerro Cóndor, provincia del Chubut

    Directory of Open Access Journals (Sweden)

    Nora Cabaleri

    2010-05-01

    Full Text Available El depocentro Cerro Cóndor representa la secuencia estratigráfica del Jurásico continental más completa de la cuenca de Cañadón Asfalto y de Sudamérica austral. Se sitúa en la Patagonia extraandina, en ambas márgenes del río Chubut medio. La sedimentación en esta cuenca pull apart, acompañada por efusiones de basalto olivínico, comenzó en el Jurásico Medio temprano. Predominan en la Formación Cañadón Asfalto los depósitos lacustres caracterizados por asociaciones de facies carbonáticas y siliciclásticas intercaladas con rocas lávicas en la base y depósitos piroclásticos hacia el techo de la unidad. Se describe el desarrollo de facies a lo largo de un corte norte-sur que abarca las secciones de estancia El Torito y de los cañadones Los Loros, Las Chacritas, Carrizal, Asfalto y Lahuincó. Las facies/microfacies carbonáticas están representadas por mudstones, wackestones,packstones, grainstones y calizas microbialíticas características de ambientes litorales, marginales y palustres. En la Formación Cañadón Asfalto se distinguen un miembro inferior (Las Chacritas, constituido por calizas, lutitas, areniscas y conglomerados, intercalados con basaltos olivínicos y por otro superior (Puesto Almada compuesto por tobas, tufitas, lutitas y areniscas. El primero es portador de una asociación palinológica de edad bajociano-bathoniana y el segundo de dinosaurios de edad tithoniana. Se describen detalladamente e ilustran las secciones estratigráficas de ambos miembros de la formación en sus localidades tipo, cañadón Las Chacritas y estancia el Torito y se reconstruyen los paleoambientes del depocentro desde el Aaleniano al Tithoniano. La edad del miembro Puesto Almada en su localidad tipo se obtuvo mediante una datación radimétrica (K/Ar de biotitas provenientes de una delgada capa de toba volcánica (147,1 ± 3,3 Ma, Tithoniano proveniente de la parte superior de la unidad.

  15. Los niveles glauconíticos de la Formación Salamanca, Chubut: su efectividad agronómica como fuente alternativa de fertilizante potásico

    Directory of Open Access Journals (Sweden)

    Liliana N Castro

    2010-05-01

    Full Text Available Las secuencias marinas del Maastrichtiano-Paleoceno inferior representadas por la Formación Salamanca y unidades equivalentes, presentan niveles con glauconita que podrían suplir parcialmente las importaciones de potasio para uso en la industria de fertilizantes. La prospección y muestreo se realizó en las nacientes del río Chico, Chubut, donde los espesores de los niveles glauconíticos alcanzan 20 metros. El trabajo se dividió en fases: fase 1, prospección, muestreo y análisis sedimentológicos y químicos de rutina; fase 2a, ensayos de concentración y tratamiento, y fase 2b, ensayos agronómicos donde se compara la efectividad agronómica de las areniscas glauconíticas (GL con el fertilizante potásico tradicional (KCl. Estos últimos se realizaron en cámara de cultivo, con las fracciones 125 μm y 250 μm, (2,85 y 2,82 % K2O respectivamente de GL y con KCl, variando las dosis aplicadas, más una muestra testigo resultando en total 7 tratamientos. A lo largo de las 4 cosechas no se observó un comportamiento diferencial significativo entre GL1, GL2 (125 y el testigo. Ambos tratamientos de GL 250 μm presentaron una mayor biomasa acumulada, superando al testigo en un 44 y 60 % respectivamente. Como conclusión, los tratamientos con GL (125 presentaron resultados poco diferenciables del testigo, en tanto que en GL (250 los valores alcanzados superaron a los obtenidos con la fertilización con KCl. Probablemente la mayor participación de feldespato potásico junto a un incremento en la velocidad de lixiviación por riego en la fracción 125 μξm origine el rendimiento diferencial observado. La gran extensión areal de la Formación Salamanca y la continuidad de los niveles glauconíticos alienta a continuar su evaluación como fertilizante o enmienda.

  16. New predatory cockroaches (Insecta: Blattaria: Manipulatoridae fam.n.) from the Upper Cretaceous Myanmar amber

    Science.gov (United States)

    Vršanský, Peter; Bechly, Günter

    2015-04-01

    We describe a new extinct lineage Manipulatoridae (new family) of cockroaches from the Upper Cretaceous (Cenomanian) amber of Myanmar. Manipulator modificaputis gen. et sp. n. is a morphologically unique extinct cockroach that represents the first (of a total of 29 known worldwide) cockroach family reported exclusively from the Myanmar amber. This family represents an early side branch of the stem group of Mantodea (most probably a sister group of Eadiidae within Blattaria/Corydioidea) because it has some synapomorphies with the Mantodea (including the stem group and Eadiidae). This family also retains symplesiomorphies that exclude a position in the crown group, and furthermore has unique autapomorphies that exclude a position as a direct ancestor of Mantodea. The unique adaptations such as strongly elongated extremities and freely movable head on a long neck suggest that these animals were pursuit predators. Five additional specimens (including two immatures) reported from the Myanmar amber suggest that this group was relatively rare but belonged to the indigenous and autochthonous inhabitants of the ancient amber forest of the Myanmar region.

  17. Influences of floral composition and environment on plant biomarkers across a Cretaceous landscape (Big Cedar Ridge)

    Science.gov (United States)

    Bush, R. T.; Diefendorf, A. F.; Wing, S. L.; McInerney, F. A.

    2013-12-01

    The Late Cretaceous fossil site at Big Cedar Ridge (BCR; late Campanian, 72.7 Ma), located in the Bighorn Basin, Wyoming, USA, contains a flora preserved in situ in a volcanic ash tuff over an organic-rich paleosol. The BCR flora is irregularly but extensively exposed along a ~4 km north-south transect and records a lowland flora that grew on a coastal delta on the western shore of the Cretaceous Interior Seaway (Meeteetse Formation). The transect spans a diverse landscape and a range of environmental gradients from very carbon-rich, swampy soils in the southern portion to less carbon-rich in the north; the landscape is also intersected by multiple inactive channel cuts that were filling with sediment and organic matter at the time of ash deposition. Recently Wing and others (2012, Ecological Monographs) described the composition of the local plant community at high resolution across the entire landscape, including identification and quantification of cover and richness for >122 taxonomic morphotypes, for each of 100 sites along the transect. Big Cedar Ridge captures an important time in the ecological development of plant communities: the site preserves ferns, gymnosperms, and angiosperms in 'fern thicket' floral assemblages, which are rare today, as well as disturbed habitats with abundant herbaceous 'dicot' angiosperms. During the Late Cretaceous angiosperms were globally increasing in abundance, displacing other plant groups as vegetational dominants. This setting allows for a novel analysis of plant biomarkers in the context of floral diversity, abundance, and landscape heterogeneity. We quantified leaf waxes (n-alkyl lipids), plant-derived terpenoids, bacterial hopanes, carbon isotope values (including bulk and compound-specific), and percent total organic carbon of the underlying paleosol for 36 sites along the transect in order to assess the influence of floral composition and soil environment on biomarker distributions and preservation. We compare lipid

  18. Evidence For Volcanic Initiation Of Cretaceous Ocean Anoxic Events (Invited)

    Science.gov (United States)

    Sageman, B. B.; Hurtgen, M. T.; McElwain, J.; Adams, D.; Barclay, R. S.; Joo, Y.

    2010-12-01

    Increasing evidence from studies of Cretaceous ocean anoxic events (OAE’s) has suggested that major changes in volcanic activity may have played a significant role in their genesis. Numerous specific mechanisms of have been proposed, including increases in atmospheric CO2 and surface temperature, leading to enhanced chemical weathering and terrestrial nutrient release, or increases in reduced trace metal fluxes, leading to oxygen depletion and possibly providing micronutrients for enhanced primary production. An additional pathway by which the byproducts of enhanced volcanic activity may have contributed to OAE genesis involves relationships between the biogeochemical cycles sulfur, iron, and phosphorus. Recent analysis of S-isotope data from carbonate-associated sulfate and pyrite collected across the Cenomanian-Turonian OAE2 in the Western Interior basin suggest that increases in sulfate to an initially sulfate-depleted ocean preceded onset of the event. Modern lake data support the idea that increases in sulfate concentration drive microbial sulfate reduction, leading to more efficient regeneration of P from sedimentary organic matter. If the early Cretaceous opening of the South Atlantic was accompanied by evaporite deposition sufficient to draw down global marine sulfate levels, and widespread anoxia leading to elevated pyrite burial helped maintain these low levels for the succeeding 30 myr, during which most Cretaceous OAE’s are found, perhaps pulses of volcanism that rapidly introduced large volumes of sulfate may have played a key role in OAE initiation. The eventually burial of S in the form of pyrite may have returned sulfate levels to a low background, thus providing a mechanism to terminate the anoxic events. This talk will review the evidence for volcanic initiation of OAE’s in the context of the sulfate-phosphorus regeneration model.

  19. The origin and evolution of the Cretaceous Benue Trough (Nigeria)

    Science.gov (United States)

    Benkhelil, J.

    The intracontinental Benue Trough was initiated during the Lower Cretaceous in relation with the Atlantic Ocean opening. The first stage of its evolution started in the Aptian, forming isolated basins with continental sedimentation. In the Albian times, a great delta developed in the Upper Benue Trough, while the first marine transgression coming from the opening Gulf of Guinea occurred in the south and reached the Middle Benue. The widespread Turonian transgression made the Atlantic and Tethys waters communicate through the Sahara, Niger basins and the Benue Trough. The tectonic evolution of the Benue Trough was closely controlled by transcurrent faulting through an axial fault system, developing local compressional and tensional regimes and resulting in basins and basement horsts along releasing and restraining bends of the faults. Two major compressional phases occurred: in the Abakaliki area (southern Benue) during the Santonian; and at the end of the Cretaceous in the Upper Benue Trough. In Abakaliki, the sedimentary infilling was severely deformed through folding and flattening, and moderate folding and fracturing occurred in the northeast. The Cretaceous magmatism was restricted to main fault zones in most of the trough but was particularly active in the Abakaliki Trough, where it has alkaline affinities. From Albian to Santonian, the magmatism was accompanied in part of the Abakaliki Trough by a low-grade metamorphism. Geophysical data indicate a crustal thinning beneath the Benue Trough and, at a superficial level, an axial basement high flanked by two elongated deep basins including isolated sub-basins. The model of the tectonic evolution of the trough is based upon a general sinistral wrenching along the trough responsible for the structural arrangement and the geometry of the sub-basins. During the early stages of the Gulf of Guinea opening the Benue Trough was probably the expression on land of the Equatorial Fracture Zones.

  20. The paleohydrology of Lower Cretaceous seasonal wetlands, Isle of Wight, southern England

    Energy Technology Data Exchange (ETDEWEB)

    Wright, V.P.; Taylor, K.G.; Beck, V.H.

    2000-05-01

    The floodplain deposits of the Wealden Group (Lower Cretaceous) of the Isle of Wight, southern England, were formed in a seasonal wetland setting, a type of environment widespread today along higher-order tropical and subtropical river systems but rarely identified in the geological record. The unit consists of four main lithofacies: sheet sandstones with dinosaur footprint casts; green-gray mudstones with vertebrate remains, abundant lignite, pyrite, and siderite; spectacularly color-mottled mudstones with goethite and locally pseudo-anticlines; and red mudstones with pseudo-anticlines, hematite, and carbonate nodules. The sheet sandstones are interpreted as crevasse deposits; the green-gray mudstones were deposited in shallow ponds on the floodplain, which acted as sinks for debris released by local floods following wildfires; the mottled mudstones represent surface-water gley soils formed in seasonally waterlogged areas; and the red mudstones resemble present-day Vertisols that formed on topographically elevated areas only intermittently flooded. These mudstones show vertical transitions from one to another, and although they could be interpreted as components of simple catenas, the absence of associated facies changes implies that topographic differences were not the only control. It is proposed that these three mudstone types formed as seasonal wetland catenas, in which differences in soil drainage conditions resulted from variations in the flooding hydroperiod affecting areas with minor relief differences, rather than drainage variability simply reflecting static topographic differences. Such seasonal wetland systems are rarely documented in the stratigraphic record despite being a widespread environment in present-day tropical regions, and the Wealden deposits are used to identify criteria for the recognition of this important environment in the rock record. These southern English wetlands are compared with other Lower Cretaceous wetlands from northern Spain

  1. A transitional snake from the Late Cretaceous period of North America.

    Science.gov (United States)

    Longrich, Nicholas R; Bhullar, Bhart-Anjan S; Gauthier, Jacques A

    2012-08-01

    Snakes are the most diverse group of lizards, but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine or terrestrial environment and how their unique feeding mechanism evolved. The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered, but until now only an isolated vertebra has been described and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.

  2. Cretaceous biota of the Triângulo Mineiro region (Brazil: A review of recent finds

    Directory of Open Access Journals (Sweden)

    Candeiro, C. R. A.

    2007-06-01

    Full Text Available The Bauru Group (Adamantina, Uberaba, and Marília Formations crop out in the Triângulo Mineiro region, Minas Gerais State, Brazil, and yield a rich continental biota. Invertebrate and vertebrate taxa from underlying and overlying strata, as well as biostratigraphical correlations with other fossil sites in Argentina, suggest an Upper Cretaceous age for this biota. The diversity of the fossil assemblage recorded in these formations is summarized here and includes: frogs, lizards, crocodiles, titanosaurs, abelisaurid and carcharodontosaurid dinosaurs. This fossil assemblage provides important clues to understand faunas from other southern landmasses, particularly those from the Cretaceous of the African continent.Los afloramientos del Grupo Bauru (formaciones Adamantina, Uberaba y Marília en la región del Triângulo Mineiro, Provincia de Minas Gerais, Brasil, posee un rico contenido de biota continental. Los taxa de invertebrados y vertebrados de estos estratos, así como las correlaciones biostratigráficas con otros yacimientos fósiles de Argentina, sugieren una edad del Cretácico Tardío. La diversidad de la asociación fósil registrada en las formaciones del Triângulo Mineiro se resume en el presente trabajo e incluye: sapos, lagartos, tortugas, cocodrilianos, titanosaurideos, dinosaurios abelisaurideos y carcharodontosaurideos. Esta asociación es importante para la comprensión de las faunas del sur de América y también de las del Cretácico de África.

  3. Origin of Cretaceous phosphorites from the onshore of Tamil Nadu, India

    Indian Academy of Sciences (India)

    V Purnachandra Rao; Pratima M Kessarkar; R Nagendra; E V S S K Babu

    2007-12-01

    Cretaceous phosphorites from the onshore of Tamil Nadu have been investigated for their origin and compared with those in the offshore. Cretaceous phosphorites occur as light brown to yellowish brown or white nodules in Karai Shale of the Uttatur Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus of the nodules consists of light and dark coloured laminae, phosphate peloids/coated grains and detrital particles interspersed between the laminae. Scanning electron microscope (SEM) studies reveal trapping and binding activity of microbial filaments. A mat structure with linearly arranged microbial filaments and hollow, cell-based coccoid cyanobacterial mat are present. Nodules contain abundant carbonate fluorapatite, followed by minor calcite, quartz and feldspar. The P2O5 content of the phosphorites ranges from 18 to 26%. The CaO/P2O5, Sr and F contents are higher than that of pure carbonate fluorapatite. Concentrations of Si, Al, K, Fe, and Ti are low. We suggest that the nuclei of the nodules represent phosphate clasts related to phosphate stromatolites formed at intertidal conditions. At high energy levels the microbial mats were disintegrated into phosphate clasts, coated with carbonate and then reworked into Karai Shale. On the other hand, Quaternary phosphorites occur as irregular to rounded, grey coloured phosphate clasts at water depths between 180 and 320m on the continental shelf of Tamil Nadu. They exhibit grain-supported texture. Despite Quaternary in age, they also resemble phosphate stromatolites of intertidal origin and reworked as phosphate clasts onto the shelf margin depressions. Benthic microbial mats probably supplied high phosphorus to the sediments. Availability of excess phosphorus seems to be a pre-requisite for the formation of phosphate stromatolites.

  4. Biostratigraphy and paleoenvironments of the Stöckelwaldgraben section (Northern Calcareous Alps, Upper Cretaceous)

    Science.gov (United States)

    Bukenberger, Patrick; Wolfgring, Erik; Wagreich, Michael

    2016-04-01

    The Stöckelwaldgraben section exposes grey marls of the Streiteck- and Grabenbach formations, Gosau-Group, Upper Cretaceous, located in Austria. Frequent tempestite events were recorded throughout the section. The Stöckelwandgraben section represents a shelf environment from the southern margin of the Penninic Ocean. Biostratigraphic data indicates the Dicarinella concavata to Dicarinella asymetrica Zone for planktic foraminifera, which covers late Coniacian to early Santonian in age. The Coniacian/Santonian boundery was marked by the first occurrence of Sigalia carpatica and the first occurrence of Dicarinella asymetrica. The primary marker, defined by the GSSP (Global Stratotype Section and Point), Platyceramus undulatoplicatus, could not be found due to bad preservation of macrofossils. A gradual sea-level rise from a shallow marine to a neritic environment was observed by changes in the planktic/benthic foraminifera ratio, the faunal compositions and the diversity of benthic foraminifera. Only few planktonic foraminifera but abundant large miliolids were found in the Coniacian samples which suggests very shallow conditions. The content of planktonic foraminifera was gradually increasing up to 40% in the Santonian, where the planktic foraminiferal fauna was consisting mostly of large sized marginotruncanids, biserial planktics, dicarinellids and archeoglobigerinids. The assumed waterdepth ranges from approximately 20 meters to a maximum of 150 meters and is based on foraminiferal paleoecology. The state of preservation of the benthic foraminifera can be considered moderate to well while planktonic foraminifera were generally found to be well preserved High-magnesium calcite tests of miliolids such as Quinqueloculina sp. and Spiroloculina sp. were decalcified and in some cases only infillings of pyrite could be observed. Observing palaeoenvironmental changes in foraminiferal communities combined with an established chronostratigraphic framework will lead to a

  5. Ginkgo from Lower Cretaceous Changcai Formation in Helong of Jilin, NE China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Based on gross morphological and cuticular study, two species of Ginkgo From the Lower Cretaceous Changcai Formation in Helong of Jilin. were identified from this area for the first time, including Ginkgo coriacea Florin and G.sibiricaHeer. The study is significant for better understanding the paleophytogeographic, paleoecologicandstratigraphic characters of the Early Cretaceous Changcai flora.

  6. On the actinopterygian fish fauna (Upper Cretaceous: Campanian) from the Kristianstad Basin, southern Sweden.

    OpenAIRE

    Bazzi, Mohamad

    2014-01-01

    Actinopterygian remains have been recovered from Upper Cretaceous (uppermost lower to lowermost upper Campanian) marine strata of the Kristianstad Basin, southern Sweden. This is the first record of Upper Cretaceous bony fish from the Fennoscandian shield. The fauna consists of higher taxa including Pachycormiformes (Pachycormidae), Elopiformes (Pachyrhizodontidae), Pycnodontiformes (Pycnodontidae), Aulopiformes (Enchodontidae), Ichthyodectiformes (Ichthyodectidae), and indeterminable teleost...

  7. Characteristics and their controlling factors of Cretaceous Kezilesu Group sandstone reservoirs in Akmomu gas field, northwestern Tarim Basin%塔西南阿克莫木气田白垩系克孜勒苏群砂岩储层特征及其控制因素

    Institute of Scientific and Technical Information of China (English)

    石石; 常志强; 徐艳梅; 阳建平; 初广震

    2012-01-01

    Characteristics of Kezilesu Group sandstone reservoirs and factors controlling their development are investigated based on the analysis of routine thin-sections,cast thin-sections,physical property and grain sizes. The results show that the reservoir rocks are dominanted by feldspathic litharemte and lithic sandstones with low porosity and permeability,and the pore types are mainly secondary pores including intragranular dissolved pores, intergranular dissolved pores and micropores. The mercury intrusion curve has high displacement pressure, indicating that the sorting of pore throats is poor and the pore structure feature in small pores and fine throats. The development of Kezilesu Group sandstone reservoirs in Akemomu gas field has strong correlation with grain sizes, debris content and diagenetic compaction, cementation and dissolution. For reservoir rocks were deposited under the control of braided rivers, their quality improves with grain size enlarging, debns content increasing and enhancing of dissolution. On the contrary, compaction and cementation of carbonate, clay and siliceous mineral formed during the post-diagenesis have adverse effects on reservoir rocks.%根据常规薄片、铸体薄片、常规物性和粒度分析,研究了塔西南阿克莫木气田克孜勒苏群砂岩储层的地质特征及其主控因素.结果表明,该套储层岩石类型以长石岩屑砂岩及岩屑砂岩为主;储层物性较差,为低孔、低渗储层;孔隙类型以次生孔隙为主,主要有粒内溶孔、粒间溶孔及微孔隙等;压汞曲线排驱压力较高,一般孔喉分选较差,总体具有小孔细喉的孔隙结构特征.阿克莫木气田克孜勒苏群砂岩储层发育程度与碎屑颗粒的粒度粗细,岩屑含量以及成岩阶段的压实、胶结和溶蚀作用具有较强的相关性.辫状水道控制下的碎屑颗粒越粗,岩屑含量相对越高,溶蚀作用越强,储层就越发育;压实作用及成岩后期的碳酸盐岩、

  8. Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections

    Institute of Scientific and Technical Information of China (English)

    Abdul Rahman Ashraf; Ashok Sahni

    2003-01-01

    The Cretaceous of Afghanistan is marked by great facies diversity. The evolution of Cretaceous basins is part of a complex accretionary history involving three distinct tectonic units namely the Asian (Russian) Block separated from the Indian plate by a rather well defined transcurrent fault (Chaman-Nuski). The southwestern component is representedby the Iran-Afghanistan plate. The Lower Cretaceous of the Asian Block is represented by the Red-Grit Series which isconformable to the underlying Upper Jurassic sequences. The transition is marked by evaporitic facies dominated by salt,gypsum and marl deposits. In south Afghanistan volcanic rocks occur at Farah, with the emplacement of plutonics inwest-central Afghanistan. The Upper Cretaceous of north Afghanistan is marked by richly fossiliferous, lime stone-dominated sequences. The Upper Cretaceous of southern Afghanistan is marked by strong ophiolitic magrmatism.

  9. Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén, Departamento Confluencia, Neuquén Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group, Confluencia, Neuquén

    Directory of Open Access Journals (Sweden)

    M.L. Sánchez

    2006-03-01

    orden, señalada por una conspicua superficie de erosión, limita la base del estilo fluvial III que corresponde a canales sinuosos donde dominan los depósitos de acreción lateral. Estos constituyen el tercio superior de la Formación Plottier y señalan una modificación abrupta en la evolución de los sistemas fluviales. La superficie erosiva y plana, seguida por cuerpos de areniscas tabulares y espesos, señala el período de caída en el nivel de base y estadio temprano de ascenso.A sedimentary succession was studied on the north margin of Los Barreales Lake, in northeastern of Neuquén, Argentina. These outcrops correspond to the Portezuelo and Plottier Formations, which are formally grouped as the Río Neuquén Subgroup of the Neuquén Group. The Plottier Formation is considered as upper Coniacian in age. In order to describe the distribution pattern and evolution of the paleoenvironments of this unit, eleven lithofacies were recognized and grouped into seven lithofacies associations that characterize different fluvial styles, which are named here as fluvial styles I, II and III. The fluvial style I is at the base of these outcrops and represents an ephemeral fluvial system characterized by isolate lenticular channels in flood plain deposits and frequent sheet floods events. Gradually, an increasing on the channel/floodplain relation is recorded. Channels becoming thicker and showing up a braided design, levees, crevasse splays and a strong multilateral relation are developed. These features are defining the fluvial style II. Large scale geometry of fluvial styles I and II are pointing out a progressive decrease on the accommodation/supply. Weather probably varied from sub-humid or semi-arid to humid climatic conditions with strong seasonal variations. These provoked important changes on the water and sediment discharge onto the fluvial system. At the middle part of Plottier Formation a 6° order discontinuity is defined. This is the border for a stacked channel

  10. Debris-carrying camouflage among diverse lineages of Cretaceous insects.

    Science.gov (United States)

    Wang, Bo; Xia, Fangyuan; Engel, Michael S; Perrichot, Vincent; Shi, Gongle; Zhang, Haichun; Chen, Jun; Jarzembowski, Edmund A; Wappler, Torsten; Rust, Jes

    2016-06-01

    Insects have evolved diverse methods of camouflage that have played an important role in their evolutionary success. Debris-carrying, a behavior of actively harvesting and carrying exogenous materials, is among the most fascinating and complex behaviors because it requires not only an ability to recognize, collect, and carry materials but also evolutionary adaptations in related morphological characteristics. However, the fossil record of such behavior is extremely scarce, and only a single Mesozoic example from Spanish amber has been recorded; therefore, little is known about the early evolution of this complicated behavior and its underlying anatomy. We report a diverse insect assemblage of exceptionally preserved debris carriers from Cretaceous Burmese, French, and Lebanese ambers, including the earliest known chrysopoid larvae (green lacewings), myrmeleontoid larvae (split-footed lacewings and owlflies), and reduviids (assassin bugs). These ancient insects used a variety of debris material, including insect exoskeletons, sand grains, soil dust, leaf trichomes of gleicheniacean ferns, wood fibers, and other vegetal debris. They convergently evolved their debris-carrying behavior through multiple pathways, which expressed a high degree of evolutionary plasticity. We demonstrate that the behavioral repertoire, which is associated with considerable morphological adaptations, was already widespread among insects by at least the Mid-Cretaceous. Together with the previously known Spanish specimen, these fossils are the oldest direct evidence of camouflaging behavior in the fossil record. Our findings provide a novel insight into early evolution of camouflage in insects and ancient ecological associations among plants and insects. PMID:27386568

  11. Evidence for global cooling in the Late Cretaceous

    Science.gov (United States)

    Linnert, Christian; Robinson, Stuart A.; Lees, Jackie A.; Bown, Paul R.; Pérez-Rodríguez, Irene; Petrizzo, Maria Rose; Falzoni, Francesca; Littler, Kate; Arz, José Antonio; Russell, Ernest E.

    2014-06-01

    The Late Cretaceous ‘greenhouse’ world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the Campanian-Maastrichtian interval (~83-66 Ma) from hemipelagic sediments deposited on the western North Atlantic shelf. Our record reveals that the North Atlantic at 35 °N was relatively warm in the earliest Campanian, with maximum SSTs of ~35 °C, but experienced significant cooling (~7 °C) after this to <~28 °C during the Maastrichtian. The overall stratigraphic trend is remarkably similar to records of high-latitude SSTs and bottom-water temperatures, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by declining atmospheric pCO2 levels.

  12. Mountain building triggered late cretaceous North American megaherbivore dinosaur radiation.

    Directory of Open Access Journals (Sweden)

    Terry A Gates

    Full Text Available Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB. Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone.

  13. Evolutionary transition of dental formula in Late Cretaceous eutherian mammals

    Science.gov (United States)

    Averianov, Alexander O.; Archibald, J. David

    2015-10-01

    Kulbeckia kulbecke, stem placental mammal from the Late Cretaceous of Uzbekistan, shows a transitional stage of evolution in the dental formula from five to four premolars. A non-replaced dP3/dp3 may occur as individual variation. In other specimens, the lower premolars are crowded with no space for development of dp3. As is evident from the CT scanning of one juvenile specimen, the development of dp3 started in a late ontogenetic stage and was confined to the pulp cavity of the developing p2. This dp3 would have been resorbed in a later ontogenetic stage, as the roots of p2 formed. The initial stage of reduction of the third premolar can be traced to stem therians ( Juramaia and Eomaia), which have both dP3 and P3 present in the adult dentition. Further delay in the development of dP3/dp3 led to the loss of the permanent P3/p3 (a possible synapomorphy for Eutheria). The dP3/dp3 was present during most of the adult stages in the Late Cretaceous stem placentals Zhelestidae and Gypsonictops. This tooth is totally absent in basal taxa of Placentalia, which normally have at most four premolars.

  14. Debris-carrying camouflage among diverse lineages of Cretaceous insects

    Science.gov (United States)

    Wang, Bo; Xia, Fangyuan; Engel, Michael S.; Perrichot, Vincent; Shi, Gongle; Zhang, Haichun; Chen, Jun; Jarzembowski, Edmund A.; Wappler, Torsten; Rust, Jes

    2016-01-01

    Insects have evolved diverse methods of camouflage that have played an important role in their evolutionary success. Debris-carrying, a behavior of actively harvesting and carrying exogenous materials, is among the most fascinating and complex behaviors because it requires not only an ability to recognize, collect, and carry materials but also evolutionary adaptations in related morphological characteristics. However, the fossil record of such behavior is extremely scarce, and only a single Mesozoic example from Spanish amber has been recorded; therefore, little is known about the early evolution of this complicated behavior and its underlying anatomy. We report a diverse insect assemblage of exceptionally preserved debris carriers from Cretaceous Burmese, French, and Lebanese ambers, including the earliest known chrysopoid larvae (green lacewings), myrmeleontoid larvae (split-footed lacewings and owlflies), and reduviids (assassin bugs). These ancient insects used a variety of debris material, including insect exoskeletons, sand grains, soil dust, leaf trichomes of gleicheniacean ferns, wood fibers, and other vegetal debris. They convergently evolved their debris-carrying behavior through multiple pathways, which expressed a high degree of evolutionary plasticity. We demonstrate that the behavioral repertoire, which is associated with considerable morphological adaptations, was already widespread among insects by at least the Mid-Cretaceous. Together with the previously known Spanish specimen, these fossils are the oldest direct evidence of camouflaging behavior in the fossil record. Our findings provide a novel insight into early evolution of camouflage in insects and ancient ecological associations among plants and insects. PMID:27386568

  15. Palaeogeographic regulation of glacial events during the Cretaceous supergreenhouse.

    Science.gov (United States)

    Ladant, Jean-Baptiste; Donnadieu, Yannick

    2016-01-01

    The historical view of a uniformly warm Cretaceous is being increasingly challenged by the accumulation of new data hinting at the possibility of glacial events, even during the Cenomanian-Turonian (∼95 Myr ago), the warmest interval of the Cretaceous. Here we show that the palaeogeography typifying the Cenomanian-Turonian renders the Earth System resilient to glaciation with no perennial ice accumulation occurring under prescribed CO2 levels as low as 420 p.p.m. Conversely, late Aptian (∼115 Myr ago) and Maastrichtian (∼70 Myr ago) continental configurations set the stage for cooler climatic conditions, favouring possible inception of Antarctic ice sheets under CO2 concentrations, respectively, about 400 and 300 p.p.m. higher than for the Cenomanian-Turonian. Our simulations notably emphasize that palaeogeography can crucially impact global climate by modulating the CO2 threshold for ice sheet inception and make the possibility of glacial events during the Cenomanian-Turonian unlikely. PMID:27650167

  16. Vertebrate assemblages from the early Late Cretaceous of southeastern Morocco: An overview

    Science.gov (United States)

    Cavin, L.; Tong, H.; Boudad, L.; Meister, C.; Piuz, A.; Tabouelle, J.; Aarab, M.; Amiot, R.; Buffetaut, E.; Dyke, G.; Hua, S.; Le Loeuff, J.

    2010-07-01

    Fossils of vertebrates have been found in great abundance in the continental and marine early Late Cretaceous sediments of Southeastern Morocco for more than 50 years. About 80 vertebrate taxa have so far been recorded from this region, many of which were recognised and diagnosed for the first time based on specimens recovered from these sediments. In this paper, we use published data together with new field data to present an updated overview of Moroccan early Late Cretaceous vertebrate assemblages. The Cretaceous series we have studied encompasses three Formations, the Ifezouane and Aoufous Formations, which are continental and deltaic in origin and are often grouped under the name "Kem Kem beds", and the Akrabou Formation which is marine in origin. New field observations allow us to place four recognised vertebrate clusters, corresponding to one compound assemblage and three assemblages, within a general temporal framework. In particular, two ammonite bioevents characterise the lower part of the Upper Cenomanian ( Calycoceras guerangeri Zone) at the base of the Akrabou Formation and the upper part of the Lower Turonian ( Mammites nodosoides Zone), that may extend into the Middle Turonian within the Akrabou Formation, and allow for more accurate dating of the marine sequence in the study area. We are not yet able to distinguish a specific assemblage that characterises the Ifezouane Formation when compared to the similar Aoufous Formation, and as a result we regard the oldest of the four vertebrate "assemblages" in this region to be the compound assemblage of the "Kem Kem beds". This well-known vertebrate assemblage comprises a mixture of terrestrial (and aerial), freshwater and brackish vertebrates. The archosaur component of this fauna appears to show an intriguingly high proportion of large-bodied carnivorous taxa, which may indicate a peculiar trophic chain, although collecting biases alter this palaeontological signal. A small and restricted assemblage, the

  17. Paleoambientes de sedimentación del tramo superior de la Formación Portezuelo, Grupo Neuquén (Cretácico Superior, Los Barreales, provincia del Neuquén Sedimentry paleoenvironments of the upper sectin of Portezuelo Formation, Neuquen Group (Upper cretaceous, Los Barreales, Neuquen Province

    Directory of Open Access Journals (Sweden)

    M.L. Sánchez

    2005-03-01

    Full Text Available Al norte del lago Los Barreales aflora el tramo superior de la Formación Portezuelo, unidad basal del Subgrupo Río Neuquén (Grupo Neuquén del Turoniano superior-Coniaciano. En ese sector se realizaron estudios sedimentológicos para determinar los paleoambientes sedimentarios, su evolución y determinar los factores de control más relevantes.Se determinaron 12 litofacies que fueron incluidas en 6 asociaciones de facies. La naturaleza y organización de las asociaciones, permiten el desarrollo de canales fluviales entrelazados gravosos y de carga mixta de baja y alta sinuosidad. Las paleocorrientes son, en general, hacia NE y NO.Los sistemas fluviales estuvieron sujetos a cambios abruptos en el régimen de descarga correlacionables con variables climáticas de corto término. Las variaciones en el tamaño de grano dominante de la carga de lecho, espesores de los cuerpos de canal y proporciones relativas de elementos de canal/llanura de inundación, responden a fluctuaciones de largo término en los niveles de descarga. También se interpreta que las modificaciones en el nivel de base controlaron la arquitectura fluvial a gran escala. El apilamiento de las unidades de canal, se relaciona con una tasa de suministro que no pudo ser, en general, compensada por la tasa de subsidencia. Un ligero incremento de ésta última hacia el tope de la unidad, dio como resultado el desarrollo de áreas anegadas dentro de la llanura de inundación y cuerpos de agua más o menos estables que fueron luego ocupadas por un sistema fluvial de carga mixta de alta sinuosidad.The upper part of the Portezuelo Formation (upper Turonian-Coniacian; Río Neuquen Subgroup of the Neuquen Group crops out to the north of the Los Barreales lake. Sedimentological studies in order to determine paleoenvironments, their evolution, and the more relevant controls on deposition were carried out in this area.Twelve lithofacies were defined and included in six facies associations. The

  18. Evolution of Palaeo-Uplift and Its Controlling on Sedimentation of Kapushaliang Group of Early Cretaceous in Western Tabei Uplift%塔北西部早白垩世卡普沙良群沉积期古隆起演化及其对沉积的控制作用

    Institute of Scientific and Technical Information of China (English)

    徐桂芬; 林畅松; 刘永福; 孙琦

    2016-01-01

    Palaeo-uplift is an important tectonic unit in the petroleum basin.The Research of palaeo-uplift distribution,its evo-lution and statement its influence on the development of sediment have important study significance for oil and gas exploration. Based on the comprehensive research of core,logging data,seismic data and outcrop,the sequence stratigraphy framework of Kapushaliang Group was established,which was divided into four third-order sequences internally.Then the palaeo-uplift dis-tribution and its evolution in each sequence developmental stages of Kapushaliang Group were reconstructed.In SQ1 period, palaeo-uplift was EW trending,across the entire work area,widening from the middle to east and west,with an erosion area of 1 946 km2 .In SQ2 period,the palaeo-uplift area was decreased and submerged in the central uplift,2 small eroded areas re-mained in the east and bigger eroded area in the west,with a total area of approximately 1 365 km2 .In SQ3 period,the palaeo-uplift area was further decreased,the east was submerged overall and the northwest residual palaeo-uplift was 899 km2 ,and the palaeo-uplift disappeared to SQ4.According to the core observation,combined with rock combination and logging data, four kinds of sedimentary system types are identified:the brainded river delta,oxidized shallow delta,beach-and-bar facies and shore-shallow lake.Finally the configuration relationship between palaeo-uplift and source-to-sink system is revealed,based on seismic data,logging,core and other analysis data,using the idea of basin analysis,and studying the factors of structure, palaeo-uplift,facies comprehensively.It is found that there are two source systems developed in the research area:the source from the palaeo-uplift to the north and south sides and source from distant southern source.The northern side near the erosion uplift area developed short provenance,which formed braided river delta deposition.With the decrease of erosion area,the brai-ded river delta

  19. THE EARTH'S MAGNETIC FIELD AND GLOBAL GEOLOGIC PHENOMENA IN MID-CRETACEOUS%白垩纪中期地球磁场与全球地质现象

    Institute of Scientific and Technical Information of China (English)

    Xixi ZHAO

    2005-01-01

    , covering about one-third of the land area. Sea levels were up to 250 m higher than present day levels. Geological evidence also points towards an unusually high rate of volcanic activity in the mid-Cretaceous. Large volumes of magmatic material flowed to Earths surface from the mantle, and not just from the typical seafloor spreading. The "large igneous provinces" or LIPs made a very important contribution to the lithosphere during the mid-Cretaceous. Several LIPs such as the Ontong Java Plateau(120 Ma), the main portion of the Kerguelen Plateau(115~80 Ma), the Madagascar LIP(84~91Ma), the High Arctic LIP(85~95 Ma), and the Caribbean LIP(88~91 Ma)were all formed during this time. Carbon dioxide emissions released by the Cretaceous LIPs may have triggered two to seven oceanic anoxic events(OAEs) and led to a greenhouse effect that raised the Earths surface temperature by roughly 10 degrees Celsius, reduced temperature gradients from the Equator to the poles, and resulted in general absence of polar ice caps and oceans much warmer than todays. The mid-Cretaceous was also a time of rapid radiation and turnover in the marine plankton, benthic foraminifera, and terrestrial plants. This evolutionary activity transformed many of these groups on an ocean-wide basis. The reorganization of the global biosphere during the mid-Cretaceous paralleled the marked changes in the ocean-climate system, suggesting a causal relationship between biotic evolution and environments. Other geologic anomalies associated with the mid-Cretaceous thermal activity include the extremely high development of the Earths diamond bearing kimberlites in mid-East and South Africa and markedly reduced(less radiogenic)seawater strontium isotope ratio(87Sr/86Sr). A key piece in the mid-Cretaceous geologic phenomena is the Cretaceous Normal Superchron. This is a period in which Earths magnetic field was uncharacteristically steady that did not switch from normal to reversed polarity for about

  20. Ontogenetic changes in the craniomandibular skeleton of the abelisaurid dinosaur Majungasaurus crenatissimus from the Late Cretaceous of Madagascar

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    Nirina O. Ratsimbaholison

    2016-06-01

    Full Text Available Abelisaurid theropods were one of the most diverse groups of predatory dinosaurs in Gondwana during the Cretaceous. The group is characterized by a tall, wide skull and robust cervical region. This morphology is thought to have facilitated specialized feeding behaviors such as prolonged contact with prey. The Late Cretaceous abelisaurid Majungasaurus crenatissimus typifies this abelisaurid cranial morphotype. Recent fossil discoveries of this species include a partial growth series that allows for the first time an investigation of ontogenetic variation in cranial morphology in a representative abelisaurid. Herein we examine growth trajectories in the shape of individual cranial bones and articulated skulls of Majungasaurus using geometric morphometrics. Several major changes in skull shape were observed through ontogeny, including an increase in the height of the jugal, postorbital, and quadratojugal, an increase in the extent of the contacts between bones, and a decrease in the circumference of the orbit. The skull transitions from relatively short in the smallest individual to tall and robust in large adults, as is seen in other theropods. Such morphological change during ontogeny would likely have resulted in different biomechanical properties and feeding behaviors between small and large individuals. These findings provide a post-hatching developmental framework for understanding the evolution of the distinctive tall skull morphology seen in abelisaurids and other large-sized theropod dinosaurs.

  1. Sedimentología y paleoambientes del Subgrupo Río Neuquén (Cretácico Superior en la quebrada de Las Chivas, departamento Confluencia, provincia de Neuquén Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group, Confluencia, Neuquén

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    M.L. Sánchez

    2006-03-01

    el estilo fluvial fue anastomosado. En la base de la Formación Plottier se identifica una discontinuidad de 6to orden. Ésta limita una sucesión de cinturones de canales entrelazados apilados. La discontinuidad neta y planar y el importante cambio en la arquitectura fluvial sugieren una fuerte disminución en la relación acomodación/suministro.The Río Neuquén Subgroup (lateTuronian-late Coniacian of the Neuquén Group, crops out to the west of the Senillosa locality. Sedimentological studies in order to determine paleoenvironments, their evolution, and relevant controls on deposition were carried out in this area. Twelve lithofacies were defined and included in six facies associations. The nature and arrangement of facies associations suggest the development of braided and anastomosig fluvial systems as well as dunes and aeolian sandsheets. The fluvial systems were subject to changes in the discharge regime, interpreted to be related to short term climatic variability. The variations of dominant grain size of the bed load, thickness of channel bodies, and relative proportions of channel/flood plain elements, respond to long term fluctuations of discharge levels. It is suggested that the modifications in base-level controlled the large-scale fluvial architecture. At the base of Portezuelo Formation thick channels show a braided design, levees, crevasse splay and a strong multilateral relation are developed. These relation of channel units, is related with a rate of sediment supply that, in general, compensated by the subsidence rate. At the flood plain aeolian dunes and sheet were developed. Gradually, a decreasing on the channel/floodplain relation is recorded. The fluvial system is characterized by isolate lenticular channels in flood plain deposits and frequent crevasse splays events.were recorded. In the top of the unit, an increase of subsidence rate resulted in the development of flooded areas within the flood plain and the anastomosed fluvial style. At

  2. A new troodontid theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America.

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    Lindsay E Zanno

    Full Text Available BACKGROUND: Troodontids are a predominantly small-bodied group of feathered theropod dinosaurs notable for their close evolutionary relationship with Avialae. Despite a diverse Asian representation with remarkable growth in recent years, the North American record of the clade remains poor, with only one controversial species--Troodon formosus--presently known from substantial skeletal remains. METHODOLOGY/PRINCIPAL FINDINGS: Here we report a gracile new troodontid theropod--Talos sampsoni gen. et sp. nov.--from the Upper Cretaceous Kaiparowits Formation, Utah, USA, representing one of the most complete troodontid skeletons described from North America to date. Histological assessment of the holotype specimen indicates that the adult body size of Talos was notably smaller than that of the contemporary genus Troodon. Phylogenetic analysis recovers Talos as a member of a derived, latest Cretaceous subclade, minimally containing Troodon, Saurornithoides, and Zanabazar. MicroCT scans reveal extreme pathological remodeling on pedal phalanx II-1 of the holotype specimen likely resulting from physical trauma and subsequent infectious processes. CONCLUSION/SIGNIFICANCE: Talos sampsoni adds to the singularity of the Kaiparowits Formation dinosaur fauna, which is represented by at least 10 previously unrecognized species including the recently named ceratopsids Utahceratops and Kosmoceratops, the hadrosaurine Gryposaurus monumentensis, the tyrannosaurid Teratophoneus, and the oviraptorosaurian Hagryphus. The presence of a distinct troodontid taxon in the Kaiparowits Formation supports the hypothesis that late Campanian dinosaurs of the Western Interior Basin exhibited restricted geographic ranges and suggests that the taxonomic diversity of Late Cretaceous troodontids from North America is currently underestimated. An apparent traumatic injury to the foot of Talos with evidence of subsequent healing sheds new light on the paleobiology of deinonychosaurians

  3. Provenance and drainage system of the Early Cretaceous volcanic detritus in the Himalaya as constrained by detrital zircon geochronology

    Institute of Scientific and Technical Information of China (English)

    Xiu-Mian Hu; Eduardo Garzanti; Wei An

    2015-01-01

    The age range of the major intra-plate volcanic event that affected the northern Indian margin in the Early Cretaceous is here deifned precisely by detrital zircon geochronol-ogy. U–Pb ages of Early Cretaceous detrital zircons found in the Cretaceous to the Paleocene sandstones cluster mainly between 142 Ma and 123 Ma in the northern Tethys Himalayan unit, and between 140 Ma and 116 Ma in the southern Tethys Himalayan unit. The youngest and oldest detrital zircons within this group indicate that volcanism in the source areas started in the latest Jurassic and ended by the early Albian. Stratigraphic data indicate that volcaniclastic sedimentation began signiifcantly earlier in southern Tibet (Tithonian) than in Nepal (Valangin-ian), and considerably later in Spiti and Zanskar (Aptian/Albian) to the west. This apparent westward migration of magmatism was explained with progressive westward propagation of extensional/transtensional tectonic activity and development of fractures cutting deeply across the Indian continental margin crust. However, detrital zircon geochronology provides no indi-cation of heterochroneity in magmatic activity in the source areas from east to west, and thus lends little support to such a scenario. Westward migration of volcaniclastic sedimentation may thus relfect instead the westward progradation of major drainage systems supplying vol-canic detritus sourced from the same volcanic centers in the east. Development of multiple radial drainage away from the domal surface uplift associated with magmatic upwelling, as observed for most large igneous provinces around the world, may also explain why U–Pb ages of detrital zircons tend to cluster around 133–132 Ma (the age of the Comei igneous province) in Tethys Himalayan units, but around 118–117 Ma (the age of the Rajmahal igneous province) in Lesser Himalayan units.

  4. Late Cretaceous intraplate silicic volcanic rocks from the Lake Chad region: An extension of the Cameroon volcanic line?

    Science.gov (United States)

    Shellnutt, J. G.; Lee, T.-Y.; Torng, P.-K.; Yang, C.-C.; Lee, Y.-H.

    2016-07-01

    Silicic volcanic rocks at Hadjer el Khamis, near Lake Chad, are considered to be an extension of the Cameroon volcanic line (CVL) but their petrogenetic association is uncertain. The silicic rocks are divided into peraluminous and peralkaline groups with both rock types chemically similar to within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma indicating the magmas erupted ˜10 million years before the next oldest CVL rocks (i.e., ˜66 Ma). The Sr isotopes (i.e., ISr = 0.7021-0.7037) show a relatively wide range but the Nd isotopes (i.e., 143Nd/144Ndi = 0.51268-0.51271) are uniform and indicate that the rocks were derived from a moderately depleted mantle source. Thermodynamic modeling shows that the silicic rocks likely formed by fractional crystallization of a mafic parental magma but that the peraluminous rocks were affected by low temperature alteration processes. The silicic rocks are more isotopically similar to Late Cretaceous basalts identified within the Late Cretaceous basins (i.e., 143Nd/144Ndi = 0.51245-0.51285) of Chad than the uncontaminated CVL rocks (i.e., 143Nd/144Ndi = 0.51270-0.51300). The age and isotopic compositions suggest the silicic volcanic rocks of the Lake Chad region are related to Late Cretaceous extensional volcanism in the Termit basin. It is unlikely that the silicic volcanic rocks are petrogenetically related to the CVL but it is possible that magmatism was structurally controlled by suture zones that formed during the opening of the Central Atlantic Ocean and/or the Pan-African Orogeny.

  5. La extensa zona de deslizamientos de la escarpa oriental de la Pampa de Salamanca, Chubut, entre los 45°00´S y 45°45´S

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    E.F. González Díaz

    2004-12-01

    Full Text Available Durante la ejecución del mapa geomorfológico de la provincia del Chubut, se identificó entre las latitudes de los 45°00´S y 45°45´S y a lo largo de unos 70-75 km, una extensa faja de deslizamientos adyacente y prácticamente paralela a la escarpa oriental de la Pampa de Salamanca. Los deslizamientos, con marcado predominio de deslizamientos rotacionales, perturban el tramo superior de la secuencia sedimentaria terciaria. En los niveles arcillosos de la Formación Chenque (= Formación Patagonia, se localizarían las superficies de despegue o corte (shear para su ocurrencia. Diferencias entre sus rasgos morfológicos, tipológicos y el promotor sugerido permiten proponer cuatro zonas (I, II, III y IV de deslizamientos. La tipología aquí propuesta es provisoria, siendo sólo una base de futuras elaboraciones. Cronológicamente se diferenciaron dos conjuntos de deslizamientos: unos antiguos, más extensos y de mayor volumen, con marcadas evidencias de erosión y aquellos modernos, más reducidos, que con excelente conservación de su morfología primaria, son producto de posteriores removilizaciones acontecidas en sectores de los antiguos, que se expresan esencialmente bajo la forma de flujos (corrientes de tierra o earthflows y más ocasionalmente como deslizamientos rotacionales secundarios (slumps. Entre los de mayor edad, los de la zona I, son definidos como afines en general a un deslizamiento rotacional con una fase distal de flujo; ocasionalmente habrían superado los límites del actual acantilado marino. A pesar de esta primera apreciación, no se descarta su consideración como ejemplos de expansiones laterales (lateral spreads. Los de la zona II, son definidos como deslizamientos rotacionales múltiples retrogradantes. Aquellos de la zona III integran un conjunto de deslizamientos con un marcado control estructural (N50°E, en sus desprendimientos. La zona IV, compone una estrecha y continua faja adyacente a la Pampa de

  6. Geological Evidence That Resolves the Baja-BC Controversy: Detrital Zircons Indicate That Vancouver Island Was Adjacent to Southern California in the Late Cretaceous

    Science.gov (United States)

    Guest, B.; Matthews, W.; Coutts, D. S.; Bain, H.; Hubbard, S. M.

    2015-12-01

    The Baja-BC hypothesis is at the center of a great earth sciences controversy. It stems from paleomagnetic observations that require large-scale displacements of continental crust from low latitudes (Baja, California) to moderate latitudes (British Columbia). Many geologists dispute the scale of the displacements due to a lack of corroborating geological evidence. We provide a robust, geological dataset that confirms the paleomagnetic observations. Detrital zircons from Cretaceous to Paleocene sandstone of the Nanaimo Group, which crops out in western Vancouver Island and the Gulf Islands of southwest British Columbia, are analyzed. The data show a clear transition from local 300 Ma grains in the Maastrichtian-Paleogene. An identical pattern is observed in detrital zircon datasets from southern California forearc basin deposits, and schists interpreted as the subducted remnants of forearc deposits. With a high-n dataset (n=3041) we are able to rule out possible >300 Ma source regions in Canada and the northern United States, and uniquely tie Nanaimo Group rocks to the Mojave-Sonora region of SW United States. This implies that at the end of the Cretaceous, Vancouver Island and western mainland BC were adjacent to southern California and northwestern Mexico, requiring 1900 km of displacement during the latest Cretaceous and Paleocene, consistent with paleomagnetic results. An implication of this result is that the western Coast Batholith of southwest BC was positioned between the northern Peninsular Ranges and southern Sierra Nevada batholiths in the late Cretaceous, and likely represents a displaced segment of a once continuous Cordilleran arc batholith. These results have broad implications for our understanding of episodic arc magmatism in the Cordillera, the tectonic evolution of western North America, Laramide orogenesis, the development and extent of the Nevadaplano, and the onset of Basin and Range extension.

  7. A temporary pond in the Early Cretaceous of southern England: palaeoclimatic implications of nonmarine "Purbeck-Wealden" ostracod faunas

    Science.gov (United States)

    Horne, D. J.

    2009-04-01

    Group in southern England. Special Papers in Palaeontology, 68, 1-18, 2 pls. Nye, E., Feist-Burkhardt, S., Horne, D. J., Ross, A. J. & Whittaker, J. E. (2008) The palaeoenvironment associated with a partial Iguanodon skeleton from the Upper Weald Clay (Barremian, Early Cretaceous) at Smokejacks Brickworks (Ockley, Surrey, UK), based on palynomorphs and ostracods. Cretaceous Research, 29, 417-444.

  8. Outcrop Analysis of the Cretaceous Mesaverde Group: Jicarilla Apache Reservation, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Ridgley, Jennie; Dunbar, Robin Wright

    2001-04-24

    Field work for this project was conducted during July and April 1998, at which time fourteen measured sections were described and correlated on or adjacent to Jicarilla Apache Reservation lands. A fifteenth section, described east of the main field area, is included in this report, although its distant location precluded use in the correlations and cross sections presented herein. Ground-based photo mosaics were shot for much of the exposed Mesaverde outcrop belt and were used to assist in correlation. Outcrop gamma-ray surveys at six of the fifteen measured sections using a GAD-6 scintillometer was conducted. The raw gamma-ray data are included in this report, however, analysis of those data is part of the ongoing Phase Two of this project.

  9. An endoparasitoid Cretaceous fly and the evolution of parasitoidism

    Science.gov (United States)

    Zhang, Qingqing; Zhang, Junfeng; Feng, Yitao; Zhang, Haichun; Wang, Bo

    2016-02-01

    Parasitoidism is a key innovation in insect evolution, and parasitoid insects, nowadays, play a significant role in structuring ecological communities. Despite their diversity and ecological impact, little is known about the early evolution and ecology of parasitoid insects, especially parasitoid true flies (Diptera). Here, we describe a bizarre fly, Zhenia xiai gen. et sp. nov., from Late Cretaceous Burmese amber (about 99 million years old) that represents the latest occurrence of the family Eremochaetidae. Z. xiai is an endoparasitoid insect as evidenced by a highly developed, hypodermic-like ovipositor formed by abdominal tergites VIII + IX that was used for injecting eggs into hosts and enlarged tridactylous claws supposedly for clasping hosts. Our results suggest that eremochaetids are among the earliest definite records of parasitoid insects. Our findings reveal an unexpected morphological specialization of flies and broaden our understanding of the evolution and diversity of ancient parasitoid insects.

  10. Cretaceous extinctions - Evidence for wildfires and search for meteoritic material

    Science.gov (United States)

    Wolbach, W. S.; Lewis, R. S.; Anders, E.

    1985-10-01

    The results of analyses of the contents of deposits in the Cretaceous-Ternary (K-T) transition at three sites worldwide are discussed. The study was undertaken to examine the composition of the object which may have struck the earth, causing widespread biotic extinction. The data indicate that most of the parent body was destroyed on impact, a condition which would also hold true for comets, suggesting that comets were not a source of prebiotic life. A four-orders-of-magnitude excess of carbon in the K-T layer is considered in terms of its source, which is suspected to be deposits from wildfires. The consequent extinctions of species are regarded as possibly making the current nuclear winter scenarios too optimistic.

  11. Geodynamic investigation of a Cretaceous superplume in the Pacific ocean

    Science.gov (United States)

    Xue, Jing; King, Scott D.

    2016-08-01

    The similarity in both age and geochemistry of the Ontong-Java, Hikurangi, and Manihiki plateaus suggests that they formed as a single superplateau from a unique mantle source. We investigate the necessity of a thermal superplume to form the Great Ontong-Java plateau at about 120 Ma using 3D spherical models of convection with imposed plate reconstruction models. The numerical simulations show that the giant plateau which formed as a result of melting due to the interaction of a plume head and the lithosphere would have been divided into smaller plateaus by spreading ridges, and end up at the present locations of Ontong-Java, Manihiki, and Hikurangi plateaus as well as a fragment in the western Caribbean. By comparing temperature and melt fraction between models with and without an initial thermal superplume, we propose that a Cretaceous superplume in Pacific at 120 Ma is required to form large igneous plateaus.

  12. Cenomanian-Coniacian Upper Cretaceous foraminiferal fauna of Lithuania

    Science.gov (United States)

    Aleksienė, Agnė

    2010-12-01

    Foraminiferal assemblages form a unique fauna succession from the Cenomanian to Maastrichtian stages in Lithuania; the Cenomanian-Coniacian succession is discussed in this paper. The first Cretaceous planktonic foraminifera species appeared in the Early Cenomanian. The Cenomanian planktonic foraminiferal association consists of the relatively abundant genus Hedbergella. However, Cenomanian planktonic foraminifera are rare compared to benthic; the latter are numerous, and their assemblage contains various calcareous and agglutinated species. As a result of environmental changes, foraminiferal assemblages gradually changed as well. The newly formed deep-water niches in the Turonian allowed spreading the keeled forms of planktonic foraminifera. Taxonomically, Turonian-Coniacian foraminiferal assemblages are mainly composed of species of the following genera: Praeglobotruncana, Helvetoglobotruncana, Dicarinella, Marginotruncana.

  13. Early Cretaceous Archaeamphora is not a carnivorous angiosperm

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    William Oki Wong

    2015-05-01

    Full Text Available Archaeamphora longicervia H.Q.Li was described as an herbaceous, Sarraceniaceae-like pitcher plant from the mid Early Cretaceous Yixian Formation of Liaoning Province, northeastern China. Here, a re-investigation of A. longicervia specimens from the Yixian Formation provides new insights into its identity and the morphology of pitcher plants claimed by Li. We demonstrate that putative pitchers of Archaeamphora are insect-induced leaf galls that consist of three components: (1 an innermost larval chamber with a distinctive outer wall; (2 an intermediate zone of nutritive tissue; and (3 an outermost zone of sclerenchyma. Archaeamphora is not a carnivorous, Sarraceniaceae-like angiosperm, but represents insect-galled leaves of the formerly reported gymnosperm Liaoningocladus boii G.Sun et al. from the Yixian Formation.

  14. Early Cretaceous Archaeamphora is not a carnivorous angiosperm.

    Science.gov (United States)

    Wong, William Oki; Dilcher, David Leonard; Labandeira, Conrad C; Sun, Ge; Fleischmann, Andreas

    2015-01-01

    Archaeamphora longicervia H. Q. Li was described as an herbaceous, Sarraceniaceae-like pitcher plant from the mid Early Cretaceous Yixian Formation of Liaoning Province, northeastern China. Here, a re-investigation of A. longicervia specimens from the Yixian Formation provides new insights into its identity and the morphology of pitcher plants claimed by Li. We demonstrate that putative pitchers of Archaeamphora are insect-induced leaf galls that consist of three components: (1) an innermost larval chamber; (2) an intermediate zone of nutritive tissue; and (3) an outermost wall of sclerenchyma. Archaeamphora is not a carnivorous, Sarraceniaceae-like angiosperm, but represents insect-galled leaves of the previously reported gymnosperm Liaoningocladus boii G. Sun et al. from the Yixian Formation. PMID:25999978

  15. Alisitos Formation, calcareous facies: Early Cretaceous episode of tectonic calm

    Energy Technology Data Exchange (ETDEWEB)

    Suarez-Vidal, F.

    1986-07-01

    The Alisitos Formation (Aptian-Albian), shaped as a marine volcanic arc, crops out along the western side of the peninsula of Baja California bounding the Peninsular Range batholith. Lithologically, this formation is formed by volcanic-breccias, porphyritic flows, biohermal limestones, and tuffaceous and pyroclastic sediments. The distribution of the different facies depends on the nature of volcanism and the distance from a volcanic center, although the presence of massive biohermal limestone indicates that in the Early Cretaceous (during the tectonic episodes), the volcanic activity decreased to the level that the environmental conditions were favorable for the development of an organic reef barrier, behind an island arc. Such conditions existed south of the Agua Blanca fault and extended to El Arco, Baja California. Based upon field observations and petrological analysis of the Alisitos limestone, an attempt is made to recreate the environmental condition in the Punta China and San Fernando, Baja California, sites.

  16. Proxy Constraints on a Warm, Fresh Late Cretaceous Arctic Ocean

    Science.gov (United States)

    Super, J. R.; Li, H.; Pagani, M.; Chin, K.

    2015-12-01

    The warm Late Cretaceous is thought to have been characterized by open Arctic Ocean temperatures upwards of 15°C (Jenkyns et al., 2004). The high temperatures and low equator-to-pole temperature gradient have proven difficult to reproduce in paleoclimate models, with the role of the atmospheric hydrologic cycle in heat transport being particularly uncertain. Here, sediments, coprolites and fish teeth of Santonian-Campanian age from two high-latitude mixed terrestrial and marine sections on Devon Island in the Canadian High Arctic (Chin et al., 2008) were analyzed using a suite of organic and inorganic proxies to evaluate the temperature and salinity of Arctic seawater. Surface temperature estimates were derived from TEX86 estimates of near-shore, shallow (~100 meters depth) marine sediments (Witkowski et al., 2011) and MBT-CBT estimates from terrestrial intervals and both suggest mean annual temperatures of ~20°C, consistent with previous estimates considering the more southerly location of Devon Island. The oxygen isotope composition of non-diagenetic phosphate from vertebrate coprolites and bony fish teeth were then measured, giving values ranging from +13‰ to +19‰. Assuming the TEX86 temperatures are valid and using the temperature calibration of Puceat 2010, the δ18O values of coprolites imply Arctic Ocean seawater δ18O values between -4‰ and -10‰, implying very fresh conditions. Lastly, the δD of precipitation will be estimated from the hydrogen isotope composition of higher plant leaf waxes (C-25, C-27, C-29 and C-31 n-alkanes) from both terrestrial and marine intervals. Data are used to model the salinity of seawater and the meteoric relationship between δD and δ18O, thereby helping to evaluate the northern high-latitude meteoric water line of the Late Cretaceous.

  17. Bridging the gap between chewing and sucking in the hemipteroid insects: new insights from Cretaceous amber.

    Science.gov (United States)

    Yoshizawa, Kazunori; Lienhard, Charles

    2016-01-01

    The diversity of feeding apparatuses in insects far exceeds that observed in any other animal group. Consequently, tracking mouthpart innovation in insects is one of the keys toward understanding their diversification. In hemipteroid insects (clade Paraneoptera or Acercaria: lice, thrips, aphids, cicadas, bugs, etc.), the transition from chewing to piercing-and-sucking mouthparts is widely regarded as the turning point that enabled hyperdiversification of the Hemiptera, the fifth largest insect order. However, the transitional process from chewing to piercing-and-sucking in the Paraneoptera was hitherto completely unknown. In this paper, we report a well preserved mid Cretaceous amber fossil of the paraneopteran insect family Archipsyllidae and describe it as Mydiognathus eviohlhoffae gen. et sp. n. This species has elongate mandibles and styliform laciniae similar to Hemiptera but retains functional chewing mouthparts. A number of morphological characters place the Archipsyllidae as the sister group of the thrips plus hemipterans, which strongly suggests that the mouthparts of M. eviohlhoffae represent a transitional condition from primitive chewing to derived piercing-and-sucking mouthparts. The clade composed of Archipsyllidae, thrips, and hemipterans is here named Pancondylognatha, a new supra-ordinal taxon. Based on newly obtained information, we also assess the monophyly of the Paraneoptera, which was called into question by recent phylogenomic analyses. A phylogenetic analysis that includes Mydiognathus strongly supports the monophyly of the Paraneoptera. PMID:27396002

  18. Cretaceous park of sex determination: sex chromosomes are conserved across iguanas.

    Science.gov (United States)

    Rovatsos, Michail; Pokorná, Martina; Altmanová, Marie; Kratochvíl, Lukáš

    2014-03-01

    Many poikilothermic vertebrate lineages, especially among amphibians and fishes, possess a rapid turnover of sex chromosomes, while in endotherms there is a notable stability of sex chromosomes. Reptiles in general exhibit variability in sex-determining systems; as typical poikilotherms, they might be expected to have a rapid turnover of sex chromosomes. However, molecular data which would enable the testing of the stability of sex chromosomes are lacking in most lineages. Here, we provide molecular evidence that sex chromosomes are highly conserved across iguanas, one of the most species-rich clade of reptiles. We demonstrate that members of the New World families Iguanidae, Tropiduridae, Leiocephalidae, Phrynosomatidae, Dactyloidae and Crotaphytidae, as well as of the family Opluridae which is restricted to Madagascar, all share homologous sex chromosomes. As our sampling represents the majority of the phylogenetic diversity of iguanas, the origin of iguana sex chromosomes can be traced back in history to the basal splitting of this group which occurred during the Cretaceous period. Iguanas thus show a stability of sex chromosomes comparable to mammals and birds and represent the group with the oldest sex chromosomes currently known among amniotic poikilothermic vertebrates. PMID:24598109

  19. New information on the anatomy of the Chinese Early Cretaceous Bohaiornithidae (Aves: Enantiornithes from a subadult specimen of Zhouornis hani

    Directory of Open Access Journals (Sweden)

    Yuguang Zhang

    2014-05-01

    Full Text Available Enantiornithines are the most diverse avian clade in the Cretaceous. However, morphological specializations indicative of specific ecological roles are not well known for this clade. Here we report on an exquisitely well-preserved specimen from the Lower Cretaceous Jehol Group of northeastern China, which pedal morphology is suggestive of a unique ecological specialization within Enantiornithes. The morphology of the new specimen is largely indistinguishable from that of the holotype of the bohaiornithid enantiornithine Zhouornis hani, albeit the latter is somewhat larger. The new specimen provides important and previously unknown details of the skull of Zhouornis hani, which add to the limited knowledge about the cranial anatomy and evolution of enantiornithines. The information offered by the new specimen also augments our understanding of the postcranial morphology of bohaiornithid enantiornithines, a clade that has been only recently recognized. With the description of this specimen, Zhouornis hani becomes one of the most anatomically complete known enantiornithine species, which will facilitate future morphological studies.

  20. Vertebrate paleontological exploration of the Upper Cretaceous succession in the Dakhla and Kharga Oases, Western Desert, Egypt

    Science.gov (United States)

    Sallam, Hesham M.; O'Connor, Patrick M.; Kora, Mahmoud; Sertich, Joseph J. W.; Seiffert, Erik R.; Faris, Mahmoud; Ouda, Khaled; El-Dawoudi, Iman; Saber, Sara; El-Sayed, Sanaa

    2016-05-01

    The Campanian and Maastrichtian stages are very poorly documented time intervals in Africa's record of terrestrial vertebrate evolution. Upper Cretaceous deposits exposed in southern Egypt, near the Dakhla and Kharga Oases in the Western Desert, preserve abundant vertebrate fossils in nearshore marine environments, but have not yet been the focus of intensive collection and description. Our recent paleontological work in these areas has resulted in the discovery of numerous new vertebrate fossil-bearing localities within the middle Campanian Qusier Formation and the upper Campanian-lower Maastrichtian Duwi Formation. Fossil remains recovered from the Campanian-aged Quseir Formation include sharks, rays, actinopterygian and sarcopterygian fishes, turtles, and rare terrestrial archosaurians, including some of the only dinosaurs known from this interval on continental Africa. The upper Campanian/lower Maastrichtian Duwi Formation preserves sharks, sawfish, actinopterygians, and marine reptiles (mosasaurs and plesiosaurs). Notably absent from these collections are representatives of Mammalia and Avialae, both of which remain effectively undocumented in the Upper Cretaceous rocks of Africa and Arabia. New age constraints on the examined rock units is provided by 23 nannofossil taxa, some of which are reported from the Duwi Formation for the first time. Fossil discoveries from rock units of this age are essential for characterizing the degree of endemism that may have developed as the continent became increasingly tectonically isolated from the rest of Gondwana, not to mention for fully evaluating origin and diversification hypotheses of major modern groups of vertebrates (e.g., crown birds, placental mammals).

  1. A Fish-Eating Enantiornithine Bird from the Early Cretaceous of China Provides Evidence of Modern Avian Digestive Features.

    Science.gov (United States)

    Wang, Min; Zhou, Zhonghe; Sullivan, Corwin

    2016-05-01

    Modern birds differ from their theropod ancestors in lacking teeth and heavily constructed bony jaws, having evolved a lightly built beak and a specialized digestive system capable of processing unmasticated food [1, 2]. Enantiornithes, the most successful clade of Mesozoic birds, represents the sister group of the Ornithuromorpha, which gave rise to living birds [3]. Nevertheless, the feeding habits of enantiornithines have remained unknown because of a lack of fossil evidence. In contrast, exceptionally preserved fossils reveal that derived avian features were present in the digestive systems of some non-enantiornithine birds with ages exceeding 125 million years [4, 5]. Here, we report a new piscivorous enantiornithine from the Early Cretaceous Jehol Biota of China. This specimen preserves a gastric pellet that includes fish bones. The new enantiornithine, like many modern piscivores and raptors, seems to have swallowed its prey whole and regurgitated indigestible materials such as bones, invertebrate exoskeletons, scales, and feathers. This fossil represents the oldest unambiguous record of an avian gastric pellet and the only such record from the Mesozoic. The pellet points to a fish diet and suggests that the alimentary tract of the new enantiornithine resembled that of extant avians in having efficient antiperistalsis and a two-chambered stomach with a muscular gizzard capable of compacting indigestible matter into a cohesive pellet. The inferred occurrence of these advanced features in an enantiornithine implies that they were widespread in Cretaceous birds and likely facilitated dietary diversification within both Enantiornithes and Ornithuromorpha. PMID:27133872

  2. Spectroscopic studies of the fish fossils (Cladocyclus gardneri and Vinctifer comptoni) from the Ipubi Formation of the Cretaceous Period

    Science.gov (United States)

    Sousa Filho, F. E.; da Silva, J. H.; Saraiva, G. D.; Abagaro, B. T. O.; Barros, O. A.; Saraiva, A. A. F.; Viana, B. C.; Freire, P. T. C.

    2016-03-01

    Fossils are mineralized remains or traces from animals, plants and other organisms aged to about 108 years. The chemical processes of fossilization are dated back from old geological periods on Earth. The understanding of these processes and the structure of the fossils are one of the goals of paleontology and geology in the sedimentary environments. Many researches have tried to unveil details about special kinds of biological samples; however, a lack of data is noticed for various other specimens. This study reports the investigations through infrared spectroscopy, X-ray fluorescence and X-ray diffraction measurements for two types of fish fossils from the Cretaceous Period. The sample of Cladocyclus gardneri and Vinctifer comptoni fossils were collected from the Ipubi Formation, being one of the less studied, among the formations that constitute the important Santana group in the Araripe Basin, Brazil. The results obtained through different techniques, showed that the C. gardneri fish fossil contains hydroxyapatite and calcite as constituents whereas its rock matrix was formed by calcite, quartz and pyrite. Regarding the V. comptoni, the measurements confirmed the presence of hydroxyapatite in the fossil and its rock matrix gypsum, pyrite, quartz and calcite. The above scientific data contributed to the understanding the fossil formation in the Ipubi Formation, an important environment of the Cretaceous Period, which is rich in well-preserved fossils from different species.

  3. The Skælskør structure in eastern Denmark – wrench-related anticline or primary Late Cretaceous sea-floor topography?

    DEFF Research Database (Denmark)

    Surlyk, Finn; Boldreel, Lars Ole; Lykke-Andersen, Holger;

    2010-01-01

    seismic studies of the Chalk Group in Øresund and Kattegat have shown that similar highs actually represent topographic highs on the Late Cretaceous – Danian seafloor formed by strong contourparallel bottom currents. Reflection seismic data collected over the Skælskør structure in order to test the...... Ringkøbing Fyn High into the Danish Basin. The elevated position is maintained due to reduced subsidence as compared with the Danish Basin north of the high. The hypothesis of wrench tectonics as origin can be refuted. The seismic data show that the upper part of the Chalk Group is characterised by irregular...

  4. Undivided Upper Cretaceous deposits in the Kaiparowits Plateau, southern Utah (kaibkd*g)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This is a polygon coverage and shapefile that contains undivided Upper Cretaceous rocks that include (in descending order) the Smoky Hollow and Tibbet Canyon Mbs....

  5. Maps showing distribution of the Middle Cretaceous unconformity in the eastern Gulf of Mexico

    Science.gov (United States)

    Massingill, L.M.; Wells, R.H.

    1987-01-01

    Several theories on the origin of the Gulf of Mexico basin have been introduced by various researchers (Beloussov, 1970; Freeland and Dietz, 1971; Malfait and Dinkelman, 1972; Wood and Walper, 1974; Pilger, 1978; Buffler and others, 1980; Dickinson and Coney, 1980; Gose and others, 1980; Schmidt-Effing, 1980; Walper, 1980; Schlager and others, 1984). Although no final agreement has been reached, one prominent geologic feature is generally recognized. The early evolution of the basin ended with a major middle Cretaceous event resulting in a Gulf-wide unconformity referred to as the middle Cretaceous unconformity (MCU). This event represents a major shift from Early Cretaceous shallow-water bank sedimentation to Late Cretaceous deeper water carbonates (Worzel and others, 1973; Mitchum, 1978).

  6. Alkylthiophenes as sensitive indicators of palaeoenvironmental changes : a study of a Cretaceous oil shale from Jordan

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Kohnen, M.E.L.; Rijpstra, W.I.C.; Leeuw, J.W. de

    1990-01-01

    Thirteen samples of the immature, Cretaceous Jurf ed Darawish oil shade (Jordan) were analysed quantitatively for aliphatic hydrocarbons and alkylthiophenes in the bitumens by gas chromatography-mass spectrometry after isolation of appropriate fractions.

  7. Cretaceous anuran and dinosaur footprints from the Patuxent Formation of Virginia

    Science.gov (United States)

    Weems, R.E.; Bachman, J.M.

    1997-01-01

    Footprints of an anuran (gen. et sp. indet.), a theropod dinosaur (Megalosauropus sp.), and an ornithopod dinosaur (Amblydactylus sp.) have been recovered from the Lower Cretaceous Patuxent Formation in Stafford County, Virginia. These footprints are the first record of terrestrial vertebrates from Cretaceous strata in Virginia, and their discovery suggests that the scarcity of bones and teeth in the Patuxent probably is an artifact of preservation. The anuran trackway provides the oldest known direct evidence for hopping locomotion among these amphibians.

  8. First Psocodean (Psocodea,Empheriidae) from the Cretaceous Amber of New Jersey

    Institute of Scientific and Technical Information of China (English)

    Dany AZAR; André NEL; Julian F.PETRULEVI(C)IUS

    2010-01-01

    Representatives of the extinct psocid family Empheriidae are known from Eocene Baltic amber,Lowermost Eocene French amber (Oise),and Lower Cretaceous Spanish amber (Alava).We report herein the first discovery of an empheriid psocid from the Cretaceous amber of New Jersey as Jerseyempheria grimaldii gen.et sp.nov.The fossil is figured and described.The new species is distinguished from related taxa.A discussion and checklist of Empheriidae are provided.

  9. Magnetostratigraphic correlation of the Upper Cretaceous System in the North Pacific

    Science.gov (United States)

    Kodama, K.

    2003-06-01

    Magnetostratigraphic data for Upper Cretaceous sedimentary strata in widely separated regions of the North Pacific, including Japan, Far East Russia and western North America, are reviewed in terms of calibration to the geomagnetic polarity time scale and regional correlation. A series of normal and reversed polarity zones are recognized in the Upper Cretaceous strata in Shikoku and Hokkaido, Japan, and South Sakhalin, Far East Russia. Combined magnetostratigraphic and biostratigraphic correlation has assigned these zones to the Late Cretaceous geomagnetic polarity chrons including C31r through C33r and the Cretaceous long normal interval. Corresponding geomagnetic reversals have been documented from the Upper Cretaceous successions of the Western Interior of North America, in combination with high-resolution ammonite biostratigraphy and radiometric age dates. Biostratigraphy of the Great Valley Sequence in California is also well-defined, but there is only one reversed interval that can be correlated with polarity chron C33r. The most complete record of polarity reversals in South Sakhalin would provide an integrated reference scheme which can be of significant use not only to correlate dissimilar faunal assemblages of disparate regions in the North Pacific, but also to contribute to a global definition of Upper Cretaceous stage boundaries.

  10. A new troodontid theropod dinosaur from the lower Cretaceous of Utah.

    Directory of Open Access Journals (Sweden)

    Phil Senter

    Full Text Available BACKGROUND: The theropod dinosaur family Troodontidae is known from the Upper Jurassic, Lower Cretaceous, and Upper Cretaceous of Asia and from the Upper Jurassic and Upper Cretaceous of North America. Before now no undisputed troodontids from North America have been reported from the Early Cretaceous. METHODOLOGY/PRINCIPAL FINDINGS: Herein we describe a theropod maxilla from the Lower Cretaceous Cedar Mountain Formation of Utah and perform a phylogenetic analysis to determine its phylogenetic position. The specimen is distinctive enough to assign to a new genus and species, Geminiraptor suarezarum. Phylogenetic analysis places G. suarezarum within Troodontidae in an unresolved polytomy with Mei, Byronosaurus, Sinornithoides, Sinusonasus, and Troodon+(Saurornithoides+Zanabazar. Geminiraptor suarezarum uniquely exhibits extreme pneumatic inflation of the maxilla internal to the antorbital fossa such that the anterior maxilla has a triangular cross-section. Unlike troodontids more closely related to Troodon, G. suarezarum exhibits bony septa between the dental alveoli and a promaxillary foramen that is visible in lateral view. CONCLUSIONS/SIGNIFICANCE: This is the first report of a North American troodontid from the Lower Cretaceous. It therefore contributes to a fuller understanding of troodontid biogeography through time. It also adds to the known dinosaurian fauna of the Cedar Mountain Formation.

  11. Palynological evidence of effects of the terminal Cretaceous event on terrestrial floras in western North America

    Science.gov (United States)

    Nichols, Douglas J.; Farley Fleming, R.; Frederiksen, Norman O.

    New and previously published palynomorph distribution data on 225 taxa from uppermost Cretaceous (K) and lowermost Tertiary (T) nonmarine strata from New Mexico to Arctic Canada and Alaska were used to evaluate the effects of the terminal Cretaceous event (TCE) on terrestrial plant life. Analyses considered presence/absence, relative abundance, species diversity, and endemism, and employed Q-mode cluster analysis. The latest Cretaceous palynoflora showed gradual, continuous variation in composition from paleolatitudes (pl) 45° to 85° N. Palynofloristic subprovinces are not easily distinguished empirically, but three are recognizable quantitatively. Abrupt disappearance of many distinctive species marked the K-T boundary, and the earliest Tertiary palynoflora was considerably reduced in diversity. However, most regionally distributed taxa, and many endemic taxa of the polar and midlatitude subprovinces, survived the TCE and three subprovinces are recognizable in the same geographic positions as in the latest Cretaceous. Relative abundances of pteridophytes and gymnosperms were slightly greater in the early Tertiary than in the latest Cretaceous, probably due in part to change in sedimentary regime, but thermophilic angiosperm taxa persisted at least as far north as pl 60° N. These data support the hypothesis that a short-lived but profound ecological crisis at the end of the Cretaceous resulted in major reorganization of the flora. The data are inconsistent with gradual climatic deterioration. Extinction was greater among angiosperms than among gymnosperms or pteridophytes, but whether or not the entire flora suffered a mass extinction remains debatable.

  12. Iridium anomaly in the Cretaceous section of the Eastern Kamchatka

    Science.gov (United States)

    Savelyev, Dmitry; Savelyeva, Olga

    2010-05-01

    The origin of iridium anomalies is widely discussed with regard to massive fauna and flora extinction at several geologic boundaries. Two hypotheses are most popular, cosmogenic and volcanogenic. Anomalies of iridium are known at many stratigraphic levels, both at the geologic series borders and within geologic series. Our studies revealed increased content of iridium in a section of Cretaceous oceanic deposits on the Kamchatsky Mys Peninsula (Eastern Kamchatka, Russia). The investigated section (56°03.353´N, 163°00.376´E) includes interbedded jaspers and siliceous limestones overlaying pillow-basalts. These deposits belong to the Smagin Formation of the Albian-Cenomanian age. In the middle and upper parts of the section two beds of black carbonaceous rocks with sapropelic organic matter were observed. Their formation marked likely episodes of oxygen depletion of oceanic intermediate water (oceanic anoxic events). Our geochemical studies revealed an enrichment of the carbonaceous beds in a number of major and trace elements (Al2O3, TiO2, FeO, MgO, K2O, P2O5, Cu, Zn, Ni, Cr, V, Mo, Ba, Y, Zr, Nb, REE, U, Au, Pt etc.) in comparison with associating jaspers and limestones. There are likely different sources which contributed to the enrichment. It is possible however to correlate the excess of Al, Ti, Zr, Nb with volcanogenic admixture, which is absent in limestones and jaspers. A possible source of the volcanogenic material was local volcanism as suggested by the close association of the investigated section with volcanic rocks (basaltic lavas and hyaloclastites). The basalts of the Smagin Formation were previously proposed to originate during Cretaceous activity of the Hawaiian mantle plume (Portnyagin et al., Geology, 2008). Neutron activation analysis indicated increased up to 9 ppb concentration of Ir at the bottom of the lower carbonaceous bed (inorganic part of the sample was analyzed comprising 46% of the bulk rock). In other samples Ir content was below

  13. Detrital and delayed CRM acquisition in redbeds: the Lower Cretaceous Zicapa Formation, southern Mexico

    Science.gov (United States)

    Sierra-Rojas, M. I.; Molina-Garza, R. S.

    2013-05-01

    The Lower Cretaceous Zicapa Formation is characterized by hematite-cemented clastic rocks interbeded with limestone and volcanic rocks, deposited in continental to transitional-marine environments. The paleomagnetic data presented here correspond to exposures in the San Juan de las Joyas locality, in the Mixteca terrain of southern Mexico. Hematite cement is derived from an important input of primary volcanic material contemporaneous with deposition and from mafic to intermediate metavolcanic sources. We sampled 17 sites in a 110 m segment of continuous depositation of fine to coarse, red to purple, lithic sandstone and siltstone. The natural magnetization is multivectorial, and AF demagnetization suggests that it resides primarily in hematite. One magnetization component is unblocked below 200C is north-directed and positive. A low-unblocking temperature magnetization (LT) is unblocked between 250-500C, and a high-unblocking-temperature component (HT) is defined between about 600-650C. Both, the LT and HT components are dual-polarity and form nearly antipodal groups of WNW (ESE) directions. NRM demagnetization and rock magnetic data suggest the presence of two kinds of particles carrying the LT and HT components. Polarity changes in the section sampled are characterized by sites that register in the HT component the magnetic field previous to the transition of polarity (which is detrital magnetization residing in specular hematite), whilst the LT registers the magnetic field after the polarity transition. Typically, in the overlying (post-transition) site the LT and HT components are of the same polarity. This suggests that the LT component is a late (or delayed) CRM that resides in small particles of pigmentary hematite. The accepted sites yield a tilt corrected mean of declination Dec= 273 degrees, inclination Inc= 33.1 degrees (α95=11.7 y k=18).The mean directions are discordant with respect to expected North America reference for Early Cretaceous indicating a

  14. Skin of the Cretaceous mosasaur Plotosaurus: implications for aquatic adaptations in giant marine reptiles.

    Science.gov (United States)

    Lindgren, Johan; Alwmark, Carl; Caldwell, Michael W; Fiorillo, Anthony R

    2009-08-23

    The physical nature of water and the environment it presents to an organism have long been recognized as important constraints on aquatic adaptation and evolution. Little is known about the dermal cover of mosasauroids (a group of secondarily aquatic reptiles that occupied a wide array of predatory niches in the Cretaceous marine ecosystems 92-65 Myr ago), a lack of information that has hindered inferences about the nature and level of their aquatic adaptations. A newly discovered Plotosaurus skeleton with integument preserved in three dimensions represents not only the first documented squamation in a mosasaurine mosasaur but also the first record of skin in an advanced member of the Mosasauroidea. The dermal cover comprises keeled and possibly osteoderm-reinforced scales that presumably contributed to an anterior-posterior channelling of the water flow and a reduction of microturbulent burst activities along the surface of the skin. Thus, hydrodynamic requirements of life in the water might have influenced the evolution of multiple-keeled body scales in advanced mosasauroids. PMID:19364713

  15. Geochemical characteristics of Early Cretaceous source rocks in Boli Basin

    Institute of Scientific and Technical Information of China (English)

    Hongmei Gao; Fuhong Gao; Fu Fan; Yueqiao Zhang

    2006-01-01

    The Early Cretaceous deposits are composed of important source rocks in Boli Basin. The types of the source rocks include black mudstones and coal (with carbonaceous mudstone). By the organic geochemical analysis methods, the authors discussed the organic petrological characters, abundance of organic matter, degree of maturity and the type of source rocks. The main micro-component of black mudstone is exinite or vitrinite, and the content of vitrinite is high in coal. The weathering of the outcrop is very serious. The abundance of organic matter in source rock reaches the poor to better rank. The major kerogens in mudstone are type-Ⅲ, type-Ⅱ2 and some type-Ⅱ1; the organic type of coal is type-Ⅲ. The thermal evolution of the source rocks in every structural unit is very different, from low-maturity to over-maturity. The depositional environment is reductive, which is good for the preservation of organic matter. The organic matter in source rocks is mainly from aquatic organisms and terrigenous input.

  16. Wildfires and animal extinctions at the Cretaceous/Tertiary boundary

    Science.gov (United States)

    Adair, Robert K.

    2010-06-01

    Persuasive models of the ejection of material at high velocities from the Chicxulub asteroid impact marking the Cretaceous/Tertiary boundary have led to the conclusion that upon return, that material, heated in passage through the upper atmosphere, generated a high level of infrared energy density over the Earth's surface. That radiant energy has been considered to be a direct source of universal wildfires, which were presumed to be a major cause of plant and animal species extinctions. The extinction of many animal species, especially the dinosaurs, has also been attributed to the immediate lethal effects of the radiation. I find that the absorption of the radiation by the atmosphere, by cloud formations, and by ejecta drifting in the lower atmosphere reduced the radiation at the surface to a level that cannot be expected to have generated universal fires. Although the reduced radiation will have likely caused severe injuries to many animals, such insults alone seem unlikely to have generated the overall species extinctions that have been deduced.

  17. Gymnosperms from the Early Cretaceous Crato Formation (Brazil. II. Cheirolepidiaceae

    Directory of Open Access Journals (Sweden)

    L. Kunzmann

    2006-08-01

    Full Text Available Conifers are common in the Early Cretaceous Crato flora. Sterile foliage shoots of several morphotypes occur. Good preservation of several of these specimens allows detailed morphological and anatomical studies. Based on these characters, two taxa of Cheirolepidiaceae, Tomaxellia biforme and Frenelopsis sp., are identified. The palaeogeographic distribution of the genus Tomaxellia currently extends from southern South America northwards to the palaeoequatorial region. The morphological and anatomical characters of both taxa might be interpreted as adaptations to a warm and temporarily dry palaeoclimate, however their habitat can not be reconstructed yet, due to scarcity of the remains. Koniferen stellen eine wesentliche Komponente der unterkretazischen Crato-Flora dar. Es kommen sterile beblätterte Zweige verschiedener Morphotypen vor. Die gute Erhaltung einiger dieser Fossilreste lässt detaillierte morphologisch-anatomische Untersuchungen zu. Auf der Basis solcher Merkmale wurden zwei Taxa der Cheirolepidiaceae, Tomaxellia biforme und Frenelopsis sp., identifiziert. Das Areal der Gattung Tomaxellia wird damit vom südlichen Südamerika nordwärts, in die paläoäquatoriale Region erweitert. Morphologische und anatomische Merkmale beider Taxa können als Anpassungserscheinungen an ein warmes und periodisch trockenes Paläoklima interpretiert werden. Auf Grund des seltenen Vorkommens solcher Fossilreste können noch keine Angaben zu ihrem ehemaligen Habitat gemacht werden. doi:10.1002/mmng.200600009

  18. The debate over the Cretaceous-Tertiary boundary

    Science.gov (United States)

    Alvarez, W.; Asaro, F.; Alvarez, L. W.; Michel, H. V.

    1988-01-01

    Large-body impact on the Earth is a rare but indisputable geologic process. The impact rate is approximately known from objects discovered in Earth-crossing orbits and from the statistics of craters on the Earth's surface. Tektite and microtektite strewn fields constitute unmistakable ejecta deposits that can be due only to large-body impacts. The Cretaceous-Tertiary (K-T) boundary coincides with an unusually severe biological trauma, and this stratigraphic horizon is marked on a worldwide basis by anomalous concentrations of noble metals in chondritic proportions, mineral spherules with relict quench-crystallization textures, and mineral and rock grains showing shock deformation. These features are precisely compatible with an impact origin. Although only impact explains all the types of K-T boundary evidence, the story may not be as simple as once thought. The original hypothesis envisioned one large impact, triggering one great extinction. Newer evidence hints at various complications. Different challenges are faced by the occupants of each apex of a three-cornered argument over the K-T event. Proponents of a non-impact explanation must show that the evidence fits their preferred model better than it fits the impact scenario. Proponents of the single impact-single extinction view must explain away the complications. Proponents of a more complex impact crisis must develop a reasonable scenario which honors the new evidence.

  19. First report on Cretaceous paleoweathering rates in western Panthalassa: Evidence of global enhancement of continental weathering during OAE 2

    Science.gov (United States)

    Ohta, T.

    2013-12-01

    Mid-Cretaceous is characterized by intensified oceanic anoxia (Oceanic Anoxic Events: OAEs) that raised global deposition of organic black shales. Several models have been proposed to explain the cause of the OAEs in conjunction with Cretaceous global warmth, active volcanism, sea-level changes and others. For example, Weissert et al. (1998) proposed a mechanism called 'weathering hypothesis'. In this model, the cause of the OAEs is explained in a following chain reaction, (1) global warmth and increase in atmospheric CO2 enhanced weathering of continental crust, (2) enhanced land weathering led excessive influx of nutrients from continents to oceans, (3) eutrophication enhanced primary productivity, (4) the excessive primary producers consumed dissolved oceanic oxygen that finally led to the OAEs. Several studies, in fact, revealed a causal relation between enhanced weathering and OAEs in northern Tethys region. However, it is necessary to collect worldwide information to unravel the global response of weathering hypothesis as a cause of OAEs. For such reason, the present contribution conducted measurements of the degree of hinterland paleoweathering during OAEs in northern Japan, for the purpose to provide a first report on the relation between continental weathering and OAEs in open ocean, the western Panthalassa Ocean. Aptian to Campanian forearc basin mudstones (Yezo Group) were analyzed by XRF and the degree of hinterland weathering was evaluated by geochemical weathering index (W index; Ohta and Arai, 2007). The W values obtained for the Yezo Group are 30~50, which is equivalent to the W values of recent soils developed in temperate mid-latitude climate. The W values show a fluctuation pattern that is concordant with the Cretaceous paleotemperature changes. This match indicates that the change in paleotemperature governed the weathering rates of East Asian continental crust. In addition, hinterland weathering rates show instantaneous increase during the OAE

  20. A New Leptoceratopsid (Ornithischia, Ceratopsia with a Unique Ischium from the Upper Cretaceous of Shandong Province, China.

    Directory of Open Access Journals (Sweden)

    Yiming He

    Full Text Available The partial skeleton of a leptoceratopsid dinosaur, Ischioceratops zhuchengensis gen. et sp. nov., was excavated from the bone-beds of the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China. This fossil represents the second leptoceratopsid dinosaur specimen recovered from the Kugou locality, a highly productive site in Zhucheng. The ischium of the new taxon is morphologically unique among known Dinosauria, flaring gradually to form an obturator process in its middle portion and resembling the shaft of a recurve bow. An elliptical fenestra perforates the obturator process, and the distal end of the shaft forms an axehead-shaped expansion. The discovery of Ischioceratops increases the known taxonomic diversity and morphological disparity of the Leptoceratopsidae.

  1. Sr-Nd isotope changes of late cretaceous to early miocene volcanic rocks in central Chile (33oS)

    International Nuclear Information System (INIS)

    A longitudinal depression, the Central Valley, separates the Coast Range from the Andean Cordillera in central Chile. It contains volcanic and volcaniclastic rocks of Late Cretaceous to Tertiary age deposited in a continental environment, and partly eroded Tertiary volcanic complexes. The age of the rocks at the northern end of the Central Valley and their grouping in formations have been a long-standing controversy in Chilean geology (Thomas, 1958; Aguirre, 1960; Drake et al., 1976; Vergara and Drake, 1979; Thiele, 1980; Moscoso et al., 1982; Gana and Wall, 1997; Lopez-Escobar and Vergara, 1997; Selles, 1999). Here, we report new 40Ar/39Ar data and Sr-Nd isotope ratios for lavas, pyroclastic flows and associated subvolcanic rocks from this part of central Chile (au)

  2. THE EARTH'S MAGNETIC FIELD AND GLOBAL GEOLOGIC PHENOMENA IN MID-CRETACEOUS%白垩纪中期地球磁场与全球地质现象

    Institute of Scientific and Technical Information of China (English)

    Xixi ZHAO

    2005-01-01

    , covering about one-third of the land area. Sea levels were up to 250 m higher than present day levels. Geological evidence also points towards an unusually high rate of volcanic activity in the mid-Cretaceous. Large volumes of magmatic material flowed to Earths surface from the mantle, and not just from the typical seafloor spreading. The "large igneous provinces" or LIPs made a very important contribution to the lithosphere during the mid-Cretaceous. Several LIPs such as the Ontong Java Plateau(120 Ma), the main portion of the Kerguelen Plateau(115~80 Ma), the Madagascar LIP(84~91Ma), the High Arctic LIP(85~95 Ma), and the Caribbean LIP(88~91 Ma)were all formed during this time. Carbon dioxide emissions released by the Cretaceous LIPs may have triggered two to seven oceanic anoxic events(OAEs) and led to a greenhouse effect that raised the Earths surface temperature by roughly 10 degrees Celsius, reduced temperature gradients from the Equator to the poles, and resulted in general absence of polar ice caps and oceans much warmer than todays. The mid-Cretaceous was also a time of rapid radiation and turnover in the marine plankton, benthic foraminifera, and terrestrial plants. This evolutionary activity transformed many of these groups on an ocean-wide basis. The reorganization of the global biosphere during the mid-Cretaceous paralleled the marked changes in the ocean-climate system, suggesting a causal relationship between biotic evolution and environments. Other geologic anomalies associated with the mid-Cretaceous thermal activity include the extremely high development of the Earths diamond bearing kimberlites in mid-East and South Africa and markedly reduced(less radiogenic)seawater strontium isotope ratio(87Sr/86Sr). A key piece in the mid-Cretaceous geologic phenomena is the Cretaceous Normal Superchron. This is a period in which Earths magnetic field was uncharacteristically steady that did not switch from normal to reversed polarity for about

  3. Rethinking ``Yellowstone in Yukon'' and Baja British Columbia: Paleomagnetism of the Late Cretaceous Swede Dome stock, northern Canadian Cordillera

    Science.gov (United States)

    McCausland, P. J. A.; Symons, D. T. A.; Hart, C. J. R.

    2005-12-01

    Paleomagnetic results obtained from the 69.8 Ma Swede Dome stock, emplaced into the pericratonic Yukon Tanana Terrane (YTT) west of Dawson, Yukon, indicate a minimal northward translation of 360 ± 575 km and a clockwise rotation of 20° ± 23° with respect to North America, in accord with the displacement of 425 km along the nearby Tintina Fault. Coeval Carmacks Group volcanics in contrast have previously indicated ˜1900 km northward translation and minimal rotation and have been proposed to be a displaced manifestation of the fixed Yellowstone hot spot, thus providing an independent estimate of the Late Cretaceous paleoposition of the "Baja British Columbia" terranes of western North America. A compilation of recent mid and Late Cretaceous paleomagnetic results from the YTT and Intermontane Belt (IMB) terranes reveals that the Carmacks Group paleomagnetic result is anomalous. The YTT and IMB terranes, which form the bulk of Baja British Columbia, appear instead to have experienced <1000 km northward translation with respect to North America since 70 Ma, consistent with geological estimates of motion along plausible accommodating faults. In addition, past mobility of the Hawaii-Emperor hot spot implies that the Pacific hot spots may have experienced ˜1200 km of southward motion from 81 to 47 Ma. If so, then the paleoposition of the Yellowstone hot spot if it existed at 70 Ma would likely have produced the Carmacks magmatism ˜1000 km north of Yellowstone's current latitude, consistent with a "moderate" (<1000 km) post-70 Ma northward translation of the YTT and IMB terranes to their present position in North America.

  4. Novel insect leaf-mining after the end-Cretaceous extinction and the demise of cretaceous leaf miners, Great Plains, USA.

    Directory of Open Access Journals (Sweden)

    Michael P Donovan

    Full Text Available Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia.

  5. Paleobiological implications of dinosaur egg-bearing deposits in the Cretaceous Gyeongsang Supergroup of Korea

    Science.gov (United States)

    Paik, In Sung; Kim, Hyun Joo; Huh, Min

    2010-05-01

    Dinosaur egg-bearing deposits in the Cretaceous Gyeongsang Basin in Korea is described in taphonomic aspect, their paleoenvironments are interpreted, and geobiological implications of dinosaur egg-bearing deposits in the world and Korea are analyzed in geographic occurrences, geological ages, paleoenvironments, and lithology. Dinosaur eggs with spheroolithids, faveoloolithid, and elongatoolithid structural types occur in several stratigraphic formations of the Cretaceous Gyeongsang Basin in South Korea, and most of the egg-bearing formations are the Late Cretaceous. The dinosaur eggs usually occur as clutches in purple sandy mudstone of floodplain deposits preserved as calcic paleosol with association of vertic paleosol features in places. Most of the eggs are top-broken and filled with surrounding sediments. The general depositional environment of dinosaur egg deposits in the Gyeongsang Supergroup are interpreted as a dried floodplain where volcanic activity occurred intermittently in the vicinity of the nesting sites. Their depositional settings on which floodplains developed are diverse from fluvial plain with meandering rivers to alluvial plain with episodic sheet flooding. The nesting areas in the Gyeongsang Basin are deemed to have been under semi-arid climate, which resulted in formation of calcic soils facilitating preservation of the dinosaur eggs. The geochronologic occurrences of dinosaur egg-bearing deposits are mostly restricted to the Late Cretaceous in the world as well as in Korea. If it has not been resulted from biased discoveries and reports of dinosaur eggs, biological rather than physical and chemical conditions for preservation of dinosaur eggs might be related with the restricted occurrences in the Late Cretaceous. Two hypotheses are suggested for probable biological causes to the geochronologically restricted occurrences of dinosaur egg-bearing deposits. One is related with the appearance of angiosperms in the Late Jurassic and the spreading

  6. Cretaceous paleomagnetism of the eastern South China Block: establishment of the stable body of SCB

    Science.gov (United States)

    Morinaga, Hayao; Liu, Yuyan

    2004-06-01

    A paleomagnetic investigation was performed on the Cretaceous red sandstones collected at the eastern side of the South China Block (SCB), China, and attempted to establish the stable part of the SCB since the Cretaceous. Paleomagnetic specimens were collected at 39, 25 and 14 sites from three independent parts: the northern, central and southern regions of eastern SCB, respectively. Characteristic directions of higher temperature components (HTCs) with an unblocking temperature of ˜680 °C were isolated from 69/78 sites. The optimal concentrations of global mean HTC directions calculated using the direction-correction tilt test were achieved at 79±19%, 95±27%, 71±37% and 117±98% untilting for the Early Cretaceous sites from the northern part, Late Cretaceous sites from the northern, central and southern parts, respectively. This treatment gives positive tilt tests or brings the optimal concentration not far from being indistinguishable from positive tilt tests, although this observation can be due to imperfect separation of a primary component (HTC) from a secondary one (lower temperature component). We adopted completely (100%) untilted directions of the HTCs as the paleomagnetic field directions during the Cretaceous, because the mean directions after complete untilting were almost equal to each mean direction after incomplete untilting showing the optimal concentration. The mean paleomagnetic poles for three independent parts were located at almost the same positions and were indistinguishable from that for Sichuan, the western side of SCB at the 95% confidence level. This observation indicates that there is no relative movement between the eastern and western sides of SCB and implies that a large part of the SCB (excluding a 400-km-wide swath along the Red River Fault) has behaved as its coherent (stable) body since the Cretaceous. The Cretaceous paleomagnetic pole for the stable body of the SCB (latitude=80.0°N, longitude=206.7°E, A95=2.5°) is worth

  7. A New Subfamily of Aphids(Hemiptera,Aphidomorpha)from the Early Cretaceous Lebanese Amber with a Description of the Oldest Apterous Morphs

    Institute of Scientific and Technical Information of China (English)

    Piotr WEGIEREK; David A.GRIMALDI

    2010-01-01

    Aphids are marked by their high polymorphism,but species reported from the Early Cretaceous are known only from alate morphs.The discovery of an apterous adult morph in Lebanese amber and a larva of the same species are very important for the understanding of both the morphological and biological evolution of this insect group at the very early stage of development.Gondvanoaphis estephani new subfamily,new genus and species of the recent aphids family Thelaxidae is described.The characters of the new genus in respect to other genera placed in Thelaxidae are reviewed.The palaeoecologicai and palaeogeographical data concerning Gondvanoaphis new genus are also discussed.

  8. The first definitive Asian spinosaurid (Dinosauria: Theropoda) from the early cretaceous of Laos

    Science.gov (United States)

    Allain, Ronan; Xaisanavong, Tiengkham; Richir, Philippe; Khentavong, Bounsou

    2012-05-01

    Spinosaurids are among the largest and most specialized carnivorous dinosaurs. The morphology of their crocodile-like skull, stomach contents, and oxygen isotopic composition of the bones suggest they had a predominantly piscivorous diet. Even if close relationships between spinosaurids and Middle Jurassic megalosaurs seem well established, very little is known about the transition from a generalized large basal tetanuran to the specialized morphology of spinosaurids. Spinosaurid remains were previously known from the Early to Late Cretaceous of North Africa, Europe, and South America. Here, we report the discovery of a new spinosaurid theropod from the late Early Cretaceous Savannakhet Basin in Laos, which is distinguished by an autapomorphic sinusoidal dorsosacral sail. This new taxon, Ichthyovenator laosensis gen. et sp. nov., includes well-preserved and partially articulated postcranial remains. Although possible spinosaurid teeth have been reported from various Early Cretaceous localities in Asia, the new taxon I. laosensis is the first definite record of Spinosauridae from Asia. Cladistic analysis identifies Ichthyovenator as a member of the sub-clade Baryonychinae and suggests a widespread distribution of this clade at the end of the Early Cretaceous. Chilantaisaurus tashouikensis from the Cretaceous of Inner Mongolia, and an ungual phalanx from the Upper Jurassic of Colorado are also referred to spinosaurids, extending both the stratigraphical and geographical range of this clade.

  9. HEFEI BASIN IN EARLY CRETACEOUS -CHARACTERIZATION AND ANALYSIS OF PETROLEUM POTENTIAL

    Institute of Scientific and Technical Information of China (English)

    YI Wanxia; ZHAO Zongju; LI Xuetian; SHEN Jinlong; ZHOU Jingao

    2003-01-01

    Comprehensive analyses were made based on seismic prospecting data, electrical prospecting data and basin simulation data as well as regional geological data and thorough discussions were conducted about the complicated structures, features and evolution of Hefei Basin in Early Cretaceous in this study,and it was derived that that Hefei Basin was a composite basin formed during the transformation of the stress field from compressive toward tensile in Early Cretaceous. In other words, this basin was a foreland basin of gliding-thrust type, which is mainly controlled by the Dabie orogenic belt in the south side in the early to middle period of Early Cretaceous, while being a strike-slip basin of pull-apart type,which is mainly controlled by the activity of Tanlu fracture in the east side in the middle to late period of Early Cretaceous. Moreover, the potential Lower Cretaceous oil and gas system in the pull-apart basin and the vista for its prospecting were explored in this study. Tectonism of the Tanlu fracture was further discussed based on the results of characterization of the basin, and it was pointed out that this is beneficial and instructive to the oil and gas prospecting in Hefei Basin

  10. Evidence of reworked Cretaceous fossils and their bearing on the existence of Tertiary dinosaurs

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, J.G. (Museum of Northern Arizona, Flagstaff (USA)); Kirkland, J.I. (Univ. of Nebraska, Lincoln (USA)); Doi, K. (Univ. of Colorado, Boulder (USA))

    1989-06-01

    The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Cannonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as there is a mixture of marine and freshwater taxa. These taxa have not been recorded elsewhere after the Cretaceous and are not known from the Cannonball Formation. Early Eocene localities at Raven Ridge, Utah, similarly contain teeth of Cretaceous marine and freshwater fish, dinosaurs, and Eocene mammals. The Cretaceous teeth are well preserved, variably abraded, and serve to cast doubts on criteria recently used to claim that dinosaur teeth recovered from the Paleocene of Montana are not reworked. Another Eocene locality in the San Juan Basin has produced an Eocene mammalian fauna with diverse Cretaceous marine sharks. Neither the nature of preservation nor the degree of abrasion could be used to distinguish reworked from contemporaneous material. The mixed environments represented by the fish taxa and recognition of the extensive pre-Tertiary extinction of both marine and freshwater fish were employed to recognize reworked specimens.

  11. The mid-Cretaceous super plume, carbon dioxide, and global warming

    Science.gov (United States)

    Caldeira, Ken; Rampino, Michael R.

    1991-01-01

    Carbon-dioxide releases associated with a mid-Cretaceous super plume and the emplacement of the Ontong-Java Plateau have been suggested as a principal cause of the mid-Cretaceous global warming. A carbonate-silicate cycle model is developed to quantify the possible climatic effects of these CO2 releases, utilizing four different formulations for the rate of silicate-rock weathering as a function of atmospheric CO2. CO2 emissions resulting from super-plume tectonics could have produced atmospheric CO2 levels from 3.7 to 14.7 times the modern preindustrial value of 285 ppm. Based on the temperature sensitivity to CO2 increases used in the weathering-rate formulations, this would cause a global warming of from 2.8 to 7.7 C over today's glogal mean temperature. Altered continental positions and higher sea level may have been contributed about 4.8 C to mid-Cretaceous warming. Thus, the combined effects of paleogeographic changes and super-plume related CO2 emissions could be in the range of 7.6 to 12.5 C, within the 6 to 14 C range previously estimated for mid-Cretaceous warming. CO2 releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20 percent of the mid-Cretaceous increase in atmospheric CO2.

  12. From nappe stacking to exhumation: Cretaceous tectonics in the Apuseni Mountains (Romania)

    Science.gov (United States)

    Reiser, Martin Kaspar; Schuster, Ralf; Spikings, Richard; Tropper, Peter; Fügenschuh, Bernhard

    2016-05-01

    New Ar-Ar muscovite and Rb-Sr biotite age data in combination with structural analyses from the Apuseni Mountains provide new constraints on the timing and kinematics of deformation during the Cretaceous. Time-temperature paths from the structurally highest basement nappe of the Apuseni Mountains in combination with sedimentary data indicate exhumation and a position close to the surface after the Late Jurassic emplacement of the South Apuseni Ophiolites. Early Cretaceous Ar-Ar muscovite ages from structurally lower parts in the Biharia Nappe System (Dacia Mega-Unit) show cooling from medium-grade conditions. NE-SW-trending stretching lineation and associated kinematic indicators of this deformation phase (D1) are overprinted by top-NW-directed thrusting during D2. An Albian to Turonian age (110-90 Ma) is proposed for the main deformation (D2) that formed the present-day geometry of the nappe stack and led to a pervasive retrograde greenschist-facies overprint. Thermochronological and structural data from the Bihor Unit (Tisza Mega-Unit) allowed to establish E-directed differential exhumation during Early-Late Cretaceous times (D3.1). Brittle detachment faulting (D3.2) and the deposition of syn-extensional sediments indicate general uplift and partial surface exposure during the Late Cretaceous. Brittle conditions persist during the latest Cretaceous compressional overprint (D4).

  13. The Wandering Indian Plate and Its Changing Biogeography During the Late Cretaceous-Early Tertiary Period

    Science.gov (United States)

    Chatterjee, Sankar; Scotese, Christopher

    Palaeobiogeographic analysis of Indian tetrapods during the Late Cretaceous-Early Tertiary time has recognized that both vicariance and geodispersal have played important roles in producing biogeographic congruence. The biogeographic patterns show oscillating cycles of geodispersal (Late Cretaceous), followed by congruent episodes of vicariance and geodispersal (Early Eocene), followed by another geodispersal event (Middle Eocene). New biogeographic synthesis suggests that the Late Cretaceous Indian tetrapod fauna is cosmopolitan with both Gondwanan and Laurasian elements. Throughout most of the Cretaceous, India was separated from the rest of Gondwana, but in the latest Cretaceous it reestablished contact with Africa through Kohistan-Dras (K-D) volcanic arc, and maintained biotic link with South America via Ninetyeast Ridge-Kerguelen-Antarctica corridor. These two geodispersal routes allowed exchanges of "pan-Gondwana" terrestrial tetrapods from Africa, South America, and Madagascar. During that time India also maintained biotic connections with Laurasia across the Neotethys via Kohistan-Dras Arc and Africa. During the Palaeocene, India, welded to the K-D Arc, rafted like a "Noah's Ark" as an island continent and underwent rapid cladogenesis because of allopatric speciation. Although the Palaeocene fossil record is blank, Early Eocene tetrapods contain both endemic and cosmopolitan elements, but Middle Eocene faunas have strong Asian character. India collided with Asia in Early and Middle Eocene time and established a new northeast corridor for faunal migration to facilitate the bidirectional "Great Asian Interchange" dispersals.

  14. Reidentification of avian embryonic remains from the cretaceous of mongolia.

    Directory of Open Access Journals (Sweden)

    David J Varricchio

    Full Text Available Embryonic remains within a small (4.75 by 2.23 cm egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.

  15. Climate model boundary conditions for four Cretaceous time slices

    Directory of Open Access Journals (Sweden)

    J. O. Sewall

    2007-06-01

    Full Text Available General circulation models (GCMs are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate system. One of the most time consuming, and often daunting, tasks facing the paleoclimate modeler, particularly those without a geological background, is the production of surface boundary conditions for past time periods. These boundary conditions consist of, at a minimum, continental configurations derived from plate tectonic modeling, topography, bathymetry, and a vegetation distribution. Typically, each researcher develops a unique set of boundary conditions for use in their simulations. Thus, unlike simulations of modern climate, basic assumptions in paleo surface boundary conditions can vary from researcher to researcher. This makes comparisons between results from multiple researchers difficult and, thus, hinders the integration of studies across the broader community. Unless special changes to surface conditions are warranted, researcher dependent boundary conditions are not the most efficient way to proceed in paleoclimate investigations. Here we present surface boundary conditions (land-sea distribution, paleotopography, paleobathymetry, and paleovegetation distribution for four Cretaceous time slices (120 Ma, 110 Ma, 90 Ma, and 70 Ma. These boundary conditions are modified from base datasets to be appropriate for incorporation into numerical studies of Earth's climate and are available in NetCDF format upon request from the lead author. The land-sea distribution, bathymetry, and topography are based on the 1°×1° (latitude x longitude paleo Digital Elevation Models (paleoDEMs of Christopher Scotese. Those paleoDEMs were adjusted using the paleogeographical reconstructions of Ronald Blakey (Northern Arizona University and published literature and were then modified for use in GCMs. The paleovegetation

  16. Climate model boundary conditions for four Cretaceous time slices

    Directory of Open Access Journals (Sweden)

    J. O. Sewall

    2007-11-01

    Full Text Available General circulation models (GCMs are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate system. One of the most time consuming, and often daunting, tasks facing the paleoclimate modeler, particularly those without a geological background, is the production of surface boundary conditions for past time periods. These boundary conditions consist of, at a minimum, continental configurations derived from plate tectonic modeling, topography, bathymetry, and a vegetation distribution. Typically, each researcher develops a unique set of boundary conditions for use in their simulations. Thus, unlike simulations of modern climate, basic assumptions in paleo surface boundary conditions can vary from researcher to researcher. This makes comparisons between results from multiple researchers difficult and, thus, hinders the integration of studies across the broader community. Unless special changes to surface conditions are warranted, researcher dependent boundary conditions are not the most efficient way to proceed in paleoclimate investigations. Here we present surface boundary conditions (land-sea distribution, paleotopography, paleobathymetry, and paleovegetation distribution for four Cretaceous time slices (120 Ma, 110 Ma, 90 Ma, and 70 Ma. These boundary conditions are modified from base datasets to be appropriate for incorporation into numerical studies of Earth's climate and are available in NetCDF format upon request from the lead author. The land-sea distribution, bathymetry, and topography are based on the 1°×1° (latitude × longitude paleo Digital Elevation Models (paleoDEMs of Christopher Scotese. Those paleoDEMs were adjusted using the paleogeographical reconstructions of Ronald Blakey (Northern Arizona University and published literature and were then modified for use in GCMs. The paleovegetation

  17. Late Cretaceous Breakup of the Pacific Margin of Southern Mexico

    Science.gov (United States)

    Guerrero-Garcia, J. C.; Herrero-Bervera, E.

    2006-12-01

    As geological, geophysical and geochemical evidence keeps accumulating over the years, there seems to be a growing general acceptance that the Chortis block (nuclear Central America) occupied a position further to the NW along the present-day margin of southwestern Mexico, sometime between Early Jurassic and Neogene time. The controversy resides no longer in the sense of motion along the coast but on the timing of events and in the latitude that the Chortis block occupied at the time of detachment. Previous studies mainly confined to the northern margin of the Chortis block, confirmed a left-lateral displacement of 130 km in Neogene time. Further studies made northwestward along the Mexican coast provided a better understanding of magmatic and metamorphic processes in the area, and suggested times of detachment increased to 30 Ma (Wadge and Burke, 1983), 40 Ma (Schaaf and others, 1995), and 66 Ma (Herrmann and others, 1994). The pre- detachment westernmost position of the block has changed, depending on the model chosen, from Puerto Vallarta and beyond, to the current position. We contend that several indicators, namely: (1) the truncated nature of the Pacific coast of SW Mexico; (2) the genesis of the Kula-Farallon ridge at 85 Ma; (3) the 2,600 km of northward transport of Baja British Columbia from the present-day latitude of the Baja California Peninsula, beginning at 85 Ma; (4) the paleomagnetic counterclockwise rotations of areas both in the Chortis block and along the Mexican coast, during Late Cretaceous-Paleogene time, and (5) the systematic NW-SE decrease of radiometric dates beginning at 85 Ma in Puerto Vallarta, point to this time and region for the onset of strike- slip drifting of the Chortis block toward its current position.

  18. Paleogeography of Cretaceous ammonoids of the Pacific coast of Russia

    Science.gov (United States)

    Jagt-Yazykova, E. A.; Zonova, T. D.

    2012-05-01

    This work presents the results of a study of the biogeographical distribution of Late Albian-Maastrichtian ammonites, found in sequences of the Pacific coast of Russia. The taxa typical of the Pacific Realm were identified, and their distribution traced beyond the borders of this region. In addition, species-migrants, distributed within the studied area were established. As a results of our works, a high level of endemism of ammonite fauna of the East of Russia was noted (75-88% of endemic species, on average). The bipolarity, previously established in the distribution of ammonoids within the Pacific Paleobiogeographical Realm, as well as their high regional provincialism, was confirmed. The following division of the studied area into faunal ammonite provinces in the Late Cretaceous was proposed: Arctic Province; Boreal-Pacific Province, including northeastern Russia (Chukotka Peninsula, the Koryak Upland, Penzhyna Gulf) and the boreal coast of North America (Alaska Peninsula, Arctic Canada and British Columbia); Northwest Pacific Province, including the Primorye Territory, Sakhalin and Shikotan Islands, the Japanese Islands; Northeast Province of the Pacific (the western coast of the United States and Mexico); Southwest Pacific (Australia, New Zealand, Oceania) and Southeast (the western coast of South America and Antarctica, Seymour and James Ross Islands) Provinces. This division is confirmed by data on inoceramid species. In addition, levels of global transgressions and general sea level rise, associated with the appearances of most of widespread marine taxa in the Pacific shelf seas, are established. These include Late Albian, Cenomanian-Turonian boundary, Late Coniacian, Late Campanian, Early-Late Maastrichtian boundary. Moreover, migration of ammonites occurred due to the Tethys Ocean extension and followed the northern sea straits in the Arctic Ocean and within the Pacific Realm, depending on warm currents. Both the counter and one-way migrations were

  19. Macrofossil evidence for a rapid and severe Cretaceous-Paleogene mass extinction in Antarctica

    Science.gov (United States)

    Witts, James D.; Whittle, Rowan J.; Wignall, Paul B.; Crame, J. Alistair; Francis, Jane E.; Newton, Robert J.; Bowman, Vanessa C.

    2016-05-01

    Debate continues about the nature of the Cretaceous-Paleogene (K-Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K-Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous-Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.

  20. A new dinosaur ichnotaxon from the Lower Cretaceous Patuxent Formation of Maryland and Virginia

    Science.gov (United States)

    Stanford, R.; Weems, R.E.; Lockley, M.G.

    2004-01-01

    In recent years, numerous dinosaur footprints have been discovered on bedding surfaces within the Lower Cretaceous Patuxent Formation of Maryland and Virginia. Among these, distinctive small tracks that display a combination of small manus with five digit impressions and a relatively much larger pes with four toe impressions evidently were made by animals belonging to the ornithischian family Hypsilophodontidae. These tracks differ from any ornithischian ichnotaxon previously described. We here name them Hypsiloichnus marylandicus and provide a description of their diagnostic characteristics. Although hypsilophodontid skeletal remains have not been found in the Patuxent, their skeletal remains are known from Lower Cretaceous strata of similar age in both western North America and Europe. Therefore, it is not surprising to find that an Early Cretaceous representative of this family also existed in eastern North America. ?? Taylor and Francis Ltd.

  1. Biostratigraphy of the Cretaceous/Tertiary boundary in the Sirwan Valley (Sulaimani Region, Kurdistan, NE Iraq)

    Science.gov (United States)

    Sharbazheri, Khalid Mahmood; Ghafor, Imad Mahmood; Muhammed, Qahtan Ahmad

    2009-10-01

    The Cretaceous/Tertiary (K/T) boundary sequence, which crops out in the studied area is located within the High Folded Zone, in the Sirwan Valley, northeastern Iraq. These units mainly consist of flysch and flysch-type successions of thick clastic beds of Tanjero/Kolosh Formations. A detailed lithostratigraphic study is achieved on the outcropping uppermost part of the Upper Cretaceous successions (upper part of Tanjero Formation) and the lowermost part of the Kolosh Formation. On the basis of the identified planktonic foraminiferal assemblages, five biozones are recorded from the uppermost part of Tanjero Formation and four biozones from the lower part of the Kolosh Formation (Lower Paleocene) in the Sirwan section. The biostratigraphic correlations based on planktonic foraminiferal zonations showed a comparison between the biostratigraphic zones established in this study and other equivalents of the commonly used planktonic zonal scheme around the Cretaceous/Tertiary boundary in and outside Iraq.

  2. A New Basal Neoceratopsian Dinosaur from the Middle Cretaceous of Jilin Province, China

    Institute of Scientific and Technical Information of China (English)

    JIN Liyong; CHEN Jun; ZAN Shuqin; Pascal GODEFROIT

    2009-01-01

    A new basal neoceratopsian dinosaur, Helioceratops brachygnathus gen. et sp. nov., is described from the Quantou Formation (late Early Cretaceous or early Late Cretaceous) in the Liufangzi locality (Jilin province, China). Helioceratops differs from other basal neoceratopsiaus with its deep dentary ramus, its steeply-inclined ventral predentary facet, its heterogeneous dentary crowns, and by the denticles and secondary ridges asymmetrically distributed on either side of the primary ridge on its dentary teeth. Along with Auroraceratops and Yamaceratops, Helioceratops represents one of the most derived non-coronosaurian neoceratopsians. The palaeogeographical distribution of basal neoceratopsians appears limited to northern China and southern Mongolia in the current state of our knowledge. It is therefore probable that this region constituted the birthplace for more advanced, Late Cretaceous Coronosauria.

  3. New Lower Cretaceous basal mantodean (Insecta from the Crato Formation (NE Brazil

    Directory of Open Access Journals (Sweden)

    Lee Shih-Wei

    2014-08-01

    Full Text Available Mantodea are very rare in the fossil record. 28 fossil species are reported since the earliest occurrence of mantodeans in the Upper Jurassic (Tithonian. Here, I describe Cretophotina santanensis n. sp. from the Aptian (Lower Cretaceous Crato Formation of Chapada do Araripe (northeastern Brazil. This species is characterized by long antenna and primitive raptorial forelegs. Morphological characters shared with the living genus Chaeteessa would support its assignment to the family Chaeteessidae. The tropical occurrence of the Early Cretaceous genus Cretophotina in Gondwana, together with occurrences of the genus Chaetessa from subtropical and temperate zones of Laurasia, implies that members of the family Chaeteessidae achieved nearly cosmopolitan distribution during the Early Cretaceous.

  4. Enantiornithine Bird with Diapsidian Skull and Its Dental Development in the Early Cretaceous in Liaoning, China

    Institute of Scientific and Technical Information of China (English)

    GONG Enpu; HOU Lianhai; WANG Lixia

    2004-01-01

    A large number of enantiornithine birds are discovered from the Early Cretaceous Jiufutang Formation in western Liaoning, China. They are all small-sized birds with a few small teeth. The enantiornithine bird from the Jiufutang Formation in the Shangheshou area, Chaoyang, Liaoning Province reported in this paper is the largest individual known in all enantiornithine birds of the Early Cretaceous.However, its teeth possess a feature of pseudoheterodont. Some different development stages of the new teeth substitute the earlier stages and the stages of development are preserved in this specimen. This development pattern is similar to that of Archaeopteryx and alligator but not dinosaur. A well-developed postorbital was also preserved in the skull, which was a diapsidian skull like that of Confuciusornis. Additionally, the distinctive preservation of its prefrontal distinguishes it from other enantiornithine birds of the Early Cretaceous.

  5. Environment and ecology of East Asian dinosaurs during the Early Cretaceous inferred from stable oxygen and carbon isotopes in apatite

    Science.gov (United States)

    Amiot, Romain; Wang, Xu; Zhou, Zhonghe; Wang, Xiaolin; Lécuyer, Christophe; Buffetaut, Eric; Fluteau, Frédéric; Ding, Zhongli; Kusuhashi, Nao; Mo, Jinyou; Philippe, Marc; Suteethorn, Varavudh; Wang, Yuanqing; Xu, Xing

    2015-02-01

    During the cold Late Barremian-Early Albian interval, terrestrial environments in East Asia were populated by rich and diverse vertebrate faunas characterized by a strong provincialism. The latitudinal gradient of temperature and the existence of geographic barriers likely accounted for some aspects of this heterogeneous distribution of faunas. Other factors, however, such as local environmental conditions and interactions within vertebrate communities, which could have influenced their distribution, have not yet been fully identified and understood. Therefore, new and published oxygen and carbon isotope compositions of apatite from Chinese and Thai reptiles (dinosaurs, crocodilians and turtles) have been analyzed and interpreted in terms of ecology, local air temperature and precipitation amounts. Differences in carbon and oxygen isotope compositions between various groups of sympatric plant-eating dinosaurs (sauropods, ornithopods and ceratopsians) indicate food resources partitioning among them most likely to avoid competition. Mid-latitude environments, where the Jehol Biota flourished, were submitted to cool temperate climatic conditions with Mean Air Temperature (MAT) of 10 ± 4 °C and Mean Annual Precipitations (MAP) of about 600 mm/yr compatible with the existence of forest environments. By contrast, sub-tropical regions, characterized by MAT of about 20-25 °C were either submitted to high amounts of seasonal precipitations (of about 1200 mm/yr in Thailand) or to significant aridity (MAP of about 400 mm/yr in South China). This difference in precipitation regime between Thailand and South China may be attributed to the occurrence of the Coastal Cordillera extending along the East margin of the South China block. These mountain ranges likely prevented humid air masses from the Pacific to penetrate some parts of South China, thus generating a "rain shadow effect". Mosaic environments characterizing East Asia during the Late Early Cretaceous may have acted

  6. Cretaceous oceanic red bed deposition, a tool for paleoenvironmental changes--Workshop of IGCP 463 & 494

    Institute of Scientific and Technical Information of China (English)

    MihaelaCarmenMelinte; RobertScott; ChengshanWANG; XiumianHU

    2005-01-01

    Members of IGCP 463, Cretaceous Oceanic Red Beds (CORBs), held the third workshop in Romania. In addition to scientific sessions,discussions of results and future plans, the participants examined exposures of Upper Cretaceous Red Beds of the Romanian Carpathians characterized both by pelagic/hemipelagic and turbiditic facies.

  7. A paleolatitude reconstruction of the South Armenian Block (Lesser Caucasus) for the Late Cretaceous : Constraints on the Tethyan realm

    NARCIS (Netherlands)

    Meijers, Maud J M; Smith, Brigitte; Kirscher, Uwe; Mensink, Marily; Sosson, Marc; Rolland, Yann; Grigoryan, Araik; Sahakyan, Lilit; Avagyan, Ara; Langereis, Cor; Müller, Carla

    2015-01-01

    The continental South Armenian Block - part of the Anatolide-Tauride South Armenian microplate - of Gondwana origin rifted from the African margin after the Triassic and collided with the Eurasian margin after the Late Cretaceous. During the Late Cretaceous, two northward dipping subduction zones we

  8. Record of the Cretaceous magnetic quiet zone: A precursor to the understanding of evolutionary history of the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Subrahmanyam, V.; Sarma, K.V.L.N.S.; Desa, M.; Rao, M.M.M.; Subrahmanyam, C.

    evolved during the Cretaceous long normal polarity epoch (superchron K-T) 118-84 Ma and is usually referred to as the Cretaceous magnetic quiet zone. Identification of this zone in the distal Bengal Fan perhaps serves as a missing link between the Early...

  9. Depositional environments of the early cretaceous Kurnub (Hathira) sandstones, North Jordan

    Science.gov (United States)

    Abed, Abdulkader M.

    1982-04-01

    The Kurnub (Hathira) sandstones in north Jordan, which are most probably of Early Cretaceous age, are about 300 m thick varicoloured, friable quartz-arenitic sandstones. Based on grain-size analysis, sedimentary structures, palaeocurrent, fossil content and petrography, these sandstones are postulated to be dominantly of fluvial origin with a few interfingering shallow marine horizons. A southward displacement of Jordan by at least 100 km would bring these sandstones opposite to similar rocks west of the Jordan-Araba rift, with Jordan being higher during the EArly Cretaceous.

  10. Lower Cretaceous turbidites of the Moray Firth: sequence stratigraphical framework and reservoir distribution

    Energy Technology Data Exchange (ETDEWEB)

    Jeremiah, J.M. [Nederlandse Ardolie Maatschappij B.V., Assen (Netherlands)

    2000-11-01

    Lower Cretaceous depositional systems of the Moray Firth are influenced by eustatic sea-level oscillations which have been dramatically overprinted by two major phases of pulsed tectonism, the Late Cimmerian and Austrian. The biostratigraphical resolution obtained has allowed the timing and differentiation of distinct tectonic/sequence boundaries, some of which are utilized as important seismo-stratigraphic markers. The construction of detailed facies maps for individual sequences has, in parallel, allowed an insight into the tectonic history of the main source areas during the Early Cretaceous. (Author)

  11. A gigantic shark from the lower cretaceous duck creek formation of Texas.

    Science.gov (United States)

    Frederickson, Joseph A; Schaefer, Scott N; Doucette-Frederickson, Janessa A

    2015-01-01

    Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous.

  12. A gigantic shark from the lower cretaceous duck creek formation of Texas.

    Directory of Open Access Journals (Sweden)

    Joseph A Frederickson

    Full Text Available Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous.

  13. A pterodactyloid pterosaur from the Upper Cretaceous Lapurr sandstone, West Turkana, Kenya.

    Science.gov (United States)

    O'Connor, Patrick M; Sertich, Joseph J W; Manthi, Fredrick K

    2011-03-01

    An isolated pterosaurian caudal cervical (~ postcervical) vertebra was recovered from the Upper Cretaceous Lapurr sandstone of West Turkana, northwestern Kenya. The vertebral centrum is short, wide, and dorsoventrally compressed. Although the specimen is lightly built similar to most pterosaurs, it is here referred to Pterodactyloidea and tentatively to the Azhdarchidae in that it lacks pneumatic features on both the centrum and neural arch. This represents one of the few pterosaurs recovered from the entirety of Afro-Arabia, the first pterosaur recovered from the Cretaceous of East Africa, and, significantly, a specimen that was recovered from fluvial deposits rather than the near-shore marine setting typical of most pterosaur discoveries.

  14. Extinction Risk of Phytoplankton Species to Potential Killing Mechanisms at the Cretaceous-Paleogene Boundary

    Science.gov (United States)

    Bralower, T. J.; Schueth, J.; Jiang, S.

    2013-05-01

    The impact at Chicxulub caused catastrophic changes in marine habitats including extended darkness, ocean acidification and eutrophication. These changes were devastating to some groups of phytoplankton at the base of the marine food chain while others escaped virtually unscathed. For example, diatoms had ~85% survival across the boundary and dinoflagellates actually increased in diversity. These non-calcareous plankton most likely survived due to their adaptation to high-stress environments and their ability to form spores and resting cysts. The calcareous nannoplankton, however, were decimated with approximately 85% of genera and 93% of species going extinct. Nannoplankton generally lack the ability to encyst and thus, as a group, would have been susceptible to darkness, ocean acidification and eutrophication. However, we still do not fully understand why certain nannofossil taxa survived while others went extinct. Extinction risk, the projected susceptibility of a taxon to extinction based on its ecology and ability to adapt, is a concept that is widely applied to extant species and higher order fossil groups, but not to phytoplankton. This concept is a useful for probing the selectivity of ancient species to mass extinction. Determining the extinction risk of latest Maastrichtian nannoplankton species would be a step towards understanding the selection of survivors. The deep-sea record contains a remarkable archive of nannoplankton extinction and recovery across the Cretaceous-Paleogene boundary. The recovery was geologically extended, enabling detailed comparisons between the ocean basins. A large, global database of assemblages had led to the discovery that the Northern Hemisphere oceans suffered higher nannoplankton extinction rates than the Southern Hemisphere with an ecological "crisis" that lasted for approximately 350 thousand years after the impact. In addition, incumbency played a major role in the origination of new species. Since extinction almost

  15. An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina

    Science.gov (United States)

    Apesteguía, Sebastián; Smith, Nathan D.; Juárez Valieri, Rubén; Makovicky, Peter J.

    2016-01-01

    Background Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit. Methodology/ Principal Findings A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton. Conclusions/ Significance Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa. PMID:27410683

  16. An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina.

    Directory of Open Access Journals (Sweden)

    Sebastián Apesteguía

    Full Text Available Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit.A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton.Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa.

  17. New material of Beelzebufo, a hyperossified frog (Amphibia: Anura from the late cretaceous of Madagascar.

    Directory of Open Access Journals (Sweden)

    Susan E Evans

    Full Text Available The extant anuran fauna of Madagascar is exceptionally rich and almost completely endemic. In recent years, many new species have been described and understanding of the history and relationships of this fauna has been greatly advanced by molecular studies, but very little is known of the fossil history of frogs on the island. Beelzebufo ampinga, the first named pre-Holocene frog from Madagascar, was described in 2008 on the basis of numerous disarticulated cranial and postcranial elements from the Upper Cretaceous (Maastrichtian Maevarano Formation of Madagascar. These specimens documented the presence of a hyperossified taxon that differed strikingly from extant Malagasy frogs in its large size and heavy coarse cranial exostosis. Here we describe and analyse new, articulated, and more complete material of the skull, vertebral column, and hind limb, as well as additional isolated elements discovered since 2008. μCT scans allow a detailed understanding of both internal and external morphology and permit a more accurate reconstruction. The new material shows Beelzebufo to have been even more bizarre than originally interpreted, with large posterolateral skull flanges and sculptured vertebral spine tables. The apparent absence of a tympanic membrane, the strong cranial exostosis, and vertebral morphology suggest it may have burrowed during seasonally arid conditions, which have been interpreted for the Maevarano Formation from independent sedimentological and taphonomic evidence. New phylogenetic analyses, incorporating both morphological and molecular data, continue to place Beelzebufo with hyloid rather than ranoid frogs. Within Hyloidea, Beelzebufo still groups with the South American Ceratophryidae thus continuing to pose difficulties with both biogeographic interpretations and prior molecular divergence dates.

  18. Geochemical fingerprints and pebbles zircon geochronology: Implications for the provenance and tectonic setting of Lower Cretaceous sediments in the Zhucheng Basin (Jiaodong peninsula, North China)

    Indian Academy of Sciences (India)

    Jin-Long Ni; Jun-Lai Liu; Xiao-Ling Tang; Xiao-Xiao Shi; Hong Zhang; Shuai Han

    2016-10-01

    This paper conducts a petrogeochemical analysis of the Lower Cretaceous Laiyang Group’s sandstones, compares the results with the Neoproterozoic and Mesozoic intrusive rocks in the southern Sulu Orogen (also called the Jiaonan Orogen), and performs an LA-ICP-MS zircon geochronology analysis of the granitic gneisses in the conglomerates of the Laiyang Group and the intrusive rocks in the JiaonanOrogen. The results show that the major element proportions of the Longwangzhuang Formation (LWZ Fm) and Qugezhuang Formation (QGZ Fm) of the Laiyang Group in the Zhucheng Basin are similar. The values of various indices for the LWZ Fm are similar to the average sandstone content of activecontinental margins, whereas, the values for the QGZ Fm are similar to those of continental island arcs. The comparison shows that the REE characteristics of the LWZ Fm and QGZ Fm of Laiyang Group are similar to those of the Neoproterozoic granitic gneisses in the Jiaonan Orogen but obviously different from those of the Early Cretaceous intrusive rocks. A tectonic setting discrimination diagram revealsthat the provenance of the Laiyang Group includes features of active continental margins and continental island arcs. A number of indicators, e.g., the sandstone type, the Chemical Index of Alteration, the Chemical Index of Weathering, the Plagioclase Index of Alteration and the Index of Chemical Constituent Variation, indicated that the sandstones did not undergo intense weathering and were deposited near the source area. The zircon ages of the granitic gneiss material in the conglomerates at the base of the Laiyang Group are 790±8.4 Ma, close to the ages of the Neoproterozoic granitic gneiss in the Jiaonan Orogen (739–819 Ma), and very different from the ages of the Early Cretaceous intrusive rocks. Combiningwith paleocurrent directions, geochemical character, the Neoproterozoic granitic gneisses in the Jiaonan Orogen may represent the primary provenance of the Laiyang Group in the

  19. The overthrusted Zaza Terrane of middle Cretaceous over the North American continental carbonate rocks of upper Jurassic-Lower Cretaceous age - relationships to oil generation

    Energy Technology Data Exchange (ETDEWEB)

    Echevarria Rodriguez, G.; Castro, J.A.; Amaro, S.V. [Centro de Investigaciones del Petroleo, La Habana (Cuba)

    1996-08-01

    The Zaza Terrane is part of the Caribbean plate thrust over the southern edge of the North American basinal and platform carbonate rocks of upper Jurassic-Lower Cretaceous age. Zaza Terrane are volcanic and ophiolitic rocks of Cretaceous age. The ophiolites are mostly serpentines which behave as reservoirs and seals. All Cuban oil fields are either within Zaza Terrane or basinal carbonates underneath, or not far away to the north of the thrust contacts. It appears that the overthrusting of the Zaza Terrane caused the generation of oil in the basinal carbonate source rocks underneath, due to the increase of rock thickness which lowered the oil window to a deeper position and increased the geothermal gradient. Oil generation was after thrusting, during post-orogenic. API gravity of oil is light toward the south and heavy to very heavy to the north. Source rocks to the south are probably of terrigenous origin.

  20. Zircon U-Pb age of the Pescadero felsite: A late Cretaceous igneous event in the forearc, west-central California Coast Ranges

    Science.gov (United States)

    Ernst, W.G.; Martens, U.C.; McLaughlin, R.J.; Clark, J.C.; Moore, Diane E.

    2011-01-01

    Weathered felsite is associated with the late Campanian-Maastrichtian Pigeon Point Formation near Pescadero, California. Poorly exposed, its age and correlation are uncertain. Is it part of the Pigeon Point section west of the San Gregorio-Hosgri fault? Does it rest on Nacimiento block basement? Is it dextrally offset from the Oligocene Cambria Felsite, ~185 km to the southeast? Why is a calc-alkaline hypabyssal igneous rock intrusive into the outboard accretionary prism? To address these questions, we analyzed 43 oscillatory-zoned zircon crystals from three incipiently recrystallized pumpellyite ?? prehnite ?? laumontite-bearing Pescadero felsite samples by sensitive high-resolution ion microprobe-reverse geometry (SHRIMPRG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) techniques. Thirty-three zircons gave late Mesozoic U-Pb ages, with single-grain values ranging from 81 to 167 Ma; ten have pre-Mesozoic, chiefl y Proterozoic ages. A group of the four youngest Pescadero zircons yielded an apparent maximum igneous age of ca. 86-90 Ma. Refl ecting broad age scatter and presence of partly digested sandstone inclusions, we interpret the rest of the zircons (perhaps all) as xenocrysts. Twenty-three zircons were separated and analyzed from two samples of the similar Cambria Felsite, yielding a unimodal 27 Ma U-Pb age. Clearly, the origin of the Upper Oligocene Cambria Felsite is different from that of the Upper Cretaceous Pescadero felsite; these rocks are not correlated, and do not constrain displacement along the San Gregorio-Hosgri fault. Peak ages differ slightly, but relative probability curves for Mesozoic and pre-Mesozoic Pescadero zircons compare well, for example, with abundant U-Pb age data for detrital zircons from Franciscan metaclastic strata ~100 km to the east in the Diablo Range- San Francisco Bay area, San Joaquin Great Valley Group turbidites, Upper Cretaceous Nacimiento block Franciscan strata, and Upper Cretaceous

  1. First planktonic foraminifera from the Early Cretaceous (Albian) of the Upper Magdalena Valley, Colombia

    Science.gov (United States)

    Blau, J.; Vergara, L.; Stock, H. W.

    1992-10-01

    Albian planktonic foraminifera have been found in the Caballos and "Villeta" formations at two localities in the Upper Magdalena Valley. This is the first documented record of Early Cretaceous planktonic foraminifera in Colombia. Hedbergellids and heterohelicids predominate; keeled forms are absent. The sedimentologic features and the associated microfauna indicate the onset of restricted environments from the middle Albian on.

  2. Resilience of Pacific pelagic fish across the Cretaceous/Palaeogene mass extinction

    Science.gov (United States)

    Sibert, Elizabeth C.; Hull, Pincelli M.; Norris, Richard D.

    2014-09-01

    Open-ocean ecosystems experienced profound disruptions to biodiversity and ecological structure during the Cretaceous/Palaeogene mass extinction about 66 million years ago. It has been suggested that during this mass extinction, a collapse of phytoplankton production rippled up the food chain, causing the wholesale loss of consumers and top predators. Pelagic fish represent a key trophic link between primary producers and top predators, and changes in their abundance provide a means to examine trophic relationships during extinctions. Here we analyse accumulation rates of microscopic fish teeth and shark dermal scales (ichthyoliths) in sediments from the Pacific Ocean and Tethys Sea across the Cretaceous/Palaeogene extinction to reconstruct fish abundance. We find geographic differences in post-disaster ecosystems. In the Tethys Sea, fish abundance fell abruptly at the Cretaceous/Palaeogene boundary and remained depressed for at least 3 million years. In contrast, fish abundance in the Pacific Ocean remained at or above pre-boundary levels for at least four million years following the mass extinction, despite marked extinctions in primary producers and other zooplankton consumers in this region. We suggest that the mass extinction did not produce a uniformly dead ocean or microbially dominated system. Instead, primary production, at least regionally, supported ecosystems with mid-trophic-level abundances similar to or above those of the Late Cretaceous.

  3. Morphologically Specialized Termite Castes and Advanced Sociality in the Early Cretaceous.

    Science.gov (United States)

    Engel, Michael S; Barden, Phillip; Riccio, Mark L; Grimaldi, David A

    2016-02-22

    A hallmark of animals that are eusocial, or those with advanced sociality, is reproductive specialization into worker and queen castes. In the most derived societies, these divisions are essentially fixed and in some arthropods, include further specialization--a tripartite system with a soldier caste that defends the colony. Eusociality has originated numerous times among insects but is believed to have appeared first in the termites (Isoptera), in the Early Cretaceous. However, all termites known from the Cretaceous have, until now, only been winged reproductives (alates and dealates); the earliest soldiers and definitive workers were known from just the Miocene (ca. 17-20 million years ago [mya]). Here, we report six termite species preserved in Early Cretaceous (ca. 100 mya) amber from Myanmar, one described as Krishnatermes yoddha gen. et sp. nov., comprising the worker/pseudergate, winged reproductive, and soldier, and a second species, Gigantotermes rex gen. et sp. nov., based on one of the largest soldier termites yet known. Phylogenetic analysis indicates that Krishnatermes are in the basal "Meiatermes-grade" of Cretaceous termites. Workers/pseudergates of another four species are briefly described, but not named. One of these workers/pseudergates reveals that ants--the most serious enemies of modern termites--lived in close proximity to termites in the Burmese paleofauna. These discoveries demonstrate the Mesozoic antiquity of specialized termite caste systems and corroborate that among all social species, termites probably had the original societies. PMID:26877085

  4. Palynology of uppermost Jurassic and lowermost Cretaceous strata in the Eastern Netherlands

    NARCIS (Netherlands)

    Burger, D.

    1965-01-01

    The present investigation is a systematical treatment of the sporomorphs from strata at the Jurassic-Cretaceous boundary in the eastern Netherlands Twente area, and an attempt to apply palynology to detailed stratigraphical study, by making use of quantitative pollen analyses. The rock samples used

  5. Dinosaur egg deposits in the Cretaceous Gyeongsang Supergroup, Korea: Diversity and paleobiological implications

    Science.gov (United States)

    Paik, In Sung; Kim, Hyun Joo; Huh, Min

    2012-08-01

    The taphonomy and depositional environments of dinosaur-egg-bearing deposits in the Cretaceous Gyeongsang Basin, Korea, are described and their paleobiological implications are discussed in the context of global geographic occurrences, geological ages, paleoenvironments, and lithology. The general depositional environment of dinosaur egg deposits in the Gyeongsang Supergroup is interpreted as dry floodplains with a semi-arid climate and intermittent volcanic activity. The diverse floodplain paleoenvironments include fluvial plains with meandering rivers to alluvial plains with episodic sheet-flooding. Both global and Korean dinosaur-egg-bearing deposits are generally restricted to the Late Cretaceous, a phenomenon for which two possible explanations are proposed. The first possible explanation for the temporal limitation of dinosaur egg preservation involves the appearance of angiosperms in the Late Jurassic, the Late Cretaceous ecological dispersion of angiosperm trees into swamps and floodplains, and the attendant change in herbivorous dinosaurs' diets. The second possible reason is related to nesting behavior in the Cretaceous. By contrast to the temporally limited occurrence of dinosaur eggs, paleoenvironments of nesting areas are diverse, ranging from inland areas to coastal areas. These hypotheses may provide new directions for the study and understanding of dinosaur egg distribution in the context of geologic time.

  6. Rapid short-term cooling following the Chicxulub impact at the Cretaceous-Paleogene boundary

    NARCIS (Netherlands)

    Vellekoop, J.; Sluijs, A.; Smit, J.; Schouten, S.; Weijers, J.W.H.; Sinninghe Damsté, J.S.; Brinkhuis, H.

    2014-01-01

    The mass extinction at the Cretaceous-Paleogene boundary, similar to 66 Ma, is thought to be caused by the impact of an asteroid at Chicxulub, present-day Mexico. Although the precise mechanisms that led to this mass extinction remain enigmatic, most postulated scenarios involve a short-lived global

  7. Late Cretaceous dwarf decapods from Guerrero, southern Mexico and their migration patterns

    NARCIS (Netherlands)

    Fraaije, R.H.B.; Vega, F.J.; Bakel, van B.W.M.; Garibay-Romero, L.M.

    2006-01-01

    Two new brachyuran species are described for the Upper Cretaceous Mexcala Formation, Guerrero State, Mexico. Longusorbis quadratus new species (Coniacian, Temalac region) is the oldest and southernmost record for the genus. Xanthosia zoquiapensis new species (Campanian, Zoquiapa region) is the first

  8. Curstal evolution and sedimentation history of the Bay of Bengal since the cretaceous

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, D.G.; Krishna, K.S.; Sar, D.

    on three latitudinal profiles) in the Bay of Bengal. The trend of the fracture zones, the locations of the magnetic chron 34, and the Cretaceous Magnetic Quiet Zone suggest that Greater India separated from Antarctica after a period of transform motion...

  9. Construction of the seawater 87Sr/86Sr curve for the Cenozoic and Cretaceous: supporting data

    International Nuclear Information System (INIS)

    We present the data used to construct the Cenozoic and Cretaceous portion of the Phanerozoic curve of seawater 87Sr/86Sr that had been given in summary form by W.H. Burke and coworkers. All Cenozoic samples (128) and 22 Cretaceous samples are foram-nannofossil oozes and limestones from DSDP cores distributed among 13 sites in the Atlantic, Pacific and Indian Oceans, and the Caribbean Sea. Non-DSDP Cretaceous samples (126) include limestone, anhydrite and phosphate samples from North America, Europe and Asia. Determination of the 87Sr/86Sr value of seawater at particular times in the past is based on comparison of ratios derived from coeval marine samples from widely separated geographic areas. The general configuration of the Cenozoic and Cretaceous curve appears to be strongly influenced by the history of plate interactions and sea-floor spreading. Specific rises and falls in the 87Sr/86Sr of seawater, however, may be caused by a variety of factors such as variation in lithologic composition of the crust exposed to weathering, configuration and topographic relief of continents, volcanic activity, rate of sea-floor spreading, extent of continental inundation by epeiric seas, and variations in both climate and paleo-oceanographic conditions. Many or all of these factors are probably related to global tectonic processes, yet their combined effect on the temporal variation of seawater 87Sr/86Sr can complicate a direct plate-tectonic interpretation for portions of the seawater curve. (Auth.)

  10. A palynological study on the Tertiary and Upper Cretaceous of British Guiana

    NARCIS (Netherlands)

    Hammen, van der T.; Wymstra, T.A.

    1964-01-01

    The pollen content of bore-hole samples and mine sections from the coast and from the bauxite belt of British Guiana has been studied. The pollen zonation is shown in fig. 6 and diagram IV. The description of the Upper Cretaceous and Tertiary pollen species is partly given in this article and partly

  11. The upper Jurassic-lower cretaceous siliciclastic system in the Morocco offshore - Prevenance, transport and deposition

    NARCIS (Netherlands)

    Bertotti, G.; Arantegui, A.; Charton, R.; Luber, T.; Redfern, J.

    2015-01-01

    The Morocco segment of the Central Atlantic passive continental margin experienced km-scale exhumation during the early post-rift (late Jurassic-Early Cretaceous). In the Meseta and the High Atlas this led to the development of a N-S trending ridge sourcing terrigenous sediments which were brought t

  12. Cretaceous source rock characterization of the Atlantic Continental margin of Morocco

    Energy Technology Data Exchange (ETDEWEB)

    Jabour, H. (ONAREP, Rabat (Morocco))

    1993-02-01

    Characterization of the petroleum potential for the Atlantic margin of Morocco has been based primarily on limited, antiently acquired organic geochemical data. These indicate the area of drilling behind the paleoshelf edge to be only fair in organic carbon and C15+ extract values with predominantly terrestrial kerogen types. Recently acquired geochemical data obtained from relatively recent drilling both behind and beyond the paleoshelf edge indicate 4 depositional facies containing hydrogen rich amorphous kerogen assemblages. These are: (1) Lower to Mid Jurassic inner shelf facies probably deposited in algal rich lagoon-like, (2) Lower Cretaceous non marine coaly facies probably deposited in algal rich swamplike environments, (3) Middle Cretaceous facies characterized by restrited anoxic environment with sediments rich in marine kerogen types deposited under sluggish wather circulation, (4) Upper Cretaceous to Tertiary outer-shelf to Upper slope facies probably deposited under algal-rich upwelling systems. Of these, the Cretaceous facies is the most widespread and represents the best source rock potential characteristics. Correlation of these facies to recently acquired good quality seismic packages allows for extrapolation of probable organic facies distribution throughout the continental margin. This should enhance the hydrocarbon potential of the Mesozoic and Cenozoic sediments both landward and seaward of the paleoshelf edge and thus permits refinement of strategies for hydrocarbon exploration in the area.

  13. Fluid flow in the northern Broad Fourteens Basin during Late Cretaceous inversion

    NARCIS (Netherlands)

    Oude Essink, Gualbert

    2003-01-01

    A basin-scale hydrogeological study of the inverted northern Broad Fourteens Basin, Netherlands offshore, has resulted in a reconstruction of geological evolution, an estimate of Late Cretaceous topography and model scenarios of syn-inversion meteoric water infiltration. This study was performed in

  14. Two new ornithurine birds from the Early Cretaceous of western Liaoning, China

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We describe two new ornithurine birds from the Early Cretaceous Jiufotang Formation of western Liaoning, northeast China: Yanornis martini gen. et sp. nov. and Yixianornis grabaui gen. et sp. nov. They represent the best fossil record of ornithurine birds known from the Early Cretaceous. They are more advanced than the most primitive ornithurine Liaoningornis, and are more similar to the other two Chinese Early Cretaceous ornithurines Chaoyangia and Songlingornis. Compared with Confuciusornis, Liaoxiornis and Eoenantiornis from the same age, the two new birds show remarkable advanced characteristics and suggest the presence of powerful flight capability like modern birds. Compared with Yixianornis and Chaoyangia, Yanornis is larger, with a more elongated skull and relatively long wings. The new discoveries indicate that by the Early Cretaceous both enantiornithine and ornithurine birds had already radiated significantly. The flight structures of Yanornis and Yixianornis are hardly distinguishable from those of modern birds; however, both retain a few primitive traits such as teeth on the jaws, wing claws and pubic symphysis, which exclude them from being the most recent ancestor of all ex-tant birds.

  15. Early Cretaceous decapod Crustacea from the Neuquén Basin, west-central Argentina

    NARCIS (Netherlands)

    Aguirre-Urreta, Maria Beatriz

    2003-01-01

    Marine deposits of the Neuquén Basin of west-central Argentina (southern South America) are richly fossiliferous; its Mesozoic invertebrate faunas, represented mostly by molluscs, have been extensively studied since the nineteenth century. However, Early Cretaceous decapod crustaceans are far less k

  16. Upper Cretaceous pelagic red beds,implications for paleoclimate and pale oc eanography

    Institute of Scientific and Technical Information of China (English)

    LubaJansa; O.Tuysuz; R.W.Scott

    2004-01-01

    Members of IGCP 463, Upper Cretaceous Oceanic Red Beds: Response to Ocean/Climate Global Change (CORBs) held their second workshop near the Black Sea in Bartin, Turkey. In addition to discussion of results and plans, the participants examined exposures of pelagic red beds in northern Turkev.

  17. Nonlinear Dynamic Study on Geomagnetic Polarity Reversal and Cretaceous Normal Superchron

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    It is generally acknowledged that geomagnetic polarity has reversed many times in geological history and an abnormal geologic phenomenon is the Cretaceous normal superchron. However, the causes have been unknown up to now. The nonlinear theory has been applied to analyze the phenomenon in geomagnetic polarity reversal and the Cretaceous normal superchron. The Cretaceous normal superchron implies that interaction of the Earth's core-mantle and liquid movement in the outer core may be the lowest energy state and the system of Earth magnetic field maintains a sort of temporal or spatial order structure by exchanging substance and energy in the outside continuously.During 121-83 Ma, there was no impact of a celestial body that would result in a geomagnetic polarity reversal, which may be a cause for occurrence of the Cretaceous normal superchron. The randomness of geomagnetic polarity reversal has the self-reversion characteristic of chaos and the chaos theory gives a simple and clear explanation for the dynamic cause of the geomagnetic polarity reversal.

  18. Maastrichtian or Maestrichtian? A proposal to the Subcommision on Cretaceous Stratigraphy (IUGS, International Commission on Stratigraphy)

    NARCIS (Netherlands)

    Herngreen, G.F.W.

    2003-01-01

    This contribution deals with the dual spelling of the terminal Cretaceous Stage, the Maastrichtian or Maestrichtian. From a historical point of view and in agreement with the recommendations of the International Stratigraphic Guide (1st and 2nd editions) only Maestrichtian is justified. Nevertheless

  19. Deshayesitid ammonites from the lower Aptian (Lower Cretaceous) of North-East Greenland

    NARCIS (Netherlands)

    Kelly, S.R.A.; Whitham, A.G.

    1999-01-01

    Two deshayesitid ammonite assemblages are described from the Lower Cretaceous succession of the north coast of Hold with Hope, North-East Greenland, and their biostratigraphical significance is assessed. In the earlier assemblage Prodeshayesites cf. bodei and P. laeviusculus occur. The second assemb

  20. Evidence for Cretaceous-Paleogene boundary bolide “impact winter” conditions from New Jersey, USA

    NARCIS (Netherlands)

    Vellekoop, J.; Esmeray-Senlet, S.; Miller, K.G.; Browning, J.V.; Sluijs, A.; van de Schootbrugge, B.; Sinninghe Damsté, J.S.; Brinkhuis, H.

    2016-01-01

    Abrupt and short-lived “impact winter” conditions have commonly been implicated as the main mechanism leading to the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (ca. 66 Ma), marking the end of the reign of the non-avian dinosaurs. However, so far only limited evidence has been availa

  1. A new Early Cretaceous relative of Gnetales: Siphonospermum simplex gen. et sp. nov. from the Yixian Formation of Northeast China

    Directory of Open Access Journals (Sweden)

    Friis Else

    2010-06-01

    Full Text Available Abstract Background Knowledge on fossil and evolutionary history of the Gnetales has expanded rapidly; Ephedra and ephedroids as well as the Gnetum-Welwitschia clade are now well documented in the Early Cretaceous. However, hypotheses on evolutionary relationships among living and fossil species are hampered by restricted knowledge of morphological variation in living groups and recent studies indicate that gnetalean diversity and character evolution may be more complex than previously assumed and involve additional extinct groups (Bennettitales, Erdtmanithecales and unassigned fossil taxa. Results Here we describe a new fossil related to Gnetales, Siphonospermum simplex from the Early Cretaceous Yixian Formation, an impression/compression of a reproductive shoot. The slender main axis bears one pair of opposite and linear leaves with primary parallel venation. The reproductive units are ovoid, without supporting bracts and borne on one median and two lateral branches. The most conspicuous feature of the fossil is the long, thread-like micropylar tube formed by the integument. Each ovule is surrounded by two different layers representing one or two seed envelopes; an inner sclerenchymatous layer and an outer probably parenchymatous layer. Conclusions The vegetative and reproductive features of Siphonospermum simplex exclude a relationship to any other group than the Gnetales. A combination of opposite phyllotaxis, linear leaves and ovules surrounded by seed envelope(s and with a long exposed micropylar tube are known only for extant and extinct Gnetales. Siphonospermum simplex constitutes a new lineage within the Gnetales. Its morphology cannot be directly linked to any previously known plant, but the organization of the reproductive units indicates that it belongs to the Gnetum-Welwitschia clade. Based on the absence of cone bracts and the inferred histology of the seed envelope(s it could be related to Gnetum, however, there are also

  2. DE GESTAS, DE SALVAJES Y DE MÁRTIRES. EL RELATO MAESTRO SOBRE EL FUERTE SAN JOSÉ RECONSIDERADO DESDE LA ARQUEOLOGÍA HISTÓRICA (PENÍNSULA VALDÉS, PCIA. DE CHUBUT, SIGLO XVIII / Savages, Epics and Martyrs. The Master Narrative about San Jose Fort reconside

    Directory of Open Access Journals (Sweden)

    Marcia Bianchi Villelli

    2015-06-01

    Full Text Available Desde inicios del siglo XX hasta el presente, la historiografía tradicional argentina se ha ocupado de estudiar la colonización española de costa patagónica de fines del siglo XVIII. La perspectiva desarrollada hasta 1980 se vinculaba principalmente a ámbitos conservadores de la historia que generaron una imagen fuertemente eurocéntrica y colonialista tanto del proceso de poblamiento como de cada uno de los tres asentamientos instalados sobre la costa patagónica entre 1779 y 1780 (el Fuerte Nuestra Señora del Carmen -Carmen de Patagones, Pcia. de Buenos Aires-, la Nueva Colonia y Fuerte de Floridablanca -Puerto San Julián, Pcia. de Santa Cruz- y el Fuerte San José -Península Valdés, Pcia. de Chubut.A partir de nuevas investigaciones realizadas en el Fuerte San José, el presente trabajo discutelas aproximaciones históricas tradicionales al mismo. Desde una perspectiva descolonial, se busca mostrar cómo el relato maestro historiográfico es solidario con la construcción del estado nación argentino, apoyándose en una mirada retrospectiva para legitimar su profundidad temporal y extensión espacial. De este modo, proponemos desde la arqueología histórica exponer la materialidad de nuevas tramas de sentidos para comprender proceso colonial en Patagonia, visibilizando otros espacios, actores, procesos y materialidades que habían quedado desdibujados en el relato maestro de la historiografía provincial y nacional.   Abstract  From the beginnings of the twentieth century up to present day, Argentinian traditional historiography has studied the late eighteenth century Spanish colonization of the Patagonian coast. The viewpoint developed until 1980 was mainly linked to conservative environmentsof historythat generated a strong Eurocentric and colonialist image of both, the process of settlement andof each of the three installed settlements on the Patagonian coast between 1779 and 1780 (Nuestra Señora del Carmen Fort -Carmen de

  3. Compositional and temperature variations of the Pacific upper mantle since the Cretaceous

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guoliang

    2016-01-01

    The geological evolution of the Earth during the mid-Cretaceous were shown to be anomalous, e.g., the pause of the geomagnetic field, the global sea level rise, and increased intra-plate volcanic activities, which could be attributed to deep mantle processes. As the anomalous volcanic activities occurred mainly in the Cretaceous Pacific, here we use basalt chemical compositions from the oceanic drilling (DSDP/ODP/IODP) sites to investigate their mantle sources and melting conditions. Based on locations relative to the Pacific plateaus, we classified these sites as oceanic plateau basalts, normal mid-ocean ridge basalts, and near-plateau seafloor basalts. This study shows that those normal mid-ocean ridge basalts formed during mid-Cretaceous are broadly similar in average Na8, La/Sm and Sm/Yb ratios and Sr-Nd isotopic compositions to modern Pacific spreading ridge (the East Pacific Rise). The Ontong Java plateau (125–90 Ma) basalts have distinctly lower Na8 and 143Nd/144Nd, and higher La/Sm and87Sr/86Sr than normal seafloor basalts, whereas those for the near-plateau seafloor basalts are similar to the plateau basalts, indicating influences from the Ontong Java mantle source. The super mantle plume activity that might have formed the Ontong Java plateau influenced the mantle source of the simultaneously formed large areas of seafloor basalts. Based on the chemical data from normal seafloor basalts, I propose that the mantle compositions and melting conditions of the normal mid-ocean ridges during the Cretaceous are similar to the fast spreading East Pacific Rise. Slight variations of mid-Cretaceous normal seafloor basalts in melting conditions could be related to the local mantle source and spreading rate.

  4. Cretaceous volcanic-intrusive magmatism in western Guangdong and its geological significance

    Institute of Scientific and Technical Information of China (English)

    GENG; Hongyan; XU; Xisheng; S.Y.O'Reilly; ZHAO; Ming; SUN; Tao

    2006-01-01

    Systematic zircon LA-ICPMS U-Pb dating reveals that Cretaceous volcanic-intrusive activities developed in western Guangdong. Representative volcanic rocks, i.e. Maanshan and Zhougongding rhyodacites, have zircon U-Pb isotopic ages of 100±1 Ma, and the intrusive ones including the Deqing monzonitic granite body and the Xinghua granodiorite body in the Shidong complex, as well as the Tiaocun granodiorite body in the Guangping complex yield ages of 99±2 Ma, ca.100 Ma, and 104±3 Ma respectively. The biotite-granites of the Shidong complex main body (461±35 Ma) and that of the Guangping complex (444±6 Ma) are Caledonian. In spite of the big time interval between Cretaceous volcanic-intrusive magmatisms and Caledonian intrusive ones, both of them are characterized by enrichment in Rb, Th, Ce, Zr, Hf, Sm, depletion in Ba, Nb, Ta, P, Ti, Eu, and weakly REE tetrad effect. Eu negative anomalies are: Cretaceous volcanic rocks (Eu/Eu*=0.74), Cretaceous intrusive rocks (Eu/Eu*=0.35-0.58), Caledonian biotite granites (Eu/Eu*=0.31-0.34). Studies of Sr-Nd isotope data show that all these igneous rocks have high initial 87Sr/86Sr ratios (0.7105-0.7518), and low εNd(t) values (-7.23--11.39) with their Nd two-stage model ages ranging from 1.6-2.0 Ga, which suggest that they all derived from the Proterozoic crustal basement of southeast China.The occurrence of Cretaceous volcanic-intrusive magmatisms in western Guangdong is related with the important lithospheric extension event in southeast China (including Nanling region) at ca. 100 Ma.The "volcanic line" defined by the large scale Mesozoic intermediate-acidic volcanic magmatisms in southeast China may further extend to the southwest margin of Nanling region.

  5. The Tethys Himalayan passive margin from Late Triassic to Early Cretaceous (South Tibet)

    Science.gov (United States)

    Jadoul, Flavio; Berra, Fabrizio; Garzanti, Eduardo

    1998-04-01

    The Mesozoic succession of South Tibet, both in lithologies and stratigraphic thicknesses, compares much more closely with that of central Nepal than has been reported in the literature. Facies distribution, from relatively proximal environments in the south to more distal settings in the north, reflects the paleogeography of the Tethys Himalaya passive margin, representing the southern edge of Neotethys. As in central Nepal and NW Himalaya, accumulation rates increased greatly in the latest Triassic, when very thick shelfal siliciclastics and locally volcaniclastics (Tarap Formation) were followed by coastal sandstones (Zhamure Formation). Contrary to reports in the literature, this latter unit reaches well into the Liassic at least in proximal southern sectors. The base of the overlying Kioto Group, yielding rich faunal associations characterized by benthic foraminifers and Lithiotis, similar to those of western Tethys carbonate platforms, is dated as middle Liassic (most probably late Pliensbachian). The monotonous growth of carbonate ramps during the middle Liassic to early Dogger was interrupted by two siliciclastic episodes related to major paleogeographic changes in the Toarcian (middle part of the Kioto Group) and in the Bajocian-Bathonian (Laptal Formation). An early Callovian flooding event (Ferruginous Oolite Formation)—widespread all along the Tethys Himalaya—was locally followed by deposition of a markedly lenticular pelagic unit, previously reported only from the Thakkhola Graben (Dangar Formation). The overlying Spiti Shale is reduced to only 20 m in southern sectors, where it is not younger than the Oxfordian, whereas in northern sectors the unit is several tens of m thick and mainly ascribed to the Tithonian. Volcaniclastic deposition (Wölong Formation)—reported herein for the first time—probably began as early as the Kimmeridgian/early Tithonian and lasted until Aptian times, when it was replaced by sedimentation of relatively deep

  6. Petrogenesis of Late Cretaceous lava flows from a Ceno-Tethyan island arc: The Raskoh arc, Balochistan, Pakistan

    Science.gov (United States)

    Siddiqui, Rehanul Haq; Qasim Jan, M.; Asif Khan, M.

    2012-10-01

    The Raskoh arc is about 250 km long, 40 km wide and trends in an ENE direction. The oldest rock unit in the Raskoh arc is an accretionary complex (Early to Late Jurassic), which is followed in age by Kuchakki Volcanic Group, the most wide spread unit of the Raskoh arc. The Volcanic Group is mainly composed of basaltic to andesitic lava flows and volcaniclastics, including agglomerate, volcanic conglomerate, breccia and tuff, with subordinate shale, sandstone, limestone and chert. The flows generally form 3-15 m thick lenticular bodies but rarely reach up to 300 m. They are mainly basaltic-andesites with minor basalts and andesites. The main textures exhibited by these rocks are hypocrystalline porphyritic, subcumulophyric and intergranular. The phenocrysts comprise mainly plagioclase (An30-54 in Nok Chah and An56-64 in Bunap). They are embedded in a micro-cryptocrystalline groundmass having the same minerals. Apatite, magnetite, titanomagnetite and hematite occur as accessory minerals. Major, trace and rare earth elements suggest that the volcanics are oceanic island arc tholeiites. Their low Mg # (42-56) and higher FeO (total)/MgO (1.24-2.67) ratios indicate that the parent magma of these rocks was not directly derived from a mantle source but fractionated in an upper level magma chamber. The trace element patterns show enrichment in LILE and depletion in HFSE relative to N-MORB. Their primordial mantle-normalized trace element patterns show marked negative Nb anomalies with positive spikes on K, Ba and Sr which confirm their island arc signatures. Slightly depleted LREE to flat chondrite normalized REE patterns further support this interpretation. The Zr versus Zr/Y and Cr versus Y studies show that their parent magma was generated by 20-30% melting of a depleted mantle source. The trace elements ratios including Zr/Y (1.73-3.10), Ti/Zr (81.59-101.83), Ti/V (12.39-30.34), La/YbN (0.74-2.69), Ta/Yb (0.02-0.05) and Th/Yb (0.11-0.75) of the volcanics are more

  7. Group X

    Energy Technology Data Exchange (ETDEWEB)

    Fields, Susannah

    2007-08-16

    This project is currently under contract for research through the Department of Homeland Security until 2011. The group I was responsible for studying has to remain confidential so as not to affect the current project. All dates, reference links and authors, and other distinguishing characteristics of the original group have been removed from this report. All references to the name of this group or the individual splinter groups has been changed to 'Group X'. I have been collecting texts from a variety of sources intended for the use of recruiting and radicalizing members for Group X splinter groups for the purpose of researching the motivation and intent of leaders of those groups and their influence over the likelihood of group radicalization. This work included visiting many Group X websites to find information on splinter group leaders and finding their statements to new and old members. This proved difficult because the splinter groups of Group X are united in beliefs, but differ in public opinion. They are eager to tear each other down, prove their superiority, and yet remain anonymous. After a few weeks of intense searching, a list of eight recruiting texts and eight radicalizing texts from a variety of Group X leaders were compiled.

  8. High Arctic paleoenvironmental and Paleoclimatic changes in the Mid-Cretaceous

    Science.gov (United States)

    Herrle, Jens; Schröder-Adams, Claudia; Selby, David; Du Vivier, Alice; Flögel, Sascha; McAnena, Alison; Davis, William; Pugh, Adam; Galloway, Jennifer; Hofmann, Peter; Wagner, Thomas

    2014-05-01

    Although major progress in Cretaceous (145-66 Ma) paleoclimate and paleoceanography has been made during the last decades (e.g., Hay, 2008, 2011; Föllmi, 2012 and references therein), our knowledge of high latitudinal environmental change remains largely unknown compared to low- and mid-latitude marine and terrestrial environments. Drilling the Arctic Ocean remains challenging and expensive, whereas the Sverdrup Basin provides excellent exposures on land. To fully understand the climate and paleoceanographic dynamics of the warm, equable greenhouse world of the Cretaceous Period it is important to determine polar paleotemperatures and to study paleoceanographic changes in a well-established and continuous bio- and chemostratigraphic context. Exceptional exposures of Cretaceous sediments on the central to southern part of Axel Heiberg Island at a Cretaceous paleolatitude of about 71°N (Tarduno et al., 1998) provide a unique window on the Cretaceous Arctic paleoenvironment and climate history (Schröder-Adams et al., 2014). Here we present high-resolution records combining sedimentological studies, U-Pb zircon geochronology, marine organic carbon isotopes and initial 187Os/188Os data, TEX86-derived sea-surface temperatures (SST) and climate modelling, that constrain the timing and magnitude of major Oceanic Anoxic Events (OAEs) and climate events constructed from a ~1.8 km sedimentary succession exposed on Axel Heiberg and Ellef Ringnens islands in the Canadian Arctic Archipelago. The first high latitude application of initial 187Os/188Os data are agreeable with global profiles (Du Vivier et al., 2014) indicating the widespread magmatic pulse of the Caribbean Large Igneous Province (LIP) at the onset of OAE2 but also record the emplacement of local High Arctic LIP prior to the OAE2 in the Sverdrup Basin. Initial SST data suggest a slightly lower meridional temperature gradient during the Middle/Late Albian compared to present and a similar to the present one during

  9. Latest Cretaceous and Cenozoic magmatic rocks of Alaska: polygon data

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map is a statewide summary of magmatic (igneous) rocks grouped into geologic units that can be portrayed cartographically at 1:2,500,000. This dataset consists...

  10. The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle

    Science.gov (United States)

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

    2002-01-01

    A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining

  11. ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

    Science.gov (United States)

    Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.

    2014-12-01

    The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as

  12. Linkages Between Cretaceous Forearc and Retroarc Basin Development in Southern Tibet

    Science.gov (United States)

    Orme, D. A.; Laskowski, A. K.

    2015-12-01

    Integrated provenance and subsidence analysis of forearc and retroarc foreland basin strata were used to reconstruct the evolution of the southern margin of Eurasia during the Early to Late Cretaceous. The Cretaceous-Eocene Xigaze forearc basin, preserved along ~600 km of the southern Lhasa terrane, formed between the Gangdese magmatic arc and accretionary complex as subduction of Neo-Tethyan oceanic lithosphere accommodated the northward motion and subsequent collision of the Indian plate. Petrographic similarities between Xigaze forearc basin strata and Cretaceous-Eocene sedimentary rocks of the northern Lhasa terrane, interpreted as a retroarc foreland basin, were previously interpreted to record N-S trending river systems connecting the retro- and forearc regions during Cretaceous time. New sandstone petrographic and U-Pb detrital zircon provenance analysis of Xigaze forearc basin strata support this hypothesis. Qualitative and statistical provenance analysis using cumulative distribution functions and Kolmogorov-Smirnov (K-S) tests show that the forearc basin was derived from either the same source region as or recycled from the foreland basin. Quartz-rich sandstones with abundant carbonate sedimentary lithic grains and rounded, cobble limestone clasts suggests a more distal source than the proximal Gangdese arc. Therefore, we interpret that the northern Lhasa terrane was a significant source of Xigaze forearc detritus and track spatial and temporal variability in the connection between the retro- and forearc basin systems during the Late Cretaceous. A tectonic subsidence curve for the Xigaze forearc basin shows a steep and "kinked" shape similar to other ancient and active forearc basins. Initial subsidence was likely driven by thermal relaxation of the forearc ophiolite after emplacement while additional periods of rapid subsidence likely result from periods of high flux magmatism in the Gangdese arc and changes in plate convergence rate. Comparison of the

  13. Hot Groups.

    Science.gov (United States)

    Vail, Kathleen

    1996-01-01

    Collaborators sparked by creative ideas and obsessed by a common task may not realize they're part of a "hot group"--a term coined by business professors Harold J. Leavitt and Jean Lipman-Blumen. Spawned by group decision making and employee empowerment, hot groups can flourish in education settings. They're typically small, short lived, and goal…

  14. Abelian Groups

    Energy Technology Data Exchange (ETDEWEB)

    Mishina, A.P.

    1995-10-15

    This fifth survey of reviews on abelian groups comprises papers reviewed in 1985-1992. Just as in the preceding surveys, the issues concerning finite abelian groups, topological groups, ordered groups, group algebras, modules (with rare exceptions), and topics on logic are not considered. The issues on the lattice of subgroups of an abelian group are included in Section 11. In contrast to the fourth survey, this one does not contain Sections 6 (N-high subgroups), 9 (rings with a given additive group), and 10 (valuated groups); since only a few papers treated these topics, the material discussed earlier in Sections 9, and 10 is now included in Section 11 and the material of the former Section 6 will be found in Sections 1, 7, 8, and 11 of this survey. On the other hand, the fifth survey has three new sections devoted to separable groups (a new Sect. 5), Butler groups (a new Sect. 6), and the endormorphism rings and automorphism groups of abelian groups (a new Sect. 9).

  15. Group morphology

    NARCIS (Netherlands)

    Roerdink, Jos B.T.M.

    2000-01-01

    In its original form, mathematical morphology is a theory of binary image transformations which are invariant under the group of Euclidean translations. This paper surveys and extends constructions of morphological operators which are invariant under a more general group TT, such as the motion group

  16. The deformation and tectonic evolution of the Huahui Basin, northeast China, during the Cretaceous-Early Cenozoic

    Science.gov (United States)

    Huang, Shiqi; Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Huang, Dezhi; Wei, Shi; Li, Zhenhong; Miao, Laicheng; Zhu, Mingshuai

    2015-12-01

    The Cretaceous Huahui basin lies along the Dunhua-Mishan fault (Dun-Mi fault), which is one of the northern branches of Tan-Lu fault in northeastern China. The study of the formation and the tectonic movements that took place in the basin can provide very important information for deciphering the tectonic evolution of northeastern China during Cretaceous-Early Cenozoic. The field analysis of fault-slip data collected from different units in the basin, demonstrates changes in the paleo-stress state that reveals a three-stage tectonic movement during the Cretaceous-Early Cenozoic. The earliest tectonic movement was NW-SE extension, which was responsible for the formation of the basin and sedimentary infilling during the Early Cretaceous. Dating of the andesite in the fill indicates it began during about 119.17 ± 0.80 Ma. The extensional structures formed in the Latest Early Cretaceous imply that this tectonic movement lasted until the beginning of the Late Cretaceous. The second stage began during the Late Cretaceous when the tectonic stress state changed and was dominated by NW-SE compression and NE-SW extension, which caused the inversion of the extensional basin. This compression folded the Early Cretaceous deposits and reactivated pre-existing faults and uplifted pre-existing granite in the basin. The strata and the unconformity in the basin shows that this compressive phase probably took place during the Late Cretaceous and ended in the Early Paleogene by a compressional regime with NE-SW compression and NW-SE extension that constitutes the third stage. The tectonic stress fields documented in the Huahui basin provide insight into the influences of plate tectonics on the crustal evolution of northeastern China during the Cretaceous to Early Cenozoic. These results show that the development of Huahui basin was controlled by the northwestward subduction of the paleo-Pacific plate during the Cretaceous, and later by the far-field effects of India-Asia collision in

  17. Detrital zircon geochronology of the Cretaceous succession from the Iberian Atlantic Margin: palaeogeographic implications

    Science.gov (United States)

    Dinis, Pedro A.; Dinis, Jorge; Tassinari, Colombo; Carter, Andy; Callapez, Pedro; Morais, Manuel

    2016-04-01

    Detrital zircon U-Pb data performed on eight Cretaceous sandstone samples (819 age isotopic results) from the Lusitanian basin (west Portugal) constrain the history of uplift and palaeodrainage of western Iberia following break-up of Pangaea and opening of the North Atlantic Ocean. We examined the links between shifts in provenance and known basinwide unconformities dated to the late Berriasian, Barremian, late Aptian and Cenomanian-Turonian. The detrital zircon record of sedimentary rocks with wider supplying areas is relatively homogenous, being characterized by a clear predominance of late Palaeozoic ages (c. 375-275 Ma) together with variable proportions of ages in the range c. 800-460 Ma. These two groups of ages are diagnostic of sources within the Variscan Iberian Massif. A few samples also reveal significant amounts of middle Palaeozoic (c. 420-385 Ma) and late Mesoproterozoic to early Neoproterozoic (c. 1.2-0.9 Ga) zircon, which are almost absent in the basement to the east of the Lusitanian basin, but are common in terranes with a Laurussia affinity found in NW Iberia and the conjugate margin (Newfoundland). The Barremian unconformity marks a sudden rise in the proportion of c. 375-275 Ma zircon ages accompanied by a decrease in the abundance of the c. 420-385 Ma and c. 1.2-0.9 Ga ages. This shift in the zircon signature, which is contemporaneous with the separation of the Galicia Bank from Flemish Cap, reflects increased denudation of Variscan crystalline rocks and a reduction in source material from NW Iberia and adjoining areas. The late Aptian unconformity, which represents the largest hiatus in the sedimentary record, is reflected by a shift in late Palaeozoic peak ages from c. 330-310 Ma (widespread in Iberia) to c. 310-290 Ma (more frequent in N Iberia). It is considered that this shift in the age spectra resulted from a westward migration of catchment areas following major uplift in northern Iberia and some transport southward from the Bay of

  18. Timing and Kinematics of Cretaceous to Paleogene inversion at the SE margin of the Central European Basin System: Part 2, Thermochronology

    Science.gov (United States)

    Hoffmann, V.-E.; Dunkl, I.; von Eynatten, H.; Jähne, F.; Voigt, T.; Kley, J.

    2009-04-01

    mixed age information two different age groups can be recognized. A major group that is similar to the one reported above points to a short but intense pulse of exhumation and inversion in Coniacian to Campanian time. A younger, less significant age cluster yields information on a second phase of cooling and exhumation in the Paleocene-Eocene. The length distribution of AFT data leads to the assumption of rapid, partially multi-phase, exhumation events. In addition, the data of this study provides indications for thick Jurassic burial that likely reflect phases of Mesozoic extensional tectonics in at least parts of the CEBS. Jacobs, J., Breitkreuz, C. (2003): Zircon and apatite fission-track thermochronology of Late Carboniferous volcanic rocks of the NE German Basin. International Journal of Earth Sciences (Geologische Rundschau), 92, 165-172. Thomson, S., Brix, M., Carter, A. (1997): Late Cretaceous denudation of the Harz Massif assessed by apatite fission track analysis. In: G. Büchel and H. Lützner (Editors), Regionale Geologie von Mitteleuropa, 149. Hauptversammlung Deutsche Geologische Gesellschaft, Jena. Schriftenreihe der Deutschen Geologischen Gesellschaft, 3, 115. Thomson, S.N., Zeh, A. (2000): Fission-track thermochronology of the Ruhla Crystalline Complex:. New constraints on the post-Variscan thermal evolution of the NW Saxo-Bohemian Massif. Tectonophysics, 324, 17-35. Ventura, B., Lisker, F., Kopp, J. (2003): Apatite fission track data from the dill-core Züllsdorf 1/63: implications for the reconstruction of the post Variscan exhumation of the Mid German Crystalline High. Zeitschrift für Geologische Wissenschaften, 31, 251-261. Voigt, T., Wiese, F., von Eynatten, H., Franzke, H.-J. & Gaupp, R. (2006): Facies evolution of syntectonic Upper Cretaceous deposits in the Subhercynian Cretaceous Basin and adjoining areas (Germany). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 157/2, 203-244.

  19. Permutation groups

    CERN Document Server

    Passman, Donald S

    2012-01-01

    This volume by a prominent authority on permutation groups consists of lecture notes that provide a self-contained account of distinct classification theorems. A ready source of frequently quoted but usually inaccessible theorems, it is ideally suited for professional group theorists as well as students with a solid background in modern algebra.The three-part treatment begins with an introductory chapter and advances to an economical development of the tools of basic group theory, including group extensions, transfer theorems, and group representations and characters. The final chapter feature

  20. Galaxy Groups

    Science.gov (United States)

    Tully, R. Brent

    2015-02-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well-studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times {{10}12}{{M}⊙ } are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of {{Ω}matter}˜ 0.15 in a flat topology, with a 68% probability of being less than 0.44.

  1. Galaxy groups

    Energy Technology Data Exchange (ETDEWEB)

    Brent Tully, R. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-02-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well-studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 10{sup 12}M{sub ⊙} are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of Ω{sub matter}∼0.15 in a flat topology, with a 68% probability of being less than 0.44.

  2. The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution.

    Science.gov (United States)

    Caldwell, Michael W; Nydam, Randall L; Palci, Alessandro; Apesteguía, Sebastián

    2015-01-27

    The previous oldest known fossil snakes date from ~100 million year old sediments (Upper Cretaceous) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation. We report here on snake fossils that extend the record backwards in time by an additional ~70 million years (Middle Jurassic-Lower Cretaceous). These ancient snakes share features with fossil and modern snakes (for example, recurved teeth with labial and lingual carinae, long toothed suborbital ramus of maxillae) and with lizards (for example, pronounced subdental shelf/gutter). The paleobiogeography of these early snakes is diverse and complex, suggesting that snakes had undergone habitat differentiation and geographic radiation by the mid-Jurassic. Phylogenetic analysis of squamates recovers these early snakes in a basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a basal position to all other snakes including Najash.

  3. NEW PTEROSAUR SPECIMENS FROM THE KEM KEM BEDS (UPPER CRETACEOUS, CENOMANIAN OF MOROCCO

    Directory of Open Access Journals (Sweden)

    TAISSA RODRIGUES

    2011-03-01

    Full Text Available Although pterosaurs from Africa are still rare, in recent years several specimens have been described from the Kem Kem beds (Upper Cretaceous, Cenomanian of Morocco. Here we describe four additional specimens from this informal lithostratigraphic unit: a jaw fragment, two mid-cervical vertebrae, and a humerus. All these specimens show three-dimensional preservation, differing much from the flat condition found in most pterosaur material. The vertebrae are particularly well preserved, and allow accurate observations on the pneumatization of the neural arch. Based on comparable material, we show that at least two edentulous pterosaur species were present in this informal lithostratigraphic unit, thus adding to the growing evidence of considerable pterosaur diversity in northwestern Africa during the "middle" Cretaceous. So far, the Kem Kem beds have the most diverse pterosaur fauna in this continent, with the presence of anhanguerids, azhdarchids, pteranodontids, and tapejarids. 

  4. Solid state {sup 13}C NMR analysis of Brazilian cretaceous ambers

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Ricardo; Azevedo, Debora A., E-mail: ricardopereira@iq.ufrj.b, E-mail: debora@iq.ufrj.b [Universidade Federal do Rio de Janeiro (IQ/UFRJ), Rio de Janeiro, RJ (Brazil). Inst. de Quimica. Lab. de Geoquimica Organica Molecular e Ambiental; San Gil, Rosane A.S. [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica. Lab. de RMN de Solidos; Carvalho, Ismar S. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Geociencias. Dept. de Geologia; Fernandes, Antonio Carlos S. [Museu Nacional (MN/UFRJ), RJ (Brazil). Dept. de Geologia e Paleontologia

    2011-07-01

    {sup 13}C cross polarization with magic angle spinning nuclear magnetic resonance ({sup 13}C CPMAS NMR) spectra have been obtained for the first time to three Cretaceous amber samples from South America. The samples were dated to Lower Cretaceous and collected in sediments from the Amazonas, Araripe and Reconcavo basins, Brazil. All samples have very similar spectra, consistent with a common paleobotanical source. Some aspects of the spectra suggest a relationship between Brazilian ambers and Araucariaceae family, such as intense resonances at 38-39 ppm. All samples are constituted by polylabdane structure associated to Class Ib resins, constituted by polymers of labdanoid diterpenes. Finally, information concerning some structural changes during maturation, such as isomerization of {Delta}{sup 8(17)} and {Delta}{sup 12(13)} unsaturations, were obtained by {sup 13}C NMR analyses. The results concerning botanical affinities are in accordance with previous results obtained by gas chromatography-mass spectrometry (GC-MS). (author)

  5. Paleo—Latitude Variation of Guizhou Terrain from Devonian to Cretaceous

    Institute of Scientific and Technical Information of China (English)

    王俊达; 李华梅

    1998-01-01

    Over 800 paleomagnetic samples were collected from 79 sample localities,ranging in age from Devonian,Carboniferous,Permian to Jurassic for paleo-latitude research on the Guizhou terrain,The area sampled covers 13 couties with an area of about 50000km2.The paleomagnetic results obtained indicate that the Guizhou terrain was at 11.4°S in Devonian,4.5°-9.3°S in Carboniferous,2.6°-4.5°S in Permian,14.8°N in Triassic and 24.5°-26.0°N in Jurassic,In the Cretaceous period.the paleo-latitude of the area was at 22.4-23.6°N. Therefore ,a variation curve of paleo-latitude is established in this paper for the Guizhou terrain from late Devoian to Late Cretaceous time.

  6. The Cretaceous of the Eastern Bangong-Nujiang Suture Zone (Tibet):Tectono-Sedimentation

    Institute of Scientific and Technical Information of China (English)

    Pujun Wang; Frank Mattern; Werner Schneider; Wanzhu Liu; Shikai Li; Cai Li

    2003-01-01

    The ophiolite-bearing Bangong-Nujiang zone (BNZ) traversing central Tibet from east to west separates the Qiangtang block in the north from the Lhasa block in the south. The Cretaceous of the area includes Chuanba Formation (K1c), Duoba Formation (K1d), Langshan Formation (K1l) and Jiangba Formation (K2j). The K1c is composed of black shale,sandy pelite, siltstone, sandstone, coal beds and volcanic rocks, of shallow marine facies. The K1d consists of terrestrial siliciclastics intercalated with some calcareous sandstone beds bearing Orbitolina sp. indicating marine influence. The K1j is carbonate platform deposits of shallow marine and lagoon. The K2j is characterized by terrestrial thick massive red conglomerate. An active margin related to B-subduction zone is considered to be the geological setting of the Cretaceous sedimentation.

  7. A New Titanosauriform Sauropod from the Early Late Cretaceous of Dongyang, Zhejiang Province

    Institute of Scientific and Technical Information of China (English)

    L(U) Junchang; Yoichi AZUMA; CHEN Rongjun; ZHENG Wenjie; JIN Xingsheng

    2008-01-01

    A new titanosauriform sauropod Dongyangosaurus sinensis gen. et sp. nov. from the early Late Cretaceous of Dongyang County, Zhejiang Province, is erected based on a partial postcranial skeleton. It is characterized by complex laminae on the lateral surface of the neural spines and postzygapophyses of dorsal vertebrae, a distinct fossa on the ventral surfaces of the prezygapophyses of dorsal vertebrae, distinct fossae are also present on the lateral surface of the postzygapophysis of anterior caudal vertebrae; pubis is shorter than ischium, the small obturator foramen of pubis elongated, and nearly closed. The lamina complexity of dorsal vertebrae in Dongyangosaurus indicates that a higher diversity of titanosauriformes occurred during the early Late Cretaceous in China.

  8. High geomagnetic intensity during the mid-Cretaceous from Thellier analyses of single plagioclase crystals.

    Science.gov (United States)

    Tarduno, J A; Cottrell, R D; Smirnov, A V

    2001-03-01

    Recent numerical simulations have yielded the most efficient geodynamo, having the largest dipole intensity when reversal frequency is low. Reliable paleointensity data are limited but heretofore have suggested that reversal frequency and paleointensity are decoupled. We report data from 56 Thellier-Thellier experiments on plagioclase crystals separated from basalts of the Rajmahal Traps (113 to 116 million years old) of India that formed during the Cretaceous Normal Polarity Superchron. These data suggest a time-averaged paleomagnetic dipole moment of 12.5 +/- 1.4 x 10(22) amperes per square meter, three times greater than mean Cenozoic and Early Cretaceous-Late Jurassic dipole moments when geomagnetic reversals were frequent. This result supports a correlation between intervals of low reversal frequency and high geomagnetic field strength. PMID:11230692

  9. Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification.

    Science.gov (United States)

    Meredith, Robert W; Janečka, Jan E; Gatesy, John; Ryder, Oliver A; Fisher, Colleen A; Teeling, Emma C; Goodbla, Alisha; Eizirik, Eduardo; Simão, Taiz L L; Stadler, Tanja; Rabosky, Daniel L; Honeycutt, Rodney L; Flynn, John J; Ingram, Colleen M; Steiner, Cynthia; Williams, Tiffani L; Robinson, Terence J; Burk-Herrick, Angela; Westerman, Michael; Ayoub, Nadia A; Springer, Mark S; Murphy, William J

    2011-10-28

    Previous analyses of relations, divergence times, and diversification patterns among extant mammalian families have relied on supertree methods and local molecular clocks. We constructed a molecular supermatrix for mammalian families and analyzed these data with likelihood-based methods and relaxed molecular clocks. Phylogenetic analyses resulted in a robust phylogeny with better resolution than phylogenies from supertree methods. Relaxed clock analyses support the long-fuse model of diversification and highlight the importance of including multiple fossil calibrations that are spread across the tree. Molecular time trees and diversification analyses suggest important roles for the Cretaceous Terrestrial Revolution and Cretaceous-Paleogene (KPg) mass extinction in opening up ecospace that promoted interordinal and intraordinal diversification, respectively. By contrast, diversification analyses provide no support for the hypothesis concerning the delayed rise of present-day mammals during the Eocene Period.

  10. Spheroids at the Cretaceous-Tertiary boundary are altered impact droplets of basaltic composition

    Energy Technology Data Exchange (ETDEWEB)

    Montanari, A.; Hay, R.L.; Alvarez, W.; Asaro, F.; Michel, H.V.; Alvarez, L.W.; Smit, J.

    1983-11-01

    Sand-size spheroids of K-feldspar in the Cretaceous-Tertiary (C-T) boundary clay at Caravaca, southern Spain, were interpreted by Smit and Klaver as having solidified from a melt resulting from the impact of a large extraterrestrial body. Sand-size spheroids of K-feldspar, glauconite, and magnetite-quartz have been found in the C-T boundary clay in northern Italy, and spheroids of K-feldspar and pyrite were found in the boundary clay at Deep Sea Drilling Project Site 465A, in the central Pacific. These spheroids have textures similar to those of rapidly crystallized feldspar and mafic silicates. They are interpreted as diagenetically altered microcrystalline spherules of basaltic composition produced by the impact of a large asteroid in an ocean basin at the end of the Cretaceous. They are analogous to the glassy microtektites produced by impacts on more siliceous target rocks. 21 references, 4 figures.

  11. The lower cretaceous volcanism in the coastal range of Central Chile: Geochronology and isotopic geochemistry

    International Nuclear Information System (INIS)

    Major factors involved in subduction zone magmatism are related to the melting of the underlying mantle, which can contain a component of aqueous fluid and/or melts derived from the subducting plate (e.g. Peate et al., 1997). The Chilean Pacific margin is a subduction zone, active from Early Mesozoic to now, in which the magmatic arc emplaced on the Paleozoic basement progressively migrate to the east. The western part of this arc constitutes the Coastal Range. In this work, isotopic and radiometric data from four E-W profiles along c. 500 km of the Lower Cretaceous volcanic rocks in the Coastal Range of Chile are presented. The aim of this research is to obtain a model for the genesis of this Cretaceous volcanic arc based on their isotopic signature (au)

  12. Terpenoid composition and botanical affinity of Cretaceous resins from India and Myanmar

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Suryendu; Mallick, Monalisa [Department of Earth Sciences, Indian Institute of Technology-Bombay (India); Kumar, Kishor [Wadia Institute of Himalayan Geology, Uttarakhand (India); Mann, Ulrich [Forschungzentrum Juelich (Germany). Institut fuer Chemie und Dynamik der Geosphaere; Greenwood, Paul F. [John De Laeter Mass Spectrometry and WA Biogeochemistry Centres (M090), University of Western Australia, Crawley (Australia)

    2011-01-01

    Fossil resins from the Cretaceous sediments of Meghalaya, India and Kachin, Myanmar (Burma) were analysed using Curie point pyrolysis-gas chromatography-mass spectrometry and thermochemolysis gas chromatography-mass spectrometry to help elucidate their botanical source. The major pyrolysis products and methyl-esterified thermochemolysis products of both the resins were abietane and labdane type diterpenoids with minor amount of sesquiterpenoids. The thermochemolysis products also included methyl-16,17-dinor callitrisate, methyl-16,17-dinor dehydroabietate and methyl-8-pimaren-18-oate - the latter two from just the Myanmarese resin. The exclusive presence of both labdane and abietane diterpenoids and the lack of phenolic terpenoids may suggest that the studied Cretaceous resins were derived from Pinaceae (pine family) conifers. (author)

  13. Galaxy Groups

    CERN Document Server

    Tully, R Brent

    2014-01-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 10^12 Msun are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosi...

  14. Biostratigraphy and microfacies of the cretaceous sediments in the Indus Basin, Pakistan

    OpenAIRE

    Khan, Suleman

    2013-01-01

    In this thesis I document the biostratigraphy of two Cretaceous sections in Pakistan, the Chichali Nala Section and the Moghal Kot Section. Furthermore, I document the stratigraphy of the so-called Oceanic Anoxic Events (OAEs) in the Moghal Kot Section. In addition, I establish potential links between the planktonic foraminiferal evolution and these OAEs in the Moghal Kot Section. Sea Surface Temperatures (SSTs) are established for the Valanginian time by using the TEX86 and δ1...

  15. A new Lower Cretaceous bird from China and tooth reduction in early avian evolution

    OpenAIRE

    Zhou, Zhonghe; Li, Fucheng Zhang Zhiheng

    2009-01-01

    A new avian genus and species, Zhongjianornis yangi gen. et sp. nov., is reported from the Lower Cretaceous lacustrine deposits of the Jiufotang Formation in Liaoning, northeast China. The new taxon is characterized by possessing the following combination of features: upper and lower jaws toothless, snout pointed, humerus with large and robust deltopectoral crest, second phalanx of the major manual digit longer than the first phalanx, unguals of the alular and major digits of similar length a...

  16. Calcareous nannofossil biostratigraphy and depositional history of the late Cretaceous to early Miocene sequence of Iraq

    OpenAIRE

    Starkie, S. P.

    1994-01-01

    This thesis presents a new calcareous nannofossil based zonation scheme for Iraq based upon the examination of 515 drill cutting, conventional core and bit samples from both southern and northern Iraq. This zonation consists of 13 zones and 7 subzones covering the Late Cretaceous to Early Miocene. To date no detailed nannofossil zonation scheme was available for Iraq and therefore the nannofossil zonation presented here breaks new ground. The new zonation scheme has also been successfully cor...

  17. The oldest micropepline beetle from Cretaceous Burmese amber and its phylogenetic implications (Coleoptera: Staphylinidae)

    Science.gov (United States)

    Cai, Chen-Yang; Huang, Di-Ying

    2014-10-01

    The staphylinid subfamily Micropeplinae includes small strongly sclerotized beetles with truncate elytra leaving the most part of abdomen exposed. Fossil micropeplines are rare and confined to Cenozoic representatives of extant genera. Here, we describe the oldest micropepline, Protopeplus cretaceus gen. and sp. n., from the Upper Cretaceous Burmese amber. Fluorescence microscope and confocal laser scanning microscopy (CLSM) were both used to reveal diagnostic features of Micropeplinae and some primitive traits that place Protopeplus very basally within Micropeplinae.

  18. Reconstruction of Late Cretaceous Magmatic Arcs in the Northern Andes: Single Versus Multiple Arc Systems

    Science.gov (United States)

    Cardona, A.; Jaramillo, J. S.; Leon, S.; Hincapie, S.; Mejia, D.; Patino, A. M.; Vanegas, J.; Zapata, S.; Valencia, V.; Jimenez, G.; Monsalve, G.

    2014-12-01

    Although magmatic rocks are major tracers of the geological evolution of convergent margins, pre-collisional events such as subduction erosion, collisional thrusting or late collisional strike slip segmentation may difficult the recognizing of multiple arc systems and therefore the existence of paleogeographic scenarios with multiple subduction systems. New field, U-Pb geochronology and whole rock geochemistry constraints from the northwestern segment of the Central Cordillera in the states of Antioquia and Caldas (Colombia) are used to understand the nature of the Late Cretaceous arc magmatism and evaluate the existence of single or multiple Pacific and Caribbean arc systems in the growth of the Northwestern Andes. The new results integrated with additional field and published information is used to suggest the existence of at least three different magmatic arcs. (1) An Eastern Continental arc built within a well defined Permian to Triassic continental crust that record a protracted 90-70 Ma magmatic evolution, (2) a 90-80 arc formed within attenuated continental crust and associated oceanic crust, (3) 90-88 Ma arc formed over a Late Cretaceous plateau crust. The eastern arcs were formed as part of double eastern vergent subduction system, where the most outboard arc represent a fringing arc formed over detached fragments of continental crust, whereas the easternmost continental arc growth by the closure an subduction of and older and broad Triassic to Early Jurassic back-arc ocean. Its closure also end up in ophiolite emplacement. The third allochtonous oceanic arc was formed over the Caribbean plateau crust and was accreted to the continental margin in the Late Cretaceous. Ongoing paleomagnetic, deformational, gravimetric and basin analysis will be integrate to test this model and understand the complex Late Cretaceous tectonic evolution of the Northern Andes.

  19. Terrestrial catastrophe caused by cometary impact at the end of Cretaceous

    Science.gov (United States)

    Hsü, Kenneth J.

    1980-05-01

    Evidence is presented indicating that the extinction, at the end of the Cretaceous, of large terrestrial animals was caused by atmospheric heating during a cometary impact and that the extinction of calcareous marine plankton was a consequence of poisoning by cyanide released by the fallen comet and of a catastrophic rise in calcite-compensation depth in the oceans after the detoxification of the cyanide.

  20. Reconstructing a mid-Cretaceous landscape from paleosols in western Canada

    Science.gov (United States)

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.; Leckie, D.

    2005-01-01

    The Albian Stage of the mid-Cretaceous was a time of equable climate conditions with high sea levels and broad shallow epeiric seas that may have had a moderating affect on continental climates. A Late Albian landscape surface that developed during a regression and subsequent sea-level rise in the Western Canada Foreland Basin is reconstructed on the basis of correlation of paleosols penetrated by cores through the Paddy Member of the Peace River Formation. Reconstruction of this landscape refines chronostratigraphic relationships and will benefit future paleoclimatological studies milizing continental sphaerosiderite proxy records. The paleosols developed in estuarine sandstones and mudstones, and they exhibit evidence of a polygenetic history. Upon initial exposure and pedogenesis, the Paddy Member developed deeply weathered, well-drained cumulative soil profiles. Later stages of pedogenesis were characterized by hydromorphic soil conditions. The stages of soil development interpreted for the Paddy Member correlate with inferred stages of pedogenic development in time-equivalent formations located both basinward and downslope (upper Viking Formation), and landward and upslope (Boulder Creek Formation). On the basis of the genetic similarity among paleosols in these three correlative formations, the paleosols are interpreted as having formed along a single, continuous landscape surface. Results of this study indicate that the catena concept of pedogenesis along sloping landscapes is applicable to ancient successions. Sphaerosiderites in the Paddy Mem ber paleosols are used to provide proxy values for meteoric ??18O values at 52?? N paleolatitude in the Cretaceous Western Interior Basin. The meteoric ??18O values are used to refine existing interpretations about the mid-Cretaceous paleolatitudinal gradient in meteoric ?? 18O values, and the mid-Cretaceous hydrologic cycle. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).

  1. Geochemical evidence for a Cretaceous oil sand (Bima oil sand) in the Chad Basin, Nigeria

    Science.gov (United States)

    Bata, Timothy; Parnell, John; Samaila, Nuhu K.; Abubakar, M. B.; Maigari, A. S.

    2015-11-01

    Paleogeographic studies have shown that Earth was covered with more water during the Cretaceous than it is today, as the global sea level was significantly higher. The Cretaceous witnessed one of the greatest marine transgressions in Earth's history, represented by widespread deposition of sands directly on underlying basement. These sand bodies hold much of the world's heavy oil. Here, we present for the first time, geochemical evidence of a Cretaceous oil sand (Bima oil sand) in the Chad Basin, Nigeria. Bima oil sand is similar to other Cretaceous oil sands, predominantly occurring at shallow depths on basin flanks and generally lacking a seal cover, making the oil susceptible to biodegradation. The bulk properties and distribution of molecular features in oils from the Bima oil sand suggest that they are biodegraded. Sterane maturity parameters and the trisnorhopane thermal indicator for the oils suggest thermal maturities consistent with oils generated as conventional light oils, which later degraded into heavy oils. These oils also show no evidence of 25-norhopane, strongly suggesting that biodegradation occurred at shallow depths, consistent with the shallow depth of occurrence of the Bima Formation at the study locality. Low diasterane/sterane ratios and C29H/C30H ratios greater than 1 suggest a carbonate source rock for the studied oil. The Sterane distribution further suggests that the oils were sourced from marine carbonate rocks. The C32 homohopane isomerization ratios for the Bima oil sand are 0.59-0.60, implying that the source rock has surpassed the main oil generation phase, consistent with burial depths of the Fika and Gongila Formations, which are both possible petroleum source rocks in the basin.

  2. Late Cretaceous marine transgressions in Ecuador and northern Peru: a refined stratigraphic framework.

    OpenAIRE

    Jaillard, Etienne; Bengtson, Peter; Dhondt, Annie V.

    2005-01-01

    Study of ammonites and bivalves along selected sections on the Andean margin of northern Peru and Ecuador has made it possible to recognize correlatable marine transgressions and to propose a refined stratigraphic framework for the Upper Cretaceous of the region. Six maximum flooding events are recognized: latest Turonian–early Coniacian (major event), late Coniacian–early Santonian, late Santonian–early Campanian, mid Campanian–early late Campanian (major event), early Maastrichtian (major e...

  3. Rebuilding biodiversity of Patagonian marine molluscs after the end-Cretaceous mass extinction.

    Science.gov (United States)

    Aberhan, Martin; Kiessling, Wolfgang

    2014-01-01

    We analysed field-collected quantitative data of benthic marine molluscs across the Cretaceous-Palaeogene boundary in Patagonia to identify patterns and processes of biodiversity reconstruction after the end-Cretaceous mass extinction. We contrast diversity dynamics from nearshore environments with those from offshore environments. In both settings, Early Palaeogene (Danian) assemblages are strongly dominated by surviving lineages, many of which changed their relative abundance from being rare before the extinction event to becoming the new dominant forms. Only a few of the species in the Danian assemblages were newly evolved. In offshore environments, however, two newly evolved Danian bivalve species attained ecological dominance by replacing two ecologically equivalent species that disappeared at the end of the Cretaceous. In both settings, the total number of Danian genera at a locality remained below the total number of late Cretaceous (Maastrichtian) genera at that locality. We suggest that biotic interactions, in particular incumbency effects, suppressed post-extinction diversity and prevented the compensation of diversity loss by originating and invading taxa. Contrary to the total number of genera at localities, diversity at the level of individual fossiliferous horizons before and after the boundary is indistinguishable in offshore environments. This indicates an evolutionary rapid rebound to pre-extinction values within less than ca 0.5 million years. In nearshore environments, by contrast, diversity of fossiliferous horizons was reduced in the Danian, and this lowered diversity lasted for the entire studied post-extinction interval. In this heterogeneous environment, low connectivity among populations may have retarded the recolonisation of nearshore habitats by survivors.

  4. Rebuilding biodiversity of Patagonian marine molluscs after the end-Cretaceous mass extinction.

    Directory of Open Access Journals (Sweden)

    Martin Aberhan

    Full Text Available We analysed field-collected quantitative data of benthic marine molluscs across the Cretaceous-Palaeogene boundary in Patagonia to identify patterns and processes of biodiversity reconstruction after the end-Cretaceous mass extinction. We contrast diversity dynamics from nearshore environments with those from offshore environments. In both settings, Early Palaeogene (Danian assemblages are strongly dominated by surviving lineages, many of which changed their relative abundance from being rare before the extinction event to becoming the new dominant forms. Only a few of the species in the Danian assemblages were newly evolved. In offshore environments, however, two newly evolved Danian bivalve species attained ecological dominance by replacing two ecologically equivalent species that disappeared at the end of the Cretaceous. In both settings, the total number of Danian genera at a locality remained below the total number of late Cretaceous (Maastrichtian genera at that locality. We suggest that biotic interactions, in particular incumbency effects, suppressed post-extinction diversity and prevented the compensation of diversity loss by originating and invading taxa. Contrary to the total number of genera at localities, diversity at the level of individual fossiliferous horizons before and after the boundary is indistinguishable in offshore environments. This indicates an evolutionary rapid rebound to pre-extinction values within less than ca 0.5 million years. In nearshore environments, by contrast, diversity of fossiliferous horizons was reduced in the Danian, and this lowered diversity lasted for the entire studied post-extinction interval. In this heterogeneous environment, low connectivity among populations may have retarded the recolonisation of nearshore habitats by survivors.

  5. Cretaceous Apparent Polar Wander Relative to the Major Cratons and Displacement Estimates of Baja British Columbia

    Science.gov (United States)

    Enkin, R. J.

    2004-12-01

    When paleogeographic interpretations derived from independent observations conflict, the methods and results from each discipline come under careful scrutiny, as illustrated by the Baja British Columbia controversy. Cretaceous paleomagnetic data from a large region of the Canadian Cordillera render paleopoles which are far-sided with respect to cratonic North American poles, suggesting this region, designated Baja British Columbia, translated northward during Late Cretaceous - Paleogene time. Criticism of this interpretation based on other geological reasoning prompted me to perform new reviews of Cretaceous to Eocene paleomagnetic results from the Cordillera and from the major cratons of the globe. The global review follows the method of Besse and Courtillot (1991; 2002). One difference between our methods is that I compiled paleomagnetic results from highly studied rock units to single results to balance data weightings spatially and temporally, thus reducing the number of individual results. For the period 160 to 40 Ma, 51 poles were included compared to 92 poles by Besse and Courtillot (2002). Differences between apparent polar wander paths in their and my analyses are never significant at 95% confidence, however mean pole positions differ by up to 500 km, which is important for paleogeographic analysis. The global distribution of sampling localities and the tight clustering of the paleomagnetic poles after plate reconstruction provide invaluable confirmation of plate tectonically derived Euler rotations, the reliability of paleomagnetic remanence directions, and the geocentric dipole geometry of the geomagnetic field. My Cordilleran review shows that paleolatitudes derived from plutons and remagnetized rocks are significantly more scattered than those derived from bedded rocks. Using bedded rocks only, the paleomagnetic record shows that Baja British Columbia sat 2100 ± 500 km south of its present position with respect to cratonic North America during the

  6. A Multilocus Molecular Phylogeny of the Parrots (Psittaciformes): Support for a Gondwanan Origin during the Cretaceous

    OpenAIRE

    Wright, Timothy F.; Schirtzinger, Erin E.; Matsumoto, Tania; Eberhard, Jessica R.; Graves, Gary R; Sanchez, Juan J.; Capelli, Sara; Müller, Heinrich; Scharpegge, Julia; Geoffrey K Chambers; Robert C Fleischer

    2008-01-01

    The question of when modern birds (Neornithes) first diversified has generated much debate among avian systematists. Fossil evidence generally supports a Tertiary diversification, whereas estimates based on molecular dating favor an earlier diversification in the Cretaceous period. In this study, we used an alternate approach, the inference of historical biogeographic patterns, to test the hypothesis that the initial radiation of the Order Psittaciformes (the parrots and cockatoos) originated...

  7. Evidence of titanosauriforms and rebbachisaurids (Dinosauria: Sauropoda) from the Early Cretaceous of Tunisia

    Science.gov (United States)

    Fanti, Federico; Cau, Andrea; Hassine, Mohsen

    2014-02-01

    Isolated sauropod remains including vertebrae and a humerus from the Aïn El Guettar Formation (Albian, Early Cretaceous) of Tunisia are described. Vertebrae include a slightly procoelous anterior caudal vertebra, amphicoelous middle caudal vertebrae, and strongly procoelous distal caudal vertebrae. The humerus has an anteroposteriorly compressed shaft, robust deltopectoral crest restricted laterally and prominent condyles bounding a distinct distal fossa. The morphological characters present in the specimens suggests that isolated remains can be referred to at least two distinct sauropod taxa.

  8. Effect of Cretaceous oceanic anoxic events on the evolutionary trend of planktonic foraminifera

    Science.gov (United States)

    Kuroyanagi, A.; Ozaki, K.; Kawahata, H.

    2014-12-01

    It is widely thought that oceanic redox state is essential for the evolutionary history of life on the earth, and "anoxic events" have been proposed as one of the causal mechanisms for mass extinctions. During mid-Cretaceous, widely known as the extremely warm period, oceanic anoxic events (OAEs) occurred several times and they would have caused a substantial impact on the biosphere. Planktonic foraminifera are marine planktons with calcite tests and their productions constitute ~30-80% of the modern deep-marine calcite budget, thus they play an important role in the global carbon cycle. Previous study reported that planktonic foraminifera displayed the high turnover (extinction and speciation) rate at or near the major OAEs. However, the impact of Cretaceous OAEs on the evolutionary trend of planktonic foraminifera remains obscure. In this study, we investigated the role of spatiotemporal extent of anoxia on the evolutionary trend of planktonic foraminifera by assessing the extinction/speciation rate of planktonic foraminifera around Cretaceous OAEs. The number of foraminiferal species increased across the OAE1a and then showed a peak after this episode. Around OAE2, several planktonic foraminifera species became extinct and several speciated, however, long-term trends in foraminiferal evolution showed no drastic changes near the event. Therefore these results suggest that the ocean surface environment at OAEs would not have a direct effect on foraminiferal extinction/speciation. This interpretation is reinforced when considering the recent culturing results, which demonstrate that modern planktonic foraminifera have a high tolerance to extremely low dissolved oxygen levels than expected. Accumulating geochemical data also suggest a spatial heterogeneity of oceanic anoxia/euxinia during OAE2. These results lead us to conclude that Cretaceous OAEs would not directly related to planktonic foraminiferal extinction due to regional distribution of anoxia/euxinia.

  9. Iridium abundance anomaly at the palynological Cretaceous-tertiary boundary in northern New Mexico

    International Nuclear Information System (INIS)

    An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct

  10. A New Sauropod Dinosaur from the Late Cretaceous Gaogou Formation of Nanyang, Henan Province

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xingliao; L(U) Junchang; XU Li; LI Jinhua; YANG Li; HU Weiyong; JIA Songhai; JI Qiang; ZHANG Chengjun

    2009-01-01

    A new sauropod dinosaur Baotianmansaurus henanensis gen. et sp. nov. from the Cretaceous Gaogou Formation of Neixiang, Henan Province is erected. It is characterized by somphospondylous presacral vertebrae; a highly-developed lamina system on the dorsal vertebrae; transverse process supported by four laminae; and the dorsal portion of the anterior centroparapophyseai lamina is bifurcated, with a small branch extending to the ventral surface of the prezygapophysis. It represents a new titanosauriform sauropod.

  11. Porosphaera globularis (Phillips, 1829) (Porifera, Calcarea) in the Campanian (Upper Cretaceous) of extra-Carpathian Poland

    Science.gov (United States)

    Jurkowska, Agata; Świerczewska-Gładysz, Ewa; Dubicka, Zofia; Olszewska-Nejbert, Danuta

    2015-03-01

    The stratigraphical distribution of Porosphaera globularis, a common calcareous sponge in the Upper Cretaceous (mostly Campanian and Maastrichtian) of Poland was studied. The presented material, both new and from museum collections, comes from the Campanian of the Miechow Synclinorium, in southern Poland, and from the Lower Campanian of Mielnik in the south-eastern part of the Mazury-Podlasie Homocline, in eastern Poland. The significance of the species in extra-regional correlation, its palaeobiogeography and stratigraphical potential is critically reviewed.

  12. Exploring the feedbacks between Cretaceous ocean circulation, oceanic redox dynamics and sediment diagenesis

    Science.gov (United States)

    Arndt, Sandra; Regnier, Pierre; Donnadieu, Yannick; Godderis, Yves

    2010-05-01

    The Mid-Cretaceous oceanic anoxic events (OAEs) are witnesses of major perturbations of the Earth climate, which resulted from important changes in structure of the ocean-atmosphere system and its biogeochemical functioning. They are globally well documented by the ubiquitous presence of organic carbon-rich black shale layers. However, the exact nature and functioning of the palaeo-environment that fostered the massive and almost ubiquitous deposition of organic carbon-rich sediments is still a matter of debate. Numerous outstanding questions remain, not only concerning the dependence of black shale deposition on ocean circulation and redox zonation, but also its influence on the global ocean-atmosphere system. A new version of the coupled Earth system model GEOCLIM, which combines a climate model (FOAM 3-D GCM) with a vertically resolved diffusion-advection box model of the global ocean, a pelagic biogeochemical model and a fully formulated diagenetic model (BNRS) is used to examine the feedbacks between paleocirculation, ocean redox dynamics, sediment diagenesis and global climate. Different scenarios are designed to assess the influence of the global circulation on the biogeochemical functioning of the ocean during a mid-Cretaceous OAE. Simulation results illustrate the strong feedbacks between Cretaceous ocean circulation, oceanic geochemical dynamics, bioproductivity and sediment diagenesis. A weakening of the deep ocean ventilation increases the importance of diagenetic processes on the geochemical characteristics of the ocean. Ocean anoxia/euxinia can easily develop if the sedimentary nutrient recycling is high enough to sustain enhanced primary production. Thus, the earth system model provides a rational support for a detailed quantitative understanding of the ocean's biogeochemical response to potential circulation changes during a mid-Cretaceous OAE.

  13. Investigation of the calcification response of foraminifera and pteropods to high CO2 environments in the Pleistocene, Paleogene and Cretaceous

    Science.gov (United States)

    Hart, M.; Pettit, L.; Wall-Palmer, D.; Smart, C.; Hall-Spencer, J.; Medina-Sanchez, A.; Prol Ledesma, R. M.; Rodolfo-Metalpa, R.; Collins, P.

    2012-04-01

    Ocean acidification is regarded as a current problem and there is an extensive literature on how various organisms are responding to changes in oceanic pH: the result of increasing atmospheric pCO2. Acidification is, however, not just a recent phenomenon and there are times in the geological record where pCO2 has been higher than present day levels (especially in the Cretaceous and Paleogene). Understanding the response of various microfossil groups to the changes in oceanic pH is on-going as part of a major investigation of ocean acidification in both modern and 'fossil' environments. Extensive carbon dioxide vents have recently been described in the Wagner Basin (northern Gulf of California, Mexico), which cause dramatic changes in carbonate chemistry. The pHT decreased from 7.88 to 7.55 near the most active vents where the lowest saturation states of aragonite (ΩArag) and calcite (ΩCalc) were 0.95 and 1.47 respectively. Foraminifera (unicellular protists) present in the top 2 cm of the sediment (both living and dead individuals) had a range of mainly calcareous taxa (including Bolivina acuminata, B. acutula, Bulimina marginata and Nonionella basispinata). This is a normal composition for these water depths. The lack of dissolution features and the generally good preservation of the tests, even when viewed under a scanning electron microscope, were striking. With no evidence of breakage caused by transportation, it is assumed that this composition is representative in terms of numbers of individuals and taxa represented. Benthic foraminifera from CO2 vents around the island of Ischia (Italy) have shown dramatic long-term effects of ocean acidification. The foraminifera of the Wagner Basin appear to be surviving in high CO2 environments comparable to those that occurred during the Cretaceous-Paleogene "greenhouse" world where atmospheric pCO2 was much higher, but with calcareous foraminifera apparently thriving. In the Pleistocene, pCO2 levels are known to have

  14. Upper Cretaceous chalk facies and depositional history recorded in the Mona-1 core, Mona Ridge, Danish North Sea: Plate 1

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2011-12-01

    Full Text Available The 331 m long core from the Mona-1 well in the Danish North Sea spans almost the entire Upper Cretaceous Chalk Group but only about 10% of Late Cretaceous time is represented. The succession comprises 14 facies representing pelagic deposition, turbidity flow, and mass-transport processes, including mudflow, debris flow, and slumping. Pelagic deposits vary mainly in terms of the concentration of siliciclastic material, the trace-fossil assemblage, and the presence or ab¬sence of primary sedimentary structures. Pelagic sedimentation was probably punctuated by the deposition of thin turbidites, and the resultant deposits were thoroughly bioturbated if deposited during normal oxygenation at the sea floor. Periodic benthic dysoxia resulted in the preservation of primary structures, as represented by laminated chalk which consists of thin pelagic laminae alternating with thin turbidites. In addition to the thin turbidites in the laminated chalk, four dif¬ferent turbidite facies are interpreted as representing high- to low-energy flows. Clast-supported chalk conglomerates have previously not been differentiated from other turbidites, but are here interpreted to be directly related to the down-slope evolution of debris flows. Debris flows are rep¬resented by matrix-supported conglomerates, which form one of the most common facies in the succession. High-concentration, gravity-driven suspension flows passed into dilute visco-plastic flows during the final stages of deposition and resulted in the deposition of structureless chalks. Limited shear deformation produced distinct quasi-facies from which the precursor facies can be deduced, whereas intense or continued shear deformation produced a shear-banded quasi-facies from which the precursor facies cannot be deduced in all cases. A series of major slump packages (14–18 in total are interpreted, forming over 40% of the succession; debrites appear to be the most common precursor facies involved in

  15. The Tendaguru formation of southeastern Tanzania, East Africa: An alternating Late Jurassic to Early Cretaceous palaeoenvironment of exceptional status

    Science.gov (United States)

    Sames, B.

    2009-04-01

    Dinosaur remains have inspired considerable scientific interest in the Tendaguru formation of southeastern Tanzania during the 20th century; however, this formation is exceptional in many other respects. The Late Jurassic to Early Cretaceous deposits of the Tendaguru formation in the southwestern Tethys are unique because they represent a marginal marine palaeoenvironment with nonmarine faunal and floral content. It is a threefold succession of marginal marine to terrestrial, carbonate-siliciclastic sediments with cyclic character, consisting of three transgressive-regressive cycles. Revisitation of the type locality (the Tendaguru, a hill approximately 60km northwest of the town of Lindi) by a German-Tanzanian expedition in summer 2000 (Heinrich et al., 2001) resulted in a new standard section (hitherto unpublished, the informal terminology is indicated by the use of lower case in Tendaguru formation), a refined environmental model (Aberhan et al., 2002) and many new insights towards its geology (with evidence of event-sedimentation, Bussert and Aberhan, 2004), biostratigraphy and a better understanding of the Tendaguru palaeo-ecosystems and the palaeoclimate. Within the scope of the designation of a new standard section at the type locality, calcareous microfossils (ostracods, charophytes) have been described to supplement the ongoing discussion about the age and palaeoecology of the Tendaguru formation (Sames, 2008). Although only a few unevenly distributed layers across the section produced calcareous microfossils, the results are very promising. A total of 40 ostracode and 2 charophyte taxa could be distinguished. The non-marine part of the ostracod fauna provides an important contribution to the documentation of Purbeck/Wealden-type nonmarine palaeoenvironments and its microfaunas and -floras previously unknown from East Africa. The marine faunal part belongs to a relatively endemic southern (Gondwana) fauna. Together with other fossil groups, the

  16. Cretaceous plutonic rocks in the Donner Lake-Cisco Grove area, northern Sierra Nevada, California

    Science.gov (United States)

    Kulow, Matthew J.; Hanson, Richard E.; Girty, Gary H.; Girty, Melissa S.; Harwood, David S.

    1998-01-01

    The northernmost occurrences of extensive, glaciated exposures of the Sierra Nevada batholith occur in the Donner Lake-Cisco Grove area of the northern Sierra Nevada. The plutonic rocks in this area, which are termed here the Castle Valley plutonic assemblage, crop out over an area of 225 km2 and for the most part are shown as a single undifferentiated mass on previously published geological maps. In the present work, the plutonic assemblage is divided into eight separate intrusive units or lithodemes, two of which each consist of two separate plutons. Compositions are dominantly granodiorite and tonalite, but diorite and granite form small plutons in places. Spectacular examples of comb layering and orbicular texture occur in the diorites. U-Pb zircon ages have been obtained for all but one of the main units and range from ~120 to 114 Ma, indicating that the entire assemblage was emplaced in a narrow time frame in the Early Cretaceous. This is consistent with abundant field evidence that many of the individual phases were intruded penecontemporaneously. The timing of emplacement correlates with onset of major Cretaceous plutonism in the main part of the Sierra Nevada batholith farther south. The emplacement ages also are similar to isotopic ages for gold-quartz mineralization in the Sierran foothills west of the study area, suggesting a direct genetic relationship between the voluminous Early Cretaceous plutonism and hydrothermal gold mineralization.

  17. Paleomagnetic study of Jurassic and Cretaceous rocks from the Mixteca terrane (Mexico)

    Science.gov (United States)

    Böhnel, Harald

    1999-11-01

    Three sites from Cretaceous limestone and Jurassic sandstone in northern Oaxaca, Mexico, were studied paleomagnetically. Thermal demagnetization isolated site-mean remanence directions which differ significantly from the recent geomagnetic field. The paleopole for the Albian-Cenomanian Morelos formation is indistinguishable from the corresponding reference pole for stable North America, indicating tectonic stability of the Mixteca terrane since the Cretaceous. Rock magnetic properties and a positive reversal test for the Bajocian Tecomazuchil sandstone suggest that the remanence could be of primary origin, although no fold test could be applied. The Tecomazuchil paleopole is rotated 10°±5° clockwise and displaced 24°±5° towards the study area, with respect to the reference pole for stable North America. Similar values were found for the Toarcien-Aalenian Rosario Formation, with 35°±6° clockwise rotation and 33°±6° latitudinal translation. These data support a post-Bajocian southward translation of the Mixteca terrane by around 25°, which was completed in mid-Cretaceous time.

  18. Global correlation for strontium isotope curve in the Late Cretaceous of Tibet and dating marine sediments

    Institute of Scientific and Technical Information of China (English)

    HUANG; Sijing; SHI; He; SHEN; Licheng; ZHANG; Meng; WU; Wen

    2005-01-01

    87Sr/86Sr ratios of marine carbonate samples collected from a sedimentary section of the Late Cretaceous in the south of Tibet were measured. Based on the absence of cathodoluminescence and a very low Mn/Sr ratio (average 0.06) of the samples, it is thought that they contain information on the original seawater strontium isotope composition. The strontium isotope evolution curve of the Late Cretaceous in Tibet we established here, is consistent with other coeval curves from Europe, North America and Antarctica, supports the notion that the strontium isotope composition of seawater is governed by global events, which provides a new approach for the inter-continental and inter-basinal correlations of Late Cretaceous in the area and is a complementarity for biostratigraphy. In addition, we attempt to determine the age of the boundaries for Campanian/Santonian and Maastrichtian/Campanian by 87Sr/86Sr ratios for Gamba section in southern Tibet. The two boundaries are located in the thickness of 217 m (83.5 Ma) and 291 m (71.3 Ma), respectively.

  19. The first record of a sauropod dinosaur from the Late Cretaceous phosphates of Morocco

    Science.gov (United States)

    Pereda Suberbiola, Xabier; Bardet, Nathalie; Iarochène, Mohamed; Bouya, Baâdi; Amaghzaz, Mbarek

    2004-09-01

    Sauropod dinosaur remains have been discovered recently in the Late Cretaceous (Maastrichtian) phosphatic deposits of the Oulad Abdoun Basin, near Khouribga (central Morocco). The material consists of right hindlimb bones (femur, tibia and fibula) from a small-sized individual. The marine associated fauna, mainly selachians, actinopterygians, turtles, mosasaurids and plesiosaurs, suggests a marine depositional environment, so that the dinosaur remains may be a remnant of a floating carcass. The femur exhibits a prominent lateral bulge on the proximal one-third, a diagnostic feature of Titanosauriformes. The Moroccan sauropod lacks synapomorphies of Titanosauria and less inclusive clades (i.e., distal tibia expanded transversely to twice mid-shaft breadth; femoral distal condyles angled dorsomedially relative to the shaft); therefore, it is here assigned to a basal titanosauriform as Titanosauriformes indet. This is the first sauropod reported from the Maastrichtian of Morocco and one of the few dinosaur records from the uppermost Cretaceous formations of northern Africa. This discovery confirms the wide geographical distribution of Titanosauriformes during the Late Cretaceous and supports their survival into the Late Maastrichtian of Africa.

  20. Burial Records of Reactive Iron in Cretaceous Black Shales and Oceanic Red Beds from Southern Tibet

    Institute of Scientific and Technical Information of China (English)

    HUANG Yongjian; WANG Chengshan; HU Xiumian; CHEN Xi

    2007-01-01

    One of the new directions in the field of Cretaceous research is to elucidate the mechanism of the sedimentary transition from the Cretaceous black shales to oceanic red beds. A chemical sequential extraction method was applied to these two types of rocks from southern Tibet to investigate the burial records of reactive iron. Results indicate that carbonate-associated iron and pyrite are relatively enriched in the black shales, but depleted or absent in red beds. The main feature of the reactive iron in the red beds is relative enrichment of iron oxides (largely hematite), which occurred during syn-depostion or early diagenesis. The ratio between iron oxides and the total iron indicates an oxygen-enriched environment for red bed deposition. A comparison between the reactive iron burial records and proxies of paleo-productivity suggests that paleo-productivity decreases when the ratio between iron oxides and the total iron increases in the red beds. This phenomenon could imply that the relationship between marine redox and productivity might be one of the reasons for the sedimentary transition from Cretaceous black shale to oceanic red bed deposition.

  1. Cretaceous Volcanic Events in Southeastern Jilin Province, China: Evidence from Single Zircon U-Pb Ages

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuejun; SUN Chunlin; SUN Yuewu; SUN Wei

    2008-01-01

    Mesozoic volcanic rocks in southeastern Jilin Province are an important component of the huge Mesozoic volcanic belt in the northeastern area. Study of the age of their formation is of great significance to recognize Mesozoic volcanic rule in northeastern China. Along with the research of rare Mesozoic biota and extensive Mesozoic mineralization in western Liaoning, a number of researchers have focused on Mesozoic volcanic events. The authors studied the ages of the Cretaceous volcanic rocks in southeastern Jilin Province using single Zircon U-Pb. The result shows that the Sankeyushu Formation volcanic rocks in the Tonghua area are 119.2 Ma in age, the Yingcheng Formation in the Jiutai area 113.4±3.1 Ma, the Jinjiatun Formation in Pinggang Town of Liaoyuan City and the Wufeng volcanic rocks in the Yanji area 103.2±4.7 Ma and 103.6±1 Ma, respectively. Combined with the data of recent publication on volcanic rocks ages; the Cretaceous volcanic events in southeastern Jilin Province can be tentatively subdivided into three eruption periods: 119 Ma, 113 Ma and 103 Ma. The result not only provides important chronology data for subdividing Mesozoic strata in southeastern Jilin Province, establishing Mesozoic volcanic event sequence, discussing geological tectonic background, and surveying the relation between noble metals to the Cretaceous volcanic rocks, but also otters important information of Mesozoic volcanism in northeastern China.

  2. A diplodocid sauropod survivor from the early cretaceous of South America.

    Directory of Open Access Journals (Sweden)

    Pablo A Gallina

    Full Text Available Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere.

  3. Cretaceous source rock sedimentation and its relation to transgressive peaks and geodynamic events for the Central Tethys

    Energy Technology Data Exchange (ETDEWEB)

    Flexer, A. (Tel Aviv Univ. (Israel)); Honigstein, A.; Rosenfeld, A. (Geological Survey of Israel, Jerusalem (Israel)); Lipson, S. (Institute of petroleum and energy, Tel Aviv (Israel)); Tarnenbaum, E. (Consultant, Tel Aviv (Israel))

    1993-02-01

    The reconstruction of the Mesozoic continents shows a wide triangle-shaped Tethys (or Neotethys) between Africa and Eurasia. The Arabian Craton comprised the central part of its southern margins. The Cretaceous period started with extension, volcanism, continued by accelerated divergence during Aptian-Turonian and terminated by convergence and folding. The sea level stand, after a major fall at the commencement, is characterized by a steady stepwise rise with some minor retreats. The global oceanic anoxic events correspond to large-extent transgressions and associated with organic rich sedimentation. The accelerated building up of mid-oceanic ridges is possibly connected to a mantle plume, active around 120-80 Ma. Sea level rise and sea floor spreading is felt mainly at these times in the passive southern margins of the central Tethys. The Senonian compressive tectonic regime transforms them into active margins (destruction of oceanic crust, obduction and thrusting); sea level highstands control dysoxic sedimentation. Dysoxic sediments were observed in the Gevaram shales (Tithonian-Hauterivian). Talme Yafe marls (Late Aptian-Albian), Daliyya Formation (latest Cenomanian-Turonian) and the Mount Scopus Group (Santonian-Maastrichtian). The organic matter in the Gevaram shales is mixed marine and terrestrial (2.6% TOC) and in the Daliyya marls mostly marine (2.5% TOC). Both units have source rock possibilities and yield petroleum upon appropriate burial. The Senonian bituminous rocks (oil shales) are rich in marine organic matter (20% TOC) and are excellent source rocks in the Dead Sea area.

  4. Denticle-embedded ampullary organs in a Cretaceous shark provide unique insight into the evolution of elasmobranch electroreceptors

    Science.gov (United States)

    Vullo, Romain; Guinot, Guillaume

    2015-10-01

    Here, we report a novel type of dermal denticle (or placoid scale), unknown among both living and fossil chondrichthyan fishes, in a Cretaceous lamniform shark. By their morphology and location, these dermal denticles, grouped into clusters in the cephalic region, appear to have been directly associated with the electrosensory ampullary system. These denticles have a relatively enlarged (˜350 μm in diameter), ornamented crown with a small (˜100 μm) asterisk- or cross-shaped central perforation connected to a multi-alveolate internal cavity. The formation of such a complex structure can be explained by the annular coalescence and fusion, around an ampullary vesicle, of several developmental units still at papillary stage (i.e. before mineralization), leading to a single denticle embedding an alveolar ampulla devoid of canal. This differs from larger typical ampullae of Lorenzini with a well-developed canal opening in a pore of the skin and may represent another adaptive response to low skin resistance. Since it has been recently demonstrated that ampullary organs arise from lateral line placodes in chondrichthyans, this highly specialized type of dermal denticle (most likely non-deciduous) may be derived from the modified placoid scales covering the superficial neuromasts (pit organs) of the mechanosensory lateral line system of many modern sharks.

  5. The giant cretaceous Coelacanth (Actinistia, Sarcopterygii Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and its bearing on Latimerioidei interrelationships.

    Directory of Open Access Journals (Sweden)

    Hugo Dutel

    Full Text Available We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.

  6. The giant cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and its bearing on Latimerioidei interrelationships.

    Science.gov (United States)

    Dutel, Hugo; Maisey, John G; Schwimmer, David R; Janvier, Philippe; Herbin, Marc; Clément, Gaël

    2012-01-01

    We present a redescription of Megalocoelacanthus dobiei, a giant fossil coelacanth from Upper Cretaceous strata of North America. Megalocoelacanthus has been previously described on the basis of composite material that consisted of isolated elements. Consequently, many aspects of its anatomy have remained unknown as well as its phylogenetic relationships with other coelacanths. Previous studies have suggested that Megalocoelacanthus is closer to Latimeria and Macropoma than to Mawsonia. However, this assumption was based only on the overall similarity of few anatomical features, rather than on a phylogenetic character analysis. A new, and outstandingly preserved specimen from the Niobrara Formation in Kansas allows the detailed description of the skull of Megalocoelacanthus and elucidation of its phylogenetic relationships with other coelacanths. Although strongly flattened, the skull and jaws are well preserved and show many derived features that are shared with Latimeriidae such as Latimeria, Macropoma and Libys. Notably, the parietonasal shield is narrow and flanked by very large, continuous vacuities forming the supraorbital sensory line canal. Such an unusual morphology is also known in Libys. Some other features of Megalocoelacanthus, such as its large size and the absence of teeth are shared with the mawsoniid genera Mawsonia and Axelrodichthys. Our cladistic analysis supports the sister-group relationship of Megalocoelacanthus and Libys within Latimeriidae. This topology suggests that toothless, large-sized coelacanths evolved independently in both Latimeriidae and Mawsoniidae during the Mesozoic. Based on previous topologies and on ours, we then review the high-level taxonomy of Latimerioidei and propose new systematic phylogenetic definitions.

  7. A Cretaceous-Palaeogene boundary geological site, revealed by planktic foraminifera and dinoflagellate cysts, at Ouled Haddou, eastern external Rif Chain, Morocco

    Science.gov (United States)

    Slimani, Hamid; Toufiq, Abdelkabir

    2013-12-01

    Cretaceous-Palaeogene boundary is placed, at the same position determined by Planktic foraminifera, immediately above the acme of Manumiella seelandica and the last appearance of few Cretaceous taxa such as Dinogymnium spp. and Alisogymnium euclaense, and directly below the first occurrences of Carpatella cornuta, Damassadinium californicum and Senoniasphaera inornata. However, in contrast to calcareous planktic foraminifera, dinoflagellate cysts did not undergo a mass extinction at the K-Pg boundary, but shows important changes in the relative abundances of different species or groups of morphologically related species. Both planktic foraminifera and dinoflagellate cyst assemblages suggest deposition in subtropical to warm temperate province, but in an austere sea environments under a regressive regime during the uppermost Maastrichtian and open sea environments under a transgressive regime during the lower Danian. Dinoflagellate cysts indicate relatively stable warm conditions during the upper Maastrichtian, followed successively by cooler conditions in the uppermost Maastrichtian and at the K-Pg boundary, a gradual warming alternated by 3 rapid successive cooling pulses in the lower most Danian, and then a gradual returning to relatively warm conditions. The Ouled Haddou section needs to be preserved as a geoheritage site, because it is the sole Moroccan section with a good quality and an easy access, and hosts a complete registration of the Cretaceous-Palaeogene boundary transition.

  8. 阿根廷非海相白垩纪孢粉生物地层学概述%NON-MARINE CRETACEOUS PALYNOMORPH BIOSTRATIGRAPHY OF ARGENTINA: A BRIEF SUMMARY

    Institute of Scientific and Technical Information of China (English)

    Mercedes B. PRAMPARO

    2012-01-01

    通过总结已发表的含有孢粉的地质体的资料,评价了阿根廷白垩纪的孢粉地层序列。在阿根廷由北向南的7个白垩纪盆地中确立了正式与非正式的生物带框架。这些盆地从北至南分别是:萨尔塔群盆地,圣路易斯盆地,内乌肯盆地,南方盆地,德赛多地块盆地,圣豪尔赫湾盆地,泛安第巴塔戈尼亚盆地。阿根廷早白垩世的孢粉组合相对被人熟知,但描述和讨论晚白垩世的微古植物群的文献则很少。在凡兰吟期至阿普特期的所有孢粉植物群中,松柏类裸子植物的花粉组合Cyclusphaera.Balmeiopsis—Classopollis占主导。Celyphusrallus(丝状蓝菌)与Cyclusphaera一起出现,但是在巴列姆期时,它们在整个巴塔戈尼亚盆地全部消失。早期被子植物的花粉化石是阿普特期和更年轻地层的重要标志,它们已被用于定义孢粉化石带。在阿根廷与山龙眼科的首现相当的Peninsulapollisgillii是出现于所有晚坎潘期至马斯特里赫特期的孢粉组合中的少数物种之一,有时也与Grapnelisporaloncochensis一起出现。这些物种的出现可能是一个孢粉化石带的标志。本文提供了孢粉化石带和白垩纪主要地层单位的初步对比表。%An evaluation of the Cretaceous palynostratigraphy of Argentina has been undertaken, by reviewing published data of the geological units with palynomorphs. Formal and informal biozonation schemes were compiled from seven Cretaceous Argentinean basins presented from north to south: the Salta Group Basin, San Luis Basin, Neuquen Basin, Austral Basin, Deseado Massif, San Jorge Gulf Basin, and extra-andean Patagonia. The Early Cretaceous paly- nological associations are relatively well-known in Argentina; however there is sparse published literature describing and discussing Late Cretaceous miofloras. The association of gymnosperm pollen grains, with conifer affinity Cy- clusphaera

  9. Hydra groups

    CERN Document Server

    Dison, Will

    2010-01-01

    We give examples of CAT(0), biautomatic, free-by-cyclic, one-relator groups which have finite-rank free subgroups of huge (Ackermannian) distortion. This leads to elementary examples of groups whose Dehn functions are similarly extravagant. This behaviour originates in manifestations of Hercules-versus-the-hydra battles in string-rewriting.

  10. Clumped isotope geochemistry of mid-Cretaceous (Barremian-Aptian) rudist shells: paleoclimatic and paleoenvironmental implications

    Science.gov (United States)

    Huck, S.; Steuber, T.; Bernasconi, S.; Weissert, H.

    2012-04-01

    The Cretaceous period is generally considered to have been a time of climate warmth, but there is an ongoing dispute about the existence of Cretaceous cool episodes - including the short-termed installation of polar ice caps. The Late Barremian-Early Aptian represents a Cretaceous key interval in terms of paleoclimate and paleoceanography, as it provides evidence for (i) a cooler climate (Pucéat et al., 2003) and (ii) a considerable seasonality of sea surface temperatures (SSTs) at low latitudes (Steuber et al., 2005). The timing and significance of these cool episodes, however, are not well constrained. Recently published TEX86 data, in contrast to oxygen isotope paleotemperature estimates, now are in support of a climate scenario with equable hot (~30° C) tropical SSTs from the Early Cretaceous onwards. The aim of this project is to reconstruct the evolution of Barremian-Aptian sea-surface temperatures (SSTs) in the tropical Tethyan realm by use of a combined geochemical approach including oxygen isotope analysis and carbonate clumped-isotope thermometry. Paleotemperature proxies are based on the isotope geochemistry of low-Mg calcite of pristine rudist bivalve shells (Toucasia, Requienia) collected from different carbonate platform settings, including the Provence platform in SE France and the Adriatic Carbonate platform in Croatia. Carbonate clumped-isotope geochemistry deals with the state of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes (13C-18O) rather than with the most abundant ones. Carbonate clumped-isotope thermometry has been shown to allow for reconstructing (i) the temperature of carbonate mineral formation and calculating (ii) the isotopic composition of the water from which carbonate minerals were formed (by using the δ18O of the analysed carbonate sample). Our approach seeks to provide insights into possible biases in temperature estimates of different paleothermometers

  11. Preliminary magnetostratigraphy and environmental magnetism of the Lower Cretaceous from the Italian Dolomites

    Science.gov (United States)

    Savian, J. F.; Jovane, L.; Florindo, F.; Lukeneder, A.

    2011-12-01

    The Lower Cretaceous (~146 to 100 Ma) represents an enigmatic time interval for paleoclimatic, paleogeography and paleomagnetic evolution of the Earth's history. The climatic changes include global oceanic anoxic events (OAEs), biotic changes, global excursions of carbon and strontium isotopes, rises in eustatic sea level and paleotemperature. Paleoceanography was marked by a rapid rate of ocean spreading in the Atlantic. The opening of the Atlantic Ocean was wide enough to allow significant circulation of masses of waters across the equator. This period is furthermore important for the oceanographic events occurring at the base of the Aptian (Selli Level). This period also present one of the most intriguing geomagnetic events: the long normal Cretaceous superchron, lasted for almost 40 million years. We study here the lower Cretaceous deposits of the Puez section in the Dolomites (northern Italy) which represents a continuous section during this period. The samples collected represent marine sedimentary materials of the Biancone and Puez formations. The Puez section consists essentially of green-grey to red limestones and calcareous marls. We present preliminary results of integrated magnetostratigraphic analysis, including a detailed lithostratigraphy and environmental magnetism. We recognize magnetic behavior that are relative to normal polarity (the normal Cretaceous superchron), with a short reverse interval that might represent the M-1r event. We also recognize a series of normal and reverse polarities (below the normal Cretaceous superchron) which can be referred to the magnetozones M1/M5. The environmental magnetic data consists of magnetic susceptibility (χ), natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 900 mT and backfield isothermal remanent magnetization (BIRM) at 100 mT and 300 mT. Derived parameters, such as S-ratio (S300=BIRM300/IRM900) and hard isothermal remanent

  12. Press/Pulse: Explaining selective terrestrial extinctions at the Cretaceous/Palaeogene boundary

    Science.gov (United States)

    Arens, Nan Crystal

    2010-05-01

    Single-cause mass extinction scenarios require extreme conditions to generate sufficiently strong kill mechanisms. Such dire effects are commonly at odds with the taxonomic selectivity that characterizes most extinction events. In response, some researchers have proposed that the interaction of a variety of factors typify episodes of elevated extinction. Previous work (Arens & West 2008 Paleobiology 34:456-471) has shown that a combination of press and pulse disturbances increases the probability of elevated extinction. The press/pulse contrast is borrowed from community ecology, where researchers have long recognized that the ecological response to long-term stress differs from that of an instantaneous catastrophe. Scaled to the macroevolutionary level, press disturbances alter community composition by placing multigenerational stress on populations. Press disturbances do not necessarily cause mortality, but reduce population size by a variety of mechanisms such as curtailed reproduction. Pulse disturbances are sudden catastrophic events that cause extensive mortality. Either press or pulse disturbances of sufficient magnitude can cause extinction, however elevated extinction occurs more commonly during the coincidence of lower-magnitude press and pulse events. The Cretaceous/Palaeogene (K/P) extinction is one of the best examples of a press/pulse extinction. Deccan Trap volcanism, which straddled the K/P boundary, altered atmospheric composition and climate. This episodic volcanism likely contributed to the climate instability observed in terrestrial ecosystems and exerted press stress. Pulse disturbance was produced by bolide impact, which punctuated the end of the Cretaceous. The press/pulse mechanism also more effectively explains selectivity in terrestrial vertebrate and plant extinctions at the K/P boundary than do single-mechanisms scenarios. For example, why do environmentally sensitive vertebrates such as amphibians experience no extinction? And why do

  13. The intra-oceanic Cretaceous (~ 108 Ma) Kata-Rash arc fragment in the Kurdistan segment of Iraqi Zagros suture zone: Implications for Neotethys evolution and closure

    Science.gov (United States)

    Ali, Sarmad A.; Ismail, Sabah A.; Nutman, Allen P.; Bennett, Vickie C.; Jones, Brian G.; Buckman, Solomon

    2016-09-01

    The Kata-Rash arc fragment is an allochthonous thrust-bound body situated near Penjween, 100 km northeast of Sulymannia city, Kurdistan Region, within the Iraqi portion of the Zagros suture zone. It forms part of the suprasubduction zone 'Upper Allochthon' terranes (designated as the Gimo-Qandil Group), which is dominated by calc-alkaline andesite and basaltic-andesite, rhyodacite to rhyolite, crosscut by granitic, granodioritic, and dioritic dykes. Previously, rocks of the Kata-Rash arc fragment were interpreted as a part of the Eocene Walash volcanic group. However, SHRIMP zircon U-Pb dates on them of 108.1 ± 2.9 Ma (Harbar volcanic rocks) and 107.7 ± 1.9 Ma (Aulan intrusion) indicate an Albian-Cenomanian age, which is interpreted as the time of igneous crystallisation. The Aulan intrusion zircons have initial εHf values of + 8.6 ± 0.2. On a Nb/Yb-Th/Yb diagram, all Kata-Rash samples fall within the compositional field of arc-related rocks, i.e. above the mid-ocean-ridge basalt (MORB)-ocean island basalt (OIB) mantle array. Primitive-mantle-normalised trace-element patterns for the Kata-Rash samples show enrichment in the large ion lithophile elements and depletion in the high-field-strength elements supporting their subduction-related character. Low Ba/La coupled with low La/Yb and Hf/Hf* temperature melt from subducted slab sediment, in an oceanic setting. This mechanism can explain the sub-DM initial εHf value, without the need to invoke melting of significantly older (continental) crust in an Andean setting. We interpret the Kata-Rash igneous rocks as a fragment of the Late Cretaceous suprasubduction zone system (named here the Kata-Rash arc) that most likely developed within the Neotethys Ocean rather than at a continental margin. Subsequently during the latest Cretaceous to Paleocene, the arc was accreted to the northern margin of the Arabian plate. The results indicate a > 3000 km continuity of Cretaceous arc activity (Oman to Cyprus), that consumed

  14. Assessment of continuous (unconventional) oil and gas resources in the Late Cretaceous Mancos Shale of the Piceance Basin, Uinta-Piceance Province, Colorado and Utah, 2016

    Science.gov (United States)

    Hawkins, Sarah J.; Charpentier, Ronald R.; Schenk, Christopher J.; Leathers-Miller, Heidi M.; Klett, Timothy R.; Brownfield, Michael E.; Finn, Tom M.; Gaswirth, Stephanie B.; Marra, Kristen R.; Le, Phoung A.; Mercier, Tracey J.; Pitman, Janet K.; Tennyson, Marilyn E.

    2016-01-01

    The U.S. Geological Survey (USGS) completed a geology-based assessment of the continuous (unconventional) oil and gas resources in the Late Cretaceous Mancos Shale within the Piceance Basin of the Uinta-Piceance Province (fig. 1). The previous USGS assessment of the Mancos Shale in the Piceance Basin was completed in 2003 as part of a comprehensive assessment of the greater UintaPiceance Province (U.S. Geological Survey Uinta-Piceance Assessment Team, 2003). Since the last assessment, more than 2,000 wells have been drilled and completed in one or more intervals within the Mancos Shale of the Piceance Basin (IHS Energy Group, 2015). In addition, the USGS Energy Resources Program drilled a research core in the southern Piceance Basin that provided significant new geologic and geochemical data that were used to refine the 2003 assessment of undiscovered, technically recoverable oil and gas in the Mancos Shale.

  15. Assessment of continuous (unconventional) oil and gas resources in the Late Cretaceous Mancos Shale of the Piceance Basin, Uinta-Piceance Province, Colorado and Utah, 2016

    Science.gov (United States)

    Hawkins, Sarah J.; Charpentier, Ronald R.; Schenk, Christopher J.; Leathers-Miller, Heidi M.; Klett, Timothy R.; Brownfield, Michael E.; Finn, Tom M.; Gaswirth, Stephanie B.; Marra, Kristen R.; Le, Phoung A.; Mercier, Tracey J.; Pitman, Janet K.; Tennyson, Marilyn E.

    2016-06-08

    The U.S. Geological Survey (USGS) completed a geology-based assessment of the continuous (unconventional) oil and gas resources in the Late Cretaceous Mancos Shale within the Piceance Basin of the Uinta-Piceance Province (fig. 1). The previous USGS assessment of the Mancos Shale in the Piceance Basin was completed in 2003 as part of a comprehensive assessment of the greater UintaPiceance Province (U.S. Geological Survey Uinta-Piceance Assessment Team, 2003). Since the last assessment, more than 2,000 wells have been drilled and completed in one or more intervals within the Mancos Shale of the Piceance Basin (IHS Energy Group, 2015). In addition, the USGS Energy Resources Program drilled a research core in the southern Piceance Basin that provided significant new geologic and geochemical data that were used to refine the 2003 assessment of undiscovered, technically recoverable oil and gas in the Mancos Shale.

  16. Late Cretaceous-early Eocene counterclockwise rotation of the Fueguian Andes and evolution of the Patagonia-Antarctic Peninsula system

    Science.gov (United States)

    Poblete, F.; Roperch, P.; Arriagada, C.; Ruffet, G.; Ramírez de Arellano, C.; Hervé, F.; Poujol, M.

    2016-02-01

    The southernmost Andes of Patagonia and Tierra del Fuego present a prominent arc-shaped structure: the Patagonian Bend. Whether the bending is a primary curvature or an orocline is still matter of controversy. New paleomagnetic data have been obtained south of the Beagle Channel in 39 out of 61 sites. They have been drilled in Late Jurassic and Early Cretaceous sediments and interbedded volcanics and in mid-Cretaceous to Eocene intrusives of the Fuegian Batholith. The anisotropy of magnetic susceptibility was measured at each site and the influence of magnetic fabric on the characteristic remanent magnetizations (ChRM) in plutonic rocks was corrected using inverse tensors of anisotropy of remanent magnetizations. Normal polarity secondary magnetizations with west-directed declination were obtained in the sediments and they did not pass the fold test. These characteristic directions are similar to those recorded by mid Cretaceous intrusives suggesting a remagnetization event during the normal Cretaceous superchron and describe a large (> 90°) counterclockwise rotation. Late Cretaceous to Eocene rocks of the Fueguian Batholith, record decreasing counterclockwise rotations of 45° to 30°. These paleomagnetic results are interpreted as evidence of a large counterclockwise rotation of the Fueguian Andes related to the closure of the Rocas Verdes Basin and the formation of the Darwin Cordillera during the Late Cretaceous and Paleocene. The tectonic evolution of the Patagonian Bend can thus be described as the formation of a progressive arc from an oroclinal stage during the closure of the Rocas Verdes basin to a mainly primary arc during the final stages of deformation of the Magallanes fold and thrust belt. Plate reconstructions show that the Antarctic Peninsula would have formed a continuous margin with Patagonia between the Early Cretaceous and the Eocene, and acted as a non-rotational rigid block facilitating the development of the Patagonian Bend.

  17. Group Grammar

    Science.gov (United States)

    Adams, Karen

    2015-01-01

    In this article Karen Adams demonstrates how to incorporate group grammar techniques into a classroom activity. In the activity, students practice using the target grammar to do something they naturally enjoy: learning about each other.

  18. MUYANG GROUP

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ With its headquarters in the historic city of Yangzhou,Jiangsu Muyang Group Co.,Ltd has since its founding in 1967 grown into a well-known group corporation whose activities cover research&development.project design,manufacturing,installation and services in a multitude of industries including feed machinery and engineering,storage engineering,grain machinery and engineering,environmental protection,conveying equipment and automatic control systems.

  19. National Assessment of Oil and Gas Quarter-Mile Cells - Upper Cretaceous Taylor and Navarro Groups, Western Gulf Province (047)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Cell maps for each oil and gas assessment unit were created by the USGS to illustrate the degree of exploration, type of production, and distribution of production...

  20. National Assessment of Oil and Gas - Upper Cretaceous Taylor and Navarro Group Assessment Units, Western Gulf Province (047)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is...

  1. Abelian groups

    CERN Document Server

    Fuchs, László

    2015-01-01

    Written by one of the subject’s foremost experts, this book focuses on the central developments and modern methods of the advanced theory of abelian groups, while remaining accessible, as an introduction and reference, to the non-specialist. It provides a coherent source for results scattered throughout the research literature with lots of new proofs. The presentation highlights major trends that have radically changed the modern character of the subject, in particular, the use of homological methods in the structure theory of various classes of abelian groups, and the use of advanced set-theoretical methods in the study of undecidability problems. The treatment of the latter trend includes Shelah’s seminal work on the undecidability in ZFC of Whitehead’s Problem; while the treatment of the former trend includes an extensive (but non-exhaustive) study of p-groups, torsion-free groups, mixed groups, and important classes of groups arising from ring theory. To prepare the reader to tackle these topics, th...

  2. Group dynamics.

    Science.gov (United States)

    Scandiffio, A L

    1990-12-01

    Group dynamics play a significant role within any organization, culture, or unit. The important thing to remember with any of these structures is that they are made up of people--people with different ideas, motivations, background, and sometimes different agendas. Most groups, formal or informal, look for a leader in an effort to maintain cohesiveness of the unit. At times, that cultural bond must be developed; once developed, it must be nurtured. There are also times that one of the group no longer finds the culture comfortable and begins to act out behaviorally. It is these times that become trying for the leader as she or he attempts to remain objective when that which was once in the building phase of group cohesiveness starts to fall apart. At all times, the manager must continue to view the employee creating the disturbance as an integral part of the group. It is at this time that it is beneficial to perceive the employee exhibiting problem behaviors as a special employee, as one who needs the benefit of your experience and skills, as one who is still part of the group. It is also during this time that the manager should focus upon her or his own views in the area of power, communication, and the corporate culture of the unit that one has established before attempting to understand another's point of view. Once we understand our own motivation and accept ourselves, it is then that we may move on to offer assistance to another. Once we understand our insecurities recognizing staff dysfunction as a symptom of system dysfunction will not be so threatening to the concept of the manager that we perceive ourselves to be. It takes a secure person to admit that she or he favors staff before deciding to do something to change things. The important thing to know is that it can be done. The favored staff can find a new way of relating to others, the special employee can find new modes of behavior (and even find self-esteem in the process), the group can find new ways

  3. Group dynamics.

    Science.gov (United States)

    Scandiffio, A L

    1990-12-01

    Group dynamics play a significant role within any organization, culture, or unit. The important thing to remember with any of these structures is that they are made up of people--people with different ideas, motivations, background, and sometimes different agendas. Most groups, formal or informal, look for a leader in an effort to maintain cohesiveness of the unit. At times, that cultural bond must be developed; once developed, it must be nurtured. There are also times that one of the group no longer finds the culture comfortable and begins to act out behaviorally. It is these times that become trying for the leader as she or he attempts to remain objective when that which was once in the building phase of group cohesiveness starts to fall apart. At all times, the manager must continue to view the employee creating the disturbance as an integral part of the group. It is at this time that it is beneficial to perceive the employee exhibiting problem behaviors as a special employee, as one who needs the benefit of your experience and skills, as one who is still part of the group. It is also during this time that the manager should focus upon her or his own views in the area of power, communication, and the corporate culture of the unit that one has established before attempting to understand another's point of view. Once we understand our own motivation and accept ourselves, it is then that we may move on to offer assistance to another. Once we understand our insecurities recognizing staff dysfunction as a symptom of system dysfunction will not be so threatening to the concept of the manager that we perceive ourselves to be. It takes a secure person to admit that she or he favors staff before deciding to do something to change things. The important thing to know is that it can be done. The favored staff can find a new way of relating to others, the special employee can find new modes of behavior (and even find self-esteem in the process), the group can find new ways

  4. Group Anonymity

    CERN Document Server

    Chertov, Oleg; 10.1007/978-3-642-14058-7_61

    2010-01-01

    In recent years the amount of digital data in the world has risen immensely. But, the more information exists, the greater is the possibility of its unwanted disclosure. Thus, the data privacy protection has become a pressing problem of the present time. The task of individual privacy-preserving is being thoroughly studied nowadays. At the same time, the problem of statistical disclosure control for collective (or group) data is still open. In this paper we propose an effective and relatively simple (wavelet-based) way to provide group anonymity in collective data. We also provide a real-life example to illustrate the method.

  5. Lego Group

    DEFF Research Database (Denmark)

    Møller Larsen, Marcus; Pedersen, Torben; Slepniov, Dmitrij

    2010-01-01

    The last years’ rather adventurous journey from 2004 to 2009 had taught the fifth-largest toy-maker in the world - the LEGO Group - the importance of managing the global supply chain effectively. In order to survive the largest internal financial crisis in its roughly 70 years of existence......, the management had, among many initiatives, decided to offshore and outsource a major chunk of its production to Flextronics. In this pursuit of rapid cost-cutting sourcing advantages, the LEGO Group planned to license out as much as 80 per cent of its production besides closing down major parts...

  6. 欧洲白垩纪非海相软体动物及其地层分布%REVIEW OF THE CRETACEOUS NON-MARINE MOLLUSCA AND THEIR STRATIGRAPHICAL DISTRIBUTION IN EUROPE

    Institute of Scientific and Technical Information of China (English)

    M.C. MUNT; G. DELVENE; 沙金庚

    2012-01-01

    本文综述了欧洲白垩纪非海相软体动物群,列出了主要产自英格兰南部、法国和西班牙早白垩世的16个不同沉积层的59个分类单元。淡水动物群以珠蚌类双壳类和田螺类腹足类为主,但在有些地点也存有肺螺类腹足类。这些化石类群与现代类型很相似,说明白垩纪淡水中的水草、氧气与营养环境良好。在欧特里沃期和巴列姆期,淡水与边缘海环境中的动物群组成都发生了显著的变化。欧洲的淡水生物群落早在巴列姆期就已存在,此时的有些类群,如著名的Margaritifera(s.1.)valdensis在欧洲西部有着广泛的分布。英格兰南部的早白垩世韦尔登群被认为是欧洲最连续的非海相白垩纪地层,其上部的生物群可与西班牙的LasHoyas动物群和法国的Wassy动物群相对比。这3个动物群,以及法国侏罗(汝拉)和英格兰南部波倍克的侏罗纪一白垩纪的过渡生物群——Purbeck动物群,是了解欧洲白垩纪淡水动物群的关键动物群。%Non-marine mollusc faunas from the Cretaceous of Europe are listed and reviewed. Fifty-nine taxa are re- corded from sixteen different deposits. The majority of sites are Early Cretaceous, principally from southern England, France and Spain. The freshwater fauna is dominated by unionid bivalves and viviparid gastropods, however pulmonate gastropods are also present at a number of localities. Analogous modern taxa indicate that Cretaceous freshwater habi- tats were well weeded, oxygen and nutrient-rich environments. Major change occurred in the composition of the fauna in both freshwater and marginal marine settings during the Hauterivian and Barremian. Some taxa, notably Margaritif- era (s.1.) valdensis were widely dispersed across western Europe by the Barremian, when a European freshwater com- munity had developed. The Early Cretaceous Wealden Group of southern England is considered to be the most

  7. Group Learning.

    Science.gov (United States)

    Black, Susan

    1992-01-01

    Research suggests that cooperative learning works best when students are first taught group-processing skills, such as leadership, decision making, communication, trust building, and conflict management. Inadequate teacher training and boring assignments can torpedo cooperative learning efforts. Administrators should reassure teachers with…

  8. Tectaria group

    NARCIS (Netherlands)

    Holttum, R.E.

    1991-01-01

    Polypodiaceae subfam. Dryopteridoideae section A, auct.: C. Chr. in Verdoorn, Man. Pteridol. (1938) 543, p.p. Aspidiaceae tribe Aspidieae auct.: Ching, Sunyatsenia 5 (1940) 250, excl. Lomariopsis and related genera. — Aspidiaceae, group of Ctenitis Copel., Gen. Fil. (1947) 153. Aspidiaceae auct.: Pi

  9. Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

    Science.gov (United States)

    Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J. J.; Lodolo, Emanuele

    2015-12-01

    The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known as the Patagonian Orocline (here renamed as Patagonian Arc), and the exhumation mechanism of an upper amphibolite facies metamorphic complex currently exposed in Cordillera Darwin. Here, we present results of anisotropy of magnetic susceptibility (AMS) from 22 sites in Upper Cretaceous to upper Eocene sedimentary rocks within the internal structural domain of the Magallanes fold-and-thrust belt in Tierra del Fuego (Argentina). AMS parameters from most sites reveal a weak tectonic overprint of the original magnetic fabric, which was likely acquired upon layer-parallel shortening soon after sedimentation. Magnetic lineation from 17 sites is interpreted to have formed during compressive tectonic phases associated to a continuous ~ N-S contraction. Our data, combined with the existing AMS database from adjacent areas, show that the Early Cretaceous-late Oligocene tectonic phases in the Southern Andes yielded continuous contraction, variable from ~ E-W in the Patagonian Andes to ~ N-S in the Fuegian Andes, which defined a radial strain field. A direct implication is that the exhumation of the Cordillera Darwin metamorphic complex occurred under compressive, rather than extensional or strike-slip tectonics, as alternatively proposed. If we agree with recent works considering the curved Magallanes fold-and-thrust belt as a primary arc (i.e., no relative vertical-axis rotation of the limbs occurs during its formation), then other mechanisms different from oroclinal bending should be invoked to explain the documented radial strain field. We tentatively propose a kinematic model in which reactivation of variably oriented Jurassic faults at the South American continental margin

  10. Variation on Foraminiferal Composition in Cretaceous Black-Gray-Red Bed Sequence of Southern Tibet, China

    Institute of Scientific and Technical Information of China (English)

    Wan Xiaoqiao; Si Jialiang

    2004-01-01

    An Upper Cretaceous black-gray-red bed sequence was deposited in the Tethys-Himalayan Sea where abundant foraminifera,especially planktons,were yielded. In the shallow shelf to the upper slope on the north margin of Indian plate was recorded an extinction-recovery-radiation cycle of foraminiferal fauna highly sensitive to paleoceanographical changes. The black unit, consisting of the Late Cenomanian-earliest Turonian beds, displays a major extinction, with keeled planktonic and many benthic species as the principal victims at the end of the Cenomanian when existed only low diversity, surface water-dwelling foraminifera. The gray unit spans a long-term recovery interval from the Turonian to the early Santonian with keeled planktonic foraminifera returning stepwise to the water column. The planktonic biota in the red unit, extremely abundant, indicate a biotic radiation during the Late Santonian and the Early Campanian, implying that the high oxygen levels had returned to all the oceanic depth levels, and that the water stratification disappeared, followed by the radiation of all depth-dwellers. The variation on foraminiferal faunas from the whole sequence refers to the extreme warm climate that appeared in the Middle Cretaceous and to the declined temperature toward the late epoch. Substantial deposits for this warming and cooling zones represent the black shales in the Middle Cretaceous and the red beds in the later period of the southern Tibet. The change in the foraminiferal composition corresponded to the formation of dysaerobic facies and to the development of high-oxidized circumstances.

  11. Paleoecology and Paleoenvironmental Interpretations of the Late Cretaceous Lower Cantwell Formation, Denali National Park, Alaska

    Science.gov (United States)

    Tomsich, C. S.; Salazar Jaramillo, S.; Jacobus, R. T.; McCarthy, P. J.; Fowell, S. J.; Fiorillo, A. R.

    2010-12-01

    The level of diversity of an ancient high-latitude fauna or flora is of interest not just for the study of species evolution and paleogeographic migration patterns, but also for the imminent response to an amplified climate change rate. Climate modelers thus focus increasingly on proxies of Polar Regions. A rich floral and faunal record indicative of a warm high-latitude paleoclimate is presently emerging from the late Campanian-Maastrichtian lower Cantwell Formation in Denali National Park, south-central Alaska. This thick (up to 4000m) alluvial fan succession was deposited during the latest accretionary phase of the Wrangellia terrane to the former southern margin of Alaska. Facies descriptions from outcrops near Sable Mountain and Polychrome Mountain record heterogeneous and laterally discontinuous lithologies characteristic of alluvial and marginal alluvial fan environments: braided channel, sandy channel, crevasse splay, sheetflood, floodplain, and lacustrine. Trace and plant fossils occur predominantly at lithological boundaries. The vertebrate fossil record encompasses tracks that can be attributed to fishes, pterosaurs, large and small non-avian theropods, birds, hadrosaurs, and ceratopsians. Hadrosaur footprints are abundant and record populations with multiple generations present. The pterosaur tracks constitute the northernmost fossil occurrence for these flying reptiles. Bird traces range from small, shore-wading bird tracks to those of a large crane-like bird. Diverse invertebrate tracks include freshwater bivalve, ostracode and gastropod trails, crayfish burrows, beetle and mole cricket tracks, wood borings and feeding traces on angiosperm leaves. Plant impression fossils represent dicotyledonous angiosperm leaves referable to nymphaealean, menispermoid, platanoid, trochodendroid and higher hamamelid groups; magnoliid seeds; diverse broad-leaved and blade-like monocot leaf fragments; the leafy shoots, leaves, cones, seeds and wood of cupressaceous and

  12. Geochemical characteristics of Cretaceous basaltic rocks in South China and constraints on Pacific plate subduction

    Institute of Scientific and Technical Information of China (English)

    CHEN Weifeng; CHEN Peirong; XU Xisheng; ZHANG Min

    2005-01-01

    Middle-Late Cretaceous Basaltic rocks (85―110 Ma) are distributed in the contemporaneous downfaulted red basins and volcanic-sedimentary basins in South China (including Hunan, Jiangxi, Guangdong, Fujian, Zhejiang provinces). They are geographically divided into two groups delimited by Wuyishan Range, namely the west area basaltic rocks (WABs) distributing over the west of Wuyishan Range and the east area basaltic rocks (EABs) distributing over the east of Wuyishan Range, and observed having distinct geochemical and isotopic characters.WABs are characterized by relatively low in K2O (0.44%―3.17%), alkalis (K2O+Na2O= 3.27%―6.80%) and Al2O3 (13.08%―16.75%) contents, but high in MgO (5.13%―8.78%) and TiO2 (1.12%―3.35%) contents. WABs are similar to ocean-island basalts (OIB) or intraplate basalts on trace elements and isotopes: no negative Nb and Ta anomalies, relatively low (REE (74.66 μg/g―287.72 μg/g) and LaN/YbN (4.49―22.10), low (87Sr/86Sr)I (average ratio is 0.704679), high εNd(t) (-1.81―8.00). In contrast, EABs display relatively high in K2O (0.55%―4.86%), alkalis (K2O+Na2O=2.95%―7.55%) and Al2O3 (15.80%―21.10%) contents, but low in MgO (2.63%―6.28%) and TiO2 (1.19%―1.86%) contents, strong negative Nb and Ta anomalies, enrichment in LILE (K, Rb, Ba and Th), relatively high ∑REE (79.68 μg/g―327.61 μg/g) and LaN/YbN (5.25―26.37), high (87Sr/86Sr)I (average ratio is 0.707658) and negative εNd(t) (-8.50― -1.22), similar to that of IAB (island arc basalts) or CAB (continental arc basalts). Accordingly, WABs were probably generated under continental rifting tectonic setting related to asthenosphere upwelling, and hence their source was characterized by mixing between EMⅡ with DM. Source of EABs may be enriched lithoshperic mantle which had ever undergone the metasomatism of fluid/melt derived from the subducted Pacific plate.This indicates that subduction of a paleo-Pacific plate (Kula) beneath the Eurasian continent had

  13. A new Cretaceous terrestrial ecosystem from Gondwana with the description of a new sauropod dinosaur

    OpenAIRE

    Jorge O. Calvo; Juan D. Porfiri; Bernardo J. González-Riga; ALEXANDER W. A. KELLNER

    2007-01-01

    A unique site at the northern area of Patagonia (Neuquén, Argentina) reveals a terrestrial ecosystem preserved in a detail never reported before in a Late Cretaceous deposit. An extraordinary diversity and abundance of fossils was found concentrated in a 0.5 m horizon in the same quarry, including a new titanosaur sauropod, Futalognkosaurus dukei n.gen., n.sp, which is the most complete giant dinosaur known so far. Several plant leaves, showing a predominance of angiosperms over gymnosperms t...

  14. Traces of a large crocodylian from the Lower Cretaceous Sousa Formation, Brazil

    DEFF Research Database (Denmark)

    Campos, Herbert B.N.; da Silva, Rafael C.; Milàn, Jesper

    2010-01-01

    Body imprints and tracks attributed to large crocodylians from the Lower Cretaceous Sousa Formation of Brazil are described and interpreted as having been produced in a subaqueous environment. In addition to the crocodylian tracks, the assemblage also comprises isolated tracks from medium......-sized theropods. The studied crocodylian traces are interpreted as subaqueous traces possibly produced by Mesoeucrocodylia crocodyles, during half-swimming and resting next to the margin of a lake. This is the first record of crocodylian traces in Brazil and confirms the potential for finds of new ichnosites...... in the Rio do Peixe basins of northeastern Brazil....

  15. Seawater strontium isotopes, acid rain, and the Cretaceous-Tertiary boundary

    Science.gov (United States)

    Macdougall, J. D.

    1988-01-01

    A large bolide impact at the end of the Cretaceous would have produced significant amounts of nitrogen oxides by shock heating of the atmosphere. The resulting acid precipitation would have increased continental weathering greatly and could be an explanation for the observed high ratio of strontium-87 to strontium-86 in seawater at about this time, due to the dissolution of large amounts of strontium from the continental crust. Spikes to high values in the seawater strontium isotope record at other times may reflect similar episodes.

  16. A New Gigantic Sauropod Dinosaur with the Deepest Known Body Cavity from the Cretaceous of Asia

    Institute of Scientific and Technical Information of China (English)

    L(U) Junchang; XU Li; ZHANG Xingliao; HU Weiyong; WU Yanhua; JIA Songhai; JI Qiang

    2007-01-01

    A new species of sauropod dinosaur Huanghetitan ruyangensis is erected based on the following characters: deepest body cavity with a dorsal rib reaching at least 2.93 m long, anterior caudal vertebrae with mushroom-shaped neural spines. Based on this new specimen of Huanghetitan found in the early Late Cretaceous Mangchuan Formation of Ruyang, Henan Province, the family Huanghetitanidae fam. nov. is proposed as a new rank to include only the genus Huanghetitan You et al.2006. At present, Huanghetitan includes two species: H. liujiaxiaensis You et al., 2006 and H.ruyangensis sp. nov. The systematic relationships of Huanghetitan among sauropod dinosaurs are briefly discussed.

  17. Using Ichthyoliths to Determine the Fish Response to the End-Cretaceous Mass Extinction

    Science.gov (United States)

    Sibert, E. C.; Norris, R. D.; Hull, P. M.

    2012-12-01

    Ichthyoliths are the small calcium phosphate fossil teeth, scales, and bone shards of fish and sharks. While it is extremely rare to find full body-fossils of fish, ichthyoliths are relatively abundant in oceanic sediments, with 10s to 100s of identifiable ichthyoliths in a few grams of sediment, most in the ocean. Rather, despite widespread extinction and upheaval in lower trophic levels, the earliest Paleocene ocean, in some regions of the planet, appears to have had ecosystems capable of supporting levels of fish comparable to or even above those of the Late Cretaceous.

  18. The upper Jurassic-lower cretaceous siliciclastic system in the Morocco offshore - Prevenance, transport and deposition

    OpenAIRE

    Bertotti, G.; Arantegui, A.; Charton, R.; Luber, T.; Redfern, J

    2015-01-01

    The Morocco segment of the Central Atlantic passive continental margin experienced km-scale exhumation during the early post-rift (late Jurassic-Early Cretaceous). In the Meseta and the High Atlas this led to the development of a N-S trending ridge sourcing terrigenous sediments which were brought to the Atlantic sea via wide rivers flowing on fairly flat plains. In correspondence with the W termination of the High Atlas, waters were deeper and no terrigenous sediments are found in the Lower ...

  19. An Early Cretaceous Avialian Bird, Shenzhouraptor sinensis from Western Liaoning, China

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This paper describes an avialian bird from the Early Cretaceous Jiufotang Formation in Yixian county,western Liaoning, China, which is named as Shenzhouraptor sinensis by Ji et al. on July 15, 2002. Shenzhouraptor sinensis is characterized by no teeth in its mouth, the forelimbs longer than the hindlimbs, a long tail with more than 23 caudal vertebrae, U-shaped wishbone, and remiges longer than the total length of ulna and manus. It is certain that the new avialian bird is really capable of powerful flight, representing a missing link between theropod dinosaurs and birds.

  20. First Record of Anisoptera (Insecta: Odonata) from mid-Cretaceous Burmese Amber.

    Science.gov (United States)

    Schädel, Mario; Bechly, Günter

    2016-01-01

    The fossil dragonfly Burmalindenia imperfecta gen. et sp. nov. is described from mid-Cretaceous Burmese amber as the first record of the odonate suborder Anisoptera for this locality and one of the few records from amber in general. The inclusion comprises two fragments of the two hind wings of a dragonfly. The fossil can be attributed to a new genus and species of the family Gomphidae, presumably in the subfamily Lindeniinae, and features a strange teratological phenomenon in its wing venation. PMID:27394756

  1. Changes of taxonomical composition of Late Jurassic Early Cretaceous palynofloras of Bureya Basin,Russia

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The changes of taxonomical composition of the Late Jurassic-Early Cretaceous palynofloras are revealed,in the upper stream of Bureya River in Bureya Basin.The palynofloras are dominated as follows:the Berriasian one by ferns (Cyatheaceae,Dicksoniaceae,Osmundaceae), Classopollis and bisaccate pollen;the Valanginian-Hauterivian one by ferns (Cyatheaceae,Dicksoniaceae), Ginkgocycadophytus and bisaccate pollen;the Barremian one by ferns(Cyatheaceae,Dieksoniaceae);the Aptian one by ferns(Cyatheaceae,Dieksoniaceae,Gleicheniaceae)and Ginkgocycadophytus;and the Albian one by ferns(Schizaeaceae)and bisaccate pollen.In the Albian the floral diversity raises with the angiosperms appearing.

  2. Exploring Early Angiosperm Fire Feedbacks using Coupled Experiments and Modelling Approaches to Estimate Cretaceous Palaeofire Behaviour

    Science.gov (United States)

    Belcher, Claire; Hudpsith, Victoria

    2016-04-01

    Using the fossil record we are typically limited to exploring linkages between palaeoecological changes and palaeofire activity by assessing the abundance of charcoals preserved in sediments. However, it is the behaviour of fires that primarily governs their ecological effects. Therefore, the ability to estimate variations in aspects of palaeofire behaviour such as palaeofire intensity and rate of spread would be of key benefit toward understanding the coupled evolutionary history of ecosystems and fire. The Cretaceous Period saw major diversification in land plants. Previously, conifers (gymnosperms) and ferns (pteridophytes) dominated Earth's ecosystems until flowering plants (angiosperms) appear in the fossil record of the Early Cretaceous (~135Ma). We have created surface fire behaviour estimates for a variety of angiosperm invasion scenarios and explored the influence of Cretaceous superambient atmospheric oxygen levels on the fire behaviour occurring in these new Cretaceous ecosystems. These estimates are then used to explore the hypothesis that the early spread of the angiosperms was promoted by the novel fire regimes that they created. In order to achieve this we tested the flammability of Mesozoic analogue fuel types in controlled laboratory experiments using an iCone calorimeter, which measured the ignitability as well as the effective heat of combustion of the fuels. We then used the BehavePlus fire behaviour modelling system to scale up our laboratory results to the ecosystem scale. Our results suggest that fire-angiosperm feedbacks may have occurred in two phases: The first phase being a result of weedy angiosperms providing an additional easily ignitable fuel that enhanced both the seasonality and frequency of surface fires. In the second phase, the addition of shrubby understory fuels likely expanded the number of ecosystems experiencing more intense surface fires, resulting in enhanced mortality and suppressed post-fire recruitment of gymnosperms

  3. Subtle traps in Cretaceous, Archuleta, Conejos, Mineral, and Rio Grande counties, Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Brown, W.T. Jr. (Coastal Oil and Gas Corp., Denver, CO (USA))

    1989-09-01

    Regional interpretation of the stratigraphy, faulting, fracturing, and hydrodynamics in Archuleta, Conejos, Mineral, and Rio Grande Counties in southern Colorado indicates that significant reserves of hydrocarbons could exist in subtle trapping situations within the Cretaceous sequences. The presence of Price-Gramps field (7 million bbl of oil ultimate recoverable), which produces primarily from the Dakota Formation, is presently anomalous in this area but is indicative of existing hydrocarbon potential. Hydrocarbon shows from drilled wells and outcrops suggest that significant quantities of hydrocarbons are present in this area, sourced both from the San Juan basin to the south and west, and from more local areas for fractured reservoirs.

  4. An archaic crested plesiosaur in opal from the Lower Cretaceous high-latitude deposits of Australia

    OpenAIRE

    Kear, Benjamin P.; Schroeder, Natalie I; Michael S Y Lee

    2006-01-01

    Umoonasaurus demoscyllus gen. et sp. nov. is a new small-bodied (approx. 2.5 m) pliosauroid plesiosaur from the Lower Cretaceous (Aptian–Albian) of southern Australia. It is represented by several partial skeletons (one with a near complete skull is the most complete opalized vertebrate fossil yet known), and is unique in having large crests on the skull midline and above the orbits. Umoonasaurus is surprisingly archaic despite its relatively late age (approx. 115 Myr ago)—being simultaneousl...

  5. An evaluation of the Early Cretaceous of Spitsbergen: new insights into stratigraphy and palaeoclimate

    Science.gov (United States)

    Vickers, Madeleine; Price, Gregory; FitzPatrick, Meriel; Watkinson, Matthew; Jerrett, Rhodri

    2015-04-01

    During the Early Cretaceous, Spitsbergen was located at a palaeolatitude of ~60°N. Abundant fossil wood derived from conifer forests, dinosaur trackways, enigmatic deposits such as glendonite horizons and rare outsized clasts, and stable isotope data from the Early Cretaceous formations of Spitsbergen suggest that the climate at that time was much more dynamic than the traditional view of "invariant greenhouse" conditions on Earth. The purpose of this study is to test the veracity of using such proxies as climate indicators, and to evaluate the climatic character of Arctic Svalbard during the Early Cretaceous. To these ends, the sedimentological and sequence stratigraphic context of glendonites and outsized clasts within the Rurikfjellet, Helvetiafjellet and Carolinefjellet formations are being documented. This is being achieved through high resolution sedimentary logging (bed-scale) of the Early Cretaceous succession at multiple locations, documentation of glendonites, outsized clasts, together with sampling (every succession at Festningen is 750m thick and is considered to have been deposited between the Berriasian and late Aptian/early Albian. The basal Rurikfjellet Formation comprises a normally regressive water to wave/storm dominated shoreface. A forced regression (expressed as a regional unconformity) marks the base of the overlying Helvetiafjellet Formation. The Helvetiafjellet and overlying Carolinefjellet Formation represent a strongly aggradational, weakly transgressive succession characterised by delta plain deposits, containing abundant terrestrial woody material and with ornithopod footprints, passing upward into deep water mudstones and rare storm beds. Abundant glendonites occur within the shoreface deposits of the upper Rurikfjellet Formation, and in the Carolinefjellet Formation. The expanded nature of the sedimentary deposits in the Carolinefjellet Formation suggest high subsidence rates and high sedimentation rates, implying that the main

  6. Preservation of ancestral Cretaceous microflora recovered from a hypersaline oil reservoir

    Science.gov (United States)

    Gales, Grégoire; Tsesmetzis, Nicolas; Neria, Isabel; Alazard, Didier; Coulon, Stéphanie; Lomans, Bart P.; Morin, Dominique; Ollivier, Bernard; Borgomano, Jean; Joulian, Catherine

    2016-03-01

    Microbiology of a hypersaline oil reservoir located in Central Africa was investigated with molecular and culture methods applied to preserved core samples. Here we show that the community structure was partially acquired during sedimentation, as many prokaryotic 16S rRNA gene sequences retrieved from the extracted DNA are phylogenetically related to actual Archaea inhabiting surface evaporitic environments, similar to the Cretaceous sediment paleoenvironment. Results are discussed in term of microorganisms and/or DNA preservation in such hypersaline and Mg-rich solutions. High salt concentrations together with anaerobic conditions could have preserved microbial/molecular diversity originating from the ancient sediment basin wherein organic matter was deposited.

  7. A New Hadrosauroid Dinosaur from the Mid-Cretaceous of Liaoning,China

    Institute of Scientific and Technical Information of China (English)

    YOU Hailu; JI Qiang; LI Jinglu; LI Yinxian

    2003-01-01

    A new hadrosauroid dinosaur, Shuangmiaosaurus gilmorei gen. et sp. nov., is described based on acomplete left maxilla with articulated premaxilla and lacrimal fragments, and a complete left dentary from the mid-Cretaceous Sunjiawan Formation of Beipiao, Liaoning, northeastern China. Cladistic analysis shows thatShuangmiaosaurus is a basal hadrosauroid, and comprises the sister taxon to Hadrosauridae. In both Shuangmiaosaurusand Hadrosauridae, the maxilla-jugal suture is butt-jointed, rather than finger-in-recess articulation as in other basalhadrosauroids. However, Shuangmiaosaurus does not possess such hadrosaurid synapomorphies as the diamond-shapedmaxillary crowns with reduced primary ridges and reduced marginal denticles.

  8. Application of the Sequence Stratigraphy in the Study of Cretaceous Tertiary of the Tarim Basin, Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    DING Xiaozhong; GUO Xianpu; PENG Yang; JI Yunlong; WANG Yineng

    2001-01-01

    According to the comprehensive study of the depositional sequence of the outcrop sections from Cretaceous to Tertiary of the Tarim Basin, and the analyses of the seismic sequence and drilling data,the strata of Cretaceous-Tertiary of the Tarim Basin can be subdivided into 30 3rd-order depositional sequences in the southwestern depression and 22 3rd-order dpositional sequences in the northwestern depression. This indicates that the 3rd-order sequences can not be correlated directly one by one because of their different tectonic settings and sedimentary environments. Whereas, based on the study of 2nd-order supersequence, the strata from Cretaceous to Tertiary can be divided into 4 supersequences and correlated isochronously in these two areas of the Tarim Basin.

  9. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group, established at the start of 2010, has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure There are now 55 CMS Centres worldwide that are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS offline and computing operations, hosting dedicated analysis efforts such as during the CMS Heavy Ion lead-lead running. With a majority of CMS sub-detectors now operating in a “shifterless” mode, many monitoring operations are now routinely performed from there, rather than in the main Control Room at P5. The CMS Communications Group, CERN IT and the EVO team are providing excellent videoconferencing support for the rapidly-increasing number of CMS meetings. In parallel, CERN IT and ...

  10. Group therapy

    International Nuclear Information System (INIS)

    Full text: In his review 'Genesis of Unified Gauge Theories' at the symposium in Honour of Abdus Salam (June, page 23), Tom Kibble of Imperial College, London, looked back to the physics events around Salam from 1959-67. He described how, in the early 1960s, people were pushing to enlarge the symmetry of strong interactions beyond the SU(2) of isospin and incorporate the additional strangeness quantum number. Kibble wrote - 'Salam had students working on every conceivable symmetry group. One of these was Yuval Ne'eman, who had the good fortune and/or prescience to work on SU(3). From that work, and of course from the independent work of Murray Gell- Mann, stemmed the Eightfold Way, with its triumphant vindication in the discovery of the omega-minus in 1964.' Yuval Ne'eman writes - 'I was the Defence Attaché at the Israeli Embassy in London and was admitted by Salam as a part-time graduate student when I arrived in 1958. I started research after resigning from the Embassy in May 1960. Salam suggested a problem: provide vector mesons with mass - the problem which was eventually solved by Higgs, Guralnik, Kibble,.... (as described by Kibble in his article). I explained to Salam that I had become interested in symmetry. Nobody at Imperial College at the time, other than Salam himself, was doing anything in groups, and attention further afield was focused on the rotation - SO(N) - groups. Reacting to my own half-baked schemes, Salam told me to forget about the rotation groups he taught us, and study group theory in depth, directing me to Eugene Dynkin's classification of Lie subalgebras, about which he had heard from Morton Hamermesh. I found Dynkin incomprehensible without first learning about Lie algebras from Henri Cartan's thesis, which luckily had been reproduced by Dynkin in his 1946 thesis, using his diagram method. From a copy of a translation of Dynkin's thesis which I found in the British Museum Library, I

  11. Intercontinental correlation of organic carbon and carbonate stable isotope records: evidence of climate and sea-level change during the Turonian (Cretaceous)

    NARCIS (Netherlands)

    Jarvis, I.; Trabucho-Alexandre, João; Gröcke, D.R.; Uličný, D.; Laurin, J.

    2015-01-01

    Carbon (d13Corg, d13Ccarb) and oxygen (d18Ocarb) isotope records are presented for an expanded Upper Cretaceous (Turonian–Coniacian) hemipelagic succession cored in the central Bohemian Cretaceous Basin, Czech Republic. Geophysical logs, biostratigraphy and stable carbon isotope chemostratigraphy pr

  12. Local Group

    Science.gov (United States)

    Mateo, M.; Murdin, P.

    2000-11-01

    Not long after EDWIN HUBBLE established that galaxies are `island universes' similar to our home galaxy, the MILKY WAY, he realized that a few of these external galaxies are considerably closer to us than any others. In 1936 he first coined the term `Local Group' in his famous book The Realm of the Nebulae to identify our nearest galactic neighbors. More than 60 yr later, the galaxies of the Loca...

  13. Paleomagnetism of Jurassic and Cretaceous rocks bounding the Santa Marta massif - NW corner of Colombia, South America

    Science.gov (United States)

    Bayona, G.; Jimenez, G.; Silva, C.

    2008-12-01

    The Santa Marta massif (SMM) is a complex terrain located in the NW margin of South America, bounded by the left-lateral Santa Marta fault to the west and the right-lateral Oca fault to the north. The SMM is cored by Precambrian metamorphic and Jurassic intrusive rocks, whereas along the SE flank crop out Jurassic volcanic rocks overlying unconformably by Limestones of Cretaceous age. Paleomagnetic analysis of 30 sites in the Jurassic and Cretaceous units in the SE region uncovered two principal magnetic components. The component "a", isolated in low coercivity and temperatures, has declinations to the north and moderate positive inclinations representing the actual field direction (n=11, D=347.6 I=23 K=30.77, a95=8.4). The component "c", with high coercivity and temperatures, has two orientations. After two-step tilt corrections, the first has northward declination and positive, low inclination (n=9, D=12, I=3, K=18.99, a95=12.1); this direction was uncovered in Cretaceous and some Jurassic rocks near to the Santa Marta fault, and we consider it as a Cretaceous component. The second direction was uncovered only in Jurassic rocks and has NNE declinations with negative-low inclinations (n=9, D=11.3 I=-14.3 K=12.36, a95=15.2); this direction represents a Jurassic component. Jurassic and Cretaceous directions isolated in areas faraway of the Santa Marta Fault suggest slight clockwise vertical-axes rotation. The Jurassic component suggests northward translation of the SMM from Paleolatitude -7.3, to near the magnetic equador in the Cretaceous, and to northern latitudes in the Cenozoic.

  14. A paleolatitude reconstruction of the South Armenian Block (Lesser Caucasus) for the Late Cretaceous: Constraints on the Tethyan realm

    Science.gov (United States)

    Meijers, Maud J. M.; Smith, Brigitte; Kirscher, Uwe; Mensink, Marily; Sosson, Marc; Rolland, Yann; Grigoryan, Araik; Sahakyan, Lilit; Avagyan, Ara; Langereis, Cor; Müller, Carla

    2015-03-01

    The continental South Armenian Block - part of the Anatolide-Tauride South Armenian microplate - of Gondwana origin rifted from the African margin after the Triassic and collided with the Eurasian margin after the Late Cretaceous. During the Late Cretaceous, two northward dipping subduction zones were simultaneously active in the northern Neo-Tethys between the South Armenian Block in the south and the Eurasian margin in the north: oceanic subduction took place below the continental Eurasian margin and intra-oceanic subduction resulted in ophiolite obduction onto the South Armenian Block in the Late Cretaceous. The paleolatitude position of the South Armenian Block before its collision with Eurasia within paleogeographic reconstructions is poorly determined and limited to one study. This earlier study places the South Armenian Block at the African margin in the Early Jurassic. To reconstruct the paleolatitude history of the South Armenian Block, we sampled Upper Devonian-Permian and Cretaceous sedimentary rocks in Armenia. The sampled Paleozoic rocks have likely been remagnetized. Results from two out of three sites sampled in Upper Cretaceous strata pass fold tests and probably all three carry a primary paleomagnetic signal. The sampled sedimentary rocks were potentially affected by inclination shallowing. Therefore, two sites that consist of a large number of samples (> 100) were corrected for inclination shallowing using the elongation/inclination method. These are the first paleomagnetic data that quantify the South Armenian Block's position in the Tethys ocean between post-Triassic rifting from the African margin and post-Cretaceous collision with Eurasia. A locality sampled in Lower Campanian Eurasian margin sedimentary rocks and corrected for inclination shallowing, confirms that the corresponding paleolatitude falls on the Eurasian paleolatitude curve. The north-south distance between the South Armenian Block and the Eurasian margin just after Coniacian

  15. Ginkgoites myrioneurus sp nov and associated shoots from the Lower Cretaceous of the Jixi Basin, Heilongjiang, China

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X.J. [Chinese Academy of Science, Nanjing (China). Nanjing Institute of Geology & Palaeontology

    2004-10-01

    Ginkgoalean leaves attributed to Ginkgoites myrioneurus sp. nov. and associated long and dwarf shoots were collected from the Lower Cretaceous coal-bearing Muling Formation of the Jixi Basin, eastern Heilongjiang, China. The common characteristic feature of the various leaves is the dense venation. The species may be distinguished from other known species of Ginkgoites from the Jurassic and Lower Cretaceous of eastern Asia in having 8-18 closely arranged oblanceolate segments each with 6-16 veins. The fragmentary long and dwarf shoots are similar to those of extant Ginkgo biloba in gross morphology. They are considered to belong to the same tree as that which produced Ginkgoites myrioneurus.

  16. Late Cretaceous-Paleogene Palynostratigraphy from the Arkhara-Boguchan Brown Coal Mine of Zeya-Bureya Depression, Russia

    Institute of Scientific and Technical Information of China (English)

    Tatyana V. Kezina

    2003-01-01

    A well-preserved Late Cretaceous-Paleogene palynological flora from the middle member of the Tsagajan Formation and the upper member of the Tsagajan Formation including the Kivda Beds is reported for the first time from the Arkhara-Boguchan brown coal mine, southeastern part of the Zeya-Bureya Basin. Four palynocomplexes were established for the Cretaceous-Tertiary transition. The climate and phytocoenoses were also analyzed,based on the detailed palynological data. The results are coincident with those of mega-flora studied by Akhmetiev et al. (2002).

  17. A Titanosaurian Sauropod Dinosaur with Opisthocoelous Caudal Vertebrae from the Early Late Cretaceous of Liaoning Province, China

    Institute of Scientific and Technical Information of China (English)

    YOU Hailu; JI Qiang; Matthew C. LAMANNA; LI Jinglu; LI Yinxian

    2004-01-01

    We describe a new titanosaurian sauropod dinosaur, Borealosaurus wimani gen. et sp. nov., based on a distinctive mid-distal caudal vertebra from the early Late Cretaceous Sunjiawan Formation exposed in the Shuangmiao village of Beipiao in Liaoning, China. We provisionally refer an isolated tooth crown, a middle caudal vertebra, and a right humerus from the same locality and horizon to this taxon. Borealosaurus is distinguished from other sauropods in its possession of opisthocoelous mid-distal caudal vertebrae. The occurrence of opisthocoelous caudals in Borealosaurus and the Mongolian sauropod Opisthocoelicaudia raises the possibility that these taxa pertain to an as-yet unrecognized titanosaurian subclade endemic to the Cretaceous Asia.

  18. Jurassic–cretaceous deformational phases in the Paraná intracratonic basin, southern Brazil

    Directory of Open Access Journals (Sweden)

    A. J. Strieder

    2015-04-01

    Full Text Available This paper examines the domes and basins, regional arcs and synclines, and brittle structures of the Paraná Basin flood volcanism to characterize the deformational phases in its Jurassic to Cretaceous history. First-stage fieldwork revealed brittle structures, extensional joints, and strike-slip faults, and second-stage fieldwork investigated the connections of the brittle structures to both open folds and dome-and-basin features. Fault-slip data inversion was performed using two different techniques to distinguish local and remote stress/strain. Geometric and kinematic analyses completed the investigations of the deformation, which characterized two deformational phases for the Jurassic to Cretaceous periods in the Paraná Basin. Both developed under regional bi-directional constrictional (σ1 ≥ σ2 ≫ σ3 stress regimes that produced a number of non-cylindrical folds. A D1 deformational phase produced the N–S and E–W orthogonally oriented domes and basins. The D2 arcs and synclines are oriented towards the NW and NE and indicate a clockwise rotation (35–40° of both horizontal principal stress tensors. The extensional joints and strike-slip faults characterize the local stress field in the outer rim of the orthogonally buckled single volcanic flow, whereas the inner rim of the buckled single flow supported constriction and thus, developed the local arcuate folds.

  19. Biogeochemical significance of pelagic ecosystem function: an end-Cretaceous case study.

    Science.gov (United States)

    Henehan, Michael J; Hull, Pincelli M; Penman, Donald E; Rae, James W B; Schmidt, Daniela N

    2016-05-19

    Pelagic ecosystem function is integral to global biogeochemical cycling, and plays a major role in modulating atmospheric CO2 concentrations (pCO2). Uncertainty as to the effects of human activities on marine ecosystem function hinders projection of future atmospheric pCO2 To this end, events in the geological past can provide informative case studies in the response of ecosystem function to environmental and ecological changes. Around the Cretaceous-Palaeogene (K-Pg) boundary, two such events occurred: Deccan large igneous province (LIP) eruptions and massive bolide impact at the Yucatan Peninsula. Both perturbed the environment, but only the impact coincided with marine mass extinction. As such, we use these events to directly contrast the response of marine biogeochemical cycling to environmental perturbation with and without changes in global species richness. We measure this biogeochemical response using records of deep-sea carbonate preservation. We find that Late Cretaceous Deccan volcanism prompted transient deep-sea carbonate dissolution of a larger magnitude and timescale than predicted by geochemical models. Even so, the effect of volcanism on carbonate preservation was slight compared with bolide impact. Empirical records and geochemical models support a pronounced increase in carbonate saturation state for more than 500 000 years following the mass extinction of pelagic carbonate producers at the K-Pg boundary. These examples highlight the importance of pelagic ecosystems in moderating climate and ocean chemistry. PMID:27114586

  20. Dinosaur footprints and other ichnofauna from the cretaceous Kem Kem beds of Morocco.

    Science.gov (United States)

    Ibrahim, Nizar; Varricchio, David J; Sereno, Paul C; Wilson, Jeffery A; Wilson, Jeff A; Dutheil, Didier B; Martill, David M; Baidder, Lahssen; Zouhri, Samir

    2014-01-01

    We describe an extensive ichnofossil assemblage from the likely Cenomanian-age 'lower' and 'upper' units of the 'Kem Kem beds' in southeastern Morocco. In the lower unit, trace fossils include narrow vertical burrows in cross-bedded sandstones and borings in dinosaur bone, with the latter identified as the insect ichnotaxon Cubiculum ornatus. In the upper unit, several horizons preserve abundant footprints from theropod dinosaurs. Sauropod and ornithischian footprints are much rarer, similar to the record for fossil bone and teeth in the Kem Kem assemblage. The upper unit also preserves a variety of invertebrate traces including Conichnus (the resting trace of a sea-anemone), Scolicia (a gastropod trace), Beaconites (a probable annelid burrow), and subvertical burrows likely created by crabs for residence and detrital feeding on a tidal flat. The ichnofossil assemblage from the Upper Cretaceous Kem Kem beds contributes evidence for a transition from predominantly terrestrial to marine deposition. Body fossil and ichnofossil records together provide a detailed view of faunal diversity and local conditions within a fluvial and deltaic depositional setting on the northwestern coast of Africa toward the end of the Cretaceous.

  1. A New Family of Sauropod Dinosaur from the Upper Cretaceous of Tianzhen, Shanxi Province, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new gigantic sauropod, Huabeisaurus allocotus gen. et sp. nov., about 20 m in length and 5 m in height, was discovered in the Upper Cretaceous Huiquanpu Formation, Tianzhen County,Shanxi Province. It is notably different from Diplodocidae, Titanosauridae and Nemegtosauridae in the following aspects: the teeth are strong, peg-like with a length ratio of the tooth crown to tooth root at about 3 to 1; the cervical vertebrae are long with forked spines; the spines in dorsal vertebrae are relatively high, unbifurcated; the caudal vertebrae are amphicoelous, with anterior neural spines and unbifurcated spines and chevrons; the femur is straight and long, narrow and flat and the tibia and fibula are long and flat. These characters show that the described genus should represent a new family, Huabeisauridae fam. nov. The discovery enriches the sauropod dinosaur record in China, and is quite significant to the study of the taxonomy, evolution, migration, extinction and palaeobiogeographic provincialism of the Late Cretaceous sauropod dinosaurs.

  2. Severity of ocean acidification following the end-Cretaceous asteroid impact.

    Science.gov (United States)

    Tyrrell, Toby; Merico, Agostino; Armstrong McKay, David Ian

    2015-05-26

    Most paleo-episodes of ocean acidification (OA) were either too slow or too small to be instructive in predicting near-future impacts. The end-Cretaceous event (66 Mya) is intriguing in this regard, both because of its rapid onset and also because many pelagic calcifying species (including 100% of ammonites and more than 90% of calcareous nannoplankton and foraminifera) went extinct at this time. Here we evaluate whether extinction-level OA could feasibly have been produced by the asteroid impact. Carbon cycle box models were used to estimate OA consequences of (i) vaporization of up to 60 × 10(15) mol of sulfur from gypsum rocks at the point of impact; (ii) generation of up to 5 × 10(15) mol of NOx by the impact pressure wave and other sources; (iii) release of up to 6,500 Pg C as CO2 from vaporization of carbonate rocks, wildfires, and soil carbon decay; and (iv) ocean overturn bringing high-CO2 water to the surface. We find that the acidification produced by most processes is too weak to explain calcifier extinctions. Sulfuric acid additions could have made the surface ocean extremely undersaturated (Ωcalcite ocean very rapidly (over a few days) and if the quantity added was at the top end of literature estimates. We therefore conclude that severe ocean acidification might have been, but most likely was not, responsible for the great extinctions of planktonic calcifiers and ammonites at the end of the Cretaceous.

  3. Carbon isotope geochemistry of the Cretaceous-Tertiary section of the Wasserfallgraben, Lattengebirge, southeast Germany

    Science.gov (United States)

    Arneth, J.-D.; Matzigkeit, U.; Boos, A.

    1985-09-01

    Carbonates and organic matter in sediments of the Cretaceous-Tertiary (C/T) section of the Wasserfallgraben, Lattengebirge (Bavaria) have been investigated. All parameters—the carbonate content (C carb), its isotopic composition ( δ 13C carb, δ 18O carb) as well as the organic carbon content (C org), its isotopic composition ( δ 13C org) and the H/C ratio of the sedimentary organic matter—display systematic variations across the C/T boundary which cannot be attributed to a single cause. The boundary zone as a whole is tectonically disturbed and shows significant features of detrital contaminations. Unidirectional shift in δ 13C carb and δ 13C org are observed when directly comparing Maastrichtian (latest Cretaceous) and Danian (earliest Tertiary) sediments. These synchronous isotope displacements towards more negative readings are interpreted to reflect the reduced photosynthetic activity as consequence of the mass extinction at the C/T boundary. The results may have some bearings on other C/T profiles investigated where measurements on the reduced carbon species are still lacking.

  4. A better-ventilated ocean triggered by Late Cretaceous changes in continental configuration.

    Science.gov (United States)

    Donnadieu, Yannick; Pucéat, Emmanuelle; Moiroud, Mathieu; Guillocheau, François; Deconinck, Jean-François

    2016-01-01

    Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened during pre-Cenozoic periods of extreme warmth. Here, to assess the role of major continental configuration changes occurring during the Late Cretaceous on oceanic circulation modes, which in turn influence the oxygenation level of the deep ocean, we use a coupled ocean atmosphere climate model. We simulate ocean dynamics during two different time slices and compare these with existing neodymium isotope data (ɛNd). Although deep-water production in the North Pacific is continuous, the simulations at 94 and 71 Ma show a shift in southern deep-water production sites from South Pacific to South Atlantic and Indian Ocean locations. Our modelling results support the hypothesis that an intensification of southern Atlantic deep-water production and a reversal of deep-water fluxes through the Caribbean Seaway were the main causes of the decrease in ɛNd values recorded in the Atlantic and Indian deep waters during the Late Cretaceous.

  5. Petrochemistry and tectonic significance of Lower Cretaceous Barros Arana Formation basalts, southernmost Chilean Andes

    Science.gov (United States)

    Stern, C. R.; Mohseni, P. P.; Fuenzalida, P. R.

    The Lower Cretaceous Barros Arana Formation (Albian, hornblende KAr age of 104 Ma), in the Magallanes region of Chile, consists of a sequence of spilitized clinopyroxene- and amphibole-bearing mafic dikes and lavas, and volcaniclastic breccias, occurring within the sedimentary infill of the Rocas Verdes marginal basin and its eastward extension onto the Cretaceous continental platform. Although the original alkali and alkaline earth element concentrations of the basaltic lavas and dikes have been altered by spilitization, the presence of relict pargasitic amphibole phenocrysts, the absence of orthopyroxene, and high LREE contents and LREE/HREE ratios imply mildly alkaline affinities for these basalts. Their low TiO 2 and HFSE (Zr, Nb, Ta, and Hf) contents and high LREE/HFSE ratios suggest affinities with convergent plate boundary arc magmas. The Barros Arana basalts are interpreted as mafic members of the mildly alkaline shoshonitic rock suite of subduction-related arcs. They may have formed as subduction geometry began to undergo the changes (flattening) that ultimately led to the initiation of the closure, deformation, and uplift of the Rocas Verdes basin by the late or post-Albian. The low initial 87Sr/ 86Sr (0.7031) and high initial 143Nd/ 144Nd (0.51277) of the basalts indicate that a generally extensional tectonic regime east of the main calc-alkaline arc allowed eruption of these mafic shoshonites without interaction with continental crust (in contrast to the contemporaneous plutons of the Patagonian batholith).

  6. Metamorphic history and geodynamic significance of the Early Cretaceous Sabzevar granulites (Sabzevar structural zone, NE Iran

    Directory of Open Access Journals (Sweden)

    M. Nasrabady

    2011-05-01

    Full Text Available The Iranian ophiolites are part of the vast orogenic suture zones that mark the Alpine-Himalayan convergence zone. Few petrological and geochronological data are available from these ophiolitic domains, hampering a full assessment of the timing and regimes of subduction zone metamorphism and orogenic construction in the region. This paper describes texture, geochemistry and the pressure-temperature path of the Early Cretaceous granulites that occur within the Tertiary Sabzevar suture zone of NE Iran. The geochemical data set document that the granulites are remnants of a MORB-type oceanic crust and thus of a (Early Cretaceous ? back-arc basin formed in the upper plate of the Neotethyan subduction and thus interpreted as portions of a dismembered dynamothermal sole formed during oceanic subduction. The metamorphic history of the granulites suggests an anticlockwise pressure-temperature loop, compatible with burial in a hot subduction zone followed by cooling during exhumation. This is interpreted as the evidence of a nascent subduction zone formed at the expenses of hot and hence young oceanic lithosphere. These data point to diachronous and independent tectonic evolutions of the different ophiolitic domains of central Iran, for which a growing heterogeneity in the timing of metamorphic equilibration and of pressure-temperature paths can be expected with further investigations.

  7. Low-magnesium calcite produced by coralline algae in seawater of Late Cretaceous composition.

    Science.gov (United States)

    Stanley, Steven M; Ries, Justin B; Hardie, Lawrence A

    2002-11-26

    Shifts in the MgCa ratio of seawater driven by changes in midocean ridge spreading rates have produced oscillations in the mineralogy of nonskeletal carbonate precipitates from seawater on time scales of 10(8) years. Since Cambrian time, skeletal mineralogies of anatomically simple organisms functioning as major reef builders or producers of shallow marine limestones have generally corresponded in mineral composition to nonskeletal precipitates. Here we report on experiments showing that the ambient MgCa ratio actually governs the skeletal mineralogy of some simple organisms. In modern seas, coralline algae produce skeletons of high-Mg calcite (>4 mol % MgCO(3)). We grew three species of these algae in artificial seawaters having three different MgCa ratios. All of the species incorporated amounts of Mg into their skeletons in proportion to the ambient MgCa ratio, mimicking the pattern for nonskeletal precipitation. Thus, the algae calcified as if they were simply inducing precipitation from seawater through their consumption of CO(2) for photosynthesis; presumably organic templates specify the calcite crystal structure of their skeletons. In artificial seawater with the low MgCa ratio of Late Cretaceous seas, the algae in our experiments produced low-Mg calcite (MgCO(3)), the carbonate mineral formed by nonskeletal precipitation in those ancient seas. Our results suggest that many taxa that produce high-Mg calcite today produced low-Mg calcite in Late Cretaceous seas. PMID:12399549

  8. Palaeointensity and palaeomagnetic study of Cretaceous and Palaeocene rocks from Western Antarctica

    Science.gov (United States)

    Shcherbakova, V. V.; Bakhmutov, V. G.; Shcherbakov, V. P.; Zhidkov, G. V.; Shpyra, V. V.

    2012-04-01

    A combined palaeodirectional and palaeointensity study of a representative collection of plutonic rocks from the Antarctic Peninsula batholith from the western part of the Antarctic Peninsula, near the Ukrainian Antarctic base 'Academik Vernadsky' were carried out. Petrographically, the collection includes gabbros, diorites and quartz diorites, tonalities, granodiorites and granites. The ages of igneous complex emplacement vary from 50 to 117 Ma with most of the rocks belonging to the Cretaceous Normal Superchron. The characteristic remanent magnetizations were isolated by stepwise thermal demagnetization over the temperature interval 440-590°C and their intensities amount to 95 per cent of the NRM. The geographic positions of palaeopoles do not contradict the 'key poles' of the Antarctic Peninsula between 90 and 60 Ma. A significant part of the collection was subjected to Coe-modified Thellier palaeointensity experiments with the pTRM checks, which yielded seven reliable palaeointensity determinations for seven different locations. The obtained VDMs are relatively low for all sites, being on average about half of the present day VDM. The analysis of available palaeointensity data for the Cretaceous, Miocene and Middle Jurassic indicates the existence of strong correlations between the mean VDM and VDM scatter versus the rate of reversals. However, due to the shortage of data, the correlations are not significant at the 5 per cent significance level.

  9. Endolithic fungi: A possible killer for the mass extinc-tion of Cretaceous dinosaurs

    Institute of Scientific and Technical Information of China (English)

    GONG YiMing; XU Ran; HU Bi

    2008-01-01

    Mycelium-like structures found under ESEM within radial sections of fragmental dinosaur eggshells would be the endolithic fungi coexistent with dinosaur eggs in the upper part of the Late Cretaceous Hugang Formation from the Wenjiaping section of Wenxian, Danjiangkou, northwestern Hubei, Central China. The endolithic fungi selectively occurred in the bad biomineral zone within the columnar layer of the eggshells, where the crowded endolithic fungi penetrated the columnar layer at near-vertical or near-horizontal angles. The endolithic fungi are needle-like, ribbon-like and silk-like, and 5-18 μm long, 0.3-0.5 μm wide at their base, with pointed tip, and are unbranched. The hyphae are mainly composed of oxygen, carbon and calcium, and are with minor sodium, potassium, chlorine and sulfur. The en-dolithic fungi and host have the same characters in lithification, fracture and main chemical composi-tion. We suggested that the episode endolithic fungi invading dinosaur eggs may have taken place in the interval between after formation of dinosaur eggshells and before their petrifaction and that dino-saur eggs invaded by endolithic fungi would not be normally incubated or would only be incubated into venerable and pathologic baby dinosaurs to be easily to aborted and contributed to the mass extinction of the dinosaurs at the end of Cretaceous.

  10. Endolithic fungi: A possible killer for the mass extinction of Cretaceous dinosaurs

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Mycelium-like structures found under ESEM within radial sections of fragmental dinosaur eggshells would be the endolithic fungi coexistent with dinosaur eggs in the upper part of the Late Cretaceous Hugang Formation from the Wenjiaping section of Wenxian, Danjiangkou, northwestern Hubei, Central China. The endolithic fungi selectively occurred in the bad biomineral zone within the columnar layer of the eggshells, where the crowded endolithic fungi penetrated the columnar layer at near-vertical or near-horizontal angles. The endolithic fungi are needle-like, ribbon-like and silk-like, and 5-18 μm long, 0.3-0.5 μm wide at their base, with pointed tip, and are unbranched. The hyphae are mainly composed of oxygen, carbon and calcium, and are with minor sodium, potassium, chlorine and sulfur. The en-dolithic fungi and host have the same characters in lithification, fracture and main chemical composi-tion. We suggested that the episode endolithic fungi invading dinosaur eggs may have taken place in the interval between after formation of dinosaur eggshells and before their petrifaction and that dino-saur eggs invaded by endolithic fungi would not be normally incubated or would only be incubated into venerable and pathologic baby dinosaurs to be easily to aborted and contributed to the mass extinction of the dinosaurs at the end of Cretaceous.

  11. The first freshwater mosasauroid (Upper Cretaceous, Hungary and a new clade of basal mosasauroids.

    Directory of Open Access Journals (Sweden)

    László Makádi

    Full Text Available Mosasauroids are conventionally conceived of as gigantic, obligatorily aquatic marine lizards (1000s of specimens from marine deposited rocks with a cosmopolitan distribution in the Late Cretaceous (90-65 million years ago [mya] oceans and seas of the world. Here we report on the fossilized remains of numerous individuals (small juveniles to large adults of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya that represent the first known mosasauroid that lived in freshwater environments. Previous to this find, only one specimen of a marine mosasauroid, cf. Plioplatecarpus sp., is known from non-marine rocks in Western Canada. Pannoniasaurus inexpectatus gen. et sp. nov. uniquely possesses a plesiomorphic pelvic anatomy, a non-mosasauroid but pontosaur-like tail osteology, possibly limbs like a terrestrial lizard, and a flattened, crocodile-like skull. Cladistic analysis reconstructs P. inexpectatus in a new clade of mosasauroids: (Pannoniasaurus (Tethysaurus (Yaguarasaurus, Russellosaurus. P. inexpectatus is part of a mixed terrestrial and freshwater faunal assemblage that includes fishes, amphibians turtles, terrestrial lizards, crocodiles, pterosaurs, dinosaurs and birds.

  12. Evidence of temporary mining in the Cretaceous fossil mine assemblage of Negev,Israel

    Institute of Scientific and Technical Information of China (English)

    Valentin A.Krassilov

    2008-01-01

    Temporary mining is a peculiar behavioral trait in leaf parasites requiring adaptations of consecutive larval stages to the endophytic and ectophytic life.The first fossil evidence for the origin of the trait comes from the Cretaceous (Turonian) plant-insect locality of the Negev Desert containing rich trace assemblages of leaf parasites,including blotch mines with leaf pieces cut out for case construction,as well as attached larval cases.The host plants are deciduous broadleafs or aquatic angiosperms with emergent leaves,suggesting that initial acquisition of the habit might have been related to leaf abscission and the risk for the larva being chocked in the mine during floods.Unlike tracks of permanent miners,temporary mines never co-occur on leaves with other type mines,which attests to their effect of enhancing plant resistance.Mine predation appears to have been widespread in the Cretaceous biotic community,suggesting a possibility of top-down regulation of mining habits at this early stage of their evolutionary development.

  13. Unconformity related traps and production, Lower Cretaceous through Mississippian Strata, central and northern Rocky Mountains

    Energy Technology Data Exchange (ETDEWEB)

    Dolson, J. (Amoco Production Co., Denver, CO (USA))

    1990-05-01

    Unconformities provide a useful means of equating stratigraphic traps between basins. Systematic mapping can define new concepts through analogy, often from geographically separate areas. Lower Cretaceous through Mississippian surfaces in the central and northern Rockies provide examples. Late Mississippian and Early Pennsylvanian surfaces formed at least four paleodrainage basins separated by the Transcontinental arch. Tyler Formation valley fills (Montana, North Dakota) have produced more than 100 million BOE. Analogous targets in Utah remain untested, but the Mid-Continent Morrow trend continues to yield new reserves. Permian and Triassic paleodrainages filled primarily with seals and form regional traps. A breached Madison trap (Mississippian, Colorado), more than 350 million BOE (Permian Minnelusa, Wyoming), more than 8 billion BOE (from the White Rim Sandstone tar deposits Permian Utah), and eastern Williston basin (Mississippian) are examples. Minor basal valley fill trapping also occurs. Transgressive carbonate facies changes have trapped more than 40 million BOE (Permian Phosphoria Formation, Wyoming). Additional deep gas potential exists. Jurassic unconformities control seal distribution over Nugget Sandstone (Jurassic) reservoirs and partially control Mississippian porosity on the Sweetgrass arch (Montana). Minor paleohill trapping also occurs. Lower Cretaceous surfaces have trapped nearly 2 billion BOE hydrocarbons in 10 paleodrainage networks. Undrilled paleodrainage basins remain deep gas targets. The systematic examination of Rocky Mountain unconformities has been understudied. New exploration concepts and reserve additions await the creative interpreter.

  14. A new pterosaur (Pterodactyloidea: Azhdarchidae from the Upper Cretaceous of Morocco.

    Directory of Open Access Journals (Sweden)

    Nizar Ibrahim

    Full Text Available The Kem Kem beds in South Eastern Morocco contain a rich early Upper (or possibly late Lower Cretaceous vertebrate assemblage. Fragmentary remains, predominantly teeth and jaw tips, represent several kinds of pterosaur although only one species, the ornithocheirid Coloborhynchus moroccensis, has been named. Here, we describe a new azhdarchid pterosaur, Alanqa saharica nov. gen. nov. sp., based on an almost complete well preserved mandibular symphysis from Aferdou N'Chaft. We assign additional fragmentary jaw remains, some of which have been tentatively identified as azhdarchid and pteranodontid, to this new taxon which is distinguished from other azhdarchids by a remarkably straight, elongate, lance-shaped mandibular symphysis that bears a pronounced dorsal eminence near the posterior end of its dorsal (occlusal surface. Most remains, including the holotype, represent individuals of approximately three to four meters in wingspan, but a fragment of a large cervical vertebra, that probably also belongs to A. saharica, suggests that wingspans of six meters were achieved in this species. The Kem Kem beds have yielded the most diverse pterosaur assemblage yet reported from Africa and provide the first clear evidence for the presence of azhdarchids in Gondwana at the start of the Late Cretaceous. This, the relatively large size achieved by Alanqa, and the additional evidence of variable jaw morphology in azhdarchids provided by this taxon, indicates a longer and more complex history for this clade than previously suspected.

  15. The bivalve Anopaea (Inoceramidae) from the Upper Jurassic-lowermost Cretaceous of Mexico

    Science.gov (United States)

    Zell, Patrick; Crame, J. Alistair; Stinnesbeck, Wolfgang; Beckmann, Seija

    2015-07-01

    In Mexico, the Upper Jurassic to lowermost Cretaceous La Casita and coeval La Caja and La Pimienta formations are well-known for their abundant and well-preserved marine vertebrates and invertebrates. The latter include conspicuous inoceramid bivalves of the genus Anopaea not formally described previously from Mexico. Anopaea bassei (Lecolle de Cantú, 1967), Anopaea cf. stoliczkai (Holdhaus, 1913), Anopaea cf. callistoensis Crame and Kelly, 1995 and Anopaea sp. are rare constituents in distinctive Tithonian-lower Berriasian levels of the La Caja Formation and one Tithonian horizon of the La Pimienta Formation. Anopaea bassei was previously documented from the Tithonian of central Mexico and Cuba, while most other members of Anopaea described here are only known from southern high latitudes. The Mexican assemblage also includes taxa which closely resemble Anopaea stoliczkai from the Tithonian of India, Indonesia and the Antarctic Peninsula, and Anopaea callistoensis from the late Tithonian to ?early Berriasian of the Antarctic Peninsula. Our new data expand the palaeogeographical distribution of the high latitude Anopaea to the Gulf of Mexico region and substantiate faunal exchange, in the Late Jurassic-earliest Cretaceous, between Mexico and the Antarctic Realm.

  16. A new saurolophine dinosaur from the latest cretaceous of far Eastern Russia.

    Directory of Open Access Journals (Sweden)

    Pascal Godefroit

    Full Text Available BACKGROUND: Four main dinosaur sites have been investigated in latest cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation, Blagoveschensk and Kundur in Russia (Udurchukan Formation. More than 90% of the bones discovered in these localities belong to hollow-crested lambeosaurine saurolophids, but flat-headed saurolophines are also represented: Kerberosaurus manakini at Blagoveschensk and Wulagasaurus dongi at Wulaga. METHODOLOGY/PRINCIPAL FINDINGS: Herein we describe a new saurolophine dinosaur, Kundurosaurus nagornyi gen. et sp. nov., from the Udurchukan Formation (Maastrichtian of Kundur, represented by disarticulated cranial and postcranial material. This new taxon is diagnosed by four autapomorphies. CONCLUSIONS/SIGNIFICANCE: A phylogenetic analysis of saurolophines indicates that Kundurosaurus nagornyi is nested within a rather robust clade including Edmontosaurus spp., Saurolophus spp., and Prosaurolophus maximus, possibly as a sister-taxon for Kerberosaurus manakini also from the Udurchukan Formation of Far Eastern Russia. The high diversity and mosaic distribution of Maastrichtian hadrosaurid faunas in the Amur-Heilongjiang region are the result of a complex palaeogeographical history and imply that many independent hadrosaurid lineages dispersed without any problem between western America and eastern Asia at the end of the Cretaceous.

  17. Paleomagnetic constraints on the late Cretaceous and Cenozoic tectonics of southeastern Asia

    Science.gov (United States)

    Achache, José; Courtillot, Vincent; Besse, Jean

    1983-04-01

    Many features of the Cenozoic tectonic history of central and southeastern Asia can be understood as direct consequences of the thrust and penetration of India into Asia. Recent indentation experiments with plasticine (Tapponnier et al. [7]) have extended this idea and have led to the prediction of a pattern of large rotations and displacements of continental blocks that can be tested by paleomagnetism. The available Cretaceous and Cenozoic paleomagnetic data from this part of the world have been reviewed and a new APWP for Eurasia has been constructed for reference. The negligible rotation of South China and large clockwise rotation of Indochina are consistent with the model, i.e., with an history of large-scale left-lateral strike-slip motion along the Altyn Tagh and Red River faults. Data from Malaya and Borneo can be reconciled with the model, although in a less straightforward fashion. The large counter clockwise rotation of South Tibet implies that it rotated in sympathy with India during the collision and suggests that future indentation experiments should include this feature. Finally a middle Cretaceous reconstruction of the south margin of Asia is proposed. One interesting result is the restored continuity of geological features in Tibet and Indochina, with active subduction of oceanic (Indian plate) crust taking place to the south at subtropical latitudes.

  18. El Niño-Southern oscillation variability from the late cretaceous marca shale of California

    Science.gov (United States)

    Davies, Andrew; Kemp, Alan E.S.; Weedon, Graham P.; Barron, John A.

    2012-01-01

    Changes in the possible behavior of El Niño–Southern Oscillation (ENSO) with global warming have provoked interest in records of ENSO from past “greenhouse” climate states. The latest Cretaceous laminated Marca Shale of California permits a seasonal-scale reconstruction of water column flux events and hence interannual paleoclimate variability. The annual flux cycle resembles that of the modern Gulf of California with diatoms characteristic of spring upwelling blooms followed by silt and clay, and is consistent with the existence of a paleo–North American Monsoon that brought input of terrigenous sediment during summer storms and precipitation runoff. Variation is also indicated in the extent of water column oxygenation by differences in lamina preservation. Time series analysis of interannual variability in terrigenous sediment and diatom flux and in the degree of bioturbation indicates strong periodicities in the quasi-biennial (2.1–2.8 yr) and low-frequency (4.1–6.3 yr) bands both characteristic of ENSO forcing, as well as decadal frequencies. This evidence for robust Late Cretaceous ENSO variability does not support the theory of a “permanent El Niño,” in the sense of a continual El Niño–like state, in periods of warmer climate.

  19. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The CMS Communications Group, established at the start of 2010, has been strengthening the activities in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The Communications Group has invested a lot of effort to support the operations needs of CMS. Hence, the CMS Centres where physicists work on remote CMS shifts, Data Quality Monitoring, and Data Analysis are running very smoothly. There are now 55 CMS Centres worldwide, up from just 16 at the start of CMS data-taking. The latest to join are Imperial College London, the University of Iowa, and the Università di Napoli. The CMS Centre@CERN in Meyrin, which is now full repaired after the major flooding at the beginning of the year, has been at the centre of CMS offline and computing operations, most recently hosting a large fraction of the CMS Heavy Ion community during the lead-lead run. A number of sub-detector shifts can now take pla...

  20. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS Offline and Computing operations, and a number of subdetector shifts can now take place there, rather than in the main Control Room at P5. A new CMS meeting room has been equipped for videoconferencing in building 42, next to building 40. Our building 28 meeting room and the facilities at P5 will be refurbished soon and plans are underway to steadily upgrade the ageing equipment in all 15 CMS meeting rooms at CERN. The CMS evaluation of the Vidyo tool indicates that it is not yet ready to be considered as a potential replacement for EVO. The Communications Group provides the CMS-TV (web) cha...