WorldWideScience

Sample records for thick late triassic

  1. A theropod tooth from the Late Triassic of southern Africa

    Indian Academy of Sciences (India)

    An isolated, large recurved and finely serrated tooth found associated with the prosauropod Euskelosaurus from the Late Triassic part of the Elliot Formation is described here. It is compared to the Triassic thecodonts and carnivorous dinosaurs and its possible affinity is discussed. The tooth possibly belongs to a basal ...

  2. Assessing the record and causes of Late Triassic extinctions

    Science.gov (United States)

    Tanner, L.H.; Lucas, S.G.; Chapman, M.G.

    2004-01-01

    Accelerated biotic turnover during the Late Triassic has led to the perception of an end-Triassic mass extinction event, now regarded as one of the "big five" extinctions. Close examination of the fossil record reveals that many groups thought to be affected severely by this event, such as ammonoids, bivalves and conodonts, instead were in decline throughout the Late Triassic, and that other groups were relatively unaffected or subject to only regional effects. Explanations for the biotic turnover have included both gradualistic and catastrophic mechanisms. Regression during the Rhaetian, with consequent habitat loss, is compatible with the disappearance of some marine faunal groups, but may be regional, not global in scale, and cannot explain apparent synchronous decline in the terrestrial realm. Gradual, widespread aridification of the Pangaean supercontinent could explain a decline in terrestrial diversity during the Late Triassic. Although evidence for an impact precisely at the boundary is lacking, the presence of impact structures with Late Triassic ages suggests the possibility of bolide impact-induced environmental degradation prior to the end-Triassic. Widespread eruptions of flood basalts of the Central Atlantic Magmatic Province (CAMP) were synchronous with or slightly postdate the system boundary; emissions of CO2 and SO2 during these eruptions were substantial, but the contradictory evidence for the environmental effects of outgassing of these lavas remains to be resolved. A substantial excursion in the marine carbon-isotope record of both carbonate and organic matter suggests a significant disturbance of the global carbon cycle at the system boundary. Release of methane hydrates from seafloor sediments is a possible cause for this isotope excursion, although the triggering mechanism and climatic effects of such a release remain uncertain. ?? 2003 Elsevier B.V. All rights reserved.

  3. Death in Guizhou — Late Triassic drowning of the Yangtze carbonate platform

    Science.gov (United States)

    Enos, Paul; Wei Jiayong; Lehrmann, Daniel J.

    1998-06-01

    The Yangtze platform in south China formed a stable palaeogeographic element from the Late Proterozoic to the end of the Middle Triassic with deposition of shallow-water carbonates during much of this time. A portion of the Yangtze platform in south-central Guizhou drowned at the transition from Permian to Triassic, as the south-adjacent Nanpanjiang basin encroached about 100 km northward, but a new, stable platform margin was established that persisted through the Early and Middle Triassic. This long history as a stable carbonate platform ended at the transition from the Ladinian to the Carnian. The latest Ladinian rocks, the Yangliujing Formation, are 490 m of shoaling-upward carbonate cycles of grapestone and bioclastic grainstone, fenestral limestone, and stromatolitic dolomudstone, commonly overprinted by extensive subaerial diagenesis. The beginning of the Carnian is marked by a rapid transition to medium-dark-grey, nodular lime mudstones containing ammonoids, conodonts and thin-shelled bivalves, the Zhuganpo Formation. The upper part of this thin pelagic limestone contains many muddy intraclasts, some slightly bored and encrusted, indicating incipient cementation. The overlying Wayao Formation is a condensed black shale with thin interbeds of dark-grey, manganiferous lime mudstone near the base. Ammonoids, conodonts, thin-shelled bivalves, and articulated crinoid stems are abundant. Fine-grained greywacke with sole marks forms prominent bundles within grey, calcareous shale in the overlying Laishike Formation. Ammonoids and thin-shelled bivalves occur sporadically in this 810-m-thick unit. Calcareous shale with thicker-shelled bivalves and packages of cleaner, coarser-grained sandstone characterize the Banan Formation, 460 m thick. The sandstone units generally coarsen and thicken upward, with ripples, medium-scale trough cross-beds, and rare U-tube burrows. Quartzose, coal-bearing siliciclastics 690 m thick form the overlying Huobachong Formation. Thick

  4. An ancestral turtle from the Late Triassic of southwestern China.

    Science.gov (United States)

    Li, Chun; Wu, Xiao-Chun; Rieppel, Olivier; Wang, Li-Ting; Zhao, Li-Jun

    2008-11-27

    The origin of the turtle body plan remains one of the great mysteries of reptile evolution. The anatomy of turtles is highly derived, which renders it difficult to establish the relationships of turtles with other groups of reptiles. The oldest known turtle, Proganochelys from the Late Triassic period of Germany, has a fully formed shell and offers no clue as to its origin. Here we describe a new 220-million-year-old turtle from China, somewhat older than Proganochelys, that documents an intermediate step in the evolution of the shell and associated structures. A ventral plastron is fully developed, but the dorsal carapace consists of neural plates only. The dorsal ribs are expanded, and osteoderms are absent. The new species shows that the plastron evolved before the carapace and that the first step of carapace formation is the ossification of the neural plates coupled with a broadening of the ribs. This corresponds to early embryonic stages of carapace formation in extant turtles, and shows that the turtle shell is not derived from a fusion of osteoderms. Phylogenetic analysis places the new species basal to all known turtles, fossil and extant. The marine deposits that yielded the fossils indicate that this primitive turtle inhabited marginal areas of the sea or river deltas.

  5. Picrite "Intelligence" from the Middle-Late Triassic Stikine arc: Composition of mantle wedge asthenosphere

    Science.gov (United States)

    Milidragovic, D.; Zagorevski, A.; Weis, D.; Joyce, N.; Chapman, J. B.

    2018-05-01

    Primitive, near-primary arc magmas occur as a volumetrically minor ≤100 m thick unit in the Canadian Cordillera of northwestern British Columbia, Canada. These primitive magmas formed an olivine-phyric, picritic tuff near the base of the Middle-Late Triassic Stuhini Group of the Stikine Terrane (Stikinia). A new 40Ar/39Ar age on hornblende from a cross-cutting basaltic dyke constrains the tuff to be older than 221 ± 2 Ma. An 87Sr/86Sr isochron of texturally-unmodified tuff samples yields 212 ± 25 Ma age, which is interpreted to represent syn-depositional equilibration with sea-water. Parental trace element magma composition of the picritic tuff is strongly depleted in most incompatible trace elements relative to MORB and implies a highly depleted ambient arc mantle. High-precision trace element and Hf-Nd-Pb isotopic analyses indicate an origin by mixing of a melt of depleted ambient asthenosphere with ≤2% of subducted sediment melt. Metasomatic addition of non-conservative incompatible elements through melting of subducted Panthalassa Ocean floor sediments accounts for the arc signature of the Stuhini Group picritic tuff, enrichment of light rare earth elements (LREE) relative to heavy rare earth elements (HREE) and high field strength elements (HFSE), and anomalous enrichment in Pb. The inferred Panthalassan sediments are similar in composition to the Neogene-Quaternary sediments of the modern northern Cascadia Basin. The initial Hf isotopic composition of the picritic tuff closely approximates that of the ambient Middle-Late Triassic asthenosphere beneath Stikinia and is notably less radiogenic than the age-corrected Hf isotopic composition of the Depleted (MORB) Mantle reservoir (DM or DMM). This suggests that the ambient asthenospheric mantle end-member experienced melt depletion (F ≤ 0.05) a short time before picrite petrogenesis. The mantle end-member in the source of the Stuhini Group picritic tuff is isotopically similar to the mantle source of

  6. Short-snouted toothless ichthyosaur from China suggests Late Triassic diversification of suction feeding ichthyosaurs.

    Directory of Open Access Journals (Sweden)

    P Martin Sander

    Full Text Available BACKGROUND: Ichthyosaurs were an important group of Mesozoic marine reptiles and existed from the Early Triassic to the early Late Cretaceous. Despite a great diversity in body shapes and feeding adaptations, all share greatly enlarged eyes, an elongated rostrum with numerous conical teeth, and a streamlined body. METHODOLOGY/PRINCIPAL FINDINGS: Based on new material from China and the restudy of Shastasaurus pacificus, we here reinterpret the classical large-bodied Late Triassic ichthyosaur genus Shastasaurus to differ greatly from the standard ichthyosaurian body plan, indicating much greater morphological diversity and range of feeding adaptations in ichthyosaurs than previously recognized. Phylogenetic analysis indicates a monophyletic clade consisting of the giant Shonisaurus sikanniensis, Guanlingsaurus liangae, and Shastasaurus pacificus to which the genus name Shastasaurus is applied. Shastasaurus liangae comb. nov. is from the Late Triassic (Carnian Xiaowa Formation of Guizhou Province, southwestern China. The species combines a diminutive head with an entirely toothless and greatly reduced snout. The species also has by far the highest vertebral count among ichthyosaurs (86 presacral vertebrae and >110 caudal vertebrae, a count that is also very high for tetrapods in general. A reduced toothless snout and a diminutive head is also apparently present in the giant S. sikanniensis and presumably in S. pacificus. CONCLUSIONS/SIGNIFICANCE: In analogy to many modern odontocetes, Shastasaurus is interpreted as a specialized suction feeder on unshelled cephalopods and fish, suggesting a unique but widespread Late Triassic diversification of toothless, suction-feeding ichthyosaurs. Suction feeding has not been hypothesized for any of the other diverse marine reptiles of the Mesozoic before, but in Shastasaurus may be linked to the Late Triassic minimum in atmospheric oxygen.

  7. OLDEST STEM TELEOSTEI FROM THE LATE LADINIAN (MIDDLE TRIASSIC OF SOUTHERN CHINA

    Directory of Open Access Journals (Sweden)

    ANDREA TINTORI

    2015-11-01

    Full Text Available The origin of the largest modern vertebrate group, the Teleostei, saw major refinements in the last decades, thanks to newly discovered and stratigraphically closely spaced Triassic Lagerstätten. Here we report the oldest Pholidophoriformes (stem teleosts that were collected during a large scale yet detailed excavation of Upper Ladinian (Middle Triassic marine deposits in Xingyi City, Guizhou Province, China. Taxonomic comparisons support the erection of a new pholidophorid genus, Malingichthys gen. nov., with two species. The new genus shows a partially fused skull roof, a preopercular bone with a hockey-stick shape and, for the first time in Pholidophoridae, supraneural elements. Most Triassic marine vertebrate clades (fishes and reptiles, Malingichthys included first emerged in the South China Block, with Late Ladinian most showing an important faunal transformation that was strengthened by our last findings. The material here described is about 2 million years older than the previous records for pholidophorids. 

  8. Osteology of the Late Triassic aetosaur Scutarx deltatylus (Archosauria: Pseudosuchia

    Directory of Open Access Journals (Sweden)

    William G. Parker

    2016-08-01

    Full Text Available Aetosaurians are some of the most common fossils collected from the Upper Triassic Chinle Formation of Arizona, especially at the Petrified Forest National Park (PEFO. Aetosaurians collected from lower levels of the park include Desmatosuchus spurensis, Paratypothorax, Adamanasuchus eisenhardtae, Calyptosuchus wellesi, and Scutarx deltatylus. Four partial skeletons collected from the park between 2002 and 2009 represent the holotype and referred specimens of Scutarx deltatylus. These specimens include much of the carapace, as well as the vertebral column, and shoulder and pelvic girdles, and a new naming convention proposed for osteoderms descriptions better differentiates portions of the carapace and ventral armor. A partial skull from the holotype specimen represents the first aetosaur skull recovered and described from Arizona since the 1930s. The key morphological feature distinguishing Scutarx deltatylus is the presence of a prominent, triangular boss located in the posteromedial corner of the dorsal surface of the dorsal paramedian osteoderms. Scutarx deltatylus can be distinguished from closely related forms Calyptosuchus wellesi and Adamanasuchus eisenhardtae not only morphologically, but also stratigraphically. Thus, Scutarx deltatylus is potentially an index taxon for the upper part of the Adamanian biozone.

  9. THE LATE TRIASSIC ARCHOSAUROMORPH TRILOPHOSAURUS AS AN ARBOREAL CLIMBER

    Directory of Open Access Journals (Sweden)

    JUSTIN A. SPIELMANN

    2005-11-01

    Full Text Available Two species of the unusual archosauromorph Trilophosaurus, T. buettneri Case and T. jacobsi Murry, are known from diverse localities in the Upper Triassic Chinle Group in the southwestern USA. Both species likely occupied similar ecological niches, based on morphological similarities in the postcrania, which are essentially identical. Trilophosaurus occurrences in the Chinle Group are relatively rare, but individual sites are exceptionally rich, suggesting that Trilophosaurus lived in a different paleoenvironment than more typical Chinle vertebrates, which lived in or near streams (phytosaurs, metoposaurs or on floodplains (aetosaurs, rauisuchians, and dinosaurs. Two potential interpretations are that Trilophosaurus was either an arboreal climber or a fossorial digger. However, the gross skeletal features of Trilophosaurus are not compatible with a fossorial mode of life: the limbs are too long and gracile, proximal limb elements are longer than distal ones, and the claws are laterally compressed, not transversely broadened. The intermittent study of Trilophosaurus has caused the theory of it being arboreal, originally proposed by Gregory, to receive little mention in subsequent studies. We reexamined the functional morphology of Trilophosaurus using a qualitative functional morphological analysis of the skeleton, a quantitative examination of claw curvature, and a quantitative examination of manus/trunk and pes/trunk ratios. Claw morphology of Trilophosaurus shows similarities to the arboreal drepanosaurs Drepanosaurus and Megalancosaurus. Our analysis provides ample evidence to suggest that Trilophosaurus was arboreal. 

  10. Late Devonian and Triassic basalts from the southern continental ...

    Indian Academy of Sciences (India)

    continental margin of the East European Platform, tracers of a single heterogeneous ... Areas of Precambrian consolidation within the Late Paleozoic orogen; 3. Areas of ...... and hydrocarbon accumulations; J. Petroleum Geology. 16 183–196.

  11. Depositional environments of Late Triassic lake, east-central New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Hester, P.M. (Bureau of Land Management, Albuquerque, NM (USA))

    1989-09-01

    The Redonda Member of the Chinle Formation represents deposition in a large, polymictic lake during the Late Triassic (Norian) in east-central New Mexico. This study documents and defines an extensive lacustrine system situated in western Pangaea which was influenced by both tectonic and climatic events. Areal extent of the lake may have been as much as 5,000 km{sup 2}.

  12. VALLESAURUS CENENSIS WILD, 1991, A DREPANOSAURID (REPTILIA DIAPSIDA FROM THE LATE TRIASSIC OF NORTHERN ITALY

    Directory of Open Access Journals (Sweden)

    SILVIO RENESTO

    2006-03-01

    Full Text Available Vallesaurus cenensis, a small drepanosaurid reptile from the Norian (Late Triassic beds of the Calcare di Zorzino (Zorzino Limestone is described. The holotype and only known specimen represents the first drepanosaurid in which the skull is preserved articulated with the postcranial skeleton. The study of Vallesaurus anatomy confirms previous data about arboreal adaptation in all known drepanosaurids and permits more firm hypotheses about the phylogenetic relationships of the Drepanosauridae to be proposed.

  13. Late Permian to Triassic intraplate orogeny of the southern Tianshan and adjacent regions, NW China

    Directory of Open Access Journals (Sweden)

    Wei Ju

    2014-01-01

    Based on previous studies and recent geochronogical data, we suggest that the final collision between the Tarim Craton and the North Asian continent occurred during the late Carboniferous. Therefore, the Permian was a period of intracontinental environment in the southern Tianshan and adjacent regions. We propose that an earlier, small-scale intraplate orogenic stage occurred in late Permian to Triassic time, which was the first intraplate process in the South Tianshan Orogen and adjacent regions. The later large-scale and well-known Neogene to Quaternary intraplate orogeny was induced by the collision between the India subcontinent and the Eurasian plate. The paper presents a new evolutionary model for the South Tianshan Orogen and adjacent regions, which includes seven stages: (I late Ordovician–early Silurian opening of the South Tianshan Ocean; (II middle Silurian–middle Devonian subduction of the South Tianshan Ocean beneath an active margin of the North Asian continent; (III late Devonian–late Carboniferous closure of the South Tianshan Ocean and collision between the Kazakhstan-Yili and Tarim continental blocks; (IV early Permian post-collisional magmatism and rifting; (V late Permian–Triassic the first intraplate orogeny; (VI Jurassic–Palaeogene tectonic stagnation and (VII Neocene–Quaternary intraplate orogeny.

  14. Late Triassic sedimentary records in the northern Tethyan Himalaya: Tectonic link with Greater India

    Directory of Open Access Journals (Sweden)

    Huawen Cao

    2018-01-01

    strata. The Tethyan Himalaya was part of the northern passive margin and was not an exotic terrane separated from India during the Permian to Early Cretaceous. This evidence suggests that the Neo-Tethyan ocean opened prior to the Late Triassic and that the Upper Triassic deposits were derived from continental crustal fragments adjacent to the northern passive continental margin of Greater India.

  15. Late Triassic paleolatitude of the Qiangtang block: Implications for the closure of the Paleo-Tethys Ocean

    Science.gov (United States)

    Song, Peiping; Ding, Lin; Li, Zhenyu; Lippert, Peter C.; Yang, Tianshui; Zhao, Xixi; Fu, Jiajun; Yue, Yahui

    2015-08-01

    To better constrain the Late Triassic paleolatitude of the Qiangtang block and the closure of the Paleo-Tethys Ocean, a combined paleomagnetic and zircon U/Pb geochronological study has been conducted on the Upper Triassic Jiapila Formation volcanic rocks on the northern edge of the Qiangtang block of Central Tibet (34.1°N, 92.4°E). These rocks are dated to 204-213 Ma. Progressive thermal or alternating field demagnetization successfully isolated stable characteristic remanent magnetizations (ChRM) that pass both the fold and reversal tests, consistent with a primary magnetization. These are the first volcanic-based paleomagnetic results from pre-Cretaceous rocks of the Qiangtang block that appear to average secular variation well enough to yield a reliable paleolatitude estimate. Based on our new paleomagnetic data from Upper Triassic lavas, we conclude that the Late Triassic pole of the Qiangtang block was located at 64.0°N, 174.7°E, with A95 = 6.6 ° (N = 29). We compile published paleomagnetic data from the Qiangtang block to calculate a Late Triassic latitude for the Qiangtang block at 31.7 ± 3.0°N. The central Paleo-Tethys Ocean basin was located between the North China (NCB) and Tarim blocks to the north and the Qiangtang block to the south during Late Paleozoic-Early Mesozoic. A comparison of published Early Triassic paleopole from the Qiangtang block with the coeval paleopoles from the NCB and Tarim indicates that the Paleo-Tethys Ocean could not have closed during the Early Triassic and that its width was approximately ∼32-38° latitude (∼3500-4200 km). However, the comparison of our new combined Late Triassic paleomagnetic result with the Late Triassic poles of the NCB and Tarim, as well as numerous geological observations, indicates that the closure of the Paleo-Tethys Ocean at the longitude of the Qiangtang block most likely occurred during the Late Triassic.

  16. The metallogeny of Late Triassic rifting of the Alexander terrane in southeastern Alaska and northwestern British Columbia

    Science.gov (United States)

    Taylor, C.D.; Premo, W.R.; Meier, A.L.; Taggart, J.E.

    2008-01-01

    A belt of unusual volcanogenic massive sulfide (VMS) occurrences is located along the eastern margin of the Alexander terrane throughout southeastern Alaska and northwestern British Columbia and exhibits a range of characteristics consistent with a variety of syngenetic to epigenetic deposit types. Deposits within this belt include Greens Creek and Windy Craggy, the economically most significant VMS deposit in Alaska and the largest in North America, respectively. The occurrences are hosted by a discontinuously exposed, 800-km-long belt of rocks that consist of a 200- to 800-m-thick sequence of conglomerate, limestone, marine elastic sedimentary rocks, and tuff intercalated with and overlain by a distinctive unit of mafic pyroclastic rocks and pillowed flows. Faunal data bracket the age of the host rocks between Anisian (Middle Triassic) and late Norian (late Late Triassic). This metallogenic belt is herein referred to as the Alexander Triassic metallogenic belt. The VMS occurrences show systematic differences in degree of structural control, chemistry, and stratigraphic setting along the Alexander Triassic metallogenic belt that suggest important spatial or temporal changes in the tectonic environment of formation. At the southern end of the belt, felsic volcanic rocks overlain by shallow-water limestones characterize the lower part of the sequence. In the southern and middle portion of the belt, a distinctive pebble conglomerate marks the base of the section and is indicative of high-energy deposition in a near slope or basin margin setting. At the northern end of the belt the conglomerates, limestones, and felsic volcanic rocks are absent and the belt is composed of deep-water sedimentary and mafic volcanic rocks. This northward change in depositional environment and lithofacies is accompanied by a northward transition from epithermal-like structurally controlled, discontinuous, vein- and pod-shaped, Pb-Zn-Ag-Ba-(Cu) occurrences with relatively simple mineralogy

  17. Isotopic evidence bearing on Late Triassic extinction events, Queen Charlotte Islands, British Columbia, and implications for the duration and cause of the Triassic/Jurassic mass extinction

    Science.gov (United States)

    Ward, P.D.; Garrison, G.H.; Haggart, J.W.; Kring, D.A.; Beattie, M.J.

    2004-01-01

    Stable isotope analyses of Late Triassic to earliest Jurassic strata from Kennecott Point in the Queen Charlotte Islands, British Columbia, Canada shows the presence of two distinct and different organic carbon isotope anomalies at the Norian/Rhaetian and Rhaetian/Hettangian (=Triassic/Jurassic) stage boundaries. At the older of these boundaries, which is marked by the disappearance of the bivalve Monotis, the isotope record shows a series of short-lived positive excursions toward heavier values. Strata approaching this boundary show evidence of increasing anoxia. At the higher boundary, marked by the disappearance of the last remaining Triassic ammonites and over 50 species of radiolarians, the isotopic pattern consists of a series of short duration negative anomalies. The two events, separated by the duration of the Rhaetian age, comprise the end-Triassic mass extinction. While there is no definitive evidence as to cause, the isotopic record does not appear similar to that of the impact-caused Cretaceous/Tertiary boundary extinction. ?? 2004 Published by Elsevier B.V.

  18. Understanding Late Triassic low latitude terrestrial ecosystems: new insights from the Colorado Plateau Coring Project (CPCP)

    Science.gov (United States)

    Irmis, R. B.; Olsen, P. E.; Parker, W.; Rasmussen, C.; Mundil, R.; Whiteside, J. H.

    2017-12-01

    The Chinle Formation of southwestern North America is a key paleontological archive of low paleolatitude non-marine ecosystems that existed during the Late Triassic hothouse world. These strata were deposited at 5-15°N latitude, and preserve extensive plant, invertebrate, and vertebrate fossil assemblages, including early dinosaurs; these organisms lived in an unpredictably fluctuating semi-arid to arid environment with very high atmospheric pCO2. Despite this well-studied fossil record, a full understanding of these ecosystems and their integration with other fossil assemblages globally has been hindered by a poor understanding of the Chinle Formation's age, duration, and sedimentation rates. Recently, the CPCP recovered a 520m continuous core through this formation from the northern portion of Petrified Forest National Park (PEFO) in northern Arizona, USA. This core has provided a plethora of new radioisotopic and magnetostratigraphic data from fresh, unweathered samples in unambiguous stratigraphic superposition. These constraints confirm that virtually all fossil-bearing horizons in Chinle outcrops in the vicinity of PEFO are Norian in age. Furthermore, they indicate that the palynomorph zone II and Adamanian vertebrate biozone are at least six million years long, whereas the overlying palynomorph zone III and Revueltian vertebrate biozone persisted for at least five million years, with the boundary between 216-214 Ma. This confirms that the rich late Adamanian-early Revueltian vertebrate fossil assemblages, where dinosaurs are exclusively rare, small-bodied carnivorous theropods, are contemporaneous with higher latitude assemblages in Europe, South America, and Africa where large-bodied herbivorous sauropodomorph dinosaurs are common. The age constraints also confirm that several palynomorph biostratigraphic ranges in the Chinle Formation differ from those of the same taxa in eastern North American (Newark Supergroup) and Europe. These data are consistent

  19. Late Triassic tropical climate of Pangea: Carbon isotopic and other insights into the rise of dinosaurs

    Science.gov (United States)

    Whiteside, J. H.; Lindström, S.; Irmis, R. B.; Glasspool, I.; Schaller, M. F.; Dunlavey, M.; Nesbitt, S. J.; Smith, N. D.; Turner, A. H.

    2015-12-01

    The rarity and species-poor nature of early dinosaurs and their relatives at low paleolatitudes persisted for 30 million years after their origin and 10-15 million years after they became abundant and speciose at higher latitudes. New environmental reconstructions from stable carbon isotope ratios of preserved organic matter (δ13Corg), atmospheric pCO2 data based on the δ13C of soil carbonate, palynological, and wildfire data from charcoal from early dinosaur-bearing strata at low paleolatitudes in western North America show that variations in δ13Corg and palynomorph ecotypes are tightly correlated, displaying large and high-frequency excursions. These variations occurred within an environment characterized by elevated and increasing atmospheric pCO2, pervasive wildfires, and rapidly fluctuating extreme climatic conditions. Whereas pseudosuchian archosaur-dominated communities were able to persist in these same regions until the end-Triassic, the large-bodied, fast-growing tachymetabolic dinosaurian herbivores were not. We hypothesize that the greater resources required by the herbivores made it difficult from them to adapt to the unstable conditions at low paleolatitudes in the Late Triassic.

  20. An early Late Triassic long-necked reptile with a bony pectoral shield and gracile appendages

    Directory of Open Access Journals (Sweden)

    Jerzy Dzik

    2016-12-01

    Full Text Available Several partially articulated specimens and numerous isolated bones of Ozimek volans gen. et sp. nov., from the late Carnian lacustrine deposits exposed at Krasiejów in southern Poland, enable a reconstruction of most of the skeleton. The unique character of the animal is its enlarged plate-like coracoids presumably fused with sterna. Other aspects of the skeleton seem to be comparable to those of the only known specimen of Sharovipteryx mirabilis from the latest Middle Triassic of Kyrgyzstan, which supports interpretation of both forms as protorosaurians. One may expect that the pectoral girdle of S. mirabilis, probably covered by the rock matrix in its only specimen, was similar to that of O. volans gen. et sp. nov. The Krasiejów material shows sharp teeth, low crescent scapula, three sacrals in a generalized pelvis (two of the sacrals being in contact with the ilium and curved robust metatarsal of the fifth digit in the pes, which are unknown in Sharovipteryx. Other traits are plesiomorphic and, except for the pelvic girdle and extreme elongation of appendages, do not allow to identify any close connection of the sharovipterygids within the Triassic protorosaurians.

  1. A new theropod dinosaur from India with remarks on the Gondwana-Laurasia connection in the Late Triassic

    Science.gov (United States)

    Chatterjee, S.

    Walkeria maleriensis (n. g., n. sp.) from the Late Triassic Maleri Formation of the Godavari Valley of India is the earliest known dinosaur from Asia. It is a small podokesaurid theropod, very similar to Procompsognathus of Germany, Coelophysis of North America, and Syntarsus from Zimbabwe and North America. The podokesaurs are of particular interest to students of organic evolution because they are the earliest known theropods from which Archaeopteryx, the oldest known fossil bird, was probably evolved. Traditionally, India has been regarded as a part of Gondwana. It is generally believed that Gondwana remained an integral geographic unit throughout the Triassic. If this is so, a strong faunal correlation between India and other Gondwana continents should be expected in Late Triassic time. Contrary to this, the Maleri fauna is overwhelmingly "northern". Walkeria occurs in association with metoposaurs, parasuchids, protorosaurs, aetosaurs, rhynchosaurs, and traversodonts. Most of these taxa have been identified in the Dockum fauna of North America, indicating a close paleontologic link between India and Laurasia. Possibly the route of faunal migration between India and North America during the Late Triassic was via northern Africa.

  2. Prolonged Permian Triassic ecological crisis recorded by molluscan dominance in Late Permian offshore assemblages.

    Science.gov (United States)

    Clapham, Matthew E; Bottjer, David J

    2007-08-07

    The end-Permian mass extinction was the largest biotic crisis in the history of animal life, eliminating as many as 95% of all species and dramatically altering the ecological structure of marine communities. Although the causes of this pronounced ecosystem shift have been widely debated, the broad consensus based on inferences from global taxonomic diversity patterns suggests that the shift from abundant brachiopods to dominant molluscs was abrupt and largely driven by the catastrophic effects of the end-Permian mass extinction. Here we analyze relative abundance counts of >33,000 fossil individuals from 24 silicified Middle and Late Permian paleocommunities, documenting a substantial ecological shift to numerical dominance by molluscs in the Late Permian, before the major taxonomic shift at the end-Permian mass extinction. This ecological change was coincident with the development of fluctuating anoxic conditions in deep marine basins, suggesting that numerical dominance by more tolerant molluscs may have been driven by variably stressful environmental conditions. Recognition of substantial ecological deterioration in the Late Permian also implies that the end-Permian extinction was the climax of a protracted environmental crisis. Although the Late Permian shift to molluscan dominance was a pronounced ecological change, quantitative counts of 847 Carboniferous-Cretaceous collections from the Paleobiology Database indicate that it was only the first stage in a stepwise transition that culminated with the final shift to molluscan dominance in the Late Jurassic. Therefore, the ecological transition from brachiopods to bivalves was more protracted and complex than their simple Permian-Triassic switch in diversity.

  3. Prolonged Permian–Triassic ecological crisis recorded by molluscan dominance in Late Permian offshore assemblages

    Science.gov (United States)

    Clapham, Matthew E.; Bottjer, David J.

    2007-01-01

    The end-Permian mass extinction was the largest biotic crisis in the history of animal life, eliminating as many as 95% of all species and dramatically altering the ecological structure of marine communities. Although the causes of this pronounced ecosystem shift have been widely debated, the broad consensus based on inferences from global taxonomic diversity patterns suggests that the shift from abundant brachiopods to dominant molluscs was abrupt and largely driven by the catastrophic effects of the end-Permian mass extinction. Here we analyze relative abundance counts of >33,000 fossil individuals from 24 silicified Middle and Late Permian paleocommunities, documenting a substantial ecological shift to numerical dominance by molluscs in the Late Permian, before the major taxonomic shift at the end-Permian mass extinction. This ecological change was coincident with the development of fluctuating anoxic conditions in deep marine basins, suggesting that numerical dominance by more tolerant molluscs may have been driven by variably stressful environmental conditions. Recognition of substantial ecological deterioration in the Late Permian also implies that the end-Permian extinction was the climax of a protracted environmental crisis. Although the Late Permian shift to molluscan dominance was a pronounced ecological change, quantitative counts of 847 Carboniferous–Cretaceous collections from the Paleobiology Database indicate that it was only the first stage in a stepwise transition that culminated with the final shift to molluscan dominance in the Late Jurassic. Therefore, the ecological transition from brachiopods to bivalves was more protracted and complex than their simple Permian–Triassic switch in diversity. PMID:17664426

  4. Volcanic sequence in Late Triassic – Jurassic siliciclastic and evaporitic rocks from Galeana, NE Mexico

    International Nuclear Information System (INIS)

    Cruz-Gómez, E.M.; Velasco-Tapia, F.; Ramírez-Fernández, J.A.; Jenchen, U.; Rodríguez-Saavedra, P.; Rodríguez-Díaz, A.A.; Iriondo, A.

    2017-01-01

    In northeastern Mexico, volcanic rocks interbedded with Late Triassic–Jurassic siliciclastic and evaporitic strata have been linked to magmatic arcs developed in the Pangea western margin during its initial phase of fragmentation. This work provides new petrographic and geochemical data for volcanism included in the El Alamar and Minas Viejas formations outcropping in the Galeana region. Andesitic dykes and sills (n= 10) in the El Alamar redbeds show SiO2= 47.5–59.1% and MgO= 1.2–4.2%, as well as a geochemical affinity to island arc magmas. This work represents the first report of this tectonic setting in the region. Geological and petrographic evidence suggest that this arc system likely developed after ~220 and before ~193Ma. Trachy-andesitic and rhyodacitic domes (n= 20) associated with the Minas Viejas gypsum-carbonates sequence show SiO2= 61.8–82.7% and MgO= 0.1–4.0% with a tectonic affinity to continental arc. A rhyodacite sample from this region has been dated by U-Pb in zircon, yielding an age of 149.4 ± 1.2Ma (n= 21), being the youngest age related to this arc. Finally, we propose a threestep model to explain the tectonic evolution from Late Triassic island arc to Jurassic continental arc system in the northeastern Mexico.

  5. Volcanic sequence in Late Triassic – Jurassic siliciclastic and evaporitic rocks from Galeana, NE Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Cruz-Gómez, E.M.; Velasco-Tapia, F.; Ramírez-Fernández, J.A.; Jenchen, U.; Rodríguez-Saavedra, P.; Rodríguez-Díaz, A.A.; Iriondo, A.

    2017-11-01

    In northeastern Mexico, volcanic rocks interbedded with Late Triassic–Jurassic siliciclastic and evaporitic strata have been linked to magmatic arcs developed in the Pangea western margin during its initial phase of fragmentation. This work provides new petrographic and geochemical data for volcanism included in the El Alamar and Minas Viejas formations outcropping in the Galeana region. Andesitic dykes and sills (n= 10) in the El Alamar redbeds show SiO2= 47.5–59.1% and MgO= 1.2–4.2%, as well as a geochemical affinity to island arc magmas. This work represents the first report of this tectonic setting in the region. Geological and petrographic evidence suggest that this arc system likely developed after ~220 and before ~193Ma. Trachy-andesitic and rhyodacitic domes (n= 20) associated with the Minas Viejas gypsum-carbonates sequence show SiO2= 61.8–82.7% and MgO= 0.1–4.0% with a tectonic affinity to continental arc. A rhyodacite sample from this region has been dated by U-Pb in zircon, yielding an age of 149.4 ± 1.2Ma (n= 21), being the youngest age related to this arc. Finally, we propose a threestep model to explain the tectonic evolution from Late Triassic island arc to Jurassic continental arc system in the northeastern Mexico.

  6. A new sphenodontian (Lepidosauria: Rhynchocephalia) from the Late Triassic of Argentina and the early origin of the herbivore opisthodontians

    Science.gov (United States)

    Martínez, Ricardo N.; Apaldetti, Cecilia; Colombi, Carina E.; Praderio, Angel; Fernandez, Eliana; Malnis, Paula Santi; Correa, Gustavo A.; Abelin, Diego; Alcober, Oscar

    2013-01-01

    Sphenodontians were a successful group of rhynchocephalian reptiles that dominated the fossil record of Lepidosauria during the Triassic and Jurassic. Although evidence of extinction is seen at the end of the Laurasian Early Cretaceous, they appeared to remain numerically abundant in South America until the end of the period. Most of the known Late Cretaceous record in South America is composed of opisthodontians, the herbivorous branch of Sphenodontia, whose oldest members were until recently reported to be from the Kimmeridgian–Tithonian (Late Jurassic). Here, we report a new sphenodontian, Sphenotitan leyesi gen. et sp. nov., collected from the Upper Triassic Quebrada del Barro Formation of northwestern Argentina. Phylogenetic analysis identifies Sphenotitan as a basal member of Opisthodontia, extending the known record of opisthodontians and the origin of herbivory in this group by 50 Myr. PMID:24132307

  7. Soft-sediment deformation structures in cores from lacustrine slurry deposits of the Late Triassic Yanchang Fm. (central China

    Directory of Open Access Journals (Sweden)

    Yang Renchao

    2016-09-01

    Full Text Available The fine-grained autochthonous sedimentation in the deep part of a Late Triassic lake was frequently interrupted by gravity-induced mass flows. Some of these mass flows were so rich in water that they must have represented slurries. This can be deduced from the soft-sediment deformation structures that abound in cores from these lacustrine deposits which constitute the Yanchang Fm., which is present in the Ordos Basin (central China.

  8. Evidence for Late Permian-Upper Triassic ocean acidification from calcium isotopes in carbonate of the Kamura section in Japan

    Science.gov (United States)

    Ye, F.; Zhao, L., Sr.; Chen, Z. Q.; Wang, X.

    2017-12-01

    Calcium and carbon cycles are tightly related in the ocean, for example, through continental weathering and deposition of carbonate, thus, very important for exploring evolutions of marine environment during the earth history. The end-Permian mass extinction is the biggest biological disaster in the Phanerozoic and there are several studies talking about variations of calcium isotopes across the Permian-Triassic boundary (PTB). However, these studies are all from the Tethys regions (Payne et al., 2010; Hinojosa et al., 2012), while the Panthalassic Ocean is still unknown to people. Moreover, evolutions of the calcium isotopes during the Early to Late Triassic is also poorly studied (Blattler et al., 2012). Here, we studied an Uppermost Permian to Upper Triassic shallow water successions (Kamura section, Southwest Japan) in the Central Panthalassic Ocean. The Kamura section is far away from the continent without any clastic pollution, therefore, could preserved reliable δ44/40Cacarb signals. Conodont zonation and carbonate carbon isotope also provide precious time framework which is necessary for the explaining of the δ44/40Cacarb profile. In Kamura, δ44/40Cacarb and δ13Ccarb both exhibit negative excursions across the PTB, the δ44/40Cacarb value in the end-Permian is 1.0398‰ then abrupt decrease to the minimum value of 0.1524‰. CO2-driven global ocean acidification best explains the coincidence of the δ44/40Cacarb excursion with negative excursions in the δ13Ccarb of carbonates until the Early Smithian(N1a, N1b, N1c, P1, N2, P2). In the Middle and the Late Triassic, the δ44/40 Cacarb average approximately 1.1‰. During the Middle and Late Triassic, strong relationships between δ44/40Cacarb and δ13Ccarb are collapsed, indicating a normal pH values of the seawater in those time. The Siberian Trap volcanism probably played a significant role on the δ44/40Cacarb until the late Early Triassic. After that, δ44/40Cacarb was mostly controlled by carbonate

  9. Provenance analysis of the Late Triassic Yichuan Basin: constraints from zircon U-Pb geochronology

    Directory of Open Access Journals (Sweden)

    Meng Xianghong

    2018-03-01

    Full Text Available Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS U-Pb dating has been performed on detrital zircons from the Chunshuyao Formation sandstone of Yichuan Basin. The ages of 85 detrital zircon grains are divided into three groups: 252-290 Ma, 1740-2000 Ma, and 2400-2600 Ma. The lack of Early Paleozoic and Neoproterozoic U-Pb ages indicates that there is no input from the Qinling Orogen, because the Qinling Orogen is characterized by Paleozoic and Neoproterozoic material. In combination with previous research, we suggest that the source of the Chunshuyao Formation is most likely recycled from previous sedimentary rocks from the North China Craton. In the Late Triassic, the Funiu ancient land was uplifted which prevented source material from the Qinling Orogen. Owing to the Indosinian orogeny, the strata to the east of the North China Craton were uplifted and eroded. The Yichuan Basin received detrital material from the North China Craton.

  10. Grooves to tubes: evolution of the venom delivery system in a Late Triassic "reptile"

    Science.gov (United States)

    Mitchell, Jonathan S.; Heckert, Andrew B.; Sues, Hans-Dieter

    2010-12-01

    Venom delivery systems occur in a wide range of extant and fossil vertebrates and are primarily based on oral adaptations. Teeth range from unmodified (Komodo dragons) to highly specialized fangs similar to hypodermic needles (protero- and solenoglyphous snakes). Developmental biologists have documented evidence for an infolding pathway of fang evolution, where the groove folds over to create the more derived condition. However, the oldest known members of venomous clades retain the same condition as their extant relatives, resulting in no fossil evidence for the transition. Based on a comparison of previously known specimens with newly discovered teeth from North Carolina, we describe a new species of the Late Triassic archosauriform Uatchitodon and provide detailed analyses that provide evidence for both venom conduction and document a complete structural series from shallow grooves to fully enclosed tubular canals. While known only from teeth, Uatchitodon is highly diagnostic in possessing compound serrations and for having two venom canals on each tooth in the dentition. Further, although not a snake, Uatchitodon sheds light on the evolutionary trajectory of venom delivery systems in amniotes and provide solid evidence for venom conduction in archosaur-line diapsids.

  11. Trajectories of Late Permian – Jurassic radiolarian extinction rates: no evidence for an end-Triassic mass extinction

    Directory of Open Access Journals (Sweden)

    W. Kiessling

    2011-02-01

    Full Text Available The hypothesis that ocean acidification was a proximate trigger of the marine end-Triassic mass extinction rests on the assumption that taxa that strongly invest in the secretion of calcium-carbonate skeletons were significantly more affected by the crisis than other taxa. An argument against this hypothesis is the great extinction toll of radiolarians that has been reported from work on local sections. Radiolarians have siliceous tests and thus should be less affected by ocean acidification. We compiled taxonomically vetted occurrences of late Permian and Mesozoic radiolarians and analyzed extinction dynamics of radiolarian genera. Although extinction rates were high at the end of the Triassic, there is no evidence for a mass extinction in radiolarians but rather significantly higher background extinction in the Triassic than in the Jurassic. Although the causes for this decline in background extinction levels remain unclear, the lack of a major evolutionary response to the end-Triassic event, gives support for the hypothesis that ocean acidification was involved in the dramatic extinctions of many calcifying taxa. doi:10.1002/mmng.201000017

  12. Astronomical tuning and magnetostratigraphy of the Upper Triassic Xujiahe Formation of South China and Newark Supergroup of North America: Implications for the Late Triassic time scale

    Science.gov (United States)

    Li, Mingsong; Zhang, Yang; Huang, Chunju; Ogg, James; Hinnov, Linda; Wang, Yongdong; Zou, Zhuoyan; Li, Liqin

    2017-10-01

    The time scale of the Late Triassic Epoch has a divergence of age models, especially for the durations of competing definitions for its Rhaetian Stage (uppermost Triassic). The astrochronology derived from relative depth of lacustrine-bearing clastic successions and astronomically tuned geomagnetic polarity time scale (APTS) of the Newark Supergroup of eastern North America provides a basis for the Late Triassic time scale. However, the Newark APTS has been challenged regarding its age scale and completeness; therefore an independent astronomical-tuned magnetic polarity zonation is required to verify the upper Newark APTS reference scale. We compiled a 6.5 million year (myr) APTS with magnetic stratigraphy from four sections of the lacustrine-fluvial, dinosaur-track-bearing Xujiahe Formation in the Sichuan Basin of South China that also has dating from detrital zircons and regional biostratigraphy. Variations in natural gamma-ray and magnetic susceptibility that reflect variable continental weathering in the source regions of the Xujiahe Formation are paced by Milankovitch cycles, especially the 100-kyr short eccentricity and 405-kyr long eccentricity. The cycle-tuned magnetostratigraphy of the Xujiahe Formation is compared directly via the magnetic-polarity zones to the depth ranks of the Newark Supergroup that are indicative of relative depths of lacustrine facies. The Sichuan APTS indicates that there is no significant hiatus between the sedimentary succession and the basalt flows at the top of the Newark Supergroup. The Sichuan APTS is compatible with the magnetostratigraphy from the candidate Global Boundary Stratotype Section and Point (GSSP) for the Norian-Rhaetian boundary interval at the Pignola-Abriola of South Italy, but does not extend downward to the proposed GSSP in Austria associated with the longer Rhaetian option. The earliest dinosaur tracks in China are from the middle of this Xujiahe Formation, therefore are implied to be middle Rhaetian in age

  13. Globacrochordiceras gen. nov. (Acrochordiceratidae, late Early Triassic and its significance for stress-induced evolutionary jumps in ammonoid lineages (cephalopods

    Directory of Open Access Journals (Sweden)

    C. Monnet

    2013-08-01

    Full Text Available Globacrochordiceras transpacificum gen. et sp. nov. is an ammonoid (Ammonoidea, Cephalopoda with a shell characterized by plicate ribbing (rounded and undulating ribs strengthening on the venter without interruption, increasing involution through ontogeny, overhanging and deep umbilical wall, absence of tuberculation, subtriangular whorl section, globose adult shape with a closed umbilicus followed by an abrupt egressive coiling, and a subammonitic adult suture line. This new taxon occurs in Nevada (USA and in Guangxi (South China. It has its typical occurrence within the Neopopanoceras haugi Zone of late Spathian age (Early Triassic. The plicate ribbing, suture line and general shell shape are diagnostic of the family Acrochordiceratidae. The large adult size, high degree of involution and subammonitic suture line of Globacrochordiceras markedly contrast with the next younger genus of the family (Paracrochordiceras of early Anisian age, Middle Triassic, which is evolute and displays a ceratitic suture shape. Shell coiling and suture line of Globacrochordiceras are closer to that of the youngest member of the family: Acrochordiceras carolinae (late middle Anisian. The latter is the end-member of a long-term morphological evolutionary trend of the family during the early and middle Anisian. This trend composed of classical increases in adult size (Cope's rule, shell involution and suture indentation, lasted ca. four Myr. The sudden morphological evolutionary jump between Globacrochordiceras and Paracrochordiceras at the Spathian/Anisian (Early/Middle Triassic boundary may correspond to a generalized morphological reset of long-term trends, a process that differs from classic paedomorphic transformations. A dramatic global sea level change and carbon isotope positive excursion at the Early/Middle Triassic boundary both indicate stressful environmental changes that may have triggered this evolutionary jump. doi:10.1002/mmng.201300010

  14. Feeding biomechanics of Late Triassic metoposaurids (Amphibia: Temnospondyli): a 3D finite element analysis approach.

    Science.gov (United States)

    Fortuny, Josep; Marcé-Nogué, Jordi; Konietzko-Meier, Dorota

    2017-06-01

    The Late Triassic freshwater ecosystems were occupied by different tetrapod groups including large-sized anamniotes, such as metoposaurids. Most members of this group of temnospondyls acquired gigantic sizes (up to 5 m long) with a nearly worldwide distribution. The paleoecology of metoposaurids is controversial; they have been historically considered passive, bottom-dwelling animals, waiting for prey on the bottom of rivers and lakes, or they have been suggested to be active mid-water feeders. The present study aims to expand upon the paleoecological interpretations of these animals using 3D finite element analyses (FEA). Skulls from two taxa, Metoposaurus krasiejowensis, a gigantic taxon from Europe, and Apachesaurus gregorii, a non-gigantic taxon from North America, were analyzed under different biomechanical scenarios. Both 3D models of the skulls were scaled to allow comparisons between them and reveal that the general stress distribution pattern found in both taxa is clearly similar in all scenarios. In light of our results, both previous hypotheses about the paleoecology of these animals can be partly merged: metoposaurids probably were ambush and active predators, but not the top predators of these aquatic environments. The FEA results demonstrate that they were particularly efficient at bilateral biting, and together with their characteristically anteropositioned orbits, optimal for an ambush strategy. Nonetheless, the results also show that these animals were capable of lateral strikes of the head, suggesting active hunting of prey. Regarding the important skull size differences between the taxa analyzed, our results suggest that the size reduction in the North American taxon could be related to drastic environmental changes or the increase of competitors. The size reduction might have helped them expand into new ecological niches, but they likely remained fully aquatic, as are all other metoposaurids. © 2017 Anatomical Society.

  15. Petrogenesis and tectonic implication of the Late Triassic post-collisional volcanic rocks in Chiang Khong, NW Thailand

    Science.gov (United States)

    Qian, Xin; Wang, Yuejun; Feng, Qinglai; Zi, Jian-Wei; Zhang, Yuzhi; Chonglakmani, Chongpan

    2016-04-01

    The volcanic rocks exposed within the Chiang Khong-Lampang-Tak igneous zone in NW Thailand provide important constraints on the tectonic evolution of the eastern Paleotethys ocean. An andesite sample from the Chiang Khong area yields a zircon U-Pb age of 229 ± 4 Ma, significantly younger than the continental-arc and syn-collisional volcanic rocks (ca. 238-241 Ma). The Chiang Khong volcanic rocks are characterized by low MgO (1.71-6.72 wt.%) and high Al2O3 (15.03-17.76 wt.%). They are enriched in LILEs and LREEs and depleted in HFSEs, and have 87Sr/86Sr (i) ratios of 0.7050-0.7065, εNd (t) of - 0.32 to - 1.92, zircon εHf (t) and δ18O values of 3.5 to - 11.7 and 4.30-9.80 ‰, respectively. The geochemical data for the volcanic rocks are consistent with an origin from the enriched lithospheric mantle that had been modified by slab-derived fluid and recycled sediments. Based on available geochronological and geochemical evidences, we propose that the Late Triassic Chiang Khong volcanic rocks are equivalent to the contemporaneous volcanic rocks in the Lancangjiang igneous zone in SW China. The formation of these volcanic rocks was possibly related to the upwelling of the asthenospheric mantle during the Late Triassic, shortly after slab detachment, which induced the melting of the metasomatized mantle wedge.

  16. Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the Early Late Triassic Ischigualasto Formation of Northwestern Argentina

    Science.gov (United States)

    Trotteyn, M. Jimena; Ezcurra, Martín D.

    2014-01-01

    Proterochampsids are crocodile-like, probably semi-aquatic, quadrupedal archosauriforms characterized by an elongated and dorsoventrally low skull. The group is endemic from the Middle-Late Triassic of South America. The most recently erected proterochampsid species is “Chanaresuchus ischigualastensis”, based on a single, fairly complete skeleton from the early Late Triassic Ischigualasto Formation of northwestern Argentina. We describe here in detail the non-braincase cranial and postcranial anatomy of this species and revisit its taxonomy and phylogenetic relationships. The phylogenetic analysis recovered ‘Chanaresuchus ischigualastensis’ as part of a trichotomy together with Gualosuchus reigi and Chanaresuchus bonapartei. Accordingly, “Chanaresuchus ischigualastensis” can be potentially more closely related to Gualosuchus reigi, or even Rhadinosuchus gracilis, than to Chanaresuchus bonapartei. In addition, after discussing previously claimed synapomorphies of Chanaresuchus, we could not find unambiguous support for the monophyly of the genus. As a result, we propose here the erection of the new genus Pseudochampsa for ‘Chanaresuchus ischigualastensis’, which results in the new combination Pseudochampsa ischigualastensis. The information provided here about the anatomy and taxonomy of Pseudochampsa ischiguaslastensis will be useful for future quantitative analyses focused on the biogeography and macroevolutionary history of proterochampsids. PMID:25426846

  17. Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae from the early late triassic ischigualasto formation of Northwestern Argentina.

    Directory of Open Access Journals (Sweden)

    M Jimena Trotteyn

    Full Text Available Proterochampsids are crocodile-like, probably semi-aquatic, quadrupedal archosauriforms characterized by an elongated and dorsoventrally low skull. The group is endemic from the Middle-Late Triassic of South America. The most recently erected proterochampsid species is "Chanaresuchus ischigualastensis", based on a single, fairly complete skeleton from the early Late Triassic Ischigualasto Formation of northwestern Argentina. We describe here in detail the non-braincase cranial and postcranial anatomy of this species and revisit its taxonomy and phylogenetic relationships. The phylogenetic analysis recovered 'Chanaresuchus ischigualastensis' as part of a trichotomy together with Gualosuchus reigi and Chanaresuchus bonapartei. Accordingly, "Chanaresuchus ischigualastensis" can be potentially more closely related to Gualosuchus reigi, or even Rhadinosuchus gracilis, than to Chanaresuchus bonapartei. In addition, after discussing previously claimed synapomorphies of Chanaresuchus, we could not find unambiguous support for the monophyly of the genus. As a result, we propose here the erection of the new genus Pseudochampsa for 'Chanaresuchus ischigualastensis', which results in the new combination Pseudochampsa ischigualastensis. The information provided here about the anatomy and taxonomy of Pseudochampsa ischiguaslastensis will be useful for future quantitative analyses focused on the biogeography and macroevolutionary history of proterochampsids.

  18. Milankovitch cyclicity in the paleotropical, fluvial, Late Triassic age strata recovered by the Colorado Plateau Coring Project (CPCP)

    Science.gov (United States)

    Olsen, P. E.; Mundil, R.; Kent, D.; Rasmussen, C.

    2017-12-01

    Two questions addressed by the CPCP are: 1) is Milankovitch-paced climate cyclicity recorded in the fluvial Late Triassic age Chinle Formation ( 227-202 Ma); and 2) do geochronological data from the Chinle support the Newark-Hartford astrochronological polarity time scale (1) (APTS). To these ends we examined the upper 157 m (stratigraphic thickness) of Petrified Forest National Park core 1A (Owl Rock, Petrified Forest, and upper Sonsela members), consisting mostly of massive red paleosols and less important fluvial sandstones. A linear age model tied to new U-Pb zircon CA ID-TIMS dates from core 1A, consistent with published data from outcrop (2), yields a duration of about 5 Myr for this interval. Magnetic susceptibility variations, interpreted as reflecting penecontemporaneous soil and sandstone redox conditions, show a clear 12 m cycle corresponding to a 400 kyr cycle based on Fourier analysis in both core and hole. Similar cyclicity is apparent in spectrophotometric data, largely reflecting hematite variability. Weak, higher frequency cycles are present consistent with 100 kyr variability. There is no interpretable 20 kyr signal. Such cyclicity is not an anticipated direct effect of Milankvitch insolation variations, but must reflect non-linear integration of variability that changes dramatically at the eccentricity-scale, brought about by the sedimentary and climate systems. Our results support a direct 405 kyr-level correlation between the fluvial medial Chinle and lacustrine Newark Basin section (middle Passaic Formation), consistent with new and published (3) paleomagnetic polarity stratigraphy from the Chinle, showing that the Milankovitch eccentricity cycles are recorded in lower accumulation rate fluvial systems. Our results also independently support the continuity of the Newark Basin section and corroborate the Newark-Hartford APTS, not allowing for a multi-million year hiatus in the Passaic Formation, as has been asserted (4). We anticipate further

  19. Hg concentrations from Late Triassic and Early Jurassic sedimentary rocks: first order similarities and second order depositional and diagenetic controls

    Science.gov (United States)

    Yager, J. A.; West, A. J.; Bergquist, B. A.; Thibodeau, A. M.; Corsetti, F. A.; Berelson, W.; Bottjer, D. J.; Rosas, S.

    2016-12-01

    Mercury concentrations in sediments have recently gained prominence as a potential tool for identifying large igneous province (LIP) volcanism in sedimentary records. LIP volcanism coincides with several mass extinctions during the Phanerozoic, but it is often difficult to directly tie LIP activity with the record of extinction in marine successions. Here, we build on mercury concentration data reported by Thibodeau et al. (Nature Communications, 7:11147, 2016) from the Late Triassic and Early Jurassic of New York Canyon, Nevada, USA. Increases in Hg concentrations in that record were attributed to Central Atlantic Magmatic Province (CAMP) activity in association with the end-Triassic mass extinction. We expand the measured section from New York Canyon and report new mercury concentrations from Levanto, Peru, where dated ash beds provide a discrete chronology, as well as St. Audrie's Bay, UK, a well-studied succession. We correlate these records using carbon isotopes and ammonites and find similarities in the onset of elevated Hg concentrations and Hg/TOC in association with changes in C isotopes. We also find second order patterns that differ between sections and may have depositional and diagenetic controls. We will discuss these changes within a sedimentological framework to further understand the controls on Hg concentrations in sedimentary records and their implications for past volcanism.

  20. Cortical thickness abnormalities in late adolescence with online gaming addiction.

    Science.gov (United States)

    Yuan, Kai; Cheng, Ping; Dong, Tao; Bi, Yanzhi; Xing, Lihong; Yu, Dahua; Zhao, Limei; Dong, Minghao; von Deneen, Karen M; Liu, Yijun; Qin, Wei; Tian, Jie

    2013-01-01

    Online gaming addiction, as the most popular subtype of Internet addiction, had gained more and more attention from the whole world. However, the structural differences in cortical thickness of the brain between adolescents with online gaming addiction and healthy controls are not well unknown; neither was its association with the impaired cognitive control ability. High-resolution magnetic resonance imaging scans from late adolescence with online gaming addiction (n = 18) and age-, education- and gender-matched controls (n = 18) were acquired. The cortical thickness measurement method was employed to investigate alterations of cortical thickness in individuals with online gaming addiction. The color-word Stroop task was employed to investigate the functional implications of the cortical thickness abnormalities. Imaging data revealed increased cortical thickness in the left precentral cortex, precuneus, middle frontal cortex, inferior temporal and middle temporal cortices in late adolescence with online gaming addiction; meanwhile, the cortical thicknesses of the left lateral orbitofrontal cortex (OFC), insula, lingual gyrus, the right postcentral gyrus, entorhinal cortex and inferior parietal cortex were decreased. Correlation analysis demonstrated that the cortical thicknesses of the left precentral cortex, precuneus and lingual gyrus correlated with duration of online gaming addiction and the cortical thickness of the OFC correlated with the impaired task performance during the color-word Stroop task in adolescents with online gaming addiction. The findings in the current study suggested that the cortical thickness abnormalities of these regions may be implicated in the underlying pathophysiology of online gaming addiction.

  1. Cortical thickness abnormalities in late adolescence with online gaming addiction.

    Directory of Open Access Journals (Sweden)

    Kai Yuan

    Full Text Available Online gaming addiction, as the most popular subtype of Internet addiction, had gained more and more attention from the whole world. However, the structural differences in cortical thickness of the brain between adolescents with online gaming addiction and healthy controls are not well unknown; neither was its association with the impaired cognitive control ability. High-resolution magnetic resonance imaging scans from late adolescence with online gaming addiction (n = 18 and age-, education- and gender-matched controls (n = 18 were acquired. The cortical thickness measurement method was employed to investigate alterations of cortical thickness in individuals with online gaming addiction. The color-word Stroop task was employed to investigate the functional implications of the cortical thickness abnormalities. Imaging data revealed increased cortical thickness in the left precentral cortex, precuneus, middle frontal cortex, inferior temporal and middle temporal cortices in late adolescence with online gaming addiction; meanwhile, the cortical thicknesses of the left lateral orbitofrontal cortex (OFC, insula, lingual gyrus, the right postcentral gyrus, entorhinal cortex and inferior parietal cortex were decreased. Correlation analysis demonstrated that the cortical thicknesses of the left precentral cortex, precuneus and lingual gyrus correlated with duration of online gaming addiction and the cortical thickness of the OFC correlated with the impaired task performance during the color-word Stroop task in adolescents with online gaming addiction. The findings in the current study suggested that the cortical thickness abnormalities of these regions may be implicated in the underlying pathophysiology of online gaming addiction.

  2. Whirling in the late Permian: ancestral Gyrinidae show early radiation of beetles before Permian-Triassic mass extinction.

    Science.gov (United States)

    Yan, Evgeny V; Beutel, Rolf G; Lawrence, John F

    2018-03-16

    Gyrinidae are a charismatic group of highly specialized beetles, adapted for a unique lifestyle of swimming on the water surface. They prey on drowning insects and other small arthropods caught in the surface film. Studies based on morphological and molecular data suggest that gyrinids were the first branch splitting off in Adephaga, the second largest suborder of beetles. Despite its basal position within this lineage and a very peculiar morphology, earliest Gyrinidae were recorded not earlier than from the Upper Triassic. Tunguskagyrus. with the single species Tunguskagyrus planus is described from Late Permian deposits of the Anakit area in Middle Siberia. The genus is assigned to the stemgroup of Gyrinidae, thus shifting back the minimum age of this taxon considerably: Tunguskagyrus demonstrates 250 million years of evolutionary stability for a very specialized lifestyle, with a number of key apomorphies characteristic for these epineuston predators and scavengers, but also with some preserved ancestral features not found in extant members of the family. It also implies that major splitting events in this suborder and in crown group Coleoptera had already occurred in the Permian. Gyrinidae and especially aquatic groups of Dytiscoidea flourished in the Mesozoic (for example Coptoclavidae and Dytiscidae) and most survive until the present day, despite the dramatic "Great Dying" - Permian-Triassic mass extinction, which took place shortly (in geological terms) after the time when Tunguskagyrus lived. Tunguskagyrus confirms a Permian origin of Adephaga, which was recently suggested by phylogenetic "tip-dating" analysis including both fossil and Recent gyrinids. This also confirms that main splitting events leading to the "modern" lineages of beetles took place before the Permian-Triassic mass extinction. Tunguskagyrus shows that Gyrinidae became adapted to swimming on the water surface long before Mesozoic invasions of the aquatic environment took place

  3. A Unique Late Triassic Dinosauromorph Assemblage Reveals Dinosaur Ancestral Anatomy and Diet.

    Science.gov (United States)

    Cabreira, Sergio Furtado; Kellner, Alexander Wilhelm Armin; Dias-da-Silva, Sérgio; Roberto da Silva, Lúcio; Bronzati, Mario; Marsola, Júlio Cesar de Almeida; Müller, Rodrigo Temp; Bittencourt, Jonathas de Souza; Batista, Brunna Jul'Armando; Raugust, Tiago; Carrilho, Rodrigo; Brodt, André; Langer, Max Cardoso

    2016-11-21

    Dinosauromorpha includes dinosaurs and other much less diverse dinosaur precursors of Triassic age, such as lagerpetids [1]. Joint occurrences of these taxa with dinosaurs are rare but more common during the latest part of that period (Norian-Rhaetian, 228-201 million years ago [mya]) [2, 3]. In contrast, the new lagerpetid and saurischian dinosaur described here were unearthed from one of the oldest rock units with dinosaur fossils worldwide, the Carnian (237-228 mya) Santa Maria Formation of south Brazil [4], a record only matched in age by much more fragmentary remains from Argentina [5]. This is the first time nearly complete dinosaur and non-dinosaur dinosauromorph remains are found together in the same excavation, clearly showing that these animals were contemporaries since the first stages of dinosaur evolution. The new lagerpetid preserves the first skull, scapular and forelimb elements, plus associated vertebrae, known for the group, revealing how dinosaurs acquired several of their typical anatomical traits. Furthermore, a novel phylogenetic analysis shows the new dinosaur as the most basal Sauropodomorpha. Its plesiomorphic teeth, strictly adapted to faunivory, provide crucial data to infer the feeding behavior of the first dinosaurs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Palaeoenvironmental changes in the Late Triassic (Rhaetian) of the Northern Calcareous Alps

    DEFF Research Database (Denmark)

    Mette, Wolfgang; Elsler, Armin; Korte, Christoph

    2012-01-01

    in the Kössen Formation and determine their significance for environmental and climatic conditions in the Rhaetian sea of the Eiberg Basin (Northern Calcareous Alps). For this purpose 60 δ 18O measurements on 43 articulate brachiopods samples from 8 different horizons were carried out. The results indicate...... to the lowest unit 3 of the Eiberg Member that parallels oxygen isotopes. This positive δ 13C trend is interrupted by a sudden ~1.5‰ negative excursion in the late Rhaetian (Late Rhaetian Event), a time span when the oxygen isotopes remain heavy....

  5. Development of a high resolution chemostratigraphy for the Late Triassic-Early Jurassic Newark Basin

    Science.gov (United States)

    Kinney, S.; Olsen, P. E.; Chang, C.

    2017-12-01

    The 6.7 km of continuous core recovered from the paleo-tropical Triassic-Jurassic Newark rift basin during the Newark Basin Coring Project (NBCP) has provided a wealth of data since the conclusion of drilling 25 years ago. These cores comprise the longest ( 30 Myr) continuously-cored record of orbitally-paced environmental change and have informed our understanding in several different areas including tropical climate change, history of CO­2, mass extinctions, the geological time scale, and solar system dynamics. Despite the utility of NBCP cores for these endeavors, a critical missing dataset is a comprehensive characterization of their geochemical variations relevant to paleoenvironmental and paleoclimatic interests, largely a consequence of the cost of analyses at an appropriate resolution using conventional techniques. With the advent of new technology permitting the rapid acquisition of reliable geochemical data, such limitations may no longer be an obstacle for constructing a high-resolution chemostratigraphic record for the NBCP. We present the results of a proof-of-concept study using both ICP-MS-calibrated scanning ITRAX XRF and handheld Laser Induced Breakdown Spectroscopy (LIBS) using the SciAps Z-300. We will show elemental abundances at resolutions as high as 500 mm obtained using these methods from correlative sections of the Titusville and Nursery cores (Lockatong Fm.). These sections are sufficiently long to capture orbital variations and include the range of lithologies present throughout the entire section. Our preliminary results are consistent with previous, semi-quantitative means (e.g., depth ranks) of assessing Milankovitch-scale orbital variations and are also consistent with core and hole geophysical data, demonstrating that these methods can acquire meaningful geochemical data from the entire NBCP. With continued work, we aim to provide an objective characterization of orbitally-paced lake level cyclicity using geochemical proxy

  6. Archosauriform remains from the Late Triassic of San Luis province, Argentina, Quebrada del Barro Formation, Marayes-El Carrizal Basin

    Science.gov (United States)

    Gianechini, Federico A.; Codorniú, Laura; Arcucci, Andrea B.; Castillo Elías, Gabriela; Rivarola, David

    2016-03-01

    Here we present archosauriform remains from 'Abra de los Colorados', a fossiliferous locality at Sierra de Guayaguas, NW San Luis Province. Two fossiliferous levels were identified in outcrops of the Quebrada del Barro Formation (Norian), which represent the southernmost outcrops of the Marayes-El Carrizal Basin. These levels are composed by massive muddy lithofacies, interpreted as floodplain deposits. The specimens consist of one incomplete maxilla (MIC-V718), one caudal vertebra (MIC-V719), one metatarsal (MIC-V720) and one indeterminate appendicular bone (MIC-V721). The materials can be assigned to Archosauriformes but the fragmentary nature and lack of unambiguous synapomorphies preclude a more precise taxomic assignment. The maxilla is remarkably large and robust and represents the posterior process. It preserved one partially erupted tooth with ziphodont morphology. This bone shows some anatomical traits and size match with 'rauisuchians' and theropods. MIC-V719 corresponds to a proximal caudal vertebra. It has a high centrum, a ventral longitudinal furrow, expanded articular processes for the chevrons, a posteriorly displaced diapophysis located below the level of the prezygapophyses, and short prezygapophyses. This vertebra would be from an indeterminate archosauriform. MIC-V720 presents a cylindrical diaphysis, with a well-developed distal trochlea, which present resemblances with metatarsals of theropods, pseudosuchians, and silesaurids, although the size matches better with theropods. MIC-V721 has a slender diaphysis and a convex triangular articular surface, and corresponds to an indeterminate archosauriform. Despite being fragmentary, these materials indicate the presence of a diverse archosauriforms association from Late Triassic beds of San Luis. Thus, they add to the faunal assemblage recently reported from this basin at San Juan Province, which is much rich and diverse than the coeval paleofauna well known from Los Colorados Formation in the

  7. PALAEOENVIRONMENTAL INTERPPRETATION OF THE LATE TRIASSIC FRAELE FORMATION (ORTLES NAPPE, AUSTROALPINE DOMAIN, LOMBARDY

    Directory of Open Access Journals (Sweden)

    FABRIZIO BERRA

    1997-03-01

    Full Text Available The Fraele Formation crops out in the Ortles Nappe (upper Valtellina, Northern Italy, structurally part of the Central Austroalpine Domain. It consists of fine siliciclastics alternating with carbonates, mostly limestones,rare dolostones and marls. The formation differs lithologically from the underlying Norian Dolomia del Cristallo because of different paleonvironmental evolution.The change in environmental parameters was controlled mainly by a climatic change to more humid conditions.This favoured on one hand the mobilisation and trasport by rivers of siliciclastic material from the continent to the Tethys gulf,and on the other influenced the sea-water chemistry.Freshwater influxes lowered salinity and inhibited early dolomitisation. Input of low density freshwater resulted in the astablishment of a permanent water mass stratification which influenced the benthic life. This paleoenvironmental reconstruction fits with the sudden clastic input which occurred in several palaeogeographic domains of the western Tethys realm (Austroalpine, Southalpine, Apennine, Hungary, Poland, Slovakia during the Late Norian.  

  8. High-precision U-Pb zircon geochronological constraints on the End-Triassic Mass Extinction, the late Triassic Astronomical Time Scale and geochemical evolution of CAMP magmatism

    Science.gov (United States)

    Blackburn, T. J.; Olsen, P. E.; Bowring, S. A.; McLean, N. M.; Kent, D. V.; Puffer, J. H.; McHone, G.; Rasbury, T.

    2012-12-01

    Mass extinction events that punctuate Earth's history have had a large influence on the evolution, diversity and composition of our planet's biosphere. The approximate temporal coincidence between the five major extinction events over the last 542 million years and the eruption of Large Igneous Provinces (LIPs) has led to the speculation that climate and environmental perturbations generated by the emplacement of a large volume of magma in a short period of time triggered each global biologic crisis. Establishing a causal link between extinction and the onset and tempo of LIP eruption has proved difficult because of the geographic separation between LIP volcanic deposits and stratigraphic sequences preserving evidence of the extinction. In most cases, the uncertainties on available radioisotopic dates used to correlate between geographically separated study areas often exceed the duration of both the extinction interval and LIP volcanism by an order of magnitude. The "end-Triassic extinction" (ETE) is one of the "big five" and is characterized by the disappearance of several terrestrial and marine species and dominance of Dinosaurs for the next 134 million years. Speculation on the cause has centered on massive climate perturbations thought to accompany the eruption of flood basalts related to the Central Atlantic Magmatic Province (CAMP), the most aerially extensive and volumetrically one of the largest LIPs on Earth. Despite an approximate temporal coincidence between extinction and volcanism, there lacks evidence placing the eruption of CAMP prior to or at the initiation of the extinction. Estimates of the timing and/or duration of CAMP volcanism provided by astrochronology and Ar-Ar geochronology differ by an order of magnitude, precluding high-precision tests of the relationship between LIP volcanism and the mass extinction, the causes of which are dependent upon the rate of magma eruption. Here we present high precision zircon U-Pb ID-TIMS geochronologic data

  9. A preliminary report on coprolites from the Late Triassic part of the Kap Stewart Formation, Jameson Land, East Greenland

    DEFF Research Database (Denmark)

    Milàn, Jesper; Clemmensen, Lars B; Adolphsen, Jan Schulz

    2012-01-01

    The basal part of the Triassic-Jurassic (Rhaetian-Sinemurian) Kap Stewart Formation, exposed at Jameson Land, East Greenland, yields an extensive coprolite collection from black, parallel-laminated mudstone (“paper shale”), representing an open lacustrine system. Preliminary investigations show t...

  10. BIRD-LIKE HEAD ON A CHAMELEON BODY: NEW SPECIMENS OF THE ENIGMATIC DIAPSID REPTILE MEGALANCOSAURUS FROM THE LATE TRIASSIC OF NORTHERN ITALY

    Directory of Open Access Journals (Sweden)

    SILVIO RENESTO

    2000-07-01

    Full Text Available Two new Megalancosaurus specimens collected from the Norian (Late Triassic Calcare di Zorzino (Zorzino Limestone Formation (Bergamo, Lombardy, Northern Italy, and from the coeval Dolomia di Forni (Forni Dolostone Formation (Udine, Friuli, North-eastern Italy improve our knowledge of skeletal anatomy and mode of life of this genus. Morphology of observable skull elements and cervical vertebrae in one of the new specimens shows some resemblance to the possible Triassic bird Protoavis, while the postcranial skeleton of Megalancosaurus is completely non-avian. This may suggest that either Megalancosaurus and Protoavis developed a similar neck structure as a response to the same functional requirement, or that part of the disarticulated material ascribed to Protoavis may indeed belong to a Megalancosaurus-like reptile. Megalancosaurus shows a very high adaptation to arboreal life and a peculiar feeding strategy. Recent suggestions that Megalancosaurus may have been a glider and a possible model for bird ancestry are discussed. Some skeletal features of Megalancosaurus may indeed be interpreted as gliding adaptation, but evidence is weak, and if this reptile was a glider, however, its gliding bauplan should have been completely different from the one usually accepted for bird ancestors, showing instead more morphological similarities with gliding squirrels, phalangeriids and putative ancestors of bats and pterosaurs (according to a non cursorial model for these latter. 

  11. Plant–insect interactions from Middle Triassic (late Ladinian of Monte Agnello (Dolomites, N-Italy—initial pattern and response to abiotic environmental perturbations

    Directory of Open Access Journals (Sweden)

    Torsten Wappler

    2015-04-01

    Full Text Available The Paleozoic–Mesozoic transition is characterized by the most massive extinction of the Phanerozoic. Nevertheless, an impressive adaptive radiation of herbivorous insects occurred on gymnosperm-dominated floras not earlier than during the Middle to Late Triassic, penecontemporaneous with similar events worldwide, all which exhibit parallel expansions of generalized and mostly specialized insect herbivory on plants, expressed as insect damage on a various plant organs and tissues. The flora from Monte Agnello is distinctive, due to its preservation in subaerially deposited pyroclastic layers with exceptionally preserved details. Thus, the para-autochthonous assemblage provides insights into environmental disturbances, caused by volcanic activity, and how they profoundly affected the structure and composition of herbivory patterns. These diverse Middle Triassic biota supply extensive evidence for insect herbivore colonization, resulting in specific and complex herbivory patterns involving the frequency and diversity of 20 distinctive damage types (DTs. These DT patterns show that external foliage feeders, piercer-and-suckers, leaf miners, gallers, and oviposition culprits were intricately using almost all tissue types from the dominant host plants of voltzialean conifers (e.g., Voltzia, horsetails, ferns (e.g., Neuropteridium, Phlebopteris, Cladophlebis and Thaumatopteris, seed ferns (e.g., Scytophyllum, and cycadophytes (e.g., Bjuvia and Nilssonia.

  12. Spatial coincidence and similar geochemistry of Late Triassic and Eocene-Oligocene magmatism in the Andes of northern Chile: evidence from the MMH porphyry type Cu-Mo deposit, Chuquicamata District

    Science.gov (United States)

    Zentilli, Marcos; Maksaev, Victor; Boric, Ricardo; Wilson, Jessica

    2018-04-01

    The MMH porphyry type copper-molybdenum deposit in northern Chile is the newest mine in the Chuquicamata District, one of largest copper concentrations on Earth. Mineralized Eocene-Oligocene porphyry intrusions are hosted by essentially barren Triassic granodiorites. Despite a century of exploitation, geologists still have problems in the mine distinguishing the Triassic granodiorite from the most important ore-carrying Eocene porphyries in the district. To resolve the problem, internally consistent high-quality geochemical analyses of the Triassic and Tertiary intrusives were carried out: explaining the confusion, they show that the rock units in question are nearly identical in composition and thus respond equally to hydrothermal alteration. In detail, the only difference in terms of chemical composition is that the main Eocene-Oligocene porphyries carry relatively less Fe and Ni. Unexpectedly, the mineralized Eocene-Oligocene porphyries have consistently less U and Th than other Tertiary intrusions in the district, a characteristic that may be valuable in exploration. The supergiant copper-molybdenum deposits in the Central Andes were formed within a narrow interval between 45 and 31 Ma, close to 7% of the 200 My duration of "Andean" magmatism, which resulted from subduction of oceanic lithosphere under South America since the Jurassic. Although recent work has shown that subduction was active on the margin since Paleozoic times, pre-Andean (pre-Jurassic) "Gondwanan" magmatism is often described as being very different, having involved crustal melting and the generation of massive peraluminous rhyolites and granites. This study shows that the indistinguishable Late Triassic and Eocene-Oligocene intrusions occupy the same narrow NS geographic belt in northern Chile. If it is accepted that magma character may determine the potential to generate economic Cu-Mo deposits, then Late Triassic volcano-plutonic centres in the same location in the South American margin

  13. Contrasting microbial community changes during mass extinctions at the Middle/Late Permian and Permian/Triassic boundaries

    Science.gov (United States)

    Xie, Shucheng; Algeo, Thomas J.; Zhou, Wenfeng; Ruan, Xiaoyan; Luo, Genming; Huang, Junhua; Yan, Jiaxin

    2017-02-01

    Microbial communities are known to expand as a result of environmental deterioration during mass extinctions, but differences in microbial community changes between extinction events and their underlying causes have received little study to date. Here, we present a systematic investigation of microbial lipid biomarkers spanning ∼20 Myr (Middle Permian to Early Triassic) at Shangsi, South China, to contrast microbial changes associated with the Guadalupian-Lopingian boundary (GLB) and Permian-Triassic boundary (PTB) mass extinctions. High-resolution analysis of the PTB crisis interval reveals a distinct succession of microbial communities based on secular variation in moretanes, 2-methylhopanes, aryl isoprenoids, steranes, n-alkyl cyclohexanes, and other biomarkers. The first episode of the PTB mass extinction (ME1) was associated with increases in red algae and nitrogen-fixing bacteria along with evidence for enhanced wildfires and elevated soil erosion, whereas the second episode was associated with expansions of green sulfur bacteria, nitrogen-fixing bacteria, and acritarchs coinciding with climatic hyperwarming, ocean stratification, and seawater acidification. This pattern of microbial community change suggests that marine environmental deterioration was greater during the second extinction episode (ME2). The GLB shows more limited changes in microbial community composition and more limited environmental deterioration than the PTB, consistent with differences in species-level extinction rates (∼71% vs. 90%, respectively). Microbial biomarker records have the potential to refine our understanding of the nature of these crises and to provide insights concerning possible outcomes of present-day anthropogenic stresses on Earth's ecosystems.

  14. A thin-shelled reptile from the Late Triassic of North America and the origin of the turtle shell.

    Science.gov (United States)

    Joyce, Walter G; Lucas, Spencer G; Scheyer, Torsten M; Heckert, Andrew B; Hunt, Adrian P

    2009-02-07

    A new, thin-shelled fossil from the Upper Triassic (Revueltian: Norian) Chinle Group of New Mexico, Chinlechelys tenertesta, is one of the most primitive known unambiguous members of the turtle stem lineage. The thin-shelled nature of the new turtle combined with its likely terrestrial habitat preference hint at taphonomic filters that basal turtles had to overcome before entering the fossil record. Chinlechelys tenertesta possesses neck spines formed by multiple osteoderms, indicating that the earliest known turtles were covered with rows of dermal armour. More importantly, the primitive, vertically oriented dorsal ribs of the new turtle are only poorly associated with the overlying costal bones, indicating that these two structures are independent ossifications in basal turtles. These novel observations lend support to the hypothesis that the turtle shell was originally a complex composite in which dermal armour fused with the endoskeletal ribs and vertebrae of an ancestral lineage instead of forming de novo. The critical shell elements (i.e. costals and neurals) are thus not simple outgrowths of the bone of the endoskeletal elements as has been hypothesized from some embryological observations.

  15. Eustatic control on epicontinental basins: The example of the Stuttgart Formation in the Central European Basin (Middle Keuper, Late Triassic)

    Science.gov (United States)

    Franz, M.; Nowak, K.; Berner, U.; Heunisch, C.; Bandel, K.; Röhling, H.-G.; Wolfgramm, M.

    2014-11-01

    The deposition of the Stuttgart Formation ('Schilfsandstein'), commonly considered as a type-example of the Carnian Pluvial Event, was controlled by high frequent 4th order sequences that resulted in pre-, intra- and post-Schilfsandstein transgressions from Tethyan waters into the epicontinental Central European Basin (CEB). The pre-Schilfsandstein transgression flooded the CEB trough gates to the Southeast and resulted in a wide-spread inland sea that was characterised by increased biological productivity, predominantly oxic conditions and enabled the immigration of euryhaline marine fauna with plankton, ostracodes, fishes, bivalves and the gastropods Omphaloptychia suebica n. sp. and Settsassia stuttgartica n. sp. The rather short-term intra- and post-Schilfsandstein transgressions flooded the CEB from the Southwest and Southeast and established a shallow brackish inland sea that stretched up to North Germany. Both, the 4th and 3rd order sequences derived from the succession in the CEB correlate well with those derived from successions of Tethyan shelfs. Therefore pronounced circum-Tethyan eustatic cycles are evidenced and may have had considerable impact on prominent middle Carnian events: Reingraben turnover, Carnian Pluvial Event, Carnian Crisis and Mid Carnian Wet Intermezzo. The broad circum-Tethyan evidence of 106-year scale cycles suggests glacioeustatic sea-level changes even in the Triassic Greenhouse period.

  16. Late Palaeozoic to Triassic formations unconformably deposited over the Ronda peridotites (Betic Cordilleras): Evidence for their Variscan time of crustal emplacement

    Energy Technology Data Exchange (ETDEWEB)

    Sanz de Galdeano, C.; Ruiz Cruz, M.D.

    2016-07-01

    The age of the emplacement of the Ronda Peridotites has been widely debated during recent decades, and ages ranging from the Palaeozoic to the early Miocene have been proposed, although most of the current interpretations suggest an Oligocene-Miocene age. In this article, we describe two meta-sedimentary formations (the lower one formed by detrital sediments and the upper one by marbles) that were unconformably deposited over the Ronda peridotites and now record low-grade metamorphism. The detrital formation contains layers of acidic rocks with an age of 269±9 Ma and the overlying marbles are assumed to be Triassic. The existence of these unconformable formations over the peridotites is crucial for the dating of the exhumation of the latter. The presence of peridotite clasts in the detrital formation indicates that peridotites were exposed during the Permian and other data suggest that peridotites were exhumed during the late Carboniferous. During the Alpine cycle, the peridotites operated as an element situated at the bottom of the tectonically higher Alpujarride/Sebtide unit (the Jubrique unit) and forming part of it, then being incorporated to the Alpine thrusts of this unit. (Author)

  17. Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina).

    Science.gov (United States)

    Kent, Dennis V; Santi Malnis, Paula; Colombi, Carina E; Alcober, Oscar A; Martínez, Ricardo N

    2014-06-03

    A measured magnetozone sequence defined by 24 sampling sites with normal polarity and 28 sites with reverse polarity characteristic magnetizations was established for the heretofore poorly age-constrained Los Colorados Formation and its dinosaur-bearing vertebrate fauna in the Ischigualasto-Villa Union continental rift basin of Argentina. The polarity pattern in this ∼600-m-thick red-bed section can be correlated to Chrons E7r to E15n of the Newark astrochronological polarity time scale. This represents a time interval from 227 to 213 Ma, indicating that the Los Colorados Formation is predominantly Norian in age, ending more than 11 My before the onset of the Jurassic. The magnetochronology confirms that the underlying Ischigualasto Formation and its vertebrate assemblages including some of the earliest known dinosaurs are of Carnian age. The oldest dated occurrences of vertebrate assemblages with dinosaurs in North America (Chinle Formation) are younger (Norian), and thus the rise of dinosaurs was diachronous across the Americas. Paleogeography of the Ischigualasto and Los Colorados Formations indicates prolonged residence in the austral temperate humid belt where a provincial vertebrate fauna with early dinosaurs may have incubated. Faunal dispersal across the Pangean supercontinent in the development of more cosmopolitan vertebrate assemblages later in the Norian may have been in response to reduced contrasts between climate zones and lowered barriers resulting from decreasing atmospheric pCO2 levels.

  18. Late Paleozoic to Triassic magmatism in the north-central High Andes, Chile: New insights from SHRIMP U-Pb geochronology and O-Hf isotopic signatures in zircon

    Science.gov (United States)

    Hernández González, Álvaro; Deckart, Katja; Fanning, Mark; Arriagada, César

    2014-05-01

    The Chilean High Andes (28o- 31oS) comprises a vast number of late Paleozoic - Triassic granitoids which give information about the last stages of Gondwana assemblage. Particularly, previous studies determined two tectonic configurations during this time: subduction related compressional setting (late Carboniferous - Late Permian) and non-subduction post-collisional extensional setting (Late Permian - Triassic), as the last stage of Gondwana assemblage. However, new O-Hf isotopic data along new U-Pb SHRIMP ages in zircon have shown that this model should be modified and updated to the new analytical data available. δ18O values indicate a strong change in the tectonic configuration approximately 270 Ma (earliest middle Permian) and thus, units can be divided into 2 mayor groups: late Carboniferous to earliest middle Permian and middle Permian to Triassic. The oldest group shows slightly low values of ɛHfi (ca. +1 to -4) with high δ18O (ca. >6.5 o/oo), indicating an elevated supracrustal component and the addition of less radiogenic continental-like material, which along significant residence time (TDM2: Mesoproterozoic) can be interpreted as magmas formed at depth in a subduction-related continental arc, and contaminated with supracrustal material and/or oceanic sediments transported through the subducted slab to the mantle-wedge. Subsequently, middle Permian - Triassic rocks show a wider range of ɛHfi values (ca. +3 to -3) with relatively low, mantle-like δ18O (ca. 4.5-6.5 o/oo), indicating a source of magmas without the addition of supracrustal material for some plutons, whilst for others, a slight input. The higher positive values of ɛHfi can be related to the influence of new juvenile material in the source of some magmas. This isotopic data can be interpreted as rocks formed as the result of melting of an old thinned mafic crust (with mantle-like δ18O values characteristic of this type of rocks) with limited addition of supracrustal material; in

  19. New information on Riograndia guaibensis Bonaparte, Ferigolo & Ribeiro, 2001 (Eucynodontia, Tritheledontidae from the Late Triassic of southern Brazil: anatomical and biostratigraphic implications

    Directory of Open Access Journals (Sweden)

    Marina B. Soares

    2011-03-01

    Full Text Available The tritheledontid Riograndia guaibensis was the first cynodont described for the "Caturrita Formation" fauna from the Late Triassic of southern Brazil (Santa Maria 2 Sequence. The type materials did not preserve anatomical information regarding braincase, occiput, basicranium, zygomatic arch, postdentary bones and craniomandibular joint. Here new materials are described and supply the missing information. Riograndia shows a suite of important anatomical features quite derived among the non-mammaliaform eucynodonts, such as the partial closure of the medial orbital wall and braincase, extensive secondary osseous palate, wide primary palate, basicranium with jugular foramen separated from the periphery of fenestra rotunda, narrow zygomatic arch and much reduced postdentary bones. Many of these features constitute synapomorphies shared only with the other members of mammaliamorpha. Thus, the almost complete cranial, mandibular and dental information from the new fossils of Riograndia can bring a significant improve in the understanding of the anatomy and phylogenetic relationships of the tritheledontids and help to elucidate the transformational steps involved in the cynodont-mammal transition. Additionally, Riograndia is a key taxon in refining the "Caturrita Formation" biostratigraphy, enabling the connection of several fossiliferous outcrops that have a rich tetrapod fauna that can be correlated with other Triassic faunas from Gondwana and Laurasia.O triteledontídeo Riograndia guiabensis foi o primeiro cinodonte descrito para a fauna da "Formação Caturrita" do Triássico Superior do sul do Brasil (Sequência Santa Maria 2. Os materiais da série-tipo não forneceram informações anatômicas relativas à caixa craniana, ociput, basicrânio, arco zigomático, ossos pós-dentários e articulação crânio-mandibular. Neste artigo são descritos novos materiais que suprem as informações anatômicas não contempladas anteriormente. Riograndia

  20. Astrochronology and magnetostratigraphy of the Xujiahe Formation of South China and Newark Supergroup of North America: implications for the Late Triassic time scale

    Science.gov (United States)

    Li, M.; Zhang, Y.; Huang, C.; Ogg, J. G.; Hinnov, L.; Wang, Y.; Zou, Z.; Li, L.; Grasby, S. E.; Zhong, Y.; Huang, K.

    2017-12-01

    The astrochronology derived from lacustrine clastic successions tied to the geomagnetic polarity time scale of the Newark Supergroup of eastern North America, known as the Newark APTS provides a basis for the Late Triassic time scale. However, the Newark APTS has been challenged regarding its age scale and completeness; therefore an independent astronomically tuned magnetic polarity zonation is required to verify the upper Newark APTS reference scale. We have compiled a 6.5 million year (myr) APTS with magnetic stratigraphy from four sections of the lacustrine-fluvial, dinosaur-track-bearing Xujiahe Formation in the Sichuan Basin of South China that has dating from detrital zircons and regional biostratigraphy. Variations in natural gamma-ray and magnetic susceptibility that reflect variable continental weathering in the source regions of the Xujiahe Formation are paced by Milankovitch cycles, especially the 100-kyr short eccentricity and 405-kyr long eccentricity. The cycle-tuned magnetostratigraphy of the Xujiahe Formation is compared directly via the magnetic-polarity zones to the depth ranks of the Newark Supergroup that are indicative of relative depositional depths of lacustrine facies. The Sichuan APTS indicates that there is no significant hiatus between the sedimentary succession and the basalt flows at the top of the Newark Supergroup. The Sichuan APTS is compatible with the magnetostratigraphy from the candidate Global Boundary Stratotype Section and Point (GSSP) for the Norian-Rhaetian boundary interval at the Pignola-Abriola section of South Italy, but does not extend downward to the proposed GSSP in Austria associated with the longer Rhaetian option. The earliest dinosaur tracks in China are from the middle of the Xujiahe Formation, therefore are implied to be middle Rhaetian in age. The Sichuan APTS helps to resolve the controversy about the completeness and reliability of the Newark APTS, and can be used in the future to verify if isotopic

  1. Merging cranial histology and 3D-computational biomechanics: a review of the feeding ecology of a Late Triassic temnospondyl amphibian

    Directory of Open Access Journals (Sweden)

    Dorota Konietzko-Meier

    2018-02-01

    water conditions, metoposaurids may have been more active ambush predators that were capable of lateral strikes of the head. The dry season required a less active mode of life when bilateral biting is particularly efficient. This, combined with their characteristically anteriorly positioned orbits, was optimal for ambush strategy. This ability to use alternative modes of food acquisition, independent of environmental conditions, might hold the key in explaining the very common occurrence of metoposaurids during the Late Triassic.

  2. A gigantic nothosaur (Reptilia: Sauropterygia) from the Middle Triassic of SW China and its implication for the Triassic biotic recovery

    Science.gov (United States)

    Liu, Jun; Hu, Shi-Xue; Rieppel, Olivier; Jiang, Da-Yong; Benton, Michael J.; Kelley, Neil P.; Aitchison, Jonathan C.; Zhou, Chang-Yong; Wen, Wen; Huang, Jin-Yuan; Xie, Tao; Lv, Tao

    2014-11-01

    The presence of gigantic apex predators in the eastern Panthalassic and western Tethyan oceans suggests that complex ecosystems in the sea had become re-established in these regions at least by the early Middle Triassic, after the Permian-Triassic mass extinction (PTME). However, it is not clear whether oceanic ecosystem recovery from the PTME was globally synchronous because of the apparent lack of such predators in the eastern Tethyan/western Panthalassic region prior to the Late Triassic. Here we report a gigantic nothosaur from the lower Middle Triassic of Luoping in southwest China (eastern Tethyan ocean), which possesses the largest known lower jaw among Triassic sauropterygians. Phylogenetic analysis suggests parallel evolution of gigantism in Triassic sauropterygians. Discovery of this gigantic apex predator, together with associated diverse marine reptiles and the complex food web, indicates global recovery of shallow marine ecosystems from PTME by the early Middle Triassic.

  3. Spondarthritis in the triassic.

    Directory of Open Access Journals (Sweden)

    Juan Carlos Cisneros

    Full Text Available BACKGROUND: The evidence of several forms of arthritis has been well documented in the fossil record. However, for pre-Cenozoic vertebrates, especially regarding reptiles, this record is rather scarce. In this work we present a case report of spondarthritis found in a vertebral series that belonged to a carnivorous archosaurian reptile from the Lower Triassic (∼245 million years old of the South African Karoo. METHODOLOGY/PRINCIPAL FINDINGS: Neutron tomography confirmed macroscopic data, revealing the ossification of the entire intervertebral disc space (both annulus fibrosus and nucleus pulposus, which supports the diagnosis of spondarthritis. CONCLUSIONS/SIGNIFICANCE: The presence of spondarthritis in the new specimen represents by far the earliest evidence of any form of arthritis in the fossil record. The present find is nearly 100 million years older than the previous oldest report of this pathology, based on a Late Jurassic dinosaur. Spondarthritis may have indirectly contributed to the death of the animal under study.

  4. EARLIEST TRIASSIC CONODONTS FROM CHITRAL, NORTHERNMOST PAKISTAN

    Directory of Open Access Journals (Sweden)

    MARIA CRISTINA PERRI

    2004-07-01

    Full Text Available Extensive tracts of very shallow water carbonates in the valleys of the Yarkhun and Mastuj rivers of Chitral (northernmost Pakistan previously though to be Permian (or Cretaceous are shown by conodonts from two horizons in sequences 110 km apart—near Torman Gol (Mastuj valley and near Sakirmul (upper Yarkhun valley—to include earliest Triassic (Scythian—Induan horizons. Both faunas have Isarcicella staeschei Dai & Zhang, Is. lobata Perri, Is. turgida (Kozur et al. and Hindeodus parvus (Kozur & Pjatakova, whereas Is. Isarcica (Huckriede has been recognised only in the Torman Gol occurrence. The presence, respectively, of Is. staeschei in the Sakirmul and Is. isarcica in the Torman Gol occurrences, allows discrimination of the staeschei and isarcica zones respectively the third and the fourth conodont biozones of the Early Triassic conodont biozonation of Perri (in Perri & Farabegoli 2003. Such faunas, consisting mainly of isarcicellids and hindeodids but lacking gondolellids, are characteristic of restricted sea environments across the Permian–Triassic boundary and in the earliest Triassic in other Tethyan areas. The conodont faunas from these two occurrences are remarkably similar, nearly contemporaneous, and indicate shallow water biofacies. They are inferred to equate with the Ailak Dolomite, a sequence of Late Permian–?Late Triassic dolostones discriminated farther up the Yarkhun valley and extending eastwards into the upper Hunza region of northernmost Pakistan. The Zait Limestone and Sakirmul carbonate sequence are consistent with extension of the previously inferred Triassic carbonate platform at least 110 km farther to the SW than previously supposed.

  5. Permian and Triassic microfloral assemblages from the Blue Nile Basin, central Ethiopia

    Science.gov (United States)

    Dawit, Enkurie L.

    2014-11-01

    Palynological investigation was carried out on surface samples from up to 400 m thick continental siliciclastic sediments, here referred to as “Fincha Sandstone”, in the Blue Nile Basin, central Ethiopia. One hundred sixty species were identified from 15 productive samples collected along a continuous road-cut exposure. Six informal palynological assemblage zones have been identified. These assemblage zones, in ascending order, are: “Central Ethiopian Permian Assemblage Zone - CEPAZ I”, earliest Permian (Asselian-Sakmarian); “CEPAZ II”, late Early Permian (Artinskian-Kungurian); CEPAZ III - Late Permian (Kazanian-Tatarian); “CETAZ IV”, Lower Triassic (Olenekian Induan); “CETAZ V”, Middle Triassic (Anisian Ladinian); “CETAZ VI”, Late Triassic (Carnian Norian). Tentative age ranges proposed herein are compared with faunally calibrated palynological zones in Gondwana. The overall composition and vertical distribution of miospores throughout the studied section reveals a wide variation both qualitatively and quantitatively. The high frequency of monosaccate pollen in CEPAZ I may reflect a Glossopterid-dominated upland flora in the earliest Permian. The succeeding zone is dominated by straite/taeniate disaccate pollen and polyplicates, suggesting a notable increase in diversity of glossopterids. The decline in the diversity of taeniate disaccate pollen and the concomitant rise in abundance of non-taeniate disaccates in CEPAZ III may suggest the decline in Glossopteris diversity, though no additional evidence is available to equate this change with End-Permian extinction. More diverse and dominant non-taeniate, disaccate, seed fern pollen assignable to FalcisporitesAlisporites in CETAZ IV may represent an earliest Triassic recovery flora. The introduction of new disaccate forms with thick, rigid sacci, such as Staurosaccites and Cuneatisporites, in CETAZ V and VI may indicate the emergence of new gymnospermous plants that might have favourably

  6. A middle Permian ophiolite fragment in Late Triassic greenschist- to blueschist-facies rocks in NW Turkey: An earlier pulse of suprasubduction-zone ophiolite formation in the Tethyan belt

    Science.gov (United States)

    Topuz, Gültekin; Okay, Aral I.; Schwarz, Winfried H.; Sunal, Gürsel; Altherr, Rainer; Kylander-Clark, Andrew R. C.

    2018-02-01

    The Eastern Mediterranean region within the Tethyan belt is characterised by two main pulses of suprasubduction-zone ophiolite formation during the Early-Middle Jurassic and Late Cretaceous. Despite vast exposures of the Permo-Triassic accretionary complexes, related suprasubduction-zone ophiolites and the timing of subduction initiation leading to the formation of Permo-Triassic accretionary complexes are unknown so far. Here we report on a 40 km long and 0.3 to 1.8 km wide metaophiolite fragment within transitional greenschist- to blueschist-facies oceanic rocks from NW Turkey. The metaophiolite fragment is made up mainly of serpentinite and minor dykes or stocks of strongly sheared metagabbro with mineral assemblages involving actinolite/winchite, chlorite, epidote, albite, titanite and phengite. The metagabbro displays (i) variable CaO and MgO contents, (ii) anomalously high Mg# (= 100 ∗ molar MgO/(MgO + FeOtot)) of 75-88, and (iii) positive Eu anomalies, together with low contents of incompatible elements such as Ti, P and Zr, suggesting derivation from former plagioclase cumulates. The serpentinites comprise serpentine, ± chlorite, ± talc, ± calcite and relict Cr-Al spinel surrounded by ferrichromite to magnetite. Relict Cr-Al spinels are characterised by (i) Cr/(Cr + Al) ratios of 0.45-0.56 and Mg/(Mg + Fe2 +) ratio of 0.76-0.22, (ii) variable contents of ZnO and MnO, and (iii) extremely low TiO2 contents. Zn and Mn contents are probably introduced into Cr-Al spinels during greenschist- to blueschist metamorphism. Compositional features of the serpentinite such as (i) Ca- and Al-depleted bulk compositions, (ii) concave U-shaped, chondrite-normalised rare earth element patterns (REE) with enrichment of light and heavy REEs, imply that serpentinites were probably derived from depleted peridotites which were refertilised by light rare earth element enriched melts in a suprasubduction-zone mantle wedge. U-Pb dating on igneous zircons from three metagabbro

  7. Subduction of Proterozoic to Late Triassic continental basement in the Guatemala suture zone: A petrological and geochronological study of high-pressure metagranitoids from the Chuacús complex

    Science.gov (United States)

    Maldonado, Roberto; Ortega-Gutiérrez, Fernando; Ortíz-Joya, Guillermo A.

    2018-05-01

    Many continental subduction complexes contain abundant granitic rocks coexisting with minor volumes of eclogite-facies rocks. Characterization of granitic protoliths is crucial to decipher the origin of subducted continental crust, whereas knowledge of its metamorphic evolution is required to constrain the mechanisms of burial and exhumation. In this work we present geochronological and petrological evidence that demonstrate the occurrence of a subducted Proterozoic to Late Triassic granitic basement in the Chuacús complex of central Guatemala. Metagranitoids exposed in this area are interlayered with eclogite and other high-pressure rocks, and their structure is considerably variable due to strain partitioning during deformation. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon data from two ferroan metagranites yield protolith crystallization ages of ca. 1.1 Ga and their trace-element abundances suggest an origin related to intraplate magmatism, while a high-silica, peraluminous metagranite is dated at 1.0 Ga and was probably originated by partial melting of a high-grade continental crust. On the other hand, two megacrystic to augen metagranitoids yield protolith crystallization ages of ca. 224 Ma, which are identical within errors to the protolith age of hosted eclogitic metabasites. Their high incompatible trace element abundances together with the observed spatial-temporal relationships with mafic protoliths suggest that Late Triassic bimodal magmatism in the Chuacús complex was probably originated in a within-plate setting. Regardless of their age or structure, the studied metagranites preserve evidences for high-pressure metamorphic equilibration, such as the occurrence of Ca-rich garnet (XCa up to 0.52) in association with phengite (Si contents of up to 3.4 pfu) and rutile. The integration of Zr-in-rutile thermometry and phengite barometry allows the peak metamorphic conditions to be constrained at 640-680 °C and 13 kbar. This

  8. Full-thickness thoracic laminar erosion after posterior spinal fusion associated with late-presenting infection.

    Science.gov (United States)

    Tribus, Clifford B; Garvey, Kathleen E

    2003-05-15

    A case report describes unilateral complete laminar erosion of the caudal thoracic spine and late-presenting infection in a patient 10 years after anteroposterior reconstruction for scoliosis. To present an unusual but significant complication that may occur after implantation of spinal instrumentation. The reported patient presented with a deep infection and persistent back pain 10 years after successful anteroposterior reconstruction for adult idiopathic scoliosis. Delayed onset infections after implantation of spinal instrumentation are infrequent, yet when present, often require hardware removal. The case of a 51-year-old woman who underwent irrigation and debridement for a late-presenting infection and removal of posterior hardware 10 years after her index procedure is presented. Interoperatively, it was noted that full-thickness laminar erosion was present from T4 to T12. The patient was taken to the operating room for wound irrigation, debridement, and hardware removal. It was discovered that a Cotrel-Dubousset rod placed on the convexity of the curve had completely eroded through the lamina of T7-T12. Infectious material was found along the entire length of both the convex and concave Cotrel-Dubousset rods. Intraoperative cultures grew Staphylococcus epidermidis and Propionibacterium acnes. Intravenous and oral antibiotics were administered, resulting in resolution of the infection and preoperative pain. The exact role of late-presenting infection with regard to the laminar erosion and rod migration seen in this case remains to be elucidated. However, the authors believe the primary cause of bony erosion was mechanical in origin. Regardless, most spine surgeons will treat many patients who have had posterior spinal implants and will perform hardware removal on a significant number of these patients during their careers. A full-thickness laminar erosion exposes the spinal cord to traumatic injury during hardware removal and debridement. This case is

  9. THE TRIASSIC/JURASSIC BOUNDARY IN THE ANDES OF ARGENTINA

    Directory of Open Access Journals (Sweden)

    ALBERTO C. RICCARDI

    2004-03-01

    Full Text Available The Arroyo Malo Formation at Alumbre Creek, on the northern bank of the Atuel River, west central Argentina, comprises a c. 300 m thick continuous marine succession across the Triassic-Jurassic System boundary, consisting of massive and laminated pelites indicative of a slope depositional environment. Late Triassic invertebrates, including ammonoids, nautiloids, bivalves, gastropods, brachiopods and corals are restricted to the lower 150 m. Beds between 125-135 m from the bottom yield Choristoceras cf. marshi Hauer, a species found in the Marshi/Crickmayi Zone of Europe and North America, together with loose fragments of Psiloceras cf. pressum Hillebrandt, coeval with the lower to middle part of the Hettangian Planorbis Zone. About 80 m higher are beds yielding Psiloceras cf. rectocostatum Hillebrandt, a species that gives name to an Andean biozone partially coeval with the Johnstoni and Plicatulum Subzones, upper Planorbis Zone. Other fossils recorded in the Rhaetian strata of this section are foraminifers, ostracods and plant remains identified as Zuberia cf. zuberi (Szaj. Freng. and Clathropteris sp. The section was also sampled for conodonts and radiolarians, thus far with negative results. A palaeomagnetic study is underway.

  10. Late Triassic Porphyritic Intrusions And Associated Volcanic Rocks From The Shangri-La Region, Yidun Terrane, Eastern Tibetan Plateau: Implications For Adakitic Magmatism And Porphyry Copper Mineralization

    Science.gov (United States)

    Wang, B.; Zhou, M.; Li, J.; Yan, D.

    2011-12-01

    The Yidun terrane, located on the eastern margin of the Tibetan plateau, has been commonly considered to be a Triassic volcanic arc produced by subduction of the Ganzi-Litang oceanic lithosphere. The Yidun terrane is characterized by numerous arc-affinity granitic intrusions located along a 500-km-long, north-south-trending belt. Among these granitic bodies, several small porphyritic intrusions in the southern segment of the terrane (Shangri-La region) are associated with large porphyry copper deposits. These porphyritc intrusions are composed of diorite and quartz diorite, and spatially associated with andesites and dacites. LA-ICP-MS zircon U-Pb ages of the intrusions range from 230 to 215 Ma. The andesites and dacites are intercalated with slates and sandstones and have ages of around 220 Ma. The intrusive and volcanic rocks have SiO2 contents from 56.6 to 67.1 wt.%, Al2O3 from 14.2 to 17.4 wt.% and MgO from 1.9 to 4.2 wt.%. They show significant negative Nb-Ta anomalies on primitive mantle-normalized spidergrams. They have high La/Yb (13-49) ratios with no prominent Eu anomalies. All the rocks have high Sr (258-1980 ppm), and low Y (13-21 ppm) with high Sr/Y ratios (29-102). The geochemical features indicate that both the volcanic rocks and porphyritic intrusions were derived from adakitic magmas. They have similar initial 87Sr/86Sr ratios (0.7058 to 0.7077) and ɛNd (-1.88 to -4.93) values, but can be further divided into two groups: high silica (HSA) and low silica adakitic rocks (LSA). The HSA, representing an early stage of magmatism (230 to 215 Ma), were derived from oceanic slab melts with limited interaction with the overlying mantle wedge. At 215 Ma, more extensive interaction resulted in the formation of LSA. We propose that HSA were produced by flat subduction leading to melting of oceanic slab, whereas subsequent slab break-off caused the significant interaction between slab melts and the mantle wedge and thus the generation of the LSA. Compared with

  11. A regional chemostratigraphically-defined correlation framework for the late Triassic TAG-I Formation in Blocks 402 and 405a, Algeria

    Energy Technology Data Exchange (ETDEWEB)

    Ratcliffe, K.T.; Martin, J.; Pearce, T.J. [Chemostrat ltd., Llanfyllin, Powys (United Kingdom); Hughes, A.D. [Bington Resources, London (United Kingdom); Lawton, D.E. [BHP Billiton Petroleum Ltd., London (United Kingdom); Wray, D. [University of Greenwich, Chatham Maritime (United Kingdom). Department of Earth Sciences; Bessa, F. [Sonatrach, Hydra (Algeria). Division Petroleum Engineering and Development

    2006-07-01

    The Triassic Argilo-Greseux Inferieur Formation (TAG-I) is one of the principal hydrocarbon reservoirs in the Berkine Basin of Algeria. Sedimentological studies have shown that it exhibits marked spatial and temporal facies variations on both a local field scale and a regional basinal scale. This variability, combined with a lack of diagnostic flora and fauna, makes regional correlation within the unit difficult. In turn, the lack of a consistent regional stratigraphic framework hampers the comparison of the various correlation schemes devised by operators in the basin. Contrasting the TAG-I in Blocks 402 and 405a exemplifies the problems encountered when attempting regionally to define a correlation framework for the interval. Between these two blocks, a distance of approximately 200 km, there are marked changes in the style of deposition from sand-dominated, proximal fluvial systems in the SW (Block 405a, MLN, MLC, KMD and MLNW fields) to a more distal, more clay-prone system in the NE (Block 402, ROD/BRSE/BSFN, SFNE and BSF fields). A chemostratigraphic study of the TAG-I in these clocks has allowed a four-fold correlation framework to be defined, where each chemostratigraphic package has distinctive geochemical features. Chemostratigraphic Package 10, the oldest unit, lies above the Hercynian Unconformity, but beneath a geochemically identifiable hiatal surface. Chemostratigraphic Package 20 lies above the hiatal surface but is separated from the overlying packages by a mineralogical change identifiable in both claystone and sandstone geochemistry. Chemostratigraphic Packages 30 and 40 are chemically somewhat similar, but are separated by a regional event interpreted as a period of dolocrete and lacustrine development. By combining the geochemical differentiation of the units and recognition of their stratal boundaries, it is possible to define a correlation for the TAG-I between Blocks 402 and 405a. The proposed correlation between the two blocks suggests that

  12. Geochronologic evidence of a large magmatic province in northern Patagonia encompassing the Permian-Triassic boundary

    Science.gov (United States)

    Luppo, Tomás; López de Luchi, Mónica G.; Rapalini, Augusto E.; Martínez Dopico, Carmen I.; Fanning, Christopher M.

    2018-03-01

    The Los Menucos Complex (northern Patagonia) consists of ∼6 km thick succession of acidic and intermediate volcanic and pyroclastic products, which has been traditionally assigned to the Middle/Late Triassic. New U/Pb (SHRIMP) zircon crystallization ages of 257 ± 2 Ma at the base, 252 ± 2 Ma at an intermediate level and 248 ± 2 Ma near the top of the sequence, indicate that this volcanic event took place in about 10 Ma around the Permian-Triassic boundary. This volcanism can now be considered as the effusive terms of the neighboring and coeval La Esperanza Plutono-Volcanic Complex. This indicates that the climax of activity of a large magmatic province in northern Patagonia was coetaneous with the end-Permian mass extinctions. Likely correlation of La Esperanza- Los Menucos magmatic province with similar volcanic and plutonic rocks across other areas of northern Patagonia suggest a much larger extension than previously envisaged for this event. Its age, large volume and explosive nature suggest that the previously ignored potential role that this volcanism might have played in climatic deterioration around the Permian-Triassic boundary should be investigated.

  13. End-Triassic nonmarine biotic events

    Directory of Open Access Journals (Sweden)

    Spencer G. Lucas

    2015-10-01

    Full Text Available The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctions took place in the marine realm, particularly affecting radiolarians, conodonts, bivalves, ammonoids and reef-building organisms. On land, the case for a Late Triassic mass extinction is much more tenuous and has largely focused on tetrapod vertebrates (amphibians and reptiles, though some workers advocate a sudden end-Triassic (TJB extinction of land plants. Nevertheless, an extensive literature does not identify a major extinction of land plants at the TJB, and a comprehensive review of palynological records concluded that TJB vegetation changes were non-uniform (different changes in different places, not synchronous and not indicative of a mass extinction of land plants. Claims of a substantial perturbation of plant ecology and diversity at the TJB in East Greenland are indicative of a local change in the paleoflora largely driven by lithofacies changes resulting in changing taphonomic filters. Plant extinctions at the TJB were palaeogeographically localized events, not global in extent. With new and more detailed stratigraphic data, the perceived TJB tetrapod extinction is mostly an artifact of coarse temporal resolution, the compiled correlation effect. The amphibian, archosaur and synapsid extinctions of the Late Triassic are not concentrated at the TJB, but instead occur stepwise, beginning in the Norian and extending into the Hettangian. There was a disruption of the terrestrial ecosystem across the TJB, but it was more modest than generally claimed. The ecological severity of the end-Triassic nonmarine biotic events are relatively low on the global scale. Biotic turnover at the end of the Triassic was likely driven by the CAMP (Central Atlantic Magmatic Province eruptions, which caused significant environmental

  14. MAGNETOSTRATIGRAPHY AND BIOSTRATIGRAPHY OF THE LATE TRIASSIC GURI ZI SECTION, ALBANIA: CONSTRAINT ON THE AGE OF THE CARNIAN-NORIAN BOUNDARY

    Directory of Open Access Journals (Sweden)

    GIOVANNI MUTTONI

    2005-07-01

    Full Text Available We present the magnetostratigraphy and conodont biostratigraphy across the Carnian-Norian boundary from a 70 m-thick limestone section located at Guri Zi in northern Albania. A total of 14 magnetozones were observed. The Carnian-Norian boundary is placed in a thin stratigraphic interval between the last occurrence of Paragondolella nodosa and the first occurrence of Epigondolella abneptis. Data from Guri Zi are in substantial agreement with already published data from Silicka Brezova in Slovakia and Pizzo Mondello in Sicily, which complessively indicate that the conodont Carnian-Norian boundary, when magnetostratigraphically traced onto the Newark astrochronological polarity time scale (APTS, has an age of ~228-227 Ma.

  15. Geochronology, geochemistry, and petrogenesis of late Permian to early Triassic mafic rocks from Darongshan, South China: Implications for ultrahigh-temperature metamorphism and S-type granite generation

    Science.gov (United States)

    Xu, Wang-Chun; Luo, Bi-Ji; Xu, Ya-Jun; Wang, Lei; Chen, Qi

    2018-05-01

    The role of the mantle in generating ultrahigh-temperature metamorphism and peraluminous S-type granites, and the extent of crust-mantle interaction are topics fundamental to our understanding of the Earth's evolution. In this study we present geochronological, geochemical, and Sr-Nd-Hf isotopic data for dolerites and mafic volcanic rocks from the Darongshan granite complex belt in western Cathaysia, South China. LA-ICP-MS U-Pb zircon analyses yielded magma crystallization ages of ca. 250-248 Ma for the dolerites, which are coeval with eruption of the mafic volcanic rocks, ultrahigh-temperature metamorphism, and emplacement of S-type granites in the Darongshan granite complex belt. The mafic volcanic rocks are high-K calc-alkaline or shoshonitic, enriched in Th, U, and light rare earth elements, and depleted in Nb, Ta and Ti. The dolerites are characterized by high Fe2O3tot (11.61-20.39 wt%) and TiO2 (1.62-3.17 wt%), and low MgO (1.73-4.38 wt%), Cr (2.8-10.8 ppm) and Ni (2.5-11.4 ppm). Isotopically, the mafic volcanic rocks have negative whole-rock εNd(t) values (-6.7 to -9.0) and high ISr values (0.71232 to 0.71767), which are slightly depleted compared with the dolerite samples (εNd(t) = -10.3 to -10.4 and ISr = 0.71796 to 0.71923). Zircons in the dolerites have εHf(t) values of -7.6 to -10.9. The mafic volcanic rocks are interpreted to have resulted from the partial melting of an enriched lithospheric mantle source with minor crustal contamination during ascent, whereas the dolerites formed by late-stage crystallization of enriched lithospheric mantle-derived magmas after fractionation of olivine and pyroxene. The formation of these mantle-derived mafic rocks may be attributed to transtension along a NE-trending strike-slip fault zone that was related to oblique subduction of the Paleo-Pacific plate beneath South China. Such underplated mafic magmas would provide sufficient heat for the generation of ultrahigh-temperature metamorphism and S-type granites, and

  16. Zircon U-Pb ages and geochemistry of migmatites and granites in the Foping dome: Evidence for Late Triassic crustal evolution in South Qinling, China

    Science.gov (United States)

    Zhang, He; Li, Shuang-Qing; Fang, Bo-Wen; He, Jian-Feng; Xue, Ying-Yu; Siebel, Wolfgang; Chen, Fukun

    2018-01-01

    Migmatites provide a record of melt formation and crustal rheology. In this study we present zircon U-Pb ages and geochemical composition of migmatites from the Foping dome and granites from the Wulong pluton. U-Pb results from migmatite zircons indicate two episodes of partial melting. Rim domains from a leucosome in the Longcaoping area yield an age of ca. 209 Ma. Migmatites collected from the Foping dome yield U-Pb zircon ages of 2910 to 190 Ma, suggesting the involvement of meta-sedimentary source components. Rim domains of the zircons with low Th/U ratios (pluton can be subdivided into high Sr/Y and low Sr/Y granites. U-Pb zircon ages vary from 219 to 214 Ma for the high Sr/Y granites and from 214 to 192 Ma for the low Sr/Y granites. High Sr/Y granites have higher Na2O and Sr contents than the low Sr/Y granites. They also lack negative Eu anomalies and are depleted in HREE compared to the low Sr/Y granites. Initial 87Sr/86Sr ratios and εNd values of all the samples roughly overlap with those of Neoproterozoic basement rocks exposed in South Qinling. Including previous studies, we propose that the high and low Sr/Y granites formed by melting of thickened and normal crust, respectively. Close temporal-spatial relationship of the high and low Sr/Y granites with the two-stage migmatization events implies variation of crustal thickness and thermal overprints of the orogenic crust in post-collisional collapse. Following the collision of South Qinling and the Yangtze block prior to 219 Ma, partial melting of the deep crust occurred. The melts migrated upwards to form the high Sr/Y granites. This process occurred rapidly and caused collapse of the thickened crust and carried heat upwards, leading to further partial melting within the shallower crust and formation of the low Sr/Y granites.

  17. Permian Triassic palynofloral transition in Chintalapudi area, Godavari Graben, Andhra Pradesh, India

    Science.gov (United States)

    Jha, Neerja; Chary, M. Basava; Aggarwal, Neha

    2012-10-01

    The entire 606 m-thick sedimentary sequence in borecore MCP-7 from Chintalapudi area, Chintalapudi sub-basin has been lithologically designated as Kamthi Formation. However, the palynological investigation revealed five distinct palynoassemblages, which essentially fall under two groups, one group (Palynoassemblage-I, II and III) having dominance of striate disaccates along with presence of some stratigraphically significant taxa, belongs to Late Permian (Raniganj) palynoflora, while the other group (Palynoassemblages IV and V) shows sharp decline in percentage of characteristic taxa of first group, i.e., striate disaccates, and consequent rise or dominance of taeniate and cingulate cavate spores, belongs to Early Triassic (Panchet) palynoflora. Palynoassemblage-I, II and III (Group I) are characterized by dominance of striate disaccates chiefly, Striatopodocarpites spp. and Faunipollenites spp. along with presence of rare but stratigraphically significant taxa, viz., Gondisporites raniganjensis, Falcisporites nuthaliensis, Klausipollenites schaubergeri, Chordasporites sp., Striomonosaccites, ovatus, Crescentipollenites multistriatus, Verticipollenites debiles, Strotersporites crassiletus, Guttulapollenites hannonicus, G. gondwanensis, Hamiapollenites insolitus, Corisaccites alutus, Lunatisporites ovatus, Weylandites spp. and Vitreisporites pallidus. Palynoassemblage-I is distinguished by significant presence of Densipollenites spp. while Palynoassemblage-II shows significant presence of Crescentipollenites spp. and Palynoassemblage-III differs from the above two assemblages in having significant presence of Guttulapollenites hannonicus. Palynoassemblage-IV (Group II) is characterized by high percentage of taeniate disaccates chiefly Lunatisporites spp., while Palynoassemblage-V (Group II) is characterized by cingulate-cavate trilete spores chiefly, Lundbladispora spp. and Densoisporites spp. Striate disaccates show a sharp decline in these two assemblages. In

  18. Triassic volcanic units in coastal region of Antofagasta, northern Chile

    International Nuclear Information System (INIS)

    Basso, M.; Cortes, J.A.; Marinovic, N

    2001-01-01

    U-Pb geochronological evidence of a Middle to Late Triassic volcanic event was found in the coastal region of Antofagasta, northern Chile (23 o -23 o 30 ). Two new ages were obtained from rhyolitic tuffs and an associated dome, which have classically been attributed to the Jurassic La Negra Formation (au)

  19. Late Cretaceous and Cenozoic seafloor and oceanic basement roughness: Spreading rate, crustal age and sediment thickness correlations

    Science.gov (United States)

    Bird, Robert T.; Pockalny, Robert A.

    1994-05-01

    Single-channel seismic data from the South Australian Basin and Argentine Basin, and bathymetry data from the flanks of the Mid-Atlantic Ridge, East Pacific Rise and Southwest Indian Ridge are analysed to determine the root-mean-square (RMS) roughness of the seafloor and oceanic basement created at seafloor spreading rates ranging from 3 to 80 km/Ma (half-rate). For these data, crustal ages range from near zero to 85 Ma and sediment thicknesses range from near zero to over 2 km. Our results are consistent with a negative correlation of basement roughness and spreading rate where roughness decreases dramatically through the slow-spreading regime (oceanic basement roughness and spreading rate appears to have existed since the late Cretaceous for slow and intermediate spreading rates, suggesting that the fundamental processes creating abyssal hill topography may have remained the same for this time period. Basement roughness does not appear to decrease (smooth) with increasing crustal age, and therefore off-ridge degradation of abyssal hill topography by mass wasting is not detected by our data. Seismic data reveal that sediment thickness increases with increasing crustal age in the South Australian Basin and Argentine Basin, but not monotonically and with significant regional variation. We show that minor accumulations of sediment can affect roughness significantly. Average sediment accumulations of less that 50 m (for our 100 km long sample seismic profiles and half-spreading rates ocean ridges.

  20. Integrated multi-stratigraphic study of the Coll de Terrers late Permian-Early Triassic continental succession from the Catalan Pyrenees (NE Iberian Peninsula): A geologic reference record for equatorial Pangaea

    Science.gov (United States)

    Mujal, Eudald; Fortuny, Josep; Pérez-Cano, Jordi; Dinarès-Turell, Jaume; Ibáñez-Insa, Jordi; Oms, Oriol; Vila, Isabel; Bolet, Arnau; Anadón, Pere

    2017-12-01

    The most severe biotic crisis on Earth history occurred during the Permian-Triassic (PT) transition around 252 Ma. Whereas in the marine realm such extinction event is well-constrained, in terrestrial settings it is still poorly known, mainly due to the lack of suitable complete sections. This is utterly the case along the Western Tethys region, located at Pangaea's equator, where terrestrial successions are typically build-up of red beds often characterised by a significant erosive gap at the base of the Triassic strata. Henceforth, documenting potentially complete terrestrial successions along the PT transition becomes fundamental. Here, we document the exceptional Coll de Terrers area from the Catalan Pyrenees (NE Iberian Peninsula), for which a multidisciplinary research is conducted along the PT transition. The red-bed succession, located in a long E-W extended narrow rift system known as Pyrenean Basin, resulted from a continuous sedimentary deposition evolving from meandering (lower Upper Red Unit) to playa-lake/ephemeral lacustrine (upper Upper Red Unit) and again to meandering settings (Buntsandstein facies). Sedimentary continuity is suggested by preliminary cyclostratigraphic analysis that warrants further analysis. Our combined sedimentological, mineralogical and geochemical data infer a humid-semiarid-humid climatic trend across the studied succession. The uppermost Permian strata, deposited under an orbitally controlled monsoonal regime, yields a relatively diverse ichnoassemblage mainly composed of tetrapod footprints and arthropod trace fossils. Such fossils indicate appropriate life conditions and water presence in levels that also display desiccation structures. These levels alternate with barren intervals formed under dry conditions, being thus indicative of strong seasonality. All these features are correlated with those reported elsewhere in Gondwana and Laurasia, and suggest that the Permian-Triassic boundary might be recorded somewhere around

  1. Unappreciated diversification of stem archosaurs during the Middle Triassic predated the dominance of dinosaurs.

    Science.gov (United States)

    Foth, Christian; Ezcurra, Martín D; Sookias, Roland B; Brusatte, Stephen L; Butler, Richard J

    2016-09-15

    Archosauromorpha originated in the middle-late Permian, radiated during the Triassic, and gave rise to the crown group Archosauria, a highly successful clade of reptiles in terrestrial ecosystems over the last 250 million years. However, scientific attention has mainly focused on the diversification of archosaurs, while their stem lineage (i.e. non-archosaurian archosauromorphs) has often been overlooked in discussions of the evolutionary success of Archosauria. Here, we analyse the cranial disparity of late Permian to Early Jurassic archosauromorphs and make comparisons between non-archosaurian archosauromorphs and archosaurs (including Pseudosuchia and Ornithodira) on the basis of two-dimensional geometric morphometrics. Our analysis recovers previously unappreciated high morphological disparity for non-archosaurian archosauromorphs, especially during the Middle Triassic, which abruptly declined during the early Late Triassic (Carnian). By contrast, cranial disparity of archosaurs increased from the Middle Triassic into the Late Triassic, declined during the end-Triassic extinction, but re-expanded towards the end of the Early Jurassic. Our study indicates that non-archosaurian archosauromorphs were highly diverse components of terrestrial ecosystems prior to the major radiation of archosaurs, including dinosaurs, while disparity patterns of the Ladinian and Carnian indicate a gradual faunal replacement of stem archosaurs by the crown group, including a short interval of partial overlap in morphospace during the Ladinian.

  2. Middle-Upper Triassic and Middle Jurassic tetrapod track assemblages of southern Tunisia, Sahara Platform

    Science.gov (United States)

    Niedźwiedzki, Grzegorz; Soussi, Mohamed; Boukhalfa, Kamel; Gierliński, Gerard D.

    2017-05-01

    Three tetrapod track assemblages from the early-middle Mesozoic of southern Tunisia are reported. The strata exposed at the Tejra 2 clay-pit near the Medenine and Rehach site, located in the vicinity of Kirchaou, contain the first tetrapod tracks found in the Triassic of Tunisia. The Middle Jurassic (early Aalenian) dinosaur tracks are reported from the Mestaoua plain near Tataouine. In the Middle Triassic outcrop of the Tejra 2 clay-pit, tridactyl tracks of small and medium-sized dinosauromorphs, were discovered. These tracks represent the oldest evidence of dinosaur-lineage elements in the Triassic deposits of Tunisia. Similar tracks have been described from the Middle Triassic of Argentina, France and Morocco. An isolated set of the manus and pes of a quadrupedal tetrapod discovered in Late Triassic Rehach tracksite is referred to a therapsid tracemaker. The Middle Jurassic deposits of the Mestaoua plain reveal small and large tridactyl theropod dinosaur tracks (Theropoda track indet. A-C). Based on comparison with the abundant record of Triassic tetrapod ichnofossils from Europe and North America, the ichnofauna described here indicates the presence of a therapsid-dinosauromorph ichnoassociation (without typical Chirotheriidae tracks) in the Middle and Late Triassic, which sheds light on the dispersal of the Middle-Upper Triassic tetrapod ichnofaunas in this part of Gondwana. The reported Middle Jurassic ichnofauna show close similarities to dinosaur track assemblages from the Lower and Middle Jurassic of northwestern Africa, North America, Europe and also southeastern Asia. Sedimentological and lithostratigraphic data of each new tracksite have been defined on published data and new observations. Taken together, these discoveries present a tantalizing window into the evolutionary history of tetrapods from the Triassic and Jurassic of southern Tunisia. Given the limited early Mesozoic tetrapod record from the region, these discoveries are of both temporal and

  3. Patterns of fossil distributions within their environmental context from the Middle Triassic in South Canyon, Central Nevada, USA

    Directory of Open Access Journals (Sweden)

    Pedro M. Monarrez

    2014-01-01

    Full Text Available The Middle Triassic records the return of diverse marine communities after the severe effects of the end-Permian mass extinction. This diversification leads to the Mesozoic/modern adaptive radiation resulting in substantial changes in marine communities in comparison to their Paleozoic predecessors. This analysis focuses on the faunal abundance, ecological patterns, and environmental interpretation of a Middle Triassic section in Central Nevada. Twelve bulk samples were collected. Visible fossils were identified and tallied from hand samples and thin-sections were used to aid in environmental interpretation. Beginning in the Late Anisian, we observed an ammonoid dominated to flat-clam, epifaunal dominated benthic community within a muddy, quiet, inner shelf depositional environment. Through time, epifaunal bivalves dominate within a middle shelf environment followed by an increase in infaunalization and shell-thickness. During this time the presence of oncoids and the reported finding of corals suggest the middle shelf environment gave way to a higher energy patch reef shelf edge environment. Finally, we observe epifaunal brachiopods communities at the top of our section deposited in a middle shelf environment. In sum, we observe the dominance of modern taxa (i.e., bivalves with Paleozoic ecologies (i.e., epifaunal, followed by the dominance of modern taxa with Modern ecologies (i.e., infaunal, thick shells and then a return to Paleozoic taxa (i.e., brachiopods and Paleozoic ecologies within an overall transgressive environment.

  4. Conodont zonation of Lower Triassic strata in Slovenia

    Directory of Open Access Journals (Sweden)

    Tea Kolar-Jurkovšek

    2015-12-01

    Full Text Available The paper presents the results of a conodont study carried out in the Triassic strata in the area of the Slovenian part of the Southern Alps, External Dinarides and the Transition region between the External and Internal Dinarides. The following conodont zones have been distinguished: Hindeodus praeparvus Z., H. parvus Z., Isarcicella lobata Z., I. staeschei – I. isarcica Z., H. postparvus Z., Hadrodontina aequabilis Z., Ha. anceps Z., Eurygnathodus costatus Z., Neospathodus planus Z., N. robustus Z., Platyvillosus corniger Z., Pl. regularis Z., Pachycladina obliqua Z., Foliella gardenae Z., Triassospathodus hungaricus Z., T. symmetricus Z., N. robustispinus - T. homeri Z. and T. triangularis Z. The introduced conodont zonation spans from the Induan, including the Permian-Triassic boundary interval to the late Olenekian and is valid for the shallow shelf environments of western Tethys.

  5. A new archosauriform (Reptilia: Diapsida) from the Manda beds (Middle Triassic) of southwestern Tanzania.

    Science.gov (United States)

    Nesbitt, Sterling J; Butler, Richard J; Gower, David J

    2013-01-01

    Archosauria and their closest relatives, the non-archosaurian archosauriforms, diversified in the Early and Middle Triassic, soon after the end-Permian extinction. This diversification is poorly documented in most Lower and Middle Triassic rock sequences because fossils of early groups of archosauriforms are relatively rare compared to those of other amniotes. The early Middle Triassic (? late Anisian) Manda beds of southwestern Tanzania form an exception, with early archosaur skeletons being relatively common and preserved as articulated or associated specimens. The Manda archosaur assemblage is exceptionally diverse for the Middle Triassic. However, to date, no non-archosaurian archosauriforms have been reported from these rocks. Here, we name a new taxon, Asperoris mnyama gen. et sp. nov., from the Manda beds and thoroughly describe the only known specimen. The specimen consists of a well-preserved partial skull including tooth-bearing elements (premaxilla, maxilla), the nasal, partial skull roof, and several incomplete elements. All skull elements are covered in an autapomorphic highly rugose sculpturing. A unique combination of character states indicates that A. mnyama lies just outside Archosauria as a stem archosaur within Archosauriformes, but more precise relationships of A. mnyama relative to other early archosauriform clades (e.g., Erythrosuchidae) cannot be determined currently. Asperoris mnyama is the first confirmed non-archosaurian archosauriform from the Manda beds and increases the morphological and taxonomic diversity of early archosauriforms known from the Middle Triassic. The direct association of A. mnyama with species referable to Archosauria demonstrates that non-archosaurian archosauriforms were present during the rise and early diversification of Archosauria. Non-archosaurian archosauriforms and archosaurs co-occur in fossil reptile assemblages across Pangaea from the late Early Triassic to the end of the Late Triassic.

  6. NEW TRIASSIC ASTEROIDEA (ECHINODERMATA SPECIMENS AND THEIR EVOLUTIONARY SIGNIFICANCE

    Directory of Open Access Journals (Sweden)

    DANIEL B. BLAKE

    2017-04-01

    Full Text Available The Paleozoic-Mesozoic transition saw the disappearance of asteroid stem groups and the ascent of the crown group, but late Paleozoic and Triassic asteroids are rare and transition events are poorly documented. Three new Middle and Late Triassic specimens augment existing data; included are a specimen of Trichasteropsis weissmanni from Germany, a specimen of Trichasteropsis? sp. indet. from Italy, and a possible member of the extant Poraniidae from Slovenia. Presence of a small ossicle at the interbrachial midline and adjacent to the marginal series of the new T. weissmanni specimen is consistent with similar expressions not only of other trichasteropsids but also occurrence of two interbrachial ossicles in Paleozoic, stem-group asterozoans; presence is in turn consistent with a hypothesis of derivation of the axillary/odontophore coupling from two ossicles rather than direct derivation of the crown-group odontophore from a single stem-group axillary. Morphology of Trichasteropsis? sp. indet., including, for example, the evenly-tapering arms are reminiscent of those of diverse crown-group asteroids whereas the enlarged distal arms of T. weissmanni are unique, the morphology of T? sp. indet. thereby potentially indicative of a plesiomorphic, stemward positioning within the Trichasteropsiidae. The range of the Poraniidae is tentatively extended to the Carnian. Similarities shared by the Poraniidae and the Trichasteropsiidae suggest stemward positioning within crown-group diversification; however, known Triassic fossils do not appear closely related to extant taxa identified in recent molecular studies as basal within the crown-group. A temperate climate is suggested as preferred by the Triassic asteroids rather than a tropical, warmer one.

  7. Early Triassic development of a foreland basin in the Canadian high Arctic: Implications for a Pangean Rim of Fire

    Science.gov (United States)

    Hadlari, Thomas; Dewing, Keith; Matthews, William A.; Alonso-Torres, Daniel; Midwinter, Derrick

    2018-06-01

    Following the amalgamation of Laurasia and Gondwana to form Pangea, some Triassic tectonic models show an encircling arc system called the "Pangean Rim of Fire". Here we show that the stratigraphy and Early Triassic detrital zircon provenance of the Sverdrup Basin in the Canadian Arctic is most consistent with deposition in a retro-arc foreland basin. Late Permian and Early Triassic volcanism was accompanied by relatively high rates of subsidence leading to a starved basin with volcanic input from a magmatic arc to the northwest. The mostly starved basin persisted through the Middle and Late Triassic with nearly continuous input of volcanic ash recorded as bentonites on the northwestern edge of the basin. In the latest Triassic it is interpreted that decreasing subsidence and a significant influx of sand-grade sediment when the arc was exhumed led to filling of the basin at the end of an orogenic cycle. Combined with other hints of Early Triassic arc activity along the western margin of Laurentia we propose that the Pangean Rim of Fire configuration spanned the entire Triassic. This proposed configuration represents the ring of external subduction zones that some models suggest are necessary for the breakup of supercontinents such as Pangea.

  8. Early archosauromorph remains from the Permo-Triassic Buena Vista Formation of north-eastern Uruguay

    Directory of Open Access Journals (Sweden)

    Martín D. Ezcurra

    2015-02-01

    Full Text Available The Permo-Triassic archosauromorph record is crucial to understand the impact of the Permo-Triassic mass extinction on the early evolution of the group and its subsequent dominance in Mesozoic terrestrial ecosystems. However, the Permo-Triassic archosauromorph record is still very poor in most continents and hampers the identification of global macroevolutionary patterns. Here we describe cranial and postcranial bones from the Permo-Triassic Buena Vista Formation of northeastern Uruguay that contribute to increase the meagre early archosauromorph record from South America. A basioccipital fused to both partial exoccipitals and three cervical vertebrae are assigned to Archosauromorpha based on apomorphies or a unique combination of characters. The archosauromorph remains of the Buena Vista Formation probably represent a multi-taxonomic assemblage composed of non-archosauriform archosauromorphs and a ‘proterosuchid-grade’ animal. This assemblage does not contribute in the discussion of a Late Permian or Early Triassic age for the Buena Vista Formation, but reinforces the broad palaeobiogeographic distribution of ‘proterosuchid grade’ diapsids in Permo-Triassic beds worldwide.

  9. Early archosauromorph remains from the Permo-Triassic Buena Vista Formation of north-eastern Uruguay.

    Science.gov (United States)

    Ezcurra, Martín D; Velozo, Pablo; Meneghel, Melitta; Piñeiro, Graciela

    2015-01-01

    The Permo-Triassic archosauromorph record is crucial to understand the impact of the Permo-Triassic mass extinction on the early evolution of the group and its subsequent dominance in Mesozoic terrestrial ecosystems. However, the Permo-Triassic archosauromorph record is still very poor in most continents and hampers the identification of global macroevolutionary patterns. Here we describe cranial and postcranial bones from the Permo-Triassic Buena Vista Formation of northeastern Uruguay that contribute to increase the meagre early archosauromorph record from South America. A basioccipital fused to both partial exoccipitals and three cervical vertebrae are assigned to Archosauromorpha based on apomorphies or a unique combination of characters. The archosauromorph remains of the Buena Vista Formation probably represent a multi-taxonomic assemblage composed of non-archosauriform archosauromorphs and a 'proterosuchid-grade' animal. This assemblage does not contribute in the discussion of a Late Permian or Early Triassic age for the Buena Vista Formation, but reinforces the broad palaeobiogeographic distribution of 'proterosuchid grade' diapsids in Permo-Triassic beds worldwide.

  10. Upper Triassic spongiomorph and coral association dredged off the northwestern Australian shelf

    Science.gov (United States)

    Stanley, G. D.

    Upper Triassic corals and spongiomorphs dredged during BMR Cruise 95 from the Rowley Terrace, offshore Canning Basin of northwestern Australia, indicate possible new occurrences of reef facies. These are comparable to counterparts known from the Norhtern Limestone Alps of central Europe. A branching spongiomorph, represented by the genus Spongiomorpha sp. and two coral taxa, Pamiroseris rectilamellosa (Winkler) and Retiophyllia tellae (Stoppani), are reported herein. Collectively, these fossils indicate a Late Triassic (Noria-Rhaetian) age. Although different in taxonomic composition, the fauna compares with one previously reported from a Late Triassic Ocean Drilling Project reef site (site 764) on the Wombat Plateau, some 350 km to the west. The Rowley Terrace occurrences may represent an eastward extension of the Wombat reefs, developed along the rifted margin of Gondwana.

  11. The Middle Triassic insect radiation revealed by isotopic age and iconic fossils from NW China

    Science.gov (United States)

    Zheng, Daran; Chang, Su-Chin; Wang, He; Fang, Yan; Wang, Jun; Feng, Chongqing; Xie, Guwei; Jarzembowski, Edmund A.; Zhang, Haichun; Wang, Bo

    2017-04-01

    Following the end-Permian mass extinction, the Triassic represented an important period witnessing the recovery and radiation of marine and terrestrial ecosystems. Terrestrial plants and vertebrates have been widely investigated; however the insects, the most diverse organisms on earth, remain enigmatic due to the rarity of Early-Middle Triassic fossils. Here we report new fossils from a Ladinian deposit dated at 238-237 Ma and a Carnian deposit in northwestern China, including the earliest definite caddisfly cases (Trichoptera) and water boatmen (Hemiptera), diverse polyphagan beetles (Coleoptera) and scorpionflies (Mecoptera). Our findings suggest that the Holometabola, comprising the majority of modern-day insect species, experienced an extraordinary diversification in the Middle Triassic and was already been dominant in some Middle and Late Triassic insect faunas, after the extinction of several ecologically dominant, Paleozoic insect groups in the latest Permian and earliest Triassic. This turnover is perhaps related to notable episodes of extreme warming and drying, leading to the eventual demise of coal-swamp ecosystems, evidenced by floral turnover during this interval. The forest revival during the Middle Triassic probably stimulated the rapid radiation and evolution of insects including some key aquatic lineages which built new associations that persist to the present day. Our results provide not only new insights into the early evolution of insect diversity and ecology, but also robust evidence for the view that the Triassic is the "Dawn of the Modern World". Besides, LA-ICP-MS U-Pb dating initially gave a late Ladinian age for the Tongchuan entomnfauna after the results: 237.41 ± 0.91 Ma and 238 ± 0.97 Ma. The age is in agreement with that of the marine Ladinian-Carnian boundary, representing a novel age constraint for the terrestrial strata near this boundary. This age can provide a calibration for marine and terrestrial correlation near Ladinian

  12. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.

    Directory of Open Access Journals (Sweden)

    Ziliang Liu

    Full Text Available A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km. The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front

  13. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.

    Science.gov (United States)

    Liu, Ziliang; Shen, Fang; Zhu, Xiaomin; Li, Fengjie; Tan, Mengqi

    2015-01-01

    A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km). The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front" character.

  14. Volatile earliest Triassic sulfur cycle

    DEFF Research Database (Denmark)

    Schobben, Martin; Stebbins, Alan; Algeo, Thomas J.

    2017-01-01

    model experiment. Exposure of evaporite deposits having a high δ 34S may account for the source change, with a possible role for the Siberian Traps volcanism by magmatic remobilization of Cambrian rock salt. A high sulfur cycle turnover rate would have left the ocean system vulnerable to development......Marine biodiversity decreases and ecosystem destruction during the end-Permian mass extinction (EPME) have been linked to widespread marine euxinic conditions. Changes in the biogeochemical sulfur cycle, microbial sulfate reduction (MSR), and marine dissolved sulfate concentrations during...... fractionation and point to a more universal control, i.e., contemporaneous seawater sulfate concentration.The MSR-trend transfer function yielded estimates of seawater sulfate of 0.6-2.8mM for the latest Permian to earliest Triassic, suggesting a balanced oceanic S-cycle with equal S inputs and outputs...

  15. Organic geochemical characterization of terrestrial source rocks of the Triassic Madygen formation (Southern Tien Shan, Kyrgyzstan)

    Energy Technology Data Exchange (ETDEWEB)

    Berner, U.; Scheeder, G.; Kus, J. [Section Geochemistry of Petroleum and Coal, BGR, Hannover (Germany); Voigt, S.; Schneider, J.W. [Geological Inst., TU Bergakademic Freiberg (Germany)

    2009-09-15

    Along the northern foothills of the Turkestan-Alai Range (SW Kyrgyzstan), a 1000 to 1500m thick succession of Mesozoic deposits is exposed recording regional changes of the paleo-landscape during Triassic to Cretaceous times. Detailed litho- and biofacies analyses, conducted by the TU Bergakademie Freiberg since 2006, provided for the first time a nearly complete columnar section of the continental Triassic Madygen Formation of Kyrgyzstan. Organic petrographical and organic geochemical methods (including RockEval pyrolyses, and biomarker analyses) have been applied to a suite of terrestrial sedimentary rocks of Triassic age with the intention to identify the depositional environment. Our investigations suggest that the potential source rocks of the terrestrial pluvial Madygen Formation might generate predominantly gaseous hydrocarbons at higher maturities. (orig.)

  16. Impact of Early and Late Visual Deprivation on the Structure of the Corpus Callosum: A Study Combining Thickness Profile with Surface Tensor-Based Morphometry.

    Science.gov (United States)

    Shi, Jie; Collignon, Olivier; Xu, Liang; Wang, Gang; Kang, Yue; Leporé, Franco; Lao, Yi; Joshi, Anand A; Leporé, Natasha; Wang, Yalin

    2015-07-01

    Blindness represents a unique model to study how visual experience may shape the development of brain organization. Exploring how the structure of the corpus callosum (CC) reorganizes ensuing visual deprivation is of particular interest due to its important functional implication in vision (e.g., via the splenium of the CC). Moreover, comparing early versus late visually deprived individuals has the potential to unravel the existence of a sensitive period for reshaping the CC structure. Here, we develop a novel framework to capture a complete set of shape differences in the CC between congenitally blind (CB), late blind (LB) and sighted control (SC) groups. The CCs were manually segmented from T1-weighted brain MRI and modeled by 3D tetrahedral meshes. We statistically compared the combination of local area and thickness at each point between subject groups. Differences in area are found using surface tensor-based morphometry; thickness is estimated by tracing the streamlines in the volumetric harmonic field. Group differences were assessed on this combined measure using Hotelling's T(2) test. Interestingly, we observed that the total callosal volume did not differ between the groups. However, our fine-grained analysis reveals significant differences mostly localized around the splenium areas between both blind groups and the sighted group (general effects of blindness) and, importantly, specific dissimilarities between the LB and CB groups, illustrating the existence of a sensitive period for reorganization. The new multivariate statistics also gave better effect sizes for detecting morphometric differences, relative to other statistics. They may boost statistical power for CC morphometric analyses.

  17. Adaptations for marine habitat and the effect of Triassic and Jurassic predator pressure on development of decompression syndrome in ichthyosaurs

    Science.gov (United States)

    Rothschild, B. M.; Xiaoting, Z.; Martin, L. D.

    2012-06-01

    Decompression syndrome (caisson disease or the "the bends") resulting in avascular necrosis has been documented in mosasaurs, sauropterygians, ichthyosaurs, and turtles from the Middle Jurassic to Late Cretaceous, but it was unclear that this disease occurred as far back as the Triassic. We have examined a large Triassic sample of ichthyosaurs and compared it with an equally large post-Triassic sample. Avascular necrosis was observed in over 15 % of Late Middle Jurassic to Cretaceous ichthyosaurs with the highest occurrence (18 %) in the Early Cretaceous, but was rare or absent in geologically older specimens. Triassic reptiles that dive were either physiologically protected, or rapid changes of their position in the water column rare and insignificant enough to prevent being recorded in the skeleton. Emergency surfacing due to a threat from an underwater predator may be the most important cause of avascular necrosis for air-breathing divers, with relative frequency of such events documented in the skeleton. Diving in the Triassic appears to have been a "leisurely" behavior until the evolution of large predators in the Late Jurassic that forced sudden depth alterations contributed to a higher occurrence of bends.

  18. TAXONOMY AND BIOSTRATIGRAPHIC RECORD OF THE UPPER TRIASSIC CONODONTS OF THE PIZZO MONDELLO SECTION (WESTERN SICILY, ITALY, GSSP CANDIDATE FOR THE BASE OF THE NORIAN

    Directory of Open Access Journals (Sweden)

    MICHELE MAZZA

    2012-03-01

    Full Text Available New taxonomic and biostratigraphic investigations on the late Carnian to Rhaetian (Upper Triassic platform conodonts from the Pizzo Mondello section (Western Sicily, Italy, Sicano basin are here presented. Pizzo Mondello is one of the two GSSP candidates for the Carnian/Norian boundary; the section is a 430 m thick continuous succession of upper Carnian to upper Norian marine limestones (Scillato Formation, characterized by uniform facies and high sedimentation rates, and ca. 20 m of Rhaetian white calcilutites (Portella Gebbia limestone. Pizzo Mondello offers one of the most complete conodont records for this time interval in the Tethys. The conodont faunas are characterized by a large variety of species, belonging to the genera Carnepigondolella, Epigondolella, Metapolygnathus, Misikella, Mockina, Neocavitella, Norigondolella, Paragondolella, and Parvigondolella. The richness of the populations allowed a detailed revision and description of all the Upper Triassic species and morphotypes recovered. The revision of the problematic species Carnepigondolella nodosa and "Metapolygnathus communisti B" was thus possible, leading to the establishment of two new species: Carnepigondolella tuvalica n.sp. and Carnepigondolella gulloae n.sp. The latter species would be a good proxy for the Carnian/Norian boundary in the case that the FAD of Halobia austriaca (sample FNP135a will be selected as the primary biomarker for the base of the Norian. 

  19. In hypertrophic cardiomyopathy reduction of relative resting myocardial blood flow is related to late enhancement, T2-signal and LV wall thickness.

    Directory of Open Access Journals (Sweden)

    Katja Hueper

    Full Text Available To quantify resting myocardial blood flow (MBF in the left ventricular (LV wall of HCM patients and to determine the relationship to important parameters of disease: LV wall thickness, late gadolinium enhancement (LGE, T2-signal abnormalities (dark and bright signal, LV outflow tract obstruction and age.Seventy patients with proven HCM underwent cardiac MRI. Absolute and relative resting MBF were calculated from cardiac perfusion MRI by using the Fermi function model. The relationship between relative MBF and LV wall thickness, T2-signal abnormalities (T2 dark and T2 bright signal, LGE, age and LV outflow gradient as determined by echocardiography was determined using simple and multiple linear regression analysis. Categories of reduced and elevated perfusion in relation to non- or mildly affected reference segments were defined, and T2-signal characteristics and extent as well as pattern of LGE were examined. Statistical testing included linear and logistic regression analysis, unpaired t-test, odds ratios, and Fisher's exact test.804 segments in 70 patients were included in the analysis. In a simple linear regression model LV wall thickness (p<0.001, extent of LGE (p<0.001, presence of edema, defined as focal T2 bright signal (p<0.001, T2 dark signal (p<0.001 and age (p = 0.032 correlated inversely with relative resting MBF. The LV outflow gradient did not show any effect on resting perfusion (p = 0.901. Multiple linear regression analysis revealed that LGE (p<0.001, edema (p = 0.026 and T2 dark signal (p = 0.019 were independent predictors of relative resting MBF. Segments with reduced resting perfusion demonstrated different LGE patterns compared to segments with elevated resting perfusion.In HCM resting MBF is significantly reduced depending on LV wall thickness, extent of LGE, focal T2 signal abnormalities and age. Furthermore, different patterns of perfusion in HCM patients have been defined, which may represent different stages of

  20. MIDDLE TRIASSIC AUTOCLASTIC DEPOSITS FROM SOUTHWESTERN BOSNIA AND HERZEGOVINA

    Directory of Open Access Journals (Sweden)

    Duje Smirčić

    2016-06-01

    Full Text Available Middle Triassic volcanic and volcaniclastic rocks have been recognized at several localities near Bosansko Grahovo, in southwestern part of Bosnia and Herzegovina in the External Dinarides. Peculiar types of autoclastic rocks were investigated. These are peperites and hyaloclastites. Regarding specific structures, mineral composition and micropetrographic characteristics it was possible to further differentiate hyaloclastites into in situ hyaloclastites and slightly resedimented hyaloclastites that represent genetic succession. All rock types occurred in a deep sea troughs that formed as a consequence of Middle Triassic extensional tectonic and rift related wrench faulting. In situ hyaloclastites and slightly resedimented hyaloclastites were formed due to quenching at the contact of lava effusions with sea water. Genesis of peperites is related to lava emplacement in unconsolidated water saturated lime mudstones that were deposited in deep sea basin. All investigated rock types represent first findings of autoclastic deposits in the External Dinarides. Biostratigraphic constraints achieved by means of conodont species Neogondolella excentrica, Paragondolella excelsa, Paragondolella trammeri and Gladigondolella tethydis indicate Late Anisian to Early Ladinian interval of the autoclastic deposits from Bosansko Grahovo.

  1. Depositional setting and vertebrate biostratigraphy of the Triassic ...

    Indian Academy of Sciences (India)

    The Dockum tetrapod diversity is reviewed in a hierarchical phylogeny with remarks on the history of ...... Triassic ecosystem. A review of ... form of fish from the Triassic beds of Texas, with remarks ..... ships and functional implications; J. Vert.

  2. Sedimentology of the Upper Triassic-Lower Jurassic (?) Mosolotsane Formation (Karoo Supergroup), Kalahari Karoo Basin, Botswana

    Science.gov (United States)

    Bordy, Emese M.; Segwabe, Tebogo; Makuke, Bonno

    2010-08-01

    The Mosolotsane Formation (Lebung Group, Karoo Supergroup) in the Kalahari Karoo Basin of Botswana is a scantly exposed, terrestrial red bed succession which is lithologically correlated with the Late Triassic to Early Jurassic Molteno and Elliot Formations (Karoo Supergroup) in South Africa. New evidence derived from field observations and borehole data via sedimentary facies analysis allowed the assessment of the facies characteristics, distribution and thickness variation as well as palaeo-current directions and sediment composition, and resulted in the palaeo-environmental reconstruction of this poorly known unit. Our results show that the Mosolotsane Formation was deposited in a relatively low-sinuosity meandering river system that drained in a possibly semi-arid environment. Sandstone petrography revealed mainly quartz-rich arenites that were derived from a continental block provenance dominated by metamorphic and/or igneous rocks. Palaeo-flow measurements indicate reasonably strong, unidirectional current patterns with mean flow directions from southeast and east-southeast to northwest and west-northwest. Regional thickness and facies distributions as well as palaeo-drainage indicators suggest that the main depocenter of the Mosolotsane Formation was in the central part of the Kalahari Karoo Basin. Separated from this main depocenter by a west-northwest - east-southeast trending elevated area, an additional depocenter was situated in the north-northeast part of the basin and probably formed part of the Mid-Zambezi Karoo Basin. In addition, data also suggests that further northeast-southwest trending uplands probably existed in the northwest and east, the latter separating the main Kalahari Karoo depocenter from the Tuli Basin.

  3. Age and provenance of Triassic to Cenozoic sediments of West and Central Sarawak, Malaysia

    Science.gov (United States)

    Breitfeld, H. Tim; Galin, Thomson; Hall, Robert

    2015-04-01

    Sarawak is located on the northern edge of Sundaland in NW Borneo. West and Central Sarawak include parts of the Kuching and Sibu Zones. These contain remnants of several sedimentary basins with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic (Sadong Formation and its deep marine equivalent Kuching Formation). They were sourced by a Triassic (Carnian to Norian) volcanic arc and reworked Paleoproterozoic detritus derived from Cathaysialand. The Upper Jurassic to Cretaceous Pedawan Formation is interpreted as forearc basin fill with distinctive zircon populations indicating subduction beneath present-day West Sarawak which initiated in the Late Jurassic. Subsequent subduction until the early Late Cretaceous formed the Schwaner Mountains magmatic arc. After collision of SW Borneo and other microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension followed and were responsible for basin development on land in West Sarawak from the latest Cretaceous onwards, probably in a pull-apart setting. The first episode is associated with sediments of the Kayan Group, deposited in the Latest Cretaceous (Maastrichtian) to Eocene, and the second episode with Upper Eocene sediments of the Ketungau Basin. Zircon ages indicate volcanic activity throughout the Early Cenozoic in NW Borneo, and inherited zircon ages indicate reworking of Triassic and Cretaceous rocks. A large deep marine basin, the Rajang Basin, was north of the Lupar Line Fault in Central Sarawak (Sibu Zone) from the Late Cretaceous to the Late Eocene. Zircons from sediments of the Rajang Basin indicate they have similar ages and provenance to contemporaneous terrestrial sediments of the Kayan

  4. A NEW SAURICHTHYS (ACTINOPTERYGII FROM THE SPATHIAN (EARLY TRIASSIC OF CHAOHU (ANHUI PROVINCE, CHINA

    Directory of Open Access Journals (Sweden)

    ANDREA TINTORI

    2014-07-01

    Full Text Available A new species of Saurichthys, S. majiashanensis , is described. It comes from a series of marine vertebrate-bearing beds of the upper member of the Nanlinghu Formation outcropping in the large quarry at the top of Majiashan (Majia Hill near Chaohu (Hefei City, Anhui Province, China. Its age is Middle Spathian (Olenekian, Early Triassic. This new species deeply differs from the several pre-Spathian species of Saurichthys mainly for having only two longitudinal scale rows together with a reduced grid-like structure for the neural elements in the vertebral column. Further derived characters are in the endoskeleton of the dorsal and anal fin, where radials articulate only to anterior lepidotrichia, the posterior ones being supported by the first scale from the caudal pedicle mid-dorsal and mid-ventral rows, deeply imbedded in the body. In addition, the haemal spines of the caudal region are much enlarged and reversed, with their distal parts pointing forwards. Though the skull is lacking, postcranial characters are enough to justify the erection of a new species. This new Saurichthys species, together with other few actinopterygians, can be considered as the oldest assemblage of the Triassic Middle Fish Fauna, which bloomed probably in the early Anisian and widespread especially all over the Tethys for the Middle Triassic and at least the Carnian in the Late Triassic. This new fish assemblage, together with some of the oldest marine reptiles, is considered as the beginning of the actual Triassic recovery among marine vertebrates.

  5. CONODONT BIOSTRATIGRAPHY AND LITHOSTRATIGRAPHY ACROSS THE PERMIAN-TRIASSIC BOUNDARY AT THE LUKAC SECTION IN WESTERN SLOVENIA

    Directory of Open Access Journals (Sweden)

    TEA KOLAR-JURKOVSEK

    2011-03-01

    Full Text Available Detailed conodont biostratigraphy and lithostratigraphy of the Late Permian and Early Triassic beds were studied at the LukaC section in western Slovenia. The analyzed section is composed of the Bellerophon Formation ("evaporite-dolomite member" and the newly introduced Lukaè Formation ("transitional beds", "streaky limestone member" and "carbonate-clastic beds member". The Permian-Triassic boundary interval is represented by "transitional beds" of carbonate facies deposited in shallow restricted marine conditions. The presence of H. parvus in sample L1 in the "transitional beds" marks the systemic boundary between Permian and Triassic. The studied interval is characterized by a diverse microfauna that contain conodonts, foraminifers, ostracods and gastropods. Six conodont zones have been recognized, in ascending order, the latest Changhsingian (uppermost Permian praeparvus Zone, and the Griesbachian (lowermost Triassic parvus, lobata, staeschei-isarcica, postparvus and anceps zones. This faunal succession represents the first known and the most complete conodont biozonation across the Permian-Triassic interval from the entire Dinaric region. The recognized conodont biozones can be correlated with the biozonation of the Southern Alps and of the GSSP Meishan D section. 

  6. Origin and tectonic evolution of upper Triassic Turbidites in the Indo-Burman ranges, West Myanmar

    Science.gov (United States)

    Yao, Wei; Ding, Lin; Cai, Fulong; Wang, Houqi; Xu, Qiang; Zaw, Than

    2017-11-01

    The Pane Chaung Formation is exposed in the Indo-Burman Ranges, and has been involved in collision between the Indian Plate and West Burma Block. However, controversies exist over the provenance and paleogeographic reconstruction of the Pane Chaung Formation. This study presents new petrographical and detrital zircon Usbnd Pb ages and Hf isotopic data from the Pane Chaung Formation in Rakhine Yoma and Chin Hills, west Myanmar. The depositional age of the Pane Chaung Formation is Late Triassic, indicated by the Carnian-Norian Halobia fossils and maximum depositional ages between 233.0 ± 2.5 Ma and 206.2 ± 1.8 Ma. Upper Triassic sandstones contain 290-200 Ma detrital zircons, εHf(t) values of - 6 to 11 and TDMC of 1.6 to 0.6 Ga, interpreted to be derived from West Papua region. The most abundant zircon age population of 750-450 Ma is derived from Pan-African orogenic belts in Australia. Zircons of 1250-900 Ma age were derived from the Grenvillian orogen in Australia. Archean zircons are interpreted to be derived from the Yilgarn and Pilbara cratons in Western Australia. Detrital zircon ages of the Pane Chaung Formation are distinct from similar aged strata in Indochina and Sibumasu, but comparable to NW Australia (Carnarvon Basin) and Greater India (Langjiexue Formation). It is suggested that the Pane Chaung Formation was deposited in a Late Triassic submarine fan along the northern margin of Australia.

  7. The geology and hydrocarbon possibilities of the Triassic-Jurassic Fundy Basin, eastern Canada

    Energy Technology Data Exchange (ETDEWEB)

    Wade, J.A.; Fensome, R.A. [Geological Survey of Canada, Dartmouth, NS (Canada). Atlantic Geoscience Centre; Brown, D.E. [Canada-Nova Scotia Offshore Petroleum Board, Halifax, NS (Canada)

    1997-09-01

    The development of the Mesozoic sedimentary basins beneath the waters of the eastern coast of North America was discussed. These basins have been linked to the rifting of the central part of Pangaea during Mid and Late Triassic time that ended in the formation of a series of grabens extending from Florida to The Grand Banks of Newfoundland, one of them being the Bay of Fundy Basin which is about 16,500 square kilometres in size. Onshore and offshore geologic mapping and seismic interpretations have shown their age range to be from the Mid Triassic Anisian or Ladinian to Mid Jurassic. Up to 12 km of Mesozoic rocks were deposited in the basin with up to 9 km still present. The depositional history of the area was described. The two areas with greatest hydrocarbon potential are the Bay of Fundy and the Chignecto subbasins.

  8. Remagnetization mechanisms in Triassic red beds from South China

    Science.gov (United States)

    Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J.; Zhao, Xiang; Roberts, Andrew P.; Yang, Zhenyu; Jin, Chunsheng; Liu, Jianxing

    2017-12-01

    Paleogeographic reconstructions based on paleomagnetic data rely on the reliability of the natural remanent magnetization (NRM) as a primary geomagnetic signal. Remagnetizations, however, can be common in many rock types, including late Paleozoic and Mesozoic red beds, and they complicate paleogeographic interpretations. Extracting the primary NRM from partially remagnetized rocks, and understanding the remagnetization mechanism are important in these contexts. We carried out a systematic paleomagnetic study of red bed samples from the Triassic Huangmaqing Formation, Nanjing (32.0°N, 118.9°E), South China. Two NRM components carried by secondary and primary hematite are isolated in 47 of the 94 samples studied, where the latter component has a direction in stratigraphic coordinates of D = 29.2 °, I = 34.6 ° (α95 = 10.9 °, 47 samples from 6 sites) that yields a paleopole of λ = 60.8°N, ϕ = 228.1°E, dp / dm = 12.5 / 7.2, which is consistent with Triassic pole positions for the South China Block. A secondary chemical remanent magnetization (CRM) (D = 227.1 °, I = 80.8 °, α95 = 7.3 °) is documented in all 94 samples from 10 sites and is carried by pigmentary hematite that is inferred to have been generated by magnetite oxidation during orogenic activity. This secondary component has steep inclinations and is interpreted to have been influenced by a combination of the remanence carried by original parent magnetite, the orogenic stress field, and the prevailing geomagnetic field direction during deformation. This CRM direction is recorded commonly by red beds from the South China Block, and is significant for regional tectonic studies in the area.

  9. U-Th-Geochemistry of Permian and Triassic sediments of the Drauzug, Carinthia, Austria

    International Nuclear Information System (INIS)

    Kurat, G.; Korkisch, J.; Niedermayr, G.; Seemann, R.

    1976-05-01

    Chemical analysis of samples of Triassic and Permian rocks from the Drauzug, Carinthia and Austria was carried out. U concentration was measured by flurimetry, Th and Cu by spectrophotometry using Thoronol method or Arsenazo III method for Th, Fe by titrimetry and V, Ba, Sr by atomic absorption spectrophotometry. The average U concentration ranged from 0.8 to 4.6 ppm and the Th concentration from 3.2 to 15.6 ppm depending upon the mineral material. The quartzporphyries contained the highest concentration of both. It was concluded that the Permian-Triassic series are very similar to the equivalent deposits in Northern Italy. Assuming a lateral displacement, the former represent the Northern marginal part of the latter and therefore are inferior in thickness and thus not favourable for larger U mineralization

  10. Exceptional vertebrate biotas from the Triassic of China, and the expansion of marine ecosystems after the Permo-Triassic mass extinction

    Science.gov (United States)

    Benton, Michael J.; Zhang, Qiyue; Hu, Shixue; Chen, Zhong-Qiang; Wen, Wen; Liu, Jun; Huang, Jinyuan; Zhou, Changyong; Xie, Tao; Tong, Jinnan; Choo, Brian

    2013-10-01

    , but a later expansion of marine reptile groups, in the late Olenekian and early Anisian. This offset in diversification patterns is matched by comparisons of feeding guild categories and body size data. New research tools will shed considerable light on the phylogenetic and ecological implications of recovery of mairne vertebrates in the Triassic.

  11. Middle Triassic chirotherid trackways on earthquake influenced intertidal limulid reproduction flats of the European Germanic Basin coasts

    Science.gov (United States)

    Diedrich, Cajus G.

    2012-09-01

    Chirotherid footprints of Synaptichnium, Chirotherium and Isochirotherium appeared during the late Early (Aegean) to early Late (Carnian) Triassic in central Europe. These taxa are partly revised herein, using both perfect and variably preserved tracks, and very long trackways from an upper Pelsonian intertidal-flat megatracksite of the Germanic Basin coast Pelsonian (Karlstadt Formation). The global Middle Triassic distribution of those footprints suggests seasonal migrations across Pangaea of possible archosauriform reptile trackmakers, such as Euparkeria, Ticinosuchus, Arizonasaurus and Batrachotomus, caused by horseshoe-crab mass migrations into tidal-flat beach reproductive zones in the Germanic Basin. Such seasonal migrations may even suggest a Pangaea-wide food-chain reaction, possibly including the mobilization of fish, marine and terrestrial reptiles, and of which situation the Germanic Basin intertidal-flats is a globally unique example.

  12. Triassic regolithization: A major stage of pre-enrichment in the formation of unconformity related deposits in Southern France

    International Nuclear Information System (INIS)

    Schmitt, J.M.; Clement, J.Y.

    1989-01-01

    The formation of unconformity related uranium deposits in Canada and Australia is currently thought to have involved some stage of preconcentration within the Proterozoic regolith. Uranium deposits in the southern Massif central (France) are spatially linked to the Mesozoic unconformity. Under this unconformity, rocks of the Hercynian basement as well as Permo-Carboniferous sediments show a regolithic alteration dating back to the Late Permian to Late Triassic period. On the elevated parts of the Triassic landscape, 30 to 50 m deep weathering profiles are preserved. Three main zones can be distinguished: a lower pink coloured zone, showing partly albitized and chloritized rocks: a middle bleached zone with neogenic clays; and an upper reddish zone with Fe-Mn oxyhydroxides. Towards the Triassic basin, much deeper (200-300 m) alteration profiles are observed on Permo-Carboniferous sediments. The two upper regolithic zones are present, but the lower albitized one is very developed with two subzones: analcite/albite at the top, and K-feldspar/albite at the bottom. Geochemical data show that potassium is fixed in the uppermost horizons of the regolith, whereas sodium is transported towards the lower horizons and basin areas and fixed in analcite/albite zones. Uranium, vanadium, copper and less mobile elements such as titanium and zirconium are strongly leached from the weathering profiles in elevated parts of the landscape but are enriched in basin zones of albitization up to 5-15 times. Thus, solutions generated from the weathering profiles have brought about a major redistribution of uranium in the Triassic landscape. The remarkable applanation and tectonic stability of the area as well as a subarid climate seem to have favoured this 'regolithization' process. In southern France, geochemical differentiation during the Triassic has thus given rise to important uranium pre-enrichment, and the regolith is a major control for later uranium deposits. (author). 16 refs, 8

  13. Investigating A Unique Open Ocean Geochemical Record Of the End Triassic Mass Extinction from Panthalassa

    Science.gov (United States)

    Marroquín, S. M.; Gill, B. C.; Them, T. R., II; Trabucho-Alexandre, J. P.; Aberhan, M.; Owens, J. D.; Gröcke, D. R.; Caruthers, A. H.

    2017-12-01

    The end-Triassic mass extinction ( 201 Ma) was a time of intense disturbance for marine communities. This event is estimated to have produced as much as a loss of 80% of known marine species. The protracted interval of elevated extinction rates is also characterized by a major carbon cycle perturbation and potentially widespread oxygen deficiency within the oceans. While the causes of extinction and environmental feedbacks are still debated it is hypothesized to have been triggered by massive volcanism associated with the Central Atlantic Magmatic Province flood basalts. However, our understanding of the Latest Triassic-Earliest Jurassic interval is limited due to the lack of well-preserved stratigraphic successions outside of the Tethys Ocean (present day Europe), with most of the records from epicontinental and marginal marine settings. To expand our understanding of this critical interval, our study seeks to document biological and environmental changes elsewhere. Specifically, we document and reconstruct these changes in the equatorial Panthalassan Ocean. We will present new data from a sedimentary succession preserved in the Wrangell Mountains of Alaska that spans the Late Triassic through Early Jurassic. The sedimentary succession represents a mixed carbonate-siliciclastic ramp that was deposited at tropical latitudes, adjacent to an island arc in the open Panthalassan Ocean. This succession affords a unique view of open marine conditions, and also holds the potential for excellent temporal control as it contains abundant ash layers throughout, as well as, key ammonite and bivalve fossil occurrences that provide biostratigraphic control. We will present an integrated geochemical and paleontological record from this site using several geochemical proxies (carbon, δ13Ccarb and % total organic carbon, sulfur, δ34S, as well as pyrite contents and iron speciation) along with ammonite and bivalve occurrence data to reconstruct the record of environmental and

  14. A new Lower Triassic ichthyopterygian assemblage from Fossil Hill, Nevada

    Directory of Open Access Journals (Sweden)

    Neil P. Kelley

    2016-01-01

    Full Text Available We report a new ichthyopterygian assemblage from Lower Triassic horizons of the Prida Formation at Fossil Hill in central Nevada. Although fragmentary, the specimens collected so far document a diverse fauna. One partial jaw exhibits isodont dentition with blunt tipped, mesiodistally compressed crowns and striated enamel. These features are shared with the Early Triassic genus Utatsusaurus known from coeval deposits in Japan and British Columbia. An additional specimen exhibits a different dentition characterized by relatively small, rounded posterior teeth resembling other Early Triassic ichthyopterygians, particularly Grippia. This Nevada assemblage marks a southward latitudinal extension for Early Triassic ichthyopterygians along the eastern margin of Panthalassa and indicates repeated trans-hemispheric dispersal events in Early Triassic ichthyopterygians.

  15. Biomechanical comments about Triassic dinosaurs from Brazil

    Directory of Open Access Journals (Sweden)

    Rafael Delcourt

    2012-01-01

    Full Text Available Triassic dinosaurs of Brazil are found in Santa Maria and Caturrita formations, Rio Grande do Sul state, Brazil. There are three species known from the Santa Maria Formation (Staurikosaurus pricei, Saturnalia tupiniquim and Pampadromaeus barberenai, and two from Caturrita Formation (Guaibasaurus candelariensis and Unaysaurus tolentinoi. These dinosaur materials are, for the most part, well preserved and allow for descriptions of musculature and biomechanical studies. The lateral rotation of the Saturnalia femur is corroborated through calculations of muscle moment arms. The enhanced supracetabular crest of Saturnalia, Guaibasaurus, Staurikosaurus, Herrerasaurus ischigualastensis, Efraasia minor and Chormogisaurus novasi suggests that basal dinosaurs may have maintained an inclination of the trunk at least 20º on the horizontal axis. The pectoral girdle articulation of basal sauropodomorphs (Saturnalia and Unaysaurus was established using a new method, the Clavicular Ring, and the scapular blade remains near 60º on the horizontal axis. This is a plesiomorphic condition among sauropodomorphs and is also seen in the articulated plateosauridae Seitaad ruessi. The Brazilian basal dinosaurs were lightweight with a body mass estimated around 18.5 kg for Staurikosaurus, 6.5 kg for Saturnalia, and 17 kg for Guaibasaurus. Pampadromaeus probably weighed 2.5 kg, but measures of its femur are necessary to confirm this hypothesis. The Triassic dinosaurs from Brazil were diversified but shared some functional aspects that were important in an evolutionary context.

  16. Triassic-Jurassic pteridosperms of Australasia: speciation, diversity and decline

    Energy Technology Data Exchange (ETDEWEB)

    Pattemore, G. A.; Rigby, J. F.; Playford, G.

    2015-07-01

    Pteridosperms are preserved abundantly in the Gondwanan Triassic, with many species exhibiting consider- able morphological variation that has been attributed to a hybridization model of speciation. This is an improbable explanation given that hybridization is very rare in gymnosperms. Allopatric speciation resulting from geographic and climatic provincialism is a more likely explanation for the morphological diversity which is well represented in Anisian Norian (Middle and Upper Triassic) floras of Australasia and elsewhere in Gondwana. Most specimens are distributed among three families: Umkomasiaceae, Peltaspermaceae and Matatiellaceae. These families, together with other possibly pteridospermous genera, are reviewed herein. Diversity in these families apparently declined by the Rhaetian and they did not persist into the Gondwanan post-Triassic. Australasian post-Triassic strata contain remarkably different floral assemblages to those of the Triassic. No fructifications are clearly pteridospermous and no remains show any obvious relationship with pteridosperms of the Gondwanan Triassic. Caytonialean fructifications are not known in Australasian strata; however, associated foliage has been reported from the Eastern Gondwanan Upper Triassic through Middle Jurassic including Australia. Much fern-like foliage, claimed to be pteridospermous from the Lower Jurassic through Eocene of Eastern Gondwana, lacks supporting evidence of such affiliation. (Author)

  17. Upper Triassic limestones from the northern part of Japan: new insights on the Panthalassa Ocean and Hokkaido Island

    Science.gov (United States)

    Peyrotty, Giovan; Peybernes, Camille; Ueda, Hayato; Martini, Rossana

    2017-04-01

    investigate and characterise Triassic limestones, particularly from western part of Sorachi-Yezo, in order to provide new crucial data allowing us to define the origin of this belt. The comparison (i.e., biotic assemblages, preservation, diagnesis, associated lithologies) of the Triassic limestones in Oshima and Sorachi-Yezo belts might highlight differences in their depositional setting as well as in geodynamic evolution of the western part of Sorachi-Yezo Belt. REFERENCES Kiessling, W., & Flügel, E. 2000: Late Paleozoic and Late Triassic Limestones from North Palawan Block (Philippines): Microfacies and Paleogeographical Implications. Facies, 43, 39-78. Onoue, T., & Sano, H. 2007: Triassic mid-oceanic sedimentation in Panthalassa Ocean: Sambosan accretionary complex, Japan. Island Arc, 16(1), 173-190. Ueda H. 2016: Hokkaido in The Geology of Japan, Taira A. Ohara Y. Wallis S. Ishawatari A.Iryu Y. Geological Society, London, 203-223.

  18. Global taxonomic diversity of anomodonts (tetrapoda, therapsida and the terrestrial rock record across the Permian-Triassic boundary.

    Directory of Open Access Journals (Sweden)

    Jörg Fröbisch

    Full Text Available The end-Permian biotic crisis (~252.5 Ma represents the most severe extinction event in Earth's history. This paper investigates diversity patterns in Anomodontia, an extinct group of therapsid synapsids ('mammal-like reptiles', through time and in particular across this event. As herbivores and the dominant terrestrial tetrapods of their time, anomodonts play a central role in assessing the impact of the end-Permian extinction on terrestrial ecosystems. Taxonomic diversity analysis reveals that anomodonts experienced three distinct phases of diversification interrupted by the same number of extinctions, i.e. an end-Guadalupian, an end-Permian, and a mid-Triassic extinction. A positive correlation between the number of taxa and the number of formations per time interval shows that anomodont diversity is biased by the Permian-Triassic terrestrial rock record. Normalized diversity curves indicate that anomodont richness continuously declines from the Middle Permian to the Late Triassic, but also reveals all three extinction events. Taxonomic rates (origination and extinction indicate that the end-Guadalupian and end-Permian extinctions were driven by increased rates of extinction as well as low origination rates. However, this pattern is not evident at the final decline of anomodont diversity during the Middle Triassic. Therefore, it remains unclear whether the Middle Triassic extinction represents a gradual or abrupt event that is unique to anomodonts or more common among terrestrial tetrapods. The end-Permian extinction represents the most distinct event in terms of decline in anomodont richness and turnover rates.

  19. Pre-Cretaceous Agaricomycetes yet to be discovered: Reinvestigation of a putative Triassic bracket fungus from southern Germany

    Directory of Open Access Journals (Sweden)

    A. P. Kiecksee

    2012-08-01

    Full Text Available Agaricomycetes are major components of extant terrestrial ecosystems; however, their fruiting bodies are exceedingly rare as fossils. Reinvestigation of a peculiar fossil from Late Triassic sediments of southern Germany interpreted as a bracket fungus revealed that this fossil in fact represents a wood abnormality, resulting from injury to the cambium and subsequent callus growth in a Baieroxylon -like ginkgoalean wood. As a result, the fossil record of the Agaricomycetes does not yet pre-date the Early Cretaceous, suggesting a late diversification of basidiomycetes possessing large fruiting bodies. doi:10.1002/mmng.201200006

  20. The evolution of a Late Cretaceous-Cenozoic intraplate basin (Duaringa Basin), eastern Australia: evidence for the negative inversion of a pre-existing fold-thrust belt

    Science.gov (United States)

    Babaahmadi, Abbas; Sliwa, Renate; Esterle, Joan; Rosenbaum, Gideon

    2017-12-01

    The Duaringa Basin in eastern Australia is a Late Cretaceous?-early Cenozoic sedimentary basin that developed simultaneously with the opening of the Tasman and Coral Seas. The basin occurs on the top of an earlier (Permian-Triassic) fold-thrust belt, but the negative inversion of this fold-thrust belt, and its contribution to the development of the Duaringa Basin, are not well understood. Here, we present geophysical datasets, including recently surveyed 2D seismic reflection lines, aeromagnetic and Bouguer gravity data. These data provide new insights into the structural style in the Duaringa Basin, showing that the NNW-striking, NE-dipping, deep-seated Duaringa Fault is the main boundary fault that controlled sedimentation in the Duaringa Basin. The major activity of the Duaringa Fault is observed in the southern part of the basin, where it has undergone the highest amount of displacement, resulting in the deepest and oldest depocentre. The results reveal that the Duaringa Basin developed in response to the partial negative inversion of the pre-existing Permian-Triassic fold-thrust belt, which has similar orientation to the extensional faults. The Duaringa Fault is the negative inverted part of a single Triassic thrust, known as the Banana Thrust. Furthermore, small syn-depositional normal faults at the base of the basin likely developed due to the reactivation of pre-existing foliations, accommodation faults, and joints associated with Permian-Triassic folds. In contrast to equivalent offshore basins, the Duaringa Basin lacks a complex structural style and thick syn-rift sediments, possibly because of the weakening of extensional stresses away from the developing Tasman Sea.

  1. The Triassic upwelling system of Arctic Alaska

    Science.gov (United States)

    Yurchenko, I.; Graham, S. A.

    2017-12-01

    The Middle to Upper Triassic Shublik Formation of Arctic Alaska is a laterally and vertically heterogeneous rock unit that has been analyzed both in outcrop and in the subsurface. The Shublik Formation sediments are distinguished by a characteristic set of lithologies that include glauconitic, phosphatic, organic-rich, and cherty facies consistent with a coastal upwelling zone deposition interpretation. It is often recognized by abundance of impressions and shells of distinctive Triassic bivalves. To understand main controls on lithofacies distributions, this study reviews and refines lithologic and paleoenvironmental interpretations of the Shublik Formation, and incorporates the newly acquired detailed geochemical analyses of two complete Shublik cores. This work focuses on organic geochemistry (analyses of biomarkers and diamondoids), chemostratigraphy (hand-held XRF), and iron speciation analysis to reconstruct paleoproductivity and redox conditions. Based on the available evidence, during Shublik deposition, an upwelling-influenced open shelf resulted in high nutrient supply that stimulated algal blooms leading to high net organic productivity, reduced water transparency, oxygen deficiency, and water column stratification. Evidence of such eutrophic conditions is indicated by the lack of photic benthic organisms, bioturbation and trace fossils, and dominance of the monospecific light-independent epibenthic bivalves. The flat, subcircular, thin shells of these carbonate-secreting organisms allowed them to adapt to dysoxic conditions, and float on soft, soupy, muddy substrate. The distinctive clay- and organic-rich facies with abundant bivalves occurred on the mid to outer stable broad shelf, and were deposited when organic productivity at times overlapped with periods of increased siliciclastic input controlled by sea level and changes in local sediment dispersal systems, and therefore are more spatially and temporally localized than the widespread clay

  2. The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation

    Science.gov (United States)

    Butler, Richard J.; Brusatte, Stephen L.; Reich, Mike; Nesbitt, Sterling J.; Schoch, Rainer R.; Hornung, Jahn J.

    2011-01-01

    Background Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3–247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains. Methodology/Principal Findings We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the ‘sail’ of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation. Conclusions/Significance Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian–Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which

  3. The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation.

    Science.gov (United States)

    Butler, Richard J; Brusatte, Stephen L; Reich, Mike; Nesbitt, Sterling J; Schoch, Rainer R; Hornung, Jahn J

    2011-01-01

    Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3-247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains. We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the 'sail' of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation. Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian-Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs.

  4. The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation.

    Directory of Open Access Journals (Sweden)

    Richard J Butler

    Full Text Available BACKGROUND: Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species. The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma, implying that the archosaur radiation began in the Early Triassic (252.3-247.2 Ma. Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains. METHODOLOGY/PRINCIPAL FINDINGS: We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene, a sail-backed reptile from the Early Triassic (late Olenekian Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the 'sail' of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation. CONCLUSIONS/SIGNIFICANCE: Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma, less than 5 million years after the Permian-Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and

  5. Sedimentary record of subsidence pulse at the Triassic/Jurassic boundary interval in the Slovenian Basin (eastern Southern Alps

    Directory of Open Access Journals (Sweden)

    Rožič Boštjan

    2017-08-01

    Full Text Available In the Alpine Realm the Early Jurassic is characterized by the disintegration and partial drowning of vast platform areas. In the eastern part of the Southern Alps (present-day NW Slovenia, the Julian Carbonate Platform and the adjacent, E-W extending Slovenian Basin underwent partial disintegration, drowning and deepening from the Pliensbachian on, whereas only nominal environmental changes developed on the large Dinaric (Friuli, Adriatic Carbonate Platform to the south (structurally part of the Dinarides. These events, however, were preceded by an earlier - and as yet undocumented extensional event - that took place near the Triassic/Jurassic boundary. This paper provides evidence of an accelerated subsidence from four selected areas within the Slovenian Basin, which show a trend of eastwardly-decreasing deformation. In the westernmost (Mrzli vrh section - the Upper Triassic platform-margin - massive dolomite is overlain by the earliest Jurassic toe-of-slope carbonate resediments and further, by basin-plain micritic limestone. Further east (Perbla and Liščak sections the Triassic-Jurassic transition interval is marked by an increase in resedimented carbonates. We relate this to the increasing inclination and segmentation of the slope and adjacent basin floor. The easternmost (Mt. Porezen area shows a rather monotonous, latest Triassic-Early Jurassic basinal sedimentation. However, changes in the thickness of the Hettangian-Pliensbachian Krikov Formation point to a tilting of tectonic blocks within the basin area. Lateral facies changes at the base of the formation indicate that the tilting occurred at and/or shortly after the Triassic/Jurassic boundary

  6. Sedimentary record of subsidence pulse at the Triassic/Jurassic boundary interval in the Slovenian Basin (eastern Southern Alps)

    Science.gov (United States)

    Rožič, Boštjan; Jurkovšek, Tea Kolar; Rožič, Petra Žvab; Gale, Luka

    2017-08-01

    In the Alpine Realm the Early Jurassic is characterized by the disintegration and partial drowning of vast platform areas. In the eastern part of the Southern Alps (present-day NW Slovenia), the Julian Carbonate Platform and the adjacent, E-W extending Slovenian Basin underwent partial disintegration, drowning and deepening from the Pliensbachian on, whereas only nominal environmental changes developed on the large Dinaric (Friuli, Adriatic) Carbonate Platform to the south (structurally part of the Dinarides). These events, however, were preceded by an earlier - and as yet undocumented extensional event - that took place near the Triassic/Jurassic boundary. This paper provides evidence of an accelerated subsidence from four selected areas within the Slovenian Basin, which show a trend of eastwardly-decreasing deformation. In the westernmost (Mrzli vrh) section - the Upper Triassic platform-margin - massive dolomite is overlain by the earliest Jurassic toe-of-slope carbonate resediments and further, by basin-plain micritic limestone. Further east (Perbla and Liščak sections) the Triassic-Jurassic transition interval is marked by an increase in resedimented carbonates. We relate this to the increasing inclination and segmentation of the slope and adjacent basin floor. The easternmost (Mt. Porezen) area shows a rather monotonous, latest Triassic-Early Jurassic basinal sedimentation. However, changes in the thickness of the Hettangian-Pliensbachian Krikov Formation point to a tilting of tectonic blocks within the basin area. Lateral facies changes at the base of the formation indicate that the tilting occurred at and/or shortly after the Triassic/Jurassic boundary

  7. Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin

    Energy Technology Data Exchange (ETDEWEB)

    Dubiel, R.F. (Geological Survey, Denver, CO (USA))

    1989-09-01

    Sedimentologic study of the Upper Triassic Chinle Formation in the San Juan basin (SJB) indicates that Late Triassic paleoclimate and tectonic movements influenced the distribution of continental lithofacies. The Shinarump, Monitor Butte, and Petrified Forest Members in the lower part of the Chinle consist of complexly interfingered fluvial, floodplain, marsh, and lacustrine rocks; the Owl Rock and Rock Point Members in the upper part consists of lacustrine-basin and eolian sandsheet strata. Facies analysis, vertebrate and invertebrate paleontology, and paleoclimate models demonstrate that the Late Triassic was dominated by tropical monsoonal circulation, which provided abundant precipitation interspersed with seasonally dry periods. Owl Rock lacustrine strata comprise laminated limestones that reflect seasonal monsoonal precipitation and larger scale, interbedded carbonates and fine-grained clastics that represent longer term, alternating wet and dry climatic cycles. Overlying Rock Point eolian sand-sheet and dune deposits indicate persistent alternating but drier climatic cyclicity. Within the Chinle, upward succession of lacustrine, alternating lacustrine/eolian sand-sheet, and eolian sand-sheet/dune deposits reflects an overall decrease in precipitation due to the northward migration of Pangaea out of low latitudes dominated by monsoonal circulation.

  8. Metamorphic and geochronogical study of the Triassic El Oro metamorphic complex, Ecuador: Implications for high-temperature metamorphism in a forearc zone

    Science.gov (United States)

    Riel, N.; Guillot, S.; Jaillard, E.; Martelat, J.-E.; Paquette, J.-L.; Schwartz, S.; Goncalves, P.; Duclaux, G.; Thebaud, N.; Lanari, P.; Janots, E.; Yuquilema, J.

    2013-01-01

    In the forearc of the Andean active margin in southwest Ecuador, the El Oro metamorphic complex exhibits a well exposed tilted forearc section partially migmatized. We used Raman spectroscopy on carbonaceous matter (RSCM) thermometry and pseudosections coupled with mineralogical and textural studies to constrain the pressure-temperature (P-T) evolution of the El Oro metamorphic complex during Triassic times. Our results show that anatexis of the continental crust occurred by white-mica and biotite dehydration melting along a 10 km thick crustal domain (from 4.5 to 8 kbar) with increasing temperature from 650 to 700 °C. In the biotite dehydration melting zone, temperature was buffered at 750-820 °C in a 5 km thick layer. The estimated average thermal gradient during peak metamorphism is of 30 °C/km within the migmatitic domain can be partitioned into two apparent gradients parts. The upper part from surface to 7 km depth records a 40-45 °C/km gradient. The lower part records a quasi-adiabatic geotherm with a 10 °C/km gradient consistent with an isothermal melting zone. Migmatites U-Th-Pb geochronology yielded zircon and monazite ages of 229.3 ± 2.1 Ma and 224.5 ± 2.3 Ma, respectively. This thermal event generated S-type magmatism (the Marcabeli granitoid) and was immediately followed by underplating of the high-pressure low-temperature (HP-LT) Arenillas-Panupalí unit at 225.8 ± 1.8 Ma. The association of high-temperature low-pressure (HT-LP) migmatites with HP-LT unit constitutes a new example of a paired metamorphic belt along the South American margin. We propose that in addition to crustal thinning, underplating of the Piedras gabbroic unit before 230 Ma provided the heat source necessary to foster crustal anatexis. Furthermore, its MORB signature shows that the asthenosphere was involved as the source of the heat anomaly. S-type felsic magmatism is widespread during this time and suggests that a large-scale thermal anomaly affected a large part of the

  9. Basin geodynamics and sequence stratigraphy of Upper Triassic to Lower Jurassic deposits of Southern Tunisia

    Science.gov (United States)

    Carpentier, Cédric; Hadouth, Suhail; Bouaziz, Samir; Lathuilière, Bernard; Rubino, Jean-Loup

    2016-05-01

    Aims of this paper are to propose a geodynamic and sequential framework for the late Triassic and early Jurassic of and south Tunisia and to evidence the impact of local tectonics on the stratigraphic architecture. Facies of the Upper Triassic to Lower Jurassic of Southern Tunisia have been interpreted in terms of depositional environments. A sequential framework and correlation schemes are proposed for outcrops and subsurface transects. Nineteen middle frequency sequences inserted in three and a half low frequency transgression/regression cycles were evidenced. Despite some datation uncertainties and the unknown durations of Lower Jurassic cycles, middle frequency sequences appear to be controlled by eustasy. In contrast the tectonics acted as an important control on low frequency cycles. The Carnian flooding was certainly favored by the last stages of a rifting episode which started during the Permian. The regression accompanied by the formation of stacked angular unconformities and the deposition of lowstand deposits during the late Carnian and Norian occured during the uplift and tilting of the northern basin margins. The transpressional activity of the Jeffara fault system generated the uplift of the Tebaga of Medenine high from the late Carnian and led to the Rhaetian regional angular Sidi Stout Unconformity. Facies analysis and well-log correlations permitted to evidence that Rhaetian to Lower Jurassic Messaoudi dolomites correspond to brecciated dolomites present on the Sidi Stout unconformity in the North Dahar area. The Early-cimmerian compressional event is a possible origin for the global uplift of the northern African margin and Western Europe during the late Carnian and the Norian. During the Rhaetian and the early Jurassic a new episode of normal faulting occured during the third low frequency flooding. This tectonosedimentary evolution ranges within the general geodynamic framework of the north Gondwana margin controlled by the opening of both

  10. Origin of the Permian-Triassic komatiites, northwestern Vietnam

    Science.gov (United States)

    Hanski, Eero; Walker, Richard J.; Huhma, Hannu; Polyakov, Gleb V.; Balykin, Pavel A.; Tran Trong Hoa; Ngo Thi Phuong

    Rare examples of Phanerozoic komatiites are found in the Song Da zone, NW Vietnam. These komatiites were erupted through continental crust and may belong to the SE extension of the Permo-Triassic Emeishan volcanic province located in SW China. They provide a good opportunity to study the source characteristics of starting plume magmas in a continental flood basalt province. Erupted on late-Permian carbonate rocks, the komatiitic rocks are interbedded with low-Ti olivine basalts. Basaltic komatiites display pyroxene spinifex textures, while more magnesian rocks (MgO up to 32 wt.%) are porphyritic, containing a single, cognate population of euhedral to elongated olivine phenocrysts with Fo up to 93.0%. This suggests a highly magnesian parental magma with 22-23 wt.% MgO. In terms of major and minor elements, the komatiites are similar to the ca. 89 Ma old Gorgona Island komatiites of Colombia. The Song Da komatiites are also strongly light-rare-earth-element- (LREE) depleted (CeN/YbN 0.30-0.62) and have unfractionated heavy rare earth element (HREE) patterns. The komatiites have high Os concentrations (up to 7.0 ppb), low but variable Re/Os ratios, and define an isochron with an age of 270+/-21 Ma, and an initial 188Os/187Os ratio of 0.12506+/- 0.00041 (γOs=+0.02+/-0.40). The Os isotopic systematics of the komatiites show no effects of crustal contamination. In contrast, their initial ɛNd values range from +3 to +8, reflecting varying but generally small degrees of contamination with Proterozoic sialic basement material. Associated low-Ti basalts have low initial ɛNd values (-0.8 to -7.5), high initial γOs values (>=15), flat or LREE-enriched REE patterns, and Nb-Ta depletion. These characteristics are also attributed to variable extents of crustal contamination.

  11. Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia and their provenance

    Directory of Open Access Journals (Sweden)

    Gawlick Hans-Jürgen

    2017-08-01

    Full Text Available Oceanic radiolarite components from the Middle Jurassic ophiolitic mélange between Trnava and Rožanstvo in the Zlatibor Mountains (Dinaridic Ophiolite Belt west of the Drina–Ivanjica unit yield Late Triassic radiolarian ages. The microfacies characteristics of the radiolarites show pure ribbon radiolarites without crinoids or thin-shelled bivalves. Beside their age and the preservation of the radiolarians this points to a deposition of the radiolarites on top of the oceanic crust of the Neo-Tethys, which started to open in the Late Anisian. South of the study area the ophiolitic mélange (Gostilje–Ljubiš–Visoka–Radoševo mélange contains a mixture of blocks of 1 oceanic crust, 2 Middle and Upper Triassic ribbon radiolarites, and 3 open marine limestones from the continental slope. On the basis of this composition we can conclude that the Upper Triassic radiolarite clasts derive either from 1 the younger parts of the sedimentary succession above the oceanic crust near the continental slope or, more convincingly 2 the sedimentary cover of ophiolites in a higher nappe position, because Upper Triassic ribbon radiolarites are only expected in more distal oceanic areas. The ophiolitic mélange in the study area overlies different carbonate blocks of an underlying carbonate-clastic mélange (Sirogojno mélange. We date and describe three localities with different Upper Triassic radiolarite clasts in a mélange, which occurs A on top of Upper Triassic fore-reef to reefal limestones (Dachstein reef, B between an Upper Triassic reefal limestone block and a Lower Carnian reef limestone (Wetterstein reef, and C in fissures of an Upper Triassic lagoonal to back-reef limestone (Dachstein lagoon. The sedimentary features point to a sedimentary and not to a tectonic emplacement of the ophiolitic mélange (= sedimentary mélange filling the rough topography of the topmost carbonate-clastic mélange below. The block spectrum of the underlying and

  12. Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia) and their provenance

    Science.gov (United States)

    Gawlick, Hans-Jürgen; Djerić, Nevenka; Missoni, Sigrid; Bragin, Nikita Yu.; Lein, Richard; Sudar, Milan; Jovanović, Divna

    2017-08-01

    Oceanic radiolarite components from the Middle Jurassic ophiolitic mélange between Trnava and Rožanstvo in the Zlatibor Mountains (Dinaridic Ophiolite Belt) west of the Drina-Ivanjica unit yield Late Triassic radiolarian ages. The microfacies characteristics of the radiolarites show pure ribbon radiolarites without crinoids or thin-shelled bivalves. Beside their age and the preservation of the radiolarians this points to a deposition of the radiolarites on top of the oceanic crust of the Neo-Tethys, which started to open in the Late Anisian. South of the study area the ophiolitic mélange (Gostilje-Ljubiš-Visoka-Radoševo mélange) contains a mixture of blocks of 1) oceanic crust, 2) Middle and Upper Triassic ribbon radiolarites, and 3) open marine limestones from the continental slope. On the basis of this composition we can conclude that the Upper Triassic radiolarite clasts derive either from 1) the younger parts of the sedimentary succession above the oceanic crust near the continental slope or, more convincingly 2) the sedimentary cover of ophiolites in a higher nappe position, because Upper Triassic ribbon radiolarites are only expected in more distal oceanic areas. The ophiolitic mélange in the study area overlies different carbonate blocks of an underlying carbonate-clastic mélange (Sirogojno mélange). We date and describe three localities with different Upper Triassic radiolarite clasts in a mélange, which occurs A) on top of Upper Triassic fore-reef to reefal limestones (Dachstein reef), B) between an Upper Triassic reefal limestone block and a Lower Carnian reef limestone (Wetterstein reef), and C) in fissures of an Upper Triassic lagoonal to back-reef limestone (Dachstein lagoon). The sedimentary features point to a sedimentary and not to a tectonic emplacement of the ophiolitic mélange (= sedimentary mélange) filling the rough topography of the topmost carbonate-clastic mélange below. The block spectrum of the underlying and slightly older

  13. Thick-skinned tectonics in a Late Cretaceous-Neogene intracontinental belt (High Atlas Mountains, Morocco): The flat-ramp fault control on basement shortening and cover folding

    Science.gov (United States)

    Fekkak, A.; Ouanaimi, H.; Michard, A.; Soulaimani, A.; Ettachfini, E. M.; Berrada, I.; El Arabi, H.; Lagnaoui, A.; Saddiqi, O.

    2018-04-01

    Most of the structural studies of the intracontinental High Atlas belt of Morocco have dealt with the central part of the belt, whose basement does not crop out. Here we study the Alpine deformation of the North Subatlas Zone, which is the part of the Western High Atlas (WHA) Paleozoic Massif that involves both Paleozoic basement units and remnants of their Mesozoic-Cenozoic cover formations. Our aim is to better constrain the geometry and kinematics of the basement faults during the Alpine shortening. Based on detail mapping, satellite imagery and field observations, we describe an array of sub-equatorial, transverse and oblique faults between the WHA Axial Zone and the Haouz Neogene basin. They define a mosaic of basement blocks pushed upon one another and upon the Haouz basement along the North Atlas Fault (NAF). The Axial Zone makes up the hanging-wall of the Adassil-Medinet Fault (AMF) south of this mosaic. The faults generally presents flat-ramp-flat geometry linked to the activation of multiple décollement levels, either within the basement where its foliation is subhorizontal or within favourable cover formations (Jurassic evaporites, Lower Cretaceous silty red beds, Upper Cretaceous evaporitic marls, Neogene basal argillites). The occurrence of the North Atlas detachment (NAD) allowed folded pop-up units to develop in front of the propagating NAF. Shortening began as early as the Campanian-Maastrichtian along the AMF. The direction of the maximum horizontal stress rotated from NNE-SSW to NNW-SSE from the Maastrichtian-Paleocene to the Neogene. The amount of shortening reaches 20% in the Azegour transect. This compares with the shortening amount published for the central-eastern High Atlas, suggesting that similar structures characterize the Paleozoic basement all along the belt. The WHA thick-skinned tectonics evokes that of the frontal Sevier belt and of the external Western Alps, although with a much minor pre-inversion burial.

  14. The new Permian-Triassic paleomagnetic pole for the East European Platform corrected for inclination shallowing

    Science.gov (United States)

    Fetisova, A. M.; Veselovskiy, R. V.; Scholze, F.; Balabanov, Yu. P.

    2018-01-01

    The results of detailed paleomagnetic studies in seven Upper Permian and Lower Triassic reference sections of East Europe (Middle Volga and Orenburg region) and Central Germany are presented. For each section, the coefficient of inclination shallowing f (King, 1955) is estimated by the Elongation-Inclination (E-I) method (Tauxe and Kent, 2004) and is found to vary from 0.4 to 0.9. The paleomagnetic directions, corrected for the inclination shallowing, are used to calculate the new Late Permian-Early Triassic paleomagnetic pole for the East European Platform (N = 7, PLat = 52.1°, PLong = 155.8°, A95 = 6.6°). Based on this pole, the geocentric axial dipole hypothesis close to the Paleozoic/Mesozoic boundary is tested by the single plate method. The absence of the statistically significant distinction between the obtained pole and the average Permian-Triassic (P-Tr) paleomagnetic pole of the Siberian Platform and the coeval pole of the North American Platform corrected for the opening of the Atlantic (Shatsillo et al., 2006) is interpreted by us as evidence that 250 Ma the configuration of the magnetic field of the Earth was predominantly dipolar; i.e., the contribution of nondipole components was at most 10% of the main magnetic field. In our opinion, the hypothesis of the nondipolity of the geomagnetic field at the P-Tr boundary, which has been repeatedly discussed in recent decades (Van der Voo and Torsvik, 2001; Bazhenov and Shatsillo, 2010; Veselovskiy and Pavlov, 2006), resulted from disregarding the effect of inclination shallowing in the paleomagnetic determinations from sedimentary rocks of "stable" Europe (the East European platform and West European plate).

  15. Permo-triassic volcanism in the San Rafael Block (Mendoza province) and its uraniferous potential

    International Nuclear Information System (INIS)

    Kleiman, L.E.

    1993-01-01

    This paper describes the Permo-triassic volcanism in the San Rafael Block, Mendoza, Argentina, which forms part of the Choiyoi province and it represents by large volumes of intermediate to silicic ignimbrites with minor sub volcanic bodies of rhyolites, andesites and basandesites. Three different suites can be distinguished: the first one (Lower Section) of Early Permian age, is composed of dacites and rhyolites (SiO 2 up to 71 %) with minor andesites, the second one (Upper Section) of Late Permian-Early Triassic age is made up of rhyolites (SiO 2 up to 77 %) with some basandesites and andesites, and the third one, of Triassic age is composed of rhyolites (SiO 2 > 75 %) and basandecites. These suites are easily distinguished by means of trace element data and are believed to represent the transition between a subduction-related magmatic arc and an extensional tectonic regime. This tectonic setting is similar to the prevalent during the Cenozoic in the Sierra Occidental of Mexico and is favourable for the development of long-lived hydrothermal systems which lead to economic U concentrations (i.e. Sierra de Pena Blanca). In the San Rafael Block, the Dr. Baulies-Los Reyunos U deposit, which is hosted in volcanic sediments, is associated to the first suite (Lower Section). Although minor U concentrations are known, up to date, to be related to the second and third suites, these rocks are fertile and seen to be potential source for the formation of uranium deposits within a volcanic caldera environment. (Author)

  16. Permo-Triassic vertebrate extinctions: A program

    Science.gov (United States)

    Olson, E. C.

    1988-01-01

    Since the time of the Authors' study on this subject, a great deal of new information has become available. Concepts of the nature of extinctions have changed materially. The Authors' conclusion that a catastrophic event was not responsible for the extinction of vertebrates has modified to the extent that hypotheses involving either the impact of a massive extra-terrestrial body or volcanism provide plausible but not currently fully testable hypotheses. Stated changes resulted in a rapid decrease in organic diversity, as the ratio of origins of taxa to extinctions shifted from strongly positive to negative, with momentary equilibrium being reached at about the Permo-Triassic boundary. The proximate causes of the changes in the terrestrial biota appear to lie in two primary factors: (1) strong climatic changes (global mean temperatures, temperature ranges, humidity) and (2) susceptibility of the dominant vertebrates (large dicynodonts) and the glossopteris flora to disruption of the equlibrium of the world ecosystem. The following proximate causes have been proposed: (1) rhythmic fluctuations in solar radiation, (2) tectonic events as Pangea assembled, altering land-ocean relationships, patterns of wind and water circulation and continental physiography, (3) volcanism, and (4) changes subsequent to impacts of one or more massive extra terrestrial objects, bodies or comets. These hypotheses are discussed.

  17. U-Pb Geochronology of non-marine Upper Triassic strata of the Colorado Plateau (western North America): implications for stratigraphic correlation and paleoenvironmental reconstruction

    Science.gov (United States)

    Rasmussen, C.; Mundil, R.; Irmis, R. B.; Keller, C. B.; Giesler, D.; Gehrels, G. E.

    2017-12-01

    The Triassic is a critical period in Earth history that witnessed the origin of modern ecosystems and frequent climate fluctuations, as well as major environmental events such as flood basalt volcanism and bolide impacts. The Chinle Formation contains a primary non-marine archive for past ecosystems in North America due to its fossil richness and well-studied sedimentology. Moreover, within these highly fossiliferous strata, a biotic turnover has been reported that has been hypothesized to coincide with one or more of the aforementioned environmental events. Unfortunately, few radioisotopic ages have been published for the Late Triassic, limiting our ability for lithological and paleoenvironmental correlations. In addition, the superposition of the Chinle Formation remains illusive due to frequent lateral facies changes and discontinuous outcrops across the Colorado Plateau. The 520 m long core 1A of the Colorado Plateau Coring Project from Petrified Forest National Park (PFNP) (Arizona) provides, for the first time, a continuous section of these early Mesozoic sedimentary strata. Many of the sand- and siltstones from this continuous succession throughout most of the Upper Triassic Chinle Formation contain euhedral zircons suitable for U-Pb analyses. We analyzed >300 crystals each from 10 samples using LA-ICPMS; these results indicated abundant Late Triassic crystals that appear to be closely associated with the depositional age of the host rock. We then selected the youngest grains from these samples to obtain precise CA-TIMS U-Pb single zircon ages in order to constrain the maximum depositional ages (using quantitative methods) of these formations. We are able to revise the proposed time scale (based on outcrop samples) for Upper Triassic strata at PFNP and evaluate whether the biotic turnover observed within the Sonsela Member of these strata coincides with the Manicouagan bolide impact event. This revised chronostratigraphic framework allows intercalibration

  18. Repeated Carbon-Cycle Disturbances at the Permian-Triassic Boundary Separate two Mass Extinctions

    Science.gov (United States)

    Nicol, J. A.; Watson, L.; Claire, M.; Buick, R.; Catling, D. C.

    2004-12-01

    Non-marine organic matter in Permian-Triassic sediments from the Blue Mountains, eastern Australia shows seven negative δ13C excursions of up to 7%, terminating with a positive excursion of 4%. Fluctuations start at the late Permian Glossopteris floral extinction and continue until just above the palynological Permian-Triassic boundary, correlated with the peak of marine mass extinction. The isotopic fluctuations are not linked to changes in depositional setting, kerogen composition or plant community, so they evidently resulted from global perturbations in atmospheric δ13C and/or CO2. The pattern was not produced by a single catastrophe such as a meteorite impact, and carbon-cycle calculations indicate that gas release during flood-basalt volcanism was insufficient. Methane-hydrate melting can generate a single -7% shift, but cannot produce rapid multiple excursions without repeated reservoir regeneration and release. However, the data are consistent with repeated overturning of a stratified ocean, expelling toxic gases that promoted sequential mass extinctions in the terrestrial and marine realms.

  19. Tectono-sedimentary evolution of the Permian-Triassic extension event in the Zagros basin (Iran): results from analogue modelling

    Science.gov (United States)

    Madani-kivi, M.; Zulauf, G.

    2015-12-01

    Since the 1970s, the largest oil and gas reservoirs have been discovered in the Permian-Early Triassic formationsin Saudi Arabia. Thus, this time period is important for the discovery of new oil reserves in Iran. The Arabian passivecontinental margin has undergone lithospheric extension during the Permian-Triassic, which led to the formation of theNeo-Tethys. The aim of this paper is to describe the development of the continental rift basin in the Zagros region basedon the tectono-sedimentological evolution. We have studied well-log data to specify the distribution of synrift depositsin the Zagros and have related this information to the modelling. Environmental changes indicated by various sedimentarysequences, from a siliciclastic basin to a carbonate platform setting, are described. The Cambrian Hormuz salt, whichoverlies the metamorphosed Precambrian basement, becomes effective as a basal detachment layer influencing the styleof overburden deformation during the Permian-Triassic extension event. We have investigated the formation of variousstructures linked to the presence or absence of the Hormuz layer by analogue modelling and relating these structures to theLate Palaeozoic sedimentation. Based on results of the analogue modelling, we argue that the basal detachment layer (Hormuzseries) has contributed to the various structural styles of the extensional basin development in the Fars domain and theLorestan domain.

  20. Mesozoic-Cenozoic evolution of the Zoige depression in the Songpan-Ganzi flysch basin, eastern Tibetan Plateau: Constraints from detrital zircon U-Pb ages and fission-track ages of the Triassic sedimentary sequence

    Science.gov (United States)

    Tang, Yan; Zhang, Yunpeng; Tong, Lili

    2018-01-01

    The Zoige depression is an important depocenter within the northeast Songpan-Ganzi flysch basin, which is bounded by the South China, North China and Qiangtang Blocks and forms the northeastern margin of the Tibetan Plateau. This paper discusses the sediment provenance and Mesozoic-Cenozoic evolution of the Zoige depression in the Songpan-Ganzi flysch basin, eastern Tibetan Plateau, using the detrital zircon U-Pb ages and apatite fission-track data from the Middle to Late Triassic sedimentary rocks in the area. The U-Pb ages of the Middle to Late Triassic zircons range from 260-280 Ma, 429-480 Ma, 792-974 Ma and 1800-2500 Ma and represent distinct source region. Our new results demonstrate that the detritus deposited during the Middle Triassic (Ladinian, T2zg) primarily originated from the Eastern Kunlun and North Qinling Orogens, with lesser contributions from the North China Block. By the Late Triassic (early Carnian, T3z), the materials at the southern margin of the North China Block were generally transported westward to the basin along a river network that flowed through the Qinling region between the North China and South China Blocks: this interpretation is supported by the predominance of the bimodal distribution of 1.8 Ga and 2.5 Ga age peaks and a lack of significant Neoproterozoic zircon. Since the Late Triassic (middle Carnian, T3zh), considerable changes have occurred in the source terranes, such as the cessation of the Eastern Kunlun Orogen and North China Block sources and the rise of the northwestern margin of the Yangtze Block and South Qinling Orogen. These drastic changes are compatible with a model of a sustained westward collision between the South China and North China Blocks during the late Triassic and the clockwise rotation of the South China Block progressively closed the basin. Subsequently, orogeny-associated folds have formed in the basin since the Late Triassic (late Carnian), and the study area was generally subjected to uplifting and

  1. Permian-Triassic maturation and multistage migration of hydrocarbons in the Assistência Formation (Irati Subgroup, Paraná Basin, Brazil: implications for the exploration model

    Directory of Open Access Journals (Sweden)

    António Mateus

    Full Text Available New lines of geological evidence strongly suggest that the main period of hydrocarbon maturation within Assistência Formation should be Permian-Triassic, stimulated by a high geothermal gradient that also sustained various manifestations of hydrothermal activity. Three main stages of fluid/hydrocarbon migration can also be inferred on the basis of multiscale observations: confined flow in late Permian to Triassic times, depending on the local build-up of fluid pressures; heterogeneous flow in Lower Cretaceous, triggered by a rejuvenated temperature gradient assisted by the early developed permeability conditions; and a late flow possibly driven by local pressure gradients, after complete cooling of dolerite dykes/sills. The early maturation and multistage migration of hydrocarbons have significant consequences in the design of exploration models to be applied in Paraná Basin.

  2. Atmospheric carbon injection linked to end-Triassic mass extinction.

    Science.gov (United States)

    Ruhl, Micha; Bonis, Nina R; Reichart, Gert-Jan; Sinninghe Damsté, Jaap S; Kürschner, Wolfram M

    2011-07-22

    The end-Triassic mass extinction (~201.4 million years ago), marked by terrestrial ecosystem turnover and up to ~50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5 per mil negative excursion, coincident with the extinction interval. These data indicate strong carbon-13 depletion of the end-Triassic atmosphere, within only 10,000 to 20,000 years. The magnitude and rate of this carbon-cycle disruption can be explained by the injection of at least ~12 × 10(3) gigatons of isotopically depleted carbon as methane into the atmosphere. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence, end-Triassic events are robustly linked to methane-derived massive carbon release and associated climate change.

  3. High precision time calibration of the Permian-Triassic boundary mass extinction event in a deep marine context

    Science.gov (United States)

    Baresel, Björn; Bucher, Hugo; Brosse, Morgane; Bagherpour, Borhan; Schaltegger, Urs

    2015-04-01

    To construct a revised and high resolution calibrated time scale for the Permian-Triassic boundary (PTB) we use (1) high-precision U-Pb zircon age determinations of a unique succession of volcanic ash layers interbedded with deep water fossiliferous sediments in the Nanpanjiang Basin (South China) combined with (2) accurate quantitative biochronology based on ammonoids, conodonts, radiolarians, and foraminifera and (3) tracers of marine bioproductivity (carbon isotopes) across the PTB. The unprecedented precision of the single grain chemical abrasion isotope-dilution thermal ionization mass spectrometry (CA-ID-TIMS) dating technique at sub-per mil level (radio-isotopic calibration of the PTB at the groups of processes. Using these alignments allows (1) positioning the PTB in different depositional setting and (2) solving the age contradictions generated by the misleading use of the first occurrence (FO) of the conodont Hindeodus parvus, whose diachronous first occurrences are arbitrarily used for placing the base of the Triassic. This new age framework provides the basis for a combined calibration of chemostratigraphic records with high-resolution biochronozones of the Late Permian and Early Triassic. Here, we present new single grain U-Pb zircon data of volcanic ash layers from two deep marine sections (Dongpan and Penglaitan) revealing stratigraphic consistent dates over several volcanic ash layers bracketing the PTB. These analyses define weighted mean 206Pb/238U ages of 251.956±0.033 Ma (Dongpan) and 252.062±0.043 Ma (Penglaitan) for the last Permian ash bed. By calibration with detailed litho- and biostratigraphy new U-Pb ages of 251.953±0.038 Ma (Dongpan) and 251.907±0.033 Ma (Penglaitan) are established for the onset of the Triassic.

  4. Lethally Hot Temperatures During the Early Triassic Greenhouse

    Science.gov (United States)

    Sun, Yadong; Joachimski, Michael M.; Wignall, Paul B.; Yan, Chunbo; Chen, Yanlong; Jiang, Haishui; Wang, Lina; Lai, Xulong

    2012-10-01

    Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery. This was manifested in the loss of calcareous algae, the near-absence of fish in equatorial Tethys, and the dominance of small taxa of invertebrates during the thermal maxima. High temperatures drove most Early Triassic plants and animals out of equatorial terrestrial ecosystems and probably were a major cause of the end-Smithian crisis.

  5. Structure of an inverted basin from subsurface and field data: the Late Jurassic-Early Cretaceous Maestrat Basin (Iberian Chain)

    Energy Technology Data Exchange (ETDEWEB)

    Nebot, M.; Guimera, J.

    2016-07-01

    The Maestrat Basin experienced two main rifting events: Late Permian-Late Triassic and Late Jurassic-Early Cretaceous, and was inverted during the Cenozoic Alpine orogeny. During the inversion, an E-W-trending, N-verging fold-and-thrust belt developed along its northern margin, detached in the Triassic evaporites, while southwards it also involved the Variscan basement. A structural study of the transition between these two areas is presented, using 2D seismic profiles, exploration wells and field data, to characterize its evolution during the Mesozoic extension and the Cenozoic contraction. The S-dipping Maestrat basement thrust traverses the Maestrat Basin from E to W; it is the result of the Cenozoic inversion of the lower segment–within the acoustic basement–of the Mesozoic extensional fault system that generated the Salzedella sub-basin. The syn-rift Lower Cretaceous rocks filling the Salzedella sub-basin thicken progressively northwards, from 350m to 1100m. During the inversion, a wide uplifted area –40km wide in the N-S direction– developed in the hanging wall of the Maestrat basement thrust. This uplifted area is limited to the North by the E-W-trending Calders monocline, whose limb is about 13km wide in its central part, dips about 5ºN, and generates a vertical tectonic step of 800-1200m. We interpreted the Calders monocline as a fault-bend fold; therefore, a flat-ramp-flat geometry is assumed in depth for the Maestrat basement thrust. The northern synformal hinge of the Calders monocline coincides with the transition from thick-skinned to thin-skinned areas. The vast uplifted area and the low-dip of the monocline suggest a very low-dip for the basement ramp, rooted in the upper crust. The Calders monocline narrows and disappears laterally, in coincidence with the outcrop of the Maestrat basement thrust. The evaporitic Middle Muschelkalk detachment conditioned the structural style. Salt structures are also related to it; they developed during the

  6. New hybodontiform and neoselachian sharks from the Lower Triassic of Oman

    DEFF Research Database (Denmark)

    Koot, Martha B.; Cuny, Gilles Guy Roger; Orchard, Michael J.

    2015-01-01

    Elasmobranchs are reported for the first time from Lower Triassic deposits in Oman. The well-preserved remains consist of isolated teeth, dermal denticles and fin spines, recovered from conodont residues. The low-palaeolatitude sections consist of Lopingian-Olenekian shallow and pelagic carbonates...... in exotics, olistoliths and breccia blocks that have been redeposited in younger allochthonous strata of the Hawasina Basin throughout the Oman Mountains at Jabal Safra (olistoliths within the Jurassic Guwayza Formation, Olenekian), as well as at Wadi Alwa (exotic Alwa Formation, Lopingian...... of the early stages of their evolution. All described taxa are new to the Oman fossil record and that of western Neotethys, apart from Omanoselache and Amelacanthus, which have been recognized from Wordian deposits, and Omanoselache is the second genus from Oman known to have survived the late Permian mass...

  7. The end-Triassic mass extinction: A new correlation between extinction events and δ13C fluctuations from a Triassic-Jurassic peritidal succession in western Sicily

    Science.gov (United States)

    Todaro, Simona; Rigo, Manuel; Randazzo, Vincenzo; Di Stefano, Pietro

    2018-06-01

    A new δ13Ccarb curve was obtained from an expanded peritidal succession in western Sicily and was used to investigate the relationships between isotopic signatures and biological events on carbonate platforms across the Triassic-Jurassic boundary (TJB). The resulting curve shows two main negative carbon isotopic excursions (CIEs) that fit well with the "Initial" and "Main" CIEs that are recognized worldwide and linked to the End-Triassic Extinction (ETE). In the studied section, the first negative CIE marks the disappearance of the large megalodontids, which were replaced by small and thin-shelled specimens, while the "Main" CIE corresponds to the last occurrence (LO) of the megalodontids and, approximately 50 m upsection, to the total demise of the Rhaetian benthic foraminifer community. Upward, the carbon curve shows a positive trend (ca. +1‰) and a gradual recovery of the benthic communities after an approximately 10 m-thick barren interval populated only by the problematic alga Thaumatoporella parvovesiculifera. A comparison between the Mt. Sparagio δ13Ccarb curve and other coeval Ccarb and Corg curves from carbonate platform, ramp and deep basin successions indicates similar isotopic trends; however, the diverse magnitudes and responses of benthic communities confirm that the carbon cycle perturbations have been globally significant, and were influenced by external forces such as CAMP volcanism. The multiphase nature of the extinction pulses could have been caused by local environmental changes related to transgression/regression phenomena. Overall, this study adds new data and a new timing to the effect of the acidification process on carbon productivity and benthic communities in different environments across the TJB.

  8. Time-scale calibration by U-Pb geochronology: Examples from the Triassic Period

    Science.gov (United States)

    Mundil, R.

    2009-05-01

    )) and the Early-Middle Triassic (Olenekian-Anisian) boundary (247.2 Ma, (8, 9)), resulting in a surprisingly short duration of the Early Triassic which has implications for the timing of biotic recovery and major changes in ocean chemistry during this time. Furthermore, the Anisian-Ladinian boundary is constrained to 242.0 Ma by new U-Pb and 40Ar/39Ar ages. Radio-isotopic ages for the Late Triassic are scarce and the only reliable and biostratigraphically controlled age is from an upper Carnian tuff dated to 230.9 Ma (10), yielding a duration of more than 35 Ma for the Late Triassic. The resulting time-scale is at odds with the most recent compilation (11) but arguably more accurate because it is entirely based on U-Pb analyses applied to closed-system zircons with uncertainties at the permil level or better. 1. T. E. Krogh, Geochimica et Cosmochimica Acta 37, 485 (1973); 2. T. E. Krogh, Geochimica et Cosmochimica Acta 46, 637 (1982); 3. J. M. Mattinson, Chemical Geology 220, 47 (2005); 4. R. Mundil, K. R. Ludwig, I. Metcalfe, P. R. Renne, Science 305, 1760 (2004); 5. U. Schaltegger, J. Guex, A. Bartolini, B. Schoene, M. Ovtcharova, Earth and Planetary Science Letters 267, 266 (2008); 6. R. Mundil, P. R. Renne, K. K. Min, K. R. Ludwig, in Eos Trans. AGU, Fall Meet. Suppl. (2006), vol. 87(52), pp. V21A-0543; 7. T. Galfetti et al., Earth and Planetary Science Letters 258, 593 (2007). 8. M. Ovtcharova et al., Earth and Planetary Science Letters 243, 463 (2006). 9. J. Ramezani et al., Earth and Planetary Science Letters 256, 244 (2007). 10. S. Furin et al., Geology 34, 1009 (2006); 11. J. G. Ogg, in A Geologic Time Scale 2004 F. M. Gradstein, J. G. Ogg, A. G. Smith, Eds. (University Press, Cambridge, 2004) pp. 271-306.

  9. Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction

    NARCIS (Netherlands)

    Ruhl, M.; Bonis, N.R.; Reichart, G.J.; Sinninghe Damsté, J.S.; Kürschner, W.M.

    2011-01-01

    The end-Triassic mass extinction (similar to 201.4 million years ago), marked by terrestrial ecosystem turnover and up to similar to 50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope

  10. Carbon cycle changes during the Triassic-Jurassic transition

    NARCIS (Netherlands)

    Ruhl, M.|info:eu-repo/dai/nl/304838357

    2010-01-01

    The end-Triassic is regarded as one of the five major mass extinction events of the Phanerozoic. This time interval is marked by up to 50% of marine biodiversity loss and major changes in terrestrial ecosystems. Mass extinction events are often marked by changes in the global carbon cycle. The

  11. Permian Triassic palynofloral transition in Chintalapudi area ...

    Indian Academy of Sciences (India)

    The entire 606 m-thick sedimentary sequence in borecore MCP-7 from Chintalapudi area, Chintalapudi sub-basin has been lithologically designated as Kamthi Formation. However, the palynological investigation revealed five distinct palynoassemblages, which essentially fall under two groups, one group ...

  12. Geomorphological stability of Permo-Triassic albitized profiles - case study of the Montseny-Guilleries High (NE Iberia)

    Science.gov (United States)

    Parcerisa, D.; Casas, L.; Franke, C.; Gomez-Gras, D.; Lacasa, G.; Nunez, J. A.; Thiry, M.

    2010-05-01

    albitization. Biotites are not or weakly chloritized. However, these "unaltered" (or primary) granites are strongly weathered into granite boulders embedded in grus by the present-day climatic conditions. The maturest paleoprofiles occur at the northern part of the Catalan Coastal Ranges (i.e. the Montseny-Guilleries High) where the Variscan basement remained exposed during Triassic times. Towards the South the profiles progressively disappear and Triassic sediments acquire their maximum thickness here. The alteration profiles are related with the Permo-Triassic paleosurface still outcroping on wide areas [Gómez-Gras and Ferrer, 1999]. They are partially covered by Triassic fluvial sandstones (Buntsandstein facies) in the South [Gómez-Gras, 1993] and by Palaeocene alluvial conglomerates in the West [Anadón et al., 1979]. The Triassic paleosurface shows a remarkable stability successively outcropping during Mesozoic and Tertiary times, the pre-Tertiary exhumation and even the present day weathering affected very little these albitized profiles. The hardness and thus preservation of the Triassic paleosurface is mainly related to the albitization. The albitized granites are entirely lacking anorthitic plagioclase, which is much more sensitive to chemo-mechanical weathering. Development of albite and additional chloritization of the primary biotite crystals render the rocks much more resistant to weathering and erosion. This stability is particularly well expressed in case of the Montseny-Guilleries High, which is limited by a high fault scarp at the south-eastern margin. The albitized top of the scarp shows remarkably hard fresh rocks, whereas the base of the scarp (formed of primary, non-albitized facies) is deeply weathered into gruss. This is causing much smother landscape reliefs in the valleys and thalwegs. Since a long time the remarkable persistence of the Triassic paleosurface expressed in the Paleozoic massifs has been highlighted by geomorphologists. Only recently we

  13. High diversity, low disparity and small body size in plesiosaurs (Reptilia, Sauropterygia from the Triassic-Jurassic boundary.

    Directory of Open Access Journals (Sweden)

    Roger B J Benson

    Full Text Available Invasion of the open ocean by tetrapods represents a major evolutionary transition that occurred independently in cetaceans, mosasauroids, chelonioids (sea turtles, ichthyosaurs and plesiosaurs. Plesiosaurian reptiles invaded pelagic ocean environments immediately following the Late Triassic extinctions. This diversification is recorded by three intensively-sampled European fossil faunas, spanning 20 million years (Ma. These provide an unparalleled opportunity to document changes in key macroevolutionary parameters associated with secondary adaptation to pelagic life in tetrapods. A comprehensive assessment focuses on the oldest fauna, from the Blue Lias Formation of Street, and nearby localities, in Somerset, UK (Earliest Jurassic: 200 Ma, identifying three new species representing two small-bodied rhomaleosaurids (Stratesaurus taylori gen et sp. nov.; Avalonnectes arturi gen. et sp. nov and the most basal plesiosauroid, Eoplesiosaurus antiquior gen. et sp. nov. The initial radiation of plesiosaurs was characterised by high, but short-lived, diversity of an archaic clade, Rhomaleosauridae. Representatives of this initial radiation were replaced by derived, neoplesiosaurian plesiosaurs at small-medium body sizes during a more gradual accumulation of morphological disparity. This gradualistic modality suggests that adaptive radiations within tetrapod subclades are not always characterised by the initially high levels of disparity observed in the Paleozoic origins of major metazoan body plans, or in the origin of tetrapods. High rhomaleosaurid diversity immediately following the Triassic-Jurassic boundary supports the gradual model of Late Triassic extinctions, mostly predating the boundary itself. Increase in both maximum and minimum body length early in plesiosaurian history suggests a driven evolutionary trend. However, Maximum-likelihood models suggest only passive expansion into higher body size categories.

  14. Early Triassic alternative ecological states driven by anoxia, hyperthermals, and erosional pulses following the end-Permian mass extinction

    Science.gov (United States)

    Pietsch, C.; Petsios, E.; Bottjer, D. J.

    2015-12-01

    The end-Permian mass extinction, 252 million years ago, was the most devastating loss of biodiversity in Earth's history. Massive volcanic eruptions of the Siberian Traps and the concurrent burning of coal, carbonate, and evaporite deposits emplaced greenhouse and toxic gasses. Hyperthermal events of the surface ocean, up to 40°C, led to reduced gradient-driven ocean circulation which yielded extensive equatorial oxygen minimum zones. Today, anthropogenic greenhouse gas production is outpacing carbon input modeled for the end-Permian mass extinction, which suggests that modern ecosystems may yet experience a severe biotic crisis. The Early Triassic records the 5 million year aftermath of the end-Permian mass extinction and is often perceived as an interval of delayed recovery. We combined a new, high resolution carbon isotope record, sedimentological analysis, and paleoecological collections from the Italian Werfen Formation to fully integrate paleoenvironmental change with the benthic ecological response. We find that the marine ecosystem experienced additional community restructuring events due to subsequent hyperthermal events and pulses of erosion. The benthic microfauna and macrofauna both contributed to disaster communities that initially rebounded in the earliest Triassic. 'Disaster fauna' including microbialites, microconchids, foraminifera, and "flat clams" took advantage of anoxic conditions in the first ~500,000 years, dominating the benthic fauna. Later, in the re-oxygenated water column, opportunistic disaster groups were supplanted by a more diverse, mollusc-dominated benthic fauna and a complex ichnofauna. An extreme temperature run-up beginning in the Late Dienerian led to an additional hyperthermal event in the Late-Smithian which co-occurred with increased humidity and terrestrial run-off. Massive siliciclastic deposits replaced carbonate deposition which corresponds to the infaunalization of the benthic fauna. The disaster taxa dominated

  15. Tectonic model for the Late Paleozoic of southeastern New England

    Energy Technology Data Exchange (ETDEWEB)

    Wintsch, R.P.; Sutter, J.F.

    1986-07-01

    Hornblende and biotite /sup 40/Ar//sup 39/Ar age spectra from rocks in south-central Connecticut help define a Permian-Triassic cooling curve for the area. Together with petrologic and structural information, a time-temperature-pressure-strain path is established. Similar data for the Narragansett basin in Rhode Island and Massachusetts allow correlation of the late Paleozoic histories of the two areas. Together, these data suggest that in the late Paleozoic, south-central New England was part of a fold-thrust belt, and the Narragansett basin was a retroarc foreland basin. NW-SE compression during the final assembly of Pangaea resulted in SE directed thrusting, causing the development of clastic wedges in adjacent Rhode Island and Massachusetts in the Late Carboniferous-Early Permian. A clockwise rotation of this deformation from NW to NNE led to northward underthrusting and concomitant uplift of both eastern Connecticut and Rhode Island in the Permian and Triassic.

  16. The Triassic dicynodont Kombuisia (Synapsida, Anomodontia) from Antarctica, a refuge from the terrestrial Permian-Triassic mass extinction.

    Science.gov (United States)

    Fröbisch, Jörg; Angielczyk, Kenneth D; Sidor, Christian A

    2010-02-01

    Fossils from the central Transantarctic Mountains in Antarctica are referred to a new species of the Triassic genus Kombuisia, one of four dicynodont lineages known to survive the end-Permian mass extinction. The specimens show a unique combination of characters only present in this genus, but the new species can be distinguished from the type species of the genus, Kombuisia frerensis, by the presence of a reduced but slit-like pineal foramen and the lack of contact between the postorbitals. Although incomplete, the Antarctic specimens are significant because Kombuisia was previously known only from the South African Karoo Basin and the new specimens extend the taxon's biogeographic range to a wider portion of southern Pangaea. In addition, the new finds extend the known stratigraphic range of Kombuisia from the Middle Triassic subzone B of the Cynognathus Assemblage Zone into rocks that are equivalent in age to the Lower Triassic Lystrosaurus Assemblage Zone, shortening the proposed ghost lineage of this taxon. Most importantly, the occurrence of Kombuisia and Lystrosaurus mccaigi in the Lower Triassic of Antarctica suggests that this area served as a refuge from some of the effects of the end-Permian extinction. The composition of the lower Fremouw Formation fauna implies a community structure similar to that of the ecologically anomalous Lystrosaurus Assemblage Zone of South Africa, providing additional evidence for widespread ecological disturbance in the extinction's aftermath.

  17. THE PALYNOLOGY AND PALAEONVIRONMENT OF THE UPPER TRIASSIC DOLOMITIC-MARLY SEQUENCE OF DOGNA VALLEY (UDINE, FRIULI-VENEZIA GIULIA, NE ITALY WITH REPTILE TRACKWAYS

    Directory of Open Access Journals (Sweden)

    GUIDO ROGHI

    1997-07-01

    Full Text Available New data and considerations about the biostratigraphy and the palaeoenvironment of a section in the Late Triassic dolomitic-marly sequence which crops out in the Dogna valley (Udine, Friuli, NE Italy are reported. In particular a unit with a surface bearing tracks of archosauromorph terrestrial reptiles has been investigated. In the layer immediately overlaying the track-bearing one, a rich palynological assemblage with Enzonalasporites vigens; Vallasporites ignacii, Patinasporites densus, Zonalasporites cinctus, Pseudoenzonalasporites summus, Samaropollenites speciosus, Camerosporites secatus and Partitisporites spp. was found, indicating a Tuvalian age (Late Carnian . Microfloral and sedimentological evidence indicate a dry climate and a coastal depositional environment subject to repeated emersions.   

  18. Geochemical and palynological records for the end-Triassic Mass-Extinction Event in the NE Paris Basin (Luxemburg)

    Science.gov (United States)

    Kuhlmann, Natascha; van de Schootbrugge, Bas; Thein, Jean; Fiebig, Jens; Franz, Sven-Oliver; Hanzo, Micheline; Colbach, Robert; Faber, Alain

    2016-04-01

    the sections shows clear signs of strong anoxia. Sedimentological observations reveal several horizons with soft sediment deformation (seismites). These are attributed to strong earthquake during the initial breakup of Pangea. The lowermost horizon at the base of the Argiles de Levallois Member exceeds the seismites in thickness and shows an erosional base and a chaotic sedimentation structure. Its sedimentological characteristics as well as its stratigraphic age makes it a possible candidate for a tsunami deposit triggered by the Rochechouart impact. As such, drill cores from Luxembourg and sourrounding areas (Eifel, W-Germany; NE-Lorraine, France) preserve a unique archive with great potential for unraveling the causes and consequences of the end-Triassic mass-extinction event.

  19. Wildfire Activity Across the Triassic-Jurassic Boundary in the Polish Basin: Evidence from New Fossil Charcoal & Carbon-isotope Data

    Science.gov (United States)

    Pointer, R.; Belcher, C.; Hesselbo, S. P.; Hodbod, M.; Pieńkowski, G.

    2017-12-01

    New fossil charcoal abundance and carbon-isotope data from two sedimentary cores provide new evidence of extreme environmental conditions in the Polish Basin during the Latest Triassic to Earliest Jurassic. Sedimentary cores from the Polish Basin provide an excellent record of terrestrial environmental conditions across the Triassic-Jurassic Boundary, a time of climatic extremes. Previous work has shown that the marine realm was affected by a large perturbation to the carbon cycle across the Triassic-Jurassic Boundary (manifested by large negative and positive carbon-isotope excursions) and limited records of charcoal abundance and organic geochemistry have indicated important changes in fire regime in the coeval ecosystems. Here we present two new carbon-isotope records generated from fossil plant matter across the Triassic-Jurassic boundary, and present new charcoal records. The charcoal abundance data confirm that there was variation in wildfire activity during the Late Triassic-Early Jurassic in the Polish Basin. Peaks in the number of fossil charcoal fragments present occur in both sedimentary cores, and increases in fossil charcoal abundance are linked to wildfires, signalling a short-lived rise in wildfire activity. Fossil charcoal abundance does not appear to be fully controlled by total organic matter content, depositional environment or bioturbation. We argue that increased wildfire activity is likely caused by an increase in ignition of plant material as a result of an elevated number of lightning strikes. Global warming (caused by a massive input of carbon into the atmosphere, as indicated by carbon-isotope data) can increase storm activity, leading to increased numbers of lightning strikes. Previous Triassic-Jurassic Boundary wildfire studies have found fossil charcoal abundance peaks at other northern hemisphere sites (Denmark & Greenland), and concluded that they represent increases in wildfire activity in the earliest Jurassic. Our new charcoal and

  20. Thick Toenails

    Science.gov (United States)

    ... in individuals with nail fungus (onychomycosis), psoriasis and hypothyroidism. Those who have problems with the thickness of their toenails should consult a foot and ankle surgeon for proper diagnosis and treatment. Find an ACFAS Physician Search Search Tools Find ...

  1. Triassic rejuvenation of unexposed Archean-Paleoproterozoic deep crust beneath the western Cathaysia block, South China

    Science.gov (United States)

    Li, Xi-Yao; Zheng, Jian-Ping; Xiong, Qing; Zhou, Xiang; Xiang, Lu

    2018-01-01

    Jurassic (ca. 150 Ma) Daoxian basalts from the western Cathaysia block (South China) entrained a suite of deep-seated crustal xenoliths, including felsic schist, gneiss and granulite, and mafic two-pyroxene granulite and metagabbro. Zircon U-Pb-Hf isotopic, whole-rock elemental and Sr-Nd-Pb isotopic compositions have been determined for these valuable xenoliths to reveal the poorly-known, unexposed deep crust beneath South China. Detrital zircons from the garnet-biotite schists show several populations of ages at 0.65-0.5 Ga, 1.1-0.75 Ga, 1.6-1.4 Ga, 1.8-1.7 Ga, 2.5-2.4 Ga, 2.8 Ga, and 3.5 Ga, representing a multi-sourced, meta-sedimentary origin with deposition time at the early Cambrian. One mafic granulite contains zircons with concordant U-Pb ages of Neoarchean ( 2520 Ma), as well as Hf model ages of 2.8-2.6 Ga and positive εHf(t) values (up to 6.3), suggesting an accretion of juvenile crust in Neoarchean, probably as the main framework of the lower crust. Geochemical and geochronological evidence shows the mafic granulite and metagabbro were produced by underplating of magmas derived from the depleted asthenosphere and mixed with EM2-type materials during the Late Triassic (205-196 Ma). This magmatic underplating also resulted in the widespread metamorphism of the mafic lower crust and felsic middle crust (e.g., the felsic granulite and gneiss) at 202-201 Ma. We suggest the existence of a highly evolved Archean-Paleoproterozoic basement beneath the western Cathaysia block, which experienced episodic accretion and reworking and the strong rejuvenation during the Triassic. A three-layered structure of the lower crust could exist beneath the Daoxian area during the Jurassic time: its upper layer is an evolved Archean-Paleoproterozoic basement; the middle hybrid layer represents a mixture of Archean-Paleoproterozoic basement with newly accreted/reworked Proterozoic to Phanerozoic materials; and the deeper layer consists of mafic granulites derived from the

  2. Geochemical characteristics of natural gas in the hydrocarbon accumulation history, and its difference among gas reservoirs in the Upper Triassic formation of Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2016-08-01

    Full Text Available The analysis of hydrocarbon generation, trap formation, inclusion homogenization temperature, authigenic illite dating, and ESR dating were used to understand the history of hydrocarbon accumulation and its difference among gas reservoirs in the Upper Triassic formation of Sichuan Basin. The results show the hydrocarbon accumulation mainly occurred during the Jurassic and Cretaceous periods; they could also be classified into three stages: (1 early hydrocarbon generation accumulation stage, (2 mass hydrocarbon generation accumulation stage before the Himalayan Epoch, (3 and parts of hydrocarbon adjustment and re-accumulation during Himalayan Epoch. The second stage is more important than the other two. The Hydrocarbon accumulation histories are obviously dissimilar in different regions. In western Sichuan Basin, the gas accumulation began at the deposition period of member 5 of Xujiahe Formation, and mass accumulation occurred during the early Middle Jurassic up to the end of the Late Cretaceous. In central Sichuan Basin, the accumulation began at the early Late Jurassic, and the mass accumulation occurred from the middle Early Cretaceous till the end of the Late Cretaceous. In southern Sichuan Basin, the accumulation began at the middle Late Jurassic, and the mass accumulation occurred from the middle of the Late Cretaceous to the end of the Later Cretaceous. The accumulation history of the western Sichuan Basin is the earliest, and the southern Sichuan Basin is the latest. This paper will help to understand the accumulation process, accumulation mechanism, and gas reservoir distribution of the Triassic gas reservoirs in the Sichuan Basin better. Meanwhile, it is found that the authigenic illite in the Upper Triassic formation of Sichuan Basin origin of deep-burial and its dating is a record of the later accumulation. This suggests that the illite dating needs to fully consider illite origin; otherwise the dating results may not accurately

  3. Geochemistry of the triassic-Jurassic alpine continental deposits: origin and geodynamic implications

    International Nuclear Information System (INIS)

    Poinssot, Ch.; Goffe, B.; Toulhoat, P.

    1997-01-01

    Mid-Triassic to mid-Jurassic Alpine continental deposits are known all along the former Brianconnais peninsula. They constitutes small karstic pockets on the thick Triassic calcareous series and their chemistry evolves between bauxites s.s. and aluminous argilites. Most of them were deeply buried during the Alpine orogenesis as recorded by HP-LT metamorphism. Only the deposits of the Pre-Alps were submitted to lower PT conditions (diagenesis-anchizone boundary) during their incorporation in the thrust wedge of the 'Prealpes Medianes'. These formations are known for containing traces of light elements (Li, F) and heavy elements (Zn, REE...). In order to understand the possible origin of these elements, we studied the geochemistry (major and trace elements) of two representative deposits, one in Vanoise which underwent a HP-LT metamorphism, the other one in the Pre-Alps, which was only submitted to diagenesis. Trace elements patterns allow us to preclude an autochthonous origin for these formations as well as the intervention of metasomatism, and demonstrate a granitic origin. Moreover, discrimination diagrams for granites indicate an obvious alkaline granitic origin for these deposits. In the framework of the Alpine palaeogeography, we then discuss the possible granitic sources. Two main sources can be invoked: either a Brianconnais s.s. formation (crystalline or sediments), which supposes a more intense erosion as classically admitted, or more distant sources such as the Corso-Sardinian alkaline acid-rocks, which supposes a complex palaeo-hydrography. This confirms the sedimentary origin of the light elements in these rocks and precludes the intervention of light elements-rich hydrothermal fluids migrating through Alpine metamorphic units. (author)

  4. Early Triassic marine biotic recovery: the predators' perspective.

    Science.gov (United States)

    Scheyer, Torsten M; Romano, Carlo; Jenks, Jim; Bucher, Hugo

    2014-01-01

    Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent.

  5. Early Triassic marine biotic recovery: the predators' perspective.

    Directory of Open Access Journals (Sweden)

    Torsten M Scheyer

    Full Text Available Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became

  6. Permian-Triassic palynofacies and chemostratigraphy in a core recovered from central Spitsbergen.

    Science.gov (United States)

    van Soelen, Els; Hasic, Edi; Planke, Sverre; Svensen, Henrik; Sleveland, Arve; Midtkandal, Ivar; Twitchett, Richard; Kürschner, Wolfram

    2017-04-01

    The Late Permian biotic crisis is one of the most severe extinction events in the history of the Earth, affecting both terrestrial and marine environments. A large igneous province (LIP) in Siberia is thought to be linked with this global event; however, correlation between the volcanic event and the biotic crisis is difficult and requires well dated and high resolution Permian-Triassic boundary successions from the Arctic region. The Svalbard end-Permian drilling project is aimed at improved correlation of the Permian-Triassic sections in Svalbard with the Siberian Traps. The core was collected from Deltadalen, in central Spitsbergen, with additional samples collected from an outcrop close to the drilling site. As part of this collaborative project, carbon isotope geochemistry, palynofacies and palynomorphs were studied in order to learn more about the biostratigraphy and to understand changes in the source(s) of organic matter. Objectives were to reconstruct the paleo-environment; to correlate the core with other sites on Svalbard, and with global records; and to identify and characterize the Late Permian extinction event in the core. A carbon isotope shift is an important global stratigraphic marker in the latest Permian and occurs near the base of the Vikinghøgda Formation in the Deltadalen core, where bulk rock values change from -24.5 to -32.7‰. Palynomorph preservation was generally poor in both core and outcrop samples which prevented detailed examination of species and limited their usefulness for biostratigraphy. Still, palynofacies were useful for correlative purposes. AOM (amorphous organic matter) in the core increases at the lithological change from sandstones to siltstones, and is indicative of anoxic conditions. Similar high levels of AOM in the outcrop samples can be correlated with the core. Palynological analyses show that the spore/pollen ratio starts to increase before the negative shift in the isotope curve. Such an increase in spore

  7. High precision time calibration of the Permo-Triassic boundary mass extinction by U-Pb geochronology

    Science.gov (United States)

    Baresel, Björn; Bucher, Hugo; Brosse, Morgane; Schaltegger, Urs

    2014-05-01

    U-Pb dating using Chemical Abrasion, Isotope Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS) is the analytical method of choice for geochronologists, who are seeking highest temporal resolution and a high degree of accuracy for single grains of zircon. The use of double-isotope tracer solutions, cross-calibrated and assessed in different EARTHTIME labs, coinciding with the reassessment of the uranium decay constants and further improvements in ion counting technology led to unprecedented precision better than 0.1% for single grain, and 0.05% for population ages, respectively. These analytical innovations now allow calibrating magmatic and biological timescales at resolution adequate for both groups of processes. To construct a revised and high resolution calibrated time scale for the Permian-Triassic boundary (PTB) we use (i) high-precision U-Pb zircon age determinations of a unique succession of volcanic ash beds interbedded with shallow to deep water fossiliferous sediments in the Nanpanjiang Basin (South China) combined with (ii) accurate quantitative biochronology based on ammonoids and conodonts and (iii) carbon isotope excursions across the PTB. Using these alignments allows (i) positioning the PTB in different depositional environments and (ii) solving age/stratigraphic contradictions generated by the index, water depth-controlled conodont Hindeodus parvus, whose diachronous first occurrences are arbitrarily used for placing the base of the Triassic. This new age framework provides the basis for a combined calibration of chemostratigraphic records with high-resolution biochronozones of the Late Permian and Early Triassic. Besides the general improvement of the radio-isotopic calibration of the PTB at the ±100 ka level, this will also lead to a better understanding of cause and effect relations involved in this mass extinction.

  8. A high resolution magnetostratigraphic profile across the Permian-Triassic boundary in the Southern Sydney Basin, eastern Australia

    Science.gov (United States)

    Belica, M. E.; Tohver, E.; Nicoll, R.; Denyszyn, S. W.; Pisarevsky, S.; George, A. D.

    2016-12-01

    The Permian-Triassic boundary (PTB) is associated with the largest mass extinction in Phanerozoic geologic history. Despite several decades of intense study, there is ongoing debate regarding the exact timing of extinction and the global correlation of marine and terrestrial P-T sections. The terrestrial record is hampered by a lack of index fossils; however, magnetostratigraphy offers an opportunity for correlation because it relies on the global synchronicity of magnetic reversals. A magnetostratigraphic profile across the Permian-Triassic boundary has been obtained from a stratigraphically continuous terrestrial section in the Southern Sydney Basin of eastern Australia. The 60 m section is located within the Narrabeen Group, which consists of fluvial to lacustrine sandstones and mudstones. Paleomagnetic samples were collected at one meter intervals to determine a detailed reversal record. Samples were stepwise thermally demagnetized to isolate a primary remanence, and magnetic susceptibility was measured in the field at 30 cm intervals with values ranging from -0.047-2.50 (10-3 SI units). Three normal and three reverse magnetozones were detected after removal of a low temperature overprint, and the results show good agreement with the Global Magnetic Polarity Timescale as well as marine Permian-Triassic sections where the PTB is well constrained. Furthermore, a reverse polarity subchron has been identified within the normal magnetozone spanning the PTB similar to results published from the Netherlands and China. The magnetic stratigraphy suggests that the Narrabeen Group was deposited during the late Changhsingian to early Induan, and provides a revised placement of the PTB in the lower Wombarra Claystone. Integration of the magnetostratigraphy with existing isotopic datasets suggests that the terrestrial extinction in eastern Australia occurred 7.5 m below the PTB in the Changhsingian Coalcliff Sandstone. A tuff within a coal seam underlying the Coalcliff

  9. Absolute Plate Motion Control Since the Triassic from the Cocos Slab and its Associated Subduction Record in Mexico

    Science.gov (United States)

    Boschman, L.; Van Hinsbergen, D. J. J.; Langereis, C. G.; Molina-Garza, R. S.; Kimbrough, D. L.; Spakman, W.

    2017-12-01

    A positive wave speed anomaly interpreted as the Cocos slab stretches from the uppermost mantle at the Middle America trench in the west, to the lowermost mantle below the Atlantic in the east. The length and continuity of this slab indicates long-lived, uninterrupted eastward subduction of the attached Cocos Plate and its predecessor, the Farallon Plate. The geological record of Mexico contains Triassic to present day evidence of subduction, of which the post-Late Cretaceous phase is of continental margin-style. Interpretations of the pre-Upper Cretaceous subduction-related rock assemblages are under debate, and vary from far-travelled exotic intra-oceanic island arc character to in-situ extended continental margin origin. We present new paleomagnetic data that show that Triassic, Jurassic and Cretaceous subduction-related rocks from the Vizcaíno Peninsula and the Guerrero terrane have a paleolatitudinal plate motion history that is equal to that of the North American continent. This suggests that these rock assemblages were part of the overriding plate and were perhaps only separated from the North American continent by temporal fore- or back-arc spreading. The entire Triassic-present day subduction record, and hence, reconstructed trench location, can therefore be linked to the Cocos slab, which provides control on longitudinal plate motion of North America since the time of Pangea. Compared to the latest state of the art mantle frames, in which longitudes are essentially unconstrained for pre-Cretaceous times, our reconstructed absolute position of North America requires a significant westward longitudinal shift for Mesozoic times.

  10. A Middle Triassic thoracopterid from China highlights the evolutionary origin of overwater gliding in early ray-finned fishes.

    Science.gov (United States)

    Xu, Guang-Hui; Zhao, Li-Jun; Shen, Chen-Chen

    2015-01-01

    Gliding adaptations in thoracopterid flying fishes represent a remarkable case of convergent evolution of overwater gliding strategy with modern exocoetid flying fishes, but the evolutionary origin of this strategy was poorly known in the thoracopterids because of lack of transitional forms. Until recently, all thoracopterids, from the Late Triassic of Austria and Italy and the Middle Triassic of South China, were highly specialized 'four-winged' gliders in having wing-like paired fins and an asymmetrical caudal fin with the lower caudal lobe notably larger than the upper lobe. Here, we show that the new genus Wushaichthys and the previously alleged 'peltopleurid' Peripeltopleurus, from the Middle Triassic (Ladinian, 235-242 Ma) of South China and near the Ladinian/Anisian boundary of southern Switzerland and northern Italy, respectively, represent the most primitive and oldest known thoracopterids. Wushaichthys, the most basal thoracopterid, shows certain derived features of this group in the skull. Peripeltopleurus shows a condition intermediate between Wushaichthys and Thoracopterus in having a slightly asymmetrical caudal fin but still lacking wing-like paired fins. Phylogenetic studies suggest that the evolution of overwater gliding of thoracopterids was gradual in nature; a four-stage adaption following the 'cranial specialization-asymmetrical caudal fin-enlarged paired fins-scale reduction' sequence has been recognized in thoracopterid evolution. Moreover, Wushaichthys and Peripeltopleurus bear hooklets on the anal fin of supposed males, resembling those of modern viviparious teleosts. Early thoracopterids probably had evolved a live-bearing reproductive strategy. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  11. Astronomical cycle origin of bedded chert: A middle Triassic bedded chert sequence, Inuyama, Japan

    Science.gov (United States)

    Ikeda, Masayuki; Tada, Ryuji; Sakuma, Hironobu

    2010-09-01

    Astronomical forcing is one of the main drivers of climate change, and astronomical cyclicity recorded in sediments provides a clue to understand the dynamics of the global climate system. Bedded cherts consist of rhythmic alternations of chert and shale beds. Although previous studies have hypothesized that the origin of bedded chert is related to astronomical cycles (e.g. Fischer, 1976; Hori et al., 1993), conclusive proof remains elusive. To explore this possibility, we established a continuous, high-resolution lithostratigraphy of middle Triassic bedded chert in Central Japan. The average duration of each chert-shale couplet is 20 kyr, similar to that of the precession cycle. Spectral analysis of a bed number series of thickness variations in chert beds was performed assuming that each chert-shale couplet represents a 20-kyr precession cycle. The results reveal cycles involving approximately 200, 20, 5, and 2-3 beds, corresponding to periodicities of approximately 4000, 400, 100, and 40-60 kyr, respectively. By further assuming that the 20-bed cycle represents a 405-kyr eccentricity cycle of constant and stable periodicity, we converted the bed number series to a time series. Spectral analysis of the time series revealed distinct periodicities of 3600, 117, 97, and 38 kyr, in addition to 405 kyr. Besides 3600 kyr, these periodicities agree well with the 120, 95, and 37 kyr periodicities for eccentricity cycles and the obliquity cycle during the Triassic. Moreover, we detected amplitude modulation of the approximately 100-kyr cycle of thickness variations in chert beds with a 405-kyr periodicity, which may correspond to amplitude modulation of 100-kyr climatic precession cycle with the 405-kyr periodicity. The approximately 3600-kyr periodicity described above and 1800-kyr periodicity manifested as the amplitude modulation of the 405-kyr cycle are correlated to present-day long-term eccentricity cycles of 2400 and 4800 kyr evolved by chaotic behavior of solar

  12. Late Paleozoic to Jurassic chronostratigraphy of coastal southern Peru: Temporal evolution of sedimentation along an active margin

    Science.gov (United States)

    Boekhout, F.; Sempere, T.; Spikings, R.; Schaltegger, U.

    2013-11-01

    We present an integrated geochronological and sedimentological study that significantly revises the basin and magmatic history associated with lithospheric thinning in southern coastal Peru (15-18°S) since the onset of subduction at ˜530 Ma. Until now, estimating the age of the sedimentary and volcanic rocks has heavily relied on paleontologic determinations. Our new geochronological data, combined with numerous field observations, provide the first robust constraints on their chronostratigraphy, which is discussed in the light of biostratigraphical attributions. A detailed review of the existing local units simplifies the current stratigraphic nomenclature and clarifies its absolute chronology using zircon U-Pb ages. We observe that the Late Paleozoic to Jurassic stratigraphy of coastal southern Peru consists of two first-order units, namely (1) the Yamayo Group, a sedimentary succession of variable (0-2 km) thickness, with apparently no nearby volcanic lateral equivalent, and (2) the overlying Yura Group, consisting of a lower, 1-6 km-thick volcanic and volcaniclastic unit, the Chocolate Formation, and an upper, 1-2 km-thick sedimentary succession that are in markedly diachronous contact across the coeval arc and back-arc. We date the local base of the Chocolate Formation, and thus of the Yura Group, to 216 Ma, and show that the underlying Yamayo Group spans a >110 Myr-long time interval, from at least the Late Visean to the Late Triassic, and is apparently devoid of significant internal discontinuities. The age of the top of the Chocolate Formation, i.e. of the volcanic arc pile, varies from ˜194 Ma to less than ˜135 Ma across the study area. We suggest that this simplified and updated stratigraphic framework can be reliably used as a reference for future studies.

  13. The Central European, Tarim and Siberian Large Igneous Provinces, Late Palaeozoic orogeny and coeval metallogeny

    NARCIS (Netherlands)

    de Boorder, H.|info:eu-repo/dai/nl/098199056

    2014-01-01

    The formation of the Central European and Tarim Large Igneous Provinces (LIPs) in the Early Permian coincided with the demise of the Variscan and the Southern Tianshan orogens, respectively. The Early Triassic Siberian LIP was formed in the wake of the Western Altaid orogeny in the Late Permian.

  14. Microbialites and global environmental change across the Permian-Triassic boundary: a synthesis.

    Science.gov (United States)

    Kershaw, S; Crasquin, S; Li, Y; Collin, P-Y; Forel, M-B; Mu, X; Baud, A; Wang, Y; Xie, S; Maurer, F; Guo, L

    2012-01-01

    Permian-Triassic boundary microbialites (PTBMs) are thin (0.05-15 m) carbonates formed after the end-Permian mass extinction. They comprise Renalcis-group calcimicrobes, microbially mediated micrite, presumed inorganic micrite, calcite cement (some may be microbially influenced) and shelly faunas. PTBMs are abundant in low-latitude shallow-marine carbonate shelves in central Tethyan continents but are rare in higher latitudes, likely inhibited by clastic supply on Pangaea margins. PTBMs occupied broadly similar environments to Late Permian reefs in Tethys, but extended into deeper waters. Late Permian reefs are also rich in microbes (and cements), so post-extinction seawater carbonate saturation was likely similar to the Late Permian. However, PTBMs lack widespread abundant inorganic carbonate cement fans, so a previous interpretation that anoxic bicarbonate-rich water upwelled to rapidly increase carbonate saturation of shallow seawater, post-extinction, is problematic. Preliminary pyrite framboid evidence shows anoxia in PTBM facies, but interbedded shelly faunas indicate oxygenated water, perhaps there was short-term pulsing of normally saturated anoxic water from the oxygen-minimum zone to surface waters. In Tethys, PTBMs show geographic variations: (i) in south China, PTBMs are mostly thrombolites in open shelf settings, largely recrystallised, with remnant structure of Renalcis-group calcimicrobes; (ii) in south Turkey, in shallow waters, stromatolites and thrombolites, lacking calcimicrobes, are interbedded, likely depth-controlled; and (iii) in the Middle East, especially Iran, stromatolites and thrombolites (calcimicrobes uncommon) occur in different sites on open shelves, where controls are unclear. Thus, PTBMs were under more complex control than previously portrayed, with local facies control playing a significant role in their structure and composition. © 2011 Blackwell Publishing Ltd.

  15. Vegetation history across the Permian-Triassic boundary in Pakistan (Amb section, Salt Range)

    NARCIS (Netherlands)

    Schneebeli-Hermann, E.; Kurschner, W.M.; Kerp, H.; Bomfleur, B.; Hochuli, P.A.; Bucher, H.; Ware, D.; Roohi, G.

    2015-01-01

    Hypotheses about the Permian–Triassic floral turnover range from a catastrophic extinction of terrestrial plant communities to a gradual change in floral composition punctuated by intervals indicating dramatic changes in the plant communities. The shallow marine Permian–Triassic succession in the

  16. Triassic arc-derived detritus in the Triassic Karakaya accretionary complex was not derived from either the S Eurasian margin (Istanbul terrane) or the N Gondwana margin (Taurides)

    Science.gov (United States)

    Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair H. F.; Gerdes, Axel; Zulauf, Gernold

    2014-05-01

    We present new U-Pb zircon source age data for Upper Triassic sandstones of the Istanbul Terrane (S Eurasian margin) and also for Triassic sandstones of the Taurides (N Gondwana margin). The main aim is to detect and quantify the contribution of Triassic magmatism as detritus to either of these crustal blocks. This follows the recent discovery of a Triassic magmatic arc source for the Triassic sandstones of the Palaeotethyan Karakaya subduction-accretion complex (Ustaömer et al. 2013; this meeting). Carboniferous (Variscan) zircon grains also form a significant detrital population, plus several more minor populations. Six sandstone samples were studied, two from the İstanbul Terrane (Bakırlıkıran Formation of the Kocaeli Triassic Basin) and four from the Tauride Autochthon (latest Triassic Üzümdere Formation and Mid-Triassic Kasımlar Formations; Beyşehir region). Detrital zircon grains were dated by the laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb method at Goethe University, Frankfurt. Our results do not reveal Triassic detritus in the Üzümdere Formation. The U-Pb age of the analysed zircon grains ranges from 267 Ma to 3.2 Ga. A small fraction of Palaeozoic zircons are Permian (267 to 296 Ma), whereas the remainder are Early Palaeozoic. Ordovician grains (4%) form two age clusters, one at ca. 450 Ma and the other at ca. 474 Ma. Cambrian-aged grains dominate the zircon population, while the second largest population is Ediacaran (576 to 642 Ma). Smaller populations occur at 909-997 Ma, 827-839 Ma, 1.8-2.0 Ga and 2.4-2.6 Ga. The sandstones of the Kasımlar Formation have similar zircon age cluster to those of the somewhat younger Üzümdere Formation, ranging from 239 Ma to 2.9 Ga. A few grains gave Anisian ages. Cambrian zircon grains are less pronounced than in the Kasımlar Formation compared to the Üzümdere Formation. The detrital zircon record of Tauride sandstones, therefore, not indicates significant contribution

  17. Paleomagnetism and magnetic fabric of the Triassic rocks from Spitsbergen

    Science.gov (United States)

    Dudzisz, K.; Szaniawski, R.; Michalski, K.; Manby, G.

    2017-12-01

    Understanding the origin and directions of the natural remanent magnetization and the tectonic deformation pattern reflected in magnetic fabric is of importance for investigation of the West Spitsbergen Fold and Thrust Belt (WSFTB) and its foreland. Previous research carried out on Triassic rocks from the study area concluded that these rocks record a composite magnetization of both, normal and reverse polarity, consisting of a primary Triassic remanence that is overlapped by a secondary post-folding component. Standard paleomagnetic procedures were conducted in order to determine the remanence components and a low-field AMS was applied to assess the degree and pattern of deformation. The AMS results from the WSFTB reveal a magnetic foliation that parallels the bedding planes and a dominantly NNW-SSE oriented magnetic lineation that is sub-parallel to the regional fold axial trend. These results imply a low to moderate degree of deformation and a maximum strain orientation parallel to that of the fold belt. These data are consistent with an orthogonal convergence model for the WSFTB formation. In turn, the magnetic fabric on the undeformed foreland displays a distinct NNE-SSW orientation that we attribute to the paleocurrent direction. Rock-magnetic analyses reveal that the dominant ferrimagnetic carriers are magnetite and titanomagnetite. The Triassic rocks are characterised by complicated NRM patterns often with overlapping unblocking temperature spectra of particular components. The dominant magnetisation is characterised, however, by a steep inclination of 70-80º. The derived paleomagnetic direction from the WSFTB falls on the Jurassic - recent sector of the apparent polar wander path (APWP) of Baltica after tectonic unfolding. These data imply that at least some of the identified secondary components could have originated before the Eurekan folding event (K/Pg), for example, in Early Cretaceous time which corresponds to the period of rifting events on Barents

  18. Testing the limits in a greenhouse ocean: Did low nitrogen availability limit marine productivity during the end-Triassic mass extinction?

    Science.gov (United States)

    Schoepfer, Shane D.; Algeo, Thomas J.; Ward, Peter D.; Williford, Kenneth H.; Haggart, James W.

    2016-10-01

    The end-Triassic mass extinction has been characterized as a 'greenhouse extinction', related to rapid atmospheric warming and associated changes in ocean circulation and oxygenation. The response of the marine nitrogen cycle to these oceanographic changes, and the extent to which mass extinction intervals represent a deviation in nitrogen cycling from other ice-free 'greenhouse' periods of Earth history, remain poorly understood. The well-studied Kennecott Point section in Haida Gwaii, British Columbia, Canada, was deposited in the open Panthalassic Ocean, and is used here as a test case to better understand changes in the nitrogen cycle and marine productivity from the pre-crisis greenhouse of the Rhaetian to the latest-Rhaetian crisis interval. We estimated marine productivity from the late Norian to the early Hettangian using TOC- and P-based paleoproductivity transform equations, and then compared these estimates to records of sedimentary nitrogen isotopes, redox-sensitive trace elements, and biomarker data. Major negative excursions in δ15N (to ≤ 0 ‰) correspond to periods of depressed marine productivity. During these episodes, the development of a stable pycnocline below the base of the photic zone suppressed vertical mixing and limited N availability in surface waters, leading to low productivity and increased nitrogen fixation, as well as ecological stresses in the photic zone. The subsequent shoaling of euxinic waters into the ocean surface layer was fatal for most Triassic marine fauna, although the introduction of regenerated NH4+ into the photic zone may have allowed phytoplankton productivity to recover. These results indicate that the open-ocean nitrogen cycle was influenced by climatic changes during the latest Triassic, despite having existed in a greenhouse state for over 50 million years previously, and that low N availability limited marine productivity for hundreds of thousands of years during the end-Triassic crisis.

  19. Palaeogeographic evolution of the marine Middle Triassic marine Germanic Basin changements - With emphasis on the carbonate tidal flat and shallow marine habitats of reptiles in Central Pangaea

    Science.gov (United States)

    Diedrich, Cajus G.

    2009-01-01

    , possibly Euparkeria, probably made the Brachychirotherium trackways that have been found across much of Central Europe. Large lepidosaurs such as Tanystrophaeus probably hunted in the tidal ponds and channels, where they locally produced Synaptichnium tracks. Recently discovered tracks made by a basal prosauropod are the world's oldest record of this group of dinosaurs, occurring in beds that have an age of about 243.5 Ma. (Pelsonian substage). This shows that very large prosauropods existed much earlier than was previously believed. These prosauropod tracks, along with tracks of small bipedal dinosaurs found in the Alps and Eastern France, show that by the middle part of the Middle Triassic the radiation and diversification of dinosaurs was already in progress. In the Germanic Basin, aquatic-adapted paraxial swimming sauropterygians are not known to have left tracks, except for occasional subaquatic swimming scratch-mark "trackways" within the coastal tidal flat zone. Marine-adapted aquatic reptiles migrated into the Germanic Basin with increasing frequency in the upper part of the Middle Triassic, when the bathymetry of the Germanic Basin was at its deepest following a strong regression that occurred due to basin uplift in the middle part of the Middle Triassic. These large marine reptiles included Pistosaurus, the ichthyosaurs Cymbospondylus or Mixosaurus, and many placodonts such as Cyamodus, Placodus and Paraplacodus, which fed on macroalgae and seem to have been the Triassic sea cows of their day. The distribution of these reptiles was mainly controlled by tectonics, but eustatic changes in sea level also were important and produced widespread environmental changes across the tidal flats up until their disappearance in the Germanic Basin in the late Middle Triassic. The initial break-up of Pangaea already had started in Middle Triassic time, and this event had begun to drastically change environments all over Central Europe. It is very interesting that dinosaurs

  20. Taphonomy of Early Triassic fish fossils of the Vega-Phroso Siltstone Member of the Sulphur Mountain Formation near Wapiti Lake, British Columbia, Canada

    Directory of Open Access Journals (Sweden)

    Karen Anderson

    2013-10-01

    Full Text Available The taphonomy of fishes living in lacustrine environments has been extensively studied in both the laboratory and the fossil record; the taphonomy of marine fishes, however, is poorly known. Triassic marine fishes with heavy ganoid and cosmoid scales, which provided protection from rapid taphonomic loss, offer a means to examine marine fish taphonomy in the fossil record. Four genera of Early Triassic fishes (the ray-finned actinopterygians Albertonia, Bobasatrania, Boreosomus, and the lobe-finned coelacanth (sarcopterygian, Whiteia from the Wapiti Lake, British Columbia locality of the Lower Triassic Sulphur Mountain Formation were examined in order to gain a better understanding of the taphonomy of fish in marine environments, determine ambient environmental conditions in the region during the Early Triassic, and ascertain the habitat and mode of life of the fish. Results indicate that environmental conditions that contributed to the preservation of the fossil fishes of the current study included deposition in deep, quiet waters, which reduced the odds of disarticulation, colder waters under higher pressure, which slowed decay and limited postmortem floatation, and waters that were anoxic, which discouraged predators and scavengers. In addition, the thickness of the primitive ganoid and cosmoid scales of the fossil fishes also increased their preservation potential. Taphonomic, physiological and environmental indicators suggest that Whiteia, Albertonia, and possibly Bobasatrania lived in deep, cold waters near the oxygen minimum zone, while Boreosomus lived higher in the water column. While the anatomical and physiological characteristics of modern fishes will likely continue to inhibit marine taphonomy studies, examination of ancient fish, particularly those with ganoid or cosmoid scales, may provide future avenues of research to gain a better understanding of marine fish taphonomy and provide a powerful tool to examine ancient fish behavior

  1. A new Triassic shortening-extrusion tectonic model for Central-EasternAsia: Structural, geochronological and paleomagnetic investigations in the Xilamulun Fault (North China)

    Science.gov (United States)

    Zhao, Pan; Faure, Michel; Chen, Yan; Xu, Bei

    2017-04-01

    At the northern margin of the North China Block (NCB), the Xilamulun Fault (XMF) is a key belt to decipher the tectonic evolution of Central-Eastern Asia, as it records the Paleozoic final closure of the Paleo-Asian Ocean, and localizes a Late Triassic intracontinental deformation. In this study, structural analysis, 40Ar-39Ar dating, and paleomagnetic studies were performed to investigate the kinematics of the XMF and to further discuss its Triassic geodynamic significance in the Central-Eastern Asia framework after the Paleozoic Central Asian Orogenic evolution. The structural analyses reveal two phases of ductile deformation. The first one (D1), which displays N-verging and E-W trending folds, is related to the Early Paleozoic collisional event between the NCB and the Songliao-Hunshandake Block (SHB). The second phase (D2) displays a high-angle foliation and a pervasive sub-horizontalE-W stretching lineation with kinematic criteria indicative of dextral strike-slip shearing. The 40Ar-39Ar dating on mylonitic granite places the main shearing event around 227-209 Ma. This D2 shearing is coeval with that of the dextral strike-slip Bayan Obo-Chifeng Fault (BCF) and the Chicheng-Fengning-Longhua Fault to the south, which together constitute a dextral shearing fault system on the northern margin of the NCB during the Late Triassic. The paleomagnetic study performed on the Middle Permian Guangxingyuan pluton, located between the XMF and BCF, documents a local clockwise rotation of this pluton with respect to the NCB and SHB. Our multidisciplinary study suggests anNNW-SSE shortening and strike-slip shearing dominated tectonic setting on the northern margin of the NCB during the Late Triassic. Combining the contemporaneous dextral strike-slip movements of the XMF and BCF in northern China and the sinistral strike-slip movement of East Gobi Fault (EGF) in southeastern Mongolia with the large-scale tectonic framework, a Late Triassic NNW-SSE shortening-eastward extrusion

  2. Discovery of a Triassic magmatic arc source for the Permo-Triassic Karakaya subduction complex, NW Turkey

    Science.gov (United States)

    Ayda Ustaömer, Petek; Ustaömer, Timur; Gerdes, Axel; Robertson, Alastair H. F.; Zulauf, Gernold

    2014-05-01

    The Permo-Triassic Karakaya Complex is well explained by northward subduction of Palaeotethys but until now no corresponding magmatic arc has been identified in the region. With the aim of determining the compositions and ages of the source units, ten sandstone samples were collected from the mappably distinct Ortaoba, Hodul, Kendirli and Orhanlar Units. Zircon grains were extracted from these sandstones and >1300 were dated by the U-Pb method and subsequently analysed for the Lu-Hf isotopic compositions by LA-MC-ICPMS at Goethe University, Frankfurt. The U-Pb-Hf isotope systematics are indicative of two different sediment provenances. The first, represented by the Ortaoba, Hodul and Kendirli Units, is dominated by igneous rocks of Triassic (250-220 Ma), Early Carboniferous-Early Permian (290-340 Ma) and Early to Mid-Devonian (385-400 Ma) ages. The second provenance, represented by the Orhanlar Unit, is indicative of derivation from a peri-Gondwanan terrane. In case of the first provenance, the Devonian and Carboniferous source rocks exibit intermediate eHf(t) values (-11 to -3), consistent with the formation at a continental margin where juvenile mantle-derived magmas mixed with (recycled) old crust having Palaeoproterozoic Hf model ages. In contrast, the Triassic arc magma exhibits higher eHf(t) values (-6 to +6), consistent with the mixing of juvenile mantle-derived melts with (recycled) old crust perhaps somewhat rejuvanated during the Cadomian period. We have therefore identified a Triassic magmatic arc as predicted by the interpretation of the Karakaya Complex as an accretionary complex related to northward subduction (Carboniferous and Devonian granites are already well documented in NW Turkey). Possible explanations for the lack of any outcrop of the source magmatic arc are that it was later subducted or the Karakaya Complex was displaced laterally from its source arc (both post 220 Ma). Strike-slip displacement (driven by oblique subduction?) can also

  3. A new chronology for the late Triassic to early Jurassic. Geologica Ultraiectina (323)

    NARCIS (Netherlands)

    Deenen, M.H.L.

    2010-01-01

    Throughout geological history of life, a small number of mass extinctions have forever changed the path of evolution. The two main mechanisms that account for these dramatic events are asteroid impacts and massive volcanic eruptions of Large Igneous Provinces (LIP’s). The interplay between

  4. Prolonged Permian–Triassic ecological crisis recorded by molluscan dominance in Late Permian offshore assemblages

    OpenAIRE

    Clapham, Matthew E.; Bottjer, David J.

    2007-01-01

    The end-Permian mass extinction was the largest biotic crisis in the history of animal life, eliminating as many as 95% of all species and dramatically altering the ecological structure of marine communities. Although the causes of this pronounced ecosystem shift have been widely debated, the broad consensus based on inferences from global taxonomic diversity patterns suggests that the shift from abundant brachiopods to dominant molluscs was abrupt and largely driven by the catastrophic effec...

  5. Triassic oils and related hydrocarbon kitchens in the Adriatic basin

    Energy Technology Data Exchange (ETDEWEB)

    Novelli, L.; Demaison, G. (AGIP, Milan (Italy))

    1988-08-01

    Without exception, the oils from both the Abruzzi basin and Albanian foredeep are of lower Liassic to Upper Triassic origin. This is demonstrated by biological marker-based correlations between the oils and stratigraphically controlled, carbonate-rich source rocks. The biomarker studies also provided proof to conclude that many of the oils possess low API gravities and high sulfur contents because they are immature rather than biodegraded. Following the geochemical investigations, a computer-aided, basinwise maturation simulation of the hydrocarbon kitchens was carried out, with backstripping in geologic time. The simulations, performed with the Tissot-Espitalie kinetic model, used basin-specific kerogen activation energies obtained by the optimum method. These simulated values were calibrated with observed values in deep wells. Two characteristics diverge from normal petroleum basin situations (e.g., the North Sea basin): sulfur-rich kerogens in the source rocks, featuring relatively low activation energy distributions, and low geothermal gradients in the subsurface. The geographic outlines of simulated Triassic-lower Liassic hydrocarbon kitchens closely coincide with the zones of petroleum occurrence and production in the Adriatic basin. Furthermore, API gravities of the oils are broadly predicted by the mathematical simulations. This methodology has once again shown its ability to rationally high-grade the petroleum-rich sectors of sedimentary basin while identifying those areas where chances of success are extremely low regardless of the presence of structures.

  6. MIDDLE TRIASSIC FORAMINIFERA FROM THE SECEDA CORE (DOLOMITES, NORTHERN ITALY

    Directory of Open Access Journals (Sweden)

    FLORIAN MAURER

    2002-11-01

    Full Text Available The assemblage of foraminifera in turbidite beds in Middle Triassic basinal deposits straddling the Anisian/Ladinian boundary interval was studied in 224 thin sections. The fauna consists mainly of shallow-water inhabitants, associated with calcareous hyaline foraminifera (Lagenina of open marine environment. Due to a well established  biostratigraphy in the studied interval, the first and last appearance of some shallow water, benthic foraminifera can be assigned to the Mid Triassic ammonoid stratigraphy. The species Meandrospira dinarica Kochansky-Devidè & Pantic and Arenovidalina chialingchiagensis Ho are limited to the Reitzi ammonoid zone. The species Variostoma alta Kristan and Hoyenella gr. sinensis both do not superate the Curionii zone in age in the studied succession.  The biostratigraphic most important event occurs at the base of the Gredleri zone,  with the appearance of the family Involutinidae Bütschli, represented by the genera Lamelliconus and Aulotortus. The faunal composition is similar to those of neighbouring paleoprovinces, but generally a lower faunistical diversification compared to foraminiferal assemblages in the Anisian or Carnian is observed.   

  7. Tetrapod tracks in Permo–Triassic eolian beds of southern Brazil (Paraná Basin

    Directory of Open Access Journals (Sweden)

    Heitor Francischini

    2018-05-01

    Full Text Available Tetrapod tracks in eolianites are widespread in the fossil record since the late Paleozoic. Among these ichnofaunas, the ichnogenus Chelichnus is the most representative of the Permian tetrapod ichnological record of eolian deposits of Europe, North America and South America, where the Chelichnus Ichnofacies often occurs. In this contribution, we describe five sets of tracks (one of which is preserved in cross-section, representing the first occurrence of Dicynodontipus and Chelichnus in the “Pirambóia Formation” of southern Brazil. This unit represents a humid desert in southwestern Pangea and its lower and upper contacts lead us to consider its age as Lopingian–Induan. The five sets of tracks studied were compared with several ichnotaxa and body fossils with appendicular elements preserved, allowing us to attribute these tracks to dicynodonts and other indeterminate therapsids. Even though the “Pirambóia Formation” track record is sparse and sub-optimally preserved, it is an important key to better understand the occupation of arid environments by tetrapods across the Permo–Triassic boundary.

  8. The African cynodont Aleodon (Cynodontia, Probainognathia in the Triassic of southern Brazil and its biostratigraphic significance.

    Directory of Open Access Journals (Sweden)

    Agustín G Martinelli

    Full Text Available In this contribution we report the first occurrence of the enigmatic African probainognathian genus Aleodon in the Middle-early Late Triassic of several localities from the state of Rio Grande do Sul in southern Brazil. Aleodon is unusual among early probainognathians in having transversely-expanded postcanine teeth, similar to those of gomphodont cynognathians. This genus was previously known from the Manda Beds of Tanzania and the upper Omingonde Formation of Namibia. The Brazilian record of this genus is based upon multiple specimens representing different ontogenetic stages, including three that were previously referred to the sectorial-toothed probainognathian Chiniquodon theotonicus. We propose a new species of Aleodon (A. cromptoni sp. nov. based on the specimens from Brazil. Additionally, we tentatively refer one specimen from the upper Omingonde Formation of Namibia to this new taxon, strengthening biostratigraphic correlations between these strata. Inclusion of A. cromptoni in a phylogenetic analysis of eucynodonts recovers it as the sister-taxon of A. brachyrhamphus within the family Chiniquodontidae. The discovery of numerous specimens of Aleodon among the supposedly monospecific Chiniquodon samples of Brazil raises concerns about chiniquodontid alpha taxonomy, particularly given the extremely broad geographic distribution of Chiniquodon. The discovery of Brazilian Aleodon and new records of the traversodontid Luangwa supports the hypothesis that at least two subzones can be recognized in the Dinodontosaurus Assemblage Zone.

  9. Evidence for long term deep CO2 confinement below thick Jurassic shales at Montmiral site (SE Basin of France)

    Science.gov (United States)

    Rubert, Y.; Ramboz, C.; Le Nindre, Y. M.; Lerouge, C.; Lescanne, M.

    2009-04-01

    Studies of natural CO2 analogues bring key information on the factors governing the long term (>1My) stability/instability of future anthropogenic CO2 storages. The main objective of this work is to trace the deep-origin CO2 migrations in fractures in the Montmiral CO2 deep natural occurrence (Valence Basin, SE France). The final objective is to document the reservoir feeding and the possible leakages through overlying series. The CO2 reservoir is hosted within a horst controlled by a N-S fault network. From the Triassic to Eocene, the Montmiral area was part of the South-East Basin of France. This period is marked by the Tethysian extension phase (Triassic-Cretaceous) followed by the closure of the basin which culminated during the Pyrenean compressive phase (Eocene). Then, from the late Eocene, the Valence Basin was individualised in particular during the Oligocene E-W rifting affecting the West of Europe. Finally the eastern border of the Basin was overthrusted by Mesozoic formations during the Alpine orogenesis (Miocene). The Montmiral CO2 reservoir is intersected by the currently productive V.Mo.2 well, drilled through Miocene to Triassic sedimentary formations, and reaching the Palaeozoic substratum at a depth of 2771 meters. The CO2 is trapped below a depth of 2340 meters, at the base of sandy, evaporitic and calcareous formations (2340-2771m), Triassic to Sinemurian in age. These units are overlain by a 575 m-thick Domerian to Oxfordian marly sequence which seals the CO2 reservoir. Above these marls, calcareous strata (1792-1095 m), Oxfordian to Cretaceous in age, and sandy clayey formations (1095-0 m), Oligocene and Miocene in age, are deposited. The various stratigraphic levels from the Miocene to the basement were cored over a total length of ~100m. From bottom to top, three lithological units, which exhibit well characterised contrasted diagenetic evolution, record various stages and effects of the CO2 migration: - Lower unit: Palaeozoic metamorphic

  10. Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

    Directory of Open Access Journals (Sweden)

    I.V. Ashchepkov

    2016-07-01

    Kharamai mantle clinopyroxenes represent three geochemical types: (1 harzburgitic with inclined linear REE, HFSE troughs and elevated Th, U; (2 lherzolitic or pyroxenitic with round TRE patterns and decreasing incompatible elements; (3 eclogitic with Eu troughs, Pb peak and high LILE content. Calculated parental melts for garnets with humped REE patterns suggest dissolution of former Cpx and depression means Cpx and garnets extraction. Clinopyroxenes from Ary-Mastakh fields show less inclined REE patterns with HMREE troughs and an increase of incompatible elements. Clinopyroxenes from Kuranakh field show flatter spoon-like REE patterns and peaks in Ba, U, Pb and Sr, similar to those in ophiolitic harzburgites. The PT diagrams for the mantle sections show high temperature gradients in the uppermost SCLM accompanied by an increase of P-Fe#Ol upward and slightly reduced thickness of the mantle keel of the Siberian craton, resulting from the influence of the Permian–Triassic superplume, but with no signs of delamination.

  11. Geochemical Methods of Inference the Thermoregulatory Strategies in Middle Triassic Marine Reptiles - A Pilot Study

    Science.gov (United States)

    Surmik, Dawid; Pelc, Andrzej

    2012-01-01

    The oxygen stable isotopes investigation to elucidate thermoregulatory strategies in Middle Triassic basal sauropterygians is currently ongoing at University of Silesia and University of Maria Curie-Skłodowska. The results of similar studies on Late Mesozoic marine reptiles indicate that some of fully aquatic reptiles like plesiosaurs or ichthyosaurs could be warm-blooded animals. Our investigation is an important part of the aim of the research project "The Marine and Terrestrial reptiles in the Middle Triassic environmental background of Southern Poland" to solve the thermoregulation issue in basal marine reptiles and show how, and when did homoiothermy evolve in Sauropterygia.. Homeothermy and gigantothermy were important physiological adaptations which allowed sauropterygian ancestors to leave the shores and conquer the open seas and oceans. Badania nad paleofizjologią kopalnych kręgowców ostatnimi laty stały się niezwykle modne. Polegają one na kompilacji danych uzyskanych wieloma komplementarnymi metodami z zakresu fizjologii (badania współczesnych form, zgodnie z zasadą aktualizmu) i geochemii izotopowej. Szczególnie interesujące stały się kwestie gospodarki termicznej u gadów kopalnych, które silnie dyskutowane są w kręgach badaczy dinozaurów (Reid, 1997; Ruben i in., 1996). Badania na izotopach stabilnych tlenu szkliwa zębowego przeprowadzone na obligatoryjnie morskich gadach okresu jurajskiego i kredowego (Bernard i in., 2010; zob. także Motani, 2010) wskazują, że ichtiozaury i plezjozaury późniejszego mezozoiku mogły być zwierzętami stałocieplnymi. Brak obecnie jednoznacznych danych dotyczących gospodarki termicznej bazalnych przedstawicieli gadów morskich z triasu, choć przyjmuje się, że te zamieszkujące nadbrzeżne i marginalne strefy mórz zwierzęta były gadami zmiennocieplnymi (pojkilotermicznymi), podobnie jak współczesny legwan morski, czy też smok z Komodo. Czy przejście z pojkilo- do homojotermii by

  12. MIDDLE TRIASSIC PLATFORM AND BASIN EVOLUTION OF THE SOUTHERN BAKONY MOUNTAINS (TRANSDANUBIAN RANGE, HUNGARY

    Directory of Open Access Journals (Sweden)

    TAMÁS BUDAI

    2006-11-01

    Full Text Available Middle Triassic history of the Southern Bakony Mts. is outlined on the base of horizontal and vertical facies changes of the formations. During the Pelsonian (Balatonicus Chron the evolution of the basins and platforms was determined basically by synsedimentary tectonics. The Felsõörs basin of the Balaton Highland opened due to the block-faulting of the Bithynian carbonate ramp (Megyehegy Dolomite. Above the drowning blocks „halfgraben” basins were formed (Felsõörs Formation, while isolated platforms developed on the uplifted ones in the middle part of the Balaton Highland and on the Veszprém plateau (Tagyon Formation. Due to the relative sea-level fall in the early Illyrian, the platforms became subaerially exposed and karstified. As a consequence of the late Illyrian tectonic subsidence (manifested by neptunian dykes the central platform of the Balaton Highland has been drowned (Camunum Subchron. On the contrary, the Anisian platform of the Veszprém plateau was totally flooded only during the latest Illyrian (Reitzi Subchron due to eustatic sea-level rise. It was followed by a short highstand period (Secedensis Chron, characterised by the first progradation of the Budaörs platform on the Veszprém plateau and highstand shedding in the basins and on the submarine high (Vászoly Limestone in the centre of the Balaton Highland basin. Due to the following rapid sea-level rise, carbonate sedimentation continued in eupelagic basin from the Fassanian (Buchenstein Formation. At the beginning of the late Longobardian highstand period (Regoledanus Chron the Budaörs platform intensively prograded from the Veszprém plateau to the southwest, causing highstand shedding in the Balaton Highland basin (Füred Limestone. 

  13. Thick melanoma in Tuscany.

    Science.gov (United States)

    Chiarugi, Alessandra; Nardini, Paolo; Borgognoni, Lorenzo; Brandani, Paola; Gerlini, Gianni; Rubegni, Pietro; Lamberti, Arianna; Salvini, Camilla; Lo Scocco, Giovanni; Cecchi, Roberto; Sirna, Riccardo; Lorenzi, Stefano; Gattai, Riccardo; Battistini, Silvio; Crocetti, Emanuele

    2017-03-14

    The epidemiologic trends of cutaneous melanoma are similar in several countries with a Western-type life style, where there is a progressive increasing incidence and a low but not decreasing mor- tality, or somewhere an increase too, especially in the older age groups. Also in Tuscany there is a steady rise in incidence with prevalence of in situ and invasive thin melanomas, with also an increase of thick melanomas. It is necessary to reduce the frequency of thick melanomas to reduce specific mortality. The objective of the current survey has been to compare, in the Tuscany population, by a case- case study, thin and thick melanoma cases, trying to find out those personal and tumour characteristics which may help to customize preventive interventions. RESULTS The results confirmed the age and the lower edu- cation level are associated with a later detection. The habit to perform skin self-examination is resulted protec- tive forward thick melanoma and also the diagnosis by a doctor. The elements emerging from the survey allow to hypothesize a group of subjects resulting at higher risk for a late diagnosis, aged over 50 and carrier of a fewer constitutional and environmental risk factors: few total and few atypical nevi, and lower sun exposure and burning. It is assumable that a part of people did not be reached from messages of prevention because does not recognize oneself in the categories of people at risk for skin cancers described in educational cam- paigns. If we want to obtain better results on diagnosis of skin melanoma we have to think a new strategy. At least to think over the educational messages discriminating people more at risk of incidence of melanoma from people more at risk to die from melanoma, and to renewed active involvement of the Gen- eral Practitioners .

  14. Recovery vs. Restructuring: Establishing Ecologic Patterns in Early and Middle Triassic Paleocommunities (Invited)

    Science.gov (United States)

    Fraiser, M.; Dineen, A.; Sheehan, P.

    2013-12-01

    Published data has been interpreted as indicating that marine ecological devastation following the end-Permian mass extinction was protracted and may have lasted 5 million years into the Middle Triassic (Anisian). However, a review of previous literature shows that understanding of biotic recovery is typically based on only a few components of the ecosystem, such as on taxonomic diversity, a single genus/phylum, or facies. Typically, paleocommunities are considered fully recovered when dominance and diversity are regained and normal ecosystem functioning has resumed. However, in addition to the biodiversity crash at the end of the Permian, taxonomic and ecologic structure also changed,with the extinction marking the faunal shift from brachiopod-rich Paleozoic Evolutionary Fauna (EF) to the mollusc-rich Modern EF. This suggests that the extreme reorganizational nature of the Triassic does not adhere to the standard definition of recovery, which is a return to previous conditions. Thus, we propose the term 'restructuring' to describe this interval, as Early and Middle Triassic communities might not exhibit the typical characteristics of a 'normal' Permian one. To more fully characterize Triassic ecologic restructuring, paleoecologists should take into account functional diversity and redundancy. We quantified functional richness and regularity in four different paleocommunities from classic Permian and Triassic sections. Functional richness was low in paleocommunities after the end-Permian mass extinction, but increased to high levels by the Middle Triassic. In contrast, functional regularity was low in the Middle Permian, but high in all the Triassic paleocommunities. The change from low to high functional regularity/redundancy at the P/T boundary may be a factor of the highly stressful Triassic environmental conditions (i.e. anoxia, hypercapnia), as high regularity in a community can boost survival in harsh environments. Parameters such as these will more

  15. Chronology of Fluctuating Sea Levels since the Triassic

    Science.gov (United States)

    Haq, Bilal U.; Hardenbol, Jan; Vail, Peter R.

    1987-03-01

    Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic frame-work. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.

  16. The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania.

    Science.gov (United States)

    Nesbitt, Sterling J; Barrett, Paul M; Werning, Sarah; Sidor, Christian A; Charig, Alan J

    2013-02-23

    The rise of dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister-taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria.

  17. Under the armor: X-ray computed tomographic reconstruction of the internal skeleton of Coahomasuchus chathamensis (Archosauria: Aetosauria) from the Upper Triassic of North Carolina, USA, and a phylogenetic analysis of Aetosauria.

    Science.gov (United States)

    Hoffman, Devin K; Heckert, Andrew B; Zanno, Lindsay E

    2018-01-01

    Aetosauria is a clade of heavily armored, quadrupedal omnivorous to herbivorous archosaurs known from the Late Triassic across what was the supercontinent of Pangea. Their abundance in many deposits relative to the paucity of other Triassic herbivores indicates that they were key components of Late Triassic ecosystems. However, their evolutionary relationships remain contentious due, in large part, to their extensive dermal armor, which often obstructs observation of internal skeletal anatomy and limits access to potentially informative characters. In an attempt to address this problem we reanalyzed the holotype of a recently described species of Coahomasuchus , C. chathamensis , from the Sanford sub-basin of North Carolina using computed tomography (CT). CT scans of the holotype specimen clarify preservation of the skeleton, revealing several articulated vertebrae and ribs, an isolated vertebra, left ulna, left scapula, and the right humerus, though none of the material resulted in updated phylogenetic scorings. Reexamination of aetosaur materials from the holotype locality also indicates that several isolated osteoderms and elements of the appendicular skeleton are newly referable. Based on these results, we update the Coahomasuchus chathamensis hypodigm and conduct a revised phylogenetic analysis with improved character scorings for Coahomasuchus and several other aetosaurs. Our study recovers Coahomasuchus in a polytomy with Aetosaurus and the Typothoracinae, in contrast with a recent analysis that recovered Coahomasuchus as a wild-card taxon.

  18. Moessbauer effect study of the diagenesis on the southern Brazilian Triassic paleoherpetofauna

    International Nuclear Information System (INIS)

    Da Costa, M.I. Jr.; Holz, M.; Schultz, C.L.

    1994-01-01

    Moessbauer spectroscopy is applied to identify the iron contents of bony elements of southern Brazilian Triassic reptile remains, and the question of the paragenetic mineral assemblage is discussed. (orig.)

  19. Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary.

    Science.gov (United States)

    Thorne, Philippa M; Ruta, Marcello; Benton, Michael J

    2011-05-17

    Ichthyosaurs were important marine predators in the Early Jurassic, and an abundant and diverse component of Mesozoic marine ecosystems. Despite their ecological importance, however, the Early Jurassic species represent a reduced remnant of their former significance in the Triassic. Ichthyosaurs passed through an evolutionary bottleneck at, or close to, the Triassic-Jurassic boundary, which reduced their diversity to as few as three or four lineages. Diversity bounced back to some extent in the aftermath of the end-Triassic mass extinction, but disparity remained at less than one-tenth of pre-extinction levels, and never recovered. The group remained at low diversity and disparity for its final 100 Myr. The end-Triassic mass extinction had a previously unsuspected profound effect in resetting the evolution of apex marine predators of the Mesozoic.

  20. Stratigraphic distribution, taphonomy and paleoenvironments of Spinicaudata in the Triassic and Jurassic of the Paraná Basin

    Science.gov (United States)

    Jenisch, Alan Gregory; Lehn, Ilana; Gallego, Oscar Florencio; Monferran, Mateo Daniel; Horodyski, Rodrigo Scalise; Faccini, Ubiratan Ferrucio

    2017-12-01

    exoskeletons is likely a function of parameters, e.g., the transport duration, the distance from life position, and the magnitude of events causing their final burial. Within the observed species, the recognition of Eustheria minuta in the stratigraphic level of the Passo das Tropas creek corroborates an age for these deposits between the late Middle Triassic and early Upper Triassic. The presence of a new form, likely related to the family Fushunograptidae in sediments from the Caturrita Formation, suggests a Jurassic age for these deposits.

  1. The first Triassic dipteran (Insecta) from South America, with review of Hennigmatidae.

    Science.gov (United States)

    Lara, María Belén; Lukashevich, Elena D

    2013-01-01

    The first Triassic dipteran from South America is described based on an isolated wing from the lower Upper Triassic deposits of Argentina (Mendoza Province, Potrerillos Formation, Quebrada del Durazno locality). Trihennigma zavattierii gen. et sp. nov. is a member of the Mesozoic family Hennigmatidae, previously recorded only from Eurasia. A key for the genera and species of Hennigmatidae is provided and systematic position of the taxa is discussed.

  2. The Triassic-Liassic volcanic sequence and rift evolution in the Saharan Atlas basins (Algeria). Eastward vanishing of the Central Atlantic magmatic province

    International Nuclear Information System (INIS)

    Meddah, A.; Bertrand, H.; Seddiki, A.; Tabeliouna, M.

    2017-01-01

    We investigate the Triassic-Liassic sequence in ten diapirs from the Saharan Atlas (Algeria). Based on detailed mapping, two episodes are identified. The first one consists of a volcano-sedimentary sequence in which three volcanic units were identified (lower, intermediate and upper units). They are interlayered and sometimes imbricated with siliciclastic to evaporitic levels which record syn-sedimentary tectonics. This sequence was deposited in a lagoonal-continental environment and is assigned to the Triassic magmatic rifting stage. The second episode, lacking lava flows (post magmatic rifting stage), consists of carbonate levels deposited in a lagoonal to marine environment during the Rhaetian-Hettangian. The volcanic units consist of several thin basaltic flows, each 0.5 to 1m thick, with a total thickness of 10–15m. The basalts are low-Ti continental tholeiites, displaying enrichment in large ion lithophile elements and light rare earth elements [(La/Yb)n= 2.5-6] with a negative Nb anomaly. Upwards decrease of light-rare-earth-elements enrichment (e.g. La/Yb) is modelled through increasing melting rate of a spinel-bearing lherzolite source from the lower (6–10wt.%) to the upper (15–20wt.%) unit. The lava flows from the Saharan Atlas share the same geochemical characteristics and evolution as those from the Moroccan Atlas assigned to the Central Atlantic magmatic province. They represent the easternmost witness of this large igneous province so far known.

  3. The Triassic-Liassic volcanic sequence and rift evolution in the Saharan Atlas basins (Algeria). Eastward vanishing of the Central Atlantic magmatic province

    Energy Technology Data Exchange (ETDEWEB)

    Meddah, A.; Bertrand, H.; Seddiki, A.; Tabeliouna, M.

    2017-11-01

    We investigate the Triassic-Liassic sequence in ten diapirs from the Saharan Atlas (Algeria). Based on detailed mapping, two episodes are identified. The first one consists of a volcano-sedimentary sequence in which three volcanic units were identified (lower, intermediate and upper units). They are interlayered and sometimes imbricated with siliciclastic to evaporitic levels which record syn-sedimentary tectonics. This sequence was deposited in a lagoonal-continental environment and is assigned to the Triassic magmatic rifting stage. The second episode, lacking lava flows (post magmatic rifting stage), consists of carbonate levels deposited in a lagoonal to marine environment during the Rhaetian-Hettangian. The volcanic units consist of several thin basaltic flows, each 0.5 to 1m thick, with a total thickness of 10–15m. The basalts are low-Ti continental tholeiites, displaying enrichment in large ion lithophile elements and light rare earth elements [(La/Yb)n= 2.5-6] with a negative Nb anomaly. Upwards decrease of light-rare-earth-elements enrichment (e.g. La/Yb) is modelled through increasing melting rate of a spinel-bearing lherzolite source from the lower (6–10wt.%) to the upper (15–20wt.%) unit. The lava flows from the Saharan Atlas share the same geochemical characteristics and evolution as those from the Moroccan Atlas assigned to the Central Atlantic magmatic province. They represent the easternmost witness of this large igneous province so far known.

  4. Permo-Triassic arc-like granitoids along the northern Lancangjiang zone, eastern Tibet: Age, geochemistry, Sr-Nd-Hf isotopes, and tectonic implications

    Science.gov (United States)

    Wang, Xinyu; Wang, Shifeng; Wang, Chao; Tang, Wenkun

    2018-05-01

    Large volumes of Permo-Triassic granitoids are exposed along the Northern Lancangjiang zone, eastern Tibet, and these rocks provide insights into the tectonic evolution of the Paleo-Tethys Ocean. We conducted detailed geological fieldwork and geochemical analysis of the Xiaochangdu and Kagong plutons that crop out along the Northern Lancangjiang magmatic belt. Zircon U-Pb data constrain the emplacement of the Xiaochangdu quartz diotites to between 263 and 257 Ma, and the Kagong granites and diorites to between 234 and 232 Ma. The Xiaochangdu quartz diorites are enriched in light rare earth (LREE) and large ion lithophile elements (LILE), depleted in high field strength elements (HFSE), have low (87Sr/86Sr)i ratios, and near-positive εNd(t) (-0.26 to 1.58) and εHf(t) (0.68-8.83) values, similar to typical subduction- related mantle-derived arc magmas. They are also characterized by high Al2O3 concentrations and low Nb/U (3.48-7.59) and Ce/Pb (3.22-4.86) ratios, indicating that their mantle source was modified by subducted pelagic sediments; Coeval granites and diorites from the Kagong pluton exhibit low A/CNK values, high LREE/HREE (heavy rare earth element) ratios, enrichment in LILE, and depletion in HFSE, also characteristic of typical arc magmas. Their variable SiO2 contents (57%- 75%), (87Sr/86Sr)i ratios, and εNd(t) (1.02-4.49) and εHf(t) (2.52-6.93) values, and relatively high zircon saturation temperatures (721-827 °C), suggest underplating of mantle-derived mafic melts beneath the lower crust. Their magmatic evolution can be explained using a MASH model. In combination with regional geological studies, our geochemical and geochronological results suggest that the late Permian Xiaochangdu and Late Triassic Kagong arc-like granitoids represent a section of a Permo-Triassic magmatic arc that was associated with the eastward subduction of the Paleo-Tethys oceanic slab beneath the Northern Qiangtang-Changdu terrane. Combined with other geological evidence

  5. Molecular Evidence for Radical Changes in Ocean Chemistry Across the Permian Triassic Boundary at Meishan in South China

    Science.gov (United States)

    Love, G. D.; Cao, C.; Jin, Y.; Summons, R. E.

    2004-12-01

    Samples from outcrop and from a new core drilled through the Permian Triassic Boundary at the type section at Meishan have been examined for biomarker and isotopic evidence of biotic and associated environmental change. Late Permian sediments from Meishan Beds 22-27 are characterized by indicators of anoxia including low Pr/Ph ratios and abundant aryl isoprenoids and isoreneieratane derived from the precursor carotenoid isorenieratene. The latter compounds are biomarkers for green sulfur bacteria (Chlorobiaceae) and are considered reliable indicators of euxinic water columns where sulfide extends to the photic zone. The peak of Chlorobiaceae biomarker abundance coincides with a rapid and synchronous drop in the ƒO13C and ƒO15N values of kerogen. On passing up into the Early Triassic, the biomarker signal for Chlorobiaceae wanes and is almost absent by Bed 30 where it is replaced by one for cyanobacteria including abundant hopanes and 2-methylhopanes and accompanying methyl and dimethyl alkanes. A very high value for the hopane/sterane ratio from Beds 30-38 indicates continuing dominant cyanobacterial productivity and only minor inputs from an algal plankton. The prevalence of aryl isoprenoids in P-Tr sediments at the Meishan section of South China is also recorded in a recently cored borehole, Hovea-3, of the Perth Basin, Western Australia. This suggests similar paleoenvironmental conditions prevailed across the Tethys Ocean during and immediately after the P-Tr Boundary. In particular, the presence of biomarkers for Chlorobiaceae at two separate locations indicates that water column euxinia was pervasive during the extinction event and suggests that sulfide may have been a key toxic agent.

  6. A basal sauropodomorph (Dinosauria: Saurischia from the Ischigualasto Formation (Triassic, Carnian and the early evolution of Sauropodomorpha.

    Directory of Open Access Journals (Sweden)

    Ricardo N Martinez

    Full Text Available BACKGROUND: The earliest dinosaurs are from the early Late Triassic (Carnian of South America. By the Carnian the main clades Saurischia and Ornithischia were already established, and the presence of the most primitive known sauropodomorph Saturnalia suggests also that Saurischia had already diverged into Theropoda and Sauropodomorpha. Knowledge of Carnian sauropodomorphs has been restricted to this single species. METHODOLOGY/PRINCIPAL FINDINGS: We describe a new small sauropodomorph dinosaur from the Ischigualsto Formation (Carnian in northwest Argentina, Panphagia protos gen. et sp. nov., on the basis of a partial skeleton. The genus and species are characterized by an anteroposteriorly elongated fossa on the base of the anteroventral process of the nasal; wide lateral flange on the quadrate with a large foramen; deep groove on the lateral surface of the lower jaw surrounded by prominent dorsal and ventral ridges; bifurcated posteroventral process of the dentary; long retroarticular process transversally wider than the articular area for the quadrate; oval scars on the lateral surface of the posterior border of the centra of cervical vertebrae; distinct prominences on the neural arc of the anterior cervical vertebra; distal end of the scapular blade nearly three times wider than the neck; scapular blade with an expanded posterodistal corner; and medial lamina of brevis fossa twice as wide as the iliac spine. CONCLUSIONS/SIGNIFICANCE: We regard Panphagia as the most basal sauropodomorph, which shares the following apomorphies with Saturnalia and more derived sauropodomorphs: basally constricted crowns; lanceolate crowns; teeth of the anterior quarter of the dentary higher than the others; and short posterolateral flange of distal tibia. The presence of Panphagia at the base of the early Carnian Ischigualasto Formation suggests an earlier origin of Sauropodomorpha during the Middle Triassic.

  7. The terminal Permian in European Russia: Vyaznikovian Horizon, Nedubrovo Member, and Permian-Triassic boundary

    Science.gov (United States)

    Lozovsky, V. R.; Balabanov, Yu. P.; Karasev, E. V.; Novikov, I. V.; Ponomarenko, A. G.; Yaroshenko, O. P.

    2016-07-01

    The comprehensive analysis of the data obtained on terrestrial vertebrata, ostracods, entomologic fauna, megaflora, and microflora in deposits of the Vyaznikovian Horizon and Nedubrovo Member, as well as the paleomagnetic data measured in enclosing rocks, confirms heterogeneity of these deposits. Accordingly, it is necessary to distinguish these two stratons in the terminal Permian of the East European Platform. The combined sequence of Triassic-Permian boundary deposits in the Moscow Syneclise, which is considered to be the most complete sequence in the East European Platform, is as follows (from bottom upward): Vyatkian deposits; Vyaznikovian Horizon, including Sokovka and Zhukovo members; Nedubrovo Member (Upper Permian); Astashikha and Ryabi members of the Vokhmian Horizon (Lower Triassic). None of the sequences of Permian-Triassic boundary deposits known in the area of study characterizes this sequence in full volume. In the north, the Triassic deposits are underlain by the Nedubrovo Member; in the south (the Klyazma River basin), the sections are underlain by the Vyaznikovian Horizon. The Permian-Triassic boundary adopted in the General Stratigraphic Scale of Russia for continental deposits of the East European platform (the lower boundary of the Astashikha Member) is more ancient than the one adopted in the International Stratigraphic Chart. The same geological situation is observed in the German Basin and other localities where Triassic continental deposits are developed. The ways of solving this problem are discussed in this article.

  8. Salt lake Laguna de Fuente de Piedra (S-Spain) as Late Quaternary palaeoenvironmental archive

    Science.gov (United States)

    Höbig, Nicole; Melles, Martin; Reicherter, Klaus

    2014-05-01

    This study deals with Late Quaternary palaeoenvironmental variability in Iberia reconstructed from terrestrial archives. In southern Iberia, endorheic basins of the Betic Cordilleras are relatively common and contain salt or fresh-water lakes due to subsurface dissolution of Triassic evaporites. Such precipitation or ground-water fed lakes (called Lagunas in Spanish) are vulnerable to changes in hydrology, climate or anthropogenic modifications. The largest Spanish salt lake, Laguna de Fuente de Piedra (Antequera region, S-Spain), has been investigated and serves as a palaeoenvironmental archive for the Late Pleistocene to Holocene time interval. Several sediment cores taken during drilling campaigns in 2012 and 2013 have revealed sedimentary sequences (up to 14 m length) along the shoreline. A multi-proxy study, including sedimentology, geochemistry and physical properties (magnetic susceptibility) has been performed on the cores. The sedimentary history is highly variable: several decimetre thick silty variegated clay deposits, laminated evaporites, and even few-centimetre thick massive gypsum crystals (i.e., selenites). XRF analysis was focussed on valuable palaeoclimatic proxies (e.g., S, Zr, Ti, and element ratios) to identify the composition and provenance of the sediments and to delineate palaeoenvironmental conditions. First age control has been realized by AMS-radiocarbon dating. The records start with approximately 2-3 m Holocene deposits and reach back to the middle of MIS 3 (GS-3). The sequences contain changes in sedimentation rates as well as colour changes, which can be summarized as brownish-beige deposits at the top and more greenish-grey deposits below as well as highly variegated lamination and selenites below ca. 6 m depth. The Younger Dryas, Bølling/Allerød, and the so-called Mystery Interval/Last Glacial Maximum have presumably been identified in the sediment cores and aligned to other climate records. In general, the cores of the Laguna de

  9. Early Jurassic diversification of pycnodontiform fishes (Actinopterygii, Neopterygii) after the end-Triassic extinction event: evidence from a new genus and species, Grimmenodon aureum.

    Science.gov (United States)

    Stumpf, Sebastian; Ansorge, Jörg; Pfaff, Cathrin; Kriwet, Jürgen

    2017-07-04

    A new genus and species of pycnodontiform fishes, Grimmenodon aureum , from marginal marine, marine-brackish lower Toarcian ( Harpoceras exaratum ammonite subzone) clay deposits of Grimmen in northeastern Germany is described. The single specimen represents a diagnostic left prearticular dentition characterized by unique tooth arrangement and ornamentation patterns. Grimmenodon aureum , gen. et sp. nov., is the second unambiguously identified pycnodontiform species from the Early Jurassic, in addition to Eomesodon liassicus from the early Lower Jurassic of western Europe. We also report an indeterminate pycnodontiform tooth crown from the upper Pliensbachian ( Pleuroceras apyrenum ammonite subzone) of the same site. The material expands the Early Jurassic range of pycnodontiforms significantly northwards and confirms their presence before and immediately following the onset of the Toarcian Oceanic Anoxic Event (T-OAE) in the marginal marine ecosystems south of the Fennoscandian Shield. Moreover, the new records indicate that the Early Jurassic diversity of pycnodontiform fishes was greater than previously assumed and probably equaled that of the Late Triassic. Therefore, it is hypothesized that the Triassic-Jurassic mass extinction event did not affect pycnodontiform fishes significantly. Micro-computed tomography was used to study the internal anatomy of the prearticular of Grimmenodon aureum , gen. et sp. nov. Our results show that no replacement teeth were formed within the tooth-bearing bone but rather were added posteriorly to functional teeth. http://zoobank.org/urn:lsid:zoobank.org:pub:A56BDE9C-40C4-4CFA-9C2E-F5FA35A66F2 Citation for this article: Stumpf, S., J. Ansorge, C. Pfaff, and J. Kriwet. 2017. Early Jurassic diversification of pycnodontiform fishes (Actinopterygii, Neopterygii) after the end-Triassic extinction event: Evidence from a new genus and species, Grimmenodon aureum . Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1344679.

  10. Duration of and decoupling between carbon isotope excursions during the end-Triassic mass extinction and Central Atlantic Magmatic Province emplacement

    Science.gov (United States)

    Yager, Joyce A.; West, A. Joshua; Corsetti, Frank A.; Berelson, William M.; Rollins, Nick E.; Rosas, Silvia; Bottjer, David J.

    2017-09-01

    Changes in δ13Ccarb and δ13Corg from marine strata occur globally in association with the end-Triassic mass extinction and the emplacement of the Central Atlantic Magmatic Province (CAMP) during the break up of Pangea. As is typical in deep time, the timing and duration of these isotopic excursions has remained elusive, hampering attempts to link carbon cycle perturbations to specific processes. Here, we report δ13Ccarb and δ13Corg from Late Triassic and Early Jurassic strata near Levanto, Peru, where intercalated dated ash beds permit temporal calibration of the carbon isotope record. Both δ13Ccarb and δ13Corg exhibit a broad positive excursion through the latest Triassic into the earliest Jurassic. The first order positive excursion in δ13Corg is interrupted by a negative shift noted in many sections around the world coincident with the extinction horizon. Our data indicate that the negative excursion lasts 85 ± 25 kyrs, longer than inferred by previous studies based on cyclostratigraphy. A 260 ± 80 kyr positive δ13Corg shift follows, during which the first Jurassic ammonites appear. The overall excursion culminates in a return to pre-perturbation carbon isotopic values over the next 1090 ± 70 kyrs. Via chronologic, isotopic, and biostratigraphic correlation to other successions, we find that δ13Ccarb and δ13Corg return to pre-perturbation values as CAMP volcanism ceases and in association with the recovery of pelagic and benthic biota. However, the initiation of the carbon isotope excursion at Levanto predates the well-dated CAMP sills from North America, indicating that CAMP may have started earlier than thought based on these exposures, or that the onset of carbon cycle perturbations was not related to CAMP.

  11. Discovery of Early Triassic conodonts in western Gangdisê and the establishment of the Tangnale Formation

    Institute of Scientific and Technical Information of China (English)

    ZHENG; YouYe; XU; RongKe; WANG; ChengYuan; MA; GuoTao; LAI; XuLong; YE; DeJin; CAO; Liang; LIANG; JiWei

    2007-01-01

    Most geologists believe that there are no Early and Middle Triassic strata in the W. Gandisê stratigraphic subregion, but the present authors have found Early Triassic conodonts for the first time in the Shiquanhe area, including five conodonts genera (Form genera): Pachycladina, Neohindeodella, Cornudina, Hadrodontina and Hibbardella sp. etc. Then we affirm that Early Triassic deposits exist in the Gandisê stratigraphic subregion, and establish the Tangnale Formation. The conclusion is new important complementary basal data for Triassic stratigraphy division of Gangdisê, reconstructing palaogeography and studying Gangdisê from Paleozoic to Mesozoic island-arc evolution and transition.

  12. U–Pb geochronology and geochemistry of late Palaeozoic volcanism in Sardinia (southern Variscides

    Directory of Open Access Journals (Sweden)

    L. Gaggero

    2017-11-01

    Full Text Available The latest Carboniferous to lower Permian volcanism of the southern Variscides in Sardinia developed in a regional continental transpressive and subsequent transtensile tectonic regime. Volcanism produced a wide range of intermediate–silicic magmas including medium- to high-K calc-alkaline andesites, dacites, and rhyolites. A thick late Palaeozoic succession is well exposed in the four most representative Sardinian continental basins (Nurra, Perdasdefogu, Escalaplano, and Seui–Seulo, and contains substantial stratigraphic, geochemical, and geochronological evidence of the area's complex geological evolution from the latest Carboniferous to the beginning of the Triassic. Based on major and trace element data and LA-ICP-MS U–Pb zircon dating, it is possible to reconstruct the timing of post-Variscan volcanism. This volcanism records active tectonism between the latest Carboniferous and Permian, and post-dates the unroofing and erosion of nappes in this segment of the southern Variscides. In particular, igneous zircon grains from calc-alkaline silicic volcanic rocks yielded ages between 299 ± 1 and 288 ± 3 Ma, thereby constraining the development of continental strike-slip faulting from south (Escalaplano Basin to north (Nurra Basin. Notably, andesites emplaced in medium-grade metamorphic basement (Mt. Cobingius, Ogliastra show a cluster of older ages at 332 ± 12 Ma. Despite the large uncertainty, this age constrains the onset of igneous activity in the mid-crust. These new radiometric ages constitute: (1 a consistent dataset for different volcanic events; (2 a precise chronostratigraphic constraint which fits well with the biostratigraphic data and (3 insights into the plate reorganization between Laurussia and Gondwana during the late Palaeozoic evolution of the Variscan chain.

  13. Triassic marine reptiles gave birth to live young.

    Science.gov (United States)

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

    2004-11-18

    Sauropterygians form the largest and most diverse group of ancient marine reptiles that lived throughout nearly the entire Mesozoic era (from 250 to 65 million years ago). Although thousands of specimens of this group have been collected around the world since the description of the first plesiosaur in 1821 (ref. 3), no direct evidence has been found to determine whether any sauropterygians came on shore to lay eggs (oviparity) like sea turtles, or gave birth in the water to live young (viviparity) as ichthyosaurs and mosasauroids (marine lizards) did. Viviparity has been proposed for plesiosaur, pachypleurosaur and nothosaur sauropterygians, but until now no concrete evidence has been advanced. Here we report two gravid specimens of Keichousaurus hui Young from the Middle Triassic of China. These exquisitely preserved specimens not only provide the first unequivocal evidence of reproductive mode and sexual dimorphism in sauropterygians, but also indicate that viviparity could have been expedited by the evolution of a movable pelvis in pachypleurosaurs. By extension, this has implications for the reproductive pattern of other sauropterygians and Mesozoic marine reptiles that possessed a movable pelvis.

  14. Ocean redox change at the Permian-Triassic mass extinction

    DEFF Research Database (Denmark)

    Ruhl, Micha; Bjerrum, Christian J.; Canfield, Donald Eugene

    2013-01-01

    Earth’s history is marked by multiple events of ocean anoxia developing along continental margins and po¬tentially into the open ocean realm. These events of¬ten coincide with the emplacement of large igneous provinces (LIPs) on continents, major perturbations of global geochemical cycles and mar...... these oceanographic changes to similar observations for the Triassic-Jurassic mass extinction and discuss environmental forcing, poten¬tially inherent to major volcanic events and leading to global environmental change and extinction...... ocean redox change over the largest mass extinction event in Earth history, at the Permian-Tri¬assic boundary (at ~252 Ma). This event is marked by a major perturbation in the global exogenic carbon cycle (and associated major negative carbon isotope excursion (CIE)), likely initiated by carbon...... (anoxic but not euxinic) coinciding with the main extinction event. Molybdenum enrichments, often indicative for freely available sulfide in the water-column, only occur dur¬ing the second phase of euxinia. This pattern of ocean redox-change in Svalbard direct¬ly reflects similar trends in Greenland...

  15. The characters of superficial exposure belt on the Yangtze platform margin and the genesis of micro-stalactite in cracks during late ladinian in Guizhou

    International Nuclear Information System (INIS)

    Xiao Jiafei; Wei Jiayong; Hu Ruizhong

    2003-01-01

    The superficial exposure belt experienced a longer time (about l Ma years), and formed a larger thickness (lt is usually between 100-150 m, the largest thickness is about 180 m) during late ladinian of Middle Triassic. There are very clear exposure features-the vadose pisolite, fenestral (birdeye) structure, middle-big type teepee structure, karst breccia. This is evidently a calcareous weathering crust under damp-semidamp climate condition at swell region. There are the micro-stalactite with three types: the drapestone, the dripstone, and the flowstone in cracks of the exposure belt. Their 18 O isotope composition is usually about -10‰ (PDB), 13 C isotope composition is generally between 1.5-2‰ (PDB). The 18 O isotope composition indicates that micro-stalactites are formed by fresh-water, but 13 C has slightly higher value than that of the freshwater sedimentary. This is probably the cause that meteoric water dissolved pro-formed limestone (bedrock) and obtained 13 C. Three shapes of the micro-stalactite above mentioned are typical fresh-water sedimentary in features of petrology. Thus the micro-stalactites are fresh water deposits proved by the characters of 18 O and 13 C isotope composition and petrology of micro-stalactite. (authors)

  16. Late Budgets

    DEFF Research Database (Denmark)

    Andersen, Asger Lau; Lassen, David Dreyer; Nielsen, Lasse Holbøll Westh

    are negative rather than positive; and when there is divided government. We test the hypotheses of the model using a unique data set of late budgets for US state governments, based on dates of budget approval collected from news reports and a survey of state budget o¢ cers for the period 1988...

  17. The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes

    Science.gov (United States)

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Litvak, Vanesa D.; Poma, Stella; Alonso, Ricardo N.; Hinton, Richard; EIMF

    2016-10-01

    The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29-31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ U-Pb dating of magmatic zircon, combined with Ar-Ar dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data. A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous ( 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle. The Late Oligocene ( 26 Ma) to Early Miocene ( 17 Ma), and Late Miocene ( 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the Permian-Triassic (P

  18. The Park Volcanics Group : field relations of an igneous suite emplaced in the Triassic-Jurassic Murihiku Terrane, South Island, New Zealand

    International Nuclear Information System (INIS)

    Coombs, D.S.; Cook, N.D.J.; Campbell, J.D.

    1992-01-01

    Park Volcanics Group is proposed for igneous rocks, either shallow intrusive or extrusive, emplaced in the Murihiku Terrane during Triassic-Jurassic times. The term replaces Park Intrusives of Mutch, some members of which are shown to be extrusive rather than intrusive. Formation status within the group is given to Gowan Andesite and Pinney Volcanics (new names) in western Southland, Glenham Porphyry in eastern Southland, and Barnicoat Andesite (new) in the Richmond area, Nelson. Gowan Andesite is a porphyritic feldspar two-pyroxene andesite with a glassy or microcrystalline groundmass. A suite of low-grade metavolcanic rocks which forms the main mass of Malakoff Hill and which has formerly been included in the 'Park Intrusives' is here excluded and ascribed to the Takitimu Group; representative chemical data are given. Glenham Porphyry is typically a porphyritic feldspar two-pyroxene andesite texturally similar to the Gowan Andesite but with significant geochemical differences. Two volumetrically minor members are recognised, Habukinini Trachydacite and Kenilworth Rhyolite. In the north of its outcrop area, Glenham Porphyry is emplaced on or into Late Triassic terrestrial beds; in the middle it overlies Kaihikuan (Middle Triassic) and is overlain by Otapirian (latest Triassic) marine beds; and in the southeast it is directly overlain by Ururoan (late Early to early Middle Jurassic) conglomerates and marine sandstones. Pinney Volcanics are restricted to a very few, probably one, massive conglomeratic horizon in the Oretian Stage. The commonest rock type is a two-pyroxene trachydacite, modified by very-low-grade burial metamorphism. Auto-brecciation is characteristic and rock types change over short distances. Hornblende-rich variants occur as well as more felsic varieties including rhyolite ignimbrite. These may have been erupted onto a bouldery floodplain or shallow-marine surface, but alternatively may have been mass-emplaced by debris avalanche resulting from

  19. A hyper-robust sauropodomorph dinosaur ilium from the Upper Triassic-Lower Jurassic Elliot Formation of South Africa: Implications for the functional diversity of basal Sauropodomorpha

    Science.gov (United States)

    McPhee, Blair W.; Choiniere, Jonah N.

    2016-11-01

    It has generally been held that the locomotory habits of sauropodomorph dinosaurs moved in a relatively linear evolutionary progression from bipedal through "semi-bipedal" to the fully quadrupedal gait of Sauropoda. However, there is now a growing appreciation of the range of locomotory strategies practiced amongst contemporaneous taxa of the latest Triassic and earliest Jurassic. Here we present on the anatomy of a hyper-robust basal sauropodomorph ilium from the Late Triassic-Early Jurassic Elliot Formation of South Africa. This element, in addition to highlighting the unexpected range of bauplan diversity throughout basal Sauropodomorpha, also has implications for our understanding of the relevance of "robusticity" to sauropodomorph evolution beyond generalized limb scaling relationships. Possibly representing a unique form of hindlimb stabilization during phases of bipedal locomotion, the autapomorphic morphology of this newly rediscovered ilium provides additional insight into the myriad ways in which basal Sauropodomorpha managed the inherited behavioural and biomechanical challenges of increasing body-size, hyper-herbivory, and a forelimb primarily adapted for use in a bipedal context.

  20. Evolution of the Early Triassic marine depositional environment in the Croatian Dinarides

    Science.gov (United States)

    Aljinović, Dunja; Smirčić, Duje; Horacek, Micha; Richoz, Sylvain; Krystyn, Leopold; Kolar-Jurkovšek, Tea; Jurkovšek, Bogdan

    2014-05-01

    In the central part of the Dinarides in Croatia, the Early Triassic depositional sequence was investigated by means of litho-, bio- and chemostratigraphy at locality Plavno (ca. 1.000m thick). Conodont and δ13C-isotope analysis were a powerfull tool to determine stage and substage boundaries. The succession begins with the second conodont zone of the Griesbachian Isarcicella staeschei and I. isarcica with low δ13C-values and a steadily increase towards the Griesbachian-Dienerian boundary. Around that boundary a minor, short, negative excursion occurs. In the Dienerian the δ13C-values increase with a steepening of the slope towards the Dienerian-Smithian boundary. Around that boundary a maximum of +5o in shallow water carbonate occurs followed by a steep and continuous drop to low, often negative values in the Smithian. Just before the Smithian-Spathian boundary a steep rise to a second maximum is documented. It is followed by decline in the Spathian and a gentle increase to a rounded peak at the Spathian-Anisian boundary. In lithological sense Plavno succession has threefold division: 1) carbonates representing the oldest Early Triassic strata (early Griesbachian); 2) dominantly red clastics (shales, siltstones and sandstones) with intercalation of oncoid/ooid or bioclast rich grainstones (uppermost Griesbachian, Dienerian and Smithian) and 3) dominantly grey carbonaceous lime mudstones, marls and calcisiltites with ammonoids representing Spathian strata. In the oldest strata (Griesbachian) in macrocrystalline subhedral dolomites rare microspheres and foraminifers Earlandia and Cornuspira point to the stressful conditions related to the end Permian mass extinction. In the uppermost Griesbachian and Dienerian strata, within dominantly clastic deposition, rare coarse oncoliths with typical microbial cortices occur. Their presence fits to the interpretation of biotical-induced precipitation related to PTB extinction and can suggest still stressful condition. The

  1. The Triassic metabasalts of Dudin Krš, near Kosovska Mitrovica, Serbia

    Directory of Open Access Journals (Sweden)

    Memović Emin

    2003-01-01

    Full Text Available This paper presents the geochemical characteristics of the metabasalts of Dudin Krš, near Kosovska Mitrovica. The Dudin Krš is the easternmost occurrence of Middle Triassic rift-related volcanic rocks in the Dinarides. Generally, these rocks show similarities to other Triassic volcanic rocks of the Dinarides. They are high-magnesian, ol and ne-normative basalts, with low Zr/Nb and medium/low Ti/Zr and Ti/Y ratios. They exhibit transitional geochemical characteristics, between E-MORB and subalkaline basalts of continental rift zones. Their presence and geochemical affinity is evidence of rifting processes along the continental slope of the Adria block during Middle Triassic.

  2. Absence of suction feeding ichthyosaurs and its implications for triassic mesopelagic paleoecology.

    Directory of Open Access Journals (Sweden)

    Ryosuke Motani

    Full Text Available Mesozoic marine reptiles and modern marine mammals are often considered ecological analogs, but the extent of their similarity is largely unknown. Particularly important is the presence/absence of deep-diving suction feeders among Mesozoic marine reptiles because this would indicate the establishment of mesopelagic cephalopod and fish communities in the Mesozoic. A recent study suggested that diverse suction feeders, resembling the extant beaked whales, evolved among ichthyosaurs in the Triassic. However, this hypothesis has not been tested quantitatively. We examined four osteological features of jawed vertebrates that are closely linked to the mechanism of suction feeding, namely hyoid corpus ossification/calcification, hyobranchial apparatus robustness, mandibular bluntness, and mandibular pressure concentration index. Measurements were taken from 18 species of Triassic and Early Jurassic ichthyosaurs, including the presumed suction feeders. Statistical comparisons with extant sharks and marine mammals of known diets suggest that ichthyosaurian hyobranchial bones are significantly more slender than in suction-feeding sharks or cetaceans but similar to those of ram-feeding sharks. Most importantly, an ossified hyoid corpus to which hyoid retractor muscles attach is unknown in all but one ichthyosaur, whereas a strong integration of the ossified corpus and cornua of the hyobranchial apparatus has been identified in the literature as an important feature of suction feeders. Also, ichthyosaurian mandibles do not narrow rapidly to allow high suction pressure concentration within the oral cavity, unlike in beaked whales or sperm whales. In conclusion, it is most likely that Triassic and Early Jurassic ichthyosaurs were 'ram-feeders', without any beaked-whale-like suction feeder among them. When combined with the inferred inability for dim-light vision in relevant Triassic ichthyosaurs, the fossil record of ichthyosaurs does not suggest the

  3. Absence of suction feeding ichthyosaurs and its implications for triassic mesopelagic paleoecology.

    Science.gov (United States)

    Motani, Ryosuke; Ji, Cheng; Tomita, Taketeru; Kelley, Neil; Maxwell, Erin; Jiang, Da-yong; Sander, Paul Martin

    2013-01-01

    Mesozoic marine reptiles and modern marine mammals are often considered ecological analogs, but the extent of their similarity is largely unknown. Particularly important is the presence/absence of deep-diving suction feeders among Mesozoic marine reptiles because this would indicate the establishment of mesopelagic cephalopod and fish communities in the Mesozoic. A recent study suggested that diverse suction feeders, resembling the extant beaked whales, evolved among ichthyosaurs in the Triassic. However, this hypothesis has not been tested quantitatively. We examined four osteological features of jawed vertebrates that are closely linked to the mechanism of suction feeding, namely hyoid corpus ossification/calcification, hyobranchial apparatus robustness, mandibular bluntness, and mandibular pressure concentration index. Measurements were taken from 18 species of Triassic and Early Jurassic ichthyosaurs, including the presumed suction feeders. Statistical comparisons with extant sharks and marine mammals of known diets suggest that ichthyosaurian hyobranchial bones are significantly more slender than in suction-feeding sharks or cetaceans but similar to those of ram-feeding sharks. Most importantly, an ossified hyoid corpus to which hyoid retractor muscles attach is unknown in all but one ichthyosaur, whereas a strong integration of the ossified corpus and cornua of the hyobranchial apparatus has been identified in the literature as an important feature of suction feeders. Also, ichthyosaurian mandibles do not narrow rapidly to allow high suction pressure concentration within the oral cavity, unlike in beaked whales or sperm whales. In conclusion, it is most likely that Triassic and Early Jurassic ichthyosaurs were 'ram-feeders', without any beaked-whale-like suction feeder among them. When combined with the inferred inability for dim-light vision in relevant Triassic ichthyosaurs, the fossil record of ichthyosaurs does not suggest the establishment of modern

  4. Late Raphael

    OpenAIRE

    Henry, Tom F. K.; Joannides, Paul; González Mozo, Ana; Martín, Bruno

    2012-01-01

    Exhibition catalogue (co-authored with P. Joannides) in English, Spanish and French by the Museo del Prado and the Musée du Louvre, 2012. English edition, publisher: Museo Nacional del Prado (ISBN 978-84-8480-237-2). 382 pages, of which 300 were co-authored with P. Joannides. This publication was the catalogue of the major exhibtion of Raphael's late work which was at the Prado and the Louvre in 2012-13. The exhibition was seen by more than 650,000 visitors, and was widely reviewed in the int...

  5. Mesozoic monazite in Neoproterozoic metasediments. Evidence for low-grade metamorphism of Sinian sediments during Triassic continental collision, Liaodong Peninsula, NE China

    International Nuclear Information System (INIS)

    Wan Yusheng; Song Tianrui; Liu Dunyi; Yang Tiannan; Yin Xiaoyan; Zhang Qiaoda; Chen Zhenyu

    2007-01-01

    Sericite phyllite from the Sinian Shisanlitai Formation, Dalian area, Liaodong Peninsula, NE China, contains an assemblage of newly-formed lower-greenschist facies minerals (sericite, chlorite, Fe minerals and Ti minerals) plus aggregates of fine-grained monazite. The texture of the monazite, its mineral inclusions, and its close association with Fe oxide minerals show that it is not detrital or diagenetic, but a product of the low-grade metamorphism. SHRIMP U-Th-Pb dating of the monazite at 217±15 Ma shows that the metamorphism, and associated regional deformation and fluid flow, occurred in the Late Triassic, coeval with the waning stages of the Dabie-Sulu orogeny. The Dabie-Sulu tectonothermal event has produced both deformation and metamorphism in rocks of the eastern North China Block at least up to ∼200 km north of the main continent-continent collision zone. (author)

  6. Provenance of the Lower Triassic Bunter Sandstone Formation: implications for distribution and architecture of aeolian vs. fluvial reservoirs in the North German Basin

    DEFF Research Database (Denmark)

    Olivarius, Mette; Weibel, Rikke; Friis, Henrik

    2017-01-01

    Zircon U–Pb geochronometry, heavy mineral analyses and conventional seismic reflection data were used to interpret the provenance of the Lower Triassic Bunter Sandstone Formation. The succession was sampled in five Danish wells in the northern part of the North German Basin. The results show...... Shield did not supply much sediment to the basin as opposed to what was previously believed. Sediment from the Variscan belt was transported by wind activity across the North German Basin when it was dried out during deposition of the aeolian part of the Volpriehausen Member (lower Bunter Sandstone......). Fluvial sand was supplied from the Ringkøbing-Fyn High to the basin during precipitation events which occurred most frequently when the Solling Member was deposited (upper Bunter Sandstone). Late Neoproterozoic to Carboniferous zircon ages predominate in the Volpriehausen Member where the dominant age...

  7. A brief exegesis of End Triassic Extinction issues

    Science.gov (United States)

    Whiteside, J. H.; Grice, K.; Fox, C.; Kent, D. V.; Olsen, P. E.; Irmis, R. B.

    2017-12-01

    Recent reports of environmental proxy records through the end-Triassic extinction (ETE), in some cases coupled with high-resolution geochronologic data, provide new insights into cause and effect. For example, the emplacement of vast volumes of basalt in the Central Atlantic Magmatic Province (CAMP) are temporally associated with carbon isotopic excursions (CIEs), indications of widespread oceanic euxinia, distinct regional and perhaps very abrupt global sea level change, massive changes in atmospheric CO2, and the proliferation of "disaster" species, both on land and ocean. In the least, these indicate major disruptions in how the Earth works. However some striking and critical issues remain unresolved at a very basic level. Most important are the uncertainties in the stratigraphic relationships of marine extinctions to the various environmental proxy sections, particularly the GSSP for the base Hettangian in Austria, and the UK sections (notably St. Audrie's Bay). Here, the sequence of sporomorph and marine "invertebrate" turnover occurs in different order relative to the proxy record and lithostratigraphy. Thus the sequence of environmental events are, at present, of uncertain relationship to the extinction. Second, it is unclear what processes the various CIEs reflect in different environments; the canonical initial isotopic excursion in the UK, demonstrably correlatable over a huge area, was recorded in a lake in a restricted basin, unlike the isotopic data from surrounding marine strata. Could some CIEs in non-marine basins be diagenetic in nature, caused by the contact effects of overlying basalts? Finally, how does the clear and dramatic tropical non-marine record of the ETE, precisely located relative to the CAMP, relate to the marine record of the ETE, particularly at higher latitudes, where continental biotic turnover is not nearly as dramatic? Do these records correlate in a sufficiently tight temporal interval such that causation can be inferred? These

  8. An integrated perspective on the Permian-Triassic "Great Dying"

    Science.gov (United States)

    Algeo, T. J.

    2017-12-01

    The 252-Ma end-Permian mass extinction (EPME), marked by the loss of 90% of marine invertebrate species, was the largest biocrisis in Earth history. Intensive study of this "Great Dying" has led to major insights and a broad consensus regarding many aspects of this event. The ultimate trigger is regarded as eruption of the Siberian Traps Large Igneous Province (STLIP), which released large quantities of greenhouse gases (CO2 and CH4) and sulfate aerosols, triggering a catastrophic global warming of 10°C and acidification of both land surfaces and the surface ocean. On land, a massive die-off of vegetation led to a transient episode of rapid soil erosion and a longer-term increase in weathering rates linked to elevated temperatures. In the ocean, widespread anoxia developed concurrently with the EPME, triggered by ocean-surface warming that reduced dissolved oxygen solubility in seawater and that intensified vertical stratification. Expanded anoxia led to massive burial of organic matter and reduced sulfur, although the evidence for this is indirect (C, U and S isotopes); few organic-rich deposits of Early Triassic age have been found, suggesting that organic sedimentation occurred mainly on continental slopes or in the deep ocean. Other aspects of the end-Permian crisis remain under debate. For example, there is no consensus regarding changes in marine productivity levels in the aftermath of the EPME, which would have been stimulated by enhanced subaerial weathering but depressed by reduced overturning circulation-the evidence to date may favor localized positive and negative changes in productivity. Also under scrutiny is evidence for volcanic eruptions and environmental perturbations during the 100 kyr prior to the EPME, which are likely to have occurred but remain poorly dated and quantified. The greatest uncertainty, however, may surround the nature of the proximate kill mechanism(s) during the EPME. Many hypotheses have been advanced including mechanisms

  9. Lipid Biomarker Records Across the Permian-Triassic Boundary from Kap Stosch, Greenland

    Science.gov (United States)

    Hays, L. E.; Love, G. D.; Foster, C. B.; Grice, K.; Summons, R. E.

    2006-12-01

    The end-Permian extinction was the most severe in the past 500 million years of the Earth's history and evidence that an oceanic anoxic event (OAE) occurred contemporaneously has been presented previously [1,2]. OAEs have, therefore, been proposed as responsible for the mass mortality, and if the anoxic ocean was also euxinic, the release of hydrogen sulfide during upwelling and/or transgression provides an extinction agent in the ocean as well as on land. Chlorobiaceae, as indicators of photic zone euxinia (PZE), utilize hydrogen sulfide as an electron donor for anoxygenic photosynthesis. The detection of isorenieratane and a series of short-chain monoaromatic aryl isoprenoids, biomarkers for Chlorobiaceae, in sediments indicates the presence of hydrogen sulfide in the photic zone of the water column during sediment deposition. The Kap Stosch area in Eastern Greenland was identified as a Permian-Triassic boundary (PTB) outcrop of homogeneous shale, silty shale, and siltstone facies [3]. Another late Permian section in Eastern Greenland, the Ravnefjeld Formation, has framboidal pyrites indicative of sulfidic deep water [4]. A sample suite from the Kap Stosch region was studied using standard organic geochemistry methods including stable isotopic analyses of organic carbon, Rock-Eval pyrolysis, and biomarker hydrocarbon analysis. Aryl isoprenoids, including isorenieratane, were present in all samples studied and the concentrations were observed to fluctuate in tandem with TOC, similar to other Mesozoic OAEs. The molecular ratios of pristane/phytane and hopanes/steranes as well as the 2-methyl-hopane index (2-MHI) fluctuated dramatically through this section as they do at the type section at Meishan and in the Perth Basin [5]. The 2-MHI shows an inverse pattern to the total aryl isoprenoids, perhaps indicative of instability in the form of primary productivity in the water column during euxinic episodes. This can result in nitrogen limitation and a competitive

  10. The Latemar: A Middle Triassic polygonal fault-block platform controlled by synsedimentary tectonics

    Science.gov (United States)

    Preto, Nereo; Franceschi, Marco; Gattolin, Giovanni; Massironi, Matteo; Riva, Alberto; Gramigna, Pierparide; Bertoldi, Luca; Nardon, Sergio

    2011-03-01

    Detailed field mapping of a Middle Triassic carbonate buildup, the Latemar in the western Dolomites, northern Italy, has been carried out. The Latemar is an isolated carbonate buildup that nucleates on a fault-bounded structural high (horst) cut into the underlying late Anisian carbonate bank of the Contrin Fm. This study demonstrates that extensional synsedimentary tectonics is the main factor controlling its geometry and provides an age for this tectonic phase. In an early phase, slopes were mostly composed of well bedded, clinostratified grainstones and rudstones. In a later stage, the deposition of grainstones was accompanied by the emplacement of clinostratified megabreccias. The upper portion of slopes is a microbial boundstone with abundant Tubiphytes and patches or lenses of grainstone. Boundstones may occasionally expand into the platform interior and downward to the base of the slope. The depositional profile was that of a mounded platform. The buildup is dissected by a dense framework of high angle fractures and faults, and by magmatic and sedimentary dikes, exhibiting two principal directions trending NNW-SSE and ENE-WSW. Faults trending WNW-ESE were also observed. Magmatic dikes are related to the emplacement of the nearby Predazzo intrusion and are thus upper Ladinian. Kinematic indicators of strike-slip activity were observed on fault planes trending NNE-SSW and NNW-SSE, that can be attributed to Cenozoic Alpine tectonics. Faults, magmatic dikes and sedimentary dikes show systematic cross-cutting relationships, with strike-slip faults cutting magmatic dikes, and magmatic dikes cutting sedimentary (neptunian) dikes. ENE-WSW and WNW-ESE faults are cut by all other structures, and record the oldest tectonic activity in the region. Structural analysis attributes this tectonic phase to an extensional stress field, with a direction of maximum extension oriented ca. N-S. Several lines of evidence, including sealed faults and growth wedge geometries allow us

  11. Permian-Triassic boundary microbialites at Zuodeng Section, Guangxi Province, South China: Geobiology and palaeoceanographic implications

    Science.gov (United States)

    Fang, Yuheng; Chen, Zhong-Qiang; Kershaw, Stephen; Yang, Hao; Luo, Mao

    2017-05-01

    A previously unknown microbialite bed in the Permian-Triassic (P-Tr) boundary beds of Zuodeng section, Tiandong County, Guangxi, South China comprises a thin (5 cm maximum thickness) stromatolite in the lower part and the remaining 6 m is thrombolite. The Zuodeng microbialite has a pronounced irregular contact between the latest Permian bioclastic limestone and microbialite, as in other sites in the region. The stromatolite comprises low-relief columnar and broad domal geometries, containing faint laminations. The thrombolite displays an irregular mixture of sparitic dark coloured altered microbial fabric and light coloured interstitial sediment in polished blocks. Abundant microproblematic calcimicrobe structures identified here as Gakhumella are preserved in dark coloured laminated areas of the stromatolite and sparitic areas in thrombolites (i.e. the calcimicrobial part, not the interstitial sediment) and are orientated perpendicular to stromatolitic laminae. Each Gakhumella individual has densely arranged segments, which form a column- to fan-shaped structure. Single segments are arch-shaped and form a thin chamber between segments. Gakhumella individuals in the stromatolite and thrombolite are slightly different from each other, but are readily distinguished from the Gakhumella- and Renalcis-like fossils reported from other P-Tr boundary microbialites in having a smaller size, unbranching columns and densely arranged, arch-shaped segments. Renalcids usually possess a larger body size and branching, lobate outlines. Filament sheath aggregates are also observed in the stromatolite and they are all orientated in one direction. Both Gakhumella and filament sheath aggregates may be photosynthetic algae, which may have played an important role in constructing the Zuodeng microbialites. Other calcimicrobes in the Zuodeng microbialite are spheroids, of which a total of five morphological types are recognized from both stromatolite and thrombolite: (1) sparry calcite

  12. Back-arc with frontal-arc component origin of Triassic Karmutsen basalt, British Columbia, Canada

    Science.gov (United States)

    Barker, F.; Sutherland, Brown A.; Budahn, J.R.; Plafker, G.

    1989-01-01

    The largely basaltic, ???4.5-6.2-km-thick, Middle to Upper Triassic Karmutsen Formation is a prominent part of the Wrangellian sequence. Twelve analyses of major and minor elements of representative samples of pillowed and massive basalt flows and sills from Queen Charlotte and Vancouver Islands are ferrotholeiites that show a range of 10.2-3.8% MgO (as normalized, H2O- and CO2-free) and related increases in TiO2 (1.0-2.5%), Zr (43-147 ppm) and Nb (5-16 ppm). Other elemental abundances are not related simply to MgO: distinct groupings are evident in Al2O3, Na2O and Cr, but considerable scatter is present in FeO* (FeO + 0.9Fe2O3) and CaO. Some of the variation is attributed to alteration during low-rank metamorphism or by seawater - including variation of Ba, Rb, Sr and Cu, but high-field-strength elements (Sc, Ti, Y, Zr and Nb) as well as Cr, Ni, Cu and rare-earth elements (REE's) were relatively immobile. REE's show chondrite-normalized patterns ranging from light-REE depleted to moderately light-REE enriched. On eleven discriminant plots these analyses fall largely into or across fields of within-plate basalt (WIP), normal or enriched mid-ocean-ridge tholeiite (MORB) and island-arc tholeiite (IAT). Karmutsen basalts are chemically identical to the stratigraphically equivalent Nikolai Greenstone of southern Alaska and Yukon Territory. These data and the fact that the Karmutsen rests on Sicker Group island-arc rocks of Paleozoic age suggest to us that: 1. (1) the basal arc, after minor carbonate-shale deposition, underwent near-axial back-arc rifting (as, e.g., the Mariana arc rifted at different times); 2. (2) the Karmutsen basalts were erupted along this rift or basin as "arc-rift" tholeiitite; and 3. (3) after subsequent deposition of carbonates and other rocks, and Jurassic magmatism, a large fragment of this basalt-sediment-covered island arc was accreted to North America as Wrangellia. The major- and minor-elemental abundances of Karmutsen basalt is modeled

  13. Triassic tholeiitic dolerites («ophites» of the El Grado diapir (Pyrenees, Huesca, Spain: emplacement and composition

    Directory of Open Access Journals (Sweden)

    Lago San José, M.

    2000-04-01

    Full Text Available Mesozoic dolerites in the south Pyrenean sector of El Grado (Huesca, Spain preserve emplacement structures (fluidity structures at the top and load structures at the base developed during their intrusion into unconsolidated marly-evaporitic Triassic sediments (Keuper facies. By analogy with other dolerites in the south Pyrenean domain, their emplacement age is equivalent to the uppermost Keuper facies terms, but prior to the final Triassic-early Liassic carbonated sediments. Radiometric ages (187-197±7 Ma show that the emplacement occurred during the lower Liassic. The petralogical differentiation from the chilled margin facies to the central facies, and also to the late pegmatitoids, is consistent with that obtained from major elements, trace elements and REE. Their tholeiitic affinity, as defined by their geochemical composition, is equivalent to that of similar racks in the Pyrenean domain. However, the rocks analyzed here, which are located at the external sector of this domain, display a greater petralogical and geochemical differentiation as compared to similar rocks in the central sectors of the Pyrenean domain.Las doleritas mesozoicas del sector surpirenaico de El Grado (Huesca conservan estructuras de emplazamiento (con desarrollo del movimiento de lava fluida al techo y de carga en su base desarrolladas al instruir en los sedimentos margo-evaporíticos en facies Keuper, todavía inconsolidados. Por similitud con otras doleritas del dominio surpirenaico, la edad del emplazamiento es equivalente a la de los términos superiores de la facies Keuper y previa a la sedimentación carbonatada del Trías terminal-Lías inferior. Las determinaciones de edades radiométricas (187-197±7 Ma indican que el emplazamiento debió tener lugar durante el Lías inferior. La diferenciación petralógica, desde la facies del borde enfriado a la central y, también, al posterior diferenciado pegmatoide concuerda con la obtenida con elementos mayores

  14. Stratigraphy and tectonics of Permo-Triassic basins in the Netherlands and surrounding areas

    NARCIS (Netherlands)

    Geluk, M.C.

    2005-01-01

    This thesis addresses different aspects of the geological development during the Permian and Triassic (300 to 200 Ma) of the Netherlands and surrounding areas. The study area encompasses the Southern Permian Basin (SPB), a large intracratonic basin stretched out from the United Kingdom in the west

  15. The continental Permian-Triassic boundary in the Netherlands: Implications for the geomagnetic polarity time scale

    NARCIS (Netherlands)

    Szurlies, M.; Geluk, M.C.; Krijgsman, W.; Kürschner, W.M.

    2012-01-01

    In Central and NW Europe, the transition from the Permian to the Triassic (i.e., the Zechstein–Buntsandstein boundary interval) is developed mainly in red bed facies. This continental sedimentary succession is marked by relatively high sedimentation rates providing a high temporal resolution

  16. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa

    Directory of Open Access Journals (Sweden)

    Alexander W.A. Kellner

    2015-06-01

    Full Text Available Eudimorphodon ranzii was the first Triassic pterosaur to be described and several specimens have been referred to this taxon mainly based on the presence of multicuspid teeth. Since this dental feature has been observed in several other pterosaurs, the revision of some specimens assigned to Eudimorphodon shows that they represent new taxa as follows: Arcticodactyluscromptonellus (comb. nov., Austriadraco dallavecchiai (gen. et sp. nov. and Bergamodactyluswildi (gen. et sp. nov.. A preliminary analysis of pterosaur ontogeny resulted in the recognition of six distinct ontogenetic stages (OS1-6. According to this classification, the holotype of Arcticodactyluscromptonellus has reached OS2, and although being ontogenetically much younger than others, the conspicuous anatomical differences lead to its exclusion from Eudimorphodon. The holotypes of Austriadraco dallavecchiai,Bergamodactyluswildi and Carniadactylus rosenfeldi have reached at least OS5, which demonstrates that the anatomical differences among them cannot be explained by ontogeny. Moreover, Bergamodactyluswildi reaches about 60% of the maximized wingspan of Carniadactylus rosenfeldi and further concurs that these specimens collected in distinct Triassic Islands of Europe are not conspecific. The present study increases the diversity of Triassic flying reptiles and further pushes the origins of this clade back to at least the Middle Triassic.

  17. Uranium isotope evidence for an expansion of marine anoxia during the end-Triassic extinction

    NARCIS (Netherlands)

    Jost, Adam B.; Bachan, Aviv; van de Schootbrugge, Bas; Lau, Kimberly V.; Weaver, Karrie L.; Maher, Kate; Payne, Jonathan L.

    The end-Triassic extinction coincided with an increase in marine black shale deposition and biomarkers for photic zone euxinia, suggesting that anoxia played a role in suppressing marine biodiversity. However, global changes in ocean anoxia are difficult to quantify using proxies for local anoxia.

  18. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks.

    Science.gov (United States)

    Fröbisch, Nadia B; Fröbisch, Jörg; Sander, P Martin; Schmitz, Lars; Rieppel, Olivier

    2013-01-22

    The biotic recovery from Earth's most severe extinction event at the Permian-Triassic boundary largely reestablished the preextinction structure of marine trophic networks, with marine reptiles assuming the predator roles. However, the highest trophic level of today's marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic and early Mesozoic. Here we report a top-tier tetrapod predator, a very large (>8.6 m) ichthyosaur from the early Middle Triassic (244 Ma), of Nevada. This ichthyosaur had a massive skull and large labiolingually flattened teeth with two cutting edges indicative of a macropredatory feeding style. Its presence documents the rapid evolution of modern marine ecosystems in the Triassic where the same level of complexity as observed in today's marine ecosystems is reached within 8 My after the Permian-Triassic mass extinction and within 4 My of the time reptiles first invaded the sea. This find also indicates that the biotic recovery in the marine realm may have occurred faster compared with terrestrial ecosystems, where the first apex predators may not have evolved before the Carnian.

  19. Palaeoclimatic trends deduced from the hydrochemistry of a Triassic sandstone aquifer, U.K

    International Nuclear Information System (INIS)

    Bath, A.H.; Edmunds, W.M.; Andrews, J.N.

    1978-01-01

    A detailed geochemical study (elemental, isotopic and dissolved inert gases) of unconfined and confined sections of the Triassic non-marine sandstone aquifer in Eastern England has been undertaken. Aspects of the recharge history of this aquifer over the past 40 000 years are revealed by examination of the data. (orig./HK) [de

  20. Characteristics of the Triassic Source Rocks of the Aitutu Formation in the (West Timor Basin

    Directory of Open Access Journals (Sweden)

    Asep Kurnia Permana

    2014-12-01

    Full Text Available DOI:10.17014/ijog.v1i3.192The Triassic rocks of the (West Timor Basin have been identified that was mainly deposited in the  marine environment. The fine grained clastics and carbonate  rocks of this Triassic marine  facies are considered to be the most promising source rocks potential in this basin. In this paper we present geochemical and petrographic data from outcrop samples of the Triassic carbonate Aitutu Formation, due to emphasized the organic maturation, kerogen type of the organic matter and the origin of the organic matter.  A representative of selected sample were subjected to the Rock-Eval Pyrolisis, vitrinite reflectance and thermal alteration index, bitumen extraction, were analyzed on the GC-MS. The samples were collected from marine deposit of the Triassic Sequence. The TOC values of the analyzed sample range between rich and rich organic richness (0.51% - 9.16%, wt.%, TOC, which consists mainly of type II and III kerogen and the organic matter consider to be predominantly oil/gas prone and gas prone potential. The thermal maturity assessed from Tmax, TAI, and vitrinite reflectance shows an immature to early peak mature stage of the organic matter. The GC-MS analyses of the biomarkers indicate mainly the organic matter derived from mixed source rocks facies containing alga debris and higher plant terrestrial origin.

  1. A tale of two extinctions : converging end-Permian and end-Triassic scenarios

    NARCIS (Netherlands)

    van de Schootbrugge, Bas; Wignall, Paul B.

    The end-Permian (c. 252 Ma) and end-Triassic (c. 201 Ma) mass-extinction events are commonly linked to the emplacement of the large igneous provinces of the Siberia Traps and Central Atlantic Magmatic Province, respectively. Accordingly, scenarios for both extinctions are increasingly convergent and

  2. Triassic Sequence Geological Development of the Arctic with focus on Svalbard and the Barents Shelf

    Energy Technology Data Exchange (ETDEWEB)

    Moerk, Atle

    1998-12-31

    Triassic rocks are of great interest for exploration in Arctic areas as they have proved to include both good hydrocarbon source rocks and potential hydrogen reservoir rocks. In this thesis, the stratigraphy and sedimentology of the Arctic Triassic successions are studied within a sequence stratigraphical framework. Inter-regional comparisons throughout the Arctic are based on comparisons of transgressive-regressive sequences. Improved dating of the studied sequences, and the recognition and correlation of sequence boundaries of second and third order, facilitate interpretation of facies distribution and the geological development both within and between the studied areas. Main emphasis is given to the Triassic succession of Svalbard and the Barents Shelf, which through this study is integrated within a circum-Arctic sequence stratigraphical framework. Good correspondence of the Triassic sequence boundaries between the different Arctic areas indicate that they are mainly controlled by eustacy, while decreasing correspondence of the sequence boundaries in the Jurassic and Cretaceous periods indicate that local and large scale tectonism becomes progressively more dominant in the circum-Arctic Realm through the Mesozoic Era. These hypotheses are further discussed. 701 refs., 110 figs., 12 tabs.

  3. Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic.

    Science.gov (United States)

    Brusatte, Stephen L; Niedźwiedzki, Grzegorz; Butler, Richard J

    2011-04-07

    The ascent of dinosaurs in the Triassic is an exemplary evolutionary radiation, but the earliest phase of dinosaur history remains poorly understood. Body fossils of close dinosaur relatives are rare, but indicate that the dinosaur stem lineage (Dinosauromorpha) originated by the latest Anisian (ca 242-244 Ma). Here, we report footprints from the Early-Middle Triassic of Poland, stratigraphically well constrained and identified using a conservative synapomorphy-based approach, which shifts the origin of the dinosaur stem lineage back to the Early Olenekian (ca 249-251 Ma), approximately 5-9 Myr earlier than indicated by body fossils, earlier than demonstrated by previous footprint records, and just a few million years after the Permian/Triassic mass extinction (252.3 Ma). Dinosauromorph tracks are rare in all Polish assemblages, suggesting that these animals were minor faunal components. The oldest tracks are quadrupedal, a morphology uncommon among the earliest dinosauromorph body fossils, but bipedality and moderately large body size had arisen by the Early Anisian (ca 246 Ma). Integrating trace fossils and body fossils demonstrates that the rise of dinosaurs was a drawn-out affair, perhaps initiated during recovery from the Permo-Triassic extinction.

  4. Anachronistic facies from a drowned Lower Triassic carbonate platform: Lower member of the Alwa Formation (Ba'id Exotic), Oman Mountains

    Science.gov (United States)

    Woods, Adam D.; Baud, Aymon

    2008-09-01

    The lower member of the Alwa Formation (Lower Olenekian), found within the Ba'id Exotic in the Oman Mountains (Sultanate of Oman), consists of ammonoid-bearing, pelagic limestones that were deposited on an isolated, drowned carbonate platform on the Neotethyan Gondwana margin. The strata contain a variety of unusual carbonate textures and features, including thrombolites, Frutexites-bearing microbialites that contain synsedimentary cements, matrix-free breccias surrounded by isopachous calcite cement, and fissures and cavities filled with large botryoidal cements. Thrombolites are found throughout the study interval, and occur as 0.5-1.0 m thick lenses or beds that contain laterally laterally-linked stromatactis cavities. The Frutexites-bearing microbialites occur less frequently, and also form lenses or beds, up to 30 cm thick; the microbialites may be laminated, and often developed on hardgrounds. In addition, the Frutexites-bearing microbialites also contain synsedimentary calcite cement crusts and botryoids (typically fracturing of the limestone and the precipitation of large, botryoidal aragonite cements in fissures that cut across the primary fabric. Environmental conditions, specifically palaeoxygenation and the degree of calcium carbonate supersaturation, likely controlled whether the thrombolites (high level of calcium carbonate supersaturation associated with vertical mixing of water masses and dysoxic conditions) or Frutexites-bearing microbialites (low level of calcium carbonate supersaturation associated with anoxic conditions and deposition below a stable chemocline) formed. The results of this study point to continued environmental stress in the region during the Early Triassic that likely contributed to the uneven recovery from the Permian-Triassic mass extinction.

  5. Lithofacies palaeogeography and biostratigraphy of the lowermost horizons of the Middle Triassic Hallstatt Limestones (Argolis Peninsula, Greece

    Directory of Open Access Journals (Sweden)

    Fotini A. Pomoni

    2013-07-01

    Taking into consideration the present location of the Hallstatt Formation, in the context of the Hellenides, an area suitable for the deposition of the Hallstatt Limestones, should be located between the sub-Pelagonian (western part of the Pelagonian zone and Pindos geotectonic zones, which during the Triassic corresponded to a platform slope and a deep ocean, respectively. The widespread Middle Triassic Han Bulog Limestones (ammonoid-bearing pelagic limestones from Triassic successions of the Eastern Alps (Dinarides, Hellenides may have formed partly in similar slope environments.

  6. Origin, evolution and sedimentary processes associated with a late Miocene submarine landslide, southeast Spain

    Science.gov (United States)

    Sola, F.; Puga-Bernabéu, Á.; Aguirre, J.; Braga, J. C.

    2018-02-01

    A submarine landslide, the Alhama de Almería Slide, influenced late Tortonian and early Messinian (late Miocene) sedimentary processes in the vicinity of Alhama de Almería in southeast Spain. Its 220-m-high headscarp and deposits are now subaerially exposed. The landslide occurred at the northern slope of the antecedent relief of the present-day Sierra de Gádor mountain range. This is a large antiform trending east-west to east-northeast-west-southwest, which has been uplifting since the late Miocene due to convergence of the African and Eurasian plates. During the Tortonian, this relief was an island separated from the Iberian Peninsula mainland by the Alpujarra corridor, a small and narrow intermontane basin of the Betic Cordillera in the western Mediterranean Sea. The materials involved in the slope failure were Triassic dolostones and phyllites from the metamorphic Alpujárride Complex and Tortonian marine conglomerates, sandstones, and marls that formed an initial sedimentary cover on the basement rocks. Coherent large masses of metamorphic rocks and Miocene deposits at the base of the headscarp distally change to chaotic deposits of blocks of different lithologies embedded in upper Tortonian marine marls, and high-strength cohesive debrites. During downslope sliding, coherent carbonate blocks brecciated due to their greater strength. Phyllites disintegrated, forming a cohesive matrix that engulfed and/or sustained the carbonate blocks. Resedimented, channelized breccias were formed by continuing clast collision, bed fragmentation, and disaggregation of the failed mass. The conditions leading to rock/sediment failure were favoured by steep slopes and weak planes at the contact between the basement carbonates and phyllites. Displacement of collapsed rocks created a canyon-like depression at the southeast edge of the landslide. This depression funnelled sediment gravity flows that were generated upslope, promoting local thick accumulations of sediments during

  7. Constraints of detrital zircon U-Pb ages and Hf isotopes on the provenance of the Triassic Yidun Group and tectonic evolution of the Yidun Terrane, Eastern Tibet

    Science.gov (United States)

    Wang, Bai-Qiu; Wang, Wei; Chen, Wei Terry; Gao, Jian-Feng; Zhao, Xin-Fu; Yan, Dan-Ping; Zhou, Mei-Fu

    2013-05-01

    Eastern Tibet to the west of the Yangtze Block consists of the Yidun and Songpan-Ganzi Terranes, separated by the Ganzi-Litang suture zone. The Yidun Terrane includes the Zhongza Massif to the west, but the eastern part of the Yidun terrane is covered by the Yidun Group extending from the south (Shangri-La region) to the north (Changtai region). The Yidun Group, from the base upward, includes the Lieyi, Qugasi, Tumugou and Lanashan formations, which are mainly composed of volcanic-flysch successions. Based on the ages of volcanic interlayers and plutonic intrusions, depositional ages of the Qugasi and Tumugou formations are considered to be slightly older than 230 Ma and ca. 220-230 Ma respectively, which are prominently older than the previous estimates. The Yidun Group in the Changtai region has two prominent detrital zircon age peaks at 400-480 and 880-980 Ma and a minor peak at 2.45-2.50 Ga. This pattern suggests a detritus source from the Zhongza Massif, which was a micro-continent separated from the western Yangtze Block. In contrast, the Yidun Group in the Shangri-La region has various zircon age spectra among different formations. The Qugasi Formation in this region has detrital zircon age patterns similar to the Yidun Group in the Changtai region. However, the overlying Tumugou Formation shows distinct age peaks at Triassic (220-240 Ma), Neoproterozoic (~ 720-880 Ma), and Paleoproterozoic (~ 1.75-1.90 Ga). This age pattern is similar to that of the Xikang Group of the Songpan-Ganzi Terrane to the east. The detrital zircon age difference between the Qugasi and Tumugou formations in this region indicates a transition of sedimentary sources from the Zhongza Massif to locally distributed Triassic magmatic rocks at ~ 230 Ma. It is thus suggested that the Songpan-Ganzi Terrane may have been connected to or collided with the southern part of the Yidun Terrane during the Late Triassic, whereas the Songpan-Ganzi Terrane and the northern part of the Yidun Terrane

  8. Lead Thickness Measurements

    International Nuclear Information System (INIS)

    Rucinski, R.

    1998-01-01

    The preshower lead thickness applied to the outside of D-Zero's superconducting solenoid vacuum shell was measured at the time of application. This engineering documents those thickness measurements. The lead was ordered in sheets 0.09375-inch and 0.0625-inch thick. The tolerance on thickness was specified to be +/- 0.003-inch. The sheets all were within that thickness tolerance. The nomenclature for each sheet was designated 1T, 1B, 2T, 2B where the numeral designates it's location in the wrap and 'T' or 'B' is short for 'top' or 'bottom' half of the solenoid. Micrometer measurements were taken at six locations around the perimeter of each sheet. The width,length, and weight of each piece was then measured. Using an assumed pure lead density of 0.40974 lb/in 3 , an average sheet thickness was calculated and compared to the perimeter thickness measurements. In every case, the calculated average thickness was a few mils thinner than the perimeter measurements. The ratio was constant, 0.98. This discrepancy is likely due to the assumed pure lead density. It is not felt that the perimeter is thicker than the center regions. The data suggests that the physical thickness of the sheets is uniform to +/- 0.0015-inch.

  9. Anisian (Middle Triassic) marine ichnocoenoses from the eastern and western margins of the Kamdian Continent, Yunnan Province, SW China: Implications for the Triassic biotic recovery

    Science.gov (United States)

    Feng, Xueqian; Chen, Zhong-Qiang; Woods, Adam; Pei, Yu; Wu, Siqi; Fang, Yuheng; Luo, Mao; Xu, Yaling

    2017-10-01

    Two Anisian (Middle Triassic) marine ichnocoenoses are reported from the Boyun and Junmachang (JMC) sections located along the eastern and western margins of the Kamdian Continent, Yunnan Province, Southwest China, respectively. The Boyun ichnoassemblage is middle Anisian in age and is dominated by robust Rhizocorallium, while the JMC ichnoassemblage is of an early Anisian age and is characterized by the presence of Zoophycos. The ichnoassemblage horizons of the Boyun section represent an inner ramp environment, while the JMC section was likely situated in a mid-ramp setting near storm wave base as indicated by the presence of tempestites. The ichnofossil-bearing successions are usually highly bioturbated in both the Boyun (BI 3-5, BPBI 5) and JMC (BI 3-4, BPBI 3-4) sections. Three large, morphologically complicated ichnogenera: 1) Rhizocorallium; 2) Thalassinoides; and, 3) Zoophycos characterize the Anisian ichnocoenoses. Of these, Rhizocorallium has mean and maximum tube diameters up to 20.4 mm and 28 mm, respectively, while Thalassinoides mean and maximum tube diameters are 14.2 mm and 22 mm, respectively. Zoophycos is present in the early Anisian strata of the JMC section, and represents the oldest known occurrence of this ichnogenus following the latest Permian mass extinction. Similar to coeval ichnoassemblages elsewhere in the world, the Yunnan ichnocoenoses embrace a relatively low ichnodiversity, but their burrows usually penetrate deeply into the sediment, and include large and complex Rhizocorallium and Thalassinoides. All of these ichnologic features are indicative of recovery stage 4 after the latest Permian crisis. Anisian ichnoassemblages occur globally in six different habitat settings, and all show similar ecologic characteristics except for slightly different degrees of ichnotaxonomic richness, indicating that depositional environment is not a crucial factor shaping the recovery of the trace-makers, but may have an impact on their ichnodiversity

  10. High sedimentation rates in the Early Triassic after latest Permian mass extinction: Carbonate production is main factor in non-Arctic regions

    Science.gov (United States)

    Horacek, Micha; Brandner, Rainer

    2016-04-01

    A substantial change in sedimentation rates towards higher values has been documented from the Late Permian to the Lower Triassic. Although it is assumed and also has been shown that the deposition of siliciclastic material increased in the Lower Triassic due to stronger erosion because of loss of land cover and increased chemical and physical weathering with extreme climate warming, the main sediment production occurred by marine carbonate production. Still, carbonate production might have been significantly influenced by weathering and erosion in the hinterland, as the transport of dust by storms into the ocean water probably was a main nutrient source for microbial carbonate producers, because "normal" nutrient supply by ocean circulation, i. e. upwelling was strongly reduced due to the elevated temperatures resulting in water-column stratification . Sediment accumulation was also clearly influenced by the paleo-geographic and latitudinal position, with lower carbonate production and sedimentation rates in moderate latitudes. The existence of a "boundary clay" and microbial carbonate mounds and layers in the immediate aftermath of the latest Permian mass extinction points towards a development from a short-timed acid ocean water - resulting in a carbonate production gap and the deposition of the boundary clay towards the deposition of the microbial mounds and layers due to the microbial production of micro-environments with higher alkalinity allowing the production of carbonate. After the return of the ocean water to normal alkalinity planktic production of carbonate resulted in a very high sedimentation rate, especially taking into account the absence of carbonate producing eukaryotic algae and animals.

  11. Osteology of a new specimen of Macrocnemus aff. M. fuyuanensis (Archosauromorpha, Protorosauria) from the Middle Triassic of Europe: potential implications for species recognition and paleogeography of tanystropheid protorosaurs

    Science.gov (United States)

    Jaquier, Vivien P.; Fraser, Nicholas C.; Furrer, Heinz; Scheyer, Torsten M.

    2017-11-01

    Over the past two decades, a wealth of marine and terrestrial reptiles, including protorosaurian archosauromorphs, has been described from Triassic shales and limestone layers in southern China. Recovered from the eastern margin of the Tethys Ocean, these forms often show remarkable similarities to taxa that were previously known and described from Europe, i.e., the western Tethyan margin. One protorosaurian that is known from the western and the eastern Tethyan province is the genus Macrocnemus, with currently three recognized species: 1) M. bassanii from the Middle Triassic Besano Formation and Meride Limestone (late Anisian – early Ladinian), UNESCO World Heritage Site Monte San Giorgio, Ticino, Switzerland; 2) M. obristi from the Prosanto Formation (early Ladinian) of the Ducan area, Grisons, Switzerland; and 3) M. fuyuanensis from the Falang Formation (Ladinian), Yunnan Province, southern China. Recently a new specimen, PIMUZ T 1559, from the upper Besano Formation at Meride, Ticino, Switzerland, was prepared, revealing a disarticulated skeleton which includes most of the cranium and lower jaw, pre-caudal vertebral column and ribs, the forelimbs, and girdle elements. Unambiguously assignable to the genus Macrocnemus, it evinces particularly gracile elongated cervical ribs, as well as a humerus/radius ratio that is comparable only to that of M. fuyuanensis from southern China. Based on this feature we tentatively recognize the new specimen as M. aff. fuyuanensis from Europe. The position and exquisite preservation of the clavicle and interclavicle in this specimen allows a revision of the shoulder girdle of Macrocnemus when articulated, which also has implications for closely related protorosaurian taxa, such as the long-necked Tanystropheus. Furthermore, differences in the shape and morphology of the interclavicle including pointed wing-like lateral processes and a short, fusiform caudal process represent rare discrete characters that allow separation of the

  12. Osteology of a New Specimen of Macrocnemus aff. M. fuyuanensis (Archosauromorpha, Protorosauria from the Middle Triassic of Europe: Potential Implications for Species Recognition and Paleogeography of Tanystropheid Protorosaurs

    Directory of Open Access Journals (Sweden)

    Vivien P. Jaquier

    2017-11-01

    Full Text Available Over the past two decades, a wealth of marine and terrestrial reptiles, including protorosaurian archosauromorphs, has been described from Triassic shales and limestone layers in southern China. Recovered from the eastern margin of the Tethys Ocean, these forms often show remarkable similarities to taxa that were previously known and described from Europe, i.e., the western Tethyan margin. One protorosaurian that is known from the western and the eastern Tethyan province is the genus Macrocnemus, with currently three recognized species: (1 Macrocnemus bassanii from the Middle Triassic Besano Formation and Meride Limestone (late Anisian–early Ladinian, UNESCO World Heritage Site Monte San Giorgio, Ticino, Switzerland; (2 Macrocnemus obristi from the Prosanto Formation (early Ladinian of the Ducan area, Grisons, Switzerland; and (3 Macrocnemus fuyuanensis from the Falang Formation (Ladinian, Yunnan Province, southern China. Recently a new specimen, PIMUZ T 1559, from the upper Besano Formation at Meride, Ticino, Switzerland, was prepared, revealing a disarticulated skeleton which includes most of the cranium and lower jaw, pre-caudal vertebral column and ribs, the forelimbs, and girdle elements. Unambiguously assignable to the genus Macrocnemus, it evinces particularly gracile elongated cervical ribs, as well as a humerus/radius ratio that is comparable only to that of M. fuyuanensis from southern China. Based on this feature we tentatively recognize the new specimen as M. aff. fuyuanensis from Europe. The position and exquisite preservation of the clavicle and interclavicle in this specimen allows a revision of the shoulder girdle of Macrocnemus when articulated, which also has implications for closely related protorosaurian taxa, such as the long-necked Tanystropheus. Furthermore, differences in the shape and morphology of the interclavicle including pointed wing-like lateral processes and a short, fusiform caudal process represent rare

  13. Review of potential host rocks for radioactive wasste disposal in the southeast United States: Triassic basin subregion

    International Nuclear Information System (INIS)

    1980-10-01

    Based on an evaluation of existing information, areas were identified within the Triassic basins of the southeastern United States with geologic properties considered favorable for containment of radioactive waste. The study region included both exposed and buried Triassic basins from Maryland to Georgia. These basins are long, narrow northeast-trending troughs filled with continental deposits derived from Paleozoic and Precambrian metamorphic and igneous rocks bordering the basins. The rocks are predominantly red in color and consist mainly of fanglomerates, conglomerates, arkosic sandstones, siltstones, claystones, shales, and argillites. The investigation identified 14 exposed and 5 buried basins within the study region. Candidate areas for further investigation were identified which meet the broad general criteria for tectonic stability, slow ground water movement, and long flow paths to the biosphere. These include: the Danville Triassic Basin in Virginia; the Dan River, Durham, and Wadesboro Triassic Basins in North Carolina; and the buried Florence and Dunbarton Triassic Basins in South Carolina. Other rock types in the southeast may prove more or less suitable as host rocks for a repository, but the available data suggest that the argillaceous Triassic rocks offer sufficient promise to be considered for additional study

  14. Exploring Late Globalization

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    2016-01-01

    literature on late globalization from sociocultural and economic perspectives. It illustrates in a vignette the character and features of late globalization observable in the withdrawal from foreign locations or deinternationalization of universities, as late globalizing entitis. The paper discusses...

  15. Trouble Upstairs: Reconstructing Permian-Triassic Climate during Siberian Traps Magmatism

    Science.gov (United States)

    Black, B. A.; Neely, R. R., III; Lamarque, J. F.; Elkins-Tanton, L. T.; Mills, M. J.

    2014-12-01

    The eruption of large igneous provinces can transfer significant masses of volatiles from Earth's interior to the atmosphere. What are the consequences of this degassing for habitability and extinction? In this presentation, we consider this question in the context of Siberian Traps magmatism, which has been shown to overlap within geochronologic uncertainty with catastrophic deterioration of Permian-Triassic marine and terrestrial ecosystems. To investigate the impacts of endogenic gases on climate, atmospheric chemistry, and ocean circulation, we conducted a series of numerical experiments with a comprehensive global model for the Permian-Triassic. Our simulations predict the intensity and distribution of acid rain and ozone depletion, with implications for terrestrial biota. We further explore feedbacks between sulfur emissions, transient cooling, and shifts in ocean circulation. We suggest that Siberian Traps magmatism may have triggered several distinct kill mechanisms in the oceans and on land, contributing to a complex combined pattern of environmental stress and latest Permian ecological failure.

  16. UPPER OLENEKIAN (SPATHIAN AMMONOIDS FROM CHIOS (LOWER TRIASSIC, GREECE: TAXONOMY AND STRATIGRAPHIC POSITIONS

    Directory of Open Access Journals (Sweden)

    DOROTHEE MERTMANN

    2003-11-01

    Full Text Available  On the Greek island of Chios, Lower Triassic sections bave delivered rich ammonoid faunas from red limestones of the Hallstatt facies. Here, we present a palaeontological description of Spathian ammonoids, which have been collected during two field campaigns by Italian-German teams (Assereto et al. 1980; Gaetani et al. 1992. The ammonoid associations are composed of Ceratitida and Phylloceratida, each order containing species of the Noritaceae, Hedenstroemiaceae, Xenodiscaceae, Dinaritaceae, Pinacocerataceae, Phyllocerataceae, Ptychitaceae, Ussuritaceae and Megaphyllitaceae. Long ranging genera, e.g. Procarnites and Leiophyllites, are present as well as endemic ones, e.g. Chiotites, which occurs exclusively in the Lower Triassic of Chios. The ammonoid association is indicative of the Prohungarites-Subcolumbites zone sensu Kummel (1973a. The haugi zone, installed as uppermost Olenekian in North America, is not represented by ammonoids on Chios. 

  17. Education and "Thick" Epistemology

    Science.gov (United States)

    Kotzee, Ben

    2011-01-01

    In this essay Ben Kotzee addresses the implications of Bernard Williams's distinction between "thick" and "thin" concepts in ethics for epistemology and for education. Kotzee holds that, as in the case of ethics, one may distinguish between "thick" and "thin" concepts of epistemology and, further, that this distinction points to the importance of…

  18. Thick film hydrogen sensor

    Science.gov (United States)

    Hoffheins, Barbara S.; Lauf, Robert J.

    1995-01-01

    A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors.

  19. Integrated geophysical study of the Triassic salt bodies' geometry and evolution in central Tunisia

    Science.gov (United States)

    Azaiez, Hajer; Amri, Dorra Tanfous; Gabtni, Hakim; Bedir, Mourad; Soussi, Mohamed

    2008-01-01

    A comprehensive study, integrating gravity, magnetic and seismic reflection data, has been used to resolve the complex Triassic salt body geometry and evolution in central Tunisia. Regional seismic lines across the study area show a detachment level in the Upper Triassic evaporites, associated with chaotic seismic facies below the Souinia, Majoura, and Mezzouna structures. The Jurassic and Lower Cretaceous seismic horizons display pinching-outs and onlapping around these structures. A stack-velocity section confirms the existence of a high-velocity body beneath the Souinia Mountain. Regional gravity and magnetic profiles in this area were elaborated from ETAP (the Tunisian Firm of Petroleum Activities) measure stations. These profiles were plotted following the same layout from the west (Souinia) to the east (Mezzouna), across the Majoura and Kharrouba mountains. They highlight associated gravity and magnetic negative anomalies. These gravity and magnetic data coupled to the reflection seismic data demonstrate that, in the Souinia, Majoura, and El Hafey zones, the Triassic salt reaches a salt pillow and a salt-dome stage, without piercing the cover. These stages are expressed by moderately low gravity anomalies. On the other hand, in the Mezzouna area (part of the North-South Axis), the Triassic salt had pierced its cover during the Upper Cretaceous and the Tertiary, reaching a more advanced stage as a salt diapir and salt wall. These stages express important low gravity and magnetic anomalies. These results confirm the model of Tanfous et al. (2005) of halokinetic movements by fault intrusions inducing, from the west to the east, structures at different stages of salt pillow, salt dome, and salt diapir.

  20. The Pangaean megamonsoon - evidence from the Upper Triassic Chinle Formation, Colorado Plateau

    Science.gov (United States)

    Dubiel, R.F.; Totman, Parrish J.; Parrish, J.M.; Good, S.C.

    1991-01-01

    The Chinle was deposited between about 5?? to 15??N paleolatitude in the western equatorial region of Pangaea, a key area for documenting the effects of the monsoonal climate. This study summarizes sedimentological and paleontologic data from the Chinle Formation on the Colorado Plateau and integrates that data with paleoclimatic models. The evidence for abundant moisture and seasonality attest to the reversal of equatorial flow and support the hypothesis that the Triassic Pangaean climate was dominated by monsoonal circulation. -from Authors

  1. Magnetic microsperules in Permian and Triassic bedded chert from Southwest Japan

    OpenAIRE

    Iwahashi,Junko; Yoshida,Masaru; Miono,Shigeyoshi; Santosh,Geetha; Santosh,M.

    1991-01-01

    Magnetic microspherules collected from the Permian and Triassic bedded cherts in Southwest Japan were studied. The size range, as estimated from 801 microspherules, vary from 3 to 100μm, with a peak size distribution between 10-20μm. Three broad shapes are recognized : spherical-, drop- and rocket-shaped, all categories including hollow particles. The surface textures as studied from scanning electron microscope show five dominant varieties : random mosaic, dendritic mosaic, feather crystal, ...

  2. A Triassic to Cretaceous Sundaland-Pacific subduction margin in West Sarawak, Borneo

    Science.gov (United States)

    Breitfeld, H. Tim; Hall, Robert; Galin, Thomson; Forster, Margaret A.; BouDagher-Fadel, Marcelle K.

    2017-01-01

    Metamorphic rocks in West Sarawak are poorly exposed and studied. They were previously assumed to be pre-Carboniferous basement but had never been dated. New 40Ar/39Ar ages from white mica in quartz-mica schists reveal metamorphism between c. 216 to 220 Ma. The metamorphic rocks are associated with Triassic acid and basic igneous rocks, which indicate widespread magmatism. New U-Pb dating of zircons from the Jagoi Granodiorite indicates Triassic magmatism at c. 208 Ma and c. 240 Ma. U-Pb dating of zircons from volcaniclastic sediments of the Sadong and Kuching Formations confirms contemporaneous volcanism. The magmatic activity is interpreted to represent a Triassic subduction margin in westernmost West Sarawak with sediments deposited in a forearc basin derived from the magmatic arc at the Sundaland-Pacific margin. West Sarawak and NW Kalimantan are underlain by continental crust that was already part of Sundaland or accreted to Sundaland in the Triassic. One metabasite sample, also previously assumed to be pre-Carboniferous basement, yielded Early Cretaceous 40Ar/39Ar ages. They are interpreted to indicate resumption of subduction which led to deposition of volcaniclastic sediments and widespread magmatism. U-Pb ages from detrital zircons in the Cretaceous Pedawan Formation are similar to those from the Schwaner granites of NW Kalimantan, and the Pedawan Formation is interpreted as part of a Cretaceous forearc basin containing material eroded from a magmatic arc that extended from Vietnam to west Borneo. The youngest U-Pb ages from zircons in a tuff layer from the uppermost part of the Pedawan Formation indicate that volcanic activity continued until c. 86 to 88 Ma when subduction terminated.

  3. Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils

    OpenAIRE

    Motani, Ryosuke; Jiang, Da-yong; Tintori, Andrea; Rieppel, Olivier; Chen, Guan-bao

    2014-01-01

    Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exc...

  4. Theropoda dinosaurs tracks from Triassic basin nd Ischigualasto - Villa Union, western Argentina

    International Nuclear Information System (INIS)

    Contreras, V.; Bracco, A.

    2004-01-01

    The Anchisauripus isp. and Theropoda indet. dinosaurs tracks from the Triassic Los Rastros and Ischigualasto formations, at the Ischigualasto-Villa Union Basin, Western Argentina, are described in this paper. This record completes the paleontological data provided by rest of bones and increases the stratigraphic range of some taxa in which bones are either missing or scarse. On the other hand, this report also allows us to enlarge the faunistic assemblage of some vertebrate assemblages [es

  5. Bone cells in birds show exceptional surface area, a characteristic tracing back to saurischian dinosaurs of the late Triassic.

    Directory of Open Access Journals (Sweden)

    John M Rensberger

    Full Text Available Dinosaurs are unique among terrestrial tetrapods in their body sizes, which range from less than 3 gm in hummingbirds to 70,000 kg or more in sauropods. Studies of the microstructure of bone tissue have indicated that large dinosaurs, once believed to be slow growing, attained maturity at rates comparable to or greater than those of large mammals. A number of structural criteria in bone tissue have been used to assess differences in rates of osteogenesis in extinct taxa, including counts of lines of arrested growth and the density of vascular canals.Here, we examine the density of the cytoplasmic surface of bone-producing cells, a feature which may set an upper limit to the rate of osteogenesis. Osteocyte lacunae and canaliculi, the cavities in bone containing osteocytes and their extensions, were measured in thin-sections of primary (woven and parallel fibered bone in a diversity of tetrapods. The results indicate that bone cell surfaces are more densely organized in the Saurischia (extant birds, extinct Mesozoic Theropoda and Sauropodomorpha than in other tetrapods, a result of denser branching of the cell extensions. The highest postnatal growth rates among extant tetrapods occur in modern birds, the only surviving saurischians, and the finding of exceptional cytoplasmic surface area of the cells that produce bone in this group suggests a relationship with bone growth rate. In support of this relationship is finding the lowest cell surface density among the saurischians examined in Dinornis, a member of a group of ratites that evolved in New Zealand in isolation from mammalian predators and show other evidence of lowered maturation rates.

  6. LATE TRIASSIC OBLIQUE EXTRUSION OF UHP/HP COMPLEXES IN THE ATBASHI ACCRETIONARY COMPLEX OF SOUTH TIANSHAN, KYRGYZSTAN

    Directory of Open Access Journals (Sweden)

    Wenjiao Xiao

    2017-01-01

    Full Text Available The exhumation and tectonic emplacement of eclogites and blueschists take place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan.

  7. Bone cells in birds show exceptional surface area, a characteristic tracing back to saurischian dinosaurs of the late Triassic.

    Science.gov (United States)

    Rensberger, John M; Martínez, Ricardo N

    2015-01-01

    Dinosaurs are unique among terrestrial tetrapods in their body sizes, which range from less than 3 gm in hummingbirds to 70,000 kg or more in sauropods. Studies of the microstructure of bone tissue have indicated that large dinosaurs, once believed to be slow growing, attained maturity at rates comparable to or greater than those of large mammals. A number of structural criteria in bone tissue have been used to assess differences in rates of osteogenesis in extinct taxa, including counts of lines of arrested growth and the density of vascular canals. Here, we examine the density of the cytoplasmic surface of bone-producing cells, a feature which may set an upper limit to the rate of osteogenesis. Osteocyte lacunae and canaliculi, the cavities in bone containing osteocytes and their extensions, were measured in thin-sections of primary (woven and parallel fibered) bone in a diversity of tetrapods. The results indicate that bone cell surfaces are more densely organized in the Saurischia (extant birds, extinct Mesozoic Theropoda and Sauropodomorpha) than in other tetrapods, a result of denser branching of the cell extensions. The highest postnatal growth rates among extant tetrapods occur in modern birds, the only surviving saurischians, and the finding of exceptional cytoplasmic surface area of the cells that produce bone in this group suggests a relationship with bone growth rate. In support of this relationship is finding the lowest cell surface density among the saurischians examined in Dinornis, a member of a group of ratites that evolved in New Zealand in isolation from mammalian predators and show other evidence of lowered maturation rates.

  8. Evidence for Late Triassic provenance areas and Early Jurassic sediment supply turnover in the Barents Sea Basin of northern Pangea

    Czech Academy of Sciences Publication Activity Database

    Klausen, T. G.; Müller, R.; Sláma, Jiří; Helland-Hansen, W.

    2017-01-01

    Roč. 9, č. 1 (2017), s. 14-28 ISSN 1941-8264 Institutional support: RVO:67985831 Keywords : U-Pb geochronology * detrial zircon * Cenozoic evolution * rocks * metamorphism Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.662, year: 2016

  9. Permian-Triassic Tethyan realm reorganization: Implications for the outward Pangea margin

    Science.gov (United States)

    Riel, Nicolas; Jaillard, Etienne; Martelat, Jean-Emmanuel; Guillot, Stéphane; Braun, Jean

    2018-01-01

    We present a new conceptual model to explain the first order Permian-Triassic evolution of the whole > 30 000 km long Pangea margin facing the Panthalassa ocean. Compilation of available geological, geochemical, geochronogical and paleomagnetic data all along this system allowed us to distinguish three part of the margin: western Laurentia, western Gondwana and eastern Gondwana. These segments record distinct tectonic and magmatic events, which all occur synchronously along the whole margin and correlate well with the main geodynamic events of this period, i.e. subduction of the Paleotethys mid-ocean ridge at 310-280 Ma, opening of the Neotethys at 280-260 Ma, counterclockwise rotation of Pangea at 260-230 Ma and closure of the Paleotethys at 230-220 Ma. Between 260 and 230 Ma, the reorganization of the Tethyan realm triggered the up to 35° rotation of Pangea around an Euler pole located in northernmost South America. This implied both an increase and a decrease of the convergence rate between the margin and the Panthalassa ocean, north and south of the Euler pole, respectively. Thus, the Permian-Triassic Pangean margin was marked: in western Laurentia by marginal sea closure, in western Gondwana by widespread bimodal magmatic and volcanic activity, in eastern Gondwana by transpressive orogenic phase. Therefore, we propose that the Permian-Triassic evolution of the outward margin of Pangea was controlled by the Tethyan realm reorganization.

  10. A basal ichthyosauriform with a short snout from the Lower Triassic of China.

    Science.gov (United States)

    Motani, Ryosuke; Jiang, Da-Yong; Chen, Guan-Bao; Tintori, Andrea; Rieppel, Olivier; Ji, Cheng; Huang, Jian-Dong

    2015-01-22

    The incompleteness of the fossil record obscures the origin of many of the more derived clades of vertebrates. One such group is the Ichthyopterygia, a clade of obligatory marine reptiles that appeared in the Early Triassic epoch, without any known intermediates. Here we describe a basal ichthyosauriform from the upper Lower Triassic (about 248 million years ago) of China, whose primitive skeleton indicates possible amphibious habits. It is smaller than ichthyopterygians and had unusually large flippers that probably allowed limited terrestrial locomotion. It also retained characteristics of terrestrial diapsid reptiles, including a short snout and body trunk. Unlike more-derived ichthyosauriforms, it was probably a suction feeder. The new species supports the sister-group relationships between ichthyosauriforms and Hupehsuchia, the two forming the Ichthyosauromorpha. Basal ichthyosauromorphs are known exclusively from south China, suggesting that the clade originated in the region, which formed a warm and humid tropical archipelago in the Early Triassic. The oldest unequivocal record of a sauropterygian is also from the same stratigraphic unit of the region.

  11. Investigation of mineral composition of differently treated devonian, quaternary and triassic clays of Latvia

    International Nuclear Information System (INIS)

    Kosorukovs, A.; Viss, R.

    1999-01-01

    Clayey fractions (particle size less than 5 μm )of the Latvian Devonian (Kuprava and Liepa deposits), Quaternary (Laza and Ugale deposits) and Triassic (Akmene deposit, Republic of Lithuania) clays have been obtained. The clayey fractions were converted in the form in which all the cations were exchanged for magnesium ions. After the ion exchange the fractions were treated with dimethyl sulfoxide or glycerol in the course for two days, one sample being subjected to thermal treatment at 550±110 C for two hours. Diffractograms for the treated samples have been obtained using a DRON-2,0 diffractometer (Co-radiation). Analysis of the obtained diffractograms show that: 1) the main clayey minerals of the Devonian clays occur to be hydromicas (mainly hydromuscovite) containing admixtures of kaolinite and quartz; 2) the main clayey minerals of the Quarternary clays also occur to be hydromicas - mixtures of hydrobiotite and hydromuscovite containing admixtures of kaolinite and iron-containing chlorite; 3) smectite occurs to be the main mineral of the Triassic clay; it contains admixtures of hydromica and chlorite; 4) the Triassic and Quaternary clays contain fine- and coarse-grained carbonates, mainly calcite, in quantities of 10-16%; 5) iron and titanium are included in fine grained minerals. (author)

  12. Synchrotron Reveals Early Triassic Odd Couple: Injured Amphibian and Aestivating Therapsid Share Burrow.

    Directory of Open Access Journals (Sweden)

    Vincent Fernandez

    Full Text Available Fossorialism is a beneficial adaptation for brooding, predator avoidance and protection from extreme climate. The abundance of fossilised burrow casts from the Early Triassic of southern Africa is viewed as a behavioural response by many tetrapods to the harsh conditions following the Permo-Triassic mass-extinction event. However, scarcity of vertebrate remains associated with these burrows leaves many ecological questions unanswered. Synchrotron scanning of a lithified burrow cast from the Early Triassic of the Karoo unveiled a unique mixed-species association: an injured temnospondyl amphibian (Broomistega that sheltered in a burrow occupied by an aestivating therapsid (Thrinaxodon. The discovery of this rare rhinesuchid represents the first occurrence in the fossil record of a temnospondyl in a burrow. The amphibian skeleton shows signs of a crushing trauma with partially healed fractures on several consecutive ribs. The presence of a relatively large intruder in what is interpreted to be a Thrinaxodon burrow implies that the therapsid tolerated the amphibian's presence. Among possible explanations for such unlikely cohabitation, Thrinaxodon aestivation is most plausible, an interpretation supported by the numerous Thrinaxodon specimens fossilised in curled-up postures. Recent advances in synchrotron imaging have enabled visualization of the contents of burrow casts, thus providing a novel tool to elucidate not only anatomy but also ecology and biology of ancient tetrapods.

  13. Precession-driven monsoon variability at the Permian-Triassic boundary — Implications for anoxia and the mass extinction

    Science.gov (United States)

    Winguth, Arne; Winguth, Cornelia

    2013-06-01

    By the end of the Late Permian, most continents had collided to form the supercontinent of Pangea. The associated climatic changes at the Permian-Triassic boundary coincided with the most severe mass extinction in the Phanerozoic. One extinction hypothesis favors a climatic response to an increase in large-scale volcanism resulting in ocean stagnation and widespread anoxia with fatal consequences for marine and land organisms. Recent interpretations of geochemical data suggest that orbitally-driven periodic upwelling of toxic hydrogen-sulfide rich water masses contributed to the extinction of species. In this paper, we use the Community Climate System Model (CCSM3) in order to explore the effect of eccentricity-modulated changes of the precession on the strength of Pangean megamonsoons and their impact on productivity and oxygen distribution. The climate model simulates high variability in monsoonal precipitation, trade winds and equatorial upwelling in response to precessional extremes, leading to remarkable fluctuations in the export of carbon from the euphotic zone and hence reduction in dissolved oxygen concentrations in subsurface layers. These findings are in general agreement with increased primary productivity, intensified euxinia within the oxygen-minimum zone, and decimation of the radiolarian zooplankton community as inferred from Japanese marine sections. Strong changes in river run-off linked to precipitation oscillations possibly led to a high variability in the nutrient supply to the Tethys Ocean, thus affecting regional productivity and oxygen distribution. The model results suggest that orbital variability in the sedimentary record and the associated extinction of species are related rather to periodic anoxia in near surface-to-intermediate depth than to widespread anoxic events in the Panthalassic deep-sea.

  14. Shyok Suture Zone, N Pakistan: late Mesozoic Tertiary evolution of a critical suture separating the oceanic Ladakh Arc from the Asian continental margin

    Science.gov (United States)

    Robertson, Alastair H. F.; Collins, Alan S.

    2002-02-01

    The Shyok Suture Zone (Northern Suture) of North Pakistan is an important Cretaceous-Tertiary suture separating the Asian continent (Karakoram) from the Cretaceous Kohistan-Ladakh oceanic arc to the south. In previously published interpretations, the Shyok Suture Zone marks either the site of subduction of a wide Tethyan ocean, or represents an Early Cretaceous intra-continental marginal basin along the southern margin of Asia. To shed light on alternative hypotheses, a sedimentological, structural and igneous geochemical study was made of a well-exposed traverse in North Pakistan, in the Skardu area (Baltistan). To the south of the Shyok Suture Zone in this area is the Ladakh Arc and its Late Cretaceous, mainly volcanogenic, sedimentary cover (Burje-La Formation). The Shyok Suture Zone extends northwards (ca. 30 km) to the late Tertiary Main Karakoram Thrust that transported Asian, mainly high-grade metamorphic rocks southwards over the suture zone. The Shyok Suture Zone is dominated by four contrasting units separated by thrusts, as follows: (1). The lowermost, Askore amphibolite, is mainly amphibolite facies meta-basites and turbiditic meta-sediments interpreted as early marginal basin rift products, or trapped Tethyan oceanic crust, metamorphosed during later arc rifting. (2). The overlying Pakora Formation is a very thick (ca. 7 km in outcrop) succession of greenschist facies volcaniclastic sandstones, redeposited limestones and subordinate basaltic-andesitic extrusives and flow breccias of at least partly Early Cretaceous age. The Pakora Formation lacks terrigenous continental detritus and is interpreted as a proximal base-of-slope apron related to rifting of the oceanic Ladakh Arc; (3). The Tectonic Melange (ocean ridge-type volcanics and recrystallised radiolarian cherts, interpreted as accreted oceanic crust. (4). The Bauma-Harel Group (structurally highest) is a thick succession (several km) of Ordovician and Carboniferous to Permian-Triassic, low

  15. Interpretation of massive sandstones in ephemeral fluvial settings: A case study from the Upper Candelária Sequence (Upper Triassic, Paraná Basin, Brazil)

    Science.gov (United States)

    Horn, Bruno Ludovico Dihl; Goldberg, Karin; Schultz, Cesar Leandro

    2018-01-01

    Ephemeral rivers display a wide range of upper- and lower-flow regime structures due to great flow-velocity changes during the floods. The development of flow structures in these setting is yet to be understood, especially in the formation of thick, massive sandstones. The Upper Triassic of Southern Gondwana was marked by a climate with great seasonal changes, yet there is no description of river systems with seasonal characteristics in Southern Gondwana. This work aims to characterize a ephemeral alluvial system of the Upper Triassic of the Paraná Basin. The characteristics of the deposits are discussed in terms of depositional processes through comparison with similar deposits from literature, flow characteristics and depositional signatures compared to flume experiments. The alluvial system is divided in four facies associations: (1) channels with wanning fill, characterized by low width/thickness ratio, tabular bodies, scour-and-fill structures with upper- and lower-flow regime bedforms; (2) channels with massive fill, characterized by low w/t ratio, sheet-like bodies, scour-and-fill structures with massive sandstones; (3) proximal sheetfloods, characterized by moderate w/t ratio, sheet-like bodies with upper- and lower-flow regime bedforms and (4) distal sheetfloods, characterized by high w/t ratio, sheet-like bodies with lower-flow regime bedforms. Evidence for the seasonal reactivation of the riverine system includes the scarcity of well-developed macroforms and presence of in-channel mudstones, thick intraformational conglomerates, and the occurrence of well- and poorly-preserved vertebrate bones in the same beds. The predominantly massive sandstones indicate deposition from a hyperconcentrated flow during abrupt changes in flow speed, caused by de-confinement or channel avulsion, whereas turbulent portions of the flow formed the upper- and lower-flow regime bedforms after the deposition of the massive layers. The upper portion of the Candelária Sequence

  16. The Permo-Triassic uranium deposits of Southern Africa within the African-South American Gondwana framework

    International Nuclear Information System (INIS)

    Toens, P.D.; Le Roux, J.P.

    1981-01-01

    The discovery of uranium in the Permo-Triassic Gondwana in South America and Africa has served to highlight the intercontinental correlations. The purpose here is to examine the uranium deposits of Southern Africa in the light of the similarities that exist between the various Gondwana formations of the two continents. This hopefully will assist in gaining some understanding of the genesis of the uranium mineralization and the sedimentary environment in which such deposits are likely to occur. Between the Upper Carboniferous and the Jurassic a tectono-sedimentary terrain existed within Gondwanaland in which broadly similar conditions prevailed over large areas, thus producing numerous partly disconnected basins practically identical in character. The basal formations are composed of glacial tillite followed by a succession of sandstone and shale which attains a thickness of up to 12,000 m. Sedimentological studies confirm that major source areas composed largely of granitic and metamorphic rocks existed to the north and south of central South America and Southern Africa, as also in the divides between the basins. Uranium mineralization occurs sporadically throughout the succession and is usually restricted to palaeoriver channels containing carbon trash. There has been little subsequent enrichment and the Colorado model does not apply. With a few exceptions, the deposits tend to have a low overall uranium tenor and individual deposits are usually not very extensive in size. Collectively, however, they may eventually assume some importance. Uraniferous coals have been recorded from a number of localities and it is suggested that the significance of these deposits has as yet not been fully appreciated or investigated. (author)

  17. Long-term oceanic changes prior the end-Triassic mass extinction

    Science.gov (United States)

    Clémence, Marie-Emilie; Mette, Wolfgang; Thibault, Nicolas; Korte, Christoph

    2014-05-01

    A number of potential causes and kill mechanisms have been proposed for the end-Triassic mass extinction such as palaeoclimatic and sea-level variations, massive volcanism and ocean acidification. Recent analysis of the stomatal index and density of fossil leaves and geochemical research on pedogenic carbonate nodules are suggestive of rising atmospheric CO2 concentration and fluctuating climate in the Rhaetian. It seems therefore probable that the end-Triassic event was preceded by large climatic fluctuations and environmental perturbations in the Rhaetian which might have partly affected the composition and diversity of the terrestrial and marine biota prior to the end-Triassic interval. The Northern Calcareous Alps (NCA) has long been favored for the study of the Rhaetian, since the GSSP of the Triassic/Jurassic (T/J) boundary and other important T/J sections are situated in this region. However, the most famous Rhaetian sections in the NCA are composed of carbonates from the Koessen Formation and were situated in a large isolated intraplatform Basin (the Eiberg Basin), bordered to the south-east by a well-developed coral reef in the NW of the Tethys border. Several Rhaetian sections composed of marls and shales of the Zlambach Formation were deposited at the same time on the other side of this reef, in the oceanic Halstatt Basin, which was in direct connection to the Tethys. Here, we present new results on sedimentology, stable isotope and trace element analysis of both intraplatform and oceanic basin deposits in the NCA. Intraplatform Rhaetian sections from the Koessen Formation bear a few minor intervals of shales with enrichments in organic matter, some of which are associated to carbon isotopic excursions. Oceanic sections from the Hallstatt Basin are characterized at the base by very cyclic marl-limestone alternations. Higher up in the section, sediments progressively turn into pure shale deposits and the top of the Formation is characterized by organic

  18. Ocean Sediment Thickness Contours

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean sediment thickness contours in 200 meter intervals for water depths ranging from 0 - 18,000 meters. These contours were derived from a global sediment...

  19. The Middle Triassic evolution of the Bangong-Nujiang Tethyan Ocean: evidence from analyses of OIB-type basalts and OIB-derived phonolites in northern Tibet

    Science.gov (United States)

    Fan, Jian-Jun; Li, Cai; Liu, Jin-Heng; Wang, Ming; Liu, Yi-Ming; Xie, Chao-Ming

    2017-12-01

    the Middle Triassic. These data, combined with data from modern ocean islands (e.g., Canary Islands, Cape Verde, Fernando de Noronha, Tristan da Cunha, and Gough in the Atlantic Ocean, and Society and Austral-Cook in the Pacific Ocean), lead us to infer that the BNTO was open for a long time before the Middle Triassic, and that the ocean had already developed into a mature ocean with a thick oceanic lithosphere by at least the Middle Triassic.

  20. Sodium storage in deep paleoweathering profiles beneath the Paleozoic-Triassic unconformity

    Science.gov (United States)

    Thiry, M.; Parcerisa, D.; Ricordel-Prognon, C.; Schmitt, J.-M.

    2009-04-01

    A major sodium accumulation has been recognized for long and by numerous authors in the Permo-Triassic salt deposits (Hay et al., 2006). Beside these basinal deposits, important masses of sodium were stored on the continents within deep palaeoweathering profiles in form of albite. Indeed, wide surfaces and huge volumes of granito-gneissic basements of the Hercynian massifs are albitized from North-Africa up to Scandinavia. These albitized rocks have usually been considered as related to tardi-magmatic metasomatic processes (Cathelineau 1986; Petersson and Eliasson 1997). Geometrical arrangement and dating of these alterations point out that these albitizations, or at least a part of them, developed under low temperature subsurface conditions in relation with the Triassic palaeosurface (Ricordel et al., 2007; Parcerisa et al., 2009). Petrology The albitized igneous rocks show a strong alteration with pseudomorphic replacement of the primary plagioclases into albite, replacement of primary biotite by chlorite and minor precipitation of neogenic minerals like albite, chlorite, apatite, haematite, calcite and titanite. Albitized rocks are characterized by their pink coloration due to the presence of minute haematite inclusions in the albite. The development and distribution of the albitization and related alterations above the unaltered basement occurs in three steps that define a vertical profile, up to 100-150 m depth. 1) In the lower part of the profile, albitization occurs within pink-colored patches in the unaltered rock, giving a pink-spotted aspect to the rock. 2) In the middle part of the profile, rocks have an overall pink coloration due to the albitization of the primary Ca-bearing igneous plagioclases. Usually, this facies develops in a pervasive manner, affecting the whole rock, but it may also be restricted to joints, giving a sharp-pink coloration to the fracture wall. 3) Finally, the top of the profile is defined by the same mineral paragenesis as in the

  1. A bird-like skull in a Triassic diapsid reptile increases heterogeneity of the morphological and phylogenetic radiation of Diapsida

    Science.gov (United States)

    Pritchard, Adam C.; Nesbitt, Sterling J.

    2017-10-01

    The Triassic Period saw the first appearance of numerous amniote lineages (e.g. Lepidosauria, Archosauria, Mammalia) that defined Mesozoic ecosystems following the end Permian Mass Extinction, as well as the first major morphological diversification of crown-group reptiles. Unfortunately, much of our understanding of this event comes from the record of large-bodied reptiles (total body length > 1 m). Here we present a new species of drepanosaurid (small-bodied, chameleon-like diapsids) from the Upper Triassic Chinle Formation of New Mexico. Using reconstructions of micro-computed tomography data, we reveal the three-dimensional skull osteology of this clade for the first time. The skull presents many archaic anatomical traits unknown in Triassic crown-group reptiles (e.g. absence of bony support for the external ear), whereas other traits (e.g. toothless rostrum, anteriorly directed orbits, inflated endocranium) resemble derived avian theropods. A phylogenetic analysis of Permo-Triassic diapsids supports the hypothesis that drepanosaurs are an archaic lineage that originated in the Permian, far removed from crown-group Reptilia. The phylogenetic position of drepanosaurids indicates the presence of archaic Permian clades among Triassic small reptile assemblages and that morphological convergence produced a remarkably bird-like skull nearly 100 Myr before one is known to have emerged in Theropoda.

  2. THALAMID SPONGES FROM THE UPPER TRIASSIC (NORIAN-RHAETIAN NAYBAND FORMATION NEAR WALI-ABAD, SE ABADEH, CENTRAL IRAN(CONTRIBUTION TO TRIASSIC PALEONTOLOGY OF IRAN 4

    Directory of Open Access Journals (Sweden)

    BABA SENOWBARI-DARYAN

    1999-03-01

    Full Text Available An association of thalamid sponges including Amblysiphonella, Nevadathalamia, Stylothalamia, and Neoguadalupia, with the hexactinellid Casearia is described from the Upper Triassic (Norian-Rhaetian Nayband Formation of Hambast-Mts. near the small town of Wali-Abad (Abadeh region, central Iran. These Norian-Rhaetian (Neoguadalupia, Amblysiphonella, Nevadathalamia and Liassic (Stylothalamia columnaris Le Maitre thalamid sponge assemblages are exceptional associations, not previously reported from Iran nor from other localities in the world. The microfacies and organism associations in the sponge-bearing carbonates is discussed. Differences of macro- and microfaunal composition, as well as flora, support the recognition of Kristan-Tollmann et al. to classify the Nayband Formation in the Abadeh region as of a distinct unit, termed the "Wali-Abad-Faziesregion". Following thalamid sponge species are described as new: Nevadathalamia waliabadensis n. sp. and Stylothalamia hambastensis n. sp. 

  3. Monitoring production target thickness

    International Nuclear Information System (INIS)

    Oothoudt, M.A.

    1993-01-01

    Pion and muon production targets at the Clinton P. Anderson Meson Physics Facility consist of rotating graphite wheels. The previous target thickness monitoring Procedure scanned the target across a reduced intensity beam to determine beam center. The fractional loss in current across the centered target gave a measure of target thickness. This procedure, however, required interruption of beam delivery to experiments and frequently indicated a different fractional loss than at normal beam currents. The new monitoring Procedure compares integrated ups and downs toroid current monitor readings. The current monitors are read once per minute and the integral of readings are logged once per eight-hour shift. Changes in the upstream to downstream fractional difference provide a nonintrusive continuous measurement of target thickness under nominal operational conditions. Target scans are now done only when new targets are installed or when unexplained changes in the current monitor data are observed

  4. The Thickness and Volume of Young Basalts Within Mare Imbrium

    Science.gov (United States)

    Chen, Yuan; Li, Chunlai; Ren, Xin; Liu, Jianjun; Wu, Yunzhao; Lu, Yu; Cai, Wei; Zhang, Xunyu

    2018-02-01

    Basaltic volcanism is one of the most important geologic processes of the Moon. Research on the thickness and volume of late-stage basalts of Mare Imbrium helps better understand the source of lunar volcanism and eruption styles. Based on whether apparent flow fronts exist or not, the late-stage basalts within Mare Imbrium were divided into two groups, namely, Upper Eratosthenian basalts (UEm) and Lower Eratosthenian basalts (LEm). Employing the topographic profile analysis method for UEm and the crater excavation technique for LEm, we studied the thickness and distribution of Eratosthenian basalts in Mare Imbrium. For the UEm units, their thicknesses were estimated to be 16-34 (±2) m with several layers of individual lava ( 8-13 m) inside. The estimated thickness of LEm units was 14-45(±1) m, with a trend of reducing thickness from north to south. The measured thickness of late-stage basalts around the Chang'E-3 landing site ( 37 ± 1 m) was quite close to the results acquired by the lunar penetrating radar carried on board the Yutu Rover ( 35 m). The total volume of the late-stage basalts in Mare Imbrium was calculated to be 8,671 (±320) km3, which is 4 times lower than that of Schaber's estimation ( 4 × 104 km3). Our results indicate that the actual volume is much lower than previous estimates of the final stage of the late basaltic eruption of Mare Imbrium. Together, the area flux and transport distance of the lava flows gradually decreased with time. These results suggest that late-stage volcanic evolution of the Moon might be revised.

  5. Preliminary study of the uranium potential of the Wadesboro Triassic basin, North Carolina

    International Nuclear Information System (INIS)

    Thayer, P.A.; Harris, W.B.

    1981-11-01

    This report presents results of a four-channel spectrometric survey of the Wadesboro Triassic basin and adjacent Piedmont, North and South Carolina. A total of 216 gamma-ray spectrometric measurements was taken at 165 sites in the Wadesboro Basin and at 37 sites in the adjacent Piedmont. The normal sampling density in the Wadesboro Basin is one site per 4.5 km 2 . Surface radiometric surveys reveal no anomalous radioactivity. Estimated uranium concentrations (eU) from the area are from 0.1 to 4.9 ppM. Average eU content of Triassic sandstones is 1.5 ppM, which is nearly the average for adjacent metavolcanic rocks (1.6 ppM). Granitic intrusives of the Pageland and Lilesville plutons display the highest eU concentrations in the area, averaging 3.3 ppM. The uranium/thorium ratio is consistently low throughout the area, from 0.01 to 0.54; the log uranium/log thorium ratio is from -1.11 to a maximum of 0.66. Triassic sandstones have the highest values, averaging 0.25. Granites of the Pageland and Lilesville plutons have an average uranium/thorium ratio of 0.21, and Slate Belt metavolcanic rocks average 0.15. On the basis of surface radiometric surveys and geologic studies, it is believed that sedimentary strata of the Wadesboro Basin are poor targets for further uranium exploration. This conclusion is based on the lack of many favorable characteristics associated with fluvial uranium deposits

  6. Systematics of putative euparkeriids (Diapsida: Archosauriformes from the Triassic of China

    Directory of Open Access Journals (Sweden)

    Roland B. Sookias

    2014-11-01

    Full Text Available The South African species Euparkeria capensis is of great importance for understanding the early radiation of archosauromorphs (including archosaurs following the Permo–Triassic mass extinction, as most phylogenetic analyses place it as the sister taxon to crown group Archosauria within the clade Archosauriformes. Although a number of species from Lower–Middle Triassic deposits worldwide have been referred to the putative clade Euparkeriidae, the monophyly of Euparkeriidae is controversial and has yet to be demonstrated by quantitative phylogenetic analysis. Three Chinese taxa have been recently suggested to be euparkeriids: Halazhaisuchus qiaoensis, ‘Turfanosuchus shageduensis’, and Wangisuchus tzeyii, all three of which were collected from the Middle Triassic Ermaying Formation of northern China. Here, we reassess the taxonomy and systematics of these taxa. We regard Wangisuchus tzeyii as a nomen dubium, because the holotype is undiagnostic and there is no convincing evidence that the previously referred additional specimens represent the same taxon as the holotype. We also regard ‘Turfanosuchus shageduensis’ as a nomen dubium as we are unable to identify any diagnostic features. We refer the holotype to Archosauriformes, and more tentatively to Euparkeriidae. Halazhaisuchus qiaoensis and the holotype of ‘Turfanosuchus shageduensis’ are resolved as sister taxa in a phylogenetic analysis, and are in turn the sister taxon to Euparkeria capensis, forming a monophyletic Euparkeriidae that is the sister to Archosauria+Phytosauria. This is the first quantitative phylogenetic analysis to recover a non-monospecific, monophyletic Euparkeriidae, but euparkeriid monophyly is only weakly supported and will require additional examination. Given their similar sizes, stratigraphic positions and phylogenetic placement, the holotype of ‘Turfanosuchus shageduensis’ may represent a second individual of Halazhaisuchus qiaoensis, but no

  7. Revision of the Dysmorphoptilidae (Hemiptera: Cicadomorpha: Prosboloidea) of the Queensland Triassic-Part 2.

    Science.gov (United States)

    Lambkin, Kevin J

    2016-03-15

    The extinct hemipteran family Dysmorphoptilidae was a major component of the Triassic insect fauna of Queensland preserved at the Denmark Hill, Dinmore, Mount Crosby and Gayndah fossil insect sites. A total of 13 species have now been identified, of which eight species in five genera were examined in the first part of this revision. This second part revises the remaining five species in three genera. Eoscartoides Evans, 1956 (= Mesonirvana Evans, 1956, syn. nov.), comprising Eoscartoides bryani Evans, 1956 (= Mesonirvana abrupta Evans, 1956, syn. nov.) (Mount Crosby), Eoscartoides orthocladus (Tillyard, 1922) comb. nov. (Denmark Hill), and Eoscartoides dmitryi sp. nov. (Dinmore), is distinguished by a strongly developed arc-like strigil in the basal costal space, a very short stem of RA, and a deeply forked M1+2. The monotypic Eoscarterella Evans, 1956, with type species Eoscarterella media Evans, 1956 (Mount Crosby), has a strongly lobate tegmen with peculiar surface sculpture and M1+2 simple. Eoscartoides and Eoscarterella differ from most dysmorphoptilids in having more or less lobate tegmina with even margins (without the antero-apical emargination so typical of the family), as well as the early entry of RA1 into the costal margin and the associated extensive and antero-apically positioned RA2. These characters are also shared with two other dysmorphoptilids, the Australian Permian Belmontocarta Evans and an unnamed Triassic species from Kyrgyzstan, and the four thus form a distinct subgroup within the family. On the other hand, the monotypic Trifidella Evans, 1956 (= Alotrifidus Evans, 1956, syn. nov.), with type species Trifidella perfecta Evans, 1956 (= Alotrifidus interruptus Evans, 1956, syn. nov.) (Mount Crosby), is a more typical dysmorphoptilid with a distinct emargination, RA entering the margin much more apically, and RA2 of limited extent. Trifidella is presumably the sister of the Queensland Triassic Dysmorphoptiloides Evans, sharing the basal

  8. Geographic range did not confer resilience to extinction in terrestrial vertebrates at the end-Triassic crisis.

    Science.gov (United States)

    Dunhill, Alexander M; Wills, Matthew A

    2015-08-11

    Rates of extinction vary greatly through geological time, with losses particularly concentrated in mass extinctions. Species duration at other times varies greatly, but the reasons for this are unclear. Geographical range correlates with lineage duration amongst marine invertebrates, but it is less clear how far this generality extends to other groups in other habitats. It is also unclear whether a wide geographical distribution makes groups more likely to survive mass extinctions. Here we test for extinction selectivity amongst terrestrial vertebrates across the end-Triassic event. We demonstrate that terrestrial vertebrate clades with larger geographical ranges were more resilient to extinction than those with smaller ranges throughout the Triassic and Jurassic. However, this relationship weakened with increasing proximity to the end-Triassic mass extinction, breaking down altogether across the event itself. We demonstrate that these findings are not a function of sampling biases; a perennial issue in studies of this kind.

  9. CHAMBERED HEXACTINELLID SPONGES FROM UPPER TRIASSIC(NORIAN-RHAETIAN? REEFS OF NAYBAND FORMATION IN CENTRAL IRAN

    Directory of Open Access Journals (Sweden)

    B. SENOWBARI-DARYAN

    2012-07-01

    Full Text Available This paper describes several chambered hexactinellid sponges, including Casearia iranica n.sp., C. vezvanensis n. sp., C. delijanensis n. sp., Esfahanella magna gen. n. n. sp., and E. parva gen. n. n. sp. from reefs of the Upper Triassic (Norian-Rhaetian Nayband Formation exposed south of the town of Delijan in central Iran. The relative abundance of chambered and non-chambered hexactinellid sponges at this locality - as compared to hypercalcified representatives - highlight the importance of this group of sponges in reef and reefal limestones in central and east Tethys (China, Caucasia, Iran. 

  10. Was it the CO2 or the sulfur that did it? The mechanism of mass extinction of continental vertebrates at the end-Triassic extinction.

    Science.gov (United States)

    Olsen, P. E.; Schaller, M. F.; Kent, D. V.; Et-Touhami, M.

    2012-04-01

    Eruption of the giant Central Atlantic Magmatic Province (CAMP) is temporally linked to the end-Triassic extinction (ETE) event (1,2,3,4,5). Proposed killing mechanisms for plants and marine biota have included both CO2 (4) and sulfur aerosols (3,6). Here we examine the kill mechanisms of the CAMP for land animals where we seek to explain the selectivity of the extinctions. One striking aspect of Late Triassic continental communities is the prominent latitudinal provinciality with diverse crurotarsians (crocodile-relatives) and other non-dinosaurs in the tropics and much higher dinosaur diversity in the higher latitudes (7). Only a very few crurotarsian lineages survived the ETE, and a near-homogenization of continental vertebrate assemblages ensued. Background high CO2 concentration in the Late Triassic resulted in lack of polar ice and probably very high-temperature tropical continental interiors. While a doubling of CO2 associated with CAMP eruptions produced a few degree increase in average temperatures (depending on the sensitivity), plausibly leading to some tropical lethality, how this produced a mass extinction in higher, cooler latitudes is harder to explain. While successive CAMP eruptions contributed to CO2 doublings over hundreds to thousands of years, taking two orders of magnitude longer to return to background, EACH major CAMP eruption produced an abrupt sulfur aerosol cooling lasting several years or decades, depending eruption duration. But there were many of these coolings as opposed to the few super-greenhouse warmings suggested by the CO2 proxy data (4,5). The scale of these sulfur injections would have been orders of magnitude larger than anything seen historically (8) possibly leading to freezing tropical temperatures. Both cruotarsians and dinosaurs as well as most other "reptiles", with their presumably uricotelic nitrogen waste systems (9) were been relatively resistant to heat induced water stress, but the former lack insolation, while the

  11. Coating thickness measurement

    International Nuclear Information System (INIS)

    1976-12-01

    The standard specifies measurements of the coating thickness, which make use of beta backscattering and/or x-ray fluorescence. For commonly used combinations of coating material and base material the appropriate measuring ranges and radionuclides to be used are given for continuous as well as for discontinuous measurements

  12. Ostracods (Crustacea associated with microbialites across the Permian-Triassic boundary in Dajiang (Guizhou Province, South China

    Directory of Open Access Journals (Sweden)

    Marie-Beatrice FOREL

    2012-08-01

    Full Text Available 26 samples were processed for a taxonomic study of ostracods from the Upper Permian (Changhsingian - Lower Triassic (Griesbachian interval of the Dajiang section, Guizhou Province, South China. 112 species belonging to 27 genera are recognized. Five new species are described: Acratia candyae sp. nov, Bairdia adelineae sp. nov., Bairdia? huberti sp. nov., Bairdia jeromei sp. nov., Orthobairdia jeanlouisi sp. nov. The unexpected survival faunas associated with microbial formations in the aftermath of the end-Permian extinction are documented for the first time. Ostracod biodiversity variations and palaeo-environmental modifications associated with microbial growth through the Permian-Triassic boundary (PTB are discussed.

  13. A new marine reptile from the Triassic of China, with a highly specialized feeding adaptation.

    Science.gov (United States)

    Cheng, Long; Chen, Xiao-Hong; Shang, Qing-Hua; Wu, Xiao-Chun

    2014-03-01

    The Luoping fauna (Anisian, Middle Triassic) is probably the oldest of Triassic faunas in Guizhou-Yunnan area, China. The reptilian assemblage is comprised of ichthyosaurs, a number of sauropterygians (pachypleurosaur-like forms), saurosphargids, protorosaurs, and archosauriforms. Here, we report on a peculiar reptile, newly found in this fauna. Its dentition is fence or comb-like and bears more than 175 pleurodont teeth in each ramus of the upper and lower jaws, tooth crown is needle-like distally and blade-shaped proximally; its rostrum strongly bends downward and the anterior end of its mandible expands both dorsally and ventrally to form a shovel-headed structure; and its ungual phalanges are hoof-shaped. The specializations of the jaws and dentition indicate that the reptile may have been adapted to a way of bottom-filter feeding in water. It is obvious that such delicate teeth are not strong enough to catch prey, but were probably used as a barrier to filter microorganisms or benthic invertebrates such as sea worms. These were collected by the specialized jaws, which may have functioned as a shovel or pushdozer (the mandible) and a grasper or scratcher (the rostrum). Our preliminary analysis suggests that the new reptile might be more closely related to the Sauropterygia than to other marine reptiles.

  14. Early Triassic wrinkle structures on land: stressed environments and oases for life

    Science.gov (United States)

    Chu, Daoliang; Tong, Jinnan; Song, Haijun; Benton, Michael J.; Bottjer, David J.; Song, Huyue; Tian, Li

    2015-06-01

    Wrinkle structures in rocks younger than the Permian-Triassic (P-Tr) extinction have been reported repeatedly in marine strata, but rarely mentioned in rocks recording land. Here, three newly studied terrestrial P-Tr boundary rock succession in North China have yielded diverse wrinkle structures. All of these wrinkles are preserved in barely bioturbated shore-shallow lacustrine siliciclastic deposits of the Liujiagou Formation. Conversely, both the lacustrine siliciclastic deposits of the underlying Sunjiagou Formation and the overlying Heshanggou Formation show rich bioturbation, but no wrinkle structures or other microbial-related structures. The occurrence of terrestrial wrinkle structures in the studied sections reflects abnormal hydrochemical and physical environments, presumably associated with the extinction of terrestrial organisms. Only very rare trace fossils occurred in the aftermath of the P-Tr extinction, but most of them were preserved together with the microbial mats. This suggests that microbial mats acted as potential oases for the surviving aquatic animals, as a source of food and oxygen. The new finds suggests that extreme environmental stresses were prevalent both in the sea and on land through most of the Early Triassic.

  15. Dobrogeria aegyssensis, a new early Spathian (Early Triassic) coelacanth from North Dobrogea (Romania)

    Science.gov (United States)

    Cavin, Lionel; Grădinaru, Eugen

    2014-06-01

    The Early Triassic witnessed the highest taxic diversity of coelacanths (or Actinistia), a clade with a single living genus today. This peak of diversity is accentuated here with the description of a new coelacanth discovered in the lower Spathian (Upper Olenekian, Lower Triassic) cropping out in the Tulcea Veche (Old Tulcea) promontory, in the city of Tulcea, in North Dobrogea, Romania. The bone remains were preserved in a block of limestone, which was chemically dissolved. The resulting 3D and matrix-free ossifications correspond mostly to elements of the skull and branchial apparatus. Posterior parietals, postparietal with associated prootic and basisphenoid allow a precise description of the neurocranium. Ossifications of the lower jaw, together with branchial and pectoral elements, complete the description of this coelacanth and support the coining of a new generic and specific name, Dobrogeria aegyssensis. A phylogenetic analysis of actinistians with the new species recovers clades which were found in most recent analyses, i.e. the Sasseniidae, the Laugiidae, the Coelacanthiformes, the Latimerioidei, the Mawsoniidae and the Latimeriidae, and identifies the new taxon as a non-latimerioid coelacanthiform.

  16. Neutron activation analysis of Permian-Triassic boundary layer samples at the Selong Site in China

    International Nuclear Information System (INIS)

    Miyamoto, Y.; Sakamoto, K.; Mingqing, W.

    1997-01-01

    Thirty samples from a limestone stratum across the Permian-Triassic (P-Tr) boundary layer in China were analyzed for 30 elements by instrumental neutron activation analysis, wavelength dispersive X-ray fluorescence and ICP-MS, and also for mineral compositions with a powder X-ray diffractometer. The depth profile was found to indicate a sudden change of elemental and mineral compositions across the P-Tr boundary. Also the profile showed several peaks in elemental concentrations in the lower Permian layered samples as well as in the overlying Triassic strata, which are associated with the change of mineral compositions. Elemental profiles were found to be classified into 4 groups and to give some insights in the geochemical records. Ir is far less abundant (0.1 ppt) compared with that of the K-T boundaries (10 ppb), and the Ir/Co ratio is outside the K-T and Cl chondrite trends. This change of elementary profile is suggestive of the internal causes rather than the external ones such as an asteroid impact for the mass extinction at the P-Tr boundary. (author)

  17. FIRST RECORD OF ICHTHYOSAURS IN SICILY(UPPER TRIASSIC OF MONTE SCALPELLO, CATANIA PROVINCE

    Directory of Open Access Journals (Sweden)

    CRISTIANO DAL SASSO

    2014-03-01

    Full Text Available Here we report for the first time on the presence of ichthyosaurs in Sicily, southern Italy. The deposit of origin (Mufara Formation can be dated to the upper Carnian (Tuvalian substage based on a typical association of ammonites, one of which (Shastites sp. is embedded in the sediment still encrusting one of the bone specimens recently found. The latter consist of two isolated vertebral centra that are referred to the Ichthyosauria thanks to their disk-like shape (i.e. they are much taller than long combined with the amphicelous condition, lack of transverse processes, and presence of rib articulations on the central sides. The largest specimen is more precisely an anterior dorsal vertebra from an adult individual, ascribed to Shastasauridae indet. By the presence of elongated reniform diapophyseal facets, cranially not truncated, and absence of parapophyses. The smaller specimen represents an anterior cervical element from an immature individual of a likely smaller-sized, indeterminate taxon. These finds indicate that the biodiversity of the Monte Scalpello Triassic fauna is higher than previously known, but above all represent the southernmost occurrence of Triassic ichthyosaurs in the western Tethys basin.

  18. Ichthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic-Jurassic boundary

    Science.gov (United States)

    Fischer, Valentin; Cappetta, Henri; Vincent, Peggy; Garcia, Géraldine; Goolaerts, Stijn; Martin, Jeremy E.; Roggero, Daniel; Valentin, Xavier

    2014-12-01

    Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian-earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial `type' series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction.

  19. A new marine reptile from the Triassic of China, with a highly specialized feeding adaptation

    Science.gov (United States)

    Cheng, Long; Chen, Xiao-Hong; Shang, Qing-Hua; Wu, Xiao-Chun

    2014-03-01

    The Luoping fauna (Anisian, Middle Triassic) is probably the oldest of Triassic faunas in Guizhou-Yunnan area, China. The reptilian assemblage is comprised of ichthyosaurs, a number of sauropterygians (pachypleurosaur-like forms), saurosphargids, protorosaurs, and archosauriforms. Here, we report on a peculiar reptile, newly found in this fauna. Its dentition is fence or comb-like and bears more than 175 pleurodont teeth in each ramus of the upper and lower jaws, tooth crown is needle-like distally and blade-shaped proximally; its rostrum strongly bends downward and the anterior end of its mandible expands both dorsally and ventrally to form a shovel-headed structure; and its ungual phalanges are hoof-shaped. The specializations of the jaws and dentition indicate that the reptile may have been adapted to a way of bottom-filter feeding in water. It is obvious that such delicate teeth are not strong enough to catch prey, but were probably used as a barrier to filter microorganisms or benthic invertebrates such as sea worms. These were collected by the specialized jaws, which may have functioned as a shovel or pushdozer (the mandible) and a grasper or scratcher (the rostrum). Our preliminary analysis suggests that the new reptile might be more closely related to the Sauropterygia than to other marine reptiles.

  20. Structural complexity at and around the Triassic-Jurassic GSSP at Kuhjoch, Northern Calcareous Alps, Austria

    Science.gov (United States)

    Palotai, M.; Pálfy, J.; Sasvári, Á.

    2017-10-01

    One of the key requirements for a Global Stratotype Section and Point (GSSP) is the absence of tectonic disturbance. The GSSP for the Triassic-Jurassic system boundary was recently defined at Kuhjoch, Northern Calcareous Alps, Austria. New field observations in the area of the Triassic-Jurassic boundary GSSP site demonstrate that the overturned, tight, and almost upright Karwendel syncline was formed at semibrittle deformation conditions, confirmed by axial planar foliation. Tight to isoclinal folds at various scales were related to a tectonic transport to the north. Brittle faulting occurred before and after folding as confirmed by tilt tests (the rotation of structural data by the average bedding). Foliation is ubiquitous in the incompetent units, including the Kendlbach Formation at the GSSP. A reverse fault (inferred to be formed as a normal fault before folding) crosscuts the GSSP sections, results in the partial tectonic omission of the Schattwald Beds, and thus makes it impossible to measure a complete and continuous stratigraphic section across the whole Kendlbach Formation. Based on these observations, the Kuhjoch sections do not fulfil the specific requirement for a GSSP regarding the absence of tectonic disturbances near boundary level.

  1. Mineralogy and petrography of samples of Permo-Triassic sedimentary strata from Cumbria

    International Nuclear Information System (INIS)

    Kemp, S.J.; Milodowski, A.E.; Bloodworth, A.J.

    1989-03-01

    The mineralogy and petrography of Permo-Triassic sediments from Cumbria are described. The samples are duplicates of those selected for sorption experiments by Harwell Laboratory and are considered representative of Permo-Triassic strata underlying the BNFL Sellafield site. The regional geological context of the samples is briefly discussed. X-ray diffraction analysis indicates that the St Bees Sandstone and Eden Shales samples are predominantly composed of quartz with minor feldspar, gypsum and hematite. The clay assemblage is formed of dioctahedral mica and trioctahedral chloride with minor kaolinite. Diagnostic testing also reveals the presence of corrensite, a regularly interstratified chlorite-smectite, in one of the samples. Possible diagenetic processes responsible for corrensite formation, including the alteration of originally deposited smectite by magnesium-rich pore waters, are discussed. Modelling of the diffraction profile indicates that the chlorite and corrensite are iron-rich species. Back scattered electron microscopy shows the samples to be typical red bed sediments exhibiting framework grain dissolution, the breakdown and replacement of unstable ferromagnesian minerals being accompanied by the precipitation of hematite and anatase. Particle-size analysis shows similar distributions for the St Bees Sandstone samples but a greater proportion of clay material in the Eden Shales. (author)

  2. SOME INOZOID SPONGES FROM UPPER TRIASSIC (NORIAN-RHAETIAN NAYBAND FORMATION OF CENTRAL IRAN

    Directory of Open Access Journals (Sweden)

    BABA SENOWBARI-DARYAN

    1997-11-01

    Full Text Available Some small-scaled Norian-Rhaetian reefs and reef mounds are imbedded within the shales, siltstones and siliciclastic-carbonate deposits of the Nayband Formation in central Iran. These deposits belong to the central Iranian plate as part of the Cimmerian Continent. Most of the biogenic rocks have a biostromal geometry, biohermal constructions are rare. Inozoid, sphinctozoid, and chaetetid sponges are, beside of corals and other reef builders, the most important reef organisms within these bioconstructions. In some reefs a variety of hexactinellid sponges also occur. The following inozoid sponges are described in this paper: Radiofibra norica n. sp., Permocorynella maxima n. sp., ?Sestrostomella robusta, Marawandia iranica, n. gen., n. sp. and Enaulofungia? triassica n. sp. The first four taxa are among the most abundant sponges within the Nayband Formation where it is exposed in several localities in central Iran. Enaulofungia? triassica, however, is not an abundant sponge there. These inozoid sponges have never been reported from the Triassic deposits of this region. Radiofibra, until now known only from the Upper Permian of Djebel Tebaga (Tunisia, is reported here for the first time from Triassic rocks. The stratigraphic as well as the paleogeographic distribution of all the genera are discussed.   

  3. A new rauisuchid (Archosauria, Pseudosuchia from the Upper Triassic (Norian of New Mexico increases the diversity and temporal range of the clade

    Directory of Open Access Journals (Sweden)

    Emily J. Lessner

    2016-09-01

    Full Text Available Rauisuchids are large (2–6 m in length, carnivorous, and quadrupedal pseudosuchian archosaurs closely related to crocodylomorphs. Though geographically widespread, fossils of this clade are relatively rare in Late Triassic assemblages. The middle Norian (∼212 Ma Hayden Quarry of northern New Mexico, USA, in the Petrified Forest Member of the Chinle Formation, has yielded isolated postcranial elements and associated skull elements of a new species of rauisuchid. Vivaron haydeni gen. et. sp. nov. is diagnosed by the presence of two posteriorly directed prongs at the posterior end of the maxilla for articulation with the jugal. The holotype maxilla and referred elements are similar to those of the rauisuchid Postosuchus kirkpatricki from the southwestern United States, but V. haydeni shares several maxillary apomorphies (e.g., a distinct dropoff to the antorbital fossa that is not a ridge, a straight ventral margin, and a well defined dental groove with the rauisuchid Teratosaurus suevicus from the Norian of Germany. Despite their geographic separation, this morphological evidence implies a close phylogenetic relationship between V. haydeni and T. suevicus. The morphology preserved in the new Hayden Quarry rauisuchid V. haydeni supports previously proposed and new synapomorphies for nodes within Rauisuchidae. The discovery of Vivaron haydeni reveals an increased range of morphological disparity for rauisuchids from the low-paleolatitude Chinle Formation and a clear biogeographic connection with high paleolatitude Pangea.

  4. Formation mechanisms and sequence response of authigenic grain-coating chlorite: evidence from the Upper Triassic Xujiahe Formation in the southern Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Yu Yu

    2016-11-01

    Full Text Available Abstract Authigenic grain-coating chlorite is widely distributed in the clastic rocks of many sedimentary basins around the world. These iron minerals were mainly derived from flocculent precipitates formed when rivers flow into the ocean, especially in deltaic environments with high hydrodynamic conditions. At the same time, sandstone sequences with grain-coating chlorites also tend to have relatively high glauconite and pyrite content. EPMA composition analysis shows that glauconites with “high Al and low Fe” content indicate slightly to semi-saline marine environments with weak alkaline and weakly reducing conditions. By analyzing the chlorite-containing sandstone bodies of the southern Sichuan Xujiahe Formation, this study found that chlorite was mainly distributed in sedimentary microfacies, including underwater distributary channels, distributary channels, shallow lake sandstone dams, and mouth bars. Chlorite had a tendency to form in the upper parts of sandstone bodies with signs of increased base level, representing the influence of marine (lacustrine transgression. This is believed to be influenced by megamonsoons in the Middle and Upper Yangtze Region during the Late Triassic Epoch. During periods of abundant precipitation, river discharges increased and more Fe particulates flowed into the ocean (lake. In the meantime, increases or decreases in lake level were only affected by precipitation for short periods of time. The sedimentary environment shifted from weakly oxidizing to weak alkaline, weakly reducing conditions as sea level increased, and Fe-rich minerals as authigenic chlorite and glauconite began to form and deposit.

  5. Coating thickness measuring device

    International Nuclear Information System (INIS)

    Joffe, B.B.; Sawyer, B.E.; Spongr, J.J.

    1984-01-01

    A device especially adapted for measuring the thickness of coatings on small, complexly-shaped parts, such as, for example, electronic connectors, electronic contacts, or the like. The device includes a source of beta radiation and a radiation detector whereby backscatter of the radiation from the coated part can be detected and the thickness of the coating ascertained. The radiation source and detector are positioned in overlying relationship to the coated part and a microscope is provided to accurately position the device with respect to the part. Means are provided to control the rate of descent of the radiation source and radiation detector from its suspended position to its operating position and the resulting impact it makes with the coated part to thereby promote uniformity of readings from operator to operator, and also to avoid excessive impact with the part, thereby improving accuracy of measurement and eliminating damage to the parts

  6. Thick brane solutions

    International Nuclear Information System (INIS)

    Dzhunushaliev, Vladimir; Minamitsuji, Masato; Folomeev, Vladimir

    2010-01-01

    This paper gives a comprehensive review on thick brane solutions and related topics. Such models have attracted much attention from many aspects since the birth of the brane world scenario. In many works, it has been usually assumed that a brane is an infinitely thin object; however, in more general situations, one can no longer assume this. It is also widely considered that more fundamental theories such as string theory would have a minimal length scale. Many multidimensional field theories coupled to gravitation have exact solutions of gravitating topological defects, which can represent our brane world. The inclusion of brane thickness can realize a variety of possible brane world models. Given our understanding, the known solutions can be classified into topologically non-trivial solutions and trivial ones. The former class contains solutions of a single scalar (domain walls), multi-scalar, gauge-Higgs (vortices), Weyl gravity and so on. As an example of the latter class, we consider solutions of two interacting scalar fields. Approaches to obtain cosmological equations in the thick brane world are reviewed. Solutions with spatially extended branes (S-branes) and those with an extra time-like direction are also discussed.

  7. Paleomagnetism and Magnetostratigraphy of Upper Permian to Lower Triassic (?) Beaufort Group Strata at Bethulie, Karoo Basin, Free State Province, South Africa

    Science.gov (United States)

    Geissman, J. W.; Gastaldo, R. A.; Neveling, J.; Makubalo, S.

    2017-12-01

    A multifaceted approach to understand the timing of interpreted environmental changes during the Late Permian to possibly Early Triassic (?) time in the Beaufort Group strata of the Karoo Basin includes work to establish robust magnetic polarity records for sections previously interpreted to encompass end-Permian extinction events. Demonstrating the preservation of an early-acquired remanence (RM) in Karoo strata is required for a robust magnetostratigraphy. Yet, this is challenging due to thermochemical effects related to the Early Jurassic (ca. 183 Ma) Karoo Large Igneous Province (LIP), and the NE to SW increase in burial diagenesis attending Cape Fold Belt tectonism. Documentation of a primary RM in these strata, which appears to be preserved in some areas, requires careful laboratory- and field-based assessment. We report data from 53 sites collected at the well-studied Bethulie section, Free State Province, in which several samples per individual horizon to assess ChRM uniformity. Strata well-removed from dikes yield both normal and reverse polarity ChRM. It is always the case that the first-removed RM is a NNW seeking, moderate to steep negative-inclination ChRM (normal polarity); NRM intensities are typically 1 to 5 mA/m. Sites BT15 and BT21, which are located in strata lying some 4 m below the often-cited "event bed" interval inferred to be the terrestrial expression of the Permian/Triassic boundary, is dominated by a well-defined reverse RM with a normal overprint RM unblocked below 400oC, implying elevated temperatures (i.e., 100 to 250oC+) for ca. 1 Ma (+/-). Contact tests are positive but complicated. Host strata collected in distances equal to or less than 1-2 dike widths from the intrusions have been thermally remagnetized and demonstrate high NRM intensities (> 50 mA/m). Collectively, we interpret these data to indicate that any ChRM, with the exception of those from host strata in baked contacts, that persists above Tlub of 425oC is pre-Karoo LIP

  8. Sr evolution in the Upper Permian and Lower Triassic carbonates, northeast Sichuan basin, China: Constraints from chemistry, isotope and fluid inclusions

    International Nuclear Information System (INIS)

    Li, Kaikai; Cai, Chunfang; Jiang, Lei; Cai, Liulu; Jia, Lianqi; Zhang, Bing; Xiang, Lei; Yuan, Yuyang

    2012-01-01

    Petrographic features, C, O and Sr isotopes, rare earth and trace elements were determined, and fluid inclusions were analyzed on various stages of interparticle cements and vug-fillings from the Upper Permian and Lower Triassic sour reservoirs in northeastern Sichuan basin. The aim was to assess the origin and evolution of palaeo-waters in the carbonates. The original water was contemporary seawater, from which marine cements precipitated with slightly high Sr contents (mean 1911 ppm), 87 Sr/ 86 Sr ratios from 0.7067 to 0.7082 and nonluminescent CL. The palaeo-seawater was diluted by meteoric water, as indicated by bright cathodoluminescence (CL) and Sr-depletion (0–516 ppm) in low-temperature calcite. When buried to temperatures of about 60–90 °C during Middle to Late Triassic, the palaeo-water was enriched in Sr released from the transformation of precursor aragonite and calcite to dolomite, resulting in precipitation of substantial pre-bitumen Sr-rich minerals (SrSO 4 and SrCO 3 ). For un-dolomitized limestone sections, aragonite neomorphism may have contributed Sr to the precipitation of small amounts of Sr-bearing minerals and calcite crystals with elevated homogenization temperatures (HTs, mainly from 90 to 130 °C) and wide Sr contents (from 34 to 3825 ppm), as recorded in stage III calcite. Since the Middle Jurassic, almost all of the early stage celestite and significant amounts of solid CaSO 4 have been consumed by reactions with hydrocarbons (i.e., TSR), resulting in water enriched in isotopically light CO 2 and HCO 3 - ,Sr 2+ ,Ba 2+ and Eu 2+ , as recorded in calcite with low δ 13 C values (down to −18.9‰), 87 Sr/ 86 Sr ratios from 0.7072 to 0.7076, high HTs (mainly 110–198 °C), positive Eu anomalies and high Sr and Ba contents. Subsequently, the water was uplifted and cooled down to about 115 °C, celestite and strontianite were precipitated with the occurrence of natural elemental S immiscible inclusions. TSR may have produced

  9. Conodont succession and reassessment of major events around the Permian-Triassic boundary at the Selong Xishan section, southern Tibet, China

    Science.gov (United States)

    Yuan, Dong-Xun; Zhang, Yi-Chun; Shen, Shu-Zhong

    2018-02-01

    A major discrepancy for the age of the Selong Group from middle Cisuralian (Early Permian) to Changhsingian resulted from previous reports of Sakmarian, Kungurian and Guadalupian (Middle Permian) conodonts and Lopingian (Late Permian) brachiopods. Recently, Cisuralian and Guadalupian conodonts were reported again from the Selong Group and the basal part of the Kangshare Formation at the Selong section, but the age discrepancy remains. We present our conodont materials based on large samples collected from the Selong Group and our interpretation based on identifications using a sample population approach. Three conodont zones are recognized in our re-investigation of the upper part of the Selong Group. They include the Vjalovognathus sp., the Mesogondolella hendersoni, and the M. sheni zones, in ascending order. These zones are overlain by the basal Triassic Hindeodus parvus Zone and the Otoceras woodwardi Zone. Our reassessment of conodonts reported by previous studies from Selong and nearby sections suggest that all specimens consistently point to a Lopingian age; the upper part of the Selong Group is latest Changhsingian in age based on the presence of Clarkina orchardi and Mesogondolella sheni. Previously reported early Cisuralian and Guadalupian conodonts are misidentified using a form species concept. A hiatus may be present at the erosional surface between the Selong Group and the Waagenites Bed of the basal part of the Kangshare Formation. However, the hiatus is minimal because conodont and brachiopod assemblages above and below this surface are very similar, and it results from a latest Changhsingian transgression just before the extinction that follows a global latest Changhsingian regression. There is a distinct rapid end-Permian mass extinction at Selong within the Waagenites Bed, as indicated by the disappearances of all benthic brachiopods, rugose corals and Permian bryozoans. The burst of Clarkina species in the Waagenites Bed and throughout the

  10. Intense and widespread seismicity during the end-Triassic mass extinction due to emplacement of a large igneous province

    DEFF Research Database (Denmark)

    Lindström, Sofie; Pedersen, Gunver Krarup; Schootbrugge, Bas van de

    2015-01-01

    Multiple levels of earthquake-induced soft-sediment deformations (seismites) are concentrated in the end-Triassic mass extinction interval across Europe. The repetitive nature of the seismites rules out an origin by an extraterrestrial impact. Instead, this intense seismic activity is linked...

  11. Disentangling Diagenesis From the Rock Record: An Example From the Permo-Triassic Wordie Creek Formation, East Greenland

    Science.gov (United States)

    Roberts, J.; Turchyn, A. V.; Wignall, P. B.; Newton, R. J.; Vane, C. H.

    2018-01-01

    The measurement of isotope ratios in sedimentary rocks deposited over geological time can provide key insights to past environmental change over important intervals in the past. However, it is important to be aware that secondary alteration can overprint the original isotopic records. We demonstrate this principle using high-resolution carbon, sulfur, and oxygen isotope measurements in organic carbon, pyrite, and carbonate minerals (δ13Corg, δ34Spyr, δ34SCAS, δ13Ccarb, and δ18Ocarb) and kerogen analyses (HI and OI) from the Wordie Creek Formation, East Greenland. These sediments were initially deposited across the Permo-Triassic transition, but as we will show, the carbonate record has been altered by interaction with meteoric water significantly after initial deposition. Comparison of the better preserved organic carbon and pyrite records with a proximal Permo-Triassic sequence reveals significant pyrite-sulfur isotope variability across the Permo-Triassic transition. This regional heterogeneity argues against basin-wide euxinia and instead suggests localized changes in sulfur fractionation in response to variations in organic carbon flux. This hypothesis can be used to explain seemingly inconsistent regional trends in other sulfur isotopes across the Permo-Triassic transition.

  12. A new stem group echinoid from the Triassic of China leads to a revised macroevolutionary history of echinoids during the end-Permian mass extinction

    Science.gov (United States)

    Thompson, Jeffrey R.; Hu, Shi-xue; Zhang, Qi-Yue; Petsios, Elizabeth; Cotton, Laura J.; Huang, Jin-Yuan; Zhou, Chang-yong; Wen, Wen; Bottjer, David J.

    2018-01-01

    The Permian-Triassic bottleneck has long been thought to have drastically altered the course of echinoid evolution, with the extinction of the entire echinoid stem group having taken place during the end-Permian mass extinction. The Early Triassic fossil record of echinoids is, however, sparse, and new fossils are paving the way for a revised interpretation of the evolutionary history of echinoids during the Permian-Triassic crisis and Early Mesozoic. A new species of echinoid, Yunnanechinus luopingensis n. sp. recovered from the Middle Triassic (Anisian) Luoping Biota fossil Lagerstätte of South China, displays morphologies that are not characteristic of the echinoid crown group. We have used phylogenetic analyses to further demonstrate that Yunnanechinus is not a member of the echinoid crown group. Thus a clade of stem group echinoids survived into the Middle Triassic, enduring the global crisis that characterized the end-Permian and Early Triassic. Therefore, stem group echinoids did not go extinct during the Palaeozoic, as previously thought, and appear to have coexisted with the echinoid crown group for at least 23 million years. Stem group echinoids thus exhibited the Lazarus effect during the latest Permian and Early Triassic, while crown group echinoids did not.

  13. Full reflector thickness and isolation thickness on neutron transport

    International Nuclear Information System (INIS)

    Sakai, Tomohiro; Naito, Yoshitaka; Komuro, Yuichi.

    1988-08-01

    A method to determine ''full reflector thickness'' and ''isolation thickness'', which is utilized for criticality safety evaluation on nuclear fuel facilities, was proposed in this paper. Firstly, a calculation was tryed to obtain the two kinds of thicknesses from the result of criticality calculations for a specific case. Then, two simple equations which calculates the two kinds of thicknesses were made from the relation between reflector (or isolator) thickness and k eff , and one-group diffusion theory. Finally, we proposed a new method to determine the thicknesses. From the method we proposed, ''full reflector thickness'' and ''isolation thickness'' can be obtain using the equations and migration length of the reflector (or isolator) and infinite and effective multiplication factor of the fuel. (author)

  14. Astronomical tuning of the end-Permian extinction and the Early Triassic Epoch of South China and Germany

    Science.gov (United States)

    Li, Mingsong; Ogg, James; Zhang, Yang; Huang, Chunju; Hinnov, Linda; Chen, Zhong-Qiang; Zou, Zhuoyan

    2016-05-01

    The timing of the end-Permian mass extinction and subsequent prolonged recovery during the Early Triassic Epoch can be established from astronomically controlled climate cycles recorded in continuous marine sedimentary sections. Astronomical-cycle tuning of spectral gamma-ray logs from biostratigraphically-constrained cyclic stratigraphy through marine sections at Meishan, Chaohu, Daxiakou and Guandao in South China yields an integrated time scale for the Early Triassic, which is consistent with scaling of magnetostratigraphy from climatic cycles in continental deposits of the Germanic Basin. The main marine mass extinction interval at Meishan is constrained to less than 40% of a 100-kyr (kilo-year) cycle (i.e., marine reptiles in the Mesozoic at Chaohu that are considered to represent a significant recovery of marine ecosystems did not appear until 4.7 myr (million years) after the end-Permian extinction. The durations of the Griesbachian, Dienerian, Smithian and Spathian substages, including the uncertainty in placement of widely used conodont biostratigraphic datums for their boundaries, are 1.4 ± 0.1, 0.6 ± 0.1, 1.7 ± 0.1 and 1.4 ± 0.1 myr, implying a total span for the Early Triassic of 5.1 ± 0.1 myr. Therefore, relative to an assigned 251.902 ± 0.024 Ma for the Permian-Triassic boundary from the Meishan GSSP, the ages for these substage boundaries are 250.5 ± 0.1 Ma for base Dienerian, 249.9 ± 0.1 Ma for base Smithian (base of Olenekian stage), 248.2 ± 0.1 Ma for base Spathian, and 246.8 ± 0.1 Ma for the base of the Anisian Stage. This astronomical-calibrated timescale provides rates for the recurrent carbon isotope excursions and for trends in sedimentation accumulation through the Early Triassic of studied sections in South China.

  15. Late ordovician stratigraphy, zircon provenance and tectonics, Lachlan Fold Belt, southeastern Australia

    International Nuclear Information System (INIS)

    Fergusson, C.L.; Fanning, C.M.

    2002-01-01

    Ordovician quartz turbidites of the Lachlan Fold Belt in southeastern Australia accumulated in a marginal sea and overlapped an adjoining island arc (Molong volcanic province) developed adjacent to eastern Gondwana. The turbidite succession in the Shoalhaven River Gorge, in the southern highlands of New South Wales, has abundant outcrop and graptolite sites. The succession consists of, from the base up, a unit of mainly thick-bedded turbidites (undifferentiated Adaminaby Group), a unit with conspicuous bedded chert (Numeralla Chert), a unit with common thin-bedded turbidites [Bumballa Formation (new name)] and a unit of black shale (Warbisco Shale). Coarse to very coarse sandstone in the Bumballa Formation is rich in quartz and similar to sandstone in the undifferentiated Adaminaby Group. Detrital zircons from sandstone in the Bumballa Formation, and from sandstone at a similar stratigraphic level from the upper Adaminaby Group of the Genoa River area in eastern Victoria, include grains as young as 453-473 Ma, slightly older than the stratigraphic ages. The dominant detrital ages are in the interval 500-700 Ma (Pacific Gondwana component) with a lessor concentration of Grenville ages (1000-1300 Ma). This pattern resembles other Ordovician sandstones from the Lachlan Fold Belt and also occurs in Triassic sandstones and Quaternary sands from eastern Australia. The Upper Ordovician succession is predominantly fine grained, which reflects reduced clastic inputs from the source in the Middle Cambrian to earliest Ordovician Ross-Delamerian Fold Belts that developed along the eastern active margin of Gondwana. Development of subduction zones in the Late Ordovician marginal sea are considered to be mainly responsible for the diversion of sediment and the resulting reduction in the supply of terrigenous sand to the island arc and eastern part of the marginal sea. Sixty zircons from each sample were analysed and results are presented. Methods following standard procedures

  16. A NEW LEPIDOSAUROMORPH REPTILE FROM THE MIDDLE TRIASSIC OF THE DOLOMITES (NORTHERN ITALY

    Directory of Open Access Journals (Sweden)

    SILVIO RENESTO

    2003-11-01

    Full Text Available A new genus and species of diapsid reptile is described. The specimen was collected from the Anisian (Middle Triassic succession of Monte Prà della Vacca (Kühwiesenkopf in the Dolomites of Braies (Bolzano/Bozen, Northern Italy. Despite being incomplete, the specimen shows enough characters to allow its placement within Lepidosauriformes, close to the Middle Jurassic genus Marmoretta. The importance of this find lies in the great rarity of lepidosauriforms of Anisian age, an epoch approximating the appearance of the first members of the true Lepidosauria (rhyncocephalians and squamates. The new genus may thus add knowledge to the diversity of early lepidosaurians. Some characters of the skeleton, mainly of the forelimb, suggest a terrestrial, perhaps arboreal life style. 

  17. Ground-water conditions in the Triassic aquifer in Deaf Smith and Swisher Counties

    International Nuclear Information System (INIS)

    Duffin, G.L.

    1984-12-01

    In April 1984, the Director of the Nuclear Waste Programs of the Governor's Office requested a study be undertaken by the Texas Department of Water Resources on the ground-water conditions in the Triassic aquifer in Deaf Smith and Swisher Counties. The need for the study was prompted by the U.S. Department of Energy's (DOE) announcement that consideration was being given to locating high-level nuclear waste repository sites in these counties and by the concern over what impacts operation of such sites might have on the ground-water resources in the area. The results of the study, including a discussion of the occurrence of ground water and a tabulation of basic data obtained during the investigation are presented in this report

  18. On origin of radium aureoles around Triassic uranium mineralization zones in the Peribaltic Syneclize

    International Nuclear Information System (INIS)

    Szewczyk, J.

    1985-01-01

    In the second half of the seventies, the Geological Institute began search for sandstone uranium deposits in the Triassic of the Peribaltic Syneclize. Detailed analysis of both laboratory and geophysical data showed presence of radium (Ra-226) aureoles around uranium ore bodies hitherto found by drillings. The mechanism of origin of the aureoles is explained and methodological proposal of their use in further search for uranium deposits is given. Theoretical modelling showed that origin of the aureoles is mainly related to movement of deposit waters percolating through uranium ore body. The influence of shape and dimensions of radium aureole-generating ore bodies on extent of the aureoles appears subordinate. Aureoles interesting from the point of view of prospecting may originate when velocity of percolating waters falls within the range from 10 -8 to 10 -6 cm/s. 23 refs., 7 figs., 1 tab. (author)

  19. Tectonic contact beetwen Paleozoic and Triassic rocks south of Podolševa (Slovenia

    Directory of Open Access Journals (Sweden)

    Bogomir Celarc

    2002-12-01

    Full Text Available Tectonic contact between Paleozoic and Triassic rocks south of Podolševa, which passes prominent cliffs over the left bank of Savinja river (Klemenča peč, Jamnikova peč, Golerjeva peč, Strevčeva peč and Huda peč, is on the basis of the new mapping a steep fault, dipping to the north. In the last phase, the fault was dextral strike – slip active, before was probably reverse, and can represent accompanying structure of Periadriatic lineament. It was under transpresive tectonic regime and complies with model of positive flower structure.We named it Podol{evski prelom (Podol{eva fault.

  20. The osteology of the basal archosauromorph Tasmaniosaurus triassicus from the Lower Triassic of Tasmania, Australia.

    Directory of Open Access Journals (Sweden)

    Martín D Ezcurra

    Full Text Available Proterosuchidae are the most taxonomically diverse archosauromorph reptiles sampled in the immediate aftermath of the Permo-Triassic mass extinction and represent the earliest radiation of Archosauriformes (archosaurs and closely related species. Proterosuchids are potentially represented by approximately 15 nominal species collected from South Africa, China, Russia, Australia and India, but the taxonomic content of the group is currently in a state of flux because of the poor anatomic and systematic information available for several of its putative members. Here, the putative proterosuchid Tasmaniosaurus triassicus from the Lower Triassic of Hobart, Tasmania (Australia, is redescribed. The holotype and currently only known specimen includes cranial and postcranial remains and the revision of this material sheds new light on the anatomy of the animal, including new data on the cranial endocast. Several bones are re-identified or reinterpreted, contrasting with the descriptions of previous authors. The new information provided here shows that Tasmaniosaurus closely resembles the South African proterosuchid Proterosuchus, but it differed in the presence of, for example, a slightly downturned premaxilla, a shorter anterior process of maxilla, and a diamond-shaped anterior end of interclavicle. Previous claims for the presence of gut contents in the holotype of Tasmaniosaurus are considered ambiguous. The description of the cranial endocast of Tasmaniosaurus provides for the first time information about the anatomy of this region in proterosuchids. The cranial endocast preserves possibly part of the vomero-nasal ( = Jacobson's system laterally to the olfactory bulbs. Previous claims of the absence of the vomero-nasal organs in archosaurs, which is suggested by the extant phylogenetic bracket, are questioned because its absence in both clades of extant archosaurs seems to be directly related with the independent acquisition of a non-ground living

  1. Development of lower Triassic wrinkle structures: implications for the search for life on other planets.

    Science.gov (United States)

    Mata, Scott A; Bottjer, David J

    2009-11-01

    Wrinkle structures are microbially mediated sedimentary structures that are a common feature of Proterozoic and earliest Phanerozoic siliciclastic seafloors on Earth and occur only rarely in post-Cambrian strata. These macroscopic microbially induced sedimentary structures are readily identifiable at the outcrop scale, and their recognition on other planetary bodies by landed missions may suggest the presence of past microbial life. Wrinkle structures of the Lower Triassic (Spathian) Virgin Limestone Member of the Moenkopi Formation in the western United States record an occurrence of widespread microbialite formation in the wake of the end-Permian mass extinction, the largest biotic crisis of the Phanerozoic. Wrinkle structures occur on proximal sandy tempestites deposited within the offshore transition. Storm layers appear to have been rapidly colonized by microbial mats and were subsequently buried by mud during fair-weather conditions. Wrinkle structures exhibit flat-topped crests and sinuous troughs, with associated mica grains oriented parallel to bedding, suggestive of trapping and binding activity. Although Lower Triassic wrinkle structures postdate the widespread occurrence of these features during the Proterozoic and Cambrian, they exhibit many of the same characteristics and environmental trends, which suggests a conservation of microbial formational and preservational processes in subtidal siliciclastic settings on Earth from the Precambrian into the Phanerozoic. In the search for extraterrestrial life, it may be these conservative characteristics that prove to be the most useful and robust for recognizing microbial features on other planetary bodies, and may add to an ever-growing foundation of knowledge for directing future explorations aimed at seeking out macroscopic microbial signatures.

  2. Radioactive thickness gauge (1962)

    International Nuclear Information System (INIS)

    Guizerix, J.

    1962-01-01

    The author describes a thickness gauge in which the scintillating crystal detector alternately 'sees' a radioactive source through the material which is to be measured and then a control source of the same material; the radiations are separated in time by an absorbing valve whose sections are alternately full and hollow. The currents corresponding to the two sources are separated beyond the photomultiplier tube by a detector synchronized with the rotation of the valve. The quotient of these two currents is then obtained with a standard recording potentiometer. It is found that the average value of the response which is in the form G = f(I 1 /I 2 ) is not affected by decay of the radioactive sources, and that it is little influenced by variations of high tension, temperature, or properties of the air in the source detector interval. The performance of the gauge is given. (author) [fr

  3. Thick-Big Descriptions

    DEFF Research Database (Denmark)

    Lai, Signe Sophus

    The paper discusses the rewards and challenges of employing commercial audience measurements data – gathered by media industries for profitmaking purposes – in ethnographic research on the Internet in everyday life. It questions claims to the objectivity of big data (Anderson 2008), the assumption...... communication systems, language and behavior appear as texts, outputs, and discourses (data to be ‘found’) – big data then documents things that in earlier research required interviews and observations (data to be ‘made’) (Jensen 2014). However, web-measurement enterprises build audiences according...... to a commercial logic (boyd & Crawford 2011) and is as such directed by motives that call for specific types of sellable user data and specific segmentation strategies. In combining big data and ‘thick descriptions’ (Geertz 1973) scholars need to question how ethnographic fieldwork might map the ‘data not seen...

  4. Personality in Late Midlife

    DEFF Research Database (Denmark)

    Mortensen, Erik Lykke; Flensborg-Madsen, Trine; Molbo, Drude

    2014-01-01

    To analyze associations in late midlife between sex, age, education and social class, and the Big Five personality traits; to analyze associations between personality traits and cognitive ability in late midlife; and to evaluate how these associations are influenced by demographic factors....

  5. Disentangling The Thick Concept Argument

    DEFF Research Database (Denmark)

    Blomberg, Olle

    2007-01-01

    Critics argue that non-cognitivism cannot adequately account for the existence and nature of some thick moral concepts. They use the existence of thick concepts as a lever in an argument against non-cognitivism, here called the Thick Concept Argument (TCA). While TCA is frequently invoked...

  6. Arsenic, barium, strontium and uranium geochemistry and their utility as tracers to characterize groundwaters from the Espadán–Calderona Triassic Domain, Spain

    Energy Technology Data Exchange (ETDEWEB)

    Giménez-Forcada, Elena, E-mail: e.gimenez@igme.es [Instituto Geológico y Minero de España — IGME, Unidad de Salamanca, Azafranal 48, 37001 Salamanca (Spain); Vega-Alegre, Marisol [University of Valladolid — UVA, Department of Analytical Chemistry, Campus Miguel Delibes, Paseo Belén 7, 47011 Valladolid (Spain)

    2015-04-15

    A set of analytical data from the Espadán–Calderona Triassic Domain aquifers was processed using hierarchical agglomerative cluster analysis (HCA) and principal component analysis (PCA), to achieve a quantitative and independent approach to investigate the characteristics of groundwater composition and possible differences between groundwater flows from Triassic aquifers from the Espadán–Calderona Triassic Domain (Spain). Mineralization in the Triassic series has led to the presence of several metals and metalloids in groundwater, including As, Mn, Fe and U. These are associated with fresher bicarbonate groundwaters, characterized by lower Sr/Ba ratios. Levels containing sulfate evaporitic salt, which are interbedded through the Triassic series, seem to exert a strong influence on the chemistry of several groundwaters, characterized by calcium sulfate facies with high Sr concentration and high Sr/Ba ratios. The application of multivariate statistical techniques to the interpretation of analytical results allows the differentiation of groundwater types occurring in the Triassic aquifers and identification of the role of a number of minor or trace elements and their ratios that can be treated as hydrogeochemical tracers. With them it was possible to correlate the different recharge waters with the tectonic morphology of the Espadán–Calderona Triassic Domain. - Highlights: • Groundwater hydrochemistry of Espadán–Calderona Triassic Domain was investigated. • Multivariate statistical analysis and metal tracers differentiated groundwater types. • The Sr/Ba ratio and As and U concentrations are good indicators of groundwater flows. • The chemistry of groundwater flows correlates with structural morphology of recharge areas.

  7. Arsenic, barium, strontium and uranium geochemistry and their utility as tracers to characterize groundwaters from the Espadán–Calderona Triassic Domain, Spain

    International Nuclear Information System (INIS)

    Giménez-Forcada, Elena; Vega-Alegre, Marisol

    2015-01-01

    A set of analytical data from the Espadán–Calderona Triassic Domain aquifers was processed using hierarchical agglomerative cluster analysis (HCA) and principal component analysis (PCA), to achieve a quantitative and independent approach to investigate the characteristics of groundwater composition and possible differences between groundwater flows from Triassic aquifers from the Espadán–Calderona Triassic Domain (Spain). Mineralization in the Triassic series has led to the presence of several metals and metalloids in groundwater, including As, Mn, Fe and U. These are associated with fresher bicarbonate groundwaters, characterized by lower Sr/Ba ratios. Levels containing sulfate evaporitic salt, which are interbedded through the Triassic series, seem to exert a strong influence on the chemistry of several groundwaters, characterized by calcium sulfate facies with high Sr concentration and high Sr/Ba ratios. The application of multivariate statistical techniques to the interpretation of analytical results allows the differentiation of groundwater types occurring in the Triassic aquifers and identification of the role of a number of minor or trace elements and their ratios that can be treated as hydrogeochemical tracers. With them it was possible to correlate the different recharge waters with the tectonic morphology of the Espadán–Calderona Triassic Domain. - Highlights: • Groundwater hydrochemistry of Espadán–Calderona Triassic Domain was investigated. • Multivariate statistical analysis and metal tracers differentiated groundwater types. • The Sr/Ba ratio and As and U concentrations are good indicators of groundwater flows. • The chemistry of groundwater flows correlates with structural morphology of recharge areas

  8. Late Ediacaran-Cambrian structures and their reactivation during the Variscan and Alpine cycles in the Anti-Atlas (Morocco)

    Science.gov (United States)

    Soulaimani, A.; Michard, A.; Ouanaimi, H.; Baidder, L.; Raddi, Y.; Saddiqi, O.; Rjimati, E. C.

    2014-10-01

    The post-Pan-African evolution of the northern border of the West African Craton is largely controlled by the remobilisation of Late Neoproterozoic basement faults. The Upper Ediacaran volcanic and volcano-sedimentary sequences of the Ouarzazate Group show dramatic and rapid thickness changes, consistent with active extensional faulting associated with post-orogenic collapse and incipient continental rifting. The geometry and kinematics of these faults differ from west to east in the Anti-Atlas. N- to NE-trending faults dominate in western Anti-Atlas in response to E-W to NW-SE pure extension, while a transtensive opening regime characterize the central (Bou Azzer) and eastern (Saghro-Ougnate) Anti-Atlas. The marine incursion in the west-central Anti-Atlas during the late Ediacaran-Early Cambrian occurred without major geodynamical break between the continental Ouarzazate Group and marine sediments of the Adoudou Fm. Extensional tectonics went on during the Early Cambrian, being concentrated in the western and central parts of the belt. From Middle Cambrian to Lower Devonian and mainly due to thermal subsidence, the Anti-Atlas basement was buried under marine sediments with dominant south-derived detrital input. Basement faults control the distribution of subsiding versus shallow areas. During the Middle-Late Devonian, the dislocation of the Saharan platform occurred, mainly in the eastern Anti-Atlas where Precambrian faults were also remobilized during the Early Carboniferous. During the Variscan orogeny, the Paleozoic series of the Anti-Atlas basin were involved in folding tectonics, concomitant with the uplift of Proterozoic basement blocks bounded by inherited basement faults. The pre-existing rift-related faults were variably inverted across the Anti-Atlas. In the westernmost part of the belt, Variscan shortening induced positive inversions along the remobilized basement faults, but in some cases, some faults preserved an apparently normal throw. Some hidden

  9. Late-Stage Caregiving

    Science.gov (United States)

    ... Caregiving Middle-Stage Caregiving Late-Stage Caregiving Behaviors Aggression & Anger Anxiety & Agitation Depression Hallucinations Memory Loss & Confusion Repetition Sleep Issues & Sundowning Suspicion & Delusions Wandering Abuse Start Here What You Need to Know Online ...

  10. New Paleomagnetic Data from Upper Permian and Lower Triassic Volcanic Sequences from Hua Binh, Quynh Nhai, and Thuan Chau Localities, Northwest Veitnam and Their Bearing on the Accretion History of Southeast Asia

    Science.gov (United States)

    Geissman, J. W.; Chi, C. T.

    2015-12-01

    New paleomagnetic data from Upper Permian to Lower Triassic volcanic rocks sampled in NW Vietnam provide more quantitative constraints on the paleogeographic setting of crustal elements that comprise the Song Da Terrane, east of the Song Ma suture, between the South China block (SCB) and north Indochina. These include results from 12 sites (125 samples) from basalts of the Vien Nam Formation, exposed at Hoa Binh Dam; eight sites (74 samples) from basalts of the Cam Thuy Formation near Thuan Chau; and 19 sites (198 samples) from andesites and basalts of the Vien Nam Formation near Quynh Nhai. The collection is limited by the quality of exposures and quantity of independent flows. Most sites yield interpretable magnetizations in progressive demagnetization, and the response implies that characteristic remanent magnetization (ChRM) components are carried by low-titanium magnetite or hematite, or a combination of both; these are isolated from secondary components. Rock magnetic data and petrography support the retention of an early-acquired thermoremanent magnetization in most sites. The Vien Nam Formation mafic volcanic rocks yield a grand mean, in geographic coordinates, of D=33.8o, I=-28.4o ( a95 = 9.5o, k =30.3, N=9 accepted sites), and a pole position at Lat=41.1N, Long=239.8E and a paleolatitude at ~15o S during the Late Permian to Early Triassic. Permian basalts of the Cam Thuy Formation provide a grand mean, corrected for structural tilt, of D=216.1o, I=+10.5o, a95=8.9o, k=107.8, and N= 4, with a pole position at Lat=45.6N, Long=226.8E. Volcanic rocks at the Quynh Nhai locality likely yield the most robust paleofield determination, as the data set is of dual polarity and passes a reversal test. The tilt corrected grand mean (normal polarity) is D=48.3o, I=-10.0o, a95=8.0o, k=27.7, N = 13, and this in turn yields an inferred paleomagnetic pole at Lat=35.7N, Long=217.4E, and a paleolatitude of 5.1oS for the late Permian. Compared with the Late Permian

  11. Paleoclimatology of Upper Triassic Playa Cycles. New Insights Into an Orbital Controlled Monsoon System (Norian, German Basin)

    OpenAIRE

    Vollmer, Thorsten

    2005-01-01

    Paleoclimatology of Upper Triassic Playa Cycles: New Insights Into an Orbital Controlled Monsoon System (Norian, German Basin) Abstract The main purpose of the project was to study the rhythmic sediments of the Steinmergel Keuper playa system in the North and South German basin in order to test the hypothesis of possible climate control on sedimentation. Furthermore, in case of there being orbital control on sedimentation, the North/South correlation was tested based on high-resolution cyclos...

  12. The Early to Middle Triassic continental–marine transition of NW Bulgaria: sedimentology, palynology and sequence stratigraphy

    OpenAIRE

    Ajdanlijsky George; Götz Annette E.; Strasser André

    2018-01-01

    Sedimentary facies and cycles of the Triassic continental–marine transition of NW Bulgaria are documented in detail from reference sections along the Iskar river gorge between the villages of Tserovo and Opletnya. The depositional environments evolved from anastomosing and meandering river systems in the Petrohan Terrigenous Group to mixed fluvial and tidal settings in the Svidol Formation, and to peritidal and shallow-marine conditions in the Opletnya Member of the Mogila Formation. For the ...

  13. Permian-Triassic thermal anomaly of the active margin of South America as a result of plate kinematics reorganization

    Science.gov (United States)

    Riel, Nicolas; Jaillard, Etienne; Guillot, Stéphane; Martelat, Jean-Emmanuel; Braun, Jean

    2013-04-01

    From Permian to Triassic times, tectonic plate reorganization provoked Pangaea breakup, counterclockwise rotation of Gondwana, closing of the Paleo-Tethys Ocean and opening of the Neo-Tethys oceanic realm. Meanwhile, the switch from arc volcanism to widespread S-type magmatism along the western South American active margin around 275-265 Ma is symptomatic of the onset of a large-scale Permian-Triassic thermal anomaly (PTTA)affecting the whole margin. Here we report metamorphic and U-Pb geochronological results from the El Oro metamorphic complex in the forearc zone of southwestern Ecuador, which recorded the last step, at 230-225 Ma, of the PTTA. The change in the drift direction of Gondwana from north to east at ca. 270 Ma was related to plate reorganization and provoked the verticalization of the subducted Panthalassa slab. As the slab verticalized, strong heat advection produced a high heat flow beneath the active margin inducing the development of a huge thermal anomaly responsible for the PTTA, which lasted 30 Ma. This voluminous magmatic activity culminated at the Permian-Triassic boundary, and may have contributed to the degradation of life conditions on the Earth surface.

  14. Timing of global regression and microbial bloom linked with the Permian-Triassic boundary mass extinction: implications for driving mechanisms.

    Science.gov (United States)

    Baresel, Björn; Bucher, Hugo; Bagherpour, Borhan; Brosse, Morgane; Guodun, Kuang; Schaltegger, Urs

    2017-03-06

    New high-resolution U-Pb dates indicate a duration of 89 ± 38 kyr for the Permian hiatus and of 14 ± 57 kyr for the overlying Triassic microbial limestone in shallow water settings of the Nanpanjiang Basin, South China. The age and duration of the hiatus coincides with the Permian-Triassic boundary (PTB) and the extinction interval in the Meishan Global Stratotype Section and Point, and strongly supports a glacio-eustatic regression, which best explains the genesis of the worldwide hiatus straddling the PTB in shallow water records. In adjacent deep marine troughs, rates of sediment accumulation display a six-fold decrease across the PTB compatible with a dryer and cooler climate as indicated by terrestrial plants. Our model of the Permian-Triassic boundary mass extinction (PTBME) hinges on the synchronicity of the hiatus with the onset of the Siberian Traps volcanism. This early eruptive phase released sulfur-rich volatiles into the stratosphere, thus simultaneously eliciting a short-lived ice age responsible for the global regression and a brief but intense acidification. Abrupt cooling, shrunk habitats on shelves and acidification may all have synergistically triggered the PTBME. Subsequently, the build-up of volcanic CO 2 induced a transient cool climate whose early phase saw the deposition of the microbial limestone.

  15. Tectonic controls on preservation of Middle Triassic Halfway reservoir facies, Peejay Field, northeastern British Columbia: a new hydrocarbon exploration model

    Energy Technology Data Exchange (ETDEWEB)

    Caplan, M. L. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Geological Sciences; Moslow, T. F. [Calgary Univ., AB (Canada). Dept. of Geology and Geophysics

    1997-12-01

    The Peejay Field in northeastern British Columbia was chosen as the site of a detailed study to establish the paleogeography, geological history and genesis of reservoir facies of Middle Triassic strata. A total of 132 cores and well logs from 345 wells were examined to establish the depositional model, to identify the origin of all reservoir facies and to construct an exploration model to improve the prediction of reservoir facies. Results show that the Middle Triassic Halfway Formation of northeastern British Columbia is comprised of at least four west-southwest prograding paleoshorelines. The Lithofacies Succession One quartz-arenites paleoshore faces have less porosity and permeability and are laterally discontinuous. For these reasons shoreface facies have minimal reservoir quality. The tidal inlet fill successions were found to have the greatest observed porosity, permeability and lateral continuity in the Peejay Field. The geometry and orientation of these tidal inlet fill deposits are controlled by tectonic processes. It was suggested that the success of hydrocarbon exploration in this structurally complex area of northeastern British Columbia and west-central Alberta depends on further stratigraphic and sedimentological examination of Middle Triassic strata on a regional scale to obtain a complete understanding of the geological history of the area. 39 refs., 13 refs.

  16. Kerogen morphology and geochemistry at the Permian-Triassic transition in the Meishan section, South China: Implication for paleoenvironmental variation

    Science.gov (United States)

    Sawada, Ken; Kaiho, Kunio; Okano, Kazuki

    2012-08-01

    Detailed fluorescent microscopic observations and organic geochemical analyses for insoluble sedimentary organic matter (kerogens) are conducted on the end-Permian to earliest Triassic sediments in the Meishan section A of South China. The main objectives of the present study are to reconstruct variations of marine and terrestrial environments, and to evaluate bulk characteristics of terrestrial input in the palaeo-Tethys ocean for the Permian-Triassic boundary (PTB). Most of kerogens in the Meishan section are mainly composed of marine algae-derived amorphous organic matter, while terrestrial plant-derived amorphous organic matter is remarkably dominant in the mass extinction horizon reported previously. The relative abundances of marine organic matter may vary depending on marine production rather than terrestrial input in the palaeo-Tethys associated with changing terrestrial vegetation. We also identified aromatic furans as major compounds in kerogen pyrolysate of all layers. It is possible that sources of aromatic furans with alkyl group, fungi and lichen, proliferated as disaster biota in terrestrial ecosystem through the PTB. Higher abundances of herbaceous organic matter are observed in the layers above the mass extinction horizon. However, the conifer biomarker retene can be identified in kerogen pyrolysates of all layers. These results imply that the productions of herbaceous plants increased as dominant pioneer biota in early stage of recovery for terrestrial ecosystem after its collapse, but also that woody plant potentially continued to be produced in land area throughout the end-Permian and earliest-Triassic.

  17. Origin and nature of the aluminium phosphate-sulfate minerals (APS) associated with uranium mineralization in triassic red-beds (Iberian Range, Spain)

    Energy Technology Data Exchange (ETDEWEB)

    Marfil, R.; Iglesia, A. la; Estupinan, J.

    2013-10-01

    This study focuses on the mineralogical and chemical study of an Aluminium-phosphate-sulphate (APS) mineralization that occurs in a classic sequence from the Triassic (Buntsandstein) of the Iberian Range. The deposit is constituted by sandstones, mud stones, and conglomerates with arenaceous matrix, which were deposited in fluvial to shallow-marine environments. In addition to APS minerals, the following diagenetic minerals are present in the classic sequence: quartz, K-feldspar, kaolinite group minerals, illite, Fe-oxides-hydroxides, carbonate-sulphate cement-replacements and secondary uraniferous minerals. APS minerals were identified and characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, and electron microprobe. Microcrystalline APS crystals occur replacing uraniferous minerals, associated with kaolinite, mica and filling pores, in distal fluvial-to-tidal arkoses-subarkoses. Given their Ca, Sr, and Ba contents, the APS minerals can be defined as a solid solution of crandallite- goyacite-gorceixite (0.53 Ca, 0.46 Sr and 0.01 Ba). The chemical composition, low LREE concentration and Sr > S suggest that the APS mineral were originated during the supergene alteration of the Buntsandstein sandstones due to the presence of the mineralizing fluids which causes the development of Ubearing sandstones in a distal alteration area precipitating from partially dissolved and altered detrital minerals. Besides, the occurrence of dickite associated with APS minerals indicates they were precipitated at diagenetic temperatures (higher than 80 degree centigrade), related to the uplifting occurred during the late Cretaceous post-rift thermal stage.(Author)

  18. Origin and nature of the aluminium phosphate-sulfate minerals (APS) associated with uranium mineralization in triassic red-beds (Iberian Range, Spain)

    International Nuclear Information System (INIS)

    Marfil, R.; Iglesia, A. la; Estupinan, J.

    2013-01-01

    This study focuses on the mineralogical and chemical study of an Aluminium-phosphate-sulphate (APS) mineralization that occurs in a classic sequence from the Triassic (Buntsandstein) of the Iberian Range. The deposit is constituted by sandstones, mud stones, and conglomerates with arenaceous matrix, which were deposited in fluvial to shallow-marine environments. In addition to APS minerals, the following diagenetic minerals are present in the classic sequence: quartz, K-feldspar, kaolinite group minerals, illite, Fe-oxides-hydroxides, carbonate-sulphate cement-replacements and secondary uraniferous minerals. APS minerals were identified and characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, and electron microprobe. Microcrystalline APS crystals occur replacing uraniferous minerals, associated with kaolinite, mica and filling pores, in distal fluvial-to-tidal arkoses-subarkoses. Given their Ca, Sr, and Ba contents, the APS minerals can be defined as a solid solution of crandallite- goyacite-gorceixite (0.53 Ca, 0.46 Sr and 0.01 Ba). The chemical composition, low LREE concentration and Sr > S suggest that the APS mineral were originated during the supergene alteration of the Buntsandstein sandstones due to the presence of the mineralizing fluids which causes the development of Ubearing sandstones in a distal alteration area precipitating from partially dissolved and altered detrital minerals. Besides, the occurrence of dickite associated with APS minerals indicates they were precipitated at diagenetic temperatures (higher than 80 degree centigrade), related to the uplifting occurred during the late Cretaceous post-rift thermal stage.(Author)

  19. Braidplain, floodplain and playa lake, alluvial-fan, aeolian and palaeosol facies composing a diversified lithogenetical sequence in the permian and triassic of South Devon (England)

    Science.gov (United States)

    Mader, Detlef

    The Permian and Triassic of South Devon (England) are a continental red bed sequence of very diversified lithogenetical composition. Within the thick series, the distribution of the main depositional environments being fluvial braidplain, fluvial floodplain and playa lake, alluvial fan, aeolian dune and calcrete palaeosol changes repeatedly in both horizontal and vertical direction. Significant sedimentary milieus such as aeolian dunes and calcrete palaeosols occur repeatedly within the succession, but are also lacking in several parts of the sequence. Fluvial braidplain deposits comprise conglomerates, sandstones, intraformational reworking horizons and mudstones and originate in channels and overbank plains of a braided river system. Conglomerates and sandstones are formed by migration of bars and spreading out of sheets during infilling of streams and aggradation of flats. Gravel is often enriched as lag pockets or veneers within steeper scour holes and kolk pots or on the plane floor of the watercourse. Finer-grained sandstones and mudstones are laid down by suspension settling in stagnant water bodies such as small lakes in the overbank area and residual pools in interbar depressions during low-stage or waning-flow in active channels or in abandoned streams. Spectacular bioturbation features in some sandstones with both horizontal tubes and vertical burrows testify to the colonization of the sediments at the bottom of the rivers with declining discharge and transport capacity. Intraformational reworking horizons with ghost-like remnants of degraded sandstones, mudstones and pedogenic carbonates document partially severe condensation of the sequence by removal of some facies elements from the depositional record. The occasionally occurring gravel-bearing mudstones or silty-clayey sandstones represent products of high-energy water surges overspilling the channel banks and transporting sandy and gravelly bed-load in limited amounts beyond the levee wall. The

  20. Effects of soil erosion and anoxic–euxinic ocean in the Permian–Triassic marine crisis

    Directory of Open Access Journals (Sweden)

    Kunio Kaiho

    2016-08-01

    Full Text Available The largest mass extinction of biota in the Earth’s history occurred during the Permian–Triassic transition and included two extinctions, one each at the latest Permian (first phase and earliest Triassic (second phase. High seawater temperature in the surface water accompanied by euxinic deep-intermediate water, intrusion of the euxinic water to the surface water, a decrease in pH, and hypercapnia have been proposed as direct causes of the marine crisis. For the first-phase extinction, we here add a causal mechanism beginning from massive soil and rock erosion and leading to algal blooms, release of toxic components, asphyxiation, and oxygen-depleted nearshore bottom water that created environmental stress for nearshore marine animals. For the second-phase extinction, we show that a soil and rock erosion/algal bloom event did not occur, but culmination of anoxia–euxinia in intermediate waters did occur, spanning the second-phase extinction. We investigated sedimentary organic molecules, and the results indicated a peak of a massive soil erosion proxy followed by peaks of marine productivity proxy. Anoxic proxies of surface sediments and water occurred in the shallow nearshore sea at the eastern and western margins of the Paleotethys at the first-phase extinction horizon, but not at the second-phase extinction horizon. Our reconstruction of ocean redox structure at low latitudes indicates that a gradual increase in temperature spanning the two extinctions could have induced a gradual change from a well-mixed oxic to a stratified euxinic ocean beginning immediately prior to the first-phase extinction, followed by culmination of anoxia in nearshore surface waters and of anoxia and euxinia in the shallow-intermediate waters at the second-phase extinction over a period of approximately one million years or more. Enhanced global warming, ocean acidification, and hypercapnia could have caused the second-phase extinction approximately 60 kyr after

  1. Static and dynamic through thickness lamina properties of thick laminates

    NARCIS (Netherlands)

    Lahuerta, F.; Nijssen, R.P.L.; Van der Meer, F.P.; Sluys, L.J.

    2015-01-01

    Thick laminates are increasingly present in large composites structures such as wind turbine blades. Different factors are suspected to be involved in the decreased static and dynamic performance of thick laminates. These include the effect of self-heating, the scaling effect, and the manufacturing

  2. Mechanical analysis of the thin- versus thick-skin tectonics in the Molasse basin and Jura thrust belt (Swiss Alps)

    Science.gov (United States)

    Maillot, Bertrand; Caer, Typhaine; Souloumiac, Pauline; Nussbaum, Christophe

    2014-05-01

    The Jura fold-and-thrust belt is classically interpreted as a thin-skin belt developed over a triasic décollement, which is itself topping Permo-carboniferous E-W transpressive grabens delimited by N-S strike-slip faults. These faults have been reactivated in eo-oligocene times as normal faults. Today, the basement is seismically active, suggesting that the Jura belt involves some amount of basement deformation. We tested both thin and thick-skin hypotheses using a simple rheological prototype with two potential décollements : a Triassic horizon extending below Jura and Molasse basin, and the upper-lower crust interface rooted deep south of the Alpine front close to the Penninic nappes region. Using the theory of limit analysis combined with automatic adaptive meshing, we demonstrate that the main Jura Triassic décollement can be activated with the present day topography, if its friction angle is below 5°, a counter-intuitive result, that was not foreseen by sand box models. In contrast, a thick-skin deformation involving all the upper crust is possible either only south of the Jura below the topographic depression of the Molasse basin if the upper-lower crust interface has an equivalent friction angle above 4.6°, or far beyond it towards the North, if it is weaker. Active thick-skin thrusting within the Jura belt requires further assumptions on the existence of weak zones, for which a good candidate could be the inherited eo-oligocene normal faults as previously suggested in the litterature. We also demonstrated the potential major role of the topographic depression of the Molasse basin in conveying deformation from the Alps to the Jura, and in localising thick-skin thrusting.

  3. Possible climate effects of the CAMP intrusive and extrusive activity and its influence on the end-Triassic mass extinction

    Science.gov (United States)

    Marzoli, A.; Davies, J.; Valeriani, L.; Preto, N.; Cirilli, S.; Panfili, G.; Dal Corso, J.; Vasconcellos, E.; Ernesto, M.; Youbi, N.; Callegaro, S.

    2017-12-01

    The end-Triassic global climate changes were probably triggered by the emplacement of the CAMP (Central Atlantic magmatic province). Here we explore the possibility that CAMP intrusions triggered global warming, while CAMP eruptions triggered short-lived cooling events. The main phase of the end-Triassic environmental changes and mass extinction was marked by two carbon isotopic excursions (CIEs). Based on stratigraphic and geochronologic data, we show that the earliest CAMP intrusions were emplaced at ca. 201.6 Ma prior to the first CIE (Davies et al., 2017). The main phase of CAMP magmatism started during the first CIE at ca. 201.5 Ma and continued until the second CIE and the Triassic-Jurassic boundary (at ca. 201.3 Ma). In particular, intrusion of the over 1 million cubic km of basaltic sills in Amazonia (Brazil) and of widespread sills from North America and Africa occurred within this interval. Multidisciplinary analyses show that organic matter rich sediments close to the sills from Brazil, Morocco, and the USA underwent contact metamorphism and organic carbon depletion. Such process may have released large amounts of thermogenic gases (CO2 and CH4) leading to global perturbation of the carbon cycle and to global warming. The timing of CAMP volcanic eruptions is well constrained by combined geochronologic, stratigraphic and palynologic data. In Morocco, newly observed palynological assemblages for sediments at the top of the lava piles are nearly identical to those found at the base of the volcanic sequences. These new data combined with carbon isotopic data indicate that over 95% of the CAMP lava flows in Morocco erupted during a short time interval at the very beginning of the end-Triassic extinction interval. A similar scenario applies possibly to the lava flows from North America. CAMP basalts are quite sulfur rich (up to 1800 ppm) suggesting that CAMP eruptions emitted large amounts of SO2. Such emissions lead possibly to short-lived cooling events

  4. Preliminary study of the uranium potential of the northern part of the Durham Triassic Basin, North Carolina

    International Nuclear Information System (INIS)

    Harris, W.B.; Thayer, P.A.

    1981-09-01

    This report presents results of a four-channel spectrometric survey of the northern part of the Durham Triassic basin and adjacent Piedmont, North Carolina. Gamma-ray spectrometric measurements were obtained at 112 localities from 136 different lithologies. The nominal sampling density in the Durham Basin is one site per 2 mi 2 . Surface radiometric surveys reveal no anomalous radioactivity in the northern part of the Durham Basin. Uranium concentrations in Triassic rocks are from 0.6 to 9.7 ppM and average 2.9 ppM. Mudrocks contain from 1.3 to 9.7 ppM, and the average is 4.5 ppM. Sandstones contain from 0.6 to 8.8 ppM, and the average is 2.5 ppM. Fanglomerates contain the lowest concentrations of uranium, from 1.4 to 2.0 ppM, for an average of 1.8 ppM. Uranium/thorium ratios average 0.27 for Triassic rocks and are from 0.04 to 1.85. The mean log uranium/log thorium for Triassic rocks is 0.37. Mudrock has the highest average uranium/thorium ratio (0.32), and the range is 0.09 to 0.66. Sandstones have an average uranium/thorium ratio of 0.26, and the range is 0.04 to 1.85. Fanglomerates have the lowest range uranium/thorium ratio (0.19), and the range is 0.12 to 0.19. On the basis of surface radiometric surveys and geologic studies, it is believed that sedimentary strata in the northern part of the Durham Basin are poor targets for further uranium exploration. This conclusion is based on the lack of favorable characteristics commonly present in fluvial uranium deposits. Among these are: (1) carbonaceous material is absent in Triassic rocks of the northern basin, (2) indicators of a reduzate facies in sandstones are not present, and (3) no tuffaceous beds are associated with sediments in the northern Durham Basin

  5. Optimum target thickness for polarimeters

    International Nuclear Information System (INIS)

    Sitnik, I.M.

    2003-01-01

    Polarimeters with thick targets are a tool to measure the proton polarization. But the question about the optimum target thickness is still the subject of discussion. An attempt to calculate the most common parameters concerning this problem, in a few GeV region, is made

  6. Extreme Modification of the Tetrapod Forelimb in a Triassic Diapsid Reptile.

    Science.gov (United States)

    Pritchard, Adam C; Turner, Alan H; Irmis, Randall B; Nesbitt, Sterling J; Smith, Nathan D

    2016-10-24

    The tetrapod forelimb is one of the most versatile structures in vertebrate evolution, having been co-opted for an enormous array of functions. However, the structural relationships between the bones of the forelimb have remained largely unchanged throughout the 375 million year history of Tetrapoda, with a radius and ulna made up of elongate, paralleling shafts contacting a series of shorter carpal bones. These features are consistent across nearly all known tetrapods, suggesting that the morphospace encompassed by these taxa is limited by some sort of constraint(s). Here, we report on a series of three-dimensionally preserved fossils of the small-bodied (reptile Drepanosaurus, from the Chinle Formation of New Mexico, USA, which dramatically diverge from this pattern. Along with the crushed type specimen from Italy, these specimens have a flattened, crescent-shaped ulna with a long axis perpendicular to that of the radius and hyperelongate, shaft-like carpal bones contacting the ulna that are proximodistally longer than the radius. The second digit supports a massive, hooked claw. This condition has similarities to living "hook-and-pull" digging mammals and demonstrates that specialized, modern ecological roles had developed during the Triassic Period, over 200 million years ago. The forelimb bones in Drepanosaurus represent previously unknown morphologies for a tetrapod and, thus, a dramatic expansion of known tetrapod forelimb morphospace. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Hydrodynamic framework of Saharan Triassic aquifers in South Tunisia and Algeria

    Science.gov (United States)

    Dhia, H. Ben; Chiarelli, A.

    The main characteristics of the lower Triassic in the Saharan part of Tunisia are presented. This first study of the aquifer is made possible because of data available from numerous petroleum wells that exist in the region. The results show that the reservoir is of importance for either geothermal energy recovering or human water needs; especially since its salinity lies in the range 2 g/l to 60 g/l. Along the Tunisian-Llibyan frontier, because of its pressure and salinity (<3 g/l), the aquifer can be used for regional needs. The study also shows that the salinity gradient (SE-NW) increases orthogonally to the runoff direction (SW-NE). This phenomenon was unexpected and it is necessary to consider the aquifer in its regional North African framework and to include its Algerian part to understand it; when the salinity and potentiometric maps include both countries, a regional pattern is evident. Furthermore, a correspondence is noted between the salinity variations and the percentage of detritic elements in the reservoir. Salinity increases toward the NW, while the detritic elements decrease in that direction. Zones with salt content lower than 5 g/l seem to be related to good reservoirs and shales, that are rich in sands, and carbonates. The aquifer water supply is primarily linked to gravity flow and secondarily to compaction flow.

  8. Heterogeneous Rates of Molecular Evolution and Diversification Could Explain the Triassic Age Estimate for Angiosperms.

    Science.gov (United States)

    Beaulieu, Jeremy M; O'Meara, Brian C; Crane, Peter; Donoghue, Michael J

    2015-09-01

    Dating analyses based on molecular data imply that crown angiosperms existed in the Triassic, long before their undisputed appearance in the fossil record in the Early Cretaceous. Following a re-analysis of the age of angiosperms using updated sequences and fossil calibrations, we use a series of simulations to explore the possibility that the older age estimates are a consequence of (i) major shifts in the rate of sequence evolution near the base of the angiosperms and/or (ii) the representative taxon sampling strategy employed in such studies. We show that both of these factors do tend to yield substantially older age estimates. These analyses do not prove that younger age estimates based on the fossil record are correct, but they do suggest caution in accepting the older age estimates obtained using current relaxed-clock methods. Although we have focused here on the angiosperms, we suspect that these results will shed light on dating discrepancies in other major clades. ©The Author(s) 2015. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. A NEW PERLEIDID FROM THE SPATHIAN (OLENEKIAN, EARLY TRIASSIC OF CHAOHU, ANHUI PROVINCE, CHINA

    Directory of Open Access Journals (Sweden)

    ZUOYU SUN

    2013-11-01

    Full Text Available A new actinopterygian genus and species, Chaohuperleidus  primus gen. n. n. sp., is described from the Upper Member of the Nanlinghu Formation (Spathian, Olenekian, Early Triassic at Majiashan (Majia Hill, Chaohu City, Anhui Province, Southeast China. The new taxon is assigned to the order Perleidiformes on the base of a combination of features: large wedge-like preoperculum with expanded infraorbital process and sensory canal running almost vertical along the posterior margin of the preoperculum itself, flank scalessomewhat higher than longer in the trunk region and presence of epaxial rays in the caudal fin.AmongPerleidiformes, the new taxonbelongsto thePerleididae, being very similar to Perleidus in the general body shape, pattern of the skull bones, the dentitionmade of peg-like marginal teeth,and number of epaxial rays. The new genus is characterized by the presence of a very large antero-dorsal process on the suboperculum, a high number (about 55 of transversal scale rows and dorsal and anal fin quite posterior. Chaohuperleidus gen. n., beingSpathianin age,represents the oldest record of the order Perleidiformes. 

  10. A small short-necked hupehsuchian from the lower Triassic of Hubei Province, China.

    Science.gov (United States)

    Chen, Xiao-hong; Motani, Ryosuke; Cheng, Long; Jiang, Da-yong; Rieppel, Olivier

    2014-01-01

    Hupehsuchia is a group of enigmatic Triassic marine reptiles that is known exclusively from two counties in Hubei Province, China. One of the common features of the group was a modestly long neck with nine to ten cervical vertebrae. We report a new species of Hupehsuchia, Eohupehsuchus brevicollis gen. et sp. nov., which for the first time shows a short neck in this group, with six cervicals. The configuration of the skull roof in Eohupehsuchus is also unique among Hupehsuchia, with narrow frontals and posteriorly shifted parietals, warranting recognition of a new species. The taxon superficially resembles Nanchangosaurus in retaining hupehsuchian plesiomorphies, such as low neural spines and small body size. However, its limbs are well-developed, unlike in Nanchangosaurus, although the latter genus is marginally larger in body length. Thus, the individual is unlikely to be immature. Also, Eohupehsuchus shares a suite of synapomorphies with Hupehsuchus, including the second and third layers of dermal ossicles above the dorsal neural spines. A phylogenetic analysis suggests that the new species is not the most basal hupehsuchian despite its short neck, and instead forms the sister taxon of Hupehsuchidae. Until recently, Hupehsuchia contained only two monotypic genera. Now there are at least four genera among Hupehsuchia, and the undescribed diversity is even higher. The left forelimb of the only specimen is incomplete, ending with broken phalanges distally. The breakage could only have occurred pre-burial. The individual may have been attacked by a predator and escaped, given that scavenging is unlikely.

  11. Spectroscopic Studies on Organic Matter from Triassic Reptile Bones, Upper Silesia, Poland

    Science.gov (United States)

    Surmik, Dawid; Boczarowski, Andrzej; Balin, Katarzyna; Dulski, Mateusz; Szade, Jacek; Kremer, Barbara; Pawlicki, Roman

    2016-01-01

    Fossil biomolecules from an endogenous source were previously identified in Cretaceous to Pleistocene fossilized bones, the evidence coming from molecular analyses. These findings, however, were called into question and an alternative hypothesis of the invasion of the bone by bacterial biofilm was proposed. Herewith we report a new finding of morphologically preserved blood-vessel-like structures enclosing organic molecules preserved in iron-oxide-mineralized vessel walls from the cortical region of nothosaurid and tanystropheid (aquatic and terrestrial diapsid reptiles) bones. These findings are from the Early/Middle Triassic boundary (Upper Roetian/Lowermost Muschelkalk) strata of Upper Silesia, Poland. Multiple spectroscopic analyses (FTIR, ToF-SIMS, and XPS) of the extracted "blood vessels" showed the presence of organic compounds, including fragments of various amino acids such as hydroxyproline and hydroxylysine as well as amides, that may suggest the presence of collagen protein residues. Because these amino acids are absent from most proteins other than collagen, we infer that the proteinaceous molecules may originate from endogenous collagen. The preservation of molecular signals of proteins within the "blood vessels" was most likely made possible through the process of early diagenetic iron oxide mineralization. This discovery provides the oldest evidence of in situ preservation of complex organic molecules in vertebrate remains in a marine environment. PMID:26977600

  12. A small short-necked hupehsuchian from the lower Triassic of Hubei Province, China.

    Directory of Open Access Journals (Sweden)

    Xiao-hong Chen

    Full Text Available Hupehsuchia is a group of enigmatic Triassic marine reptiles that is known exclusively from two counties in Hubei Province, China. One of the common features of the group was a modestly long neck with nine to ten cervical vertebrae. We report a new species of Hupehsuchia, Eohupehsuchus brevicollis gen. et sp. nov., which for the first time shows a short neck in this group, with six cervicals. The configuration of the skull roof in Eohupehsuchus is also unique among Hupehsuchia, with narrow frontals and posteriorly shifted parietals, warranting recognition of a new species. The taxon superficially resembles Nanchangosaurus in retaining hupehsuchian plesiomorphies, such as low neural spines and small body size. However, its limbs are well-developed, unlike in Nanchangosaurus, although the latter genus is marginally larger in body length. Thus, the individual is unlikely to be immature. Also, Eohupehsuchus shares a suite of synapomorphies with Hupehsuchus, including the second and third layers of dermal ossicles above the dorsal neural spines. A phylogenetic analysis suggests that the new species is not the most basal hupehsuchian despite its short neck, and instead forms the sister taxon of Hupehsuchidae. Until recently, Hupehsuchia contained only two monotypic genera. Now there are at least four genera among Hupehsuchia, and the undescribed diversity is even higher. The left forelimb of the only specimen is incomplete, ending with broken phalanges distally. The breakage could only have occurred pre-burial. The individual may have been attacked by a predator and escaped, given that scavenging is unlikely.

  13. Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.

    Science.gov (United States)

    Motani, Ryosuke; Jiang, Da-yong; Tintori, Andrea; Rieppel, Olivier; Chen, Guan-bao

    2014-01-01

    Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction.

  14. Large-Diameter Burrows of the Triassic Ischigualasto Basin, NW Argentina: Paleoecological and Paleoenvironmental Implications

    Science.gov (United States)

    Colombi, Carina E.; Fernández, Eliana; Currie, Brian S.; Alcober, Oscar A.; Martínez, Ricardo; Correa, Gustavo

    2012-01-01

    Large-diameter ichnofossils comprising three morphotypes have been identified in the Upper Triassic Ischigualasto and Los Colorados formations of northwestern Argentina. These burrows add to the global record of the early appearance of fossorial behavior during early Mesozoic time. Morphotypes 1 and 2 are characterized by a network of tunnels and shafts that can be assigned to tetrapod burrows given similarities with previously described forms. However, differences in diameter, overall morphology, and stratigraphic occurrence allow their independent classification. Morphotype 3 forms a complex network of straight branches that intersect at oblique angles. Their calcareous composition and surface morphology indicate these structures have a composite biogenic origin likely developed due to combined plant/animal interactions. The association of Morphotypes 1 and 2 with fluvial overbank lithologies deposited under an extremely seasonal arid climate confirms interpretations that the early appearance of burrowing behavior was employed by vertebrates in response to both temperature and moisture-stress associated with seasonally or perpetually dry Pangean paleoclimates. Comparisons of burrow morphology and biomechanical attributes of the abundant paleovertebrate fauna preserved in both formations permit interpretations regarding the possible burrow architects for Morphotypes 1 and 2. In the case of the Morphotype 1, the burrow constructor could be one of the small carnivorous cynodonts, Ecteninion or Probelesodon. Assigning an architect for Morphotype 2 is more problematic due to mismatches between the observed burrow morphology and the size of the known Los Colorados vertebrates. PMID:23227195

  15. Spectroscopic Studies on Organic Matter from Triassic Reptile Bones, Upper Silesia, Poland.

    Directory of Open Access Journals (Sweden)

    Dawid Surmik

    Full Text Available Fossil biomolecules from an endogenous source were previously identified in Cretaceous to Pleistocene fossilized bones, the evidence coming from molecular analyses. These findings, however, were called into question and an alternative hypothesis of the invasion of the bone by bacterial biofilm was proposed. Herewith we report a new finding of morphologically preserved blood-vessel-like structures enclosing organic molecules preserved in iron-oxide-mineralized vessel walls from the cortical region of nothosaurid and tanystropheid (aquatic and terrestrial diapsid reptiles bones. These findings are from the Early/Middle Triassic boundary (Upper Roetian/Lowermost Muschelkalk strata of Upper Silesia, Poland. Multiple spectroscopic analyses (FTIR, ToF-SIMS, and XPS of the extracted "blood vessels" showed the presence of organic compounds, including fragments of various amino acids such as hydroxyproline and hydroxylysine as well as amides, that may suggest the presence of collagen protein residues. Because these amino acids are absent from most proteins other than collagen, we infer that the proteinaceous molecules may originate from endogenous collagen. The preservation of molecular signals of proteins within the "blood vessels" was most likely made possible through the process of early diagenetic iron oxide mineralization. This discovery provides the oldest evidence of in situ preservation of complex organic molecules in vertebrate remains in a marine environment.

  16. New absolute paleointensity determinations for the Permian-Triassic boundary from the Kuznetsk Trap Basalts.

    Science.gov (United States)

    Kulakov, E.; Metelkin, D. V.; Kazansky, A.

    2015-12-01

    We report the results of a pilot absolute paleointensity study of the ~250 Ma basalts of Kuznetsk traps (Kuznetsk Basin, Altai-Sayan folded area). Studied samples are characterized by a reversed polarity of natural remanent magnetization that corresponds to the lower part of Siberian Trap basalts sequence. Geochemical similarity of Kuznets basalts with those from Norilsk region supports this interpretation. Primary origin of thermal remanence in our sample is confirmed by a positive backed contact test. Rock magnetic analyses indicate that the ChRM is carried by single-domain titanomagnetite. The Coe-version of the Thellier-Therllier double-heating method was utilized for the paleointensity determinations. In contrast to the previous studies of the Permian-Triassic Siberian trap basalts, our data indicate that by the P-T boundary the paleofield intensity was relatively high and comparable with geomagnetic field strength for the last 10 millions of years. New results question the duration of the "Mesozoic dipole-low".

  17. Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.

    Directory of Open Access Journals (Sweden)

    Ryosuke Motani

    Full Text Available Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia, which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic. This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction.

  18. A Middle Triassic stem-turtle and the evolution of the turtle body plan.

    Science.gov (United States)

    Schoch, Rainer R; Sues, Hans-Dieter

    2015-07-30

    The origin and early evolution of turtles have long been major contentious issues in vertebrate zoology. This is due to conflicting character evidence from molecules and morphology and a lack of transitional fossils from the critical time interval. The ∼220-million-year-old stem-turtle Odontochelys from China has a partly formed shell and many turtle-like features in its postcranial skeleton. Unlike the 214-million-year-old Proganochelys from Germany and Thailand, it retains marginal teeth and lacks a carapace. Odontochelys is separated by a large temporal gap from the ∼260-million-year-old Eunotosaurus from South Africa, which has been hypothesized as the earliest stem-turtle. Here we report a new reptile, Pappochelys, that is structurally and chronologically intermediate between Eunotosaurus and Odontochelys and dates from the Middle Triassic period (∼240 million years ago). The three taxa share anteroposteriorly broad trunk ribs that are T-shaped in cross-section and bear sculpturing, elongate dorsal vertebrae, and modified limb girdles. Pappochelys closely resembles Odontochelys in various features of the limb girdles. Unlike Odontochelys, it has a cuirass of robust paired gastralia in place of a plastron. Pappochelys provides new evidence that the plastron partly formed through serial fusion of gastralia. Its skull has small upper and ventrally open lower temporal fenestrae, supporting the hypothesis of diapsid affinities of turtles.

  19. The origin of high hydrocarbon groundwater in shallow Triassic aquifer in Northwest Guizhou, China.

    Science.gov (United States)

    Liu, Shan; Qi, Shihua; Luo, Zhaohui; Liu, Fangzhi; Ding, Yang; Huang, Huanfang; Chen, Zhihua; Cheng, Shenggao

    2018-02-01

    Original high hydrocarbon groundwater represents a kind of groundwater in which hydrocarbon concentration exceeds 0.05 mg/L. The original high hydrocarbon will significantly reduce the environment capacity of hydrocarbon and lead environmental problems. For the past 5 years, we have carried out for a long-term monitoring of groundwater in shallow Triassic aquifer in Northwest Guizhou, China. We found the concentration of petroleum hydrocarbon was always above 0.05 mg/L. The low-level anthropogenic contamination cannot produce high hydrocarbon groundwater in the area. By using hydrocarbon potential, geochemistry and biomarker characteristic in rocks and shallow groundwater, we carried out a comprehensive study in Dalongjing (DLJ) groundwater system to determine the hydrocarbon source. We found a simplex hydrogeology setting, high-level water-rock-hydrocarbon interaction and obviously original hydrocarbon groundwater in DLJ system. The concentration of petroleum hydrocarbon in shallow aquifer was found to increase with the strong water-rock interaction. Higher hydrocarbon potential was found in the upper of Guanling formation (T 2 g 3 ) and upper of Yongningzhen formation (T 1 yn 4 ). Heavily saturated carbon was observed from shallow groundwater, which presented similar distribution to those from rocks, especially from the deeper groundwater. These results indicated that the high concentrations of original hydrocarbon in groundwater could be due to the hydrocarbon release from corrosion and extraction out of strata over time.

  20. Biostratigraphic reappraisal of the Lower Triassic Sanga do Cabral Supersequence from South America, with a description of new material attributable to the parareptile genus Procolophon

    Science.gov (United States)

    Dias-da-Silva, Sérgio; Pinheiro, Felipe L.; Stock Da-Rosa, Átila Augusto; Martinelli, Agustín G.; Schultz, Cesar L.; Silva-Neves, Eduardo; Modesto, Sean P.

    2017-11-01

    The Sanga do Cabral Supersequence (SCS), comprises the Brazilian Sanga do Cabral Formation (SCF) and the Uruguayan Buena Vista Formation (BVF). So far, the SCS has yielded temnospondyls, parareptiles, archosauromorphs, putative synapsids, and a number of indeterminate specimens. In the absence of absolute dates for these rocks, a biostratigraphic approach is necessary to establish the ages of the SCF and the BVF. It is well established that the SCF is Early Triassic mainly due to the presence of the widespread Gondwanan reptile Procolophon trigoniceps. Conversely, the age of the BVF is subject of great controversy, being regarded alternatively as Permian, Permo-Triassic, and Early Triassic. The BVF has yielded the definite procolophonid Pintosaurus magnidentis. Procolophonoidea is one of the most diverse and conspicuous terrestrial tetrapod groups of the Lower Triassic Lystrosaurus Assemblage Zone in the Karoo Basin of South Africa, which preserves tetrapods from the aftermath of the end-Permian extinction event. Based on a previous interpretation that the fauna of the BVF is Permian, and in the reinterpretation of disarticulated vertebrae from SCF with 'swollen' neural arches as belonging to either seymouriamorphs or diadectomorphs, it was recently suggested that at least part of the SCF is Permian in age, which prompted this comprehensive reevaluation of both SCS's faunal content and geology. Moreoever, new, strikingly large procolophonid specimens (skull, vertebra, and a mandibular fragment) from the SCF are described and referred to the genus Procolophon. The large procolophonid vertebra described here contradicts the recent hypothesis that similar specimens from the SCF belong to seymouriamorphs or diadectomorphs, because its morphology is consistent with that found in Procolophon. There is not a single diagnostic specimen that supports the inference of Permian levels in the SCS. Accordingly, because all diagnostic and biostratigraphically informative fossils

  1. Late onset endophthalmitis

    Directory of Open Access Journals (Sweden)

    Abdulaziz AlHadlaq

    2016-04-01

    Full Text Available We report an extremely rare presentation of late-onset endophthalmitis in a young adult patient with an unexposed Ahmed tube implant. The implant was inserted 11 years prior to presentation. There was no history of trauma or any obvious exposure on clinical examination and the tube plate was filled with purulent material. After aqueous and vitreous tap, the patient underwent intracameral, intravitreal subconjunctival antibiotic injections and was started on systemic antibiotics with good response. Endophthalmitis associated with tube drainage device can present as late as 11 years and even without an unexposed tube.

  2. Lateness to School Remediation Game

    Science.gov (United States)

    Ugwuegbulam, Charles N.; Ibrahim, Haj. Naheed

    2015-01-01

    Primary and secondary school in Nigeria encourage punctuality to school yet a good number of the learners came late to school. This is especially true in the case of day students. Learners who come late to school are usually punished in one way or the other yet the lateness to school phenomenon still persist. Lateness to school behaviour affects…

  3. Taphonomy of a thick Terebratula bioherm from the Pliocene of southeastern Spain

    Science.gov (United States)

    García-Ramos, Diego A.

    2015-04-01

    Brachiopods were extremely abundant during the Paleozoic era but underwent a dramatic loss of biodiversity at the Permo-Triassic boundary. The comparison of brachiopod and bivalve diversity through geological time shows that the latter were the most successful counterpart at best recovering from mass extinction events. Nonetheless, there are cases where Post-Paleozoic brachiopods stand out as the dominant marine benthos in particular environments, forming paucispecific brachiopod-dominated bioherms. This note describes an example of shallow-water brachiopod bioherm dominated by the terebratulid Terebratula calabra. The shell bed is found in mixed siliciclastic-temperate carbonate deposits of late Early Pliocene age nearby Águilas (southeastern Spain). This unique brachiopod concentration may be helpful to understand the particular success of large-sized brachiopods like Terebratula in Cenozoic environments typically dominated by bivalves. The bioherm attains 1.5 meters in thickness and crops out along a band up to 140 meters wide. The lithology consists of bioturbated fine-grained sands containing poorly sorted bioclasts, mostly fragments of Terebratula. This shell bed also records a diverse fauna, including five brachiopod genera, pectinids (4 genera), oysters (3 genera), in addition to rare gastropods, echinoids, bryozoans, etc. The density and sorting of bioclasts is laterally variable, and the biofabrics range from loosely dispersed to densely-packed, including examples of concave-up vertical stacking and nesting of shells. Most of the fragments of Terebratula preserve the posterior part of the shell only. These fragments generally display corrasion (rounded fractured margins, rounded to completely missing symphytium), bioerosion (prevailing the ichnogenera Entobia, Gnathichnus and Podichnus) and encrustation (mainly by bryozoans, Ancistrocrania, and Pododesmus). The good preservation of Pododesmus contrasts with that of most fragments of Terebratula, although

  4. Constraining lithospheric removal and asthenospheric input to melts in Central Asia: A geochemical study of Triassic to Cretaceous magmatic rocks in the Gobi Altai (Mongolia)

    Science.gov (United States)

    Sheldrick, Thomas C.; Barry, Tiffany L.; Van Hinsbergen, Douwe J. J.; Kempton, Pamela D.

    2018-01-01

    Throughout northeast China, eastern and southern Mongolia, and eastern Russia there is widespread Mesozoic intracontinental magmatism. Extensive studies on the Chinese magmatic rocks have suggested lithospheric mantle removal was a driver of the magmatism. The timing, distribution and potential diachroneity of such lithospheric mantle removal remains poorly constrained. Here, we examine successions of Mesozoic lavas and shallow intrusive volcanic plugs from the Gobi Altai in southern Mongolia that appear to be unrelated to regional, relatively small-scale deformation; at the time of magmatism, the area was 200 km from any active margin, or, after its Late Jurassic-Early Cretaceous closure, from the suture of the Mongol-Okhotsk Ocean. 40Ar/39Ar radiometric age data place magmatic events in the Gobi Altai between 220 to 99.2 Ma. This succession overlaps Chinese successions and therefore provides an opportunity to constrain whether Mesozoic lithosphere removal may provide an explanation for the magmatism here too, and if so, when. We show that Triassic to Lower Cretaceous lavas in the Gobi Altai (from Dulaan Bogd, Noyon Uul, Bulgantiin Uul, Jaran Bogd and Tsagaan Tsav) are all light rare-earth element (LREE) and large-ion lithophile element (LILE)-enriched, with negative Nb and Ta anomalies (Nb/La and Ta/La ≤ 1). Geochemical data suggest that these lavas formed by low degrees of partial melting of a metasomatised lithospheric mantle that may have been modified by melts derived from recycled rutile-bearing eclogite. A gradual reduction in the involvement of garnet in the source of these lavas points towards a shallowing of the depth of melting after 125 Ma. By contrast, geochemical and isotope data from the youngest magmatic rocks in the area - 107-99 Ma old volcanic plugs from Tsost Magmatic Field - have OIB-like trace element patterns and are interpreted to have formed by low degrees of partial melting of a garnet-bearing lherzolite mantle source. These rocks did

  5. Late effecten van kankerbehandeling

    NARCIS (Netherlands)

    Langeveld, Nelia E.

    2004-01-01

    In dit artikel wordt ingegaan op de lange termijn effecten van kanker op de kinderleeftijd. Vervolgens wordt een kort overzicht gegeven van de belangrijkste late gevolgen die kunnen optreden na een oncologische behandeling met radio- en/of chemotherapie toegepast in de kinderleeftijd. Er wordt kort

  6. Late-modern hipsters

    DEFF Research Database (Denmark)

    Andersen, Bjørn Schiermer

    2014-01-01

    The article deals with the cultural significance of a new figure in late-modern Western culture: the hipster. The current hipster culture, so I argue, can be used as a magnifying glass that makes impending changes to our conception of culture and of cultural development visible. It ushers...

  7. Big Java late objects

    CERN Document Server

    Horstmann, Cay S

    2012-01-01

    Big Java: Late Objects is a comprehensive introduction to Java and computer programming, which focuses on the principles of programming, software engineering, and effective learning. It is designed for a two-semester first course in programming for computer science students.

  8. Late Embryogenesis Abundant Proteins

    NARCIS (Netherlands)

    Shih, M.D.; Hoekstra, F.A.; Hsing, Y.I.C.

    2008-01-01

    During the late maturation stage of seed development, water content decreases greatly. One of the most striking characteristics of mature orthodox seeds is their ability to withstand severe desiccation. Mechanisms of plant drought/desiccation tolerance have been studied by numerous groups, and a

  9. Late Disciform Endotheliitis after LASIK

    Directory of Open Access Journals (Sweden)

    Faik Oruçoğlu

    2013-08-01

    Full Text Available Clinical and imaging features of the patient with late herpetic keratouveitis after LASIK were investigated. A 25-year-old male patient applied with a chief complaint of blurred vision and photophobia in the left eye. He had a history of herpetic keratitits and elsewhere underwent LASIK procedure in 2005. Oral and topical acyclovir treatments were started a week ago when his complaints started. His corrected distance visual acuity was 0.2 and intraocular pressure was 14 mmHg on the left eye. Slit-lamp revealed deep central disciform edema, keratic precipitates, and 2 positive cells in the anterior chamber. Although the patient had myopic LASIK ablation, the central corneal thickness was 652 microns. Scheimpflug imaging was drawing attention to the thickening of the posterior cornea and the keratic precipitates. Sagital and anterior elevation maps were not affected, however, posterior elevation map showed marked central flattening. Asphericity value Q was within normal limits anteriorly (Q=-0.14 and it was in oblate appearance posteriorly (Q=+5.24. In addition to the antiviral medications, a topical dexamethasone treatment was started. The vision improved to 0.6, and the edema was markedly reduced after 4 days of treatment. Scheimpflug imaging parameters were significantly improved. (Turk J Ophthalmol 2013; 43: 282-5

  10. Magnetostratigraphy of a Marine Triassic-Jurassic Boundary Section, Kennecott Point, Queen Charlotte Islands: Implications for the Temporal Correlation of a 'Big Five' Mass Extinction Event.

    Science.gov (United States)

    Hilburn, I. A.; Kirschvink, J. L.; Ward, P. D.; Haggart, J. W.; Raub, T. D.

    2008-12-01

    Several causes have been proposed for Triassic-Jurassic (T-J) boundary extinctions, including global ocean anoxia/euxinia, an impact event, and/or eruption of the massive Central Atlantic Magmatic Province (CAMP), but poor intercontinental correlation makes testing these difficult. Sections at Kennecott Point, Queen Charlotte Islands, British Columbia span the late Norian through Rhaetian (Triassic) and into the earliest Hettangian (Jurassic) and provide the best integrated magneto- and chemostratigraphic framework for placing necessary temporal constraints upon the T-J mass extinctions. At Kennecott Point, turnover of radiolaria and ammonoids define the T-J boundary marine extinction and are coincident with a 2 ‰ negative excursion in δ13Corg similar in magnitude to that observed at Ferguson Hill (Muller Canyon), Nevada (1, 2). With Conodont Alteration Index values in the 1-2 range, Kennecott Point provides the ideal setting for use of magnetostratigraphy to tie the marine isotope excursion into the chronostratigraphic framework of the Newark, Hartford, and Fundy Basins. In the summer of 2005, we collected a ~1m resolution magnetostratigraphic section from 105 m of deep marine, silt- and sandstone turbidites and interbedded mudstones, spanning the T-J boundary at Kennecott Point. Hybrid progressive demagnetization - including zero-field, low-temperature cycling; low-field AF cleaning; and thermal demagnetization in ~25°C steps to 445°C under flowing N2 gas (3) - first removed a Northerly, steeply inclined component interpreted to be a Tertiary overprint, revealing an underlying dual-polarity component of moderate inclination. Five major polarity zones extend through our section, with several short, one-sample reversals interspersed amongst them. Comparison of this pattern with other T-J boundary sections (4-6) argues for a Northern hemisphere origin of our site, albeit with large vertical-axis rotations. A long normal chron bounds the T-J boundary punctuated

  11. Corneal thickness: measurement and implications.

    Science.gov (United States)

    Ehlers, Niels; Hjortdal, Jesper

    2004-03-01

    The thickness of the cornea was reported in more than 100-year-old textbooks on physiological optics (Helmholtz, Gullstrand). Physiological interest was revived in the 1950s by David Maurice, and over the next 50 years, this 'simple' biological parameter has been studied extensively. Several techniques for its measurement have been described and physiological and clinical significance have been studied. In this review, the different methods and techniques of measurement are briefly presented (optical, ultrasound). While the corneal thickness of many animals are the same over a considerable part of the surface, in the human cornea anterior and posterior curvature are not concentric giving rise to a problem of definition. Based on this the precision and accuracy of determining the central corneal thickness are discussed. Changes in corneal thickness reflects changes in function of the boundary layers, in particular the endothelial barrier. The absolute value of thickness is of importance for the estimation of IOP but also in diagnosis of corneal and systemic disorders. Finally it is discussed to what extent the thickness is a biometric parameter of significance, e.g. in the progression of myopia or in the development of retinal detachment.

  12. Mass-wasting triggered by the end-Triassic mass-extinction

    Science.gov (United States)

    van de Schootbrugge, Bas; Vecoli, Marco; Strother, Paul; Lindstrom, Sofie; Oschmann, Wolfgang

    2014-05-01

    The end-Triassic dieback of tree-forming vegetation across NW Europe and the proliferation of a low-growing herbaceous pioneer vegetation composed of ferns and fern allies, likely had a major impact on weathering and erosion of emerged land masses. In a recently drilled core from northern Germany (Schandelah), palynological analyses provide evidence for this scenario. The uppermost Rhaetian Triletes Beds show increasing amounts of reworked Palaeozoic acritarchs and prasinophytes of up to 30% of the palynomorph fraction. Most of the acritarchs are singletons and can be assigned to Ordovician and Silurian species, such as Ankyrotrochus crispum, Oppilatala eoplanktonica, and Evittia spp. The average age of the reworked acritarch assemblages is observed to increase during the latest Rhaetian, leading to an inverted stratigraphy among Palaeozoic species. Further North, in the Stenlille cores from the Danish Basin, reworked Palaeozoic palynomorphs appear to constitute mainly sphaeromorphic prasinophytes and other Palaeozoic microfossils such as chitinozoans and carboniferous spores. Further south, at Mingolsheim (S Germany) the Triletes Beds contain a clear sign of soil reworking, including mycorrhizal fungal remains and cysts from probable soil organisms. These peculiar changes in palynological assemblages go hand-in-hand with important changes in sedimentology. The reworking of soil and bedrock is occurring in an interval that also contains evidence for earthquake activity in the form of widespread seismites. All these observations may be attributed to a number of mutually non-exclusive mechanisms, including decreased plant cover, an intensified hydrological cycle due to greenhouse warming, and the doming of the Central Atlantic Magmatic Province leading to continental-scale tectonic steepening of basin margins.

  13. Impact of diagenesis and low grade metamorphosis on Triassic sabkha dolomite δ26Mg

    Science.gov (United States)

    Immenhauser, A.; Geske, A.; Richter, D.; Buhl, D.; Niedermayr, A.

    2012-12-01

    Dolomite is a common rock forming mineral in the geological record but its value as archive of ancient seawater δ26Mg signatures and their variations in time are at present underexplored. Unknown factors include the sensitivity of δ26Mg ratio to processes in the diagenetic and low grade metamorphic domain. Here, we document and discusses the first detailed δ26Mg data set from early diagenetic and burial dolomites. Samples come from the Upper Triassic Hauptdolomit (Dolomia Principale; The Dolomites, Italy) and include coeval dolmicrites that underwent differential burial diagenesis in a temperature range between about 100 and more than 350°C. As indicated by dolmicrite 87/86Sr ratios, sabkha calcian D1 dolomites precipitated from evaporated seawater and stabilized at an early diagenetic stage to D2 dolomites analysed here. With increasing burial temperature, dolomite δ26Mg ratio scatter in the data set decreases with increasing Mg/Ca ratio and degree of order. Specifically, δ26Mg ratio variability is reduced from ~0.7‰ at burial temperatures beneath 100°C to about ~0.2‰ at temperatures in excess of 350°C, respectively, with mean δ26Mg values ranging constantly near -1.9‰. This suggests that, at least for the rock buffered system investigated here, dolmicrite δ26Mg proxy data are conservative and preserve near pristine values even at elevated burial temperatures. At present, the main element of uncertainty is the Mg-isotope fractionation factor between (evaporated) seawater and dolomite. A possible solution to this problem includes the compilation of a data from modern sabkha environments including pore water and calcian dolomite δ26Mg isotope signatures.

  14. A new saurichthyiform (Actinopterygii with a crushing feeding mechanism from the Middle Triassic of Guizhou (China.

    Directory of Open Access Journals (Sweden)

    Feixiang Wu

    Full Text Available Equipped with an effective predatory feeding mechanism enhanced by large and sharp teeth, pointed snout and elongate body, saurichthyiform fishes are considered common fish-eaters in the early Mesozoic aquatic ecosystems. Additionally, because of the similar body plan across species, saurichthyiforms are also regarded evolutionally conservative, with few morphological and ecological changes during their long history. However, their phylogenetic affinity remains unclear as to whether they are chondrostean, neopterygian or stem-actinopteran, and likewise the intrarelationships of the group have rarely been explored.Here we report a new saurichthyiform from the Middle Triassic of Guizhou, China, based on the well-preserved specimens including a 3-D braincase. The new taxon, Yelangichthys macrocephalus gen. et sp. nov., is unique among saurichthyiforms in having a peculiar neurocranium with a broad orbital tectum, paired posterior myodomes, a deep, transverse fossa in the posterodorsal part of the orbit, and a feeding mechanism structured for durophagy. Phylogenetic analysis places Yelangichthys gen. nov. at the most basal position in the Saurichthyiformes as the sister to Saurichthyidae, and a new family Yelangichthyidae is erected to include only Y. macrocephalus gen. et sp. nov. The monophyly of the Chondrostei comprising [Saurichthyiformes + Acipenseriformes] Birgeriiformes is supported, but not the monophyly of Saurichthys, the type genus of Saurichthyidae. With its outstanding osteological details, Yelangichthys gen. nov. greatly increases the neurocranial variations in saurichthyiforms, and its novel feeding structure suggests the consumption of hard-preys instead of fishes.Our findings highlight the detailed osteology of a saurichthyiform braincase and its feeding design. We suggest that saurichthyiforms are closely allied to the Acipenseriformes. Saurichthyiforms were very diverse in the cranial osteology and they might have undergone a

  15. A New Saurichthyiform (Actinopterygii) with a Crushing Feeding Mechanism from the Middle Triassic of Guizhou (China)

    Science.gov (United States)

    Wu, Feixiang; Chang, Mee-mann; Sun, Yuanlin; Xu, Guanghui

    2013-01-01

    Background Equipped with an effective predatory feeding mechanism enhanced by large and sharp teeth, pointed snout and elongate body, saurichthyiform fishes are considered common fish-eaters in the early Mesozoic aquatic ecosystems. Additionally, because of the similar body plan across species, saurichthyiforms are also regarded evolutionally conservative, with few morphological and ecological changes during their long history. However, their phylogenetic affinity remains unclear as to whether they are chondrostean, neopterygian or stem-actinopteran, and likewise the intrarelationships of the group have rarely been explored. Methodology/Principal Findings Here we report a new saurichthyiform from the Middle Triassic of Guizhou, China, based on the well-preserved specimens including a 3-D braincase. The new taxon, Yelangichthys macrocephalus gen. et sp. nov., is unique among saurichthyiforms in having a peculiar neurocranium with a broad orbital tectum, paired posterior myodomes, a deep, transverse fossa in the posterodorsal part of the orbit, and a feeding mechanism structured for durophagy. Phylogenetic analysis places Yelangichthys gen. nov. at the most basal position in the Saurichthyiformes as the sister to Saurichthyidae, and a new family Yelangichthyidae is erected to include only Y. macrocephalus gen. et sp. nov. The monophyly of the Chondrostei comprising [Saurichthyiformes + Acipenseriformes] Birgeriiformes is supported, but not the monophyly of Saurichthys, the type genus of Saurichthyidae. With its outstanding osteological details, Yelangichthys gen. nov. greatly increases the neurocranial variations in saurichthyiforms, and its novel feeding structure suggests the consumption of hard-preys instead of fishes. Conclusions/Significance Our findings highlight the detailed osteology of a saurichthyiform braincase and its feeding design. We suggest that saurichthyiforms are closely allied to the Acipenseriformes. Saurichthyiforms were very diverse in the

  16. Electrical Spectroscopy of Permo-Triassic Sandstone From the United Kingdom

    Science.gov (United States)

    Scott, J.; Barker, R.

    2003-12-01

    Electrical spectroscopy measurements in the range of mHz to kHz have been made on the dominantly red Permo-Triassic sandstone from the United Kingdom. Samples have been selected from borehole cores from all of the main outcrop areas of sandstone and represent a wide variety of lithologies. This sandstone is an important aquifer for several major cities including Manchester and Birmingham. The samples have been fully saturated with sodium chloride brines and a synthetic groundwater solution that is higher in calcium and magnesium ions than sodium and which closely matches the cation concentrations of the groundwater at Birmingham. Electrical measurements were made using a four-electrode arrangement of silver-silver chloride electrodes. Most of the electrical spectra show a clear, slightly asymmetric, electrical relaxation phenomenon with relaxation peaks in the range of 0.001 Hz to 20 Hz. These relaxation phenomena can be fitted very well by a generalised Cole-Cole model. The relaxation time from this model is found to correlate closely with the dominant pore-throat size from mercury injection. Normalising the chargeability, Cole-Cole m parameter, by the conductivity gives a polarisation magnitude which correlates well with the pore surface to volume ratio (SPOR) for sandstone samples with an even distribution of surface coating clays. The information obtained from the electrical spectra is very useful. The pore-throat size is important in controlling the permeability and in particular the flow of non-aqueous phase fluids. The pore surface area has links to the sorbtion properties of the rock, which are important in estimating contaminant transport. The electrical spectra also provide a useful fingerprint of individual lithologies which could be used for correlation between boreholes or outcrops.

  17. Uranium isotope evidence for an expansion of marine anoxia during the end-Triassic extinction

    Science.gov (United States)

    Jost, Adam B.; Bachan, Aviv; van de Schootbrugge, Bas; Lau, Kimberly V.; Weaver, Karrie L.; Maher, Kate; Payne, Jonathan L.

    2017-08-01

    The end-Triassic extinction coincided with an increase in marine black shale deposition and biomarkers for photic zone euxinia, suggesting that anoxia played a role in suppressing marine biodiversity. However, global changes in ocean anoxia are difficult to quantify using proxies for local anoxia. Uranium isotopes (δ238U) in CaCO3 sediments deposited under locally well-oxygenated bottom waters can passively track seawater δ238U, which is sensitive to the global areal extent of seafloor anoxia due to preferential reduction of 238U(VI) relative to 235U(VI) in anoxic marine sediments. We measured δ238U in shallow-marine limestones from two stratigraphic sections in the Lombardy Basin, northern Italy, spanning over 400 m. We observe a ˜0.7‰ negative excursion in δ238U beginning in the lowermost Jurassic, coeval with the onset of the initial negative δ13C excursion and persisting for the duration of subsequent high δ13C values in the lower-middle Hettangian stage. The δ238U excursion cannot be realistically explained by local mixing of uranium in primary marine carbonate and reduced authigenic uranium. Based on output from a forward model of the uranium cycle, the excursion is consistent with a 40-100-fold increase in the extent of anoxic deposition occurring worldwide. Additionally, relatively constant uranium concentrations point toward increased uranium delivery to the oceans from continental weathering, which is consistent with weathering-induced eutrophication following the rapid increase in pCO2 during emplacement of the Central Atlantic Magmatic Province. The relative timing and duration of the excursion in δ238U implies that anoxia could have delayed biotic recovery well into the Hettangian stage.

  18. Aggregations and parental care in the Early Triassic basal cynodonts Galesaurus planiceps and Thrinaxodon liorhinus

    Directory of Open Access Journals (Sweden)

    Sandra C. Jasinoski

    2017-01-01

    Full Text Available Non-mammaliaform cynodonts gave rise to mammals but the reproductive biology of this extinct group is still poorly known. Two exceptional fossils of Galesaurus planiceps and Thrinaxodon liorhinus, consisting of juveniles closely associated with an adult, were briefly described more than 50 years ago as examples of parental care in non-mammaliaform cynodonts. However, these two Early Triassic fossils have largely been excluded from recent discussions of parental care in the fossil record. Here we re-analyse these fossils in the context of an extensive survey of other aggregations found in these two basal cynodont taxa. Our analysis revealed six other unequivocal cases of aggregations in Thrinaxodon, with examples of same-age aggregations among immature or adult individuals as well as mixed-age aggregations between subadult and adult individuals. In contrast, only one additional aggregation of Galesauruswas identified. Taking this comprehensive survey into account, the two previously described cases of parental care in Galesaurus and Thrinaxodon are substantiated. The juveniles are the smallest specimens known for each taxon, and the size difference between the adult and the two associated juveniles is the largest found for any of the aggregations. The juveniles of Thrinaxodon are approximately only 37% of the associated adult size; whereas in Galesaurus, the young are at least 60% of the associated adult size. In each case, the two juvenile individuals are similar in size, suggesting they were from the same clutch. Even though parental care was present in both Galesaurus and Thrinaxodon, intraspecific aggregations were much more common in Thrinaxodon, suggesting it regularly lived in aggregations consisting of both similar and different aged individuals.

  19. Palaeoclimatic trends deduced from the hydrochemistry of a Triassic sandstone aquifer, United Kingdom

    International Nuclear Information System (INIS)

    Bath, A.H.; Edmunds, W.M.; Andrews, J.N.

    1979-01-01

    A detailed geochemical study (elemental, isotopic and dissolved inert gases) of unconfined and confined sections of the Triassic non-marine sandstone aquifer in eastern England has been undertaken. Aspects of the recharge history of this aquifer over the past 40,000 years are revealed by examination of the data. 14 C activity and delta 13 C values show downgradient decrease and increase, respectively, the latter from -12 to -13 per mille (PDB) at outcrop to -8.5 per mille in deep confined groundwaters, indicating a continuing reaction between water and carbonate mineral phases. Although the bulk carbonate contained in sandstone samples gives delta 13 C around -7 per mille, modelling of the carbon isotopic evolution and consideration of the resulting 14 C age corrections suggest that a carbonate with delta 13 C closer to 0 per mille has played a major role in at least the earlier stages of hydrochemical evolution. The corrected radiocarbon age ranges, generated by the computer program WATEQF-ISOTOP, are used as a framework in which the palaeo-environmental information from oxygen and hydrogen isotope data, inert gas contents, and chloride levels are discussed. The measurement of dissolved helium levels demonstrates an excess of 4 He in many samples, which correlates with radiocarbon ages. The assumption of bulk chemical and physical properties for the aquifer rock allows independent 'excess 4 He' ages to be computed, which are mostly in excess of the corrected 14 C ages. The trend of delta 18 O is from about -8 per mille at outcrop to -9.7 per mille (SMOW) downgradient, which is significantly more depleted than has been found in previous studies of UK basins. The delta 2 H and delta 18 O values are related by the regression line delta 2 H=6.6delta 18 O+1; data from other UK studies also lie close to this trend

  20. Depositional environments and cyclo- and chronostratigraphy of uppermost Carboniferous-Lower Triassic -lacustrine deposits, southern Bogda Mountains, NW China - A terrestrfluvialial paleoclimatic record of mid-latitude NE Pangea

    Science.gov (United States)

    Yang, W.; Feng, Q.; Liu, Yajing; Tabor, N.; Miggins, D.; Crowley, J.L.; Lin, J.; Thomas, S.

    2010-01-01

    Two uppermost Carboniferous–Lower Triassic fluvial–lacustrine sections in the Tarlong–Taodonggou half-graben, southern Bogda Mountains, NW China, comprise a 1834 m-thick, relatively complete sedimentary and paleoclimatic record of the east coast of mid-latitude NE Pangea. Depositional environmental interpretations identified three orders (high, intermediate, and low) of sedimentary cycles. High-order cycles (HCs) have five basic types, including fluvial cycles recording repetitive changes of erosion and deposition and lacustrine cycles recording repetitive environmental changes associated with lake expansion and contraction. HCs are grouped into intermediate-order cycles (ICs) on the basis of systematic changes of thickness, type, and component lithofacies of HCs. Nine low-order cycles (LCs) are demarcated by graben-wide surfaces across which significant long-term environmental changes occurred. A preliminary cyclostratigraphic framework provides a foundation for future studies of terrestrial climate, tectonics, and paleontology in mid-latitude NE Pangea.Climate variabilities at the intra-HC, HC, IC, and LC scales were interpreted from sedimentary and paleosol evidence. Four prominent climatic shifts are present: 1) from the humid–subhumid to highly-variable subhumid–semiarid conditions at the beginning of Sakamarian; 2) from highly-variable subhumid–semiarid to humid–subhumid conditions across the Artinskian-Capitanian unconformity; 3) from humid–subhumid to highly-variable subhumid–semiarid conditions at early Induan; and 4) from the highly-variable subhumid–semiarid to humid–subhumid conditions across the Olenekian-Anisian unconformity. The stable humid–subhumid condition from Lopingian to early Induan implies that paleoclimate change may not have been the cause of the end-Permian terrestrial mass extinction. A close documentation of the pace and timing of the extinction and exploration of other causes are needed. In addition, the

  1. A carapace-like bony 'body tube' in an early triassic marine reptile and the onset of marine tetrapod predation.

    Science.gov (United States)

    Chen, Xiao-hong; Motani, Ryosuke; Cheng, Long; Jiang, Da-yong; Rieppel, Olivier

    2014-01-01

    Parahupehsuchus longus is a new species of marine reptile from the Lower Triassic of Yuan'an County, Hubei Province, China. It is unique among vertebrates for having a body wall that is completely surrounded by a bony tube, about 50 cm long and 6.5 cm deep, comprising overlapping ribs and gastralia. This tube and bony ossicles on the back are best interpreted as anti-predatory features, suggesting that there was predation pressure upon marine tetrapods in the Early Triassic. There is at least one sauropterygian that is sufficiently large to feed on Parahupehsuchus in the Nanzhang-Yuan'an fauna, together with six more species of potential prey marine reptiles with various degrees of body protection. Modern predators of marine tetrapods belong to the highest trophic levels in the marine ecosystem but such predators did not always exist through geologic time. The indication of marine-tetrapod feeding in the Nanzhang-Yuan'an fauna suggests that such a trophic level emerged for the first time in the Early Triassic. The recovery from the end-Permian extinction probably proceeded faster than traditionally thought for marine predators. Parahupehsuchus has superficially turtle-like features, namely expanded ribs without intercostal space, very short transverse processes, and a dorsal outgrowth from the neural spine. However, these features are structurally different from their turtle counterparts. Phylogeny suggests that they are convergent with the condition in turtles, which has a fundamentally different body plan that involves the folding of the body wall. Expanded ribs without intercostal space evolved at least twice and probably even more among reptiles.

  2. A carapace-like bony 'body tube' in an early triassic marine reptile and the onset of marine tetrapod predation.

    Directory of Open Access Journals (Sweden)

    Xiao-hong Chen

    Full Text Available Parahupehsuchus longus is a new species of marine reptile from the Lower Triassic of Yuan'an County, Hubei Province, China. It is unique among vertebrates for having a body wall that is completely surrounded by a bony tube, about 50 cm long and 6.5 cm deep, comprising overlapping ribs and gastralia. This tube and bony ossicles on the back are best interpreted as anti-predatory features, suggesting that there was predation pressure upon marine tetrapods in the Early Triassic. There is at least one sauropterygian that is sufficiently large to feed on Parahupehsuchus in the Nanzhang-Yuan'an fauna, together with six more species of potential prey marine reptiles with various degrees of body protection. Modern predators of marine tetrapods belong to the highest trophic levels in the marine ecosystem but such predators did not always exist through geologic time. The indication of marine-tetrapod feeding in the Nanzhang-Yuan'an fauna suggests that such a trophic level emerged for the first time in the Early Triassic. The recovery from the end-Permian extinction probably proceeded faster than traditionally thought for marine predators. Parahupehsuchus has superficially turtle-like features, namely expanded ribs without intercostal space, very short transverse processes, and a dorsal outgrowth from the neural spine. However, these features are structurally different from their turtle counterparts. Phylogeny suggests that they are convergent with the condition in turtles, which has a fundamentally different body plan that involves the folding of the body wall. Expanded ribs without intercostal space evolved at least twice and probably even more among reptiles.

  3. Source and Extent of Volcanic Ashes at the Permian-Triassic Boundary in South China and Its implications

    Science.gov (United States)

    Wang, M.; Zhong, Y. T.; Hou, Y. L.; He, B.

    2017-12-01

    Highly correlated with the Permian-Triassic Boundary (PTB) Mass Extinction in stratigraphic section, volcanic ashes around the P-T Boundary in South China have been suggested to be a likely cause of the PTB Mass Extinction. So the nature, source and extent of these volcanic ashes have great significance in figuring out the cause of the PTB Mass Extinction. In this study, we attempt to constrain the source and extent of the PTB volcanic ashes in South China by studying pyroclastic sedimentary rocks and the spatial distribution of tuffs and ashes in South China. The detrital zircons of tuffaceous sandstones from Penglaitan section yield an age spectrum peaked at 252Ma, with ɛHf(t) values varying from -20 to -5 ,and have Nb/Hf, Th/Nb and Hf/Th ratios similar to those from arc/orogenic-related settings. Coarse tuffaceous sandstones imply that their source is in limited distance. Those pyroclastic sedimentary rocks in Penglaitan are well correlated with the PTB volcanic ashes in Meishan GSSP section in stratigraphy. In the spatial distribution, pyroclastic sedimentary rocks and tuffs distribute only in southwest of South China, while finer volcanic ashes are mainly in the northern part. This spatial distribution suggests the source of tuffs and ashes was to the south or southwest of South China. Former studies especially that of Permian-Triassic magmatism in Hainan Island have supported the existence of a continental arc related to the subduction and closure of Palaeo-Tethys on the southwestern margin of South China during Permian to early Triassic. It is suggested that the PTB ashes possibly derived from this Paleo-Tethys continental arc. The fact that volcanic ashes haven't been reported or found in PTB stratum in North China or Northwest China implies a limited extent of the volcanism, which thus is too small to cause the PTB mass extinction.

  4. Preliminary study of the uranium potential of the Triassic Sanford basin and Colon cross structure, North Carolina

    International Nuclear Information System (INIS)

    Lee, C.H.

    1978-01-01

    A preliminary geologic investigation was conducted to determine if Triassic sedimentary rocks of the Sanford basin and Colon cross structure in North Carolina are favorable hosts for uranium deposits. Rocks of adjacent Carolina slate belt were also examined as a potential source of uranium. On the basis of favorability criteria for sandstone-type uranium deposits, and geologic and geophysical investigations of the study area, the most favorable sites for further investigation are (1) at the contacts between the Pekin and Cumnock and between the Pekin and Sanford Formations near the Colon cross structure and (2) at the base of the Jonesboro fault, which lies below the Sanford Formation, northwest of Sanford. The highly weathered granites southeast of the Jonesboro fault were a source of the detritus deposited on the cross structure and may have been a primary source of uranium. Uranium leached from the coarse sediment (Pekin Formation) of the cross structure may have been transported downdip and may have been precipitated by the carbonaceous shales of the Cumnock Formation on the western side of the cross structure or at the Pekin-Sanford contact to the east. The Jonesboro fault may provide an impermeable barrier to ground-water migration in the metamorphosed basement rocks below the Triassic sediments. Such a barrier would constitute a favorable site for the precipitation and retention of uranium. Scintillometer surveys and laboratory analyses indicate no anomalous surface radioactivity in the study area. However, deep surface weathering may have caused the uranium to be leached from the exposed rocks and redeposited at depth. Geologic investigations show that conditions which have proven favorable for deposition of uranium in other areas are present in the Triassic rocks of the Sanford basin and Colon cross structure. However, because of deep surface weathering, further subsurface studies are necessary to confirm the favorability of the rocks as hosts for uranium

  5. Timing of global regression and microbial bloom linked with the Permian-Triassic boundary mass extinction: implications for driving mechanisms

    Science.gov (United States)

    Baresel, Bjoern; Bucher, Hugo; Bagherpour, Borhan; Brosse, Morgane; Guodun, Kuang; Schaltegger, Urs

    2017-04-01

    High-precision U-Pb dating of single-zircon crystals by chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) is applied to volcanic beds that are intercalated in sedimentary sequences across the Permian-Triassic boundary (PTB). By assuming that the zircon crystallization age closely approximate that of the volcanic eruption and subsequent deposition, U-Pb zircon geochronology is the preferred approach for dating abiotic and biotic events, such as the formational PTB and the Permian-Triassic boundary mass extinction (PTBME). We will present new U-Pb zircon dates for a series of volcanic ash beds in shallow-marine Permian-Triassic sections in the Nanpanjiang Basin, South China. These high-resolution U-Pb dates indicate a duration of 90 ± 38 kyr for the Permian sedimentary hiatus and a duration of 13 ± 57 kyr for the overlying Triassic microbial limestone in the shallow water settings of the Nanpanjiang pull apart Basin. The age and duration of the hiatus coincides with the formational PTB and the extinction interval in the Meishan Global Stratotype Section and Point, thus strongly supporting a glacio-eustatic regression, which best explains the genesis of the worldwide hiatus straddling the PTB in shallow water records. In adjacent deep marine troughs, rates of sediment accumulation display a six-fold decrease across the PTB compatible with a dryer and cooler climate during the Griesbachian as indicated by terrestrial plants. Our model of the PTBME hinges on the synchronicity of the hiatus with the onset of the Siberian Traps volcanism. This early eruptive phase likely released sulfur-rich volatiles into the stratosphere, thus simultaneously eliciting a short-lived ice age responsible for the global regression and a brief but intense acidification. Abrupt cooling, shrunk habitats on shelves and acidification may all have synergistically triggered the PTBME. Subsequently, the build-up of volcanic CO2 induced this transient cool

  6. New results of microfaunal and geochemical investigations in the Permian-Triassic boundary interval from the Jadar Block (NW Serbia)

    Science.gov (United States)

    Sudar, Milan N.; Kolar-Jurkovšek, Tea; Nestell, Galina P.; Jovanović, Divna; Jurkovšek, Bogdan; Williams, Jeremy; Brookfield, Michael; Stebbins, Alan

    2018-04-01

    Detail results of microfaunal, sedimentological and geochemical investigations are documented from a newly discovered section of the Permian-Triassic boundary (PTB) interval in the area of the town of Valjevo (northwestern Serbia). The presence of various and abundant microfossils (conodonts, foraminifers, and ostracodes) found in the Upper Permian "Bituminous limestone" Formation enabled a determination of the Changhsingian Hindeodus praeparvus conodont Zone. This paper is the first report of latest Permian strata from the region, as well as from all of Serbia, where the PTB interval sediments have been part of a complex/integrated study by means of biostratigraphy and geochemistry.

  7. Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico

    Science.gov (United States)

    Gehrels, G.E.; Stewart, John H.

    1998-01-01

    One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40-1.45 and 1.62-1.78 Ga igneous rocks that are widespread in the southwestern United States and northwestern Mexico. Zircons with ages of approximately 1.11 Ga are common in Cambrian strata and were apparently shed from granite bodies near the sample site. The sources of 225-280 Ma zircons in our Triassic sample are more problematic, as few igneous rocks of these ages are recognized in northwestern Mexico. Such sources may be present but unrecognized, or the grains could have been derived from igneous rocks of the appropriate ages to the northwest in the Mojave Desert region, to the east in Chihuahua and Coahuila, or to the south in accreted(?) arc-type terranes. Because the zircon grains in our Cambrian and Devonian to Triassic samples could have accumulated in proximity to basement rocks near their present position or in the Death Valley region of southern California, our data do not support or refute the existence of the Mojave-Sonora megashear. Ordovician strata of both miogeoclinal and eugeoclinal affinity are dominated by >1.77 Ga detrital zircons, which are considerably older than most basement rocks in the region. Zircon grains in the miogeoclinal sample were apparently derived from the Peace River arch area of northwestern Canada and transported southward by longshore currents. The eugeoclinal grains may also have come from the Peace River arch region, with southward transport by either sedimentary or tectonic processes, or they may have been shed from off-shelf slivers of continents (perhaps Antarctica?) removed from the Cordilleran margin during Neoproterozoic rifting. It is also possible that the

  8. New results of microfaunal and geochemical investigations in the Permian–Triassic boundary interval from the Jadar Block (NW Serbia

    Directory of Open Access Journals (Sweden)

    Sudar Milan N.

    2018-04-01

    Full Text Available Detail results of microfaunal, sedimentological and geochemical investigations are documented from a newly discovered section of the Permian–Triassic boundary (PTB interval in the area of the town of Valjevo (northwestern Serbia. The presence of various and abundant microfossils (conodonts, foraminifers, and ostracodes found in the Upper Permian “Bituminous limestone” Formation enabled a determination of the Changhsingian Hindeodus praeparvus conodont Zone. This paper is the first report of latest Permian strata from the region, as well as from all of Serbia, where the PTB interval sediments have been part of a complex/integrated study by means of biostratigraphy and geochemistry.

  9. Late-Onset Asthma

    DEFF Research Database (Denmark)

    Ulrik, Charlotte Suppli

    2017-01-01

    Late-onset asthma is common, associated with poor outcome, underdiagnosed and undertreated, possibly due to the modifying effect of ageing on disease expression. Although the diagnostic work-up in elderly individuals suspected of having asthma follows the same steps as in younger individuals (case......, to objectively confirm asthma. If necessary, a trial of oral or inhaled corticosteroid might be necessary. Asthma can be diagnosed when increased airflow variability is identified in a symptomatic patient, and if the patient does not have a history of exposure, primarily smoking, known to cause chronic...... obstructive pulmonary disease, the diagnosis is asthma even if the patient does not have fully reversible airflow obstruction. Pharmacological therapy in patients with late-onset asthma follows international guidelines, including treatment with the lowest effective dose of inhaled corticosteroid to minimize...

  10. Late Babylonian Astrology

    Science.gov (United States)

    Steele, John M.

    The last five centuries BC saw the development of several new forms of astrology in Babylonia. Key to these new astrological techniques was the invention of the zodiac in about 400 BC. These new forms of astrology include personal horoscopes, astral medicine, and the exploitation of geometrical relationships between the position of heavenly bodies. Several Late Babylonian astrological doctrines were later adopted within Greek astrology.

  11. Late Palaeozoic plants.

    Science.gov (United States)

    Feng, Zhuo

    2017-09-11

    Land plants are one of the major constituents of terrestrial ecosystems on Earth, and play an irreplaceable role in human activities today. If we are to understand the extant plants, it is imperative that we have some understanding of the fossil plants from the deep geological past, particularly those that occurred during their early evolutionary history, in the late Palaeozoic. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Late somatic effects

    International Nuclear Information System (INIS)

    Gilbert, E.S.

    1989-01-01

    Late effects are by definition effects that occur at least one year, and in most cases decades, after the time of exposure. The late effects considered in this chapter are limited to latent cancer incidence and mortality, and benign thyroid disease. A model is provided for estimating risks of late effects resulting from the radiation exposure likely to be received in the event of a nuclear power plant accident. It is assumed that exposure to high-LET radiation would be negligible in such an accident, and thus only risks from low-LET exposure are evaluated. Separate estimates are provided for risks of leukemia, bone cancer, lung cancer, gastrointestinal cancers, thyroid cancer, skin cancer, and the residual group of all other cancers; estimates of leukemia and other cancers due to in utero exposure are also provided. Risks are expressed in absolute terms as the number of cancer deaths (or cases) per million persons exposed to a particular dose. Because the time of death is also important in assessing the impact of an accident, and because the quality of life after the occurrence of cancer will often be reduced, the number of years of life lost and the number of years of life lived after the occurrence of cancer are also estimated

  13. 57Fe Mössbauer analysis of the Upper Triassic-Lower Jurassic deep-sea chert: Paleo-redox history across the Triassic-Jurassic boundary and the Toarcian oceanic anoxic event

    International Nuclear Information System (INIS)

    Sato, Tomohiko; Isozaki, Yukio; Shozugawa, Katsumi; Seimiya, Kimiko; Matsuo, Motoyuki

    2012-01-01

    We investigated the paleo-redox change across the Triassic-Jurassic (T-J) boundary (∼200 Ma) and the Early Toarcian oceanic anoxic event (T-OAE; ∼183 Ma) recorded in the Upper Triassic to Lower Jurassic pelagic deep-sea cherts in the Inuyama area, Central Japan. The present 57 Fe Mössbauer spectroscopic analysis for these cherts identified five iron species, i.e., hematite (α-Fe 2 O 3 ), pyrite (FeS 2 ), paramagnetic Fe 3 +  , and two paramagnetic Fe 2 +  with different quadrupole splittings. The occurrence of hematite and pyrite in deep-sea cherts essentially indicates primary oxidizing and reducing depositional conditions, respectively. The results confirmed that oxidizing conditions persisted in deep-sea across the T-J boundary. In contrast, across the T-OAE, deep-sea environment shifted to reducing conditions. The first appearance of the gray pyrite-bearing chert marked the onset of the deep-sea oxygen-depletion in the middle Pliensbachian, i.e., clearly before the shallow-sea T-OAE.

  14. Coping – Late Side Effects

    Science.gov (United States)

    Cancer treatment can cause late side effects that may not show up for months or years after treatment. These late effects may include heart and lung problems, bone loss, eye and hearing changes, lymphedema, and other problems

  15. Improving global paleogeography since the late Paleozoic using paleobiology

    Directory of Open Access Journals (Sweden)

    W. Cao

    2017-12-01

    Full Text Available Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eustatic and regional sea level change, paleoclimate and ocean circulation, deep Earth resources and to constrain and interpret the dynamic topography predicted by mantle convection models. Global paleogeographic maps have been compiled and published, but they are generally presented as static maps with varying map projections, different time intervals represented by the maps and different plate motion models that underlie the paleogeographic reconstructions. This makes it difficult to convert the maps into a digital form and link them to alternative digital plate tectonic reconstructions. To address this limitation, we develop a workflow to restore global paleogeographic maps to their present-day coordinates and enable them to be linked to a different tectonic reconstruction. We use marine fossil collections from the Paleobiology Database to identify inconsistencies between their indicative paleoenvironments and published paleogeographic maps, and revise the locations of inferred paleo-coastlines that represent the estimated maximum transgression surfaces by resolving these inconsistencies. As a result, the consistency ratio between the paleogeography and the paleoenvironments indicated by the marine fossil collections is increased from an average of 75 % to nearly full consistency (100 %. The paleogeography in the main regions of North America, South America, Europe and Africa is significantly revised, especially in the Late Carboniferous, Middle Permian, Triassic, Jurassic, Late Cretaceous and most of the Cenozoic. The global flooded continental areas since the Early Devonian calculated from the revised paleogeography in this study are generally consistent with results derived from other paleoenvironment and paleo-lithofacies data and with the strontium isotope record in marine carbonates. We also estimate the terrestrial areal change over time

  16. The late Cainozoic East Antarctic ice sheet

    International Nuclear Information System (INIS)

    Colhoun, E.A.

    1999-01-01

    A review, mainly of East Antarctic late Cainozoic (post 40 Ma) geological and geomorphological evidence, supports the hypothesis of the continuous presence of an ice sheet, of about the present size, since the late Miocene. Evidence is presented and the view advanced that, during the late Wisconsin maximum of isotope stage 2, ice was not nearly as thick or extensive over the continental shelf as required by the model of 'maximum' Antarctic glaciation. Some of the factors influencing the contribution of Antarctica to post-glacial sea-level rise are discussed. It is considered that Antarctica's contribution was probably considerably less than previously estimated. The dating of marine and freshwater sequences in the Vestfold and Bunger Hills is consistent with deglaciation around the Pleistocene Holocene boundary, after the Late Wisconsin maximum. A date of ∼25 ka BP from permafrost in the Larsemann Hills means that either the Larsemann Hills were not glaciated during the Late Wisconsin or the ice failed to erode much of the permafrost surface. The degree of weathering of rock and glacial drifts in the Vestfold, Larsemann and Bunger Hills suggests a long time for formation, perhaps considerably longer than indicated by the dated marine and freshwater sediment sequences. Cosmogenic isotope dating in the Vestfold Hills has provided equivocal ages for deglaciation. While the results could indicate deglaciation before 80 ka BP, they do not confirm such early deglaciation. If the ice cover was thin and failed to remove the previous rock exposure profile, then the assays could predate the last ice advance. Weathered iron crust fragments in the till suggest little erosion. The raised beaches of the oases are Holocene. Assuming they have been produced by post Late Wisconsin isostatic uplift and by the Holocene transgression, calculations show that the Antarctic continental ice sheet could not have been more than ∼500 m thicker in the inner shelf-coastal zone. The

  17. Late onset corneal ectasia after LASIK surgery.

    Science.gov (United States)

    Said, Ashraf; Hamade, Issam H; Tabbara, Khalid F

    2011-07-01

    To report late onset corneal ectasia following myopic LASIK. A retrospective cohort case series. Nineteen patients with late onset corneal ectasia following LASIK procedure were examined at The Eye Center, Riyadh, Saudi Arabia. Patients underwent LASIK for myopia with spherical equivalent ranging from -1.4 to -13.75 diopters. Age and gender, history of systemic or local diseases, and time of onset of corneal ectasia were recorded. Eye examination and corneal topographical analyses were done before and after LASIK surgery. Nineteen patients (29 eyes) with late onset corneal ectasia were identified from 1998 to 2008 in 13 male and six female patients. The mean follow-up period was 108 ± 23 months (range 72-144 months). No patient had pre-operative identifiable risk factors for corneal ectasia and the mean time of onset was 57 ± 24 months (range 24-120 months after LASIK). The pre-operative values included mean central pachymetry 553 ± 25 μm, mean keratometry reading of 42.9 ± 1.5 diopters, average oblique cylinder of 1.4 ± 1.2 diopters, posterior surface elevation of 26 ± 2.1 diopters, corneal flap thickness of 160 μm, mean spherical equivalent of -5.6 ± 3.6 diopters, and calculated residual corneal stromal bed thickness was 288 ± 35 μm. Three (5 eyes) patients developed ectasia after pregnancy. Three (4 eyes) patients developed corneal ectasia following severe adenoviral keratoconjunctivitis and had positive PCR for adenovirus type 8. Corneal ectasia may develop many years after LASIK surgery and symptoms could go undetected for some time. Pregnancy and adenoviral keratoconjunctivitis occurred post-operatively in six patients.

  18. Are galaxy discs optically thick?

    International Nuclear Information System (INIS)

    Disney, Michael; Davies, Jonathan; Phillipps, Steven

    1989-01-01

    We re-examine the classical optical evidence for the low optical depths traditionally assigned to spiral discs and argue that it is highly model-dependent and unconvincing. In particular, layered models with a physically thin but optically thick dust layer behave like optically thin discs. The opposite hypotheses, that such discs are optically thick is then examined in the light of modern evidence. We find it to be consistent with the near-infrared and IRAS observations, with the surface brightnesses, with the HI and CO column densities and with the Hα measurements. (author)

  19. Allogenic controls on the fluvial architecture and fossil preservation of the Upper Triassic Ischigualasto Formation, NW Argentina

    Science.gov (United States)

    Colombi, Carina E.; Limarino, Carlos O.; Alcober, Oscar A.

    2017-12-01

    The Upper Triassic Ischigualasto Formation in NW Argentina was deposited in a fluvial system during the synrift filling of the extensional Ischigualasto-Villa Unión Basin. The expansive exposures of the fluvial architecture and paleosols provide a framework to reconstruct the paleoenvironmental evolution of this basin during the Upper Triassic using continental sequence stratigraphy. The Ischigualasto Formation deposition can be divided into seven sequential sedimentary stages: the 1) Bypass stage; 2) Confined low-accommodation stage; 3) Confined high accommodation stage; 4) Unstable-accommodation stage; 5) Unconfined high-accommodation stage; 6) Unconfined low-accommodation stage; and finally, 7) Unconfined high-accommodation stage. The sedimentary evolution of the Ischigualasto Formation was driven by different allogenic controls such as rises and falls in lake levels, local tectonism, subsidence, volcanism, and climate, which also produced modifications of the equilibrium profile of the fluvial systems. All of these factors result in different accommodations in central and flank areas of the basin, which led to different architectural configurations of channels and floodplains. Allogenic processes affected not only the sequence stratigraphy of the basin but also the vertebrate and plant taphocenosis. Therefore, the sequence stratigraphy can be used not only as a predictive tool related to fossil occurrence but also to understand the taphonomic history of the basin at each temporal interval.

  20. Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction.

    Science.gov (United States)

    Zatoń, Michał; Niedźwiedzki, Grzegorz; Blom, Henning; Kear, Benjamin P

    2016-11-08

    The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (>30°N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

  1. The Early to Middle Triassic continental-marine transition of NW Bulgaria: sedimentology, palynology and sequence stratigraphy

    Science.gov (United States)

    Ajdanlijsky, George; Götz, Annette E.; Strasser, André

    2018-04-01

    Sedimentary facies and cycles of the Triassic continental-marine transition of NW Bulgaria are documented in detail from reference sections along the Iskar river gorge between the villages of Tserovo and Opletnya. The depositional environments evolved from anastomosing and meandering river systems in the Petrohan Terrigenous Group to mixed fluvial and tidal settings in the Svidol Formation, and to peritidal and shallow-marine conditions in the Opletnya Member of the Mogila Formation. For the first time, the palynostratigraphic data presented here allow for dating the transitional interval and for the precise identification of a major sequence boundary between the Petrohan Terrigenous Group and the Svidol Formation (Iskar Carbonate Group). This boundary most probably corresponds to the major sequence boundary Ol4 occurring in the upper Olenekian of the Tethyan realm and thus enables interregional correlation. The identification of regionally traceable sequence boundaries based on biostratigraphic age control is a first step towards a more accurate stratigraphic correlation and palaeogeographic interpretation of the Early to early Middle Triassic in NW Bulgaria.

  2. Triassic North American paleodrainage networks and sediment dispersal of the Chinle Formation: A quantitative approach utilizing detrital zircons

    Science.gov (United States)

    Blum, M. D.; Umbarger, K.

    2017-12-01

    The Triassic Chinle Formation is a fluvial succession deposited in a backarc setting across the present-day Colorado Plateau of the southwestern United States. Existing studies have proposed various mechanisms responsible for the unique stratigraphic architecture and depositional sequences of the Chinle. However, these studies lack necessary age control to correlate stratigraphic patterns with contemporaneous mechanisms. This study will collect new samples for detrital zircon analysis, as well as upgrade existing samples (to n=300) from Dickinson and Gehrels (2008), to improve the resolution of Triassic sediment provenance from source-to-sink. The improved dataset allows appraisal of the multiple provenance terranes that contributed to the Chinle depositional system to delineate and reconstruct paleodrainage patterns. The additional samples will be collected systematically from the base of the Chinle, and vertically throughout the section to capture a regional story of how the continental scale drainage reorganized through time. U-Pb ages of detrital zircons will be utilized to provide quantitative fingerprinting information to constrain interpretations for the origin and transport history of the Chinle fluvial succession in time and space.

  3. The Early to Middle Triassic continental–marine transition of NW Bulgaria: sedimentology, palynology and sequence stratigraphy

    Directory of Open Access Journals (Sweden)

    Ajdanlijsky George

    2018-04-01

    Full Text Available Sedimentary facies and cycles of the Triassic continental–marine transition of NW Bulgaria are documented in detail from reference sections along the Iskar river gorge between the villages of Tserovo and Opletnya. The depositional environments evolved from anastomosing and meandering river systems in the Petrohan Terrigenous Group to mixed fluvial and tidal settings in the Svidol Formation, and to peritidal and shallow-marine conditions in the Opletnya Member of the Mogila Formation. For the first time, the palynostratigraphic data presented here allow for dating the transitional interval and for the precise identification of a major sequence boundary between the Petrohan Terrigenous Group and the Svidol Formation (Iskar Carbonate Group. This boundary most probably corresponds to the major sequence boundary Ol4 occurring in the upper Olenekian of the Tethyan realm and thus enables interregional correlation. The identification of regionally traceable sequence boundaries based on biostratigraphic age control is a first step towards a more accurate stratigraphic correlation and palaeogeographic interpretation of the Early to early Middle Triassic in NW Bulgaria.

  4. Two types of bone necrosis in the Middle Triassic Pistosaurus longaevus bones: the results of integrated studies

    Science.gov (United States)

    Surmik, Dawid; Rothschild, Bruce M.; Dulski, Mateusz; Janiszewska, Katarzyna

    2017-07-01

    Avascular necrosis, diagnosed on the basis of either a specific pathological modification of the articular surfaces of bone or its radiologic appearance in vertebral centra, has been recognized in many Mesozoic marine reptiles as well as in present-day marine mammals. Its presence in the zoological and paleontologic record is usually associated with decompression syndrome, a disease that affects secondarily aquatic vertebrates that could dive. Bone necrosis can also be caused by infectious processes, but it differs in appearance from decompression syndrome-associated aseptic necrosis. Herein, we report evidence of septic necrosis in the proximal articular surface of the femur of a marine reptile, Pistosaurus longaevus, from the Middle Triassic of Poland and Germany. This is the oldest recognition of septic necrosis associated with septic arthritis in the fossil record so far, and the mineralogical composition of pathologically altered bone is described herein in detail. The occurrence of septic necrosis is contrasted with decompression syndrome-associated avascular necrosis, also described in Pistosaurus longaevus bone from Middle Triassic of Germany.

  5. Late induced abortion.

    Science.gov (United States)

    Savage, W

    1990-09-01

    In the UK in 1988, 13.3% of abortions were performed at 13 weeks' gestation or later. Reasons for this delay, in addition to the diagnosis through amniocentesis of a fetal abnormality, include late recognition of pregnancy, a change of mind about completing the pregnancy, a failure of primary care physicians to entertain the diagnosis of pregnancy, travel or financial problems, and referral difficulties and scheduling delays. Women with little education and very young women are most likely to present for late abortions. From 13-16 weeks, dilatation and evacuation is the safest method of pregnancy termination. The procedure can be made easier through preparation of the cervix with a prostaglandin pessary or Foley catheter. After 16 weeks, an instillation method is recommended; prostaglandin administration can be intro- or extra-amniotic. Complication rates at 13-19 weeks are 14.5/1000 for vaginal methods of abortion and 7.2/1000 for prostaglandin methods. The risk of complications is 3 times higher for women who have 2nd-trimester abortions through the National Health Service. Although it is not realistic to expect that late abortions ever can be eliminated, improved sex education and contraceptive reliability as well as reforms in the National Health Service could reduce the number substantially. To reduce delay, it is suggested that the National Health Service set up satellite day care units and 1-2 central units in each region to deal quickly with midtrimester abortions. Delays would be further reduced by legislation to allow abortion on request in at least the 1st trimester of pregnancy.

  6. Refined permo-triassic paleomagnetic pole for the Siberian platform and geomagnetic secular variations at the Paleozoic-Mesozoic boundary as recorded in volcanic traps key sections of northern Siberia

    Science.gov (United States)

    Pavlov, V. E.; Veselovskiy, R. V.; Khokhlov, A.; Latyshev, A. V.; fluteau, F.

    2011-12-01

    Two new volcanic key sections of the Siberian traps erupted ~ 250 million years ago have been studied in the Norilsk region (NW of the Siberian platform). Along with results obtained earlier from both this area (Heunemann et al., 2004) and Maymecha-Kotuy region (northern Siberian platform, Pavlov et al., 2011) these data constitute rather extensive database, including paleomagnetic information on about 200 volcanic flows. Using this information we can not only get refined permo-triassic paleomagnetic pole for the Siberian platform, based exceptionally on lava flows data, but also estimate amplitude of geomagnetic secular variation at the Paleozoic-Mesozoic boundary and check their compatibility with statistic models, suggested for description of recent (Late Cenozoic) Earth's magnetic field. Moreover, our results can be also used to obtain additional time constraints on duration of the trap emplacement and to isolate volcanic pulses within the traps sections. We present a report where we discuss all these topics. This work was supported by grants NSF # EAR 0807585 and RBRF #09-05-01180, 11-05-00601,10-05- 00557.

  7. Late Washing efficiency

    International Nuclear Information System (INIS)

    Morrissey, M.F.

    1992-01-01

    Interim Waste Technology has demonstrated the Late Washing concept on the Experimental Laboratory Filter (ELF) at TNX. In two tests, washing reduced the [NO 2 - ] from 0.08 M to approximately 0.01 M on slurries with 2 year equivalent radiation exposures and 9.5 wt. % solids. For both washes, the [NO 2 - ] decreased at rates near theoretical for a constant volume stirred vessel, indicating approximately l00% washing efficiency. Permeate flux was greater than 0.05 gpm/ft 2 for both washes at a transmembrane pressure of 50 psi and flow velocity of 9 ft/sec

  8. Late-onset hypogonadism

    Directory of Open Access Journals (Sweden)

    Piotr Dudek

    2017-06-01

    Full Text Available In Poland, the number of men over the age of 50 years exceeds 6 million. It is estimated that about 2-6% of this population develops symptoms of late-onset hypogonadism (LOH. In men, testosterone deficiency increases slightly with age. LOH is a clinically and biochemically defined disease of older men with serum testosterone level below the reference parameters of younger healthy men and with symptoms of testosterone deficiency, manifested by pronounced disturbances of quality of life and harmful effects on multiple organ systems. Testosterone replacement therapy may give several benefits regarding body composition, metabolic control, and psychological and sexual parameters.

  9. Early and late motherhood

    DEFF Research Database (Denmark)

    Christoffersen, Mogens; Lausten, Mette

    2009-01-01

    The study investigates parental child rearing methods, structural factors relating to the family during adolescence geographic segregation, individual resource deficits and social background of first time late live births among 32 to 37 years old women and compare to teenagers before becoming...... economic and social gradient for first-time teenage mothers. Teenagers who had experienced family separation or who were formerly in out-of-home care in particular had an increased risk of early childbearing. Results showed that teenage mothers were in every respect in a more disadvantaged position than...

  10. Late Triassic porphyritic intrusions and associated volcanic rocks from the Shangri-La region, Yidun terrane, Eastern Tibetan Plateau: Adakitic magmatism and porphyry copper mineralization

    Science.gov (United States)

    Wang, Bai-Qiu; Zhou, Mei-Fu; Li, Jian-Wei; Yan, Dan-Ping

    2011-11-01

    Early Mesozoic porphyritic intrusions in the Shangri-La region, southern Yidun terrane, SW China, are spatially associated with andesites and dacites. These intrusions are composed of diorite and quartz diorite, and are closely related to copper mineralization. LA-ICP-MS zircon U-Pb ages of the intrusions range from 230 to 215 Ma. The associated andesites and dacites are interlayered with slates and sandstones and have ages of around 220 Ma. All of the intrusive and extrusive rocks have similar, highly fractionated REE patterns and high La/Yb (13-49) ratios with no prominent Eu anomalies. They display pronounced negative Nb-Ta and Ti anomalies on primitive mantle-normalized spidergrams. Their SiO2 contents range from 56.6 to 67.1 wt.%, Al2O3 from 14.2 to 17.4 wt.% and MgO from1.9 to 4.2 wt.%. All the rocks have high Sr (258-1980 ppm), and low Y (13-21 ppm) with high Sr/Y ratios (29-102). These features suggest that both the volcanic rocks and porphyritic intrusions were derived from adakitic magmas. They have similar initial 87Sr/86Sr ratios (0.7058 to 0.7077) and εNd (- 1.88 to - 4.93) values, but belong to high silica (HSA) and low silica adakitic rocks (LSA). The HSA represent an early stage of magmatism (230 to 215 Ma) and were derived from oceanic slab melts with limited interaction with the overlying mantle wedge during ascent. At 215 Ma, more extensive interaction produced the LSA. We propose that the early adakitic magmas (HSA) formed by flat subduction leading to melting of oceanic slab, whereas subsequent slab break-off caused the significant interaction between slab melts and the mantle wedge and thus the generation of the later adakitic magmas (LSA).

  11. Late Triassic granites from Bangka, Indonesia: A continuation of the Main Range granite province of the South-East Asian Tin Belt

    Science.gov (United States)

    Ng, Samuel Wai-Pan; Whitehouse, Martin J.; Roselee, Muhammad H.; Teschner, Claudia; Murtadha, Sayed; Oliver, Grahame J. H.; Ghani, Azman A.; Chang, Su-Chin

    2017-05-01

    The South-East Asian Tin Belt is one of the most tin-productive regions in the world. It comprises three north-south oriented granite provinces, of which the arc-related Eastern granite province and the collision-related Main Range granite province run across Thailand, Singapore, and Indonesia. These tin-producing granite provinces with different mineral assemblages are separated by Paleo-Tethyan sutures exposed in Thailand and Malaysia. The Eastern Province is usually characterised by granites with biotite ± hornblende. Main Range granites are sometimes characterised by the presence of biotite ± muscovite. However, the physical boundary between the two types of granite is not well-defined on the Indonesian Tin Islands, because the Paleo-Tethyan suture is not exposed on land there. Both hornblende-bearing (previously interpreted as I-type) and hornblende-barren (previously interpreted as S-type) granites are apparently randomly distributed on the Indonesian Tin Islands. Granites exposed on Bangka, the largest and southernmost Tin Island, no matter whether they are hornblende-bearing or hornblende-barren, are geochemically similar to Malaysian Main Range granites. The average ɛNd(t) value obtained from the granites from Bangka (average ɛNd(t) = -8.2) falls within the range of the Main Range Province (-9.6 to -5.4). These granites have SIMS zircon U-Pb ages of ca. 225 Ma and ca. 220 Ma, respectively that are both within the period of Main Range magmatism (∼226-201 Ma) in the Peninsular Malaysia. We suggest that the granites exposed on Bangka represent the continuation of the Main Range Province, and that the Paleo-Tethyan suture lies to the east of the island.

  12. Changes in size and growth rate of "Lilliput'' animals in the earliest Triassic

    NARCIS (Netherlands)

    Metcalfe, B.; Twitchett, R.J.; Price-Lloyd, N.

    2010-01-01

    Marine invertebrate taxa that survived the late Permian (latest Changhsingian) mass extinction event are all much smaller than they were prior to the event, an example of the Lilliput effect. New taxa that first appeared in the immediate extinction aftermath are also small compared to their size in

  13. [Endoscopic full-thickness resection].

    Science.gov (United States)

    Meier, B; Schmidt, A; Caca, K

    2016-08-01

    Conventional endoscopic resection techniques such as endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD) are powerful tools for the treatment of gastrointestinal (GI) neoplasms. However, those techniques are limited to the superficial layers of the GI wall (mucosa and submucosa). Lesions without lifting sign (usually arising from deeper layers) or lesions in difficult anatomic positions (appendix, diverticulum) are difficult - if not impossible - to resect using conventional techniques, due to the increased risk of complications. For larger lesions (>2 cm), ESD appears to be superior to the conventional techniques because of the en bloc resection, but the procedure is technically challenging, time consuming, and associated with complications even in experienced hands. Since the development of the over-the-scope clips (OTSC), complications like bleeding or perforation can be endoscopically better managed. In recent years, different endoscopic full-thickness resection techniques came to the focus of interventional endoscopy. Since September 2014, the full-thickness resection device (FTRD) has the CE marking in Europe for full-thickness resection in the lower GI tract. Technically the device is based on the OTSC system and combines OTSC application and snare polypectomy in one step. This study shows all full-thickness resection techniques currently available, but clearly focuses on the experience with the FTRD in the lower GI tract.

  14. Late Cretaceous extension and exhumation of the Stong Complex and Taku Schist, NE Peninsular Malaysia

    Science.gov (United States)

    François, Thomas; Afiq Md, Muhammad; Matenco, Liviu; Willingshofer, Ernst; Fatt Ng, Tham; Iskandar Taib, N.; Kamal Shuib, Mustaffa

    2017-04-01

    Dismembering large continental areas by post-orogenic extension requires favourable geodynamic conditions and frequently occurs along pre-existing suture zones or nappe contacts as exemplified by the Stong Complex and Taku Schist of northern Peninsular Malaysia. For this particular case we have employed a field and microstructural kinematic study combined with low temperature thermo-chronology to analyse the tectonic and exhumation history. The results show that the late Palaeozoic - Triassic Indosinian orogeny created successive phases of burial related metamorphism, shearing and contractional deformation. This orogenic structure was then dismembered during a Cretaceous thermal event that culminated in the formation of a large scale late Santonian - early Maastrichtian extensional detachment, genetically associated with crustal melting, the emplacement of syn-kinematic plutons and widespread migmatisation. The emplacement of these magmatic rocks led to an array of simultaneously formed structures that document deformation conditions over a wide temperature range, represented by amphibolite-facies mylonites and more brittle structures, such as cataclastic zones and normal faults that formed during exhumation in the footwall of the detachment. The formation of this detachment and a first phase of Late Cretaceous cooling was followed by renewed Eocene - Oligocene exhumation evidenced from our apatite fission track ages. We infer that an initial Cretaceous thermal anomaly was responsible for the formation of an extensional gneiss dome associated with simple shear and normal fault rotation. These Cretaceous processes played a critical role in the establishment of the presently observed crustal structure of Peninsular Malaysia.

  15. Gammatography of thick lead vessels

    International Nuclear Information System (INIS)

    Raghunath, V.M.; Bhatnagar, P.K.; Sundaram, V.M.

    1979-01-01

    Radiography, scintillation and GM counting and dose measurements using ionisation chamber equipment are commonly used for detecting flaws/voids in materials. The first method is mostly used for steel vessels and to a lesser extent thin lead vessels also and is essentially qualitative. Dose measuring techniques are used for very thick and large lead vessels for which high strength radioactive sources are required, with its inherent handling problems. For vessels of intermediate thicknesses, it is ideal to use a small strength source and a GM or scintillation counter assembly. At the Reactor Research Centre, Kalpakkam, such a system was used for checking three lead vessels of thicknesses varying from 38mm to 65mm. The tolerances specified were +- 4% variation in lead thickness. The measurements also revealed the non concentricity of one vessel which had a thickness varying from 38mm to 44mm. The second vessel was patently non-concentric and the dimensional variation was truly reproduced in the measurements. A third vessel was fabricated with careful control of dimensions and the measurements exhibited good concentricity. Small deviations were observed, attributable to imperfect bondings between steel and lead. This technique has the following advantages: (a) weaker sources used result in less handling problems reducing the personnel exposures considerably; (b) the sensitivity of the instrument is quite good because of better statistics; (c) the time required for scanning a small vessel is more, but a judicious use of a scintillometer for initial fast scan will help in reducing the total scanning time; (d) this method can take advantage of the dimensional variations themselves to get the calibration and to estimate the deviations from specified tolerances. (auth.)

  16. Thick resist for MEMS processing

    Science.gov (United States)

    Brown, Joe; Hamel, Clifford

    2001-11-01

    The need for technical innovation is always present in today's economy. Microfabrication methods have evolved in support of the demand for smaller and faster integrated circuits with price performance improvements always in the scope of the manufacturing design engineer. The dispersion of processing technology spans well beyond IC fabrication today with batch fabrication and wafer scale processing lending advantages to MEMES applications from biotechnology to consumer electronics from oil exploration to aerospace. Today the demand for innovative processing techniques that enable technology is apparent where only a few years ago appeared too costly or not reliable. In high volume applications where yield and cost improvements are measured in fractions of a percent it is imperative to have process technologies that produce consistent results. Only a few years ago thick resist coatings were limited to thickness less than 20 microns. Factors such as uniformity, edge bead and multiple coatings made high volume production impossible. New developments in photoresist formulation combined with advanced coating equipment techniques that closely controls process parameters have enable thick photoresist coatings of 70 microns with acceptable uniformity and edge bead in one pass. Packaging of microelectronic and micromechanical devices is often a significant cost factor and a reliability issue for high volume low cost production. Technologies such as flip- chip assembly provide a solution for cost and reliability improvements over wire bond techniques. The processing for such technology demands dimensional control and presents a significant cost savings if it were compatible with mainstream technologies. Thick photoresist layers, with good sidewall control would allow wafer-bumping technologies to penetrate the barriers to yield and production where costs for technology are the overriding issue. Single pass processing is paramount to the manufacturability of packaging

  17. Triassic to Cenozoic multi-stage intra-plate deformation focused near the Bogd Fault system, Gobi Altai, Mongolia

    Directory of Open Access Journals (Sweden)

    Douwe J.J. van Hinsbergen

    2015-09-01

    Full Text Available The Gobi Altai region of southern Mongolia has been in the Eurasian plate interior since the mid-Mesozoic, yet has experienced episodic phases of deformation since that time. In this paper, we document field evidence to characterize and date the intra-plate tectonic history of the Gobi Altai region from the Triassic to the present. To this end, we provide detailed mapping of the structure and stratigraphy of the eastern flanks of Mt. Ih Bogd that contains the widest variety of rock-time units in the area. We carry out geochronological analysis of basaltic lavas and basement granite in the area. We demonstrate that a crystalline basement with a 502 ± 8 Ma granitoid (U/Pb underwent two phases of basin formation in the Mesozoic, which we date with new 40Ar/39Ar lava ages of 218.5 ± 1.5, 123.2 ± 0.7 and 124.8 ± 1.2 Ma, respectively. Both phases are linked to deposition of fluvio-lacustrine sediments and trap-like basaltic volcanics, with cumulative thicknesses of 1000–1500 m. Both basins were likely north-facing half-grabens that developed under ∼N–S extension, but were subsequently overthrusted by Paleozoic and older crystalline basement during a less well constrained, but likely mid-Cretaceous phase of N–S shortening and basin inversion. Our results are consistent with recent seismic imaging of rift basins ∼100 km to the NE of the study area where a similar history was reconstructed. The multiple phases of intra-plate deformation appear to have parallel structural trends, most likely due to reactivated Paleozoic basement structures created during the original terrane amalgamation of the Central Asian Orogenic Belt continental crust. This strong basement heterogeneity may predispose it to reactivation, and make it sensitive to changes in the overall stress field of the Eurasian plate driven by forces at its margins and base. Detailed study of Mongolia's multi-stage tectonic history may thus provide a key proxy for the long

  18. Prediction of late failure after medical abortion from serial beta-hCG measurements and ultrasonography

    DEFF Research Database (Denmark)

    Rørbye, C; Nørgaard, M; Nilas, Lisbeth

    2004-01-01

    on day 15 were greater among late failures than successes. Used as a predictive test, the positive predictive values of these variables were low. CONCLUSION: Neither beta-hCG nor endometrial thickness can be used clinically as diagnostic tests in predicting late failure after medical abortion.......BACKGROUND: Surgical treatment of failed medical abortion may be performed several weeks after initiation of the abortion. There are no recognized methods for early identification of these late failures. We assessed the prognostic values of beta-hCG and ultrasonography in predicting late failure...... thickness by ultrasonography was performed on day 15 after induction of medical abortion. Failures diagnosed after day 15 and within 15 weeks were identified and classified as late failures. All interventions in this group were due to bleeding problems. The predictive values of different absolute...

  19. A new stem-neopterygian fish from the Middle Triassic of China shows the earliest over-water gliding strategy of the vertebrates.

    Science.gov (United States)

    Xu, Guang-Hui; Zhao, Li-Jun; Gao, Ke-Qin; Wu, Fei-Xiang

    2013-01-07

    Flying fishes are extraordinary aquatic vertebrates capable of gliding great distances over water by exploiting their enlarged pectoral fins and asymmetrical caudal fin. Some 50 species of extant flying fishes are classified in the Exocoetidae (Neopterygii: Teleostei), which have a fossil record no older than the Eocene. The Thoracopteridae is the only pre-Cenozoic group of non-teleosts that shows an array of features associated with the capability of over-water gliding. Until recently, however, the fossil record of the Thoracopteridae has been limited to the Upper Triassic of Austria and Italy. Here, we report the discovery of exceptionally well-preserved fossils of a new thoracopterid flying fish from the Middle Triassic of China, which represents the earliest evidence of an over-water gliding strategy in vertebrates. The results of a phylogenetic analysis resolve the Thoracopteridae as a stem-group of the Neopterygii that is more crown-ward than the Peltopleuriformes, yet more basal than the Luganoiiformes. As the first record of the Thoracopteride in Asia, this new discovery extends the geographical distribution of this group from the western to eastern rim of the Palaeotethys Ocean, providing new evidence to support the Triassic biological exchanges between Europe and southern China. Additionally, the Middle Triassic date of the new thoracopterid supports the hypothesis that the re-establishment of marine ecosystems after end-Permian mass extinction is more rapid than previously thought.

  20. The quest for chron E23r at Partridge Island, bay of Fundy, Canada: CAMP emplacement postdates the end-Triassic extinction event at the North American craton

    NARCIS (Netherlands)

    Deenen, M.H.L.; Krijgsman, W.; Ruhl, M.

    2011-01-01

    The Partridge Island stratigraphic section at the Bay of Fundy, Maritime Canada, reveals a continental sedimentary succession with the end-Triassic mass extinction level closely followed by basalts of the Central Atlantic Magmatic Province (CAMP). New Paleomagnetic data show that a short reverse

  1. Siliciclastics in the Upper Triassic dolomite formations of the Krizna Unit (Maid Fatra Mountains, Western Carpathians): constraints for the Carnian Pluvial Event in the Fatric Basin

    Czech Academy of Sciences Publication Activity Database

    Sýkora, M.; Siblík, Miloš; Soták, J.

    2011-01-01

    Roč. 62, č. 2 (2011), s. 121-138 ISSN 1335-0552 Institutional research plan: CEZ:AV0Z30130516 Keywords : Carnian event * Upper Triassic dolomites * Western Carpathians * Krizna Unit * shaly interbeds * lingulids * conchostracans Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.787, year: 2011

  2. Late-Modern Symbolism

    DEFF Research Database (Denmark)

    Andersen, Bjørn Schiermer

    2015-01-01

    Through analysis of key texts, I seek to demonstrate the explanative potential of Durkheim’s sociology of religion in the present context. I critically readdress the idea, found in his early work, that modernity is characterized by a rupture with pre-modern forms of solidarity. First, I investigate...... the ways in which Durkheim sets up a stark distinction between the pre-modern and the modern in his early work, and how this distinction is further cemented by his orthodox critique of the modern economy and its negative effects on social life. Second, I show how another timeless and positive understanding...... of “mechanical” solidarity is to be found behind the “symbolist” template crystalizing in Durkheim’s late work. Third, I develop this template for a modern context by critically addressing and removing other obstacles and prejudices on Durkheim’s part....

  3. Late somatic effects

    International Nuclear Information System (INIS)

    Gilbert, E.

    1985-01-01

    A model is provided for estimating risks of late effects resulting from low-LET radiation exposure likely to be received in the event of a nuclear power plant accident. Separate estimates are provided for risks of leukemia, cancers of the bones, lungs, gastrointestinal tract, thyroid, skin, and the residual group of all other cancers; estimates of leukemia and other cancers due to in utero exposure are also provided. Risks are expressed in absolute terms as the number of cancer deaths (or cases) per million persons exposed to a particular dose. In addition, the number of years of life lost and the number of years of life lived after the occurrence of cancer are also estimated. The model used in the earlier Reactor Safety Study has been modified to reflect additional epidemiological data and these changes are described in detail. 37 references, 1 figure, 13 tables

  4. Sedimentology of the Essaouira Basin (Meskala Field) in context of regional sediment distribution patterns during upper Triassic pluvial events

    Science.gov (United States)

    Mader, Nadine K.; Redfern, Jonathan; El Ouataoui, Majid

    2017-06-01

    Upper Triassic continental clastics (TAGI: Trias Argilo-Greseux Inferieur) in the Essaouira Basin are largely restricted to the subsurface, which has limited analysis of the depositional environments and led to speculation on potential provenance of the fluvial systems. Facies analysis of core from the Meskala Field onshore Essaouira Basin is compared with tentatively time-equivalent deposits exposed in extensive outcrops in the Argana Valley, to propose a process orientated model for local versus regional sediment distribution patterns in the continuously evolving Moroccan Atlantic rift during Carnian to Norian times. The study aims to unravel the climatic overprint and improve the understanding of paleo-climatic variations along the Moroccan Atlantic margin to previously recognised Upper Triassic pluvial events. In the Essaouira Basin, four facies associations representing a progressive evolution from proximal to distal facies belts in a continental rift were established. Early ephemeral braided river systems are succeeded by a wet aeolian sandflat environment with a strong arid climatic overprint (FA1). This is followed by the onset of perennial fluvial deposits with extensive floodplain fines (FA2), accompanied by a distinct shift in fluvial style, suggesting increase in discharge and related humidity, either locally or in the catchment area. The fluvial facies transitions to a shallow lacustrine or playa lake delta environment (FA3), which exhibits cyclical abandonment. The delta is progressively overlain by a terminal playa with extensive, mottled mudstones (FA4), interpreted to present a return from cyclical humid-arid conditions to prevailing aridity in the basin. In terms of regional distribution and sediment source provenance, paleocurrent data from Carnian to Norian deposits (T5 to T8 member) in the Argana Valley suggest paleoflow focused towards the S and SW, not directed towards the Meskala area in the NW as previously suggested. A major depo

  5. Macular Choroidal Small-Vessel Layer, Sattler's Layer and Haller's Layer Thicknesses: The Beijing Eye Study.

    Science.gov (United States)

    Zhao, Jing; Wang, Ya Xing; Zhang, Qi; Wei, Wen Bin; Xu, Liang; Jonas, Jost B

    2018-03-13

    To study macular choroidal layer thickness, 3187 study participants from the population-based Beijing Eye Study underwent spectral-domain optical coherence tomography with enhanced depth imaging for thickness measurements of the macular small-vessel layer, including the choriocapillaris, medium-sized choroidal vessel layer (Sattler's layer) and large choroidal vessel layer (Haller's layer). In multivariate analysis, greater thickness of all three choroidal layers was associated (all P  0.05) associated with the prevalence of open-angle glaucoma or diabetic retinopathy. There was a tendency (0.07 > P > 0.02) toward thinner choroidal layers in chronic angle-closure glaucoma. The ratio of small-vessel layer thickness to total choroidal thickness increased (P layer and Haller's layer thickness to total choroidal thickness decreased. A higher ratio of small-vessel layer thickness to total choroidal thickness was significantly associated with a lower prevalence of AMD (early type, intermediate type, late geographic type). Axial elongation-associated and aging-associated choroidal thinning affected Haller's and Sattler's layers more markedly than the small-vessel layer. Non-exudative and exudative AMD, except for geographic atrophy, was associated with slightly increased choroidal thickness.

  6. Post-Triassic thermal history of the Tazhong Uplift Zone in the Tarim Basin, Northwest China: Evidence from apatite fission-track thermochronology

    Directory of Open Access Journals (Sweden)

    Caifu Xiang

    2013-11-01

    Full Text Available The Tarim Basin is a representative example of the basins developed in the northwest China that are characterized by multiple stages of heating and cooling. In order to better understand its complex thermal history, apatite fission track (AFT thermochronology was applied to borehole samples from the Tazhong Uplift Zone (TUZ. Twelve sedimentary samples of Silurian to Triassic depositional ages were analyzed from depths coinciding with the apatite partial annealing zone (∼60–120 °C. The AFT ages, ranging from 132 ± 7 Ma (from a Triassic sample to 25 ± 2 Ma (from a Carboniferous sample, are clearly younger than their depositional ages and demonstrate a total resetting of the AFT thermometer after deposition. The AFT ages vary among different tectonic belts and decrease from the No. Ten Faulted Zone (133–105 Ma in the northwest, the Central Horst Zone in the middle (108–37 Ma, to the East Buried Hill Zone in the south (51–25 Ma. Given the low magnitude of post-Triassic burial heating evidenced by low vitrinite reflectance values (Ro < 0.7%, the total resetting of the AFT system is speculated to result from the hot fluid flow along the faults. Thermal effects along the faults are well documented by younger AFT ages and unimodal single grain age distributions in the vicinity of the faults. Permian–early Triassic basaltic volcanism may be responsible for the early Triassic total annealing of those samples lacking connectivity with the fault. The above arguments are supported by thermal modeling results.

  7. Accurate thickness measurement of graphene

    International Nuclear Information System (INIS)

    Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T

    2016-01-01

    Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1–1.3 nm to 0.1–0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials. (paper)

  8. Soliton models for thick branes

    International Nuclear Information System (INIS)

    Peyravi, Marzieh; Riazi, Nematollah; Lobo, Francisco S.N.

    2016-01-01

    In this work, we present new soliton solutions for thick branes in 4+1 dimensions. In particular, we consider brane models based on the sine-Gordon (SG), φ 4 and φ 6 scalar fields, which have broken Z 2 symmetry in some cases and are responsible for supporting and stabilizing the thick branes. The origin of the symmetry breaking in these models resides in the fact that the modified scalar field potential may have non-degenerate vacua. These vacua determine the cosmological constant on both sides of the brane. We also study the geodesic equations along the fifth dimension, in order to explore the particle motion in the neighborhood of the brane. Furthermore, we examine the stability of the thick branes, by determining the sign of the w 2 term in the expansion of the potential for the resulting Schroedinger-like equation, where w is the five-dimensional coordinate. It turns out that the φ 4 brane is stable, while there are unstable modes for certain ranges of the model parameters in the SG and φ 6 branes. (orig.)

  9. Soliton models for thick branes

    Energy Technology Data Exchange (ETDEWEB)

    Peyravi, Marzieh [Ferdowsi University of Mashhad, Department of Physics, School of Sciences, Mashhad (Iran, Islamic Republic of); Riazi, Nematollah [Shahid Beheshti University, Physics Department, Tehran (Iran, Islamic Republic of); Lobo, Francisco S.N. [Faculdade de Ciencias da Universidade de Lisboa, Instituto de Astrofisica e Ciencias do Espaco, Lisbon (Portugal)

    2016-05-15

    In this work, we present new soliton solutions for thick branes in 4+1 dimensions. In particular, we consider brane models based on the sine-Gordon (SG), φ{sup 4} and φ{sup 6} scalar fields, which have broken Z{sub 2} symmetry in some cases and are responsible for supporting and stabilizing the thick branes. The origin of the symmetry breaking in these models resides in the fact that the modified scalar field potential may have non-degenerate vacua. These vacua determine the cosmological constant on both sides of the brane. We also study the geodesic equations along the fifth dimension, in order to explore the particle motion in the neighborhood of the brane. Furthermore, we examine the stability of the thick branes, by determining the sign of the w{sup 2} term in the expansion of the potential for the resulting Schroedinger-like equation, where w is the five-dimensional coordinate. It turns out that the φ{sup 4} brane is stable, while there are unstable modes for certain ranges of the model parameters in the SG and φ{sup 6} branes. (orig.)

  10. The importance of Hindeodus parvus (Conodonta for the definition of the Permian-Triassic boundary and evaluation of the proposed sections for a global stratotype section and point (GSSP for the base of the Triassic

    Directory of Open Access Journals (Sweden)

    Yurij D. Zakharov

    1995-12-01

    Full Text Available The biostratigraphic Permian/Triassic (P/T boundary is defined by the first appearance of H. parvus. The first appearance of H. parvus within the dine H. latidentatus-H. parvus is a globally recognizable event in the conodont evolution.The first appearance of H. parvus is not facies related and can be observed both in ammonoid-free shallow-water deposits and in ammonoid-bearing pelagic deposits. H. parvus is a common, easily determinable species known so far from the entire Tethys, Japan, western North America, Boreal realm (Greenlandand the Tethyan margin of Gondwana. H. parvus is the first species withworld-wide distribution to appear after the absolute minimum in the faunal diversity indicated by the minimum in The Meishan section (South China contains a continuous, pelagic sedimentaryrecord across the P/T boundary without stratigraphie gaps. It is nearly unaltered thermally (CAI = 1-1.5. Its fossil content (ammonoids, conodonts, foraminifers,bivalves, brachiopods, sporomorphs etc. and event succession have been thoroughlystudied. Absolute age and magnetostratigraphy have also been subjected to intensive studies. The section is readily accessible and under protection of the government. This section is best suitable as a global stratotype section and point (GSSP for the base of the Triassic. No other section in the world is known tobe qualified for defining the P/T boundary in a GSSP. H. parvus made its earliest appearence in the middle part of Boundary Bed 2 (Bed 27 at Meishan. It evolved within Bed 27 from H. latidentatus within a phylomorphogenetic continuum in a continuous and monofacial stratum. The biostratigraphic P/T boundary lies very close to the event boundary (15 cm above the event boundary at the baseof Boundary Bed 1 = Bed 25, and a few centimetres above the minimum in Ô'13C in the lower Boundary Bed 2.

  11. Clays as tracers of diagenetic and hydrothermal paleo-conditions. Search for mineralogical and geochemical evidences of hydrothermal circulations in clayey, sandstone-like and carbonated diagenetic Triassic formations of the Paris Basin

    International Nuclear Information System (INIS)

    Ploquin, Florian

    2011-01-01

    Within the framework of the multi-organization TAPSS 2000 program - GNR-FORPRO, led on the Bure site (Meuse-France), the ANDRA Company realized a deep drilling (named EST 433) to investigate the local Trias because the grounds Triassic levels constituting the bed rock of Clayey level for the storage of the nuclear waste. The drilling cut the Trias rocks on a total thickness of 700 m, successively from the bottom up: (1) the Buntsandstein (120 m) is characterized by sandy-conglomerate facies; (2) the Muschelkalk (150 m) is essentially consisted of clayey-sandy-siltstone series headed by a dolomitic deposit system; (3) the Keuper part (450 m) is an alternation of sandy clay-stone or silty clay-stone deposits with insertions of saliferous levels; (4) finally the Rethian part of the drilling associated with Hettangian (80 m), are characterized by clayey-shale facies. This litho-stratigraphy can redraw the evolution of the sedimentary paleo-environments since fluviatile circles (Buntsandstein) then lagoon (upper Muschelkalk), to large floods plains systems occasionally invaded by sea (Keuper) and, finally, in an epi-continental sea context (Rhetian-Hettangian) announcing the generalized transgressive phase of which the progressive evolution coming from the border towards the center of the basin. The nearness of the continental areas is recorded in the detrital fraction of the Triassic sediments. The geochemistry of these materials signs their continental crust character and their associated isotopic Nd-Sm values gives a Hercynian meta-sediments and granites origin with from time to time a contribution of young forming rock. The mineralogy of the clayey fraction (< 0,2μm) shows that only the conglomerate on the base of the drilling consists of an assembly of dickite and illites strictly associated with regular illite / smectite mixed-layer of R=1 type illite-rich. These last ones are the main part of the clayey mineralogy of the draining facies of Buntsandstein and are

  12. Late effects of radiation therapy on the gastrointestinal tract

    International Nuclear Information System (INIS)

    Coia, Lawrence R.; Myerson, Robert J.; Tepper, Joel E.

    1995-01-01

    Late gastrointestinal complications of radiation therapy have been recognized but not extensively studied. In this paper, the late effects of radiation on three gastrointestinal sites, the esophagus, the stomach, and the bowel, are described. Esophageal dysmotility and benign stricture following esophageal irradiation are predominantly a result of damage to the esophageal wall, although mucosal ulcerations also may persist following high-dose radiation. The major late morbidity following gastric irradiation is gastric ulceration caused by mucosal destruction. Late radiation injury to the bowel, which may result in bleeding, frequency, fistula formation, and, particularly in small bowel, obstruction, is caused by damage to the entire thickness of the bowel wall, and predisposing factors have been identified. For each site a description of the pathogenesis, clinical findings, and present management is offered. Simple and reproducible endpoint scales for late toxicity measurement were developed and are presented for each of the three gastrointestinal organs. Factors important in analyzing late complications and future considerations in evaluation and management of radiation-related gastrointestinal injury are discussed

  13. A Tale of Amalgamation of Three Permo-Triassic Collage Systems in Central Asia: Oroclines, Sutures, and Terminal Accretion

    Science.gov (United States)

    Xiao, Wenjiao; Windley, Brian F.; Sun, Shu; Li, Jiliang; Huang, Baochun; Han, Chunming; Yuan, Chao; Sun, Min; Chen, Hanlin

    2015-05-01

    The Central Asian Orogenic Belt records the accretion and convergence of three collage systems that were finally rotated into two major oroclines. The Mongolia collage system was a long, N-S-oriented composite ribbon that was rotated to its current orientation when the Mongol-Okhotsk orocline was formed. The components of the Kazakhstan collage system were welded together into a long, single composite arc that was bent to form the Kazakhstan orocline. The cratons of Tarim and North China were united and sutured by the Beishan orogen, which terminated with formation of the Solonker suture in northern China. All components of the three collage systems were generated by the Neoproterozoic and were amalgamated in the Permo-Triassic. The Central Asian Orogenic Belt evolved by multiple convergence and accretion of many orogenic components during multiple phases of amalgamation, followed by two phases of orocline rotation.

  14. 40Ar/39Ar dates in the Central Cordillera of Colombia: Evidence for an upper triassic regional tecnomagmatic event

    International Nuclear Information System (INIS)

    Vinasco, C.J.; Cordani, U.G.; Vasconcelos, P

    2001-01-01

    The Coastal, Western, Central and the Eastern Cordilleras constitute four independent mountain ranges in the Northern Andes. The Coastal and Western Cordillera comprises allochthonous oceanic sequences of basic volcanic rocks and marine sediments of Cenozoic and Upper Cretaceous age (Aspden et al., 1987). The so-called Central Cordillera Polymetamorphic Complex (Restrepo and Toussaint, 1982), made up the pre-Mesozoic Central Cordillera basement, consists of low through high-grade metamorphic rocks intruded by Meso-Cenozoic batholiths. The Eastern Cordillera is a polydeformed continental mountain range consisting of Precambrian and Paleozoic metamorphic and igneous rocks overlain by Paleozoic to Mesozoic sedimentary covers. The northern part of the Central Cordillera has been described as a suspect terrain affected by several tectonometamorphic episodes. The most important of them have been always considered those related to the Hercynian orogeny, in Devonian and Carboniferous times, and those occurring at the beginning of the Andean Cycle in the Cretaceous (Restrepo and Toussaint, 1982). A possible Lower Paleozoic and even Precambrian age for the basement of the terrain has also been proposed. Although some indications of a Permo-Triassic event are already available, this period was not considered as of great importance for the geologic evolution of the region. The available radiometric dates in the 200-250 Ma interval, for the Central Cordillera, are as follows: 1. One K-Ar whole rock age for a Granulite of 251±21 Ma. (Restrepo et al, 1991) of the El Retiro group SE of Medellin. However, a K-Ar biotite age of 110±10 Ma. (Toussaint et al., 1978) was obtained for a migmatite rock associated with the same group. 2. A Sm/Nd garnet and whole rock age of 226±17 Ma in rocks associated to granulites, SE of Medellin, interpreted as metamorphic ages (Correa and Martins, 2001). 3. K-Ar biotite dates for the Puqui metamorphic complex, occurring north of Medellin, ranging

  15. PALAEOECOLOGICAL CHANGES AFTER THE END-PERMIAN MASS EXTINCTION: EARLY TRIASSIC OSTRACODS FROM NORTHWESTERN GUANGXI PROVINCE,SOUTH CHINA

    Directory of Open Access Journals (Sweden)

    SYLVIE CRASQUIN-SOLEAU

    2006-03-01

    Full Text Available Early Triassic (Griesbachian to Spathian ostracod faunas are here first discovered and described form the Guangxi Province, South China. Thirty-seven species belonging to fourteen genera are recognized. Seven species are new: Bairdia fengshanensis n.sp., Bairdia wailiensis n.sp., Liuzhinia guangxiensis n.sp., Ptychobairdia luciaae n.sp., Ptychobairdia aldaae n.sp., Paracypris jinyaensis n.sp. and Paracypris gaetanii n.sp. The Griesbachian assemblage from the basal microbial limestone is well diversified and does not suggest any abnormal palaeoenvironmental conditions in terms of salinity, temperature or oxygen content. Particularly, the ostracods are typical of well oxygenated water and do not reflect any anoxia. Dienerian and Smithian ostracods are evidenced for the first time and the assemblages suggest less favourable palaeoenviromental conditions. Diversity and abundance of ostracod assemblages recovered from the Spathian on. The main taxonomic turnover among ostracod assemblages occurred seemingly between the Griesbachian and the Spathian.

  16. Triassic aragonite in carbonate source-rock from Ragusa Basin (Sicily): geochemistry, comparison with recent sediments and origin

    International Nuclear Information System (INIS)

    Loreau, J.P.; Sabbadini, S.; Brosse, E.; Frixa, A.

    1995-01-01

    Aragonitic muds from the upper Triassic occur in laminites between two laminae rich in clays and/or organic matter. Two types of aragonite are identified. The first shows rod or needle morphology, with Sr content (9,300 ppm), δ 18 O(-1.1 to -1.7) and δ 13 C(+2.1 to +2.8) mostly similar to aragonite of Recent sediments. It is not biodetrital in origin but results from direct precipitation at 22-30 deg C in sea water with a m Sr 2+ / m Ca 2+ ratio very near to Recent values. The second aragonite showing greater prismatic crystals with inclusions of relics of rods and needles, a high content in strontium (15,800 ppm) and a negative δ 13 C(-13.0 to -14.4), is diagenetic. (authors). 23 refs., 6 figs

  17. Late Carboniferous to Late Permian carbon isotope stratigraphy

    DEFF Research Database (Denmark)

    Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria

    2015-01-01

    An integrated study of the litho-, bio-, and isotope stratigraphy of carbonates in the Southern Alps was undertaken in order to better constrain δ13C variations during the Late Carboniferous to Late Permian. The presented high resolution isotope curves are based on 1299 δ13Ccarb and 396 δ13Corg...

  18. Sommerxylon spiralosus from Upper Triassic in southernmost Paraná Basin (Brazil: a new taxon with taxacean affinity

    Directory of Open Access Journals (Sweden)

    Etiene F. Pires

    2004-09-01

    Full Text Available The anatoical description of silici?ed Gymnospermae woods from Upper Triassic sequences of southernmost Paraná Basin (Brazil has allowed the identi?cation of a new taxon: Sommerxylon spiralosus n.gen. et n.sp. Diagnostic parameters, such as heterocellular medulla composed of parenchymatous and sclerenchymatous cells, primary xylem endarch, secondary xylem with dominant uniseriate bordered pits, spiral thickenings in the radial walls of tracheids, medullar rays homocellular, absence of resiniferous canals and axial parenchyma, indicate its relationship with the family Taxaceae, reporting on the first recognition of this group in the Triassic on Southern Pangea. This evidence supports the hypothesis that the Taxaceae at the Mesozoic were not con?ned to the Northern Hemisphere.A descrição anatômica de lenhos silicificados de Gymnospermae em seqüência do Triássico Superior no sul da Bacia do Paraná (Brasil, possibilitou a identificação de um novo taxon: Sommerxylon spiralosus n.gen. et n.sp. Parâmetros diagnósticos tais como medula heterocelular, composta por células parenquimáticas e esclerenquimáticas, xilema primário endarco, xilema secundário com pontoações areoladas unisseriadas dominantes, espessamentos espiralados nas paredes radiais dos traqueídeos, raios lenhosos homocelulares, ausência de canais resiníferos e de parênquima axial, indicam a sua vinculação à família Taxaceae, constituindo-se em reconhecimento inédito da presença deste grupo no Triássico Superior no sul do Pangea. Esta evidência suporta a hipótese de que a família Taxaceae não estava confinada ao Hemisfério Norte durante o Mesozóico.

  19. Records of Triassic volcanism in Pangean Great Lakes, and implications for reconstructing the distal effects of Large Igneous Provinces

    Science.gov (United States)

    Whiteside, J. H.; Percival, L.; Kinney, S.; Olsen, P. E.; Mather, T. A.; Philpotts, A.

    2017-12-01

    Documentation of the precise timing of volcanic eruptions in sedimentary records is key for linking volcanic activity to both historical and geological episodes of environmental change. Deposition of tuffs in sediments, and sedimentary enrichment of trace metals linked to igneous processes, are both commonly used for such correlations. In particular, sedimentary mercury (Hg) enrichments have been used as a marker for volcanic activity from Large Igneous Provinces (LIPs) to support their link to episodes of major climate change and mass extinction in the geological record. However, linking such enrichments to a specific eruption or eruption products is often challenging or impossible. In this study, the mercury records from two exactly contemporaneous latest Triassic-earliest Jurassic rift lakes are presented. Both sedimentary records feature igneous units proposed to be related to the later (Early Jurassic) stages of volcanism of the Central Atlantic Magmatic Province (CAMP). These CAMP units include a small tuff unit identified by thin-section petrology and identified at 10 localities over a distance of over 200 km, and a major CAMP basalt flow overlying this tuff (and dated at 200.916±0.064 Ma) which is also known across multiple sedimentary basins in both North America and Morocco and is thought to have been emplaced about 120 kyr after the tuff. A potential stratigraphic correlation between Hg enrichments and the igneous units is considered, and compared to the established records of mercury enrichments from the latest Triassic that are thought to be coeval with the earlier stages of CAMP volcanism. Investigating the Hg records of sedimentary successions containing tuffs and basalt units is an important step for demonstrating whether the mercury emissions from specific individual volcanic eruptions in the deep past can be identified in the geological record, and are thus important tools for interpreting the causes of associated past geological events, such as

  20. High influx of carbon in walls of agglutinated foraminifers during the Permian-Triassic transition in global oceans

    Science.gov (United States)

    Nestell, Galina P.; Nestell, Merlynd K.; Ellwood, Brooks B.; Wardlaw, Bruce R.; Basu, Asish R.; Ghosh, Nilotpal; Phuong Lan, Luu Thi; Rowe, Harry D.; Hunt, Andrew G.; Tomkin, Jonathan H.; Ratcliffe, Kenneth T.

    2015-01-01

    The Permian–Triassic mass extinction is postulated to be related to the rapid volcanism that produced the Siberian flood basalt (Traps). Unrelated volcanic eruptions producing several episodes of ash falls synchronous with the Siberian Traps are found in South China and Australia. Such regional eruptions could have caused wildfires, burning of coal deposits, and the dispersion of coal fly ash. These eruptions introduced a major influx of carbon into the atmosphere and oceans that can be recognized in the wallstructure of foraminiferal tests present in survival populations in the boundary interval strata. Analysis of free specimens of foraminifers recovered from residues of conodont samples taken at aPermian–Triassic boundary section at Lung Cam in northern Vietnam has revealed the presence of a significant amount of elemental carbon, along with oxygen and silica, in their test wall structure, but an absence of calcium carbonate. These foraminifers, identified as Rectocornuspira kalhori, Cornuspira mahajeri, and Earlandia spp. and whose tests previously were considered to be calcareous, are confirmed to be agglutinated, and are now referred to as Ammodiscus kalhori and Hyperammina deformis. Measurement of the 207Pb/204Pb ratios in pyrite clusters attached to the foraminiferal tests confirmed that these tests inherited the Pb in their outer layer from carbon-contaminated seawater. We conclude that the source of the carbon could have been either global coal fly ash or forest fire-dispersed carbon, or a combination of both, that was dispersed into the Palaeo-Tethys Ocean immediately after the end-Permian extinction event.

  1. The crustal thickness of Australia

    Science.gov (United States)

    Clitheroe, G.; Gudmundsson, O.; Kennett, B.L.N.

    2000-01-01

    We investigate the crustal structure of the Australian continent using the temporary broadband stations of the Skippy and Kimba projects and permanent broadband stations. We isolate near-receiver information, in the form of crustal P-to-S conversions, using the receiver function technique. Stacked receiver functions are inverted for S velocity structure using a Genetic Algorithm approach to Receiver Function Inversion (GARFI). From the resulting velocity models we are able to determine the Moho depth and to classify the width of the crust-mantle transition for 65 broadband stations. Using these results and 51 independent estimates of crustal thickness from refraction and reflection profiles, we present a new, improved, map of Moho depth for the Australian continent. The thinnest crust (25 km) occurs in the Archean Yilgarn Craton in Western Australia; the thickest crust (61 km) occurs in Proterozoic central Australia. The average crustal thickness is 38.8 km (standard deviation 6.2 km). Interpolation error estimates are made using kriging and fall into the range 2.5-7.0 km. We find generally good agreement between the depth to the seismologically defined Moho and xenolith-derived estimates of crustal thickness beneath northeastern Australia. However, beneath the Lachlan Fold Belt the estimates are not in agreement, and it is possible that the two techniques are mapping differing parts of a broad Moho transition zone. The Archean cratons of Western Australia appear to have remained largely stable since cratonization, reflected in only slight variation of Moho depth. The largely Proterozoic center of Australia shows relatively thicker crust overall as well as major Moho offsets. We see evidence of the margin of the contact between the Precambrian craton and the Tasman Orogen, referred to as the Tasman Line. Copyright 2000 by the American Geophysical Union.

  2. Late nonstochastic changes in pig skin after β irradiation

    International Nuclear Information System (INIS)

    Peel, D.M.; Hopewell, J.W.; Wells, J.; Charles, M.W.

    1985-01-01

    Late radiation-induced changes in pig skin have been assessed following irradiation with β-rays from a 22.5- or 15-mm-diameter 90 Sr/ 90 Y source and a 19- or 9-mm-diameter 170 Tm source. Late damage, in terms of dermal atrophy, was assessed 2 years after irradiation from measurements of dermal thickness of 40-50% of the control value, occurred at a dose of approx. 40 Gy from the 22.5-mm source and approx. 75 Gy from the 15-mm source. In the case of 170 Tm the 19- and 9-mm sources produced similar degrees of atrophy at equal doses. Maximum atrophy occurred at approx. 70 Gy, when the dermis was approx. 70% of the thickness of normal skin. Significant late tissue atrophy was seen at doses, from both types of radiation, which only produced minimal erythema in the early reaction. Such late reactions need to be taken into account when revised radiological protection criteria are proposed for skin

  3. The late administration of surfactant

    African Journals Online (AJOL)

    HMD and 4 as having congenital pneumonia. Overall there was a significant and sustained improvement ... 3 infants weighing> 2 400 g with congenital pneumonia responded to a single delayed dose of SRT. Late SRT is ..... pneumonia and meconium aspiration syndrome.' It does not appear that late SRT compromised the ...

  4. K-Ar Geochronology and isotopic composition of the late oligocene- early miocene Ancud volcanic complex, Chiloe

    International Nuclear Information System (INIS)

    Munoz B, Jorge; Duhart O, Paul; Farmer, G. Lang; Stern, Charles R

    2001-01-01

    The Ancud Volcanic Complex (Gally and Sanchez , 1960) forms a portion of the Mid-Tertiary Coastal Magmatic Belt which outcrops in the area of northern Chiloe island. Main exposures occur at Ancud, Punta Polocue, Punihuil, Pumillahue, Tetas de Teguaco and Bahia Cocotue. The Ancud Volcanic Complex consists of basaltic to basaltic andesites lava flows and volcanic necks and rhyolitic pyroclastic flows and vitric domes. Previous studies indicate a Late Oligocene-Early Miocene age (Garcia et al., 1988; Stern and Vergara, 1992; Munoz et al., 2000). The Ancud Volcanic Complex covers and intrudes Palaeozoic-Triassic metamorphic rocks and is partially covered by an early to middle Miocene marine sedimentary sequence known as Lacui Formation (Valenzuela, 1982) and by Pleistocene glacial deposits (Heusser, 1990). At Punihuil locality, lava flows are interbedded with the lower part of the marine sedimentary sequence, which includes significant amounts of redeposited pyroclastic components. Locally, the presence of hyaloclastic breccias suggests interaction of magma with marine water (au)

  5. A Review on Permian to Triassic Active or Convergent Margin in Southeasternmost Gondwanaland: Possibility of Exploration Target for Tin and Hydrocarbon Deposits in the Eastern Indonesia

    Directory of Open Access Journals (Sweden)

    Amiruddin Amiruddin

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol4no1.20094An active convergence of continental margin is probably generated in Gondwanaland during Permian to Triassic period which is characterized by the presence of magmatic and volcanic belts and back-arc ba- sins occupied respectively by Permian to Triassic rocks. The magmatic belt is occupied by peraluminous granitic plutons showing characteristics of S- type granite and is considered as tin-bearing granites. The back-arc basins are occupied by the Southern Papua and Galille-Bowen-Gunnedah-Sydney Basins. Those large basins are respectivelly filled by fluvial, fluvio- deltaic to marine Permian-Triassic sediments, which are unconformably overlain by the Jurrassic-Cretaceous marine succession. The paleomagnetic data, confirmed by flora content found in Australia and Papua, indicate that those areas initially belong to the Gondwanaland before part of them were drifted and rotated into the present day position. Tectonically, the presence of those Permian-Triassic magmatic-volcanic belts and back-arc basins in behind, indicates that at the time there were huge compressive activities: convergence of paleo-oceanic Pasific Plate moving westward, collided and subducted into the Southeastern Gondwana Continental Plate, moved relatively eastwards. This phenomenon resembles to the formation of Sumatera Tertiary tectonic zones producing back-arc basins, i.e. South Sumatera, Central, and North Sumatera Basins including the Tertiary Magmatic Arc. Concerning the similarity of Permian-Triassic geological condition of the magmatic arc and back-arc basins in Eastern Indonesia and Eastern Australia including paleoposition, paleotectonic setting, strati- graphic succession, and lithologic composition, it is suggested to carry out an increase in a more intens- ive tin exploration in the Eastern Indonesia, e.g. Bird Head area and Banggai Sula Island, and also for hydrocarbon target (coal, coalbed methane, oil and gas, and oil

  6. Late Jurassic low latitude of Central Iran: paleogeographic and tectonic implications

    Science.gov (United States)

    Mattei, Massimo; Muttoni, Giovanni; Cifelli, Francesca

    2014-05-01

    The individual blocks forming present-day Central Iran are now comprised between the Zagros Neo-Tethys suture to the south and the Alborz Palaeo-Tethys suture to the north. At the end of the Palaeozoic, the Iranian blocks rifted away from the northern margin of Gondwana as consequence of the opening of the Neo-Tethys, and collided with Eurasia during the Late Triassic, giving place to the Eo-Cimmerian orogeny. From then on, the Iranian block(s) should have maintained European affinity. Modern generations of apparent polar wander paths (APWPs) show the occurrence in North American and African coordinates of a major and rapid shift in pole position (=plate shift) during the Middle-Late Jurassic. This so-called monster polar shift is predicted also for Eurasia from the North Atlantic plate circuit, but Jurassic data from this continent are scanty and problematic. Here, we present paleomagnetic data from the Kimmeridgian-Tithonian (Upper Jurassic) Garedu Formation of Iran. Paleomagnetic component directions of primary (pre-folding) age indicate a paleolatitude of deposition of 10°N ± 5° that is in excellent agreement with the latitude drop predicted for Iran from APWPs incorporating the Jurassic monster polar shift. We show that paleolatitudes calculated from these APWPs, used in conjunction with simple zonal climate belts, better explain the overall stratigraphic evolution of Iran during the Mesozoic.

  7. Thickly Syndetical Sensitivity of Topological Dynamical System

    Directory of Open Access Journals (Sweden)

    Heng Liu

    2014-01-01

    Full Text Available Consider the surjective continuous map f:X→X, where X is a compact metric space. In this paper we give several stronger versions of sensitivity, such as thick sensitivity, syndetic sensitivity, thickly syndetic sensitivity, and strong sensitivity. We establish the following. (1 If (X,f is minimal and sensitive, then (X,f is syndetically sensitive. (2 Weak mixing implies thick sensitivity. (3 If (X,f is minimal and weakly mixing, then it is thickly syndetically sensitive. (4 If (X,f is a nonminimal M-system, then it is thickly syndetically sensitive. Devaney chaos implies thickly periodic sensitivity. (5 We give a syndetically sensitive system which is not thickly sensitive. (6 We give thickly syndetically sensitive examples but not cofinitely sensitive ones.

  8. three dimensional photoelastic investigations on thick rectangular

    African Journals Online (AJOL)

    user

    1983-09-01

    Sep 1, 1983 ... Thick rectangular plates are investigated by means of three-dimensional photoelasticity ... a thin plate theory and a higher order thick plate theory. 1. ..... number of fringes lest the accuracy of the results will be considerably.

  9. Non-contact radiation thickness gauge

    International Nuclear Information System (INIS)

    Tsujii, T.; Okino, T.

    1983-01-01

    A noncontact thickness gauge system for measuring the thickness of a material comprising a source of radiation, a detector for detecting the amount of radiation transmitted through the material which is a function of the absorptance and thickness of the material, a memory for storing the output signals of the detector and curve-defining parameters for a plurality of quadratic calibration curves which correspond to respective thickness ranges, and a processor for processing the signals and curve defining parameters to determine the thickness of the material. Measurements are made after precalibration to obtain calibration curves and these are stored in the memory, providing signals representative of a nominal thickness and an alloy compensation coefficient for the material. The calibration curve corresponding to a particular thickness range is selected and the curve compensated for drift; the material is inserted into the radiation path and the detector output signal processed with the compensated calibration curve to determine the thickness of the material. (author)

  10. Autonomous Sea-Ice Thickness Survey

    Science.gov (United States)

    2016-06-01

    the conductivity of an infinitely thick slab of sea ice. Ice thickness, Hice, is then obtained by subtracting the height of the ...Thickness Survey of Sea Ice Runway” ERDC/CRREL SR-16-4 ii Abstract We conducted an autonomous survey of sea -ice thickness using the Polar rover Yeti...efficiency relative to manual surveys routinely con- ducted to assess the safety of roads and runways constructed on the sea ice. Yeti executed the

  11. Discovery of a landscape-wide drape of late-glacial aeolian silt in the western Northern Calcareous Alps (Austria): First results and implications

    Science.gov (United States)

    Gild, Charlotte; Geitner, Clemens; Sanders, Diethard

    2018-01-01

    Aeolian deposits record palaeoenvironmental conditions and may coin soil properties. Whereas periglacial loess is extensively investigated for 200 years, the study of the intramontane wind-blown deposits of the Alps has just stuttered along. Herein, we describe a drape of polymictic siliciclastic silt interpreted as an aeolian deposit that veneers extensive areas in the western Northern Calcareous Alps (NCA), from kames terraces near valley floors up to last-glacial nunataks. The NCA - part of the Eastern Alps mountain range - consist mainly of Triassic carbonate rocks; these are overlain by deposits of the Last Glacial Maximum (LGM) and its deglacial-paraglacial aftermath (e.g., glacial tills, fluvio-lacustrine successions, alluvial fans, scree slopes) - and a regional drape of polymictic silt newly described herein. The drape is typically a few decimeters in thickness and slightly modified by soil formation; it consists mainly of well-sorted silt of quartz, feldspars, phyllosilicates (muscovite, chlorite, biotite), amphiboles and, rarely, calcite or dolomite. The drape is unrelated to the substrate: it overlies carbonate bedrock and - in lateral continuity - abandoned deposystems such as colluvial slopes of redeposited till, kames, alluvial fans, scree slopes, and rock avalanche deposits. The drape was spotted from near the present valley floors up to LGM nunataks, over a vertical range of some 2000 m; it is also present in catchments of the NCA that were not overridden by far-travelled ice streams and that lack metamorphic rock fragments. Two OSL quartz ages of the drape from two distinct locations (18.77 ± 1.55 ka; 17.81 ± 1.68 ka) fall into the early Alpine late-glacial interval shortly after the collapse of pleniglacial ice streams; this fits with geological and geomorphological evidence, respectively, that the drape should be of early late-glacial age, and that it accumulated during a specific interval of time. In the NCA, localized minor deposition of

  12. doped ZnO thick film resistors

    Indian Academy of Sciences (India)

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ...

  13. Macular thickness and volume in the elderly

    DEFF Research Database (Denmark)

    Subhi, Yousif; Forshaw, Thomas; Sørensen, Torben Lykke

    2016-01-01

    manifests in the macula of the elderly focusing on clinical relevant measures that are thicknesses and volumes of different macular areas. Ageing seems to increase center point foveal thickness. Ageing does not seem to change the center subfield thickness significantly. Ageing decreases the inner and outer...

  14. The Triassic eucynodont Candelariodon barberenai revisited and the early diversity of stem prozostrodontians

    Directory of Open Access Journals (Sweden)

    Agustín G. Martinelli

    2017-09-01

    Full Text Available The dental anatomy of Candelariodon barberenai from the Dinodontosaurus Assemblage Zone (Pinheiros-Chiniquá Sequence, Santa Maria Supersequence, late Ladinian–early Carnian of south Brazil, is redescribed. Candelariodon was originally classified as Eucynodontia incertae sedis and our analysis recovered this taxon deeply nested within Probainognathia, as the sister taxon of Potheriodon plus Prozostrodontia. The lower postcanine dentition of Candelariodon has several apomorphies shared with Prozostrodon, Santacruzgnathus, Brasilodon/Brasilitherium, and some basal mammaliaforms (Morganucodon, Megazostrodon, such as a lingual cingulum with discrete cusps e and g and two distinct morphologies in the tooth row. The reinterpretation of Candelariodon as a probainognatian cynodont more derived than Probainognathus and the rich Brazilian fossil record document an important adaptive radiation of non-mammaliaform prozostrodontians and closely related forms prior to the origin of the mammaliaform clade.

  15. 7 CFR 920.112 - Late payments.

    Science.gov (United States)

    2010-01-01

    ... Miscellaneous Provisions § 920.112 Late payments. Pursuant to § 920.41(a), interest will be charged at a 1.5 percent monthly simple interest rate. Assessments for kiwifruit shall be deemed late if not received... late charge will be assessed when payment becomes 30 days late. Interest and late payment charges shall...

  16. Paleomagnetic evidence for a Tertiary not Triassic age for rocks in the lower part of the Grober-Fuqua #1 well, southeastern Albuquerque Basin, New Mexico

    Science.gov (United States)

    Hudson, M.R.; Grauch, V.J.S.

    2003-01-01

    A sedimentary sequence penetrated in the lower part of the Grober-Fuqua #1 well in the southeastern Albuquerque Basin has previously been interpreted as either Triassic or Eocene in age. Paleomagnetic study of three specimens from two core fragments yielded a 54.5?? mean inclination of remanent magnetization relative to bedding. This inclination is like that expected in Tertiary time and is distinct from an expected low-angle Triassic inclination. Although the data are very few, when considered in combination with stratigraphic relations and the presence of a gravity low in this southeastern part of the basin, the paleomagnetic evidence favors a Tertiary age for strata in the lower part of the Grober-Fuqua #1 well.

  17. Provenance of Permian-Triassic Gondwana Sequence Units Accreted to the Banda Arc: Constraints from U/Pb and Hf Analysis of Zircons and Igneous Geochemistry

    Science.gov (United States)

    Flores, J. A.; Spencer, C. J.; Harris, R. A.; Hoiland, C.

    2011-12-01

    Analysis of zircons from Australian affinity Permo-Triassic units of the Timor region yield age distributions with large peaks at 230-400 Ma and 1750-1900 Ma (n=435). Similar zircon age peaks are also found in rocks from NE Australia and the eastern Cimmerian block. It is likely that these terranes, which are now widely separated, were once part of the northern edge of Gondwana near what is now the NW margin of Australia. The Cimmerian Block was removed from Gondwana during Early Permian rifting and initiation of the Neo-Tethys Ocean. Hf analysis of zircon from the Aileu Complex in Timor and Kisar shows bimodal (juvenial and evolved) magmatism in the Gondwana Sequence of NW Australia at ~300 Ma. The magmatic event produced basalt with rift valley and ocean floor geochemical affinities, and rhyolite. Similar rock types and isotopic signatures are also found in Permo-Triassic igneous units throughout the Cimmerian continental block. The part of the Cimmerian Block with zircon distributions most like the Gondwana Sequence of NW Australia is the terranes of northern Tibet and Malaysia. The large 1750-1900 Ma zircon peak is much more wide spread, and appears in terranes from Baoshan (SW China) to Borneo. The Permo-Triassic rocks of the Timor region fill syn-rift intracratonic basins that successfully rifted in the Jurassic to form the NW margin of Australia. This passive continental margin first entered the Sunda Trench in the Timor region at around 8 Ma causing the Permo-Triassic rocks to accrete to the edge of the Asian Plate and emerge as a series of mountainous islands in the young collision zone. Eventually, the Australian continental margin will collide with the southern edge of the Asian plate and these Gondwana terranes will rejoin. However, it may be difficult to reconstruct the various ventures of they made over the past 300 Ma.

  18. Geochemical evidences for palaeoclimatic fluctuations at the Triassic-Jurassic boundary: southwestern margin of the Neotethys in the Salt Range, Pakistan

    Science.gov (United States)

    Iqbal, Shahid; Wagreich, Michael; Jan, Irfanullah; Kürschner, Wolfram Michael; Gier, Susanne

    2017-04-01

    The Triassic-Jurassic boundary interval reveals a change from warm-arid to a warm and humid climate in the Tethyan domain. Sea-level reconstruction records across the European basins during this interval reveal an end-Triassic global regression event and is linked to the Central Atlantic Magmatic Province (CAMP) activity and Pangaea breakup. In the Tethyan Salt Range of Pakistan a succession of Upper Triassic dolomites/green-black mudstones (Kingriali Formation), overlying quartzose sandstone, mudstones, laterites and Lower Jurassic conglomerates/pebbly sandstones (Datta Formation) provides information on the palaeoclimatic evolution of the area. Preliminary palynological results from the mudstones indicate a Rhaetian age for the Kingriali Formation and a Hettangian age for the Datta Formation. X-ray diffraction (XRD) analysis of the mudstones (upper part of the Kingriali Formation) indicates the presence of mainly illite while kaolinite is a minor component. The kaolinite content, a reflection of the advanced stage of chemical weathering and hence warm-humid conditions, increases up-section in the overlying sandstone-mudstone succession. The overlying laterite-bauxite horizons lack illite/smectite and are entirely composed of kaolinite, boehmite and haematite. At places these kaolinite rich horizons are mined in the area (Western Salt Range). The bulk rock geochemistry of the succession confirms a similar trend. The Chemical Index of Alteration (CIA) displays an increasing trend from the Upper Triassic shales (CIA 75-80) through the overlying sandstones/mudstones-laterites to the overlying quartz rich sandstones and mudstones (CIA 90-97). The overall results for the succession reveal an increasing chemical maturity trend (increase in the intensity of chemical weathering) from Rhaetian to Hettangian thereby supporting a change from warm-arid to a warm-humid palaeoclimate, probably extreme greenhouse conditions.

  19. Vaginal bleeding in late pregnancy

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000627.htm Vaginal bleeding in late pregnancy To use the sharing ... JavaScript. One out of 10 women will have vaginal bleeding during their 3rd trimester. At times, it ...

  20. A Middle Triassic pachypleurosaur (Diapsida: Eosauropterygia) from a restricted carbonate ramp in the Western Carpathians (Gutenstein Formation, Fatric Unit): paleogeographic implications

    Science.gov (United States)

    Čerňanský, Andrej; Klein, Nicole; Soták, Ján; Olšavský, Mário; Šurka, Juraj; Herich, Pavel

    2018-02-01

    An eosauropterygian skeleton found in the Middle Triassic (upper Anisian) Gutenstein Formation of the Fatric Unit (Demänovská dolina Valley, Low Tatra Mountains, Slovakia) represents the earliest known occurrence of marine tetrapods in the Western Carpathians. The specimen represents a partly articulated portion of the postcranial skeleton (nine dorsal vertebrae, coracoid, ribs, gastral ribs, pelvic girdle, femur and one zeugopodial element). It is assigned to the Pachypleurosauria, more precisely to the Serpianosaurus-Neusticosaurus clade based on the following combination of features: (1) small body size; (2) morphology of vertebrae, ribs and femur; (3) tripartite gastral ribs; and (4) microanatomy of the femur as revealed by μCT. Members of this clade were described from the epicontinental Germanic Basin and the Alpine Triassic (now southern Germany, Switzerland, Italy), and possibly from Spain. This finding shows that pachypleurosaur reptiles attained a broader geographical distribution during the Middle Triassic, with their geographical range reaching to the Central Western Carpathians. Pachypleurosaurs are often found in sediments formed in shallow, hypersaline carbonate-platform environments. The specimen found here occurs in a succession with vermicular limestones in a shallow subtidal zone and stromatolitic limestones in a peritidal zone, indicating that pachypleurosaurs inhabited hypersaline, restricted carbonate ramps in the Western Carpathians.

  1. A Middle Triassic pachypleurosaur (Diapsida: Eosauropterygia from a restricted carbonate ramp in the Western Carpathians (Gutenstein Formation, Fatric Unit: paleogeographic implications

    Directory of Open Access Journals (Sweden)

    Čerňanský Andrej

    2018-02-01

    Full Text Available An eosauropterygian skeleton found in the Middle Triassic (upper Anisian Gutenstein Formation of the Fatric Unit (Demänovská dolina Valley, Low Tatra Mountains, Slovakia represents the earliest known occurrence of marine tetrapods in the Western Carpathians. The specimen represents a partly articulated portion of the postcranial skeleton (nine dorsal vertebrae, coracoid, ribs, gastral ribs, pelvic girdle, femur and one zeugopodial element. It is assigned to the Pachypleurosauria, more precisely to the Serpianosaurus–Neusticosaurus clade based on the following combination of features: (1 small body size; (2 morphology of vertebrae, ribs and femur; (3 tripartite gastral ribs; and (4 microanatomy of the femur as revealed by μCT. Members of this clade were described from the epicontinental Germanic Basin and the Alpine Triassic (now southern Germany, Switzerland, Italy, and possibly from Spain. This finding shows that pachypleurosaur reptiles attained a broader geographical distribution during the Middle Triassic, with their geographical range reaching to the Central Western Carpathians. Pachypleurosaurs are often found in sediments formed in shallow, hypersaline carbonate-platform environments. The specimen found here occurs in a succession with vermicular limestones in a shallow subtidal zone and stromatolitic limestones in a peritidal zone, indicating that pachypleurosaurs inhabited hypersaline, restricted carbonate ramps in the Western Carpathians.

  2. Hydrogeological study of the Triassic series in the JeffaraDahar region (Southern part of Tunisia): Contribution of well logs data and seismic reflection

    Energy Technology Data Exchange (ETDEWEB)

    Ben Lasmar, R.; Guellala, R.; Zouhri, L.; Sarsar Naouali, B.; Garrach, M.; Inoubli, M.H.

    2016-07-01

    The present study concentrates on the interpretation of well logs and seismic reflection data in the JeffaraDahar region (Southeast part of Tunisia) for a better characterization of the Triassic aquifer, a potential target of water supply. Lithological columns and their corresponding well logs reveal that Sidi Stout, Kirchaou and Touareg. sandstones as well as Mekraneb and Rehach dolomites are the main reservoirs of the Triassic aquifer. Well log analysis highlights many permeable and fractured layers that could play an important role in the groundwater circulation. The interpreted seismic sections and the resulting isochrone maps show a tectonic influence on the Triassic aquifer geometry in the Jeffara-Dahar region. The normal faulting of E-W and NW-SE accidents created an aquifer compartmentalized by raised and tilted blocks. Seismic cross-sections reveal that this structure controls the depth of permeable formations and the circulation of groundwater. These results will be useful for rationalising the future hydrogeological research that will be undertaken in the Jeffara-Dahar area. (Author)

  3. Intelligent processing for thick composites

    Science.gov (United States)

    Shin, Daniel Dong-Ok

    2000-10-01

    Manufacturing thick composite parts are associated with adverse curing conditions such as large in-plane temperature gradient and exotherms. The condition is further aggravated because the manufacturer's cycle and the existing cure control systems do not adequately counter such affects. In response, the forecast-based thermal control system is developed to have better cure control for thick composites. Accurate cure kinetic model is crucial for correctly identifying the amount of heat generated for composite process simulation. A new technique for identifying cure parameters for Hercules AS4/3502 prepreg is presented by normalizing the DSC data. The cure kinetics is based on an autocatalytic model for the proposed method, which uses dynamic and isothermal DSC data to determine its parameters. Existing models are also used to determine kinetic parameters but rendered inadequate because of the material's temperature dependent final degree of cure. The model predictions determined from the new technique showed good agreement to both isothermal and dynamic DSC data. The final degree of cure was also in good agreement with experimental data. A realistic cure simulation model including bleeder ply analysis and compaction is validated with Hercules AS4/3501-6 based laminates. The nonsymmetrical temperature distribution resulting from the presence of bleeder plies agreed well to the model prediction. Some of the discrepancies in the predicted compaction behavior were attributed to inaccurate viscosity and permeability models. The temperature prediction was quite good for the 3cm laminate. The validated process simulation model along with cure kinetics model for AS4/3502 prepreg were integrated into the thermal control system. The 3cm Hercules AS4/3501-6 and AS4/3502 laminate were fabricated. The resulting cure cycles satisfied all imposed requirements by minimizing exotherms and temperature gradient. Although the duration of the cure cycles increased, such phenomena was

  4. Late prematurity: a systematic review

    Directory of Open Access Journals (Sweden)

    Luís Carlos Machado Júnior

    2014-06-01

    Full Text Available Objective: this study aimed to review the literature regarding late preterm births (34 weeks to 36 weeks and 6 days of gestation in its several aspects. Sources: the MEDLINE, LILACS, and Cochrane Library databases were searched, and the references of the articles retrieved were also used, with no limit of time. Data synthesis: numerous studies showed a recent increase in late preterm births. In all series, late preterm comprised the majority of preterm births. Studies including millions of births showed a strong association between late preterm birth and neonatal mortality. A higher mortality in childhood and among young adults was also observed. Many studies found an association with several neonatal complications, and also with long-term disorders and sequelae: breastfeeding problems, cerebral palsy, asthma in childhood, poor school performance, schizophrenia, and young adult diabetes. Some authors propose strategies to reduce late prete