WorldWideScience

Sample records for upper miocene evaporites

  1. Mammal extinctions in the Vallesian (Upper Miocene)

    Science.gov (United States)

    Agusti, J.; Moya-Sola, S.

    The term Vallesian was created by Crusafont (1950) to designate the first European Mammalian palaeofaunas containing the equid Hipparion, the remainder of the faunas being composed of typical elements coming from the Middle Miocene such as Micromeryx, Euprox, Sansanosmilus, Pseudaelurus, and Listriodon. Thus, the Aragonian-Vallesian boundary does not show a strong change among European Miocene mammalian faunas (Agusti et al., 1984). On the other hand, the Lower Vallesian/Upper Vallesian transition corresponds to a major biotic crisis. This boudnary is characterized by the disappearence of most of the Aragonian artiodactyl forms such as Protragocerus, Miotragocerus, Listriodon, Hyotherium, Parachleusastochoerus, etc. Among the rodents, this crisis affects the family Eomyidae and most of the cricetid and glirid species. On the other hand, a number of eastern elements appear in the area at the same time. This is the case of the suid Schizochoerus and the murid Progonomys. Other eastern forms are Tragoportax, Graecoryx, Adcrocuta, Paramachairodus, Microstonyx, etc. Most of these are typical elements of the next Mammal stage, the Turolian. Thus, whereas the Lower Vallesian fauna has a typical Aragonian composition except for Hipparion. After the Middle Vallesian event, the Upper Vallesian faunas are already largely Turolian in character. The possible factors involved in this extinction event are discussed.

  2. Lithostratigraphy of the Upper Oligocene - Miocene succession of Denmark

    Directory of Open Access Journals (Sweden)

    Piasecki, Stefan

    2010-12-01

    Full Text Available This paper presents a revised lithostratigraphic scheme for the uppermost Upper Oligocene – Miocene succession of Denmark. The marine Oligocene Brejning Clay Member is upgraded to formation status and includes the Sydklint Member and the Øksenrade Member (new. The shallow marine and deltaic deposits of mainly Early Miocene age are included in the Ribe Group (new while the fully marine Middle and Upper Miocene clay-rich deposits are referred to the Måde Group (new. The Ribe Group is subdivided into 6 formations: the Vejle Fjord Formation is revised and includes the Skansebakke Member,the Billund Formation (new includes the Addit and Hvidbjerg Members (new, the Klintinghoved Formation is redefined formally and includes the Koldingfjord Member (new, the Bastrup Formation(new includes the Resen Member (new, the Vandel Member is a new member in the Arnum Formation (revised, the Odderup Formation is redefined and includes the Stauning Member (new and the coalbearing Fasterholt Member. The Måde Group is subdivided into the Hodde, Ørnhøj (new, Gram and Marbæk (new Formations. Subdivision of the Upper Oligocene – Miocene succession into two groups, the Ribe and Måde Groups, is compatible with the North Sea lithostratigraphic framework where they correlate with the upper part of the Hordaland Group and the Nordland Group, respectively. The revised lithostratigraphic framework correlated in three dimensions provides rigorous constraints on the palaeogeographic interpretation of the Late Oligocene – Miocene period. Three major deltaic units (Billund, Bastrup and Odderup Formations prograded from the north and north-east into the North Sea Basin during the Early – early Middle Miocene. Delta progradation was punctuated by deposition of marine clay and silt associated with minor transgressive events (Vejle Fjord, Klintinghoved and Arnum Formations. During the Middle–Late Miocene, marine depositional conditions dominated (Hodde, Ørnhøj and

  3. Miocene

    Indian Academy of Sciences (India)

    (Malvaceae s.l.), is described from the Sindhudurg Formation. (Miocene) at the ... described along with palynofossils (Phadtare and. Kulkarni 1980a ... D istrict,. Maharash tra,. India, star indicates fossil lo cality; and. ( b. ) litholog o f the. Kalviw adi .... Following collision of the two plates, land connections ... The occur- rence of ...

  4. Rodents from the Upper Miocene Tuğlu Formation (Çankırı Basin, Central Anatolia, Turkey)

    NARCIS (Netherlands)

    Joniak, Peter; de Bruijn, Hans

    2015-01-01

    The upper Miocene assemblages of rodents collected from two layers of the type section of the Tuğlu Formation (Çankırı Basin, Central Anatolia, Turkey) are described. The assemblage from the lower level is considerably less diverse than that from the upper level. It contains Progonomys together with

  5. Rodents from the Upper Miocene Tuğlu Formation (Çankırı Basin, Central Anatolia, Turkey)

    OpenAIRE

    Joniak, Peter; de Bruijn, Hans

    2015-01-01

    The upper Miocene assemblages of rodents collected from two layers of the type section of the Tuğlu Formation (Çankırı Basin, Central Anatolia, Turkey) are described. The assemblage from the lower level is considerably less diverse than that from the upper level. It contains Progonomys together with Megacricetodon, which is a very unusual association. The assemblage from the upper layer shows a relatively high diversity with four species of Gliridae instead of only one in the lower layer. Apa...

  6. Integrated stratigraphy and 40Ar/39Ar chronology of the Early to Middle Miocene Upper Freshwater Molasse in eastern Bavaria (Germany)

    NARCIS (Netherlands)

    Abdul Aziz, H.; Böhme, M.; Rocholl, A.; Zwing, A.; Prieto, J.; Wijbrans, J.R.; Heissig, K.; Bachtadse, V.

    2008-01-01

    A detailed integrated stratigraphic study was carried out on middle Miocene fluvial successions of the Upper Freshwater Molasse (OSM) from the North Alpine Foreland Basin, in eastern Bavaria, Germany. The biostratigraphic investigations yielded six new localities thereby refining the OSM

  7. Paleoecology and environments of bioestromes and path reefs , its ostreid , enhdolith and epibionts ( Camacho formation - middle upper Miocene; Uruguay)

    International Nuclear Information System (INIS)

    Sprechmann, P.; Verde, M.; Martinez, S.; Gaucher, C.

    1998-01-01

    A special lithofacies of the Camacho formation (Middle-Upper Miocene, Uruguay), exposed at Puerto Arazati, is studied from a sedimentologic and paleontologic point of view. Ostreid biostromes and patch reefs show different kinds of growings patterns. Two kinds of ostreid concentration s, biogenic and sedimentologic were distinguished in Puerto Arazati based on taphonomic evidence. Endolith association and epibionts from biostrome and patch reef hardgrounds were also analysed in Puerto Arazati. Both sedimentologic and paleontologic evidence indicates a free of sediment, shallow water depositional environment, in the photic zone. Complementary data about endoliths from other outcrops of the Camacho Formation are included (author)

  8. The Upper Miocene of the Rostov Dome (Eastern Paratethys: Implication of the chronostratigraphy and bivalvia-based biostratigraphy

    Directory of Open Access Journals (Sweden)

    Ruban Dmitry A.

    2005-01-01

    Full Text Available The Rostov Dome is located in the south of the Russian Platform. In the Late Miocene this area was embraced by the Eastern Paratethys. The implications of a recently developed Neogene chronostratigraphy to the studied area are discussed. The Sarmatian regional stage corresponds to the upper part of the Langhian, the entire Serravalian and the lower part of the Tortonian global stages; the Maeotian regional stage corresponds to the upper part of the Tortonian and the lowermost horizons of the Messinian global stages; the Pontian regional stage corresponds to most of the Messinian and the lowermost Zanclean global stages. A first Bivalvia-based bio-stratigraphic framework is proposed for the territory of the Rostov Dome. Five biozones were established within the Serravalian-Messinian: Tapes vitalianus, Cerastoderma fittoni-Cerastoderma subfittoni, Congeria panticapaea, Congeria amygdaloides navicula and Monodacna pseudocatillus-Prosodacna schirvanica.

  9. Paleo-environment in the upper amazon basin during early to middle Miocene times

    Science.gov (United States)

    van Soelen, Els; Hoorn, Carina; Santos, Roberto V.; Dantas, Elton L.; Sinninghe Damsté, Jaap S.; Kim, Jung-Hyun

    2014-05-01

    The Amazon River has the largest catchment in the world and is responsible for the largest water discharge from land to the ocean. The river system that flows from the Andes to the Atlantic Equatorial Margin exists since the late Miocene, and results from Andean uplift which strongly affected erosion/deposition and major flow patterns in northern South-America. Two outcrop sites from the Solimões basin, Mariñame (17.7-16.1 Ma) and Los Chorros (14.2-12.7 Ma), may shed light on the inland paleo-environmental conditions during a period of active Andean uplift in the early to middle Miocene. Earlier works revealed the Mariñame outcrops to represent a river born in Amazonia. Instead the Los Chorros outcrops are relics of the Amazon River system, characterized by extensive wetlands consisting of swamps, shallow lakes, crevasse splays channels and crevasse-delta lakes (e.g. Hoorn et al., 2010). The freshwater ecosystems alternate with some intervals that are rich in marine palynomorphs (such as dinocysts), mangrove pollen, brackish tolerant molluscs and ostracods, which indicate brackish conditions and a marine influence. It is thought that these marine incursion are related to phases of global sea-level rise and rapid subsidence in the Andean foreland (Marshall & Lundberg, 1996). Still, much remains unknown about the Miocene river systems, like the extent and diversity of the wetland system and the nature of the marine incursions. To get a better understanding of the sources of the (in)organic material, geochemical methods were used. Strontium (Sr) and Neodymium (Nd) isotopes were analyzed on bulk sediments, and used for a paleo-provenance study. The Sr and Nd isotopic signature in the older section (Mariñame) is in general more radiogenic compared to the Los Chorros section. The most radiogenic values are comparable to those found nowadays in the the Precambrian Guyana shield. A Guyana sediment source would suggest a distinctly different flow direction of the major

  10. A Middle-Upper Miocene fluvial-lacustrine rift sequence in the Song Ba Rift, Vietnam

    DEFF Research Database (Denmark)

    Lars H., Nielsen; Henrik I., Petersen; Nguyen D., Dau

    2007-01-01

    The small Neogene Krong Pa graben is situated within the continental Song Ba Rift, which is bounded by strike-slip faults that were reactivated as extensional faults in Middle Miocene time. The 500 m thick graben-fill shows an overall depositional development reflecting the structural evolution...... subsidence rate and possibly a higher influx of water from the axial river systems the general water level in the graben rose and deep lakes formed. High organic preservation in the lakes prompted the formation of two excellent oil-prone lacustrine source-rock units. In the late phase of the graben...... as carrier beds, whereas the braided fluvial sandstones and conglomerates along the graben margins may form reservoirs. The Krong Pa graben thus contains oil-prone lacustrine source rocks, effective conduits for generated hydrocarbons and reservoir sandstones side-sealed by the graben faults toward...

  11. Origin of natural waters and gases within the Upper Carboniferous coal-bearing and autochthonous Miocene strata in South-Western part of the Upper Silesian Coal Basin, Poland

    International Nuclear Information System (INIS)

    Kotarba, Maciej J.; Pluta, Irena

    2009-01-01

    The molecular and stable isotope compositions of coalbed gases from the Upper Carboniferous strata and natural gases accumulated within the autochthonous Upper Miocene Skawina Formation of the Debowiec-Simoradz gas deposit were determined, as well as the chemical and stable isotope compositions of waters from the Skawina Formation and waters at the top of the Upper Carboniferous strata of the Kaczyce Ridge (the abandoned 'Morcinek' coal mine) in the South-Western part of the Upper Silesian Coal Basin. Two genetic types of natural gases within the Upper Carboniferous coal-bearing strata were identified: thermogenic (CH 4 , small amounts of higher gaseous hydrocarbons, and CO 2 ) and microbial (CH 4 , very small amounts of ethane, and CO 2 ). Thermogenic gases were generated during the bituminous stage of coalification and completed at the end of the Variscan orogeny. Degassing (desorption) of thermogenic gases began at the end of late Carboniferous until the late Miocene time-period and extended to the present-day. This process took place in the Upper Carboniferous strata up to a depth of about 550 m under the sealing Upper Miocene cover. A primary accumulation zone of indigenous, thermogenic gases is present below the degassing zone. Up to 200 m depth from the top of the Upper Carboniferous strata, within the weathered complex, an accumulation zone of secondary, microbial gas occurs. Waters within these strata are mainly of meteoric origin of the infiltration period just before the last sea transgression in the late Miocene and partly of marine origin having migrated from the Upper Miocene strata. Then, both methanogenic archaebacteria and their nutrients were transported by meteoric water into the near-surface Carboniferous strata where the generated microbial CH 4 saturated coal seams. Waters within the Miocene strata of the Debowiec-Simoradz and Zablocie are of marine origin, and natural gases accumulated within autochthonous Miocene strata of the Debowiec

  12. Environmental significance of Upper Miocene phosphorites at hominid sites in the Lukeino Formation (Tugen Hills, Kenya)

    Science.gov (United States)

    Dericquebourg, Perrine; Person, Alain; Ségalen, Loïc; Pickford, Martin; Senut, Brigitte; Fagel, Nathalie

    2015-08-01

    The Lukeino Formation contains an important sedimentary and fossiliferous record of the late Miocene (6.09-5.68 Ma), which has in particular yielded the fossil remains of the oldest East African bipedal hominid called Orrorin tugenensis. This fluvio-lacustrine sedimentary succession crops out in the Kenyan part of the East African Rift. It is mainly composed of clay to sandy clay deposits intercalated with volcanic ash horizons, and localized layers of carbonates and diatomites. A detailed sedimentological and mineralogical study of the Lukeino Formation was conducted to throw light on the environmental conditions in which the hominids lived. Several centimetric, relatively continuous and indurated phosphatic horizons, of sedimentary origin, were identified at two sites (Sunbarua and Kapcheberek). Mineralogical (XRD) and geochemical analyses as well as observations by SEM, which was coupled with an energy dispersive spectroscopy (EDS) microprobe, indicate that the autochthonous phosphate layers are composed of a micritic matrix of francolite (38-93%), with incorporation of silicates in variable proportions from one layer to another. The phosphate matrix contains very well preserved and abundant diatom frustules in the basal phosphate layer. These diatoms are identified as Aulacoseira granulata, implying a pH of 7.8-8.2 for freshwaters of the Palaeolake Lukeino. Calcitic tubular structures, linked to a possible bacterial origin, are also observed locally. Phosphate layers occur abruptly within a thick clay-sandy series, associated with an intense runoff phase during the deposition of this interval of the Lukeino Formation. The massive and cyclic input of phosphorus to the lake promoted productivity to the stage where it caused a diatom bloom. The establishment of several phosphate horizons testifies to successive phases of eutrophication of Palaeolake Lukeino. The diatom cells provided some of the organic matter, which was decomposed by bacterial activity at the

  13. Record of Carcharocles megalodon in the Eastern Guadalquivir Basin (Upper Miocene, South Spain

    Directory of Open Access Journals (Sweden)

    Reolid, M.

    2015-12-01

    Full Text Available Tortonian diatomites of the San Felix Quarry (Porcuna, in the Eastern Guadalquivir Basin, have given isolated marine vertebrate remains that include a large shark tooth (123.96 mm from apex to the baseline of the root. The large size of the crown height (92.2 mm, the triangular shape, the broad serrated crown, the convex lingual face and flat labial face, and the robust, thick angled root determine that this specimen corresponds to Carcharocles megalodon. The symmetry with low slant shows it to be an upper anterior tooth. The total length estimated from the tooth crown height is calculated by means of different methods, and comparison is made with Carcharodon carcharias. The final inferred total length of around 11 m classifies this specimen in the upper size range of the known C. megalodon specimens. The palaeogeography of the Guadalquivir Basin close to the North Betic Strait, which connected the Atlantic Ocean to the Mediterranean Sea, favoured the interaction of the cold nutrient-rich Atlantic waters with warmer Mediterranean waters. The presence of diatomites indicates potential upwelling currents in this context, as well as high productivity favouring the presence of large vertebrates such as mysticetid whales, pinnipeds and small sharks (Isurus. These large vertebrates recorded in the Eastern Guadalquivir Basin were potential prey of C. megalodon.Las diatomitas tortonienses de la antigua Cantera de San Félix (Porcuna, Jaén, en el sector oriental de la Cuenca del Guadalquivir, han proporcionado restos aislados de vertebrados marinos entre los que destaca un gran diente de tiburón (123.96 mm desde el ápice hasta la línea basal de la raiz. La altura de la corona (92.2 mm, su forma triangular con bordes aserrados, la presencia de una cara lingual convexa y una labial plana, conjuntamente con la raíz angulosa y robusta, permiten determinar que este diente perteneció a un ejemplar de Carcharocles megalodon. La alta simetría de la pieza

  14. Constraining controls on carbonate sequences with high-resolution chronostratigraphy: Upper Miocene, Cabo de Gata region, SE Spain

    Science.gov (United States)

    Montgomery, P.; Farr, M.R.; Franseen, E.K.; Goldstein, R.H.

    2001-01-01

    A high-resolution chronostratigraphy has been developed for Miocene shallow-water carbonate strata in the Cabo de Gata region of SE Spain for evaluation of local, regional and global factors that controlled platform architecture prior to and during the Messinian salinity crisis. Paleomagnetic data were collected from strata at three localities. Mean natural remanent magnetization (NRM) ranges between 1.53 ?? 10-8 and 5.2 ?? 10-3 Am2/kg. Incremental thermal and alternating field demagnetization isolated the characteristic remanent magnetization (ChRM). Rock magnetic studies show that the dominant magnetic mineral is magnetite, but mixtures of magnetite and hematite occur. A composite chronostratigraphy was derived from five stratigraphic sections. Regional stratigraphic data, biostratigraphic data, and an 40Ar/39Ar date of 8.5 ?? 0.1 Ma, for an interbedded volcanic flow, place the strata in geomagnetic polarity Chrons C4r to C3r. Sequence-stratigraphic and diagenetic evidence indicate a major unconformity at the base of depositional sequence (DS)3 that contains a prograding reef complex, suggesting that approximately 250 000 yr of record (Subchrons C3Br.2r to 3Br.1r) are missing near the Messinian-Tortonian boundary. Correlation to the GPTS shows that the studied strata represent five third- to fourth-order DSs. Basal units are temperate to subtropical ramps (DS1A, DS1B, DS2); these are overlain by subtropical to tropical reefal platforms (DS3), which are capped by subtropical to tropical cyclic carbonates (Terminal Carbonate Complex, TCC). Correlation of the Cabo de Gata record to the Melilla area of Morocco, and the Sorbas basin of Spain indicate that early - Late Tortonian ramp strata from these areas are partially time-equivalent. Similar strata are extensively developed in the Western Mediterranean and likely were influenced by a cool climate or influx of nutrients during an overall rise in global sea-level. After ramp deposition, a sequence boundary (SB3) in

  15. Evaporite-hosted native sulfur in Trans-Pecos Texas: Relation to late-phase basin and range deformation

    International Nuclear Information System (INIS)

    Hentz, T.F.; Henry, C.D.

    1989-01-01

    Major deposits of biogenic native sulfur are associated with narrow, northeast-trending grabens and normal faults that disrupt the gently tilted, east-dipping Upper Permian evaporite succession of the western Delaware Basin in Trans-Pecos Texas. Orebodies are restricted to geologic traps in the fractured and dissolution-modified downfaulted blocks of the grabens. Other parallel, regionally distributed grabens and normal faults are commonly the sites of noncommercial sulfur deposits and genetically related secondary-replacement (diagenetic) limestone bodies. The sulfur-bearing structures probably formed during the later of two episodes of Basin and Range extension that have not previously been differentiated in Texas but are well defined elsewhere in the western United States. In Texas several lines of evidence collectively support the existence of late-phase, northwest-directed extension that was initiated in the middle Miocene

  16. Quantitative controls on location and architecture of carbonate depositional sequences: upper miocene, cabo de gata region, se Spain

    Science.gov (United States)

    Franseen, E.K.; Goldstein, R.H.; Farr, M.R.

    1998-01-01

    Sequence stratigraphy, pinning-point relative sea-level curves, and magnetostratigraphy provide the quantitative data necessary to understand how rates of sea-level change and different substrate paleoslopes are dominant controls on accumulation rate, carbonate depositional sequence location, and internal architecture. Five third-order (1-10 my) and fourth-order (0.1-1.0 my) upper Miocene carbonate depositional sequences (DS1A, DS1B, DS2, DS3, TCC) formed with superimposed higher-frequency sea-level cycles in an archipelago setting in SE Spain. Overall, our study indicates when areas of high substrate slope (> 15??) are in shallow water, independent of climate, the location and internal architecture of carbonate deposits are not directly linked to sea-level position but, instead, are controlled by location of gently sloping substrates and processes of bypass. In contrast, if carbonate sediments are generated where substrates of low slope ( 15.6 cm/ky to ??? 2 cm/ky and overall relative sea level rose at rates of 17-21.4 cm/ky. Higher frequency sea-level rates were about 111 to more than 260 cm/ky, producing onlapping, fining- (deepening-) upward cycles. Decreasing accumulation rates resulted from decreasing surface area for shallow-water sediment production, drowning of shallow-water substrates, and complex sediment dispersal related to the archipelago setting. Typical systems tract and parasequence development should not be expected in "bypass ramp" settings; facies of onlapping strata do not track base level and are likely to be significantly different compared to onlapping strata associated with coastal onlap. Basal and upper DS2 reef megabreccias (indicating the transition from cool to warmer climatic conditions) were eroded from steep upslope positions and redeposited downslope onto areas of gentle substrate during rapid sea-level falls (> 22.7 cm/ky) of short duration. Such rapid sea-level falls and presence of steep slopes are not conducive to formation of

  17. Suitability of Gypsum for the Production of Gypsum Plaster an Example from the Abu-Ruweis Evaporites (Upper Triassic), as Subayhi Area, Northwest Jordan

    International Nuclear Information System (INIS)

    Saqqa, W.; Arikat, M.

    2003-01-01

    The gypsum of Abu Ruweis Formation (Upper Triassic) of the northwestern Jordan was chemically, physically and mechanically assessed for likely industrial uses. Chemical results indicate that the investigated gypsum (calcium sulfate dihydrate) is highly pure. This is confirmed by the high ratios of CaO (32-33%) andSO 3 (41-43%) and the very low content of other elements such as Mg, Al and Si. Trace elements are also negligible. The CaSO 4 % (86-88%), purity ratio (CaO/SO 3 ) (0.85) , and combined water (≅5%) for β-hemihydrate gypsum agree well with the jordanian standards for gypsum plaster. Thermal analyses indicate that the temperature required to obtain hemihydrate gypsum falls between 175deg-200deg. A significant mass variation or maximum loss on weight (-20%) was achieved after initial dehydration by heating to 200deg. Heating to 225deg is far enough to evolve all combined water molecules. The results of fineness, consistency, setting time, compressive strength and flexural strength for β-hemilhydrate agree, in most of the case, with the local and international standards intended for gypsum building components. The study showed that the absorption and consistency ratios for final gypsum product are proportional to porosity, whilst the consistency itself decreases with the increase of applied stresses. (author)

  18. The age of volcanic tuffs from the Upper Freshwater Molasse (North Alpine Foreland Basin) and their possible use for tephrostratigraphic correlations across Europe for the Middle Miocene

    Science.gov (United States)

    Rocholl, Alexander; Schaltegger, Urs; Gilg, H. Albert; Wijbrans, Jan; Böhme, Madelaine

    2018-03-01

    The Middle Miocene Upper Freshwater Molasse sediments represent the last cycle of clastic sedimentation during the evolution of the North Alpine Foreland Basin. They are characterized by small-scale lateral and temporal facies changes that make intra-basin stratigraphic correlations at regional scale difficult. This study provides new U-Pb zircon ages as well as revised 40Ar/39Ar data of volcanic ash horizons in the Upper Freshwater Molasse sediments from southern Germany and Switzerland. In a first and preliminary attempt, we propose their possible correlation to other European tephra deposits. The U-Pb zircon data of one Swiss (Bischofszell) and seven southern German (Zahling, Hachelstuhl, Laimering, Unterneul, Krumbad, Ponholz) tuff horizons indicate eruption ages between roughly 13.0 and 15.5 Ma. The stratigraphic position of the Unterneul and Laimering tuffs, bracketing the ejecta of the Ries impact (Brockhorizon), suggests that the Ries impact occurred between 14.93 and 15.00 Ma, thus assigning the event to the reversed chron C5Bn1r (15.032-14.870 Ma) which is in accordance with paleomagnetic evidence. We combine our data with published ages of tuff horizons from Italy, Switzerland, Bavaria, Styria, Hungary, and Romania to derive a preliminary tephrochronological scheme for the Middle Miocene in Central Europe in the age window from 13.2 to 15.5 Ma. The scheme is based on the current state of knowledge that the Carpathian-Pannonian volcanic field was the only area in the region producing explosive calc-alkaline felsic volcanism. This preliminary scheme will require verification by more high-quality ages complemented by isotopic, geochemical and paleomagnetic data.

  19. Origin and chemical composition of evaporite deposits

    Science.gov (United States)

    Moore, George William

    1960-01-01

    the sea to the south. Mixing of the two water layers at their interface diluted the lower layer so as to prevent halite formation, but at the same time the depressed solubility of calcium sulfate in the mixture at the interface caused precipitation of gypsum. The upper water layer is believed to have supported a flourishing microscopic biota whose remains descended into semisterile brine below where reducing conditions prevailed. This environment generated the bituminous gypsum rock. At times, microcrystalline calcium carbonate of probable biochemical origin formed in the upper layer and settled below to form limestone laminae such as those of the lower part of the Castile formation. Chemical analyses of Permian and present-day salt were compared with analyses of marine salt as old as Cambrian age to determine if evaporite deposits can contribute information on the geologic history of sea water. The results contain uncertainties that cannot be fully resolved, but they suggest that the ratio between ions in sea water has been approximately constant since Precambrian time. In addition, the abrupt initial appearance of rock salt deposits in Cambrian time suggests that the Precambrian ocean may have been rather dilute, but this apparent relationship also could have been caused by other factors.

  20. Sr isotope evidence for a lacustrine origin for the upper Miocene to Pliocene Bouse Formation, lower Colorado River trough, and implications for timing of Colorado Plateau uplift

    Science.gov (United States)

    Spencer, J.E.; Patchett, P.J.

    1997-01-01

    The upper Miocene to Pliocene Bouse Formation in the lower Colorado River trough, which consists largely of siltstone with basal tufa and marl, has been interpreted as estuarine on the basis of paleontology. This interpretation requires abrupt marine inundation that has been linked to early rifting in the Gulf of California and Salton trough. New strontium isotope measurements reported here from carbonates and invertebrate shells in the Bouse Formation reveal no evidence of marine water, but are consistent with deposition in a lake or chain of lakes fed by the Colorado River. Furthermore, the absence of a southward decrease in 87Sr/86Sr within the Bouse Formation does not support the estuarine model in which low 87Sr/86Sr marine Sr would have dominated the mouth of the hypothetical Bouse estuary. Elevation of originally marine 87Sr/86Sr in the Bouse Formation to its present level, due to postdepositional interaction with ground water, is unlikely because Sr from secondary calcite above, below, and within the Bouse Formation is consistently less radiogenic, not more, than Bouse marl and shells. In contrast to Bouse Sr, strontium from mollusks in tidal-flat and delta-front paleoenvironments in the contemporaneous Imperial Formation in the Salton trough and from the subsurface south of Yuma was derived from sea water and confirms the dominance of marine strontium near or at the mouth of the late Miocene to early Pliocene Colorado River. Inferred post-early Pliocene uplift of the Bouse Formation from below sea level to modern elevations of up to 550 m has been used to support a late Cenozoic uplift age for the nearby Colorado Plateau. This constraint on uplift timing is eliminated if the Bouse Formation is lacustrine.

  1. The Upper Miocene Lake Pannon marl from the Filijala Open Pit (Beočin, northern Serbia: New geological and paleomagnetic data

    Directory of Open Access Journals (Sweden)

    Ganić Meri

    2010-01-01

    Full Text Available This work presents major lithological, structural, paleontological and paleomagnetic characteristics of the Upper Miocene Pannonian marl in the Filijala Open Pit of the La Farge Cement Plant near Beočin, northern Serbia. Pannonian marl lies between the underlying heterogeneous Sarmatian deposits and the overlying set of Pontian sand beds and Quaternary sediments. The open pit is located on the NE range of Fruška Gora, a horst structure with a core of Paleozoic, Mesozoic and Paleogene rocks in a complex structural pattern. Pannonian sediments, which are part of a younger structural stage, deposited on the horst limbs. The Pannonian marl strata dip at angles from 12° to 26° (to the NNW, forming a monocline. The strata deformations are a consequence of radial tectonics and are a potential source of landslides. The many mollusks (7 gastropod and 9 bivalve species and ostracodes (27 species and their biostratigraphical position indicate marl deposition throughout the Pannonian age. A paleomagnetic investigation established that the marl has inconsistent remanent magnetization (with bad statistical parameters, which originates from neoformed magnetite.

  2. Deposition of Boron in Possible Evaporite Deposits in Gale Crate

    Science.gov (United States)

    Gasda, P. J.; Peets, E.; Lamm, S. N.; Rapin, W.; Lanza, N.; Frydenvang, J.; Clark, B. C.; Herkenhoff, K. E.; Bridges, J.; Schwenzer, S. P.; Haldeman, E. B.; Wiens, R. C.; Maurice, S.; Clegg, S. M.; Delapp, D.; Sanford, V.; Bodine, M. R.; McInroy, R.

    2017-12-01

    Boron has been previously detected in Gale crater using the ChemCam instrument on board the NASA Curiosity rover within calcium sulfate fracture fill hosted by lacustrine mudstone and eolian sandstone units. Recent results show that up to 300 ppm B is present in the upper sections of the lacustrine unit. Boron has been detected in both the groundwater-emplaced calcium sulfate fracture fill materials and bedding-parallel calcium sulfate layers. The widespread bedding-parallel calcium sulfate layers within the upper strata of the lacustrine bedrock that Curiosity has encountered recently could be interpreted as primary evaporite deposits. We have two hypotheses for the history of boron in Gale crater. In both hypotheses, borates were first deposited as lake water evaporated, depositing primary evaporates that were later re-dissolved by groundwater, which redistributed the boron into secondary evaporitic calcium sulfate fracture fill deposits. In the first scenario, Gale crater may have undergone a period of perennial lake formation during a drier period of martian history, depositing layers of evaporitic minerals (including borates) among lacustrine mudstone layers. In the second scenario, lake margins could have become periodically exposed during cyclic drops in lake level and subsequently desiccated. Evaporites were deposited and desiccation features were formed in lowstand deposits. Either hypothetical scenario of evaporite deposition would promote prebiotic chemical reactions via wet-dry cycles. Boron may be an important prebiotic element, and as such, its presence in ancient martian surface and groundwater provides evidence that important prebiotic chemical reactions could occur on Mars if organics were present. The presence of boron in ancient Gale crater groundwater also provides additional evidence that a habitable environment existed in the martian subsurface well after the expected disappearance of liquid water on the surface of Mars. We will report on the

  3. Controls on facies and sequence stratigraphy of an upper Miocene carbonate ramp and platform, Melilla basin, NE Morocco

    Science.gov (United States)

    Cunningham, K.J.; Collins, Luke S.

    2002-01-01

    that bound the upper surface of the ramp and upper surface of the oldest platform parasequence are related to relative falls in sea level induced by local volcanism and associated tectonic uplift. These local relative falls had little influence on a broader-scale rise to stillstand in relative sea level that controlled development of the transgressive and early highstand systems tracts represented in the ramp and platform, respectively. ?? 2002 Elsevier Science B.V. All rights reserved.

  4. SEQUENCE STRATIGRAPHY AND PALEONTOLOGY OF THE UPPER MIOCENE PISCO FORMATION ALONG THE WESTERN SIDE OF THE LOWER ICA VALLEY (ICA DESERT, PERU

    Directory of Open Access Journals (Sweden)

    CLAUDIO DI CELMA

    2017-04-01

    Full Text Available The sequence stratigraphic framework and a summary of the fossil fauna of the upper Miocene portion of the Pisco Formation exposed along the western side of the Ica River (southern Peru is presented through a new geological map encompassing an area of about 200 km2 and detailed chronostratigraphic analyses. Extensive field mapping and sedimentological study of outcrop sections have shown that the Pisco Formation is a cyclical sediment unit composed of at least three fining-upward, unconformity-bounded depositional sequences, designated P0, P1, and P2 from oldest to youngest. In the study area, these sequences progressively onlap a composite basal unconformity from southwest to northeast. Integration of biostratigraphic and tephrochronologic age determinations constrains the ages of the three Pisco sequences within the study area. Based on the age of surrounding sediments, a conservative estimate of the age of P0 suggests deposition of these strata between 17.99 ± 0.10 Ma and 9.00 ± 0.02 Ma, whereas diatom biostratigraphy and calculated 40Ar/39Ar ages converge to indicate that strata of the P1 sequence were deposited sometime between 9.5 Ma and 8.9 Ma and that those of the P2 sequence are younger than 8.5 Ma and older than 6.71 ± 0.02 Ma. Our survey for both vertebrate and macro-invertebrate remains in the three sequences confirms the outstanding paleontological value of the Pisco Formation and contributes to depict regional faunal shifts in the fossil assemblage.

  5. Experimental simulations of ethylene evaporites on Titan

    Science.gov (United States)

    Czaplinski, E.; Farnsworth, K.; Singh, S.; Chevrier, V.

    2017-12-01

    Titan has an abundance of lakes and seas, as identified by the Cassini spacecraft. Major components of these liquid bodies include methane (CH4) and ethane (C2H6), however minor constituents are also thought to exist (e.g. ethylene (C2H4)). As the lakes and seas evaporate, 5-μm-bright deposits, resembling evaporite deposits on Earth, are left behind in a "bathtub ring" fashion. Previous studies include models of evaporites, and observations of the 5-μm-bright regions, but the community is still lacking a complete suite of experimental evaporite studies. In this study, we experimentally investigate evaporites in order to determine their composition and how they affect infrared spectra during the evaporation process. The University of Arkansas owns a specialized chamber that simulates the surface conditions of Titan ( 90 K and 1.5 bar). Gaseous hydrocarbons are condensed within the chamber and analyzed with Fourier Transform Infrared (FTIR) Spectroscopy and band depth calculations. In this study, three types of experiments were performed: ethane/ethylene, methane/ethylene, and methane/ethane/ethylene. For these experiments, methane was the only species that readily evaporated at Titan conditions (due to its high volatility), while ethane, being the more stable solvent, did not readily evaporate. Therefore, we will present spectral results of ethylene evaporite formation within these mixtures. Our results imply that evaporite formation is strongly dependent on the composition of the solvent. The north polar lakes of Titan are predicted to be methane-rich, indicating that they may be more likely to form evaporites. Alternatively, Ontario Lacus, a south polar lake, is predominately composed of ethane, which may make it more difficult to form evaporites. As we continue to study Titan's mysterious lakes and seas, we hope to draw insights on their exact composition, conditions for evaporite formation, habitability potential, and comparing Titan to prebiotic Earth.

  6. Drilling through the Messinian evaporites: the beginning of a new adventure?

    Science.gov (United States)

    Bassetti, M. A.; Lofi, J.

    2009-04-01

    The sensitivity of past environments tell us a lot about the nature of changes, either of climatic or geodynamic origin. In this respect, the Mediterranean basin represents the ideal natural laboratory for studying the interaction between deep processes, tectonics, sedimentary fluxes and sea-level oscillation that are at the origin of the sedimentary records. A spectacular example of reactivity of this system have been experienced less than 6 Myrs ago, when the pan-Mediterranean realm underwent rapid and abrupt changes of paleo-environmental parameters that led to the well known Messinian Salinity Crisis (MSC, Hsü et al., 1973). This short-term event at the geological scale (~5.96-5.32 Ma) results from the progressive closure of the two-way connection between the Atlantic Ocean and the Mediterranean Sea. The most important characteristics of this event are: (1) a reduction of the Atlantic water supply having as a consequence, an increased salinity and in the precipitation of thick evaporites within shallow water marginal basins (presently disconnected from the deep basins); (2) a subsequent major sea-level fall exceeding 2000 m and resulting in the massive erosion of the margins and the development of deep subaerial canyons; (3) the accumulation of the product of the erosion in the downslope domain of the margins; (4) the deposition of thick evaporites (up to 3000 m thick) above the deep Mediterranean abyssal plains and (5) and a very rapid refilling of the Mediterranean basin during the Latest Miocene/Lower Pliocene, following the re-connection between Atlantic and Mediterranean through the Gibraltar straight. Timing, causes and chronology of the MSC are not yet fully understood, but different scenarii have been proposed to explain in details the modalities of this catastrophic event. Certainly, the ongoing discussion about not fully conclusive interpretations are mainly linked to the fact that so far, only the deepest and buried Mediterranean basins might offer

  7. The sequence stratigraphy, sedimentology, and economic importance of evaporite carbonate transitions: a review

    Science.gov (United States)

    Sarg, J. F.

    2001-04-01

    -energy, shallow water grainstones and packstones to nonporous evaporitic lagoonal dolomite and sabkha anhydrite occurs in the Upper Permian San Andres/Grayburg sequences of the Permian basin. This facies change provides the trap for secondary oil pools on the basinward flanks of fields that are productive from highstand facies identical to the lowstand dolograinstones. Type 2 lowstand systems, like the Smackover Limestone of the Gulf of Mexico, show a similar relationship. Commonly, these evaporite systems are a facies mosaic of salina and sabkha evaporites admixed with wadi siliciclastics. They overlie and seal highstand carbonate platforms containing reservoir facies of shoalwater nonskeletal and skeletal grainstones. Further basinward these evaporites change facies into similar porous platform facies, and contain separate hydrocarbon traps. Transgressions in arid settings over underfilled platforms (e.g. Zechstein (Permian) of Europe; Ferry Lake Anhydrite (Cretaceous), Gulf of Mexico) can result in deposition of alternating cyclic carbonates and evaporites in broad, shallow subaqueous hypersaline environments. Evaporites include bedded and palmate gypsum layers. Mudstones and wackestones are deposited in mesosaline, shallow subtidal to low intertidal environments during periodic flooding of the platform interior. Highstand systems tracts are characterized by thick successions of m-scale, brining upward parasequences in platform interior settings. The Seven Rivers Formation (Guadalupian) of the Permian basin typifies this transition. An intertonguing of carbonate and sulfates is interpreted to occur in a broad, shallow subaqueous hypersaline shelf lagoon behind the main restricting shelf-edge carbonate complex. Underlying paleodepositional highs appear to control the position of the initial facies transition. Periodic flooding of the shelf interior results in widespread carbonate deposition comprised of mesosaline, skeletal-poor peloid dolowackestones/mudstones. Progressive

  8. Character of the contact and biostratigraphical feature of distribution of the microfauna on border between productive series (PS) and underlying upper Miocene sediments of Absheron oil and gas bearing region

    International Nuclear Information System (INIS)

    Shikhlinsky, S.A.

    2002-01-01

    Full text: Productive Series (PS) is a basic hydrocarbon object and has a wide distribution in the Absheron Oil and Gas Bearing Region (AOGBR).In the normal stratigraphic sequences PS lays between Akchagylian and Pontian Regiostages (Pontian).From microfauna point of view, PS contains rare native ostracods , fish teeth, otolithes and forams.In situ, in PS, there are 34 of microfauna species present and more than half of them are transitional, which appear in the Upper Miocene and finish the existence in the Akchagylian-Apsheronian sediments.Others taxons are having the strict stratigraphical distribution and very important for the definition of the age of different lithostratones inside PS.Stratigraphical distribution of these species has been tested in numerous natural outcrops and well sections.The large interest for geologists is the boundary between PS and underlying Upper Miocene.The stratigraphic character of the given intermediate complex of sediments depends on paleotectonic conditions and different sections on the way it is expressed differently.In one section, in other-the gradual transition from Pontian to Kalinskaya Suite (KaS).The detailed study of the samples from the numerous old explorationwells drilled before 1972 and from new contract areas located in the Caspian sea, such as Karabakh, Dan Ulduzu, Ashrafi, where sampling was made very detailed, allowed us to discover the characteristic biomarkers and to specify the character of distribution of the microfauna on the Pontian-KaS boundary.The similar contact between KaC and Pontian is observed in the Karabakh field too.KaS here is represented by monotonous carbonated shale, clay and claystone, almost not distinguished from the black Potian shale, with increase at the contact with water.Despite of it, the boundary is precisely beaten by microfauna.In the Pontian sediments we have discovered a characteristic complex of Ostracoda and microscopic Pelecypoda.

  9. THE BRECCE DELLA RENGA FORMATION: AGE AND SEDIMENTOLOGY OF A SYN-TECTONIC CLASTIC UNIT IN THE UPPER MIOCENE OF CENTRAL APENNINES. INSIGHTS FROM FIELD GEOLOGY

    Directory of Open Access Journals (Sweden)

    SIMONE FABBI

    2014-07-01

    Full Text Available In the NE Simbruini Mountains, the “Brecce della Renga Fm.” is a clastic unit documenting sedimentation controlled by late Miocene extensional tectonics.The unit has been subdivided into three lithofacies and six sublithofacies, based on the arenite/rudite/pelite ratio. Massive and coarser (up to megablock size intervals are interpreted as rockfall deposits (likely induced by earthquakes at the toe of steep submarine escarpments. By contrast, finer levels are interpreted as having been sedimented through avalanching and turbidity flows in more distal settings, and are partly lateral to basinal hemipelagites and siliciclastic turbidites. Pelite lenses, found at various stratigraphic levels, are the result of ponded sedimentation along the clastic margin. Calcareous nannofossils analyses have been performed for age determinations on 60 fossiliferous samples, which were collected in each sublithofacies of the “Brecce della Renga Fm.”. The unit ranges from early Tortonian (MNN8b to early Messinian (MNN11c. The age and field geometries of the older breccias document the existence of a Tortonian extensional phase, which predated the late Messinian thrusting. A progradation of the clastic wedge can be observed in the Tortonian, while Messinian deposits show a fining upwards trend. The distribution curve of clastics over time can, given the number of synsedimentary faults mapped in the area, be put in relation with the seismicity induced by the activity along such faults, which after reaching an acme in the Tortonian gradually reached a quiescent state in the early Messinian, causing the backstepping of clastic facies.

  10. Exceptional preservation of Miocene pollen: plasmolysis captured in salt?

    Energy Technology Data Exchange (ETDEWEB)

    Durska, W.

    2016-07-01

    Exceptionally well-preserved Miocene pollen from the Bochnia salt mine of southern Poland is reported herein. The halite deposits within the salt mine belonging to Late Badenian (Miocene) marine evaporites originated in the Paratethys. Rounded and angular structures are present inside pollen grains. On the basis of the similarity with plasmolyzed pollen grains of modern plants, these structures are considered to represent cytoplasms plasmolyzed in the condensed brine prior to fossilization. Two forms of plasmolyzed cytoplasms (concave and convex) can be observed in modern pollen. Both are distinguished in the investigated fossil material. In porate and colporate grains the shape of the plasmolyzed cellular content is concave while in inaperturate it is convex. The plasmolysis form depends on the type of apertures and pollen shape. The percentage of pollen with fossilized cytoplasms within individual taxa is a valuable environmental indicator, as it depends on the proximity of the pollen-producing plant assemblages to the depositional setting. (Author)

  11. Karst in evaporites in southeastern New Mexico

    International Nuclear Information System (INIS)

    Bachman, G.O.

    1987-09-01

    Permian evaporites in southeastern New Mexico include gypsum, anhydrite, and salt, which are subject to both blanket and local, selective dissolution. Dissolution has produced many hundreds of individual karst features including collapse sinks, karst valleys, blind valleys, karst plains, caves, and breccia pipes. Dissolution began within some formations during Permian time and has been intermittent but continual ever since. Karst features other than blanket deposits of breccia are not preserved from the early episodes of dissolution, but some karst features preserved today - such as breccia pipes - are remnants of karst activity that was active at least as early as mid-Pleistocene time. Rainfall was much more abundant during Late Pleistocene time, and many features visible today may have been formed then. The drainage history of the Pecos River is related to extensive karstification of the Pecos Valley during mid-Pleistocene time. Large-scale stream piracy and dissolution of salt in the subsurface resulted in major shifts and excavations in the channel. In spite of intensive groundwater studies that have been carried out in the region, major problems in near-surface evaporite karst remain to be solved. Among these are determination of recharge areas and time of recharge. 109 refs., 31 figs., 1 tab

  12. Danburite in evaporites of the Paradox basin, Utah.

    Science.gov (United States)

    Raup, O.B.; Madsen, B.M.

    1986-01-01

    Danburite (CaB2Si2O8) has been found as nodules in Pennsylvanian age marine evaporites. The occurrence of danburite and its relation to the host rock in the Paradox basin evaporites indicates that it most likely formed by diagenetic reaction of boron-rich, high-salinity brines with constituents in the anhydrite host rock.-from Authors

  13. Evaporite karst of northern lower Michigan

    Science.gov (United States)

    Black, T.J.

    1997-01-01

    Michigan has three main zones of evaporite karst: collapse breccia in Late Silurian deposits of the Mackinac Straits region; breccia, collapse sinks, and mega-block collapse in Middle Devonian deposits of Northern Lower Michigan, which overlaps the preceding area; and areas of soil swallows in sinks of Mississippian deposits between Turner and Alabaster in Arenac and Iosco counties, and near Grand Rapids in Kent County. The author has focused his study on evaporite karst of the Middle Devonian deposits. The Middle Devonian depos its are the Detroit River Group: a series consisting of limestone, dolomite, shale, salt, gypsum, and anhydrite. The group occurs from subcrop, near the surface, to nearly 1400 feet deep from the northern tip of the Southern Peninsula to the south edge of the "solution front" Glacial drift is from zero to 350 feet thick. Oil and gas exploration has encountered some significant lost-circulation zones throughout the area. Drilling without fluid returns, casing-seal failures, and lost holes are strong risks in some parts of the region. Lost fluid returns near the top of the group in nearby areas indicate some karst development shortly after deposition. Large and irregular lost-circulation zones, linear and patch trends of large sink holes, and 0.25 mile wide blocks of down-dropped land in the northern Lower Peninsula of Michigan were caused by surface- and ground-water movement along faults into the Detroit River Group. Glaciation has removed some evidence of the karst area at the surface. Sinkhole development, collapse valleys, and swallows developed since retreat of the glacier reveal an active solution front in the Detroit River Group.

  14. EVAPORITE MICROBIAL FILMS, MATS, MICROBIALITES AND STROMATOLITES

    Energy Technology Data Exchange (ETDEWEB)

    Brigmon, R; Penny Morris, P; Garriet Smith, G

    2008-01-28

    Evaporitic environments are found in a variety of depositional environments as early as the Archean. The depositional settings, microbial community and mineralogical composition vary significantly as no two settings are identical. The common thread linking all of the settings is that evaporation exceeds precipitation resulting in elevated concentrations of cations and anions that are higher than in oceanic systems. The Dead Sea and Storrs Lake are examples of two diverse modern evaporitic settings as the former is below sea level and the latter is a coastal lake on an island in the Caribbean. Each system varies in water chemistry as the Dead Sea dissolved ions originate from surface weathered materials, springs, and aquifers while Storrs Lake dissolved ion concentration is primarily derived from sea water. Consequently some of the ions, i.e., Sr, Ba are found at significantly lower concentrations in Storrs Lake than in the Dead Sea. The origin of the dissolved ions are ultimately responsible for the pH of each system, alkaline versus mildly acidic. Each system exhibits unique biogeochemical properties as the extreme environments select certain microorganisms. Storrs Lake possesses significant biofilms and stromatolitic deposits and the alkalinity varies depending on rainfall and storm activity. The microbial community Storrs Lake is much more diverse and active than those observed in the Dead Sea. The Dead Sea waters are mildly acidic, lack stromatolites, and possess a lower density of microbial populations. The general absence of microbial and biofilm fossilization is due to the depletion of HCO{sub 3} and slightly acidic pH.

  15. Ichnological analysis of the Upper Miocene in the ANH-Tumaco-1-ST-P well: assessing paleoenvironmental conditions at the Tumaco Basin, in the Colombian Pacific

    Science.gov (United States)

    Giraldo-Villegas, Carlos A.; Celis, Sergio A.; Rodríguez-Tovar, Francisco J.; Pardo-Trujillo, Andrés; Vallejo-Hincapié, Diego F.; Trejos-Tamayo, Raúl A.

    2016-11-01

    .3-1677.1 m) dominated by massive and laminated mudrocks and 1 to 6 ichnofabric indexes and, 2) the upper segment (1677.1-1640.4 m) characterized by the increase of the sandstone facies, and ichnofabric indexes from 1 to 5. Along these segments, four ichnofabrics have been identified: 1) Phycosiphon-Planolites, 2) Planolites-Thalassinoides, 3) Zoophycos-Chondrites, and 4) Phycosiphon-Thalassinoides, reflecting stable sedimentary conditions with low-moderate energy, low-moderate sedimentation rates, and dominant aerobic facies. Minor variations in these parameters (sedimentation rate, energy conditions, substrate consistency, oxygenation and organic matter), however, induced changes in the macrobenthic tracemaker community, and consequently in the registered trace fossil assemblages.

  16. Dissolution of Kansas evaporites: the radioactive waste disposal problem

    International Nuclear Information System (INIS)

    Smith, B.J.

    1977-01-01

    The radioactive waste repository at Lyons, Kansas, focused attention on the problem of evaporite dissolution. More study is needed in the determination of the mechanisms responsible for deterioration. Also, recent water-use policies have been questioned with the need pointed out for increased effectiveness in planning. Good water planning has to take into account the role of evaporite dissolution in water quality. 23 references

  17. Evaporite-hydrocarbon relationships: The case of the Laminite-reef-evaporite system in the Messinian of the Mediterranean area

    Energy Technology Data Exchange (ETDEWEB)

    Rouchy, J.M. (Museum d' Histoire Naturelle, Paris (France))

    1988-08-01

    The peripheral Messinian evaporitic basins of the Mediterranean frequently show the association between pre-evaporitic laminites, carbonate complexes (red algae, corals, and stromatolites), and evaporites which constitute a sedimentary system, including potential source rocks, reservoirs, and a cover. The pre-evaporitic laminites (mainly diatomites and carbonates) characterize two different highly productive hydrodynamic systems which follow one another: (1) coastal upwellings during lower Messinian high sea level (transgressive phase), and (2) restriction (semiclosed or land-locked basins) related to closure from the Atlantic and subsequent lower sea level (regressive phase). Preservation of the organic matter results from periodic water stratification: local O{sub 2} minimum intermediary layer and anoxic bottom conditions mainly related to hypersalinity. Extensive carbonate complexes overlie the shores and the high areas - biogenic buildups (mainly red algae and poorly diversified corals) and bioclastic accumulations locally overlapped by a stromatolitic blanket. Diagenesis and dissolution-karstification during drawdown periods (hypersaline episodes) increase the primary porosity. The evaporites constitute an efficient cover. One major property of hypersaline environments is their high primary production whose traces are identified in the Messinian series as organic-rich layers (marine or hypersaline-adapted flora and fauna) and calcareous or gypsified stromatolites. Stratified waters or reducing conditions in the pore waters favor preservation of organic matter. The evaporitic conditions greatly influence the reservoir properties, increasing porosity or destroying it by interstitial precipitation.

  18. Potential Evaporite Biomarkers from the Dead Sea

    Science.gov (United States)

    Morris, Penny A.; Wentworth, Susan J.; Thomas-Keprta, Kathie; Allen, Carlton C.; McKay, David S.

    2001-01-01

    The Dead Sea is located on the northern branch of the African-Levant Rift systems. The rift system, according to one model, was formed by a series of strike slip faults, initially forming approximately two million years ago. The Dead Sea is an evaporite basin that receives freshwater from springs and from the Jordan River. The Dead Sea is different from other evaporite basins, such as the Great Salt Lake, in that it possesses high concentrations of magnesium and has an average pH of 6.1. The dominant cation in the Great Salt Lake is sodium, and the pH is 7.7. Calcium concentrations are also higher in the Dead Sea than in the Great Salt Lake. Both basins are similar in that the dominant anion is chlorine and the salinity levels are approximately 20 %. Other common cations that have been identified from the waters of the Dead Sea and the Great Salt Lake include sodium and potassium. A variety of Archea, Bacteria, and a single genus of a green algal, Dunaliella, has been described from the Dead Sea. Earlier studies concentrated on microbial identification and analysis of their unique physiology that allows them to survive in this type of extreme environment. Potential microbial fossilization processes, microbial fossils, and the metallic ions associated with fossilization have not been studied thoroughly. The present study is restricted to identifying probable microbial morphologies and associated metallic ions. XRD (X Ray Diffraction) analysis indicates the presence of halite, quartz, and orthoclase feldspar. In addition to these minerals, other workers have reported potassium chloride, magnesium bromide, magnesium chloride, calcium chloride, and calcium sulfate. Halite, calcium sulfate, and orthoclase were examined in this report for the presence of microbes, microbially induced deposits or microbial alteration. Neither the gypsum nor the orthoclase surfaces possesses any obvious indications of microbial life or fossilization. The sand-sized orthoclase particles are

  19. The Messinian evaporites in the Levant Basin: lithology, deformation and its evolution

    Science.gov (United States)

    Feng, Ye; Steinberg, Josh; Reshef, Moshe

    2017-04-01

    The lithological composition of the Messinian evaporite in the Levant Basin remains controversial and salt deformation mechanisms are still not fully understood, due to the lack of high resolution 3D depth seismic data and well logs that record the entire evaporite sequence. We demonstrate how 3D Pre-stack depth migration (PSDM) and intra-salt tomography can lead to improved salt imaging. Using 3D PSDM seismic data with great coverage and deepwater well log data from recently drilled boreholes, we reveal intra-salt reflective units associated with thin clastic layers and a seismic transparent background consisting of uniform pure halite. Structural maps of all internal reflectors are generated for stratigraphy and attributes analysis. High amplitude fan structures in the lowermost intra-salt reflector are observed, which may indicate the source of the clastic formation during the Messinian Salinity Crisis (MSC). The Messinian evaporite in the Levant Basin comprises six units; the uppermost unit thickens towards the northwest, whereas the other units are uniform in thickness. The top of salt (TS) horizon is relatively horizontal, while all other intra-salt reflectors and base of salt (BS) dip towards the northwest. Different seismic attributes are used for identification of intra-salt deformation patterns. Maximum curvature maps show NW-striking thrust faults on the TS and upper intra-salt units, and dip azimuth maps are used to show different fold orientations between the TS and intra-salt units, which indicate a two-phase deformation mechanism: basin NW tilting as syn-depositional phase and NNE spreading of Plio-Pleistocene overburden as post-depositional phase. RMS amplitude maps are used to identify a channelized system on the TS. An evaporite evolution model during the MSC of the Levant Basin is therefore established based on all the observations. Finally the mechanical properties of the salts will be utilized to explore salt deformation in the Levant Basin

  20. COMPOSITIONAL SIMILARITIES AND DISTINCTIONS BETWEEN TITAN’S EVAPORITIC TERRAINS

    Energy Technology Data Exchange (ETDEWEB)

    MacKenzie, S. M.; Barnes, Jason W., E-mail: mack3108@vandals.uidaho.edu [Department of Physics, University of Idaho, Moscow, ID 83844-0903 (United States)

    2016-04-10

    We document the similarities in composition between the equatorial basins Tui Regio, Hotei Regio, and other 5-μm-bright materials, notably the north polar evaporites, by investigating the presence and extent of an absorption feature at 4.92 μm. In most observations, Woytchugga Lacuna, Ontario Lacus, MacKay Lacus, deposits near Fensal, some of the lakes and dry lake beds south of Ligeia, and the southern shores of Kraken Mare share the absorption feature at 4.92 μm observed in the spectra of Tui and Hotei. Besides Woytchugga and at Fensal, these 5-μm-bright deposits are geomorphologically substantiated evaporites. Thus, the similarity in composition strengthens the hypothesis that Tui and Hotei once contained liquid. Other evaporite deposits, however, do not show the 4.92 μm absorption, notably Muggel Lacus and the shores of Ligeia Mare at the north pole. This difference in composition suggests that there is more than one kind of soluble material in Titan’s lakes that can create evaporite and/or that the surface properties at the Visual and Infrared Mapping Spectrometer wavelength scale are not uniform between the different deposits (crystal size, abundance, etc.). Our results indicate that the surface structure, composition, and formation history of Titan’s evaporites may be at least as dynamic and complex as their Earth counterparts.

  1. A macroecological glance at the structure of late Miocene rodent assemblages from Southwest Europe

    Science.gov (United States)

    Cano, Ana Rosa Gómez; Cantalapiedra, Juan L.; Álvarez-Sierra, M. Ángeles; Fernández, Manuel Hernández

    2014-10-01

    Deep-time perspectives in macroecology are essential with regard to understanding the impact of climate forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are generalists in the southern province and specialists of forested habitats in the northern province. Finally, we identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the Miocene. These three broad ecological groups showed differential responses to a complex set of interconnected circumstances, including the biogeographic structure of the study area and climatic changes throughout time.

  2. Miocene Antarctic Terrestrial Realm

    Science.gov (United States)

    Ashworth, A. C.; Lewis, A.; Marchant, D. R.

    2009-12-01

    The discovery of several locations in the Transantarctic Mountains that contain macrofossils and pollen is transforming our understanding of late Cenozoic Antarctica. The most southerly location is on the Beardmore Glacier (85.1°S) about 500 km from the South Pole. The environment was an active glacial margin in which plants, insects and freshwater mollusks inhabited the sand and gravel bars and small lakes on an outwash plain. In addition to leaves and wood of dwarf Nothofagus (Southern Beech) shrubs, achenes of Ranunculus (Buttercup), in situ cushion growth forms of mosses and a vascular plant, the assemblages contains various exoskeletal parts of carabid and curculionid beetles and a cyclorrhaphan fly, the shells of freshwater bivalve and gastropod species and a fish tooth. Initially the deposits were assigned a Pliocene age (3.5 Ma) but a mid- to early Miocene age is more probable (c. 14 - 25 Ma) based on correlation of fossil pollen from the deposits with 39Ar/40Ar dated pollen assemblages from the McMurdo Dry Valleys locations. The oldest location within the Dry Valleys also involved an active ice margin but was part of a valley system that was completely deglaciated for intervals long enough for thick paleosols to develop. The Friis Hills fossil deposits of the Taylor Valley region (77.8°S) are at least 19.76 Ma based on the 39Ar/40Ar age of a volcanic ash bed. The valley floor during the non-glacial phases had poorly-drained soils and the extensive development of mossy mires. Wood and leaves of Nothofagus are abundant in lacustrine deposits. The silts of shallow fluvial channels contain abundant megaspores and spiky leaves of the aquatic lycopod Isoetes (Quillwort). Fossils of beetles are also present in these deposits. During the glacial phases, proglacial lakes were surrounded by dwarfed, deciduous Nothofagus shrubs. The youngest fossils recovered from the Dry Valleys are from the Olympus Range (77.5°S) with an age of 14.07 Ma. The environment was an

  3. A Transitional Gundi (Rodentia: Ctenodactylidae from the Miocene of Israel.

    Directory of Open Access Journals (Sweden)

    Raquel López-Antoñanzas

    Full Text Available We describe a new species of gundi (Rodentia: Ctenodactylidae: Ctenodactylinae, Sayimys negevensis, on the basis of cheek teeth from the Early Miocene of the Rotem Basin, southern Israel. The Rotem ctenodactylid differs from all known ctenodactylid species, including Sayimys intermedius, which was first described from the Middle Miocene of Saudi Arabia. Instead, it most resembles Sayimys baskini from the Early Miocene of Pakistan in characters of the m1-2 (e.g., the mesoflexid shorter than the metaflexid, the obliquely orientated hypolophid, and the presence of a strong posterolabial ledge and the upper molars (e.g., the paraflexus that is longer than the metaflexus. However, morphological (e.g., presence of a well-developed paraflexus on unworn upper molars and dimensional (regarding, in particular, the DP4 and M1 or M2 differences between the Rotem gundi and Sayimys baskini distinguish them and testify to the novelty and endemicity of the former. In its dental morphology, Sayimys negevensis sp. nov. shows a combination of both the ultimate apparition of key-characters and incipient features that would be maintained and strengthened in latter ctenodactylines. Thus, it is a pivotal species that bridges the gap between an array of primitive ctenodactylines and the most derived, Early Miocene and later, gundis.

  4. Two New Mylagaulid Rodents from the Early Miocene of China.

    Directory of Open Access Journals (Sweden)

    Xiaoyu Lu

    Full Text Available Mylagaulid fossorial rodents are a common component of North American Miocene fossil faunas. However outside of North America, only three species are known from Asia. Here we report two new mylagaulids, Irtyshogaulus minor gen. et sp. nov. and Irtyshogaulus major gen. et sp. nov., recovered from early Miocene sediments in the Junggar Basin in northwestern China. The two new taxa are small-sized, high-crowned promylagauline rodents. Their lower molars possess high metastylid crests, small mesostylids, broad and posterolingually expanded labial inflections, and transversely extending metalophid IIs. The mesoconid is absent in both species. The anterior and posterior fossettids are large and equally developed. Their upper M1-2s possess a square occlusal surface with five deep fossettes. The two new taxa are distinguished from each other mainly by their size, the morphology of fossettes and fossettids, development of mesial and distal lophs, posterior reduction of M3, and the orientation of m2 hypolophid. Our phylogenetic analysis indicates that Irtyshogaulus and Lamugaulus (another early Miocene Asian mylagaulid are sister taxa. The two genera are nested among the North American promylagaulines, and share a common ancestor from North America, indicating early Miocene intercontinental dispersal within this clade of rodents.

  5. Frictional properties and slip stability of active faults within carbonate-evaporite sequences: The role of dolomite and anhydrite

    NARCIS (Netherlands)

    Scuderi, M.M.; Niemeijer, A.R.; Collettini, C.; Marone, C.

    2013-01-01

    Seismological observations show that many destructive earthquakes nucleate within, or propagate through, thick sequences of carbonates and evaporites. For example, along the Apennines range (Italy) carbonate and evaporite sequences are present at hypocentral depths for recent major earthquakes

  6. The Upper Permian in the Netherlands

    NARCIS (Netherlands)

    Visser, W.A.

    1955-01-01

    The Upper Permian in the Netherlands, as known from borehole data, is deposited in a mainly evaporitic facies north of the Brabant and Rhenish Massifs. In the extreme south (Belgian Campine, de Peel) a near-shore facies of reef dolomites and elastics occurs. In the western and central Netherlands

  7. Meta-evaporite in the Carajás mineral province, northern Brazil

    Science.gov (United States)

    Riehl, Walter; Cabral, Alexandre Raphael

    2018-05-01

    Evidence for connecting evaporite-sourced high-salinity fluids with iron-oxide-copper-gold (IOCG) deposits in the Carajás mineral province has solely been based on boron-isotope compositions of tourmaline. Presence of meta-evaporitic rocks remains unrecognised. Here, we report laminated albitite, tourmalinite and banded albite-phlogopite rock, intercepted by exploratory drilling in a clastic metasedimentary sequence. These rocks represent evaporite precursors. Their location in the copper-gold prospects Açaí and Angélica, in the westernmost part of the Carajás mineral province, indicates that (i) evaporite-sourced fluids were regional and (ii) evaporite-bearing metasedimentary sequences may have been an important source of high-salinity fluids and/or sulfur for the IOCG deposits of the Carajás mineral province.

  8. Uranium-Bearing Evaporite Mineralization Influencing Plume Persistence. Literature Review and DOE-LM Site Surveys

    International Nuclear Information System (INIS)

    2016-01-01

    This report on evaporite mineralization was completed as an Ancillary Work Plan for the Applied Studies and Technology program under the U.S. Department of Energy (DOE) Office of Legacy Management (LM). This study reviews all LM sites under Title I and Title II of the Uranium Mill Tailings Radiation Control Act (UMTRCA) and one Decontamination and Decommissioning site to provide (1) a summary of which sites have evaporite deposits, (2) any available quantitative geochemical and mineralogical analyses, and (3) references to relevant reports. In this study, 'evaporite' refers to any secondary mineral precipitate that occurs due to a loss of water through evaporative processes. This includes efflorescent salt crusts, where this term refers to a migration of dissolved constituents to the surface with a resulting salt crust, where 'salt' can refer to any secondary precipitate, regardless of constituents. The potential for the formation of evaporites at LM sites has been identified, and may have relevance to plume persistence issues. Evaporite deposits have the potential to concentrate and store contaminants at LM sites that could later be re-released. These deposits can also provide a temporary storage mechanism for carbonate, chloride, and sulfate salts along with uranium and other contaminants of concern (COCs). Identification of sites with evaporites will be used in a new technical task plan (TTP), Persistent Secondary Contaminant Sources (PeSCS), for any proposed additional sampling and analyses. This additional study is currently under development and will focus on determining if the dissolution of evaporites has the potential to hinder natural flushing strategies and impact plume persistence. This report provides an initial literature review on evaporites followed by details for each site with identified evaporites. The final summary includes a table listing of all relevant LM sites regardless of evaporite identification.

  9. Disposal of radioactive waste in evaporite formations - a review of published radiological assessments and their relevance to the UK

    International Nuclear Information System (INIS)

    Lawson, G.

    1983-11-01

    Radiological assessments of the disposal of radioactive waste in evaporite formations, principally halite, have been reviewed. These assessments were carried out in the USA, the Netherlands, Denmark and West Germany. The general nature of evaporite formations in the UK is discussed and comments are given on the broad relevance of the assessments to the potential disposal of radioactive waste in UK evaporite formations. (author)

  10. Uranium-Bearing Evaporite Mineralization Influencing Plume Persistence. Literature Review and DOE-LM Site Surveys

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2016-05-01

    This report on evaporite mineralization was completed as an Ancillary Work Plan for the Applied Studies and Technology program under the U.S. Department of Energy (DOE) Office of Legacy Management (LM). This study reviews all LM sites under Title I and Title II of the Uranium Mill Tailings Radiation Control Act (UMTRCA) and one Decontamination and Decommissioning site to provide (1) a summary of which sites have evaporite deposits, (2) any available quantitative geochemical and mineralogical analyses, and (3) references to relevant reports. In this study, “evaporite” refers to any secondary mineral precipitate that occurs due to a loss of water through evaporative processes. This includes efflorescent salt crusts, where this term refers to a migration of dissolved constituents to the surface with a resulting salt crust, where “salt” can refer to any secondary precipitate, regardless of constituents. The potential for the formation of evaporites at LM sites has been identified, and may have relevance to plume persistence issues. Evaporite deposits have the potential to concentrate and store contaminants at LM sites that could later be re-released. These deposits can also provide a temporary storage mechanism for carbonate, chloride, and sulfate salts along with uranium and other contaminants of concern (COCs). Identification of sites with evaporites will be used in a new technical task plan (TTP), Persistent Secondary Contaminant Sources (PeSCS), for any proposed additional sampling and analyses. This additional study is currently under development and will focus on determining if the dissolution of evaporites has the potential to hinder natural flushing strategies and impact plume persistence. This report provides an initial literature review on evaporites followed by details for each site with identified evaporites. The final summary includes a table listing of all relevant LM sites regardless of evaporite identification.

  11. Hydrated Minerals and Evaporites as Key Targets for a Mars Sample Return Mission

    Science.gov (United States)

    Adeli, S.; Hauber, E.; Jaumann, R.

    2018-04-01

    Here we focus on hydrated minerals and evaporites as paleo-environment indicators with preservation capacity. Thus, samples from these materials would increase our knowledge about the past aqueous activities of Mars and its habitability potentials.

  12. A new baleen whale from the Late Miocene of Denmark and early mysticete hearing

    DEFF Research Database (Denmark)

    Steeman, Mette Elstrup

    2009-01-01

    here is a new, almost complete fossil baleen whale Uranocetus gramensis gen. et sp. nov. from the Upper Miocene Gram Formation in South West Denmark. It is the first stem-balaenopterid that has an initial stage of reduction in the mandibular cavity and a rostral configuration that is intermediate...

  13. Calcareous nannofossil events in the pre-evaporitic Messinian

    Science.gov (United States)

    Negri, Alessandra; Lozar, Francesca

    2017-04-01

    During the Messinian (7.2 to 5.3 Ma) the Mediterranean area experienced fast and deep climatic and eustatic structural changes. The stratigraphic framework for this interval is relatively well constrained and the beginning of the Messinian salinity crisis dated at 5.97 Ma determine a duration of at least 1.2 Ma for the pre-evaporitic Messinian that is object of this study. Several sites (Faneromeni, Pissouri, Polemi Fanantello borehole, Lemme, Pollenzo, Govone, Moncalvo; Wade and Bown, 2006; Kouwenhoven et al 2006, Morigi et al 2007, Lozar et al 2010, Dela Pierre et al 2011) show similar calcareous nannofossil record behavior, with several Sphenolithus spp. peaks recognised at different quotes in each of the sections. Aim of the present work is to compare the calcareous nannofossil data achieved in the above mentioned sections: interestingly, the occurrence of strongly oligotypic assemblages related to high salinity and unstable environments, appear to correlate precisely among the investigated sites and occur immediately before the onset of the Messinian salinity crisis, then offering the possibility to use them as bioevents for regional correlation. References Dela Pierre, F., Bernardi, E., Cavagna, S., Clari, P., Gennari, R., Irace, A., Lozar, F., Lugli, S., Manzi, V., Natalicchio, M., Roveri, M., Violanti, D., 2011. The record of the Messinian salinity crisis in the Tertiary Piedmont Basin (NW Italy): The Alba section revisited. Palaeogeography, Palaeoclimatology, Palaeoecology 310, 238-255. Kouwenhoven, T.J., Morigi, C., Negri, A., Giunta, S., Krijgsman, W., Rouchy, J.M., 2006 Paleoenvironmental evolution of the eastern Mediterranean during the Messinian: Constraints from integrated microfossil data of the Pissouri Basin (Cyprus). Marine Micropaleontology 60, 17-44. Lozar, F., Violanti, D., Dela Pierre, F., Bernardi, E., Cavagna, S., Clari, P., Irace, A., Martinetto, E., Trenkwalder, S., 2010. Calcareous nannofossils and foraminifers herald the Messinian

  14. Hydrology and Hydraulic Properties of a Bedded Evaporite Formation

    International Nuclear Information System (INIS)

    BEAUHEIM, RICHARD L.; ROBERTS, RANDALL M.

    2000-01-01

    The Permian Salado Formation in the Delaware Basin of New Mexico is an extensively studied evaporite deposit because it is the host formation for the Waste Isolation Pilot Plant, a repository for transuranic wastes. Geologic and hydrologic studies of the Salado conducted since the mid-1970's have led to the development of a conceptual model of the hydrogeology of the formation that involves far-field permeability in anhydrite layers and at least some impure halite layers. Pure halite layers and some impure halite layers may not possess an interconnected pore network adequate to provide permeability. Pore pressures are probably very close to lithostatic pressure. In the near field around an excavation, dilation, creep, and shear have created and/or enhanced permeability and decreased pore pressure. Whether flow occurs in the far field under natural gradients or only after some threshold gradient is reached is unknown. If far-field flow does occur, mean pore velocities are probably on the order of a meter per hundreds of thousands to tens of millions of years. Flow dimensions inferred from most hydraulic-test responses are subradial, which is believed to reflect channeling of flow through fracture networks, or portions of fractures, that occupy a diminishing proportion of the radially available space, or through percolation networks that are not ''saturated'' (fully interconnected). This is probably related to the directional nature of the permeability created or enhanced by excavation effects. Inferred values of permeability cannot be separated from their associated flow dimensions. Therefore, numerical models of flow and transport should include heterogeneity that is structured to provide the same flow dimensions as are observed in hydraulic tests. Modeling of the Salado Formation around the WIPP repository should also include coupling between hydraulic properties and the evolving stress field because hydraulic properties change as the stress field changes

  15. Estimating Rheological Parameters of Anhydrite from Folded Evaporite sequences: Implications for Internal Dynamics of Salt Structure

    Science.gov (United States)

    Adamuszek, Marta; Dabrowski, Marcin; Schmalholz, Stefan M.; Urai, Janos L.; Raith, Alexander

    2015-04-01

    Salt structures have been identified as a potential target for hydrocarbon, CO2, or radioactive waste storage. The most suitable locations for magazines are considered in the thick and relatively homogeneous rock salt layers. However, salt structures often consist of the evaporite sequence including rock salt intercalated with other rock types e.g.: anhydrite, gypsum, potassium and magnesium salt, calcite, dolomite, or shale. The presence of such heterogeneities causes a serious disturbance in the structure management. Detailed analysis of the internal architecture and internal dynamics of the salt structure are crucial for evaluating them as suitable repositories and also their long-term stability. The goal of this study is to analyse the influence of the presence of anhydrite layers on the internal dynamics of salt structures. Anhydrite is a common rock in evaporite sequences. Its physical and mechanical properties strongly differ from the properties of rock salt. The density of anhydrite is much higher than the density of salt, thus anhydrite is likely to sink in salt causing the disturbance of the surrounding structures. This suggestion was the starting point to the discussion about the long-term stability of the magazines in salt structures [1]. However, the other important parameter that has to be taken into account is the viscosity of anhydrite. The high viscosity ratio between salt and anhydrite can restrain the layer from sinking. The rheological behaviour of anhydrite has been studied in laboratory experiments [2], but the results only provide information about the short-term behaviour. The long-term behaviour can be best predicted using indirect methods e.g. based on the analysis of natural structures that developed over geological time scale. One of the most promising are fold structures, the shape of which is very sensitive to the rheological parameters of the deforming materials. Folds can develop in mechanically stratified materials during layer

  16. Crocodilian faunal renewal in the Upper Oligocene of Western Europe

    Science.gov (United States)

    Antunes, Miguel Telles; Cahuzac, Bruno

    1999-01-01

    The presence of Tomistomine Crocodilians ( Tomistoma sp.) is first recorded in the Upper Oligocene of Western Europe (Chattian, Saint-Geours-de-Maremne, Aquitaine basin). Immigration, probably of Asiatic origin, occurred ca. 26 Ma, prior to the previously earliest records for Lowermost Miocene. Tomistoma points to warm, at least subtropical environments, in agreement with data on invertebrates and fish fauna. Immigrations to Western Europe of Tomistoma (and of Gavialis, in Miocene times) during Upper Oligocene and Lower-Middle Miocene seem related to climatic warming and eustatic rise events. There was a renewal of the European Crocodilian fauna, much impoverished in Late Eocene and reduced to Diplocynodon.

  17. Mediterranean salt giants beyond the evaporite model: The Sicily perspective

    Science.gov (United States)

    Carmelo Manuella, Fabio; Scribano, Vittorio; Carbone, Serafina; Hovland, Martin; Johnsen, Hans-Konrad; Rueslåtten, Håkon

    2017-04-01

    Mediterranean salt giants, occurring both in sub-seafloor and in onshore settings (the "Gessoso Solfifera Group"), are traditionally explained by repeated cycles of desiccation and replenishment of the entire basin. However, such hypotheses are strongly biased by mass balance calculations and geodynamic considerations. In addition, any hypothesis without full desiccation, still based on the evaporite model, should consider that seawater brines start to precipitate halite when 2/3 of the seawater has evaporated, and hence the level of the basin cannot be the same as the adjacent ocean. On the other hand, hydrothermal venting of hot saline brines onto the seafloor can precipitate salt in a deep marine basin if a layer of heavy brine exists along the seafloor. This process, likely related to sub-surface boiling or supercritical out-salting (Hovland et al., 2006), is consistent with geological evidence in the Red Sea "Deeps" (Hovland et al., 2015). Although supercritical out-salting and phase separation can sufficiently explain the formation of several marine salt deposits, even in deep marine settings, the Mediterranean salt giant formations can also be explained by the serpentinization model (Scribano et al., 2016). Serpentinization of abyssal peridotites does not involve seawater salts, and large quantities of saline brines accumulate in pores and fractures of the sub-seafloor serpentinites. If these rocks undergo thermal dehydration, for example, due to igneous intrusions, brines and salt slurries can migrate upwards as hydrothermal plumes, eventually venting at the seafloor, giving rise to giant salt deposits over time. These hydrothermal processes can take place in a temporal sequence, as it occurred in the "Caltanissetta Basin" (Sicily). There, salt accumulation associated with serpentinization started during Triassic times (and even earlier), and venting of heavy brines onto the seafloor eventually occurred in the Messinian via the hydrothermal plume mechanism

  18. Hypsodont Myomiminae (Gliridae, Rodentia) from the Miocene and the Oligocene-Miocene boundary interval of Spain

    NARCIS (Netherlands)

    Daams, R.

    1990-01-01

    Fifty-one localities from the Oligocene-Miocene boundary interval and the Miocene of Spain have yielded nearly 4000 teeth of hypsodont Gliridae (Armantomys and Praearmantomys). The phylogeny and palaeoecology are discussed. Two new species of Armantomys (A. parsani sp. nov. from Ramblar 1 and A.

  19. Petrographic study of evaporite deformation near the Waste Isolation Pilot Plant (WIPP)

    International Nuclear Information System (INIS)

    Borns, D.J.

    1983-06-01

    The Delaware Basin of southeastern New Mexico contains about 1000 m of layered evaporites. Areas in the northern Delaware Basin, bordering the Capitan reef, have anomalous seismic reflection characteristics, such as loss in reflector continuity. Core from holes within this zone exhibits complex mesoscopic folds and extension structures. On a larger scale, anticlines and synclines are indicated by structure contours based on boreholes. The deformation is probably gravity-driven. Such a process is initiated by basin tilting during either a Mesozoic or Cenozoic period of uplift. Small-scale structures suggest that deformation was episodic with an early, syndepositional stage of isoclinal folding. Later, open-to-tight asymmetric folding is more penetrative and exhibits a sense of asymmetry opposite to that of the earlier isoclinal folding. The younger folds are associated with development of zonal crenulation cleavage and microboundinage of more competent carbonate layers. At the same time, halite beds developed dimensional fabrics and convolute folds in anhydrite stringers. Late-stage, near-vertical fractures formed in competent anhydrite layers. Microscopic textures exhibit rotated anhydrite porphyroblasts, stress shadow growth, and microboundinage. Except during late-stage deformation, anhydrite and halite recrystallized synkinematically. Drastic strength reduction in anhydrites through dynamic recrystallization occurs experimentally near 200 0 C. However, evaporites of the WIPP site never experienced temperatures > 40 0 C. Microscopic fabrics and P, T history of the evaporites suggest that pressure solution was the active mechanism during deformation of evaporites at the WIPP site

  20. Hydraulic testing of Salado Formation evaporites at the Waste Isolation Pilot Plant site: Second interpretive report

    Energy Technology Data Exchange (ETDEWEB)

    Beauheim, R.L. [Sandia National Labs., Albuquerque, NM (United States); Roberts, R.M.; Dale, T.F.; Fort, M.D.; Stensrud, W.A. [INTERA, Inc., Austin, TX (United States)

    1993-12-01

    Pressure-pulse, constant-pressure flow, and pressure-buildup tests have been performed in bedded evaporites of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) site to evaluate the hydraulic properties controlling brine flow through the Salado. Transmissivities have been interpreted from six sequences of tests conducted on five stratigraphic intervals within 15 m of the WIPP underground excavations.

  1. Hydraulic testing of Salado Formation evaporites at the Waste Isolation Pilot Plant site: Second interpretive report

    International Nuclear Information System (INIS)

    Beauheim, R.L.; Roberts, R.M.; Dale, T.F.; Fort, M.D.; Stensrud, W.A.

    1993-12-01

    Pressure-pulse, constant-pressure flow, and pressure-buildup tests have been performed in bedded evaporites of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) site to evaluate the hydraulic properties controlling brine flow through the Salado. Transmissivities have been interpreted from six sequences of tests conducted on five stratigraphic intervals within 15 m of the WIPP underground excavations

  2. Controls on the quality of Miocene reservoirs, southern Gulf of Mexico

    Science.gov (United States)

    Gutiérrez Paredes, Hilda Clarisa; Catuneanu, Octavian; Hernández Romano, Ulises

    2018-01-01

    An investigation was conducted to determine the main controls on the reservoir quality of the middle and upper Miocene sandstones in the southern Gulf of Mexico based on core descriptions, thin section petrography and petrophysical data; as well as to explore the possible link between the sequence stratigraphic framework, depositional facies and diagenetic alterations. The Miocene deep marine sandstones are attributed to the falling-stage, lowstand, and transgressive systems tracts. The middle Miocene falling-stage systems tract includes medium-to very fine-grained, and structureless sandstones deposited in channels and frontal splays, and muddy sandstones, deposited in lobes of debrites. The lowstand and transgressive systems tracts consist of medium-to very fine-grained massive and normally graded sandstones deposited in channel systems within frontal splay complexes. The upper Miocene falling-stage systems tract includes medium-to coarse-grained, structureless sandstones deposited in channel systems and frontal splay, as well as lobes of debrites formed by grain flows and hybrid-flow deposits. The lowstand and transgressive systems tracts include fine-grained sandstones deposited in overbank deposits. The results reveal that the depositional elements with the best reservoir quality are the frontal splays deposited during the falling-stage system tracts. The reservoir quality of the Miocene sandstones was controlled by a combination of depositional facies, sand composition and diagenetic factors (mainly compaction and calcite cementation). Sandstone texture, controlled primarily by depositional facies appears more important than sandstone composition in determining reservoir quality; and compaction was more important than cementation in porosity destruction. Compaction was stopped, when complete calcite cementation occurred.

  3. Late Miocene mollusks from the Queen Charlotte Islands, British Columbia, Canada

    Science.gov (United States)

    Addicott, Warren O.

    1978-01-01

    A fauna of bivalve mollusks, scattered gastropods, and an echinoid from exposures of the Skonun Formation in the northeastern part of Graham Island is indicative of an early late Miocene age and correlation with the provincial Wishkahan Stage. The molluscan assemblages are from the upper 600 of the 1800-m-thick marine and nonmarine formation, which appears to be entirely of late Miocene age. The Skonun Formation is the strandline fa.cies of marginal marine and nonmarine deposits of the northwestern part of the Queen Charlotte basin, a Nieogene embayment paralleling the modern mainland coast. The molluscan fauna and associated lignite beds are known from a few widely scattered outcrops; they are indicative of alternating marine and nonmarine to brackish-water environments in the upper part of the formation. The Skonun fauna occurs near the northern boundary of the Pacific Northwest Neogene molluscan province. It is the only marine Neogene molluscan fauna known from the British Columbia coast. The fauna has strong taxonomic ties with the fauna of the Empire Formation of southwestern Oregon and has several species in common with the upper Miocene of the Lituya district, southeastern Alaska, implying that these three faunas are coeval.

  4. Miocene denudation history of Himalaya deduced from IODP Exp. 354 Bengal Fan

    Science.gov (United States)

    Kohki, Y.; Cruz, J. W.; Osaki, A.; Manoj, M. C.; Hatano, N.; France-Lanord, C.; Spiess, V.; Klaus, A.

    2017-12-01

    The submarine Bengal Fan is the largest submarine fan on Earth and covers the whole Bay of Bengal. The sediments are fed by the Ganges and Brahmaputra rivers reflecting India-Asia plate collision. The sediments recovered from IODP Expedition 354 Bengal Fan record the uplift history of the Himalayan orogenic system. We examined the chemical composition of detrital garnets in the Miocene deposits from Site U1451, where drilling reached to basal horizon of the fan deposits, in order to reveal the detailed denudation history of Himalayan metamorphic rocks. For this purpose, the comparison of chemical composition between detrital garnet in the Bengal Fan deposits and metamorphic garnet in Himalayan metamorphic rocks was carried out. The chemical composition of the metamorphic garnet from Higher Himalayan Crystalline (HHC) in Karnali and Kaligandaki areas, western Nepal, was examined for chemical reference to detrital garnets in Bengal Fan. The metamorphic garnets in "Formation I (Le Fort, 1975)" in HHC are characterized by almandine-rich garnet with high pyrope content. Also, the garnets in "Formation II" are remarked by two types of garnets, i.e., almandine-rich and grandite-rich garnets. Meanwhile, the composition of garnets in "Formation III" is almandine-rich garnet with low pyrope content. In the Bengal Fan deposits, the characteristic garnets, which show the similarity to the metamorphic garnet in HHC, is not found from the Lower Miocene (Burdigalian) deposits. In the Middle and Upper Miocene deposits, the almandine-rich garnets characteristic in Formation I, are normally included. At the basal part of the Middle Miocene (Langhian), almandine-rich garnets with low pyrope content, suggesting the derivation from Formation III, are remarkable. The grandite-rich garnets from Formation II are sporadically found In the Upper Miocene deposits (Tortonian-Messinian). Above chemical comparison between the detrital garnets in Bengal Fan and metamorphic garnets from HHC

  5. Miocene freshwater Mollusca from western Brazilian Amazonia

    NARCIS (Netherlands)

    Wesselingh, F.P.; Ranzi, A.; Räsänen, M.E.

    2006-01-01

    Thirteen species of fossil molluscs are reported from the Solimões Formation of western Brazilian Amazonia. Based on mammalian chronology of the Solimões Formation and radiometric ages reported from coeval deposits in adjacent Peru, the age of the fauna is established as Late Miocene. The fauna

  6. Late Miocene magnetostratigraphy in the Mediterranean

    NARCIS (Netherlands)

    Langereis, C.G.

    1984-01-01

    Reversals of the geomagnetic field In the geological past are recorded globally in the natural remanent magnetization (NRM) of igneous and sedimentary rock sequences. The accurate and rei iable reconstruction of this record is the basis of magnetostratigraphy. The magnetostratigraphy of Late Miocene

  7. Middle Miocene E-W tectonic horst structure of Crete through extensional detachment faults

    International Nuclear Information System (INIS)

    Papanikolaou, D; Vassilakis, E

    2008-01-01

    Two east-west trending extensional detachment faults have been recognized in Crete, one with top-to-the-north motion of the hanging wall toward the Cretan Sea and one with top-to-the-south motion of the hanging wall toward the Libyan Sea. The east-west trending zone between these two detachment faults, which forms their common footwall, comprises a tectonic horst formed during Middle Miocene slip on the detachment faults. The detachment faults disrupt the overall tectono-stratigraphic succession of Crete and are localized along pre-existing thrust faults and along particular portions of the stratigraphic sequence, including the transition between the Permo-Triassic Tyros Beds and the base of the Upper Triassic-Eocene carbonate platform of the Tripolis nappe. By recognizing several different tectono-stratigraphic formations within what is generally termed the 'phyllite-quartzite', it is possible to distinguish these extensional detachment faults from thrust faults and minor discontinuities in the sequence. The deformation history of units within Crete can be summarized as: (i) compressional deformation producing arc-parallel east-west trending south-directed thrust faults in Oligocene to Early Miocene time (ii) extensional deformation along arc-parallel, east-west trending detachment faults in Middle Miocene time, with hanging wall motion to the north and south; (iii) Late Miocene-Quaternary extensional deformation along high-angle normal and oblique normal faults that disrupt the older arc-parallel structures

  8. Impact of Diagenesis on Biosignature Preservation Potential in Playa Lake Evaporites of the Verde Formation, Arizona: Implications for Mars Exploration

    Science.gov (United States)

    Shkolyar, S.; Farmer, J. D.

    2016-05-01

    We studied evaporite subfacies in the Verde Fmn., AZ. We identified diagenetic pathways and assessed how diagenesis affected biosignature preservation potential (BPP) in each. Results revealed eight pathways, each with diverse impacts on BPP.

  9. Earth analogs for Martian life - Microbes in evaporites, a new model system for life on Mars

    Science.gov (United States)

    Rothschild, Lynn J.

    1990-01-01

    It is suggested that 'oases' in which life forms may persist on Mars could occur, by analogy with terrestrial cases, in (1) rocks, as known in endolithic microorganisms, (2) polar ice caps, as seen in snow and ice algae, and (3) volcanic regions, as witnessed in the chemoautotrophs which live in ocean-floor hydrothermal vents. Microorganisms, moreover, have been known to survive in salt crystals, and it has even been shown that organisms can metabolize while encrusted in evaporites. Evaporites which may occur on Mars would be able to attenuate UV light, while remaining more transparent to the 400-700 nm radiation useful in photosynthesis. Suggestions are made for the selection of Martian exobiological investigation sites.

  10. Latest Miocene-Pliocene Tiliviche Paleolake, Atacama Desert, Northern Chile 19.5°S: Paleoclimatic and Paleohydrologic Implications

    Science.gov (United States)

    Kirk-Lawlor, N. E.; Jordan, T. E.; Rech, J.; Lehmann, S.

    2010-12-01

    Endorheic paleolake deposits of diatomite, mudstone, sandstone, and evaporites are exposed in the Atacama Desert of northern Chile. This study focuses on a major latest Miocene-Pliocene paleolake system centered at 19.5°S, near Tiliviche. A diatiomite unit, up to 35m thick, composed of 0.2-1.5m thick beds of massive, white diatiomite, free of plant matter and root traces, is interpreted have formed from lacustrine diatom blooms. At its maximum extent, the lake would have had a surface area of roughly 200 km2, based on the extent of the diatomite unit, and might have been 50-100 m deep, as inferred by the relationship between the diatomite unit and modern topography. The Tiliviche paleolake initially formed before 6.4 Ma, and much of its sedimentary record formed under a wetter climatic and hydrologic regime than the present. Prior to 3.5 Ma, the lake had evolved into a groundwater-fed saltpan. Polygonally fractured efflorescent halite evaporite and bedded gypsum and gypsarenite evaporite deposits that overlie the diatomite unit are evidence of this saltpan environment. The modern Atacama Desert is hyperarid, with an average precipitation of 2 mm/yr in the driest areas. The paleosol record demonstrates that hyperarid conditions dominated this region since the middle Miocene, albeit with multiple fluctuations to less arid conditions of short to moderately long duration. This hyperaridity is due to the desert’s latitude, ocean currents and the rainshadow created by the Andes. There is no evidence that the rainshadow effect has diminished since the late Miocene, hence global climate changes affecting ocean temperatures and atmospheric patterns likely caused the wetter periods in the Atacama. In particular, prior workers noted wetter conditions in the region ~6-5 Ma, followed by a return to hyper-arid conditions. The regional Pliocene return to hyperaridity coincided with the desiccation of the Tiliviche endorheic lake system. During the late Miocene (~6-5 Ma) wetter

  11. Geochemical study of evaporite and clay mineral-oxyhydroxide samples from the Waste Isolation Pilot Plant site

    International Nuclear Information System (INIS)

    Brookins, D.G.

    1993-06-01

    Samples of clay minerals, insoluble oxyhydroxides, and their host evaporites from the WIPP site have been studied for their major and minor elements abundances, x-ray diffraction characteristics, K-Ar ages, and Rb-Sr ages. This study was undertaken to determine their overall geochemical characteristics and to investigate possible interactions between evaporates and insoluble constituents. The evaporite host material is water-soluble, having Cl/Br ratios typical of marine evaporites, although the Br content is low. Insoluble material (usually a mixture of clay minerals and oxyhydroxide phases) yields very high Cl/Br ratios, possibly because of Cl from admixed halide minerals. This same material yields K/Rb and Th/U ratios in the normal range for shales; suggesting little, if any, effect of evaporite-induced remobilization of U, K, or Rb in the insoluble material. The rare-earth element (REE) data also show normal REE/chondrite (REE/CHON) distribution patterns, supporting the K/Rb and Th/U data. Clay minerals yield K-Ar dates in the range 365 to 390 Ma and a Rb-Sr isochron age of 428 ± 7 Ma. These ages are well in excess of the 220- to 230-Ma formational age of the evaporites, and confirm the detrital origin of the clays. The ages also show that any evaporite or clay mineral reactions that might have occurred at or near the time of sedimentation and diagenesis were not sufficient to reset the K-Ar and Rb-Sr systematics of the clay minerals. Further, x-ray data indicate a normal evaporitic assemblage of clay minerals and Fe-rich oxyhydroxide phases. The clay minerals and other insoluble material appear to be resistant to the destructive effects of their entrapment in the evaporites, which suggests that these insoluble materials would be good getters for any radionuclides (hypothetically) released from the storage of radioactive wastes in the area

  12. Miocene metamorphism of pan-African granites in the Edough Massif (NE Algeria)

    International Nuclear Information System (INIS)

    Hammor, D.; Lancelot, J.

    1998-01-01

    The Edough Massif is the eastern most crystalline core of the Maghrebides that represents the African segment of the west Mediterranean Alpine belt. U-Pb zircon dating provides upper intercept ages of 595± My and 606±55 My and orthogneiss of the lower unit and a deformed leucogranite of the upper pelitic unit, respectively. These ages suggest emplacement of the two granitoids during the Pan-African orogeny. Monazites from a paragneiss sample gave a 18± My U-Pb age that points to a Miocene age of the high-temperature metamorphism. (authors)

  13. Stable isotope stratigraphy of Latest Miocene sequences in northwest Morocco: The Bou Regreg section

    Science.gov (United States)

    Hodell, David A.; Benson, Richard H.; Kennett, James P.; Rakic-El Bied, Kruna

    1989-08-01

    Oxygen and carbon isotopic ratios of foraminifers were measured from outcrop and drill core sequences from the Bou Regreg Section, northwest Morocco. This composite section was located at the western end of the Rifian Corridor during the late Miocene and thus potentially contains a record of water exchange between the Atlantic and Mediterranean during the late Tortonian and Messinian stages. Here we correlate isotopic and sedimentologic events in the Bou Regreg Section with Mediterranean and deep-sea sequences during the time leading up to and including the deposition of the Messinian evaporites. The late Miocene chron 6 carbon shift was identified in two Moroccan sequences, providing a valuable 6.3-Ma datum level. In both sections, the carbon shift coincides with the first occurrence of Globorotalia conomiozea and the Tortonian/Messinian boundary. Near this boundary, a major faunal turnover occurred in ostracod, planktonic foraminiferal, and nannofossil assemblages that indicates a cooling of surface and deep water in the Rifian Corridor. At 6.1 Ma, just above the Tortonian/Messinian boundary, mean ∂18O values of benthic foraminifers increased by 0.4-0.5‰ suggesting decreased temperature and/or increased continental ice volume. The faunal and isotopic changes are interpreted as reflecting a reversal in the direction of deep water flow through the Rifian Corridor that occurred between 6.3 and 6.1 Ma. At this time, cold, nutrient-rich waters filled the Mediterranean basins from intermediate depths of the Atlantic, and the production of Mediterranean Outflow Water ceased. The upwelling of nutrient-rich Atlantic intermediate water stimulated productivity in the Mediterranean, which led to the deposition of organic-rich strata such as those found in the Tripoli Formation. At ˜5.5 Ma, coincident with a coiling shift in Neogloboquadrina acostaensis, the variability of the benthic ∂18O signal increased markedly, and strong color variations appeared in the sediments

  14. The role of evaporites in the formation of gems during metamorphism of carbonate platforms: a review

    Science.gov (United States)

    Giuliani, Gaston; Dubessy, Jean; Ohnenstetter, Daniel; Banks, David; Branquet, Yannick; Feneyrol, Julien; Fallick, Anthony E.; Martelat, Jean-Emmanuel

    2018-01-01

    The mineral and fluid inclusions trapped by gemstones during the metamorphism of carbonate platform successions are precious markers for the understanding of gem genesis. The nature and chemical composition of inclusions highlight the major contribution of evaporites through dissolution or fusion, depending on the temperature of formation from greenschist to granulite facies. The fluids are highly saline NaCl-brines circulating either in an open system in the greenschist facies (Colombian and Afghan emeralds) and with huge fluid-rock metasomatic interactions, or sulphurous fluids (ruby, garnet tsavorite, zoisite tanzanite and lapis-lazuli) or molten salts formed in a closed system with a low fluid mobility (ruby in marble) in the conditions of the amphibolite to granulite facies. These chloride-fluoride-sulphate ± carbonate-rich fluids scavenged the metals essential for gem formation. At high temperature, the anions SO4 2-, NO3 -, BO3 - and F- are powerful fluxes which lower the temperature of chloride- and fluoride-rich ionic liquids. They provided transport over a very short distance of aluminium and/or silica and transition metals which are necessary for gem growth. In summary, the genetic models proposed for these high-value and ornamental gems underline the importance of the metamorphism of evaporites formed on continental carbonate shelves and emphasise the chemical power accompanying metamorphism at moderate to high temperatures of evaporite-rich and organic matter-rich protoliths to form gem minerals.

  15. The role of the Anaxagoras Mountain in the Miocene to Recent tectonic evolution of the eastern Mediterranean

    Science.gov (United States)

    Colbourne, Mark; Hall, Jeremy; Aksu, Ali; Çifçi, Günay

    2014-05-01

    The Anaximander Mountains are one of the many enigmatic structures situated along the morphologically and structurally complicated junction between the Hellenic and Cyprus Arcs, in the eastern Mediterranean. Interpretation of ~750 km of marine multi-channel seismic reflection data show that the present day Anaximander Mountains underwent several distinct phases of tectonic activity since Miocene. During the mid-late Miocene, a protracted, contractional tectonic regime produced the east-west trending, south-verging fold-thrust belt observed in the area. The Messinian was a period of relatively low tectonic activity, and is marked by the deposition of an evaporite layer. This phase lasted until the latest Miocene - earliest Pliocene, when a major erosional event associated with the Messinian salinity crisis occurred. Beginning in the early-mid Pliocene-Quaternary a transpressional and rotational tectonic regime prevailed over the area. The Anaximander Mountain (sensu stricto) and Anaximenes Mountain developed in the Pliocene-Quaternary associated with the reactivation, uplift and rotation of a linked, thick skinned pre-Messinian imbricate thrust fan. Back thrusting in the region accentuated the morphology of these mountains. The Anaxagoras Mountain differs both lithologically and morphologically from the Anaximander Mountain (sensu stricto) and the Anaximenes Mountain. It is probably developed associated with the emplacement of the ophiolitic Antalya Nappe Complex. Faulting in the Anaxagoras region is characterized by southwest striking thrust and/or oblique thrust faults. Due to the similarities in morphology between the Isparta Angle of southwestern Turkey and the Anaximander Mountains (sensu lato), it is hypothesized that the tectonic evolution of the two regions are similar in nature. The Anaximander Mountains (sensu lato) can thus be considered the offshore replication of the Isparta Angle, produced by similar mechanisms, but being of a younger age.

  16. Miocene Soil Database: Global paleosol and climate maps of the Middle Miocene Thermal Maximum

    Science.gov (United States)

    Metzger, C. A.

    2013-12-01

    Paleosols, which record past climatic, biologic, and atmospheric conditions, can be used as a proxy to understand ancient terrestrial landscapes, paleoclimate, and paleoenvironment. In addition, the middle Miocene thermal maximum (~16 Ma) provides an ancient analog for understanding the effects of current and future climate change on soil and ecosystem regimes, as it contains records of shifts similar in magnitude to expected global climate change. The Miocene Soil Database (MSDB) combines new paleosol data from Australia and Argentina with existing and previously uncollated paleosol data from the literature and the Paleobiology Database. These data (n = 507) were then used to derive a paleogeographic map of climatically significant soil types zones during the Middle Miocene. The location of each diagnostic paleosol type (Aridisol, Alfisol, Mollisol, Histosol, Oxisol, and Ultisol) was plotted and compared with the extent of these soil types in the modern environment. The middle Miocene soil map highlights the extension of tropical soils (Oxisols, Ultisols), accompanied by thermophilic flora and fauna, into northern and southern mid-latitudes. Peats, lignites, and Histosols of wetlands were also more abundant at higher latitudes, especially in the northern hemisphere, during the middle Miocene. The paleosol changes reflect that the Middle Miocene was a peak of global soil productivity and carbon sequestration, with replacement of unproductive Aridisols and Gelisols with more productive Oxisols, Alfisols, Mollisols and Histosols. With expansion to include additional data such as soil texture, moisture, or vegetation type, the MSDB has the potential to provide an important dataset for computer models of Miocene climate shifts as well as future land use considerations of soils in times of global change.

  17. The upper Tortonian-lower Messinian at Monte dei Corvi (Northern Apennines, Italy) : Completing a Mediterranean reference section for the Tortonian Stage

    NARCIS (Netherlands)

    Hüsing, S. K.; Kuiper, K. F.; Link, W.; Hilgen, Frederik J.; Krijgsman, W.

    2009-01-01

    A high-resolution integrated stratigraphy including biostratigraphy, magnetostratigraphy, tephrostratigraphy and cyclostratigraphy is presented for the upper Tortonian and lower Messinian (Upper Miocene) at Monte dei Corvi. Numerical age control comes from a combination of magnetobiostratigrapic

  18. Assessment of groundwater quality of the Tatlicay aquifer and relation to the adjacent evaporitic formations (Cankiri, Turkey).

    Science.gov (United States)

    Apaydın, Ahmet; Aktaş, Sibel Demirci

    2012-04-01

    One of the most important hydrogeologic problems in and adjacent areas of evaporitic formations is severe quality degradation of groundwaters. These kinds of groundwaters contain high content of dissolved solids and generally have some limitations for use. Tatlicay basin (north-central Turkey) is an example to effects of the evaporites on groundwater quality in the adjacent alluvium aquifer. Gypsum and anhydrites in the two evaporite formations (Bayindir and Bozkir) effect of the groundwater quality in the alluvium adversely, by dissolution of the evaporites by surface drainage and infiltration into the alluvium aquifer (widespread effect) and by infiltration of low quality gypsum springs (local effect) into the aquifer. Evaporitic formations significantly increased EC, TDS, Ca and SO(4) parameters in the alluvium aquifer in the central and downstream regions. EC has increased roughly from 500-800 to 1,700-2,000 μS/cm, Ca has roughly increased from 3-4 to 10 meq/l, SO(4) has increased 0.5-1 to 11-12 meq/l. Consequently, three clusters were distinguished in the basin; (1) nonevaporitic waters in low TDS, Na, Ca, Mg, Cl and SO(4), (2) diluted waters in high TDS and relatively high Cl, moderate-relatively high Na, Ca, Mg, SO(4), (3) gypsum springs in highest TDS, Ca, SO(4), but moderate Mg and low Na, Cl.

  19. Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani Planum, Mars

    Science.gov (United States)

    McLennan, S.M.; Bell, J.F.; Calvin, W.M.; Christensen, P.R.; Clark, B. C.; de Souza, P.A.; Farmer, J.; Farrand, W. H.; Fike, D.A.; Gellert, Ralf; Ghosh, A.; Glotch, T.D.; Grotzinger, J.P.; Hahn, B.; Herkenhoff, K. E.; Hurowitz, J.A.; Johnson, J. R.; Johnson, S.S.; Jolliff, B.; Klingelhofer, G.; Knoll, A.H.; Learner, Z.; Malin, M.C.; McSween, H.Y.; Pocock, J.; Ruff, S.W.; Soderblom, L.A.; Squyres, S. W.; Tosca, N.J.; Watters, W.A.; Wyatt, M.B.; Yen, A.

    2005-01-01

    Impure reworked evaporitic sandstones, preserved on Meridiani Planum, Mars, are mixtures of roughly equal amounts of altered siliciclastic debris, of basaltic provenance (40 ?? 10% by mass), and chemical constituents, dominated by evaporitic minerals (jarosite, Mg-, Ca-sulfates ?? chlorides ?? Fe-, Na-sulfates), hematite and possibly secondary silica (60 ?? 10%). These chemical constituents and their relative abundances are not an equilibrium evaporite assemblage and to a substantial degree have been reworked by aeolian and subaqueous transport. Ultimately they formed by evaporation of acidic waters derived from interaction with olivine-bearing basalts and subsequent diagenetic alteration. The rocks experienced an extended diagenetic history, with at least two and up to four distinct episodes of cementation, including stratigraphically restricted zones of recrystallization and secondary porosity, non-randomly distributed, highly spherical millimeter-scale hematitic concretions, millimeter-scale crystal molds, interpreted to have resulted from dissolution of a highly soluble evaporite mineral, elongate to sheet-like vugs and evidence for minor synsedimentary deformation (convolute and contorted bedding, possible teepee structures or salt ridge features). Other features that may be diagenetic, but more likely are associated with relatively recent meteorite impact, are meter-scale fracture patterns, veins and polygonal fractures on rock surfaces that cut across bedding. Crystallization of minerals that originally filled the molds, early cement and sediment deformation occurred syndepositionally or during early diagenesis. All other diagenetic features are consistent with formation during later diagenesis in the phreatic (fluid saturated) zone or capillary fringe of a groundwater table under near isotropic hydrological conditions such as those expected during periodic groundwater recharge. Textural evidence suggests that rapidly formed hematitic concretions post

  20. Synchronous onset of the Messinian evaporite precipitation: First Mediterranean offshore evidence

    Science.gov (United States)

    Ochoa, Diana; Sierro, Francisco J.; Lofi, Johanna; Maillard, Agnès; Flores, Jose-Abel; Suárez, Mercedes

    2015-10-01

    The Messinian Salinity Crisis (MSC) was a major ecological crisis affecting shallow and deep-water settings over the entire Mediterranean basin. However, the evolution of the MSC and its ecological impacts have mainly been explained on the basis of sediments from onshore outcrops. Lack of complete and physically connected records from onshore and offshore settings has inhibited comprehensive understanding of basin behaviour during the MSC. Herein we present a continuous record from an intermediate-depth basin on the Balearic Promontory that comprises late Tortonian-Messinian marls and evaporitic beds from the first MSC phase (i.e., Primary Lower Gypsum-PLG stage). Well-log and biostratigraphic data allow us establishing a large-scale calibration to the astronomical solutions, and to correlate pre-MSC sediments with classical rhythmic successions outcropping onshore. Thickness and characteristic sedimentary patterns observed in the offshore evaporitic records resemble those from marginal PLG sequences. Furthermore, seismic reflectors from a Bedded Unit (BU), which corresponds to an evaporitic interval according to well-to-seismic ties, are correlated with the onshore PLG sequences. This correlation constitutes the first attempt to link well-known marginal sequences with intermediate-depth offshore settings, which have previously only been studied through seismic imaging. Our time-calibration provides direct evidence supporting a synchronous onset of the PLG phase between onshore and offshore settings along the southwestern Balearic Promontory margin. Those BU reflectors, which were positively correlated to the PLG, were likely precipitated offshore the continental shelf at Messinian times. These results suggest that gypsum precipitation and/or preservation was not always limited to 200 m water-depths and could occur in non-silled basins. Finally, we only found a major erosion at the top of the PLG sequences, implying that the MSC drawdown occurred after the

  1. Provenance of Miocene Hinterland Basins in Ecuador: Implications for the Growth of Topographic Barriers in the Northern Andes

    Science.gov (United States)

    George, S. W. M.; Horton, B. K.; Vallejo, C.; Nogales, V.

    2017-12-01

    Establishment of the Eastern Cordillera of Ecuador as an Andean topographic barrier caused significant drainage reorganization, perhaps even as dramatic as the reversal of the Amazon River. Cenozoic growth of this barrier coincided with substantial increases in speciation rates in Andean and Amazonian environments. Situated in the Interandean Depression between the Eastern Cordillera and Western Cordillera of Ecuador, a series of well-preserved Miocene intermontane basins offer a unique opportunity to constrain the along-strike development of the flanking north-trending cordilleras as drainage divides in the Northern Andes. Here were provide detrital zircon U-Pb geochronological results for 17 samples from Ecuadorian hinterland basins (Cuenca, Giron-Santa Isabel, Nabón, Loja, and Vilcabamba), supplemented with measured sections in the Cuenca Basin, to provide insights on orogenic development of the cordilleras of Ecuador during the Miocene. In addition, we characterize the age distributions of basement units to more precisely determine sediment routing patterns through time. Detrital zircon geochronological data yields regional upsection trends throughout Miocene stratigraphic sections marked by: (1) middle Miocene deposits containing a strong syndepositional age peak, with a complementary Eocene-Oligocene peak in varying abundances, and subsidiary low-intensity Paleozoic-Proterozoic age peaks; and (2a) upper Miocene deposits maintaining similar trends to that of the middle Miocene, or (2b) upper Miocene deposits showing a dramatic shutoff of most Cenozoic populations and a switch to Paleozoic-Proterozoic sources, as seen in the Nabón and Loja basins. Syndepositional signatures reflect derivation from the magmatic arc, while varying inputs of Eocene-Oligocene zircons were derived from the Eocene-Oligocene volcanic rocks that comprise the effective basement of much of the Interandean Depression. The late Miocene shift to Paleozoic-Proterozoic sources observed in

  2. The Miocene carnivore assemblage of Greece

    Directory of Open Access Journals (Sweden)

    Koufos, G. D.

    2011-12-01

    Full Text Available The Miocene carnivore assemblage of Greece includes a great number of taxa, described in numerous articles since the first decades of the 19th Century. The present article is a revision of all these taxa, providing information about their history, localities, age, as well as their stratigraphic distribution and palaeoenvironment. The Early/Middle Miocene carnivore record of Greece is poor as the available fossiliferous sites and material are rare. However, the Late Miocene one is quite rich, including numerous taxa. The Miocene localities with carnivores and their age are given in a stratigraphic table covering the European Mammal zones from MN 4 to MN 13. The type locality, holotype, and some historical and morphological remarks are given for each taxon. Several carnivore taxa were erected from Greek material and new photos of their holotypes are given. The stratigraphic distribution of the Greek carnivore taxa indicates that they are covering the time span from ~19.0-5.3Ma. The majority of the Miocene taxa (Adcrocuta, Hyaenictitherium, Plioviverrops, Protictitherium, Ictitherium, Indarctos, Dinocrocuta, Promephitis disappeared at the end of Miocene. The composition of the Early/Middle Miocene carnivore assemblage of Greece includes mainly viverrids (Lophocyon, Euboictis, while the hyaenids, percrocutids, felids and mustelids are very few. On the contrary the Late Miocene assemblage is richer, including more subfamilies and species; the hyaenids and mustelids dominate, while the viverrids are absent. The Late Miocene carnivore guild structure is similar to that of the modern Serengeti, indicating a relatively open, savannah-like environment.

    La asociación de carnívoros miocenos de Grecia incluye un gran número de taxones, descritos en numerosos artículos desde las primeras décadas del siglo XIX. El presente artículo supone un esfuerzo de síntesis de todos estos taxones, suministrando información sobre su

  3. 40Ar/ 39Ar dating of Late Permian evaporites, southeastern New Mexico, USA

    Science.gov (United States)

    Renne, Paul R.; Sharp, Warren D.; Montañez, Isabel P.; Becker, Tim A.; Zierenberg, Robert A.

    2001-12-01

    40Ar/ 39Ar dating of the potassium-magnesium sulfate mineral langbeinite from Permian evaporites of the Salado formation near Carlsbad, New Mexico, provides quantitative evidence that some salts in these deposits have not recrystallized for 251 Myr since deposition. Survival of Permian salts supports the possibility that Bacillus bacteria recovered from nearby halite was isolated in a closed system and represents a sample of uncontaminated Permian life. Local recrystallization of langbeinite and other nearby minerals is also indicated by the dating, suggesting both the need and the opportunity to document closed system behavior more rigorously. The shoaling and desiccation event recorded by the Salado formation began at least 1 Myr before the Permian-Triassic boundary. Temporal correlation of the Salado with the Zechstein evaporites of north-central Europe supports previously inferred regression models for the origin of these deposits. Significant paleoenvironmental change at the Permian-Triassic boundary thus occurred on a time scale more protracted than that implied by geologically instantaneous events such as bolide impacts.

  4. Miocene and Pleistocene mollusks from San Andres Island (Caribbean Sea, Colombia) and Paleogeographic considerations

    International Nuclear Information System (INIS)

    Diaz M, Juan Manuel; Garcia Llano, Cesar Fernando

    2010-01-01

    San Andres Island is the largest emerged portion of the oceanic archipelago of San Andres and Providencia, southwestern Caribbean Sea; it originated as a coralline atoll during Miocene times. The central and highest part of the island consists of a calcareous crest, the San Andres Formation, formed by Neogene lagoonal and reefal deposits. This crest is surrounded by a calcareous platform of Pleistocene age (San Luis Formation) which emerges only along the island coast, whereas its most part is submerged and covered by a Recent reef complex. Fossil material of molluscs from these two formations was collected in various sites throughout the island and taxonomically identified. In the four sites sampled in the San Andres Formation, material belonging to 19 gastropod and 37 bivalve species was obtained, most of them relatively well represented in other geologic formations of the Caribbean region that are stratigraphically situated between the upper Miocene and the middle Pliocene. Some elements occurring in this formation, such as Ostrea haitiensis, Meretrix dariena and Siphocypraea henekeni, were widely distributed in the Caribbean Miocene Province. In the San Luis Formation, material belonging to 18 gastropod and 11 bivalve species was obtained, most of them also represented in the Recent molluscan fauna of the region. The estimated age of this formation is Sangamonian, hence corresponding to similar formations occurring in Grand Cayman, Jamaica, Hispaniola, the Netherlands Antilles and other Caribbean islands, with which it also shows a great similarity in the composition of the molluscan fauna.

  5. A partial skeleton of a new lamniform mackerel shark from the Miocene of Europe

    Directory of Open Access Journals (Sweden)

    Jürgen Kriwet

    2015-12-01

    Full Text Available Cenozoic lamniform sharks are mostly represented by isolated teeth and vertebrae, whereas articulated skeletal remains are usually very scarce. Here, we describe a partial skeleton of an extinct lamniform shark consisting of 42 slightly disarticulated teeth, 49 vertebrae, and additional unidentifiable cranial and postcranial remains. The specimen originates from the Miocene mica-clay of Groß Pampau (North Germany, which is of late Langenfeldian age (= Serravallian-Tortonian boundary; middle–late Miocene. A total of 13 measurements of each tooth, as well as morphological features, were used to reconstruct the dentition of this specimen and to provide detailed taxonomic information. Additionally, the total body size and age at death were established using methodologies based on vertebral and tooth measurements and vertebral centra growth ring counts, respectively. The specimen undoubtedly represents the most complete individual of “Carcharodon (= Isurus escheri”, previously known only from a few isolated teeth. The dental pattern (e.g., marked dignathic and monognathic heterodonty patterns; only slightly labio-lingually compressed upper teeth; upper teeth slender with distally inclined or curved main cusps; massive, hook-like upper intermediate tooth; main cusps with crenulated cutting edges; lateral cusplets in teeth of all ontogenetic stages clearly separates this shark from all hitherto known Cenozoic and Recent lamnids and a new genus, Carcharomodus, consequently is introduced. Carcharomodus escheri comb. nov. is a characteristic element of late early Miocene to the Pliocene Western and Central European fish faunas. All previously identified Pacific occurrences represent a different taxon. We estimate that the specimen had a total body length of about 4 m and that it was older than 10 years and thus might have reached maturity before death, as indicated by all available evidence.

  6. Molluscan radiations and landscape evolution in Miocene Amazonia

    NARCIS (Netherlands)

    Wesselingh, F.P.

    2008-01-01

    This PhD study aims to exploit the rich archive provided by the Miocene mollusc fauna of the Pebas Formation and other inland Miocene Amazonian formations to reconstruct landscape evolution and biotic development in lowland Amazonia during the Neogene. Over 160 samples from more than 70 Pebas

  7. Large mammal burrows in late Miocene calcic paleosols from central Argentina: paleoenvironment, taphonomy and producers

    Directory of Open Access Journals (Sweden)

    María Cristina Cardonatto

    2018-05-01

    Full Text Available Large cylindrical sediment-filled structures interpreted as mammal burrows occur within the loess-paleosol sequence of the late Miocene Cerro Azul Formation of central Argentina. A total of 115 burrow fills from three localities were measured. They are typically shallowly dipping, subcylindrical, unbranched structures with rounded ends and lacking enlargements. The horizontal diameter of the burrows range between 0.15 and 1.50 m, with most of the burrows in the interval of 0.39 to 0.98 m. Geometric morphometric analysis of transverse cross-sections support their distinct subcircular and elliptical (horizontally flattened shapes. Burrow fills are typically laminated in the lower part and massive in the upper part. The laminated intervals reflect pulses of flowing water entering the abandoned burrow during moderate rains, whereas massive intervals reflect mass flow input of dense sediment-water mixtures during heavy rains that produced sheet floods. Approximately 1% of the burrows contained fragmentary, disarticulated and weathered mammal bones that were introduced in the open burrow by currents along with other sedimentary particles. Analysis of the tetrapod burrow fossil record suggests that Miocene burrows, including those studied herein, reflect a remarkable increase in the average size of the fossorial fauna. We conclude that large late Miocene mammals dug burrows essentially as a shelter against environmental extremes and to escape predation. The simple architecture of the burrows suggests that the producers essentially foraged aboveground. Several mammal groups acquired fossorial habits in response to cold and seasonally dry climatic conditions that prevailed during the late Miocene in southern South America. The considerable range of horizontal diameters of the studied burrows can be attributed to a variety of producers, including dasypodids, the notoungulate Paedotherium minor, Glyptodontidae and Proscelidodon sp.

  8. Paleocene to Middle Miocene planktic foraminifera of the southwestern Salisbury Embayment, Virginia and Maryland: biostratigraphy, allostratigraphy, and sequence stratigraphy

    Science.gov (United States)

    Poag, C.W.; Commeau, J.A.

    1995-01-01

    The Paleocene to Middle Miocene sedimentary fill of the southwestern Salisbury Embayment contains a fragmental depositional record, interrupted by numerous local diastems and regional unconformities. Using planktic foraminiferal biostratigraphy, 15 unconformity-bounded depositional units have been identified, assigned to six formations and seven alloformations previously recognized in the embayment. The units correlate with second- and third-order sequences of the Exxon sequence stratigraphy model, and include transgressive and highstand systems tracts. Alloformation, formation, and sequence boundaries are marked by abrupt, scoured, burrowed, erosional surfaces, which display lag deposits, biostratigraphic gaps, and intense reworking of microfossils above and below the boundaries.Paleocene deposits represent the upper parts of upper Pleocene Biochronozones P4 and P5, and rest uncomformably  on Cretaceous sedimentary beds of various ages (Maastrichtian to Albian). Lower Eocene deposits represent parts of Biochronozones P6 and P9. Middle Eocene strata represent mainly parts of Biochronozones P11, P12, and P14. Upper Eocene sediments include parts of Biochronozones P15, P16, and P17. Oligocene deposits encompass parts of Biochronozones. N4b to N7 undifferentiated, P21a, and, perhaps, N4a. Lower Miocene deposits encompass parts of Biochronozones N4b to N7 undifferentiated. Middle Miocene strata represent mainly parts of Biochronorones N8, N9, and N10.Nine plates of scanning electron micrographs illustrate the principal planktic foraminifera used to establish the biostratigraphic framework. Two new informal formine of Praeterenuitella praegemma Li, 1987, are introduced.

  9. Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE) - an amphibious drilling proposal

    Science.gov (United States)

    Flecker, Rachel

    2017-04-01

    Today Mediterranean seawater flows out through the Gibraltar Straits, forming a saline plume at intermediate depths in the Atlantic. The plume's sedimentary record of distinctive, contouritic deposits has recently been recovered during IODP Leg 339 in the Gulf of Cadiz documenting a Mediterranean contribution to Atlantic thermohaline circulation since the Pliocene. However, before the Pliocene, the conduit for Mediterranean-Atlantic exchange is unclear. Gibraltar may have already been open, but two additional marine corridors also existed through northern Morocco and southern Spain. The restriction and closure of these Miocene connections resulted in extreme salinity fluctuations in the Mediterranean, leading to the precipitation of thick evaporites. This event is known as the Messinian Salinity Crisis (MSC) and recovering a complete record of the MSC is the target of current IODP drilling proposals (e.g. DREAM). Understanding both the causes of high-amplitude salinity change in the Mediterranean and its global consequences for thermohaline circulation in the Atlantic is dependent on recovering a complete record of Mediterranean-Atlantic exchange before, during and after the MSC. This key objective of the IMMAGE drilling proposal requires core recovery on-shore at the mouths of the Betic and Rifian corridors which are now exposed on land, as well as offshore, in the Alborán Sea and on the Atlantic continental margin. Consequently to meet this objective, an amphibious drilling strategy is necessary, involving both IODP and ICDP targets. In addition to allowing us to reconstruct Mediterranean-Atlantic exchange during high amplitude salinity fluctuations and identify the conduit through which exchange occurred, the sediments recovered from IMMAGE drilling will also provide us with a unique and explicit test for ocean physics hypotheses describing the location, size and velocity of overflow plumes under conditions where the density contrast between the two water

  10. Identification, prediction, and mitigation of sinkhole hazards in evaporite karst areas

    Science.gov (United States)

    Gutierrez, F.; Cooper, A.H.; Johnson, K.S.

    2008-01-01

    Sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas. This is because evaporites have a higher solubility and, commonly, a lower mechanical strength. Subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world, but the causes are only well understood in a few areas. To deal with these hazards, a phased approach is needed for sinkhole identification, investigation, prediction, and mitigation. Identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources. Detailed sinkhole maps can be constructed from sequential historical maps, recent topographical maps, and digital elevation models (DEMs) complemented with building-damage surveying, remote sensing, and high-resolution geodetic surveys. On a more detailed level, information from exposed paleosubsidence features (paleokarst), speleological explorations, geophysical investigations, trenching, dating techniques, and boreholes may help in investigating dissolution and subsidence features. Information on the hydrogeological pathways including caves, springs, and swallow holes are particularly important especially when corroborated by tracer tests. These diverse data sources make a valuable database-the karst inventory. From this dataset, sinkhole susceptibility zonations (relative probability) may be produced based on the spatial distribution of the features and good knowledge of the local geology. Sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation, alignment, and nearest neighbor analysis. More objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors. Chronological information on sinkhole formation is required to estimate the probability of

  11. Regional stratigraphy, sedimentology, and tectonic significance of Oligocene-Miocene sedimentary and volcanic rocks, northern Baja California, Mexico

    Science.gov (United States)

    Dorsey, Rebecca J.; Burns, Beverly

    1994-01-01

    Upper Oligocene (?) to middle Miocene sedimentary and volcanic rocks in northern Baja California were deposited along the western margin of North America during subduction of the Guadalupe plate and southward migration of the Rivera Triple Junction. Regional mapping and compilation of stratigraphic data reveal a sequence of three regionally traceable stratigraphic units. (1) Oligocene (?) to lower Miocene Mesa Formation: basal quartz-rich fluvial sandstone, grus, conglomerate, and accessory facies, whose detrital compositions reflect the composition of local pre-Tertiary basement rock. (2) Lower to middle Miocene Comondú Formation: laterally variable sequence of volcaniclastic conglomerate, breccia, sandstone, tuff and minor volcanic flow units. (3) Widespread mesa-capping rhyolite tuff, typically welded and crystal-rich, probably upper Miocene in age. The Mesa Formation overlies a highly irregular and deeply dissected erosional surface developed on pre-Tertiary basement rock. The shift from pre-Mesa erosion to widespread (though localized) deposition and valley-filling records the final phase of late Cretaceous to middle Tertiary regional subsidence and eastward transgression that resulted from slow cooling and thermal contraction of Cretaceous arc crust during a temporal gap in magmatic activity along the western Cordilleran margin. Nonmarine sediments of the Mesa Formation were deposited in small, steep-walled paleovalleys and basins that gradually filled and evolved to form through-going, low-energy ephemeral stream systems. The gradational upward transition from the Mesa to Comondú Formation records the early to middle Miocene onset of subduction-related arc magmatism in eastern Baja California and related westward progradation of alluvial volcaniclastic aprons shed from high-standing eruptive volcanic centers. Pre-existing streams were choked with the new influx of volcanic detritus, causing the onset of rapid sediment deposition by stream flows and dilute

  12. Groundwater flow and potential effects on evaporite dissolution in the Paradox Basin, SE Utah

    Science.gov (United States)

    Reitman, N.; Ge, S.; Mueller, K. J.

    2012-12-01

    A hydrogeologic study was conducted in the portion of the Paradox Basin south of the Needles District of Canyonlands National Park, Utah. Geology of the study area comprises fractured and faulted Paleozoic sandstone, limestone, and shale, which are underlain by evaporite cycles of the Paradox Formation. The evaporite deposits deform and dissolve when they come in contact with groundwater, generating land subsidence, saline groundwater, and salt input to the Colorado River. Active faults in the region slip at a rate of approximately 2 mm/year, likely due to evaporite dissolution. The objective of this study is to better understand groundwater flow and solute transport dynamics and to help determine the rate and timing of subsurface salt dissolution, which is an important control on the salt tectonics in the region. Study methods include hydrologic fieldwork, laboratory tests, and numerical modeling. No groundwater wells exist in the study area. Water samples from springs and seeps were collected throughout the study area. Analysis of total dissolved solids (TDS), stable oxygen (δ18O) and deuterium (δD) isotopes, spring and seep locations, and prior data are used to gain a preliminary understanding of the shallow groundwater flow in the region. Stable isotope ratios of oxygen (18O/16O) and deuterium (D/H) are used to constrain the source of spring water. Measured δ values are compared to predicted δ values for precipitation from WaterIsotopes.org for each sample site. Measured isotopic values range from -14.9 ‰ to -10.7 ‰ for δ18O and -108 ‰ to -78 ‰ for δD. The majority of samples from above 2000 m match predicted isotopic values for precipitation. Most samples taken below 2000 m are lighter than predicted isotopic values for precipitation. The TDS of spring samples measured in the lab show they range from 184 mg/L to 1552 mg/L with the majority of samples between 220 - 430 mg/L. TDS shows a weak correlation (R2 = 0.54) with altitude, where lower TDS

  13. Evaporite deposition in a shallow perennial lake, Qaidam basin, western China

    Energy Technology Data Exchange (ETDEWEB)

    Schubel, K.A.; Lowenstein, T.K. (SUNY, Binghampton, NY (United States)); Spencer, R.J. (Univ. of Calgary, Alberta (Canada)); Pengxi, Z. (Institute of Salt Lakes, Xining (China))

    1991-03-01

    Evaporites accumulate in ephemeral saline-pans, shallow perennial lakes or lagoons, and deep perennial systems. Continuous brine trench exposures of Holocene evaporites from the Qaidam basin provide criteria for the recognition of shallow perennial lake sediments. Based on Landsat photographs, lateral extent of beds (at least 7 km), and sequence thicknesses (maximum 2.5 m), the paleolake is interpreted to have been less than 2.5 m deep and at least 120 km{sup 2} in area. Sediments consist of laminated siliciclastic mud overlain by mud-halite couplets (mm- to cm-scale layers), which represent one vertical shallowing- and concentrating-upwards sequence. The basal laminite marks the onset of deposition in this shallow perennial paleolake. Syndepositional halite textures and fabrics in the overlying mud-halite couplets include cumulates, rafts, and chevrons, draped by mud laminae, and halite layers truncated by horizontal dissolution surfaces (increasing in frequency upwards). Paleolake brines, determined from fluid inclusion melting temperatures, are Na-Mg-Cl-rich and evolve from 0.84 m Mg{sup 2} to 1.52 m Mg{sup 2+} (near the surface). Combinations of the following criteria may be used for the recognition of shallow, nonstratified, perennial lake sediments: lateral continuity of layers; muds undisrupted by subaerial exposure; vertical bottom-growth of halite; halite layers conformably overlain by mud; halite layers truncated by nonuniformly spaced horizontal dissolution surfaces; erosional scours and channels filled with cross-laminated gypsum, halite, and siliciclastic sand and mud; and salinity fluctuations over small stratigraphic intervals within an overall concentrating-upwards sequence.

  14. Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

    Science.gov (United States)

    Poisson, André; Vrielynck, Bruno; Wernli, Roland; Negri, Alessandra; Bassetti, Maria-Angela; Büyükmeriç, Yesim; Özer, Sacit; Guillou, Hervé; Kavak, Kaan S.; Temiz, Haluk; Orszag-Sperber, Fabienne

    2016-01-01

    We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene-Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments

  15. Some observations on the Miocene foraminifera from Kachchh, Western India

    Digital Repository Service at National Institute of Oceanography (India)

    Jauhri, A.K.; Khare, N.

    The foraminiferal species described from the Miocene sequence exposed at the village Vinjhan of Kachchh are widely distributed in the comparable successions of the Middle East and Greece. They can be used for inter-regional correlation...

  16. Paleofaunal and Environmental Research on Miocene Fossil Sites TVOR SE and TVOR S on Fort Polk, Louisiana, with Continued Survey, Collection, Processing, and Documentation of other Miocene Localities

    National Research Council Canada - National Science Library

    Schiebout, Judith

    2004-01-01

    Focus of paleontological research on the Miocene of Fort Polk is currently the marine locality TVOR SE, which also has yielded large and small terrestrial Miocene vertebrates, and a single Cretaceous...

  17. Messinian Salinity Crisis' Primary Evaporites: the shallow gypsum vs. deep dolomite formation paradox solved

    Science.gov (United States)

    De Lange, G. J.; Krijgsman, W.

    2015-12-01

    The Messinian Salinity Crisis (MSC) is a dramatic event that took place ~ 5.9 Ma ago, resulting in deposition of 1-3 km thick evaporites at the Mediterranean seafloor. A considerable, long-lasting controversy existed on the modes of their formation, including the observed shallow gypsum versus deep dolostone deposits for the early phase of MSC. The onset of MSC is marked by deposition of gypsum/sapropel-like alternations, thought to relate to arid/humid climate conditions at a precessional rhythm. Gypsum precipitation only occurred at marginal- and dolomite formation at deeper settings. A range of potential explanations was given, most of which cannot satisfactorily explain all observations. Biogeochemical processes during MSC are commonly neglected but may explain that different deposits formed in shallow vs deep environments without exceptional physical boundary conditions for each. A unifying mechanism is presented in which gypsum formation occurs at all shallow water depths but its preservation is limited to shallow sedimentary settings. In contrast, ongoing deep-basin anoxic organic matter (OM) degradation processes result in dolomite formation. Gypsum precipitation in evaporating seawater takes place at 3-7 times concentrated seawater; seawater is always oversaturated relative to dolomite but its formation is inhibited by the presence of dissolved sulphate. Thus conditions for formation of gypsum exclude those for formation of dolomite and vice versa. Another process linking the saturation states of gypsum and dolomite is that of OM degradation by sulphate reduction. In stagnant deep water, ongoing OM-degradation may result in reducing the sulphate and enhancing the dissolved carbonate content. Such low-sulphate / high carbonate conditions in MSC deepwater are. unfavorable for gypsum preservation and favorable for dolomite formation, and always coincide with anoxic, i.e. oxygen-free conditions. Including dynamic biogeochemical processes in the thusfar static

  18. Isotopic Zonation Within Sulfate Evaporite Mineral Crystals Reveal Quantitative Paleoenvironment Details

    Science.gov (United States)

    Coleman, M.; Rhorssen, M.; Mielke, R. E.

    2008-12-01

    Isotopic variations measured within a single crystal of hydrated magnesium sulfate are greater than 30 permil for delta 2-H, almost 10 permil for δ18O in water of hydration; and greater than 3 permil in sulfate oxygen. These results are interpreted to indicate the relative humidity of the system during evaporation (15 to 20 percent in this test case) and constrain the volume of water involved. The theoretical basis of this system is the isotopic fractionation between the species in solution and those precipitated as evaporite salts. Precipitation preferentially accumulates more of the heavy isotopes of sulfur and oxygen in mineral sulfate, relative to sulfate in solution. During the course of mineral growth this leads to successive depletion of the respective heavier isotopes in the residual brine reflected in a parallel trend in successive precipitates or even in successive zones within a single crystal. The change in isotopic composition at any one time during the process, relative to the initial value, can be described by an isotopic version of the Rayleigh Fractionation equation, depending only on the extent of the completion of the process and the relevant fractionation factor. Evaporation preferentially removes isotopically lighter hydrogen and oxygen leading to successive extents of enrichment in the respective heavier isotopes in the residual water. However, the relative effects on hydrogen and oxygen isotopes differs as function of relative humidity [1]. ALL OF THESE CHANGES ARE PRESERVED IN THE MINERAL ISOTOPE COMPOSITIONS. We precipitated barium sulfate from epsomite or gypsum samples, which was reduced at 1450°C in the presence of graphite and glassy carbon in a Finnigan TC/EA to produce CO for O isotopic analysis in a Finnigan 253 mass spectrometer, while a separate subsample was oxidized to SO2 in a Costech Elemental Analyzer. However, to make progress with this approach we needed to make a large number of measurements of hydration water and so we

  19. Geophysical investigation of an upper tertiary subbasin in the southern Egyptian Red Sea shelf and its bearing on oil exploration

    Science.gov (United States)

    Khattab, M. M.

    Several narrow, elongate and Red Sea-trending gravity lows, suggested recently as due to depositional troughs, are shown on the Egyptian Red Sea shelf Bouguer map. Few drilling data and poor reflectivity below the Pliocene-Miocene uncorformity hinder subsurface evaluation. A 1 mgal anomaly (25 km north of Ras Benas Peninsula) was analysed along a crossing sessmic reflection line. The interpretation was aided by: lithology at an off-shore well, seismic data above the unconformity and aeromagnetic data in the southerly-located Foul Bay. The best fit of computed to observed gravity was for a three-layers model (water, post-evaporites and evaporites) where maximum sediment thickness was 3.8 km of which layers 2 and 3 constittted 1.6 and 2.2 km. The subbasin configuration was found to be controlled by Quaternary (similar to that mapped at Egyptian and Saudi Arabian coastal provinces) and pre-middle Miocence (affecting only middle Miocene evaprites beneath a reflection line at the western margin of the main trough near latitude 24°N) faulting which supports the conceot of Red Sea arching and subsequent faulting at marginal shelves. This subbasin is found associated, in part, with a sea--floor trough and with part of Foul Bay magnetic lineations (interpreted recently as caused by oceanic crust) which, in turn, are shown to constitute continuation of mapped onshore tholeiitic dikes.

  20. Depositional environment, organic matter characterization and hydrocarbon potential of Middle Miocene sediments from northeastern Bulgaria (Varna-Balchik Depression

    Directory of Open Access Journals (Sweden)

    Zdravkov Alexander

    2015-10-01

    Full Text Available The depositional environments and hydrocarbon potential of the siliciclastic, clayey and carbonate sediments from the Middle Miocene succession in the Varna-Balchik Depression, located in the south-eastern parts of the Moesian Platform, were studied using core and outcrop samples. Based on the lithology and resistivity log the succession is subdivided from base to top into five units. Siliciclastic sedimentation prevailed in the lower parts of units I and II, whereas their upper parts are dominated by carbonate rocks. Unit III is represented by laminated clays and biodetritic limestone. Units IV and V are represented by aragonitic sediments and biomicritic limestones, correlated with the Upper Miocene Topola and Karvuna Formations, respectively. Biogenic silica in the form of diatom frustules and sponge spicules correlates subunit IIa and unit III to the lower and upper parts of the Middle Miocene Euxinograd Formation. Both (subunits contain organic carbon contents in the order of 1 to 2 wt. % (median: 0.8 for subunit IIa; 1.3 for unit III, locally up to 4 wt. %. Based on Hydrogen Index values (HI and alkane distribution pattern, the kerogen is mainly type II in subunit IIa (average HI= 324 mg HC/g TOC and type III in unit III (average HI ~200 mg HC/g TOC. TOC and Rock Eval data show that subunit IIa holds a fair (to good hydrocarbon generative potential for oil, whereas the upper 5 m of unit III holds a good (to fair potential with the possibility to generate gas and minor oil. The rocks of both units are immature in the study area. Generally low sulphur contents are probably due to deposition in environments with reduced salinity. Normal marine conditions are suggested for unit III. Biomarker composition is typical for mixed marine and terrestrial organic matter and suggests deposition in dysoxic to anoxic environments.

  1. Summary of United States Geological Survey investigations of fluid-rock-waste reactions in evaporite environments under repository conditions

    International Nuclear Information System (INIS)

    Stewart, D.B.; Jones, B.F.; Roedder, E.; Potter, R.W. II

    1980-01-01

    The interstitial and inclusion fluids contained in rock salt and anhydrite, though present in amounts less than 1 weight per cent, are chemically aggressive and may react with canisters or wastes. The three basic types of fluids are: (1) bitterns residual from saline mineral precipitation including later recrystallization reactions; (2) brines containing residual solutes from the formation of evaporite that have been extensively modified by reactions with contiguous carbonate of clastic rocks; and (3) re-solution brines resulting from secondary dehydration of evaporite minerals or solution of saline minerals by undersaturated infiltrating waters. Fluid composition can indicate that meteoric flow systems have contacted evaporites or that fluids from evaporites have migrated into other formations. The movement of fluids trapped in fluid inclusions in salt from southeast New Mexico is most sensitive to ambient temperature and to inclusion size, although several other factors such as thermal gradient and vapour/liquid ratio are also important. There is no evidence of a threshold temperature for movement of inclusions. Empirical data are given for determining the amount of brine reaching the heat source if the temperature, approximate amount of total dissolved solids, and Ca:Mg ratio in the brine are known. SrCl 2 and CsCl can reach high concentrations in saturated NaCl solutions and greatly depress the liquidus. The possibility that such fluids, if generated, could migrate from a high-level waste repository must be minimized because the fluid would contain its own radiogenic energy source in the first decades after repository closure, thus changing the thermal evolution of the repository from designed values. (author)

  2. A model study of the first ventilated regime of the Arctic Ocean during the early Miocene

    Directory of Open Access Journals (Sweden)

    Bijoy Thompson

    2012-07-01

    Full Text Available The tectonic opening of Fram Strait during the Neogene was a significant geological event that transferred the Arctic Ocean from a poorly ventilated enclosed basin, with weak exchange with the North Atlantic, to a fully ventilated “ocean stage”. Previous tectonic and physical oceanographic analyses suggest that the early Miocene Fram Strait was likely several times narrower and less than half as deep as the present-day 400 km wide and 2550 m deep strait. Here we use an ocean general circulation model with a passive age tracer included to further address the effect of the Fram Strait opening on the early Miocene Arctic Ocean circulation. The model tracer age exhibits strong spatial gradient between the two major Arctic Ocean deep basins: the Eurasian and Amerasian basins. There is a two-layer stratification and the exchange flow through Fram Strait shows a bi-layer structure with a low salinity outflow from the Arctic confined to a relatively thin upper layer and a saline inflow from the North Atlantic below. Our study suggests that although Fram Strait was significantly narrower and shallower during early Miocene, and the ventilation mechanism quite different in our model, the estimated ventilation rates are comparable to the chemical tracer estimates in the present-day Arctic Ocean. Since we achieved ventilation of the Arctic Ocean with a prescribed Fram Strait width of 100 km and sill depth of 1000 m, ventilation may have preceded the timing of a full ocean depth connection between the Arctic Ocean and North Atlantic established through seafloor spreading and the development of the Lena Trough.

  3. Impact of evaporite dissolution and collapse on highways and other cultural features in the Texas Panhandle and Eastern New Mexico

    International Nuclear Information System (INIS)

    Simpkins, W.W.; Gustavson, T.C.; Alhades, A.B.; Hoadley, A.D.

    1981-01-01

    Geological investigations in the Texas Panhandle and eastern New Mexico indicate that regional subsurface dissolution of Permian evaporites has occurred and is an ongoing process. Evidence of removal of large volumes of evaporites (mainly halite) and collapse of overlying beds is demonstrated by cross sections constructed from gamma-ray logs. Surface manifestation of subsurface dissolution and collapse is clearly shown in Hall County, Texas, where over 400 sinkholes and undrained depressions have been identified from aerial photographs. Sinkhole diameters up to approximately 100 m (300 ft) and depths to 15 m (50 ft) have been observed. Eleven active northeast- and southwest-trending fractures and faults have been recognizd, some of which are demonstrated as patched sections of highways. Formation of collapse features and faults that damage highways is a recognized problem in the region. Stock tanks and large reservors are also affected to a lesser degree. Dissolution and collapse pose difficult problems for geologists, highway engineers, and maintenance crews. Areas of active subsurface dissolution have been identified, but development of collapse features and faults at the surface generally follows no predictable pattern. The history of, and potential for, evaporite dissolution sould be investigated in each area before construction of highways, reservoirs, and stock tanks. Areas with high densities of collapse features, fractures, and faults should be avoided when possible

  4. Deformation of evaporites near the Waste Isolation Pilot Plant (WIPP) site

    International Nuclear Information System (INIS)

    Borns, D.J.; Barrows, L.J.; Powers, D.W.; Snyder, R.P.

    1983-03-01

    Layered evaporite units of Ochoan age in the Delaware Basin are 1000 m thick. They are divided into three stratigraphic units (listed in order of increasing age): the Rustler Formation, the Salado Formation, the Castile Formation. These units, especially the Castile, are deformed along portions of the margin of the Delaware Basin and in some areas internal to the basin. Hypotheses of origin of deformation considered are: gravity foundering; gravity sliding; gypsum dehydration; dissolution; and depositional variations. Gravity foundering and sliding are considered the most probable causes of deformation. However, no hypothesis adequately answers why the deformation has a limited areal distribution. A possible explanation would be areal variations in rock strength caused by variations of intergranular water content. Age and timing of deformation are also crucial. Standard stratigraphic arguments based on superposition may not apply to such a highly incompetent material as halite. Gravity foundering could have happened at any time since deposition including the present; gravity sliding would probably have occurred since basin tilting began in the Cenozoic. Deformation could be ongoing. However, the strain rates are such (10 - 16 s - 1 ) that deformation would progress slowly relative to the facility's time frame of 2.5 x 10 5 y. Deformation of Salado units would be minimal ( 4 to 10 6 y to develop. At these strain rates, fractures that connect the fractured anhydrites of the Castile with the middle Salado could not develop. Deformation should not directly jeopardize the facility over the next 2.5 x 10 5 y

  5. 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.

  6. 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.

  7. Strategy for investigation of fluid migration in evaporites (Waste Isolation Pilot Plant - WIPP)

    International Nuclear Information System (INIS)

    Lambert, S.J.; Shefelbine, H.C.

    1980-03-01

    The proposed strategy for WIPP project investigations of fluid migration in evaporites focuses upon a quantitative evaluation of each of several processes. Potential short- and long-term problems arising from fluid migration are complication of waste retrieval and mobilization of waste nuclides. The strategy will attempt to determine the degree to which these potentials are realized with respect to five hypothetical types of waste-rock interactions: movement of waste containers, migration of nuclides, formation of radioactive brine pocket, radiolytic generation of gas, and degradation of waste container. Of eight identified processes whose combinations could lead to the five types of interactions, only five are to be quantitatively investigated by the studies of fluid migration per se: presence of fluids, fluid mobilization toward heat-producing and contact-handled waste, encounter of fluids with influence of waste form, reversal of direction of fluid mobilization, and entrainment of nuclides in fluids. Methods of investigation entail an iterative combination of laboratory experimentation and mathematical modeling

  8. Evaporite dissolution relevant to the WIPP site, northern Delaware Basin, southeastern New Mexico

    International Nuclear Information System (INIS)

    Lambert, S.J.

    1982-01-01

    Evaluation of the threat of natural dissolution of host evaporites to the integrity of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico has taken into consideration (1) the volume of missing rock salt, (2) the occurrence (or not) of characteristic dissolution brines, (3) geomorphic features, some of which are unrelated to dissolution, and (4) the time intervals over which dissolution may have been active. Even under the assumption that all missing halite was originally present and has been removed by dissolution, there is no evidence of active preferential removal of the lower Salado Formation halite by any geologically reasonable process. The geologic record contains evidence of dissolution in the Triassic and Jurassic; to constrain all removal of basinal halite to the late Cenozoic yields an unrealistically high rate of removal. Application to the lower Salado of a stratabound mechanism known to be active in Nash Draw, a near-surface feature within the Basin, allows a minimum survival time of 2,500,000 years to be predicted for the subsurface facility for storage of radioactive waste at WIPP. This calculation is based on an analysis of all known dissolution features in the Delaware Basin, and takes into account the wetter (pluvial) climate during the past 600,000 years. 2 figures, 1 table

  9. Migration of sharks into freshwater systems during the Miocene and implications for Alpine paleoelevation

    Science.gov (United States)

    Kocsis, László; Vennemann, Torsten W.; Fontignie, Denis

    2007-05-01

    Trace-element and isotopic compositions of fossilized shark teeth sampled from Miocene marine sediments of the north Alpine Molasse Basin, the Vienna Basin, and the Pannonian Basin generally show evidence of formation in a marine environment under conditions geochemically equivalent to the open ocean. In contrast, two of eight shark teeth from the Swiss Upper Marine Molasse locality of La Molière have extremely low δ18O values (10.3‰ and 11.3‰) and low 87Sr/86Sr ratios (0.707840 and 0.707812) compared to other teeth from this locality (21.1‰ 22.4‰ and 0.708421 0.708630). The rare earth element (REE) abundances and patterns from La Molière not only differ between dentine and enameloid of the same tooth, but also between different teeth, supporting variable conditions of diagenesis at this site. However, the REE patterns of enameloid from the “exotic” teeth analyzed for O and Sr isotopic compositions are similar to those of teeth that have O and Sr isotopic compositions typical of a marine setting at this site. Collectively, this suggests that the two “exotic” teeth were formed while the sharks frequented a freshwater environment with very low 18O-content and Sr isotopic composition controlled by Mesozoic calcareous rocks. This is consistent with a paleogeography of high-elevation (˜2300 m) Miocene Alps adjacent to a marginal sea.

  10. Geology, geochemistry and 40K-40Ar geochronometry of Miocene magmatism in Algiers area, Northern Algeria

    International Nuclear Information System (INIS)

    Belanteur, O.; Ouabadi, A.; Semroud, B.; Megartsi, M.H.; Fourcade, S.

    1995-01-01

    Miocene magmatic rocks outcrop within a narrow coastal strip east of Algiers. They include basaltic and andesitic lava flows and intrusions (Dellys, Cap Djinet), the Thenia granodioritic plug and the dacitic to rhyolitic lavas and pyroclastic flows from Zemmouri El Bahri and El Kerma. Despite the effects of hydrothermal alteration, 40 K- 40 Ar ages coupled with micropalaeontological data lead to recognition of two emplacement events at 16-15 and 14-12 Ma, respectively. All the studied calc-alkaline to potassic calc-alkaline rocks are enriched in highly incompatible elements and display negative Nb anomalies. Acid magmas have a pronounced crustal imprint ( 87 Sr 86 Sr i =3D 0.7082 to 0.7155; δ 18 O =3D +9 to +13 per mill) which together with La/Nb ratios argues for the occurrence of upper crustal contamination processes. However, the Nb-depletion of the associated basalts suggest that the studied magmas derive from a mantle source which underwent subduction-related metasomatic enrichments prior to their Miocene emplacement. (authors). 13 refs., 3 figs., 2 tabs

  11. Sedimentologic indicators of the Miocene tectonic evolution in the Nunchia syncline

    International Nuclear Information System (INIS)

    Ramirez Arias, Juan Carlos; Mora, Andres; Parra, Mauricio

    2010-01-01

    The study area corresponds to the Nunchia syncline, which is located in the eastern foothills of the eastern cordillera of Colombia. This structure is bounded by the Yopal thrust to the east, and Guaicaramo thrust to the west. This syncline has mostly outcrops of Miocene units, which belong to the Carbonera (C1-C5), Leon and Guayabo formations. Here we use sedimentologic data, especially in the Guayabo Formation, in order to determine the influence of active tectonics during its deposition. Petrographic analyses of sandstones indicate the presence of components associated with upper Cretaceous - Paleocene formations in the eastern cordillera. Paleocurrent orientation shows a preferential trend towards the se during the deposition of most of the studied formations, with a reversal in flow direction towards the W-NW during the deposition of the middle Guayabo Formation preserved in the Nunchia syncline. The collected data allows establishing a structural evolution in the Nunchia syncline which was therefore active during most of the Miocene. This evolution appears to be continuous, although fragmentation of the geological record shows more specific periods of tectonic activity.

  12. Miocene oceanographic changes of the western equatorial Atlantic (Ceara Rise) based on calcareous dinoflagellate cysts

    Science.gov (United States)

    Heinrich, S.; Zonneveld, K. A. F.; Willems, H.

    2010-09-01

    The middle- and upper Miocene represent a time-interval of major changes in palaeoceanography that favoured the cooling of the climate and culminated in the Northern Hemisphere Glaciation (NHG). The basis for the development of the modern deepwater circulation pattern, e.g. thermohaline circulation, was hereby established. Tectonic events played a key role in the progressing Miocene oceanography, such as the narrowing of the Panama gateway (e.g. Duque-Caro 1990) and the possible linked changes in North Atlantic Deep Water formation (Lear et al. 2003). However, the complex interaction between the closing of the Panama Gateway, the development of NADW, and thus the oceanographic progression towards our present day circulation is far from being fully understood. We want to improve the understanding of these processes by establishing a detailed palaeoceanographic reconstruction of the western equatorial Atlantic Ocean on the basis of calcareous dinoflagellate cyst (dinocyst) associations. Within this study, we investigated sediment samples from ODP Site 926A by defining the calcareous dinocyst assemblage. Site 926A is located at the southwestern flank of the Ceara Rise, an area of highest sensitivity to global deep water circulation changes. At about 12 Ma, when NADW production increased (e.g. Wright et al. 1992), we see a distinct increase in the absolute abundances of the calcareous dinocysts. This might be related to enhanced productivity or to better carbonate preservation. At 11.3 Ma, Leonella granifera, a species known to be strongly related to terrestrial input occurs. This could be a signal for the initiation of the Amazon River as a transcontinental river with the development of the Amazon fan (11.8 - 11.3 Ma; Figueiredo et al. 2009) in relation to Andean tectonism. References: Duque-Caro, H. (1990): Neogene stratigraphy, paleoceanography and palebiology in Northwest South America and the evolution of the Panama Seaway. Palaeogeography, Palaeoclimatology

  13. Late Miocene-Recent evolution of the Finike Basin and its linkages with the Beydağlari complex and the Anaximander Mountains, eastern Mediterranean

    Science.gov (United States)

    Aksu, A. E.; Hall, J.; Yaltırak, C.; Çınar, E.; Küçük, M.; Çifçi, G.

    2014-11-01

    Interpretation of ~ 2500 km of high-resolution multi-channel seismic reflection profiles shows that the Finike Basin evolved during the Pliocene-Quaternary as the result of dramatic subsidence associated with loading of large imbricate thrust panels that carry the western Tauride Mountains in the north in the Late Miocene. The stacked, seaward prograded Quaternary deltas presently resting at 1000-1500 m water depths corroborate the rapid subsidence of the region. The ubiquitous presence of evaporites in the 2000-2400 m-deep Antalya Basin and their absence in the 3000-3200 m deep Finike Basin suggest that the morphology of the Finike Basin and environs must have been considerably different during the Messinian and that this region must have remained above the depositional base of evaporites during this time. The transition from the Messinian to the Pliocene-Quaternary is marked by partitioning of stress into several discrete spatial domains. A dextral strike-slip fault zone developed along the western Antalya Basin, extending from the apex of the Isparta Angle southward into the Anaximander Mountains. This fault zone, referred to as the Antalya Fault zone, transected the Anaximander Mountains (sensu lato) separating the Anaxagoras Mountain from the Anaximander and Anaximenes Mountains. Hence, the Finike Basin, Sırrı Erinç Plateau and the Anaximander and Anaximenes Mountains remained part of the onland Beydağları Block and experienced ~ 20° counterclockwise rotation during the Late Miocene. We envisage the boundaries of the Beydağları Block as the Burdur-Fethiye Fault zone in the west, the newly delineated Antalya Fault zone in the east and the east-west trending sector of the Sırrı Erinç Plateau in the southwest. Kinematic evaluation of the structural elements mapped across the Finike Basin and the Sırrı Erinç Plateau suggest that two additional strike-slip zones developed during the Pliocene-Quaternary relaying the stress between the Antalya Fault

  14. Thermochronometrically constrained anatomy and evolution of a Miocene extensional accommodation zone and tilt domain boundary: The southern Wassuk Range, Nevada

    Science.gov (United States)

    Gorynski, Kyle E.; Stockli, Daniel F.; Douglas Walker, J.

    2013-06-01

    (AHe) and Zircon (ZHe) (U-Th)/He thermochronometric data from the southern Wassuk Range (WR) coupled with 40Ar/39Ar age data from the overlying tilted Tertiary section are used to constrain the thermal evolution of an extensional accommodation zone and tilt-domain boundary. AHe and ZHe data record two episodes of rapid cooling related to the tectonic exhumation of the WR fault block beginning at ~15 and ~4 Ma. Extension was accommodated through fault-block rotation and variably tilted the southern WR to the west from ~60°-70° in the central WR to ~15°-35° in the southernmost WR and Pine Grove Hills, and minimal tilting in the Anchorite Hills and along the Mina Deflection to the south. Middle Miocene geothermal gradient estimates record heating immediately prior to large-magnitude extension that was likely coeval with the extrusion of the Lincoln Flat andesite at ~14.8 Ma. Geothermal gradients increase from ~19° ± 4°C/km to ≥ 65° ± 20°C/km toward the Mina Deflection, suggesting that it was the focus of Middle Miocene arc magmatism in the upper crust. The decreasing thickness of tilt blocks toward the south resulted from a shallowing brittle/ductile transition zone. Postmagmatic Middle Miocene extension and fault-block advection were focused in the northern and central WR and coincidentally moderated the large lateral thermal gradient within the uppermost crust.

  15. Primary Evaporites for the Messinian Salinity Crisis: the shallow gypsum vs. deep dolomite formation paradox solved

    Science.gov (United States)

    De Lange, Gert J.; Krijgsman, Wout

    2014-05-01

    The Messinian Salinity Crisis (MSC) is a dramatic event that took place ~ 5.9 Ma ago, and resulted in the deposition of 0.3-3 km thick evaporites at the Mediterranean seafloor. A considerable and long-lasting controversy existed on the modes of their formation. During the CIESM Almeria Workshop a consensus was reached on several aspects. In addition, remaining issues to be solved were identified, such as for the observed shallow gypsum versus deep dolostone deposits for the early phase of MSC. The onset of MSC is marked by deposition of gypsum/sapropel-like alternations, thought to relate to arid/humid climate conditions. Gypsum precipitation only occurred at marginal settings, while dolomite containing rocks have been reported from deeper settings. A range of potential explanations have been reported, most of which cannot satisfactorily explain all observations. Biogeochemical processes during MSC are poorly understood and commonly neglected. These may, however, explain that different deposits formed in shallow versus deep environments without needing exceptional physical boundary conditions for each. We present here a unifying mechanism in which gypsum formation occurs at all shallow water depths but its preservation is mostly limited to shallow sedimentary settings. In contrast, ongoing anoxic organic matter (OM) degradation processes in the deep basin result in the formation of dolomite. Gypsum precipitation in evaporating seawater takes place at 3-7 times concentrated seawater; seawater is always largely oversaturated relative to dolomite but its formation is thought to be inhibited by the presence of dissolved sulphate. Thus the conditions for formation of gypsum exclude those for the formation of dolomite and vice versa. Another process that links the saturation states of gypsum and dolomite is that of OM degradation by sulphate reduction. In stagnant deep water, oxygen is rapidly depleted through OM degradation, then sulphate becomes the main oxidant for OM

  16. Dynamic properties of anhydrites, marls and salts of the Gachsaran evaporitic formation, Iran

    International Nuclear Information System (INIS)

    Gorjian, M; Memarian, H; Moosavi, M; Mehrgini, B

    2013-01-01

    A large carbonate oil field in Iran is suffering from severe casing collapses and related operational problems in anhydrite, marl and salt sequences of the Gachsaran cap rock formation. To investigate the causes and cures of operational problems, specifically casing collapse, knowing geomechanical properties of anhydrite, marl and salt of this formation is a prerequisite. However, taking cores in this formation is virtually impossible due to high solubility and weakness of the rocks. Moreover, there are insufficient well log data in this formation and the only available running well log is V p . In this paper, in order to obtain the dynamic parameters of the Gachsaran formation, V p , V s and ρ b in anhydrite, marl and salt cores, which had been taken from depths up to 300 m, were measured. Moreover, V p and V s in salt cores under different triaxial and hydrostatic stress conditions were obtained. The V p –V s, (V p /V s )–V p and V p –ρ b relations in anhydrite, marl and salt were investigated. The established relations in these anhydrite samples were verified by the data derived from limited cores which were taken from 3600 m depth. The relations between dynamic properties of salt with lateral and hydrostatic stresses were investigated. In conclusion, V s , ρ b and the ratio of V p /V s in anhydrite and marl can be estimated through the established relations and having V p logs in the Gachsaran formation. As a result, the dynamic properties of these rocks can be calculated in different depths of this evaporitic formation. Furthermore, the dynamic properties of salt rock seem to be constant in various depths and under differing triaxial and hydrostatic stress conditions. (paper)

  17. Late Miocene volcanic activity in the České středohoří Mountains, Ohře (Eger) Graben, northern Bohemia

    Czech Academy of Sciences Publication Activity Database

    Cajz, Vladimír; Rapprich, V.; Erban, V.; Pécskay, Z.; Radoň, M.

    2009-01-01

    Roč. 60, č. 6 (2009), s. 519-533 ISSN 1335-0552 R&D Projects: GA AV ČR IAA300130612 Institutional research plan: CEZ:AV0Z30130516 Keywords : Upper Miocene * České středohoří Mts. * volcanostratigraphy * Štrbice Formation * geochemistry * K-Ar dating * cinder cone * basanite Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.963, year: 2009

  18. Life-history traits of the Miocene Hipparion concudense (Spain inferred from bone histological structure.

    Directory of Open Access Journals (Sweden)

    Cayetana Martinez-Maza

    Full Text Available Histological analyses of fossil bones have provided clues on the growth patterns and life history traits of several extinct vertebrates that would be unavailable for classical morphological studies. We analyzed the bone histology of Hipparion to infer features of its life history traits and growth pattern. Microscope analysis of thin sections of a large sample of humeri, femora, tibiae and metapodials of Hipparion concudense from the upper Miocene site of Los Valles de Fuentidueña (Segovia, Spain has shown that the number of growth marks is similar among the different limb bones, suggesting that equivalent skeletochronological inferences for this Hipparion population might be achieved by means of any of the elements studied. Considering their abundance, we conducted a skeletechronological study based on the large sample of third metapodials from Los Valles de Fuentidueña together with another large sample from the Upper Miocene locality of Concud (Teruel, Spain. The data obtained enabled us to distinguish four age groups in both samples and to determine that Hipparion concudense tended to reach skeletal maturity during its third year of life. Integration of bone microstructure and skeletochronological data allowed us to identify ontogenetic changes in bone structure and growth rate and to distinguish three histologic ontogenetic stages corresponding to immature, subadult and adult individuals. Data on secondary osteon density revealed an increase in bone remodeling throughout the ontogenetic stages and a lesser degree thereof in the Concud population, which indicates different biomechanical stresses in the two populations, likely due to environmental differences. Several individuals showed atypical growth patterns in the Concud sample, which may also reflect environmental differences between the two localities. Finally, classification of the specimens' age within groups enabled us to characterize the age structure of both samples, which is

  19. Climate aberrations during the middle Miocene: evidence from the eastern North Atlantic Ocean

    NARCIS (Netherlands)

    Quaijtaal, W.; Donders, T.H.; Schouten, S.; Louwye, S.

    2013-01-01

    During the Middle Miocene Climatic Optimum (MMCO; 17-14.5 Ma) the relatively warm climate of the Miocene reached peak temperatures. After the MMCO, the global climate started cooling through several short-lived cooling events, represented by positive oxygen isotope excursions: the Mi-events (Miocene

  20. An initial examination of carbonate variability in the western equatorial Pacific: XRF results from the lower to middle Miocene of IODP Site U1490

    Science.gov (United States)

    Valerio, D. A.; Kulhanek, D. K.; Rosenthal, Y.; Holbourn, A. E.

    2017-12-01

    International Ocean Discovery Program (IODP) Expedition 363 sought to determine the nature of and driving forces behind climate variability in the Western Pacific Warm Pool (WPWP) region throughout the Neogene on millennial, orbital, and geologic timescales. Our research focuses on the Miocene (19-9 Ma) sediment record from IODP Site U1490 to examine changes in carbonate production and burial in the WPWP as a record of variations in the regional/global carbon cycle. This interval is of particular interest because it spans the Middle Miocene Climatic Optimum, the Middle Miocene Climate Transition, and the late Miocene carbonate crash. Site U1490 is located on the northern edge of Eauripik Rise at 05°58.95'N, 142°39.27'E in the northern part of the WPWP. At 2341 m water depth, today the site is bathed in Upper Circumpolar Deepwater. Miocene sediment at Site U1490 primarily consists of clay-bearing to clay-rich foraminifer-rich nannofossil ooze, although biogenic silica (primarily radiolaria) is a significant component in the lowermost part of the record. The sedimentation rate in the early to middle Miocene was very low (calcium carbonate content of 87 wt% throughout the site, with the most significant variations in the lower to middle Miocene, where contents range from 20 to 85 wt%. We collected X-ray fluorescence (XRF) data at 1 cm resolution along the composite stratigraphic section over the 19-9 Ma interval to obtain a qualitative measure of the bulk chemistry of the sediment. We will use the weight percent calcium carbonate of discrete samples to calibrate the XRF data to generate a high-resolution carbonate record. We observe cyclical variations in the Ca/Ba, which may reflect variations in productivity and/or dissolution through this interval, although additional work is needed to fully interpret these data. Ultimately our research will allow for comparison between records obtained from these cores located in the western equatorial Pacific to those obtained

  1. STRONTIUM ISOTOPE STRATIGRAPHY AS A CONTRIBUTION FOR DATING MIOCENE SHELF CARBONATES (S. MARINO FM., NORTHERN APENNINES

    Directory of Open Access Journals (Sweden)

    CLAUDIO ARGENTINO

    2017-01-01

    Full Text Available This paper provides new data on strontium isotope stratigraphy applied to the Miocene heterozoan shelfal carbonates of the S. Marino Fm. (Marecchia Valley, northern Apennines. Sr isotopic analyses were carried out on oyster shells, bryozoans and bulk-rocks from the lower-middle carbonate portion of the section. In the upper part of the succession that shows evidence of detrital influx,87Sr/86Sr analyses were performed on foraminifera tests, separating planktonic and benthic forms. Results were compared with calcareous nannofossil biostratigraphic data from the same levels, in order to test the reliability of Sr dating in mixed carbonate-siliciclastic sediments. Mean ages obtained from oysters range between 16.9 Ma and 16.3 Ma. Very similar results are obtained using bryozoans (16.5 Ma to 16.1 Ma and bulk-rocks (16.8 Ma to 16.2 Ma. These results allow to better constrain the age of the massive carbonate shelf, referable to the upper Burdigalian. In the upper carbonate-siliciclastic portion of the shelf, numerical ages obtained from planktonic and benthic foraminifera are in good agreement with nannofossil biozones (mean ages respectively around 15.3 Ma and 14.5 Ma although they display wide confidence intervals. These wide age uncertainties depend on the slow rate of change of marine 87Sr/86Sr through time that characterizes the interval between ~15 and ~13.5 Ma.

  2. Paleoecology of benthic foraminifera from the Miocene of the San Jacinto Basin, Colombia

    Science.gov (United States)

    Poveda, John Sebastian; Fiorini, Flavia; Andres Trejos, Raul; Vallejo, Diego Felipe; Pardo, Andres

    2015-04-01

    Quantitative benthic foraminifera analysis was conducted on 34 samples collected from a borehole core (393.72m deep) drilled by Colombian Hydrocarbon Agency (ANH) on 2009 in the San Jacinto basin (Northern Colombia). The aims of the research were to define a taxonomical data-bank of Miocene benthic foraminifera for this region, to use the benthic foraminifera assemblages to interpret the paleoenvironment and to identify paleoenvironmental changes. The bottom of the section was dated between lowest Burdigalian to middle Langhian (20.393-17.721 Ma) based on calcareous nannofossils bioevents: LO Helicosphaera ampliaperta, HCO Sphenolithus belemnos and LCO Sphenolithus heteromorphus. The benthic foraminifera fauna identified in the studied samples is composed for the majority of calcareous hyaline tests and is dominated by infaunal taxas. Species belonging to the genera Uvigerina and Lenticulina are commonly occurring in the studied section together with other species typical of outer-shelf upper-bathyal environment. Cibicidoides spp., abundant in the lower part of the section, abruptly decreases in abundance in the upper part. Species belonging to the opportunistic genera Bulimina and Bolivina are more abundant in the upper part of the section. Variability in the abundance of opportunistic species can be associated with tectonic disturbance on the Sinu-San Jacinto fold belt (NW of Colombia) as a result of collision of the Caribbean plate against NW of South America. The tectonics could lead a perturbation on deep ocean sedimentation and circulation.

  3. Palynological Zonation of Oligocene to Early Miocene Sediments of ...

    African Journals Online (AJOL)

    ADOWIE PERE

    2017-12-31

    Dec 31, 2017 ... Keywords: Lithozones; Niger delta Basin; Palynomorphs; Oligocene to Early Miocene; Depobelt. The Niger Delta is ... province on the West African continental margin. It lies mainly in the ... Nigeria depends largely on the oil and gas derived from it. ... generation, accumulation and retention of hydrocarbons.

  4. Molluscan fauna from the Miocene sediments of Kachchh, Gujarat ...

    Indian Academy of Sciences (India)

    geological mapping of Kachchh was assigned to. Fedden and Wynne in the late ... Figure 1. Geological map of parts of Kachchh Region, Gujarat State, India; slightly modified after Biswas and Deshpande. Formational boundaries ...... division and correlation of Oligo–Miocene petroleum bearing strata in India and future ...

  5. Avian fossils from the Early Miocene Moghra Formation of Egypt ...

    African Journals Online (AJOL)

    Avian remains from the Early Miocene (~17 Ma) Moghra Formation of Egypt include new records of 'waterbirds' (storks, herons, pelicans and allies) and a ratite. Only a single avian fossil has been previously reported from Wadi Moghra and, thus, additional knowledge of the avifauna complements previously documented ...

  6. Larger benthic foraminifera in Miocene carbonates of Indonesia

    NARCIS (Netherlands)

    Novak, Vibor

    2014-01-01

    Present day Southeast Asia represents the region that supports the most diverse marine ecosystems on Earth. The origin of this biodiversity is still unresolved, but it is proposed to be present at least since the Early Miocene. Therefore, the data acquired from the fossil assemblages may contribute

  7. A southern North Sea Miocene dinoflagellate cyst zonation

    NARCIS (Netherlands)

    Munsterman, D.K.; Brinkhuis, H.

    2004-01-01

    An integrated stratigraphical analysis emphasizing organic-walled dinoflagellate cyst (dinocyst) distribution has been carried out on multiple boreholes penetrating the Miocene in the subsurface of the Netherlands (southern North Sea Basin). The bulk of the investigated successions is attributed to

  8. A major reorganization of Asian climate by the early Miocene

    Directory of Open Access Journals (Sweden)

    Z. T. Guo

    2008-08-01

    Full Text Available The global climate system experienced a series of drastic changes during the Cenozoic. In Asia, these include the climate transformation from a zonal pattern to a monsoon-dominated pattern, the disappearance of typical subtropical aridity, and the onset of inland deserts. Despite major advances in the last two decades in characterizing and understanding these climate phenomena, disagreements persist relative to the timing, behaviors and underlying causes.

    This paper addresses these issues mainly based on two lines of evidence. First, we compiled newly collected data from geological indicators of the Cenozoic environment in China as paleoenvironmental maps of ten intervals. In confirming the earlier observation that a zonal climate pattern was transformed into a monsoonal one, the maps within the Miocene indicate that this change was achieved by the early Miocene, roughly consistent with the onset of loess deposition in China. Although a monsoon-like regime would have existed in the Eocene, it was restricted to tropical-subtropical regions. The latitudinal oscillations of the climate zones during the Paleogene are likely attributable to the imbalance in evolution of polar ice-sheets between the two hemispheres.

    Secondly, we examine the relevant depositional and soil forming processes of the Miocene loess-soil sequences to determine the circulation characteristics with emphasis on the early Miocene. Continuous eolian deposition in the middle reaches of the Yellow River since the early Miocene firmly indicates the formation of inland deserts, which have been constantly maintained during the past 22 Ma. Grain-size gradients between loess sections indicate northerly dust-carrying winds from northern sources, a clear indication of an Asian winter monsoon system. Meanwhile, well-developed Luvisols show evidence that moisture from the oceans reached northern China. This evidence shows the coexistence of two kinds of

  9. The early to mid-Miocene environment of Antarctica

    Science.gov (United States)

    Ashworth, A. C.; Lewis, A.

    2012-12-01

    Paleoecological studies in the Transantarctic Mountains of the McMurdo region provide evidence that the climate was both warmer and wetter in the early to mid-Miocene than it was during the late Miocene. The climate change was accompanied by a shift from wet- to cold-based glaciation in the TAM and the probable growth of the polar ice sheet. Terrestrial and freshwater aquatic fossil assemblages from the Friis Hills (77°S) and the Olympus Range (77°S), with endpoint 40Ar/39Ar ages on tephras of 19.76 Ma and 14.07 Ma, respectively, indicate climatic cooling during the interval. At c.14 Ma, the temperature dropped below the threshold required to support the plants and insects of a tundra biome, and they became extinct. This interpretation is supported by pollen studies from Ross Sea cores. The extinction of the tundra biota on the continent appears to have been time-transgressive, occurring at 12.8 Ma on the Antarctic Peninsula. Evidence of climatic cooling from early to mid-Miocene is based on a decrease in biodiversity. During interglacial phases of the early Miocene, the poorly drained valley of the Friis Hills supported a sexually-reproducing moss community dominated by Campylium cf. polygamum, which today grows on the margins of lakes and in soil between boulders. Wood and leaves of Nothofagus (Southern Beech), and the seeds of at least five other angiosperm species are preserved as fossils. In addition, there are abundant megaspores and spiny, curved leaves of the aquatic lycopod Isoetes (Quillwort), as well as chitinous remains of curculionid beetles and Chironomidae (midges). During glacial phases, the only fossils found are Nothofagus leaves of a species which appears to be different than that associated with the interglacial phases. Pollen supports the interpretation that there was more than one species of Nothofagus in the vegetation. The types and numbers of species indicate that the vegetation was a shrub tundra. The closest modern analog for the fossil

  10. Bacterial and Archaeal Lipids Recovered from Subsurface Evaporites of Dalangtan Playa on the Tibetan Plateau and Their Astrobiological Implications

    Science.gov (United States)

    Cheng, Ziye; Xiao, Long; Wang, Hongmei; Yang, Huan; Li, Jingjing; Huang, Ting; Xu, Yi; Ma, Nina

    2017-11-01

    Qaidam Basin (Tibetan Plateau) is considered an applicable analogue to Mars with regard to sustained extreme aridity and abundant evaporites. To investigate the possibility of the preservation of microbial lipids under these Mars analog conditions, we conducted a mineralogical and organic geochemistry study on samples collected from two Quaternary sections in Dalangtan Playa, northwestern Qaidam Basin, which will enhance our understanding of the potential preservation of molecular biomarkers on Mars. Two sedimentary units were identified along two profiles: one salt unit characterized by a predominance of gypsum and halite, and one detrital unit with a decrease of gypsum and halite and enrichment in siliciclastic minerals. Bacterial fatty acids and archaeal acyclic diether and tetraether membrane lipids were detected, and they varied throughout the sections in concentration and abundance. Bacterial and archaeal biomolecules indicate a dominance of Gram-positive bacteria and halophilic archaea in this hypersaline ecosystem that is similar to those in other hypersaline environments. Furthermore, the abundance of bacterial lipids decreases with the increase of salinity, whereas archaeal lipids showed a reverse trend. The detection of microbial lipids in hypersaline environments would indicate, for example on Mars, a high potential for the detection of microbial biomarkers in evaporites over geological timescales.

  11. Visible and near-infrared (0.4-2.5 μm) reflectance spectra of playa evaporite minerals

    Science.gov (United States)

    Crowley, James K.

    1991-01-01

    Visible and near-infrared (VNIR; 0.4–2.4 μm) reflectance spectra were recorded for 35 saline minerals that represent the wide range of mineral and brine chemical compositions found in playa evaporite settings. The spectra show that many of the saline minerals exhibit diagnostic near-infrared absorption bands, chiefly attributable to vibrations of hydrogen-bonded structural water molecules. VNIR reflectance spectra can be used to detect minor hydrate phases present in mixtures dominated by anhydrous halite or thenardite, and therefore will be useful in combination with X ray diffraction data for characterizing natural saline mineral assemblages. In addition, VNIR reflectance spectra are sensitive to differences in sample hydration state and should facilitate in situ studies of minerals that occur as fragile, transitory dehydration products in natural salt crusts. The use of spectral reflectance measurements in playa studies should aid in mapping evaporite mineral distributions and may provide insight into the geochemical and hydrological controls on playa mineral and brine development.

  12. Fluids circulation during the Miocene rifting of the Penedès half-graben, NE Iberian Peninsula

    Science.gov (United States)

    Baqués, Vinyet; Travé, Anna; Cantarero, Irene

    2013-04-01

    The Penedès half-graben, located in the north-western part of the Mediterranean, is a NE-SW oriented basin generated during the Miocene rifting. This graben is bounded to the northwest by the SE-dipping Vallès-Penedès fault, which places the Mesozoic rocks in contact with the Miocene basin-fill. The basin is filled with an up to 4 km thick succession of sediments divided into three lithostratigraphic units. From base to top: (1) a lower continental complex, (2) a continental to marine complex and (3) an upper continental complex. These units are covered by Pliocene deposits which onlap a Messinian regional erosive surface. The structural features within the Penedès half-graben allow defining three deformational phases during the Miocene rifting. The first, during the syn-rift, two successive stages of NE-SW normal faults were formed. The second, during the early post-rift, one stage of NE-SW normal faults and one minor compression phase with a dextral directional developed. The third, during the late post-rift, two successive stages of N-S trending extensional fractures (faults and joints) and one minor compression with a sinistral component developed. The fractures related to the syn-rift stage acted as conduits for meteoric fluids both, in the phreatic and in the vadose zone. During the early post-rift, Fe2+- rich fluids precipitated oxides along the NE-SW fault planes. The dextral directional faults served as conduits for meteoric fluids which reequilibrated totally the marine Miocene host rocks under the phreatic environment. The late post-rift stage was characterized by marine fluids upflowing through the N-S fractures, probably derived from the Miocene marine interval, which mixed with meteoric fluids producing dolomitization. The second set of N-S fractures served as conduits for meteoric fluids characterised by δ13C-depleted soil-derived CO2 attributed to precipitation in the vadose zone. The change from phreatic to vadose meteoric environment and the

  13. Reduction in Surface Ocean Carbon Storage across the Middle Miocene

    Science.gov (United States)

    Babila, T. L.; Sosdian, S. M.; Foster, G. L.; Lear, C. H.

    2017-12-01

    During the Middle Miocene, Earth underwent a profound climate shift from the warmth of the Miocene Climatic Optimum (MCO; 14-17 Ma) to the stable icehouse of today during the Middle Miocene Climate transition (MMCT). Elevated atmospheric carbon dioxide concentrations (pCO2) revealed by boron isotope records (δ11B) link massive volcanic outputs of Columbia River Flood Basalts to the general warmth of MCO. Superimposed on the long-term cooling trend (MMCT) is a gradual pCO2 decline and numerous positive carbon isotope (δ13C) excursions that indicate dynamic variations in the global carbon cycle. Enhanced organic carbon burial via marine productivity, increased silicate weathering and volcanic emission cessation are each invoked to explain the drawdown of pCO2. To better constrain the oceanic role in carbon sequestration over the Middle Miocene detailed records of carbonate chemistry are needed. We present high resolution Boron/Calcium (B/Ca) and δ13C records in planktonic foraminifer T.trilobus spanning 12-17 Ma at ODP 761 (tropical eastern Indian Ocean) to document changes in surface ocean carbonate chemistry. An overall 30% increase in B/Ca ratios is expressed as two stepwise phases occurring at 14.7 and 13 Ma. Cyclic B/Ca variations are coherent with complimentary δ13C records suggesting a tight coupling between ocean carbonate chemistry parameters. Lower resolution B/Ca data at DSDP 588 (Pacific) and ODP 926 (Atlantic) corroborate the trends observed at ODP 761. We employ a paired approach that combines B/Ca (this study) to δ11B (Foster et al., 2012) and an ad hoc calibration to estimate changes in surface ocean dissolved inorganic carbon (DIC). We estimate a substantial decrease in surface ocean DIC spanning the Middle Miocene that culminates with modern day like values. This gradual decline in surface ocean DIC is coeval with existing deep-ocean records which together suggests a whole ocean reduction in carbon storage. We speculate that enhanced weathering

  14. Soft-sediment deformation structures in seismically affected deep-sea Miocene turbidites (Cilento Basin, southern Italy

    Directory of Open Access Journals (Sweden)

    Valente Alessio

    2014-07-01

    Full Text Available Soft-sediment deformation structures (SSDS are widespread in the upper part of the S. Mauro Formation (Cilento Group, Middle-Late Miocene. The succession is represented mainly by thick and very thick, massive, coarse-grained sandstones, deposited by rapid sedimentation of high-density turbidity currents. The most common SSDS are short pillars, dishes, sedimentary sills and convolutions. They occur mostly in the upper parts of sandstone beds. Vertical tubes of 4-5 cm in diameter and up to 50 cm long constitute the most striking structures. They begin in the middle part of sandstone beds, which are basically massive or contain faint dish structures. These tubes can bifurcate upwards and/ or pass into bedding-parallel veins or dikes. The vertical tubes sometimes form sand volcanoes on the then sedimentary surface.

  15. The extinct river shark Glyphis pagoda from the Miocene of Myanmar and a review of the fossil record of the genus Glyphis (Carcharhiniformes: Carcharhinidae).

    Science.gov (United States)

    Shimada, Kenshu; Egi, Naoko; Tsubamoto, Takehisa; Maung-Maung, Maung-Maung; Thaung-Htike, Thaung-Htike; Zin-Maung-Maung-Thein, Zin-Maung-Maung-Thein; Nishioka, Yuichiro; Sonoda, Teppei; Takai, Masanaru

    2016-09-05

    We redescribe an extinct river shark, Glyphis pagoda (Noetling), on the basis of 20 teeth newly collected from three different Miocene localities in Myanmar. One locality is a nearshore marine deposit (Obogon Formation) whereas the other two localities represent terrestrial freshwater deposits (Irrawaddy sediments), suggesting that G. pagoda from the Irrawaddy sediments was capable of tolerating low salinity like the extant Glyphis. Glyphis pagoda likely reached up to at least 185 cm in total body length and was probably piscivorous. The fossil species occurs in rocks of Myanmar and eastern and western India and stratigraphically ranges at least from the Lower Miocene (Aquitanian) to the lower Upper Miocene (mid-Tortonian). It has been classified under at least eight other genera to date, along with numerous taxonomic synonyms largely stemming from the lack of understanding of the heterodonty in extant Glyphis in the original description. Our literature review suggests that known Miocene shark faunas, particularly those in India, are manifested with unreliable taxonomic identifications and outdated classifications that warrant the need for a comprehensive taxonomic review in order to evaluate the evolutionary history and diversity pattern of Miocene shark faunas. The genus Glyphis has a roughly 23-million-year-long history, and its success may be related to the evolution of its low salinity tolerance. While extant Glyphis spp. are considered to be particularly vulnerable to habitat degradation and overfishing, the fossil record of G. pagoda provides renewed perspective on the natural history of the genus that can be taken into further consideration for conservation biology of the extant forms.

  16. The Rajang Unconformity: Major provenance change between the Eocene and Miocene sequences in NW Borneo

    Science.gov (United States)

    Breitfeld, H. T.; Hennig, J.; BouDagher-Fadel, M.; Hall, R.

    2017-12-01

    The offshore Sarawak Basin NW of North Sarawak is a major hydrocarbon province in SE Asia. A very thick sedimentary sequence of Oligocene to ?Early Miocene age, named Cycle 1, is an important hydrocarbon source and reservoir. Despite numerous wells the stratigraphy and tectonic history is not very well understood. The Nyalau Formation of onshore North Sarawak is the supposed equivalent of the offshore Cycle 1 sequence. The Nyalau Formation is a thick sedimentary sequence of mainly tidal to deltaic deposits. The formation is dominated by well-bedded sandstone-mudstone alternations and thicker sandstones with abundant bioturbation. The sandstones are predominantly arenaceous. Various lithic fragments and feldspar indicate multiple sources and fresh input from igneous and metamorphic rocks. Interbedded thin limestone beds and marls yielded Early Miocene foraminifera for the upper part of the succession. Zircons separated from the sandstones yielded mainly Cretaceous and Triassic ages. The Triassic is the dominant age population. The Nyalau Formation conformably overlies the Buan Shale and the Tatau Formation, and in places unconformably overlies the Belaga Formation. The Belaga Formation is part of the Rajang Group that represents remnants of a large submarine fan deposited in the Late Cretaceous to Eocene in Central Sarawak. In contrast to the Nyalau Formation, the majority of zircons from the Rajang Group have Cretaceous ages. This marks an important change in provenance at the major unconformity separating the Belaga and Nyalau Formations. This unconformity was previously interpreted as the result of an orogeny in the Late Eocene. However, there is no evidence for a subduction or collision event at this time in Sarawak. We interpret it to mark plate reorganisation in the Middle Eocene and name it the Rajang Unconformity. Borneo is the principal source of Cretaceous zircons which were derived from the Schwaner Mountains and West Sarawak. The dominant Triassic zircon

  17. 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

  18. Inverse modeling of groundwater flow in the semiarid evaporitic closed basin of Los Monegros, Spain

    Science.gov (United States)

    Samper-Calvete, F. J.; García-Vera, M. A.

    Only minor attention has been given in the past to the study of closed-basin hydrogeology in evaporitic environments, because these basins usually contain poor-quality groundwater. The motivation for hydrogeological research in the Los Monegros area in northeastern Spain was the approval in 1986 of a large irrigation project in the Ebre River basin. The irrigation of 60,000 ha is planned, partly in an evaporitic closed basin containing playa lakes. The project has given rise to environmental concerns. The evaluation of the hydrologic impacts of irrigation requires quantifying properly the hydrogeology of the area. With the available information, a conceptual hydrogeological model was formulated that identifies two main aquifers connected through a leaky aquitard. On the basis of the conceptual model, a numerical model was calibrated under steady-state conditions using the method of maximum-likelihood automatic parameter estimation (Carrera and Neuman, 1986a). The calibrated model reproduces the measured hydraulic heads fairly well and is consistent with independent information on groundwater discharge. By the solution of the inverse problem, reliable parameter estimates were obtained. It is concluded that anisotropy plays a major role in some parts of the lower aquifer. The geometric average of model conductivity is almost two orders of magnitude larger than the average conductivity derived from small-scale field tests. This scale effect in hydraulic conductivity is consistent with the findings of Neuman (1994) and Sánchez-Vila et al. (1996). Résumé Dans le passé, on s'est peu intéresséà l'hydrogéologie des bassins fermés en milieu évaporitique, parce que ces bassins possèdent en général de l'eau souterraine de qualité médiocre. L'intérêt porté aux recherches hydrogéologiques dans la région de Los Monegros, dans le nord-est de l'Espagne est dûà l'approbation en 1986 d'un vaste projet d'irrigation dans le bassin de l'Ebre. L'irrigation de 60000

  19. Paleoenvironmental reconstruction of the Oligocene-Miocene deposits of the Tethyan Seaway, Qom Formation, Central Iran

    Science.gov (United States)

    Dabaghi Sadr, Fatemeh; Schmiedl, Gerhard

    2017-04-01

    The Cenozoic climate transition from greenhouse to icehouse conditions was associated with major paleogeographic changes in the Tethyan realm. The closure of the Tethyan Seaway and its Iranian gateways during the terminal Paleogene and early Neogene, between approximately 28 and 18 million years, influenced the latitudinal exchange of water masses and energy and is documented in sediment successions of the Qom formation in central Iran. Little is known on the spatial expression and the exact depositional histories of the Qom Formation on orbital time-scales, including a lack of quantitative sea-level reconstructions and studies on the impact of climatic and tectonic changes on marine ecosystems and sedimentation processes. The PhD project focuses on the investigation of lithostratigraphy, biostratigraphy, paleoecology and paleoenvironmental evolution of the Iranian gateways based on late Oligocene to early Miocene foraminiferal faunas and carbonate facies from selected sediment sections of the Qom Basin. The Qom Formation was deposited in the Central Iranian back-arc basin during the Oligocene-Miocene. In this study foraminiferal faunas and carbonate microfacies were studied based on total 191 samples of two section of Qom Formation. One of them is Molkabad section, which is located northwest of Molkabad mountains, southeast of Garmsar. The section mainly consists of limestones, calcareous marls, marls, and gypsum-bearing marls with a total thickness of 760 meters. The Qom Formation at Molkabad section overlies Eocene rocks with an unconformity and consists of the following lithostratigraphic units (from the lower to upper part): Lithothamnium Limestone, Lower Marl Limestone, Bryozoa Limestone, and Upper Marl Group. The Molkabad fault separates the Qom Formation from the overlying Upper Red Formation. The other section is located at Navab anticline in Qom Formation .The section mainly consist of limestone, marl, and gypsum with a total thickness of 318 meters Navab

  20. Palaeoredox indicators from the organic-rich Messinian early post-evaporitic deposits of the Apennines (Central Italy)

    Science.gov (United States)

    Sampalmieri, G.; Iadanza, A.; Cipollari, P.; Cosentino, D.; Lo Mastro, S.

    2009-04-01

    Bottom redox conditions in marine and lacustrine ancient basins are often inferred by the occurrence of peculiar sedimentological structures and microfaunal assemblages. The co-occurrence, in such environments, of authigenic uranium, framboidal pyrite, barite and Fe-Mn nodules and encrustations, provides a good constraint for palaeo reconstructions. Authigenic uranium is a common constituent of hydrocarbon source rocks: it forms at the sediment-water interface under oxygen-deficient conditions and accumulates together with organic matter (OM). Its precipitation is triggered by the reduction of the soluble U6+ion in seawater to insoluble U4+. With respect to black shales, uranium content has even been used to estimate the TOC. Also authigenic pyrite forms under anoxic conditions and replaces organic matter: 1) the increase in pyrite content and in organic matter are directly correlated; 2) the size distribution of framboidal pyrite (consistent with sulphate-reducing bacterial activity) is considered a measure of redox conditions within the sediment. Barite is an authigenic mineral related to Corg content, since its organic precipitation is triggered by sulphate-reduction processes occurring in decaying OM-bearing microenvironments. Finally, also Fe-Mn oxyhydroxide are typical indicators of redox conditions. About 6 My ago the Mediterranean Sea underwent a giant event of concentration referred to as Messinian Salinity Crisis, which can be roughly subdivided into an evaporitic and a post evaporitic phase. The post evaporitic phase (p-ev; 5.61-5.33 Ma) developed in a context of humid conditions and can be further distinguished into two steps: p-ev1 (early post evaporitic phase) and p-ev2 (late post evaporitic phase). Previous works focused on pev2, which is interpreted to represent the establishment of brackish water conditions (Lago-Mare biofacies). In other respects, the palaeoenvironment of p-ev1 deposits, mostly represented by resedimented evaporitic deposits or

  1. Fish vertebra from Miocene beds at Govce, Slovenia

    Directory of Open Access Journals (Sweden)

    Vasja Mikuž

    2014-07-01

    Full Text Available The article discusses a vertebra and a small shark tooth found in the Miocene Govce sandstone near Govce west of Laško in central Slovenia. The vertebra belongs to a shark of the superorder Galeomorphii but we could not determine it with greater precision. The small tooth was assigned to Carcharias cf. taurus Rafinesque, 1810. The nannofossils in the sample are scarce and did not allow dating at biozone precision.

  2. EARLY MIOCENE INSULAR VERTEBRATES FROM LAERRU (SARDINIA, ITALY): PRELIMINARY NOTE

    OpenAIRE

    DANIEL ZOBOLI; GIAN LUIGI PILLOLA

    2017-01-01

    A new vertebrate assemblage was discovered in an Early  Miocene lacustrine deposit near the village of Laerru (northern Sardinia, Italy). The assemblage is composed by mammals, reptiles and a bird. The mammals are represented by three ruminants (cf. Sardomeryx oschiriensis, Pecora indet. small size and Pecora indet. very small size) and one dormouse (Peridyromys aff. murinus) while reptiles are represented by turtles (Trionychidae?) and crocodiles (cf. Diplocynodon sp.). A bird bone fragment ...

  3. Rb-Sr geochronology of some Miocene West Australian lamproites

    International Nuclear Information System (INIS)

    Allsopp, H.L.; Scott Smith, B.H.; Danchin, R.V.

    1985-01-01

    Rb-Sr ages are presented for four lamproite intrusions (Mount North, Old Leopold Hill, Mount Rose and Seltrust Pipe 2) located in the west Kimberley region of West Australia. The data are in agreement with the early Miocene ages previously obtained for the lamproites of this area. The lamproites are characterized by high initial-Sr ratios, indicative of derivation from an enriched source. Localized and regional mantle heterogeneity is indicated by new and existing data

  4. Speculations about the upper Miocene change in abyssal Pacific dissolved bicarbonate delta13C

    International Nuclear Information System (INIS)

    Bender, M.L.; Keigwin, L.D. Jr

    1979-01-01

    New data from three Tasman Sea cores support Kleigwin's observation that the delta 13 C of Pacific benthic foraminifera (and by inference bottom-water TCO 2 ) decreased by 0.7 per thousand at about 6.5 Myr B.P. Simple box models are developed and used to test several hypotheses about the cause of the delta 13 C decrease. The authors favor the idea that the delta 13 C shift was due to a rapid change in TCO 2 cycling within the oceans (such as would result from either a decrease in upwelling rate, or an increase in the fraction of PO 4 3- reaching the deep oceans in particulate organic matter and a corresponding drop in the performed PO 4 3- concentration). The delta 13 C decrease across the shift might reflect either a global decrease in upwelling rate, or a different abyssal circulation pattern before the shift. (Auth.)

  5. The Upper Miocene rodents from the Pezinok in the Danube Basin, Slovakia

    OpenAIRE

    Peter Joniak

    2016-01-01

    Rodent assemblages are described from two sampled sites at the Pezinok clay pit in the Danube Basin. Although these assemblages contain material poor in specimens, the following eleven rodent taxa are distinguished and described: Progonomys hispanicus, Kowalskia sp., Microtocricetus molassicus, Anomalomys gaillardi, Graphiurops austriacus, Paraglirulus sp., Eomyops catalaunicus, Keramidomys sp., Spermophilinus sp., Albanensia sp. and Euroxenomys minutum. The co-occurrence of very primitive Pr...

  6. Updated chronology for the Miocene hominoid radiation in Western Eurasia

    Science.gov (United States)

    Casanovas-Vilar, Isaac; Alba, David M.; Garcés, Miguel; Robles, Josep M.; Moyà-Solà, Salvador

    2011-01-01

    Extant apes (Primates: Hominoidea) are the relics of a group that was much more diverse in the past. They originated in Africa around the Oligocene/Miocene boundary, but by the beginning of the Middle Miocene they expanded their range into Eurasia, where they experienced a far-reaching evolutionary radiation. A Eurasian origin of the great ape and human clade (Hominidae) has been favored by several authors, but the assessment of this hypothesis has been hampered by the lack of accurate datings for many Western Eurasian hominoids. Here we provide an updated chronology that incorporates recently discovered Iberian taxa and further reevaluates the age of many previously known sites on the basis of local biostratigraphic scales and magnetostratigraphic data. Our results show that identifiable Eurasian kenyapithecins (Griphopithecus and Kenyapithecus) are much younger than previously thought (ca. 14 Ma instead of 16 Ma), which casts serious doubts on the attribution of the hominoid tooth from Engelswies (16.3–16.5 Ma) to cf. Griphopithecus. This evidence is further consistent with an alternative scenario, according to which the Eurasian pongines and African hominines might have independently evolved in their respective continents from similar kenyapithecin ancestors, resulting from an early Middle Miocene intercontinental range extension followed by vicariance. This hypothesis, which would imply an independent origin of orthogrady in pongines and hominines, deserves further testing by accurately inferring the phylogenetic position of European dryopithecins, which might be stem pongines rather than stem hominines. PMID:21436034

  7. Interaction of Extreme Halophilic Archaea With the Evaporites of the Solar Salterns Guerrero Negro Baja California, Mexico

    Science.gov (United States)

    Tamez, P.; Lopez-Cortés, A.

    2008-12-01

    Hypersaline environments have been significant reservoirs for the long-term evolution of specifically adapted microorganisms. Characterized to have higher salt concentrations (up to 35 g/L), they are worldwide distributed and have a commercial significance. Exportadora de Sal, Guerrero Negro, Mexico has a multipond salterns system designed to harvest common salt (NaCl) from sea water. To achieve this purpose, sea water is pumped through a set of shallow ponds where water evaporates and salts concentrate. Sequential precipitation of CaCO3, CaSO4 2H2O and NaCl occurs in a mineral formations call it evaporites. In the interior of those gypsum-encrusted and halite-encrusted minerals, communities of extremely salt-loving archaea prosper. Previous studies have showed the influence of Haloarchaeal cells in the formation of larger fluid inclusions than crystals formed in sterile salt solutions. S-layer envelopes and cells of Haloarcula strain SP8807 contributed to the nucleation of new crystals of NaCl. Given the significance of the scope in phylogenetic archaeal diversity research, this study had a polyphasic approach. SEM micrographs from a 21- 31% (w/v) gradient salt multipond system evaporites, gave an insight profile of the extreme halophilic archaeal communities thriving in the surface of the gypsum and halite evaporites. Halite crystals were form after 21 days of incubation in solid medium with archaeal cells. Both culture and non-culture dependent methods, Nested-PCR-DGGE analysis and sequencing of 16S rDNA amplified fragment genes from environmental samples and isolated strains were used for this purpose. We isolate three strains from Pond 9 (21.07% total salt concentration) and one strain from Cristallizer 20 (25.15% total salt concentration). 16S rDNA signaling gave 99% of similarity with Halogeometricum borinquense, sequence AF002984, two other strains were 99% of similarity with Halobacterium salinarum, sequence AJ496185 these strains shown different colony

  8. Miocene tectonic history of the Central Tauride intramontane basins, and the paleogeographic evolution of the Central Anatolian Plateau

    Science.gov (United States)

    Koç, Ayten; Kaymakci, Nuretdin; Van Hinsbergen, Douwe J. J.; Kuiper, Klaudia F.

    2017-11-01

    Marine Lower-Upper Miocene deposits uplifted to > 2 km elevation in the Tauride mountains of southern Turkey are taken as evidence for the rise of a nascent plateau. The dynamic causes of this uplift are debated, but generally thought to be a regional dynamic topographic effect of slab motions or slab break-off. Immediately adjacent to the high Tauride mountains lie the Central Tauride Intramontane Basins, which consist of Miocene and younger fluvio-lacustrine basins, at much lower elevations than the highly uplifted marine Miocene rocks. These basins include the previously analyzed Altınapa and Yalvaç basins, as well as the until now undescribed Ilgın Basin. In this paper, we aim to constrain the paleogeography of the Central Tauride Intramontane Basins and determine the role of the tectonics driving the formation of the high Miocene topography in southern Turkey. Therefore, we provide new data on the stratigraphy, sedimentology and structure of the continental Ilgın Basin. We provide an 40Ar/39Ar age of 11.61 ± 0.05 Ma for pumice deposits in the stratigraphy. We provide paleostress inversion analysis based on growth faults showing that the basin formed during multi-directional extension, with NE-SW to E-W dominating over subordinate Nsbnd S extension. We conclude that major, still-active normal faults like the Akşehir Fault also controlled Miocene Ilgın basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocenter. The Ilgın Basin was a local depocenter, but it may have connected with the adjacent Altınapa Basin during high lake levels in late Serravallian time. The Ilgın Basin and the other continental basins provide key constraints on the paleogeography and tectonic history of the region. These continental basins were likely close to the paleo-coastline during the Late Miocene after which there must have been major differential uplift of the Taurides. We

  9. Considerations on the parent material in the soil developed on the evaporite deposits from Stana (Cluj district

    Directory of Open Access Journals (Sweden)

    Horea Bedelean

    2003-09-01

    Full Text Available This research concerned three profiles developed on Eocene (Priabonian gypsum parent material from Stana (Cluj district in order to investigate their properties. The soil and parent material samples were collected from individual horizons in each profile. Both the mineralogical and structural-textural features of the parent material (evaporitic deposits reflect the depositional context. From a mineralogical point of view, the deposits are represented by gypsum, and anhydrite. Typical sulfate facies are present: laminitic, nodular, gypscretic, and entherolitic. Physical and mineralogical properties of the soil layers were determined in the laboratory. The field observations and the results of the analyses allowed us to classify the soil as a rendzinic regosol, according to the Romanian System of Soil Taxonomy (S.R.T.S. 2000.

  10. Boron isotope evidence for the involvement of non-marine evaporites in the origin of the Broken Hill ore deposits

    Science.gov (United States)

    Slack, J.F.; Palmer, M.R.; Stevens, B.P.J.

    1989-01-01

    IDENTIFYING the palaeogeographic setting and mode of origin of stratabound ore deposits can be difficult in high-grade metamorphic terranes, where the effects of metamorphism may obscure the nature of the protoliths. Here we report boron isotope data for tourmalines from the early Proterozoic Broken Hill block, in Australia, which hosts giant lead-zinc-silver sulphide deposits. With one exception the 11B/10B ratios are lower than those for all other tourmalines from massive sulphide deposits and tour-malinites elsewhere in the world. We propose that these low ratios reflect leaching of boron from non-marine evaporitic borates by convecting hydrothermal fluids associated with early Proterozoic continental rifting. A possible modern analogue is the Salton Sea geothermal field in California. ?? 1989 Nature Publishing Group.

  11. Microbial diversity in sediment ecosystems (evaporites domes, microbial mats and crusts of hypersaline Laguna Tebenquiche, Salar de Atacama, Chile

    Directory of Open Access Journals (Sweden)

    Ana Beatriz Fernandez

    2016-08-01

    Full Text Available We combined nucleic acid-based molecular methods, biogeochemical measurements and physicochemical characteristics to investigate microbial sedimentary ecosystems of Laguna Tebenquiche, Atacama Desert, Chile. Molecular diversity and biogeochemistry of hypersaline microbial mats, rhizome-associated concretions and an endoevaporite were compared with: The V4 hypervariable region of the 16S rRNA gene was amplified by pyrosequencing to analyze the total microbial diversity (i.e., bacteria and archaea in bulk samples and, in addition, in detail on a millimeter scale in one microbial mat and in one evaporite. Archaea were more abundant than bacteria. Euryarchaeota was one of the most abundant phyla in all samples, and particularly dominant (97% of total diversity in the most lithified ecosystem, the evaporite. Most of the euryarchaeal OTUs could be assigned to the class Halobacteria or anaerobic and methanogenic archaea. Planctomycetes potentially also play a key role in mats and rhizome-associated concretions, notably the aerobic organoheterotroph members of the class Phycisphaerae. In addition to cyanobacteria, members of Chromatiales and possibly the candidate family Chlorotrichaceae contributed to photosynthetic carbon fixation. Other abundant uncultured taxa such as the candidate division MSBL1, the uncultured MBGB and the phylum Acetothermia potentially play an important metabolic role in these ecosystems. Lithifying microbial mats contained calcium carbonate precipitates, whereas endoevoporites consisted of gypsum and halite. Biogeochemical measurements revealed that based on depth profiles of O2 and sulfide, metabolic activities were much higher in the non-lithifying mat (peaking in the least lithified systems than in lithifying mats with the lowest activity in endoevaporites. This trend in decreasing microbial activity reflects the increase in salinity, which may play an important role in the biodiversity.

  12. A new species of Nyanzachoerus (Cetartiodactyla: Suidae from the late Miocene Toros-Ménalla, Chad, central Africa.

    Directory of Open Access Journals (Sweden)

    Jean-Renaud Boisserie

    Full Text Available During the latest Miocene and the early Pliocene, tetraconodontine suids were the most predominant large omnivorous mammals in Africa. Yet, new species were often identified on the grounds of limited evidence, a situation impacting their value for biochronological correlations as well as for environmental and biogeographical reconstructions. The description of the most abundant known collection of craniodental remains attributed to the tetraconodontine Nyanzachoerus helps to improve this situation. These specimens were collected in the upper Miocene deposits at Toros-Ménalla, northern Chad, central Africa, by the Mission Paléoanthropologique Franco-Tchadienne. We compared them with Nyanzachoerus from eastern and southern Africa, using extant species as a reference for patterns of morphological variation. Thanks to a large sample of observations, our work focused as much on craniomandibular morphology as on dental morphology and metrics (improved by an index scoring for the complexity of distal third molars and a detailed investigation of premolar-molar ratios. We recognized two taxa at Toros-Ménalla: Nyanzachoerus khinzir nov. sp. and Ny. cf. australis. We also revised the taxonomic status for other species, including: the restriction of Ny. syrticus to its holotype specimen from Sahabi (Libya, the resurrection of the nomen Ny. tulotos, and the synonymy of Ny. kuseralensis with Ny. waylandi. At Toros-Ménalla, Ny. khinzir was the only suid coexisting with the anthracotheriid Libycosaurus and the hominid Sahelanthropus, whereas Ny. cf. australis was associated with a different, probably younger faunal context. Nyanzachoerus. khinzir, which probably had a diversified diet, supports a latest Miocene biogeographical distinction between central Africa and eastern Africa.

  13. Miocene vegetation shift and climate change: Evidence from the Siwalik of Nepal

    Science.gov (United States)

    Srivastava, Gaurav; Paudayal, Khum N.; Utescher, Torsten; Mehrotra, R. C.

    2018-02-01

    We reconstruct climate and vegetation applying the Coexistence Approach (CA) methodology on two palaeofloras recovered from the Lower (middle Miocene; 13-11 Ma) and Middle Siwalik (late Miocene; 9.5-6.8 Ma) sediments of Surai Khola section, Nepal. The reconstructed mean annual temperature (MAT) and cold month mean temperature (CMT) show an increasing trend, while warm month mean temperature (WMT) remains nearly the same during the period. The reconstructed precipitation data indicates that the summer monsoon precipitation was nearly the same during the middle and late Miocene, while the winter season precipitation significantly decreased in the late Miocene. The overall precipitation infers increased rainfall seasonality during the late Miocene. The vegetation during the middle Miocene was dominated by wet evergreen taxa, whereas deciduous ones increased significantly during the late Miocene. The reconstructed climate data indicates that high temperature and significantly low precipitation during the winter season (dry season) in the late Miocene might have enhanced forest fire which favoured the expansion of C4 plants over C3 plants during the period. This idea gets further support not only from a recent forest fire in northern India that was caused by the weakening of winter precipitation, but also from the burnt wood recovered from the late Miocene Siwalik sediments of northern India.

  14. Geology, geochemistry and {sup 40}K-{sup 40}Ar geochronometry of Miocene magmatism in Algiers area, Northern Algeria; La magmatisme miocene de l`Est Algerois, geologie, geochimie et geochronologie {sup 40}K-{sup 40}Ar

    Energy Technology Data Exchange (ETDEWEB)

    Belanteur, O; Ouabadi, A; Semroud, B; Megartsi, M H [Algiers Univ. (Algeria). Faculte des Sciences; Bellon, H; Maury, R C; Coutelle, A [Brest Univ., 29 (France); Fourcade, S [Rennes-1 Univ., 35 (France)

    1996-12-31

    Miocene magmatic rocks outcrop within a narrow coastal strip east of Algiers. They include basaltic and andesitic lava flows and intrusions (Dellys, Cap Djinet), the Thenia granodioritic plug and the dacitic to rhyolitic lavas and pyroclastic flows from Zemmouri El Bahri and El Kerma. Despite the effects of hydrothermal alteration, {sup 40}K-{sup 40}Ar ages coupled with micropalaeontological data lead to recognition of two emplacement events at 16-15 and 14-12 Ma, respectively. All the studied calc-alkaline to potassic calc-alkaline rocks are enriched in highly incompatible elements and display negative Nb anomalies. Acid magmas have a pronounced crustal imprint ({sup 87}Sr{sup 86}Sr{sub i} =3D 0.7082 to 0.7155; {delta}{sup 18}O =3D +9 to +13 per mill) which together with La/Nb ratios argues for the occurrence of upper crustal contamination processes. However, the Nb-depletion of the associated basalts suggest that the studied magmas derive from a mantle source which underwent subduction-related metasomatic enrichments prior to their Miocene emplacement. (authors). 13 refs., 3 figs., 2 tabs.

  15. Miocene to recent tectonic and sedimentary evolution of the Anaximander Seamounts; eastern Mediterranean Sea

    Science.gov (United States)

    Cranshaw, Jennifer

    This thesis is focused on the Messinian to Recent tectonic and sedimentary evolution of the Anaximander Mountains and surrounding environs in the eastern Mediterranean Sea. It is based on processing of high-resolution seismic reflection data and the interpretation and mapping of seismic reflection profiles collected from this area during the 2001 and 2007 research cruises. The data show that the greater Anaximander Mountains region experienced a short interval of tectonic quiescence during the Messinian when a thin evaporite unit was deposited across a major erosional surface. This phase of limited tectonic activity ended in the latest Miocene and was replaced by an erosional phase. Major unconformities in the area are interpreted to develop during the desiccation of the eastern Mediterranean associated with the so-called Messinian salinity crisis. During the early Pliocene, the region experienced an increase in tectonic activity, dominated by transpression. Small amounts of growth observed in Pliocene-Quaternary sediments suggested that the tectonic activity remained low during the early Pliocene-Quaternary. However, the extensive growth strata wedges developed in older sediments indicate a period of accelerated tectonic activity during the mid-late Pliocene-Quaternary. This study suggests that the Anaximander Mountain (sensu stricto ) and the Anaximenes Mountain developed during the Pliocene-Quaternary as the result of a crustal-scale thick-skinned linked imbricate thrust fan. The development of back thrusts in both mountains heightened the seafloor morphology of these submarine mountains and brought Eocene-Oligocene sediments into the core of these mountains. The Sim Erinc Plateau represents a 30-40 km wide transpressional fault zone developed during the Pliocene-Quaternary. In this region the corrugated seafloor morphology observed in the multibeam bathymetry map is the reflection of high-angle faults. It is speculated that this transpressional fault zone

  16. High resolution biostratigraphy of Oligo-Miocene Leon and Chama Formations: An integrated approach for sequence stratigraphy analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pittelli, R.; Rull, V. (Maraven S.A., Caracas (Venezuela))

    1993-02-01

    Based on foraminiferal and palynological high resolution studies, a set of Sequence Boundaries (SB) and Maximum Flooding Surfaces (MSF) were identified for the Venezuelan Northwestern Andean Foothills Leon and Chama formations. Changes in abundance patterns of forminifera palynomorphs, in faunal/floral composition and distribution, together with quantitative studies of particulate organic matter allowed picking SB 30, 21 and 15.5 (very low values of fossil abundance and faunal discontinuities, recognized by a rapid stratigraphic change in biofacies and faunal assemblage and the associated mineralogical contents) and MFS 18.5, 16, and 15 (abundant fossils). The Leon Formation represents coastal plain and swamp deposits with some minor fluctuations in the seawater level. The top of the Leon Formation shaly unit is bounded by SB 30, according to Hag B.U. et al (version 1992), marked by a decrease in fossil abundance. An increase in faunal/floral content close to the top of the section coincides with the MFS 18.5. The upper part of the formation is marked by a sandy unit with SB 16.5, characterized again by a decrease in fossil abundance at its top. The Chama Formation was deposited in a transitional environment, with minor seawater level fluctuations. Climate type was tropical humid, with seasonal precipitations, except at the Early Miocene arid or semiarid phase. Mangrove and rain forest vegetation dominated throughout the Early to Middle Miocene. MFS 16 was picked on the basis of a high abundance of microforams and glauconite.

  17. Middle Miocene carnivorans from the Monarch Mill Formation, Nevada

    Directory of Open Access Journals (Sweden)

    Kent Smith

    2016-02-01

    Full Text Available he lowest part of the Monarch Mill Formation in the Middlegate basin, west-central Nevada, has yielded a middle Miocene (Barstovian Land Mammal Age vertebrate assemblage, the Eastgate local fauna. Paleobotanical evidence from nearby, nearly contemporaneous fossil leaf assemblages indicates that the Middle Miocene vegetation in the area was mixed coniferous and hardwood forest and chaparral-sclerophyllous shrubland, and suggests that the area had been uplifted to 2700–2800 m paleoaltitude before dropping later to near its present elevation of 1600 m. Thus, the local fauna provides a rare glimpse at a medium- to high-altitude vertebrate community in the intermountain western interior of North America. The local fauna includes the remains of fish, amphibians, reptiles, birds, and 25 families of mammals. Carnivorans, the focus of this study, include six taxa (three of which are new belonging to four families. Canidae are represented by the borophagine Tomarctus brevirostris and the canine Leptocyon sp. indet. The earliest record and second North American occurrence of the simocyonine ailurid Actiocyon is represented by A. parverratis sp. nov. Two new mustelids, Brevimalictis chikasha gen. et sp. nov. and Negodiaetictis rugatrulleum gen. et sp. nov., may represent Galictinae but are of uncertain subfamilial and tribal affinity. The fourth family is represented by the felid Pseudaelurus sp. indet. Tomarctus brevirostris is limited biochronologically to the Barstovian land mammal age and thus is consistent with the age indicated by other members of the Eastgate local fauna as well as by indirect tephrochronological dates previously associated with the Monarch Mill Formation. Actiocyon parverratis sp. nov. extends the temporal range of the genus Actiocyon from late Clarendonian back to the Barstovian. The Eastgate local fauna improves our understanding of mammalian successions and evolution, during and subsequent to the Mid-Miocene Climatic Optimum

  18. Natural product terpenoids in Eocene and Miocene conifer fossils.

    Science.gov (United States)

    Otto, Angelika; White, James D; Simoneit, Bernd R T

    2002-08-30

    Numerous saturated and aromatic hydrocarbons, but not polar compounds, originating from plants and microorganisms (biomarkers) have been reported in sediments, coals, and petroleum. Here we describe natural product terpenoids found in two fossil conifers, Taxodium balticum (Eocene) and Glyptostrobus oregonensis (Miocene). A similar terpenoid pattern is also observed in extant Taxodium distichum. The preservation of characteristic terpenoids (unaltered natural products) in the fossil conifers supports their systematic assignment to the Cypress family (Cupressaceae sensu lato). The results also show that fossil conifers can contain polar terpenoids, which are valuable markers for (paleo)chemosystematics and phylogeny.

  19. Miocene shale tectonics in the Moroccan margin (Alboran Sea)

    Science.gov (United States)

    Do Couto, D.; El Abbassi, M.; Ammar, A.; Gorini, C.; Estrada, F.; Letouzey, J.; Smit, J.; Jolivet, L.; Jabour, H.

    2011-12-01

    The Betic (Southern Spain) and Rif (Morocco) mountains form an arcuate belt that represents the westernmost termination of the peri-mediterranean Alpine mountain chain. The Miocene Alboran Basin and its subbasins is located in the hinterland of the Betic-Rif belt. It is considered to be a back-arc basin that developed during the coeval westward motion of the Alboran domain and the extensional collapse of previously thickened crust of the Betic-Rif belt. The Western Alboran Basin (WAB) is the major sedimentary depocenter with a sediment thickness in excess of 10 km, it is bordered by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge. Part of the WAB is affected by shale tectonics and associated mud volcanism. High-quality 2D seismic profiles acquired on the Moroccan margin of the Alboran Basin during the last decade reveal the multiple history of the basin. This study deals with the analysis of a number of these seismic profiles that are located along and orthogonal to the Moroccan margin. Seismic stratigraphy is calibrated from industrial wells. We focus on the interactions between the gravity-driven tectonic processes and the sedimentation in the basin. Our seismic interpretation confirms that the formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). The fast subsidence of the basin floor coeval to massive sedimentation induced the undercompaction of early miocene shales during their deposition. Downslope migration of these fine-grained sediments initiated during the deposition of the Langhian siliciclastics. This gravity-driven system was accompanied by continuous basement subsidence and induced disharmonic deformation in Mid Miocene units (i.e. not related to basement deformation). The development of shale-cored anticlines and thrusts in the deep basin is the result of compressive deformation at the front of the gravity-driven system and lasted for ca. 15 Ma. The compressive front has been re-activated by strong

  20. Shark-bitten vertebrate coprolites from the Miocene of Maryland

    Science.gov (United States)

    Godfrey, Stephen J.; Smith, Joshua B.

    2010-05-01

    Coprolites (fossilized feces) preserve a wide range of biogenic components, from bacteria and spores to a variety of vertebrate tissues. Two coprolites from the Calvert Cliffs outcrop belt (Miocene-aged Chesapeake Group), MD, USA, preserve shark tooth impressions in the form of partial dental arcades. The specimens are the first known coprolites to preserve vertebrate tooth marks. They provide another example of trace fossils providing evidence of prehistoric animal behaviors that cannot be directly approached through the study of body fossils. Shark behaviors that could account for these impressions include: (1) aborted coprophagy, (2) benthic or nektonic exploration, or (3) predation.

  1. An Early Miocene bumble bee from northern Bohemia (Hymenoptera, Apidae

    Directory of Open Access Journals (Sweden)

    Jakub Prokop

    2017-10-01

    Full Text Available A new species of fossil bumble bee (Apinae: Bombini is described and figured from Early Miocene (Burdigalian deposits of the Most Basin at the Bílina Mine, Czech Republic. Bombus trophonius sp. n., is placed within the subgenus Cullumanobombus Vogt and distinguished from the several species groups therein. The species is apparently most similar to the Nearctic B. (Cullumanobombus rufocinctus Cresson, the earliest-diverging species within the clade and the two may be related only by symplesiomorphies. The age of the fossil is in rough accordance with divergence estimations for Cullumanobombus.

  2. Mg- and K-bearing borates and associated evaporites at Eagle Borax spring, Death Valley, California: A spectroscopic exploration

    Science.gov (United States)

    Crowley, J.K.

    1996-01-01

    Efflorescent crusts at the Eagle Borax spring in Death Valley, California, contain an array of rare Mg and K borate minerals, several of which are only known from one or two other localities. The Mg- and/or K-bearing borates include aristarainite, hydroboracite, kaliborite, mcallisterite, pinnoite, rivadavite, and santite. Ulexite and probertite also occur in the area, although their distribution is different from that of the Mg and K borates. Other evaporite minerals in the spring vicinity include halite, thenardite, eugsterite, gypsum-anhydrite, hexahydrite, and bloedite. Whereas the first five of these minerals are found throughout Death Valley, the last two Mg sulfates are more restricted in occurrence and are indicative of Mg-enriched ground water. Mineral associations observed at the Eagle Borax spring, and at many other borate deposits worldwide, can be explained by the chemical fractionation of borate-precipitating waters during the course of evaporative concentration. The Mg sulfate and Mg borate minerals in the Eagle Borax efflorescent crusts point to the fractionation of Ca by the operation of a chemical divide involving Ca carbonate and Na-Ca borate precipitation in the subsurface sediments. At many other borate mining localities, the occurrence of ulexite in both Na borate (borax-kernite) and Ca borate (ulexite-colemanite) deposits similarly reflects ulexite's coprecipitation with Ca carbonate at an early concentration stage. Such ulexite may perhaps be converted to colemanite by later reaction with the coexisting Ca carbonate - the latter providing the additional Ca2+ ions needed for the conversion. Mg and Ca-Mg borates are the expected late-stage concentration products of waters forming ulexite-colemanite deposits and are therefore most likely to occur in the marginal zones or nearby mud facies of ulexite-colemanite orebodies. Under some circumstances, Mg and Ca-Mg borates might provide a useful prospecting guide for ulexite-colemanite deposits

  3. Paleoclimatic and paleoenvironmental records of the Oligocene-Miocene transition, central Jylland, Denmark

    NARCIS (Netherlands)

    Sliwinska, K.K.; Dybkjær, K.; Schoon, P.L.; Beyer, C.; King, C.; Schouten, S.; Nielsen, O.B.

    2014-01-01

    A multidisciplinary study of the Oligocene/Miocene (O/M) transition was carried in two boreholes (Harre-1 and Horn-1) from the Danish land area in order to improve the understanding of the paleodimatological and environmental changes across the Mi-1, the earliest Miocene cooling event.

  4. Miocene fish faunas from the northwestern Amazonia basin (Colombia, Peru, Brazil) with evidence of marine incursions

    NARCIS (Netherlands)

    Monsch, KA

    1998-01-01

    New evidence indicates marine influences during the Miocene in the northwestern Amazonia basin. This is the first major survey of the ichthyofauna from this area in the Miocene. Fossil fish remains from taxa such as the Dasyatoidea, Myliobatoidea, Characiformes, Siluriformes and Sciaenidae are

  5. Acoustic Impedance Inversion To Identify Oligo-Miocene Carbonate Facies As Reservoir At Kangean Offshore Area

    Science.gov (United States)

    Zuli Purnama, Arif; Ariyani Machmud, Pritta; Eka Nurcahya, Budi; Yusro, Miftahul; Gunawan, Agung; Rahmadi, Dicky

    2018-03-01

    Model based inversion was applied to inversion process of 2D seismic data in Kangean Offshore Area. Integration acoustic impedance from wells and seismic data was expected showing physical property, facies separation and reservoir quality of carbonate rock, particularly in Kangean Offshore Area. Quantitative and qualitative analysis has been conducted on the inversion results to characterize the carbonate reservoir part of Kujung and correlate it to depositional facies type. Main target exploration in Kangean Offshore Area is Kujung Formation (Oligo-Miocene Carbonate). The type of reservoir in this area generate from reef growing on the platform. Carbonate rock is a reservoir which has various type and scale of porosity. Facies determination is required to to predict reservoir quality, because each facies has its own porosity value. Acoustic impedance is used to identify and characterize Kujung carbonate facies, also could be used to predict the distribution of porosity. Low acoustic impedance correlated with packstone facies that has acoustic impedance value below 7400 gr/cc*m/s. In other situation, high acoustic impedance characterized by wackestone facies above 7400 gr/cc*m/s. The interpretation result indicated that Kujung carbonate rock dominated by packstone facies in the upper part of build-up and it has ideal porosity for hydrocarbon reservoir.

  6. Sedimentologic development of a Late Oligocene Miocene forearc embayment, Valdivia Basin Complex, southern Chile

    Science.gov (United States)

    le Roux, J. P.; Elgueta, Sara

    2000-01-01

    Deposition of Tertiary sediments in the southeastern part of the Valdivia Basin commenced during the Late Oligocene with the rapid incision of rivers draining the Palaeo-Coastal Range. Alluvial fans developing along the steep valley flanks joined gravelly braided streams transporting bedload to the coast. Tectonic and eustatic stability lasting into the Early Miocene subsequently allowed lateral erosion of the valley flanks and the development of extensive fluvial and estuarine peat swamps. This stable period was interrupted briefly by a volcanic eruption at 23.5 Ma. Shortly after 23 Ma, rapid uplift caused by an acceleration in plate convergence resulted in renewed erosion of the landscape, as reflected in the deposition of coarse river gravels. Basin subsidence and marine transgression proceeding up the river valleys subsequently formed still, deep embayments, occasionally disturbed by debris flows and turbidity currents originating on the steep, wooded valley flanks. At the upper limits of the inlets, bayhead deltas, tidal flats and beaches existed. In some areas, fan deltas prograded into the embayments, as reflected in the interfingering relationship between conglomerates and marine mudrocks. In the deeper parts of the embayments, the frequency of debris flows and turbidity currents increased markedly during periods of relative sea-level lowstand. The landscape was eventually inundated by continued subsidence and marine transgression, which lasted until a possibly eustatic sea-level fall in the early Tortonian.

  7. Tropical sea surface temperature variability near the Oligocene - Miocene boundary

    Science.gov (United States)

    Zhang, Y.; Pagani, M.

    2010-12-01

    The Oligocene/Miocene (O-M) boundary is characterized by a period of rapid and intense glaciation labeled Mi-1 at ~ 23.1 Ma. An abrupt 1.5‰ increase in the benthic foraminifera oxygen isotope composition that characterizes Mi-1 may indicate a (1) significant deep-water temperature decrease; (2) major ice-sheet expansion, or the combination of both. Current coarse Mg/Ca-based temperature estimations for the early Miocene suggests that deep-ocean temperatures were ~2°C warmer than Today [1, 2]. However, Mg/Ca based temperatures can also be influenced by changes in the carbonate ion concentration, vital effects, and diagenesis. In particular, recent evidence from mid-ocean ridge flank carbonate veins shows dramatic seawater Mg/Ca ratio changes during the Neogene (Mg/Ca from ~2.2 to 5.3, [3]), which further challenges the application of Mg/Ca thermometry. Owing to poor temperature constraints, current ice volume estimations for the late Oligocene/early Miocene range from 125% of the present-day East Antarctic Ice Sheet (EAIS) to a nearly complete collapse of the Antarctic glaciers [4]. Here we present tropical sea surface temperatures (SSTs) records based on TEX86 and alkenone UK37 near the O-M boundary. Sediment samples from Ocean Drilling Program (ODP) Site 926 in the Ceara Rise (tropical Atlantic) and Site 1148 in the South China Sea (tropical Pacific) were subject to lipid extraction, separation, gas chromatography, and liquid chromatography-mass spectrometry analysis. TEX86-based SST indicates that the tropics were ~3-4°C warmer than today and relatively stable during Mi-1. This suggests that ice-sheet dynamics, rather than temperature, might be responsible for the observed oxygen isotope changes during the O-M boundary. Further, O-M boundary averaged temperatures recorded at site 926 is ~ 0.5°C higher relative to the late Eocene from site 925 (a nearby site [5]). Given late Oligocene benthic δ18O that suggests at least 1‰ enrichment relative to the late

  8. Ostracods biostratigraphy of the Oligocene-Miocene carbonate platform in the Northeastern Amazonia coast and its correlation with the Caribbean region

    Science.gov (United States)

    Nogueira, Anna Andressa Evangelista; Nogueira, Afonso César Rodrigues

    2017-12-01

    Oligocene-Miocene ostracods biozones are proposed for the ∼65 m-thick platform carbonate succession exposed in the Northeastern Amazonia coast, Brazil. Previous biostratigraphic studies based on planktonic foraminifera, nannofossils and palynomorphs are poorly age constrained and have hindered the correlation with other units of the Atlantic Equatorial margin. Tectonic stability of the Northeastern Amazonia coast during Neogene, associated with reduced riverine inflow and continuous sea level rise, allowed the establishment of lagoon/mangroves, tidal channel and shallow platform settings favoring massive proliferation of benthic ostracods. The recurrence of these depositional systems along of entire Oligocene-Miocene succession contributed mainly for the preservation of typical assemblages of lagoonal ostracods. Among thirty-two ostracods genera identified, the most of them are generally polyhalines associated with a mesohaline genus as Perissocytheridea. Rare ostracods genera typical of offshore zone indicate limited oceanic connection with lagoon. Additionally, the rare presence of Cyprideis indicates a relatively stable salinity degree suggesting change in the lagoon dynamic until estuarine conditions. The ostracods comprise more than 100 species, ranging from Upper Oligocene to Lower Miocene with five index species correspondent to a single zone called the Cytherella stainforthi Zone that was subdivided in four sub-biozones: 1) Jugosocythereis pannosa, 2) Quadracythere brachypygaia, 3) Triebelina crumena and 4) Neocaudites macertus. This new zonation was calibrated with the Blow's and Wade's planktonic foraminifers zones (N.3 to N.7 zones corresponding to O6 to M4b of Wade) and with van den Bold's zonation in the Neogene Caribbean region. Ostracod assemblages described here provide an excellent biostragraphic framework for local, intrabasinal and regional correlation for the Oligocene-Miocene deposits of the Northeastern Amazonia coast and Caribbean regions

  9. Pre-Miocene birth of the Yangtze River

    Science.gov (United States)

    Zheng, Hongbo; Clift, Peter D.; Wang, Ping; Tada, Ryuji; Jia, Juntao; He, Mengying; Jourdan, Fred

    2013-01-01

    The development of fluvial systems in East Asia is closely linked to the evolving topography following India–Eurasia collision. Despite this, the age of the Yangtze River system has been strongly debated, with estimates ranging from 40 to 45 Ma, to a more recent initiation around 2 Ma. Here, we present 40Ar/39Ar ages from basalts interbedded with fluvial sediments from the lower reaches of the Yangtze together with detrital zircon U–Pb ages from sand grains within these sediments. We show that a river containing sediments indistinguishable from the modern river was established before ∼23 Ma. We argue that the connection through the Three Gorges must postdate 36.5 Ma because of evaporite and lacustrine sedimentation in the Jianghan Basin before that time. We propose that the present Yangtze River system formed in response to regional extension throughout eastern China, synchronous with the start of strike–slip tectonism and surface uplift in eastern Tibet and fed by strengthened rains caused by the newly intensified summer monsoon. PMID:23610418

  10. Combined tide and storm influence on facies sedimentation of miocene Miri Formation, Sarawak

    International Nuclear Information System (INIS)

    Yuniarta Ulfa; Nasiman Sapari; Zuhar Zahir Tuan Harith

    2011-01-01

    This study was conducted on the sedimentary rocks belonging to the Miri Formation (Middle - Late Miocene). The primary objective of the present study is to provide additional interpretation on the stratigraphy of the Miri Formation in the Miri Field based on the new information gathered from new outcrops in the area. Five outcrops were examined in detail on sedimentology and stratigraphy. Based on lithology, sedimentary structures, bedding geometry and traces fossil, the sediments of the Miri Formation were grouped into fourteen lithofacies. Influence of tide and storm during the depositional processes of the formation were indicated by the group of two main facies associations which are: (i) tide-dominated estuary; and (ii) wave-and-storm dominated facies associations. The tide-dominated estuary system of the Miri Formation are includes variety of sub environments: estuary mouth or tidal channel and sand bars (characterized by trough cross-stratified sandstone with mud drapes facies), estuary channel or upper flow regime of sand flat (characterized by parallel stratified sandstone with mud-laminas facies), mixed-tidal flat (characterized by wavy and flaser bedded sandstone facies), and mud-tidal flat (characterized by rhythmic stratified sandstone-mudstone and lenticular bedding facies). The wave-and-storm dominated varied from lower to middle shore face (characterized by hummocky cross-stratified sandstone and rhythmic parallel stratified sandstone and laminated siltstone facies), upper shore face (characterized by swaley cross-stratified sandstone), lower shore face inter bedded to bioturbated sandstone and siltstone facies), and offshore transitional (characterized by bioturbated sandstone and mudstone inter bedding with parallel to hummocky cross-stratified sandstone facies). (author)

  11. Low temperature geothermal systems in carbonate-evaporitic rocks: Mineral equilibria assumptions and geothermometrical calculations. Insights from the Arnedillo thermal waters (Spain).

    Science.gov (United States)

    Blasco, Mónica; Gimeno, María J; Auqué, Luis F

    2018-02-15

    Geothermometrical calculations in low-medium temperature geothermal systems hosted in carbonate-evaporitic rocks are complicated because 1) some of the classical chemical geothermometers are, usually, inadequate (since they were developed for higher temperature systems with different mineral-water equilibria at depth) and 2) the chemical geothermometers calibrated for these systems (based on the Ca and Mg or SO 4 and F contents) are not free of problems either. The case study of the Arnedillo thermal system, a carbonate-evaporitic system of low temperature, will be used to deal with these problems through the combination of several geothermometrical techniques (chemical and isotopic geothermometers and geochemical modelling). The reservoir temperature of the Arnedillo geothermal system has been established to be in the range of 87±13°C being the waters in equilibrium with respect to calcite, dolomite, anhydrite, quartz, albite, K-feldspar and other aluminosilicates. Anhydrite and quartz equilibria are highly reliable to stablish the reservoir temperature. Additionally, the anhydrite equilibrium explains the coherent results obtained with the δ 18 O anhydrite - water geothermometer. The equilibrium with respect to feldspars and other aluminosilicates is unusual in carbonate-evaporitic systems and it is probably related to the presence of detrital material in the aquifer. The identification of the expected equilibria with calcite and dolomite presents an interesting problem associated to dolomite. Variable order degrees of dolomite can be found in natural systems and this fact affects the associated equilibrium temperature in the geothermometrical modelling and also the results from the Ca-Mg geothermometer. To avoid this uncertainty, the order degree of the dolomite present in the Arnedillo reservoir has been determined and the results indicate 18.4% of ordered dolomite and 81.6% of disordered dolomite. Overall, the results suggest that this multi

  12. Lower Miocene stratigraphy along the Panama Canal and its bearing on the Central American Peninsula.

    Directory of Open Access Journals (Sweden)

    Michael Xavier Kirby

    Full Text Available Before the formation of the Central American Isthmus, there was a Central American Peninsula. Here we show that southern Central America existed as a peninsula as early as 19 Ma, based on new lithostratigraphic, biostratigraphic and strontium chemostratigraphic analyses of the formations exposed along the Gaillard Cut of the Panama Canal. Land mammals found in the Miocene Cucaracha Formation have similar body sizes to conspecific taxa in North America, indicating that there existed a terrestrial connection with North America that allowed gene flow between populations during this time. How long did this peninsula last? The answer hinges on the outcome of a stratigraphic dispute: To wit, is the terrestrial Cucaracha Formation older or younger than the marine La Boca Formation? Previous stratigraphic studies of the Panama Canal Basin have suggested that the Cucaracha Formation lies stratigraphically between the shallow-marine Culebra Formation and the shallow-to-upper-bathyal La Boca Formation, the latter containing the Emperador Limestone. If the La Boca Formation is younger than the Cucaracha Formation, as many think, then the peninsula was short-lived (1-2 m.y., having been submerged in part by the transgression represented by the overlying La Boca Formation. On the other hand, our data support the view that the La Boca Formation is older than the Cucaracha Formation. Strontium dating shows that the La Boca Formation is older (23.07 to 20.62 Ma than both the Culebra (19.83-19.12 Ma and Cucaracha (Hemingfordian to Barstovian North American Land Mammal Ages; 19-14 Ma formations. The Emperador Limestone is also older (21.24-20.99 Ma than the Culebra and Cucaracha formations. What has been called the "La Boca Formation" (with the Emperador Limestone, is re-interpreted here as being the lower part of the Culebra Formation. Our new data sets demonstrate that the main axis of the volcanic arc in southern Central America more than likely existed as a

  13. Lower Miocene stratigraphy along the Panama Canal and its bearing on the Central American Peninsula.

    Science.gov (United States)

    Kirby, Michael Xavier; Jones, Douglas S; MacFadden, Bruce J

    2008-07-30

    Before the formation of the Central American Isthmus, there was a Central American Peninsula. Here we show that southern Central America existed as a peninsula as early as 19 Ma, based on new lithostratigraphic, biostratigraphic and strontium chemostratigraphic analyses of the formations exposed along the Gaillard Cut of the Panama Canal. Land mammals found in the Miocene Cucaracha Formation have similar body sizes to conspecific taxa in North America, indicating that there existed a terrestrial connection with North America that allowed gene flow between populations during this time. How long did this peninsula last? The answer hinges on the outcome of a stratigraphic dispute: To wit, is the terrestrial Cucaracha Formation older or younger than the marine La Boca Formation? Previous stratigraphic studies of the Panama Canal Basin have suggested that the Cucaracha Formation lies stratigraphically between the shallow-marine Culebra Formation and the shallow-to-upper-bathyal La Boca Formation, the latter containing the Emperador Limestone. If the La Boca Formation is younger than the Cucaracha Formation, as many think, then the peninsula was short-lived (1-2 m.y.), having been submerged in part by the transgression represented by the overlying La Boca Formation. On the other hand, our data support the view that the La Boca Formation is older than the Cucaracha Formation. Strontium dating shows that the La Boca Formation is older (23.07 to 20.62 Ma) than both the Culebra (19.83-19.12 Ma) and Cucaracha (Hemingfordian to Barstovian North American Land Mammal Ages; 19-14 Ma) formations. The Emperador Limestone is also older (21.24-20.99 Ma) than the Culebra and Cucaracha formations. What has been called the "La Boca Formation" (with the Emperador Limestone), is re-interpreted here as being the lower part of the Culebra Formation. Our new data sets demonstrate that the main axis of the volcanic arc in southern Central America more than likely existed as a peninsula

  14. Clay-mineral assemblages from some levels of K-118 drill core of Maha Sarakham evaporites, northeastern Thailand

    Science.gov (United States)

    Suwanich, Parkorn

    Clay-mineral assemblages in Middle Clastic, Middle Salt, Lower Clastic, Potash Zone, and Lower Salt, totalling 13 samples from K-118 drill core, in the Maha Sarakham Formation, Khorat Basin, northeastern Thailand were studied. The clay-size particles were separated from the water-soluble salt by water leaching. Then the samples were leached again in the EDTA solution and separated into clay-size particles by using the timing sedimentation. The EDTA-clay residues were divided and analyzed by using the XRD and XRF method. The XRD peaks show that the major-clay minerals are chlorite, illite, and mixed-layer corrensite including traces of rectorite? and paragonite? The other clay-size particles are quartz and potassium feldspar. The XRF results indicate Mg-rich values and moderate MgAl atom ratio values in those clay minerals. The variable Fe, Na, and K contents in the clay-mineral assemblages can explain the environment of deposition compared to the positions of the samples from the core. Hypothetically, mineralogy and the chemistry of the residual assemblages strongly indicate that severe alteration and Mg-enrichment of normal clay detritus occurred in the evaporite environment through brine-sediment interaction. The various Mg-enrichment varies along the various members reflecting whether sedimentation is near or far from the hypersaline brine.

  15. Petrophysical and Petrographic Characterization, Mixed Carbonate - Siliciclastic - Evaporite Cclic System, upper Desmoinesian (Middle Pennsylvanian) of the Paradox Basin (SE Utah, U.S.A.)

    OpenAIRE

    Nussbaumer, Christophe

    1999-01-01

    Pour la caractérisation pétrophysique et pétrographique des roches du système mixte carbonaté, siliciclastique et évaporitique du Desmoinesien supérieur du Bassin du Paradox (Utah, USA), trois affleurements de terrain et six carottes de forage ont été visités. Les données pétrophysiques mesurées sur échantillon sont la densité, la porosité, la perméabilité, et les vitesses ultrasoniques des ondes P et S. Pour la pétrographie, les observations en lame mince (texture, composants, porosité, type...

  16. Comments to Middle Miocene closure of the Central American Seaway

    Science.gov (United States)

    Coates, A.G.; Stallard, Robert F.

    2016-01-01

    In a recent paper proposing an early (mid-Miocene) closure of the Central American Seaway (CAS), Montes et al. 2015 (1) disregard existing paleogeographic data that invalidate Panama as a source for zircons, and inappropriately ignore the evidence for trans-isthmian marine connections until 4-3 Ma. They also fail to cite previous work (2, 3), that had reconstructed the Central American arc already docked with South America by 12 Ma. Montes et al. 2015 (1) (Fig. 1) disregard the Atrato-San Juan sedimentary basin (3), a shallowing Oligocene to Pliocene, Pacific to Caribbean seaway (3, 4, 5). This deep graben (6) is filled with thousands of meters of Pre-Pliocene marine sediments (3, 5, 6) that now occupy a lowland between the Baudo uplift to the west and the Western Cordillera to the east. The Mande Batholith and numerous Eocene and younger volcanic rocks (4), the most proximal source of the zircons, are situated to the east of this seaway and would have shed zircons eastward towards the Cordillera Central. There is no evidence for any rivers crossing the seaway (3, 5), and thus no Panamanian source of zircons. Instead this seaway is evidence of a significant marine connection between the Pacific and Atlantic oceans into the Pliocene. The authors assume that the middle Miocene closure of the CAS effectively creates a continuous land bridge connecting North and South America and separating the Atlantic from the Pacific. They acknowledge, but then discount, marine connections across the Isthmus until 4-3 Ma even though these satisfactorily explain (Coates and Stallard, 2014 (6)) the oceanographic, molecular and Great American Biological Interchange events ignore unexplained by Montes et al. 2015. Only by conspicuously ignoring these events can they imply that the Isthmus was formed at 15-13 Ma. References 1. C. Montes et al., Middle Miocene closure of the Central American Seaway. Science 348, 226-229 (2015). 2. A. G. Coates, R. F. Stallard, How old is the Isthmus of

  17. Large-scale gravity sliding in the Miocene Shadow Valley Supradetachment Basin, Eastern Mojave Desert, California

    Science.gov (United States)

    Davis, G. A.; Friedmann, S. J.

    2005-12-01

    The Miocene Shadow Valley basin in the eastern Mojave Desert of California developed above the active west-dipping Kingston Range-Halloran Hills extensional detachment fault system between 13.5 and ca. 7 mybp. Although mass-wasting processes are common phenomena in supradetachment basins, the Shadow Valley basin is an exceptional locale for the study of such processes, especially rock-avalanches and gravity sliding. A score of megabreccias, interpreted as rock-avalanche deposits, and half that number of very large (> 1 km 2, up to 200 m thick), internally intact gravity-driven slide sheets are interbedded with various sedimentary facies. The slide sheets, variably composed of Proterozoic crystalline rocks and Proterozoic, Paleozoic, and Tertiary sedimentary strata, moved across both depositional and erosional surfaces in the basin. Although the majority consist of Paleozoic carbonate rocks, the largest slide sheet, the Eastern Star crystalline allochthon, contains Proterozoic gneisses and their sedimentary cover and is now preserved as klippen atop Miocene lacustrine and alluvial fan deposits over an area > 40 km 2. Estimates of slide sheet runouts into the basin from higher eastern and northern source terranes range from approximately a few km to > 10 km; in most cases the exact provenances of the slide blocks are not known. The basal contacts of Shadow Valley slide sheets are characteristically knife sharp, show few signs of lithologic mixing of upper- and lower-plate rocks, and locally exhibit slickensided and striated, planar fault-like bases. Pronounced folding of overridden Miocene lacustrine and fan deposits beneath the Eastern Star allochthon extends to depths up to 40 m at widely scattered localities. We conclude that this slow moving slide sheet encountered isolated topographic asperities (hills) and that stress transfer across the basal slide surface produced folding of footwall strata. Synkinematic gypsum veins in footwall playa sediments, with fibers

  18. EARLY MIOCENE INSULAR VERTEBRATES FROM LAERRU (SARDINIA, ITALY: PRELIMINARY NOTE

    Directory of Open Access Journals (Sweden)

    DANIEL ZOBOLI

    2017-01-01

    Full Text Available A new vertebrate assemblage was discovered in an Early  Miocene lacustrine deposit near the village of Laerru (northern Sardinia, Italy. The assemblage is composed by mammals, reptiles and a bird. The mammals are represented by three ruminants (cf. Sardomeryx oschiriensis, Pecora indet. small size and Pecora indet. very small size and one dormouse (Peridyromys aff. murinus while reptiles are represented by turtles (Trionychidae? and crocodiles (cf. Diplocynodon sp.. A bird bone fragment is also reported and referred to Palaeortyx cf. brevipes (Galliformes. The assemblage can be related to the “Oschiri fauna”, one of the oldest endemic insular fauna known in the Mediterranean. The age of the Laerru vertebrates is early-middle Burdigalian, between 18.8 and 18.3 Ma, corresponding to the mammal unit of the main land MN3. The predominance of ruminants confirms the good capacity of these mammals to colonize insular environments.

  19. Changing seasonality patterns in Central Europe from Miocene Climate Optimum to Miocene Climate Transition deduced from the Crassostrea isotope archive

    Science.gov (United States)

    Harzhauser, Mathias; Piller, Werner E.; Müllegger, Stefan; Grunert, Patrick; Micheels, Arne

    2011-03-01

    The Western Tethyan estuarine oyster Crassostrea gryphoides is an excellent climate archive due to its large size and rapid growth. It is geologically long lived and allows a stable isotope-based insight into climatic trends during the Miocene. Herein we utilised the climate archive of 5 oyster shells from the Miocene Climate Optimum (MCO) and the subsequent Miocene Climate Transition (MCT) to evaluate changes of seasonality patterns. MCO shells exhibit highly regular seasonal rhythms of warm-wet and dry-cool seasons. Optimal conditions resulted in extraordinary growth rates of the oysters. δ 13C profiles are in phase with δ 18O although phytoplankton blooms may cause a slight offset. Estuarine waters during the MCO in Central Europe display a seasonal temperature range of c. 9-10 °C. Absolute water temperatures have ranged from 17 to 19 °C during cool seasons and up to 28 °C in warm seasons. Already during the early phase of the MCO, the growth rates are distinctly declining, although gigantic and extremely old shells have been formed at that time. Still, a very regular and well expressed seasonality is dominating the isotope profiles, but episodically occurring extreme climate events influence the environments. The seasonal temperature range is still c. 9 °C but the cool season temperature seems to be slightly lower (16 °C) and the warm season water temperature does not exceed c. 25 °C. In the later MCT at c. 12.5-12.0 Ma the seasonality pattern is breaking down and is replaced by successions of dry years with irregular precipitation events. No correlation between δ 18O and δ 13C is documented maybe due to a suboptimal nutrition level which would explain the low growth rates and small sizes. The amplitude of seasonal temperature range is decreasing to 5-8 °C. No clear cooling trend can be postulated for that time as the winter season water temperatures range from 15 to 20 °C. This may point to unstable precipitation rhythms on a multi-annual to

  20. Gulf of Mexico miocene CO₂ site characterization mega transect

    Energy Technology Data Exchange (ETDEWEB)

    Meckel, Timothy [Univ. of Austin, Austin, TX (United Staes); Trevino, Ramon [Univ. of Austin, Austin, TX (United Staes)

    2014-12-01

    This project characterized the Miocene-age sub-seafloor stratigraphy in the near-offshore portion of the Gulf of Mexico adjacent to the Texas coast. The large number of industrial sources of carbon dioxide (CO₂) in coastal counties and the high density of onshore urbanization and environmentally sensitive areas make this offshore region extremely attractive for long-term storage of carbon dioxide emissions from industrial sources (CCS). The study leverages dense existing geologic data from decades of hydrocarbon exploration in and around the study area to characterize the regional geology for suitability and storage capacity. Primary products of the study include: regional static storage capacity estimates, sequestration “leads” and prospects with associated dynamic capacity estimates, experimental studies of CO₂-brine-rock interaction, best practices for site characterization, a large-format ‘Atlas’ of sequestration for the study area, and characterization of potential fluid migration pathways for reducing storage risks utilizing novel high-resolution 3D (HR3D) seismic surveys. In addition, three subcontracted studies address source-to-sink matching optimization, offshore well bore management and environmental aspects. The various geologic data and interpretations are integrated and summarized in a series of cross-sections and maps, which represent a primary resource for any near-term commercial deployment of CCS in the area. The regional study characterized and mapped important geologic features (e.g., Clemente-Tomas fault zone, the regionally extensive Marginulina A and Amphistegina B confining systems, etc.) that provided an important context for regional static capacity estimates and specific sequestration prospects of the study. A static capacity estimate of the majority of the Study area (14,467 mi2) was estimated at 86 metric Gigatonnes. While local capacity estimates are likely to be lower due to reservoir-scale characteristics, the

  1. POLYPLACOPHORA FROM THE MIOCENE OF NORTH ITALY. PART 2: CALLOCHITONIDAE, CHITONIDAE, LEPIDOCHITONIDAE, ACANTHOCHITONIDAE AND CRYPTOPLACIDAE

    Directory of Open Access Journals (Sweden)

    BRUNO DELL’ ANGELO

    2016-10-01

    Full Text Available This study completes the description of the chiton fauna (Mollusca, Polyplacophora from deposits of the Miocene marine sequence of North Italy, located in Piedmont and Emilia Romagna regions. This second and final part describes chitons belonging to five families: Callochitonidae, Chitonidae, Lepidochitonidae, Acanthochitonidae and Cryptoplacidae. Nineteen species were identified, of which two are described as new (Chiton sulcomarginatus sp. n. and Craspedochiton brunettii sp. n., and 17 were already known. Craspedochiton mutinocrassus is the new name attributed to the species previously known as Acanthochiton costatus or A. costatus var. mutinocrassa; Chiton sulcomarginatus sp. n., Lepidochitona monterosatoi, L. pliocinerea, and Acanthochitona oblonga, previously known only up to Pliocene, are reported for the first time from the Miocene of Italy. The stratigraphic distribution of numerous species thought to first appear in the Late Miocene (Callochiton doriae, Chiton olivaceus, C. corallinus, Acanthochitona fascicularis, A. crinita, and Craspedochiton altavillensis is here extended to the Early Miocene. The distribution of Cryptoplax weinlandi is extended to the Middle Miocene (Serravallian. In total 35 chiton species (with 3.003 valves were identified in the Italian Miocene (including both parts of this series. Ten species became extinct at the end of the Miocene, six in the Pliocene, two in the Pleistocene, and 17 are extant. Of the extant species nine occur both in the Atlantic and Mediterranean, two exclusively in the Atlantic and six only in the Mediterranean. The number of species reported from the Torino Hill assemblages (Burdigalian? is increased from three listed by Sacco (1897 to nine. Thirty-four of the 35 species (excluding only Lepidopleurus benoisti occur in the Tortonian-Messinian Po Basin. Thirteen (37% of the species are also found in the Miocene Paratethys (Austria, Poland, Czech Republic, Hungary, Romania and Ukraine, which

  2. Source of sulphur in the Ebro Basin (Northern Spain). Tertiary nonmarine evaporite deposits as evidenced by sulphur isotopes

    International Nuclear Information System (INIS)

    Birnbaum, S.J.; Coleman, D.

    1979-01-01

    The Ebro Basin is an intermontane basin, located in northern Spain, filled with Tertiary (largely Oligocene and Miocene) elastic and chemical deposits. Sulphur isotopes are utilized to determine the source of sulphur in the sulphate deposits (predominantly gypsum with accessory thenardite, mirabolite and epsomite). Data obtained from Tertiary gypsum rocks produce a range of delta 34 S values from +9.16% to + 14.02% with a mean of +13.61%. Data obtained from Triassic gypsum rocks (in source area) produce a range from +13.73% to +15.14%, with a mean of +14.66%. Values for Tertiary marine water range from +18% to +24%. These data indicate a nonmarine origin for sulpur within the Tertiary sulphate rocks. The contribution of Triassic sulphur to the groundwater system, plus varying degrees of dilution by isotopically lighter (atmospheric and sulphide) sulphur, best explains the isotopic ratios observed in the Tertiary Basin deposits. (Auth.)

  3. Evaporite karst geohazards in the Delaware Basin, Texas: review of traditional karst studies coupled with geophysical and remote sensing characterization

    Directory of Open Access Journals (Sweden)

    Kevin W. Stafford

    2017-06-01

    Full Text Available Evaporite karst throughout the Gypsum Plain of west Texas is complex and extensive, including manifestations ranging from intrastratal brecciation and hypogene caves to epigene features and suffosion caves. Recent advances in hydrocarbon exploration and extraction has resulted in increased infrastructure development and utilization in the area; as a result, delineation and characterization of potential karst geohazards throughout the region have become a greater concern. While traditional karst surveys are essential for delineating the subsurface extent and morphology of individual caves for speleogenetic interpretation, these methods tend to underestimate the total extent of karst development and require surficial manifestation of karst phenomena. Therefore, this study utilizes a composite suite of remote sensing and traditional field studies for improved karst delineation and detection of potential karst geohazards within gypsum karst. Color InfraRed (CIR imagery were utilized for delineation of lineaments associated with fractures, while Normalized Density Vegetation Index (NDVI analyses were used to delineate regions of increased moisture flux and probable zones of shallow karst development. Digital Elevation Models (DEM constructed from high-resolution LiDAR (Light Detection and Ranging data were used to spatially interpret sinkholes, while analyses of LiDAR intensity data were used in a novel way to categorize local variations in surface geology. Resistivity data, including both direct current (DC and capacitively coupled (CC resistivity analyses, were acquired and interpreted throughout the study area to delineate potential shallow karst geohazards specifically associated with roadways of geohazard concern; however, detailed knowledge of the surrounding geology and local karst development proved essential for proper interpretation of resistivity inversions. The composite suite of traditional field investigations and remotely sensed karst

  4. Late Miocene radiolarian biostratigraphy and paleoceanography of Sawai Bay formation, Neill Island, Andamans, India

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.; Srinivasan, M.S.

    Late Miocene radiolarian zones are encountered from mudstone strata of Sawai Bay Formation, Neill Island, Andamans. Percentage data of forty-five coarser taxonomic groups of radiolarians were subjected to Q-mode cluster analysis. Based...

  5. Koristocetus pescei gen. et sp. nov., a diminutive sperm whale (Cetacea: Odontoceti: Kogiidae from the late Miocene of Peru

    Directory of Open Access Journals (Sweden)

    A. Collareta

    2017-12-01

    Full Text Available Among odontocetes, members of the family Kogiidae (pygmy and dwarf sperm whales are known as small-sized and in many respects enigmatic relatives of the great sperm whale Physeter macrocephalus. Most of the still scanty fossil record of Kogiidae is represented by isolated skulls and ear bones from Neogene deposits of the Northern Hemisphere, with the significant exception of Scaphokogia, a highly autapomorphic genus from late Miocene deposits of the Pisco Formation exposed along the southern coast of Peru. Here we report on a new fossil kogiid from Aguada de Lomas, a site where the late Miocene beds of the Pisco Formation are exposed. This specimen consists of an almost complete cranium representing a new taxon of Kogiidae: Koristocetus pescei gen. et sp. nov. Koristocetus mainly differs from extant Kogia spp. by displaying a larger temporal fossa and well-individualized dental alveoli on the upper jaws. Coupled with a relatively elongated rostrum, these characters suggest that Koristocetus retained some degree of raptorial feeding abilities, contrasting with the strong suction feeding specialization seen in Recent kogiids. Our phylogenetic analysis recognizes Koristocetus as the earliest branching member of the subfamily Kogiinae. Interestingly, Koristocetus shared the southern coast of present-day Peru with members of the genus Scaphokogia, whose unique convex rostrum and unusual neurocranial morphology seemingly indicate a peculiar foraging specialization that has still to be understood. In conclusion, Koristocetus evokes a long history of high diversity, morphological disparity, and sympatric habits in fossil kogiids, thus suggesting that our comprehension of the evolutionary history of pygmy and dwarf sperm whales is still far from being exhaustive.

  6. Facies architecture of basin-margin units in time and space: Lower to Middle Miocene Sivas Basin, Turkey

    Science.gov (United States)

    Çiner, A.; Kosun, E.

    2003-04-01

    The Miocene Sivas Basin is located within a collision zone, forming one of the largest basins in Central Turkey that developed unconformably on a foundered Paleozoic-Mesozoic basement and Eocene-Oligocene deposits. The time and space relationships of sedimentary environments and depositional evolution of Lower to Middle Miocene rocks exposed between Zara and Hafik towns is studied. A 4 km thick continuous section is subdivided into the Agilkaya and Egribucak Formations. Each formation shows an overall fining upward trend and contains three members. Although a complete section is present at the western part (near Hafik) of the basin, to the east the uppermost two members (near Zara) are absent. The lower members of both formations are composed of fluvial sheet-sandstone and red mudstone that migrate laterally on a flood basin within a semi-arid fan system. In the Agilkaya Formation that crops out near Zara, alluvial fans composed of red-pink volcanic pebbles are also present. The middle members are composed of bedded to massive gypsum and red-green mudstone of a coastal and/or continental sabkha environment. While the massive gypsum beds reach several 10’s of m in Hafik area, near Zara, they are only few m thick and alternate with green mudstones. In Hafik, bedded gypsums are intercalated with lagoonal dolomitic limestone and bituminous shale in the Agilkaya Formation and with fluvial red-pink sandstone-red mudstone in the Egribucak Formation. The upper members are made up of fossiliferous mudstone and discontinuous sandy limestone beds with gutter casts, HCS, and 3-D ripples. They indicate storm-induced sedimentation in a shallow marine setting. The disorganized accumulations of ostreid and cerithiid shells, interpreted as coquina bars, are the products of storm generated reworking processes in brackish environments. Rapid vertical and horizontal facies changes and the facies associations in both formations reflect the locally subsiding nature of this molassic

  7. Origin of an Assemblage Massively Dominated by Carnivorans from the Miocene of Spain

    Science.gov (United States)

    Domingo, M. Soledad; Alberdi, M. Teresa; Azanza, Beatriz; Silva, Pablo G.; Morales, Jorge

    2013-01-01

    Carnivoran-dominated fossil sites provide precious insights into the diversity and ecology of species rarely recovered in the fossil record. The lower level assemblage of Batallones-1 fossil site (Late Miocene; Madrid Basin, Spain) has yielded one of the most abundant and diversified carnivoran assemblage ever known from the Cenozoic record of mammals. A comprehensive taphonomic study is carried out here in order to constrain the concentration mode of this remarkable assemblage. Another distinctive feature of Batallones-1 is that the accumulation of carnivoran remains took place in the context of a geomorphological landform (cavity formation through a piping process) practically unknown in the generation of fossil sites. Two characteristics of the assemblage highly restrict the probable causes for the accumulation of the remains: (1) the overwhelming number of carnivorans individuals; and (2) the mortality profiles estimated for the four most abundant taxa do not correspond to the classic mortality types but rather were the consequence of the behavior of the taxa. This evidence together with other taphonomic data supports the hypothesis that carnivoran individuals actively entered the cavity searching for resources (food or water) and were unable to exit. The scarcity of herbivores implies that the shaft was well visible and avoided by these taxa. Fossil bones exhibit a very good preservation state as a consequence of their deposition in the restricted and protective environment of the chamber. Batallones-1 had another assemblage (upper level assemblage) that was dominated by herbivore remains and that potentially corresponded to the final stages of the cavity filling. PMID:23650542

  8. A secondary nursery area for the copper shark Carcharhinus brachyurus from the late Miocene of Peru

    Science.gov (United States)

    Landini, Walter; Collareta, Alberto; Pesci, Fabio; Di Celma, Claudio; Urbina, Mario; Bianucci, Giovanni

    2017-10-01

    The life history strategies of sharks often include the use of protected nursery areas by young-of-the-year and juveniles. Nursery areas can be primary (i.e., grounds where the sharks are born and spend the very first part of their lives) or secondary (i.e., grounds inhabited by slightly older but not yet mature individuals). Criteria utilized to recognize these strategic habitats include: high concentration of young sharks, high food availability, and low predation risk. Since the fossil record of sharks consists mainly of isolated teeth, identification of paleonurseries involves a series of problems due to difficult application of actualistic criteria. A rich shark tooth-bearing level (ST-low1) has recently been discovered in the upper Miocene deposits of the Pisco Formation exposed at Cerro Colorado (southern coast of Peru). Most of the teeth collected from this level belong to the extant copper shark Carcharhinus brachyurus. These teeth are small and compatible with those of extant juveniles. This observation, coupled with other paleoenvironmental considerations, indicates that the ST-low1 horizon could have represented a nursery ground for juvenile individuals of C. brachyurus. The absence of very small-sized teeth (i.e., referable to young-of-the-year) suggests a secondary nursery ground inhabited by immature copper sharks. Observations on the tooth size of other Lamniformes, Carcharhiniformes, and Myliobatiformes occurring along with C. brachyurus point to a significantly juvenile structure of this elasmobranch assemblage, thus supporting the hypothesis of a communal use of the Cerro Colorado paleonursery.

  9. Application of carbon isotope stratigraphy to late miocene shallow marine sediments, new zealand.

    Science.gov (United States)

    Loutit, T S; Kennett, J P

    1979-06-15

    A distinct (0.5 per mil) carbon-13/carbon-12 isotopic shift in the light direction has been identified in a shallow marine sedimentary sequence of Late Miocene age at Blind River, New Zealand, and correlated with a similar shift in Late Miocene Deep Sea Drilling Project sequences throughout the Indo-Pacific. A dated piston core provides an age for the shift of 6.2 +/- 0.1 million years. Correlations based on the carbon isotopic change require a revision of the previously established magnetostratigraphy at Blind River. The carbon shift at Blind River occurs between 6.2 and 6.3 +/- 0.1 million years before present. A new chronology provides an age for the evolutionary first appearance datum of Globorotalia conomiozea at 6.1 +/- 0.1 million years, the beginning of a distinct latest Miocene cooling event associated with the Kapitean stage at 6.2 +/- 0.1 million years, and the beginning of a distinct shallowing of water depths at 6.1 +/- 0.1 million years. The Miocene-Pliocene boundary as recognized in New Zealand is now dated at 5.3 +/- 0.1 million years. Extension of carbon isotope stratigraphy to other shallow Late Miocene sequences should provide an important datum for international correlation of Late Miocene shallow and deep marine sequences.

  10. Response of deep-sea benthic foraminifera to Miocene paleoclimatic events, DSDP site 289

    International Nuclear Information System (INIS)

    Woodruff, F.; Douglas, R.G.

    1981-01-01

    Changes in the Miocene deep-sea benthic foraminifera at DSDP Site 289 closely correlate to the climatically induced variations in deep and bottom waters in the Pacific Ocean. In early Miocene time, oxygen and carbon isotopes indicate that bottom waters were relatively warm and poorly oxygenated. Benthic foraminiferal assemblages are characterized by various species inherited from the Oligocene. Expansion of the Antarctic icecap in the early middle Miocene, 14-16 m.y. ago, increased oxygen isotope values, produced cold, more oxygenated bottom waters and lead to a turnover in the benthic foraminifera. An Oligocene-early Miocene assemblage was replaced by a cibicidoid-dominated assemblage. Some species became extinct and benthic faunas became more bathymetrically restricted with the increased stratification of deep waters in the ocean. In mid-Miocene time, Epistominella exigua and E. umbonifera, indicative of young, oxygenated bottom waters, are relatively common at DSDP Site 289. Further glacial expansion 5-9 m.y. ago lowered sealevel, increased oceanic upwelling and associated biological productivity and intensified the oxygen minima. Abundant hispid and costate uvigerines become a dominant faunal element at shallow depths above 2500 m as E. umbonifera becomes common to abundant below 2500 m. By late Miocene time, benthic faunas similar in species composition and proportion to modern faunas on the Ontong-Java plateau, had become established. (Auth.)

  11. New gadiform fishes (Teleostei, Gadiformes) from the Miocene of Algeria

    Science.gov (United States)

    Carnevale, Giorgio

    2007-02-01

    As part of the completion of studies on the Miocene fishes of the Chelif Basin (north-western Algeria), this paper represents a contribution to the knowledge of the Messinian gadiform diversity of this western Mediterranean, semi-enclosed, Neogene basin. A new genus and species of the family Macrouridae is erected ( Razelainia paradoxa n. gen. et sp.), two specimens are tentatively referred to already existing taxa ( Gadiculus cf. jonas; Merluccius cf. merluccius), and a species formerly assigned to the gadid genus Brosme is transferred to the genus Gaidropsarus ( Gaidropsarus murdjadjensis). The macrourid Razelainia paradoxa n. gen. et sp. is characterized by an unusual combination of: plesiomorphic gadiform features, such as low vertebral number (presumed), well-developed caudal-fin rays, presence of a single continuous dorsal fin originating just posterior to the neurocranium, anal-fin rays slightly longer than dorsal-fin rays; and derived, typically macrourid features, such as the presence of spinoid scales and the anterior anal-fin pterygiophores extending forward over the abdominal wall. A paleoecological analysis reveals that the Messinian gadiform assemblage of the Chelif Basin had a subtropical/warm temperate affinity, with a marked north-eastern Atlantic-Mediterranean biogeographic character.

  12. Resource partitioning among top predators in a Miocene food web.

    Science.gov (United States)

    Domingo, M Soledad; Domingo, Laura; Badgley, Catherine; Sanisidro, Oscar; Morales, Jorge

    2013-01-07

    The exceptional fossil sites of Cerro de los Batallones (Madrid Basin, Spain) contain abundant remains of Late Miocene mammals. From these fossil assemblages, we have inferred diet, resource partitioning and habitat of three sympatric carnivorous mammals based on stable isotopes. The carnivorans include three apex predators: two sabre-toothed cats (Felidae) and a bear dog (Amphicyonidae). Herbivore and carnivore carbon isotope (δ(13)C) values from tooth enamel imply the presence of a woodland ecosystem dominated by C(3) plants. δ(13)C values and mixing-model analyses suggest that the two sabre-toothed cats, one the size of a leopard and the other the size of a tiger, consumed herbivores with similar δ(13)C values from a more wooded portion of the ecosystem. The two sabre-toothed cats probably hunted prey of different body sizes, and the smaller species could have used tree cover to avoid encounters with the larger felid. For the bear dog, δ(13)C values are higher and differ significantly from those of the sabre-toothed cats, suggesting a diet that includes prey from more open woodland. Coexistence of the sabre-toothed cats and the bear dog was likely facilitated by prey capture in different portions of the habitat. This study demonstrates the utility of stable isotope analysis for investigating the behaviour and ecology of members of past carnivoran guilds.

  13. Horizontal drilling in Miocene thin sand of Lake Maracaibo

    Energy Technology Data Exchange (ETDEWEB)

    Partidas, C. [PDVSA Exploration and Production (Venezuela)

    1998-12-31

    Horizontal drilling in the mature Lake Maracaibo field in Venezuela as a means of stimulating production are discussed. The Miocene sand where the horizontal well technology was applied, presented a number of intervals of unconsolidated sand of varied continuity, pay intervals at ten to twenty feet thickness, and reservoir pressures mostly at hydrostatic or below hydrostatic values. This paper evaluates a horizontal drilling program in the Lagunallis Lago Production Unit of Maracaibo, involving 91 wells to date (since 1995). When assessed in economic terms, results indicate that horizontal wells are a better economic alternative than vertical wells. The same results also showed that drainage from thin sand reservoirs resulted in better production with horizontal well technology than production from vertical wells. Payout was less than two years for 50 per cent of the horizontal wells while 40 per cent had payouts of between two and four years. Profit to investment ratio was greater than two in the case of about 70 per cent of the horizontal wells drilled in 1996. 2 tabs., 10 figs.

  14. Peatmoss (Sphagnum) diversification associated with Miocene Northern Hemisphere climatic cooling?

    Science.gov (United States)

    Shaw, A Jonathan; Devos, Nicolas; Cox, Cymon J; Boles, Sandra B; Shaw, Blanka; Buchanan, Alex M; Cave, Lynette; Seppelt, Rodney

    2010-06-01

    Global climate changes sometimes spark biological radiations that can feed back to effect significant ecological impacts. Northern Hemisphere peatlands dominated by living and dead peatmosses (Sphagnum) harbor almost 30% of the global soil carbon pool and have functioned as a net carbon sink throughout the Holocene, and probably since the late Tertiary. Before that time, northern latitudes were dominated by tropical and temperate plant groups and ecosystems. Phylogenetic analyses of mosses (phylum Bryophyta) based on nucleotide sequences from the plastid, mitochondrial, and nuclear genomes indicate that most species of Sphagnum are of recent origin (ca. Sphagnum species are not only well-adapted to boreal peatlands, they create the conditions that promote development of peatlands. The recent radiation that gave rise to extant diversity of peatmosses is temporally associated with Miocene climatic cooling in the Northern Hemisphere. The evolution of Sphagnum has had profound influences on global biogeochemistry because of the unique biochemical, physiological, and morphological features of these plants, both while alive and after death. 2010 Elsevier Inc. All rights reserved.

  15. Ecological tolerances of Miocene larger benthic foraminifera from Indonesia

    Science.gov (United States)

    Novak, Vibor; Renema, Willem

    2018-01-01

    To provide a comprehensive palaeoenvironmental reconstruction based on larger benthic foraminifera (LBF), a quantitative analysis of their assemblage composition is needed. Besides microfacies analysis which includes environmental preferences of foraminiferal taxa, statistical analyses should also be employed. Therefore, detrended correspondence analysis and cluster analysis were performed on relative abundance data of identified LBF assemblages deposited in mixed carbonate-siliciclastic (MCS) systems and blue-water (BW) settings. Studied MCS system localities include ten sections from the central part of the Kutai Basin in East Kalimantan, ranging from late Burdigalian to Serravallian age. The BW samples were collected from eleven sections of the Bulu Formation on Central Java, dated as Serravallian. Results from detrended correspondence analysis reveal significant differences between these two environmental settings. Cluster analysis produced five clusters of samples; clusters 1 and 2 comprise dominantly MCS samples, clusters 3 and 4 with dominance of BW samples, and cluster 5 showing a mixed composition with both MCS and BW samples. The results of cluster analysis were afterwards subjected to indicator species analysis resulting in the interpretation that generated three groups among LBF taxa: typical assemblage indicators, regularly occurring taxa and rare taxa. By interpreting the results of detrended correspondence analysis, cluster analysis and indicator species analysis, along with environmental preferences of identified LBF taxa, a palaeoenvironmental model is proposed for the distribution of LBF in Miocene MCS systems and adjacent BW settings of Indonesia.

  16. Petrology of the Miocene igneous rocks in the Altar region, main Cordillera of San Juan, Argentina. A geodynamic model within the context of the Andean flat-slab segment and metallogenesis

    Science.gov (United States)

    Maydagán, Laura; Franchini, Marta; Chiaradia, Massimo; Pons, Josefina; Impiccini, Agnes; Toohey, Jeff; Rey, Roger

    2011-07-01

    The Altar porphyry Cu-(Au-Mo) deposit (31° 29' S, 70° 28' W) is located in the Andean Main Cordillera of San Juan Province (Argentina), in the southern portion of the flat-slab segment (28-33°S), 25 km north of the world-class porphyry Cu-Mo deposits of Los Pelambres and El Pachón. Igneous rocks in the area have been grouped into the Early Miocene Lower Volcanic Complex -composed of intercalations of lava flows and thin volcaniclastic units that grade upwards to a thick massive tuff- and the Middle-Late Miocene Upper Subvolcanic Suite that consists of a series of porphyritic stocks and dikes and magmatic and hydrothermal breccias. The Lower Volcanic Complex represents an Early Miocene arc (20.8 Ma ± 0.3 Ma; U-Pb age) erupted over a steep subduction zone. Their magmas equilibrated with an assemblage consisting of plagioclase- and pyroxene-dominated mineral residues, and experienced fractional crystallization and crustal contamination procesess. Their radiogenic signatures are interpreted to indicate conditions of relatively thickened continental crust in Altar during the Early Miocene, compared to the south and west. The Upper Subvolcanic Suite represents the development of a Middle-Late Miocene arc (11.75 ± 0.24 Ma, 10.35 ± 0.32 Ma; U-Pb ages) emplaced over a shallow subduction zone. A magmatic gap in Altar area betwen the Lower Volcanic Complex and Upper Subvolcanic Suite correlates with documented higher rates of compression in this period, that may have favored the storage of the USS magmas in cameras within the crust. Magmas of the Upper Subvolcanic Suite require a hornblende-bearing residual mineral assemblage that is interpreted to reflect their higher water contents. The relatively uniform radiogenic isotope compositions of the Upper Subvolcanic Suite magmas suggest a homogeneously mixed crust-mantle contribution in the source region. They have similar REE signatures as other fertile intrusives of the flat-slab. The differences observed in their

  17. POLYPLACOPHORA FROM THE MIOCENE OF NORTH ITALY. PART 1: LEPTOCHITONIDAE, HANLEYIDAE, ISCHNOCHITONIDAE AND CALLISTOPLACIDAE

    Directory of Open Access Journals (Sweden)

    BRUNO DELL’ANGELO

    2015-11-01

    Full Text Available This study describes the chiton fauna (Mollusca, Polyplacophora from deposits of the Miocene marine sequence of North Italy, located in Piedmont and Emilia Romagna regions. This first part of the work describes the chitons pertaining to four families: Leptochitonidae, Hanleyidae, Ischnochitonidae and Callistoplacidae. The studied fossils consist of 377 valves from 13 sites (Sciolze, Valle Ceppi, Rocco di Passerano, Albugnano, Monchio di Sarzano Casina, Villa Monti, Rio di Bocca d’Asino, Sant’Agata Fossili, Vargo, Vigoleno, Montegibbio, Borelli, and Moncucco Torinese ranging from the Early Miocene (Burdigalian to the Late Miocene (Messinian. We identified 16 species, 12 of which were already known, two are identified only at generic level (Stenosemus sp. A & sp. B, and two are described as new: Parachiton statianus sp. n., and Callistochiton borellianus sp. n. Some species found are particularly noteworthy; Lepidopleurus benoisti is the new name attributed to the species previously known as Middendorffia subcajetana or Gymnoplax orbignyi, based on the study of the type material; Leptochiton salicensis, previously known only from the Early Pleistocene of Salice (Messina, Sicily; Hanleya mediterranea is reported for the first time from the Miocene of Italy; Ischnochiton ligusticus, previously known only from the Early Pliocene of Western Liguria; the distribution of Stenoplax paviai, recently described from the Late Miocene (Rio di Bocca d’Asino, is extended to the Early Miocene (Langhian. A complete discussion on the chiton fauna from the North Italian Miocene, consisting of all the species treated in both parts, will be given in the second part of this work.

  18. Miocene squat lobsters (Decapoda, Anomura, Galatheoidea) of the Central Paratethys - a review, with description of a new species of Munidopsis.

    Science.gov (United States)

    Hyžný, M; Gašparič, R; Robins, C M; Schlögl, J

    2014-10-01

    All squat lobsters of the families Galatheidae, Munididae and Munidopsidae from the Miocene of the Central Paratethys are reviewed taxonomically. Based on additional observations emended diagnoses are provided for Agononida cerovensis and Galathea weinfurteri , from the Lower and Middle Miocene, respectively. Munidopsis is represented by two species in the study area; additional data for M. lieskovensis from the Lower Miocene of Slovakia are presented and a new species, M. palmuelleri , from the Middle Miocene of Slovenia is erected. Implications for palaeoenvironmental reconstructions are briefly discussed for each taxon.

  19. The impact of droughts and climate change on sinkhole occurrence. A case study from the evaporite karst of the Fluvia Valley, NE Spain.

    Science.gov (United States)

    Linares, Rogelio; Roqué, Carles; Gutiérrez, Francisco; Zarroca, Mario; Carbonel, Domingo; Bach, Joan; Fabregat, Ivan

    2017-02-01

    This work introduces the concept that sinkhole frequency in some karst settings increases during drought periods. This conception is tested in a sector of the Fluvia River valley in NE Spain, where subsidence phenomena is related to the karstification of folded Eocene evaporite formations. In the discharge areas, the evaporites behave as confined aquifers affected by hypogene karstification caused by aggressive artesian flows coming form an underlying carbonate aquifer. A sinkhole inventory with chronological data has been constructed, revealing temporal clusters. Those clusters show a good correlation with drought periods, as revealed by precipitation, river discharge and piezometric data. This temporal association is particularly obvious for the last and current drought starting in 1998, which is the most intense of the record period (1940-present). Climatic projections based on recent studies foresee an intensification of the droughts in this sector of NE Spain, which could be accompanied by the enhancement of the sinkhole hazard and the associated risks. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. The late Miocene Phractocephalus catfish (Siluriformes: Pimelodidae from Urumaco, Venezuela: additional specimens and reinterpretation as a distinct species

    Directory of Open Access Journals (Sweden)

    John G. Lundberg

    Full Text Available Based on additional specimens the fossil pimelodid catfish from the upper Miocene Urumaco Formation, Falcón State, Venezuela originally assigned to the extant species Phractocephalus hemioliopterus is described as a new, extinct species. †Phractocephalus nassi n. sp. is diagnosed by the following combination of characters: 1 posterior half of frontals and anterior half of supraoccipital with elongate, coarse ridges and sulci in addition to reticulating ridges and subcircular pits; 2 very broad and ornamented mesethmoid bone; 3 lateral ethmoid margin convex and eliminating orbital notch but not projecting far anteriorly over palatine condyle; 4 anterior cranial fontanelle closed or represented by a small pit; 5 supraoccipital process rounded laterally and posterolaterally, concave posteriorly and completely concealing Weberian complex in dorsal view; 6 opercle covered with reticulating ridges and pits; 7 cleithrum coarsely ornamented along ventral edge and bulging outward lateral to spine articulation; 8 pectoral spine mostly ornamented with coarse ridges and sulci. †Phractocephalus nassi is compared to modern P. hemioliopterus and an undescribed extinct species from the upper Miocene Solimões Formation, Acre, Brazil. New diagnostic characters of Phractocephalus are presented that apply to the modern and fossil species, including: 1 ornamentation of skull, pectoral girdle and fin spines comprising a coarse meshwork of reticulating ridges surrounding rounded pits plus some elongate ridges and sulci; 2 supraoccipital posterior process greatly expanded laterally and posteriorly behind occipital wall; 3 lateral ethmoid and sphenotic broadly sutured behind eye; 4 anterior cranial fontanelle reduced or completely closed and posterior cranial fontanelle closed; 5 vomerine tooth plate large, roughly pentagonal to triangular in form, and with fine teeth. Today Phractocephalus ranges widely throughout the lowland Orinoco, Amazon and Essequibo basins

  1. A Miocene wave-dominated estuarine system in the Paraíba Basin, northeastern Brazil

    Science.gov (United States)

    Gandini, Rosana; Rossetti, Dilce de Fátima; Netto, Renata Guimarães; Góes, Ana Maria

    2017-11-01

    A number of publications have documented the effect of the Miocene transgression on several coasts of the world. However, this event is incompletely documented along the Brazilian margin, despite the existence of an impressive record of Miocene deposits exposed mostly as several coastal cliffs along more than 5000 km of distance. The transgressive nature of Miocene deposits, so far recognized only in a few localities of northeastern Brazil, needs to be amplified in order to better characterize the impact of the Miocene transgression in eastern South America. In this work, we provide facies analysis of early/middle Miocene strata exposed in the Paraíba Basin, northeastern Brazil, aiming reconstruct the depositional paleoenvironments and analyze their evolution within the context of relative sea-level fluctuations data. The results revealed deposits characterized by several features that were related to the action of tidal currents, such as alternating thicker/thinner forest packages, abundant reactivation surfaces, mud drapes and oppositely-dipping (herringbone) cross sets. These sedimentary structures were associated with an ichnological assemblage indicative of marine-influenced and brackish water, best represented by Ophiomorpha, Planolites-Palaeophycus-Thalassinoides and Thallassinoides-Planolites-Palaeophycus ichnofabrics. Sedimentation occurred in environments consisting of estuarine channel, estuarine central basin, tidal inlet/tidal channel, tidal delta/washover, tidal flat/shoal and foreshore, which were related to an estuarine setting, at least in part of a wave-dominated type. Analysis of facies stratal patterns led to suggest that the estuarine deposits of the Paraíba Basin reflect a rise in relative sea level probably during the transgressive and/or highstand stage of a depositional sequence formed directly overlying Cretaceous rocks. This rise can be correlated with the worldwide early/mid Miocene marine transgression. However, while the eustatic sea

  2. Provenance of the lower Miocene of the Gulf of Mexico from detrital zircon double dating

    Science.gov (United States)

    xu, J.

    2013-12-01

    The lower Miocene interval of the Gulf of Mexico (GOM) has recently gained increasing attention from oil and gas industry due to its hydrocarbon potential below the salt canopy. However, it has been less well studied than both the underlying Oligocene and overlying middle Miocene strata. The lower Miocene worldwide is a transitional period of tectonic, climatic, and oceanographic change. In particular, it is a period of major tectonic reorganization in the western interior of North America (Rocky Mountains), involving a shift from the Oligocene thermal phase, with abundant volcanic activity recorded in the thick Frio/Vicksburg succession of the GOM, to the Miocene Basin-Range extensional phase. Climatic conditions also changed from a relatively arid Oligocene to wetter Miocene, resulting in increased sediment yields from exhumed tectonic structures. Previous provenance studies used proportions of quartz, feldspar and lithic fragments and consideration of likely river courses through known paleogeomorphological elements. Only limited detrital zircon (DZ) U-Pb studies on Paleocene strata have been undertaken and there has been no previous U-Pb and (U-Th)/He double dating in the GOM. In this study we apply the latest analytical approaches, such as DZ U-Pb dating to gain robust source terranes ages and more fully elucidate the complex sediment provenance and dispersal history of GOM. We also employ DZ (U-Th)/He (ZHe) dating, combined with DZ U-Pb, to not only define sedimentary provenance but also the exhumation histories of detrital source regions. Samples of lower Miocene outcrop exposures in Texas and Louisiana have been collected to discriminate the varied tectonic and drainage system changes across the basin in lateral. In addition, samples from the Eocene, Oligocene and middle Miocene have been obtained to reveal vertical shift of source terranes contributions. Our initial age data show detrital zircons of lower Miocene sediments come from a wide range of source

  3. A NEW RECORD OF MESSAPICETUS FROM THE PIETRA LECCESE (LATE MIOCENE, SOUTHERN ITALY: ANTITROPICAL DISTRIBUTION IN A FOSSIL BEAKED WHALE (CETACEA, ZIPHIIDAE

    Directory of Open Access Journals (Sweden)

    GIOVANNI BIANUCCI

    2016-03-01

    Full Text Available A new partial fossil skeleton of Messapicetus longirostris (Cetacea: Odontoceti: Ziphiidae collected in Cisterna quarry (Lecce from Tortonian (upper Miocene sediments of the "Pietra leccese" is described. It comprises the fragmentary skull (including most of the rostrum, parts of the mandibles, five teeth, the fragmentary right scapula, and one vertebral centrum. This new record, here referred to a juvenile individual, expands our knowledge about the skeletal anatomy of M. longirostris; this species was until now only known by the holotype, an almost complete skull from the same Cisterna quarry. Moreover, the new specimen confirms the distinction between M. longirostris and M. gregarius (late Miocene, Pisco Formation, Peru based on several osteological characters (e.g., the presence of a distinct maxillary tubercle and prominential notch in the latter species. New dating of layers in Cerro Colorado, the type locality of M. gregarius, suggests that M. longirostris and M. gregarius were contemporaneous sister-species with an antitropical distribution (a biogeographical pattern currently shown by two extant ziphiid genera. Unlike extant ziphiids, feeding predominantly on squid and benthopelagic fish in deep waters, the stem ziphiid M. gregarius was recently proposed to have been a raptorial piscivore who may have fed mainly on schools of epipelagic fish. Similarities at the level of the morphology and proportions of the oral apparatus suggest that the two species of Messapicetus may have occupied roughly identical ecological and trophic niches, a hypothesis supported by the characterization of the Pietra leccese environment as neritic.

  4. Sedimentology and biostratigraphy of the Early-Middle Miocene transition in NW Transylvanian Basin (Pâglişa and Dej sections

    Directory of Open Access Journals (Sweden)

    Claudia Beldean

    2013-01-01

    Full Text Available The Early - Middle Miocene transition can be studied in several sections from the north-western Transylvanian Basin, across the boundary between the Hida and Dej Formations. The Pâglişa and Râpa Dracului (Dej locally outcrop sections offer a very good record of the changes in the sedimentary facies and micropaleontological content across the boundary. The lower parts of the sections display the upper Hida Formation with prodelta fine grained sediments covered by coarser grained sediments related to a delta front progradation. Four sedimentary facies associations have been separated based on grain size and associated sedimentary structures. Micropaleontological assemblages are moderately to poorly preserved, with a low abundance and diversity. Planktonic Streptochilus pristinum is the main taxon associated with rare (< 10% calcareous benthic foraminifera (Bulimina, Bolivina, Cibibicidoides. The Dej Formation consists of stacked channel lag deposits associated with lateral accretion bars and crevasse splays followed by fall-out tuffs and redeposited low density tuffites interbedded with low density fine siliciclastics. The deposits of Dej Formation from the investigated areas were separated in four facies associations based on grain size/petrography and primary sedimentary structures. Micropaleontological assemblages contain typical early Badenian planktonic foraminifera (species of Orbulina, Praeorbulina, Globigerinoides, and Globorotalia associated to the main phase of the marine transgresion from the beginning of the Middle Miocene.

  5. BENTHIC FORAMINIFERAL BIOSTRATIGRAPHY OF MALATYA OLIGO-MIOCENE SUCCESSION (EASTERN TAURIDS, EASTERN TURKEY

    Directory of Open Access Journals (Sweden)

    Fatma GEDİK

    2015-10-01

    Full Text Available The benthic foraminiferal biostratigraphy of Oligo-Miocene aged Muratlı and Petekkaya formations which crop out over wide regions around Akçadağ town, west of Malatya pro- vince in Eastern Taurids were revealed in this study. Systematical sampling was carried out in measured stratigraphical sections in four locations in order to perform stratigraphical and paleontological investigations. Benthic foraminifera taken from 182 hard rock samples were defined and three biozones were determined as; SBZ 21-22, belonging to Oligocene (Rupe- lian - Early Chattian, SBZ 23 (Late Chattian and SBZ 25 belonging to Lower Miocene in shallow marine deposits in the region. It was stated that the assemblage of planktic forami- nifer and nannoplankton which stratigraphically detected within Chattian - Burdigalian units in the succession most probably indicated Aquitanian age. Besides; Oligo-Miocene transition in the region was approved with this study based on biostratigraphical locations of benthic foraminiferal taxa.

  6. Carbonate pseudotachylite? from a Miocene extensional detachment, W. Cyclades, Greece.

    Science.gov (United States)

    Rice, A. Hugh N.; Grasemann, Bernhard

    2016-04-01

    Most pseudotachylites, both impact- and fault-related, occur in silicate-rich rocks, typically with 'granitoid' compositions. Examples of melting in carbonate rocks, excluding magmatic sources, are restricted to impact-events, except for a carbonate pseudotachylite in the Canalone Fault, S. Italy (Viganò et al. 2011). Another potential example of carbonate pseudotachylite, shown here, comes from the Miocene-aged W. Cycladic Detachment System, in Greece. Top-SSE ductile to brittle movement on this detachment, with a maximum displacement estimated at tens of kilometers, exhumed of HP-rocks. The carbonate pseudotachylite occurs within an 43 mm thick), consists of dark (hematitic) red, ultra-fine grained unlayered carbonate with up to 40x10 mm rather rounded clasts of earlier generations of cataclasite, many with a quartzite composition. These clasts are fractured and partially separated, with a fine red carbonate matrix. No layering of the matrix or clasts is apparent. The clasts become finer and more abundant towards the boundary with Layer B. Layers B and D (~57 & ~20 mm thick) dominantly comprises protocataclasite with greyish quartz fragments separated by a carbonate matrix along narrow fractures. Zone C and E (~23 m & >15 mm thick) comprise pale pink carbonate-dominated rocks with abundant material and may have darker (?reaction) rims. No layering is seen in the pale pink groundmass although this is present in some elongate clasts. All layer boundaries are irregular and no principle slip surfaces have been seen. Injection veins from 1 to 9 mm wide and up to at least 100 mm long derive from the central layer (C), cutting the overall layering at a high angle and branching in several places. These veins contain clasts comparable to those in Layer C. Both thick and thin injection-veins are rimmed by impersistent white calcite suggesting that injection was associated with precipitation of calcite. Whether Layer C (and perhaps E also) is a carbonate pseudotachylite is

  7. Mid-miocene cooling in the northern Qilian Shan, northeastern margin of the Tibetan plateau, revealed by apatite fission-track and VR analysis

    International Nuclear Information System (INIS)

    George, A.D.; Wyrwoll, K.-H.; Jie, C.; Yanchou, L.

    1999-01-01

    Full text: Growth of the Tibetan Plateau along its northeastern margin by crustal shortening and thickening is linked to the Altyn Tagh Fault, a ∼1500 km long sinistral strike-slip fault which has played a significant role in accommodating the convergence of India and Eurasia. The NW-trending Qilian Shan (mountains) that mark the northeastern edge of the plateau rise nearly 5000 m above the adjacent Juice Basin of the Hexi Corridor. The Qilian Shan is a mid-Paleozoic orogenic suture belt composed of numerous thrust slices of deformed Lower Paleozoic (Cambrian-Silurian) metasedimentary and metavolcanic strata. The older Precambrian basement is also exposed in some thrust sheets, as are remnants of Upper Paleozoic-Jurassic strata. Cretaceous fluvial sandstones and conglomerates are locally preserved. The neighbouring Juice Basin contains a thick succession of Neogene-Quaternary fluvial strata (∼3.5 km thick) which unconformably overlies Lower Cretaceous rocks. Adjacent to the Qilian Shan, the oldest Neogene strata in the Juice Basin are Miocene in age overlain by more extensive Pliocene and Quaternary sediments, whereas basal Oligocene strata are exposed on the northern side of the basin. Neogene and Quaternary strata are being actively deformed by thrust-related folding along the margins and within the Jiuxi Basin. Apatite fission-track and vitrinite reflectance data were obtained from Precambrian to Tertiary outcrop samples from the northern Qilian Shan and Juice Basin to provide constraints on timing of exhumation and cooling. All the samples record multiple cooling episodes. Tertiary cooling from peak paleotemperatures (40-120 deg C) beginning sometime between 20 and 10 Ma (mid-Miocene) is common to all samples. This age is significantly older than previous models which proposed initiation of uplift in the Pliocene-Pleistocene, i.e., no older than 5-6 Ma. For any reasonable paleo-geothermal gradient, the degree of mid-Miocene cooling requires km

  8. Integrated stratigraphy and 40Ar/39Ar chronology of early Middle Miocene sediments from DSDP Leg 42A, Site 372 (Western Mediterranean)

    NARCIS (Netherlands)

    Abdul Aziz, H.; di Stefano, A.; Foresi, L. M.; Hilgen, Frederik J.; Iaccarino, S. M.; Kuiper, K. F.; Lirer, F.; Salvatorini, G.; Turco, E.

    2008-01-01

    An integrated magneto-biostratigraphic framework is presented for Middle Miocene sediments of DSDP Site 372 located in the Western Mediterranean. Detailed biostratigraphic analysis shows a nearly complete sequence of early Middle Miocene calcareous plankton bioevents in the Mediterranean, including

  9. Architecture and growth history of a Miocene carbonate platform from 3D seismic reflection data; Luconia province, offshore Sarawak, Malaysia

    NARCIS (Netherlands)

    Zampetti, V.; Schlager, W.; van Konijnenburg, J.H; Everts, A.J.

    2004-01-01

    Using 3D seismic reflection data and wireline logs we reconstruct in detail the architecture and growth history of a Miocene carbonate platform in the Luconia province, offshore Sarawak, Malaysia. Platform growth started in the Late Oligocene to Early Miocene, by coalescence of isolated patch reefs.

  10. Eocene and miocene rocks off the northeastern coast of the United States

    Science.gov (United States)

    Gibson, T.G.

    1965-01-01

    A grab sample from a depth of 1675 m at a point south of Cape Cod contains early Eocene planktonic Foraminifera and is correlated with the Globorotalia rex zone of Trinidad. The assemblage indicates a depth comparable to that existing today. Regional relations suggest that the Cretaceous and Eocene deposits deepen to the west toward New Jersey. Two mollusk-bearing blocks dredged from the northern side of Georges Bank are correlative with the Miocene Yorktown Formation. Rocks from two other stations are probably Miocene. Benthonic Foraminifera in one sample indicate deposition in cool temperate waters of less than 60 m depth. ?? 1965.

  11. Large landslides, composed of megabreccia, interbedded in Miocene basin deposits, southeastern Arizona

    Science.gov (United States)

    Krieger, Medora Louise Hooper

    1977-01-01

    The landslides in the Kearny and El Capitan Mountain quadrangles, Pinal and Gila Counties, Ariz., are tabular or lens like masses of megabreccia enclosed in Miocene basin deposits. The megabreccias within individual slide blocks are composed of pervasively brecciated Precambrian and younger formations that remain in normal stratigraphic sequence, indicating that each landslide moved as a fairly coherent mass. The megabreccias consist of fresh, mostly angular rock fragments in a comminuted matrix of the same composition as the fragments. The matrix ranges in amount from sparse to abundant. Where the matrix is sparse, the fragments fit tightly with little or no rotation. Locally fragments are rotated but not moved far; most units within a slide block are lithologically homogeneous. The Kearny landslides are conformably interbedded in steeply east-dipping playa and alluvial deposits. They form map units from a few tens of meters to nearly 4 km long and from less than 1 to 270 m wide. Narrow ridges expose sections through the landslides at about right angles to the direction of movement. The upper (proximal) ends have been eroded; the lower (distal) ends are buried. The El Capitan landslide dips very gently southward. Although partly dissected during erosion of the enclosing alluvial and lakebed deposits, its approximate original outline is still preserved. It forms a thin sheet, 5-15 m thick and at least 3.8 km long; the maximum outcrop width, near its distal end, is about 1.5 km. The Kearny landslides show little evidence of having exerted differential pressure on the underlying soft playa and alluvial deposits, and the contacts with the underlying sediments have little relief. The distal end of the El Capitan landslide, on the other hand, has considerable relief. As the landslide came to an abrupt stop, the end plowed into the underlying sediments, compressing them into fol9.s and forming sandstone dikes. The source of the El Capitan landslide is a well

  12. Climate Proxy Signals in the Plio-Pleistocene Chemeron and Miocene Lukeino Formations, Baringo Basin, Kenya

    Science.gov (United States)

    Deino, A. L.; Kingston, J.; Hill, A.; Wilson, K. E.; Edgar, R.; Goble, E.

    2009-12-01

    in the Tugen Hills to diatomaceous sequences between ~8-6 Ma that would specifically implicate precessional control as a pervasive factor in the formation of rift lake systems and by inference climate. Reconnaissance in summer ’09 of these older strata have revealed extensive lacustrine deposits indicating that this portion of the rift was inundated by major lake systems during the upper Miocene.

  13. Geological and Hydrodynamical Examination of the Bathyal Tsunamigenic Origin of Miocene Conglomerates in Chita Peninsula, Central Japan

    Science.gov (United States)

    Tachibana, Toru; Tsuji, Yoshinobu

    2011-06-01

    A conglomerate appears on a rocky coast called "Tsubutega-ura Coast", located on the southwestern coast near the southern tip of the Chita Peninsula, Aichi Prefecture, central Japan. The conglomerate belongs to Miocene sedimentary rocks termed the Morozaki Group. The conglomerate includes meter-scale boulders, indicating that it was formed by an extraordinary event. In the geological investigation, we observed that the conglomerate shows alternate changes of paleocurrent directions between seaward and landward. This feature is supposed to be formed by tsunami currents. In the hydrodynamical investigation, we obtained following results: (1) the lowest limit of a current velocity to move a boulder of about 3 m in diameter would be about 2-3 m/s, (2) the speed of tsunami currents reproduced by tsunami simulation exceeds 3 m/s at 300 m in depth when the tsunami is generated by a gigantic earthquake with magnitude 9.0 or more, (3) the transport distance of the boulder would be several hundred meters to several kilometers by one tsunami event caused by a gigantic earthquake. We conclude that tsunamis best explain the formation of the conglomerate deposited in upper bathyal environments about 200-400 m depth, both from geological and hydrodynamical viewpoints.

  14. Molecular indicators for palaeoenvironmental change in a Messinian evaporitic sequence (Vena del Gesso, Italy) II. Stratigraphic changes in abundances and (13)C contents of free and sulphur-bound skeletons in a single marl bed

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Kenig, F.; Frewin, N.L.; Hayes, J.M.

    1995-01-01

    The extractable organic matter of 10 immature samples from a marl bed of one evaporitic cycle of the Vena del Gesso sediments (Gessoso-solfifera Fm., Messinian, Italy) was analyzed quantitatively for free hydrocarbons and organic sulphur compounds. Nickel boride was used as a desulphurizing agent to

  15. Upper Gastrointestinal (GI) Series

    Science.gov (United States)

    ... standard barium upper GI series, which uses only barium a double-contrast upper GI series, which uses both air and ... evenly coat your upper GI tract with the barium. If you are having a double-contrast study, you will swallow gas-forming crystals that ...

  16. Origin and distribution of saline groundwaters in the upper Miocene aquifer system, coastal Rhodope area, northeastern Greece

    Science.gov (United States)

    Petalas, C. P.; Diamantis, I. B.

    1999-06-01

    This paper describes the origins and distribution of saline groundwaters in the coastal area of Rhodope, Greece. The aquifer system includes two aquifers within coarse-grained alluvial sediments in the coastal part of the study area. Two major water-quality groups occur in the study area, namely Ca2+-rich saline groundwater and Ca2+-poor, almost fresh groundwater. The main process controlling the groundwater chemistry is the exchange of calcium and sodium between the aquifer matrix and intruding seawater. The natural salt water in the study area is probably residual water that infiltrated the aquifer system during repeated marine transgressions in late Pleistocene time. Seawater intrusion into the coastal aquifer system occurs as a result of overpumping in two seawater wedges separated vertically by a low-permeability layer. The rate of intrusion averages 0.8 m/d and is less than expected due to a decline of the aquifer's permeability at the interface with the seawater. The application of several hydrochemical techniques (Piper and Durov diagrams; Na+/Cl-, Ca2+/Cl-, Mg2+/Cl-, and Br-/Cl- molar ratios; Ca2+/Mg2+ weight ratio; and chloride concentrations), combined with field observations, may lead to a better explanation of the origin of the saline groundwater.

  17. Molecular indicators for palaeoenvironmental change in a Messinian evaporitic sequence (Vena del Gesso, Italy). II: High-resolution variations in abundances and 13C contents of free and sulphur-bound carbon skeletons in a single marl bed

    Science.gov (United States)

    Kenig, F.; Damste, J. S.; Frewin, N. L.; Hayes, J. M.; De Leeuw, J. W.

    1995-01-01

    The extractable organic matter of 10 immature samples from a marl bed of one evaporitic cycle of the Vena del Gesso sediments (Gessoso-solfifera Fm., Messinian, Italy) was analyzed quantitatively for free hydrocarbons and organic sulphur compounds. Nickel boride was used as a desulphurizing agent to recover sulphur-bound lipids from the polar and asphaltene fractions. Carbon isotopic compositions (delta vs PDB) of free hydrocarbons and of S-bound hydrocarbons were also measured. Relationships between these carbon skeletons, precursor biolipids, and the organisms producing them could then be examined. Concentrations of S-bound lipids and free hydrocarbons and their delta values were plotted vs depth in the marl bed and the profiles were interpreted in terms of variations in source organisms, 13 C contents of the carbon source, and environmentally induced changes in isotopic fractionation. The overall range of delta values measured was 24.7%, from -11.6% for a component derived from green sulphur bacteria (Chlorobiaceae) to -36.3% for a lipid derived from purple sulphur bacteria (Chromatiaceae). Deconvolution of mixtures of components deriving from multiple sources (green and purple sulphur bacteria, coccolithophorids, microalgae and higher plants) was sometimes possible because both quantitative and isotopic data were available and because either the free or S-bound pool sometimes appeared to contain material from a single source. Several free n-alkanes and S-bound lipids appeared to be specific products of upper-water-column primary producers (i.e. algae and cyanobacteria). Others derived from anaerobic photoautotrophs and from heterotrophic protozoa (ciliates), which apparently fed partly on Chlorobiaceae. Four groups of n-alkanes produced by algae or cyanobacteria were also recognized based on systematic variations of abundance and isotopic composition with depth. For hydrocarbons probably derived from microalgae, isotopic variations are well correlated with

  18. Response of Mediterranean circulation to Miocene shoaling and closure of the Indian Gateway : A model study

    NARCIS (Netherlands)

    De La Vara, Alba; Meijer, Paul

    2016-01-01

    In this regional ocean model study, we explore the effect of the Early to Middle Miocene shoaling and closure of the Indian Gateway on Mediterranean circulation and its exchange with the adjacent oceans. For this we use the regional ocean circulation model "sbPOM" and a collection of bathymetries

  19. The development of the Amazonian mega-wetland (Miocene; Brazil, Colombia, Peru, Bolivia)

    NARCIS (Netherlands)

    Hoorn, C.; Wesselingh, F.P.; Hovikoski, J.; Guerrero, J.; Hoorn, C.; Wesselingh, F.P.

    2010-01-01

    The scenery of Western Amazonia once consisted of fluvial systems that originated on the Amazonian Craton and were directed towards the sub-Andean zone and the Caribbean. In the course of the Early Miocene these fluvial systems were largely replaced by lakes, swamps, tidal channels and marginal

  20. The Middle Miocene Climate Transition in the Central Mediterranean. Geologica Ultraiectina (326)

    NARCIS (Netherlands)

    Mourik, A.A.|info:eu-repo/dai/nl/304849383

    2010-01-01

    The Middle Miocene Climate Transition (~15-13.7 Ma) is one of the major steps in Cenozoic climate evolution. The rapid expansion of the East Antarctic Ice Sheet at ~13.9 – 13.7 Ma caused important climate changes on a global scale. The aim of this PhD research has been to study the effects of the

  1. Fish remains from Miocene beds of Višnja vas near Vojnik, Slovenia

    Directory of Open Access Journals (Sweden)

    Aleš Šoster

    2013-06-01

    Full Text Available This paper discusses fossil teeth of sharks (Elasmobranchii, Neoselachii and porgies (Teleostei, Sparidae fromthe Miocene glauconite sandstones of Vi{nja vas near Vojnik. The remains of fish teeth, mostly tooth crowns, belongto cartilaginous fishes of the genera Notorynchus, Carcharias, Carcharoides, Isurus and Cosmopolitodus and to abony fish genus Pagrus.

  2. New Odostomia species (Gastropoda, Heterobranchia, Pyramidellidae) from the Miocene Pebas Formation of Western Amazonia (Peru, Colombia)

    NARCIS (Netherlands)

    Aartsen, van J.J.; Wesselingh, F.P.

    2000-01-01

    Odostomia nuttalli spec. nov. and O. coluhensis spec. nov. are described from the Miocene Pebas Formation of Peruvian and Columbian Amazonia. A third pyramidellid snail is also diagnosed. These species are indicators for marine influence in the late Middle to early Late Miocence of Western Amazonia.

  3. The Middle Miocene climate as modelled in an atmosphere-ocean-biosphere model

    Directory of Open Access Journals (Sweden)

    M. Krapp

    2011-11-01

    Full Text Available We present simulations with a coupled atmosphere-ocean-biosphere model for the Middle Miocene 15 million years ago. The model is insofar more consistent than previous models because it captures the essential interactions between ocean and atmosphere and between atmosphere and vegetation. The Middle Miocene topography, which alters both large-scale ocean and atmospheric circulations, causes a global warming of 0.7 K compared to present day. Higher than present-day CO2 levels of 480 and 720 ppm cause a global warming of 2.8 and 4.9 K. The associated water vapour feedback enhances the greenhouse effect which leads to a polar amplification of the warming. These results suggest that higher than present-day CO2 levels are necessary to drive the warm Middle Miocene climate, also because the dynamic vegetation model simulates a denser vegetation which is in line with fossil records. However, we do not find a flatter than present-day equator-to-pole temperature gradient as has been suggested by marine and terrestrial proxies. Instead, a compensation between atmospheric and ocean heat transport counteracts the flattening of the temperature gradient. The acclaimed role of the large-scale ocean circulation in redistributing heat cannot be supported by our results. Including full ocean dynamics, therefore, does not solve the problem of the flat temperature gradient during the Middle Miocene.

  4. Simulating a Dynamic Antarctic Ice Sheet in the Early to Middle Miocene

    Science.gov (United States)

    Gasson, E.; DeConto, R.; Pollard, D.; Levy, R. H.

    2015-12-01

    There are a variety of sources of geological data that suggest major variations in the volume and extent of the Antarctic ice sheet during the early to middle Miocene. Simulating such variability using coupled climate-ice sheet models is problematic due to a strong hysteresis effect caused by height-mass balance feedback and albedo feedback. This results in limited retreat of the ice sheet once it has reached the continental size, as likely occurred prior to the Miocene. Proxy records suggest a relatively narrow range of atmospheric CO2 during the early to middle Miocene, which exacerbates this problem. We use a new climate forcing which accounts for ice sheet-climate feedbacks through an asynchronous GCM-RCM coupling, which is able to better resolve the narrow Antarctic ablation zone in warm climate simulations. When combined with recently suggested mechanisms for retreat into subglacial basins due to ice shelf hydrofracture and ice cliff failure, we are able to simulate large-scale variability of the Antarctic ice sheet in the Miocene. This variability is equivalent to a seawater oxygen isotope signal of ~0.5 ‰, or a sea level equivalent change of ~35 m, for a range of atmospheric CO2 between 280 - 500 ppm.

  5. 3-D seismic characterization of submarine landslides on a Miocene carbonate platform (Luconia Province, Malaysia)

    NARCIS (Netherlands)

    Zampetti, V.; Schlager, W.; van Konijnenburg, J.H; Everts, A.J.

    2004-01-01

    3-D seismic reflection data and a variance cube are used to determine the architecture and investigate the triggering processes of submarine landslides affecting the flanks of a Miocene carbonate platform in the Luconia Province, Malaysia. The slide masses exhibit, in time-slice displays, chaotic,

  6. Effect of ocean gateways on the global ocean circulation in the late Oligocene and early Miocene

    NARCIS (Netherlands)

    von der Heydt, A.S.|info:eu-repo/dai/nl/245567526; Dijkstra, H.A.|info:eu-repo/dai/nl/073504467

    2006-01-01

    We investigate the effect of changes in the tectonic boundary conditions on global ocean circulation patterns. Using a fully coupled climate model in an idealized setup, we compare situations corresponding to the late Oligocene, the early Miocene, and present day. The model results show the

  7. Geochemical history of a Lower Miocene lake, the Cypris Formation, Sokolov Basin, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Kříbek, B.; Knésl, I.; Rojík, P.; Sýkorová, Ivana; Martínek, K.

    2017-01-01

    Roč. 58, č. 2 (2017), s. 169-190 ISSN 0921-2728 R&D Projects: GA ČR GA205/09/1162 Institutional support: RVO:67985891 Keywords : intracontinental Miocene * Czech Republic * geochemistry * organic matter * paleolake evolution Subject RIV: DD - Geochemistry OBOR OECD: Geology Impact factor: 2.017, year: 2016

  8. A new short-rostrum odontocete (Mammalia: Cetacea) from the middle Miocene of the Eastern Netherlands

    NARCIS (Netherlands)

    Bianucci, G.; Landini, W.

    2002-01-01

    An incomplete odontocete (Mammalia, Cetacea) skull from Middle Miocene Miste Bed (near Winterswijk in the eastern part of The Netherlands) is described as Vanbreenia trigonia, a new genus and species. The skull exhibits a short rostrum with only two maxillary teeth for each toothrow and with narrow

  9. Whiting–related sediment export along the Middle Miocene carbonate ramp of Great Bahama Bank.

    NARCIS (Netherlands)

    Turpin, M.; Emmanuel, L.; Reijmer, J.J.G.; Renard, M.

    2011-01-01

    Modern aragonite needles are present all along the modern leeward margin of Great Bahama Bank (ODP Leg 166), while Middle Miocene sediments contain needles only in more distal areas (Sites 1006 and 1007). In contrast to the rimmed, flat-topped platform topography during the Plio-Pleistocene, the

  10. The westernmost tarsier: A new genus and species from the Miocene of Pakistan

    NARCIS (Netherlands)

    Zijlstra, Jelle S.; Flynn, Lawrence J.; Wessels, Wilma

    2013-01-01

    As the closest living sister group of anthropoids, tarsiers (Family Tarsiidae) are an important group in primate evolution. However, their fossil record is poor: only four species have been described, two from the Eocene of China and two from the Miocene of Thailand. All are from outside the range

  11. The influence of late Miocene exhumation on the petroleum systems of the greater Caucasus foreland basins

    International Nuclear Information System (INIS)

    Andy, A.; Colin, D.; Sally, H.; Simon, O.

    2002-01-01

    Full text: Northwards impingement of Arabia during the Cenozoic led to the inversion of the Mesozoic Greater Caucasus Basin and the associated development of areas of enhanced subsidence. However, there is great debate regarding the timing of initiation of thrusting and uplift in the Caucasus region.Traditionally, ages ranging from Middle Eocene through to Middle Miocene have been proposed.More recently. It has become clear that although deformation and flexural subsidence may have initiated during the Late Miocene to Pliocene.The potential causative mechanisms for this late uplift and exhumation did not begin until the Late Miocene to Pliocene.The potential causative mechanisms for this late uplift event have been identified.The late Miocene to Pliocene event influenced a broad region and had important implications for reservoir rock deposition and the generation,migration,trapping and preservation of hydrocarbons in the surrounding basins (e.g. Indolo-Kuban,Terek-Caspian, South Caspian, Kura-Kartli, Rion, Black Sea).One area of particular interest is the development of the Stavropol Arch through time,since foreland basins are presently restricted to the Indolo-Kuban and Terek-Caspian Sub-basins.The Stavropol Arch lies immediately north of the central, most elevated parts of the Caucasus Mountains and separates the main areas of enhanced foreland subsidence.Although in most palaeogeographic reconstructions of the area, the Stavropol Arch is shown as an uplifted massif during much of the Mesozoic and Lower Cenozoic, it seems likely from recent studies that it is a feature of Late Miocene to Pliocene exhumation.One major potential implication is that an Oligocene to Miocene (foreland) succession developed in a major basin across the whole region north of the Greater Caucasus.Much of this was subsequently eroded from the Stavropol Arch during uplift and exhumation, separating the Indolo-Kuban and Terek-Caspian foreland basins.From qualitative section balancing we

  12. Orbitally-paced variations of water availability in the SE Asian Monsoon region following the Miocene Climate Transition

    Science.gov (United States)

    Heitmann, Emma O.; Ji, Shunchuan; Nie, Junsheng; Breecker, Daniel O.

    2017-09-01

    Middle Miocene Earth had several boundary conditions similar to those predicted for future Earth including similar atmospheric pCO2 and substantial Antarctic ice cover but no northern hemisphere ice sheets. We describe a 12 m outcrop of the terrestrial Yanwan Section in the Tianshui Basin, Gansu, China, following the Miocene Climate Transition (13.9-13.7 Ma). It consists of ∼25 cm thick CaCO3-cemented horizons that overprint siltstones every ∼1 m. We suggest that stacked soils developed in siltstones under a seasonal climate with a fluctuating water table, evidenced by roots, clay films, mottling, presence of CaCO3 nodules, and stacked carbonate nodule δ13 C and δ18 O profiles that mimic modern soils. We suggest that the CaCO3-cemented horizons are capillary-fringe carbonates that formed in an arid climate with a steady water table and high potential evapotranspiration rates (PET), evidenced by sharp upper and basal contacts, micrite, sparite, and root-pore cements. The CaCO3 of the cemented horizons and the carbonate nodules have similar mean δ18 O and δ13 C values but the cements have significantly smaller variance in δ13 C and δ18 O values and a different δ18 O versus δ13 C slope, supporting the conclusion that these carbonates are from different populations. The magneto-stratigraphic age model indicates obliquity pacing of the arid conditions required to form the CaCO3-cemented horizons suggesting an orbital control on water availability. We suggest two possible drivers for the obliquity pacing of arid conditions: 1) variability in the cross-equatorial pressure gradient that controls summer monsoon (ASM) strength and is influenced by obliquity-paced variations of Antarctic ice volume and 2) variability in Western Pacific Ocean-East Asian continent pressure gradient controlled by the 25-45°N meridional insolation gradient. We also suggest that variations in aridity were influenced by variations in PET and sensible heating of the regional land

  13. Organic geochemical characteristics and paleoclimate conditions of the Miocene coals at the Çan-Durali (Çanakkale)

    Science.gov (United States)

    Hoş-Çebi, Fatma

    2017-05-01

    In this study, n-alkane and isoprenoid, saturated and aromatic biomarker distributions of Miocene coals in the Çan (Çanakkale) region, were studied to investigate organic geochemical characteristics, depositional environment, and hydrocarbon potential of these coals. Çan formation (Middle Miocene) unconformably overlies the basement Çan volcanites (Upper Oligocene-Lower Miocene). This formation is composed of lignite, clayey lignite, and ligniferous clayey levels of various thicknesses interlayering with clay and tuffite. The formation represents sediments of small lacustrine basins that are isolated by faults that are formed contemporaneously with Early-Middle Eocene volcanism. Coaliferous units are overlain by lower agglomerate levels. The Rock Eval analyses show that the average TOC (Total Organic Carbon) content of the coal is 53.71% and the average HI (Hydrogen Index) value is 180.5 mgHC/gTOC. OI (Oxygen Index) values (avg. 22.33 mgCO2/gTOC) show that the depositional environment of peat deposits is suboxic. According to HI-Tmax, S2-TOC classification diagrams and Pr/n-C17vs. Ph/n-C18 diagram, the organic matter is composed of Type II and Type III kerogen mixing and represents a transitional environment. In gas chromatograms, n-alkanes with high, mostly odd-numbered carbons are dominant and they are associated with a slight algal contribution. CPI22-30 (Carbon Preference Index) and TARHC (Terrigenous/Aquatic Ratio) values indicate a dominance of high-carbon numbered n-alkanes, indicating the presence of terrestrial organic matter. Paq (aquatic plant n-alkane proxy) values (0.2; 0.3) indicate a climate with relatively wet conditions or low precipitation, the presence of emergent macrophyteses, and the scarcity of hydrophilic plants. Pwax (vascular plant n-alkane proxy) ratio (0.8; 0.7) shows moderately wet conditions and a relatively low water level. The TOC, ACL (n-alkane average chain length), Qwood/grass, Qwood/plant, and Qgrass/plant values indicate the

  14. New sedimentological and palynological data from surface Miocene strata in the central Amazonas Basin area

    Directory of Open Access Journals (Sweden)

    Emílio Alberto Amaral Soares

    Full Text Available ABSTRACT The scarcity of stratigraphic data has hindered the demarcation of the outcropping area of Miocene deposits of the Amazon Basin, represented informally by the Novo Remanso Formation. Moreover, this unit is characterized by a sparse and irregular geographic distribution due to its sedimentological features and rare fossil content. Miocene deposits cropping out in central Amazonas Basin area were described in sedimentological terms and analyzed palynologically. All analyses were undertaken in samples collected at the Uatumã River banks (Itapiranga and São Sebastião do Uatumã cities. Lithostratigraphic data shows that Novo Remanso Formation consists of sandstones, with subordinate conglomerates and pelites, characteristic of a meandering fluvial paleosystem, with fluvial channel, point bar, floodplain and crevasse splay facies. The palynoflora retrieved from five samples consists exclusively of continental-origin palynomorphs dominated by angiosperms species. Trilete spores are well represented, while gymnosperms pollen grains are minor components. The presence of Psilastephanoporites tesseroporus, Syncolporites poricostatus, Jandufouria seamrogiformis and Polypodiaceoisporites potoniei ensure these deposits fits into the Grimsdalea magnaclavata palynozone (Regali et al. 1974a, b, and the Grimsdalea magnaclavata/Crassoretitriletes vanraadshooveni palynozones of Jaramillo et al. (2011 considered Middle Miocene age. This age is confirmed by the zonation of Jaramillo et al. (2011, based on the LADs of Bombacacidites baumfalki (11.57Ma and Crototricolpites annemariae (12.91Ma; and the FAD of Psilastephanoporites tesseroporus (14.00Ma. With these new data presented herein, it is possible to assume that the Miocene strata represented by the Novo Remanso Formation covers a larger area in the basin than previously considered, and that it may be extended for about 300 km until the Manacapuru village, indicating a Miocene subsidence phase.

  15. Plate tectonic model for the oligo-miocene evolution of the western Mediterranean

    Science.gov (United States)

    Cohen, Curtis R.

    1980-10-01

    This paper outlines a plate tectonic model for the Oligo-Miocene evolution of the western Mediterranean which incorporates recent data from several tectonic domains (Corsica, Sardinia, the Kabylies, Balearic promontory, Iberia, Algero-Provençal Basin and Tunisian Atlas). Following late Mesozoic anticlockwise rotation of the Iberian peninsula (including the Balearic promontory and Sardinia), late Eocene collision occurred between the Kabylies and Balearic promontory forming a NE-trending suture with NW-tectonic polarity. As a result of continued convergence between the African and European plates, a polarity flip occurred and a southward-facing trench formed south of the Kabylie—Balearic promontory suture. During late Oligocene time an E-W-trending arc and marginal basin developed behind the southward-facing trench in the area of the present-day Gulf of Lion. Opening of this basin moved the Corsica—Sardinia—Calabria—Petit Kabylie—Menorca plate southward, relative to the African plate. Early Miocene back-arc spreading in the area between the Balearic promontory and Grand Kabylie emplaced the latter in northern Algeria and formed the South Balearic Basin. Coeval with early Miocene back-arc basin development, the N-S-extension in the Gulf of Lion marginal basin changed to a more NW-SE direction causing short-lived extension in the area of the present-day Valencia trough and a 30° anticlockwise rotation of the Corsica-Sardinia-Calabria—Petit Kabylie plate away from the European plate. Early—middle Miocene deformation along the western Italian and northeastern African continental margins resulted from this rotation. During the early late Miocene (Tortonian), spreading within a sphenochasm to the southwest of Sardinia resulted in the emplacement of Petit Kabylie in northeastern Algeria.

  16. The early Miocene balaenid Morenocetus parvus from Patagonia (Argentina and the evolution of right whales

    Directory of Open Access Journals (Sweden)

    Mónica R. Buono

    2017-12-01

    Full Text Available Balaenidae (right and bowhead whales are a key group in understanding baleen whale evolution, because they are the oldest surviving lineage of crown Mysticeti, with a fossil record that dates back ∼20 million years. However, this record is mostly Pliocene and younger, with most of the Miocene history of the clade remaining practically unknown. The earliest recognized balaenid is the early Miocene Morenocetus parvus Cabrera, 1926 from Argentina. M. parvus was originally briefly described from two incomplete crania, a mandible and some cervical vertebrae collected from the lower Miocene Gaiman Formation of Patagonia. Since then it has not been revised, thus remaining a frequently cited yet enigmatic fossil cetacean with great potential for shedding light on the early history of crown Mysticeti. Here we provide a detailed morphological description of this taxon and revisit its phylogenetic position. The phylogenetic analysis recovered the middle Miocene Peripolocetus as the earliest diverging balaenid, and Morenocetus as the sister taxon of all other balaenids. The analysis of cranial and periotic morphology of Morenocetus suggest that some of the specialized morphological traits of modern balaenids were acquired by the early Miocene and have remained essentially unchanged up to the present. Throughout balaenid evolution, morphological changes in skull arching and ventral displacement of the orbits appear to be coupled and functionally linked to mitigating a reduction of the field of vision. The body length of Morenocetus and other extinct balaenids was estimated and the evolution of body size in Balaenidae was reconstructed. Optimization of body length on our phylogeny of Balaenidae suggests that the primitive condition was a relatively small body length represented by Morenocetus, and that gigantism has been acquired independently at least twice (in Balaena mysticetus and Eubalaena spp., with the earliest occurrence of this trait in the late

  17. A new age model for the early-middle Miocene in the North Alpine Foreland Basin

    Science.gov (United States)

    Reichenbacher, Bettina; Krijgsman, Wout; Pippèrr, Martina; Sant, Karin; Kirscher, Uwe

    2016-04-01

    The establishment of high-resolution age models for sedimentary successions is crucial for numerous research questions in the geosciences and related disciplines. Such models provide an absolute chronology that permits precise dating of depositional episodes and related processes such as mountain uplift or climate change. Recently, our work in the Miocene sediments of the North Alpine Foreland Basin (NAFB) has revealed a significantly younger age (16.6 Myr) for sediments that were thought to have been deposited 18 Myr ago. This implies that a fundamentally revised new age model is needed for the entire suite of lower-middle Miocene sedimentary rocks in the NAFB (20 to 15-Myr). Our new data also indicate that previously published reconstructions of early-middle Miocene palaeogeography, sedimentation dynamics, mountain uplift and climate change in the NAFB all require a critical review and revision. Further, the time-span addressed is of special interest, since it encompasses the onset of a global warming phase. However, it appears that a fundamentally revised new age model for the entire suite of lower-middle Miocene sedimentary rocks in the NAFB can only be achieved based on a 500 m deep drilling in the NAFB for which we currently seek collaboration partners to develop a grant application to the International Continental Deep Drilling Program (ICDP). Reference: Reichenbacher, B., W. Krijgsman, Y. Lataster, M. Pippèrr, C. G. C. Van Baak, L. Chang, D. Kälin, J. Jost, G. Doppler, D. Jung, J. Prieto, H. Abdul Aziz, M. Böhme, J. Garnish, U. Kirscher, and V. Bachtadse. 2013. A new magnetostratigraphic framework for the Lower Miocene (Burdigalian/Ottnangian, Karpatian) in the North Alpine Foreland Basin. Swiss Journal of Geosciences 106:309-334.

  18. The early Miocene balaenid Morenocetus parvus from Patagonia (Argentina) and the evolution of right whales

    Science.gov (United States)

    Cozzuol, Mario A.; Fitzgerald, Erich M.G.

    2017-01-01

    Balaenidae (right and bowhead whales) are a key group in understanding baleen whale evolution, because they are the oldest surviving lineage of crown Mysticeti, with a fossil record that dates back ∼20 million years. However, this record is mostly Pliocene and younger, with most of the Miocene history of the clade remaining practically unknown. The earliest recognized balaenid is the early Miocene Morenocetus parvus Cabrera, 1926 from Argentina. M. parvus was originally briefly described from two incomplete crania, a mandible and some cervical vertebrae collected from the lower Miocene Gaiman Formation of Patagonia. Since then it has not been revised, thus remaining a frequently cited yet enigmatic fossil cetacean with great potential for shedding light on the early history of crown Mysticeti. Here we provide a detailed morphological description of this taxon and revisit its phylogenetic position. The phylogenetic analysis recovered the middle Miocene Peripolocetus as the earliest diverging balaenid, and Morenocetus as the sister taxon of all other balaenids. The analysis of cranial and periotic morphology of Morenocetus suggest that some of the specialized morphological traits of modern balaenids were acquired by the early Miocene and have remained essentially unchanged up to the present. Throughout balaenid evolution, morphological changes in skull arching and ventral displacement of the orbits appear to be coupled and functionally linked to mitigating a reduction of the field of vision. The body length of Morenocetus and other extinct balaenids was estimated and the evolution of body size in Balaenidae was reconstructed. Optimization of body length on our phylogeny of Balaenidae suggests that the primitive condition was a relatively small body length represented by Morenocetus, and that gigantism has been acquired independently at least twice (in Balaena mysticetus and Eubalaena spp.), with the earliest occurrence of this trait in the late Miocene

  19. Petroleum systems of the Upper Magdalena Valley, Colombia

    Energy Technology Data Exchange (ETDEWEB)

    Sarmiento, L.F.; Rangel, A. [Instituto Colombiano del Petroleo, Bucaramanga (Colombia). ECOPETROL

    2004-03-01

    In the Upper Magdalena Valley, Colombia, four petroleum systems were identified. Two petroleum systems are located in the Girardot sub-basin and the other two in the Neiva sub- basin. Limestones laterally changing to shales of the lower part of the Villeta Gp, deposited during Albian and Turonian marine flooding events, constitutes the main source rocks of the oil families. These rocks contain 1-4% TOC and type II kerogen. The littoral quartz arenites of the Caballos (Albian) and Monserrate (Maastrichtian) Fms. are the main reservoir rocks. Seal rocks are Cretaceous and Paleocene shales. Overburden includes the Cretaceous rocks and the Tertiary molasse deposited simultaneously with development of two opposite verging thrust systems during Cenozoic time. These deformation events were responsible for trap creation. Except for the Villarrica area, where the source rock reached maturity during the Paleocene, generation occurred during Miocene. Two oil families are identified, each in both sub-basins: One derived from a clay-rich source and the second from a carbonate-rich source rock lithofacies of the lower part of Villeta Gp. Geochemical source-rock to oil correlations are demonstrated for the three of the petroleum systems. Up-dip lateral migration distances are relatively short and faults served as vertical migration pathways. A huge amount of oil was probably degraded at surface, as a result of Miocene deformation and erosion. (author)

  20. Gratkorn - A new late Middle Miocene vertebrate fauna from Styria (Late Sarmatian, Austria)

    Science.gov (United States)

    Gross, M.; Böhme, M.; Prieto, J.

    2009-04-01

    Integrated stratigraphic approaches provide precise correlations of global standard stages with regional Paratethys stages. Nevertheless, higher resolution stratigraphic matching of terrestrial deposits remains challenging due to the lack of a practical continental biostratigraphy. The mostly used tool for biostratigraphic correlation of non-marine deposits in the Old World is still the concept of Neogene Mammal-zones (MN-zones). However, at higher biostratigraphic resolution (reptiles (scincids, lacertids, gekkonids, anguids, varanids, colubrids, testudinids, emydids), birds (coliiformes), rodents and lagomorphs (cricetids, glirids, eomyids, sciurids, castorids), insectivores and chiropterans (erinaceids, soricids, talpids), and large mammals (suids, tragulids, moschids, cervids, ?palaeomerycids, equids, chalicotheriids, rhinos, proboscidians, carnivors). Litho- and biostratigraphy (terrestrial gastropods) as well as magnetostratigraphic data and the sequence stratigraphic and geodynamic frame indicate an age of 12-12.2 Ma (early Late Sarmatian s.str., chron 5An.1n) for the locality. Therefore, Gratkorn is one of richest and most complete fauna of the late Middle Miocene of Central Europe and will be confidentially one of the key faunas for a high-resolution continental biostratigraphy and the comprehension of the faunal succession and interchanges near the Middle/Late Miocene transition. Acknowledgements This is a preliminary overview of the Gratkorn vertebrate fauna. Several taxa are still under investigation. We are especially grateful to Gudrun Daxner-Höck, Ursula Göhlich (both Natural History Museum Vienna) and Getrud Rössner (University of Munich) for their comments to the rodents, ruminants, proboscidians and bird remains. References Böhme, M., Ilg, A., Winklhofer, M. 2008. Late Miocene "washhouse" climate in Europe.- Earth and Planetary Science Letters, 275: 393-401. Gross, M., 2008. A limnic ostracod fauna from the surroundings of the Central

  1. Nonvariceal upper gastrointestinal bleeding

    International Nuclear Information System (INIS)

    Burke, Stephen J.; Weldon, Derik; Sun, Shiliang; Golzarian, Jafar

    2007-01-01

    Nonvariceal upper gastrointestinal bleeding (NUGB) remains a major medical problem even after advances in medical therapy with gastric acid suppression and cyclooxygenase (COX-2) inhibitors. Although the incidence of upper gastrointestinal bleeding presenting to the emergency room has slightly decreased, similar decreases in overall mortality and rebleeding rate have not been experienced over the last few decades. Many causes of upper gastrointestinal bleeding have been identified and will be reviewed. Endoscopic, radiographic and angiographic modalities continue to form the basis of the diagnosis of upper gastrointestinal bleeding with new research in the field of CT angiography to diagnose gastrointestinal bleeding. Endoscopic and angiographic treatment modalities will be highlighted, emphasizing a multi-modality treatment plan for upper gastrointestinal bleeding. (orig.)

  2. Nonvariceal upper gastrointestinal bleeding

    Energy Technology Data Exchange (ETDEWEB)

    Burke, Stephen J.; Weldon, Derik; Sun, Shiliang [University of Iowa, Department of Radiology, Iowa, IA (United States); Golzarian, Jafar [University of Iowa, Department of Radiology, Iowa, IA (United States); University of Iowa, Department of Radiology, Carver College of Medicine, Iowa, IA (United States)

    2007-07-15

    Nonvariceal upper gastrointestinal bleeding (NUGB) remains a major medical problem even after advances in medical therapy with gastric acid suppression and cyclooxygenase (COX-2) inhibitors. Although the incidence of upper gastrointestinal bleeding presenting to the emergency room has slightly decreased, similar decreases in overall mortality and rebleeding rate have not been experienced over the last few decades. Many causes of upper gastrointestinal bleeding have been identified and will be reviewed. Endoscopic, radiographic and angiographic modalities continue to form the basis of the diagnosis of upper gastrointestinal bleeding with new research in the field of CT angiography to diagnose gastrointestinal bleeding. Endoscopic and angiographic treatment modalities will be highlighted, emphasizing a multi-modality treatment plan for upper gastrointestinal bleeding. (orig.)

  3. Structural and numerical modeling of fluid flow and evolving stress fields at a transtensional stepover: A Miocene Andean porphyry copper system as a case study.

    Science.gov (United States)

    Nuñez, R. C.; Griffith, W. A.; Mitchell, T. M.; Marquardt, C.; Iturrieta, P. C.; Cembrano, J. M.

    2017-12-01

    Obliquely convergent subduction orogens show both margin-parallel and margin-oblique fault systems that are spatially and temporally associated with ore deposits and geothermal systems within the volcanic arc. Fault orientation and mechanical interaction among different fault systems influence the stress field in these arrangements, thus playing a first order control on the regional to local-scale fluid migration paths as documented by the spatial distribution of fault-vein arrays. Our selected case study is a Miocene porphyry copper-type system that crops out in the precordillera of the Maule region along the Teno river Valley (ca. 35°S). Several regional to local faults were recognized in the field: (1) Two first-order, N-striking subvertical dextral faults overlapping at a right stepover; (2) Second-order, N60°E-striking steeply-dipping, dextral-normal faults located at the stepover, and (3) N40°-60°W striking subvertical, sinistral faults crossing the stepover zone. The regional and local scale geology is characterized by volcano-sedimentary rocks (Upper Eocene- Lower Miocene), intruded by Miocene granodioritic plutons (U-Pb zircon age of 18.2 ± 0.11 Ma) and coeval dikes. We implement a 2D boundary element displacement discontinuity method (BEM) model to test the mechanical feasibility of kinematic model of the structural development of the porphyry copper-type system in the stepover between N-striking faults. The model yields the stress field within the stepover region and shows slip and potential opening distribution along the N-striking master faults under a regionally imposed stress field. The model shows that σ1 rotates clockwise where the main faults approach each other, becoming EW when they overlap. This, in turn leads to the generation of both NE- and NW-striking faults within the stepover area. Model results are consistent with the structural and kinematic data collected in the field attesting for enhanced permeability and fluid flow transport

  4. High-precision zircon U-Pb geochronology of astronomically dated volcanic ash beds from the Mediterranean Miocene

    NARCIS (Netherlands)

    Wotzlaw, Jörn Frederik; Hüsing, Silja K.; Hilgen, Frederik J.; Schaltegger, Urs

    2014-01-01

    Several orbitally tuned Miocene sedimentary sequences around the Mediterranean contain abundant intercalated volcanic ash beds. These sequences provide the rare opportunity to directly compare radioisotopic dating methods with independent and accurate deposition ages derived from astrochronology. We

  5. Supra-generic radiolarian transfer function based late Miocene palaeomonsoonal changes in the northeastern tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.; Fernandes, A.A.

    and PPT changes using % data of the late Miocene radiolarian sequence from the Sawai Bay Formation, Neill Island, Andamans. Estimated SST and salinity during southwest monsoon are not only conformable with the qualitative paleoceanography in terms...

  6. Fossil mice and rats show isotopic evidence of niche partitioning and change in dental ecomorphology related to dietary shift in Late Miocene of Pakistan.

    Science.gov (United States)

    Kimura, Yuri; Jacobs, Louis L; Cerling, Thure E; Uno, Kevin T; Ferguson, Kurt M; Flynn, Lawrence J; Patnaik, Rajeev

    2013-01-01

    Stable carbon isotope analysis in tooth enamel is a well-established approach to infer C3 and C4 dietary composition in fossil mammals. The bulk of past work has been conducted on large herbivorous mammals. One important finding is that their dietary habits of fossil large mammals track the late Miocene ecological shift from C3 forest and woodland to C4 savannah. However, few studies on carbon isotopes of fossil small mammals exist due to limitations imposed by the size of rodent teeth, and the isotopic ecological and dietary behaviors of small mammals to climate change remain unknown. Here we evaluate the impact of ecological change on small mammals by fine-scale comparisons of carbon isotope ratios (δ(13)C) with dental morphology of murine rodents, spanning 13.8 to ∼2.0 Ma, across the C3 to C4 vegetation shift in the Miocene Siwalik sequence of Pakistan. We applied in-situ laser ablation GC-IRMS to lower first molars and measured two grazing indices on upper first molars. Murine rodents yield a distinct, but related, record of past ecological conditions from large herbivorous mammals, reflecting available foods in their much smaller home ranges. In general, larger murine species show more positive δ(13)C values and have higher grazing indices than smaller species inhabiting the same area at any given age. Two clades of murine rodents experienced different rates of morphological change. In the faster-evolving clade, the timing and trend of morphological innovations are closely tied to consumption of C4 diet during the vegetation shift. This study provides quantitative evidence of linkages among diet, niche partitioning, and dental morphology at a more detailed level than previously possible.

  7. Facies associations, depositional environments and stratigraphic framework of the Early Miocene-Pleistocene successions of the Mukah-Balingian Area, Sarawak, Malaysia

    Science.gov (United States)

    Murtaza, Muhammad; Rahman, Abdul Hadi Abdul; Sum, Chow Weng; Konjing, Zainey

    2018-02-01

    Thirty-five stratigraphic section exposed along the Mukah-Selangau road in the Mukah-Balingian area have been studied. Sedimentological and palynological data have been integrated to gain a better insight into the depositional architecture of the area. Broadly, the Mukah-Balingian area is dominated by fluvial, floodplain and estuarine related coal-bearing deposits. The Balingian, Begrih and Liang formations have been described and interpreted in terms of seven facies association. These are: FA1 - Fluvial-dominated channel facies association; FA2 - Tide-influenced channel facies association; FA3 - Tide-dominated channel facies association; FA4 - Floodplain facies association; FA5 - Estuarine central basin-mud flats facies association; FA6 - Tidal flat facies association and FA7 - Coastal swamps and marshes facies association. The Balingian Formation is characterised by the transgressive phase in the base, followed by a regressive phase in the upper part. On the basis of the occurrence of Florscheutzia trilobata with Florscheutzia levipoli, the Early to Middle Miocene age has been assigned to the Balingian Formation. The distinct facies pattern and foraminifera species found from the samples taken from the Begrih outcrop imply deposition in the intertidal flats having pronounced fluvio-tidal interactions along the paleo-margin. Foraminiferal data combined with the pronounced occurrence of Stenochlaena laurifolia suggest at least the Late Miocene age for the Begrih Formation. The internal stratigraphic architecture of the Liang Formation is a function of a combination of sea level, stable tectonic and autogenic control. Based on stratigraphic position, the Middle Pliocene to Pleistocene age for the Liang Formation is probable. The Balingian, Begrih and Liang formations display deposits of multiple regressive-transgressive cycles while the sediments were derived from the uplifted Penian high and Rajang group.

  8. Fossil Mice and Rats Show Isotopic Evidence of Niche Partitioning and Change in Dental Ecomorphology Related to Dietary Shift in Late Miocene of Pakistan

    Science.gov (United States)

    Kimura, Yuri; Jacobs, Louis L.; Cerling, Thure E.; Uno, Kevin T.; Ferguson, Kurt M.; Flynn, Lawrence J.; Patnaik, Rajeev

    2013-01-01

    Stable carbon isotope analysis in tooth enamel is a well-established approach to infer C3 and C4 dietary composition in fossil mammals. The bulk of past work has been conducted on large herbivorous mammals. One important finding is that their dietary habits of fossil large mammals track the late Miocene ecological shift from C3 forest and woodland to C4 savannah. However, few studies on carbon isotopes of fossil small mammals exist due to limitations imposed by the size of rodent teeth, and the isotopic ecological and dietary behaviors of small mammals to climate change remain unknown. Here we evaluate the impact of ecological change on small mammals by fine-scale comparisons of carbon isotope ratios (δ13C) with dental morphology of murine rodents, spanning 13.8 to ∼2.0 Ma, across the C3 to C4 vegetation shift in the Miocene Siwalik sequence of Pakistan. We applied in-situ laser ablation GC-IRMS to lower first molars and measured two grazing indices on upper first molars. Murine rodents yield a distinct, but related, record of past ecological conditions from large herbivorous mammals, reflecting available foods in their much smaller home ranges. In general, larger murine species show more positive δ13C values and have higher grazing indices than smaller species inhabiting the same area at any given age. Two clades of murine rodents experienced different rates of morphological change. In the faster-evolving clade, the timing and trend of morphological innovations are closely tied to consumption of C4 diet during the vegetation shift. This study provides quantitative evidence of linkages among diet, niche partitioning, and dental morphology at a more detailed level than previously possible. PMID:23936324

  9. Fossil mice and rats show isotopic evidence of niche partitioning and change in dental ecomorphology related to dietary shift in Late Miocene of Pakistan.

    Directory of Open Access Journals (Sweden)

    Yuri Kimura

    Full Text Available Stable carbon isotope analysis in tooth enamel is a well-established approach to infer C3 and C4 dietary composition in fossil mammals. The bulk of past work has been conducted on large herbivorous mammals. One important finding is that their dietary habits of fossil large mammals track the late Miocene ecological shift from C3 forest and woodland to C4 savannah. However, few studies on carbon isotopes of fossil small mammals exist due to limitations imposed by the size of rodent teeth, and the isotopic ecological and dietary behaviors of small mammals to climate change remain unknown. Here we evaluate the impact of ecological change on small mammals by fine-scale comparisons of carbon isotope ratios (δ(13C with dental morphology of murine rodents, spanning 13.8 to ∼2.0 Ma, across the C3 to C4 vegetation shift in the Miocene Siwalik sequence of Pakistan. We applied in-situ laser ablation GC-IRMS to lower first molars and measured two grazing indices on upper first molars. Murine rodents yield a distinct, but related, record of past ecological conditions from large herbivorous mammals, reflecting available foods in their much smaller home ranges. In general, larger murine species show more positive δ(13C values and have higher grazing indices than smaller species inhabiting the same area at any given age. Two clades of murine rodents experienced different rates of morphological change. In the faster-evolving clade, the timing and trend of morphological innovations are closely tied to consumption of C4 diet during the vegetation shift. This study provides quantitative evidence of linkages among diet, niche partitioning, and dental morphology at a more detailed level than previously possible.

  10. Lineage-specific responses of tooth shape in murine rodents (murinae, rodentia) to late Miocene dietary change in the Siwaliks of Pakistan.

    Science.gov (United States)

    Kimura, Yuri; Jacobs, Louis L; Flynn, Lawrence J

    2013-01-01

    Past ecological responses of mammals to climate change are recognized in the fossil record by adaptive significance of morphological variations. To understand the role of dietary behavior on functional adaptations of dental morphology in rodent evolution, we examine evolutionary change of tooth shape in late Miocene Siwalik murine rodents, which experienced a dietary shift toward C4 diets during late Miocene ecological change indicated by carbon isotopic evidence. Geometric morphometric analysis in the outline of upper first molars captures dichotomous lineages of Siwalik murines, in agreement with phylogenetic hypotheses of previous studies (two distinct clades: the Karnimata and Progonomys clades), and indicates lineage-specific functional responses to mechanical properties of their diets. Tooth shapes of the two clades are similar at their sympatric origin but deviate from each other with decreasing overlap through time. Shape change in the Karnimata clade is associated with greater efficiency of propalinal chewing for tough diets than in the Progonomys clade. Larger body mass in Karnimata may be related to exploitation of lower-quality food items, such as grasses, than in smaller-bodied Progonomys. The functional and ecophysiological aspects of Karnimata exploiting C4 grasses are concordant with their isotopic dietary preference relative to Progonomys. Lineage-specific selection was differentially greater in Karnimata, and a faster rate of shape change toward derived Karnimata facilitated inclusion of C4 grasses in the diet. Sympatric speciation in these clades is most plausibly explained by interspecific competition on resource utilization between the two, based on comparisons of our results with the carbon isotope data. Interspecific competition with Karnimata may have suppressed morphological innovation of the Progonomys clade. Pairwise analyses of morphological and carbon isotope data can uncover ecological causes of sympatric speciation and define

  11. Lineage-specific responses of tooth shape in murine rodents (murinae, rodentia to late Miocene dietary change in the Siwaliks of Pakistan.

    Directory of Open Access Journals (Sweden)

    Yuri Kimura

    Full Text Available Past ecological responses of mammals to climate change are recognized in the fossil record by adaptive significance of morphological variations. To understand the role of dietary behavior on functional adaptations of dental morphology in rodent evolution, we examine evolutionary change of tooth shape in late Miocene Siwalik murine rodents, which experienced a dietary shift toward C4 diets during late Miocene ecological change indicated by carbon isotopic evidence. Geometric morphometric analysis in the outline of upper first molars captures dichotomous lineages of Siwalik murines, in agreement with phylogenetic hypotheses of previous studies (two distinct clades: the Karnimata and Progonomys clades, and indicates lineage-specific functional responses to mechanical properties of their diets. Tooth shapes of the two clades are similar at their sympatric origin but deviate from each other with decreasing overlap through time. Shape change in the Karnimata clade is associated with greater efficiency of propalinal chewing for tough diets than in the Progonomys clade. Larger body mass in Karnimata may be related to exploitation of lower-quality food items, such as grasses, than in smaller-bodied Progonomys. The functional and ecophysiological aspects of Karnimata exploiting C4 grasses are concordant with their isotopic dietary preference relative to Progonomys. Lineage-specific selection was differentially greater in Karnimata, and a faster rate of shape change toward derived Karnimata facilitated inclusion of C4 grasses in the diet. Sympatric speciation in these clades is most plausibly explained by interspecific competition on resource utilization between the two, based on comparisons of our results with the carbon isotope data. Interspecific competition with Karnimata may have suppressed morphological innovation of the Progonomys clade. Pairwise analyses of morphological and carbon isotope data can uncover ecological causes of sympatric speciation

  12. lower and Middle Miocene Foraminiferal Paleoecology of Southwest Sinai Area, Egypt

    International Nuclear Information System (INIS)

    El Ashwah, A.A.E.; Mandur, M.M.; Obeid, F.L.

    2005-01-01

    The planktonic and benthonic foraminifera content of the lower and middle miocene successions exposed at southwest Sinai in Egypt have been studied. One hundred and thirty three foraminifera species were identified (30 planktonic species and 103 benthonic species). This study aims to contribute in the understanding of the paleoecology, paleobathymetry and tectonic history of these sedimentary sequences. These sediments are subdivided into four rock units, from base to top, as follow: Nukhul, Rudeis, Kareem and Balayim formations. According to the foraminifera content the studied successions are subdivided into five eco zones. The environment of each ec ozone is deduced. These environments point to outer neritic for the Nukhul formation, middle to inner neritic for the Rudeis formation, inner to littoral neritic for the Kareem formation and littoral neritic for the Belayim formation. A proposed paleobathymetric curve is presented. The interpretation of this curve helped to deduce the tectonic history of the lower and Middle Miocene sediments in the studied area

  13. Miocene small-bodied ape from Eurasia sheds light on hominoid evolution.

    Science.gov (United States)

    Alba, David M; Almécija, Sergio; DeMiguel, Daniel; Fortuny, Josep; Pérez de los Ríos, Miriam; Pina, Marta; Robles, Josep M; Moyà-Solà, Salvador

    2015-10-30

    Miocene small-bodied anthropoid primates from Africa and Eurasia are generally considered to precede the divergence between the two groups of extant catarrhines—hominoids (apes and humans) and Old World monkeys—and are thus viewed as more primitive than the stem ape Proconsul. Here we describe Pliobates cataloniae gen. et sp. nov., a small-bodied (4 to 5 kilograms) primate from the Iberian Miocene (11.6 million years ago) that displays a mosaic of primitive characteristics coupled with multiple cranial and postcranial shared derived features of extant hominoids. Our cladistic analyses show that Pliobates is a stem hominoid that is more derived than previously described small catarrhines and Proconsul. This forces us to reevaluate the role played by small-bodied catarrhines in ape evolution and provides key insight into the last common ancestor of hylobatids (gibbons) and hominids (great apes and humans). Copyright © 2015, American Association for the Advancement of Science.

  14. Differential responses of Miocene rodent metacommunities to global climatic changes were mediated by environmental context.

    Science.gov (United States)

    Blanco, Fernando; Gómez Cano, Ana Rosa; Cantalapiedra, Juan L; Domingo, M Soledad; Domingo, Laura; Menéndez, Iris; Flynn, Lawrence J; Hernández Fernández, Manuel

    2018-02-06

    The study of how long-term changes affect metacommunities is a relevant topic, that involves the evaluation of connections among biological assemblages across different spatio-temporal scales, in order to fully understand links between global changes and macroevolutionary patterns. We applied multivariate statistical analyses and diversity tests using a large data matrix of rodent fossil sites in order to analyse long-term faunal changes. Late Miocene rodent faunas from southwestern Europe were classified into metacommunities, presumably sharing ecological affinities, which followed temporal and environmental non-random assembly and disassembly patterns. Metacommunity dynamics of these faunas were driven by environmental changes associated with temperature variability, but there was also some influence from the aridity shifts described for this region during the late Miocene. Additionally, while variations in the structure of rodent assemblages were directly influenced by global climatic changes in the southern province, the northern sites showed a pattern of climatic influence mediated by diversity-dependent processes.

  15. Pollen analysis of coal-bearing Miocene sedimentary rocks from the Seyitomer basin (Kutahya), western Anatolia

    Energy Technology Data Exchange (ETDEWEB)

    Yavuz-Isik, N. [Ondokuz Mayis University, Kurupelit (Turkey). Dept. of Civil Engineering

    2007-09-15

    The late Early-Middle Miocene sequences of the Seyitomer Basin (western Anatolia) were palynologically investigated. Fifty-five taxa belonging to seven gymnospermous and 48 angiospermous pollen genera were identified in the 19 productive samples. Two pollen zones were recognised based on the changing abundance of individual tree taxa. Zone 1 is characterized by predominance of Pinus and Cedrus. Zone 2 is characterized by predominance of deciduous Quercus and evergreen Quercus and a marked reduction in representation of Taxodiaceae. The differences in the pollen spectra between Zone 1 and Zone 2 may reflect the global Middle Miocene cooling. These results are largely comparable to pollen data derived from the neighbouring areas. The vegetation of the Seyitomer Basin was dominated by trees. This palynological analysis reveals the existence of a swamp-forest developed in a subtropical to warm-temperate humid climate.

  16. Magnetostratigraphy of the Vallesian (late Miocene) in the Vallès-Penedès Basin (northeast Spain)

    Science.gov (United States)

    Garcés, M.; Agustí, J.; Cabrera, L.; Parés, J. M.

    1996-08-01

    The magnetostratigraphic analysis of the late Miocene continental deposits from the Vallès-Penedès Basin, combined with its well-documented fossil mammal record, has provided a well-resolved chronology for the upper basin infill. The study is based on the biostratigraphic and magnetostratigraphic cross-correlation of 12 sections throughout the alluvial sequences in the western Vallès area. The biostratigraphic framework consists of 21 mammal localities corresponding to the Mammal Neogene MN9 and MN10 units. The composite magnetic polarity sequence is based on 400 paleomagnetic sites. Correlation with the Geomagnetic Polarity Time Scale (GPTS) has led to an absolute dating of the faunal events and a precise chronostratigraphy of the Vallesian mammal stage in its type area. The Hipparion First Appearance Datum (FAD), at the MN8/MN9 boundary, is dated at 11.1 Ma in the Vallès-Penedès Basin. This age, compared to other radiometrically dated localities in Europe, North Africa and Turkey, is consistent with an isochronous dispersal of this equid through the Mediterranean region. A possible isochrony at a larger geographical scale (Old World, Mesogea) must await more reliable ages of the Hipparion FAD in Asia and Africa. The Cricetulodon FAD ( MN9a/MN9b boundary) is dated to 10.4 Ma, in chron C5n. The Progonomys FAD ( MN9/MN10 boundary), corresponding to the intra-Vallesian faunal crisis, is dated at 9.7 Ma (C4Ar.3r). The Vallesian spans 2.4 Myr, from 11.1 Ma (C5r.1n) to 8.7 Ma (C4An) and correlates to the early Tortonian.

  17. Sedimentology, provenance and geochronology of the Miocene Qiuwu Formation: Implication for the uplift history of Southern Tibet

    Directory of Open Access Journals (Sweden)

    Jiawei Zhang

    2017-07-01

    Full Text Available Located on the south of the Gangdese, the Qiuwu Formation has traditionally been considered as Eocene coal-bearing clastic sediments consisting of sandstone, mudstone and conglomerate, unconformably on top of Gangdese batholith. However, its precise age and depositional environment remain ambiguous. Here, we present a newly measured stratigraphic section near the Ngamring County, western Xigaze. Detrital zircon U–Pb ages were also applied to trace the provenance of sediments and to constrain the maximum depositional age of the Qiuwu Formation. Sedimentary facies analyses indicate subaqueous fan and alluvial fan depositional environments. Clast composition of the conglomerate is dominated by magmatic rocks at the lower part, while chert and mafic detritus occur in the upper part, suggesting a southern source. Sandstone modal analyses indicate that the compositions of quartz, feldspar and lithic grains changed from transitional arc to dissected arc, implying the unroofing of the Gangdese arc. Detrital zircon U–Pb ages of the Qiuwu Formation are compared with those from Gangdese magmatic rocks and Yarlung-Zangbo ophiolites, suggesting that the Gangdese arc is a main source of the Qiuwu detritus and that the southern source played a role during the later stage. The major peak of detrital zircon ages is at 45–55 Ma, which corresponds to Linzizong volcanic rocks in southern Gangdese arc. The weighted mean age of the five youngest zircons from the lower part of the section is 21.0 ± 2.2 Ma, suggesting that the Qiuwu Formation was deposited in early Miocene, coeval with other conglomerates exposed along the southern margin of Gangdese. Combining new observations with previously published data, we propose that the provenance of the Qiuwu Formation had shifted from a single northern source to double sources from both the north and the south. Activities of Great Counter Thrust were primarily responsible for the shift by making the south area a

  18. Miocene block uplift and basin formation in the Patagonian foreland: The Gastre Basin, Argentina

    Science.gov (United States)

    Bilmes, A.; D'Elia, L.; Franzese, J. R.; Veiga, G. D.; Hernández, M.

    2013-08-01

    The intraplate fault-block mountains and intermontane deposits of the Gastre Basin, which are recorded more than 550 km east of the Andean trench in central Patagonia, Argentina, are analyzed. The Gastre Basin is one of the largest Patagonian intermontane basins, limited by uplifted blocks strongly oblique to the Andean chain. It was originated by reverse faulting and inversion of pre-existing normal faults associated with a Mesozoic rift basin and defined by older crustal heterogeneities. The deformational event occurred during the middle Miocene, related to a short contractional episode (16.1-14.86 Ma), probably in response to an eastward migration of the Andean fold and thrust belt. During Pliocene to Quaternary times, neither younger fault-block uplifts nor reconfigurations of the basin occurred. Similarities between the study area and other parts of the Patagonian foreland - such as the presence of Miocene reverse or inversion tectonics, as well as the accommodation of the Miocene sedimentary successions - suggest that the Gastre Basin is part of a major late early to middle Miocene broken foreland system (i.e. the Patagonian broken foreland) that exhumed discrete fault-block mountains and generated contemporary basins along more than 950 km parallel to the Andean trench (i.e. between 40°00' and 48°00' south latitude). Based on recent studies on the southern Andean Margin, this continental-scale contractional episode may be the result of a flat-slab subduction segment. Nevertheless, such a hypothesis is very difficult to support when analyzing such a large flat subduction segment along the entire Patagonian trench. This suggests the need to consider alternative flat-slab trigger mechanisms or other factors in the generation of broken foreland systems.

  19. Miocene climate variations in the Moesian Platform sediments based on sedimentology and biomarkers

    Science.gov (United States)

    Butiseaca, Geanina; Vasiliev, Iuliana; Rabagia, Traian; Dinu, Corneliu; Mulch, Andreas

    2017-04-01

    During the Miocene the Moesian Platform (southern Romania and northern Bulgaria) had a complicated flexural behavior due to the mobility of the nearby orogens. The different behavior induced varying sediment charges, sediment distribution and sediment types. The northern part of the study area (on which the Dacian Basin is overlaid) is characterized by siliciclastic units with dominantly deep facieses, while the southern part is characterized by carbonate production in shallower basin waters. Since the Miocene, the Dacian and Black Sea basins have been highly sensitive to fluctuations in the hydrological cycle. To establish the dynamic evolution of the basin and the climate variations during the Miocene, we have sampled both northern and southern margins of the basin. To discriminate between the tectonic imprint and the eustatic influence over the sedimentation rate we have chosen a multidisciplinary approach including sedimentology, tectonics and organic geochemistry based reconstructions. The sedimentary succession is interrupted by few unconformities correspondent with the main phases of orogeny (in the Carpathian Foredeep) while the southern part seems to have been exposed more often expressed in the geological record by a higher number of unconformities and paleo-soils levels. The n-alkanes distribution recovered from the lipids extracted from the sedimentary rocks indicates a mixture of terrestrial and marine input in the northern, Romanian, closer to Carpathians, part of the Dacian Basin. Surprisingly, the southern, Bulgarian side, showed a more predominant terrestrial input (with higher contribution of the long chain n-alkanes) at least for the Sarmatian (arround 10 Ma). The estimated paleotemperatures based on branched GDGT's indicate much warmer conditions than present day, up to a value of 20 C mean annual temperatures. We will further investigate the paleoenvironmental changes during the latest Miocene of the Dacian basin, using the biomarker approach

  20. The first fossil brown lacewing from the Miocene of the Tibetan Plateau (Neuroptera, Hemerobiidae

    Directory of Open Access Journals (Sweden)

    Qiang Yang

    2018-01-01

    Full Text Available A new species of Hemerobiidae, Wesmaelius makarkini Yang, Pang & Ren, sp. n. is described from the Lower Miocene, Garang Formation of Zeku County, Qinghai Province (northeastern Tibetan Plateau, China. The species is assigned to the widely distributed extant genus Wesmaelius Krüger (Hemerobiinae. The species represents the first named fossil of this family from China, which sheds light on the historical distribution of Wesmaelius and early divergences within Hemerobiinae.

  1. Miocene to Recent structural evolution of the Nevado de Toluca volcano region, Central Mexico

    Science.gov (United States)

    García-Palomo, A.; Macías, J. L.; Garduño, V. H.

    2000-03-01

    Based on aerial photography, satellite imagery, and detailed field work, a geological and structural model of Nevado de Toluca and its surroundings is presented. The Nevado de Toluca volcano is built upon the intersection of three complex fault systems of different age, orientation, and kinematics. These systems from the older to the younger are: (a) The Taxco-Querétaro Fault System (NNW-SSE) with clear expression south of the volcano; (b) The San Antonio Fault System (NE-SW) that runs between the San Antonio and Nevado de Toluca volcanoes; and (c) The Tenango Fault System (E-W) located to the east of Nevado de Toluca volcano. Our field data, supported by previous studies, suggest that these systems have coexisted since the late Miocene. In addition, the stratigraphy, chronology, and kinematics of fault planes point to the existence of at least three main deformation events that have affected the region since the late Miocene. During the early Miocene, an extensional phase with the same deformation style as the Basin and Range tectonics of northern Mexico caused the formation of horsts and grabens south of Nevado de Toluca and allowed the intrusion of sub-vertical dikes oriented NW-SE and NNW-SSE. During the middle Miocene, a transcurrent episode generated NE-SW faults that presented two main motions: the first movement was left-lateral with a σ3 oriented NW-SE and later turned into normal through a counter-clockwise rotation of σ3 up to a N-S position. The latest deformation phase started during the late Pliocene and produced oblique extension ( σ3 oriented NE-SW) along E-W-trending faults that later changed to pure extension by shifting of σ3 to a N-S orientation. These faults appear to control the late Pleistocene to Holocene monogenetic volcanism, the flank collapses of Nevado de Toluca volcano and the seismic activity of the region.

  2. Petrology and organic geochemistry of the lower Miocene lacustrine sediments (Most Basin, Eger Graben, Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Havelcová, Martina; Sýkorová, Ivana; Mach, K.; Trejtnarová, Hana; Blažek, Jaroslav

    2015-01-01

    Roč. 139, Special issue (2015), s. 26-39 ISSN 0166-5162 R&D Projects: GA ČR(CZ) GA13-18482S Institutional support: RVO:67985891 Keywords : Most Basin * Miocene * coal facies indices * coal petrology * organic geochemistry Subject RIV: DD - Geochemistry Impact factor: 3.294, year: 2015 http://www.sciencedirect.com/science/article/pii/S0166516214001529#

  3. Influence of leachate on the Oligocene-Miocene clays of the İstanbul area, Turkey

    OpenAIRE

    ÖZTOPRAK, SADIK; LAÇİN, DAVUT

    2018-01-01

    Oligo-Miocene clay outcrops on the European side (west and northwest part) of İstanbul were analysed. Formerly, a landfill and sanitary landfill were built on the clay. Mineral liners of the current and extending parts of the İstanbul landfill consist of these clays, since they include a considerable amount of smectite, illite, and kaolinite. With this feature, these clays are also an important candidate for the buffer material of repositories for nuclear wastes of newly planned nuclear power...

  4. Smilax (Smilacaceae) from the Miocene of western Eurasia with Caribbean biogeographic affinities.

    Science.gov (United States)

    Denk, Thomas; Velitzelos, Dimitrios; Güner, H Tuncay; Ferrufino-Acosta, Lilian

    2015-03-01

    • Recent molecular studies provide a phylogenetic framework and some dated nodes for the monocot genus Smilax. The Caribbean Havanensis group of Smilax is part of a well-supported "New World clade" with a few disjunct taxa in the Old World. Although the fossil record of the genus is rich, it has been difficult to assign fossil taxa to extant groups based on their preserved morphological characters.• Leaf fossils from Europe and Asia Minor were studied comparatively and put into a phylogenetic and biogeographic context using a molecular phylogeny of the genus.• Fossils from the early Miocene of Anatolia represent a new species of Smilax with systematic affinities with the Havanensis group. The leaf type encountered in the fossil species is exclusively found in species of the Havanensis group among all modern Smilax. Scattered fossils of this type from the Miocene of Greece and Austria, previously referred to Quercus (Fagaceae), Ilex (Aquifoliaceae), and Mahonia (Berberidaceae) also belong to the new species.• The new Smilax provides first fossil evidence of the Havanensis group and proves that this group had a western Eurasian distribution during the Miocene. The age of the fossils is in good agreement with the (molecular-based) purported split between the Havanensis and Hispida groups within Smilax. The Miocene Smilax provides evidence that all four subclades within the "New World clade" had a disjunct intercontinental distribution during parts of the Neogene involving trans-Atlantic crossings (via floating islands or the North Atlantic land bridge) and the Beringia land bridge. © 2015 Botanical Society of America, Inc.

  5. Etisus evamuellerae, a new xanthid crab (Decapoda, Brachyura) from the Middle Miocene of Austria and Hungary

    Science.gov (United States)

    Hyžný, M.; van Bakel, B.W.M.; Guinot, D.

    2015-01-01

    On the basis of several carapaces, a new species of xanthid crab, Etisus evamuellerae, is described from the Middle Miocene of the Vienna (Austria) and Great Hungarian basins. It differs from the coeval xanthids, Xantho moldavicus and Pilodius vulgaris, in having a distinctly protruding front and comparatively longer carapace. Contrary to those two species, the new one makes up for just a small percentage in the decapod crustacean assemblages studied. PMID:25983383

  6. Magnetostratigraphy of the Miocene sediments at Háj u Duchcova and Sokolov (West Bohemia)

    Czech Academy of Sciences Publication Activity Database

    Schnabl, Petr; Man, Otakar; Matys Grygar, Tomáš; Mach, K.; Kdýr, Šimon; Čížková, Kristýna; Pruner, Petr; Martínek, K.; Rojík, P.

    2017-01-01

    Roč. 19, EGU General Assembly 2017 (2017) ISSN 1029-7006. [European Geosciences Union General Assembly. 23.04.2017-28.04.2017, Vienna] R&D Projects: GA ČR(CZ) GA16-00800S Institutional support: RVO:67985831 ; RVO:61388980 Keywords : DP-333-09 * JP-585-10 * Burdigalian * spectral analysis * magnetostratigraphy * Miocene Subject RIV: DE - Earth Magnetism, Geodesy, Geography http://meetingorganizer.copernicus.org/EGU2017/EGU2017-19330.pdf

  7. Clay mineralogy indicates a mildly warm and humid living environment for the Miocene hominoid from the Zhaotong Basin, Yunnan, China

    Science.gov (United States)

    Zhang, Chunxia; Guo, Zhengtang; Deng, Chenglong; Ji, Xueping; Wu, Haibin; Paterson, Greig A.; Chang, Lin; Li, Qin; Wu, Bailing; Zhu, Rixiang

    2016-01-01

    Global and regional environmental changes have influenced the evolutionary processes of hominoid primates, particularly during the Miocene. Recently, a new Lufengpithecus cf. lufengensis hominoid fossil with a late Miocene age of ~6.2 Ma was discovered in the Shuitangba (STB) section of the Zhaotong Basin in Yunnan on the southeast margin of the Tibetan Plateau. To understand the relationship between paleoclimate and hominoid evolution, we have studied sedimentary, clay mineralogy and geochemical proxies for the late Miocene STB section (~16 m thick; ca. 6.7–6.0 Ma). Our results show that Lufengpithecus cf. lufengensis lived in a mildly warm and humid climate in a lacustrine or swamp environment. Comparing mid to late Miocene records from hominoid sites in Yunnan, Siwalik in Pakistan, and tropical Africa we find that ecological shifts from forest to grassland in Siwalik are much later than in tropical Africa, consistent with the disappearance of hominoid fossils. However, no significant vegetation changes are found in Yunnan during the late Miocene, which we suggest is the result of uplift of the Tibetan plateau combined with the Asian monsoon geographically and climatically isolating these regions. The resultant warm and humid conditions in southeastern China offered an important refuge for Miocene hominoids. PMID:26829756

  8. The significance of marine microfossils for paleoenvironmental reconstruction of the Solimões Formation (Miocene), western Amazonia, Brazil

    Science.gov (United States)

    Linhares, Ana Paula; Gaia, Valber do Carmo de Souza; Ramos, Maria Inês Feijó

    2017-11-01

    Micropalaeontological studies of borehole cores 1AS-7D-AM and 1AS-8-AM, from Atalaia do Norte, Amazonas state, Brazil, support previous evidence for Miocene marine ingressions in Western Amazonia. Three marine incursion events are recorded: the first in the Early/early Middle Miocene (in both cores), the second in the late Middle/early Late Miocene (1AS-8-AM), and the third in the Late Miocene (1AS-7D-AM). The first event is characterized by exclusively mangrove taxa, and the last two present a mixture of marine, fresh, and brackish water taxa. However, at the end of the third event an increase of fluvial influence is demonstrated by the predominance of freshwater taxa. These marine incursions reached the study area through narrow and geographically limited connections, controlled by the tectonic setting, at a time between the Early/early Middle Miocene and late Middle/Late Miocene. Thereafter, fluvial conditions were reestablished before Pliocene times.

  9. Terpenoid Compositions and Botanical Origins of Late Cretaceous and Miocene Amber from China

    Science.gov (United States)

    Shi, Gongle; Dutta, Suryendu; Paul, Swagata; Wang, Bo; Jacques, Frédéric M. B.

    2014-01-01

    The terpenoid compositions of the Late Cretaceous Xixia amber from Central China and the middle Miocene Zhangpu amber from Southeast China were analyzed by gas chromatography-mass spectrometry (GC-MS) to elucidate their botanical origins. The Xixia amber is characterized by sesquiterpenoids, abietane and phyllocladane type diterpenoids, but lacks phenolic abietanes and labdane derivatives. The molecular compositions indicate that the Xixia amber is most likely contributed by the conifer family Araucariaceae, which is today distributed primarily in the Southern Hemisphere, but widely occurred in the Northern Hemisphere during the Mesozoic according to paleobotanical evidence. The middle Miocene Zhangpu amber is characterized by amyrin and amyrone-based triterpenoids and cadalene-based sesquiterpenoids. It is considered derived from the tropical angiosperm family Dipterocarpaceae based on these compounds and the co-occurring fossil winged fruits of the family in Zhangpu. This provides new evidence for the occurrence of a dipterocarp forest in the middle Miocene of Southeast China. It is the first detailed biomarker study for amber from East Asia. PMID:25354364

  10. A middle Pleistocene through middle Miocene moraine sequence in the central Transantarctic Mountains, Antarctica

    Science.gov (United States)

    Balter, A.; Bromley, G. R.; Balco, G.; Thomas, H.; Jackson, M. S.

    2017-12-01

    Ice-free areas at high elevation in the central Transantarctic Mountains preserve extensive moraine sequences and drift deposits that comprise a geologic record of former East Antarctic Ice Sheet thickness and extent. We are applying cosmogenic-nuclide exposure dating to determine the ages of these moraine sequences at Roberts Massif and Otway Massif, at the heads of the Shackleton and Beardmore Glaciers, respectively. Moraines at these sites are for the most part openwork boulder belts characteristic of deposition by cold-based ice, which is consistent with present climate and glaciological conditions. To develop our chronology, we collected samples from 30 distinct ice-marginal landforms and have so far measured >100 3He, 10Be, and 21Ne exposure ages. Apparent exposure ages range from 1-14 Ma, which shows that these landforms record glacial events between the middle Pleistocene and middle Miocene. These data show that the thickness of the East Antarctic Ice Sheet in this region was similar to or thicker than present for long periods between the middle Miocene and today. The time range represented by these moraine sequences indicates that they may also provide direct geologic evidence for East Antarctic Ice Sheet behavior during past periods of warmer-than-present climate, specifically the Miocene and Pliocene. As the East Antarctic Ice Sheet is the largest ice sheet on earth, understanding its sensitivity to warm-climate conditions is critical for projections of ice sheet behavior and sea-level rise in future warm climates.

  11. Rapid middle Miocene extension and unroofing of the southern Ruby Mountains, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Howard, Keith A.; Fleck, Robert J.; Wooden, Joseph L.

    2010-01-01

    Paleozoic rocks in the northern Ruby Mountains were metamorphosed during Mesozoic crustal shortening and Cenozoic magmatism, but equivalent strata in the southern Ruby Mountains were never buried deeper than stratigraphic depths prior to exhumation in the footwall of a west dipping brittle normal fault. In the southern Ruby Mountains, Miocene sedimentary rocks in the hanging wall of this fault date from 15.2 to 11.6 Ma and contain abundant detritus from the Paleozoic section. Apatite fission track and (U-Th)/He samples of the Eocene Harrison Pass pluton record rapid cooling that peaked ca. 17–15 Ma, while apatite fission track data from Jurassic plutons east and west of the southern Ruby Mountains indicate near-surface temperatures (pluton to be partially reset rather than to directly record fault slip. Our new data, together with published data on the distribution and composition of Miocene basin fill, suggest that rapid middle Miocene slip took place on the west dipping brittle detachment that bounds the Ruby Mountains and East Humboldt Range for 150 km along strike. This fault was thus active during a period of rapid extension (ca. 17–15 to 12–10 Ma) documented widely across the northern Basin and Range Province.

  12. Miocene Fossils Reveal Ancient Roots for New Zealand's Endemic Mystacina (Chiroptera and Its Rainforest Habitat.

    Directory of Open Access Journals (Sweden)

    Suzanne J Hand

    Full Text Available The New Zealand endemic bat family Mystacinidae comprises just two Recent species referred to a single genus, Mystacina. The family was once more diverse and widespread, with an additional six extinct taxa recorded from Australia and New Zealand. Here, a new mystacinid is described from the early Miocene (19-16 Ma St Bathans Fauna of Central Otago, South Island, New Zealand. It is the first pre-Pleistocene record of the modern genus and it extends the evolutionary history of Mystacina back at least 16 million years. Extant Mystacina species occupy old-growth rainforest and are semi-terrestrial with an exceptionally broad omnivorous diet. The majority of the plants inhabited, pollinated, dispersed or eaten by modern Mystacina were well-established in southern New Zealand in the early Miocene, based on the fossil record from sites at or near where the bat fossils are found. Similarly, many of the arthropod prey of living Mystacina are recorded as fossils in the same area. Although none of the Miocene plant and arthropod species is extant, most are closely related to modern taxa, demonstrating potentially long-standing ecological associations with Mystacina.

  13. Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

    Science.gov (United States)

    Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

    2014-12-01

    Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

  14. Tertiary evolution of the Shimanto belt (Japan): A large-scale collision in Early Miocene

    Science.gov (United States)

    Raimbourg, Hugues; Famin, Vincent; Palazzin, Giulia; Yamaguchi, Asuka; Augier, Romain

    2017-07-01

    To decipher the Miocene evolution of the Shimanto belt of southwestern Japan, structural and paleothermal studies were carried out in the western area of Shikoku Island. All units constituting the belt, both in its Cretaceous and Tertiary domains, are in average strongly dipping to the NW or SE, while shortening directions deduced from fault kinematics are consistently orientated NNW-SSE. Peak paleotemperatures estimated with Raman spectra of organic matter increase strongly across the southern, Tertiary portion of the belt, in tandem with the development of a steeply dipping metamorphic cleavage. Near the southern tip of Ashizuri Peninsula, the unconformity between accreted strata and fore-arc basin, present along the whole belt, corresponds to a large paleotemperature gap, supporting the occurrence of a major collision in Early Miocene. This tectonic event occurred before the magmatic event that affected the whole belt at 15 Ma. The associated shortening was accommodated in two opposite modes, either localized on regional-scale faults such as the Nobeoka Tectonic Line in Kyushu or distributed through the whole belt as in Shikoku. The reappraisal of this collision leads to reinterpret large-scale seismic refraction profiles of the margins, where the unit underlying the modern accretionary prism is now attributed to an older package of deformed and accreted sedimentary units belonging to the Shimanto belt. When integrated into reconstructions of Philippine Sea Plate motion, the collision corresponds to the oblique collision of a paleo Izu-Bonin-Mariana Arc with Japan in Early Miocene.

  15. Global warming and South Indian monsoon rainfall-lessons from the Mid-Miocene.

    Science.gov (United States)

    Reuter, Markus; Kern, Andrea K; Harzhauser, Mathias; Kroh, Andreas; Piller, Werner E

    2013-04-01

    Precipitation over India is driven by the Indian monsoon. Although changes in this atmospheric circulation are caused by the differential seasonal diabatic heating of Asia and the Indo-Pacific Ocean, it is so far unknown how global warming influences the monsoon rainfalls regionally. Herein, we present a Miocene pollen flora as the first direct proxy for monsoon over southern India during the Middle Miocene Climate Optimum. To identify climatic key parameters, such as mean annual temperature, warmest month temperature, coldest month temperature, mean annual precipitation, mean precipitation during the driest month, mean precipitation during the wettest month and mean precipitation during the warmest month the Coexistence Approach is applied. Irrespective of a ~ 3-4 °C higher global temperature during the Middle Miocene Climate Optimum, the results indicate a modern-like monsoonal precipitation pattern contrasting marine proxies which point to a strong decline of Indian monsoon in the Himalaya at this time. Therefore, the strength of monsoon rainfall in tropical India appears neither to be related to global warming nor to be linked with the atmospheric conditions over the Tibetan Plateau. For the future it implies that increased global warming does not necessarily entail changes in the South Indian monsoon rainfall.

  16. An Investigation of Abnormal Fluid Pressure within an Evaporitic Cap Rock in the Gavbandi Area of Iran and its Impact on the Planning of Gas Exploration Wells

    Directory of Open Access Journals (Sweden)

    Mahdi Najafi

    2014-01-01

    Full Text Available A synthesis of well logs was carried out and drilling mud weight data were analyzed to figure out anomalous high fluid pressure within the Triassic evaporitic cap rock (the Dashtak formation and study its impact on the geometry of anticlinal traps in the gas rich Gavbandi province located in the southeast part of the Zagros Mountains. The results indicated that the location of anticlinal traps at the depth in which the Permian Dehram Group reservoir unit exists is horizontally displaced with respect to surficial crest of many anticlines within the Gavbandi area. This crestal shift may be induced by abnormally high fluid pressure in the “A evaporate” member of the Dashtak formation, detected in many exploration wells across the area. When fluid pressure increases due to compaction during shortening, the higher shaliness could probably cap more fluids and consequently increase the fluid pressure within the Dashtak formation. Anomalous high fluid pressure decreases internal friction and shear strength of rock units and facilitates fracturing and faulting within the Dashtak formation, which consequently causes crestal shift of anticlinal traps. This should be taken into account when planning a new exploration well in Gavbandi area in order to prevent trap drilling.

  17. Upper respiratory tract (image)

    Science.gov (United States)

    The major passages and structures of the upper respiratory tract include the nose or nostrils, nasal cavity, mouth, throat (pharynx), and voice box (larynx). The respiratory system is lined with a mucous membrane that ...

  18. ACA Federal Upper Limits

    Data.gov (United States)

    U.S. Department of Health & Human Services — Affordable Care Act Federal Upper Limits (FUL) based on the weighted average of the most recently reported monthly average manufacturer price (AMP) for...

  19. The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system

    Science.gov (United States)

    Latrubesse, Edgardo M.; Cozzuol, Mario; da Silva-Caminha, Silane A. F.; Rigsby, Catherine A.; Absy, Maria Lucia; Jaramillo, Carlos

    2010-05-01

    On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimões Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian-Mesopotamian mammalian biozones, spanning 9-6.5 Ma. Additionally, we present results that demonstrate that deposits in Peruvian Amazonia attributed to Miocene tidal environments are actually fluvial sediments that have been misinterpreted (both environmentally and chronologically) by several authors. The entire Late Miocene sequence was deposited in a continental environment within a subsiding basin. The facies analysis, fossil fauna content, and palynological record indicate that the environment of deposition was dominated by avulsive rivers associated with megafan systems, and avulsive rivers in flood basins (swamps, lakes, internal deltas, and splays). Soils developed on the flatter, drier areas, which were dominated by grasslands and gallery forest in a tropical to subtropical climate. These Late Miocene sediments were deposited from westward of the Purus arch up to the border of Brazil with Peru (Divisor Ranges) and Bolivia (Pando block). Eastward of the Iquitos structural high, however, more detailed studies, including vertebrate paleontology, need to be performed to calibrate with more precision the ages of the uppermost levels of the Solimões Formation. The evolution of the basin during the late Miocene is mainly related to the tectonic behavior of the Central Andes (˜ 3°-15°S). At approximately 5 Ma, a segment of low angle of subduction was well developed in the Nazca Plate, and the deformation in the Subandean foreland produced the inland reactivation of the Divisor/Contamana Ranges and tectonic arrangements in the Eastern Andes. During the Pliocene southwestern Brazilian Amazonia ceased to be an effective sedimentary

  20. Upper gastrointestinal bleeding.

    Science.gov (United States)

    Feinman, Marcie; Haut, Elliott R

    2014-02-01

    Upper gastrointestinal (GI) bleeding remains a commonly encountered diagnosis for acute care surgeons. Initial stabilization and resuscitation of patients is imperative. Stable patients can have initiation of medical therapy and localization of the bleeding, whereas persistently unstable patients require emergent endoscopic or operative intervention. Minimally invasive techniques have surpassed surgery as the treatment of choice for most upper GI bleeding. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Upper GI Bleeding in Children

    Science.gov (United States)

    Upper GI Bleeding in Children What is upper GI Bleeding? Irritation and ulcers of the lining of the esophagus, stomach or duodenum can result in upper GI bleeding. When this occurs the child may vomit blood ...

  2. Results of Hydraulic Tests in Miocene Tuffaceous Rocks at the C-Hole Complex, 1995 to 1997, Yucca Mountain, Nye County, Nevada

    Science.gov (United States)

    Geldon, Arthur L.; Umari, Amjad M.A.; Fahy, Michael F.; Earle, John D.; Gemmell, James M.; Darnell, Jon

    2002-01-01

    Four hydraulic tests were conducted by the U.S. Geological Survey at the C-hole complex at Yucca Mountain, Nevada, between May 1995 and November 1997. These tests were conducted as part of ongoing investigations to determine the hydrologic and geologic suitability of Yucca Mountain as a potential site for permanent underground storage of high-level nuclear waste. The C-hole complex consists of three 900-meter-deep boreholes that are 30.4 to 76.6 meters apart. The C-holes are completed in fractured, variably welded tuffaceous rocks of Miocene age. Six hydrogeologic intervals occur within the saturated zone in these boreholes - the Calico Hills, Prow Pass, Upper Bullfrog, Lower Bullfrog, Upper Tram, and Lower Tram intervals. The Lower Bullfrog and Upper Tram intervals contributed about 90 percent of the flow during hydraulic tests. The four hydraulic tests conducted from 1995 to 1997 lasted 4 to 553 days. Discharge from the pumping well, UE-25 c #3, ranged from 8.49 to 22.5 liters per second in different tests. Two to seven observation wells, 30 to 3,526 meters from the pumping well, were used in different tests. Observation wells included UE-25 c #1, UE-25 c #2, UE-25 ONC-1, USW H-4, UE-25 WT #14, and UE-25 WT #3 in the tuffaceous rocks and UE-25 p #1 in Paleozoic carbonate rocks. In all hydraulic tests, drawdown in the pumping well was rapid and large (2.9-11 meters). Attributable mostly to frictional head loss and borehole-skin effects, this drawdown could not be used to analyze hydraulic properties. Drawdown and recovery in intervals of UE-25 c #1 and UE-25 c #2 and in other observation wells typically was less than 51 centimeters. These data were analyzed. Hydrogeologic intervals in the C-holes have layered heterogeneity related to faults and fracture zones. Transmissivity, hydraulic conductivity, and storativity generally increase downhole. Transmissivity ranges from 4 to 1,600 meters squared per day; hydraulic conductivity ranges from 0.1 to 50 meters per day

  3. Ecomorphological characterization of murines and non-arvicoline cricetids (Rodentia from south-western Europe since the latest Middle Miocene to the Mio-Pliocene boundary (MN 7/8–MN13

    Directory of Open Access Journals (Sweden)

    Ana R. Gomez Cano

    2017-09-01

    Full Text Available Rodents are the most speciose group of mammals and display a great ecological diversity. Despite the greater amount of ecomorphological information compiled for extant rodent species, studies usually lack of morphological data on dentition, which has led to difficulty in directly utilizing existing ecomorphological data of extant rodents for paleoecological reconstruction because teeth are the most common or often the only micromammal fossils. Here, we infer the environmental ranges of extinct rodent genera by extracting habitat information from extant relatives and linking it to extinct taxa based on the phenogram of the cluster analysis, in which variables are derived from the principal component analysis on outline shape of the upper first molars. This phenotypic “bracketing” approach is particularly useful in the study of the fossil record of small mammals, which is mostly represented by isolated teeth. As a case study, we utilize extinct genera of murines and non-arvicoline cricetids, ranging from the Iberoccitanian latest middle Miocene to the Mio-Pliocene boundary, and compare our results thoroughly with previous paleoecological reconstructions inferred by different methods. The resultant phenogram shows a predominance of ubiquitous genera among the Miocene taxa, and the presence of a few forest specialists in the two rodent groups (Murinae and Cricetidae, along with the absence of open environment specialists in either group of rodents. This appears to be related to the absence of enduring grassland biomes in the Iberian Peninsula during the late Miocene. High consistency between our result and previous studies suggests that this phenotypic “bracketing” approach is a very useful tool.

  4. Ecomorphological characterization of murines and non-arvicoline cricetids (Rodentia) from south-western Europe since the latest Middle Miocene to the Mio-Pliocene boundary (MN 7/8–MN13)

    Science.gov (United States)

    Kimura, Yuri; Blanco, Fernando; Menéndez, Iris; Álvarez-Sierra, María A.; Hernández Fernández, Manuel

    2017-01-01

    Rodents are the most speciose group of mammals and display a great ecological diversity. Despite the greater amount of ecomorphological information compiled for extant rodent species, studies usually lack of morphological data on dentition, which has led to difficulty in directly utilizing existing ecomorphological data of extant rodents for paleoecological reconstruction because teeth are the most common or often the only micromammal fossils. Here, we infer the environmental ranges of extinct rodent genera by extracting habitat information from extant relatives and linking it to extinct taxa based on the phenogram of the cluster analysis, in which variables are derived from the principal component analysis on outline shape of the upper first molars. This phenotypic “bracketing” approach is particularly useful in the study of the fossil record of small mammals, which is mostly represented by isolated teeth. As a case study, we utilize extinct genera of murines and non-arvicoline cricetids, ranging from the Iberoccitanian latest middle Miocene to the Mio-Pliocene boundary, and compare our results thoroughly with previous paleoecological reconstructions inferred by different methods. The resultant phenogram shows a predominance of ubiquitous genera among the Miocene taxa, and the presence of a few forest specialists in the two rodent groups (Murinae and Cricetidae), along with the absence of open environment specialists in either group of rodents. This appears to be related to the absence of enduring grassland biomes in the Iberian Peninsula during the late Miocene. High consistency between our result and previous studies suggests that this phenotypic “bracketing” approach is a very useful tool. PMID:28966888

  5. Miocene squat lobsters (Decapoda, Anomura, Galatheoidea) of the Central Paratethys – a review, with description of a new species of Munidopsis

    Science.gov (United States)

    Hyžný, M.; Gašparič, R.; Robins, C.M.; Schlögl, J.

    2015-01-01

    All squat lobsters of the families Galatheidae, Munididae and Munidopsidae from the Miocene of the Central Paratethys are reviewed taxonomically. Based on additional observations emended diagnoses are provided for Agononida cerovensis and Galathea weinfurteri, from the Lower and Middle Miocene, respectively. Munidopsis is represented by two species in the study area; additional data for M. lieskovensis from the Lower Miocene of Slovakia are presented and a new species, M. palmuelleri, from the Middle Miocene of Slovenia is erected. Implications for palaeoenvironmental reconstructions are briefly discussed for each taxon. PMID:26005283

  6. Miocene Basaltic Lava Flows and Dikes of the Intervening Area Between Picture Gorge and Steens Basalt of the CRBG, Eastern Oregon

    Science.gov (United States)

    Cahoon, E. B.; Streck, M. J.

    2016-12-01

    Mid-Miocene basaltic lavas and dikes are exposed in the area between the southern extent of the Picture Gorge Basalt (PGB) and the northern extent of Steens Basalt in a wide corridor of the Malheur National Forest, eastern Oregon. An approximate mid-Miocene age of sampled basaltic units is indicated by stratigraphic relationships to the 16 Ma Dinner Creek Tuff. Lavas provide an opportunity to extend and/or revise distribution areas of either CRBG unit and explore the petrologic transition between them. The PGB and the Steens Basalt largely represent geochemically distinct tholeiitic units of the CRBG; although each unit displays internal complexity. Lavas of PGB are relatively primitive (MgO 5-9 wt.%) while Steens Basalt ranges in MgO from >9 to 3 wt.% but both units are commonly coarsely porphyritic. Conversely, Steens Basalt compositions are on average more enriched in highly incompatible elements (e.g. Rb, Th) and relatively enriched in the lesser incompatible elements (e.g. Y, Yb) compared to the Picture Gorge basalts. These compositional signatures produce inclined and flat patterns on mantle-normalized incompatible trace element plots but with similar troughs and spikes, respectively. New compositional data from our study area indicate basaltic lavas can be assigned as PGB lava flows and dikes, and also to a compositional group chemically distinct between Steens Basalt and PGB. Distribution of lava flows with PGB composition extend this CRBG unit significantly south/southeast closing the exposure gap between PGB and Steens Basalt. We await data that match Steens Basalt compositions but basaltic lavas with petrographic features akin to Steens Basalt have been identified in the study area. Lavas of the transitional unit share characteristics with Upper Steens and Picture Gorge basalt types, but identify a new seemingly unique composition. This composition is slightly more depleted in the lesser incompatible elements (i.e. steeper pattern) on mantle normalized

  7. Messinian post-evaporitic paleogeography of the Po Plain-Adriatic region by 3D numerical modeling: implications for the Central Mediterranean desiccation during the MSC

    Science.gov (United States)

    Amadori, Chiara; Garcia-Castellanos, Daniel; Di Giulio, Andrea; Fantoni, Roberto; Ghielmi, Manlio; Sternai, Pietro; Toscani, Giovanni

    2017-04-01

    In the last decades the Messinian Salinity Crisis (MSC) has been the topic of a number of studies, in particular in onshore areas, as they offer a unique opportunity to analyze the controlling factors and the geological consequences of the estimated 1.5 km sea-level drop. During the MSC, the geometry of western and eastern sides of the Mediterranean basin was similar to the present day basin while, important changes took place in the central portion as a consequence of the (still ongoing) tectonic activity of the Apennine domain. Recent high-resolution 2D seismo-stratigraphic and 1D backstripping analysis by Eni E&P group described a step-wise sea-level lowering during evaporitic and post-evaporitic MSC phases in the Po Plain-Northern Adriatic foreland (PPAF), with a sea-level drop not exceeding 900 m. Thanks to a dense grid of 2D seismic profiles, integrated with ca. 200 well logs (confidential data, courtesy of ENI E&P), a 3D reconstruction of the entire northern PPAF basin geometry and the facies distribution during the Latest Messinian time has been carried out. In this study, we performed a 3D backstripping and lithospheric scale uplift calculations of the northern PPAF basin testing the 800-900m of sea-level draw down. The resulted restored Latest Messinian paleotopography (corresponding to the bottom Pliocene in the most of the study area) and related shoreline position, strongly fit with the recentmost continental/marine facies distribution maps. The latest Messinian morphology shows deep marine basins persisting during the entire MSC period, filled by clastic turbiditic sediments and a wide emerged area along the Southern Alps margin and Friulian-Venetian basin. A 3D reconstruction of the Latest Messinian surface shows peculiar river incisions along the Southern Alps margin; these V-shape canyons perfectly fit with the present day fluvial network, dating back the drainage origin at least at the Messinian acme. Moreover, if in a well-constrained marginal

  8. 4D Monitoring of Active Sinkholes with a Terrestrial Laser Scanner (TLS: A Case Study in the Evaporite Karst of the Ebro Valley, NE Spain

    Directory of Open Access Journals (Sweden)

    Alfonso Benito-Calvo

    2018-04-01

    Full Text Available This work explores, for the first time, the application of a Terrestrial Laser Scanner (TLS and a comparison of point clouds in the 4D monitoring of active sinkholes. The approach is tested in three highly-active sinkholes related to the dissolution of salt-bearing evaporites overlain by unconsolidated alluvium. The sinkholes are located in urbanized areas and have caused severe damage to critical infrastructure (flood-control dike, a major highway. The 3D displacement models derived from the comparison of point clouds with exceptionally high spatial resolution allow complex spatial and temporal subsidence patterns within one of the sinkholes to be resolved. Detected changes in the subsidence activity (e.g., sinkhole expansion, translation of the maximum subsidence zone, development of incipient secondary collapses are related to potential controlling factors such as floods, water table changes or remedial measures. In contrast, with detailed mapping and high-precision leveling, the displacement models, covering a relatively short time span of around 6 months, do not capture the subtle subsidence (<0.6–1 cm that affects the marginal zones of the sinkholes, precluding precise mapping of the edges of the subsidence areas. However, the performance of TLS can be adversely affected by some methodological limitations and local conditions: (1 limited accuracy in large investigation areas that require the acquisition of a high number of scans, increasing the registration error; (2 surface changes unrelated to sinkhole activity (e.g., vegetation, loose material; (3 traffic-related vibrations and wind blast that affect the stability of the scanner.

  9. An X-ray spectroscopic perspective on Messinian evaporite from Sicily: Sedimentary fabrics, element distributions, and chemical environments of S and Mg

    Science.gov (United States)

    Yoshimura, Toshihiro; Kuroda, Junichiro; Lugli, Stefano; Tamenori, Yusuke; Ogawa, Nanako O.; Jiménez-Espejo, Francisco J.; Isaji, Yuta; Roveri, Marco; Manzi, Vinicio; Kawahata, Hodaka; Ohkouchi, Naohiko

    2016-04-01

    The Messinian salinity crisis is a dramatic hydrological and biological crisis that occurred in the Mediterranean basin at 5.97-5.33 Ma. The interpretation of the facies and stratigraphic associations of the Messinian salt deposits is still the object of active research because of the absence of modern depositional analogues of comparable scale. In this study, the spatial distributions of Na, Mg, S, O, Si, and Al in a potassic-magnesian salt and a halite layers of Messinian evaporites from the Realmonte mine on Sicily were determined using synchrotron based micro-X-ray fluorescence. The dominant molecular host site of Mg and S obtained by X-ray absorption near edge structure (XANES) is applied to specify the hydrochemistry of hypersaline brines and the presence of diagenetic minerals, thus shedding light on evaporative concentration processes in the Caltanissetta Basin of Sicily. Mg and S K-edge XANES spectra revealed the presence of highly soluble Mg-bearing sulfates. The massive halite layer "unit C," contains less soluble minerals, thus did not exceed the stage of halite crystallization. We infer that as evaporative concentration increased, the density of the brine at the shallow margin of the basin increased as salinity increased to concentrations over 70 times the starting values, creating brines that were oversaturated with Mg-sulfate. Density stratification of the deep basin caused heavy brines to sink to the bottom and become overlain by more dilute brines. We propose lateral advection of dense Mg-sulfate brines that certainly affected marine biota.

  10. Conditions for the formation and atmospheric dispersion of a toxic, heavy gas layer during thermal metamorphism of coal and evaporite deposits by sill intrusion

    Science.gov (United States)

    Storey, Michael; Hankin, Robin K. S.

    2010-05-01

    There is compelling evidence for massive discharge of volatiles, including toxic species, into the atmosphere at the end of the Permian. It has been argued that most of the gases were produced during thermal metamorphism of coal and evaporite deposits in the East Siberia Tunguska basin following sill intrusion (Retallack and Jahren, 2008; Svensen et al., 2009). The release of the volatiles has been proposed as a major cause of environmental and extinction events at the end of the Permian, with venting of carbon gases and halocarbons to the atmosphere leading to global warming and atmospheric ozone depletion (Svensen et al., 2009) Here we consider the conditions required for the formation and dispersion of toxic, heavier than air, gas plumes, made up of a mixture of CO2, CH4, H2S and SO2 and formed during the thermal metamorphism of C- and S- rich sediments. Dispersion models and density considerations within a range of CO2/CH4 ratios and volatile fluxes and temperatures, for gas discharge by both seepage and from vents, allow the possibility that following sill emplacement much of the vast East Siberia Tunguska basin was - at least intermittently - covered by a heavy, toxic gas layer that was unfavorable for life. Dispersion scenarios for a heavy gas layer beyond the Siberian region during end-Permian times will be presented. REFERENCES G. J. Retallack and A. H. Jahren, Methane release from igneous intrusion of coal during Late Permian extinction events, Journal of Geology, volume 116, 1-20, 2008 H. Svensen et al., Siberian gas venting and the end-Permian environmental crisis, Earth and Planetary Science Letters, volume 277, 490-500, 2009

  11. Right upper quadrant pain

    International Nuclear Information System (INIS)

    Ralls, P.W.; Colletti, P.M.; Boswell, W.D. Jr.; Halls, J.M.

    1984-01-01

    Historically, assessment of acute right upper quadrant abdominal pain has been a considerable clinical challenge. While clinical findings and laboratory data frequently narrow the differential diagnosis, symptom overlap generally precludes definitive diagnosis among the various diseases causing acute right upper quadrant pain. Fortunately, the advent of newer diagnostic imaging modalities has greatly improved the rapidity and reliability of diagnosis in these patients. An additional challenge to the physician, with increased awareness of the importance of cost effectiveness in medicine, is to select appropriate diagnostic schema that rapidly establish accurate diagnoses in the most economical fashion possible. The dual goals of this discussion are to assess not only the accuracy of techniques used to evaluate patients with acute right upper quadrant pain, but also to seek out cost-effective, coordinated imaging techniques to achieve this goal

  12. Constrained Magnetostratigraphic Dating of a Continental Middle Miocene Section in the Arid Central Asia

    Directory of Open Access Journals (Sweden)

    Verena Verestek

    2018-05-01

    Full Text Available The Neogene succession of the Aktau Mountains in the Ili Basin, southeast Kazakhstan, is a terrestrial archive well suited for researching the role of Central Asia in Miocene climate evolution. We present an integrated approach for dating the well-exposed Bastau Formation, based on magnetostratigraphy and constraints from cyclostratigraphy and biostratigraphy. Stepwise demagnetization yielded characteristic remanence directions that are consistent with those expected for the Miocene in Central Asia. The reddish-colored alluvial floodplain deposits and gray lacustrine deposits show partly complex magnetic behavior with magnetite and hematite as the main magnetic carriers, with variable demagnetization behavior and non-dipolar normal and reverse polarity directions. The observed magnetic properties are best explained by depositional variability and magneto-mineralogical alteration effects of both dissolution and neo-formation of magnetite, including significant secondary magnetization. The mean of reverse polarity directions is flatter than the expected Middle Miocene Earth magnetic field, which is an indicator for the existence of inclination shallowing that supports a primary origin. Detailed rock magnetic analyses are used to analyze the nature of the characteristic remanent magnetization and to discriminate primary and secondary remanence directions in order to obtain a reliable magnetostratigraphic result. The proposed age of 15.3–13.9 Ma for the Bastau Formation corresponds to the known biostratigraphic setting, matches with typical sedimentation rates of foreland basins in Central Asia, and coincides with spectral analysis of geochemical proxies of that section. The resulting age model serves as a robust framework for paleoclimate reconstruction of Neogene climate dynamics in Central Asia.

  13. Dynamic Antarctic ice sheet during the early to mid-Miocene

    Science.gov (United States)

    Gasson, Edward; DeConto, Robert M.; Pollard, David; Levy, Richard H.

    2016-03-01

    Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate-ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet-climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52-0.66‰, or a sea level equivalent change of 30-36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability.

  14. Ancient nursery area for the extinct giant shark megalodon from the Miocene of Panama.

    Directory of Open Access Journals (Sweden)

    Catalina Pimiento

    Full Text Available BACKGROUND: As we know from modern species, nursery areas are essential shark habitats for vulnerable young. Nurseries are typically highly productive, shallow-water habitats that are characterized by the presence of juveniles and neonates. It has been suggested that in these areas, sharks can find ample food resources and protection from predators. Based on the fossil record, we know that the extinct Carcharocles megalodon was the biggest shark that ever lived. Previous proposed paleo-nursery areas for this species were based on the anecdotal presence of juvenile fossil teeth accompanied by fossil marine mammals. We now present the first definitive evidence of ancient nurseries for C. megalodon from the late Miocene of Panama, about 10 million years ago. METHODOLOGY/PRINCIPAL FINDINGS: We collected and measured fossil shark teeth of C. megalodon, within the highly productive, shallow marine Gatun Formation from the Miocene of Panama. Surprisingly, and in contrast to other fossil accumulations, the majority of the teeth from Gatun are very small. Here we compare the tooth sizes from the Gatun with specimens from different, but analogous localities. In addition we calculate the total length of the individuals found in Gatun. These comparisons and estimates suggest that the small size of Gatun's C. megalodon is neither related to a small population of this species nor the tooth position within the jaw. Thus, the individuals from Gatun were mostly juveniles and neonates, with estimated body lengths between 2 and 10.5 meters. CONCLUSIONS/SIGNIFICANCE: We propose that the Miocene Gatun Formation represents the first documented paleo-nursery area for C. megalodon from the Neotropics, and one of the few recorded in the fossil record for an extinct selachian. We therefore show that sharks have used nursery areas at least for 10 millions of years as an adaptive strategy during their life histories.

  15. Correlating Mediterranean shallow water deposits with global Oligocene–Miocene stratigraphy and oceanic events☆

    Science.gov (United States)

    Reuter, Markus; Piller, Werner E.; Brandano, Marco; Harzhauser, Mathias

    2013-01-01

    Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene–Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene–Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene–late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale. PMID:25844021

  16. Systematics and Evolution of the Miocene Three-Horned Palaeomerycid Ruminants (Mammalia, Cetartiodactyla.

    Directory of Open Access Journals (Sweden)

    Israel M Sánchez

    Full Text Available Palaeomerycids were strange three-horned Eurasian Miocene ruminants known through fossils from Spain to China. We here study their systematics, offering the first cladistic phylogeny of the best-known species of the group, and also reassess their phylogenetic position among ruminants, which is currently disputed. The beautifully preserved remains of a new palaeomerycid from middle Miocene deposits of Spain, Xenokeryx amidalae gen. et sp. nov., helps us to better understand palaeomerycid anatomy, especially that of the nuchal region in the skull, significantly improving our current knowledge on these enigmatic ruminants. Our results show two main lineages of palaeomerycids, one containing the genus Ampelomeryx diagnosed by a characteristic type of cranium / cranial appendages and some dental derived traits, and another one that clusters those forms more closely related to Triceromeryx than to Ampelomeryx, characterized by a more derived dentition and a set of apomorphic cranial features. Xenokeryx branches as a basal offshoot of this clade. Also, we find that Eurasian palaeomerycids are not closely related to North American dromomerycids, thus rejecting the currently more accepted view of palaeomerycids as the Eurasian part of the dromomerycid lineage. Instead of this, palaeomerycids are nested with the African Miocene pecoran Propalaeoryx and with giraffoids. On the other hand, dromomerycids are closely related to cervids. We define a clade Giraffomorpha that includes palaeomerycids and giraffids, and propose an emended diagnosis of the Palaeomerycidae based on cranial and postcranial characters, including several features of the cranium not described so far. We also define the Palaeomerycidae as the least inclusive clade of pecorans containing Triceromeryx and Ampelomeryx. Finally, we reassess the taxonomy of several palaeomerycid taxa.

  17. Correlating Mediterranean shallow water deposits with global Oligocene-Miocene stratigraphy and oceanic events.

    Science.gov (United States)

    Reuter, Markus; Piller, Werner E; Brandano, Marco; Harzhauser, Mathias

    2013-12-01

    Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene-Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene-Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene-late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO 3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale.

  18. The Evolution of Indian and Pacific Ocean Denitrification and Nitrogen Dynamcs since the Miocene

    Science.gov (United States)

    Ravelo, A. C.; Carney, C.; Rosenthal, Y.; Holbourn, A.; Kulhanek, D. K.

    2017-12-01

    The feedbacks between geochemical cycles and physical climate change are poorly understood; however, there has been tremendous progress in developing coupled models to help predict the direction and strength of these feedbacks. As such, there is a need for more data to validate and test these models. To this end, the nitrogen (N) cycle, and its links to the biological pump and to climate, is an active area of paleoceanographic research. Using N isotope records, Robinson et al. (2014) showed that pelagic denitrification in the Indian and Pacific Oceans intensified as climate cooled and subsurface ventilation decreased since the Pliocene. They pointed out that a more ventilated warm Pliocene contrasts with glacial-interglacial patterns wherein more ventilation occurs during cold phases, indicating that different mechanisms may occur at different timescales. Our objective is to better understand the nature of the feedbacks between the oceanic N cycle and climate by focusing on the large dynamic range of conditions that occurred during and since the Miocene. We used new cores drilled during IODP Expedition 363 to generate bulk sediment N isotope records at three western tropical Pacific sites (U1486, U1488, U1490) and one southeastern tropical Indian Ocean site (U1482). We find that the N isotope trends since the Pliocene are in agreement with previous studies showing increasing denitrification as climate cooled. In the Miocene, the Indian Ocean record shows no long-term N isotope trend whereas the Pacific Ocean records show a trend that is roughly coupled to changes in global climate suggesting that pelagic denitrification in the Pacific was strongly influenced by greater ventilation during global warmth. However, there are notable deviations from this coupling during several intervals in the Miocene, and there are site-to-site differences in trends. These deviations and differences can be explained by changes in tropical productivity (e.g., late Miocene biogenic

  19. Ferroan dolomites in Miocene sediments of the Xisha Islands and their genetic model

    Science.gov (United States)

    Xu, Hong; Zhang, Weiwei; Wei, Kai; He, Qingkun; Jiang, Yunshui; Xu, Tingting; Jiang, Xuejun; Yan, Guijing; Song, Hongying; Wang, Jianghai

    2018-01-01

    Carbonate rocks are important reservoirs for global petroleum exploration. The largest oilfield in the South China Sea, Liuhua 11-1, is distributed in the massive carbonate reef area of the Zhujiang (Pearl) River Mouth Basin. Previous studies showed that one 802.17-m-long core from well Xichen-1 in the South China Sea mainly consisted of white and light gray-white organic reefs. Recently, a Miocene whole core (161.9 m long) of well Xiyong-2, near well Xichen-1, was found to contain six layers of yellowish brown, light yellowish gray, iron black, or light yellowish gray-white organic reefs. Scanning electron microscope images of these layers reveal a typical ferroan dolomite rich in Fe (up to 29%), with the high concentrations of Mn, Cu, W, Zn, Cr, Ni, and Co. Systematic X-ray powder diffraction analysis yields a 1.9-6.1 match in phase ratio with ankerite, 5.4-26.9 with dolomite, and zero with calcite, which indicate that the samples can be classified as ferroan dolomite. The iron and heavy metals are inferred to be originated from multiple volcanic eruptions of Gaojianshi Island in the Dongdao Atoll during the middle-late Miocene. These elements were dissolved in seawater, likely as a sol, and carried to Yongxing Island in the Xuande Atoll by sea currents and tides enhanced by prevailing winds, and deposited as a part of the sedimentation process in the study area. The ferroan dolomite has Sr content of (125-285)×10-6, which is lower than the accepted Sr boundary value of dolomite. This finding suggests that dolomitization occurred during large-scale global glacial regression in the late Miocene. The isolated Xisha carbonate platform, exposed to air, underwent freshwater leaching and dolomitization induced by mixed water, and caused the extensive Fe-Mg exchange along the organic reef profile to form ankerite and ferroan dolomite. These results may help to understand paleoceanographic environmental changes in the South China Sea during the Miocene.

  20. Biostratigraphy of the Miocene of Zeven, county of Bremervoerde, based on mollusks

    Energy Technology Data Exchange (ETDEWEB)

    Hinsch, W

    1969-06-01

    Cores from 2 water wells and a gas well, containing a very rich assemblage of fossil mollusks, were used to clarify the biostratigraphy of the Miocene near Zeven, especially in the sands corresponding to the brown coal deposits. The overburden contains the fauna of the Reinbek, the underburden 2 faunas of the Hemmoor, one of brachyhaline and one of euhaline characteristics. A list of the 174 species found, and of those most useful for age determinations, is given. The correspondence between several local nomenclatures in the Helvetian, Burdigalian and Aquitanian formations is tabulated. (12 refs.)

  1. Late Miocene Pacific plate kinematic change explained with coupled global models of mantle and lithosphere dynamics

    DEFF Research Database (Denmark)

    Stotz, Ingo Leonardo; Iaffaldano, Giampiero; Davies, DR

    2017-01-01

    and the consequent subduction polarity reversal. The uncertainties associated with the timing of this event, however, make it difficult to quantitatively demonstrate a dynamical association. Here, we first reconstruct the Pacific plate's absolute motion since the mid-Miocene (15 Ma), at high-temporal resolution....../lithosphere system to test hypotheses on the dynamics driving this change. These indicate that the arrival of the OJP at the Melanesian arc, between 10 and 5 Ma, followed by a subduction polarity reversal that marked the initiation of subduction of the Australian plate underneath the Pacific realm, were the key...... drivers of this kinematic change....

  2. Late Miocene (Proto-Gulf) Extension and Magmatism on the Sonoran Margin

    Science.gov (United States)

    Gans, P.; MacMillan, I.; Roldan-Quintana, J.

    2003-12-01

    Constraints on the magnitude and character of late Miocene (Proto-Gulf) deformation on the Sonoran margin of the Gulf of California extensional province are key to understanding how and when Baja California was captured by the Pacific plate and how strain was partitioned during the early stages of this transtensional rift system. Our new geologic mapping in southwestern Sonora and 40Ar/39Ar dating of pre-, syn-, and post-tectonic volcanic units indicate that late Miocene deformation and volcanic activity were largely restricted to a NW-trending, 100-120 km wide belt adjacent to the coast. Inboard of this belt, NW-SE extension is mainly older (>15 Ma) and occurred in an intra-arc or back-arc setting. Proto-Gulf deformation within the coastal belt was profoundly transtensional, with NW-striking, dextral strike slip faults operating in concert with N-S and NNE-striking normal and oblique slip faults to produce an inferred NW or NNW tectonic transport direction. The total amount of late Miocene NW directed dextral shear within the coastal belt is still poorly constrained, but may exceed 100 km. The locus of deformation and volcanic activity migrated westward or northwestward within the Sonoran coastal belt. in the eastern portion (Sierra Libre and Sierra El Bacatete) major volcanic activity commenced at ˜13.0 Ma and peaked at 12.0 Ma, and major faulting and tilting is bracketed between 12.0 and 10.6 Ma. Further west in the Sierra El Aguaje/San Carlos region, major volcanic activity commenced at 11.5 Ma and peaked at 10.5 Ma, and most faulting and tilting is bracketed between 10.7 and 9.3 Ma. On the coastal mountains northwest of San Carlos, rift related faulting and tilting continued after 8.5 Ma. Voluminous late Miocene (13-8 Ma) volcanic rocks within the Sonoran coastal belt were erupted from numerous centers (e.g. Sierra Libre, Guaymas, Sierra El Aguaje). These thick volcanic sections are compositionally diverse (basalt to rhyolite, with abundant dacite and

  3. Late Miocene marine tephra beds : recorders of rhyolitic volcanism in North Island, New Zealand

    International Nuclear Information System (INIS)

    Shane, P.; Black, T.; Eggins, S.; Westgate, J.

    1998-01-01

    A deep-sea sequence of 72 rhyolitic tephra beds, now exposed at Mahia Peninsula in the Hawke's Bay region of the east coast, North Island, New Zealand, provides a record of Late Miocene volcanism of the Coromandel Volcanic Zone (CVZ): the precursor to large-scale explosive volcanism of the Quaternary Taupo Volcanic Zone (TVZ). The geochemical signature of the glasses in the Miocene tephra has been protected from hydrothermal alteration and prolonged subaerial exposure that have affected proximal CVZ deposits. The tephra beds are primarily eruption-driven sediment gravity flows that have been emplaced into a trench-slope basin, some 300 km from active volcanoes. Their occurrence is consistent with long-distance fluvial transport followed by a point-source discharge into the deep-sea environment, and has no implications for the paleogeographic location of the basins relative to the volcanic arc. The tephra beds are calc-alkaline rhyolites with SiO 2 contents in the range 72-78 wt% (recalculated on a volatile-free basis), and are broadly similar to glassy rocks of the CVZ. Their major oxide, trace element, and REE compositions are indistinguishable from glasses of TVZ rhyolites. The trace element and REE compositional variability in the Late Miocene tephra beds, which were erupted over an estimated duration of c. 0.5-2.4 m.y. is no greater than that of large silicic eruptives of the last 350 ka, and is suggestive of a long-lived source and/or similar magmatic processes. However, the individual tephra beds are products of discrete homogeneous magma batches. New fission track ages of the Miocene tephra beds suggest the main period of volcaniclastic deposition occurred in the interval c. 9-7 Ma. This corresponds well with the initiation of rhyolitic volcanism in the CVZ at c. 10 Ma, and a major period of caldera formation that took place to c. 7 Ma. The ages suggest a sediment accumulation rate of between 0.23 and 1.2 m/ka (av. 0.4 m/ka), and a frequency of eruption of

  4. Upper airway evaluation

    International Nuclear Information System (INIS)

    Hoffman, E.A.; Gefter, W.B.; Schnall, M.; Nordberg, J.; Listerud, J.; Lenkinski, R.E.

    1988-01-01

    The authors are evaluating upper-airway sleep disorders with magnetic resonance (MR) imaging and x-ray cine computed tomography (CT). Fixed structural anatomy is visualized with multisection spin-echo MR imaging, the dynamic component with cine CT. Unique aspects of the study are described in this paper

  5. Miocene isotope zones, paleotemperatures, and carbon maxima events at intermediate water-depth, Site 593, Southwest Pacific

    International Nuclear Information System (INIS)

    Cooke, P.J.; Nelson, C.S.; Crundwell, M.P.

    2008-01-01

    Oxygen and carbon isotopic stratigraphies are presented from both benthic and planktic foraminifera for the late early Miocene to earliest Pliocene interval (c. 19-5 Ma) of intermediate water-depth DSDP Site 593 in the southern Tasman Sea. The benthic values are interpreted as recording Miocene Southern Component Intermediate Water, while the planktic species record the Miocene mode and surface water signals. Comparisons are made between temperate Site 593 and the intermediate-depth polar Site 747 in the southern Indian Ocean. Glacial Mi zones Mi1b-Mi6, representing extreme glacial events, are evident in both the Site 593 intermediate and surface water records. Miocene Southern Component Intermediate Water δ 18 O values are generally lighter than the Holocene equivalent (Antarctic Intermediate Water), indicating slightly warmer intermediate waters and/ or less global ice volume. The benthic-planktic gradient is interpreted as indicating a less stratified Tasman Sea during the Miocene. The benthic δ 13 C record contains most of the global carbon maxima (CM) events, CM1-7 (CM1-6 = the Monterey Excursion). Like global deep-water records, the Tasman Sea intermediate water δ 13 C values indicate that most CM events correspond with Mi glacials, including Mi4 at Site 593, not reported previously. Intermediate waters play an important role in propagating climatic changes from the polar regions to the tropics, and the Site 593 dataset provides a full water column record of the structure of Miocene intermediate to surface watermasses prior to the modern situation. (author). 132 refs., 8 figs., 4 tabs

  6. Occlusal enamel complexity in middle miocene to holocene equids (Equidae: Perissodactyla of North America.

    Directory of Open Access Journals (Sweden)

    Nicholas A Famoso

    Full Text Available Four groups of equids, "Anchitheriinae," Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate.

  7. IODP Expeditions 303 and 306 Monitor Miocene- Quaternary Climate in the North Atlantic

    Directory of Open Access Journals (Sweden)

    Carlos Alvarez-Zarikian

    2006-03-01

    Full Text Available Introduction The IODP Expeditions 303 and 306 drilling sites were chosen for two reasons: (1 to capture Miocene-Quaternary millennial-scale climate variability in sensitive regions at the mouth of the Labrador Sea and in the North Atlantic icerafted debris (IRD belt (Ruddiman et al., 1977, and (2 to provide the sedimentary and paleomagnetic attributes, including adequate sedimentation rates, for constructinghigh-resolution isotopic and magnetic stratigraphies.High accumulation rates, reaching 20 cm ky-1, permit the study of millennial-scale variations in climate and in the Earth's magnetic fi eld over the past several million years, when the amplitude and frequency of climate variability changed substantially. Shipboard logging and scanning data (magnetic susceptibility and remanence, density, natural gamma radiation, digital images and color refl ectance and post-expedition x-ray fl uorescence (XRF scanning datahave revealed that the sediment cores recovered on Expeditions 303 and 306 contain detailed histories of millennial-scale climate and geomagnetic fi eld variability throughout the late Miocene to Quaternary epochs. The climate proxies will be integrated with paleomagnetic data to place the records of millennial-scale climate change into a high resolution stratigraphy based on oxygen isotope andrelative paleomagnetic intensity (RPI. The paleomagnetic record of polarity reversals, excursions and RPI in these cores is central to the construction of the stratigraphic template and will provide detailed documentation of geomagnetic fi eld behavior.

  8. Amazonian Amphibian Diversity Is Primarily Derived from Late Miocene Andean Lineages

    Science.gov (United States)

    Santos, Juan C; Coloma, Luis A; Summers, Kyle; Caldwell, Janalee P; Ree, Richard; Cannatella, David C

    2009-01-01

    The Neotropics contains half of remaining rainforests and Earth's largest reservoir of amphibian biodiversity. However, determinants of Neotropical biodiversity (i.e., vicariance, dispersals, extinctions, and radiations) earlier than the Quaternary are largely unstudied. Using a novel method of ancestral area reconstruction and relaxed Bayesian clock analyses, we reconstructed the biogeography of the poison frog clade (Dendrobatidae). We rejected an Amazonian center-of-origin in favor of a complex connectivity model expanding over the Neotropics. We inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. We found three episodes of lineage dispersal with two interleaved periods of vicariant events between South and Central America. During the late Miocene, Amazonian, and Central American-Chocoan lineages significantly increased their diversity compared to the Andean and Guianan-Venezuelan-Brazilian Shield counterparts. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. The effects of Miocene paleogeographic events on Neotropical diversification dynamics provided the framework under which Quaternary patterns of endemism evolved. PMID:19278298

  9. Rapid diversification of falcons (Aves: Falconidae) due to expansion of open habitats in the Late Miocene.

    Science.gov (United States)

    Fuchs, Jérôme; Johnson, Jeff A; Mindell, David P

    2015-01-01

    Understanding how and why lineages diversify is central to understanding the origins of biological diversity. The avian family Falconidae (caracaras, forest-falcons, falcons) has an uneven distribution of species among multiple well-supported clades, and provides a useful system for testing hypotheses about diversification rate and correlation with environmental changes. We analyzed eight independent loci for 1-7 individuals from each of the 64 currently recognized Falconidae species, together with two fossil falconid temporal calibrations, to assess phylogeny, absolute divergence times and potential shifts in diversification rate. Our analyses supported similar diversification ages in the Early to Middle Miocene for the three traditional subfamilies, Herpetotherinae, Polyborinae and Falconinae. We estimated that divergences within the subfamily Falconinae began about 16mya and divergences within the most species-rich genus, Falco, including about 60% of all Falconidae species, began about 7.5mya. We found evidence for a significant increase in diversification rate at the basal phylogenetic node for the genus Falco, and the timing for this rate shift correlates generally with expansion of C4 grasslands beginning around the Miocene/Pliocene transition. Concomitantly, Falco lineages that are distributed primarily in grassland or savannah habitats, as opposed to woodlands, and exhibit migratory, as opposed to sedentary, behavior experienced a higher diversification rate. Published by Elsevier Inc.

  10. First hominoid from the Late Miocene of the Irrawaddy Formation (Myanmar.

    Directory of Open Access Journals (Sweden)

    Jean-Jacques Jaeger

    2011-04-01

    Full Text Available For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l. associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l. indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia.

  11. Development of Miocene-Pliocene reef trend, St. Croix, U. S. Virgin Islands

    Energy Technology Data Exchange (ETDEWEB)

    Gill, I.; Eby, D.E.; Hubbard, D.K.; Frost, S.H.

    1988-01-01

    The Miocene-Pliocene reef trend on St. Croix, U.S. Virgin Islands, rims the present southern western coasts of the island and includes accompanying lagoonal and forereef facies. The reef trend was established on a foram-algal bank facies that represents basinal shallowing from the deep-water pelagic and hemipelagic facies of the Miocene Kingshill Limestone. Information on facies distribution and thickness is derived from rock exposures and 22 test wells drilled to a maximum depth of 91 m. The greatest thickness of the reef facies exists in a subsidiary graben on the south coast of St. Croix. The thickness of the reef section in this locality is due to preservation of the section in a downdropped block. Reef faunas include extant corals, as well as several extinct genera. Extant corals (e.g. Montastrea annularis, Diploria sp., and Porites porites) and extinct corals (e.g., Stylophora affinis, Antillea bilobata, and Thysanus sp.) are the main reef frame-builders. Coralline algea and large benthic foraminifera are significant contributors to the sediments both prior to and during scleractinian reef growth. Dolomitization and calcite cementation occur prominantly in an area corresponding to a Holocene lagoon. The spatial distribution of the dolomite suggests that the lagoon is a Tertiary feature directly related to the dolomitization process. Stable isotopic values suggest dolomitization of fluids of elevated salinity.

  12. Andegameryx andegaviensis Ginsburg, 1971 (Artiodactyla, Ruminantia, from the early Miocene site of Estrepouy (MN3, France

    Directory of Open Access Journals (Sweden)

    Morales, J.

    2011-12-01

    Full Text Available Several dental remains from the Early Miocene of Estrepouy (MN3, France previously reported as Amphitragulus aurelianensis by Roman & Viret (1934 are described in this work and assigned to Andegameryx andegaviensis Ginsburg, 1971. The re-study of this material and the comparison with other remains of A. andegaviensis from several european localities of the early Miocene, including the type locality of the species, have permitted us to confirm the presence of A. andegaviensis in the ruminant fauna from Estrepouy.En esta nota describimos algunos de los restos del yacimiento del Mioceno inferior de Estrepouy (MN3, Francia atribuidos por Roman & Viret (1934 a Amphitragulus aruelianensis, cambiando su asignación a Andegameryx andegaviensis Ginsburg, 1971. El reestudio del material y su comparación con los restos de A. andegaviensis de otras localidades europeas del Mioceno inferior, incluyendo la localidad tipo de la especie, permiten confirmar su presencia entre la fauna de rumiantes fósiles de Estrepouy.

  13. A MIDDLE MIOCENE BALEEN WHALE FROM BELE VODE IN BELGRADE, SERBIA

    Directory of Open Access Journals (Sweden)

    PAVEL GOL’DIN

    2018-01-01

    Full Text Available There was a fauna of baleen whales (Cetacea: Mysticeti in the Central Paratethys, a Miocene water body which covered the area of present-day Central Europe. Most of the fossil baleen whales from the Central Paratethys have been found in strata assigned to the regional Badenian age and comprise endemic forms, known only from this region. Here a new description is provided for a fragmentary skeleton of a whale found in Belgrade, Serbia, and its age context and biological aspects are discussed. This specimen, consisting of a fragmentary horizontal ramus of the mandible and eight caudal vertebrae, is tentatively identified as ?Parietobalaena sp., a globally known Miocene taxon, with related forms having been recorded earlier from the Eastern Paratethys. An early Sarmatian age (i.e., about 12.7-12.4 Ma is proposed for the specimen. Based on epiphyseal fusion of caudal vertebrae, the specimen’s age is identified as a subadult, with a body length of around 2.5 m and an estimated adult body length around 3-3.5 m, which is extremely small for baleen whales. This find represents one of the latest records of baleen whales in the Central Paratethys and one of the latest published records of Parietobalaena-like taxa in the world.

  14. Quality and petrographic characteristics of the lacustrine Ermenek coal (early Miocene), Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Demirel, I.H.; Karayigit, A.I. [Hacettepe Univ., Beytepe-Ankara (Turkey). Dept. of Geological Engineering

    1999-05-01

    The early Miocene Yenimahalle Formation including alluvial-lacustrine sediments and a mineable coal steam with an average of 5 m in thickness rests unconformably upon the basement and is also unconformably overlain by marine limestones of the middle-late Miocene Mut Formation in the Ermenek coal basin. The coal basin in the present study has been subdivided into two areas, Canakci and Pamuklu-Tepebasi, which are separated by the basement and a fault, in order to determine coal properties in detail. The investigated subbituminous coals with an average of 0.40%Ro huminite reflectance often contain gastropod shells (Planorbidae) which commonly maintain the original aragonite and calcite composition. The coals have similar chemical properties and petrographic composition in the two areas, but their sulphur contents are clearly different. In the Canakci area the coals on an air-dried basis contain distinctly less total sulphur (avg. 1.3%) and organic sulphur contents (0.13--0.15%) than in the Pamuklu-Tepebasi area (avg. 4.5% and 4.25%, respectively). This difference is interpreted to be controlled by mire chemistry and sedimentation during peat formation.

  15. Quality and petrographic characteristics of the Lacustrine Ermenek Coal (Early Miocene), Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Demirel, I.H.; Karayigit, A.I.

    1999-04-15

    The early Miocene Yenimahalle Formation including alluvial-lacustrine sediments and a mineable coal seam with an average of 5 m in thickness rests unconformably upon the basement and is also unconformably overlain by marine limestones of the middle-late Miocene Mut Formation in the Ermenek coal basin. The coal basin in the present study has been subdivided into two areas, Canakci and Pamuklu-Tepebasi, which are separated by the basement and a fault, in order to determine coal properties in detail. The investigated subbituminous coals with an average of 0.40% Ro huminite reflectance often contain gastropod shells (Planorbidae) which commonly maintain the original aragonite and calcite composition. The coals have similar chemical properties and petrographic composition in the two areas, but their sulphur contents are clearly different. In the Canakci area the coals on an air-dried basis contain distinctly less total sulphur (avg. 1.3%) and organic sulphur contents (0.13 0.15%) than in the Pamuklu-Tepebasi area (avg. 4.5% and 4.25%, respectively). This difference is interpreted to be controlled by mire chemistry and sedimentation during peat formation. (author)

  16. Enhanced Structural Interpretation Using Multitrace Seismic Attribute For Oligo-Miocene Target at Madura Strait Offshore

    Science.gov (United States)

    Pratama Wahyu Hidayat, Putra; Hary Murti, Antonius; Sudarmaji; Shirly, Agung; Tiofan, Bani; Damayanti, Shinta

    2018-03-01

    Geometry is an important parameter for the field of hydrocarbon exploration and exploitation, it has significant effect to the amount of resources or reserves, rock spreading, and risk analysis. The existence of geological structure or fault becomes one factor affecting geometry. This study is conducted as an effort to enhance seismic image quality in faults dominated area namely offshore Madura Strait. For the past 10 years, Oligo-Miocene carbonate rock has been slightly explored on Madura Strait area, the main reason because migration and trap geometry still became risks to be concern. This study tries to determine the boundary of each fault zone as subsurface image generated by converting seismic data into variance attribute. Variance attribute is a multitrace seismic attribute as the derivative result from amplitude seismic data. The result of this study shows variance section of Madura Strait area having zero (0) value for seismic continuity and one (1) value for discontinuity of seismic data. Variance section shows the boundary of RMKS fault zone with Kendeng zone distinctly. Geological structure and subsurface geometry for Oligo-Miocene carbonate rock could be identified perfectly using this method. Generally structure interpretation to identify the boundary of fault zones could be good determined by variance attribute.

  17. Occlusal enamel complexity in middle miocene to holocene equids (Equidae: Perissodactyla) of North America.

    Science.gov (United States)

    Famoso, Nicholas A; Davis, Edward Byrd

    2014-01-01

    Four groups of equids, "Anchitheriinae," Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate.

  18. Sedimentology and paleoenvironments of a new fossiliferous late Miocene-Pliocene sedimentary succession in the Rukwa Rift Basin, Tanzania

    Science.gov (United States)

    Mtelela, Cassy; Roberts, Eric M.; Hilbert-Wolf, Hannah L.; Downie, Robert; Hendrix, Marc S.; O'Connor, Patrick M.; Stevens, Nancy J.

    2017-05-01

    This paper presents a detailed sedimentologic investigation of a newly identified, fossiliferous Late Neogene sedimentary succession in the Rukwa Rift Basin, southwestern Tanzania. This synrift deposit is a rare and significant new example of a fossiliferous succession of this age in the Western Branch of East Africa Rift System. The unit, informally termed the lower Lake Beds succession, is late Miocene to Pliocene in age based on cross-cutting relationships, preliminary biostratigraphy, and U-Pb geochronology. An angular unconformity separates the lower Lake Beds from underlying Cretaceous and Oligocene strata. Deposition was controlled by rapid generation of accommodation space and increased sediment supply associated with late Cenozoic tectonic reactivation of the Rukwa Rift and synchronous initiation of the Rungwe Volcanic Centre. The lower Lake Beds, which have thus far only been identified in three localities throughout the Rukwa Rift Basin, are characterized by two discrete lithologic members (herein A and B). The lower Member A is a volcanic-rich succession composed mostly of devitrified volcanic tuffs, and volcaniclastic mudstones and sandstones with minor conglomerates. The upper Member B is a siliciclastic-dominated succession of conglomerates, sandstones, mudstones and minor volcanic tuffs. Detailed facies analysis of the lower Lake Beds reveals various distinctive depositional environments that can be grouped into three categories: 1) alluvial fan; 2) fluvial channel; and 3) flood basin environments, characterized by volcanoclastic-filled lakes and ponds, abandoned channel-fills and pedogenically modified floodplains. Member A represents a shallow lacustrine setting filled by tuffaceous sediments, which grade up into a system of alluvial fans and high-energy, proximal gravel-bed braided rivers. An unconformity marks the contact between the two members. Member B shows an upward transition from a high-energy, gravel-bed braided river system to a sandy

  19. Simulation de la sédimentation dans un bassin évaporitique à niveau d'eau sous influence eustatique. Application au bassin paléogène de Mulhouse (Alsace, France Simulation of Sedimentation in an Evaporitic Basin At Water Level under Eustatic Influence. Application to the Paleogene Mulhouse Basin (Alsace, France

    Directory of Open Access Journals (Sweden)

    Carpentier B.

    2006-11-01

    lower body of salt water (salt saturated, an upper body of salt water (with varying salinity and sometimes at the surface a body of low-salt water linked to the supply of continental water. The lower body of salt water, called captive brine , is defined as the water layer underneath the threshold. Its height during time depends on the difference between the depth of the sediments deposited and the subsidence. We will assume that the depth of the basin (and hence the subsidence is always sufficient for the captive brineto be able to exist. The upper body of salt water, called active body of water , is defined as the salt water layer located topographically above the threshold. It is in communication with the transfer zone or the open marine domain/basin . Its height during time thus depends on eustatic variations. The body of low-salt water corresponds to a body of pellicular water whose existence is defined by the presence or absence of influxes of fresh continental water in the mesh. On the scale of the basin, this body of low-salt water has a geographic extension that is governed by the regional hydrologic balance (influxes of continental water and evaporation. It may not exist at the level of the mesh considered, and its presence at the top is linked to the very strong contrast of density between the low-salt water and the underlying brines. In the model, sedimentation as a function of time is governed by the alternating passage of the regional hydrologic balance between the two states:(a State 1 ( dryperiod in which the volume of continental water supplied to the top of the mesh is lower than the volume of water evaporated. There is no body of low-salt water, and sedimentation is evaporitic. (b State 2 ( wetperiod in which the volume of continental water supplied to the top of the mesh is greater than the volume of water evaporated. A body of low-salt water exists at the top of the mesh, and sedimentation is shaly. The duration of each stateand the regional

  20. Upper urinary tract tumors

    DEFF Research Database (Denmark)

    Gandrup, Karen L; Nordling, Jørgen; Balslev, Ingegerd

    2014-01-01

    BACKGROUND: Computed tomography urography (CTU) is used widely in the work-up of patients with symptoms of urinary tract lesions. Preoperative knowledge of whether a tumor is invasive or non-invasive is important for the choice of surgery. So far there are no studies about the distinction...... of invasive and non-invasive tumors in ureter and renal pelvis based on the enhancement measured with Hounsfield Units. PURPOSE: To examine the value of CTU using split-bolus technique to distinguish non-invasive from invasive urothelial carcinomas in the upper urinary tract. MATERIAL AND METHODS: Patients...... obtained at CTU could distinguish between invasive and non-invasive lesions. No patients had a CTU within the last year before the examination that resulted in surgery. CONCLUSION: A split-bolus CTU cannot distinguish between invasive and non-invasive urothelial tumors in the upper urinary tract...

  1. Post-collisional magmatism and ore-forming systems in the Menderes massif: new constraints from the Miocene porphyry Mo-Cu Pınarbaşı system, Gediz-Kütahya, western Turkey

    Science.gov (United States)

    Delibaş, Okan; Moritz, Robert; Chiaradia, Massimo; Selby, David; Ulianov, Alexey; Revan, Mustafa Kemal

    2017-12-01

    The Pınarbaşı Mo-Cu prospect is hosted within the Pınarbaşı intrusion, which is exposed together with the NW-SE-trending Koyunoba, Eğrigöz, and Baklan plutons along the northeastern border of the Menderes massif. The Pınarbaşı intrusion predominantly comprises monzonite, porphyritic granite, and monzodiorite. All units of the Pınarbaşı intrusion have sharp intrusive contacts with each other. The principal mineralization style at the Pınarbaşı prospect is a porphyry-type Mo-Cu mineralization hosted predominantly by monzonite and porphyritic granite. The porphyry type Mo-Cu mineralization consists mostly of stockwork and NE- and EW-striking sub-vertical quartz veins. Stockwork-type quartz veins hosted by the upper parts of the porphyritic granite within the monzonite, are typically enriched in chalcopyrite, molybdenite, pyrite, and limonite. The late NE- and EW-striking normal faults cut the stockwork vein system and control the quartz-molybdenite-chalcopyrite-sphalerite-fahlore-galena veins, as well as molybdenite-hematite-bearing silicified zones. Lithogeochemical and whole-rock radiogenic isotope data (Sr, Nd and Pb) of the host rocks, together with Re-Os molybdenite ages (18.3 ± 0.1 Ma - 18.2 ± 0.1 Ma) reveal that the monzonitic and granitic rocks of the Pınarbaşı intrusion were derived from an enriched lithospheric mantle-lower crust during Oligo-Miocene post-collisional magmatism. The lithospheric mantle was metasomatised by fluids and subducted sediments, and the mantle-derived melts interacted with lower crust at 35-40 km depth. This mechanism explains the Mo and Cu enrichments of the Pınarbaşı intrusion during back-arc magmatism. We conclude that the melt of the Pınarbaşı intrusion could have rapidly ascended to mid-crustal levels, with only limited crustal assimilation along major trans-lithospheric faults as a result of thinning of the middle to upper crust during regional extension, and resulted in the development of porphyry

  2. Land subsidence and caprock dolines caused by subsurface gypsum dissolution and the effect of subsidence on the fluvial system in the Upper Tigris Basin (between Bismil Batman, Turkey)

    Science.gov (United States)

    Doğan, Uğur

    2005-11-01

    Karstification-based land subsidence was found in the Upper Tigris Basin with dimensions not seen anywhere else in Turkey. The area of land subsidence, where there are secondary and tertiary subsidence developments, reaches 140 km 2. Subsidence depth ranges between 40 and 70 m. The subsidence was formed as a result of subsurface gypsum dissolution in Lower Miocene formation. Although there are limestones together with gypsum and Eocene limestone below them in the area, a subsidence with such a large area is indicative of karstification in the gypsum. The stratigraphical cross-sections taken from the wells and the water analyses also verify this fact. The Lower Miocene gypsum, which shows confined aquifer features, was completely dissolved by the aggressive waters injected from the top and discharged through by Zellek Fault. This resulted in the development of subsidence and formation of caprock dolines on loosely textured Upper Miocene-Pliocene cover formations. The Tigris River runs through the subsidence area between Batman and Bismil. There are four terrace levels as T1 (40 m), T2 (30 m), T3 (10 m) and T4 (4-5 m) in the Tigris River valley. It was also found that there were some movements of the levels of the terraces in the valley by subsidence. The subsidence developed gradually throughout the Quaternary; however no terrace was formed purely because of subsidence.

  3. Petrologic evolution of Miocene-Pliocene mafic volcanism in the Kangal and Gürün basins (Sivas-Malatya), central east Anatolia: Evidence for Miocene anorogenic magmas contaminated by continental crust

    Science.gov (United States)

    Kocaarslan, Ayça; Ersoy, E. Yalçın

    2018-06-01

    This study discusses the geochemical features of the Early-Middle Miocene and Pliocene basaltic (SiO2 = 46-52; MgO = 6-10 wt%) to andesitic (SiO2 = 59; MgO = 4 wt%) rocks exposed in the Gürün and Kangal basins (Sivas, eastern part of central Anatolia), respectively. The basaltic rocks are characterized by alkaline to tholeiitic affinities, while the more evolved andesitic samples show calc-alkaline affinity. Trace element variations reveal that they can be evaluated in three sub-groups, each represented by different contents of trace elements for given Nb contents. Primary magmas of each groups were likely produced by different degrees of partial melting ( 1-2, 2-3, 7-10% respectively) from a common mantle source, subsequently underwent different degrees of fractionation and crustal contamination. Derivation from a common mantle source of the primitive magmas of each group is supported by similar Sr, Nd and Pb isotopic ratios. Increasing degrees of partial melting seem to be responsible for the alkaline to tholeiitic variation among the basaltic samples, while higher degrees of crustal contamination (AFC) resulted in calc-alkaline affinity of the more evolved samples. Most primitive Pliocene samples show intra-plate (anorogenic) geochemical features, while the more evolved Miocene calc-alkaline samples resemble geochemically subduction-related (orogenic) magmatic rocks. However, on the basis of detailed geochemical models, we propose that the calc-alkaline affinity among the Miocene samples can also be gained by crustal contamination of their primary magmas which were also anorogenic in character. If this is true, overall, the Miocene and Pliocene basaltic to andesitic rocks in the Gürün and Kangal basins appear to may have formed by variable degrees of partial melting of a common anorogenic mantle that had not been subject to subduction-related metasomatism. This is an alternative approach to the general view assuming the Early-Middle Miocene magmatic activity

  4. Petrographic And Geochemical Relationships And Environmentally Significant Trace Element Contents Of Miocene Coals in The Çayirli (Erzincan) Area, Eastern Anatolia, Turkey

    Science.gov (United States)

    Yalcin Erik, Nazan

    2014-05-01

    This study has done related to the petrographic, coal-quality and the environmental influences of the Çayırlı coal field in the Eastern Anatolia. The region is one of the best examples of a continental collision zone in the world and located in a North-south converging collision zone between the Eurasian and the Arabian Plates. The geological units on the North of the basin are the peridotites and on the South, the Upper Triassic to Lower Cretaceous limestone. Tertiary sedimentary units also occupy a significant part of the geological features. Lower Miocene sediments include recifal limestone, marls, green clay and coal seams. The Çayırlı mining area in Eastern Anatolia region, contains these Miocene aged coals. These coals is characterized by high vitrinite and inertinite and low liptinite contents. The coals are Bituminous coal rank, with vitrinite reflectance ranging from 0.53 to 0.58%. Chemically, the coal in this study is characterised by low moisture, ash yield and sulfur content. The Çayırlı coal consist mainly of SiO2 and CaO, with secondary Fe2O3, Al2O3, and minor proportions of TiO2, P2O5 and other oxides. Several trace elements of environmental concern namely As, U and Be in Çayırlı coal are above the world averages, while Ni and Pb concentrations are less than the world average. However, As, Co, Cr, Ni, Pb, U and V contents of this coal are below Turkish averages. It can clearly observed that the concentration of the elements is highest in the high ash coal levels. Among the potentially hazardous trace elements, Be, Co, Ni, Se and U may be of little or no health and environmental concerns, wheras As, Pb, Sb, and Th require further examination for their potential health and environmental concerns. These properties may be related to evaluation of the coal forming environment from more reducing contitions in a marine influenced lower delta plain environment for investigated coals. On the basis of analytical data, there is no possibility that

  5. Astrochronology of a Late Oligocene to Early Miocene Magnetostratigraphy from the Northwest Atlantic

    Science.gov (United States)

    van Peer, T. E.; Xuan, C.; Liebrand, D.; Lippert, P. C.; Wilson, P. A.

    2016-12-01

    The Oligocene-Miocene Boundary is defined by the geomagnetic polarity reversal C6Cn.2n/C6Cn.2r with an astronomically tuned age of 23 Ma. For late Oligocene to early Miocene reversals, only a few records (mainly from the equatorial Pacific and South Atlantic) integrate magneto- and cyclo-stratigraphy with astronomical tuning. Reversal ages acquired from these records show differences up to 100 kyr. We report new astronomically tuned ages for reversals between 21-26.5 Ma, based on integrated palaeomagnetic and X-Ray Fluorescence (XRF) data from rapidly accumulated drift sediments (mean sedimentation rate of 2.5 cm/kyr) at Integrated Ocean Drilling Program (IODP) Site U1406 (northwest Atlantic). The natural remanence preserved in the sediments is relatively weak (especially at high demagnetisation steps) and prone to influence from measurement noise. We introduce an optimisation protocol to improve the estimation of component directions used to define the reversals. For each 1-cm interval measurement, the protocol searches for the combination of a fixed number of steps of demagnetisation data that minimises the maximum angular deviation, statistically excluding the noisy measurement steps. For the tuning, we use the logarithm of the calcium over potassium ratio ln(Ca/K) from XRF core scanning data, a proxy of carbonate content in the sediment. Spectral and wavelet analyses of the 140-m long ln(Ca/K) record highlight dominant obliquity (including the 178 and 1200 kyr modulation) and additional eccentricity forcing. Supported by preliminary stable isotope analysis on benthic foraminifera, we tuned ln(Ca/K) minima to obliquity minima and eccentricity maxima. The resulting age model yield new independent ages for all reversals between C6Ar/C6AAn to C8r/C9n. Our results are generally consistent (within an obliquity cycle) with the Ocean Drilling Program (ODP) Site 1090 age model [Billups et al., 2004], but deviate up to 80 kyr relative to ODP Site 1218 [Pälike et al

  6. Evidence for a dynamic East Antarctic ice sheet during the mid-Miocene climate transition

    Science.gov (United States)

    Pierce, Elizabeth L.; van de Flierdt, Tina; Williams, Trevor; Hemming, Sidney R.; Cook, Carys P.; Passchier, Sandra

    2017-11-01

    The East Antarctic ice sheet underwent a major expansion during the Mid-Miocene Climate Transition, around 14 Ma, lowering sea level by ∼60 m. However, direct or indirect evidence of where changes in the ice sheet occurred is limited. Here we present new insights on timing and locations of ice sheet change from two drill sites offshore East Antarctica. IODP Site U1356, Wilkes Land, and ODP Site 1165, Prydz Bay are located adjacent to two major ice drainage areas, the Wilkes Subglacial Basin and the Lambert Graben. Ice-rafted detritus (IRD), including dropstones, was deposited in concentrations far exceeding those known in the rest of the Miocene succession at both sites between 14.1 and 13.8 Ma, indicating that large amounts of IRD-bearing icebergs were calved from independent drainage basins during this relatively short interval. At Site U1356, the IRD was delivered in distinct pulses, suggesting that the overall ice advance was punctuated by short periods of ice retreat in the Wilkes Subglacial Basin. Provenance analysis of the mid-Miocene IRD and fine-grained sediments provides additional insights on the movement of the ice margin and subglacial geology. At Site U1356, the dominant 40Ar/39Ar thermochronological age of the ice-rafted hornblende grains is 1400-1550 Ma, differing from the majority of recent IRD in the area, from which we infer an inland source area of this thermochronological age extending along the eastern part of the Adélie Craton, which forms the western side of the Wilkes Subglacial Basin. Neodymium isotopic compositions from the terrigenous fine fraction at Site U1356 imply that the ice margin periodically expanded from high ground well into the Wilkes Subglacial Basin during periods of MMCT ice growth. At Site 1165, MMCT pebble-sized IRD are sourced from both the local Lambert Graben and the distant Aurora Subglacial Basin drainage area. Together, the occurrence and provenance of the IRD and glacially-eroded sediment at these two marine

  7. Two new species of .i.Prolagus./i. (Lagomorpha, Mammalia) from the Late Miocene of Hungary: taxonomy, biochronology, and palaeobiogeography

    Czech Academy of Sciences Publication Activity Database

    Angelone, Ch.; Čermák, Stanislav

    2015-01-01

    Roč. 89, č. 4 (2015), s. 1023-1038 ISSN 0031-0220 Institutional support: RVO:67985831 Keywords : evolutionary trends * Hungary * isolated species * Late Miocene * P. latiuncinatus sp. nov * Prolagus pannonicus sp. nov Subject RIV: EG - Zoology Impact factor: 1.545, year: 2015

  8. Mid-Miocene C4 expansion on the Chinese Loess Plateau under an enhanced Asian summer monsoon

    Science.gov (United States)

    Dong, Jibao; Liu, Zhonghui; An, Zhisheng; Liu, Weiguo; Zhou, Weijian; Qiang, Xiaoke; Lu, Fengyan

    2018-06-01

    Atmospheric CO2 starvation, aridity, fire and warm season precipitation have all been proposed as major contributors to C4 plant expansion during the Late Miocene. However, the driving factors responsible for the distribution of C4 plants in the early and mid-Miocene still remain enigmatic. Here we report pedogenic carbon and oxygen isotope data (δ13Cpedo, δ18Opedo), along with magnetic susceptibility (MS) results, from the Zhuang Lang drilling core on the Chinese Loess Plateau (CLP). Elevated δ13Cpedo values (>-5‰) signal a prominent C4 expansion and substantially increased δ18Opedo and MS values indicate enhanced Asian summer monsoon (ASM) precipitation. Both of these conditions are observed during the Mid-Miocene Climatic Optimum (MMCO), 14.5-17 million years ago. The marked increase in C4 plants, associated with warm temperatures and increased precipitation, strongly suggests the control of an enhanced ASM on C4 expansion on the CLP during the MMCO. This finding contrasts with the late-Miocene C4 expansion associated with cooling and drying conditions observed in low latitudes and argues for regionally specific control of C4 plant distribution/expansion.

  9. A box model of the Late Miocene Mediterranean Sea: implications from combined 87Sr/86Sr and salinity data

    NARCIS (Netherlands)

    Topper, R.P.M.; Flecker, R.; Meijer, P.Th.; Wortel, M.J.R.

    2011-01-01

    Under certain conditions the strontium isotope ratio in the water of a semi‐enclosed basin is known to be sensitive to the relative size of ocean water inflow and river input. Combining Sr‐isotope ratios measured in Mediterranean Late Miocene successions with data on past salinity, one can derive

  10. Updated chronology for Middle to Late Miocene mammal sites of the Daroca area (Calatayud-Montalbán Basin, Spain)

    NARCIS (Netherlands)

    van Dam, Jan A.; Krijgsman, Wout; Abels, Hemmo A.; Álvarez-Sierra, Maria A.; Garci´a-Paredes, Israel; Lo´pez-Guerrero, Paloma; Peláez-Campomanes, Pablo; Ventra, Dario

    The micromammal sequence of the Calatayud-Montalbán Basin in Northeast Central Spain is exceptional in terms of its faunal richness and dating accuracy. However, until now, several classical localities with ages close to the Middle to Late Miocene transition have never been directly tied to the

  11. Evolutionary history of the thicket rats (genus Grammomys) mirrors the evolution of African forests since late Miocene

    Czech Academy of Sciences Publication Activity Database

    Bryja, J.; Šumbera, R.; Kerbis Peterhans, J. C.; Aghová, T.; Bryjová, A.; Mikula, Ondřej; Nicolas, V.; Denys, C.; Verheyen, E.

    2017-01-01

    Roč. 44, č. 1 (2017), s. 182-194 ISSN 0305-0270 Institutional support: RVO:67985904 Keywords : Arvicanthini * coastal forests * late Miocene Subject RIV: EA - Cell Biology OBOR OECD: Biology (theoretical, mathematical, thermal, cryobiology, biological rhythm), Evolutionary biology Impact factor: 4.248, year: 2016

  12. Evolutionary history of the thicket rats (genus Grammomys) mirrors the evolution of African forests since late Miocene

    Czech Academy of Sciences Publication Activity Database

    Bryja, Josef; Šumbera, R.; Kerbis Peterhans, J. C.; Aghová, Tatiana; Bryjová, Anna; Mikula, Ondřej; Nicolas, V.; Denys, C.; Verheyen, E.

    2017-01-01

    Roč. 44, č. 1 (2017), s. 182-194 ISSN 0305-0270 Institutional support: RVO:68081766 Keywords : Arvicanthini * coastal forests * late Miocene * lowland forests * mountain forests * phylogeography * Plio-Pleistocene climate changes * Rodentia * tropical Africa Subject RIV: EG - Zoology OBOR OECD: Ecology Impact factor: 4.248, year: 2016

  13. Marine connections of Amazonia: Evidence from foraminifera and dinoflagellate cysts (early to middle Miocene, Colombia/Peru)

    NARCIS (Netherlands)

    Boonstra, M.; Ramos, M.I.F.; Lammertsma, E.I.; Antoine, P.-O; Hoorn, C.

    2015-01-01

    Species composition in the present-day Amazonian heartland has an imprint of past marine influence. The exact nature, timing and extent of this marine influence, however, are largely unresolved. Here we use calcareous tests of foraminifera and marine palynomorphs from Miocene sediments in

  14. Four new species of deep water agglutinated foraminifera from the Oligocene-Miocene of the Congo Fan (offshore Angola)

    OpenAIRE

    Kender, S.; Kaminski, M. A.; Jones, R. W.

    2006-01-01

    Four new species of deep-water agglutinated benthic foraminifera are described from the Oligocene and Miocene of the Congo Fan, offshore Angola. Scherochorella congoensis n.sp., Paratrochamminoides goroyskiformis n.sp., Haplophragmoides nauticus n.sp. and Portatrochammina profunda n.sp. all occur in deep-sea turbiditic shales and sands from the distal section of the Congo Fan.

  15. The Mendel Formation: Evidence for Late Miocene climatic cyclicity at the northern tip of the Antarctic Peninsula

    Czech Academy of Sciences Publication Activity Database

    Nývlt, D.; Košler, J.; Mlčoch, B.; Mixa, P.; Lisá, Lenka; Bubík, M.; Hendriks, B. W. H.

    2011-01-01

    Roč. 299, 1/2 (2011), s. 363-384 ISSN 0031-0182 Institutional research plan: CEZ:AV0Z30130516 Keywords : Mendel Formation * Late Miocene * chmate * Antarctic Peninsula Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.392, year: 2011

  16. Age and stratigraphic context of Pliopithecus and associated fauna from Miocene sedimentary strata at Damiao, Inner Mongolia, China

    NARCIS (Netherlands)

    Kaakinen, Anu; Abdul Aziz, Hayfaa; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Salminen, Johanna; Wang, Lihua; Krijgsman, Wout; Fortelius, Mikael

    2015-01-01

    Since the discovery of mammalian fossils in Central Inner Mongolia in the beginning of the 20th century, this area has produced a rich and diverse record of Miocene faunas. Nevertheless, the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous

  17. Microfacies models and sequence stratigraphic architecture of the Oligocene–Miocene Qom Formation, south of Qom City, Iran

    Directory of Open Access Journals (Sweden)

    Mahnaz Amirshahkarami

    2015-07-01

    Full Text Available The Oligocene–Miocene Qom Formation has different depositional models in the Central Iran, Sanandaj–Sirjan and Urumieh-Dokhtar magmatic arc provinces in Iran. The Kahak section of the Qom Formation in the Urumieh-Dokhtar magmatic arc has been studied, in order to determinate its microfacies, depositional model and sequence stratigraphy. The textural analysis and faunal assemblages reveal ten microfacies. These microfacies are indicative of five depositional settings of open marine, patch reef, lagoon, tidal flat and beach of the inner and middle ramp. On the basis of the vertical succession architecture of depositional system tracts, four third-order sequences have been recognized in the Oligocene–Miocene Kahak succession of Qom Formation. Based on the correlation charts, the transgression of the Qom Sea started from the southeast and continued gradually towards the north. This resulted in widespread northward development of the lagoon paleoenvironment in the Aquitanian-Burdigalian stages. Also, the sequence stratigraphic model of the Oligocene–Miocene Qom Formation has an architecture similar to those that have developed from Oligocene–Miocene global sea level changes.

  18. The Miocene fish Marosichthys, a putative tetraodontiform, actually a perciform surgeon fish (Acanthuridae) related to the recent Naso

    NARCIS (Netherlands)

    Tyler, James C.

    1997-01-01

    Marosichthys huismani (de Beaufort, 1926), a fish from the Miocene of the Celebes, was described in the tripod fish family Triacanthidae, Tetraodontiformes. It is shown here to be a valid genus of the surgeon fish family Acanthuridae, Perciformes, and closely related to the Recent genus Naso.

  19. New method to estimate paleoprecipitation using fossil amphibians and reptiles and the middle and late Miocene precipitation gradients in Europe

    Science.gov (United States)

    Böhme, M.; Ilg, A.; Ossig, A.; Küchenhoff, H.

    2006-06-01

    Existing methods for determining paleoprecipitation are subject to large errors (±350 400 mm or more using mammalian proxies), or are restricted to wet climate systems due to their strong facies dependence (paleobotanical proxies). Here we describe a new paleoprecipitation tool based on an indexing of ecophysiological groups within herpetological communities. In recent communities these indices show a highly significant correlation to annual precipitation (r2 = 0.88), and yield paleoprecipitation estimates with average errors of ±250 280 mm. The approach was validated by comparison with published paleoprecipitation estimates from other methods. The method expands the application of paleoprecipitation tools to dry climate systems and in this way contributes to the establishment of a more comprehensive paleoprecipitation database. This method is applied to two high-resolution time intervals from the European Neogene: the early middle Miocene (early Langhian) and the early late Miocene (early Tortonian). The results indicate that both periods show significant meridional precipitation gradients in Europe, these being stronger in the early Langhian (threefold decrease toward the south) than in the early Tortonian (twofold decrease toward the south). This pattern indicates a strengthening of climatic belts during the middle Miocene climatic optimum due to Southern Hemisphere cooling and an increased contribution of Arctic low-pressure cells to the precipitation from the late Miocene onward due to Northern Hemisphere cooling.

  20. in upper gastrointestinal endoscopy

    Directory of Open Access Journals (Sweden)

    Sinan Uzman

    2016-07-01

    Full Text Available Introduction : There is increasing interest in sedation for upper gastrointestinal endoscopy (UGE. Prospective randomized studies comparing sedation properties and complications of propofol and midazolam/meperidine in upper gastrointestinal endoscopy (UGE are few. Aim: To compare propofol and midazolam/meperidine sedation for UGE in terms of cardiopulmonary side effects, patient and endoscopist satisfaction and procedure-related times. Material and methods: This was a prospective, randomized, double-blind study of propofol versus midazolam and meperidine in 100 patients scheduled for diagnostic upper gastrointestinal endoscopy. The patients were divided into propofol and midazolam/meperidine groups. Randomization was generated by a computer. Cardiopulmonary side effects (hypotension, bradycardia, hypoxemia, procedure-related times (endoscopy time, awake time, time to hospital discharge, and patient and endoscopist satisfaction were compared between groups. Results: There was no significant difference between the groups with respect to the cost, endoscopy time, or demographic and clinical characteristics of the patients. Awake time and time to hospital discharge were significantly shorter in the propofol group (6.58 ±4.72 vs. 9.32 ±4.26 min, p = 0.030 and 27.60 ±7.88 vs. 32.00 ±10.54 min, p = 0.019. Hypotension incidence was significantly higher in the propofol group (12% vs. 0%, p = 0.027. The patient and endoscopist satisfaction was better with propofol. Conclusions : Propofol may be preferred to midazolam/meperidine sedation, with a shorter awake and hospital discharge time and better patient and endoscopist satisfaction. However, hypotension risk should be considered with propofol, and careful evaluation is needed, particularly in cardiopulmonary disorders.

  1. Upper extremity golf injuries.

    Science.gov (United States)

    Cohn, Michael A; Lee, Steven K; Strauss, Eric J

    2013-01-01

    Golf is a global sport enjoyed by an estimated 60 million people around the world. Despite the common misconception that the risk of injury during the play of golf is minimal, golfers are subject to a myriad of potential pathologies. While the majority of injuries in golf are attributable to overuse, acute traumatic injuries can also occur. As the body's direct link to the golf club, the upper extremities are especially prone to injury. A thorough appreciation of the risk factors and patterns of injury will afford accurate diagnosis, treatment, and prevention of further injury.

  2. Otoliths in situ from Sarmatian (Middle Miocene) fishes of the Paratethys. Part I

    DEFF Research Database (Denmark)

    Schwarzhans, Werner; Carnevale, Giorgio; Bannikov, Alexandre F.

    2017-01-01

    to two otolith-based species so far identified from the same time interval in the Paratethys---Atherina austriaca and Atherina gidjakensis. Our correlation of isolated otoliths and otolith in situ documents in this case that A. suchovi is not synonymous to any of the otolith-based species, although...... it appears to be closely related to A. gidjakensis. A list is presented and briefly discussed showing Sarmatian skeleton-based fish records from the Central and Eastern Paratethys with an overview of known and currently studied fishes with otoliths in situ.......Several well-preserved otoliths were extracted from four slabs containing fish specimens of Atherina suchovi. Atherina suchovi is one of the five Atherina species recorded from the Middle Miocene of the Central and Eastern Paratethys established on articulated skeletal remains. This corresponds...

  3. Early Miocene benthic foraminifera and biostratigraphy of the Qom Formation, Deh Namak, Central Iran

    Science.gov (United States)

    Daneshian, Jahanbakhsh; Dana, Leila Ramezani

    2007-03-01

    A total of 165 samples were collected from the Qom Formation investigated in a stratigraphic section north of Deh Namak, in Central Iran. From these, 35 genera and 47 species of benthic foraminifera were identified. The age of the studied section is Early Miocene (Aquitanian to Early Burdigalian) based on the occurrence of Borelis melo curdica, Meandropsina anahensis, Meandropsina iranica, Elphidium sp. 14, Peneroplis farsensis, and Triloculina tricarinata. The thickness of the Qom Formation is 401 m of which 161.2 m is early Burdigalian in age. Foraminiferal assemblages in the Deh Namak section are referable to the Borelis melo group- Meandropsina iranica Assemblage Zone and Miogypsinoides- Archaias-Valvulinid Assemblage Zone of [Adams, T.D., Bourgeois, F., 1967. Asmari biostratigraphy. Iranian Oil Operating Companies, Geological and Exploration Division, Report1074 (unpublished) 1-37.] described originally from the Asmari Formation.

  4. Enhanced Continental Weathering on Antarctica During the Mid Miocene Climatic Optima Based on Pb Isotopes

    Science.gov (United States)

    Martin, E. E.; Fenn, C.; Basak, C.

    2012-12-01

    Feedbacks between climate and continental weathering can be monitored over geologic time scales using Pb isotopes preserved in marine sediments. During chemical weathering, radiogenic Pb is preferentially released to the dissolved phase, producing weathering solutions with more radiogenic isotopic values than the parent rock. The offset between the composition of the solution and rock tend to increase with the intensity of incongruent weathering (von Blanckenburg and Nägler, 2001; Harlavan and Erel, 2002). The seawater isotopic signal extracted from Fe-Mn oxides on bulk marine sediments is interpreted to represent the composition of local dissolved weathering inputs. For example, increasing seawater Pb isotopes observed during the most recent deglaciation are believed to reflect enhanced weathering of newly exposed glacial rock flour under warm conditions (Foster and Vance, 2006; Kurzweil et al., 2010). For this study we evaluated Nd and Pb isotopes from both the seawater fraction (extracted from Fe-Mn oxides) and parent rock (the detrital fraction of marine sediment) during the Mid-Miocene Climatic Optimum (MMCO) and subsequent cooling and East Antarctic Ice Sheet (EAIS) expansion (18 to 8 Ma) from Ocean Drilling Program site 744 on Kerguelen Plateau (2300 m; Indian sector) and sites 689 and 690 on Maud Rise (2080 m and 2914 m; Atlantic sector). The absolute value of seawater 206Pb/204Pb and separation between values for seawater and detrital fractions increased during the MMCO, suggesting enhanced weathering in proglacial and deglaciated areas exposed by ice sheet meltback during the warm interval. During the ensuing cooling, seawater values and the offset between the two archives decreased. Similar trends are displayed by 207Pb/204Pb and 208Pb/204Pb, although 207Pb/204Pb detrital values tend to be higher than seawater values. Reconstructions of atmospheric pCO2 in the Miocene have suggested both 1) decoupling between pCO2 and climate with consistently low

  5. PROPOTAMOCHOERUS SP. (SUIDAE, MAMMALIA FROM THE LATE MIOCENE OF GRAVITELLI (MESSINA, SICILY, ITALY REDISCOVERED

    Directory of Open Access Journals (Sweden)

    GIANNI GALLAI

    2006-07-01

    Full Text Available This paper describes two casts of a suid from the Late Miocene of Gravitelli (Messina, Sicily, originally described by Seguenza in 1902. The entire Gravitelli faunal collection was lost in the early 1900¡¦s. The recent rediscovery of two casts in the collections of the Museo di Storia Naturale of the University of Florence represent the only available material from this locality (in addition to the original description and illustration by Seguenza. The study of these casts allow a revision of the Gravitelli suid and its attribution to the genus Propotamochoerus. Although a specific determination is not possible, we suggest probable affinities with the species P. hysudricus or P. provincialis.

  6. Paleomagnetic record of a geomagnetic field reversal from late miocene mafic intrusions, southern nevada.

    Science.gov (United States)

    Ratcliff, C D; Geissman, J W; Perry, F V; Crowe, B M; Zeitler, P K

    1994-10-21

    Late Miocene (about 8.65 million years ago) mafic intrusions and lava flows along with remagnetized host rocks from Paiute Ridge, southern Nevada, provide a high-quality paleomagnetic record of a geomagnetic field reversal. These rocks yield thermoremanent magnetizations with declinations of 227 degrees to 310 degrees and inclinations of -7 degrees to 49 degrees , defining a reasonably continuous virtual geomagnetic pole path over west-central Pacific longitudes. Conductive cooling estimates for the intrusions suggest that this field transition, and mafic magmatism, lasted only a few hundred years. Because this record comes principally from intrusive rocks, rather than sediments or lavas, it is important in demonstrating the longitudinal confinement of the geomagnetic field during a reversal.

  7. A new Miocene baleen whale from Peru deciphers the dawn of cetotheriids

    Science.gov (United States)

    Marx, Felix G.; Lambert, Olivier; de Muizon, Christian

    2017-09-01

    Cetotheriidae are an iconic, nearly extinct family of baleen whales (Mysticeti) with a highly distinct cranial morphology. Their origins remain a mystery, with even the most archaic species showing a variety of characteristic features. Here, we describe a new species of archaic cetotheriid, Tiucetus rosae, from the Miocene of Peru. The new material represents the first mysticete from the poorly explored lowest portion of the highly fossiliferous Pisco Formation (allomember P0), and appears to form part of a more archaic assemblage than observed at the well-known localities of Cerro Colorado, Cerro los Quesos, Sud-Sacaco and Aguada de Lomas. Tiucetus resembles basal plicogulans (crown Mysticeti excluding right whales), such as Diorocetus and Parietobalaena, but shares with cetotheriids a distinct morphology of the auditory region, including the presence of an enlarged paroccipital concavity. The distinctive morphology of Tiucetus firmly places Cetotheriidae in the context of the poorly understood `cetotheres' sensu lato, and helps to resolve basal relationships within crown Mysticeti.

  8. Anatomy and origin of carbonate structures in a Miocene cold-seep field

    Science.gov (United States)

    Aiello, Ivano W.; Garrison, Robert E.; Moore, J. Casey; Kastner, Miriam; Stakes, Debra S.

    2001-12-01

    Miocene calcite concretions resembling modern carbonate structures that form at cold seeps are present in fractured opal- CT porcelanites that are interbedded with mudstones in coastal cliffs at Santa Cruz, California. The morphologies of the carbonate structures differ markedly from conventional concretions and are spatially aligned with orthogonal joints in the porcelanites. The structures contain tubular holes that are identical to fluid and gas conduits in modern carbonate seep structures; the orientations of these tubes suggest that fluid and gas flow was both vertical and horizontal, the latter along extensional joints that formed preferentially in the brittle, silica-rich layers that had enhanced bedding- parallel permeability. Petrographic and isotopic characteristics of the carbonate structures indicate that calcite precipitation occurred in a shallow, subseafloor environment in either the zone of microbial sulfate reduction or of methanogenesis, prior to or possibly simultaneously with the silica phase transformation of opal- A in diatom shells to opal-CT.

  9. Palaeobotanical data for climate change during the late Miocene - early Pliocene in Western Bulgaria

    International Nuclear Information System (INIS)

    Hristova, Viktoria; Ivanov, Dimiter; Bozukov, Vladimir

    2015-01-01

    The Coexistence Approach (CA) analysis was applied to plant macro- and microfossils from the Late Miocene to Early Pliocene sites in western Bulgaria to obtain quantitative climate data and reconstruct climate dynamics. Calculated new values for the Sofia macro flora confirmed a warm-temperate and humid climate with mean annual temperature (MAT) between 12–170C, mean temperature of the warmest month (WMT) 23.6–280C, mean temperature of the coldest month (CMT) 0–50C and mean annual precipitation (MAP) 843–1179 mm. This is consistent with the climatic parameters obtained from the microflora – MAT 13.6–16, WMT 23.6–27.9, CMT 3.7–6 and MAP 803–1308mm. All presented data are in good accordance with other regional palaeoclimate reconstructions from Bulgarian and Europaean floras. Key words: Late Miocene–Early Pliocene, palaeoclimate, Sofia Basin

  10. MIDDLE EOCENE TO EARLY MIOCENE FORAMINIFERAL BIOSTRATIGRAPHY IN THE EPILIGURIAN SUCCESSION (NORTHERN APENNINES, ITALY

    Directory of Open Access Journals (Sweden)

    NICOLETTA MANCIN

    2001-11-01

    Full Text Available A quantitative biostratigraphical study was performed on the foraminiferal assemblages from 15 stratigraphic sections of the Epiligurian Succession (Middle Eocene-Early Miocene, Northern Apennines, Italy. This study enabled us to identify the presence of some of the standard bioevents and to note that other bioevents are absent or show a different chronostratigraphic range. Other additional bioevents, identified throughout the area, have therefore been utilised to improve the biostratigraphical resolution of the Epiligurian sediments. These bioevents include the massive extinction of the muricate species at the Bartonian/Priabonian boundary; the increasing abundance of Paragloborotalia opima opima near Subzone P21a/P21b and the Rupelian/Chattian boundaries; and the FO of Globoquadrina dehiscens at the Subzone N4a/N4b boundary. 

  11. Oligo-Miocene reservoir sequence characterization and structuring in the Sisseb El Alem-Kalaa Kebira regions (Northeastern Tunisia)

    Science.gov (United States)

    Houatmia, Faten; Khomsi, Sami; Bédir, Mourad

    2015-11-01

    The Sisseb El Alem-Enfidha basin is located in the northeastern Tunisia, It is borded by Nadhour - Saouaf syncline to the north, Kairouan plain to the south, the Mediterranean Sea to the east and Tunisian Atlassic "dorsale" to the west. Oligocene and Miocene deltaic deposits present the main potential deep aquifers in this basin with high porosity (25%-30%). The interpretation of twenty seismic reflection profiles, calibrated by wire line logging data of twelve oil wells, hydraulic wells and geologic field sections highlighted the impact of tectonics on the structuring geometry of Oligo-Miocene sandstones reservoirs and their distribution in raised structures and subsurface depressions. Miocene seismostratigraphy analysis from Ain Ghrab Formation (Langhian) to the Segui Formation (Quaternary) showed five third-order seismic sequence deposits and nine extended lenticular sandy bodies reservoirs limited by toplap and downlap surfaces unconformities, Oligocene deposits presented also five third- order seismic sequences with five extended lenticular sandy bodies reservoirs. The Depth and the thickness maps of these sequence reservoir packages exhibited the structuring of this basin in sub-basins characterized by important lateral and vertical geometric and thichness variations. Petroleum wells wire line logging correlation with clay volume calculation showed an heterogeneous multilayer reservoirs of Oligocene and Miocene formed by the arrangement of fourteen sandstone bodies being able to be good reservoirs, separated by impermeable clay packages and affected by faults. Reservoirs levels correspond mainly to the lower system tract (LST) of sequences. Intensive fracturing by deep seated faults bounding the different sub-basins play a great role for water surface recharge and inter-layer circulations between affected reservoirs. The total pore volume of the Oligo-Miocene reservoir sandy bodies in the study area, is estimated to about 4 × 1012 m3 and equivalent to 4

  12. First North American fossil monkey and early Miocene tropical biotic interchange

    Science.gov (United States)

    Bloch, Jonathan I.; Woodruff, Emily D.; Wood, Aaron R.; Rincon, Aldo F.; Harrington, Arianna R.; Morgan, Gary S.; Foster, David A.; Montes, Camilo; Jaramillo, Carlos A.; Jud, Nathan A.; Jones, Douglas S.; MacFadden, Bruce J.

    2016-05-01

    New World monkeys (platyrrhines) are a diverse part of modern tropical ecosystems in North and South America, yet their early evolutionary history in the tropics is largely unknown. Molecular divergence estimates suggest that primates arrived in tropical Central America, the southern-most extent of the North American landmass, with several dispersals from South America starting with the emergence of the Isthmus of Panama 3-4 million years ago (Ma). The complete absence of primate fossils from Central America has, however, limited our understanding of their history in the New World. Here we present the first description of a fossil monkey recovered from the North American landmass, the oldest known crown platyrrhine, from a precisely dated 20.9-Ma layer in the Las Cascadas Formation in the Panama Canal Basin, Panama. This discovery suggests that family-level diversification of extant New World monkeys occurred in the tropics, with new divergence estimates for Cebidae between 22 and 25 Ma, and provides the oldest fossil evidence for mammalian interchange between South and North America. The timing is consistent with recent tectonic reconstructions of a relatively narrow Central American Seaway in the early Miocene epoch, coincident with over-water dispersals inferred for many other groups of animals and plants. Discovery of an early Miocene primate in Panama provides evidence for a circum-Caribbean tropical distribution of New World monkeys by this time, with ocean barriers not wholly restricting their northward movements, requiring a complex set of ecological factors to explain their absence in well-sampled similarly aged localities at higher latitudes of North America.

  13. Enamel microwear texture properties of IGF 11778 (Oreopithecus bambolii) from the late Miocene of Baccinello, Italy.

    Science.gov (United States)

    L' Engle Williams, Frank

    2013-01-01

    Late Miocene Oreopithecus bambolii has been posited as a folivore from its pronounced molar shearing crests. However, scanning electron microscopy yields conflicting results with one study of Oreopithecus showing folivory and another indicating a coarser diet was consumed. To address this debate, the dietary proclivities of the well-known IGF 11778 Oreopithecus bambolii specimen are reconstructed by comparing the enamel texture properties of this specimen to extant Alouatta palliata (n = 11), Cebus apella (n = 13), Gorilla gorilla (n = 9), Lophocebus albigena (n = 15), Pan troglodytes (n = 17) and Trachypithecus cristatus (n = 12). Dental microwear is captured by scanning facet 9, a Phase II facet on the hypoconid surface, using white-light confocal microscopy at 100x. The scanning was followed by scale-sensitive fractal analysis, yielding four texture characteristics. These were ranked before ANOVA with post-hoc tests of significance and multivariate analyses were conducted. Oreopithecus specimen IGF 11778 does not match any of the extant taxa consistently but in some analyses is associated with Lophocebus, and secondarily with Pan, Gorilla and Cebus outliers suggesting mixed-fruit and hard-object feeding characterized at least a portion of its diet. The partially open habitat of late Miocene Baccinello may have had resources with mechanically resistant foods, or foods found near ground level were consumed. Hard, brittle foods, insects, and or extraneous grit may have contributed to the greater use-wear complexity of the enamel surface observed in IGF 11778 compared to extant folivores. IGF 11778 does not exhibit the degree of anisotropy characterizing Trachypithecus and Alouatta. The partial resemblance of IGF 11778 to some great ape specimens may indicate intermittent extractive and or terrestrial foraging.

  14. Oligo-Miocene peatland ecosystems of the Gippsland Basin and modern analogues

    Science.gov (United States)

    Korasidis, Vera A.; Wallace, Malcolm W.; Wagstaff, Barbara E.; Holdgate, Guy R.

    2017-02-01

    A detailed examination of the brown coal facies preserved in the Latrobe Valley Morwell 1B seam indicates that the type of peat-forming environment and the associated hydrological regime are the main factors influencing the development of lithotypes in brown coal deposits. New palynological data from the Morwell 1B seam suggests that each respective lithotype in the lightening-upwards lithotype cycles was deposited in a particular depositional environment that was characterised by a distinct floral community. The laminated dark lithotype represents a fire-prone emergent marsh that grew on the margins of a coastal lagoon and/or freshwater swamp. This facies grades into the dark lithotype, representing the transition from a meadow marsh to a periodically flooded ombrogenous forested bog. The medium and lighter lithotypes are interpreted as being deposited in an angiosperm-dominated ombrogenous forest bog that was intolerant of fire. These peat-forming environments are interpreted as being largely controlled by moisture and relative depth to water table. Each environment produces distinct lithotypes and lightening-upwards cycles are interpreted as terrestrialization cycles. As the peat grew upwards and above the water table, less moist conditions prevailed and lighter lithotypes were produced. The observed change in colour, from darker to lighter lithotypes, results from the environment evolving from anaerobic/inundated to less anaerobic/less moist settings via terrestrialization. The thin and laterally extensive light and pale lithotypes that top the cycles are interpreted to represent a residual layer of concentrated, oxidation resistant peat-forming elements that result from intense weathering and aerobic degradation of the peats. At a generic level, modern lowland bogs of South Westland in New Zealand have remarkably similar floral/ecological gradients to those of the Oligo-Miocene Morwell 1B brown coal cycles in Australia. This suggests that modern New Zealand

  15. Oligocene stratigraphy across the Eocene and Miocene boundaries in the Valley of Lakes (Mongolia).

    Science.gov (United States)

    Daxner-Höck, Gudrun; Badamgarav, Demchig; Barsbold, Rinchen; Bayarmaa, Baatarjav; Erbajeva, Margarita; Göhlich, Ursula Bettina; Harzhauser, Mathias; Höck, Eva; Höck, Volker; Ichinnorov, Niiden; Khand, Yondon; López-Guerrero, Paloma; Maridet, Olivier; Neubauer, Thomas; Oliver, Adriana; Piller, Werner; Tsogtbaatar, Khishigjav; Ziegler, Reinhard

    2017-01-01

    Cenozoic sediments of the Taatsiin Gol and TaatsiinTsagaan Nuur area are rich in fossils that provide unique evidence of mammal evolution in Mongolia. The strata are intercalated with basalt flows. 40 Ar/ 39 Ar data of the basalts frame the time of sediment deposition and mammal evolution and enable a composite age chronology for the studied area. We investigated 20 geological sections and 6 fossil localities of Oligocene and early Miocene deposits from this region. Seventy fossil beds yielded more than 19,000 mammal fossils. This huge collection encompasses 175 mammal species: 50% Rodentia, 13% Eulipotyphla and Didelphomorphia, and 12% Lagomorpha. The remaining 25% of species are distributed among herbivorous and carnivorous large mammals. The representation of lower vertebrates and gastropods is comparatively poor. Several hundred SEM images illustrate the diversity of Marsupialia, Eulipotyphla, and Rodentia dentition and give insight into small mammal evolution in Mongolia during the Oligocene and early Miocene. This dataset, the radiometric ages of basalt I (∼31.5 Ma) and basalt II (∼27 Ma), and the magnetostratigraphic data provide ages of mammal assemblages and time ranges of the Mongolian biozones: letter zone A ranges from ∼33 to ∼31.5 Ma, letter zone B from ∼31.5 to ∼28 Ma, letter zone C from ∼28 to 25.6 Ma, letter zone C1 from 25.6 to 24 Ma, letter zone C1-D from 24 to ∼23 Ma, and letter zone D from ∼23 to ∼21 Ma.

  16. K-Ar ages of Early Miocene arc-type volcanoes in northern New Zealand

    International Nuclear Information System (INIS)

    Hayward, B.W.; Black, P.M.; Smith, I.E.M.; Ballance, P.F.; Itaya, T.; Doi, M.; Takagi, M.; Bergman, S.; Adams, C.J.; Herzer, R.H.; Robertson, D.J.

    2001-01-01

    Understanding the temporal and spatial development of the Early Miocene Northland Volcanic Arc is critical to interpreting the patterns of volcanic activity in northern New Zealand through the Late Cenozoic. The northwesterly trending arc is considered to have developed above a southwest-dipping subduction system. The distribution of its constituent eruptive centres is described in terms of an eastern belt that extends along the eastern side of Northland and a complementary broad western belt which includes subaerial and submarine volcanic edifices. Critical examination of all 216 K-Ar ages available, including 180 previously unpublished ages, and their assessment against tectonic, lithostratigraphic, seismic stratigraphic, and biostratigraphic constraints, leads us to deduce a detailed chronology of periods of activity for the various Early (and Middle) Miocene arc-type volcanic complexes and centres of northern New Zealand: Waipoua Shield Volcano Complex (19-18 Ma, Altonian); Kaipara Volcanic Complex (23-16 Ma, Waitakian-Altonian); Manukau Volcanic Complex (c. 23-15.5 Ma, Waitakian-Clifdenian); North Cape Volcanic Centre (23-18 Ma, Waitakian-Altonian); Whangaroa Volcanic Complex (22.5-17.5 Ma, Waitakian-Altonian); Taurikura Volcanic Complex (22-15.5 Ma, Otaian-Clifdenian); Parahaki Dacites (22.5-18 Ma, Waitakian-Altonian); Kuaotunu Volcanic Complex (18.5-11 Ma, Altonian-Waiauan). In general, volcanic activity does not show geographic migration with time, and the western (25-15.5 Ma) and eastern (23-11 Ma) belts appear to have developed concurrently. (author). 123 refs., 9 figs., 1 tab

  17. Carnivores from the Middle Miocene Ngorora Formation (13-12 Ma, Kenya

    Directory of Open Access Journals (Sweden)

    Pickford, M.

    2005-12-01

    Full Text Available The late Middle Miocene Ngorora Formation has yielded several interesting carnivore fossils. Among these are a huge creodont, Megistotherium osteothlastes, at 12 Ma, possibly the youngest record of the species, an amphicyonid, two species of mustelids (an otter and a honey badger, two kinds of viverrids (one about the size of a civet, one the size of a genet and an extremely small herpestid the size of a dwarf mongoose. It has also yielded remains of a moderate sized percrocutid. Perhaps the most interesting carnivore is a new genus and species of bundont viverrid that is intermediate in size and morphology between Early Miocene Orangictis on the one hand and Plio-Pleistocene Pseudocivetta on the other. This lineage of bundont viverrids appears to have been restricted to Africa.La Formación Mioceno medio final de Ngorora (Kenia ha suministrado carnívoros muy interesantes. Entre los que se encuentran un enorme creodonto, Megistotherium osteothlastes, de 12 Ma, que posiblemente es el registro más moderno de la especie, un amphicyonido, dos especies de mustélidos (una nutria y un melivorino, dos diferentes tipos de vivérridos (uno de la talla de una civeta y el otro de la de una jineta y un herpéstido diminuto de la talla de una mangosta enana. También hay fósiles de un percrocútido de talla moderada. Tal vez el carnívoro más interesante es un nuevo género y especie de vivérrido bunodonto que presenta una talla y morfología intermedia entre Oragictis del Mioceno inferior y Pseudocivetta del Plio-Pleistoceno. Esta línea de vivérridos bunodontos parece estar restringida a Africa.

  18. Morphology and distribution of Oligocene and Miocene pockmarks in the Danish North Sea -implications for bottom current activity and fluid migration

    DEFF Research Database (Denmark)

    Andresen, Katrine Juul; Huuse, Mads; Clausen, O.R.

    2008-01-01

    This study gives the first description of 33 mid-Oligocene and 646 late Miocene pockmarks mapped in the Danish part of the central North Sea. The pockmarks are all highly elongated, with average long- and short axes of 2.5 km and 700 m, and average internal depth of 30 m. The Miocene pockmarks...... the timing and location of the pockmarks. The pockmarks thus tell a story of thermogenic gas venting to the surface and paleo-current scour of the seabed in the eastern part of the central North Sea during the mid Oligocene and late Miocene....

  19. Oriental upper blepharoplasty.

    Science.gov (United States)

    Weng, Chau-Jin

    2009-02-01

    Aesthetic surgery of the upper eyelids is a very common procedure performed in cosmetic practices around the world. The word blepharoplasty, however, has a different meaning in Asia than it does elsewhere. Orientals have different periorbital anatomic characteristics, their motivations for seeking eyelid treatment are different, and operative techniques have been adapted consequently. There are also many eyelid shapes among Orientals, mostly with regard to the presence and location of the supratarsal fold and/or presence of an epicanthal fold. The surgeon must therefore master a range of surgical procedures to treat these variations adequately. It is critical to know the indications for each blepharoplasty technique as well as their complications to select the right surgery and avoid unfavorable results. Epicanthoplasty performed on the right patient can greatly improve aesthetic results while retaining ethnic characteristics. This article will discuss Oriental eyelid characteristics, preoperative patient assessment, commonly used corrective techniques for the "double-eyelid" creation, and complications and how to avoid them.

  20. Microfacies, sedimentary environment and diagenesis of the upper part of Dalan and Kangan Formations in the Kuh-e Surmeh area, Folded Zagros

    Directory of Open Access Journals (Sweden)

    Mohammadhossein Adabi

    2012-01-01

    Full Text Available The upper part of Dallan and Kangan formations (Permian-Triassic, are located in the Kuh-e Surmeh area in folded Zagros Basin with a thickness of 325 m overlying by Nar evaporite member and underlying by Dashtak Formation. Dominant lithology of these formations are limestone and dolomite. Our purpose in this study is to identify microfacieses, sedimentary environment and diagenetic proceses. To overcome this aim, thin sections petrographic studies, leaded to identify 12 microfacieses related to 4 facieses belt: tidal flat, lagoon, shoal and open marine. The observed microfacies patterns indicate a ramp carbonate platform as depositional environment. Based on petrographic studies, the important diagenetic processes in these formations consist of: micritization, dolomitization, cementation, stilolitization and chemical and physical compactions. Burial diagenesis is dominated diagenetic event. The observed porosities in this section are primary and secondary such as fenestral, vuggy, fracture, moldic, interparticle, intraparticle and channel

  1. THE BAIKAL RIFT: PLIOCENE (MIOCENE – QUATERNARY EPISODE OR PRODUCT OF EXTENDED DEVELOPMENT SINCE THE LATE CRETACEOUS UNDER VARIOUS TECTONIC FACTORS. A REVIEW

    Directory of Open Access Journals (Sweden)

    V. D. Mats

    2015-01-01

    Full Text Available The article reviews three typical concepts concerning the age of the Baikal rift (BR which development is still underway: 5 Ma (the BR development start in the Late Pliocene, 30 Ma (Miocene or Oligocene, and 60–70 Ma (the Late Cretaceous. Under the concept of the young BR age (Pliocene–Quaternary [Artyushkov, 1993; Nikolaev et al., 1985; Buslov, 2012], according to E.V. Artyushkov, BR is not a rift, but a graben due to the fact that the pre‐Pliocene structure of BR does not contain any elements that would be indicative of tensile stresses. However, field studies reported in [Lamakin, 1968; Ufimtsev, 1993; Zonenshain et al., 1995; Mats, 1993, 2012; Mats et al., 2001] have revealed that extension structures, such as tilted blocks and listric faults, are abundant in the Baikal basin (BB, and thus do not supportE.V. Artyushkov’s argumentation. The opinion that BR is young is shared by M.M. Buslov [2012]; he refers to studies of  Central Asia and states that only the Pliocene‐Quaternary structure of BB is a rift, while the oldest Cenozoic structures (Upper Cretaceous – Miocene are just fragments of the large Cenozoic Predbaikalsky submontane trough (PBT which are not related to the rift. However, the coeval Cenozoic lithological compositions, thicknesses of sediment layers and types of tectonic structures in PBT and BB have nothing in common. Across the area separating PBT and BB, there are no sediments or structures to justify a concept that BR and PBT may be viewed as composing a single region with uniform structures and formations. The idea of the Pliocene‐Quaternary age of BR should be rejected as it contradicts with the latest geological and geophysical data. Seismic profiling in BB has revealed the syn‐rift sedimentary bed which thickness exceeds 7.5 km. Results of drilling through the 600‐metre sedimentary sequence of Lake Baikal suggest the age of 8.4 Ma [Horiuchi et al., 2004], but M.M. Buslov believes

  2. Application of organic facies in sedimentological-stratigraphical model of the Oligo-Miocene and Miocene of the Campos Basin; Aplicacao da faciologia organica no modelo sedimentologico-estratigrafico do Oligo-Mioceno e Mioceno da Bacia de Campos

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca Filho, Joao Graciano; Mendonca, Joalice de Oliveira; Oliveira, Antonio Donizeti de; Torres, Jaqueline [Universidade Federal do Rio de Janeiro (UFRJ). Centro de Ciencias Exatas e da Natureza. Inst. de Geociencias (Brazil)], e-mails: graciano@geologia.ufrj.br, donizeti@lafo.geologia.ufrj.br, joalice@lafo.geologia.ufrj.br, jaqueline@lafo.geologia.ufrj.br; Menezes, Taissa Rego [Centro de Pesquisas da Petrobras (CENPES), RJ (Brazil). P e D em Geociencias. Gerencia de Geoquimica], e-mail: taissamenezes@petrobras.com.br; Santos, Viviane Sampaio Santiago dos; Arienti, Luci Maria [Centro de Pesquisas da Petrobras (CENPES), RJ (Brazil). P e D em Geociencias. Gerencia de Sedimentologia e Estratigrafia], e-mails: vsss@petrobras.com.br, arienti@petrobras.com.br

    2010-05-15

    This study integrates palynofacies analyses and the sedimentological and stratigraphic model of the Oligo-Miocene/Miocene siliciclastic deposits from the stratigraphic interval of the shallow continental platform up to the slope/basin of the Oligo-Miocene/ Miocene of the Campos Basin proposed. The main objective of the palynofacies study was to characterize the particulate sedimentary organic matter to obtain information about the proximal-distal relationship and the sedimentary organic matter preservation and depositional environmental conditions. The 158 core samples collected in 29 wells of the 9 oil production fields (Albacora, Barracuda, Marlim Sul, Marlim, Voador, Marlim Leste, Moreia and Albacora Leste), were studied. This technique provides information about the proximal-distal relationship and the paleoenvironmental conditions of deposition and preservation of sedimentary organic matter, to facilitate the evaluation and comparisons between the associations of particulate organic components. Thus, the palynofacies technique can be used as another tool in the characterization of depositional systems, based on the spatial and temporal distribution of sedimentary intervals. In general the palynofacies assemblages showed the predominance of the Phytoclast Group (terrestrial derived organic matter) at various degradation stages due to the selective preservation process diagnosed in the studied samples. Some samples, revealed high dinocysts percentages indicative of transgressive depositional conditions. From the obtained data, it was possible to characterize the stratigraphic sequences according to the distribution of particulate organic content (e.g. influence of fluvio-deltaic systems, oxygen system, regressive-transgressive tendencies of each sequence). Additional analyses of Total Organic Carbon (% wt) showed the control of the particulate components from the Phytoclast Group on the TOC (% wt) content, suggesting that the relative sea-level variation curves

  3. Mastritherium (Artiodactyla, Anthracotheriidae) from Wadi Sabya, southwestern Saudi Arabia; an earliest Miocene age for continental rift-valley volcanic deposits of the Red Sea margin

    Science.gov (United States)

    Madden, Gary T.; Schmidt, Dwight Lyman; Whitmore, Frank C.

    1983-01-01

    A lower jaw fragment with its last molar (M/3) from the Baid formation in Wadi Sabya, southwestern Saudi Arabia, represents the first recorded occurrence in the Arabian Peninsula of an anthracotheriid artiodactyl (hippo-like, even-toed ungulate). This fossil is identified as a primitive species of Masritherium, a North and East African genus restricted, previously to the later early Miocene. This identification indicates that the age of the Baid formation, long problematical, is early Miocene and, moreover, shows that the age of the fossil site is earliest Miocene (from 25 to 21Ma). The Wadi Sabya anthracothere is the first species of fossil mammal recorded from western Saudi Arabia, and more important, it indicates an early Miocene age for the volcanic deposits of a continental rift-valley that preceded the initial sea-floor spreading of the Red Sea.

  4. New Late Miocene .i.Alilepus./i. (Lagomorpha, Mammalia) from Eastern Europe - a new light on the evolution of the earliest old world Leporinae

    Czech Academy of Sciences Publication Activity Database

    Čermák, Stanislav; Angelone, Ch.; Sinitsa, M. V.

    2015-01-01

    Roč. 90, č. 2 (2015), s. 431-451 ISSN 1214-1119 Institutional support: RVO:67985831 Keywords : Alilepus * Eastern Europe * Late Miocene * phylogeny * Pliocene * taxonomy Subject RIV: EG - Zoology Impact factor: 1.700, year: 2015

  5. Upper airway resistance syndrome.

    Science.gov (United States)

    Montserrat, J M; Badia, J R

    1999-03-01

    This article reviews the clinical picture, diagnosis and management of the upper airway resistance syndrome (UARS). Presently, there is not enough data on key points like the frequency of UARS and the morbidity associated with this condition. Furthermore, the existence of LIARS as an independent sleep disorder and its relation with snoring and obstructive events is in debate. The diagnosis of UARS is still a controversial issue. The technical limitations of the classic approach to monitor airflow with thermistors and inductance plethysmography, as well as the lack of a precise definition of hypopnea, may have led to a misinterpretation of UARS as an independent diagnosis from the sleep apnea/hypopnea syndrome. The diagnosis of this syndrome can be missed using a conventional polysomnographic setting unless appropriate techniques are applied. The use of an esophageal balloon to monitor inspiratory effort is currently the gold standard. However, other sensitive methods such as the use of a pneumotachograph and, more recently, nasal cannula/pressure transducer systems or on-line monitoring of respiratory impedance with the forced oscillation technique may provide other interesting possibilities. Recognition and characterization of this subgroup of patients within sleep breathing disorders is important because they are symptomatic and may benefit from treatment. Management options to treat UARS comprise all those currently available for sleep apnea/hypopnea syndrome (SAHS). However, the subset of patients classically identified as LIARS that exhibit skeletal craneo-facial abnormalities might possibly obtain further benefit from maxillofacial surgery.

  6. Upper Illinois River basin

    Science.gov (United States)

    Friedel, Michael J.

    1998-01-01

    During the past 25 years, industry and government made large financial investments that resulted in better water quality across the Nation; however, many water-quality concerns remain. Following a 1986 pilot project, the U.S. Geological Survey began implementation of the National Water-Quality Assessment (NAWQA) Program in 1991. This program differs from other national water-quality assessment studies in that the NAWQA integrates monitoring of surface- and ground-water quality with the study of aquatic ecosystems. The goals of the NAWQA Program are to (1) describe current water-quality conditions for a large part of the Nation's freshwater streams and aquifers (water-bearing sediments and rocks), (2) describe how water quality is changing over time, and (3) improve our understanding of the primary natural and human factors affecting water quality.The Upper Illinois River Basin National Water- Quality Assessment (NAWQA) study will increase the scientific understanding of surface- and ground-water quality and the factors that affect water quality in the basin. The study also will provide information needed by water-resource managers to implement effective water-quality management actions and evaluate long-term changes in water quality.

  7. Lineage-Specific Responses of Tooth Shape in Murine Rodents (Murinae, Rodentia) to Late Miocene Dietary Change in the Siwaliks of Pakistan

    OpenAIRE

    Kimura, Yuri; Jacobs, Louis L.; Flynn, Lawrence J.

    2013-01-01

    Past ecological responses of mammals to climate change are recognized in the fossil record by adaptive significance of morphological variations. To understand the role of dietary behavior on functional adaptations of dental morphology in rodent evolution, we examine evolutionary change of tooth shape in late Miocene Siwalik murine rodents, which experienced a dietary shift toward C4 diets during late Miocene ecological change indicated by carbon isotopic evidence. Geometric morphometric analy...

  8. New Miocene sulid birds from Peru and considerations on their Neogene fossil record in the Eastern Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Marcelo Stucchi

    2016-06-01

    Full Text Available Boobies and gannets (family Sulidae are the most specialized plunge divers among seabirds. Their fossil record along the Pacific coast of South America extends to the early Middle Miocene. Here we describe three new species of sulids: Sula brandi sp. nov., Sula figueroae sp. nov., and Ramphastosula aguirrei sp. nov., from the early Late Miocene of the Pisco Formation (Peru. Two of them are relatives of the living genus Sula, which represents medium and large-sized boobies. A new species of the extinct genus Ramphastosula is also described, adding to the discussion of possible alternative feeding strategies among sulids. The fossil record suggests that sympatric sulids exhibit different body sizes at least since the Oligocene epoch, a strategy related with resource partitioning. Furthermore, we find current analysis and knowledge of the fossil record unsuitable to evaluate properly seabird diversity changes through time.

  9. 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)

  10. Reinvestigation of the Miocene palynoflora from the Daotaiqiao Formation of north-eastern China using SEM

    Science.gov (United States)

    Akyurt, Elvan; Grímsson, Friðgeir; Zetter, Reinhard; Leng, Qin; Bouchal, Johannes Martin

    2016-04-01

    Here we report the first results of an ongoing study on the Miocene palynoflora from the Daotaiqiao Formation of north-eastern China. Using the single grain technique, we examined individual pollen and spores using both light and scanning electron microscopy. A previous study by Grímsson et al. (2012) on Onagraceae pollen grains from this locality, using the same technique identified five different species. Such a variety of Onagraceae from a single palynoflora is unknown elsewhere. The ongoing study suggests a remarkably rich pollen and spore flora with at least 15 different types of spores, one Ginkgo and one Ephedra type pollen, 11 conifer pollen types and approximately 145 angiosperm pollen types. Spores are very rare in the samples (≤1%). Conifer pollen grains are regularly observed but are not a dominant component (ca. 16 %). The samples yield a high quantity and diversity of angiosperm pollen (ca. 80%). The conifers include representatives of Cupressaceae (2 spp.), Pinaceae (Larix, Picea, Pinus, Tsuga) and Sciadopityaceae. The angiosperm pollen cover at least 40 families. Prominent elements are pollen of the Betulaceae (Alnus, Betula, Carpinus, Corylus), Cercidiphyllaceae (Cercidiphyllum), Ericaceae (8 spp.), Eucommiaceae (Eucommia), Fagaceae (Fagus, Quercus spp., Castaneoideae), Juglandaceae (Carya, Cyclocarya, Juglans, Pterocarya), Rosaceae (11 spp.), Sapindaceae (Acer, Aesculus) and Ulmaceae (Hemiptelia, Ulmus, Zelkova). The high angiosperm pollen diversity indicates a varying landscape with a relatively high variety of niches including riparian, dry and mesic forests. Most of the potential modern analogues of the fossil taxa are currently thriving under humid temperate (Cfa- and Cwa)-climates, pointing to paleoclimate conditions not unlike those found today in the lowlands and adjacent mountain regions of the (south-) eastern United States, the humid-meridional region of western Eurasia, and central and southern China, and Honshu (Japan). References

  11. Late Miocene climate and time scale reconciliation: Accurate orbital calibration from a deep-sea perspective

    Science.gov (United States)

    Drury, Anna Joy; Westerhold, Thomas; Frederichs, Thomas; Tian, Jun; Wilkens, Roy; Channell, James E. T.; Evans, Helen; John, Cédric M.; Lyle, Mitch; Röhl, Ursula

    2017-10-01

    Accurate age control of the late Tortonian to early Messinian (8.3-6.0 Ma) is essential to ascertain the origin of benthic foraminiferal δ18O trends and the late Miocene carbon isotope shift (LMCIS), and to examine temporal relationships between the deep-sea, terrasphere and cryosphere. The current Tortonian-Messinian Geological Time Scale (GTS2012) is based on astronomically calibrated Mediterranean sections; however, no comparable non-Mediterranean stratigraphies exist for 8-6 Ma suitable for testing the GTS2012. Here, we present the first high-resolution, astronomically tuned benthic stable isotope stratigraphy (1.5 kyr resolution) and magnetostratigraphy from a single deep-sea location (IODP Site U1337, equatorial Pacific Ocean), which provides unprecedented insight into climate evolution from 8.3-6.0 Ma. The astronomically calibrated magnetostratigraphy provides robust ages, which differ by 2-50 kyr relative to the GTS2012 for polarity Chrons C3An.1n to C4r.1r, and eliminates the exceptionally high South Atlantic spreading rates based on the GTS2012 during Chron C3Bn. We show that the LMCIS was globally synchronous within 2 kyr, and provide astronomically calibrated ages anchored to the GPTS for its onset (7.537 Ma; 50% from base Chron C4n.1n) and termination (6.727 Ma; 11% from base Chron C3An.2n), confirming that the terrestrial C3:C4 shift could not have driven the LMCIS. The benthic records show that the transition into the 41-kyr world, when obliquity strongly influenced climate variability, already occurred at 7.7 Ma and further strengthened at 6.4 Ma. Previously unseen, distinctive, asymmetric saw-tooth patterns in benthic δ18O imply that high-latitude forcing played an important role in late Miocene climate dynamics from 7.7-6.9 Ma. This new integrated deep-sea stratigraphy from Site U1337 can act as a new stable isotope and magnetic polarity reference section for the 8.3-6.0 Ma interval.

  12. Conodont color alteration index and upper Paleozoic thermal history of the Amazonas Basin, Brazil

    Science.gov (United States)

    Cardoso, Cassiane Negreiros; Sanz-López, Javier; Blanco-Ferrera, Silvia; Lemos, Valesca Brasil; Scomazzon, Ana Karina

    2015-12-01

    The conodont color alteration index (CAI) was determined in elements from core samples of the Frasnian Barreirinha Formation (one well) and of the Pennsylvanian-Permian Tapajós Group (twenty three wells and one limestone quarry) in the Amazonas Basin. The thermal history of the basin is analyzed using the CAI value distribution represented in maps and stratigraphic sections through correlation schemes, and in conjunction with previously published data. The pattern of palaeotemperatures for CAI values of 1.5-3 is coincident with organic matter maturation under a sedimentary overburden providing diagenetic conditions in the oil/gas window. Locally, conodonts show metamorphism (CAI value of 6-7) in relation to the intrusion of diabase bodies in beds including high geothermal gradient evaporites. Microtextural alteration on the surface conodonts commonly shows several types of overgrowth microtextures developed in diagenetic conditions. Locally, recrystallization in conodonts with a high CAI value is congruent with contact metamorphism in relation to Mesozoic intrusions. The CAI values of 1.5 or 2 observed close to the surface in several areas of the basin may be interpreted in relation to a high thermal palaeogradient derived from the magmatic episode or/and to the local denudation of the upper part of the Paleozoic succession prior to this thermal event.

  13. Cyclicity and reservoir properties of Lower-Middle Miocene sediments of South Kirinsk oil and gas field

    Science.gov (United States)

    Kurdina, Nadezhda

    2017-04-01

    Exploration and additional exploration of oil and gas fields, connected with lithological traps, include the spreading forecast of sedimentary bodies with reservoir and seal properties. Genetic identification and forecast of geological bodies are possible in case of large-scale studies, based on the study of cyclicity, structural and textural features of rocks, their composition, lithofacies and depositional environments. Porosity and permeability evaluation of different reservoir groups is also an important part. Such studies have been successfully completed for productive terrigenous Dagi sediments (Lower-Middle Miocene) of the north-eastern shelf of Sakhalin. In order to identify distribution of Dagi reservoirs with different properties in section, core material of the one well of South Kirinsk field has been studied (depth interval from 2902,4 to 2810,5 m). Productive Dagi deposits are represented by gray-colored sandstones with subordinate siltstones and claystones (total thickness 90,5 m). Analysis of cyclicity is based on the concepts of Vassoevich (1977), who considered cycles as geological body, which is the physical result of processes that took place during the sedimentation cycle. Well section was divided into I-X units with different composition and set of genetic features due to layered core description and elementary cyclites identification. According to description of thin sections and results of cylindrical samples porosity and permeability studies five groups of reservoirs were determined. There are coarse-grained and fine-coarse-grained sandstones, fine-grained sandstones, fine-grained silty sandstones, sandy siltstones and siltstones. It was found, in Dagi section there is interval of fine-coarse-grained and coarse-grained sandstones with high petrophysical properties: permeability 3000 mD, porosity more than 25%, but rocks with such properties spread locally and their total thickness is 6 meters only. This interval was described in the IV unit

  14. Depositional environment and sedimentary of the basinal sediments in the Eibiswalder Bucht (Radl Formation and Lower Eibiswald Beds), Miocene Western Styrian Basin, Austria

    Science.gov (United States)

    Stingl, K.

    1994-12-01

    The Eibiswald Bucht is a small subbasin of the Western Styrian Basin exposing sediments of Lower Miocene age. In the past the entire sequence exposed in the Eibiswalder Bucht has been interpreted as being of fluvial/lacustrine origin; here, results are presented of detailed sedimentological investigations that lead to a revision of this concept. The lowermost siliciclastic sedimentary unit of the Eibiswalder Bucht sequence is the Radl Formation. It is overlain by the Eibiswald Beds, which are subdivided into the Lower, Middle and Upper Eibiswald Beds. The Radl Formation and the Lower Eibiswald Beds are interpreted as a fan delta complex deposited along NNW-SSE striking faults. Based on the sedimentary facies this fan delta can be subdivided into a subaerial alluvial fan facies group, a proximal delta facies group and a distal delta/prodelta facies group. The Radl Formation comprises the alluvial fan and proximal delta facies groups, the Lower Eibiswald Beds the distal delta/prodelta facies group. The alluvial fan and the proximal delta consist of diverse deposits of gravelly flows. The distal delta/prodelta consists of wave-reworked, bioturbated, low density turbidites intercalated with minor gravelly mass flows. The prodelta can be regarded as as the basin facies of the small and shallow Eibiswalder Bucht, where marine conditions prevailed. The basin was probably in part connected with the Eastern Styrian Basin, the contemporary depositional environment of the Styrian Schlier (mainly turbiditic marine offshore sediments in the Eastern Styrian Basin). Analysis of the clast composition, in conjunction with the paleotransport direction of the coarse delta mass flows of the Radl Formation, shows that the source rocks were exclusively crystalline rocks ranging from greenschists to eclogites.

  15. Mineralogical and geochemical characteristics of Miocene pelitic sedimentary rocks from the south-western part of the Pannonian Basin System (Croatia: Implications for provenance studies

    Directory of Open Access Journals (Sweden)

    Anita Grizelj

    2017-01-01

    Full Text Available Fifty-two samples of Miocene pelitic sedimentary rock from outcrops on Medvednica, Moslavačka Gora and Psunj Mts., and boreholes in the Sava Depression and the Požega Sub-depression were investigated. These sediments formed in different marine (with normal and reduced salinity, brackish, and freshwater environments, depending on the development stage of the Pannonian Basin System. Carbonate minerals, clay minerals and quartz are the main constituents of all pelitic sedimentary rocks, except in those from Moslavačka Gora Mt in which carbonate minerals are not present. Feldspars, pyrite, opal-CT, and hematite are present as minor constituents in some rocks. Besides calcite, dependent on the sedimentary environment and diagenetic changes, high-magnesium calcite, aragonite, dolomite and ankerite/Ca-dolomite are also present. Smectite or illite-smectite is the main clay minerals in the samples. Minor constituents, present in almost all samples, are detrital illite and kaolinite. In some samples chlorite is also present in a low amount. Major elements, trace elements and rare earth elements patterns used in provenance analysis show that all analysed samples have a composition similar to the values of the upper continental crust (UCC. The contents of major and trace elements as well as SiO2/Al2O3, K2O/Al2O3, Na2O/K2O, Eu/Eu*, La/Sc, Th/Sc, La/Co Th/Co, Th/Cr, Ce/Ce* and LREE/HREE ratios, show that the analysed pelitic sedimentary rocks were formed by weathering of different types of mostly acidic (silicic, i.e. felsic rocks.

  16. Evolution and classification of Elaphoglossum and Asplenium ferns on Cuba, and discovery of a Miocene Elaphoglossum in Dominican amber

    OpenAIRE

    Lóriga Piñero, Josmaily

    2018-01-01

    This dissertation deals with the systematics and evolution of Neotropical ferns of the genera Elaphoglossum and Asplenium, with particular focus on the species of Cuba and the West Indies. It also includes an analysis and description of an Elaphoglossum frond fragment preserved in Miocene Dominican amber. The worldwide genera Elaphoglossum with 600 species and Asplenium with 685 species are the most species-rich groups of leptosporangiate ferns. On Cuba, Elaphoglossum has 34 species and Asple...

  17. On Prophoca and Leptophoca (Pinnipedia, Phocidae from the Miocene of the North Atlantic realm: redescription, phylogenetic affinities and paleobiogeographic implications

    Directory of Open Access Journals (Sweden)

    Leonard Dewaele

    2017-02-01

    Full Text Available Background Prophoca and Leptophoca represent the oldest known genera of phocine seals, dating from the latest early to middle Miocene. Originally, Prophoca rousseaui and Prophoca proxima were described based on fragmentary remains from the Miocene of Belgium. However, several researchers contested the union of Prophoca rousseaui and Prophoca proxima into one genus, without providing evidence. The stratigraphic context of Prophoca remained poorly constrained due to the lack of precise data associated with the original specimens collected in the area of Antwerp (north of Belgium. Methods Prophoca and Leptophoca are redescribed and their phylogenetic position among Phocidae is reassessed using PAUP. Dinoflagellate biostratigraphy has been carried out on sediment samples associated with specimens from Prophoca and Leptophoca to elucidate their approximate ages. Results Whereas the species Prophoca rousseaui is redescribed, Prophoca proxima is considered synonymous to Leptophoca lenis, with the proposal of a new combination Leptophoca proxima (Van Beneden, 1877. Sediment samples from specimens of both taxa have been dated to the late Langhian–early Serravallian (middle Miocene. Following a reinvestigation of Leptophoca amphiatlantica, characters from the original diagnosis are questioned and the specimens of Leptophoca amphiatlantica are considered Leptophoca cf. L. proxima. In a phylogenetic analysis, Prophoca rousseaui and Leptophoca proxima constitute early branching stem-phocines. Discussion Leptophoca proxima from the North Sea Basin is younger than the oldest known find of Leptophoca proxima from North America, which does not contradict the hypothesis that Phocinae originated along the east coast of North America during the late early Miocene, followed by dispersal to Europe shortly after. Morphological features of the appendicular skeleton indicate that Prophoca rousseaui and Leptophoca proxima have archaic locomotory modes, retaining a more

  18. Late Miocene extensional systems in northern Tunisia and their relation with SE directed delamination of the African subcontinental mantle lithosphere

    Science.gov (United States)

    Booth-Rea, Guillermo; Gaidi, Seif; Melki, Fetheddine; Pérez-Peña, Vicente; Marzougui, Wissem; Azañón, Jose Miguel; Galve, Jorge Pedro

    2017-04-01

    Recent work has proposed the delamination of the subcontinental mantle lithosphere under northern Tunisia during the late Miocene. This process is required to explain the present location of the Tunisian segment of the African slab, imaged by seismic tomography, hanging under the Gulf of Gabes to the south of Tunisia. Thus, having retreated towards the SE several hundred km from its original position under the Tellian-Atlas nappe contact that crops out along the north of Tunisia. However, no tectonic structures have been described which could be related to this mechanism of lithospheric mantle peeling. Here we describe for the first time extensional fault systems in northern Tunisia that strongly thinned the Tellian nappes, exhuming rocks from the Tunisian Atlas in the core of folded extensional detachments. Two normal fault systems with sub-orthogonal extensional transport occur. These were active during the late Miocene associated to the extrusion of 13 Ma granodiorite and 9 Ma rhyodacite in the footwall of the Nefza detachment. We have differentiated an extensional system formed by low-angle normal faults with NE- and SW-directed transport cutting through the Early to Middle Miocene Tellian nappen stack and a later system of low and high-angle normal faults that cuts down into the underlying Tunisian Atlas units with SE-directed transport, which root in the Nefza detachment. Both normal fault systems have been later folded and cut by thrusts during Plio-Quaternary NW-SE directed compression. These findings change the interpretation of the tectonic evolution of Tunisia that has always been framed in a transpressive to compressive setting, manifesting the extensional effects of Late Miocene lithospheric mantle delamination under northern Tunisia.

  19. Discovery of the oldest .i.Gobius./i. (Teleostei, Gobiiformes) from a marine ecosystem of Early Miocene age

    Czech Academy of Sciences Publication Activity Database

    Reichenbacher, B.; Gregorová, R.; Holcová, K.; Šanda, R.; Vukić, J.; Přikryl, Tomáš

    2018-01-01

    Roč. 16, č. 6 (2018), s. 493-513 ISSN 1477-2019 R&D Projects: GA ČR(CZ) GA16-21523S Institutional support: RVO:67985831 Keywords : Gobiidae * Miocene * comparative anatomy * marine ecosystem * Outer Carpathian flysh zone * Outer Carpathian flysch zone * Ždánice-Hustopeče Formation Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Paleontology Impact factor: 2.963, year: 2016

  20. Coexisting Miocene Alkaline Volcanic Series Associated with the Cheb-Domažlice Graben (W Bohemia): Geochemical Characteristics

    Czech Academy of Sciences Publication Activity Database

    Ulrych, Jaromír; Štěpánková, Jana; Lloyd, F. E.; Balogh, K.

    2003-01-01

    Roč. 54, č. 1 (2003), s. 53-64 ISSN 1335-0552 R&D Projects: GA ČR GA205/99/0907 Grant - others:Hungarian Academy of Sciences Foundation(HU) T 014961 Institutional research plan: CEZ:AV0Z3013912 Keywords : W Bohemia * Miocene volkanism * geochemistry Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.397, year: 2003 http://www.geologicacarpathica.sk/src/main.php

  1. Eocene and Miocene extension, meteoric fluid infiltration, and core complex formation in the Great Basin (Raft River Mountains, Utah)

    Science.gov (United States)

    Methner, Katharina; Mulch, Andreas; Teyssier, Christian; Wells, Michael L.; Cosca, Michael A.; Gottardi, Raphael; Gebelin, Aude; Chamberlain, C. Page

    2015-01-01

    Metamorphic core complexes (MCCs) in the North American Cordillera reflect the effects of lithospheric extension and contribute to crustal adjustments both during and after a protracted subduction history along the Pacific plate margin. While the Miocene-to-recent history of most MCCs in the Great Basin, including the Raft River-Albion-Grouse Creek MCC, is well documented, early Cenozoic tectonic fabrics are commonly severely overprinted. We present stable isotope, geochronological (40Ar/39Ar), and microstructural data from the Raft River detachment shear zone. Hydrogen isotope ratios of syntectonic white mica (δ2Hms) from mylonitic quartzite within the shear zone are very low (−90‰ to −154‰, Vienna SMOW) and result from multiphase synkinematic interaction with surface-derived fluids. 40Ar/39Ar geochronology reveals Eocene (re)crystallization of white mica with δ2Hms ≥ −154‰ in quartzite mylonite of the western segment of the detachment system. These δ2Hms values are distinctively lower than in localities farther east (δ2Hms ≥ −125‰), where 40Ar/39Ar geochronological data indicate Miocene (18–15 Ma) extensional shearing and mylonitic fabric formation. These data indicate that very low δ2H surface-derived fluids penetrated the brittle-ductile transition as early as the mid-Eocene during a first phase of exhumation along a detachment rooted to the east. In the eastern part of the core complex, prominent top-to-the-east ductile shearing, mid-Miocene 40Ar/39Ar ages, and higher δ2H values of recrystallized white mica, indicate Miocene structural and isotopic overprinting of Eocene fabrics.

  2. The Early Miocene Critical Zone at Karungu, Western Kenya: An Equatorial, Open Habitat with Few Primate Remains

    Science.gov (United States)

    Lukens, William E.; Lehmann, Thomas; Peppe, Daniel J.; Fox, David L.; Driese, Steven G.; McNulty, Kieran P.

    2017-10-01

    Early Miocene outcrops near Karungu, Western Kenya, preserve a range of fluvio-lacustrine, lowland landscapes that contain abundant fossils of terrestrial and aquatic vertebrates. Primates are notably rare among these remains, although nearby early Miocene strata on Rusinga Island contain a rich assemblage of fossilized catarrhines and strepsirrhines. To explore possible environmental controls on the occurrence of early Miocene primates, we performed a deep-time Critical Zone (DTCZ) reconstruction focused on floodplain paleosols at the Ngira locality in Karungu. We specifically focused on a single stratigraphic unit (NG15), which preserves moderately developed paleosols that contain a microvertebrate fossil assemblage. Although similarities between deposits at Karungu and Rusinga Island are commonly assumed, physical sedimentary processes, vegetative cover, soil hydrology, and some aspects of climate state are notably different between the two areas. Estimates of paleoclimate parameters using paleosol B horizon elemental chemistry and morphologic properties are consistent with seasonal, dry subhumid conditions, occasional waterlogging, and herbaceous vegetation. The reconstructed small mammal community indicates periodic waterlogging and open-canopy conditions. Based on the presence of herbaceous root traces, abundant microcharcoal, and pedogenic carbonates with high stable carbon isotope ratios, we interpret NG15 to have formed under a warm, seasonally dry, open riparian woodland to wooded grassland, in which at least a subset of the vegetation was likely C4 biomass. Our results, coupled with previous paleoenvironmental interpretations for deposits on Rusinga Island, demonstrate that there was considerable environmental heterogeneity ranging from open to closed habitats in the early Miocene. We hypothesize that the relative paucity of primates at Karungu was driven by their environmental preference for locally abundant closed canopy vegetation, which was likely

  3. The Early Miocene Critical Zone at Karungu, Western Kenya: An Equatorial, Open Habitat with Few Primate Remains

    Directory of Open Access Journals (Sweden)

    William E. Lukens

    2017-10-01

    Full Text Available Early Miocene outcrops near Karungu, Western Kenya, preserve a range of fluvio-lacustrine, lowland landscapes that contain abundant fossils of terrestrial and aquatic vertebrates. Primates are notably rare among these remains, although nearby early Miocene strata on Rusinga Island contain a rich assemblage of fossilized catarrhines and strepsirrhines. To explore possible environmental controls on the occurrence of early Miocene primates, we performed a deep-time Critical Zone (DTCZ reconstruction focused on floodplain paleosols at the Ngira locality in Karungu. We specifically focused on a single stratigraphic unit (NG15, which preserves moderately developed paleosols that contain a microvertebrate fossil assemblage. Although similarities between deposits at Karungu and Rusinga Island are commonly assumed, physical sedimentary processes, vegetative cover, soil hydrology, and some aspects of climate state are notably different between the two areas. Estimates of paleoclimate parameters using paleosol B horizon elemental chemistry and morphologic properties are consistent with seasonal, dry subhumid conditions, occasional waterlogging, and herbaceous vegetation. The reconstructed small mammal community indicates periodic waterlogging and open-canopy conditions. Based on the presence of herbaceous root traces, abundant microcharcoal, and pedogenic carbonates with high stable carbon isotope ratios, we interpret NG15 to have formed under a warm, seasonally dry, open riparian woodland to wooded grassland, in which at least a subset of the vegetation was likely C4 biomass. Our results, coupled with previous paleoenvironmental interpretations for deposits on Rusinga Island, demonstrate that there was considerable environmental heterogeneity ranging from open to closed habitats in the early Miocene. We hypothesize that the relative paucity of primates at Karungu was driven by their environmental preference for locally abundant closed canopy vegetation

  4. Integrating geomorphological mapping, InSAR, GPR and trenching for the identification and investigation of buried sinkholes in the mantled evaporite karst of the Ebro Valley (NE Spain)

    Science.gov (United States)

    Gutiérrez, Francisco; Galve, Jorge Pedro; Lucha, Pedro; Bonachea, Jaime; Castañeda, Carmen

    2010-05-01

    The first and most important step in sinkhole hazard analysis is the construction of a cartographic sinkhole inventory. The effectiveness of the mitigation measures and the reliability of the susceptibility and hazard maps will depend on the completeness and accuracy of the sinkhole inventories on which they are based. Sinkhole data bases preferably should include information on the following aspects: (1) Precise location of the sinkholes edges. (2) Morphometric parameters. (3) Geomorphological and hydrological context. (4) Genetic type; that is subsidence mechanisms and material affected by subsidence. (5) Chronology; this information is essential to calculate probability of occurrence values. (6) Active or inactive character. (7) Kinematical regime (gradual, episodic or mixed). (8) Current and/or long-term subsidence rates. (9) Evolution of the subsidence and its relationship with causal factors. Sinkholes are generally mapped using conventional geomorphological methods like aerial photographs, topographic maps and field surveys. However, the usefulness of these methods may be limited in areas where the geomorphic expression of sinkholes has been obliterated by natural processes or anthropogenic fill. Additionally, gaining data on some of the practical aspects indicated above requires the application of other techniques. In this contribution we present the main findings learnt through the construction of a sinkhole inventory in a terrace of the Ebro River valley (NE Spain). The study area covers around 27.5 ha and is located west of Zaragoza city. The bedrock consists of subhorizontal evaporites including gypsum, halite and glauberite. The terrace is situated at 7-10 m above the channel and the alluvium, 10-30 m thick, is composed of unconsolidated gravels and subordinate fines. Previous studies carried out in this sector of the valley reveal that: (1) Three main types of sinkholes may be differentiated: cover collapse, cover and bedrock collapse, and cover and

  5. The identification of Oligo-Miocene mammalian palaeocommunities from the Riversleigh World Heritage Area, Australia and an appraisal of palaeoecological techniques

    Science.gov (United States)

    Black, Karen H.; Archer, Michael; Hand, Suzanne J.

    2017-01-01

    Fourteen of the best sampled Oligo-Miocene local faunas from the Riversleigh World Heritage Area, north-western Queensland, Australia are analysed using classification and ordination techniques to identify potential mammalian palaeocommunities and palaeocommunity types. Abundance data for these faunas are used, for the first time, in conjunction with presence/absence data. An early Miocene Faunal Zone B and two middle Miocene Faunal Zone C palaeocommunities are recognised, as well as one palaeocommunity type. Change in palaeocommunity structure, between the early Miocene and middle Miocene, may be the result of significant climate change during the Miocene Carbon Isotope Excursion. The complexes of local faunas identified will allow researchers to use novel palaeocommunities in future analyses of Riversleigh’s fossil faunas. The utility of some palaeoecological multivariate indices and techniques is examined. The Dice index is found to outperform other binary similarity/distance coefficients, while the UPGMA algorithm is more useful than neighbour joining. Evidence is equivocal for the usefulness of presence/absence data compared to abundance. PMID:28674663

  6. ON THE PRESENCE OF PYRAMIODONTHERIUM (MAMMALIA, XENARTHRA, MEGATHERIIDAE IN THE LATE MIOCENE OF NORTHEASTERN ARGENTINA AND ITS BIOGEOGRAPHICAL IMPLICATIONS

    Directory of Open Access Journals (Sweden)

    DIEGO BRANDONI

    2009-03-01

    Full Text Available The biochron of the subfamily Megatheriinae, large to very large terrestrial sloths typified by Megatherium Cuvier, in Argentina extends from the middle Miocene of Patagonia to the late Pleistocene-early Holocene. Megatheriines reached their highest diversity in the lower levels (="conglomerado osífero", late Miocene of the Ituzaingó Formation in Entre Ríos Province, northeastern Argentina. Among the four megatheriines that occur in this unit, the genera Promegatherium Ameghino, Eomegatherium Kraglievich and Pliomegatherium Kraglievich represent relatively small to medium-sized taxa. Here we describe new material assigned to Pyramiodontherium, the largest of the four genera from the same bed and comparable in size to some Quaternary species of Megatherium. Three valid species of Pyramiodontherium have been recognized, all distributed mainly in northwestern Argentina, from the late Miocene in Catamarca Province (and probably also in Tucumán Province, and the late Pliocene in La Rioja Province. The presence of this genus in northeastern Argentina extends its known paleobiogeographical distribution. 

  7. A southern species of the tropical catfish genus Phractocephalus (Teleostei: Siluriformes) in the Miocene of South America

    Science.gov (United States)

    Azpelicueta, María de las Mercedes; Cione, Alberto Luis

    2016-04-01

    Catfish bones from Tortonian (Miocene) freshwater beds of central Argentina are here identified as pertaining to a new species of the tropical pimelodid genus Phractocephalus. The new species differs from the other recent and fossil species of the genus in skull, pectoral girdle and spine characters. The material was found in different localities near the city of Paraná, Entre Ríos Province. The bearing horizon is the so-called "Conglomerado osífero" which constitutes the lowermost beds of the fluvial Ituzaingó Formation. The aquatic vertebrate fauna occurring in the bearing bed shows a similar generic composition to several northern South American Miocene units where Phractocephalus remains were found. This report extends the range of Phractocephalus more than 2000 km to the South. The record is in agreement with higher global temperatures and putative ample hydrographic connections of the river basins in the Paraná area with the Amazon basin until at least the early late Miocene.

  8. A new large squalodelphinid (Cetacea, Odontoceti) from Peru sheds light on the Early Miocene platanistoid disparity and ecology

    Science.gov (United States)

    Bianucci, Giovanni; Bosio, Giulia; Malinverno, Elisa; de Muizon, Christian; Villa, Igor M.; Urbina, Mario; Lambert, Olivier

    2018-04-01

    The South Asian river dolphin (Platanista gangetica) is the only extant survivor of the large clade Platanistoidea, having a well-diversified fossil record from the Late Oligocene to the Middle Miocene. Based on a partial skeleton collected from the Chilcatay Formation (Chilcatay Fm; southern coast of Peru), we report here a new squalodelphinid genus and species, Macrosqualodelphis ukupachai. A volcanic ash layer, sampled near the fossil, yielded the 40Ar/39Ar age of 18.78 ± 0.08 Ma (Burdigalian, Early Miocene). The phylogenetic analysis places Macrosqualodelphis as the earliest branching squalodelphinid. Combined with several cranial and dental features, the large body size (estimated body length of 3.5 m) of this odontocete suggests that it consumed larger prey than the other members of its family. Together with Huaridelphis raimondii and Notocetus vanbenedeni, both also found in the Chilcatay Fm, this new squalodelphinid further demonstrates the peculiar local diversity of the family along the southeastern Pacific coast, possibly related to their partition into different dietary niches. At a wider geographical scale, the morphological and ecological diversity of squalodelphinids confirms the major role played by platanistoids during the Early Miocene radiation of crown odontocetes.

  9. Fruits and wood of Parinari from the early Miocene of Panama and the fossil record of Chrysobalanaceae.

    Science.gov (United States)

    Jud, Nathan A; Nelson, Chris W; Herrera, Fabiany

    2016-02-01

    Chrysobalanaceae are woody plants with over 500 species in 20 genera. They are among the most common trees in tropical forests, but a sparse fossil record has limited our ability to test evolutionary and biogeographic hypotheses, and several previous reports of Chrysobalanaceae megafossils are doubtful. We prepared fossil endocarps and wood collected from the lower Miocene beds along the Panama Canal using the cellulose acetate peel technique and examined them using light microscopy. We compared the fossil endocarps with previously published fossils and with fruits from herbarium specimens. We compared the fossil wood with photographs and descriptions of extant species. Parinari endocarps can be distinguished from other genera within Chrysobalanaceae by a suite of features, i.e., thick wall, a secondary septum, seminal cavities lined with dense, woolly trichomes, and two ovate to lingulate basal germination plugs. Fossil endocarps from the Cucaracha, Culebra, and La Boca Formations confirm that Parinari was present in the neotropics by the early Miocene. The earliest unequivocal evidence of crown-group Chrysobalanaceae is late Oligocene-early Miocene, and the genus Parinari was distinct by at least 19 million years ago. Parinari and other Chrysobalanaceae likely reached the neotropics via long-distance dispersal rather than vicariance. The presence of Parinari in the Cucaracha flora supports the interpretation of a riparian, moist tropical forest environment. Parinari was probably a canopy-dominant tree in the Cucaracha forest and took advantage of the local megafauna for seed dispersal. © 2016 Botanical Society of America.

  10. Two fossil species of Metrosideros (Myrtaceae) from the Oligo-Miocene Golden Fleece locality in Tasmania, Australia.

    Science.gov (United States)

    Tarran, Myall; Wilson, Peter G; Macphail, Michael K; Jordan, Greg J; Hill, Robert S

    2017-06-01

    The capsular-fruited genus Metrosideros (Myrtaceae) is one of the most widely distributed flowering plant genera in the Pacific but is extinct in Australia today. The center of geographic origin for the genus and the reason for and timing of its extinction in Australia remain uncertain. We identify fossil Metrosideros fruits from the newly discovered Golden Fleece fossil flora in the Oligo-Miocene of Tasmania, Australia, shedding further light on these problems. Standard paleopalynological techniques were used to date the fossil-bearing sediments. Scanning electron microscopy and an auto-montage camera system were used to take high-resolution images of fossil and extant fruits taken from herbarium specimens. Fossils are identified using a nearest-living-relative approach. The fossil-bearing sediments are palynostratigraphically dated as being Proteacidites tuberculatus Zone Equivalent (ca. 33-16 Ma) in age and provide a confident Oligo-Miocene age for the macrofossils. Two new fossil species of Metrosideros are described and are here named Metrosideros dawsonii sp. nov. and Metrosideros wrightii sp. nov. These newly described fossil species of Metrosideros provide a second record of the genus in the Cenozoic of Australia, placing them in the late Early Oligocene to late Early Miocene. It is now apparent not only that Metrosideros was present in Australia, where the genus is now extinct, but that at least several Metrosideros species were present during the Cenozoic. These fossils further strengthen the case for an Australian origin of the genus. © 2017 Botanical Society of America.

  11. First fossil occurrence of a filefish (Tetraodontiformes; Monacanthidae) in Asia, from the Middle Miocene in Nagano Prefecture, central Japan.

    Science.gov (United States)

    Miyajima, Yusuke; Koike, Hakuichi; Matsuoka, Hiroshige

    2014-04-10

    A new fossil filefish, Aluterus shigensis sp. nov., with a close resemblance to the extant Aluterus scriptus (Osbeck), is described from the Middle Miocene Bessho Formation in Nagano Prefecture, central Japan. It is characterized by: 21 total vertebrae; very slender and long first dorsal spine with tiny anterior barbs; thin and lancet-shaped basal pterygiophore of the spiny dorsal fin, with its ventral margin separated from the skull; proximal tip of moderately slender first pterygiophore of the soft dorsal fin not reaching far ventrally; soft dorsal-fin base longer than anal-fin base; caudal peduncle having nearly equal depth and length; and tiny, fine scales with slender, straight spinules. The occurrence of this fossil filefish from the Bessho Formation is consistent with the influence of warm water currents suggested by other fossils, but it is inconsistent with the deep-water sedimentary environment of this Formation. This is the first fossil occurrence of a filefish in Asia; previously described fossil filefishes are known from the Pliocene and Pleistocene of Italy, the Pliocene of Greece, and the Miocene and Pliocene of North America. These fossil records suggest that the genus Aluterus had already been derived and was widely distributed during the Middle Miocene with taxa closely resembling Recent species.

  12. A new large squalodelphinid (Cetacea, Odontoceti) from Peru sheds light on the Early Miocene platanistoid disparity and ecology

    Science.gov (United States)

    Bosio, Giulia; Malinverno, Elisa; Villa, Igor M.; Urbina, Mario

    2018-01-01

    The South Asian river dolphin (Platanista gangetica) is the only extant survivor of the large clade Platanistoidea, having a well-diversified fossil record from the Late Oligocene to the Middle Miocene. Based on a partial skeleton collected from the Chilcatay Formation (Chilcatay Fm; southern coast of Peru), we report here a new squalodelphinid genus and species, Macrosqualodelphis ukupachai. A volcanic ash layer, sampled near the fossil, yielded the 40Ar/39Ar age of 18.78 ± 0.08 Ma (Burdigalian, Early Miocene). The phylogenetic analysis places Macrosqualodelphis as the earliest branching squalodelphinid. Combined with several cranial and dental features, the large body size (estimated body length of 3.5 m) of this odontocete suggests that it consumed larger prey than the other members of its family. Together with Huaridelphis raimondii and Notocetus vanbenedeni, both also found in the Chilcatay Fm, this new squalodelphinid further demonstrates the peculiar local diversity of the family along the southeastern Pacific coast, possibly related to their partition into different dietary niches. At a wider geographical scale, the morphological and ecological diversity of squalodelphinids confirms the major role played by platanistoids during the Early Miocene radiation of crown odontocetes.

  13. Variation in the pelvic and pectoral girdles of Australian Oligo–Miocene mekosuchine crocodiles with implications for locomotion and habitus

    Directory of Open Access Journals (Sweden)

    Michael D. Stein

    2017-06-01

    Full Text Available Australian Oligo–Miocene mekosuchines (Crocodylia; Crocodyloidea display wide diversity in cranial shape and inferred hunting strategies. Terrestrial habitus has been inferred for these distinctive predators. A direct morphological signal for locomotion can be expected in the postcrania, particularly the pelvic and pectoral girdles. Here we describe fossil materials of the girdles, which chart their morphological variation in the subfamily from Eocene through to Middle Miocene. Over this period, both girdles undergo significant morphological changes. Notably, an enclosed, ventrally orientated acetabulum in the ilium is developed in one lineage. This recapitulates the erect parasagittal configuration of the pelvic limb seen in many Mesozoic crocodylomorph lineages, suggesting consistent use of erect high-walking in these mekosuchines. Other pelves from the same Oligo–Miocene deposits display morphology closer to modern crocodilians, suggesting a partitioning of locomotory strategy among sympatric mekosuchines. Plesiomorphic and derived pelvic girdles are distinguishable by parsimony analysis, and the earliest examples of the mekosuchine pelvis more closely resemble gavialids and alligatorids while latter forms converge on crown group crocodylids in the morphology of the iliac crest. This suggests that a revaluation of the base relationship of Mekosuchinae within Eusuchia is necessary.

  14. Geochemical and Isotopic Characteristics of Quaternary Aquifer in Sohag District, Upper Egypt

    International Nuclear Information System (INIS)

    Ahmed, M.A.

    2008-01-01

    Thc Nile River valley represent one of the most important regions for agriculture and land reclamation in our area. Environmental isotopes and hydrochemical compositions in conjunction with geological and hydrogeological data were used to define chemical characteristics, sources of salinity, ground water origin and the possible recharge sources to the Nile Valley aquifer in Sohag district, Upper Egypt. The total dissolved solids of the ground water samples have higher values (445-7828 mg/L) than surface water (291-348 mg/L). The ground water in the Nile flood plain is very similar to that of the river water except at the margins of the basin. This ground water contains isotopic contents comparable to the river Nile with low TDS. The change of water quality at the old alluvium plain could be due to extensive use of fertilizers to improve soil characteristics in new reclamation area. Mineral saturation indices suggest that the dissolution of evaporites and halite is significant in the ground water and responsible for most of the ground water salinization. The relationships between Na + ,Cl - , Ca 2+ , Mg 2+ ,HCO 3 - and SO 4 2- show that complex geochemical processes control the chemical history of ground water: (I) continuous dissolution of evaporites and halite and precipitation of carbonate rocks, (2) cation exchange between ground water and clay minerals, (3) excessive use of fertilizers rich in MgSO 4 in the reclamation projects. The isotopic contents of surface water raged from 2.03 to 2.93%0 for δ 18 O, from 15.3 to 28.4%0 for δ 3 H, and from 4.6 to 7.8 TU for tritium while the isotopic contents of ground water ranged from -8,41 to 3,86% o for δ 18 O, from -67.8 to 29.9%0 for δ 2 H, and from 0.5 to 11.3 TU for tritium. The isotopic data reveals that the rechargability of this water is attributed to Nile flood water which was depleted in its isotopic content. Significant contribution from the palaeowater, which stored in the Nubia sandstone aquifer system

  15. Reciprocal sedimentation and noncorrelative hiatuses in marine-paralic siliciclastics: Miocene outcrop evidence

    Energy Technology Data Exchange (ETDEWEB)

    Kidwell, S.M.

    1988-07-01

    Deepening-upward paralic sequences present within a thicker record of shallowing-upward shelf and nonmarine sequences in Miocene siliciclastics of Maryland provide rare stratigraphic evidence for (1) coastal trapping of sediment during marine transgression, with simultaneous starvation on the open shelf (recorded by condensed skeletal lags), and (2) reciprocal switching of depositional and nondepositional conditions during regression. It follows that the regressive disconformities that define hemicyclic coastal sequences are not laterally continuous with the transgressive disconformities and condensed lags that define open-shelf hemicyclic sequences, although they are commonly depicted or assumed as such. Nor are these disconformities age correlative: marine-to-nonmarine correlations that assume lateral continuity of small-scale sequences (1 to 10 m thick; seismic parasequences) will err by as much as one-half cycle, restricting the applicability of models of punctuated aggradational cycles. The stratigraphic anatomy of parasequences is most comparable to reciprocal patterns inherent in hierarchically larger scale sequences in passive margins, where subaerial unconformities and submarine condensed intervals have recently been biostratigraphically verified as offset in age.

  16. Chemical evolution of Miocene wood: Example from the Belchatow brown coal deposit, central Poland

    Science.gov (United States)

    Drobniak, A.; Mastalerz, Maria

    2006-01-01

    Miocene conifer wood samples from the Belchatow brown coal deposit in Poland were studied in order to discuss a range of chemical variations that occur as a result of biochemical coalification. Petrographic analysis, ultimate analysis, electron microprobe technique, and FTIR spectroscopy were used in this study. Our data show several progressive trends in functional groups distribution that take place during the wood transformation from group 1 to group 4, such as an overall increase in aromaticity, an increase in lignin/cellulose ratio, and an increase in oxygen functionalities. Other observations include an increase in aliphatic stretching and bending functionalities from groups 1 to 3; followed by a decrease in the wood of group 4; appearance of aliphatic out-of-plane bands in group 3 and increase in group 4; an increase in CH2/CH3 in group 4 compared to the other groups; and decrease in O-H groups in group 4 compared to other groups. These observations, together with other chemical and petrological observations, indicate that the progressive elimination of cellulose and modification of lignin are dominant processes of the wood transformation. ?? 2005 Elsevier B.V. All rights reserved.

  17. The Miocene "Pteropod event" in the SW part of the Central Paratethys (Medvednica Mt., northern Croatia)

    Science.gov (United States)

    Bošnjak, Marija; Sremac, Jasenka; Vrsaljko, Davor; Aščić, Šimun; Bosak, Luka

    2017-08-01

    Deep marine Miocene deposits exposed sporadically in the Medvednica Mt. (northern Croatia) comprise pelagic organisms such as coccolithophores, planktic foraminifera and pteropods. The pteropod fauna from yellow marls at the Vejalnica locality (central part of Medvednica Mt.) encompasses abundant specimens of Vaginella austriaca Kittl, 1886, accompanied with scarce Clio fallauxi (Kittl, 1886). Calcareous nannoplankton points to the presence of NN5 nannozone at this locality. Highly fossiliferous grey marls at the Marija Bistrica locality (north-eastern area of Medvednica Mt.) comprise limacinid pteropods: Limacina valvatina (Reuss, 1867), L. gramensis (Rasmussen, 1968) and Limacina sp. Late Badenian (NN5 to NN6 nannozone) age of these marls is presumed on the basis of coccolithophores. Most of the determined pteropods on species level, except V. austriaca have been found and described from this region for the first time. New pteropod records from Croatia point to two pteropod horizons coinciding with the Badenian marine transgressions in Central Paratethys. These pteropod assemblages confirm the existence of W-E marine connection ("Transtethyan Trench Corridor") during the Badenian NN5 nannozone. Limacinids point to the possible immigration of the "North Sea fauna" through a northern European marine passage during the Late Badenian (end of NN5-beginning of NN6 zone), as previously presumed by some other authors.

  18. The nasal and paranasal architecture of the Middle Miocene ape Pierolapithecus catalaunicus (primates: Hominidae): phylogenetic implications.

    Science.gov (United States)

    Pérez de Los Ríos, Miriam; Moyà-Solà, Salvador; Alba, David M

    2012-09-01

    The internal (nasal and paranasal) cranial anatomy of the Middle Miocene (11.9 Ma [millions of years ago]) great ape Pierolapithecus catalaunicus (Hominidae: Dryopithecini) is described on the basis of computed-tomography scans of the holotype specimen (IPS21350), with particular emphasis on its phylogenetic implications. Pierolapithecus displays the following characters: an anteriorly-restricted maxillary sinus that posteriorly spreads towards the ethmoidal area (thus resembling the pongine condition), although being situated well above the molar roots (as in kenyapithecins, other dryopithecins and pongines); lack of frontal sinus (a synapomorphy of derived pongines, independently acquired by both cercopithecoids and hylobatids); posteriorly-situated turbinals (as in Pongo); anteriorly-projecting nasolacrimal canal (as in Pongo); and probably stepped nasal floor with non-overlapping premaxillary-maxillary contact (as in dryopithecines and stem hominoids, although it cannot be conclusively shown due to bone damage). Overall, Pierolapithecus displays a mosaic of primitive hominid and derived pongine features that are inconsistent with this taxon being a hominine (as previously suggested). Two alternative phylogenetic interpretations are possible: Pierolapithecus may be a stem member of the Hominidae as previously suggested in its original description, or alternatively this taxon may be a stem member of the Ponginae s.l. (with the European dryopithecines being the sister taxon to the Asian pongines). Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Out of Africa:Miocene Dispersal, Vicariance, and Extinction within Hyacinthaceae Subfamily Urgineoideae

    Institute of Scientific and Technical Information of China (English)

    Syed Shujait Ali; Martin Pfosser; Wolfgang Wetschnig; Mario MartnezAzorn; Manuel B. Crespo; Yan Yu

    2013-01-01

    Disjunct distribution patterns in plant lineages are usually explained according to three hypotheses:vicariance, geodispersal, and long-distance dispersal. The role of these hypotheses is tested in Urgineoideae (Hyacinthaceae), a subfamily disjunctly distributed in Africa, Madagascar, India, and the Mediterranean region. The potential ancestral range, dispersal routes, and factors responsible for the current distribution in Urgineoideae are investigated using divergence time estimations. Urgineoideae originated in Southern Africa approximately 48.9 Mya. Two independent dispersal events in the Western Mediterranean region possibly occurred during Early Oligocene and Miocene (29.9-8.5 Mya) via Eastern and Northwestern Africa. A dispersal from Northwestern Africa to India could have occurred between 16.3 and 7.6 Mya. Vicariance and extinction events occurred approximately 21.6 Mya. Colonization of Madagascar occurred between 30.6 and 16.6 Mya, after a single transoceanic dispersal event from Southern Africa. The current disjunct distributions of Urgineoideae are not satisfactorily explained by Gondwana fragmentation or dispersal via boreotropical forests, due to the younger divergence time estimates. The flattened winged seeds of Urgineoideae could have played an important role in long-distance dispersal by strong winds and big storms, whereas geodispersal could have also occurred from Southern Africa to Asia and the Mediterranean region via the so-called arid and high-altitude corridors.

  20. Morphometry, bite-force, and paleobiology of the late miocene caiman Purussaurus brasiliensis.

    Directory of Open Access Journals (Sweden)

    Tito Aureliano

    Full Text Available Purussaurus brasiliensis thrived in the northwestern portion of South America during the Late Miocene. Although substantial material has been recovered since its early discovery, this fossil crocodilian can still be considered as very poorly understood. In the present work, we used regression equations based on modern crocodilians to present novel details about the morphometry, bite-force and paleobiology of this species. According to our results, an adult Purussaurus brasiliensis was estimated to reach around 12.5 m in length, weighing around 8.4 metric tons, with a mean daily food intake of 40.6 kg. It was capable of generating sustained bite forces of 69,000 N (around 7 metric tons-force. The extreme size and strength reached by this animal seems to have allowed it to include a wide range of prey in its diet, making it a top predator in its ecosystem. As an adult, it would have preyed upon large to very large vertebrates, and, being unmatched by any other carnivore, it avoided competition. The evolution of a large body size granted P. brasiliensis many advantages, but it may also have led to its vulnerability. The constantly changing environment on a large geological scale may have reduced its long-term survival, favoring smaller species more resilient to ecological shifts.

  1. Subaqueous rhyolite block lavas in the Miocene Ushikiri Formation, Shimane Peninsula, SW Japan

    Science.gov (United States)

    Kano, Kazuhiko; Takeuchi, Keiji; Yamamoto, Takahiro; Hoshizumi, Hideo

    1991-06-01

    A rhyolite mass of the Miocene Ushikiri Formation in the western part of the Shimane Peninsula, SW Japan, is a small subaqueous edifice about 600 m high and 4 km wide, formed at water depths between 200 and 1000 m. It consists mainly of three relatively flat, lava-flow units 50-300 m in maximum thickness, each of which includes lobes and their polyhedral fragments. The lava lobes are poorly to well vesiculated, glassy to microcrystalline and flow-banded and -folded. Compared with mafic pillows, they are large, having thick, quenched and brecciated, glassy crusts because of their high viscosity, surface tension and thermal conductivity. Their surfaces disintegrate into polyhedral fragments and grade into massive volcanic breccia. The massive volcanic breccia composed of the lobe fragments is poorly sorted and covered with stratified volcanic breccia of the same rock type. The rhyolite lavas commonly bifurcate in a manner similar to mafic pillow lavas. However, they are highly silicic with 1-5 vol.% phenocrysts and have elongated vesicles and flow-folds, implying that they were visco-plastic during flowage. Their surface features are similar to those of subaerial block lava. With respect to rheological and morphological features, they are subaqueous equivalents of block lava.

  2. C4 Photosynthesis Promoted Species Diversification during the Miocene Grassland Expansion

    Science.gov (United States)

    Spriggs, Elizabeth L.; Christin, Pascal-Antoine; Edwards, Erika J.

    2014-01-01

    Identifying how organismal attributes and environmental change affect lineage diversification is essential to our understanding of biodiversity. With the largest phylogeny yet compiled for grasses, we present an example of a key physiological innovation that promoted high diversification rates. C4 photosynthesis, a complex suite of traits that improves photosynthetic efficiency under conditions of drought, high temperatures, and low atmospheric CO2, has evolved repeatedly in one lineage of grasses and was consistently associated with elevated diversification rates. In most cases there was a significant lag time between the origin of the pathway and subsequent radiations, suggesting that the ‘C4 effect’ is complex and derives from the interplay of the C4 syndrome with other factors. We also identified comparable radiations occurring during the same time period in C3 Pooid grasses, a diverse, cold-adapted grassland lineage that has never evolved C4 photosynthesis. The mid to late Miocene was an especially important period of both C3 and C4 grass diversification, coincident with the global development of extensive, open biomes in both warm and cool climates. As is likely true for most “key innovations”, the C4 effect is context dependent and only relevant within a particular organismal background and when particular ecological opportunities became available. PMID:24835188

  3. Late Miocene Pacific plate kinematic change explained with coupled global models of mantle and lithosphere dynamics

    Science.gov (United States)

    Stotz, I. L.; Iaffaldano, G.; Davies, D. R.

    2017-07-01

    The timing and magnitude of a Pacific plate motion change within the past 10 Ma remains enigmatic, due to the noise associated with finite-rotation data. Nonetheless, it has been hypothesized that this change was driven by the arrival of the Ontong Java Plateau (OJP) at the Melanesian arc and the consequent subduction polarity reversal. The uncertainties associated with the timing of this event, however, make it difficult to quantitatively demonstrate a dynamical association. Here, we first reconstruct the Pacific plate's absolute motion since the mid-Miocene (15 Ma), at high-temporal resolution, building on previous efforts to mitigate the impact of finite-rotation data noise. We find that the largest change in Pacific plate-motion direction occurred between 10 and 5 Ma, with the plate rotating clockwise. We subsequently develop and use coupled global numerical models of the mantle/lithosphere system to test hypotheses on the dynamics driving this change. These indicate that the arrival of the OJP at the Melanesian arc, between 10 and 5 Ma, followed by a subduction polarity reversal that marked the initiation of subduction of the Australian plate underneath the Pacific realm, were the key drivers of this kinematic change.

  4. A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands.

    Science.gov (United States)

    Salas-Gismondi, Rodolfo; Flynn, John J; Baby, Patrice; Tejada-Lara, Julia V; Wesselingh, Frank P; Antoine, Pierre-Olivier

    2015-04-07

    Amazonia contains one of the world's richest biotas, but origins of this diversity remain obscure. Onset of the Amazon River drainage at approximately 10.5 Ma represented a major shift in Neotropical ecosystems, and proto-Amazonian biotas just prior to this pivotal episode are integral to understanding origins of Amazonian biodiversity, yet vertebrate fossil evidence is extraordinarily rare. Two new species-rich bonebeds from late Middle Miocene proto-Amazonian deposits of northeastern Peru document the same hyperdiverse assemblage of seven co-occurring crocodylian species. Besides the large-bodied Purussaurus and Mourasuchus, all other crocodylians are new taxa, including a stem caiman-Gnatusuchus pebasensis-bearing a massive shovel-shaped mandible, procumbent anterior and globular posterior teeth, and a mammal-like diastema. This unusual species is an extreme exemplar of a radiation of small caimans with crushing dentitions recording peculiar feeding strategies correlated with a peak in proto-Amazonian molluscan diversity and abundance. These faunas evolved within dysoxic marshes and swamps of the long-lived Pebas Mega-Wetland System and declined with inception of the transcontinental Amazon drainage, favouring diversification of longirostrine crocodylians and more modern generalist-feeding caimans. The rise and demise of distinctive, highly productive aquatic ecosystems substantially influenced evolution of Amazonian biodiversity hotspots of crocodylians and other organisms throughout the Neogene. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  5. Miocene tectonics of the Maramures area (Northern Romania): implications for the Mid-Hungarian fault zone

    Science.gov (United States)

    Tischler, M.; Gröger, H. R.; Fügenschuh, B.; Schmid, S. M.

    2007-06-01

    The interplay between the emplacement of crustal blocks (e.g. “ALCAPA”, “Tisza”, “Dacia”) and subduction retreat is a key issue for understanding the Miocene tectonic history of the Carpathians. Coeval thrusting and basin formation is linked by transfer zones, such as the Mid-Hungarian fault zone, which seperates ALCAPA from Tisza-Dacia. The presented study provides new kinematic data from this transfer zone. Early Burdigalian (20.5 to ˜18.5 Ma) SE-directed thrusting of the easternmost tip of ALCAPA (Pienides), over Tisza-Dacia is linked to movements along the Mid-Hungarian fault zone and the Periadriatic line, accommodating the lateral extrusion of ALCAPA. Minor Late Burdigalian (˜18.5 to 16 Ma) NE-SW extension is interpreted as related to back-arc extension. Post Burdigalian (post-16 Ma) NE SW shortening and NW SE extension correlate with “soft collision” of Tisza-Dacia with the European foreland coupled with southward migration of active subduction. During this stage the Bogdan-Voda and Dragos-Voda faults were kinematically linked to the Mid-Hungarian fault zone. Sinistral transpression (16 to 12 Ma) at the Bogdan-Voda fault was followed by sinistral transtension (12 10 Ma) along the coupled Bogdan-Dragos-Voda fault system. During the transtensional stage left-lateral offset was reduced eastwards by SW trending normal faults, the fault system finally terminating in an extensional horse-tail splay.

  6. From Late Miocene to Holocene: processes of differentiation within the Telestes genus (Actinopterygii: Cyprinidae.

    Directory of Open Access Journals (Sweden)

    Vincent Dubut

    Full Text Available Investigating processes and timing of differentiation of organisms is critical in the understanding of the evolutionary mechanisms involved in microevolution, speciation, and macroevolution that generated the extant biodiversity. From this perspective, the Telestes genus is of special interest: the Telestes species have a wide distribution range across Europe (from the Danubian district to Mediterranean districts and have not been prone to translocation. Molecular data (mtDNA: 1,232 bp including the entire Cyt b gene; nuclear genome: 11 microsatellites were gathered from 34 populations of the Telestes genus, almost encompassing the entire geographic range. Using several phylogenetic and molecular dating methods interpreted in conjunction with paleoclimatic and geomorphologic evidence, we investigated the processes and timing of differentiation of the Telestes lineages. The observed genetic structure and diversity were largely congruent between mtDNA and microsatellites. The Messinian Salinity Crisis (Late Miocene seems to have played a major role in the speciation processes of the genus. Focusing on T. souffia, a species occurring in the Danube and Rhone drainages, we were able to point out several specific events from the Pleistocene to the Holocene that have likely driven the differentiation and the historical demography of this taxon. This study provides support for an evolutionary history of dispersal and vicariance with unprecedented resolution for any freshwater fish in this region.

  7. Early Miocene amber inclusions from Mexico reveal antiquity of mangrove-associated copepods.

    Science.gov (United States)

    Huys, Rony; Suárez-Morales, Eduardo; Serrano-Sánchez, María de Lourdes; Centeno-García, Elena; Vega, Francisco J

    2016-10-12

    Copepods are aquatic microcrustaceans and represent the most abundant metazoans on Earth, outnumbering insects and nematode worms. Their position of numerical world predominance can be attributed to three principal radiation events, i.e. their major habitat shift into the marine plankton, the colonization of freshwater and semiterrestrial environments, and the evolution of parasitism. Their variety of life strategies has generated an incredible morphological plasticity and disparity in body form and shape that are arguably unrivalled among the Crustacea. Although their chitinous exoskeleton is largely resistant to chemical degradation copepods are exceedingly scarce in the geological record with limited body fossil evidence being available for only three of the eight currently recognized orders. The preservation of aquatic arthropods in amber is unusual but offers a unique insight into ancient subtropical and tropical ecosystems. Here we report the first discovery of amber-preserved harpacticoid copepods, represented by ten putative species belonging to five families, based on Early Miocene (22.8 million years ago) samples from Chiapas, southeast Mexico. Their close resemblance to Recent mangrove-associated copepods highlights the antiquity of the specialized harpacticoid fauna living in this habitat. With the taxa reported herein, the Mexican amber holds the greatest diversity of fossil copepods worldwide.

  8. Oligocene-Miocene burial and exhumation of the southernmost Gangdese mountains from sedimentary and thermochronological evidence

    Science.gov (United States)

    Ge, Yukui; Li, Yalin; Wang, Xiaonan; Qian, Xinyu; Zhang, Jiawei; Zhou, Aorigele; Liu-Zeng, Jing

    2018-01-01

    The Kailas conglomerates crop out ubiquitously along the southernmost boundary of the Gangdese batholith. They unconformably overlie the Gangdese batholith and are displaced by the Great Counter thrust (GCT) fault, forming a fault contact with the Xigaze forearc basin, the associated subduction complex and the Tethyan Himalayan sequence. These strata furnish a record of uplift and paleoenvironmental change in the Indus-Yarlung suture zone during the Oligocene-Miocene. Our new and previously published low-temperature thermochronometric data from the Gangdese batholith and the Kailas conglomerates indicate a period of rapid exhumation beginning approximately 17-15 Ma centered on the southern margin of the Gangdese batholith, whereas regional uplift commenced significantly earlier during the deposition of the Kailas conglomerates, based on the presence of an abrupt facies transition from deep-water lacustrine deposits to red alluvial fan or fluvial deposits. The period of rapid exhumation probably lagged behind the initiation of faster uplift, while the related changes in the depositional environment were most likely recorded immediately in the basin stratigraphy. Subsequently, the Kailas conglomerates were buried in association with the development of the north-directed Great Counter thrust, while rapid exhumation was facilitated by efficient incision by the paleo-Yarlung river at approximately 17-15 Ma.

  9. The Miocene Roof Mapping Using Microtremor Recording and Electrical Survey Method in Blida City, Algeria

    Science.gov (United States)

    Bouchelouh, Assia; Bensalem, Rabah; Zaourar, Naima; Machane, Djamel; Moulouel, Hakim; Oubaiche, El Hadi

    2018-01-01

    Bedrock depths in the Mitidja basin in general and in the Blida region in particular are still poorly known despite, the existence of some relatively deep hydraulic boreholes that intersect only superficial alluvial formations. To assess the seismic risk of Blida town, knowledge of soil amplification requires the thickness and properties of sedimentary formations that cover the substratum. For the purposes of our study, the thicknesses obtained by the vertical electric soundings, carried out in the hydrogeological study of the basin, were combined with horizontal-to-vertical spectral ratio (HVSR) microtremor recordings. This combination made it possible to determine an empirical relationship between frequency and thickness specific to the Blida site area, which enabled the roof of the Miocene to be mapped and shows slight undulations with directions compatible with the tectonic constraints of the region. The boundaries between the low and high frequencies obtained by HVSR are well materialized, at south by Sidi El Kebir river, at west by Chiffa river and in the central part by a line of direction SE-NW corresponding to the old passage of Sidi El Kebir river. The presence of low frequencies attributed to the old alluvial deposits with significant thicknesses that originate just after Sidi El Kebir river confirms that the South Mitidjian contact is subvertical.

  10. A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands

    Science.gov (United States)

    Salas-Gismondi, Rodolfo; Flynn, John J.; Baby, Patrice; Tejada-Lara, Julia V.; Wesselingh, Frank P.; Antoine, Pierre-Olivier

    2015-01-01

    Amazonia contains one of the world's richest biotas, but origins of this diversity remain obscure. Onset of the Amazon River drainage at approximately 10.5 Ma represented a major shift in Neotropical ecosystems, and proto-Amazonian biotas just prior to this pivotal episode are integral to understanding origins of Amazonian biodiversity, yet vertebrate fossil evidence is extraordinarily rare. Two new species-rich bonebeds from late Middle Miocene proto-Amazonian deposits of northeastern Peru document the same hyperdiverse assemblage of seven co-occurring crocodylian species. Besides the large-bodied Purussaurus and Mourasuchus, all other crocodylians are new taxa, including a stem caiman—Gnatusuchus pebasensis—bearing a massive shovel-shaped mandible, procumbent anterior and globular posterior teeth, and a mammal-like diastema. This unusual species is an extreme exemplar of a radiation of small caimans with crushing dentitions recording peculiar feeding strategies correlated with a peak in proto-Amazonian molluscan diversity and abundance. These faunas evolved within dysoxic marshes and swamps of the long-lived Pebas Mega-Wetland System and declined with inception of the transcontinental Amazon drainage, favouring diversification of longirostrine crocodylians and more modern generalist-feeding caimans. The rise and demise of distinctive, highly productive aquatic ecosystems substantially influenced evolution of Amazonian biodiversity hotspots of crocodylians and other organisms throughout the Neogene. PMID:25716785

  11. Morphometry, Bite-Force, and Paleobiology of the Late Miocene Caiman Purussaurus brasiliensis

    Science.gov (United States)

    Aureliano, Tito; Ghilardi, Aline M.; Guilherme, Edson; Souza-Filho, Jonas P.; Cavalcanti, Mauro; Riff, Douglas

    2015-01-01

    Purussaurus brasiliensis thrived in the northwestern portion of South America during the Late Miocene. Although substantial material has been recovered since its early discovery, this fossil crocodilian can still be considered as very poorly understood. In the present work, we used regression equations based on modern crocodilians to present novel details about the morphometry, bite-force and paleobiology of this species. According to our results, an adult Purussaurus brasiliensis was estimated to reach around 12.5 m in length, weighing around 8.4 metric tons, with a mean daily food intake of 40.6 kg. It was capable of generating sustained bite forces of 69,000 N (around 7 metric tons-force). The extreme size and strength reached by this animal seems to have allowed it to include a wide range of prey in its diet, making it a top predator in its ecosystem. As an adult, it would have preyed upon large to very large vertebrates, and, being unmatched by any other carnivore, it avoided competition. The evolution of a large body size granted P. brasiliensis many advantages, but it may also have led to its vulnerability. The constantly changing environment on a large geological scale may have reduced its long-term survival, favoring smaller species more resilient to ecological shifts. PMID:25689140

  12. Diagenetic history of late Oligocene-early Miocene carbonates in East Sabah, Malaysia

    Science.gov (United States)

    Zainal Abidin, N. S.; Raymond, R. R.; Bashah, N. S. I.

    2017-10-01

    Limestones are particularly susceptible to drastic early diagenesis modifications, mainly cementation and dissolution. During the early Miocene, a major tectonic deformation has caused a widespread of uplift in Sabah. This has resulted change in depositional environment from deep to shallow marine, which favours the deposition of Gomantong Limestone. This study aims to investigate the diagenetic history of Gomantong Limestone in East Sabah. Thorough understanding of the diagenetic processes may provide data to unravel the tectonic activities which affected the reservoir quality of the carbonates. Combining the data from comprehensive petrographic analysis, and Scanning Electron Microscopy (SEM) of 30 samples, two main cements type were identified. These are microcrystalline cement and Mg-calcite cement of granular and blocky mosaics which are dominantly seen in all samples. The sequence of diagenesis events are determined as (1) micritization; (2) grain scale compaction; (3) cementation (pore-filling); (4) mechanical compaction and cementation infilling fractures and (5) chemical compaction. These diagenetic events are interpreted as reflection of changes in diagenetic environment from shallow marine to deep burial. The massive cementation in the Gomantong Limestone has resulted into a poor reservoir quality.

  13. Frontier seismic geologic techniques and the exploration of the Miocene reefs in offshore Palawan, Philippines

    Science.gov (United States)

    Biswas, Buddhadeb

    An 88 km grid of Seislog sections (synthetic sonic log traces) was used to supplement the conventional seismic interpretation to assess the hydrocarbon potential of Lower Miocene reefs of offshore Palawan, Philippines. The porosity distribution in the zone of interest as well as the oil-water contact in and around the Tara and Libro patch reefs were mapped. The structural mapping was also fine tuned, including mapping of faults with small displacements. The paradox of pooling of hydrocarbons is evident in the maximum fill in the front line of traps near the shelf-slope break that are in the lowest structural position. Progressively dwindling amounts of fill in the structurally higher updip basin positions are interpreted to be due to the migration of hydrocarbons from the hydrocarbon kitchen in the Palawan Trough. The front line of traps had the benefit of maximum fill, the traps at the rear only of residual fill that spilled past the frontal traps. Three play types corresponding to the front line of traps, the rear line of traps and the most remote line of traps have been identified. Frontal reefs are considered to have the highest hydrocarbon potential. Diminishing hydrocarbon potential is inferred for closures in the updip direction. A thorough screening of all available seismic control for mapping all the patch reefs that might compensate for their dimensions by their numbers as well as for detecting possible pinnacle reefs in the downdip basin position has been suggested.

  14. Herds Overhead: Nimbadon lavarackorum (Diprotodontidae), Heavyweight Marsupial Herbivores in the Miocene Forests of Australia

    Science.gov (United States)

    Black, Karen H.; Camens, Aaron B.; Archer, Michael; Hand, Suzanne J.

    2012-01-01

    The marsupial family Diprotodontidae (Diprotodontia, Vombatiformes) is a group of extinct large-bodied (60–2500 kg) wombat-like herbivores that were common and geographically widespread in Cenozoic fossil deposits of Australia and New Guinea. Typically they are regarded to be gregarious, terrestrial quadrupeds and have been likened in body form among placental groups to sheep, rhinoceros and hippopotami. Arguably, one of the best represented species is the zygomaturine diprotodontid Nimbadon lavarackorum which is known from exceptionally well-preserved cranial and postcranial material from the middle Miocene cave deposit AL90, in the Riversleigh World Heritage Area, northwestern Queensland. Here we describe and functionally analyse the appendicular skeleton of Nimbadon lavarackorum and reveal a far more unique lifestyle for this plesiomorphic and smallest of diprotodontids. Striking similarities are evident between the skeleton of Nimbadon and that of the extant arboreal koala Phascolarctos cinereus, including the powerfully built forelimbs, highly mobile shoulder and elbow joints, proportionately large manus and pes (both with a semi-opposable digit I) and exceedingly large, recurved and laterally compressed claws. Combined with the unique (among australidelphians) proportionately shortened hindlimbs of Nimbadon, these features suggest adept climbing ability, probable suspensory behaviour, and an arboreal lifestyle. At approximately 70 kg, Nimbadon is the largest herbivorous mammal to have occupied the forest canopies of Australia - an ecological niche that is no longer occupied in any Australian ecosystem and one that further expands the already significant niche diversity displayed by marsupials during the Cenozoic. PMID:23185250

  15. Herds overhead: Nimbadon lavarackorum (Diprotodontidae, heavyweight marsupial herbivores in the Miocene forests of Australia.

    Directory of Open Access Journals (Sweden)

    Karen H Black

    Full Text Available The marsupial family Diprotodontidae (Diprotodontia, Vombatiformes is a group of extinct large-bodied (60-2500 kg wombat-like herbivores that were common and geographically widespread in Cenozoic fossil deposits of Australia and New Guinea. Typically they are regarded to be gregarious, terrestrial quadrupeds and have been likened in body form among placental groups to sheep, rhinoceros and hippopotami. Arguably, one of the best represented species is the zygomaturine diprotodontid Nimbadon lavarackorum which is known from exceptionally well-preserved cranial and postcranial material from the middle Miocene cave deposit AL90, in the Riversleigh World Heritage Area, northwestern Queensland. Here we describe and functionally analyse the appendicular skeleton of Nimbadon lavarackorum and reveal a far more unique lifestyle for this plesiomorphic and smallest of diprotodontids. Striking similarities are evident between the skeleton of Nimbadon and that of the extant arboreal koala Phascolarctos cinereus, including the powerfully built forelimbs, highly mobile shoulder and elbow joints, proportionately large manus and pes (both with a semi-opposable digit I and exceedingly large, recurved and laterally compressed claws. Combined with the unique (among australidelphians proportionately shortened hindlimbs of Nimbadon, these features suggest adept climbing ability, probable suspensory behaviour, and an arboreal lifestyle. At approximately 70 kg, Nimbadon is the largest herbivorous mammal to have occupied the forest canopies of Australia - an ecological niche that is no longer occupied in any Australian ecosystem and one that further expands the already significant niche diversity displayed by marsupials during the Cenozoic.

  16. SILICEOUS SPONGE SPICULES FROM THE MIOCENE MEM MONIZ MARLS (PORTUGAL AND THEIR ENVIRONMENTAL SIGNIFICANCE

    Directory of Open Access Journals (Sweden)

    ANDRZEJ PISERA

    2006-07-01

    Full Text Available The Miocene (middle Serravalian Mem Moniz marls from Algarve (Portugal contain a rich and well preserved assemblage of siliceous sponge spicules, which is described here for the first time. The assemblage indicates that the sponge fauna was dominated by Astrophorida, and in particular by Geodiidae. The presence of Eurylus sp. and probably Geodia sp. (both Astrophorida, Samus sp. (Spirophorida and Alectona wallichii (Hadromerida is also reported. Samus sp. and Alectona wallichii are reported from the fossil record for the first time. Additionally, the occurrence of lithistid demosponges (represented by Theonellidae and rhizomorinids, Hadromerida, Spirophorida and Hexactinellida is also shown. Ancorinidae, Pachastrellidae (and/or Cathropellidae, both Astrophorida, were also clearly recognized. Less certain is the occurrence, in the Mem Moniz marls, of Tethyidae (Hadromerida. Bathymetric reconstructions based on sponges are imprecise due to the fact that these organisms often have very wide bathymetric ranges. However, the studied sponge assemblage is clearly neither characteristic of very shallow nor very deep marine environments. The dominance of astrophorids and the presence of lithistids and hexactinellids suggest a depth of at least several tens to one hundred metres, or even more.

  17. Metasomatized mantle as the source of Mid-Miocene-Quaternary volcanism in NW-Iranian Azerbaijan: Geochronological and geochemical evidence

    Science.gov (United States)

    Lechmann, Anna; Burg, Jean-Pierre; Ulmer, Peter; Guillong, Marcel; Faridi, Mohammad

    2018-04-01

    Middle Miocene to Quaternary volcanic rocks cover large areas of the Azerbaijan Province in NW Iran. This study reports two separate age clusters out of 23 new LA-ICP-MS U-Pb zircon ages: (1) Middle Miocene (16.2-10.6 Ma) and (2) Latest Miocene-Late Pleistocene (5.5-0.4 Ma). Major and trace element bulk rock geochemistry and initial Sr, Nd, Pb radiogenic isotope data on the dated rocks provide new constraints on the Mid-Miocene to Quaternary volcanism in this region. The analyses are distributed over a large compositional range from low-K to high-K calc-alkaline andesites and dacites/rhyolites to more alkaline trachybasalts and dacites with shoshonitic affinities. Chondrite-normalized REE patterns are steep with significant enrichment in LREE and low abundances of HREE indicating a garnet control. Plots of primitive mantle-normalized trace elements show negative Ti and Nb-Ta anomalies indicative of an arc signature. The wide compositional range and the ubiquitous presence of an arc signature reveal that the source mantle is heterogeneous and metasomatically altered. Sr, Nd and Pb radiogenic isotope data further point towards an enriched mantle source and/or crustal contamination. Crustal contamination is best recognized by inherited zircon cores, which yield Late Neoproterozoic to Early Cambrian ages typical for the Iranian basement. The occurrence of adakite-like compositions with elevated magnesium numbers, Cr and Ni concentrations argue against a fractionation-driven process but point to a subcrustal origin. Overall, the analyzed lavas show no spatial and temporal relation to a potential subduction zone, confirming the dated volcanics to be post-collisional and not related to singular processes such as slab retreat or delamination of a continuous lower crustal sliver. We propose three hypotheses to explain the reported disparity in distribution, age and composition and favour small-scale sublithospheric convection or incorporation of crustal material into the

  18. How We Got to the Northern Hemisphere Ice Ages: Late Miocene Global Cooling and Plate Tectonic CO2 Forcing

    Science.gov (United States)

    Herbert, T.; Dalton, C. A.; Carchedi, C.

    2017-12-01

    The evolution of Earth's climate between "refrigeration" of East Antarctica and the onset of cyclic Northern Hemisphere glaciation spanned more than 11 Myr. In the latest Miocene (Messinian) time, approximately half way on this journey, changes on land, ranging from the expansion of arid zones to major floral and faunal ecosystem shifts, accelerated. Recent compilations of marine surface temperatures reveal that global cooling from the Miocene Optimum (14-16Ma) also accelerated in late Miocene (7-5.35 Ma) time to reach temperatures not much above Holocene conditions. Both hemispheres cooled in parallel, with the changes amplified at higher latitudes in comparison to the tropics. Despite the strong circumstantial case for CO2 decline as the dominant cause of late Miocene climatic and evolutionary change, proxy indicators of CO2concentrations paint an equivocal picture of greenhouse forcing. Here we provide evidence that global sea floor spreading (SFS) rates decelerated at exactly the times of major climatic cooling, linking a decline in tectonic degassing (at both subduction zones and mid-ocean ridges) to fundamental shifts in the global carbon cycle. Our work utilizes newly available global compilations of seafloor fabric and marine magnetic anomalies provided by the NSF-funded Global Seafloor Fabric and Magnetic Lineation Data Base Project. Previous global compilations of SFS typically binned estimates over 10 Myr increments, losing critical resolution on the timescale of late Neogene climate changes. We further improve the signal:noise of SFS estimates by incorporating recent advances in the astronomical calibration of the Miocene geomagnetic polarity timescale. We use two approaches to compile spreading rate estimates over the past 20 Myr at each spreading system: optimized finite rotation calculations, and averages of sea floor-spreading derived from the distances of magnetic lineations along flow lines on the sea floor. Weighted by ridge length, we find an 25

  19. Cryptic diversity and deep divergence in an upper Amazonian leaflitter frog, Eleutherodactylus ockendeni

    Directory of Open Access Journals (Sweden)

    Dávila José A

    2007-12-01

    Full Text Available Abstract Background The forests of the upper Amazon basin harbour some of the world's highest anuran species richness, but to date we have only the sparsest understanding of the distribution of genetic diversity within and among species in this region. To quantify region-wide genealogical patterns and to test for the presence of deep intraspecific divergences that have been documented in some other neotropical anurans, we developed a molecular phylogeny of the wide-spread terrestrial leaflitter frog Eleutherodactylus ockendeni (Leptodactylidae from 13 localities throughout its range in Ecuador using data from two mitochondrial genes (16S and cyt b; 1246 base pairs. We examined the relation between divergence of mtDNA and the nuclear genome, as sampled by five species-specific microsatellite loci, to evaluate indirectly whether lineages are reproductively isolated where they co-occur. Our extensive phylogeographic survey thus assesses the spatial distribution of E. ockendeni genetic diversity across eastern Ecuador. Results We identified three distinct and well-supported clades within the Ecuadorean range of E. ockendeni: an uplands clade spanning north to south, a northeastern and central lowlands clade, and a central and southeastern clade, which is basal. Clades are separated by 12% to 15% net corrected p-distance for cytochrome b, with comparatively low sequence divergence within clades. Clades marginally overlap in some geographic areas (e.g., Napo River basin but are reproductively isolated, evidenced by diagnostic differences in microsatellite PCR amplification profiles or DNA repeat number and coalescent analyses (in MDIV best modelled without migration. Using Bayesian (BEAST and net phylogenetic estimates, the Southeastern Clade diverged from the Upland/Lowland clades in the mid-Miocene or late Oligocene. Lowland and Upland clades speciated more recently, in the early or late Miocene. Conclusion Our findings uncover previously

  20. Late Eocene to middle Miocene (33 to 13 million years ago) vegetation and climate development on the North American Atlantic Coastal Plain (IODP Expedition 313, Site M0027)

    Science.gov (United States)

    Kotthoff, U.; Greenwood, D. R.; McCarthy, F. M. G.; Müller-Navarra, K.; Prader, S.; Hesselbo, S. P.

    2014-08-01

    We investigated the palynology of sediment cores from Site M0027 of IODP (Integrated Ocean Drilling Program) Expedition 313 on the New Jersey shallow shelf to examine vegetation and climate dynamics on the east coast of North America between 33 and 13 million years ago and to assess the impact of over-regional climate events on the region. Palynological results are complemented with pollen-based quantitative climate reconstructions. Our results indicate that the hinterland vegetation of the New Jersey shelf was characterized by oak-hickory forests in the lowlands and conifer-dominated vegetation in the highlands from the early Oligocene to the middle Miocene. The Oligocene witnessed several expansions of conifer forest, probably related to cooling events. The pollen-based climate data imply an increase in annual temperatures from ∼11.5 °C to more than 16 °C during the Oligocene. The Mi-1 cooling event at the onset of the Miocene is reflected by an expansion of conifers and mean annual temperature decrease of ∼4 °C, from ∼16 °C to ∼12 °C around 23 million years before present. Relatively low annual temperatures are also recorded for several samples during an interval around ∼20 million years before present, which may reflect the Mi-1a and the Mi-1aa cooling events. Generally, the Miocene ecosystem and climate conditions were very similar to those of the Oligocene. Miocene grasslands, as known from other areas in the USA during that time period, are not evident for the hinterland of the New Jersey shelf, possibly reflecting moisture from the proto-Gulf Stream. The palaeovegetation data reveal stable conditions during the mid-Miocene climatic optimum at ∼15 million years before present, with only a minor increase in deciduous-evergreen mixed forest taxa and a decrease in swamp forest taxa. Pollen-based annual temperature reconstructions show average annual temperatures of ∼14 °C during the mid-Miocene climatic optimum, ∼2 °C higher than today

  1. Latest Miocene-earliest Pliocene evolution of the ancestral Rio Grande at the Española-San Luis Basin boundary, northern New Mexico

    Science.gov (United States)

    Daniel J. Koning,; Aby, Scott B.; Grauch, V. J.; Matthew J. Zimmerer,

    2016-01-01

    We use stratigraphic relations, paleoflow data, and 40Ar/39Ar dating to interpret net aggradation, punctuated by at least two minor incisional events, along part of the upper ancestral Rio Grande fluvial system between 5.5 and 4.5 Ma (in northern New Mexico). The studied fluvial deposits, which we informally call the Sandlin unit of the Santa Fe Group, overlie a structural high between the San Luis and Española Basins. The Sandlin unit was deposited by two merging, west- to southwest-flowing, ancestral Rio Grande tributaries respectively sourced in the central Taos Mountains and southern Taos Mountains-northeastern Picuris Mountains. The river confluence progressively shifted southwestward (downstream) with time, and the integrated river (ancestral Rio Grande) flowed southwards into the Española Basin to merge with the ancestral Rio Chama. Just prior to the end of the Miocene, this fluvial system was incised in the southern part of the study area (resulting in an approximately 4–7 km wide paleovalley), and had sufficient competency to transport cobbles and boulders. Sometime between emplacement of two basalt flows dated at 5.54± 0.38 Ma and 4.82±0.20 Ma (groundmass 40Ar/39Ar ages), this fluvial system deposited 10–12 m of sandier sediment (lower Sandlin subunit) preserved in the northern part of this paleovalley. The fluvial system widened between 4.82±0.20 and 4.50±0.07 Ma, depositing coarse sand and fine gravel up to 14 km north of the present-day Rio Grande. This 10–25 m-thick sediment package (upper Sandlin unit) buried earlier south- to southeast-trending paleovalleys (500–800 m wide) inferred from aeromagnetic data. Two brief incisional events are recognized. The first was caused by the 4.82±0.20 Ma basalt flow impounding south-flowing paleodrainages, and the second occurred shortly after emplacement of a 4.69±0.09 Ma basalt flow in the northern study area. Drivers responsible for Sandlin unit aggradation may include climate

  2. A review of current practices and the future for deep well injection in the upper Miocene Stevens sand, Kern County, California

    International Nuclear Information System (INIS)

    Kiser, S.C.; Chenot, D.W.

    1991-01-01

    Waste-water disposal is a major concern of the petroleum business, especially because of complications associated with many produced-water surface-impoundment percolation facilities. In the San Joaquin Valley, California, the current environmental regulations protecting the potentially usable groundwaters are stringent. the Stevens has significant potential as a disposal zone that may offer considerable capacity when the project is designed using proper geologic and engineering studies. The Stevens sands are well known for their oil-producing capabilities, however, not much has been published regarding its suitability as a zone for deep well injection. Conditions that make the Stevens potentially suitable include (1) adequate confinement providing geologic separation from the groundwater sources in the basin, (2) storage capacity, and (3) large areal extent. Because the search for acceptable disposal options is becoming critical, the current class II disposal options is becoming critical, the current class II disposal activities in the Stevens sands were reviewed and the areas offering the greatest future potential were identified. The authors then discuss class II disposal projects in Stevens sands in the West Bellevue and Midway Sunset oil fields and estimate the ultimate basin-wide disposal capacity of the Stevens

  3. Extensive upper respiratory tract sarcoidosis

    Science.gov (United States)

    Soares, Mafalda Trindade; Sousa, Carolina; Garanito, Luísa; Freire, Filipe

    2016-01-01

    Sarcoidosis is a chronic granulomatous disease of unknown aetiology. It can affect any part of the organism, although the lung is the most frequently affected organ. Upper airway involvement is rare, particularly if isolated. Sarcoidosis is a diagnosis of exclusion, established by histological evidence of non-caseating granulomas and the absence of other granulomatous diseases. The authors report a case of a man with sarcoidosis manifesting as a chronic inflammatory stenotic condition of the upper respiratory tract and trachea. PMID:27090537

  4. Miocene magmatism and tectonics within the Peri-Alboran orogen (western Mediterranean)

    Science.gov (United States)

    El Azzouzi, M.; Bellon, H.; Coutelle, A.; Réhault, J.-P.

    2014-07-01

    The aim of this paper concerns Miocene igneous activity in the Alboran Sea and Peri-Alboran area (northern Morocco, western Algeria and Betic Cordilleras in Spain), considering its age and its location with regard to major tectonics structures. We have compiled previous K-Ar isotopic ages of lavas and plutonic boulders and intrusives with an error of ±1σ and completed this set by a new K-Ar isotopic age for andesitic tuffites from Alboran Island. Geochemistry of most of these samples has been considered after previous analyses completed with new data for Spain magmatism. These two sets of data allow us to place the magmatic activity within the regional stratigraphy and tectonics and their chronological framework of the three major tectonic phases of the Maghrebian orogen, at 17 Ma (Burdigalian), 15 Ma (Langhian) and 9 Ma (Tortonian). Petro-geochemical characteristics are compared through time and geographical locations. A major goal of this coupled approach is to help the elaboration of possible geodynamical processes. As an application, we present the case study of the Dellys, Djinet and Thenia region (east of Algiers) where the successive magmatic events between 19.4 ± 1 and 11.6 ± 0.5 Ma are closely related to the local tectonics and sedimentation. The Peri-Alboran igneous activity is placed in a multidisciplinary framework. Timing of activity is defined according to the ages of the neighbouring sedimentary units and the K-Ar ages of igneous rocks. In Spain, the Cabo de Gata-Carboneras magmatic province displays late Oligocene and early Miocene leucogranitic dikes, dated from 24.8 ± 1.3 to 18.1 ± 1.2 Ma; three following andesitic to rhyolitic events took place around 15.1 ± 0.8 to 14.0 ± 0.7 Ma, 11.8 ± 0.6 to 9.4 ± 0.4 Ma, 8.8 ± 0.4 to 7.9 ± 0.4 Ma; this last event displays also granitic rocks. Lamproitic magmas dated between 8.4 ± 0.4 and 6.76 ± 0.04 Ma were emplaced after the Tortonian phase. In Morocco, after the complex building of the Ras Tarf

  5. A possible cause of the Miocene uplift and volcanism in the central Anatolian plateau

    Science.gov (United States)

    Bartol, J.; Govers, R. M.; Wortel, M. J.

    2010-12-01

    During the middle and late Miocene (13-5Ma) several seemingly unrelated events occurred in central Anatolia, Turkey; (1) a new epoch of widespread volcanic activity with a mantle signature, (2) sudden uplift and disruption of a Oligocene-lower Miocene palaeo drainage system in the Western Taurus (southwest Turkey) and (3) a regional regression across southern Turkey (Antalya, Adana, Mut) coeval with volcanic activity. These observations suggest an uplift (>1000 meters) of the central Anatolian plateau by a mechanism which also triggered widespread volcanic activity. In eastern Anatolia, similar events are attributed to delamination of the lithospheric mantle [e.g. Keskin et al., 2003]. Results from tomography [W.Spakman, pers. com]) suggest that the (deeper) Bitlis slab was laterally continuous below the eastern and central Anatolian plateau. We therefore propose that the scenario developed for eastern Anatolian plateau also applies to the central Anatolian plateau. In this scenario, delamination started along the Izmir-Ankara-Erzincan suture zone and was possibly induced by remnants of a northern Neotethys slab or continental collision between Arabia and Eurasia. As the lithospheric mantle separated from the crust it sank into the asthenosphere and was replaced by hot mantle material. If true, delamination is expected to have had a thermal and isostatic imprint. Using a three-dimensional thermal-flexural model and taking changes of the effective elastic thickness due to thermal perturbation into account, we aim to quantify the possible imprints in the geological record of the central and eastern Anatolian plateau. Our model results show that delamination of the lithospheric mantle can explain the present day elevation (1500 m) of the central Anatolian plateau. For the eastern Anatolian plateau, however, delamination of the lithospheric mantle alone can only explain half (1000 m) of the present day elevation. Thickening of the eastern Anatolia crust by 1-5 km (β=1

  6. Stratigraphic condensation of marine transgressive records: Origin of major shell deposits in the Miocene of Maryland

    Energy Technology Data Exchange (ETDEWEB)

    Kidwell, S.M. (Univ. of Chicago, IL (USA))

    1989-01-01

    Cyclic stratigraphic sequences in shallow marine records are commonly charaterized by a condensed transgressive lag at the base of thicker, shallowing-upward facies. The standard actualistic model for these thin fossiliferous lags, by which most of the shelf is starved owing to coastal trapping of sediment and fossils are suspected of being reworked because of the association with an erosional ravinement, is contradicted by detailed stratigraphic and taphonomic analysis of Miocene examples in the Maryland coastal plain. The complex internal stratigraphies of the shell deposits and the mixture of soft- and shell-bottom faunas indicate condensation under a regime of dynamic bypassing rather than complete sediment starvation; bypassed fine sediments accumulated in deeper water environments below storm wavebase. Deeper, even more basinward parts of the shelf were starved of all sediment size fractions and accumulated shell-poor, bone-rich condensed deposits that lie mid-cycle (bracketing the time of maximum water depth). The base-of-cycle shell deposits and mid-cycle bone bed differ not only in composition and in environment and dynamics of condensation, but also in chronostratigraphic value: the onlapping shell deposits must be diachronous to some degree, whereas the mid-cycle bone bed approximates an isochronous marker for correlation. Thus, in some settings at least, transgressive shelves present a spatial mosaic of condensational and depositional regimes. Regardless of origin, all condensed intervals can time-average assemblages and telescope biostratigraphic datums. They otherwise differ widely, however, in paleontologic attributes and are characterized by highly variable and complex stratigraphic anatomies.

  7. A new species of great ape from the late Miocene epoch in Ethiopia.

    Science.gov (United States)

    Suwa, Gen; Kono, Reiko T; Katoh, Shigehiro; Asfaw, Berhane; Beyene, Yonas

    2007-08-23

    With the discovery of Ardipithecus, Orrorin and Sahelanthropus, our knowledge of hominid evolution before the emergence of Pliocene species of Australopithecus has significantly increased, extending the hominid fossil record back to at least 6 million years (Myr) ago. However, because of the dearth of fossil hominoid remains in sub-Saharan Africa spanning the period 12-7 Myr ago, nothing is known of the actual timing and mode of divergence of the African ape and hominid lineages. Most genomic-based studies suggest a late divergence date-5-6 Myr ago and 6-8 Myr ago for the human-chimp and human-gorilla splits, respectively-and some palaeontological and molecular analyses hypothesize a Eurasian origin of the African ape and hominid clade. We report here the discovery and recognition of a new species of great ape, Chororapithecus abyssinicus, from the 10-10.5-Myr-old deposits of the Chorora Formation at the southern margin of the Afar rift. To the best of our knowledge, these are the first fossils of a large-bodied Miocene ape from the African continent north of Kenya. They exhibit a gorilla-sized dentition that combines distinct shearing crests with thick enamel on its 'functional' side cusps. Visualization of the enamel-dentine junction by micro-computed tomography reveals shearing crest features that partly resemble the modern gorilla condition. These features represent genetically based structural modifications probably associated with an initial adaptation to a comparatively fibrous diet. The relatively flat cuspal enamel-dentine junction and thick enamel, however, suggest a concurrent adaptation to hard and/or abrasive food items. The combined evidence suggests that Chororapithecus may be a basal member of the gorilla clade, and that the latter exhibited some amount of adaptive and phyletic diversity at around 10-11 Myr ago.

  8. Provenance and evolution of miocene turbidite sedimentation in the central Apennines, Italy

    Science.gov (United States)

    Chiocchini, Ugo; Cipriani, Nicola

    1992-05-01

    A study of the siliciclastic detritus within the calcareous Miocene turbidite sandstones of the central Apennines has elucidated the provenance of these sandstones. Three ratios: Q/(Q+F), K/F, and Mc/M, have been used and binary correlations of these parameters show that: (1) the sandstones of the Marnoso-Arenacea are characterized by a northern Alpine supply, mainly derived from metamorphic rocks and subordinately from granitic rocks; (2) a secondary supply of western provenance, interbedded within the Marnoso-Arenacea, shows a typical arkosic composition and suggests that granitic rocks of Alpine-type were associated with the Ligurides; (3) the Urbania and Serraspinosa sandstones consist of detritus derived from sources almost identical to those supplying the Marnoso-Arenacea; (4) all the sandstones of the remaining central Apennine basins are characterized by a siliciclastic supply similar to the arkosic one; the rare carbonate fragments can be referred to the Apennine units. The continuity of the Alpine are in the Tyrrhenian area strongly suggests a connection between the western crystalline units and turbidite sedimentation in the basins examined. The crystalline units are associated with a segment of the Alpine chain tectonically linked to the Liguride nappes (Apennine source areas) during the eastwards migration of the Apennines deformation. The crystalline units were gradually eroded during the Burdigalian to Early Pliocene interval when the Laga basin was completely filled. Currently the term "Alpine" is used as synonymous with northern provenance. However, a detailed study carried out over ten years, revealed a western Alpine supply associated with an Apennine source area; we therefore suggest that it is necessary to distinguish a northern Alpine provenance from a western Alpine supply.

  9. The Oligocene-Miocene stratigraphic evolution of the Majella carbonate platform (Central Apennines, Italy)

    Science.gov (United States)

    Brandano, Marco; Cornacchia, Irene; Raffi, Isabella; Tomassetti, Laura

    2016-03-01

    The stratigraphic architecture of the Bolognano Formation documents the evolution of the Majella carbonate platform in response to global and local changes that affected the Mediterranean area during the Oligocene-Miocene interval. The Bolognano Formation consists of a homoclinal ramp that developed in a warm, subtropical environment. Five different lithofacies associations have been identified: Lepidocyclina calcarenites, cherty marly limestones, bryozon calcarenites, hemipelagic marls and marly limestones, and Lithothamnion limestones. Each association corresponds to a single lithostratigraphic unit except for the Lepidocyclina calcarenites that form two distinct lithostratigraphic units (Lepidocyclina calcarenites 1 and 2). These six units reflect alternation of shallow-water carbonate production and drowning. Specifically, two of the three stages of shallow-water carbonate production regard the development of wide dune fields within the middle ramp, one stage dominated by red algae and a sea-grass carbonate factory, whereas the two drowning phases are represented by marly cherty limestones and calcareous marls. A new biostratigraphic framework for Bolognano Formation is presented, based on high-resolution analysis of calcareous nannofossil assemblages, which proved to be very useful for biostratigraphic constraints also in shallow-water settings. Using this approach, we have linked the first drowning phase, late Chattian-Aquitanian p.p. in age, to western Mediterranean volcanism and the Mi-1 event, and the second drowning phase, late Burdigalian-Serravallian in age, to the closure of the Indo-Pacific passage and the occurrence of the global Monterey event. These results permit a new deciphering, in terms of sequence stratigraphy, of the Bolognano Formation that is interpreted as a 2nd-order super-sequence that can be subdivided into 3 transgressive-regressive sequences.

  10. FIRST RECORD OF FOSSIL CYSTOPHORINAE (CARNIVORA, PHOCIDAE: MIDDLE MIOCENE SEALS FROM THE NORTHERN PARATETHYS

    Directory of Open Access Journals (Sweden)

    IRINA A. KORETSKY

    2013-11-01

    Full Text Available Despite a long history of phocid studies, no fossil members of the Subfamily Cystophorinae have ever been described. New fossil material from the Middle Sarmatian (11.2-12.3 Ma in the Paratethyan Basin of Ukraine allows emended diagnoses and redescriptions to help clarify phylogenetic relationships within the Family Phocidae. After cladistic and morphological analyses of the material, a new genus ( Pachyphoca  was erected, with two new species of extinct fossil true seals ( Pachyphoca ukrainica and Pachyphoca chapskii , belonging to the Subfamily Cystophorinae. This new material shows exceptional pachyosteosclerotic bones, which is uncommon for the family as a whole. The new Miocene genus shares numerous characters with several Recent species of Cystophora and Mirounga , providing the first opportunity to study sexual dimorphism of limb bones and mandibles in the Subfamily Cystophorinae. Sexual dimorphism in postcranial bones and mandibles in living members of Cystophorinae is more obvious than in other representatives of true seals. Examination of anatomical traits demonstrated that both new species are more primitive and better adapted for terrestrial locomotion than any living representatives of Cystophorinae. The smaller Pachyphoca ukrainica is more adapted to terrestrial locomotion than its larger relative, P . chapskii . Phylogenetic analysis suggests that seals with 10 incisors (Phocinae are more primitive than those with 8 (Monachinae, and that Monachinae are more primitive than seals with 6 incisors (Cystophorinae.These findings indicate that the Subfamily Cystophorinae includes not only elephant and hooded seals, but also the two new Middle Sarmatian pachyosteosclerotic seals. 

  11. Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene

    Science.gov (United States)

    Zhang, Zhongshi; Ramstein, Gilles; Schuster, Mathieu; Li, Camille; Contoux, Camille; Yan, Qing

    2014-09-01

    It is widely believed that the Sahara desert is no more than ~2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ~2-3 Myr ago. The later discovery, however, of aeolian dune deposits ~7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (~7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa.

  12. Aridification of the Sahara desert caused by Tethys Sea shrinkage during Late Miocene

    Science.gov (United States)

    Zhang, Z.; Ramstein, G.; Schuster, M.; Li, C.; Contoux, C.; Yan, Q.

    2014-12-01

    It is widely believed that the Sahara desert is no more than ~2-3 million years (Myr) old, with geological evidence showing a remarkable aridification of north Africa at the onset of the Quaternary ice ages. Before that time, north African aridity was mainly controlled by the African summer monsoon (ASM), which oscillated with Earth's orbital precession cycles. Afterwards, the Northern Hemisphere glaciation added an ice volume forcing on the ASM, which additionally oscillated with glacial-interglacial cycles. These findings led to the idea that the Sahara desert came into existence when the Northern Hemisphere glaciated ~2-3 Myr ago. The later discovery, however, of aeolian dune deposits ~7 Myr old suggested a much older age, although this interpretation is hotly challenged and there is no clear mechanism for aridification around this time. Here we use climate model simulations to identify the Tortonian stage (~7-11 Myr ago) of the Late Miocene epoch as the pivotal period for triggering north African aridity and creating the Sahara desert. Through a set of experiments with the Norwegian Earth System Model and the Community Atmosphere Model, we demonstrate that the African summer monsoon was drastically weakened by the Tethys Sea shrinkage during the Tortonian, allowing arid, desert conditions to expand across north Africa. Not only did the Tethys shrinkage alter the mean climate of the region, it also enhanced the sensitivity of the African monsoon to orbital forcing, which subsequently became the major driver of Sahara extent fluctuations. These important climatic changes probably caused the shifts in Asian and African flora and fauna observed during the same period, with possible links to the emergence of early hominins in north Africa.

  13. Stratigraphy, age and environments of the late Miocene Mpesida Beds, Tugen Hills, Kenya.

    Science.gov (United States)

    Kingston, John D; Fine Jacobs, Bonnie; Hill, Andrew; Deino, Alan

    2002-01-01

    Interpretations of faunal assemblages from the late Miocene Mpesida Beds in the Tugen Hills of the Central Kenyan Rift Valley have figured prominently in discussions of faunal turnover and establishment of the modern East African communities. These faunal changes have important implications for the divergence of the human lineage from the African apes ca. 8-5 Ma. While fossil material recovered from the Mpesida Beds has traditionally been analyzed collectively, accumulating evidence indicates that Mpesida facies span the 7-6 Ma interval and are scattered more than 25 km along the eastern flanks of the Tugen Hills. Stratigraphic distinctions between Mpesida facies and younger sediments in the sequence, such as the Lukeino Formation, are not yet fully resolved, further complicating temporal assessments and stratigraphic context of Mpesida facies. These issues are discussed with specific reference to exposures of Mpesida facies at Rurmoch, where large fossil tree fragments were swept up in an ancient ash flow. Preserved anatomical features of the fossil wood as well as estimated tree heights suggest a wet, lowland rainforest in this portion of the rift valley. Stable isotopic analyses of fossil enamel and paleosol components indicate the presence of more open habitats locally. Overlying air-fall tuffs and epiclastic debris, possibly associated with the ash flow, have yielded an assemblage of vertebrate fossils including two teeth belonging to one of the earliest colombines of typical body size known from Africa, after the rather small Microcolobus. Single-crystal, laser-fusion,(40)Ar/(39)Ar dates from a capping trachyte flow as well as tuffs just below the lava contact indicate an age of greater than 6.37 Ma for the fossil material. Copyright 2002 Academic Press.

  14. Middle Miocene paleoenvironmental crises in Central Eurasia caused by changes in marine gateway configuration

    Science.gov (United States)

    Palcu, D. V.; Golovina, L. A.; Vernyhorova, Y. V.; Popov, S. V.; Krijgsman, W.

    2017-11-01

    Marine gateways prove to be important factors for changes in the ecology and biochemistry of marginal seas. Changes in gateway configuration played a dominant role in the Middle Miocene paleogeographic evolution of the Paratethys Sea that covered Central Eurasia. Here, we focus on the connection between the Central (CP) and Eastern Paratethys (EP) to understand the paleoenvironmental changes caused by the evolution of this marine gateway. We first construct an integrated magneto-biostratigraphic framework for the late Langhian-Serravallian (Chokrakian-Karaganian-Konkian-Volhynian) sedimentary record of the eastern domain, which allows a correlation to the well-dated successions west of the gateway. The magneto-biostratigraphic results from the Zelensky-Panagia section on the Black Sea coast of Russia show that the Chokrakian/Karaganian boundary has an age of 13.8 Ma, the Karaganian/Konkian boundary is dated at 13.4 Ma, and the Konkian/Volhynian boundary at 12.65 Ma. We identify three major phases on gateway functioning that are reflected in specific environmental changes. During the Karaganian, the EP turned into a lake-sea that supplied a unidirectional flow of low-salinity waters to the west, where the CP sea experienced its Badenian Salinity Crisis. This configuration is remarkably similar to the Mediterranean during its Messinian Salinity Crisis. The second phase is marked by a marine transgression from the west, reinstalling open-marine conditions in the CP and causing marine incursions in the EP during the Konkian. The Volhynian is characterized by a new gateway configuration that allows exchange between CP and EP, creating unified conditions all over the Paratethys. We hypothesize that a density driven pumping mechanism is triggered by the increase in connectivity at the Konkian/Volhynian boundary, which simultaneously caused major paleoenvironmental changes at both sides of the gateway and led to the Badenian-Sarmatian extinction event in the CP.

  15. Electron microscopy and microanalysis of uranium phases in primary ores, Eocene and Miocene of south Texas

    International Nuclear Information System (INIS)

    Liang, L.C.; Price, J.G.; Bobeck, P.

    1984-01-01

    Two contrasting types of roll-front uranium deposits occur in south Texas. In the barrier-bar sands of the Eocene Jackson Group, organic matter was essential to uranium reduction, whereas in the fluvial sands of the Miocene Oakville Formation, epigenetic pyrite was the reductant. In a sample of reduced Oakville ore, a uranium phase with grains ranging in diameter from < 1 to 20μm was recognized by SEM backscattered-electron imaging and wavelength-dispersive spectrometer (WDS) elemental-dot mapping. Quantitative microprobe analyses indicated that the phase is a uranium-calcium silicate-phosphate with molar Ca/P approximately equal to 1.0, U/P equal to 2.8 +/- 0.4 (n = 27), and U/Si approaching 1.0 in samples uncontaminated with quartz, feldspar, or clay minerals. Highest uranium content is 59%. Oakville ore is typically easy to leach by in-situ methods. Jackson ore contains 2 uranium phases. Sulfur-rich organic matter contains 4.1 +/- 1.6% uranium (n = 27). Although individual grains of a possible uranium mineral within the organic matter are too small to be resolved by electron imaging, a consistent molar U/Fe (0.5 +/- 0.1) suggests a uranium-iron oxide phase. Alternatively, uranium is adsorbed by or otherwise bound to the organic matter. The second phase is a uranium-calcium silicate-phosphate that differs from the Oakville ore. Molar Ca/P equals 0.8 +/- 0.2 (n = 13), and U/P equals 4.7 +/- 0.4. Small grain size (generally less than 1 μm) prevented analysis of samples uncontaminated with quartz and pyrite. The grain with highest uranium content (43%) has U/Si equal to 0.34. Jackson ore is less favorable for in-situ leaching than Oakville ore in part because the organic-associated uranium is difficult to extract

  16. Shallow Miocene basaltic magma reservoirs in the Bahia de Los Angeles basin, Baja California, Mexico

    Science.gov (United States)

    Delgado-Argote, Luis A.; García-Abdeslem, Juan

    1999-01-01

    The basement in the Bahía de Los Angeles basin consists of Paleozoic metamorphic rocks and Cretaceous granitoids. The Neogene stratigraphy overlying the basement is formed, from the base to the top, by andesitic lava flows and plugs, sandstone and conglomeratic horizons, and Miocene pyroclastic flow units and basaltic flows. Basaltic dikes also intrude the whole section. To further define its structure, a detailed gravimetric survey was conducted across the basin about 1 km north of the Sierra Las Flores. In spite of the rough and lineal topography along the foothills of the Sierra La Libertad, we found no evidence for large-scale faulting. Gravity data indicates that the basin has a maximum depth of 120 m in the Valle Las Tinajas and averages 75 m along the gravimetric profile. High density bodies below the northern part of the Sierra Las Flores and Valle Las Tinajas are interpreted to be part of basaltic dikes. The intrusive body located north of the Sierra Las Flores is 2.5 km wide and its top is about 500 m deep. The lava flows of the top of the Sierra Las Flores, together with the distribution of basaltic activity north of this sierra, suggests that this intrusive body continues for 20 km along a NNW-trending strike. Between the sierras Las Flores and Las Animas, a 0.5-km-wide, 300-m-thick intrusive body is interpreted at a depth of about 100 m. This dike could be part of the basaltic activity of the Cerro Las Tinajas and the small mounds along the foothills of western Sierra Las Animas. The observed local normal faulting in the basin is inferred to be mostly associated with the emplacement of the shallow magma reservoirs below Las Flores and Las Tinajas.

  17. Petrographic characteristics and depositional environment of Miocene Can coals, Canakkale-Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Guerdal, Guelbin; Bozcu, Mustafa [Canakkale Onsekiz Mart University, Engineering and Architecture Faculty (Turkey)

    2011-01-01

    In this study, petrographic examinations along with proximate, calorific value, ultimate, sulphur form and XRD analyses were performed in order to determine the coal characteristics and the depositional environment of the Miocene Can coals. Seventy coal samples were taken from cores and open pit mines. The investigated Can coals are humic coals and classified as lignite to sub-bituminous coal based on the random huminite reflectance (0.38-0.54% R{sub r}), volatile matter (45.50-62.25 wt.%, daf) and calorific value (3419-6479 kcal/kg, maf). The sulphur content of the Can coals changes from 0.30 up to 12.23 wt.%, and a broad range of ash contents was observed varying between 2.46 wt.% and 41.19 wt.%. Huminite is the most abundant maceral group (74-95 vol.% mmf) consisting of mostly humocollinite (gelinite) which is followed by relatively low liptinite (2-18 vol.% mmf) and inertinite content (2-13 vol.% mmf). In general, major mineral contents of coal samples are clay minerals, quartz, mica, pyrite and feldspar. The Can-Etili lignite basin consists of mainly volcano-clastics, fluviatile and lacustrine clastic sediments and contains only one lignite seam with 17 m average thickness. In order to assess the development of paleo-mires, coal facies diagrams were obtained from maceral composition. According to the Vegetation Index (VI) and Ground Water Index (GWI), the Can coal accumulated in inundated marsh, limnic and swamp environments under a rheotrophic hydrological regime. In general, the facies interpretations are in accordance with the observed sedimentalogical data. (author)

  18. Early Miocene rapid exhumation in southern Tibet: Insights from P-T-t-D-magmatism path of Yardoi dome

    Science.gov (United States)

    Wang, Jia-Min; Wu, Fu-Yuan; Rubatto, Daniela; Liu, Kai; Zhang, Jin-Jiang; Liu, Xiao-Chi

    2018-04-01

    Reconstructing the evolution of Gneiss domes within orogenic belts poses challenges because domes can form in a variety of geodynamic settings and by multiple doming mechanisms. For the North Himalayan gneiss domes (NHGD), it is debated whether they formed during shortening, extension or collapse of the plateau, and what is the spatial and temporal relationship of magmatism, metamorphism and deformation. This study investigates the Yardoi dome in southern Tibet using field mapping, petrography, phase equilibria modelling and new monazite ages. The resulting P-T-time-deformation-magmatism path for the first time reveals the spatial and temporal relationship of metamorphism, deformation and magmatism in the Yardoi dome: a) the dome mantle recorded prograde loading to kyanite-grade Barrovian metamorphic conditions of 650 ± 30 °C and 9 ± 1 kbar (M2) in the Early Miocene (18-17 Ma); b) the main top-to-the-north deformation fabric (D2) formed syn- to post-peak-metamorphism; c) the emplacement of leucorgranites related to doming is syn-metamorphism at 19-17 Ma. The link between the detachment shear zone in the Yardoi dome and the South Tibetan detachment system (STDS) is confirmed. By comparing with orogen-scale tectonic processes in the Himalaya, we suggest that north-south extension in a convergent geodynamic setting during Early Miocene accounts for formation of the Yardoi dome. In a wider tectonic context, the Early Miocene rapid exhumation of deep crustal rocks was contemporaneous with the rapid uplift of southern Tibet and the Himalayan orogen.

  19. Entrapment bias of arthropods in Miocene amber revealed by trapping experiments in a tropical forest in Chiapas, Mexico.

    Science.gov (United States)

    Solórzano Kraemer, Mónica M; Kraemer, Mónica M Solórzano; Kraemer, Atahualpa S; Stebner, Frauke; Bickel, Daniel J; Rust, Jes

    2015-01-01

    All entomological traps have a capturing bias, and amber, viewed as a trap, is no exception. Thus the fauna trapped in amber does not represent the total existing fauna of the former amber forest, rather the fauna living in and around the resin producing tree. In this paper we compare arthropods from a forest very similar to the reconstruction of the Miocene Mexican amber forest, and determine the bias of different trapping methods, including amber. We also show, using cluster analyses, measurements of the trapped arthropods, and guild distribution, that the amber trap is a complex entomological trap not comparable with a single artificial trap. At the order level, the most similar trap to amber is the sticky trap. However, in the case of Diptera, at the family level, the Malaise trap is also very similar to amber. Amber captured a higher diversity of arthropods than each of the artificial traps, based on our study of Mexican amber from the Middle Miocene, a time of climate optimum, where temperature and humidity were probably higher than in modern Central America. We conclude that the size bias is qualitatively independent of the kind of trap for non-extreme values. We suggest that frequent specimens in amber were not necessarily the most frequent arthropods in the former amber forest. Selected taxa with higher numbers of specimens appear in amber because of their ecology and behavior, usually closely related with a tree-inhabiting life. Finally, changes of diversity from the Middle Miocene to Recent time in Central and South America can be analyzed by comparing the rich amber faunas from Mexico and the Dominican Republic with the fauna trapped using sticky and Malaise traps in Central America.

  20. Chronology of Eocene-Miocene sequences on the New Jersey shallow shelf: implications for regional, interregional, and global correlations

    Science.gov (United States)

    Browning, James V.; Miller, Kenneth G.; Sugarman, Peter J.; Barron, John; McCarthy, Francine M.G.; Kulhanek, Denise K.; Katz, Miriam E.; Feigenson, Mark D.

    2013-01-01

    Integrated Ocean Drilling Program Expedition 313 continuously cored and logged latest Eocene to early-middle Miocene sequences at three sites (M27, M28, and M29) on the inner-middle continental shelf offshore New Jersey, providing an opportunity to evaluate the ages, global correlations, and significance of sequence boundaries. We provide a chronology for these sequences using integrated strontium isotopic stratigraphy and biostratigraphy (primarily calcareous nannoplankton, diatoms, and dinocysts [dinoflagellate cysts]). Despite challenges posed by shallow-water sediments, age resolution is typically ±0.5 m.y. and in many sequences is as good as ±0.25 m.y. Three Oligocene sequences were sampled at Site M27 on sequence bottomsets. Fifteen early to early-middle Miocene sequences were dated at Sites M27, M28, and M29 across clinothems in topsets, foresets (where the sequences are thickest), and bottomsets. A few sequences have coarse (∼1 m.y.) or little age constraint due to barren zones; we constrain the age estimates of these less well dated sequences by applying the principle of superposition, i.e., sediments above sequence boundaries in any site are younger than the sediments below the sequence boundaries at other sites. Our age control provides constraints on the timing of deposition in the clinothem; sequences on the topsets are generally the youngest in the clinothem, whereas the bottomsets generally are the oldest. The greatest amount of time is represented on foresets, although we have no evidence for a correlative conformity. Our chronology provides a baseline for regional and interregional correlations and sea-level reconstructions: (1) we correlate a major increase in sedimentation rate precisely with the timing of the middle Miocene climate changes associated with the development of a permanent East Antarctic Ice Sheet; and (2) the timing of sequence boundaries matches the deep-sea oxygen isotopic record, implicating glacioeustasy as a major driver

  1. Oncoplastic Surgery for Upper/Upper Inner Quadrant Breast Cancer.

    Science.gov (United States)

    Lin, Joseph; Chen, Dar-Ren; Wang, Yu-Fen; Lai, Hung-Wen

    2016-01-01

    Tumors located in the upper/upper inner quadrant of the breast warrant more attention. A small lesion relative to the size of breast in this location may be resolved by performing a level I oncoplastic technique. However, a wide excision may significantly reduce the overall quality of the breast shape by distorting the visible breast line. From June 2012 to April 2015, 36 patients with breast cancer located in the upper/upper inner quadrant underwent breast-conservation surgery with matrix rotation mammoplasty. According to the size and location of the tumor relative to the nipple-areola complex, 11 patients underwent matrix rotation with periareolar de-epithelialization (donut group) and the other 25 underwent matrix rotation only (non-donut group). The cosmetic results were self-assessed by questionnaires. The average weights of the excised breast lumps in the donut and non-donut groups were 104.1 and 84.5 g, respectively. During the 3-year follow-up period, local recurrence was observed in one case and was managed with nipple-sparing mastectomy followed by breast reconstruction with prosthetic implants. In total, 31 patients (88.6%) ranked their postoperative result as either acceptable or satisfactory. The treated breasts were also self-evaluated by 27 patients (77.1%) to be nearly identical to or just slightly different from the untreated side. Matrix rotation is an easy breast-preserving technique for treating breast cancer located in the upper/upper inner quadrant of the breast that requires a relatively wide excision. With this technique, a larger breast tumor could be removed without compromising the breast appearance.

  2. Oncoplastic Surgery for Upper/Upper Inner Quadrant Breast Cancer.

    Directory of Open Access Journals (Sweden)

    Joseph Lin

    Full Text Available Tumors located in the upper/upper inner quadrant of the breast warrant more attention. A small lesion relative to the size of breast in this location may be resolved by performing a level I oncoplastic technique. However, a wide excision may significantly reduce the overall quality of the breast shape by distorting the visible breast line. From June 2012 to April 2015, 36 patients with breast cancer located in the upper/upper inner quadrant underwent breast-conservation surgery with matrix rotation mammoplasty. According to the size and location of the tumor relative to the nipple-areola complex, 11 patients underwent matrix rotation with periareolar de-epithelialization (donut group and the other 25 underwent matrix rotation only (non-donut group. The cosmetic results were self-assessed by questionnaires. The average weights of the excised breast lumps in the donut and non-donut groups were 104.1 and 84.5 g, respectively. During the 3-year follow-up period, local recurrence was observed in one case and was managed with nipple-sparing mastectomy followed by breast reconstruction with prosthetic implants. In total, 31 patients (88.6% ranked their postoperative result as either acceptable or satisfactory. The treated breasts were also self-evaluated by 27 patients (77.1% to be nearly identical to or just slightly different from the untreated side. Matrix rotation is an easy breast-preserving technique for treating breast cancer located in the upper/upper inner quadrant of the breast that requires a relatively wide excision. With this technique, a larger breast tumor could be removed without compromising the breast appearance.

  3. A long-living species of the hydrophiloid beetles: Helophorus sibiricus from the early Miocene deposits of Kartashevo (Siberia, Russia

    Directory of Open Access Journals (Sweden)

    Martin Fikácek

    2011-09-01

    Full Text Available The recent hydrophiloid species Helophorus (Gephelophorus sibiricus (Motschulsky, 1860 is recorded from the early Miocene deposits of Kartashevo assigned to the Ombinsk Formation. A detailed comparison with recent specimens allowed a confident identification of the fossil specimen, which is therefore the oldest record of a recent species for the Hydrophiloidea. The paleodistribution as well as recent distribution of the species is summarized, and the relevance of the fossil is discussed. In addition, the complex geological settings of the Kartashevo area are briefly summarized.

  4. Two flat-backed polydesmidan millipedes from the Miocene Chiapas-amber Lagerstätte, Mexico.

    Directory of Open Access Journals (Sweden)

    Francisco Riquelme

    Full Text Available Two species of fossil polydesmidan millipedes (Diplopoda: Polydesmida embedded in amber are described from Miocene strata near Simojovel, in the Chiapas Highlands, Mexico. Maatidesmus paachtun gen. et sp. nov., placed into Chelodesmidae Cook, 1895, and Anbarrhacus adamantis gen. et sp. nov., assigned in the family Platyrhacidae Pocock, 1895. Morphological data from fossil specimens have been recovered using 3D X-ray micro-computed tomography and regular to infrared-reflected microscopy. Both fossil species are recognizable as new primarily but not exclusively, by collum margin modification and remarkable paranotal and metatergite dorsal sculpture.

  5. Two Flat-Backed Polydesmidan Millipedes from the Miocene Chiapas-Amber Lagerstätte, Mexico

    Science.gov (United States)

    Riquelme, Francisco; Hernández-Patricio, Miguel; Martínez-Dávalos, Arnulfo; Rodríguez-Villafuerte, Mercedes; Montejo-Cruz, Maira; Alvarado-Ortega, Jesús; Ruvalcaba-Sil, José L.; Zúñiga-Mijangos, Luis

    2014-01-01

    Two species of fossil polydesmidan millipedes (Diplopoda: Polydesmida) embedded in amber are described from Miocene strata near Simojovel, in the Chiapas Highlands, Mexico. Maatidesmus paachtun gen. et sp. nov., placed into Chelodesmidae Cook, 1895, and Anbarrhacus adamantis gen. et sp. nov., assigned in the family Platyrhacidae Pocock, 1895. Morphological data from fossil specimens have been recovered using 3D X-ray micro-computed tomography and regular to infrared-reflected microscopy. Both fossil species are recognizable as new primarily but not exclusively, by collum margin modification and remarkable paranotal and metatergite dorsal sculpture. PMID:25162220

  6. A new genus and species of tettigarctid cicada from the early Miocene of New Zealand: Paratettigarcta zealandica (Hemiptera, Auchenorrhyncha, Tettigarctidae)

    Science.gov (United States)

    Kaulfuss, Uwe; Moulds, Max

    2015-01-01

    Abstract A new genus and species of primitive cicada (Hemiptera: Tettigarctidae) is described from the early Miocene of southern New Zealand. Paratettigarcta zealandica gen. et sp. n. is the first cicada (Cicadoidea) fossil from New Zealand and exhibits wing venation patterns typical for the subfamily Tettigarctinae. It differs from other fossil taxa and the extant genus Tettigarcta in the early divergence of CuA2 from the nodal line in the forewing, its parallel-sided subcostal cell, the early bifurcation of vein M and long apical cells of the hindwing, and in wing pigmentation patterns. PMID:25829843

  7. Phylogenetic and paleobotanical evidence for late Miocene diversification of the Tertiary subtropical lineage of ivies (Hedera L., Araliaceae).

    Science.gov (United States)

    Valcárcel, V; Guzmán, B; Medina, N G; Vargas, P; Wen, J

    2017-06-22

    Hedera (ivies) is one of the few temperate genera of the primarily tropical Asian Palmate group of the Araliaceae, which extends its range out of Asia to Europe and the Mediterranean basin. Phylogenetic and phylogeographic results suggested Asia as the center of origin and the western Mediterranean region as one of the secondary centers of diversification. The bird-dispersed fleshy fruits of ivies suggest frequent dispersal over long distances (e.g. Macaronesian archipelagos), although reducing the impact of geographic barriers to gene flow in mainland species. Genetic isolation associated with geographic barriers and independent polyploidization events have been postulated as the main driving forces of diversification. In this study we aim to evaluate past and present diversification patterns in Hedera within a geographic and temporal framework to clarify the biogeographic history of the genus. Phylogenetic (biogeographic, time divergence and diversification) and phylogeographic (coalescence) analyses using four DNA regions (nrITS, trnH-psbA, trnT-trnL, rpl32) revealed a complex spatial pattern of lineage divergence. Scarce geographic limitation to gene flow and limited diversification are observed during the early-mid Miocene, followed by a diversification rate increase related to geographic divergence from the Tortonian/Messinian. Genetic and palaeobotanical evidence points the origin of the Hedera clade in Asia, followed by a gradual E-W Asian extinction and the progressive E-W Mediterranean colonization. The temporal framework for the E Asia - W Mediterranean westward colonization herein reported is congruent with the fossil record. Subsequent range expansion in Europe and back colonization to Asia is also inferred. Uneven diversification among geographic areas occurred from the Tortonian/Messinian onwards with limited diversification in the newly colonized European and Asian regions. Eastern and western Mediterranean regions acted as refugia for Miocene and

  8. Late oligocene and miocene faulting and sedimentation, and evolution of the southern Rio Grande rift, New Mexico, USA

    Science.gov (United States)

    Mack, Greg H.; Seager, William R.; Kieling, John

    1994-08-01

    The distribution of nonmarine lithofacies, paleocurrents, and provenance data are used to define the evolution of late Oligocene and Miocene basins and complementary uplifts in the southern Rio Grande rift in the vicinity of Hatch, New Mexico, USA. The late Oligocene-middle Miocene Hayner Ranch Formation, which consists of a maximum of 1000 m of alluvial-fan, alluvial-flat, and lacustrine-carbonate lithofacies, was deposited in a narrow (12 km), northwest-trending, northeast-tilted half graben, whose footwall was the Caballo Mountains block. Stratigraphic separation on the border faults of the Caballo Mountains block was approximately 1615 m. An additional 854 m of stratigraphic separation along the Caballo Mountains border faults occurred during deposition of the middle-late Miocene Rincon Valley Formation, which is composed of up to 610 m of alluvial-fan, alluvial-flat, braided-fluvial, and gypsiferous playa lithofacies. Two new, north-trending fault blocks (Sierra de las Uvas and Dona Ana Mountains) and complementary west-northwest-tilted half graben also developed during Rincon Valley time, with approximately 549 m of stratigraphic separation along the border fault of the Sierra de las Uvas block. In latest Miocene and early Pliocene time, following deposition of the Rincon Valley Formation, movement continued along the border faults of the Caballo Mountains, Dona Ana Mountains, and Sierra de las Uvas blocks, and large parts of the Hayner Ranch and Rincon Valley basins were segmented into smaller fault blocks and basins by movement along new, largely north-trending faults. Analysis of the Hayner Ranch and Rincon Valley Formations, along with previous studies of the early Oligocene Bell Top Formation and late Pliocene-early Pleistocene Camp Rice Formation, indicate that the traditional two-stage model for development of the southern Rio Grande rift should be abandoned in favor of at least four episodes of block faulting beginning 35 Ma ago. With the exception of

  9. Constraints on the Miocene landscape evolution of the Eastern Alps from the Kalkspitze region, Niedere Tauern (Austria)

    Science.gov (United States)

    Dertnig, Florian; Stüwe, Kurt; Woodhead, Jon; Stuart, Finlay M.; Spötl, Christoph

    2017-12-01

    In order to unravel aspects of the Miocene landscape evolution of the eastern European Alps, we present geomorphic and isotopic data from the western Niedere Tauern region (Austria). The region is critical for such interpretations, because it is one of the few regions along the topographic axis of the Eastern Alps where the highest peaks (up to 2500 m a.s.l.) are dominated by limestone. As such, the region contains a record of Miocene landscape-forming events that survived the Pleistocene glaciations, not preserved elsewhere in the central Eastern Alps. This record includes karst caves, karstified planation surfaces and crystalline fluvial pebbles (Augenstein Formation) preserved on planation surfaces and in karst caves. Caves in the region occur in three distinct levels that correlate with well-known cave levels in the Northern Calcareous Alps, although they are somewhat higher in the Niedere Tauern. In part, these cave elevations also correlate with three planation surfaces and knickpoints of major streams draining the region, testifying their pre-glacial origin. We report details of a karst cave (Durchgangshöhle) from the highest cave level located at 2340 m a.s.l. In this cave, allochthonous fluvial gravels are present, overgrown by speleothems. One speleothem yielded an early middle Pleistocene U-Pb age (682 ± 17 ka). We regard this as a minimum age for the erosion of the fluvial cave deposits during Marine Isotope Stages 17 or 16. Carbon and oxygen isotope data of these speleothems imply a climate that is consistent with this interpretation. Cosmogenic 21Ne data of fluvial quartz clasts collected from the surface on plateaus of the Northern Calcareous Alps suggest minimum exposure durations of 115 and 262 ka. They probably reflect successive exposure since removal of the sediment cover of the Oligocene Augenstein Formation during the Pleistocene. While our geochronological data fail to record aspects of the earlier Miocene uplift history, they are

  10. Upper atmosphere research at INPE

    International Nuclear Information System (INIS)

    Clemesha, B.R.

    1984-01-01

    Upper atmosphere research at INPE is mainly concerned with the chemistry and dynamics of the stratosphere, upper mesosphere and lower thermosphere, and the middle thermosphere. Experimental work includes lidar observations of the stratospheric aerosol, measurements of stratospheric ozone by Dobson spectrophotometers and by balloon and rocket-borne sondes, lidar measurements of atmospheric sodium, and photometric observations of O, O 2 , OH and Na emissions, including interferrometric measurements of the OI6300 emission for the purpose of determing thermospheric winds and temperature. The airglow observations also include measurements of a number of emissions produced by the precipitation of energetic neutral particles generated by charge exchange in the ring current. Some recent results of INPE's upper atmosphere program are presented. (Author) [pt

  11. A first possible chameleon from the late Miocene of India (the hominoid site of Haritalyangar): a tentative evidence for an Asian dispersal of chameleons.

    Science.gov (United States)

    Sankhyan, Anek R; Čerňanský, Andrej

    2016-12-01

    Miocene rare fossils from India, tentatively attributed to chameleons, are described for the first time. The material consists of a fragment of the left squamosal and an element interpreted as a posterodorsal process of the parietal. The specimens come from a late Miocene site of the Nagri Formation (Middle Siwaliks, ~ 9 Mya) at Haritalyangar, North India. This material presents a possible evidence for a chameleon dispersal to Asia. Based on molecular data, the dispersion of an Asian chamaeleonid lineage from Africa to Arabia/Asia is dated at approximately 13 Mya and its diversification in situ at around 6-8 Mya. However, till now, no Miocene-age fossil record has been described to support crown chamaeleonid presence in this area. The material described herein is very fragmented. If correctly allocated, the Haritalyangar chameleons show the oldest known occurrence of this clade in India, at least approximately 9 Mya ago.

  12. Geochemistry, environmental and provenance study of the Middle Miocene Leitha limestones (Central Paratethys)

    Science.gov (United States)

    Ali, Ahmed; Wagreich, Michael

    2017-06-01

    Mineralogical, major, minor, REE and trace element analyses of rock samples were performed on Middle Miocene limestones (Leitha limestones, Badenian) collected from four localities from Austria (Mannersdorf, Wöllersdorf, Kummer and Rosenberg quarries) and the Fertőrákos quarry in Hungary. Impure to pure limestones (i.e. limited by Al2O3 contents above or below 0.43 wt. %) were tested to evaluate the applicability of various geochemical proxies and indices in regard to provenance and palaeoenvironmental interpretations. Pure and impure limestones from Mannersdorf and Wöllersdorf (southern Vienna Basin) show signs of detrital input (REEs = 27.6 ± 9.8 ppm, Ce anomaly = 0.95 ± 0.1 and the presence of quartz, muscovite and clay minerals in impure limestones) and diagenetic influence (low contents of, e.g., Sr = 221 ± 49 ppm, Na is not detected, Ba = 15.6 ± 8.8 ppm in pure limestones). Thus, in both limestones the reconstruction of original sedimentary palaeoenvironments by geochemistry is hampered. The Kummer and Fertőrákos (Eisenstadt-Sopron Basin) comprise pure limestones (e.g., averages Sr = 571 ± 139 ppm, Na = 213 ± 56 ppm, Ba = 21 ± 4 ppm, REEs = 16 ± 3 ppm and Ce anomaly = 0.62 ± 0.05 and composed predominantly of calcite) exhibiting negligible diagenesis. Deposition under a shallow-water, well oxygenated to intermittent dysoxic marine environment can be reconstructed. Pure to impure limestones at Rosenberg-Retznei (Styrian Basin) are affected to some extent by detrital input and volcano-siliciclastic admixture. The Leitha limestones at Rosenberg have the least diagenetic influence among the studied localities (i.e. averages Sr = 1271 ± 261 ppm, Na = 315 ± 195 ppm, Ba = 32 ± 15 ppm, REEs = 9.8 ± 4.2 ppm and Ce anomaly = 0.77 ± 0.1 and consist of calcite, minor dolomite and quartz). The siliciclastic sources are characterized by immobile elemental ratios (i.e. La/Sc and Th/Co) which apply not only for the siliciclastics, but also for marls and

  13. Understanding climate's influence on the extinction of Oreopithecus (late Miocene, Tusco-Sardinian paleobioprovince, Italy).

    Science.gov (United States)

    DeMiguel, Daniel; Rook, Lorenzo

    2018-03-01

    Despite its long history of scientific study, the causes underlying the extinction of the insular hominoid Oreopithecus bambolii are still a matter of ongoing debate. While some authors consider intense tectonism and invading species the cause of its extinction ca. 6.7 Ma, others propose climatic change as the main contributing factor. We rely on long-term patterns of tooth wear and hypsodonty of the Baccinello and Fiume Santo herbivore-faunas to reconstruct changes in habitat prior to, during and after the extinction. While a mosaic of habitats was represented in Baccinello V1 (as shown by a record of browsers, mixed feeders and species engaged in grazing), more closed forests (higher proportion of browsers, shortage of mixed feeders and lack of grazers) characterised Baccinello V2. Finally, there was a partial loss of canopy cover and development of open-patches and low-abrasive grasses in Baccinello V3 (as denoted by new records of taxa involved in grazing)-although still dominated by a forested habitat (since browse was a component in all diets). Our results provide evidence for two perceptible shifts in climate, one between 8.1 and 7.1 Ma and other ca. 6.7 Ma, though this latter was not drastic enough to lead to intensive forest loss, substantially alter the local vegetation or affect Oreopithecus lifestyle-especially if considering the growing evidence of its versatile diet. Although the disappearance of Oreopithecus is complex, our data reject the hypothesis of environmental change as the main factor in the extinction of Oreopithecus and Maremma fauna. When our results are analysed together with other evidence, faunal interaction and predation by invading species from mainland Europe seems to be the most parsimonious explanation for this extinction event. This contrasts with European hominoid extinctions that were associated with major climatic shifts that led to environmental uniformity and restriction of the preferred habitats of Miocene apes. Copyright

  14. Diagenetic history of the Surma Group sandstones (Miocene) in the Surma Basin, Bangladesh

    Science.gov (United States)

    Rahman, M. Julleh Jalalur; McCann, Tom

    2012-02-01

    This study examines the various diagenetic controls of the Miocene Surma Group sandstones encountered in petroleum exploration wells from the Surma Basin, which is situated in the northeastern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals/cements in the Surma Group sandstones are Fe-carbonates (with Fe-calcite dominating), quartz overgrowths and authigenic clays (predominantly chlorite, illite-smectite and minor kaolin). The isotopic composition of the carbonate cement revealed a narrow range of δ 18O values (-10.3‰ to -12.4‰) and a wide range of δ 13C value (+1.4‰ to -23.1‰). The δ 13C VPDB and δ 18O VPDB values of the carbonate cements reveal that carbon was most likely derived from the thermal maturation of organic matter during burial, as well as from the dissolution of isolated carbonate clasts and precipitated from mixed marine-meteoric pore waters. The relationship between the intergranular volume (IGV) versus cement volume indicates that compaction played a more significant role than cementation in destroying the primary porosity. However, cementation also played a major role in drastically reducing porosity and permeability in sandstones with poikilotopic, pore-filling blocky cements formed in early to intermediate and deep burial areas. In addition to Fe-carbonate cements, various clay minerals including illite-smectite and chlorite occur as pore-filling and pore-lining authigenic phases. Significant secondary porosity has been generated at depths from 2500 m to 4728 m. The best reservoir rocks found at depths of 2500-3300 m are well sorted, relatively coarse grained; more loosely packed and better rounded sandstones having good porosities (20-30%) and high permeabilities (12-6000 mD). These good quality reservoir rocks are, however, not uniformly distributed and can be considered to be compartmentalized as a result of interbedding with sandstone layers of low to moderate porosities, low permeabilities owing to poor

  15. Tectonic implications of a paleomagnetic direction obtained from a Miocene dike swarm in central Honshu, Japan

    Science.gov (United States)

    Hoshi, H.; Sugisaki, Y.

    2017-12-01

    Central Honshu of Japan is an ideal field for the study of crustal deformation related to arc-arc collision. In this study we obtained rock magnetic and paleomagnetic results from early Miocene igneous rocks in central Honshu in order to examine rotational deformation caused by the collision of the Izu-Bonin-Mariana (IBM) arc with central Honshu. In Takane of the Hida region, gabbro intrusions and older sedimentary rocks are intruded by numerous andesitic dikes that comprise a parallel dike swarm. The dikes formed under two different normal-faulting paleostress conditions, which were suggested using a method of clustering dike orientations. Cross-cutting relationships indicate that the two paleostress conditions existed during the same period. More than 240 oriented cores were taken at 38 sites in two localities for magnetic study. The andesites and gabbros generally have magnetite, and some andesites also contain pyrrhotite. The magnetite records easterly deflected remanent magnetization directions of dual polarities that pass the reversals test. Positive baked contact tests at two sites demonstrate that the easterly deflected direction is a thermoremanent magnetization acquired at the time of intrusion. The overall in situ (i.e., in geographic coordinates) mean direction for andesitic dikes is judged to be highly reliable, although there are two possible scenarios for explaining the easterly deflection: (1) clockwise rotation and (2) tilting to the northwest. We prefer the former scenario and conclude that 45° clockwise rotation occurred in Takane with respect to the North China Block of the Asian continent. This rotation must represent the clockwise rotation of entire Southwest Japan during the opening period of the Japan Sea. Very little difference is observed between the amount of the easterly deflection in Takane and those in the Tokai and Hokuriku regions, indicating no significant relative rotation. Thus, the crust beneath Takane has not suffered rotation

  16. Quantifying incision rates since the early Miocene: novelties, potentialities and limitations

    Science.gov (United States)

    Sartégou, A.; Braucher, R.; Blard, P. H.; Bourlès, D. L.; Zimmermann, L.; Tibari, B.; Voinchet, P.; Bahain, J. J.; Sorriaux, P.; Leanni, L.; Team, A.

    2017-12-01

    The rates and chronologies of valley incision are closely modulated by the tectonic uplift of active mountain ranges and were controlled by repeated climate changes during the Quaternary. The Pyrenees are a continental collision between the Iberian and Eurasian plates induced a double vergence orogen, which has been considered as a mature mountain range in spite of significant seismicity and evidence of neotectonics. Nevertheless, recent studies indicate that the range may have never reached a steady state. One option for resolving this controversy is to quantify the incision rates since the Miocene by reconstructing the vertical movement of geometric markers. However, the few available ages from the Pyrenean terrace systems do not exceed the middle Pleistocene. To enlarge the time span of this dataset, we studied alluvium-filled horizontal epiphreatic passages in limestone karstic networks, which represent former valley floors. They record the transient position of former local base levels during the process of valley deepening. We used various suitable geochronological methods (26Al/10Be, 10Be/21Ne, ESR and OSL burial durations on quartz) on intrakarstic alluvial deposits from three valleys of the central and eastern Pyrenees, as well as on a recent analogue. In the Pyrenean context, under particular conditions, these geochronometers allow us to document incision processes since 16-13 Ma, and to study influences of external forcing and eustatism. In comparison with other studies, it appears that incision rates are higher in the central Pyrenees and for the Spanish slope. However, the density of horizontal levels on an altimetric range, the geodynamical and paleoclimatic contexts, the reorganization of the drainage networks can make the filling stories of the networks more complex than expected. Indeed, these radiometric approaches may be limited when some formations are reworked inside and/or outside the karst. The validity of dosimetric methods in a mountainous

  17. Geochemistry, environmental and provenance study of the Middle Miocene Leitha limestones (Central Paratethys

    Directory of Open Access Journals (Sweden)

    Ali Ahmed

    2017-06-01

    Full Text Available Mineralogical, major, minor, REE and trace element analyses of rock samples were performed on Middle Miocene limestones (Leitha limestones, Badenian collected from four localities from Austria (Mannersdorf, Wöllersdorf, Kummer and Rosenberg quarries and the Fertőrákos quarry in Hungary. Impure to pure limestones (i.e. limited by Al2O3 contents above or below 0.43 wt. % were tested to evaluate the applicability of various geochemical proxies and indices in regard to provenance and palaeoenvironmental interpretations. Pure and impure limestones from Mannersdorf and Wöllersdorf (southern Vienna Basin show signs of detrital input (REEs = 27.6 ± 9.8 ppm, Ce anomaly = 0.95 ± 0.1 and the presence of quartz, muscovite and clay minerals in impure limestones and diagenetic influence (low contents of, e.g., Sr = 221 ± 49 ppm, Na is not detected, Ba = 15.6 ± 8.8 ppm in pure limestones. Thus, in both limestones the reconstruction of original sedimentary palaeoenvironments by geochemistry is hampered. The Kummer and Fertőrákos (Eisenstadt–Sopron Basin comprise pure limestones (e.g., averages Sr = 571 ± 139 ppm, Na = 213 ± 56 ppm, Ba = 21 ± 4 ppm, REEs = 16 ± 3 ppm and Ce anomaly = 0.62 ± 0.05 and composed predominantly of calcite exhibiting negligible diagenesis. Deposition under a shallow-water, well oxygenated to intermittent dysoxic marine environment can be reconstructed. Pure to impure limestones at Rosenberg–Retznei (Styrian Basin are affected to some extent by detrital input and volcano-siliciclastic admixture. The Leitha limestones at Rosenberg have the least diagenetic influence among the studied localities (i.e. averages Sr = 1271 ± 261 ppm, Na = 315 ± 195 ppm, Ba = 32 ± 15 ppm, REEs = 9.8 ± 4.2 ppm and Ce anomaly = 0.77 ± 0.1 and consist of calcite, minor dolomite and quartz. The siliciclastic sources are characterized by immobile elemental ratios (i.e. La/Sc and Th/Co which apply not only for the siliciclastics, but also

  18. Late Miocene (Pannonian) Vegetation from the Northern Part of Central Paratethys

    Science.gov (United States)

    Kováčová, M.; Doláková, N.

    2009-04-01

    During Late Miocene, the Western Carpathian paleogeography started to change. The Lake Pannon retreated southwards, and the northern coast of the back arc basin was slightly elevated due to progradation of deltaic and alluvial facies, especially in the lowlands. The studied „Pannonian lake" sediments come from the Czech and Slovak parts of Central Paratethys. Changes of the sedimentary environment from deep to shallow lake and deltaic environment, followed by development of alluvial plains were noticed. Salinity crisis due to Paratethys isolation led to development of total freshwater environment to the end of this period. Samples from 3 surficial localities and 15 boreholes were palynologically studied. Occasional occurences of Dinoflagellates indicate a slightly higher salinity, whereas green algae Pediastrum, aquatic ferns Azolla, and aquatic and coastal plants (Nelumbo, Nymphaea, Myriophyllum, Sparganium, Potamogeton, Cyperaceae etc.) represent a freshwater environment. Due to paleogeographic changes and climatic oscillations the number of thermophilous taxa decreased and some of them disappeared completely from this area (f. e. Sapotaceae, Palmae). Mostly broad-leaved deciduous elements of mixed mesophytic forests (Quercus, Celtis, Carya, Tilia, Carpinus, Betula, Juglans) with some thermophilous elements admixture of Engelhardia, Castanea, Trigonobalanopsis, Symplocos, Cornaceaepollis satzveyensis generally dominate. Variously high relief of the uplifted mountainy chains created ideal conditions for higher presence of extrazonal vegetation (Cedrus, Tsuga, Picea, Cathaya) in the investigated area. Zonal type of vegetation including marshes, riparian forests with Alnus, Salix, Pterocarya, Liquidambar, Betula, Fraxinus, shrubs and lianas on dryer substrates associated riparian forest (Buxus, Ericaceae, Vitaceae, Lonicera, Rosaceae type Rubus), and coastal swamps with Taxodiaceae, Nyssa, Myrica, Sciadopitys were growing in the floodplain lowlands of Vienna Basin

  19. Paleomagnetism and Anisotropy of Magnetic Susceptibility study of the Miocene Jack Springs Tuff (Nevada, USA)

    Science.gov (United States)

    Shields, S.; Petronis, M. S.; Pluhar, C. J.; Gordon, L.

    2014-12-01

    The mid-Miocene Jack Springs Tuff (JST) outcrops across the western Mina Deflection accommodation zone, west-central Nevada and into eastern California. Previously, the source location for the JST was unknown, yet recent studies northwest of Mono Lake, CA have identified a relatively un-rotated structural block in which to reference the paleomagnetic data. Although new studies have indicated that this block may be rotated up to 13º, we argue that the probable source area is located near the Bodie Hills, CA. At this site, the paleomagnetic reference direction is D = 353°, I = 43°, α95 = 7.7° (Carlson et al, 2013). Based on these data, the JST can be used to measure absolute vertical-axis rotation as well as enable reconstruction of the paleo-topography using the corrected anisotropy of magnetic susceptibility (AMS) data. A total of 19 sites were sampled to constrain Cenozoic to recent vertical axis rotation within the region and AMS experiments were conducted to determine the flow direction of the JST. Curie point estimates indicate that the JST ranges in titanium concentration from 0.042 to 1.10, indicating a low to moderate titanomagnetite phase (Akimoto, 1962). Demagnetization experiments reveal mean destructive fields of the NRM ranging between 15mT and 40mT suggesting that both multi-domain to pseudo-single domain grains are the dominant ferromagnetic phases that carry the remanence and AMS fabric. Preliminary paleomagnetic data yield stable single component demagnetization behavior for most sites that, after structural correction, indicate clockwise vertical axis rotation ranging from +20°± 10° to +60°± 11° between multiple fault blocks. The uncorrected AMS data yield oblate magnetic fabrics that can be used to infer the transport direction, source region, and paleovalley geometry of the JST. These data are tentatively interpreted to indicate west to east transport of the JST across the Mono Basin region into the Mina Deflection that was erupted and

  20. Petrophysical characterization of three commercial varieties of miocene sandstones from the Ebro valley

    Directory of Open Access Journals (Sweden)

    Gisbert, J.

    2007-08-01

    Full Text Available Miocene sandstones studied were used extensively to build Aragon’s architectural heritage, are still used in modern construction. The quarries presently located on the edge of the Ebro Valley depression. The present paper describes an exhaustive petrophysical study of these materials, which while, of the same age and from the same deposition basin, exhibit different mineralogical and textural characteristics and as a result, different physical and mechanical properties and durability. The petrographic and petrophysical characteristics of these materials were evaluated with tests prescribed in UNE (Spanish, NORMAL and ASTM standards. All the results were subjected to statistical analysis to identify possible textural and compositional nonuniformities in the material that may underlie behavioural changes. The results of the present paper show that their petrophysical characteristics afford these sandstones substantial industrial value as construction materials. Durability was found to be longest in the Alcañiz stone, as a result of the geometry of its pore network.Las areniscas miocenas estudiadas han sido y son ampliamente utilizadas en patrimonio histórico y en obra civil moderna, localizándose las canteras actuales en el borde de la depresión del Ebro. Se ha realizado un exhaustivo estudio de las características petrofísicas de estos materiales, que pese a presentar la misma edad y pertenecer a la misma cuenca sedimentaria presentan características mineralógicas y texturales diferentes que les confieren diferentes propiedades físicas, mecánicas y una diferente durabilidad. Las características petrográficas y petrofísicas se han evaluado mediante la realización de ensayos según las normas UNE, NORMAL y ASTM. Para todos los ensayos se ha realizado un tratamiento estadístico de los resultados para evaluar las posibles inhomogeneidades texturales y composicionales presentes en el material y que pueden originar modificaciones en

  1. Lateral variations in vegetation in the Himalaya since the Miocene and implications for climate evolution

    Science.gov (United States)

    Vögeli, Natalie; Najman, Yani; van der Beek, Peter; Huyghe, Pascale; Wynn, Peter M.; Govin, Gwladys; van der Veen, Iris; Sachse, Dirk

    2017-08-01

    The Himalaya has a major influence on global and regional climate, in particular on the Asian monsoon system. The foreland basin of the Himalaya contains a record of tectonics and paleoclimate since the Miocene. Previous work on the evolution of vegetation and climate has focused on the central and western Himalaya, where a shift from C3 to C4 vegetation has been observed at ∼7 Ma and linked to increased seasonality, but the climatic evolution of the eastern part of the orogen is less well understood. In order to track vegetation as a marker of monsoon intensity and seasonality, we analyzed δ13 C and δ18 O values of soil carbonate and associated δ13 C values of bulk organic carbon from previously dated sedimentary sections exposing the syn-orogenic detrital Dharamsala and Siwalik Groups in the west, and, for the first time, the Siwalik Group in the east of the Himalayan foreland basin. Sedimentary records span from 20 to 1 Myr in the west (Joginder Nagar, Jawalamukhi, and Haripur Kolar sections) and from 13 to 1 Myr in the east (Kameng section), respectively. The presence of soil carbonate in the west and its absence in the east is a first indication of long-term lateral climatic variation, as soil carbonate requires seasonally arid conditions to develop. δ13 C values in soil carbonate show a shift from around -10‰ to -2‰ at ∼7 Ma in the west, which is confirmed by δ13 C analyses on bulk organic carbon that show a shift from around -23‰ to -19‰ at the same time. Such a shift in isotopic values is likely to be associated with a change from C3 to C4 vegetation. In contrast, δ13 C values of bulk organic carbon remain at ∼ - 23 ‰ in the east. Thus, our data show that the current east-west variation in climate was established at 7 Ma. We propose that the regional change towards a more seasonal climate in the west is linked to a decrease of the influence of the Westerlies, delivering less winter precipitation to the western Himalaya, while the east

  2. A new species of Miocene terrestrial gastropod Gastrocopta from Poland and the validity of 'Pupa (Vertigo) suevica'

    Energy Technology Data Exchange (ETDEWEB)

    Stworzewicz, E.; Prisyazhnyuk, V.A. [Polish Academy of Science, Krakow (Poland)

    2006-03-15

    We describe Gastrocopta sandbergeri sp. nov. from the Miocene brown coal deposits of the open-cast mine Belchatow (central Poland) and identify it as conspecific with Pupa (Vertigo) suevica Sandberger, 1875 (nomen nudum) from the Miocene of Steinheim. The new species is most similar to Gastrocopta nouletiana (Dupuy, 1850) but differs in having smaller and always slender shell, less convex whorls, much weaker crest on the body whorl (or even absent) and generally rather weakly developed teeth (6-7) in the aperture.

  3. D/H of late Miocene meteoric waters in Western Australia: Paleoenvironmental conditions inferred from the δD of (U-Th)/He-dated CID goethite

    Science.gov (United States)

    Yapp, Crayton J.; Shuster, David L.

    2017-09-01

    Nineteen (U-Th)/He ages were determined for eight samples from a core drilled in an ore-grade channel iron deposit (CID) of the Robe Pisolite (Robe Formation) of Mesa J in Western Australia. With one exception, uncorrected ages of the analyzed aliquots range from 6.7(±0.4) Ma to 30.2(±3.1) Ma, while molar ratios of Th/U range from 0.42 to 5.06. The exception is an aliquot with an apparent age of 2.7 Ma and Th/U of 5.70. A three-component mixing model involving one generation of goethite and two generations of hematite suggests that the age of crystallization of the oolitic goethites is ∼7(±1) Ma. If so, the goethites have effectively been closed systems for ∼7 million years and should preserve a stable hydrogen isotope record of late Miocene rainfall in the vicinity of Mesa J. Cenozoic movement of the Australian continent had placed Mesa J and environs in the subtropics at a paleolatitude of about 29 °S during the late Miocene. Al-adjusted δD values of oolitic goethite in the eight CID samples range from -153‰ to -146‰ and imply that the δD of the late Miocene meteoric waters ranged from -61‰ to -53‰, with an average of -56‰. These relatively negative δD values might indicate that near-coastal, late Miocene rain was derived primarily from summer-season tropical cyclones with storm tracks that extended into the subtropics of western Australia. The postulated late Miocene tropical cyclones would have occurred more often and/or exhibited greater intensity at a paleolatitude of 29 °S than is the case for modern sites at approximately 30 °S on the west coast of Australia (e.g., Perth). Higher fluxes of meteoric water in the Miocene summers would have facilitated dissolution and removal of BIF-sourced silica with concomitant enrichment in oxidized Fe. Moreover, wetter late Miocene summers could have promoted multiple cycles of microbially mediated dissolution and recrystallization of Fe(III) oxides in the aerobic systems. The oolitic textures may

  4. Megalictis, the Bone-Crushing Giant Mustelid (Carnivora, Mustelidae, Oligobuninae) from the Early Miocene of North America

    Science.gov (United States)

    Valenciano, Alberto; Baskin, Jon A.; Abella, Juan; Pérez-Ramos, Alejandro; Álvarez-Sierra, M. Ángeles; Morales, Jorge; Hartstone-Rose, Adam

    2016-01-01

    We describe cranial and mandibular remains of three undescribed individuals of the giant mustelid Megalictis ferox Matthew, 1907 from the latest Arikareean (Ar4), Early Miocene mammal fauna of Nebraska, and Wyoming (USA) housed at the American Museum of Natural History (New York, USA). Our phylogenetic hypothesis indicates that Ar4 specimens assigned to M. ferox constitute a monophyletic group. We assign three additional species previously referred to Paroligobunis to Megalictis: M. simplicidens, M. frazieri, and “M.” petersoni. The node containing these four species of Megalictis and Oligobunis forms the Oligobuninae. We test the hypothesis that Oligobuninae (Megalictis and Oligobunis) is a stem mustelid taxon. Our results indicate that the Oligobuninae form the sister clade to the crown extant mustelids. Based on the cranium, M. ferox is a jaguar-size mustelid and the largest terrestrial mustelid known to have existed. This new material also sheds light on a new ecomorphological interpretation of M. ferox as a bone-crushing durophage (similar to hyenas), rather than a cat-like hypercarnivore, as had been previously described. The relative large size of M. ferox, together with a stout rostrum and mandible made it one of the more powerful predators of the Early Miocene of the Great Plains of North America. PMID:27054570

  5. A major Early Miocene thermal pulse due to subduction segmentation and rollback in the western Mediterranean region

    Science.gov (United States)

    Spakman, W.; Van Hinsbergen, D. J.; Vissers, R.

    2012-12-01

    Geological studies have shown that Eo-Oligocene subduction related high-pressure, low-temperature metasediments and peridotites of the Alboran region (Spain, Morocco) and the Kabylides (Algeria) experienced a major Early Miocene (~21 Ma) thermal pulse requiring asthenospheric temperatures at ~60 km depth. Despite earlier propositions, the cause of this thermal pulse is still controversial while also the paleogeographic origin of the Alboran and Kabylides units is debated. Here, we relate the thermal pulse to segmentation of the West Alpine-Tethyan slab under the SE Iberian margin (Baleares-Sardinia). We restore the Alboran rocks farther east than previously assumed, to close to the Balearic Islands, adjacent to Sardinia. We identify three major lithosphere faults, the NW-SE trending North Balearic Transform Zone (NBTZ) and the ~W-E trending Emile Baudot and North African transforms that accommodated the Miocene subduction evolution of slab segmentation, rollback, and migration of Alboran and Kabylides rocks to their current positions. The heat pulse occurred S-SE of the Baleares where slab segmentation along the NBTZ triggered radially outgrowing S-SW rollback opening a slab window that facilitated local ascent of asthenosphere below the rapidly extending Alboran-Kabylides accretionary prism. Subsequent slab rollback carried the Kabylides and Alboran domains to their present positions. Our new reconstruction is in line with tomographically imaged mantle structure and focuses attention on the crucial role of evolving subduction segmentation driving HT-metamorphism and subsequent extension, fragmentation, and dispersion of geological terrains.

  6. Stable carbon isotope ratios and intrinsic water-use efficiency of Miocene fossil leaves compared to modern congeners

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, J.D.; Zhang, J.; Rember, W.C.; Jennings, D.; Larson, P. (Univ. of Idaho, Moscow, ID (United States))

    1994-06-01

    Miocene fossil leaves of forest trees were extracted from the Clarkia, Idaho fossil beds and their stable carbon isotope ratios were analyzed. Fossils had higher lignin concentrations and lower cellulose concentrations that modern leaves due to diagenesis and the HF used to extract the fossils. Therefore, [delta][sup 13]C of extracted fossil lignin was compared to that of modern lignin. Fossil lignin [delta][sup 13]C was significantly different from that of congeneric modern leaves (paired t-test, P<0.0001), but was 1.9% less negative. Gymnosperms (Metasequoia, Taxodium) were less negative than angiosperms (e.g., Magnolia, Quercus, Acer, Persea), but no difference between evergreen and deciduous species was detected. Using published estimates of the concentration and [delta][sup 13]C of atmospheric CO[sub 2] during the Miocene was estimated the CO[sub 2] partial pressure gradient across the stomata (intrinsic water-use efficiency). Intrinsic water-use efficiency was at least 70% higher during this past [open quotes]greenhouse[close quotes] period than at present.

  7. Paleomagnetism of the Miocene intrusive suite of Kidd Creek: Timing of deformation in the Cascade arc, southern Washington

    Science.gov (United States)

    Hagstrum, J.T.; Swanson, D.A.; Snee, L.W.

    1998-01-01

    Paleomagnetic study of the intrusive suite of Kidd Creek in the southern Washington Cascades (23 sites in dikes and sills) was undertaken to help determine if these rocks are comagmatic and whether they postdate regional folding of the volcanic arc. Fission track and 40Ar-39Ar age determinations indicate an age of ???12.7 Ma (middle Miocene) for these rocks. The similarity of normal-polarity characteristic directions for most samples corroborate the available geochemical data indicating that these rocks are most likely comagmatic. Reversed-polarity directions for samples from four sites, however, show that emplacement of Kidd Creek intrusions spanned at least one reversal of the geomagnetic field. The paleomagnetic directions for the dikes and sills fail a fold test at the 99% confidence level indicating that the Kidd Creek rocks postdate regional folding. The mean in situ direction also indicates that the Kidd Creek and older rocks have been rotated 22?? ?? 6??