Sample records for late jurassic fossil

  1. Exceptionally preserved insect fossils in the Late Jurassic lagoon of Orbagnoux (Rhône Valley, France)

    PubMed Central

    Nel, Patricia; Krieg-Jacquier, Régis; Pouillon, Jean-Marc

    2014-01-01

    The Late Kimmeridgian marine limestones of the area around Orbagnoux (Rhône, France) are well known for their fish fauna and terrestrial flora. Here we record the first insects and their activities (mines on leaves and trails in sediments) from these layers, including the oldest record of the gerromorphan bugs, as a new genus and species Gallomesovelia grioti, attributed to the most basal family Mesoveliidae and subfamily Madeoveliinae. These new fossils suggest the presence of a complex terrestrial palaeoecosystem on emerged lands near the lagoon where the limestones were deposited. The exquisite state of preservation of these fossils also suggests that these outcrops can potentially become an important Konservat-Lagerstätte for the Late Jurassic of Western Europe. PMID:25210652

  2. Dinosaurs and other fossil vertebrates from the Late Jurassic and Early Cretaceous of the Galve area, NE Spain

    E-print Network

    Benton, Michael

    Dinosaurs and other fossil vertebrates from the Late Jurassic and Early Cretaceous of the Galve noted, including fishes, crocodyliforms, pterosaurs, dinosaurs and mammals. The Galve fossil sites occur­Wealden succession of southern England, among others. There are many similarities with dinosaur faunas from North

  3. A Late Jurassic fossil assemblage in Gondwana: Biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay

    NASA Astrophysics Data System (ADS)

    Perea, Daniel; Soto, Matías; Veroslavsky, Gerardo; Martínez, Sergio; Ubilla, Martín

    2009-08-01

    The Tacuarembó Formation has yielded a fossil assemblage that includes the best known body fossils, consisting of isolated scales, teeth, spines, and molds of bones, recovered from thin and patchy bonebeds, from the Botucatu Desert, Parana Basin, South America. The remains are preserved in the sandstones widespread around the city of Tacuarembó. We propose a new formalized nomenclature for the Tacuarembó Formation, naming its "Lower" and "Upper" members as the Batoví (new name) and Rivera (new rank) members, respectively. An assemblage zone is defined for the Batoví Member (fluviolacustrine and aeolian deposits). In this unit, the freshwater hybodontid shark Priohybodusarambourgi D'Erasmo is well represented. This species was previously recorded in Late Jurassic-Early Cretaceous units of the Sahara and the southern Arabian Peninsula. Globally considered, the fossil assemblage of this member ( P. arambourgi, dipnoan fishes, Ceratosaurus-like theropods, and conchostracans) is indicative of a Kimmeridgian-Tithonian age, which in combination with the stratigraphic relationships of the Tacuarembó Formation with the overlying basalts of the Arapey Formation (132 My average absolute age) implies that the latter was deposited during the Kimmeridgian-Hauterivian interval.

  4. Application of neoichnological studies to behavioural and taphonomic interpretation of fossil bird-like tracks from lacustrine settings: The Late Triassic–Early Jurassic? Santo Domingo Formation, Argentina

    Microsoft Academic Search

    Jorge F. Genise; Ricardo N. Melchor; Miguel Archangelsky; Luis O. Bala; Roberto Straneck; Silvina de Valais

    2009-01-01

    The purpose of this study is to apply neoichnological observations to the behavioural and taphonomic interpretation of a Late Triassic–Early Jurassic track surface from the Santo Domingo Formation (Argentina) containing hundreds of bird-like tracks and trackways. In addition, the factors affecting the formation and preservation of bird tracks in lacustrine settings are particularly addressed. The 5.5 m2 fossil track surface contains

  5. Partial diagenetic overprint of Late Jurassic belemnites from New Zealand: Implications for the preservation potential of ?7Li values in calcite fossils

    NASA Astrophysics Data System (ADS)

    Ullmann, Clemens V.; Campbell, Hamish J.; Frei, Robert; Hesselbo, Stephen P.; Pogge von Strandmann, Philip A. E.; Korte, Christoph

    2013-11-01

    The preservation potential and trends of alteration of many isotopic systems (e.g. Li, Mg, Ca) that are measured in fossil carbonates are little explored, yet extensive paleoenvironmental interpretations have been made on the basis of these records. Here we present a geochemical dataset for a Late Jurassic (˜153 Ma) belemnite (Belemnopsis sp.) from New Zealand that has been partially overprinted by alteration. We report the physical pathways and settings of alteration, the resulting elemental and isotopic trends including ?7Li values and Li/Ca ratios, and assess whether remnants of the primary shell composition have been preserved or can be extrapolated from the measured values. The ?18O and ?13C values as well as Sr/Ca and Mn/Ca ratios were analysed along two profiles. In addition, 6 samples were analysed for 87Sr/86Sr, Sr/Ca and Mn/Ca ratios. Five samples from the same specimen and 2 from the surrounding sediment were analysed for ?7Li values, Li/Ca, Sr/Ca and Mn/Ca ratios and are compared to results for 6 other Late Jurassic belemnite rostra (Belemnopsis sp. andHibolithes sp.) from the same region. The 87Sr/86Sr ratios are lower (less radiogenic) in the most altered part of the rostrum, whereas ?7Li values become more positive with progressive alteration. The direction and magnitude of the trends in the geochemical record indicate that one main phase of alteration that occurred in the Late Cretaceous caused most of the diagenetic signature in the calcite. Despite relatively deep burial, down to 4 km, and thus elevated temperatures, this diagenetic signature has subsequently been preserved even for the highly mobile element lithium, suggesting that primary lithium-isotope values can be maintained over geological timescales, at least in thick macrofossil shells. Our best ?7Li estimate for pristine Late Jurassic (˜155-148 Ma) belemnites is +27 ± 1‰, which points to a Late Jurassic seawater ?7Li of ˜29-32‰, compatible with the modern value of 31‰.

  6. Late Jurassic salamandroid from western Liaoning, China.

    PubMed

    Gao, Ke-Qin; Shubin, Neil H

    2012-04-10

    A Jurassic salamander, Beiyanerpeton jianpingensis (gen. et sp. nov.), from a recently found site in western Liaoning Province, China is the earliest known record of Salamandroidea. As a Late Jurassic record of the group, it extends the range of the clade by ~40 Ma. The Late Jurassic taxon is neotenic and represented by exceptionally preserved specimens, including fully articulated cranial and postcranial skeletons and bony gill structures close to the cheek region. The fossil beds, consisting of dark-brown volcanic ash shales of the Upper Jurassic Tiaojishan (Lanqi) Formation (Oxfordian), underlie trachyandesite rocks that have yielded a SHRIMP zircon U-Pb date of 157 ± 3 Ma. The fossiliferous beds are substantially older than the Jehol Group, including the Yixian Formation ((40)Ar/(39)Ar dates of 122-129 Ma), but slightly younger than the Middle Jurassic Daohugou horizon ((40)Ar/(39)Ar date of 164 ± 4 Ma). The early fossil taxon shares with extant salamandroids derived character states, including: separated nasals lacking a midline contact, angular fused to the prearticular in the lower jaw, and double-headed ribs on the presacral vertebrae. In contrast to extant salamandroids, however, the salamander shows a discrete and tooth-bearing palatine, and unequivocally nonpedicellate and monocuspid marginal teeth in large and presumably mature individuals. The finding provides insights into the evolution of key characters of salamanders, and also provides direct evidence supporting the hypothesis that the split between Cryptobranchoidea and Salamandroidea had taken placed before the Late Jurassic Oxfordian time. In this aspect, both paleontological and molecular data now come to agree. PMID:22411790

  7. A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago.

    PubMed

    Göhlich, Ursula B; Chiappe, Luis M

    2006-03-16

    Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the tail, the new fossil is the best-preserved predatory, non-avian dinosaur in Europe. It possesses a suite of characters that support its identification as a basal coelurosaur. A cladistic analysis indicates that the new taxon is closer to maniraptorans than to tyrannosauroids, grouping it with taxa often considered to be compsognathids. Large portions of integument are preserved along its tail. The absence of feathers or feather-like structures in a fossil phylogenetically nested within feathered theropods indicates that the evolution of these integumentary structures might be more complex than previously thought. PMID:16541071

  8. Direct evidence of hybodont shark predation on Late Jurassic ammonites

    Microsoft Academic Search

    Romain Vullo

    2011-01-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body\\u000a fossil associations attesting to this predator–prey relationship have never been described so far. Here, I report a unique\\u000a finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont

  9. A basal alvarezsauroid theropod from the early Late Jurassic of Xinjiang, China.

    PubMed

    Choiniere, Jonah N; Xu, Xing; Clark, James M; Forster, Catherine A; Guo, Yu; Han, Fenglu

    2010-01-29

    The fossil record of Jurassic theropod dinosaurs closely related to birds remains poor. A new theropod from the earliest Late Jurassic of western China represents the earliest diverging member of the enigmatic theropod group Alvarezsauroidea and confirms that this group is a basal member of Maniraptora, the clade containing birds and their closest theropod relatives. It extends the fossil record of Alvarezsauroidea by 63 million years and provides evidence for maniraptorans earlier in the fossil record than Archaeopteryx. The new taxon confirms extreme morphological convergence between birds and derived alvarezsauroids and illuminates incipient stages of the highly modified alvarezsaurid forelimb. PMID:20110503

  10. A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago

    Microsoft Academic Search

    Ursula B. Göhlich; Luis M. Chiappe

    2006-01-01

    Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the

  11. Testing the fossil record: Sampling proxies and scaling in the British TriassicJurassic

    E-print Network

    Benton, Michael

    Testing the fossil record: Sampling proxies and scaling in the British Triassic­Jurassic Alexander March 2014 Available online 30 March 2014 Keywords: Palaeodiversity Fossil record Sampling Proxy Triassic Jurassic The quality of the fossil record varies immensely across taxa, geographic regions

  12. Direct evidence of hybodont shark predation on Late Jurassic ammonites

    NASA Astrophysics Data System (ADS)

    Vullo, Romain

    2011-06-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body fossil associations attesting to this predator-prey relationship have never been described so far. Here, I report a unique finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont shark Planohybodus. Some possible tooth puncture marks are also observed. This is the first direct evidence of such a trophic link between these two major Mesozoic groups, allowing an accurate identification of both organisms. Although Planohybodus displays a tearing-type dentition generally assumed to have been especially adapted for large unshelled prey, our discovery clearly shows that this shark was also able to attack robust ammonites such as aspidoceratids. The direct evidence presented here provides new insights into the Mesozoic marine ecosystem food webs.

  13. Direct evidence of hybodont shark predation on Late Jurassic ammonites.

    PubMed

    Vullo, Romain

    2011-06-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body fossil associations attesting to this predator-prey relationship have never been described so far. Here, I report a unique finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont shark Planohybodus. Some possible tooth puncture marks are also observed. This is the first direct evidence of such a trophic link between these two major Mesozoic groups, allowing an accurate identification of both organisms. Although Planohybodus displays a tearing-type dentition generally assumed to have been especially adapted for large unshelled prey, our discovery clearly shows that this shark was also able to attack robust ammonites such as aspidoceratids. The direct evidence presented here provides new insights into the Mesozoic marine ecosystem food webs. PMID:21452053

  14. Late Jurassic plutonism in the southwest U.S. Cordillera

    USGS Publications Warehouse

    Barth, A.P.; Wooden, J.L.; Howard, K.A.; Richards, J.L.

    2008-01-01

    Although plate reconstructions suggest that subduction was an approximately steady-state process from the mid-Mesozoic through the early Tertiary, recent precise geochronologic studies suggest highly episodic emplacement of voluminous continental-margin batholiths in the U.S. Cordillera. In central and southern California and western Arizona, major episodes of batholithic magmatism are known to have occurred in Permian-Triassic, Middle Jurassic, and late Early to Late Cretaceous time. However, recent studies of forearc-basin and continental-interior sediments suggest that Late Jurassic time was probably also a period of significant magmatism, although few dated plutons of this age have been recognized. We describe a belt of Late Jurassic plutonic and hypabyssal rocks at least 200 km in length that extends from the northwestern Mojave Desert through the Transverse Ranges. The belt lies outboard of both the voluminous Middle Jurassic arc and the ca. 148 Ma Independence dike swarm at these latitudes. The plutons include two intrusive suites emplaced between 157 and 149 Ma: a calc-alkaline suite compositionally unlike Permian-Triassic and Middle Jurassic mon-zonitic suites but similar to Late Cretaceous arc plutons emplaced across this region, and a contemporaneous but not comagmatic alkaline suite. The Late Jurassic was thus a time of both tectonic and magmatic transitions in the southern Cordillera. ?? 2008 The Geological Society of America.

  15. A giant pliosaurid skull from the late Jurassic of England.

    PubMed

    Benson, Roger B J; Evans, Mark; Smith, Adam S; Sassoon, Judyth; Moore-Faye, Scott; Ketchum, Hilary F; Forrest, Richard

    2013-01-01

    Pliosaurids were a long-lived and cosmopolitan group of marine predators that spanned 110 million years and occupied the upper tiers of marine ecosystems from the Middle Jurassic until the early Late Cretaceous. A well-preserved giant pliosaurid skull from the Late Jurassic Kimmeridge Clay Formation of Dorset, United Kingdom, represents a new species, Pliosaurus kevani. This specimen is described in detail, and the taxonomy and systematics of Late Jurassic pliosaurids is revised. We name two additional new species, Pliosaurus carpenteri and Pliosaurus westburyensis, based on previously described relatively complete, well-preserved remains. Most or all Late Jurassic pliosaurids represent a globally distributed monophyletic group (the genus Pliosaurus, excluding 'Pliosaurus' andrewsi). Despite its high species diversity, and geographically widespread, temporally extensive occurrence, Pliosaurus shows relatively less morphological and ecological variation than is seen in earlier, multi-genus pliosaurid assemblages such as that of the Middle Jurassic Oxford Clay Formation. It also shows less ecological variation than the pliosaurid-like Cretaceous clade Polycotylidae. Species of Pliosaurus had robust skulls, large body sizes (with skull lengths of 1.7-2.1 metres), and trihedral or subtrihedral teeth suggesting macropredaceous habits. Our data support a trend of decreasing length of the mandibular symphysis through Late Jurassic time, as previously suggested. This may be correlated with increasing adaptation to feeding on large prey. Maximum body size of pliosaurids increased from their first appearance in the Early Jurassic until the Early Cretaceous (skull lengths up to 2360 mm). However, some reduction occurred before their final extinction in the early Late Cretaceous (skull lengths up to 1750 mm). PMID:23741520

  16. Pangean (Late Carboniferous–Middle Jurassic) paleoenvironment and lithofacies

    Microsoft Academic Search

    J Golonka; D Ford

    2000-01-01

    Six time interval maps were constructed that depict the plate tectonic configuration, paleogeography and lithofacies for Pangea from the Late Carboniferous through the Middle Jurassic. Generally, the individual maps illustrate the conditions present during the maximum marine transgressions of higher frequency cyclicity within the Absaroka sequence of Sloss. The relative sea-level cyclicity, chronostratigraphy and regional unconformities provide the basis to

  17. The earliest fossil record of Panorpidae (Mecoptera) from the Middle Jurassic of China

    PubMed Central

    Ding, He; Shih, Chungkun; Bashkuev, Alexei; Zhao, Yunyun; Ren, Dong

    2014-01-01

    Abstract The early history of Panorpidae (Mecoptera) is poorly known due to sparse fossil records. Up to date, only nine fossil species have been described, all from the Paleogene, except the Early Cretaceous Solusipanorpa gibbidorsa Lin, 1980. However, we suggest S. gibbidorsa is too incompletely preserved to permit even family classification. A new genus with two new species, Jurassipanorpa impunctata gen. et sp. n. and Jurassipanorpa sticta sp. n., are described based on four well-preserved specimens from the late Middle Jurassic Jiulongshan Formation of Daohugou, Inner Mongolia, China. These two new species are the earliest fossil records of Panorpidae. The new genus is erected based on a combination of forewing characters: both R1 and Rs1 with two branches, 1A reaching posterior margin of wing distad of the forking of Rs from R1, and no crossveins or only one crossvein between veins of 1A and 2A. In all four specimens, long and robust setae ranging from 0.09 to 0.38 mm in length and pointing anteriorly, are present on anal veins of forewings. The function of these setae is enigmatic. PMID:25152669

  18. Paleointensity Determination on the Late Jurassic Lavas in Northeastern China

    NASA Astrophysics Data System (ADS)

    Shi, R.; Zhu, R.; Pan, Y.

    2003-12-01

    The variations in the strength of the geomagnetic field over geologic time is crucial to a complete understand of the workings of Earth­_s dynamo. While many paleointensity data were recently reported and hence enhancing our understanding of the geodynamo, few data except one datum from SBG in the present paleointensity database were obtained from the late Jurassic by passing certain criteria (Thellier method with system p-TRM check and so on) and, in particular, the lack of data from East Asia. We recently carried out an integrated paleomagnetic, rock-magnetic and paleointensity study of the late Jurassic volcanic succession from Beipiao in the west of Liaoning province, northeastern China. A total of 19 lava flows were sampled. The eruption ages of these lava flows were dated by SHRIMP, about 145Ma. Detailed rock magnetic experiments of thermomagnetic curves and hysteresis loops show the primary carrier of remanence to be pseudo-single domain hematite. Stepwise alternating field and thermal demagnetizations isolated a well-defined direction of characteristic remanent magnetization in all studied lava flows. The modified version (Coe, 1967) of Thellier method with system p-TRM check was used to determine paleointensity. Eight out of nineteen lava flows met the selection criteria (positive p-TRM check, at least three points in a line) and the paleointensity and corresponded VDM values were calculated. An average of about fifth of the present day magnetic field, (1.5+/-0.6)E+22 Am2, was recorded by the eight lava flows. This is the first paleointensity results obtained from the Chinese lava flows erupted in the late Jurassic and well-consistent with the results from SBG (Juarez et al., 1998), suggesting the MDL into the late Jurassic, and further confirming the inverse relationship between reversal frequency and paleointensity.

  19. Fossils from the Middle Jurassic Wanakah formation near Delta in western Colorado

    USGS Publications Warehouse

    O'Sullivan, R. B.; Carey, M.A.; Good, S.C.

    2006-01-01

    The Middle Jurassic Wanakah Formation averages about 30 m in thickness in Colorado. Fossils are sparse and include fish, ostracodes, and trace fossils. A thin (0.03-0.45 m) fossil bed near the middle of the formation extends for some 48 km along the northeast flank of the Uncompahgre Plateau near Delta. The fossil bed at one locality contains one pelecypod identified possibly as Modiolus cf. M. subimbricatus (Meek), as well as other specimens too poorly preserved for identification. Previously, Mytilus was found in the same fossil bed at another locality by C.N. Holmes. The Wanakah Formation is primarily of terrestrial origin, but the fossil bed represents a shallow-marine incursion.

  20. 2006 Nature Publishing Group A new carnivorous dinosaur from the Late Jurassic

    E-print Network

    Cai, Long

    © 2006 Nature Publishing Group A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago Ursula B. Go¨hlich1 & Luis M. Chiappe2 Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus1

  1. The Late Triassic and Late Jurassic stress fields and tectonic transmission of North China craton

    NASA Astrophysics Data System (ADS)

    Hou, Guiting; Wang, Yanxin; Hari, K. R.

    2010-09-01

    The transmission of the tectonic regime from the Paleo-Asian Ocean to the Pacific Ocean during Mesozoic era was reconstructed using the modeling of Late Triassic (T 3) and Late Jurassic (J 3) stress fields employing two dimensional linear finite element models (2-D FEM). The model at T 3 proposes that Qinling-Dabie-Sulu orogens coevally collided and the model J 3 proposes that Subei block continued to collide with the North China block along the Sulu orogen while the collision of the Qinling-Dabie orogen was terminated. The stress fields at T 3 and J 3 during the two episodes were calculated based on mechanical conditions under different deviatoric stresses acting along the boundaries of the North China craton by elastic finite modeling. The transmission between two episodes of stress fields resulted from Qinling-Dabie-Sulu collision between North China and South China in the Late Triassic period, and from continued collision between the Subei block and North China by the NW-trending movement of Izanagi plate during Late Jurassic. The results from modeling of the Mesozoic stress fields of the North China suggest that late Jurassic was the key transmission period of the tectonic regime of the North China block when large scale thrusting triggered the subsequent destruction of the North China craton.

  2. Ice age at the Middle-Late Jurassic transition?

    NASA Astrophysics Data System (ADS)

    Dromart, G.; Garcia, J.-P.; Picard, S.; Atrops, F.; Lécuyer, C.; Sheppard, S. M. F.

    2003-08-01

    A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (?18O values of shark tooth enamel) indicates a severe cooling at the Middle-Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1-3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle-Late Callovian widespread deposition of organic-rich marine sediments (e.g. northwestern Europe, Central Atlantic, and Arabian Peninsula). This thermal deterioration can thus be ascribed to a downdraw in atmospheric CO2 via enhanced organic carbon burial which acted as a negative feedback effect (i.e. the inverse greenhouse effect). The glacial episode of the MLJT climaxed in the Late Callovian, lasted about 2.6 Myr, and had a pronounced asymmetrical pattern composed of an abrupt (˜0.8 Myr) temperature fall opposed to a long-term (˜1.8 Myr), stepwise recovery. The glacial conditions at the MLJT reveal that atmospheric CO2 levels could have dropped temporarily to values lower than 500 ppmv during Mesozoic times.

  3. A NEW LATE JURASSIC TURTLE FROM SPAIN: PHYLOGENETIC IMPLICATIONS, TAPHONOMY AND

    E-print Network

    Benton, Michael

    A NEW LATE JURASSIC TURTLE FROM SPAIN: PHYLOGENETIC IMPLICATIONS, TAPHONOMY AND PALAEOECOLOGY.schouten@bristol.ac.uk Typescript received 26 October 2010; accepted in revised form 27 May 2011 Abstract: The Jurassic was an important period in the evo- lution of Testudinata and encompasses the origin of many clades

  4. Detailed record of the mid-Oxfordian (Late Jurassic) positive carbon-isotope excursion in two hemipelagic sections (France

    E-print Network

    Gilli, Adrian

    Detailed record of the mid-Oxfordian (Late Jurassic) positive carbon-isotope excursion in two 2007 Abstract The Oxfordian (Late Jurassic) was a time of widespread change in Jurassic marine coincide with the first calcareous sediments recurring after a period of reduced carbonate accumulation

  5. Chasing the Late Jurassic APW Monster Shift in Ontario Kimberlites

    NASA Astrophysics Data System (ADS)

    Kent, D. V.; Muttoni, G.; Gee, J. S.; Kjarsgaard, B. A.

    2012-12-01

    A 30° gap was recognized in a composite APW path when global poles from predominantly igneous rocks were assembled in North American coordinates using plate reconstructions (Kent & Irving 2010 JGR). The 'monster shift' occurred between a 160-190 Ma cluster of mean poles at 75-80°N 90-110°E to a 140-145 Ma grouping centered at 60-65°N ~200°E. There are hardly any intermediate igneous poles whereas the rather divergent directions from the Late Jurassic Morrison Formation published by Steiner & Helsley (1975 GSA Bulletin) are subject to adjustments for Colorado Plateau rotation and sedimentary inclination error, neither of which are precisely known for this redbed unit sampled in Colorado. On the other hand, similar large rapid swings have been recognized in the Late Jurassic APW path for Adria (Channell et al. 2010 Paleo3), suggesting a global phenomena. In an effort to fill the data gap between ~145 and 160 Ma, we sampled accessible outcrops/subcrops of kimberlites in the Timiskaming area of Ontario, Canada, that are associated with high precision U-Pb perovskite ages (Heamon & Kjarsgaard 2000 EPSL). We report initial results from two of the intrusions: the 153.6±2.4 Ma Peddie kimberlite from outcrop and the Triple B kimberlite that was accessible by trenching and is assumed to be the same age as the nearby 153.7±1.8 Ma Seed kimberlite as delineated by aeromagnetic surveys and borings. Systematic progressive thermal demagnetization indicated in each unit a dominant characteristic component with unblocking temperatures to 575° that presumably reflect a magnetite carrier that will be checked by further rock magnetic experiments. Samples from the Peddie kimberlite had stable downward (normal polarity) magnetizations whose mean direction gives a paleopole at 73°N 184°E. In contrast, samples from the Triple B kimberlite have upward (reverse polarity) magnetizations with a well-grouped direction whose (north) paleopole is 78°N 197°E, proximal to the Peddie pole. The normal and reverse polarities suggest that sufficient time elapsed between emplacement of the Triple B and Peddie to give an opportunity to average secular variation. The combined ~154 Ma Triple B and Peddie pole encouragingly lies about halfway between igneous poles from North America nearest in age: the 169 Ma Moat volcanics and the 142 Ma Ithaca kimberlites. However, preliminary paleomagnetic results from some of the other sampled kimberlite bodies are more problematical and require further paleomagnetic and geochronological work.

  6. Late Jurassic-Early Cretaceous evolution of the eastern Indian Ocean adjacent to northwest Australia 

    E-print Network

    Fullerton, Lawrence Gilliam

    1987-01-01

    LATE JURASSIC-EARLY CRETACEOUS EVOLUTION OF THE EASTERN INDIAN OCEAN ADJACENT TO NORTHWEST AUSTRALIA A Thesis by LAWRENCE GILLIAM FULLERTON Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1987 Major Subject: Oceanography LATE JURASSIC-EARLY CRETACEOUS EVOLUTION OF THE EASTERN INDIAN OCEAN ADJACENT TO NORTHWEST AUSTRALIA A Thesis by LAWRENCE GILLIAM FULLERTON Approved as to style and content by...

  7. Revision of the Late Jurassic teleosaurid genus Machimosaurus (Crocodylomorpha, Thalattosuchia)

    PubMed Central

    Young, Mark T.; Hua, Stéphane; Steel, Lorna; Foffa, Davide; Brusatte, Stephen L.; Thüring, Silvan; Mateus, Octávio; Ruiz-Omeñaca, José Ignacio; Havlik, Philipe; Lepage, Yves; De Andrade, Marco Brandalise

    2014-01-01

    Machimosaurus was a large-bodied genus of teleosaurid crocodylomorph, considered to have been durophagous/chelonivorous, and which frequented coastal marine/estuarine ecosystems during the Late Jurassic. Here, we revise the genus based on previously described specimens and revise the species within this genus. We conclude that there were three European Machimosaurus species and another taxon in Ethiopia. This conclusion is based on numerous lines of evidence: craniomandibular, dental and postcranial morphologies; differences in estimated total body length; geological age; geographical distribution; and hypothetical lifestyle. We re-diagnose the type species Machimosaurus hugii and limit referred specimens to only those from Upper Kimmeridgian–Lower Tithonian of Switzerland, Portugal and Spain. We also re-diagnose Machimosaurus mosae, demonstrate that it is an available name and restrict the species to the uppermost Kimmeridgian–lowermost Tithonian of northeastern France. We re-diagnose and validate the species Machimosaurus nowackianus from Harrar, Ethiopia. Finally, we establish a new species, Machimosaurus buffetauti, for the Lower Kimmeridgian specimens of France and Germany (and possibly England and Poland). We hypothesize that Machimosaurus may have been analogous to the Pliocene–Holocene genus Crocodylus in having one large-bodied taxon suited to traversing marine barriers and additional, geographically limited taxa across its range.

  8. Late Triassic-Jurassic paleogeography and origin of Gulf of Mexico basin

    SciTech Connect

    Salvador, A.

    1987-04-01

    The basic structural and stratigraphic framework of the Gulf of Mexico Basin was established during the Late Triassic and the Jurassic. During the Late Triassic and Early Jurassic, as the North American plate started to separate from the South American and African plates, the area of the future basin was part of an extensive landmass broken by tensional grabens that were filled by red beds and volcanics. Marine deposition was restricted to embayments of the Pacific Ocean in northwestern and central Mexico. These marine embayments persisted during the early Middle Jurassic, but seawater did not reach the future Gulf of Mexico Basin until the Callovian. Widespread salt deposits known today from two separate areas of the basin resulted from this initial flooding. During the Late Jurassic, marine conditions progressively extended over increasingly larger parts of the Gulf of Mexico Basin. However, the basin was not connected to the Atlantic Ocean until late in the Jurassic. This paleogeographic reconstruction suggests that the Gulf of Mexico Basin formed as a result of the southward drift of the Yucatan continental block away from the remainder of the North American plate. The separation began in the Late Triassic, continued slowly and sporadically during the Early and Middle Jurassic, and quickened after the Middle Jurassic salt formed. As a result, the salt deposits were split into the two segments known today, and oceanic crust formed in the center of the basin. Early in the Late Jurassic, the Yucatan platform reached its present position and the Gulf of Mexico Basin was born. 14 figures.

  9. Mass extinctions in the fossil record of late Palaeozoic and Mesozoic tetrapods

    NASA Astrophysics Data System (ADS)

    Benton, Michael J.

    The fossil record of tetrapods is very patchy because of the problems of preservation in terrestrial sediments, and because vertebrates are rarely very abundant. However, the fossil record of tetrapods has the advantages that it is easier to establish a phylogenetic taxonomy than for many invertebrate groups (many characters; fast evolution), and there is the potential for more detailed ecological analyses (greater knowledge of modern tetrapod ecology). The diversity of tetrapods increased during the Devonian, the Carboniferous, and the Permian, but it remained generally constant during the Triassic, the Jurassic, and the Early Cretaceous. Overall diversity then began to increase in the Late Cretaceous, and continued to do so during the Tertiary. The rapid radiation of modern tetrapod groups — frogs, salamanders, lizards, snakes, turtles, crocodiles, birds and mammals — was hardly affected by the celebrated end-Cretaceous extinction event.

  10. Constraints on the paleogeographic evolution of the North China Craton during the Late Triassic-Jurassic

    NASA Astrophysics Data System (ADS)

    Li, Hong-Yan; Huang, Xiao-Long

    2013-07-01

    This paper reports U-Pb-Hf isotopes of detrital zircons from Late Triassic-Jurassic sediments in the Ordos, Ningwu, and Jiyuan basins in the western-central North China Craton (NCC), with the aim of constraining the paleogeographic evolution of the NCC during the Late Triassic-Jurassic. The early Late Triassic samples have three groups of detrital zircons (238-363 Ma, 1.5-2.1 Ga, and 2.2-2.6 Ga), while the latest Late Triassic and Jurassic samples contain four groups of detrital zircons (154-397 Ma, 414-511 Ma, 1.6-2.0 Ga, and 2.2-2.6 Ga). The Precambrian zircons in the Late Triassic-Jurassic samples were sourced from the basement rocks and pre-Late Triassic sediments in the NCC. But the initial source for the 238-363 Ma zircons in the early Late Triassic samples is the Yinshan-Yanshan Orogenic Belt (YYOB), consistent with their negative zircon ?Hf(t) values (-24 to -2). For the latest Late Triassic and Jurassic samples, the initial source for the 414-511 Ma zircons with ?Hf(t) values of -18 to +9 is the Northern Qinling Orogen (NQO), and that for the 154-397 Ma zircons with ?Hf(t) values of -25 to +12 is the YYOB and the southeastern Central Asian Orogenic Belt (CAOB). In combination with previous data of late Paleozoic-Early Triassic sediments in the western-central NCC and Permian-Jurassic sediments in the eastern NCC, this study reveals two shifts in detrital source from the late Paleozoic to Jurassic. In the Late Permian-Early Triassic, the western-central NCC received detritus from the YYOB, southeastern CAOB and NQO. However, in the early Late Triassic, detritus from the CAOB and NQO were sparse in basins located in the western-central NCC, especially in the Yan'an area of the Ordos Basin. We interpret such a shift of detrital source as result of the uplift of the eastern NCC in the Late Triassic. In the latest Late Triassic-Jurassic, the southeastern CAOB and the NQO restarted to be source regions for basins in the western-central NCC, as well as for basins in the eastern NCC. The second shift in detrital source suggests elevation of the orogens surrounding the NCC and subsidence of the eastern NCC in the Jurassic, arguing against the presence of a paleo-plateau in the eastern NCC at that time. It would be subsidence rather than elevation of the eastern NCC in the Jurassic, due to roll-back of the subducted paleo-Pacific plate and consequent upwelling of asthenospheric mantle.

  11. A revised time scale of magnetic reversals for the Early Cretaceous and Late Jurassic

    Microsoft Academic Search

    Roger L. Larson; Thomas W. C. Hilde

    1975-01-01

    A magnetic reversal block model for the Early Cretaceous-Late Jurassic period was developed from four closely spaced profiles across the Hawaiian lineation pattern by Hilde (1973) and Hilde el al. (1974). Larson (1974) independently developed an improved model of this reversal period by reanalyzing the data presented by Larson and Chase (1972) plus a profile collected during Deep Sea Drilling

  12. Late Jurassic rifting along the Australian North West Shelf: margin geometry and spreading ridge

    E-print Network

    Müller, Dietmar

    for the evolution of the North West Shelf for the early stages after the breakup. The main difference between the Argo Abyssal Plain in the east and the Wharton Basin/ Christmas Island area in the west, the GascoyneLate Jurassic rifting along the Australian North West Shelf: margin geometry and spreading ridge

  13. Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus

    Microsoft Academic Search

    Daniela Schwarz; Guido Fritsch

    2006-01-01

    The presacral vertebrae of sauropod dinosaurs were surrounded and invaded by a complex system of pneumatic diverticula, which originated most probably from cervical air sacs connected with the respiratory apparatus. Cervical vertebrae of Brachiosaurus brancai and Dicraeosaurus sp., two sauropods from the Late Jurassic (?Oxfordian-Kimmerigian-Tithonian) eastern African locality Tendaguru, were examined with computed tomography to visualize internal pneumatic structures. With

  14. Paleoecology of the Quarry 9 vertebrate assemblage from Como Bluff, Wyoming (Morrison Formation, Late Jurassic)

    Microsoft Academic Search

    Matthew T. Carrano; Jorge Velez-Juarbe

    2006-01-01

    Quarry 9 is among the richest microvertebrate localities in the Morrison Formation, having thus far produced the remains of dozens of Late Jurassic taxa. Because this lenticular claystone deposit records such a high diversity of contemporaneous species, it provides an exceptionally detailed view of their paleoecology and local paleoenvironment. In this study, we reexamined the entire Quarry 9 collection, totaling

  15. A new pipoid anuran from the Late Jurassic Morrison Formation at Dinosaur National Monument, Utah

    Microsoft Academic Search

    Amy C. Henrici

    1998-01-01

    Rhadinosteus parvus is a small anuran whose diagnosis is based on several partial skeletons and some isolated bones representing metamorphic to newly transformed ontogenetic stages from the Late Jurassic Morrison Formation at the Rainbow Park Microsite, Utah. This frog is a member of the Pipoidea on the basis of an azygous frontoparietal and parasphenoid that lacks lateral alae and is

  16. A new Semionotid (Actinopterygii, Neopterygii) from the Late Jurassic–Early Cretaceous of Thailand

    Microsoft Academic Search

    Lionel Cavin; Varavudh Suteethorn; Sasidhorn Khansubha; Eric Buffetaut; Haiyan Tong

    2003-01-01

    A new semionotid fish, Lepidotes buddhabutrensis n. sp., is described from the continental Late Jurassic–Early Cretaceous Phu Kradung Formation, Phu Nam Jun, Kalasin Province. L. buddhabutrensis is characterized notably by the pattern of its cheek bones, by its short preorbital region, and by its numerous and well-developed premaxillary teeth. L. buddhabutrensis is provisionally placed in the genus Lepidotes; it shares,

  17. Late Jurassic weather forecast, Four Corners area: Dry, hot, and partly sunny

    SciTech Connect

    Turner-Peterson, C.E.; Fishman, N.S. (Geological Survey, Denver, CO (USA))

    1989-09-01

    Interfingering between members of the Upper Jurassic Morrison Formation and inferences based on their various environments of deposition permit interpretation of a persistent paleoclimate during the Late Jurassic in the Colorado Plateau region. Paleoclimate interpretation is based on evaporites in the Tidwell member, at the base of the Morrison; eolian deposits in the Recapture and Bluff Sandstone members; and saline, alkaline-lake deposits (which indicate high evaporation rates) in the Brushy Basin member at the top of the Morrison. Interfingering of these members with all other members of the Morrison Formation implies that a semiarid to arid climate was likely throughout Morrison time. The semiarid to arid interpretation is consistent with the global climatic zone inferred from the paleogeographic/paleotectonic setting. The Four Corners area during the Late Jurassic was in the middle latitudes of the Northern Hemisphere and thus was affected by prevailing westerly winds. A magmatic arc located several hundred kilometers to the west of the Morrison depositional basin may have caused a broad rain-shadow effect, which contributed to a dry continental climate downwind. A typical Late Jurassic day in the Four Corners area is predicted to have been hot and dry, although seasonally heavy rains probably fed intermittent streams that transported sediments into the region. Explosive eruptions of silicic volcanic ash may have darkened the skies episodically, and thus partly sunny would have been a conservative forecast.

  18. Geochemical features of metabasic rocks from an Early to Middle Jurassic Accretionary Complex (Refahiye metamorphics, Eastern Pontides, NE Turkey): Implications for Late Jurassic-Early Cretaceous magmatic lull

    NASA Astrophysics Data System (ADS)

    Göçmengil, G.; Topuz, G.; Çelik, Ö. F.; Alt?nta?, Ä.°. E.; Özkan, M.

    2012-04-01

    The Refahiye metamorphics (Eastern Pontides, NE Turkey) represent a metamorphosed accretionary complex of Early to Middle Jurassic age and occur as an interleave between coeval ophiolite. This Early to Middle Jurassic metamorphics and ophiolites are bound by a Permo-Triassic accretionary complex in the north and a Late Cretaceous accretionary complex in the south. The Refahiye metamorphics are made up of greenschist, marble, serpentine, phyllite and subordinately amphibolite, micaschist, eclogite and metachert knockers. The Jurassic and Late Cretaceous accretionary complexes in Eastern Mediterranean are related to the consumption of a Mesozoic ocean, the so-called Neo-Tethys. Regional geology in the Eastern Pontides indicate that the Early to Middle Jurassic and Late Cretaceous times correspond to volumious igneous activity, while Late Jurassic and Early Cretaceous time to an igneous lull. Here we present whole-rock geochemical data on metabasic rocks from the Refahiye accretionary complex, and discuss these data in terms of accreted material and its implications for the Jurassic evolution of the Eastern Pontides. All the metabasic rocks are well recrystallized, free of any relict texture and are variably hydrated (LOI ~ 1.3-5.1 wt%). Some samples are characterized by the unusually high-Al2O3 contents (up to 20.8 wt%) suggestive of derivation from high-Al basalts. Geochemically three distinct metabasic group are distinguished, on the basis of fluid immobile HFSEs and REEs. Group I is characterized by moderately to strongly fractionated REE patterns [(La/Yb)cn ~8-18], absence of any Nb-Ta anomaly in multi element variation diagrams and high Ti and low Zr/Nb ratios (3.68-5.72), corresponding to unorogenic alkaline basalts (ocean island basalt). Group II characterized by moderately fractionated REE ratios [(La/Yb)cn ~0.6-2.6], absence of any Nb-Ta anomaly, resembling unorogenic tholeiitic basalts (E and N-MORB). Group III on the other hand, displays unfractionated, nearly flat REE patterns [(La/Yb)cn ~0.6-1.1], negative Nb-Ta anomaly and enormously high Zr/Nb values (38-62), corresponding to orogenic tholeeitic basalts. These data indicate accretion of unorogenic alkaline and tholeiitic basalts similar to those in seamounts, MORB and IAB during the Early to Middle Jurassic subduction. This together with widespread Early to Middle Jurassic magmatism in Eastern Pontides and Crimea and absence in the southern Menderes-Taurus continental block, conclusively indicate for a northvergent subduction. On the basis of the general absence of a Middle to Upper Jurassic unconformity, we tentatively ascribe the Late Jurassic-Early Cretaceous magmatic lull to the accretion of large submarine topographic highs to the subduction zone.

  19. Strontium and carbon isotope stratigraphy of the Late Jurassic shallow marine limestone in western Palaeo-Pacific, northwest Borneo

    E-print Network

    Gilli, Adrian

    Palaeo-Pacific, northwest Borneo Yoshihiro Kakizaki a, , Helmut Weissert b , Takashi Hasegawa c carbonate sec- tion within the Late Jurassic Bau Limestone at the SSF quarry in northwest Borneo, Malaysia

  20. An enigmatic plant-eating theropod from the Late Jurassic period of Chile.

    PubMed

    Novas, Fernando E; Salgado, Leonardo; Suárez, Manuel; Agnolín, Federico L; Ezcurra, Martín D; Chimento, Nicolás R; de la Cruz, Rita; Isasi, Marcelo P; Vargas, Alexander O; Rubilar-Rogers, David

    2015-06-18

    Theropod dinosaurs were the dominant predators in most Mesozoic era terrestrial ecosystems. Early theropod evolution is currently interpreted as the diversification of various carnivorous and cursorial taxa, whereas the acquisition of herbivorism, together with the secondary loss of cursorial adaptations, occurred much later among advanced coelurosaurian theropods. A new, bizarre herbivorous basal tetanuran from the Upper Jurassic of Chile challenges this conception. The new dinosaur was discovered at Aysén, a fossil locality in the Upper Jurassic Toqui Formation of southern Chile (General Carrera Lake). The site yielded abundant and exquisitely preserved three-dimensional skeletons of small archosaurs. Several articulated individuals of Chilesaurus at different ontogenetic stages have been collected, as well as less abundant basal crocodyliforms, and fragmentary remains of sauropod dinosaurs (diplodocids and titanosaurians). PMID:25915021

  1. Oxfordian-Kimmeridgian (Late Jurassic) reservoir sandstones in the Witch Ground Graben, U. K. North Sea

    SciTech Connect

    Harker, S.D. (Occidental Petroleum (Caledonia) Ltd., Aberdeen (United Kingdom)); Mantel, K.A. (Narwhal, London (United Kingdom)); Morton, D.J. (Deminex U.K. Oil and Gas Ltd., London (United Kingdom)); Riley, L.A. (Paleoservices, Watford (United Kingdom))

    1991-03-01

    Oil-bearing Late Jurassic Oxfordian-Kimmeridgian sandstones of the Sgiath and Piper formations are of major economic importance in the Witch Ground Graben. They form the reservoirs in Scott, which in 1993 will be the largest producing North Sea oil field to come on stream for more than a decade. Together with Scott, the Piper, Saltire, Tartan, Highlander, Petronella, Rob Roy, and Ivanhoe fields contained almost 2 Bbbl of recoverable reserves in these formations. The Sgiath and Piper represent two phases of Late Jurassic transgression and regression, initially represented by paralic deposited sand culminating in a wave-dominated delta sequence. The history of the Sgiath and Piper formations is reviewed and lithostratigraphic and biostratigraphic correlations presented to illustrate the distribution of the reservoir sandstones.

  2. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia.

    PubMed

    Rauhut, Oliver W M; Remes, Kristian; Fechner, Regina; Cladera, Gerardo; Puerta, Pablo

    2005-06-01

    Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark of sauropod dinosaurs and is usually regarded as a key feeding adaptation. Here we describe a new dicraeosaurid sauropod, from the latest Jurassic period of Patagonia, that has a particularly short neck. With a neck that is about 40% shorter than in other known dicraeosaurs, this taxon demonstrates a trend opposite to that seen in most sauropods and indicates that the ecology of dicraeosaurids might have differed considerably from that of other sauropods. The new taxon indicates that there was a rapid radiation and dispersal of dicraeosaurids in the Late Jurassic of the Southern Hemisphere, after the separation of Gondwana from the northern continents by the late Middle Jurassic. PMID:15931221

  3. A total petroleum system of the Browse Basin, Australia; Late Jurassic, Early Cretaceous-Mesozoic

    USGS Publications Warehouse

    Bishop, M.G.

    1999-01-01

    The Browse Basin Province 3913, offshore northern Australia, contains one important petroleum system, Late Jurassic, Early Cretaceous-Mesozoic. It is comprised of Late Jurassic through Early Cretaceous source rocks deposited in restricted marine environments and various Mesozoic reservoir rocks deposited in deep-water fan to fluvial settings. Jurassic age intraformational shales and claystones and Cretaceous regional claystones seal the reservoirs. Since 1967, when exploration began in this 105,000 km2 area, fewer than 40 wells have been drilled and only one recent oil discovery is considered potentially commercial. Prior to the most recent oil discovery, on the eastern side of the basin, a giant gas field was discovered in 1971, under a modern reef on the west side of the basin. Several additional oil and gas discoveries and shows were made elsewhere. A portion of the Vulcan sub-basin lies within Province 3913 where a small field, confirmed in 1987, produced 18.8 million barrels of oil (MMBO) up to 1995 and has since been shut in.

  4. A depositional model for late Jurassic Reef Building in the East Texas Basin

    SciTech Connect

    Norwood, E.M. [Marathon Oil Co., Tyler, TX (United States); Brinton, L. [Marathon Oil Co., Littleton, CO (United States)

    1996-12-31

    The authors propose a depositional setting for the Upper Jurassic reef facies occurring at the upper Cotton Valley Lime, (Gilmer) sequence boundary in the East Texas Basin. The development of uncommonly thick, microbially bound reefal buildups positioned near the western margin of the basin was controlled by sea-level variations and gravity faulting, suggested to be concurrent. Gas bearing reefs occur as isolated features along faulted margins and have been successfully located using 3-D seismic. Reefs of this type and age appear to be rare in their occurrence worldwide. Structurally generated circumstances facilitated margin bypass of terrigenous clastics shed from the north and west. Protection from clastic influx contributed to conditions required for development of the 400 feet of reefal buildup penetrated by the Marathon Oil Company Poth No. 1 during early 1993. Core from this well provides insight into character, composition, and depositional setting of reefs along the western flank of the East Texas Basin during Late Jurassic time.

  5. A depositional model for late Jurassic Reef Building in the East Texas Basin

    SciTech Connect

    Norwood, E.M. (Marathon Oil Co., Tyler, TX (United States)); Brinton, L. (Marathon Oil Co., Littleton, CO (United States))

    1996-01-01

    The authors propose a depositional setting for the Upper Jurassic reef facies occurring at the upper Cotton Valley Lime, (Gilmer) sequence boundary in the East Texas Basin. The development of uncommonly thick, microbially bound reefal buildups positioned near the western margin of the basin was controlled by sea-level variations and gravity faulting, suggested to be concurrent. Gas bearing reefs occur as isolated features along faulted margins and have been successfully located using 3-D seismic. Reefs of this type and age appear to be rare in their occurrence worldwide. Structurally generated circumstances facilitated margin bypass of terrigenous clastics shed from the north and west. Protection from clastic influx contributed to conditions required for development of the 400 feet of reefal buildup penetrated by the Marathon Oil Company Poth No. 1 during early 1993. Core from this well provides insight into character, composition, and depositional setting of reefs along the western flank of the East Texas Basin during Late Jurassic time.

  6. Fossil Plants and Global Warming at the Triassic-Jurassic Boundary.

    PubMed

    McElwain; Beerling; Woodward

    1999-08-27

    The Triassic-Jurassic boundary marks a major faunal mass extinction, but records of accompanying environmental changes are limited. Paleobotanical evidence indicates a fourfold increase in atmospheric carbon dioxide concentration and suggests an associated 3 degrees to 4 degrees C "greenhouse" warming across the boundary. These environmental conditions are calculated to have raised leaf temperatures above a highly conserved lethal limit, perhaps contributing to the >95 percent species-level turnover of Triassic-Jurassic megaflora. PMID:10464094

  7. The potential ocean acidification event at the Triassic-Jurassic boundary: Constraining carbonate chemistry using the presence of corals and coral reefs in the fossil record

    NASA Astrophysics Data System (ADS)

    Martindale, R. C.; Berelson, W.; Corsetti, F. A.; Bottjer, D. J.; West, A.

    2011-12-01

    Ocean acidification associated with emplacement of the Central Atlantic Magmatic Province (CAMP) has been hypothesized as a kill mechanism for the Triassic-Jurassic (T-J) mass extinction (~200Ma), but few direct proxies for ancient ocean acidity are available. Here, we suggest that the presence of fossil corals and coral reefs can constrain palaeocean acidity. Modern scleractinian corals lose the ability to biomineralize a robust skeleton below aragonite saturation states (?Arag) of 2 and modern shallow water coral reefs are only found in ?Arag > 3; we use these minima to constrain ancient ocean carbonate chemistry when corals or coral reefs are preserved in the fossil record. Atmospheric pCO2 reconstructions are combined with the coral ?Arag limitations to calculate the total dissolved inorganic carbon (TCO2) in the Late Triassic Ocean, which is a measure of the buffering capacity or ocean sensitivity to acidification. Our results suggest that Late Triassic TCO2 values were low to moderate (2000-3000 ?mol/kg) such that the pCO2 increases across the T-J boundary would have depressed saturation state to the point where coral biomineralization would have been challenging (?Arag < 2), likely resulting in the observed coral and reef gap in the fossil record. While the average pCO2 elevations recorded in stomatal and pedogenic proxies are not sufficient to cause complete carbonate undersaturation, modeled scenarios for CAMP-related T-J pCO2 increases suggest that aragonite undersaturation is plausible and in extreme cases calcite undersaturation is possible. Thus, a short but extreme acidification in an ocean with a low TCO2 concentration could occur and would satisfactorily explain the significant extinction of calcareous organisms, the coral gap, and possibly the T-J carbonate crisis.

  8. Plume type ophiolites in Japan, East Russia and Mongolia: Peculiarity of the Late Jurassic examples

    NASA Astrophysics Data System (ADS)

    Ishiwatari, Akira; Ichiyama, Yuji; Ganbat, Erdenesaikhan

    2013-04-01

    Dilek and Furnes (2011; GSAB) provided a new comprehensive classification of ophiolites. In addition to the mid-ocean ridge (MOR) and supra-subduction zone (SSZ) types that are known for decades, they introduced rift-zone (passive margin) type, volcanic arc (active margin) type, and plume type. The last type is thought to be originated in oceanic large igneous provinces (LIPs; oceanic plateaus), and is preserved in the subduction-accretion complexes in the Pacific margins. The LIP-origin greenstones occur in the Middle Paleozoic (Devonian) accretionary complex (AC) in central Mongolia (Ganbat et al. 2012; AGU abst.). The Late Paleozoic and Mesozoic plume-type ophiolites are abundant in Japan. They are Carboniferous greenstones covered by thick limestone in the Akiyoshi belt (Permian AC, SW Japan; Tatsumi et al., 2000; Geology), Permian greenstones in the Mino-Tamba belt (Jurassic AC, SW Japan; Ichiyama et al. 2008; Lithos), and Late Jurassic-Early Cretaceous greenstone in the Sorachi (Hokkaido; Ichiyama et al, 2012; Geology) and Mikabu (SW Japan; this study) belts. The LIP origin of these greenstones is indicated by abundance of picrite (partly komatiite and meimechite), geochemical features resembling HIMU basalts (e.g. high Nb/Y and Zr/Y) and Mg-rich (up to Fo93) picritic olivines following the "mantle array", suggesting very high (>1600oC) temperature of the source mantle plume. The Sorachi-Mikabu greenstones are characterized by the shorter time interval between magmatism and accretion than the previous ones, and are coeval with the meimechite lavas and Alaskan-type ultramafic intrusions in the Jurassic AC in Sikhote-Alin Mountains of Primorye (E. Russia), that suggest a superplume activity in the subduction zone (Ishiwatari and Ichiyama, 2004; IGR). The Mikabu greenstones extend for 800 km along the Pacific coast of SW Japan, and are characterized by the fragmented "olistostrome" occurrence of the basalts, gabbros and ultramafic cumulate rocks (but no mantle peridotite), suggesting tectonism in a sediment-starved subduction zone or a transform fault zone that transected the thick oceanic LIP crust. The Sorachi greenstones are associated with depleted mantle peridotite, and are covered by the thick Cretaceous turbidite formation (Yezo Group), and Takashima et al. (2002; JAES) concluded the marginal basin origin for the "Sorachi ophiolite". We know that some oceanic LIPs were developed into marginal basins (e.g. Caribbean basin). The Late Jurassic-Early Cretaceous greenstone belts of Japan and eastern Russia may represent relics of a 2000 km-size superplume activity that hit the subduction zone and the adjacent ocean floor in NW Pacific.

  9. The rediscovery and redescription of the holotype of the Late Jurassic turtle Plesiochelys etalloni

    PubMed Central

    Deschamps, Sylvie; Claude, Julien

    2014-01-01

    Plesiochelyidae are a major component of Late Jurassic shallow marine environments throughout Europe. However, the taxonomy of plesiochelyid turtles is rather confused. Over the years, many taxa have been synonymized with Plesiochelys etalloni, one of the first described species. However, the holotype of P. etalloni (and only specimen known from Lect, the type locality) was lost for more than 150 years. This specimen has been recently rediscovered in the collections of the Musée d’archéologie du Jura in Lons-le-Saunier, France. For the first time since its original description in 1857, the holotype of P. etalloni is redescribed and compared to relevant material. The taxonomic status of this taxon is revised accordingly. Based on the morphology of the newly rediscovered holotype and on a reassessment of specimens from Solothurn (Switzerland), the species P. solodurensis, P. sanctaeverenae and P. langii are synonymized with P. etalloni. Known skull-shell associations for P. etalloni are re-evaluated in light of the new morphological information available since the rediscovery of this holotype specimen. Finally, we confirm that Plesiochelys is represented by a single species in the Late Jurassic of the Jura Mountains. PMID:24688842

  10. Degradation processes and consolidation of Late Jurassic sandstone dinosaur tracks in museum environment (Museum of Lourinhã, Portugal)

    NASA Astrophysics Data System (ADS)

    Leal, Sofia; mateus, Octavio; Tomas, Carla; Dionisio, Amelia

    2014-05-01

    The current study aims to conciliate conservation and restoration museology diagnosis with paleontological and geological curational needs and has, as subject of study, dinosaur footprints (vertebrates fossils). The footprints have been being exposed since 2004 in the paleontology hall of the Museum of Lourinhã, Portugal, and are part of a important paleontological collection of Late Jurassic vertebrate fossils from Lourinhã Formation. Presently, it is considered a unique heritage in danger of disappearing due to high decay level of disaggregation of its geological structure. The dinosaur footprints, (ML557) found, more precisely, on a coastline cliff in Lourinhã, Porto das Barcas, Lagido do Forno (coordinate 39° 14. 178'N, 9° 20. 397'W), Jurassic period, on the 5th of June 2001, by Jesper Milàn. This cliff of high slope presents sedimentary stratigraphic characteristics of a sandstone/siltstone of gray and red colors, by the '' Munsell scale and Color Chart''. Geological the tracks are Late Jurassic in age, and colected in the Lourinhã Formation, Praia Azul Member, of the Lusitanian Basin. There are three natural infills tridactyl tracks, possibly ascribed to ornithopod, a bipedal herbivore, resultant of a left foot movement, right and left. Footprints have 300-400mm of wide and 330-360mm of height with round fingers, which are elongated due to some degradation/erosion. In 2001, the footprints were collected from the field, cleaned, consolidated and glued in the laboratory of the Museum of Lourinhã before being exhibited in a museum display. Stone matrix was removed and a consolidation product applied, probably a polyvinyl acetate, of the brand Plexigum. The footprint with broken central digit was glued with an epoxy resin, Araldite. Both applied products were confirmed by analysis of µ-FTIR (Fourier Transform Infrared Spectroscopy) and both presented colour change and detachment surface problems. After collecting and storing, in 2004, footprints were transferred to the current public paleontology hall, ground floor, placed on the floor without any protection framework or environmental control (temperature and relative humidity). Presently, footprints show major geological structure disintegration/deterioration problems and were diagnosed several pathologies :"Blistering", "Powdering", "Exfoliation"' as well as "Dirt", "Fracture"', "Inscriptions", "Consolidates" and "Adhesives". Several laboratorial analysed were conducted to evaluate the presence of salts. Moreover a microclimatic study was conducted inside the museum to evaluate the influence of thermohygrometric parameters on the decay processes observed. As future procedures, all tracks will suffer a superficial cleaning (dust removal) with brush without any solvent and also the application of a consolidant aiming to restore some coehesion of these footprints. Since stone consolidation is a very risky intervention, several laboratory tests are being conducted with stone samples taken from the same layer and location from Porto das Barcas and using different commercial consolidation products.

  11. A Jurassic mammal from South America.

    PubMed

    Rauhut, Oliver W M; Martin, Thomas; Ortiz-Jaureguizar, Edgardo; Puerta, Pablo

    2002-03-14

    The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and from trackway evidence from Argentina. Here we report a Jurassic mammal represented by a dentary, which is the first, to our knowledge, from South America. The tiny fossil from the Middle to Late Jurassic of Patagonia is a representative of the recently termed Australosphenida, a group of mammals from Gondwanaland that evolved tribosphenic molars convergently to the Northern Hemisphere Tribosphenida, and probably gave rise to the monotremes. Together with other mammalian evidence from the Southern Hemisphere, the discovery of this new mammal indicates that the Australosphenida had diversified and were widespread in Gondwanaland well before the end of the Jurassic, and that mammalian faunas from the Southern Hemisphere already showed a marked distinction from their northern counterparts by the Middle to Late Jurassic. PMID:11894091

  12. Late Pleistocene Vertebrates and Other Fossils from Epiguruk, Northwestern Alaska

    USGS Publications Warehouse

    Hamilton, T.D.; Ashley, G.M.; Reed, K.M.; Schweger, C.E.

    1993-01-01

    Sediments exposed at Epiguruk, a large cutbank on the Kobuk River about 170 km inland from Kotzebue Sound, record multiple episodes of glacial-age alluviation followed by interstadial downcutting and formation of paleosols. Vertebrate remains from Epiguruk include mammoth, bison, caribou, an equid, a canid, arctic ground squirrel, lemmings, and voles. Radiocarbon ages of bone validated by concordant ages of peat and wood span the interval between about 37,000 and 14,000 yr B.P. The late Pleistocene pollen record is dominated by Cyperaceae, with Artemisia, Salix, Betula, and Gramineae also generally abundant. The fossil record from Epiguruk indicates that the Kobuk River valley supported tundra vegetation with abundant riparian willows during middle and late Wisconsin time. Large herbivores were present during the height of late Wisconsin glaciation as well as during its waning stage and the preceding interstadial interval. The Kobuk River valley would have been a favorable refugium for plants, animals, and possibly humans throughout the last glaciation.

  13. Scenes from the past: initial investigation of early jurassic vertebrate fossils with multidetector CT.

    PubMed

    Bolliger, Stephan A; Ross, Steffen; Thali, Michael J; Hostettler, Bernhard; Menkveld-Gfeller, Ursula

    2012-01-01

    The study of fossils permits the reconstruction of past life on our planet and enhances our understanding of evolutionary processes. However, many fossils are difficult to recognize, being encased in a lithified matrix whose tedious removal is required before examination is possible. The authors describe the use of multidetector computed tomography (CT) in locating, identifying, and examining fossil remains of crocodilians (Mesosuchia) embedded in hard shale, all without removing the matrix. In addition, they describe how three-dimensional (3D) reformatted CT images provided details that were helpful for extraction and preparation. Multidetector CT can help experienced paleontologists localize and characterize fossils in the matrix of a promising rock specimen in a nondestructive manner. Moreover, with its capacity to generate highly accurate 3D images, multidetector CT can help determine whether the fossils warrant extraction and can assist in planning the extraction process. Thus, multidetector CT may well become an invaluable tool in the field of paleoradiology. PMID:22977034

  14. A REVIEW OF THE VERTEBRATE FAUNA OF THE LOWER JURASSIC NAVAJO SANDSTONE IN ARIZONA

    Microsoft Academic Search

    RANDALL B. IRMIS

    2005-01-01

    The Lower Jurassic Navajo Sandstone of northern Arizona and southern Utah has yielded a diverse assemblage of late Early Jurassic terrestrial tetrapods from eolian and associated paleoenvironments. Although rare, vertebrate body fossils are represented by specimens of tritylodonts, crocodylomorphs, sauropodomorphs, and basal theropods (including Segisaurus halli). The vertebrate ichnofossil record is diverse and includes synapsids (Brasilichnium), crocodylomorphs (cf. Batrachopus), ornithischians

  15. Astrochronology of the late Jurassic Kimmeridge Clay (Dorset, England) and implications for Earth system processes

    NASA Astrophysics Data System (ADS)

    Huang, Chunju; Hesselbo, Stephen P.; Hinnov, Linda

    2010-01-01

    The Late Jurassic Kimmeridge Clay Formation (KCF) is an economically important, organic-rich source rock of Kimmeridgian-Early Tithonian age. The main rock types of the KCF in Dorset, UK, include grey to black laminated shale, marl, coccolithic limestone, and dolostone, which occur with an obvious cyclicity at astronomical timescales. In this study, we examine two high-resolution borehole records (Swanworth Quarry 1 and Metherhills 1) obtained as part of a Rapid Global Geological Events (RGGE) sediment drilling project. Datasets examined were total organic carbon (TOC), and borehole wall microconductivity by Formation Microscanner (FMS). Our intent is to assess the rhythmicity of the KCF with respect to the astronomical timescale, and to discuss the results with respect to other key Late Jurassic geological processes. Power spectra of the untuned data reveal a hierarchy of cycles throughout the KCF with ˜ 167 m, ˜ 40 m, 9.1 m, 3.8 m and 1.6 m wavelengths. Tuning the ˜ 40 m cycles to the 405-kyr eccentricity cycle shows the presence of all the astronomical parameters: eccentricity, obliquity, and precession index. In particular, ˜ 100-kyr and 405-kyr eccentricity cycles are strongly expressed in both records. The 405-kyr eccentricity cycle corresponds to relative sea-level changes inferred from sequence stratigraphy. Intervals with elevated TOC are associated with strong obliquity forcing. The 405-kyr-tuned duration of the lower KCF (Kimmeridgian Stage) is 3.47 Myr, and the upper KCF (early part of the Tithonian Stage, elegans to fittoni ammonite zones) is 3.32 Myr. Two other chronologies test the consistency of this age model by tuning ˜ 8-10 m cycles to 100-kyr (short eccentricity), and ˜ 3-5 m cycles to 36-kyr (Jurassic obliquity). The 'obliquity-tuned' chronology resolves an accumulation history for the KCF with a variation that strongly resembles that of Earth's orbital eccentricity predicted for 147.2 Ma to 153.8 Ma. There is evidence for significant non-deposition (up to 1 million years) in the lowermost KCF ( baylei- mutabilis zones), which would indicate a Kimmeridgian/Oxfordian boundary age of 154.8 Ma. This absolute calibration allows assignment of precise numerical ages to zonal boundaries, sequence surfaces, and polarity chrons of the lower M-sequence.

  16. Late Jurassic-Cenozoic reconstructions of the Indonesian region and the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Hall, Robert

    2012-10-01

    The heterogeneous Sundaland region was assembled by closure of Tethyan oceans and addition of continental fragments. Its Mesozoic and Cenozoic history is illustrated by a new plate tectonic reconstruction. A continental block (Luconia-Dangerous Grounds) rifted from east Asia was added to eastern Sundaland north of Borneo in the Cretaceous. Continental blocks that originated in western Australia from the Late Jurassic are now in Borneo, Java and Sulawesi. West Burma was not rifted from western Australia in the Jurassic. The Banda (SW Borneo) and Argo (East Java-West Sulawesi) blocks separated from western Australia and collided with the SE Asian margin between 110 and 90 Ma, and at 90 Ma the Woyla intra-oceanic arc collided with the Sumatra margin. Subduction beneath Sundaland terminated at this time. A marked change in deep mantle structure at about 110°E reflects different subduction histories north of India and Australia since 90 Ma. India and Australia were separated by a transform boundary that was leaky from 90 to 75 Ma and slightly convergent from 75 to 55 Ma. From 80 Ma, India moved rapidly north with north-directed subduction within Tethys and at the Asian margin. It collided with an intra-oceanic arc at about 55 Ma, west of Sumatra, and continued north to collide with Asia in the Eocene. Between 90 and 45 Ma Australia remained close to Antarctica and there was no significant subduction beneath Sumatra and Java. During this interval Sundaland was largely surrounded by inactive margins with some strike-slip deformation and extension, except for subduction beneath Sumba-West Sulawesi between 63 and 50 Ma. At 45 Ma Australia began to move north; subduction resumed beneath Indonesia and has continued to the present. There was never an active or recently active ridge subducted in the Late Cretaceous or Cenozoic beneath Sumatra and Java. The slab subducted between Sumatra and east Indonesia in the Cenozoic was Cretaceous or older, except at the very western end of the Sunda Arc where Cenozoic lithosphere has been subducted in the last 20 million years. Cenozoic deformation of the region was influenced by the deep structure of Australian fragments added to the Sundaland core, the shape of the Australian margin formed during Jurassic rifting, and the age of now-subducted ocean lithosphere within the Australian margin.

  17. Fauna and Predator-Prey Relationships of Ettling, an Actinopterygian Fish-Dominated Konservat-Lagerstätte from the Late Jurassic of Southern Germany

    PubMed Central

    Ebert, Martin; Kölbl-Ebert, Martina; Lane, Jennifer A.

    2015-01-01

    The newly recognized Konservat-Lagerstätte of Ettling (Bavaria), field site of the Jura-Museum Eichstätt (JME), is unique among Late Jurassic plattenkalk basins (Solnhofen region) in its abundant, extremely well preserved fossil vertebrates, almost exclusively fishes. We report actinopterygians (ginglymodins, pycnodontiforms, halecomorphs, aspidorynchiforms, “pholidophoriforms,” teleosts); turtles; and non-vertebrates (echinoderms, arthropods, brachiopods, mollusks, jellyfish, sponges, biomats, plants) in a current faunal list. Ettling has yielded several new fish species (Bavarichthys incognitus; Orthogonikleithrus hoelli; Aspidorhynchus sanzenbacheri; Macrosemimimus fegerti). Upper and lower Ettling strata differ in faunal content, with the lower dominated by the small teleost Orthogonikleithrus hoelli (absent from the upper layers, where other prey fishes, Leptolepides sp. and Tharsis sp., occur instead). Pharyngeal and stomach contents of Ettling fishes provide direct evidence that Orthogonikleithrus hoelli was a primary food source during early Ettling times. Scarcity of ammonites and absence of vampyromorph coleoids at Ettling differ markedly from the situation at other nearby localities in the region (e.g., Eichstätt, Painten, Schamhaupten, the Mörnsheim beds), where they are more common. Although the exact biochronological age of Ettling remains uncertain (lack of suitable index fossils), many Ettling fishes occur in other plattenkalk basins of Germany (e.g., Kelheim) and France (Cerin) dated as Late Kimmeridgian to Early Tithonian (eigeltingense horizon), suggesting a comparable geologic age. The Ettling deposits represent an independent basin within the larger Upper Jurassic “Solnhofen Archipelago”, a shallow subtropical sea containing scattered islands, sponge-microbial and coral reefs, sandbars, and deeper basins on a vast carbonate platform along the northern margin of the Tethys Ocean. PMID:25629970

  18. Ediacaran fossils from the Innerelv Member (late Proterozoic) of the Tanafjorden area, northeastern Finnmark

    E-print Network

    Farmer, Jack D.

    Ediacaran fossils from the Innerelv Member (late Proterozoic) of the Tanafjorden area, northeastern Finnmark, northern Norway. The fossil assemblage is dominated by discoidal which share certain affinities with the cosmopolitan genera. and However, our specimens differ from these and other discoidal Ediacaran fossils

  19. A fossil primate of uncertain affinities from the earliest late Eocene of Egypt

    E-print Network

    Boyer, Doug M.

    A fossil primate of uncertain affinities from the earliest late Eocene of Egypt Erik R. Seifferta,1- mate from the earliest late Eocene (37 Ma) of northern Egypt, Nos- mipsaenigmaticus, whosephylogenetic of fossil primates from the Eocene of Algeria (1) and Egypt (2­4), Africa's role in the early evolution

  20. An Investigation of mid to late Holocene fossil insects from raised bogs

    E-print Network

    Sheldon, Nathan D.

    1 An Investigation of mid to late Holocene fossil insects from raised bogs in the Irish Midlands the results of late Holocene insect fossil analysis from six raised bogs in the Irish Midlands. A distribution) to the dome (centre) of Ballykean Bog, County Offaly, Ireland. The purpose of this study was to detect any

  1. Late Jurassic Crustal Thickening in the Mesozoic Arc of Ecuador and Colombia: Implications on the Evolution of Continental Arcs.

    NASA Astrophysics Data System (ADS)

    Vanegas, J.; Cardona, A.; Blanco-Quintero, I.; Valencia, V.

    2014-12-01

    The tectonic evolution of South America during the Jurassic is related to the subduction of the Farallon plate and the formation of a series of continental arcs. In the northern Andes such arcs have been considered as controlled by extensional dominated tectonics. Paleomagnetic constraints have also suggested that between the Early and Late Jurassic several crustal domains were translate along the continental margin in association with strain partitioning in the convergent margin. A review of the character of the Salado terrane in the Cordillera Real of Ecuador indicates that it includes extensively deformed and metamorphosed volcano-sedimentary rocks that have achieved a greenschist to amphibolite facies event with chloritoid and garnet. This rocks are tightly associated with a ca. 143 Ma syn-tectonic granodiorite to monzogranite batholith that is also extensively milonitized.A similar Late Jurassic crustal thickening event that apparently affected volcano-sedimentary rocks have been also recently suspected in the Central Cordillera of the Colombian Andes in association with Jurassic plutonic rocks (Blanco-Quintero et al., 2013) It is therefore suggested that during the Late Jurassic the Northern Andes experienced significant contractional tectonics. Such crustal thickening may be related to either the active subduction setting were the crustal slivers formed in relation to oblique convergence are transfered and re-accreted to the margin and triggered the deformational event or to a collisional event associated to the arrival of an allocthonous terrane. New geochronological constraints on the metamorphic evolution and precise understanding on the relations between magmatism and deformation are going to be obtain in the Salado Terrane to appropriately test this hypothesis and contribute to the understanding of the extensional to compressional tectonic switching in continental arcs. Blanco-Quintero, I. F., García-Casco, A., Ruíz, E. C., Toro, L. M., Moreno, M., & Vinasco, C. J. (2013). New Petrological and Geochronological Data frtom the Cajamarca Complex (Central Cordillera, Colombia) In the Cajamarca-Ibague Region: Late Jurassic Thermal Resetting of Triassic Metamorphic Ages or Jurassic Orogenic Metamorphism? In XIV Congreso Colombiano de Geología. Bogotá.

  2. Late Jurassic to Eocene geochemical evolution of volcanic rocks in Puerto Rico

    SciTech Connect

    Schellekens, J.H. (Univ. of Puerto Rico, Mayaguez (Puerto Rico))

    1991-03-01

    The Late Jurassic to Eocene deformed volcanic, volcaniclastic and sedimentary rocks of Puerto Rico are divided into three igneous provinces, the southwestern, central, and northeastern igneous province. Based on the stratigraphic position approximate ages could be assigned to the flow rocks in these provinces. Ba/Nb and La/Sm diagrams are presented to illustrate the origin and evolution of the flow rocks. The oldest rock in the southwestern province may include MORB. Early Cretaceous volcanic rocks in the central and northeastern province have low Ba/nb and La/Sm, that are interpreted as an early island arc stage, with none or only minor contribution of slab-derived material. The Late Cretaceous to Eocene volcanic rocks have a wide range of values for the Ba/Nb and La/Sm that are interpreted as the result of admixture of a variable amount of slab-derived material. The Maricao Basalt (Maastrichtian to Eocene) in the southeastern igneous province has the geochemical signature of magmas formed in an extensional setting.

  3. Analysis of late Jurassic-recent paleomagnetic data from active plate margins of South America

    NASA Astrophysics Data System (ADS)

    Beck, Myrl E.

    Paleomagnetic results for rocks of late Mesozoic and Cenozoic age from South America are analyzed and interpreted. Emphasis is placed on the active margins of the continent. Some important conclusions are reached, with varying degrees of certainty: (1) The reference APW path for stable South America is fairly well defined for the Late Jurassic and Cretaceous, and is not much different from the present rotation axis. (2) The so-called "Bolivian orocline" involved counterclockwise rotations in Peru and northernmost Chile and clockwise rotations in Chile south of about latitude 18.5S. These rotations probably are a result of in situ small-block rotations in response to shear, not actual oroclinal bending. (3) The Bonaire block of northern Venezuela and Colombia has been rotated clockwise relative to the stable interior of South America by about 90°. It also seems to have drifted northward relative to the craton by as much as 1600 km. It probably represents a true accreted terrane, one of very few recognized in South America so far. (4) The "Magellanes orocline" at the southern tip of South America apparently involves some counterclockwise rotation of paleomagnetic vectors, but this too is probably the result of distributed shear. (5) Tectonic processes have very thoroughly "rearranged" the rocks making up the active margins of South America. "Rearrange" here denotes displacement of crustal blocks relative to their surroundings, without significant internal deformation By analogy with North America "rearrangement" might entail in situ block rotation, translation of crustal blocks along the continental margin, and accretion of exotic "tectonostratigraphic terranes". However, in western South America "rearrangement" seems to have consisted dominantly of block rotations that were essentially in situ. For the parts of the Andes investigated so far, late Mesozoic and Cenozoic accretion of exotic terranes and large-scale translation of crustal slivers, as found in western North America, seem to be absent.

  4. Detrital Zircon Ages from Late Jurassic-Early Cretaceous Myrgovaam Basin Sandstones (Rauchua Trough), Western Chukotka, NE Russia

    Microsoft Academic Search

    E. L. Miller; J. Toro; G. Gehrels; M. Tuchkova; S. Katkov

    2004-01-01

    Late Jurassic to Early Cretaceous Myrgovaam Basin sediments (previously Rauchua Trough) are regionally significant because of the stratigraphic constraints they provide on the age and progression of deformation in the Chukotka fold belt, a possible along-strike continuation of the Alaskan Brooks Range fold-and-thrust belt. Existing descriptions of the structural and stratigraphic relations of Myrgovaam Basin sediments to underlying strata are

  5. Species of plated dinosaur Stegosaurus (Morrison Formation, Late Jurassic) of western USA: new type species designation needed

    Microsoft Academic Search

    Peter M. Galton

    2010-01-01

    Stegosaurus armatus Marsh 1877, based on a partial tail and a very large dermal plate from the Morrison Formation (Late Jurassic) of Morrison, Wyoming,\\u000a USA, is a nomen dubium. Valid Morrison stegosaur species (with possible autapomorphies, dermal “armor” considered if present), with most holotypes\\u000a consisting of a disarticulated partial postcranial skeleton at most, include: Hypsirhophus discurus Cope 1878 (characters of

  6. Tectostratigraphic evidence for Late Paleozoic Pacific plate collision and post-Upper Jurassic transpression in northeastern Chihuahua, Mexico

    SciTech Connect

    Montgomery, H.A.

    1985-01-01

    The rocks of Mina Plomosas, Chihuahua include a structurally complex association of Ordovician to Permian and Upper Jurassic strata. The structural deformation has historically been considered as two-fold including late Paleozoic compression associated with the collision of North and Afro-South America followed by loosely defined Laramide influences. These interpretations, however, are inconsistent with respect to timing, direction and style of deformation and the tectostratigraphic development of northeastern Mexico. Paleozoic strata which are folded, overturned and thrusted to the southwest are in opposition to the predicted, and elsewhere observed, northwestward compression. More likely, deformation is the result of late Paleozoic, northeastward directed Pacific plate collision causing underthrusting of the Paleozoic strata. Typical Laramide deformations are also in question. Upper Jurassic La Casita-equivalent rocks are twisted into distally thrusted, arcuate, en echelon, omega-folded anticlines which rotate into the trend of the suspected continuation of the oblique strike-slip San Marcos Fault. Such structures are diagnostic of transpressive mobile belts. The implications of late Paleozoic Pacific plate interactions and post-middle Paleozoic transpressive tectonics are that northern Mexico was located to the northwest during the Paleozoic and was repositioned following deposition of Upper Jurassic strata.

  7. A basal ceratopsian with transitional features from the Late Jurassic of northwestern China

    PubMed Central

    Xu, Xing; Forster, Catherine A; Clark, James M; Mo, Jinyou

    2006-01-01

    Although the Ceratopsia and Pachycephalosauria, two major ornithischian groups, are united as the Marginocephalia, few synapomorphies have been identified due to their highly specialized body-plans. Several studies have linked the Heterodontosauridae with either the Ceratopsia or Marginocephalia, but evidence for these relationships is weak, leading most recent studies to consider the Heterodontosauridae as the basal member of another major ornithischian radiation, the Ornithopoda. Here, we report on a new basal ceratopsian dinosaur, Yinlong downsi gen. et. sp. nov., from the Late Jurassic upper part of the Shishugou Formation of Xinjiang, China. This new ceratopsian displays a series of features transitional between more derived ceratopsians and other ornithischians, shares numerous derived similarities with both the heterodontosaurids and pachycephalosaurians and provides strong evidence supporting a monophyletic Marginocephalia and its close relationship to the Heterodontosauridae. Character distributions along the marginocephalian lineage reveal that, compared to the bipedal Pachycephalosauria, which retained a primitive post-cranial body-plan, the dominantly quadrupedal ceratopsians lost many marginocephalian features and evolved their own characters early in their evolution. PMID:16901832

  8. Exceptionally preserved juvenile megalosauroid theropod dinosaur with filamentous integument from the Late Jurassic of Germany

    PubMed Central

    Rauhut, Oliver W. M.; Foth, Christian; Tischlinger, Helmut; Norell, Mark A.

    2012-01-01

    Recent discoveries in Asia have greatly increased our understanding of the evolution of dinosaurs’ integumentary structures, revealing a previously unexpected diversity of “protofeathers” and feathers. However, all theropod dinosaurs with preserved feathers reported so far are coelurosaurs. Evidence for filaments or feathers in noncoelurosaurian theropods is circumstantial and debated. Here we report an exceptionally preserved skeleton of a juvenile megalosauroid, Sciurumimus albersdoerferi n. gen., n. sp., from the Late Jurassic of Germany, which preserves a filamentous plumage at the tail base and on parts of the body. These structures are identical to the type 1 feathers that have been reported in some ornithischians, the basal tyrannosaur Dilong, the basal therizinosauroid Beipiaosaurus, and, probably, in the basal coelurosaur Sinosauropteryx. Sciurumimus albersdoerferi represents the phylogenetically most basal theropod that preserves direct evidence for feathers and helps close the gap between feathers reported in coelurosaurian theropods and filaments in ornithischian dinosaurs, further supporting the homology of these structures. The specimen of Sciurumimus is the most complete megalosauroid yet discovered and helps clarify significant anatomical details of this important basal theropod clade, such as the complete absence of the fourth digit of the manus. The dentition of this probably early-posthatchling individual is markedly similar to that of basal coelurosaurian theropods, indicating that coelurosaur occurrences based on isolated teeth should be used with caution. PMID:22753486

  9. Tooth serration morphologies in the genus Machimosaurus (Crocodylomorpha, Thalattosuchia) from the Late Jurassic of Europe

    PubMed Central

    Young, Mark T.; Steel, Lorna; Brusatte, Stephen L.; Foffa, Davide; Lepage, Yves

    2014-01-01

    Machimosaurus was a large-bodied durophagous/chelonivorous genus of teleosaurid crocodylomorph that lived in shallow marine and brackish ecosystems during the Late Jurassic. Among teleosaurids, Machimosaurus and its sister taxon ‘Steneosaurus’ obtusidens are characterized by having foreshortened rostra, proportionally enlarged supratemporal fenestrae and blunt teeth with numerous apicobasal ridges and a shorter anastomosed ridged pattern in the apical region. A recent study on ‘S.’ obtusidens dentition found both true denticles and false serrations (enamel ridges which contact the carinae). Here, we comprehensively describe and figure the dentition of Machimosaurus, and find that Machimosaurus buffetauti and Machimosaurus hugii have four types of serration or serration-like structures, including both denticles and false denticles on the carinae. The denticles are irregularly shaped and are not always discrete units, whereas the false denticles caused by the interaction between the superficial enamel ridges and the carinae are restricted to the apical region. Peculiarly, the most ‘denticle-like’ structures are discrete, bulbous units on the apicobasal and apical anastomosed ridges of M. hugii. These ‘pseudo-denticles’ have never, to our knowledge, previously been reported among crocodylomorphs, and their precise function is unclear. They may have increased the surface area of the apical region and/or strengthened the enamel, both of which would have been advantageous for a durophagous taxon feeding on hard objects such as turtles.

  10. Paleomagnetism of the Front Range (Colorado) Morrison Formation and an alternative model of Late Jurassic North American apparent polar wander

    SciTech Connect

    Fossen, M.C. Van; Kent, D.V. (Columbia Univ., Palisades, NY (United States))

    1992-03-01

    A paleomagnetic study of the Upper Jurassic Morrison Formation in the Front Range of central Colorado yields high-unblocking-temperature, dual-polarity magnetizations. With respect to known paleohorizontal, the inclinations (absolute mean = 57.3{degree}, 95% confidence interval = 52.3{degree} to 63.1{degree}, N = 8 sites) pass tilt and reversal tests, whereas the dispersion in declinations can be attributed to apparent or real tectonic rotations and sedimentary processes. The site-centered colatitudinal locus of possible Front Range Morrison poles partially overlaps the 'upper' pole, but it excludes the 'lower' pole from the Morrison Formation on the Colorado Plateau as well as the 151 Ma Glance conglomerate pole from the Basin and Range province of southeastern Arizona. The authors offer various explanations for these disparities and suggest an alternative model of Late Jurassic North American apparent polar wander through {approximately}70{degree}N which is supported by Late Jurassic European poles (with positive stability tests) transferred to North American coordinates.

  11. A reappraisal of the late Quaternary fossil vertebrates of Pyramid Valley Swamp, North Canterbury, New Zealand

    Microsoft Academic Search

    R. N. Holdaway; T. H. Worthy

    1997-01-01

    The late Quaternary fossil vertebrate fauna from deposits at Pyramid Valley, North Canterbury, New Zealand is reassessed. The faunal composition as contained in previous lists is updated, and minimum numbers of individuals represented are given. Measures of faunal diversity are presented and compared with values for present New Zealand systems and other fossil sites. The revised faunal list includes a

  12. Chemostratigraphic Constraints on Late Jurassic Paleoceanography of the East Texas Basin, Southern Margin of North America

    NASA Astrophysics Data System (ADS)

    Mainali, P.; Rowe, H. D.

    2010-12-01

    Late Jurassic deposition of organic-rich muds occurred in the East Texas Basin of modern-day Texas and Louisiana in a ramp-style marine setting during the early formation of the Gulf of Mexico. These mudrocks are regional known as the Haynesville and Bossier Formations. The goals of the current project are to 1) develop a better understanding of the paleoceanographic conditions and the depositional environment, and 2) develop linkages between the record from the southern margin of North America and other well-documented paleoceanographic records of Kimmeridgian age. Ten drill cores from the study area have been studied for their geochemistry. Each core was scanned at a 1-foot interval using a handheld x-ray fluorescence instrument, providing rapid, quantitative analysis of the following elemental concentrations: Mg, Al, S, Si, P, K, Ti, Ca, Mn, Fe, Mo, Cr, Ni, Cu, Zn, Th, Rb, U, Sr, Zr, and V. In addition, preliminary interpretations for total inorganic carbon (TIC), total organic carbon (TOC), total nitrogen (%N), and bulk rock TOC and N isotopic composition of core samples reveal distinct differences between the Bossier and Haynesville formations. Results from previous geochemical studies suggest that the siliciclastic-dominated Bossier formation has less TOC than the underlying Haynesville formation. Furthermore, the Haynesville is much more carbonate-rich (calcite) than the overlying Bossier. An upwardly increasing trend in Si/Al in some cores suggests increasing detrital quartz influx. A linear relationship between Fe and Al suggest that iron is primarily in clay mineral phases in the Haynesville. Enrichments in Mo concentrations and Cr/V ratios reveal periods of anoxic conditions.

  13. Impact of climate on the evolution of carbonate systems during the Middle and Late Jurassic : (Paris Basin, France)

    NASA Astrophysics Data System (ADS)

    Brigaud, Benjamin; Vincent, Benoît

    2013-04-01

    Reconstructions of the Middle and Late Jurassic Sea Surface Temperatures (SST) of western tethyan ocean display short-term changes (0.5 m.y. to 1 m.y.). Recent shallow-marine carbonate systems are potentially very sensitive to climatic variations, as shown during quaternary period (Deschamps et al., 2012). In contrast, in ancient sedimentary systems, the impact of palaeoclimatic variations on carbonate factories is not easy to identify because of interplay between different controlling factors such as eustasy, tectonic, the variety of carbonate producers, and sediment supply. The objective of this study is to propose a detailed facies and stratigraphic framework (at the resolution of a million years) for the Middle and Late Jurassic carbonates (about 30My) of the Paris Basin in order to compare the evolution of the carbonate systems with palaeoclimatic variations, recently well documented for the Jurassic of the western European domain (Dera et al., 2011). The microfacies study display 18 lithofacies that can be merged into seven facies associations along a carbonate ramp. Late Bajocian is marked by the appearance of carbonate facies with scleractinian corals forming lens-shaped bodies and dome-shaped bioherms buildups reaching 10 m thick and 10-20 m lateral extent. Associated to a sea-level fall, an increase of SST seems to favor the development of these corallian buildups. Protected lagoonal environments extend during the Bathonian and are characterized by mioliolid-rich micritic facies. A 2nd order sea-level rise, flooding the Middle Jurassic carbonate ramp system, is followed by a brief drop in SST, suggesting a link between the demise of shallow-marine carbonate factories and the cooling event at the Callovian/Oxfordian transition. The recovery of carbonate production and the location of the carbonate platform during the Oxfordian is controlled by three factors: (1) the geometry of the stratigraphic architecture of thick clay-rich prograding wedges, (2) a 2nd order regressive trend, and (3) a rapid increase of SST during cordatum and transversarium ammonite zones. Protected lagoonal environments developing during the Middle Oxfordian climatic optimum are characterized by an extensive microbial production (Bacinella / Lithocodium, thrombolithic facies). The Late Jurassic begins with another association of (1) sea-level rise, (2) a decrease of SST, and (3) a succession of variable influxes of clastic sediments regularly and increasingly hampering the efficiency of shallow-marine carbonate factories. Finally, the Late Jurassic ends with a drastic change with the appearance of dolomitic facies during a potentially more arid period, coeval with the end of a 1st order regression trend. Ancient carbonate systems are very sensitive to several controlling factors, and only a strong constraint on the evolution of facies and stratigraphic architectures are necessary to isolate the potential climatic influence. Dera, G. et al., 2011. Climatic ups and downs in a disturbed Jurassic world. Geology, 39(3): 215-218. Deschamps, P. et al., 2012. Ice-sheet collapse and sea-level rise at the Bolling warming 14,600 years ago. Nature, 483(7391): 559-564.

  14. Late Jurassic - Early Cretaceous convergent margins of Northeastern Asia with Northwestern Pacific and Proto-Arctic oceans

    NASA Astrophysics Data System (ADS)

    Sokolov, Sergey; Luchitskaya, Marina; Tuchkova, Marianna; Moiseev, Artem; Ledneva, Galina

    2013-04-01

    Continental margin of Northeastern Asia includes many island arc terranes that differ in age and tectonic position. Two convergent margins are reconstructed for Late Jurassic - Early Cretaceous time: Uda-Murgal and Alazeya - Oloy island arc systems. A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk thrust-fold belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeastern Asia and Northwestern Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal island arc system were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos late Paleozoic to early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in backarc basin. Alazeya-Oloy island arc systems consists of Paleozoic and Mesozoic complexes that belong to the convergent margin between Northeastern Asia and Proto-Artic Ocean. It separated structures of the North American and Siberian continents. The Siberian margin was active whereas the North American margin was passive. The Late Jurassic was characterized by termination of a spreading in the Proto-Arctic Ocean and transformation of the latter into the closing South Anyui turbidite basin. In the beginning the oceanic lithosphere and then the Chukotka microcontinent had been subducted beneath the Alazeya-Oloy volcanic belt

  15. Climate-ocean isotopic signals from Late Jurassic-Early Cretaceous (Volgian-Hauterivian) subpolar belemnites, Western Siberia

    NASA Astrophysics Data System (ADS)

    Price, G. D.; Mutterlose, J.

    2003-04-01

    Our understanding of Cretaceous climate and environments has been hampered by the lack of data from high latitudes. This study presents new isotopic data from a late Jurassic-early Cretaceous (Volgian-Hauterivian) interval from the Yatria River, subpolar Urals, Western Siberia. The succession consists of ~70 m of highly fossiliferous silty claystones. These were deposited, during the early Cretaceous, on the southern margin of a large boreal epicontinental marine embayment at a palaeolatitude of ~60-65 degrees N. Oxygen and carbon isotopic compositions have been determined from well preserved belemnite genera Lagonibelus sp., Cylindroteuthis sp. and Acroteuthis sp. The estimated temperatures reveal a shift to cooler temperatures from Late Volgian times through into the Late Valanginian. Some warmer phases are clearly recognised in the earliest Berriasian and the earliest Valanginian. Carbon isotopes display a pattern of relatively stable values across the Jurassic-Cretaceous boundary, followed by a rapid excursion to more positive values in the Valanginian (equivalent to the Campylotoxus zone), which subsequently return to pre-excursion values in the earliest Hauterivian. Surprisingly, these most positive carbon isotope values correspond with the most positive oxygen isotope values (and hence coldest palaeotemperatures) and a period characterised by inferred eustatic sea level fall. In conjunction with identified increases in both glendonites and dropstones for these times, the data support the possibility of limited polar ice during the early Cretaceous. Coincidental falls of sea level imparts further confidence that these events were of a magnitude to effect the Earth as a whole.

  16. A calibrated composite section for the Late Jurassic Reuchenette Formation in northwestern Switzerland

    E-print Network

    Wetzel, Andreas

    Switzerland (?Oxfordian, Kimmeridgian sensu gallico, Ajoie-Region) MARKUS JANK1,ANDREAS WETZEL2 & CHRISTIAN A. MEYER3 Key words. Stratigraphy, biostratigraphy, Kimmeridgian, Jurassic, NW Switzerland, Banné Marls ABSTRACT A new stratigraphical frame for Kimmeridgian sediments of northwestern Switzerland has been

  17. The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia)

    Microsoft Academic Search

    Ursula B. Göhlich; Luis M. Chiappe; James M. Clark; Hans-Dieter Sues

    2005-01-01

    Macelognathus vagans was described by O.C. Marsh in 1884, based on a mandibular symphysis from the Upper Jurassic Morrison Formation of Wyoming. Often considered a dinosaur but later tentatively referred to the Crocodylia, its phylogenetic identity has until now been enigmatic. New material of this species from the Morrison Formation of western Colorado demonstrates its affinities with basal crocodylomorphs commonly

  18. [The Journal of Geology, 2004, volume 112, p. 643653] 2004 by The University of Chicago. All rights reserved. 0022-1376/2004/11206-0003$15.00 Late Jurassic Climates, Vegetation, and Dinosaur Distributions

    E-print Network

    Rees, Allister

    rights reserved. 0022-1376/2004/11206-0003$15.00 643 Late Jurassic Climates, Vegetation, and Dinosaur, and dinosaurs to infer broadscale geographic patterns for the Late Jurassic. These provide a context for our the poles. Most dinosaur remains are known from low-latitude to mar- ginally midlatitude regions where plant

  19. Did an ice sheet exist in Northeast Asia at the Middle-Late Jurassic boundary? (Critical remarks on the article by Y. Donnadieu et al. (2011) "A mechanism for brief glacial episodes in the Mesozoic greenhouse")

    NASA Astrophysics Data System (ADS)

    Chumakov, N. M.; Zakharov, V. A.; Rogov, M. A.

    2014-11-01

    Results of climate modeling of Northeast Russia for the Middle-Late Jurassic boundary (Donnadieu et al., 2011) are critically reviewed. Geological and paleontological data are presented that indicate that the giant ice sheet which, according to the model, covered the entire territory in question at the Middle-Late Jurassic boundary did not exist.

  20. Forced sea-level change in a forearc basin related to subduction of a spreading ridge: the Fossil Bluff Group (Jurassic-Cretaceous), Alexander Island, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Macdonald, David

    2015-04-01

    During the Mesozoic, the Antarctic Peninsula was the site of an active volcanic arc related to the eastwards subduction of proto-Pacific oceanic crust. Alexander Island is the largest of the many islands that lie on the western (fore-arc) side of the Antarctic Peninsula; it forms one of the best-exposed ancient fore-arcs in the world. The pre-Tertiary rocks can be divided into two main units. The LeMay Group (Jurassic-Tertiary) forms the structural basement to Alexander Island and comprises greenschist-facies metasedimentary rocks. It is interpreted as a Mesozoic accretionary prism. The Fossil Bluff Group unconformably overlies and is faulted against the LeMay Group; it represents the sedimentary fill of a coeval fore-arc basin. Subduction ceased due to a series of Cenozoic ridge-trench collisions which began off Alexander Island at 50 Ma and got progressively younger to the north. However, the approach of the ridge can be inferred from the Mesozoic deposits of the Fossil Bluff Group (Jurassic-Cretaceous) in Alexander Island. In this paper, I will show that the ocean floor being subducted became progressively shallower through Jurassic and Cretaceous time (by at least 1,000 m). The result in the forearc basin was a sudden shallowing in water depths from at least 1,000 m at 125 Ma, to emergent at 100 Ma. This forced shallowing ended sedimentation in the basin and resulted in considerable topography on Alexander Island that persists to the present day.

  1. A Late Jurassic Early Cretaceous convergent margin of Northeastern Asia and sedimentary serpentinite

    Microsoft Academic Search

    S. D. Sokolov; Y. Lagabrielle; A. V. Ganelin; D. Kamenetsky; M. I. Tuchkova

    2003-01-01

    The Upper Jurassic Lower Cretaceous complexes of Uda-Murgal island arc were formed along the convergent boundary between the Northeastern Asia and northwestern Pacific plates. The northern part of the complex exposes volcanic, pyroclastic, and sedimentary deposits from the axial zone of the palaeo-volcanic arc; the central part consists of terrigenous\\/tuffaceous rocks of the ancient forearc; and the southern part expose

  2. Geology, petrology and tectonic setting of the Late Jurassic ophiolite in Hokkaido, Japan

    Microsoft Academic Search

    Reishi Takashima; Hiroshi Nishi; Takeyoshi Yoshida

    2002-01-01

    The Gokurakudaira Formation, which has a N–S zonal distribution within a latest Jurassic greenstone belt in Hokkaido Island, Japan, constitutes the uppermost ultramafic–mafic unit of the Horokanai Ophiolite. The following three hypotheses for the origin of the ophiolite have been proposed: (1) a mid-oceanic ridge; (2) an oceanic plateau; and (3) an island arc. The Gokurakudaira Formation can be subdivided

  3. DISCOVERY OF DESEADAN FOSSILS IN THE UPPER MOQUEGUA FORMATION (LATE OLIGOCENE--?EARLY MIOCENE) OF SOUTHERN PERU

    E-print Network

    Sargis, Eric J.

    NOTE DISCOVERY OF DESEADAN FOSSILS IN THE UPPER MOQUEGUA FORMATION (LATE OLIGOCENE--?EARLY MIOCENE. The Deseadan SALMA fossils were found in the Upper Mo- quegua Formation at the summits of Cerro Pan de Azúcar reptile, and a large, predaceous bird. GEOGRAPHIC AND GEOLOGIC SETTING The fossil-bearing sediments

  4. Reevaluation of Australodocus bohetii, a putative diplodocoid sauropod from the Tendaguru Formation of Tanzania, with comment on Late Jurassic sauropod faunal diversity and palaeoecology

    Microsoft Academic Search

    John A. Whitlock

    2011-01-01

    The Late Jurassic sauropod Australodocus bohetii was originally assigned to Diplodocidae, primarily on the basis of bifurcate neural spines. The holotype and paratype materials of A. bohetii are re-examined and found to have closer affinities with Brachiosaurus and relatives than with any diplodocoid. The presence of a second titanosauriform sauropod in the Tanzanian fauna is important for understanding the palaeoecology

  5. Comparative analysis of Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco): implications for sauropod ichnotaxonomy

    Microsoft Academic Search

    Daniel Marty; Matteo Belvedere; Christian A. Meyer; Paolo Mietto; Géraldine Paratte; Christel Lovis; Basil Thüring

    2010-01-01

    Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco) are described and compared. Emphasis is put on track preservation and trackway configuration. The trackways are similar with respect to preservation and the pes and manus track outlines, but they show a large range of trackway configuration. Only one of the trackways reveals

  6. Late Cretaceous Extreme Polar Warmth recorded by Vertebrate Fossils from the High Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Vandermark, D.; Tarduno, J. A.; Brinkman, D.

    2006-12-01

    A vertebrate fossil assemblage from Late Cretaceous (Coniacian-Turonian, ~92 to 86 Ma) rocks on Axel Heiberg Island in the High Canadian Arctic reflects what was once a diverse community of freshwater fishes and reptiles. Paleomagnetic data indicate a paleolatitude of ~71° N for the site; the fossils are from non-migratory fauna, so they can provide insight into Late Cretaceous polar climate. The fossil assemblage includes large (> 2.4 m long) champsosaurs (extinct crocodilelike reptiles). The presence of large champsosaurs suggests a mean annual temperature > 14 °C (and perhaps as great as 25 °C). Here we summarize findings and analyses following the discovery of the fossil-bearing strata in 1996. Examination of larger fish elements, isolated teeth and SEM studies of microstructures indicates the presence of lepisosteids, amiids and teleosts (Friedman et al., 2003) Interestingly, the only other known occurrence of amiids and lepisosteids, fossil or recent, are from intervals of extreme warmth during the Tertiary. Turtles present in the assemblage include Boreralochelys axelheibergensis, a generically indeterminate eucryptodire and a trioychid (Brinkman and Tarduno, 2005). The level of turtle diversity is also comparable to mid-latitude assemblages with a mean annual paleotemperature of at least 14 °C. A large portion of the champsosaur fossil assemblage is comprised of elements from subadults. This dominance of subadults is similar to that seen from low latitude sites. Because of the sensitivity of juveniles to ice formation, the make-up of the Arctic champsosaur population further indicates that the Late Cretaceous saw an interval of extreme warmth and low seasonality. We note the temporal coincidence of these fossils with volcanism at large igneous provinces (including high Arctic volcanism) and suggest that a pulse in volcanic carbon dioxide emissions helped cause the global warmth.

  7. Phytogeographical Implication of Bridelia Will. (Phyllanthaceae) Fossil Leaf from the Late Oligocene of India

    PubMed Central

    Srivastava, Gaurav; Mehrotra, R.C.

    2014-01-01

    Background The family Phyllanthaceae has a predominantly pantropical distribution. Of its several genera, Bridelia Willd. is of a special interest because it has disjunct equally distributed species in Africa and tropical Asia i.e. 18–20 species in Africa-Madagascar (all endemic) and 18 species in tropical Asia (some shared with Australia). On the basis of molecular phylogenetic study on Bridelia, it has been suggested that the genus evolved in Southeast Asia around 33±5 Ma, while speciation and migration to other parts of the world occurred at 10±2 Ma. Fossil records of Bridelia are equally important to support the molecular phylogenetic studies and plate tectonic models. Results We describe a new fossil leaf of Bridelia from the late Oligocene (Chattian, 28.4–23 Ma) sediments of Assam, India. The detailed venation pattern of the fossil suggests its affinities with the extant B. ovata, B. retusa and B. stipularis. Based on the present fossil evidence and the known fossil records of Bridelia from the Tertiary sediments of Nepal and India, we infer that the genus evolved in India during the late Oligocene (Chattian, 28.4–23 Ma) and speciation occurred during the Miocene. The stem lineage of the genus migrated to Africa via “Iranian route” and again speciosed in Africa-Madagascar during the late Neogene resulting in the emergence of African endemic clades. Similarly, the genus also migrated to Southeast Asia via Myanmar after the complete suturing of Indian and Eurasian plates. The emergence and speciation of the genus in Asia and Africa is the result of climate change during the Cenozoic. Conclusions On the basis of present and known fossil records of Bridelia, we have concluded that the genus evolved during the late Oligocene in northeast India. During the Neogene, the genus diversified and migrated to Southeast Asia via Myanmar and Africa via “Iranian Route”. PMID:25353345

  8. Detrital Zircon Ages from Late Jurassic-Early Cretaceous Myrgovaam Basin Sandstones (Rauchua Trough), Western Chukotka, NE Russia

    NASA Astrophysics Data System (ADS)

    Miller, E. L.; Toro, J.; Gehrels, G.; Tuchkova, M.; Katkov, S.

    2004-12-01

    Late Jurassic to Early Cretaceous Myrgovaam Basin sediments (previously Rauchua Trough) are regionally significant because of the stratigraphic constraints they provide on the age and progression of deformation in the Chukotka fold belt, a possible along-strike continuation of the Alaskan Brooks Range fold-and-thrust belt. Existing descriptions of the structural and stratigraphic relations of Myrgovaam Basin sediments to underlying strata are contradictory. Some maps portray the basin fill as deposited unconformably over deformed Triassic and Jurassic strata of the Chukotka fold-belt. In other publications, the deposits are described as structurally detached and imbricated by N-verging thrust sheets (Baranov, 1996). Field studies reveal that underlying strata are tightly folded compared to overlying strata and that the contact is a structural discordance not an unconformity. More locally, we observed arkosic sandstones typical of the Myrgovaam Basin interbedded with underlying Late Jurassic strata or present as submarine channel deposits cut into older rocks, suggesting an original stratigraphic relationship. To reconcile these observations we suggest regional deformation post-dates deposition of Myrgovaam Basin deposits, and that the disharmony in deformational style between underlying thin-bedded Triassic sandstones and shales and (stratigraphically) overlying massive quartzites, is due to their different mechanical properties. Petrographic studies indicate that fine-grained Triassic-early Jurassic sandstones represent a distal recycled orogen source, while Myrgovaam Basin sandstones originated from a proximal orogenic source containing granitoid and crystalline basement rocks (microcline, biotite, muscovite and fragments of multiply deformed schist) and intermediate to felsic volcanic rocks. Laser Ablation ICPMS was used to date zircons (100 grains) from sandstones of the Myrgovaam Basin and compare them to those in Triassic sandstones (300 grains) and verify that Myrgovaam Basin deposits represent a major change in clastic source regions. Zircon populations from Triassic sandstones have age peaks in cumulative probability plots at 247, 298, 380, 453, 504 and 566 Ma (63 percent of zircon population). Only 12 percent of the grains are older than 1.8 Ga. In contrast, zircons from Rauchua Formation sandstones have age peaks at 180, 270, 322, 390-420 (43 percent of the grains). Over 40 percent of the zircons are 1.8-2.2 Ga. The immaturity of sandstones of the Myrgovaam Basin and their abundance of Precambrian zircons, suggest basement-involved faulting during deposition. Since Myrgovaam Basin deposits likely pre-date folding in the Chukotka fold-belt, faulting could be related to either the onset of rifting of the Arctic Alaska-Chukotka plate away from its parental continent or to the beginning of collision-related thrust faulting, but there are no known exposures of 1.8-2.2 Ga rocks in Chukotka. Jurassic zircons, representing a very small part of the population, suggest a proximal magmatic source and provide a maximum age for these strata.

  9. Seasonality in low latitudes during the Oxfordian (Late Jurassic) reconstructed via high-resolution stable isotope analysis of the oyster Actinostreon marshi (J. Sowerby, 1814) from the Kachchh Basin, western India

    NASA Astrophysics Data System (ADS)

    Alberti, Matthias; Fürsich, Franz T.; Pandey, Dhirendra K.

    2013-07-01

    A high-resolution stable isotope (?18O, ?13C) analysis of a specimen of the oyster Actinostreon marshi (J. Sowerby, 1814) from the Lower Oxfordian of the Kachchh Basin in western India was used to reconstruct average seasonal temperatures over a consecutive time interval of 10 years. The recorded temperatures during this period varied around a mean of 13 °C (maximum: 15.1 °C; minimum: 11.4 °C) with a generally low seasonality between 1 and 3 °C. Such weak seasonal changes can be expected from a subtropical palaeolatitude between 25° and 30°S. However, the low average temperatures are in contrast to studies on broadly contemporaneous fossils from Europe and the southern Malagasy Gulf which point to much warmer conditions in these areas. It is therefore proposed that the low temperatures in the Kachchh Basin are caused by upwelling currents which influenced the north-western coast of India during the Late Jurassic.

  10. Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth.

    PubMed

    Hendrickx, Christophe; Mateus, Octávio

    2014-01-01

    Theropod dinosaurs form a highly diversified clade, and their teeth are some of the most common components of the Mesozoic dinosaur fossil record. This is the case in the Lourinhã Formation (Late Jurassic, Kimmeridgian-Tithonian) of Portugal, where theropod teeth are particularly abundant and diverse. Four isolated theropod teeth are here described and identified based on morphometric and anatomical data. They are included in a cladistic analysis performed on a data matrix of 141 dentition-based characters coded in 60 taxa, as well as a supermatrix combining our dataset with six recent datamatrices based on the whole theropod skeleton. The consensus tree resulting from the dentition-based data matrix reveals that theropod teeth provide reliable data for identification at approximately family level. Therefore, phylogenetic methods will help identifying theropod teeth with more confidence in the future. Although dental characters do not reliably indicate relationships among higher clades of theropods, they demonstrate interesting patterns of homoplasy suggesting dietary convergence in (1) alvarezsauroids, therizinosaurs and troodontids; (2) coelophysoids and spinosaurids; (3) compsognathids and dromaeosaurids; and (4) ceratosaurids, allosauroids and megalosaurids.        Based on morphometric and cladistic analyses, the biggest tooth from Lourinhã is referred to a mesial crown of the megalosaurid Torvosaurus tanneri, due to the elliptical cross section of the crown base, the large size and elongation of the crown, medially positioned mesial and distal carinae, and the coarse denticles. The smallest tooth is identified as Richardoestesia, and as a close relative of R. gilmorei based on the weak constriction between crown and root, the "eight-shaped" outline of the base crown and, on the distal carina, the average of ten symmetrically rounded denticles per mm, as well as a subequal number of denticles basally and at mid-crown. Finally, the two medium-sized teeth belong to the same taxon and exhibit pronounced interdenticular sulci between distal denticles, hooked distal denticles for one of them, an irregular enamel texture, and a straight distal margin, a combination of features only observed in abelisaurids. They provide the first record of Abelisauridae in the Jurassic of Laurasia and one of the oldest records of this clade in the world, suggesting a possible radiation of Abelisauridae in Europe well before the Upper Cretaceous. PMID:24869965

  11. Late Triassic rifting and Jurassic-Cretaceous passive margin development of the Southern Neotethys: evidence from the Ad?yaman area, SE Turkey

    NASA Astrophysics Data System (ADS)

    Robertson, A. H. F.; Parlak, O.; Y?ld?r?m, N.; Dumitrica, P.; Tasl?, K.

    2015-05-01

    Evidence of rifting and continental break-up to form the S Neotethys is found within the volcanic-sedimentary Koçali Complex. This is a folded, thrust-imbricated succession that includes lavas, volcaniclastic sediments, pelagic carbonates, radiolarites and manganiferous deposits. Interbedded ribbon cherts contain radiolarians of Late Triassic to Late Jurassic age. The lower part of the succession of Mid?-Late Triassic age (Tarasa Formation) is dominated by enriched mid-ocean ridge basalt (E-MORB). The overlying Late Triassic to Mid-Jurassic interval (Konak Formation) is characterised by intercalations of ocean island basalt and E-MORB. Taking account of structural position, the basalts erupted within the outer part of a continent-ocean transition zone. Continental break-up probably occurred during the Late Triassic (Carnian-Norian). Early to Mid-Jurassic lavas and volcaniclastic sediments record volcanism probably after continental break-up. In addition, the Karadut Complex is a broken formation that is located at a relatively low structural position just above the Arabian foreland. Pelagic carbonates, redeposited carbonates and radiolarites predominate. Radiolarians are dated as Early to Mid-Jurassic and Late Cretaceous in age. The pelagic carbonates include planktic foraminifera of Late Cretaceous age. The Karadut Complex resulted from the accumulation of calcareous gravity flows, pelagic carbonate and radiolarites in a relatively proximal, base-of-slope setting. After continental break-up, MORB and ophiolitic rocks formed within the S Neotethys further north. Tectonic emplacement onto the Arabian platform took place by earliest Maastrichtian time. Regional interpretation is facilitated by comparisons with examples of Triassic rifting and continental break-up in the eastern Mediterranean region and elsewhere.

  12. Current Status of the Late Triassic and Early Jurassic APTS from Continental Sediments and Correlation with Standard Marine Stages

    NASA Astrophysics Data System (ADS)

    Kent, D. V.; Olsen, P. E.; Muttoni, G.

    2014-12-01

    A reproducible geomagnetic polarity template for the Late Triassic and earliest Jurassic continues to be that determined from ~5,000 meters of cored section in the Newark basin and ~2,500 meters of outcrop section in the Hartford basin, sampled at nominal ~20 kyr intervals according to a well-developed climate cyclicity that characterizes the lacustrine strata present in all but the fluviatile portions of the basins [Kent & Olsen, 1999, 2008 JGR]. The age model is based on the 405 kyr Milankovich climate cycle and pegging the sequence to high precision U-Pb dating of the Central Atlantic Magmatic Province (CAMP) at 201.6 to 200.9 Ma [Blackburn+2013 Science], the initiation of which is practically coincident with the end-Triassic extinction level (formerly set to 202 Ma) and within a climatic precession cycle after magnetochron E23r. The resulting astrochronostratigraphic polarity time scale (APTS) has 66 Poisson-distributed polarity intervals from chrons E8r (~225 Ma) to H27n (~199 Ma) with a constant sediment-accumulation rate extrapolation to chron E1r (~233 Ma). Magnetostratigraphic correlations from the most complete and usually the thickest Tethyan marine sections suggest that the Carnian/Norian boundary occurs within ~E7n [Channell+2003 PPP; Muttoni+2004 GSAB] at an APTS age of 227.5 Ma and for the Norian/Rhaetian boundary anywhere from E16n [Husing+2011 EPSL] at ~210.5 Ma to E20r [Maron+2014 Geology] at ~205.4 Ma depending on choice of conodont taxa, whereas the Hettangian/Sinemurian boundary can be placed at ~199.5 Ma within the marine equivalent of H25r [Husing+2014 EPSL]. These APTS ages are in substantive agreement with available high-precision dates in marine strata for the late Carnian [231 Ma: Furin+2006 Geology], latest Norian [205.5 Ma: Wotslaw+2014 Geology], and the boundaries of the Triassic/Jurassic [201.3 Ma: Guex+2012 PPP] and the Hettangian/Sinemurian [199.5 Ma: Schaltegger+2008 EPSL]. Carnian magnetostratigraphy needs to be improved but attempts to make a composite magnetostratigraphic sequence for the Late Triassic by merging disparate marine and non-marine records have not produced a clearer signal. The Newark-Hartford APTS already provides a framework for long-distance correlation and dating, for example, the timing of dinosaur dispersal across Pangea [Kent+2014 PNAS].

  13. Paleomagnetism of the Middle-Late Jurassic to Cretaceous red beds from the Peninsular Thailand: Implications for collision tectonics

    NASA Astrophysics Data System (ADS)

    Yamashita, Itaru; Surinkum, Adichat; Wada, Yutaka; Fujihara, Makoto; Yokoyama, Masao; Zaman, Haider; Otofuji, Yo-ichiro

    2011-02-01

    Jurassic to Cretaceous red sandstones were sampled at 33 sites from the Khlong Min and Lam Thap formations of the Trang Syncline (7.6°N, 99.6°E), the Peninsular Thailand. Rock magnetic experiments generally revealed hematite as a carrier of natural remanent magnetization. Stepwise thermal demagnetization isolates remanent components with unblocking temperatures of 620-690 °C. An easterly deflected declination ( D = 31.1°, I = 12.2°, ?95 = 13.9°, N = 9, in stratigraphic coordinates) is observed as pre-folding remanent magnetization from North Trang Syncline, whereas westerly deflected declination ( D = 342.8°, I = 22.3°, ?95 = 12.7°, N = 13 in geographic coordinates) appears in the post-folding remanent magnetization from West Trang Syncline. These observations suggest an occurrence of two opposite tectonic rotations in the Trang area, which as a part of Thai-Malay Peninsula received clockwise rotation after Jurassic together with Shan-Thai and Indochina blocks. Between the Late Cretaceous and Middle Miocene, this area as a part of southern Sundaland Block experienced up to 24.5° ± 11.5° counter-clockwise rotation with respect to South China Block. This post-Cretaceous tectonic rotation in Trang area is considered as a part of large scale counter-clockwise rotation experienced by the southern Sundaland Block (including the Peninsular Malaysia, Borneo and south Sulawesi areas) as a result of Australian Plate collision with southeast Asia. Within the framework of Sundaland Block, the northern boundary of counter-clockwise rotated zone lies between the Trang area and the Khorat Basin.

  14. Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal

    PubMed Central

    Araújo, Ricardo; Castanhinha, Rui; Martins, Rui M. S.; Mateus, Octávio; Hendrickx, Christophe; Beckmann, F.; Schell, N.; Alves, L. C.

    2013-01-01

    The non-avian saurischians that have associated eggshells and embryos are represented only by the sauropodomorph Massospondylus and Coelurosauria (derived theropods), thus missing the basal theropod representatives. We report a dinosaur clutch containing several crushed eggs and embryonic material ascribed to the megalosaurid theropod Torvosaurus. It represents the first associated eggshells and embryos of megalosauroids, thus filling an important phylogenetic gap between two distantly related groups of saurischians. These fossils represent the only unequivocal basal theropod embryos found to date. The assemblage was found in early Tithonian fluvial overbank deposits of the Lourinhã Formation in West Portugal. The morphological, microstructural and chemical characterization results of the eggshell fragments indicate very mild diagenesis. Furthermore, these fossils allow unambiguous association of basal theropod osteology with a specific and unique new eggshell morphology. PMID:23722524

  15. Ecpagloxylon mathiesenii gen. nov. et sp. nov., a Jurassic wood from Greenland with several primitive angiosperm features

    Microsoft Academic Search

    Marc Philippe; Gilles Cuny; Arden Bashforth

    2010-01-01

    Fossil wood specimens from the late Early–early Middle Jurassic of Jameson Land, Eastern Greenland, have several unexpected\\u000a features: tracheids of irregular size and shape, thinly pitted ray cell walls, heterogeneous rays, partially scalariform radial\\u000a pitting, both areolate and simple pits, and pitted elements associated with rays. These characters diverge markedly from those\\u000a typical of Jurassic wood, which usually conform to

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  17. Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas

    Microsoft Academic Search

    D. W. Steadman; Richard Franz; G. S. Morgan; N. A. Albury; Brian Kakuk; Kenneth Broad; S. E. Franz; Keith Tinker; M. P. Pateman; T. A. Lott; D. M. Jarzen; D. L. Dilcher

    2007-01-01

    We report Quaternary vertebrate and plant fossils from Sawmill Sink, a ''blue hole'' (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from 4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species

  18. Contemporaneous Trace and Body Fossils from a Late Pleistocene Lakebed in Victoria, Australia, Allow Assessment of Bias in the Fossil Record

    PubMed Central

    Camens, Aaron Bruce; Carey, Stephen Paul

    2013-01-01

    The co-occurrence of vertebrate trace and body fossils within a single geological formation is rare and the probability of these parallel records being contemporaneous (i.e. on or near the same bedding plane) is extremely low. We report here a late Pleistocene locality from the Victorian Volcanic Plains in south-eastern Australia in which demonstrably contemporaneous, but independently accumulated vertebrate trace and body fossils occur. Bite marks from a variety of taxa are also present on the bones. This site provides a unique opportunity to examine the biases of these divergent fossil records (skeletal, footprints and bite marks) that sampled a single fauna. The skeletal record produced the most complete fauna, with the footprint record indicating a markedly different faunal composition with less diversity and the feeding traces suggesting the presence, amongst others, of a predator not represented by either the skeletal or footprint records. We found that the large extinct marsupial predator Thylacoleo was the only taxon apparently represented by all three records, suggesting that the behavioral characteristics of large carnivores may increase the likelihood of their presence being detected within a fossil fauna. In contrast, Diprotodon (the largest-ever marsupial) was represented only by trace fossils at this site and was absent from the site's skeletal record, despite its being a common and easily detected presence in late Pleistocene skeletal fossil faunas elsewhere in Australia. Small mammals absent from the footprint record for the site were represented by skeletal fossils and bite marks on bones. PMID:23301008

  19. A Late Jurassic Early Cretaceous convergent margin of Northeastern Asia and sedimentary serpentinite

    NASA Astrophysics Data System (ADS)

    Sokolov, S. D.; Lagabrielle, Y.; Ganelin, A. V.; Kamenetsky, D.; Tuchkova, M. I.

    2003-04-01

    The Upper Jurassic Lower Cretaceous complexes of Uda-Murgal island arc were formed along the convergent boundary between the Northeastern Asia and northwestern Pacific plates. The northern part of the complex exposes volcanic, pyroclastic, and sedimentary deposits from the axial zone of the palaeo-volcanic arc; the central part consists of terrigenous/tuffaceous rocks of the ancient forearc; and the southern part expose turbidites and terrigenous melanges of the accretionary prism. Serpentinite bodies and associated sedimentary serpentinites occur among Lower Cretaceous terrigeneous rocks of the Upupkin terrane in the central part of the Penzhina segment of the island arc. All the serpentinite bodies are rootless and, in plan view, are equant or elongate in shape. The largest ultramafic outcrop (42 km2 in area, 12 km long, 4 km in maximal width) is exposed on the slopes of Mt. Dlinnaya among terrigenous rocks of the Tylakryl Fm. (Hauterivian Barremian). In cross section, this is a sheet ca. 1 km thick dipping generally S30° 60°E Ultramafic rocks include massive and brecciated, serpentinites and serpentinized harzburgites; lherzolites, and dunites. Minor bodies of amphibolized gabbro are less abundant. Sedimentary serpentinites are represented by breccias, conglomerates, gravelstones, sandstones, and siltstones. Monomict, polymict, well-bedded, and chaotic varieties are distinguished. The "monomictic" sedimentary serpentinite lithologies consist only of fragments of ultramafic rocks of various types. The “polymictic” lithologies contain fragments of gabbro, metavolcanites, diabase, amphibolite, spilite, metachert, siltstone, quartz mica schist, and marble along with fragments of various types of serpentinite. Sedimentary serpentinites of the Penzhina segment were formed on the forearc slope of the Uda Murgal island arc due to emplacement and erosion of serpentinite diapirs and are viewed as possible equivalent of forearc serpentinite seamounts of the Mariana and Izu Bonin convergent boundary (ODP Leg 125). Research is supported by INTAS (96-1880) and RFBR (02-05-64217) grants.

  20. New geochronologic constraints on Early, Middle, and Late Jurassic orogenesis in the Klamath Mountains

    SciTech Connect

    Donato, M.M. (Geological Survey, Menlo Park, CA (United States)); Hacker, B.R.; McWilliams, M.O.

    1993-04-01

    More than 40 new Ar/Ar ages, in conjunction with radiometric data published by many other authors, allow improved recognition of the spatial and temporal ranges of magmatic, metamorphic and deformational events associated with the formation of continental crust in the Klamath Mountains. Magmatism in earliest Jurassic time, [approx]200 Ma, is now recognized to have been widespread. Volcanoplutonic arcs of this age are present in upper levels of the Rattlesnake Creek terrane and in lower levels of the North Fork/Salmon River terrane. Roughly 200 Ma metaplutonic rocks are also found in the basement of the Rogue/Chetco arc, Preston Peak mafic complex, and Lems Ridge olistostrome. From 167--155 Ma, magmatic and structural extension occurred along a NW-SE corridor restricted to the northern Klamaths. Igneous rocks include the Wooley Creek, Preston Peak, Josephine, and Rogue/Chetco suites, and the Marble Mountains fault may represent a contemporaneous normal fault. The southern edge of the extended corridor is the Salmon tectonic line of Irwin (1985), but the northern boundary has not been recognized or named. Both boundaries were presumably transfer zones accommodating differential subhorizontal extension, but many details are still to be determined. The Siskiyou and Nevadan orogenies can no longer be assigned specific, narrow time windows and may have outlived their usefulness as currently defined. Enough geochronologic data are now available to consider the ages and characteristics of specific plutons, deformation fabrics, and metamorphic minerals in individual areas, rather than assuming such events occur throughout the orogen within specific time ranges.

  1. Late glacial climate estimates for southern Nevada: The ostracode fossil record

    SciTech Connect

    Forester, R.M. [Geological Survey, Denver, CO (United States); Smith, A.J. [Kent State Univ., OH (United States)

    1995-10-01

    Climate change plays an important role in determining as possible long term hydrological performance of the potential high level nuclear waste repository within Yucca Mountain, Nevada. Present-day global circulation results in this region having an arid to semi-arid climate characterized by hot and relatively dry summers. Global circulation during the late glacial (about 14 to 20 ka) was very different from the present-day. Preliminary study of late-glacial fossil ostracodes from {open_quotes}marsh deposits{close_quotes} in the upper Las Vegas Valley suggests mean annual precipitation may have been four times higher, while mean annual temperature may have been about 10{degrees}C cooler than today. A major difference between present-day and late-glacial climate was likely the existence of cooler, cloudier, and wetter summers in the past.

  2. A Jurassic mammal from South America

    Microsoft Academic Search

    Oliver W. M. Rauhut; Thomas Martin; Edgardo Ortiz-Jaureguizar; Pablo Puerta

    2002-01-01

    The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and

  3. Growth and linkage of a segmented normal fault zone; the Late Jurassic Murchison Statfjord North Fault, northern North Sea

    NASA Astrophysics Data System (ADS)

    Young, Mike J.; Gawthorpe, Rob L.; Hardy, Stuart

    2001-12-01

    The structure of the 25 km long northeastern portion of the Murchison-Statfjord North Fault Zone and adjacent syn-rift stratigraphy are integrated to reconstruct the temporal and spatial evolution during c. 30.5 myr of Late Jurassic, North Sea rifting. Based on a structural analysis ( D- d data) alone, approximately 14 precursor fault strands are identified. Incorporation of stratigraphic data shows that only six of these strands were important in controlling stratal architecture and distribution. Three main stages in the evolution of the fault zone are recorded in the syn-rift stratigraphy and are biostratigraphically constrained. These are: (1) following initiation of rifting, six isolated fault strands developed (each <4 km long) and controlled the stratigraphy for c. 13 myr; (2) the isolated strands linked along-strike forming two >9 km long fault segments separated by a 2 km wide relay ramp, that controlled the stratigraphy for at least the following c. 10.5 myr; and (3) the two fault segments hard-linked forming a single, continuous fault trace during the final c. 7 myr of rifting. The results of this study reveal the necessity to adopt an integrated structural and stratigraphic approach when reconstructing the evolution of normal fault zones. The results may also help to further constrain models of fault evolution.

  4. The Science Behind Jurassic Park

    NSDL National Science Digital Library

    "The Science Behind Jurassic Park" is an html document describing how world renowned paleontologist Jack Horner is using computers and CAT scan machines to peer inside 30 million year old dinosaur fossils.

  5. Tectonic reconstruction of Uda-Murgal arc and the Late Jurassic and Early Cretaceous convergent margin of Northeast Asia-Northwest Pacific

    NASA Astrophysics Data System (ADS)

    Sokolov, S. D.; Bondarenko, G. Ye.; Khudoley, A. K.; Morozov, O. L.; Luchitskaya, M. V.; Tuchkova, M. I.; Layer, P. W.

    2009-09-01

    A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk fold and thrust belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeast Asia and Northwest Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal arc were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos Late Paleozoic to Early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in a backarc basin. Accretionary prisms of the Uda-Murgal arc and accreted terranes contain fragments of Permian, Triassic to Jurassic and Jurassic to Cretaceous (Tithonian-Valanginian) oceanic crust and Jurassic ensimatic island arcs. Paleomagnetic and faunal data show significant displacement of these oceanic complexes and the terranes of the Taigonos Peninsula were originally parts of the Izanagi oceanic plate.

  6. The Late Precambrian fossil Kimberella is a mollusc-like bilaterian organism

    NASA Astrophysics Data System (ADS)

    Fedonkin, Mikhail A.; Waggoner, Benjamin M.

    1997-08-01

    The fossil Kimberella quadrata was originally described from late Precambrian rocks of southern Australia. Reconstructed as a jellyfish, it was later assigned to the cubozoans (`box jellies'), and has been cited as a clear instance of an extant animal lineage present before the Cambrian. Until recently, Kimberella was known only from Australia, with the exception of some questionable north Indian specimens. We now have over thirty-five specimens of this fossil from the Winter Coast of the White Sea in northern Russia. Our study of the new material does not support a cnidarian affinity. We reconstruct Kimberella as a bilaterally symmetrical, benthic animal with a non-mineralized, univalved shell, resembling a mollusc in many respects. This is important evidence for the existence of large triploblastic metazoans in the Precambrian and indicates that the origin of the higher groups of protostomes lies well back in the Precambrian.

  7. Trace fossil evidence for late Permian shallow water condition in Guryul ravine, Kashmir, India

    NASA Astrophysics Data System (ADS)

    Parcha, Suraj; Horacek, Micha; Krystyn, Leopold; Pandey, Shivani

    2015-04-01

    The present study is focused on the Late Permian (Changhsingian) succession, present in the Guryul ravine, Kashmir Basin. The basin has a complete Cambro-Triassic sequence and thus contains a unique position in the geology of Himalaya. The Guryul Ravine Permian mainly comprises of mixed siliciclastic-carbonate sediments deposited in a shallow-shelf or ramp setting. The present assemblage of Ichnofossils is the first significant report of trace fossils in the Guryul ravine since early reports in the 1970s. The Ichnofossils reported from this section include: Diplichnites, Dimorphichnus, Monomorphichnus, Planolites, Skolithos along with burrow, scratch marks and annelid worm traces?. The ichnofossils are mainly preserved in medium grain sandstone-mudstone facies. The Ichnofossils are widely distributed throughout the section and are mostly belonging to arthropods and annelid origin, showing behavioral activity, mainly dwelling and feeding, and evidence the dominant presence of deposit feeders. The vertical to slightly inclined biogenic structures are commonly recognized from semi-consolidated substrate which are characteristic features of the near shore/foreshore marine environment, with moderate to high energy conditions. The topmost layer of silty shale contains trace fossils like Skolithos and poorly preserved burrows. The burrow material filled is same as that of host rock. The studied Zewan C and D sequence represents the early to late part of the Changhsingian stage, from 40 to 5 m below the top of Zewan D member with bioturbation still evident in some limestone layers till 2 metres above. No trace fossils could be recognized in the topmost 3 m beds of Zewan D due to their gliding related amalgamated structure. The widespread distribution of traces and their in situ nature will be useful for interpretation of the paleoecological and paleoenvironmental conditions during the late Permian in the Guryul ravine of Kashmir.

  8. Post-Late Jurassic, pre-late Eocene strike-slip faulting in west-central Utah

    SciTech Connect

    Robinson, J.P.

    1993-04-01

    Two events of strike-slip faulting interpreted to be of Late Mesozoic-Early Tertiary age are recorded in the northern Deep Creek Mountains. These fault systems display principal detachment zones that strike N50W and N84E. Both fault systems are manifested as fault mosaics, locally anastomosing with local duplex formation. They are interpreted to represent first-order structures that operated independently of other strain regimes. A quartz monzonite stock dated 38 Ma displays strong control of the intrusion by the NW-striking faults. That, in addition to cross-cutting relationships between the NW-striking faults and a granodiorite dated 152 Ma place age constraints on the strike-slip faulting. The ENE-striking faults are younger than the NW-striking faults and are interpreted to be older than the quartz monzonite, although this relationship is ambiguous. Strike-separation on the major NW-striking faults is on the order of 3 km. Offsets of similar magnitude or greater are interpreted for the ENE-striking faults, although this remains unquantified. Despite the small area of influence, relatively minor displacements, and broad time frame of occurrence, these faults have some regional significance. If Cretaceous-aged, the strike-slip faults are markedly different than the extensional structures that formed in the internal zone' of the Cordilleran thrust belt. If Tertiary-aged, the strike-slip faults represent an age of structure with few documented examples in the eastern Basin and Range.

  9. The Cranial Osteology and Feeding Ecology of the Metriorhynchid Crocodylomorph Genera Dakosaurus and Plesiosuchus from the Late Jurassic of Europe

    PubMed Central

    Young, Mark T.; Brusatte, Stephen L.; de Andrade, Marco Brandalise; Desojo, Julia B.; Beatty, Brian L.; Steel, Lorna; Fernández, Marta S.; Sakamoto, Manabu; Ruiz-Omeñaca, Jose Ignacio; Schoch, Rainer R.

    2012-01-01

    Background Dakosaurus and Plesiosuchus are characteristic genera of aquatic, large-bodied, macrophagous metriorhynchid crocodylomorphs. Recent studies show that these genera were apex predators in marine ecosystems during the latter part of the Late Jurassic, with robust skulls and strong bite forces optimized for feeding on large prey. Methodology/Principal Findings Here we present comprehensive osteological descriptions and systematic revisions of the type species of both genera, and in doing so we resurrect the genus Plesiosuchus for the species Dakosaurus manselii. Both species are diagnosed with numerous autapomorphies. Dakosaurus maximus has premaxillary ‘lateral plates’; strongly ornamented maxillae; macroziphodont dentition; tightly fitting tooth-to-tooth occlusion; and extensive macrowear on the mesial and distal margins. Plesiosuchus manselii is distinct in having: non-amblygnathous rostrum; long mandibular symphysis; microziphodont teeth; tooth-crown apices that lack spalled surfaces or breaks; and no evidence for occlusal wear facets. Our phylogenetic analysis finds Dakosaurus maximus to be the sister taxon of the South American Dakosaurus andiniensis, and Plesiosuchus manselii in a polytomy at the base of Geosaurini (the subclade of macrophagous metriorhynchids that includes Dakosaurus, Geosaurus and Torvoneustes). Conclusions/Significance The sympatry of Dakosaurus and Plesiosuchus is curiously similar to North Atlantic killer whales, which have one larger ‘type’ that lacks tooth-crown breakage being sympatric with a smaller ‘type’ that has extensive crown breakage. Assuming this morphofunctional complex is indicative of diet, then Plesiosuchus would be a specialist feeding on other marine reptiles while Dakosaurus would be a generalist and possible suction-feeder. This hypothesis is supported by Plesiosuchus manselii having a very large optimum gape (gape at which multiple teeth come into contact with a prey-item), while Dakosaurus maximus possesses craniomandibular characteristics observed in extant suction-feeding odontocetes: shortened tooth-row, amblygnathous rostrum and a very short mandibular symphysis. We hypothesise that trophic specialisation enabled these two large-bodied species to coexist in the same ecosystem. PMID:23028723

  10. Evolutionary History of Atmospheric CO2 during the Late Cenozoic from Fossilized Metasequoia Needles

    PubMed Central

    Wang, Yuqing; Momohara, Arata; Wang, Li; Lebreton-Anberrée, Julie; Zhou, Zhekun

    2015-01-01

    The change in ancient atmospheric CO2 concentrations provides important clues for understanding the relationship between the atmospheric CO2 concentration and global temperature. However, the lack of CO2 evolution curves estimated from a single terrestrial proxy prevents the understanding of climatic and environmental impacts due to variations in data. Thus, based on the stomatal index of fossilized Metasequoia needles, we reconstructed a history of atmospheric CO2 concentrations from middle Miocene to late Early Pleistocene when the climate changed dramatically. According to this research, atmospheric CO2 concentration was stabile around 330–350 ppmv in the middle and late Miocene, then it decreased to 278–284 ppmv during the Late Pliocene and to 277–279 ppmv during the Early Pleistocene, which was almost the same range as in preindustrial time. According to former research, this is a time when global temperature decreased sharply. Our results also indicated that from middle Miocene to Pleistocene, global CO2 level decreased by more than 50 ppmv, which may suggest that CO2 decrease and temperature decrease are coupled. PMID:26154449

  11. Carbon-isotope record of the Early Jurassic (Toarcian) Oceanic Anoxic Event from fossil wood and marine carbonate (Lusitanian Basin, Portugal)

    NASA Astrophysics Data System (ADS)

    Hesselbo, Stephen P.; Jenkyns, Hugh C.; Duarte, Luis V.; Oliveira, Luiz C. V.

    2007-01-01

    The Toarcian Oceanic Anoxic Event (OAE) in the Early Jurassic (˜ 183 Ma ago) was characterized by widespread near-synchronous deposition of organic-rich shales in marine settings, as well as perturbations to several isotopic systems. Characteristically, two positive carbon-isotope excursions in a range of materials are separated by an abrupt negative shift. Carbon-isotope profiles from Toarcian fossil wood collected in England and Denmark have previously been shown to exhibit this large drop (˜ - 7‰) in ?13C values, interpreted as due to an injection of isotopically light CO 2 into the ocean-atmosphere system. However, the global nature of this excursion has been challenged on the basis of carbon-isotope data from nektonic marine molluscs (belemnites), which exhibit heavier than expected carbon-isotope values. Here we present new data, principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at Peniche, coastal Portugal. This section is low in organic carbon (average TOC = ˜ 0.5%), and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin. The carbon-isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion, which parallels exactly the profile based on bulk carbonate samples from the same section, albeit with approximately twice the amplitude (˜ - 8‰ in wood versus ˜ - 3.5‰ in carbonate). These data indicate that the negative carbon-isotope excursion affected the atmosphere and, by implication, the global ocean as well. The difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion, for which there is independent evidence from marine osmium-isotope records and, plausibly, changes in atmospheric CO 2 content, for which independent evidence is also available. The Peniche succession is also notable for the occurrence of re-deposited sediments: their lowest occurrence coincides with the base of the negative excursion and their highest occurrence coincides with its top. Thus, slope instability and sediment supply could have been strongly linked to the global environmental perturbation, an association that may misleadingly simulate the effects of sea-level fall.

  12. Fossil plant relative abundances indicate sudden loss of Late Triassic biodiversity in East Greenland.

    PubMed

    McElwain, Jennifer C; Wagner, Peter J; Hesselbo, Stephen P

    2009-06-19

    The pace of Late Triassic (LT) biodiversity loss is uncertain, yet it could help to decipher causal mechanisms of mass extinction. We investigated relative abundance distributions (RADs) of six LT plant assemblages from the Kap Stewart Group, East Greenland, to determine the pace of collapse of LT primary productivity. RADs displayed not simply decreases in the number of taxa, but decreases in the number of common taxa. Likelihood tests rejected a hypothesis of continuously declining diversity. Instead, the RAD shift occurred over the upper two-to-four fossil plant assemblages and most likely over the last three (final 13 meters), coinciding with increased atmospheric carbon dioxide concentration and global warming. Thus, although the LT event did not induce mass extinction of plant families, it accompanied major and abrupt change in their ecology and diversity. PMID:19541995

  13. Strontium isotopes in Early Jurassic seawater

    NASA Astrophysics Data System (ADS)

    Jones, Charles E.; Jenkyns, Hugh C.; Hesselbo, Stephen P.

    1994-02-01

    The analysis of well-preserved, well-dated belemnites and oysters from the Jurassic of Great Britain has resulted in a well-constrained, detailed seawater strontium isotope curve for the Early Jurassic. The preservation of fossil low-Mg calcite was monitored using Mn, Fe, ?13C, and ?18O. Iron was the most useful indicator, with about 75% of the samples containing more than 150 ppm Fe showing 87Sr /86Sr ratios elevated relative to adjacent points on the curve. High Mn concentrations less often correlated with elevated 87Sr /86Sr ratios; however, low Mn concentrations (<25 ppm Mn) were consistently associated with apparently well-preserved 87Sr /86Sr . ?13C and ?18O proved to be insensitive to diagenesis as it affects 87Sr /86Sr . The principal features of the strontium isotope curve include a rise to about 0.70772 in the latest Triassic and earliest Jurassic (Hettangian). From the Hettangian, the curve begins a roughly linear descent through the Sinemurian and Pliensbachian. Following a small levelling off and increase in the late Pliensbachian, the curve falls rapidly to its Early Jurassic minimum of 0.70706. It then gently increases through the Toarcian until the falciferum zone, where it shows an apparently abrupt increase to 0.70719 before continuing its slow increase to 0.70728 in the Aalenian-Bajocian (Middle Jurassic). This reversal of the downwards trend established in the Sinemurian and Pliensbachian had not been previously identified. The Sinemurian and Pliensbachian section of the curve potentially allows correlation and dating to within 1 or 2 ammonite subzones (±0.5 to 1 Ma).

  14. Multi-stage metamorphism in the South Armenian Block during the Late Jurassic to Early Cretaceous: Tectonics over south-dipping subduction of Northern branch of Neotethys

    NASA Astrophysics Data System (ADS)

    Hässig, M.; Rolland, Y.; Sahakyan, L.; Sosson, M.; Galoyan, G.; Avagyan, A.; Bosch, D.; Müller, C.

    2015-04-01

    The geologic evolution of the South Armenian Block (SAB) in the Mesozoic is reconstructed from a structural, metamorphic, and geochronologic study including U-Pb and 40Ar/39Ar dating. The South Armenian Block Crystalline Basement (SABCB) outcrops solely in a narrow tectonic window, NW of Yerevan. The study of this zone provides key and unprecedented information concerning closing of the Northern Neotethys oceanic domain north of the Taurides-Anatolides platform from the Middle Jurassic to the Early Cretaceous. The basement comprises of presumed Proterozoic orthogneiss overlain by metamorphosed pelites as well as intrusions of granodiorite and leucogranite during the Late Jurassic and Early Cretaceous. Structural, geochronological and petrological observations show a multiphased evolution of the northern margin of the SAB during the Late Jurassic and Early Cretaceous. A south-dipping subduction under the East Anatolian Platform-South Armenian Block (EAP-SAB) is proposed in order to suit recent findings pertaining emplacement of relatively hot subduction related granodiorite as well as the metamorphic evolution of the crystalline basement in the Lesser Caucasus area. The metamorphism is interpreted as evidencing: (1) M1 Barrovian MP-MT conditions (staurolite-kyanite) at c. 157-160 Ma and intrusion of dioritic magmas at c. 150-156 Ma, (2) near-adiabatic decompression is featured by partial melting and production of leucogranites at c. 153 Ma, followed by M2 HT-LP conditions (andalusite-K-feldspar). A phase of shearing and recrystallization is ascribed to doming at c. 130-150 Ma and cooling at 400 °C by c. 123 Ma (M3). Structural observations show (1) top to the north shearing during M1 and (2) radial extension during M2. The extensional event ends by emplacement of a thick detrital series along radial S, E and W-dipping normal faults. Further, the crystalline basement is unconformably covered by Upper Cretaceous-Paleocene series dated by nannofossils, evolving from Maastrichtian marly sandstones to Paleocene limestones.

  15. An unusual braincase (?Stokesosaurus clevelandi) from the Cleveland-Lloyd Dinosaur Quarry, Utah (Morrison Formation; Late Jurassic)

    Microsoft Academic Search

    Daniel J. Chure; James H. Madsen

    1998-01-01

    A basicranium from the Cleveland-Lloyd Dinosaur Quarry is the most advanced of any Jurassic theropod, combining features considered synapomorphies for two different Cretaceous theropod families, the Itemiridae and Tyrannosauridae. The basicranium has large pockets on the basipterygoid processes, flat basal tubera, and is extremely shortened, so that the basisphenoidal sinus is visible only in occipital view and the basiptyerygoid processes

  16. Tracking the Late Jurassic apparent (or true) polar shift in U-Pb-dated kimberlites from cratonic North America (Superior Province of Canada)

    NASA Astrophysics Data System (ADS)

    Kent, Dennis V.; Kjarsgaard, Bruce A.; Gee, Jeffrey S.; Muttoni, Giovanni; Heaman, Larry M.

    2015-04-01

    Different versions of a composite apparent polar wander (APW) path of variably selected global poles assembled and averaged in North American coordinates using plate reconstructions show either a smooth progression or a large (˜30°) gap in mean paleopoles in the Late Jurassic, between about 160 and 145 Ma. In an effort to further examine this issue, we sampled accessible outcrops/subcrops of kimberlites associated with high-precision U-Pb perovskite ages in the Timiskaming area of Ontario, Canada. The 154.9 ± 1.1 Ma Peddie kimberlite yields a stable normal polarity magnetization that is coaxial within less than 5° of the reverse polarity magnetization of the 157.5 ± 1.2 Ma Triple B kimberlite. The combined ˜156 Ma Triple B and Peddie pole (75.5°N, 189.5°E, A95 = 2.8°) lies about midway between igneous poles from North America nearest in age (169 Ma Moat volcanics and the 146 Ma Ithaca kimberlites), showing that the polar motion was at a relatively steady yet rapid (˜1.5°/Myr) pace. A similar large rapid polar swing has been recognized in the Middle to Late Jurassic APW path for Adria-Africa and Iran-Eurasia, suggesting a major mass redistribution. One possibility is that slab breakoff and subduction reversal along the western margin of the Americas triggered an episode of true polar wander.

  17. Late Early Permian plant fossils from the Canadian High Arctic: a rare paleoenvironmental\\/climatic window in northwest Pangea

    Microsoft Academic Search

    Ben A LePage; Benoit Beauchamp; Hermann W Pfefferkorn; John Utting

    2003-01-01

    Recently discovered megafossil plant remains in late Early Permian (Kungurian) marine sediments on northern Axel Heiberg Island, Canadian Arctic Archipelago, provide a much needed datum point for paleobiogeographic considerations in this part of North America. The fossil plants represent at least ten families belonging to several major groups (sphenopsids, ferns, pteridosperms, ginkgos, cordaitaleans, and conifers). The conifers Rufloria and Walchia

  18. Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas.

    PubMed

    Steadman, David W; Franz, Richard; Morgan, Gary S; Albury, Nancy A; Kakuk, Brian; Broad, Kenneth; Franz, Shelley E; Tinker, Keith; Pateman, Michael P; Lott, Terry A; Jarzen, David M; Dilcher, David L

    2007-12-11

    We report Quaternary vertebrate and plant fossils from Sawmill Sink, a "blue hole" (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from approximately 4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species (tortoise Chelonoidis undescribed sp. and Caracara Caracara creightoni) and two extant species no longer in The Bahamas (Cuban crocodile, Crocodylus rhombifer; and Cooper's or Gundlach's Hawk, Accipiter cooperii or Accipiter gundlachii). A different, inorganic bone deposit on a limestone ledge in Sawmill Sink is a Late Pleistocene owl roost that features lizards (one species), snakes (three species), birds (25 species), and bats (four species). The owl roost fauna includes Rallus undescribed sp. (extinct; the first Bahamian flightless rail) and four other locally extinct species of birds (Cooper's/Gundlach's Hawk, A. cooperii/gundlachii; flicker Colaptes sp.; Cave Swallow, Petrochelidon fulva; and Eastern Meadowlark, Sturnella magna) and mammals (Bahamian hutia, Geocapromys ingrahami; and a bat, Myotis sp.). The exquisitely preserved fossils from Sawmill Sink suggest a grassy pineland as the dominant plant community on Abaco in the Late Pleistocene, with a heavier component of coppice (tropical dry evergreen forest) in the Late Holocene. Important in its own right, this information also will help biologists and government planners to develop conservation programs in The Bahamas that consider long-term ecological and cultural processes. PMID:18077421

  19. Exceptionally well preserved late Quaternary plant and vertebrate fossils from a blue hole on Abaco, The Bahamas

    PubMed Central

    Steadman, David W.; Franz, Richard; Morgan, Gary S.; Albury, Nancy A.; Kakuk, Brian; Broad, Kenneth; Franz, Shelley E.; Tinker, Keith; Pateman, Michael P.; Lott, Terry A.; Jarzen, David M.; Dilcher, David L.

    2007-01-01

    We report Quaternary vertebrate and plant fossils from Sawmill Sink, a “blue hole” (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from ?4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species (tortoise Chelonoidis undescribed sp. and Caracara Caracara creightoni) and two extant species no longer in The Bahamas (Cuban crocodile, Crocodylus rhombifer; and Cooper's or Gundlach's Hawk, Accipiter cooperii or Accipiter gundlachii). A different, inorganic bone deposit on a limestone ledge in Sawmill Sink is a Late Pleistocene owl roost that features lizards (one species), snakes (three species), birds (25 species), and bats (four species). The owl roost fauna includes Rallus undescribed sp. (extinct; the first Bahamian flightless rail) and four other locally extinct species of birds (Cooper's/Gundlach's Hawk, A. cooperii/gundlachii; flicker Colaptes sp.; Cave Swallow, Petrochelidon fulva; and Eastern Meadowlark, Sturnella magna) and mammals (Bahamian hutia, Geocapromys ingrahami; and a bat, Myotis sp.). The exquisitely preserved fossils from Sawmill Sink suggest a grassy pineland as the dominant plant community on Abaco in the Late Pleistocene, with a heavier component of coppice (tropical dry evergreen forest) in the Late Holocene. Important in its own right, this information also will help biologists and government planners to develop conservation programs in The Bahamas that consider long-term ecological and cultural processes. PMID:18077421

  20. Late Pleistocene fossil find in Svalbard: the oldest remains of a polar bear (Ursus maritimus Phipps, 1744) ever discovered

    E-print Network

    Ingólfsson, Ólafur

    (Ursus arctos L., 1758), the American black bear (Ursus americanus Pallas, 1780) and the Asiatic blackLate Pleistocene fossil find in Svalbard: the oldest remains of a polar bear (Ursus maritimus in Svalbard, a well preserved subfossil left mandible of a polar bear (Ursus maritimus Phipps, 1774

  1. Correlation between environment and Late Mesozoic ray-finned fish evolution

    Microsoft Academic Search

    Lionel Cavin; Peter L. Forey; Christophe Lécuyer

    2007-01-01

    In order to better understand the parameters that drove evolution of actinopterygian fishes from the Late Jurassic to the Late Cretaceous (this being the time of diversification of crown group teleosts, by far the dominant fish group today), we define three environmental indicators, which are detectable as concordant patterns in the geological and fossil records. These are 1) freshwater radiations,

  2. Paleomagnetism of the Front Range (Colorado) Morrison Formation and an alternative model of Late Jurassic North American apparent polar wander

    Microsoft Academic Search

    Mickey C. van Fossen; Dennis V. Kent

    1992-01-01

    A paleomagnetic study of the Upper Jurassic Morrison Formation in the Front Range of central Colorado yields high-unblocking-temperature, dual-polarity magnetizations. With respect to known paleohorizontal, the inclinations (absolute mean = 57.3°, 95% confidence interval = 52.3° to 63.1°, N = 8 sites) pass tilt and reversal tests, whereas the dispersion in declinations can be attributed to apparent or real tectonic

  3. Tectonic setting of the Late Triassic volcaniclastic series of the Luang Prabang Basin, Laos, and geodynamic implications from the Triassic to Jurassic in SE Asia

    NASA Astrophysics Data System (ADS)

    Rossignol, Camille; Bourquin, Sylvie; Dabard, Marie-Pierre; Hallot, Erwan; Poujol, Marc; Nalpas, Thierry

    2014-05-01

    The Luang Prabang Basin, located on the eastern margin of the Indochina block, is mainly composed of volcaniclastic continental deposits. The interpretation of U-Pb zircon geochronological dates shows that volcanism is contemporaneous with the sedimentation during the Late Triassic (c.a. 225 to 215 Ma; Blanchard et al., 2013, J. Asian Earth Sci., 70-71; 8-26). At the same time, volcanism is also known along the Eastern margin of the Indochina block (present day Thailand). There are currently two main contrasting interpretations concerning the tectonic setting related to these volcanic events: are they arc-related (e.g. Barr et al., 2006, J. Geol. Soc. London, 163; 1037-1046) or post collisional (e.g. Srichan et al., 2009, Island Arc, 18; 32-51)? We have performed geochemical analysis on both sedimentary and volcanic rocks of the Luang Prabang Basin in order to evaluate the relationships between the volcanic events and to propose a geodynamic interpretation. The geochemical characteristics of the Luang Prabang Late Triassic volcaniclastic and volcanic rocks are compatible with a volcanic arc setting. The confrontation of these results with the stratigraphic evolution of the eastern margin of the Indochina block leads to reconsider the Late Triassic to Jurassic geodynamic evolution of this area. Arc-related volcanism seems to occur during nearly the whole Triassic, implying a subduction of the Paleotethys beneath the Indochina block. As the stratigraphic record of north-eastern Thailand and western Myanmar shows an important stratigraphic gap spanning from the Early to the Middle Jurassic, the collision between the Indochina and the Sibumasu blocks likely occurred at that period.

  4. Stratigraphic evolution of a Late Triassic to Early Jurassic intracontinental basin in southeastern South China: A consequence of flat-slab subduction?

    NASA Astrophysics Data System (ADS)

    Pang, Chong-Jin; Krapež, Bryan; Li, Zheng-Xiang; Xu, Yi-Gang; Liu, Hai-Quan; Cao, Jun

    2014-04-01

    An intracontinental basin formed on a young orogen in South China during the Late Triassic to Early Jurassic (T3-J1). A > 2000 m-thick siliciclastic sedimentary succession in the Daxi section, in northern Guangdong Province, near the depocentre of the basin, is correlated with the published Zhuyuan section and three other sections. The combined Daxi-Zhuyuan sections record a marine-influenced deltaic succession of Carnian to Early Toarcian age, spanning a period of ~ 55 Myr. Tectonic controls, rather than eustasy and climate, are interpreted to have played a primary role in the cyclic development of the basin fill. Four regional-scale tectonostratigraphic stages are recognised. Stage 1 features a retrogradation-progradation cycle characterised by increasing then slowly decreasing subsidence rates, accompanied by slow to medium sedimentation rates. Stage 2 is broadly an aggradational cycle with multiple smaller-scale retrogradational-progradational cycles. A complex interplay between moderate subsidence rates, high sedimentation rates and eustasy is interpreted for this stage. Stage 3 represents a retrogradational-aggradational-progradational cycle during which the impact of global sea level was much reduced. This period was characterised by mostly high sedimentation and high subsidence rates, but a change to lower subsidence and sedimentation rates took place prior to the intracontinental uplift that inverted the basin. Stage 4 records continued uplift and the subsequent development of a Late Jurassic-Cretaceous basin-and-range province. The temporal-spatial evolution of the basin could be best explained by the gravitational pull of a subducted flat-slab and its subsequent foundering.

  5. K/Ar chronologies of tephra units from the Middle Jurassic Sundance, and Late Early Cretaceous Mowry and Shell Creek Formations, Big Horn Basin, WY

    NASA Astrophysics Data System (ADS)

    Jiang, H.; Meyer, E. E.; Johnson, G. D.

    2013-12-01

    The Middle Jurassic Sundance and Late Early Cretaceous Shell Creek and Mowry Formations of the Big Horn Basin, Wyoming, contain an extensive record of altered tephra. These tephra are likely related to contemporary volcanic activity in the Sierra Nevada and various Coast Range terranes to the west and provide valuable chronometric control on the sedimentary record within a portion of the Sevier-aged and later Cordilleran foreland basin. In addition, several of these altered tephra (bentonites) provide a valuable economic resource. Despite the prominence of these strata across the basin, few isotopic ages have been reported to date. Here we present new K/Ar ages on biotite phenocrysts from those tephra occurrences as a chronometric check on samples that contained zircons with significant Pb loss, that preclude more precise U/Pb age determinations. A bulk biotite sample extracted from an altered tuff in the Lower Sundance Formation gives an age of 167.5 × 5 Ma. This tuff occurs just above a dinosaur track-bearing peritidal sequence. Bulk biotite ages from the lower Shell Creek Formation give an age of 100.3 × 3 Ma and are statistically indistinguishable from biotite grains dated at 103.1 × 3 Ma extracted from the economically important 'Clay Spur' bentonite found at the top of the Mowry Shale. This work provides important new chronometric constraints on a portion of the Medial Jurassic to Late Early Cretaceous stratigraphy of the Big Horn Basin, Wyoming, and may be useful in understanding the regional tectonics that helped shape the development of the Sevier foreland basin and Western Interior Seaway.

  6. High resolution reservoir architecture of late Jurassic Haynesville ramp carbonates in the Gladewater field, East Texas Salt Basin

    SciTech Connect

    Goldhammer, R.K. [Texas Bureau of Mines and Geology, Houston, TX (United States)

    1996-12-31

    The East Texas Salt Basin contains numerous gas fields within Upper Jurassic Haynesville ramp-complex reservoirs. A sequenced-keyed, high-resolution zonation scheme was developed for the Haynesville Formation in Gladewater field by integrating core description, well-log, seismic, porosity and permeability data. The Haynesville at Gladewater represents a high-energy ramp system, localized on paleotopographic highs induced by diapirism of Callovian Age Salt (Louann). Ramp crest grainstones serve as reservoirs. We have mapped the distribution of reservoir facies within a hierarchy of upward-shallowing parasequences grouped into low-frequency sequences. The vertical stacking patterns of parasequences and sequences reflect the interplay of eustasy, sediment accumulation patterns, and local subsidence (including salt movement and compaction). In this study we draw on regional relations from analogous, Jurassic systems in Mexico to constrain the stratigraphic architecture, age model, and facies model. Additionally, salt-cored Holocene, grain-rich shoals from the Persian Gulf provide excellent facies analogs. The result is a new high-resolution analysis of reservoir architecture at a parasequence scale that links reservoir facies to depositional facies. The new stratigraphy scheme demonstrates that different geographic portions of the field have markedly distinct reservoir intervals, both in terms of total pay and the sequence-stratigraphic interval within which it occurs. Results from this study are used to evaluate infill drill well potential, in well planning, for updating reservoir models, and in refining field reserve estimates.

  7. High resolution reservoir architecture of late Jurassic Haynesville ramp carbonates in the Gladewater field, East Texas Salt Basin

    SciTech Connect

    Goldhammer, R.K. (Texas Bureau of Mines and Geology, Houston, TX (United States))

    1996-01-01

    The East Texas Salt Basin contains numerous gas fields within Upper Jurassic Haynesville ramp-complex reservoirs. A sequenced-keyed, high-resolution zonation scheme was developed for the Haynesville Formation in Gladewater field by integrating core description, well-log, seismic, porosity and permeability data. The Haynesville at Gladewater represents a high-energy ramp system, localized on paleotopographic highs induced by diapirism of Callovian Age Salt (Louann). Ramp crest grainstones serve as reservoirs. We have mapped the distribution of reservoir facies within a hierarchy of upward-shallowing parasequences grouped into low-frequency sequences. The vertical stacking patterns of parasequences and sequences reflect the interplay of eustasy, sediment accumulation patterns, and local subsidence (including salt movement and compaction). In this study we draw on regional relations from analogous, Jurassic systems in Mexico to constrain the stratigraphic architecture, age model, and facies model. Additionally, salt-cored Holocene, grain-rich shoals from the Persian Gulf provide excellent facies analogs. The result is a new high-resolution analysis of reservoir architecture at a parasequence scale that links reservoir facies to depositional facies. The new stratigraphy scheme demonstrates that different geographic portions of the field have markedly distinct reservoir intervals, both in terms of total pay and the sequence-stratigraphic interval within which it occurs. Results from this study are used to evaluate infill drill well potential, in well planning, for updating reservoir models, and in refining field reserve estimates.

  8. Trace element signature of Late Jurassic siliciclastic-carbonate sedimentary strata from western Montana, southeastern British Columbia and southern Alberta

    SciTech Connect

    Sablock, J. (Elizabeth City State Univ., NC (United States). Dept. of Geosciences)

    1992-01-01

    A trace element signature, a characteristic pattern of enrichment and depletion of trace elements, was determined for a group of siliciclastic-carbonate Oxfordian and Kimmeridgian sedimentary strata, collected from outcrops in western Montana, southeastern British Columbia and southern Alberta. The average values, by petrofacies, of 10 major and 18 trace elements were measured for 40 samples. These data were normalized to Upper Continental Crust (UCC), and plotted against averaged published values of graywackes from the same facies. The rare earth elements (REEs), as well as Ti, Zr, Nb and Y are considered immobile even through diagenesis, and at least low level metamorphism. So these elements should form a reliable part of the geochemical signature. Compared to UCC and average graywacke, Jurassic samples are very depleted in Zr, Nb and Y. Oxfordian samples have slightly higher rare earth element values, i.e. La, Ce and Nd, than either other Jurassic samples or average graywacke. The most likely source of REE values are garnets and tourmaline which occur as inclusions in monocrystalline quartz grains. This pattern, and petrological study, point to a sedimentary source area, deficient in feldspar, heavy minerals and rock fragments. The consistency of the signature throughout this time may indicate slow uplift of a widespread sedimentary source area, or could be an effect of greater mixing and shorter residence time of dissolved materials in an epeiric sea.

  9. Three new Jurassic euharamiyidan species reinforce early divergence of mammals.

    PubMed

    Bi, Shundong; Wang, Yuanqing; Guan, Jian; Sheng, Xia; Meng, Jin

    2014-10-30

    The phylogeny of Allotheria, including Multituberculata and Haramiyida, remains unsolved and has generated contentious views on the origin and earliest evolution of mammals. Here we report three new species of a new clade, Euharamiyida, based on six well-preserved fossils from the Jurassic period of China. These fossils reveal many craniodental and postcranial features of euharamiyidans and clarify several ambiguous structures that are currently the topic of debate. Our phylogenetic analyses recognize Euharamiyida as the sister group of Multituberculata, and place Allotheria within the Mammalia. The phylogeny suggests that allotherian mammals evolved from a Late Triassic (approximately 208 million years ago) Haramiyavia-like ancestor and diversified into euharamiyidans and multituberculates with a cosmopolitan distribution, implying homologous acquisition of many craniodental and postcranial features in the two groups. Our findings also favour a Late Triassic origin of mammals in Laurasia and two independent detachment events of the middle ear bones during mammalian evolution. PMID:25209669

  10. Stratigraphy of the Jurassic system in northern Egypt

    SciTech Connect

    Keeley, M.L.; Shaw, D.; Forbes, G.A.

    1988-08-01

    A regional synthesis is presented of the stratigraphy of Jurassic strata in Egypt north of 30/degree/N, based on the study of about 80 wells and outcrops from northeastern Egypt. Almost all fossil groups have been investigated for biostratigraphic control. Published work on ammonite faunas from Gebel el Maghara (north Sinai) is integrated with extensive original work on palynofloras (and, to a lesser extent, ostracod/foraminiferal faunas) recovered from marine rocks in the subsurface. The recovery of rich dinocyst assemblages enables the recognition of a ten-fold zonation scheme, largely within the Middle-Late Jurassic sedimentary package. The upper limit of this package is marked by the Cimmerian erosional event; strata younger than Oxfordian are rarely preserved. Only east of 30/degree/E is significant sedimentation known to have occurred immediately prior to the major early Bajocian transgressive event. Thereafter mean sea level rose steadily. The Lower Triassic-Lower Jurassic sedimentary package is poorly understood, largely the result of scanty and ambiguous stratigraphic evidence. However, regional correlations suggest that only very thin earliest Jurassic (Hettangian ) clastic deposition succeeded a sequence of Upper Triassic carbonates and evaporites (Wadi en Natrun Formation) in the north. Arising from these studies is a standard lithostratigraphical scheme. The upper sedimentary package, the Gebel el Maghara Group, comprises three formations (Masajid, Khatatba, and Inmar) and seven members; new units are defined and old units redefined.

  11. Early and Middle Jurassic climate changes: implications for palaeoceanography and tectonics

    NASA Astrophysics Data System (ADS)

    Korte, Christoph; Hesselbo, Stephen P.; Ullmann, Clemens V.; Ruhl, Micha; Thibault, Nicolas R.

    2014-05-01

    The occurrence of 'ice ages' within the overall warm Jurassic Period has been the subject of much controversy. It has been suggested on the basis of occurrence of glendonites in circum-Arctic basins that cold episodes took place in the Jurassic (Price, 1999; Rogov and Zakharov, 2010). Here we present new high-resolution oxygen isotope datasets from marine calcitic fossils of different European basins that indicate strong temperature fluctuations during the Pliensbachian-Bajocian time span. The already reported cold Late Pliensbachian episode comprises at least three pronounced oxygen isotope 'Ice Age' cycles. The subsequent well known Toarcian Oceanic Anoxic 'supergreenhouse' Event is followed by very warm seawater temperatures in the late Toarcian. A very pronounced cooling occurred during the latest Toarcian to early Aalenian (Early-Middle Jurassic Boundary Event). This episode resulted in substantial expansion of Arctic climates to palaeolatitudes as low as 45° and in distinctly cooler seawater temperatures in lower latitude European seas. We propose that the extensive cooling at the Early-Middle Jurassic Boundary Event was driven by substantial changes in oceanic current patterns initiated by uplift of the North Sea Dome preventing the transport of heat to Polar Regions via the Viking Corridor. Literature Price, G. D. (1999). The evidence and implications of polar ice during the Mesozoic, Earth-Sci. Rev., 48, 183-210. Rogov, M. A., Zakharov, V. A. (2010). Jurassic and Lower Cretaceous glendonite occurrences and their implication for Arctic paleoclimate reconstructions and stratigraphy. Earth Science Frontiers 17, 345-347.

  12. Petrographic and geochemical characteristics of dolomitization in the Late Jurassic-Early Cretaceous platform carbonates, Ba?oba Yayla (Eastern Pontides, NE Turkey)

    NASA Astrophysics Data System (ADS)

    Y?ld?z, Merve; Ziya K?rmac?, M.; Kandemir, Raif; Ero?lu, Tu?ba

    2015-04-01

    The Late Jurassic-Early Cretaceous Berdiga Formation with a wide distribution in E-W direction in the eastern Pontides (NE Turkey) is composed of platform carbonates. The formation with distinct lithofacies properties in both lateral and vertical directions was deposited on carbonate shelf changing from supratidal to platform margin reef and was buried until the end of Late Cretaceous. One of the typical exposures of formation is found around the Ba?oba Yayla area (Trabzon, NE Turkey) in northern zone of the eastern Pontides where the formation has a limited distribution. In this area, platform carbonates are 250 m in thickness and from bottom to top composed of dolomite, grainstone-packstone and skeleton wackestone. The 120-m thickened dolomite facies which comprises the lower part of formation contains four dolomite phases as replacement (Rd) and cement (Cd) types. Replacement dolomites (Rd) that are cut by low-amplitude stylolites are developed as 1) thin crystalline planar-s dolomite (Rd1), 2) thin-medium crystalline, texture-protective planar-s dolomite (Rd2) dolomite and 3) medium-coarse crystalline planar-s dolomite (Rd3). Coarse-very coarse crystalline dolomite cement (Cd) filling dissolution spaces and fractures in Rd1 dolomites are cogenetic with low-amplitude stylolites. Replacement dolomites are Ca-rich and non-stoichiometric (Ca56-60Mg40-44) and geochemically have two-population distribution and uniform dull red/non-luminescence appearance. The ?18O compositions of replacement dolomites are from -15.3 to -4.2 o VPDB, ?13C values are 1.5-3.7 o VPDB and 87Sr/86Sr ratios are 0.70675 to 0.70731. Sr, Na, Mn and Fe contents of these dolomites are 74-163 ppm, bdl-200 ppm, 94-553 ppm and 1400-3800 ppm, respectively. Petrographic and geochemical date yield that replacement dolomites (Rd) are formed before the chemical compression at shallow-moderate burial depths from Jurassic-Early Cretaceous seawater and/or seawater partly modified by rock-water interaction and recrystallized by hydrothermal waters of marine origin at enhanced temperatures and progressing burial depths. Like replacement dolomites, dolomite cement (Cd) are Ca-rich and non-stoichiometric (Ca58-60Mg40-42) and are represented by Sr (106-201), Na (

  13. Late Triassic-early Jurassic block tilting along E-W faults, in southern Tunisia: New interpretation of the Tebaga of Medenine

    NASA Astrophysics Data System (ADS)

    Raulin, Camille; Lamotte, Dominique Frizon de; Bouaziz, Samir; Khomsi, Sami; Mouchot, Nicolas; Ruiz, Geoffrey; Guillocheau, François

    2011-08-01

    The Tebaga of Medenine is a puzzling structure situated at the northern edge of the Jeffara plain in southern Tunisia. It presents the unique outcropping marine Permian sequence in Africa as well as spectacular angular unconformities related to Mesozoic tectono-sedimentary events. Many hypotheses have been proposed to explain this structure but some questions still remain. We present the result of an integrated study of the Mesozoic tectonic evolution of the region, based on new field work and a reassessment of some subsurface data. We propose a new structural hypothesis in which the Tebaga of Medenine is interpreted as resulting from large scale block tilting, mainly controlled by inherited E-W major faults, the Azizia fault system. These E-W faults running along the Jeffara plain may represent inherited structural features in relation with deep faulting in the Paleozoic substratum. This rifting occurring during late Triassic up to the end of early Jurassic, is finally integrated in the general frame of the East Mediterranean.

  14. Possible animal body fossils from the Late Neoproterozoic interglacial successions in the Kimberley region, northwestern Australia

    Microsoft Academic Search

    Zhong-Wu Lan; Zhong-Qiang Chen

    New specimens of the enigmatic Ediacara-type fossil Palaeopascichnus have been identified from the upper part of the Neoproterozoic Ranford Formation in the Kimberley region, northwest Australia. New material is morphologically similar to Palaeopascichnus and represents the largest species of this genus. They resemble the present-day xenophyophore protists in chamber morphology and growth patterns, supporting the interpretation that Palaeopascichnus is possibly

  15. Stable iron isotopes and microbial mediation in red pigmentation of the Rosso Ammonitico (mid-late Jurassic, Verona area, Italy).

    PubMed

    Préat, Alain R; de Jong, Jeroen T M; Mamet, Bernard L; Mattielli, Nadine

    2008-08-01

    The iron (Fe) isotopic composition of 17 Jurassic limestones from the Rosso Ammonitico of Verona (Italy) have been analyzed by Multiple-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS). Such analysis allowed for the recognition of a clear iron isotopic fractionation (mean -0.8 per thousand, ranging between -1.52 to -0.06 per thousand) on a millimeter-centimeter scale between the red and grey facies of the studied formation. After gentle acid leaching, measurements of the Fe isotopic compositions gave delta(56)Fe values that were systematically lower in the red facies residues (median: -0.84 per thousand, range: -1.46 to +0.26 per thousand) compared to the grey facies residues (median: -0.08 per thousand, range: -0.34 to +0.23 per thousand). In addition, the red facies residues were characterized by a lighter delta(56)Fe signal relative to their corresponding leachates. These Fe isotopic fractionations could be a sensitive fingerprint of a biotic process; systematic isotopic differences between the red and grey facies residues, which consist of hematite and X-ray amorphous iron hydroxides, respectively, are hypothesized to have resulted from the oxidizing activity of iron bacteria and fungi in the red facies. The grey Fe isotopic data match the Fe isotopic signature of the terrestrial baseline established for igneous rocks and low-C(org) clastic sedimentary rocks. The Fe isotopic compositions of the grey laminations are consistent with the influx of detrital iron minerals and lack of microbial redox processes at the water-interface during deposition. Total Fe concentration measurements were performed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) (confirmed by concentration estimations obtained by MC-ICP-MS analyses of microdrilled samples) on five samples, and resultant values range between 0.30% (mean) in the grey facies and 1.31% (mean) in the red facies. No correlation was observed between bulk Fe content and pigmentation or between bulk Fe content and Fe isotopic compositions. The rapid transformation of the original iron oxyhydroxides to hematite could have preserved the original isotopic composition if it had occurred at about the same temperature. This paper supports the use of Fe isotopes as sensitive tracers of biological activities recorded in old sedimentary sequences that contain microfossils of iron bacteria and fungi. However, a careful interpretation of the iron isotopic fractionation in terms of biotic versus abiotic processes requires supporting data or direct observations to characterize the biological, (geo)chemical, or physical context in relation to the geologic setting. This will become even more pertinent when Fe isotopic studies are expanded to the interplanetary realm. PMID:18759562

  16. Non-marine carbonate facies, facies models and palaeogeographies of the Purbeck Formation (Late Jurassic to Early Cretaceous) of Dorset (Southern England).

    NASA Astrophysics Data System (ADS)

    Gallois, Arnaud; Bosence, Dan; Burgess, Peter

    2015-04-01

    Non-marine carbonates are relatively poorly understood compared with their more abundant marine counterparts. Sedimentary facies and basin architecture are controlled by a range of environmental parameters such as climate, hydrology and tectonic setting but facies models are few and limited in their predictive value. Following the discovery of extensive Early Cretaceous, non-marine carbonate hydrocarbon reservoirs in the South Atlantic, the interest of understanding such complex deposits has increased during recent years. This study is developing a new depositional model for non-marine carbonates in a semi-arid climate setting in an extensional basin; the Purbeck Formation (Upper Jurassic - Lower Cretaceous) in Dorset (Southern England). Outcrop study coupled with subsurface data analysis and petrographic study (sedimentology and early diagenesis) aims to constrain and improve published models of depositional settings. Facies models for brackish water and hypersaline water conditions of these lacustrine to palustrine carbonates deposited in the syn-rift phase of the Wessex Basin will be presented. Particular attention focusses on the factors that control the accumulation of in-situ microbialite mounds that occur within bedded inter-mound packstones-grainstones in the lower Purbeck. The microbialite mounds are located in three units (locally known as the Skull Cap, the Hard Cap and the Soft Cap) separated by three fossil soils (locally known as the Basal, the Lower and the Great Dirt Beds) respectively within three shallowing upward lacustrine sequences. These complex microbialite mounds (up to 4m high), are composed of tabular small-scale mounds (flat and long, up to 50cm high) divided into four subfacies. Many of these small-scale mounds developed around trees and branches which are preserved as moulds (or silicified wood) which are surrounded by a burrowed mudstone-wackestone collar. Subsequently a thrombolite framework developed on the upper part only within bedded inter-mound packestones-grainstones. Finally a discontinuous basal laminated subfacies can be found overlaying the fossil soils. The overall control on facies and their distribution is the tectonic control as highlighted by the activity of the two main extensional faults during Purbeck times. The tectonic control on development of microbialite mounds is indicated by their relationship with the relay ramp. Their occurrence is controlled by palaeotopography generated on sub-aerial exposure surfaces, palaesols and early conifer trees and developed mainly on the shallowest area of the lake as indicated by their relationship with the inter-mound packstone-grainstone facies and the palaeosols. The new depositional models developed in this study integrate sedimentological facies models with the syn-rift setting of the Wessex Basin to explain the distribution of the microbialite mounds.

  17. First record of fossil wood and phytolith assemblages of the Late Pleistocene in El Palmar National Park (Argentina)

    NASA Astrophysics Data System (ADS)

    Zucol, A. F.; Brea, M.; Scopel, A.

    2005-10-01

    Two paleoxylologic assemblages and two phytolith assemblages were recovered from Late Pleistocene sediments of El Palmar Formation. These deposits are found in outcrops along the western margin of the Uruguay River. The spectra of taxa obtained in both sets by different methods is complementary. The fossil remains are characterized in terms of floristic composition and paleoclimate. Seven families are recognized: Podostemaceae, Myrtaceae, Anacardiaceae, Mimosoideae, Arecaceae, Poaceace, and Cyperaceae. Sponge siliceous spicules also have been found in these assemblages. The state of preservation of the phytoliths and their weathering degree is analyzed. These studies can be used as a potential paleoecological tool for alluvial sediments. The comparison of fossil assemblages with modern analogs clarifies the paleoecological requirements and composition of two paleocommunities, one dominated by woody forests and the other by palms. The climatic conditions inferred from the reconstructed vegetation and sedimentary deposits indicate a temperate-warm, humid climate. The results constitute the first evidence of the floral diversity of the vegetation in El Palmar National Park during the Late Pleistocene.

  18. Two new species of Archaeohelorus (Hymenoptera, Proctotrupoidea, Heloridae) from the Middle Jurassic of China

    PubMed Central

    Shi, Xiaoqing; Zhao, Yunyun; Shih, Chungkun; Ren, Dong

    2014-01-01

    Abstract Two new fossil species, Archaeohelorus polyneurus sp. n. and A. tensus sp. n., assigned to the genus Archaeohelorus Shih, Feng & Ren, 2011 of Heloridae (Hymenoptera), are reported from the late Middle Jurassic, Jiulongshan Formation of Inner Mongolia, China. Based on the well-preserved forewings and hind wings of these specimens, the diagnosis of the Archaeohelorus is emended: forewing 2cu-a intersecting Cu and Rs+M at the same point or postfurcal, and hind wing may have tubular veins C, Sc+R, R, Rs, M+Cu, M and Cu distinct, or simplified venation. The new findings also elucidate the evolutionary trend of forewing and hind wing venation and body size for the Heloridae from the late Middle Jurassic to now. PMID:24478588

  19. Late Paleocene fossils from the Cerrejón Formation, Colombia, are the earliest record of Neotropical rainforest

    PubMed Central

    Wing, Scott L.; Herrera, Fabiany; Jaramillo, Carlos A.; Gómez-Navarro, Carolina; Wilf, Peter; Labandeira, Conrad C.

    2009-01-01

    Neotropical rainforests have a very poor fossil record, making hypotheses concerning their origins difficult to evaluate. Nevertheless, some of their most important characteristics can be preserved in the fossil record: high plant diversity, dominance by a distinctive combination of angiosperm families, a preponderance of plant species with large, smooth-margined leaves, and evidence for a high diversity of herbivorous insects. Here, we report on an ?58-my-old flora from the Cerrejón Formation of Colombia (paleolatitude ?5 °N) that is the earliest megafossil record of Neotropical rainforest. The flora has abundant, diverse palms and legumes and similar family composition to extant Neotropical rainforest. Three-quarters of the leaf types are large and entire-margined, indicating rainfall >2,500 mm/year and mean annual temperature >25 °C. Despite modern family composition and tropical paleoclimate, the diversity of fossil pollen and leaf samples is 60–80% that of comparable samples from extant and Quaternary Neotropical rainforest from similar climates. Insect feeding damage on Cerrejón fossil leaves, representing primary consumers, is abundant, but also of low diversity, and overwhelmingly made by generalist feeders rather than specialized herbivores. Cerrejón megafossils provide strong evidence that the same Neotropical rainforest families have characterized the biome since the Paleocene, maintaining their importance through climatic phases warmer and cooler than present. The low diversity of both plants and herbivorous insects in this Paleocene Neotropical rainforest may reflect an early stage in the diversification of the lineages that inhabit this biome, and/or a long recovery period from the terminal Cretaceous extinction. PMID:19833876

  20. The utility of late Early to Middle Cambrian small shelly fossils from the western Mediterranean

    Microsoft Academic Search

    Olaf Elicki

    2005-01-01

    New data on Cambrian small shelly fossils from Germany and Sardinia, and Spain are discussed with respect to their stratigraphical,\\u000a paleogeographical, and paleoecological value. It is shown that these small shelly assemblages represent very useful tools\\u000a for reconstruction of geological processes and of the Perigondwanan history in the Mediterranean area, especially, if trilobites\\u000a are absent or hard to recover from

  1. Late Paleocene fossils from the Cerrejon Formation, Colombia, are the earliest record of Neotropical rainforest.

    PubMed

    Wing, Scott L; Herrera, Fabiany; Jaramillo, Carlos A; Gómez-Navarro, Carolina; Wilf, Peter; Labandeira, Conrad C

    2009-11-01

    Neotropical rainforests have a very poor fossil record, making hypotheses concerning their origins difficult to evaluate. Nevertheless, some of their most important characteristics can be preserved in the fossil record: high plant diversity, dominance by a distinctive combination of angiosperm families, a preponderance of plant species with large, smooth-margined leaves, and evidence for a high diversity of herbivorous insects. Here, we report on an approximately 58-my-old flora from the Cerrejón Formation of Colombia (paleolatitude approximately 5 degrees N) that is the earliest megafossil record of Neotropical rainforest. The flora has abundant, diverse palms and legumes and similar family composition to extant Neotropical rainforest. Three-quarters of the leaf types are large and entire-margined, indicating rainfall >2,500 mm/year and mean annual temperature >25 degrees C. Despite modern family composition and tropical paleoclimate, the diversity of fossil pollen and leaf samples is 60-80% that of comparable samples from extant and Quaternary Neotropical rainforest from similar climates. Insect feeding damage on Cerrejón fossil leaves, representing primary consumers, is abundant, but also of low diversity, and overwhelmingly made by generalist feeders rather than specialized herbivores. Cerrejón megafossils provide strong evidence that the same Neotropical rainforest families have characterized the biome since the Paleocene, maintaining their importance through climatic phases warmer and cooler than present. The low diversity of both plants and herbivorous insects in this Paleocene Neotropical rainforest may reflect an early stage in the diversification of the lineages that inhabit this biome, and/or a long recovery period from the terminal Cretaceous extinction. PMID:19833876

  2. First discovery of colobine fossils from the Late Miocene/Early Pliocene in central Myanmar.

    PubMed

    Takai, Masanaru; Thaung-Htike; Zin-Maung-Maung-Thein; Soe, Aung Naing; Maung, Maung; Tsubamoto, Takehisa; Egi, Naoko; Nishimura, Takeshi D; Nishioka, Yuichiro

    2015-07-01

    Here we report two kinds of colobine fossils discovered from the latest Miocene/Early Pliocene Irrawaddy sediments of the Chaingzauk area, central Myanmar. A left mandibular corpus fragment preserving M1-3 is named as a new genus and species, Myanmarcolobus yawensis. Isolated upper (M(1)?) and lower (M2) molars are tentatively identified as Colobinae gen. et sp. indet. Although both forms are medium-sized colobines, they are quite different from each other in M2 morphology. The isolated teeth of the latter show typical colobine-type features, so it is difficult to identify their taxonomic position, whereas lower molars of Myanmarcolobus have unique features, such as a trapezoid-shaped long median lingual notch, a deeply concave median buccal cleft, a strongly developed mesiobuccal notch, and rather obliquely running transverse lophids. Compared with fossil and living Eurasian colobine genera, Myanmarcolobus is most similar in lower molar morphology to the Pliocene Dolichopithecus of Europe rather than to any Asian forms. In Dolichopithecus, however, the tooth size is much larger and the median lingual notch is mesiodistally much shorter than that of Myanmarcolobus. The discovery of Myanmarcolobus in central Myanmar is the oldest fossil record in Southeast Asia not only of colobine but also of cercopithecid monkeys and raises many questions regarding the evolutionary history of Asian colobine monkeys. PMID:25978976

  3. Climate-vegetation modelling and fossil plant data suggest low atmospheric CO2 in the late Miocene

    NASA Astrophysics Data System (ADS)

    Forrest, M.; Eronen, J. T.; Utescher, T.; Knorr, G.; Stepanek, C.; Lohmann, G.; Hickler, T.

    2015-06-01

    There is increasing need to understand the pre-Quaternary warm climates, how climate-vegetation interactions functioned in the past, and how we can use this information for understanding the present. Here we report vegetation modelling results for the Late Miocene (11-7 Ma) to study the mechanisms of vegetation dynamics and the role of different forcing factors that influence the spatial patterns of vegetation coverage. One of the key uncertainties is the atmospheric concentration of CO2 during past climates. Estimates for the last 20 million years range from 280 to 500 ppm. We simulated Late Miocene vegetation using two plausible CO2 concentrations, 280 and 450 ppm CO2, with a dynamic global vegetation model (LPJ-GUESS) driven by climate input from a coupled AOGCM (Atmosphere-Ocean General Circulation Model). The simulated vegetation was compared to existing plant fossil data for the whole Northern Hemisphere. For the comparison we developed a novel approach that uses information of the relative dominance of different Plant Functional Types (PFTs) in the palaeobotanical data to provide a quantitative estimate of the agreement between the simulated and reconstructed vegetation. Based on this quantitative assessment we find that pre-industrial CO2 levels are largely consistent with the presence of seasonal temperate forests in Europe (suggested by fossil data) and open vegetation in North America (suggested by multiple lines of evidence). This suggests that during the Late Miocene the CO2 levels have been relatively low, or that other factors that are not included in the models maintained the seasonal temperate forests and open vegetation.

  4. Late Jurassic to Early Cretaceous transpression, Pine Nut and Luning-Fencemaker fault system, west-central Nevada

    SciTech Connect

    Oldow, J.S. (Rice Univ., Houston, TX (United States). Dept. of Geology and Geophysics)

    1993-04-01

    Recent studies of the Mesozoic tectonic evolution of the western U.S. Cordillera have called for substantial transcurrent displacement between the Sierra Nevada and the western Great Basin. The location, timing, and sense of shear of the postulated transcurrent fault system(s) are controversial, and to a larger degree the controversy has centered on the Pine Nut fault (PNF) of western Nevada. The northwest-trending Pine Nut fault juxtaposes two coeval assemblages of the Mesozoic marine province of the northwestern Great Basin that have distinctly different structural histories. On the east, Mesozoic rocks are deformed in the late Mesozoic Luning-Fencemaker fold and thrust belt (LFT). To the west, coeval rocks are not involved in structures of the LFT but rather share a structural history with the eastern Sierra Nevada. A segment of the PNF is expressed as a brittle shear zone, up to 3 km wide, mapped discontinuously for over 50 km in the eastern Wassuk Range in west-central Nevada. Cataclasites of the brittle fault zone are superposed on ductility deformed lower Mesozoic layered and intrusive rocks with structures indicating top to the east shear. The ductile deformation, which predated post-kinematic plutons dated by U-Pb as 169 Ma, was accompanied by metamorphism ranging from lower greenschist to amphibolite-facies conditions. The PNF and LFT formed during sinistral transpression and represent components of oblique plate-convergence along the late Mesozoic Sierran are system.

  5. Portlandemys gracilis n. sp., a New Coastal Marine Turtle from the Late Jurassic of Porrentruy (Switzerland) and a Reconsideration of Plesiochelyid Cranial Anatomy

    PubMed Central

    Anquetin, Jérémy; Püntener, Christian; Billon-Bruyat, Jean-Paul

    2015-01-01

    Background Several groups of stem cryptodires became adapted to coastal marine environments as early as the Late Jurassic, 40 million years before the Pan-Chelonioidea. The Plesiochelyidae are a major component of this first radiation of crown-group turtles into marine habitats. They are abundant in many European localities, but their systematics is still greatly confused. Only three species are represented by cranial material: Plesiochelys etalloni, Plesiochelys planiceps, and Portlandemys mcdowelli. Methodology/Principal Findings In the present study, we describe a cranium and a mandible from the Kimmeridgian of Porrentruy (Switzerland), which we refer to a new species, Portlandemys gracilis n. sp. This new taxon differs from Portlandemys mcdowelli in several aspects of the cranium and mandible, notably in being generally more gracile, but the two species share a narrow skull, a more acute angle between the labial ridges on the mandible, and a unique configuration of the anterodorsal part of the basicranium. The cranial anatomy of plesiochelyid turtles is discussed in details based primarily on these new specimens and new cranial material of Plesiochelys etalloni from Solothurn, Switzerland. Conclusions/Significance Several characters (e.g., the contribution of the parietal to the foramen nervi trigemini, the configuration of the dorsum sellae and sella turcica, the presence of an infolding ridge on the posterior surface of the quadrate) appear as potential candidates to help elucidate plesiochelyid relationships. Some of these characters are included in a previously published phylogenetic dataset and help to stabilize the relationships of plesiochelyid turtles and closely related taxa. For the first time, our results suggest that plesiochelyids, 'Thalassemys' moseri, and Solnhofia parsonsi (representing the Eurysternidae) form a clade at the base of Eucryptodira. PMID:26106888

  6. Elemental and Sr-Nd-Hf isotopic constraints on the origin of Late Jurassic adakitic granodiorite in central Fujian province, southeast China

    NASA Astrophysics Data System (ADS)

    Wang, Guo-Chang; Jiang, Yao-Hui; Liu, Zheng; Ni, Chun-Yu; Qing, Long; Zhang, Qiao

    2015-04-01

    This paper presents the first detailed SHRIMP or LA-ICP-MS zircon U-Pb dating, major and trace element geochemical and Sr-Nd-Hf isotopic data of an adakitic pluton (Tangquan pluton) and an I-type granitic pluton (Xiadao pluton) in central Fujian. SHRIMP and LA-ICP-MS zircon U-Pb dating indicates that the Tangquan and Xiadao plutons were emplaced in the Late Jurassic (~160 Ma) and Early Cretaceous (~143 Ma), respectively. The Tangquan pluton is mainly composed of high-K calc-alkaline granodiorite. The rocks show adakitic affinities, characterized by high Sr and low Y and Yb contents, with high Sr/Y ratios, and by high Mg#. They have initial 87Sr/86Sr of 0.7084-0.7087, ?Nd (T) of -8.8 to -9.0 and ?Hf (T) (in-situ zircon) of -11.2. Detailed elemental and isotopic data suggest that the Tangquan adakitic granodiorite was formed by partial melting of Paleoproterozoic metamorphic basement at a depth of ~40 km (P ~12.5 kbar) plus additional input from coeval basaltic magma. The Xiadao pluton consists of monzogranite, syenogranite and alkali-feldspar granite. These granites are high-K calc-alkaline and belong to I-type. They have relatively low Sr and high Y and Yb contents and show similar Mg# to pure crustal melts. The Xiadao granites have slightly higher initial 87Sr/86Sr (0.7095-0.7102) and lower ?Nd (T) (-9.0 to -9.4) and ?Hf (T) (-14.4; in-situ zircon) than the Tangquan granitoids. Detailed elemental and isotopic data suggest that the Xiadao I-type granites were formed by partial melting of Paleoproterozoic metamorphic basement at a depth of ~30 km (P ~10 kbar).

  7. Physical stratigraphy of Swift-Morrison and Kootenai-Colorado depositional sequences in the Late Jurassic-Early Cretaceous overfilled backarc and foreland basins, western Montana

    SciTech Connect

    Meyers, J.H. (Winona State Univ., MN (United States). Dept. of Geology); O'Malley, P.J. (Indiana Univ., Bloomington, IN (United States). Dept. of Geosciences)

    1993-04-01

    Late Jurassic-Early Cretaceous sedimentation in western Montana includes two depositional sequences. The older sequence (Swift-Morrison Formations) was deposited in the Sundance foreland basin and ensuing Morrison back-arc basin. The younger sequence (Kootenal Formation-Colorado Group) was deposited in the overfilled early Rocky Mountain foreland basin. Swift strata record coastal onlap and marine progradation over a dissected structural complex (Belt Island) and include a laterally restricted basal conglomerate (0--4 m-thick) representing estuarine paleovalley fill, and an overlying pervasive 16--25 m-thick upward-fining sandstone body dominated by tidal features. To the south, the sandstone body is conformably overlain by distal alluvial-fan and coastal-plain green mudstone, interbedded thin micritic limestone, and red mudstone of the lower and middle Morrison Formation. Morrison red mudstones contain thin sheet sandstones and sparse thick lenticular sandstones, representing northeastward dispersal of detritus in a mud-dominated distal alluvial fan. Northward, the Morrison thins and is mostly green and gray mudstone with thin interbedded sheet sandstone and rare intraformational-pebble-bearing ribbon sandstone. To the south, Kootenai rocks unconformably overlie the Morrison Formation and include a thick basal sandstone deposited in northeast-flowing truck rivers whose courses were controlled by subtle structural topography developed along reactivated basement faults. In the Great Falls area this sandstone (K1-Cutbank of Foster, 1992) may represent distributary channels in a prograding fluvial-dominated delta in the Sunburst sea. Overlying mudstones and thick nodular limestones (K2) represent alluvial-plain sedimentation and paleosol development. Thin shallow-marine sandstone (K3-Sunburst) caps the fluvial-deltaic sequence in the Great Falls area.

  8. Late Pleistocene and Holocene Seasonal Temperatures Reconstructed from Fossil Beetle Assemblages in the Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Elias, Scott A.

    1996-11-01

    Mutual Climatic Range (MCR) analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14,500 to 400 yr B.P. The fossil sites represent a transect of the Rocky Mountain region from northern Montana to central Colorado. The analyses yielded estimates of mean July and mean January temperatures. The oldest assemblage (14,500 yr B.P.) yielded mean July values of 10-11°C colder than present and mean January values 26-30°C colder than present. Postglacial summer warming was rapid, as indicated by an assemblage dating 13,200 yr B.P., with mean July values only 3-4°C cooler than modern. By 10,000 yr B.P., several assemblages indicate warmer-than-modern mean summer and winter values. By 9000 yr B.P., MCR reconstructions indicate that both summer and winter temperatures were already declining from an early Holocene peak. Mean July values remained above modern levels and mean January values remained below modern levels until 3000 yr B.P. A series of small-scale oscillations followed.

  9. Alternative models for Late Jurassic and Early Cretaceous paleogeography of the western Cordillera, California to SE Alaska

    SciTech Connect

    Cowan, D.S. (Univ. of Washington, Seattle, WA (United States). Geological Sciences)

    1993-04-01

    The Franciscan-Great Valley-Sierran triad is indisputable evidence for late Mesozoic, west-facing subduction along the California sector of the N. American margin. In the northwestern sector (N of 48[degree]N), however, neither the configuration of plate boundaries, nor the paleogeographic disposition of the Insular and Intermontane superterranes, is confidently established. Models divide into two groups. One set, based entirely on geologic evidence such as the age and nature of deformational events, or putative stratigraphic links among terranes, places the two superterranes exclusively to the north of the Franciscan-Sierran system from 150 to 90 Ma. These hypotheses, which ignore or reject paleomagnetic data from mid-Cretaceous rocks, yield a paleogeography not too different from today's, but they are incompatible with the Franciscan and Great Valley rocks caught between the superterranes in the mid-Cretaceous San Juan-Cascade thrust system. An alternative model fully respecting paleomagnetic data from mid-Cretaceous rocks with paleohorizontal control restores most of the Intermontane superterrane [approximately]1,200 km south of its expected (i.e. present) latitudinal position with respect to North America, and the Insular superterrane [approximately]2,900 km south, at 95--105 Ma. The mid-Cretaceous thrust system along the eastern margin of the Insular superterrane records the collision of Wrangellia et al. with the southern continuation of the Franciscan subduction zone. The thrust system, a silver of hanging wall, and the Insular superterrane were all subsequently translated > 2,500 km northward by post-80, pre-60 Ma coast-parallel dextral slip, accommodated on the proto-Pasayten and proto-Yalakom faults, and along or near the Coast Range shear zone.

  10. New data on Late Vendian problematic fossils from the genus Harlaniella

    NASA Astrophysics Data System (ADS)

    Ivantsov, A. Yu.

    2013-11-01

    The morphology and stratigraphic distribution of Harlaniella podolica Sokolov, 1972 and H. ingriana Ivantsov, sp. nov. were investigated using the collection of impressions sampled recently in Upper Vendian sections of Russia (southeastern White Sea region) and Ukraine (Podoliya). These fossils, which were previously considered as representing coprolites or grazing or locomotion traces, are interpreted as internal casts and impressions of fragments of tubes of initially organic composition. Streptichnus narbonnei Jensen et Runnegar, 2005 from Vendian-Cambrian boundary strata of Namibia are also attributed to this group. It is assumed that the tubes are similar to remains of the algal genera Vendotaenia Gnilovskaya, 1971 from Vendian deposits of the East European Platform and Liulingjitaenia Chen et Xiao, 1992 from Sinian sections of China.

  11. Upper jurassic dinosaur egg from utah.

    PubMed

    Hirsch, K F; Stadtman, K L; Miller, W E; Madsen, J H

    1989-03-31

    The Upper Jurassic egg described here is the first known egg from the 100-million-year gap in the fossil record between Lower Jurassic (South Africa) and upper Lower Cretaceous (Utah). The discovery of the egg, which was found mixed in with thousands of dinosaur bones rather than in a nest, the pathological multilayering of the eggshell as found in modern and fossil reptilians, and the pliable condition of the eggshell at the time of burial indicate an oviducal retention of the egg at the time of burial. PMID:17751281

  12. Quantification of Aridity Changes During the Late Holocene From the Carbon Isotope Composition of Fossil Charcoal

    NASA Astrophysics Data System (ADS)

    Voltas, J.; Ferrio, P.; Espinar, C.

    2006-12-01

    Climate dynamics during the Holocene can be characterized by a variety of proxies that provide information at a different scale and accuracy. In seasonally dry climates, the carbon isotope composition of tree-rings has been related to variables such as rainfall or evaporative demand. Extensive tree-ring records, however, are not always available owing to factors such as human-induced deforestation or harsh conditions for most long-lived trees to thrive. An illustrative example concerns the Mediterranean region. In this work, we aim to show that the original climate signal of wood ?13C is preserved in fossil charcoal (recovered from archaeological sites), and thus can be used to quantify past changes in water availability. We present two case studies on climate reconstruction at the temporal and spatial dimensions from Eastern Spain. We first describe, for a restricted area, the evolution of aridity during the last 4000 years using charcoals ranging from the Bronze Age (ca. 2100 BCE) to the Modern Age (XVIII ca. CE) (1). Further, we characterize, for a larger region, the transition between Bronze and Iron Ages, the so called Cold Iron Age Epoch (ca. 700-500 BCE), using remains from a set of contemporary sites (2). Climatic inferences were obtained after calibration of quantitative models predicting rainfall from wood ?13C. For case (1), charcoals of Mediterranean trees (Aleppo pine, several oaks, mastic) were analysed for ?13C. We found similar trends for the time course of changes in this parameter regardless of the species. Estimated rainfall in the past was 25% to 40% higher than present, with phases of greater water availability (1500-900 BCE; 300 BCE-300 CE) alternating with drier periods (900-300 BCE; 900-1100 CE). For case (2), we combined data from Aleppo pine and Holm oak, which exhibit differential responses to changes in climate seasonality, to provide information on intra-annual rainfall dynamics. The divergence in ?13C between pines and oaks can be interpreted as an increase in winter precipitation, along with a decrease in spring-summer rainfall, in agreement with other proxies for this period.

  13. Tectonic reconstruction of Uda-Murgal arc and the Late Jurassic and Early Cretaceous convergent margin of Northeast Asia-Northwest Pacific

    Microsoft Academic Search

    S. D. Sokolov; G. Ye. Bondarenko; A. K. Khudoley; O. L. Morozov; M. V. Luchitskaya; M. I. Tuchkova; P. W. Layer

    2009-01-01

    A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk fold and thrust belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeast Asia and Northwest Meso-Pacific. Several segments

  14. Transitional fossil earwigs - a missing link in Dermaptera evolution

    PubMed Central

    2010-01-01

    Background The Dermaptera belongs to a group of winged insects of uncertain relationship within Polyneoptera, which has expanded anal region and adds numerous anal veins in the hind wing. Evolutional history and origin of Dermaptera have been in contention. Results In this paper, we report two new fossil earwigs in a new family of Bellodermatidae fam. nov. The fossils were collected from the Jiulongshan Formation (Middle Jurassic) in Inner Mongolia, northeast China. This new family, characterized by an unexpected combination of primitive and derived characters, is bridging the missing link between suborders of Archidermaptera and Eodermaptera. Phylogenetic analyses support the new family to be a new clade at the base of previously defined Eodermaptera and to be a stem group of (Eodermaptera+Neodermaptera). Conclusion Evolutional history and origin of Dermaptera have been in contention, with dramatically different viewpoints by contemporary authors. It is suggested that the oldest Dermaptera might possibly be traced back to the Late Triassic-Early Jurassic and they had divided into Archidermaptera and (Eodermaptera+Neodermaptera) in the Middle Jurassic. PMID:21062504

  15. Remarkable Fossils

    Microsoft Academic Search

    Thomas Wm. Cowan

    1874-01-01

    ONE of the most remarkable collections of Wealden fossils ever seen, was lately on loan for a few days to the exhibition then open at Horsham, and is one that is not to be equalled by any at our public museums in the country. So remarkable is it that I am induced to give you a short description. As you

  16. An overview of the dinosaur fossil record from Chile

    NASA Astrophysics Data System (ADS)

    Rubilar-Rogers, David; Otero, Rodrigo A.; Yury-Yáñez, Roberto E.; Vargas, Alexander O.; Gutstein, Carolina S.

    2012-08-01

    In Chile, the record of dinosaurs in Jurassic and Cretaceous sediments is often restricted to footprints, with few skeletal remains. Tetanuran theropods are known in the Upper Jurassic, and bones of titanosaur sauropods in the Late Cretaceous, including partial skeletons (e.g. Atacamatitan chilensis Kellner et al.). Also from the late Cretaceous, an ornithopod vertebra, a pair of theropod teeth and one tarsometatarsus of a gaviiform bird (Neogaeornis wetzeli Lambrecht) have been reported. The Cenozoic fossil record comprises abundant and well-preserved marine birds from Eocene and Miocene units, with a specially abundant record of Sphenisciformes and less frequently, Procellariiformes. There is an excellent Miocene-Pliocene record of other birds such as Odontopterygiformes, including the most complete skeleton ever found of a pelagornithid, Pelagornis chilensis Mayr and Rubilar-Rogers. Fossil birds are also known from Pliocene and Pleistocene strata. A remarkable collection of birds was discovered in lacustrine sediments of late Pleistocene age associated to human activity. The perspectives in the study of dinosaurs in Chile are promising because plenty of material stored in institutional collections is not described yet. The record of Chilean dinosaurs is relevant for understanding the dynamics and evolution of this group of terrestrial animals in the western edge of Gondwana, while Cenozoic birds from the Region may contribute to the understanding of current biogeography for instance, the effect of the emergence and establishment of the Humboldt Current.

  17. First Fossil Record of Alphonsea Hk. f. & T. (Annonaceae) from the Late Oligocene Sediments of Assam, India and Comments on Its Phytogeography

    PubMed Central

    Srivastava, Gaurav; Mehrotra, Rakesh C.

    2013-01-01

    A new fossil leaf impression of Alphonsea Hk. f. & T. of the family Annonaceae is described from the Late Oligocene sediments of Makum Coalfield, Assam, India. This is the first authentic record of the fossil of Alphonsea from the Tertiary rocks of South Asia. The Late Oligocene was the time of the last significant globally warm climate and the fossil locality was at 10°–15°N palaeolatitude. The known palaeoflora and sedimentological studies indicate a fluvio-marine deltaic environment with a mosaic of mangrove, fluvial, mire and lacustrine depositional environments. During the depositional period the suturing between the Indian and Eurasian plates was not complete to facilitate the plant migration. The suturing was over by the end of the Late Oligocene/beginning of Early Miocene resulting in the migration of the genus to Southeast Asia where it is growing profusely at present. The present study is in congruence with the earlier published palaeofloral and molecular phylogenetic data. The study also suggests that the Indian plate was not only a biotic ferry during its northward voyage from Gondwana to Asia but also a place for the origin of several plant taxa. PMID:23349701

  18. Harvestmen (Arachnida: Opiliones) from the Middle Jurassic of China

    NASA Astrophysics Data System (ADS)

    Huang, Diying; Selden, Paul A.; Dunlop, Jason A.

    2009-08-01

    Harvestmen (Arachnida: Opiliones) are familiar animals in most terrestrial habitats but are rare as fossils, with only a handful of species known from each of the Palaeozoic, Mesozoic, and Cenozoic eras. Fossil harvestmen from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China, are described as Mesobunus martensi gen. et sp. nov. and Daohugopilio sheari gen. et sp. nov.; the two genera differ primarily in the relative length of their legs and details of the pedipalps. Jurassic arachnids are extremely rare and these fossils represent the first Jurassic, and only the fourth Mesozoic, record of Opiliones. These remarkably well-preserved and modern-looking fossils are assigned to the Eupnoi, whereby M. martensi demonstrably belongs in Sclerosomatidae. It thus represents the oldest record of a modern harvestman family and implies a high degree of evolutionary stasis among one of the most widespread and abundant groups of long-legged, round-bodied harvestmen.

  19. Middle and upper jurassic depositional environments at outer shelf and slope of Baltimore Canyon Trough

    Microsoft Academic Search

    L. A. Gamboa; P. L. Stoffa; M. Truchan

    1985-01-01

    New CDP data acquired in the Baltimore Canyon Trough during project LASE made it possible to map a continuous Jurassic sedimentary sequence from the continental margin to the abyssal plain without interruption by basement structures. Intense carbonate sedimentation is inferred at the outer shelf during the Middle and Late Jurassic. Carbonate sedimentation probably started during the Middle Jurassic with a

  20. Geological Society of America Paleogeographic and tectonic implications of Jurassic sedimentary

    E-print Network

    Busby, Cathy

    -marine rocks as Jurassic instead of Triassic suggests a period of uplift and erosion or nondeposition extending of Jurassic sedimentary and volcanic sequences in the central Mojave block Elizabeth R. Schermer Department that at least part, and possibly all, of the Fairview Valley For- mation is late Early Jurassic in age. We

  1. Jurassic Paleolatitudes, Paleogeography, and Climate Transitions In the Mexican Subcontinen

    NASA Astrophysics Data System (ADS)

    Molina-Garza, R. S.; Geissman, J. W.; Lawton, T. F.

    2014-12-01

    Jurassic northward migration of Mexico, trailing the North America plate, resulted in temporal evolution of climate-sensitive depositional environments. Lower-Middle Jurassic rocks in central Mexico contain a record of warm-humid conditions, which are indicated by coal and compositionally mature sandstone deposited in continental environments. Preliminary paleomagnetic data indicate that these rocks were deposited at near-equatorial paleolatitudes. The Middle Jurassic (ca. 170 Ma) Diquiyú volcanic sequence in central Oaxaca give an overall mean of D=82.2º/ I= +4.1º (n=10; k=17.3, ?95=12º). In the Late Jurassic, the Gulf of Mexico formed as a subsidiary basin of the Atlantic Ocean, when the supercontinent Pangaea ruptured. Upper Jurassic strata, including eolianite and widespread evaporite deposits, across Mexico indicate dry-arid conditions. Available paleomagnetic data (compaction-corrected) from eolianites in northeast Mexico indicate deposition at ~15-20ºN. As North America moved northward during Jurassic opening of the Atlantic, different latitudinal regions experienced coeval Late Jurassic climatic shifts. Climate transitions have been widely recognized in the Colorado plateau region. The plateau left the horse-latitudes in the late Middle Jurassic to reach temperate humid climates at ~40ºN in the latest Jurassic. In turn, the southern end of the North America plate (central Mexico) reached arid horse-latitudes in the Late Jurassic. At that time, epeiric platforms developed in the circum-Gulf region after a long period of margin extension. We suggest that Upper Jurassic hydrocarbon source rocks in the circum-Gulf region accumulated on these platforms as warm epeiric hypersaline seas and the Gulf of Mexico itself were fertilized by an influx of wind-blown silt from continental regions. Additional nutrients were brought to shallow zones of photosynthesis by ocean upwelling driven by changes in the continental landmass configuration.

  2. Fossil Halls: Timelines

    NSDL National Science Digital Library

    Part of a larger virtual tour of the Museum's famed Fossil Halls, this Web site allows students to travel back in time to several prehistoric points in the history of Earth. At each, they'll find a fleshed-out portrait of the period's creatures and their environment. The eight periods students will visit, some of which include more than one point-in-time snapshot, are Pleistocene, Miocene, Oligocene, Eocene, Cretaceous, Jurassic, Permian and Devonian Periods.

  3. Triassic-Jurassic organic carbon isotope stratigraphy of key sections in the western Tethys realm (Austria)

    NASA Astrophysics Data System (ADS)

    Ruhl, Micha; Kürschner, Wolfram M.; Krystyn, Leopold

    2009-05-01

    The late Triassic period is recognized as one of the five major mass extinctions in the fossil record. All these important intervals in earth history are associated with excursions in C-isotope records thought to have been caused by perturbations in the global carbon cycle. The nature and causes of C-isotopic events across the Triassic-Jurassic (T-J) transition however, are poorly understood. We present several new high resolution organic C-isotope records from the Eiberg Basin, Austria, including the proposed Global boundary Stratotype Section and Point (GSSP) for the base of the Jurassic. The Triassic-Jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions (CIE) of up to 8‰. The initial and main CIEs are biostratigraphically constrained by first and last occurrences of boundary defining macro- and microfossils (e.g. ammonites). High resolution C-isotope records appear to be an excellent correlation proxy for this period in the Eiberg Basin. Pyrolysis analysis demonstrates increased Hydrogen Index (HI) values for organic matter coinciding with the initial CIE. Terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the C-isotope composition of the sedimentary organic matter. This may have contributed to the extreme amplitude of the initial CIE in the Eiberg Basin.

  4. Paleomagnetic and rock magnetic evidence for a secondary yet early magnetization in large sandstone pipes and host Late Middle Jurassic (Callovian) Summerville Formation and Bluff Sandstone near Mesita, west central New Mexico

    NASA Astrophysics Data System (ADS)

    Geissman, John W.; Harlan, Stephen S.

    2004-07-01

    Processes responsible for the acquisition of ancient yet secondary magnetizations are important facets of the geologic history of rocks and, when the age of such magnetizations can be estimated with confidence, provide useful information on the ancient geomagnetic field. In west central New Mexico near Mesita, on the Colorado Plateau, hematitic sandstone and siltstone beds of the Middle Jurassic (Callovian) Summerville Formation and overlying Bluff Sandstone are host to numerous large (up to 100 m2 in map area) pipe-like sandstone bodies. The pipes are as strongly cemented by hematite (colors range from 10R 6/6 to 10R 3/4) as the host strata; paleomagnetic data from them and their host strata are interpreted to indicate that these rocks have been remagnetized, probably in association with sandstone pipe formation. Reverse polarity magnetizations isolated in both alternating field and thermal demagnetization from pipes are well grouped and are similar to, and not statistically distinct from, those in adjacent host strata. The grand-mean direction for 16 sites (7 sites in sandstone pipes and 9 in host strata), corrected for slight (5°) west-northwest tilt of the strata, is D = 163.0°, I = -44.3° (?95 = 2.7°, k = 169). This direction yields a pole position of 72.8°N, 135.7°E (dp = 2.1°, dm = 3.4°). Assuming a modest (i.e., ˜5°) clockwise rotation of the Colorado Plateau, the pole lies at 68.7°N, 143.8°E. Median destructive fields for the remanence in pipes and host strata are typically 40-50 mT; over 90% of the remanence is "unblocked" or removed during changes in the magnetic mineralogy by temperatures of ˜400-450°C. Isothermal remanent magnetization (IRM) acquisition data, and thermal demagnetization of "saturation" IRM, however, demonstrate that the dominant magnetic phase is of high coercivity and relatively high (above 600°C) laboratory unblocking temperatures in both sandstone pipes and host strata, yet it does not appear to contribute significantly to the characteristic remanent magnetization. The similarity in demagnetization properties between pipes and adjacent host strata, the absence of a well-defined high unblocking temperature remanence that is more typical of hematite-cemented detrital strata, and the essentially uniform reverse polarity of the remanence are all interpreted to indicate that pipes and host strata contain secondary, yet early acquired magnetizations and that magnetization acquisition continued after pipe injection. We propose that acquisition of the secondary magnetization took place in the presence of alkaline, high pH brines formed by the dissolution of the underlying gypsum-dominated Lower Jurassic Todilto Formation strata and therefore the remanence is early in age. On the basis of a comparison with Summerville and Morrison (Middle and Late Jurassic) paleomagnetic poles from rocks on the Colorado Plateau, we interpret the secondary remanence in Summerville strata and sandstone pipes near Laguna to be latest Middle to Late Jurassic in age. If realistic, this interpretation further emphasizes the importance of fluid-rock interaction in the acquisition of secondary magnetizations.

  5. ?44/40Ca variations of seawater from Cenozoic and Mesozoic fossil corals

    NASA Astrophysics Data System (ADS)

    Gothmann, A. O.; Higgins, J. A.; Blättler, C. L.; Stolarski, J.; Adkins, J. F.; Bender, M. L.

    2013-12-01

    Numerous archives including fossil carbonates, marine barite, and authigenic phosphates have shown that the Ca-isotope composition of seawater has varied throughout the Phanerozoic. Such changes are thought to be driven by oscillations between calcite seas and aragonite seas, with relatively heavy seawater ?44/40Ca occurring when aragonite deposition is favored and relatively light seawater ?44/40Ca when calcite deposition is favored[1,2]. While the Ca-isotope composition of Neogene and Late Paleogene seawater has been fairly well characterized, current records lack redundancy for ages >35Ma, and are sparsely sampled during the Late Mesozoic and Early Cenozoic. Fossil scleractinian corals may be good candidates for supplementing existing records of seawater Ca isotopes. Although the coral Ca-isotope effect has been shown to be somewhat variable between different taxa, it has also been shown that the Ca-isotope composition of scleractinians exhibits a weak temperature dependence, and is essentially independent of salinity and calcification rate[3]. We measured a suite of ~35 well-preserved fossil corals for Ca isotopes, ranging in age from Jurassic through Recent. We find that the ?44/40Ca seawater composition reconstructed from Neogene-age fossil corals is broadly consistent with existing records. However, Cretaceous and Late Jurassic fossil corals are ~1.1‰ lighter in ?44/40Ca than modern corals. The Cretaceous and Jurassic data support a record from Cretaceous-age authigenic phosphates, but indicate a ?44/40Ca of seawater that is ~0.8‰ lower than that inferred from fossil brachiopods and belemnites of similar ages. We are uncertain which record may best reflect the isotopic composition of seawater, but the differences between these reconstructions have implications for our current understanding of calcite and aragonite seas, and for the global calcium cycle. It is also possible that part of the depletion observed in Jurassic and Cretaceous age corals reflects a varying coral Ca-isotope effect as a result of changes in the seawater Ca concentration. [1] Blätter, C.L., et al. (2012) Geology, 40, 843-846. [2] F?rkas, J., et al. (2007) Geochimica et Cosmochimica Acta, 71, 5117-5134. [3] Pretet, C. et al. (2013) Chemical Geology, 340, 49-58.

  6. Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona)

    NASA Astrophysics Data System (ADS)

    Padian, Kevin

    1989-05-01

    The Glen Canyon Group (Moenave, Wingate, Kayenta and Navajo Formations) of northern Arizona represents an extensive outcrop of early Mesozoic age terrestrial sediments. The age of these formations has long been disputed because independent stratigraphic data from marine tie-ins, paleobotanical and palynological evidence, and radiometric calibrations have been scanty or absent. The fauna of the Kayenta Formation in particular has been problematic because it has appeared to contain both typical Late Triassic and Early Jurassic taxa Here I report that the principal evidence for Late Triassic taxa, dermal scutes previously assigned to an aetosaur, in fact belongs to the thyreophoran ornithischian dinosaur Scelidosaurus, previously known only as a washed-in form found in marine sediments in the Early Jurassic of England. The presence of this dinosaur represents the first vertebrate biostratigraphic tie-in of the Glen Canyon Group horizons with reliably dated marine deposits in Europe. Together with revised systematic assessments of other vertebrates and independent evidence from fossil pollen, it supports an Early Jurassic age for the Kayenta Formation and most or all of the Glen Canyon Group.

  7. Demography of late Miocene rhinoceroses (Teleoceras proterum and Aphelops malacorhinus) from Florida: linking mortality and sociality in fossil assemblages

    Microsoft Academic Search

    Matthew C. Mihlbachler

    2003-01-01

    Among polygynous mammals, a heightened risk of mortality is linked to the intensity of intragender competition and life-history stages, such as sexual maturity, where inexperienced individuals are vulnerable to the aggressive behaviors of dominant individuals. In this respect, the age- and sex-specific mortality patterns found in fossil assemblages could be informative of soci- ality in extinct species. This possibility was

  8. Late Quaternary continental and marine sediments of northeastern Buenos Aires province (Argentina): Fossil content and paleoenvironmental interpretation

    Microsoft Academic Search

    Enrique Fucks; Marina Aguirre; Cecilia M. Deschamps

    2005-01-01

    Abundant invertebrate and vertebrate fossil remains that exhibit excellent preservation and were collected from deposits of both continental and marine origins at Pilar (Buenos Aires, Argentina) add paleoenvironmental data from the northeastern Buenos Aires province area linked to sea-level oscillations and climate variability since approximately 120ka BP (marine oxygen isotope stage [MOIS] 5e). Two new fossiliferous localities discovered in the

  9. Thorough assessment of DNA preservation from fossil bone and sediments excavated from a late Pleistocene-Holocene cave deposit on Kangaroo Island, South Australia

    NASA Astrophysics Data System (ADS)

    Haouchar, Dalal; Haile, James; McDowell, Matthew C.; Murray, Dáithí C.; White, Nicole E.; Allcock, Richard J. N.; Phillips, Matthew J.; Prideaux, Gavin J.; Bunce, Michael

    2014-01-01

    Fossils and sediments preserved in caves are an excellent source of information for investigating impacts of past environmental changes on biodiversity. Until recently studies have relied on morphology-based palaeontological approaches, but recent advances in molecular analytical methods offer excellent potential for extracting a greater array of biological information from these sites. This study presents a thorough assessment of DNA preservation from late Pleistocene-Holocene vertebrate fossils and sediments from Kelly Hill Cave Kangaroo Island, South Australia. Using a combination of extraction techniques and sequencing technologies, ancient DNA was characterised from over 70 bones and 20 sediment samples from 15 stratigraphic layers ranging in age from >20 ka to ˜6.8 ka. A combination of primers targeting marsupial and placental mammals, reptiles and two universal plant primers were used to reveal genetic biodiversity for comparison with the mainland and with the morphological fossil record for Kelly Hill Cave. We demonstrate that Kelly Hill Cave has excellent long-term DNA preservation, back to at least 20 ka. This contrasts with the majority of Australian cave sites thus far explored for ancient DNA preservation, and highlights the great promise Kangaroo Island caves hold for yielding the hitherto-elusive DNA of extinct Australian Pleistocene species.

  10. New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary

    PubMed Central

    Fischer, Valentin; Maisch, Michael W.; Naish, Darren; Kosma, Ralf; Liston, Jeff; Joger, Ulrich; Krüger, Fritz J.; Pérez, Judith Pardo; Tainsh, Jessica

    2012-01-01

    Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. Methodology/Principal Findings Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian–Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian–Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian–Barremian interval and the JCB records one of the highest survival rates of the interval. Conclusions/Significance There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle Jurassic to their total extinction at the beginning of the Late Cretaceous. PMID:22235274

  11. Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis

    Microsoft Academic Search

    Christine E. Turner; Fred Peterson

    2004-01-01

    A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic\\/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early

  12. Paleontology, paleoclimatology and paleoecology of the late middle miocene Musselshell Creek flora, Clearwater County Idaho. A preliminary study of a new fossil flora

    SciTech Connect

    Baghai, N.L. [Univ. of Texas, Austin, TX (United States); Jorstad, R.B. [Eastern Illinois Univ., Charleston, IL (United States)

    1995-10-01

    The Musselshell Creek flora (12.0-10.5 Ma) of northern Idaho is used to reconstruct paleoclimatic and paleoecologic parameters of the Pacific Northwest during the late Middle Miocene. Other megafossil and microfossil floral records spanning 12.0-6.4 Ma are unknown from this region. The Musselshell Creek fossil flora, previously undescribed, is preserved in lacustrine clays and sediments that accumulated in a narrow valley surrounded by rugged terrain. Dominant taxa include dicotyledons and conifers. Most of the leaves are preserved as impressions or compressions. Some fossil leaves retained their original pigmentation, cellular anatomy, and organic constituents. Other fossils include excellent remains of pollen and spores, dispersed leaf cuticle, pyritized wood, and disarticulated fish bones. A destructive statistical analysis of one block of sediment, approximately 30 cm x 45 cm (1.5 sq. ft) recovered 14 orders, 23 families, and 34 genera of spermatophyte plant fossils. These floral elements are compared with two other earlier Miocene floras which were similarly sampled. Common megafossil genera include Quercus, Zizy-phoides, Taxodium, Alnus, Castanea, Magnolia, Acer, Ex-bucklandia, Sequoia, Populus, and Betula. The rare occurrence of Ginkgo leaves is a first record of this taxon in the Idaho Miocene. Additional plant taxa, are represented by palynomorphs. Common pollen taxa are Pinus, Abies, Carya, Quercus, and Tilia. Most of the megafossil and microfossil flora assemblage is characteristic of a streambank to floodplain environment that existed in a warm to cool temperate climate similar to the modern Mid-Atlantic coast of the United States. 47 refs., 5 figs., 4 tabs.

  13. Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology and oxygen

    E-print Network

    Schöne, Bernd R.

    Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology Abstract Fossil biogenic phosphate of fast-growing primary bone tissue of dinosaurs can preserve dinosaurs with different histologic patterns of bone growth, high-resolution oxygen isotope profiles were

  14. New Early Jurassic Tetrapod Assemblages Constrain Triassic-Jurassic Tetrapod Extinction Event

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.; Shubin, N. H.; Anders, M. H.

    1987-08-01

    The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all ``typical Triassic'' forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.

  15. X-ray Synchrotron Microtomography of a silicified Jurassic Cheirolepidiaceae (Conifer) cone: histology and morphology of Pararaucaria collinsonae sp. nov.

    PubMed Central

    Steart, David C.; Spencer, Alan R.T.; Garwood, Russell J.; Hilton, Jason; Munt, Martin C.; Needham, John

    2014-01-01

    We document a new species of ovulate cone (Pararaucaria collinsonae) on the basis of silicified fossils from the Late Jurassic Purbeck Limestone Group of southern England (Tithonian Stage: ca. 145 million years). Our description principally relies on the anatomy of the ovuliferous scales, revealed through X-ray synchrotron microtomography (SRXMT) performed at the Diamond Light Source (UK). This study represents the first application of SRXMT to macro-scale silicified plant fossils, and demonstrates the significant advantages of this approach, which can resolve cellular structure over lab-based X-ray computed microtomography (XMT). The method enabled us to characterize tissues and precisely demarcate their boundaries, elucidating organ shape, and thus allowing an accurate assessment of affinities. The cones are broadly spherical (ca. 1.3 cm diameter), and are structured around a central axis with helically arranged bract/scale complexes, each of which bares a single ovule. A three-lobed ovuliferous scale and ovules enclosed within pocket-forming tissue, demonstrate an affinity with Cheirolepidiaceae. Details of vascular sclerenchyma bundles, integument structure, and the number and attachment of the ovules indicate greatest similarity to P. patagonica and P. carrii. This fossil develops our understanding of the dominant tree element of the Purbeck Fossil Forest, providing the first evidence for ovulate cheirolepidiaceous cones in Europe. Alongside recent discoveries in North America, this significantly extends the known palaeogeographic range of Pararaucaria, supporting a mid-palaeolatitudinal distribution in both Gondwana and Laurasia during the Late Jurassic. Palaeoclimatic interpretations derived from contemporaneous floras, climate sensitive sediments, and general circulation climate models indicate that Pararaucaria was a constituent of low diversity floras in semi-arid Mediterranean-type environments. PMID:25374776

  16. Palaeo-equatorial temperatures and carbon-cycle evolution at the Triassic- Jurassic boundary: A stable isotope perspective from shallow-water carbonates from the UAE

    NASA Astrophysics Data System (ADS)

    Honig, M. R.; John, C. M.

    2013-12-01

    The Triassic-Jurassic boundary was marked by global changes including carbon-cycle perturbations and the opening of the Atlantic Ocean. These changes were accompanied by one of the major extinction events of the Phanerozoic. The carbon-cycle perturbations have been recorded in carbon isotope curves from bulk carbonates, organic carbon and fossil wood in several Tethyan locations and have been used for chemostratigraphic purposes. Here we present data from shallow-marine carbonates deposited on a homoclinal Middle Eastern carbonate ramp (United Arab Emirates). Our site was located at the equator throughout the Late Triassic and the Early Jurassic, and this study provides the first constraints of environmental changes at the low-latitudes for the Triassic-Jurassic boundary. Shallow-marine carbonate depositional systems are extremely sensitive to palaeoenvironmental changes and their usefulness for chemostratigraphy is being debated. However, the palaeogeographic location of the studied carbonate ramp gives us a unique insight into a tropical carbonate factory at a time of severe global change. Stable isotope measurements (carbon and oxygen) are being carried out on micrite, ooids and shell material along the Triassic-Jurassic boundary. The stable isotope results on micrite show a prominent negative shift in carbon isotope values of approximately 2 ‰ just below the inferred position of the Triassic-Jurassic boundary. A similar isotopic trend is also observed across the Tethys but with a range of amplitudes (from ~2 ‰ to ~4 ‰). These results seem to indicate that the neritic carbonates from our studied section can be used for chemostratigraphic purposes, and the amplitudes of the carbon isotope shifts provide critical constraints on the magnitude of carbon-cycle perturbations at low latitudes across the Triassic-Jurassic boundary. Seawater temperatures across the Triassic-Jurassic boundary will be constrained using the clumped isotope palaeo-thermometer applied to blocky calcite, bulk carbonate, oyster shells and echinoids. Assuming a pristine depositional signal can be extracted from one of the components, clumped isotopes will either shed light on the palaeoenvironmental conditions and the isotopic composition of a tropical ocean during the Late Triassic / Early Jurassic, or on the diagenetic history of the platform. We gratefully acknowledge funding from Qatar Petroleum, Shell, and Qatar Science & Technology Park.

  17. Zircon U-Pb ages and petrogenesis of a tonalite-trondhjemite-granodiorite (TTG) complex in the northern Sanandaj-Sirjan zone, northwest Iran: Evidence for Late Jurassic arc-continent collision

    NASA Astrophysics Data System (ADS)

    Azizi, Hossein; Zanjefili-Beiranvand, Mina; Asahara, Yoshihiro

    2015-02-01

    The Ghalaylan Igneous Complex is located in the northern part of the Sanandaj-Sirjan zone (SSZ) in northwest Iran. At the surface, the complex is ellipsoidal or ring-shaped. The igneous rocks, which are medium- to fine-grained, were intruded into a Jurassic metamorphic complex and are cut by younger dikes. Zircon U-Pb ages indicate that the crystallization of the main body occurred from 157.9 ± 1.6 to 155.6 ± 5.6 Ma. The igneous complex includes granodiorite, tonalite, and quartz monzonite, as well as subvolcanic to volcanic rocks such as dacite and rhyolite. The rocks have high concentrations of Al2O3 (15-19 wt.%), SiO2 (65-70 wt.%), and Sr (700-1100 ppm), high (La/Yb)N ratios (15-40), and very low concentrations of MgO (< 0.83 wt.%), Ni (< 7 ppm), and Cr (usually < 50 ppm). There is a lack of negative Eu anomalies. These geochemical features show that the rocks are similar to high-silica adakites and Archaean tonalite-trondhjemite-granodiorite (TTG) rocks. The initial ratios of 87Sr/86Sr and 143Nd/144Nd vary from 0.70430 to 0.70476 and from 0.51240 to 0.51261, respectively, values that are similar to those of primitive mantle and the bulk Earth. The chemical compositions of the igneous rocks of the complex, and their isotope ratios, differ from those of neighboring granitic bodies in the northern SSZ. Based on our results, we suggest a new geodynamic model for the development of this complex, as follows. During the generation of the Songhor-Ghorveh island arc in the Neotethys Ocean, an extensional basin, such as a back-arc, developed between the island arc and the Sanandaj-Sirjan zone (SSZ). As a consequence, basaltic magma was injected from the asthenosphere without the development of a mature oceanic crust. During arc-continent collision in the Late Jurassic, hot basaltic rocks were present beneath the SSZ at depths of 30-50 km, and the partial melting of these rocks led to the development of TTG-type magmas, forming the source of the Ghalaylan Igneous Complex.

  18. From Back-arc Drifting to Arc Accretion: the Late Jurassic-Early Cretaceous Evolution of the Guerrero Terrane Recorded by a Major Provenance Change in Sandstones from the Sierra de los Cuarzos, Central Mexico

    NASA Astrophysics Data System (ADS)

    Palacios Garcia, N. B.; Martini, M.

    2014-12-01

    The Guerrero terrane composed of Middle Jurassic-Early Cretaceous arc assemblages, were drifted from the North American continental mainland during lower Early Cretaceous spreading in the Arperos back arc basin, and subsequently accreted back to the continental margin in the late Aptian. Although the accretion of the Guerrero terrane represents one of the major tectonic processes that shaped the southern North American Pacific margin, the stratigraphic record related to such a regional event was not yet recognized in central Mexico. Due to the Sierra de los Cuarzos is located just 50 km east of the Guerrero terrane suture belt, its stratigraphic record should be highly sensitive to first order tectonic changes and would record a syn-tectonic deposits related to this major event. In that study area, were identified two main Upper Jurassic-Lower Cretaceous clastic units. The Sierra de los Cuarzos formation represents the lowermost exposed stratigraphic record. Sedimentary structures, sandstones composition, and U-Pb detrital zircon ages document that the Sierra de los Cuarzos formation reflects a vigorous mass wasting along the margin of the North American continental mainland, representing the eastern side of the Arperos back arc basin. Sandstones of the Sierra de los Cuarzos formation are free from detrital contributions related to the Guerrero terrane juvenile sources, indicating that the Arperos Basin acted like an efficient sedimentological barrier that inhibited the influence of the arc massifs on the continental mainland deposits. The Sierra de los Cuarzos formation is overlain by submarine slope deposits of the Pelones formation, which mark a sudden change in the depositional conditions. Provenance analysis documents that sandstones from the Pelones formation were fed by the mafic to intermediate arc assemblages of the Guerrero terrane, as well as by quartz-rich sources of the continental mainland, suggesting that, by the time of deposition of the Pelones formation, the Arperos Basin was closed and the Guerrero terrane was juxtaposed to the continental domain. Based on these data, we interpret the Pelones formation as the record of the major crustal reorganization in central Mexico related to the inversion of the Arperos back arc basin and accretion of the Guerrero terrane to the continental mainland.

  19. Jurassic Park Safety Audit

    NSDL National Science Digital Library

    Using the first 30 minutes of the film Jurassic Park, the student will audit it for violations of safety rules and regulations, OSHA violations, and violations of HASP's. Access to the activity required free and quick registration with ATEEC.

  20. Triassic/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama

    SciTech Connect

    Hutley, J.K.

    1985-02-01

    Two major fault systems influenced Jurassic structure and deposition on the Conecuh Ridge, southwest Alabama. Identification and dating of these fault systems are based on seismic-stratigraphic interpretation of a 7-township grid in Monroe and Conecuh Counties. Relative time of faulting is determined by fault geometry and by formation isopachs and isochrons. Smackover and Norphlet Formations, both Late Jurassic in age, are mappable seismic reflectors and are thus reliable for seismicstratigraphic dating. The earlier of the 2 fault systems is a series of horsts and grabens that trends northeast-southwest and is Late Triassic to Early Jurassic in age. The system formed in response to tensional stress associated with the opening of the Atlantic Ocean. The resulting topography was a series of northeast-southwest-trending ridges. Upper Triassic Eagle Mills and Jurassic Werner Formations were deposited in the grabens. The later fault system is also a series of horsts and grabens trending perpendicular to the first. This system was caused by tensional stress related to a pulse in the opening of the Gulf of Mexico. Faulting began in Early Jurassic and continued into Late Jurassic, becoming progressively younger basinward. At the basin margin, faulting produced a very irregular shoreline. Submerged horst blocks became centers for shoaling or carbonate buildups. Today, these blocks are exploration targets in southwest Alabama.

  1. Jurassic Reef Park

    NSDL National Science Digital Library

    Reinhold Leinfelder

    This is a bilingual, educational website from Munich, Germany. The main feature is a virtual field trip to the reefs of the Jurassic period. Besides a view of the Jurassic reefs, their builders, and their ecological settings, there is also an emphasis on the importance of modern reefs as indicators of the state-of-health of the globe and evidence of how some changes in the composition of reefs may represent the forerunners of catastrophic, regional or global, environmental change.

  2. Jurassic Reef Park

    NSDL National Science Digital Library

    Dr. Reinhold Leinfelder of the University of Stuttgart, Germany created this interesting site in English and German, offering a "virtual trip to the reefs of the Jurassic Period." In the Introduction, viewers will find background material and comparisons of modern and ancient reefs. Further information is provided in the sections on reef architecture, reef formation, Jurassic reefs, and reefs and global climate change. Although the English language is slightly quirky, the content and images more than compensate, making this a worthwhile site.

  3. Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages

    NASA Astrophysics Data System (ADS)

    Thompson, Woodrow B.; Griggs, Carol B.; Miller, Norton G.; Nelson, Robert E.; Weddle, Thomas K.; Kilian, Taylor M.

    2011-05-01

    Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 14C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/-20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 14C yr BP ( Mytilus edulis) and 12,800 ± 55 14C yr BP ( Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England.

  4. Reconstructions of Late Holocene Climate Using Ice-entombed Mosses and Sub-fossil Peat on the Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng; Loisel, Julie; Beilman, David; Cleary, Kate

    2015-04-01

    The western Antarctic Peninsula (WAP) is one of three regions on Earth that have experienced the greatest warming over recent decades. Here we used paleo records from fossil mosses and peats on the WAP to explore a new paleoclimate archive that links climate, cryosphere and ecosystem dynamics for reconstructing climate change in recent millennia. Continuing retreat of ice and permanent snow has recently exposed numerous entombed mosses and intact peatbank ecosystems along the WAP around 65°S latitude that have been buried under ice and snow during the cold "Little Ice Age" (LIA). Radiocarbon dating indicates ages of 850-600 cal yr BP from re-exposed moss samples from retreating ice and of 100 cal yr BP from near shrinking snow. This age difference suggests that initial climate cooling and subsequent ice advance overran peatbanks immediately below the ice margin at the onset of the LIA, followed by permanent snow expansion often from low elevation upslope at the end of the LIA. Furthermore, detailed macrofossil and pollen analysis of a peat core from a moss peatbank on nearby mainland Antarctic Peninsula show dramatic shifts from a waterlogged peatland dominated by pure stands of Antarctic hairgrass (Deschampsia antarctica) before the LIA at 2400-600 cal yr BP to an aerobic peatbank dominated by erect mosses Polytrichum strictum and Chorisodontium aciphyllum in the last 50 years. At present the nearest known occurrence of Deschampsia "bog peats" is in South Georgia, about 1900 km north at 54°S, a location having a mean annual temperature 6°C higher than the study region on the WAP. If we use this modern spatial relationship as an analogue, then this suggests that the climate a few centuries ago was much warmer (up to 6°C) than today and supported very different ecosystems on the WAP. Our results show that these re-exposed sub-fossil mosses and peats are potentially very useful for the reconstructions of coastal low-elevation terrestrial climates. These records will not only complement climate histories as we know mostly from marine and ice core records but also provide more relevant environmental settings for understanding animal and ecosystem dynamics on the WAP.

  5. Jurassic crustal deformation in west-central part of Colorado Plateau

    SciTech Connect

    Peterson, F.

    1985-05-01

    Although the Jurassic Period is commonly thought of as a time of tectonic quiescence, updated isopach maps and new sedimentologic information indicate that it was a time of notable crustal deformation on the Colorado Plateau. A significant change in structural style occurred in Middle Jurassic time, especially during the erosion interval that produced the J-3 unconformity. Prior to late Middle Jurassic time, the region had been tilted westward and structural troughs formed in the area of the present-day Circle Cliffs uplift and in the vicinity of the Circle Cliffs and Black Mesa regions were uplifted and the nearby Henry and Kaiparowits regions began to be downwarped as troughs or basins. It cannot be determined if or how the present-day monoclines flexed during the Jurassic. However, the direction of structural tilt across these areas changed from west side down to east side down during the late Middle and early Late Jurassic. The Monument region, the largest and most persistent structural element in the region, changed from a structural bench to a positive structure in the early Late Jurassic. In most cases the positive structures subsided more slowly than adjacent downwarps. Two exceptions during the Late Jurassic are the Black Mesa and Emery uplifts. These are the only uplifts that actually rose above the level of sediment accumulation. Jurassic rocks are not known to contain significant hydrocarbon resources in this region, but their tectonic history may offer clues to the structural history of underlying Paleozoic strata, which are the primary hydrocarbon exploration targets.

  6. Radiometric Dating of Ignimbrite from Inner Mongolia Provides no Indication of a Post-Middle Jurassic Age for the Daohugou Beds

    Microsoft Academic Search

    GAO Ke-Qin; REN Dong

    Lacustrine deposits exposed at Daohugou, Inner Mongolia, China, have yielded superbly preserved vertebrate fossils. The fossil beds were first misinterpreted as of Early Cretaceous age, based on alleged occurrences of key fossils of the Jehol Biota. Compelling evidence revealed by more rigorous research involving regional biostratigraphy, radiometric dating, and paleontology supports the Middle Jurassic age of the fossil beds. Despite

  7. High-elevation late Pleistocene (MIS 6-5) vertebrate faunas from the Ziegler Reservoir fossil site, Snowmass Village, Colorado

    NASA Astrophysics Data System (ADS)

    Sertich, Joseph J. W.; Stucky, Richard K.; McDonald, H. Gregory; Newton, Cody; Fisher, Daniel C.; Scott, Eric; Demboski, John R.; Lucking, Carol; McHorse, Brianna K.; Davis, Edward B.

    2014-11-01

    The vertebrate record at the Ziegler Reservoir fossil site (ZRFS) near Snowmass Village, Colorado ranges from ~ 140 to 77 ka, spanning all of Marine Oxygen Isotope Stage (MIS) 5. The site contains at least 52 taxa of macro- and microvertebrates, including one fish, three amphibian, four reptile, ten bird, and 34 mammal taxa. The most common vertebrate is Ambystoma tigrinum (tiger salamander), which is represented by > 22,000 elements representing the entire life cycle. The mastodon, Mammut americanum, is the most common mammal, and is documented by > 1800 skeletal elements making the ZRFS one of the largest accumulations of proboscidean remains in North America. Faunas at the ZRFS can be divided into two groups, a lake-margin group dating to ~ 140-100 ka that is dominated by woodland taxa, and a lake-center group dating to ~ 87-77 ka characterized by taxa favoring more open conditions. The change in faunal assemblages occurred between MIS 5c and 5a (vertebrates were absent from MIS 5b deposits), which were times of significant environmental change at the ZRFS. Furthermore, the ZRFS provides a well-dated occurrence of the extinct Bison latifrons, which has implications for the timing of the Rancholabrean Mammal Age in the region.

  8. Trace fossils and sedimentology of a Late Cretaceous Progradational Barrier Island sequence: Bearpaw and Horseshoe Canyon Formations, Dorothy, Alberta

    SciTech Connect

    Saunders, T.D.; Pemberton, A.G.; Ranger, M.J. (Univ. of Alberta, Edmonton (Canada))

    1990-05-01

    A well-exposed example of a regressive barrier island succession crops out in the Alberta badlands along the Red Deer River Valley. In the most landward (northwestern) corner of the study area, only shallow-water and subaerial deposits are represented and are dominated by tidal inlet related facies. Seaward (southeast), water depth increases and the succession is typified by open-marine beach to offshore-related facies arranged in coarsening-upward progradational sequence. Detailed sedimentologic and ichnologic analyses of this sequence have allowed for its division into three distinct environmental zones (lower, middle, and upper). The lower zone comprises a laterally diverse assemblage of storm-influenced, lower shoreface through offshore deposits. Outcrop in the northeast is dominated by thick beds of hummocky and/or swaley cross-stratified storm sand. In the southeast, storm events have only minor influence. This lower zone contains a wide diversity of well-preserved trace fossils whose distribution appears to have been influenced by gradients in wave energy, bottom stagnation, and the interplay of storm and fair-weather processes. The middle zone records deposition across an upper shoreface environment. Here, horizontal to low-angle bedding predominates, with interspersed sets of small- and large-scale cross-bedding increasing toward the top. A characteristic feature of the upper part of this zone is the lack of biogenic structures suggesting deposition in an exposed high-energy surf zone. The upper zone records intertidal to supratidal progradation of the shoreline complex. Planar-laminated sandstone forms a distinct foreshore interval above which rhizoliths and organic material become increasingly abundant, marking transition to the backshore. A significant feature of this zone is the occurrence of an intensely bioturbated interval toward the top of the foreshore.

  9. Fern ecological implications from the Lower Jurassic in Western Hubei, China

    Microsoft Academic Search

    Yongdong Wang

    2002-01-01

    The Lower Jurassic Hsiangchi Formation in western Hubei, China is well known for its abundant and diverse fossil ferns, including Marattiaceae, Osmundaceae, Matoniaceae, Dipteridaceae and Dicksoniaceae. Through recent collections and investigation of the fossil plants in this area, an autochthonous\\/hypoautochthonous fern community has been recognised from the upper part of the Hsiangchi Formation in Zigui, Hubei. This community is dominated

  10. Tracing climatic conditions during the deposition of late Cretaceous-early Eocene phosphate beds in Morocco by geochemical compositions of biogenic apatite fossils

    NASA Astrophysics Data System (ADS)

    Kocsis, L.; Gheerbrant, E.; Mouflih, M.; Cappetta, H.; Yans, J.; Ulianov, A.; Amaghzaz, M.

    2012-04-01

    Morocco's Western Atlantic coast was covered by shallow seas during the late Cretaceous-early Eocene when large amount of phosphate rich sediments were deposited. This time interval envelops a major part of the last greenhouse period and gives the opportunity to study the event's characteristics in shallow water settings. These phosphate deposits are extremely rich in vertebrate fossils, while other types of fossils are rare or often poorly preserved. Hence the local stratigraphy is based on the most abundant marine vertebrate fossils, on the selachian fauna (sharks and rays). Our geochemical investigations were also carried out on these remains, though in some cases frequently found coprolites were involved as well. The main goal of our study was to test whether stable isotope compositions (?18OPO4, ?13C) of these fossils reflect any of the hyperthermal events and/or the related perturbations in the carbon cycle during the early Paleogene (Lourens et al. 2005) and whether these geochemical signals can be used to refine the local stratigraphy. Additionally, the samples were analyzed for trace element composition in order to better assess local taphonomy and burial conditions. The samples came from two major phosphate regions, the Ouled Abdoun and the Ganntour Basins and they were collected either directly on the field during excavations (Sidi Chennane) or were obtained from museum collections with known stratigraphical position (Sidi Daoui, Ben Guerrir). The phosphate oxygen isotopic compositions of shark teeth display large range across the entire series (18.5-22.4 ) which can partly be related to the habitat of sharks. For instance the genus Striatolamnia often yielded the highest ?18O values indicating possible deep water habitat. Despite the large variation in ?18O values, a general isotope trend is apparent. In the Maastrichtian after a small negative shift, the ?18O values increase till the Danian from where the trend decrease till the Ypresian. The latter negative shift can be linked to the globally recognized Early Eocene Climatic Optimum (Zachos et al., 2001). In terms of carbon isotopic composition, shark teeth enameloid yielded often positive ?13C values, while dentine are always negative and sometimes following clear trend along the series. Coprolites have similar values to dentine, however they display greater variation reflecting the burial milieu and the special environment of phosphatization with the intensive organic matter recycling. Bone-beds show even more variations that could be caused by reworked specimens and also possible enhanced oxidation of organic matter at these levels. Nevertheless, the Sidi Chennane section shows a negative ?13C trend in the early Ypresian, which is compatible with global observations at the time. Moreover, the lowest ?13C values are from the transitional layer between the Ypresian and Thanetian beds which might relate to the Paleocene-Eocene boundary event, though it must be further confirmed. All the fossils display very similar rare earth element (REE) distribution that resembles typical seawater pattern with negative Ce-anomaly and heavy REE enrichment. However the large amount of analyses revealed a general drift in the magnitude of the Ce-anomaly from the older to younger beds that can be used in paleoenvironmental reconstruction.

  11. Late Pliocene and early Pleistocene sea-level timing and amplitudes derived from fossil ostracod assemblages: Canterbury Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Kusunoki, S.; Yamada, K.; Hoyanagi, K.

    2013-12-01

    IODP Expedition 317 cruise drilled cores at three shelf sites (U1353, U1354 and U1351) and one slope site (U1352), in water depths between 85 and 344 m, to understand relationships between sea-level change and sequence stratigraphy. The shelf sites are well suited to reconstruction of high-resolution sea-level fluctuations because of high sedimentation rates from the uplifting Southern Alps. We examined fossil ostracod assemblages from the shelf sites to reconstruct paleo-water depth fluctuations and their amplitudes. We identified 178 ostracod species and 70 genera from more than 160 samples. Q-mode factor analysis was performed on ostracod taxa with abundances of >3.5 % in each sample containing >50 specimens. Six varimax factors were explained 70.8% of the total variance. Paleo-water depths in each factor were calibrated with reference to recent ostracodes occurring around the sites as follows: first factor, middle shelf (50-80 m); second factor, middle to outer shelf (60-130 m); third factor, middle to outer shelf (55-115 m); fourth factor, lagoon, estuary and inner shelf (0-50 m); fifth factor, middle to outer shelf (80-200 m); sixth factor, outer shelf (130-200 m). Factor analysis of ostracod assemblages reveal at least, eight transgressive- and regressive-cycles at Site U1353, seventeen at Site U1354 and two at Site U1351. These cycles probably correspond to a subset of MIS stages between MIS M2 and MIS 40. Furthermore, amplitudes of these paleo-water-depth cycles are expected to equate to eustatic amplitudes because shelf sedimentation has been continuous and minimal subsidence can have occurred during the short time period involved. We therefore estimate that eustatic amplitudes were: 10 - 30 m from 3.1 to 2.8 Ma, ca. 100 m from 2.8 to 2.6 Ma, and 30 - 115 m from 1.8 to1.2 Ma. These amplitudes, together with the timing of the increase in amplitudes (~2.7 Ma), agree with estimates derived from oxygen isotopic records (Raymo et al., 2005), suggesting that the Canterbury Basin sequences responded to global climate change. However, comparison with sea-level amplitude estimates from the North Island of New Zealand (Naish, 1997) suggests that sea-level amplitudes increased in the Canterbury Basin 200 thousand years earlier than in the North Island.

  12. Jurassic hot spring deposits of the Deseado Massif (Patagonia, Argentina): Characteristics and controls on regional distribution

    Microsoft Academic Search

    Diego M. Guido; Kathleen A. Campbell

    2011-01-01

    The Deseado Massif, Santa Cruz Province, Argentinean Patagonia, hosts numerous Middle to Late Jurassic age geothermal and epithermal features represented by siliceous and calcareous chemical precipitates from hot springs (sinters and travertines, respectively), hydrothermal breccias, quartz veins, and widespread hydrothermal silicification. They indicate pauses in explosive volcanic activity, marking the final stages in the evolution of an extensive Jurassic (ca.

  13. Jurassic crustal deformation in west-central part of Colorado Plateau

    Microsoft Academic Search

    1985-01-01

    Although the Jurassic Period is commonly thought of as a time of tectonic quiescence, updated isopach maps and new sedimentologic information indicate that it was a time of notable crustal deformation on the Colorado Plateau. A significant change in structural style occurred in Middle Jurassic time, especially during the erosion interval that produced the J-3 unconformity. Prior to late Middle

  14. Journal of the Geological Society, London, Vol. 161, 2004, pp. 365379. Printed in Great Britain. Sea-level change and facies development across potential TriassicJurassic

    E-print Network

    Hesselbo, Stephen P.

    or a global context. Keywords: Triassic, Jurassic, extinction, sea-level change. Period boundaries commonly. 365 Sea-level change and facies development across potential Triassic­Jurassic boundary horizons, SW: The Late Triassic to Early Jurassic aged succession of SW Britain (the Penarth and lower Lias Groups

  15. Warm Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jenkyns, H. C.; Schouten-Huibers, L.; Schouten, S.; Sinninghe Damsté, J. S.

    2012-02-01

    Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26-30 °C) existed from this interval (∼160 Ma) to the Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian-Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (∼26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite ?18O data, assuming an isotopic composition of waters inhabited by these fossils of -1‰ SMOW, give palaeotemperatures throughout the Upper Jurassic-Lower Cretaceous interval that are consistently lower by ∼14 °C than does TEX86 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

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

    PubMed

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

    2013-12-01

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

  17. An Analytical Approach for Estimating Fossil Record and Diversification Events in Sharks, Skates and Rays

    PubMed Central

    Guinot, Guillaume; Adnet, Sylvain; Cappetta, Henri

    2012-01-01

    Background Modern selachians and their supposed sister group (hybodont sharks) have a long and successful evolutionary history. Yet, although selachian remains are considered relatively common in the fossil record in comparison with other marine vertebrates, little is known about the quality of their fossil record. Similarly, only a few works based on specific time intervals have attempted to identify major events that marked the evolutionary history of this group. Methodology/Principal Findings Phylogenetic hypotheses concerning modern selachians’ interrelationships are numerous but differ significantly and no consensus has been found. The aim of the present study is to take advantage of the range of recent phylogenetic hypotheses in order to assess the fit of the selachian fossil record to phylogenies, according to two different branching methods. Compilation of these data allowed the inference of an estimated range of diversity through time and evolutionary events that marked this group over the past 300 Ma are identified. Results indicate that with the exception of high taxonomic ranks (orders), the selachian fossil record is by far imperfect, particularly for generic and post-Triassic data. Timing and amplitude of the various identified events that marked the selachian evolutionary history are discussed. Conclusion/Significance Some identified diversity events were mentioned in previous works using alternative methods (Early Jurassic, mid-Cretaceous, K/T boundary and late Paleogene diversity drops), thus reinforcing the efficiency of the methodology presented here in inferring evolutionary events. Other events (Permian/Triassic, Early and Late Cretaceous diversifications; Triassic/Jurassic extinction) are newly identified. Relationships between these events and paleoenvironmental characteristics and other groups’ evolutionary history are proposed. PMID:22957091

  18. The Earliest Case of Extreme Sexual Display with Exaggerated Male Organs by Two Middle Jurassic Mecopterans

    PubMed Central

    Wang, Qi; Shih, Chungkun; Ren, Dong

    2013-01-01

    Background Many extant male animals exhibit exaggerated body parts for display, defense or offence in sexual selection, such as male birds of paradise showing off colorful and elegant feathers and male moose and reindeers bearing large structured antlers. For insects, male rhinoceros and stag beetles have huge horn-like structure for fighting and competition and some male Leptopanorpa scorpionflies have very long abdominal terminal segments for sexual display and competition. Fossil records of insects having exaggerated body parts for sexual display are fairly rare. One example is two male holcorpids with elongate abdominal segments from sixth (A6) to eighth (A8) and enlarged male genitalia from Eocene, suggesting evolution of these characters occurred fairly late. Principal Findings We document two mecopterans with exaggerated male body parts from the late Middle Jurassic Jiulongshan Formation in northeastern China. Both have extremely extended abdominal segments from A6 to A8 and enlarged genitalia, which might have been used for sexual display and, to less extent, for fighting with other males in the competition for mates. Although Fortiholcorpa paradoxa gen. et sp. nov. and Miriholcorpa forcipata gen. et sp. nov. seem to have affinities with Holcorpidae, we deem both as Family Incertae sedis mainly due to significant differences in branching pattern of Media (M) veins and relative length of A8 for F. paradoxa, and indiscernible preservation of 5-branched M veins in hind wing for M. forcipata. Conclusions/Significance These two new taxa have extended the records of exaggerated male body parts of mecopterans for sexual display and/or selection from the Early Eocene to the late Middle Jurassic. The similar character present in some Leptopanorpa of Panorpidae suggests that the sexual display and/or sexual selection due to extremely elongated male abdominal and sexual organs outweigh the negative impact of bulky body and poor mobility in the evolutionary process. PMID:23977031

  19. The Lower Jurassic of the Eastern Caspian region and the Middle Caspian Basin: Lithology, facies, taphonomy

    NASA Astrophysics Data System (ADS)

    Kiritchkova, A. I.; Nosova, N. V.

    2014-09-01

    Lithofacies of the productive Upper Triassic-Lower Jurassic deposits of the Eastern Caspian region, studied in wells on the Caspian coast and exposed in the outcrops of the Mountainous Mangyshlak, are described and analyzed. The similarity of the structure of the Mesozoic sedimentary beds of the Middle Caspian Basin and of those of the land adjacent to its eastern coast is confirmed. Comparative analysis of lithofacies allowed the reconstruction of the paleogeographic setting and depositional environments in the studied region during the Early Jurassic. A unique fossil plant occurrence is discovered in the upper part of the Lower Jurassic series (in the lower subformation of the Kokala Formation; Eastern Caspian region). Fossil plant taphonomy and the lithology of host rocks in the occurrence resulted from unusual paleogeographic settings that existed in the Middle Caspian Basin at the time of the Early-Middle Jurassic boundary.

  20. Depositional and diagenetic history of some Jurassic carbonates, Indian Rock-Gilmer Field, Upshur County, Texas

    E-print Network

    Fall, Steven Anthony

    1974-01-01

    as late as Eagle Mills time (Eaton, 1960; Halbouty, 1966), Jurassic transgression of the Texas portion of the uplift is confirmed Amerada No . 1 Stri ckland well in Shelby County, Texas, which penetrated a weathered syenite basement beneath Eagle Mills...

  1. A new species of Progonocimicidae (Hemiptera, Coleorrhyncha) from the Middle Jurassic of China

    Microsoft Academic Search

    Qiu-ping Dong; Yun-zhi Yao; Dong Ren

    2012-01-01

    Dong Q.P., Yao Y.Z. & Ren D., 2012. A new species of Progonocimicidae (Hemiptera, Coleorrhyncha) from the Middle Jurassic of China. Alcheringa, 1–7. ISSN 0311-5518. A new fossil species, Cicadocoris assimilis, of the family Progonocimicidae is described from the Middle Jurassic Jiulongshan Formation of Daohugou Village, Inner Mongolia, China. Cicadocoris Becker-Migdisova, 1958 and Mesocimex Hong, 1983 show no significant differences

  2. Filamentous microbial fossil from low-grade metamorphosed basalt in northern Chichibu belt, central Shikoku, Japan

    NASA Astrophysics Data System (ADS)

    Sakakibara, M.; Sugawara, H.; Tsuji, T.; Ikehara, M.

    2014-05-01

    The past two decades have seen the reporting of microbial fossils within ancient oceanic basalts that could be identical to microbes within modern basalts. Here, we present new petrographic, mineralogical, and stable isotopic data for metabasalts containing filamentous structures in a Jurassic accretionary complex within the northern Chichibu Belt of the Yanadani area of central Shikoku, Japan. Mineralized filaments within these rocks are present in interstitial domains filled with calcite, pumpellyite, or quartz, and consist of iron oxide, phengite, and pumpellyite. ?13CPDB values for filament-bearing calcite within these metabasalts vary from -2.49‰ to 0.67‰. A biogenic origin for these filamentous structures is indicated by (1) the geological context of the Yanadani metabasalt, (2) the morphology of the filaments, (3) the carbon isotope composition of carbonates that host the filaments, and (4) the timing of formation of these filaments relative to the timing of low-grade metamorphism in a subduction zone. The putative microorganisms that formed these filaments thrived between eruption (Late Paleozoic) and accretion (Early Jurassic) of the basalt. The data presented here indicate that cryptoendolithic life was present within water-filled vesicles in pre-Jurassic intraplate basalts. The mineralogy of the filaments reflects the low-grade metamorphic recrystallization of authigenic microbial clays similar to those formed by the encrustation of prokaryotes in modern iron-rich environments. These findings suggest that a previously unusual niche for life is present within intraplate volcanic rocks in accretionary complexes.

  3. Paleomagnetic and rock magnetic evidence for a secondary yet early magnetization in large sandstone pipes and host Late Middle Jurassic (Callovian) Summerville Formation and Bluff Sandstone near Mesita, west central New Mexico

    Microsoft Academic Search

    John W. Geissman; Stephen S. Harlan

    2004-01-01

    Processes responsible for the acquisition of ancient yet secondary magnetizations are important facets of the geologic history of rocks and, when the age of such magnetizations can be estimated with confidence, provide useful information on the ancient geomagnetic field. In west central New Mexico near Mesita, on the Colorado Plateau, hematitic sandstone and siltstone beds of the Middle Jurassic (Callovian)

  4. Significance of Jurassic radiolarians from the Cache Creek terrane, British Columbia

    NASA Astrophysics Data System (ADS)

    Cordey, Fabrice; Mortimer, N.; Dewever, Patrick; Monger, J. W. H.

    1987-12-01

    The discovery of new radiolarian localities in the western belt of the Cache Creek terrane in southern British Columbia possibly changes its upper age limit from Late Triassic to Early or Middle Jurassic. It favors a Middle Jurassic, rather than a Late Triassic, age of amalgamation for the Cache Creek terrane and Quesnellia (parts of superterrane I) in southern British Columbia. The new Jurassic ages also mean that the western Cache Creek terrane could be equivalent in age to the Bridge River Hozameen terrane in British Columbia and to terranes containing the Tethyan fusulinid Yabeina in northwest Washington and the Klamath Mountains of California.

  5. Fossil primates 1 Fossil primates

    E-print Network

    Delson, Eric

    Fossil primates 1 Fossil primates Extinct members of the order of mammals to which humans belong group of living primates. However, the chewing teeth and the locomotor anatomy of these fossil forms). These animals are also known from fossil deposits on Ellesmere Island, in Arctic Canada, which was then covered

  6. Jurassic epithermal Au–Ag deposits of Patagonia, Argentina

    Microsoft Academic Search

    I. B Schalamuk; M Zubia; A Genini; R. R Fernandez

    1997-01-01

    Important precious metal deposits have been discovered during the last 10 years in the Deseado Massif region of Patagonia, Argentina. This region is a plateau consisting of Middle to Upper Jurassic volcanic rocks that host fracture-controlled epithermal Au–Ag mineralization. These mineral deposits represent low sulfidation type hydrothermal systems and formed following the main period of volcanism, probably during the Late

  7. Investigation of the geomagnetic field polarity during the Jurassic

    Microsoft Academic Search

    Maureen B. Steiner

    1980-01-01

    A large number of sedimentary rock formation the Colorado Plateau and in the Wyoming foreland have been investigated paleomagnetically in an attempt to determine the geomagnetic polarity during the Middle and the early Late Jurassic, a period frequently postulated to have been of constant normal polarity. A survey of published paleomagnetic litature shows this postulate to be without grounds. A

  8. INVESTIGATION OF THE GEOMAGNETIC FIELD POLARITY DURING THE JURASSIC

    Microsoft Academic Search

    Maureen B. Steiner

    1980-01-01

    A large number of sedimentary rock formations on the Colorado Plateau and in the Wyoming foreland have been investigated paleo- magnetically in an attempt to determine the geo- magnetic polarity during the Middle and the ear- ly Late Jurassic, a period frequently postulated to have been of constant normal polarity. A sur- vey of published paleomagnetic litature shows this postulate

  9. Phylogeny of Dictyoptera: Dating the Origin of Cockroaches, Praying Mantises and Termites with Molecular Data and Controlled Fossil Evidence

    PubMed Central

    Legendre, Frédéric; Nel, André; Svenson, Gavin J.; Robillard, Tony; Pellens, Roseli; Grandcolas, Philippe

    2015-01-01

    Understanding the origin and diversification of organisms requires a good phylogenetic estimate of their age and diversification rates. This estimate can be difficult to obtain when samples are limited and fossil records are disputed, as in Dictyoptera. To choose among competing hypotheses of origin for dictyopteran suborders, we root a phylogenetic analysis (~800 taxa, 10 kbp) within a large selection of outgroups and calibrate datings with fossils attributed to lineages with clear synapomorphies. We find the following topology: (mantises, (other cockroaches, (Cryptocercidae, termites)). Our datings suggest that crown-Dictyoptera—and stem-mantises—would date back to the Late Carboniferous (~ 300 Mya), a result compatible with the oldest putative fossil of stem-dictyoptera. Crown-mantises, however, would be much more recent (~ 200 Mya; Triassic/Jurassic boundary). This pattern (i.e., old origin and more recent diversification) suggests a scenario of replacement in carnivory among polyneopterous insects. The most recent common ancestor of (cockroaches + termites) would date back to the Permian (~275 Mya), which contradicts the hypothesis of a Devonian origin of cockroaches. Stem-termites would date back to the Triassic/Jurassic boundary, which refutes a Triassic origin. We suggest directions in extant and extinct species sampling to sharpen this chronological framework and dictyopteran evolutionary studies. PMID:26200914

  10. Jurassic hydrocarbon exploration of southern Florida

    SciTech Connect

    Mitchell-Tapping, H.J. [Retog, Inc., DeSoto, TX (United States)

    1994-09-01

    South Florida Jurassic exploration has been overlooked as a viable exploration target due to lack of data and plate-tectonics application. In Florida, {open_quotes}basement{close_quotes} is defined as crystalline, igneous, metamorphic, and unmetamorphosed sediments of Paleozoic age. Age-dating of zircons has proven that the Florida lower Paleozoic terrane is not akin to that of North America but is part of the West African Guinean shield. Previous published reconstructions of late Paleozoic fits of crustal plates and continents have failed to account for the differences in peninsula Florida basement and the geologic and tectonic continuities of peninsula Florida, Yucatan, Cuba, Hispaniola, and Bahamas. Pre-Atlantic reconstruction of the Gulf of Mexico in this study proposes that there was a Florida connection to Yucatan-Cuba-Africa during the Triassic. This reconstruction also shows that the Jurassic sediments that are well known in the northern Gulf Coast should have been deposited in similar depositional environments in southern Florida. Deep drilling on the Florida peninsula has confirmed this hypothesis. By using plate tectonic reconstruction based on the rising of the North Atlantic Ocean and evidence from petrology of basement samples from deep wells together with petrographic analyses of Jurassic sediments, a Smackover-equivalent exploration play can be developed. Petrographic and petrophysical analysis of these wells that have encountered Jurassic marine shales, anhydrite, dolomite, carbonate, and elastic sediments has determined that these sediments are from shallow-water subtidal, tidal, intertidal, and supratidal environments. Excellent gas shows, oil stain in the pores and high TOC values in the marine shales, indicate that large accumulations of hydrocarbon are present.

  11. Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event

    PubMed

    Hesselbo; Grocke; Jenkyns; Bjerrum; Farrimond; Morgans Bell HS; Green

    2000-07-27

    In the Jurassic period, the Early Toarcian oceanic anoxic event (about 183 million years ago) is associated with exceptionally high rates of organic-carbon burial, high palaeotemperatures and significant mass extinction. Heavy carbon-isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon, which is isotopically light. In contrast, examples of light carbon-isotope values from marine organic matter of Early Toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12C versus 13C (refs 1,2,5,6). Here, however, we report carbon-isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic, biospheric and atmospheric carbon reservoirs, and that this occurred despite the enhanced burial of organic carbon. We propose that--as has been suggested for the Late Palaeocene thermal maximum, some 55 million years ago--the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental-margin sediments. PMID:10935632

  12. Squid 'ear bones' (statoliths) from the Jurassic succession of South-west England

    NASA Astrophysics Data System (ADS)

    Hart, Malcolm; Page, Kevin; Price, Gregory; Smart, Christopher

    2015-04-01

    Squid 'ear bones' - or statoliths - are a part of the balancing organs of modern and probably most fossil squids. Over the course of the last 10 years fossil statoliths have been discovered in the Jurassic sediments of the Wessex Basin (South-west England). They are probably all related to teuthids, such as Belemnotheutis antiquus Pearce, of Callovian-Oxfordian age. Thus far, we have identified four possible 'species' of statolith that are in the process of being formally described, named and their potential relationships determined. The sediments from which these statoliths have been recorded also contain squid hooklets (onycites), otoliths (fish 'ear bones') and other microfossils (including foraminifera). All are, therefore, of marine origin. In the case of the Christian Malford and Ashton Keynes lagerstätte (of late Callovian age), the statoliths are associated with exceptional, soft-bodied preservation of squid and it may be possible to determine the parent animal of the recorded statoliths. A number of museum collections (Natural History Museum [London], Natural History Museum [Paris], Senckenberg [Frankfurt], Smithsonian Institution [Washington], etc.) are being investigated in order to trace the possible host animals for all of the recorded statoliths. Despite many thousands of samples of Cretaceous sediments being investigated for foraminifera over the past 40+ years, no statoliths have been recorded and none are known from the literature.

  13. Ostracoda (marine\\/nonmarine) and palaeoclimate history in the Upper Jurassic of Central Europe and North America

    Microsoft Academic Search

    Michael E. Schudack

    1999-01-01

    The role of Ostracoda in determining climate developments in the Upper Jurassic of Central Europe and North America is reviewed, based upon two different studies. The Late Jurassic is a period of time for which a change from a humid to a more arid climate has been suggested for several parts of the world. However, a correlation, though almost logical,

  14. Triassic-Jurassic mass extinction as trigger for the Mesozoic radiation of crocodylomorphs.

    PubMed

    Toljagic, Olja; Butler, Richard J

    2013-06-23

    Pseudosuchia, one of the two main clades of Archosauria (Reptilia: Diapsida), suffered a major decline in lineage diversity during the Triassic-Jurassic (TJ) mass extinction (approx. 201 Ma). Crocodylomorpha, including living crocodilians and their extinct relatives, is the only group of pseudosuchians that survived into the Jurassic. We reassess changes in pseudosuchian morphological diversity (disparity) across this time interval, using considerably larger sample sizes than in previous analyses. Our results show that metrics of pseudosuchian disparity did not change significantly across the TJ boundary, contrasting with previous work suggesting low pseudosuchian disparity in the Early Jurassic following the TJ mass extinction. However, a significant shift in morphospace occupation between Late Triassic and Early Jurassic taxa is recognized, suggesting that the TJ extinction of many pseudosuchian lineages was followed by a major and geologically rapid adaptive radiation of crocodylomorphs. This marks the onset of the spectacularly successful evolutionary history of crocodylomorphs in Jurassic and Cretaceous ecosystems. PMID:23536443

  15. Jurassic faults of southwest Alabama and offshore areas

    SciTech Connect

    Mink, R.M.; Tew, B.H.; Bearden, B.L.; Mancini, E.A. (Geological Survey of Alabama, Tuscaloosa (United States))

    1991-03-01

    Four fault groups affecting Jurassic strata occur in the southwest and offshore Alabama areas. They include the regional basement rift trend, the regional peripheral fault trend, the Mobile graben fault system, and the Lower Mobile Bay fault system. The regional basement system rift and regional peripheral fault trends are distinct and rim the inner margin of the eastern Gulf Coastal Plain. The regional basement rift trend is genetically related to the breakup of Pangea and the opening of the Gulf of Mexico in the Late Triassic-Early Jurassic. This fault trend is thought to have formed contemporaneously with deposition of Late Triassic-Early Jurassic Eagle Mills Formation and to displace pre-Mesozoic rocks. The regional peripheral fault trend consists of a group of en echelon extensional faults that are parallel or subparallel to regional strike of Gulf Coastal Plain strata and correspond to the approximate updip limit of thick Louann Salt. Nondiapiric salt features are associated with the trend and maximum structural development is exhibited in the Haynesville-Smackover section. No hydrocarbon accumulations have been documented in the pre-Jurassic strata of southwest and offshore Alabama. Productive hydrocarbon reservoirs occur in Jurassic strata along the trends of the fault groups, suggesting a significant relationship between structural development in the Jurassic and hydrocarbon accumulation. Hydrocarbon traps are generally structural or contain a major structural component and include salt anticlines, faulted salt anticlines, and extensional fault traps. All of the major hydrocarbon accumulations are associated with movement of the Louann Salt along the regional peripheral fault trend, the Mobile graben fault system, or the Lower Mobile Bay fault system.

  16. Do fossil plants signal palaeoatmospheric carbon dioxide concentration in the geological past?

    PubMed Central

    McElwain, J. C.

    1998-01-01

    Fossil, subfossil, and herbarium leaves have been shown to provide a morphological signal of the atmospheric carbon dioxide environment in which they developed by means of their stomatal density and index. An inverse relationship between stomatal density/index and atmospheric carbon dioxide concentration has been documented for all the studies to date concerning fossil and subfossil material. Furthermore, this relationship has been demonstrated experimentally by growing plants under elevated and reducedcarbon dioxide concentrations. To date, the mechanism that controls the stomatal density response to atmospheric carbon dioxide concentration remains unknown. However, stomatal parameters of fossil plants have been successfully used as a proxy indicator of palaeo-carbon dioxide levels. This paper presents new estimates of palaeo-atmospheric carbon dioxide concentrations for the Middle Eocene (Lutetian), based on the stomatal ratios of fossil Lauraceae species from Bournemouth in England. Estimates of atmospheric carbon dioxide concentrations derived from stomatal data from plants of the Early Devonian, Late Carboniferous, Early Permian and Middle Jurassic ages are reviewed in the light of new data. Semi-quantitative palaeo-carbon dioxide estimates based on the stomatal ratio (a ratio of the stomatal index of a fossil plant to that of a selected nearest living equivalent) have in the past relied on the use of a Carboniferous standard. The application of a new standard based on the present-day carbon dioxide level is reported here for comparison. The resultant ranges of palaeo-carbon dioxide estimates made from standardized fossil stomatal ratio data are in good agreement with both carbon isotopic data from terrestrial and marine sources and long-term carbon cycle modelling estimates for all the time periods studied. These data indicate elevated atmospheric carbon dioxide concentrations during the Early Devonian, Middle Jurassic and Middle Eocene, and reduced concentrations during the Late Carboniferous and Early Permian. Such data are important in demonstrating the long-term responses of plants to changing carbon dioxide concentrations and in contributing to the database needed for general circulation model climatic analogues.

  17. Jurassic Polar Movement Relative to North America

    Microsoft Academic Search

    ANY C. E. HELSLEY

    1972-01-01

    Previous palcomagnetic studies of Jurassic rocks have not given concordant results and have led to the conclusion that the Jurassic pole position was possibly close to the present geographic pole. To test that supposition, the Kayenta, Carmel, Entrada, and Summerville formations were sampled from the extensive Jurassic sedimentary sequence in eastern Utah. The Lower and Upper Jurassic Kayenta and Summerville

  18. A New Basal Sauropod Dinosaur from the Middle Jurassic of Niger and the Early Evolution of Sauropoda

    PubMed Central

    Remes, Kristian; Ortega, Francisco; Fierro, Ignacio; Joger, Ulrich; Kosma, Ralf; Marín Ferrer, José Manuel; Ide, Oumarou Amadou; Maga, Abdoulaye

    2009-01-01

    Background The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification. Principal Findings A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography. Conclusions Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification. PMID:19756139

  19. The oldest known snakes from the Middle Jurassic-Lower Cretaceous provide insights on snake evolution.

    PubMed

    Caldwell, Michael W; Nydam, Randall L; Palci, Alessandro; Apesteguía, Sebastián

    2015-01-01

    The previous oldest known fossil snakes date from ~100 million year old sediments (Upper Cretaceous) and are both morphologically and phylogenetically diverse, indicating that snakes underwent a much earlier origin and adaptive radiation. We report here on snake fossils that extend the record backwards in time by an additional ~70 million years (Middle Jurassic-Lower Cretaceous). These ancient snakes share features with fossil and modern snakes (for example, recurved teeth with labial and lingual carinae, long toothed suborbital ramus of maxillae) and with lizards (for example, pronounced subdental shelf/gutter). The paleobiogeography of these early snakes is diverse and complex, suggesting that snakes had undergone habitat differentiation and geographic radiation by the mid-Jurassic. Phylogenetic analysis of squamates recovers these early snakes in a basal polytomy with other fossil and modern snakes, where Najash rionegrina is sister to this clade. Ingroup analysis finds them in a basal position to all other snakes including Najash. PMID:25625704

  20. Fossil Excavation

    NSDL National Science Digital Library

    In this activity students excavate their own fossil from a teacher-prepared "rock biscuit". Students chip away the matrix with wooden stirring rods (or sharpened wooden dowels) and glue brushes. In each biscuit is a genuine fossil such as a shark's tooth. The activity is designed to be the culmination of a lesson about fossil collecting, the importance of recording data, and different preparation methods.

  1. Depositional history of Jurassic rocks in the area of the Powder River basin, northeastern Wyoming and southeastern Montana

    SciTech Connect

    Not Available

    1992-01-01

    This paper summarizes the history of clastic sedimentation in the eastern part of the middle Western Interior during the Middle and Late Jurassic. Fourteen lithostratigraphic units are discussed in relation to five separate marine inundations and six intervening erosional events.

  2. Fossil Fuels.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with fossil fuels. Some topics covered are historic facts, development of fuels, history of oil production, current and future trends of the oil industry, refining fossil fuels, and environmental problems. Material in each unit may…

  3. Fossil spiders.

    PubMed

    Selden, Paul A; Penney, David

    2010-02-01

    Over the last three decades, the fossil record of spiders has increased from being previously biased towards Tertiary ambers and a few dubious earlier records, to one which reveals a much greater diversity in the Mesozoic, with many of the modern families present in that era, and with clearer evidence of the evolutionary history of the group. We here record the history of palaeoarachnology and the major breakthroughs which form the basis of studies on fossil spiders. Understanding the preservation and taphonomic history of spider fossils is crucial to interpretation of fossil spider morphology. We also review the more recent descriptions of fossil spiders and the effect these discoveries have had on the phylogenetic tree of spiders. We discuss some features of the evolutionary history of spiders and present ideas for future work. PMID:19961468

  4. Fossil Fuels

    NSDL National Science Digital Library

    Iowa Public Television. Explore More Project

    2004-01-01

    How much does the United States depend on fossil fuels? This web page, part of a site on the future of energy, introduces students to fossil fuels as an energy source. Here students read about the uses, benefits, and limitations of fossil fuels. There is also information on how these fuels are distributed geographically and how they affect the U.S. economy through supply and demand. Thought-provoking questions afford students opportunities to reflect on what they've read. Articles about clean coal, the national energy policy, and the formation of fossil fuels, together with a fossil fuels fact sheet, are accessible from a sidebar. In addition, five PBS NewsHour links to energy-related stories are included.

  5. New murid (Mammalia, Rodentia) fossils from a late Pliocene (2.4 Ma) locality, Hadar A.L. 894, Afar Region, Ethiopia

    Microsoft Academic Search

    Denné N. Reed

    2011-01-01

    This paper describes a new assemblage of fossil murids (Mammalia: Rodentia) from an Oldowan archeological site, Hadar, A.L. 894. The dates for the site are well constrained to between 2.35 and 2.9 Ma and the site itself has an estimated age of 2.4 Ma. The A.L. 894 assemblage is the first described from the younger Busidima Formation at Hadar and

  6. Coupled organic and carbonate ?13C records of the late Triassic and early Jurassic in northern Italy: implications for carbon cycling during the aftermath of the end-Triassic mass extinction

    NASA Astrophysics Data System (ADS)

    Bachan, A.; van de Schootbrugge, B.; Payne, J.

    2011-12-01

    A large protracted positive carbon isotope excursion has been observed in the lowermost Jurassic following the end-Triassic mass extinction. However, the lack of paired records from carbonate rocks (?13Ccarb) and organic carbon (?13Corg) and limited biostratigraphic constraints leave open the possibility that variations in ?13Ccarb and ?13Corg are not correlative and do not represent a shift in the ?13C of the global carbon pool. Consequently, the long term carbon cycle behavior following the end-Triassic mass extinction remains incompletely understood. Here we present the first extended, coupled ?13Ccarb and ?13Corg records of the uppermost Triassic and lowermost Jurassic from stratigraphic sections in the Lombardy Basin of northern Italy. The large positive excursion previously observed in the carbonates also occurs in the organics from the same samples, but with a smaller magnitude. Because few post-depositional mechanisms affect the isotopic composition of Ccarb and Corg in similar ways, the correspondence of the two curves presents strong support for a primary origin for the large positive isotopic excursion. The more muted response of the organics is consistent with variation in the fractionation between carbonates and organic carbon, mixing of contemporaneous organic matter with extrabasinal organic carbon of a constant isotopic composition, or some combination of the two. In either case, the occurrence of the positive excursion in multiple locations globally in both carbonates and organic matter is best explained by a change in the isotopic value of the global carbon reservoir. The elevated ?13C values and increased magnitude of the difference between the carbonates and organics is consistent with the predicted biogeochemical consequences of heightened pCO2. The coincidence of the extinction and carbon cycle disturbance with emplacement of the Central Atlantic Magmatic Province suggests that volatiles derived from its emplacement were the likely source of the perturbation.

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

    PubMed

    Benson, Roger B J; Evans, Mark; Druckenmiller, Patrick S

    2012-01-01

    Invasion of the open ocean by tetrapods represents a major evolutionary transition that occurred independently in cetaceans, mosasauroids, chelonioids (sea turtles), ichthyosaurs and plesiosaurs. Plesiosaurian reptiles invaded pelagic ocean environments immediately following the Late Triassic extinctions. This diversification is recorded by three intensively-sampled European fossil faunas, spanning 20 million years (Ma). These provide an unparalleled opportunity to document changes in key macroevolutionary parameters associated with secondary adaptation to pelagic life in tetrapods. A comprehensive assessment focuses on the oldest fauna, from the Blue Lias Formation of Street, and nearby localities, in Somerset, UK (Earliest Jurassic: 200 Ma), identifying three new species representing two small-bodied rhomaleosaurids (Stratesaurus taylori gen et sp. nov.; Avalonnectes arturi gen. et sp. nov) and the most basal plesiosauroid, Eoplesiosaurus antiquior gen. et sp. nov. The initial radiation of plesiosaurs was characterised by high, but short-lived, diversity of an archaic clade, Rhomaleosauridae. Representatives of this initial radiation were replaced by derived, neoplesiosaurian plesiosaurs at small-medium body sizes during a more gradual accumulation of morphological disparity. This gradualistic modality suggests that adaptive radiations within tetrapod subclades are not always characterised by the initially high levels of disparity observed in the Paleozoic origins of major metazoan body plans, or in the origin of tetrapods. High rhomaleosaurid diversity immediately following the Triassic-Jurassic boundary supports the gradual model of Late Triassic extinctions, mostly predating the boundary itself. Increase in both maximum and minimum body length early in plesiosaurian history suggests a driven evolutionary trend. However, Maximum-likelihood models suggest only passive expansion into higher body size categories. PMID:22438869

  8. High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) from the Triassic–Jurassic Boundary

    PubMed Central

    Benson, Roger B. J.; Evans, Mark; Druckenmiller, Patrick S.

    2012-01-01

    Invasion of the open ocean by tetrapods represents a major evolutionary transition that occurred independently in cetaceans, mosasauroids, chelonioids (sea turtles), ichthyosaurs and plesiosaurs. Plesiosaurian reptiles invaded pelagic ocean environments immediately following the Late Triassic extinctions. This diversification is recorded by three intensively-sampled European fossil faunas, spanning 20 million years (Ma). These provide an unparalleled opportunity to document changes in key macroevolutionary parameters associated with secondary adaptation to pelagic life in tetrapods. A comprehensive assessment focuses on the oldest fauna, from the Blue Lias Formation of Street, and nearby localities, in Somerset, UK (Earliest Jurassic: 200 Ma), identifying three new species representing two small-bodied rhomaleosaurids (Stratesaurus taylori gen et sp. nov.; Avalonnectes arturi gen. et sp. nov) and the most basal plesiosauroid, Eoplesiosaurus antiquior gen. et sp. nov. The initial radiation of plesiosaurs was characterised by high, but short-lived, diversity of an archaic clade, Rhomaleosauridae. Representatives of this initial radiation were replaced by derived, neoplesiosaurian plesiosaurs at small-medium body sizes during a more gradual accumulation of morphological disparity. This gradualistic modality suggests that adaptive radiations within tetrapod subclades are not always characterised by the initially high levels of disparity observed in the Paleozoic origins of major metazoan body plans, or in the origin of tetrapods. High rhomaleosaurid diversity immediately following the Triassic-Jurassic boundary supports the gradual model of Late Triassic extinctions, mostly predating the boundary itself. Increase in both maximum and minimum body length early in plesiosaurian history suggests a driven evolutionary trend. However, Maximum-likelihood models suggest only passive expansion into higher body size categories. PMID:22438869

  9. NYSGA 2010 Trip 4 -Olsen Fossil Great Lakes of the Newark Supergroup

    E-print Network

    Olsen, Paul E.

    NYSGA 2010 Trip 4 - Olsen 101 Fossil Great Lakes of the Newark Supergroup ­ 30 Years Later Paul E: THE TRIASSIC-JURASSIC GREAT LAKES OF CENTRAL PANGEA This guidebook focuses of the deposits, fossils dimension comparable to the scale of the American Great Lakes or the East African Great Lakes and perhaps

  10. Fossil Halls

    NSDL National Science Digital Library

    The American Museum of Natural History is home to the world's largest collection of vertebrate fossils, totaling nearly one million specimens. This Web site offers visitors a virtual visit to the Museum's famed Fossil Halls. It features sections on Cladistics, Vertebrate Evolution, Exhibit Specimens, a collection of 19 biographies of important people in paleontology and Virtual Tours of four of the halls. There is also an elementary school teacher guide to the museum exhibit.

  11. The oldest haplogyne spider (Araneae: Plectreuridae), from the Middle Jurassic of China.

    PubMed

    Selden, Paul A; Huang, Diying

    2010-05-01

    New fossil spiders (Arachnida: Araneae) from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China are described as Eoplectreurys gertschi gen. et sp. nov. and referred to the modern haplogyne family Plectreuridae. This small family is restricted to southwestern USA, Mexico, and the adjacent Caribbean area today and hitherto has only a sparse Cenozoic fossil record. The morphology of Eoplectreurys is remarkably similar to modern forms and thus demonstrates great evolutionary conservatism. This new discovery not only extends the fossil record of the family by at least 120 Ma to the Middle Jurassic but also supports the hypothesis of a different distribution of the family in the past than today and subsequent extinction over much of its former range. PMID:20140419

  12. Direct chemical evidence for eumelanin pigment from the Jurassic period.

    PubMed

    Glass, Keely; Ito, Shosuke; Wilby, Philip R; Sota, Takayuki; Nakamura, Atsushi; Bowers, C Russell; Vinther, Jakob; Dutta, Suryendu; Summons, Roger; Briggs, Derek E G; Wakamatsu, Kazumasa; Simon, John D

    2012-06-26

    Melanin is a ubiquitous biological pigment found in bacteria, fungi, plants, and animals. It has a diverse range of ecological and biochemical functions, including display, evasion, photoprotection, detoxification, and metal scavenging. To date, evidence of melanin in fossil organisms has relied entirely on indirect morphological and chemical analyses. Here, we apply direct chemical techniques to categorically demonstrate the preservation of eumelanin in two > 160 Ma Jurassic cephalopod ink sacs and to confirm its chemical similarity to the ink of the modern cephalopod, Sepia officinalis. Identification and characterization of degradation-resistant melanin may provide insights into its diverse roles in ancient organisms. PMID:22615359

  13. Direct chemical evidence for eumelanin pigment from the Jurassic period

    PubMed Central

    Glass, Keely; Ito, Shosuke; Wilby, Philip R.; Sota, Takayuki; Nakamura, Atsushi; Bowers, C. Russell; Vinther, Jakob; Dutta, Suryendu; Summons, Roger; Briggs, Derek E. G.; Wakamatsu, Kazumasa; Simon, John D.

    2012-01-01

    Melanin is a ubiquitous biological pigment found in bacteria, fungi, plants, and animals. It has a diverse range of ecological and biochemical functions, including display, evasion, photoprotection, detoxification, and metal scavenging. To date, evidence of melanin in fossil organisms has relied entirely on indirect morphological and chemical analyses. Here, we apply direct chemical techniques to categorically demonstrate the preservation of eumelanin in two > 160 Ma Jurassic cephalopod ink sacs and to confirm its chemical similarity to the ink of the modern cephalopod, Sepia officinalis. Identification and characterization of degradation-resistant melanin may provide insights into its diverse roles in ancient organisms. PMID:22615359

  14. A New Look at the Magnetostratigraphy and Paleomagnetism of the Upper Triassic to Lower Jurassic Moenave Formation, St. George Area, Southwestern Utah

    Microsoft Academic Search

    L. L. Donohoo-Hurley; J. W. Geissman; S. G. Lucas; M. Roy

    2006-01-01

    Paleomagnetic data from rocks exposed on and off the Colorado Plateau provide poles that young westward during the Late Triassic (to about 52^{O} E longitude) and young eastward during the Early Jurassic. This pattern has been used to posit the existence of a J-1 cusp in the North American APW path at the Triassic- Jurassic boundary (TJB), at about 199.6

  15. Jurassic and Cretaceous Hagiastridae from the Blake-Bahama Basin /Site 5A, JOIDES Leg I/ and the Great Valley Sequence, California Coast Ranges.

    NASA Technical Reports Server (NTRS)

    Pessagno, E. A., Jr.

    1971-01-01

    Description of a total of 24 new species and four genuses of Jurassic and Cretaceous Hagiastridae found in the Great Valley Sequence of the California Coast Ranges. Also described are four new species from the late Jurassic strata of the Blake-Bahama Basin. Spumellariina with a spongy meshwork is included in the superfamily Spongodiscacea Haeckel.

  16. What drove late Mesozoic extension of the northern China–Mongolia tract?

    Microsoft Academic Search

    Qing-Ren Meng

    2003-01-01

    The northern China–Mongolia tract exhibited a tectonic transition from contractional to extensional deformation in late Mesozoic time. Late Middle to early Late Jurassic crustal shortening is widely thought to have resulted from collision of an amalgamated North China–Mongolia block and the Siberian plate, but widespread late Late Jurassic–Early Cretaceous extension has not been satisfactorily explained by existing models. Some prominent

  17. New model of succession of Middle and Late Pennsylvanian fossil communities in north Texas, Mid-Continent, and Appalachians with implications on black shale controversy

    SciTech Connect

    Boardman, D.R. II; Yancey, T.E.; Mapes, R.H.; Malinky, J.M.

    1983-03-01

    A new model for the succession of Pennsylvanian fossil communities, preserved in cyclothems, is proposed on the basis of more than 200 fossil localities in the Mid-Continent, Appalachians, and north Texas. Early models for Mid-Continent cyclothems placed the black shales in shallow water, with maximum transgression at the fusulinid-bearing zone in the overlying limestone. The most recent model proposed that the black phosphatic shales, which commonly occur between two subtidal carbonates, are widespread and laterally continuous over great distances and represent maximum transgression. The black phosphatic shales contain: ammonoids; inarticulate brachiopods; radiolarians; conularids; shark material and abundant and diverse conodonts. The black shales grade vertically and laterally into dark gray-black shales which contain many of the same pelagic and epipelagic forms found in the phosphatic black shales. This facies contains the deepest water benthic community. Most of these forms are immature, pyritized, and generally are preserved as molds. The dark gray-black facies grades into a medium gray shale facies which contains a mature molluscan fauna. The medium gray shale grades into a lighter gray facies, which is dominated by brachiopods, crinoids, and corals, with occasional bivalves and gastropods. (These facies are interpreted as being a moderate to shallow depth shelf community). The brachiopid-crinoid community is succeeded by shallow water communities which may have occupied shoreline, lagoonal, bay, interdeltaic, or shallow prodeltaic environments.

  18. Late Pleistocene sediments and fossils near the mouth of Mad River, Humboldt County, California: Facies analysis, sequence development, and possible age correlation

    Microsoft Academic Search

    1994-01-01

    Study of late Pleistocene-age sediments near the mouth of the Mad River revealed a sequence of nearshore marine and shallow bay deposits. This sequence, bounded by unconformities, is informally named the Mouth of Mad unit. The Mouth of mad unit can be divided into four distinct depositional facies at the study site. The lowest facies are the Nearshore Sand and

  19. Jurassic Lake T'oo'dichi': a large alkaline, saline lake, Morrison Formation, eastern Colorado Plateau

    USGS Publications Warehouse

    Turner, C.E.; Fishman, N.S.

    1991-01-01

    Recognition of alkaline, saline-lake deposits in the Morrison Formation significantly alters interpretations of depositional environments of this formation, and it also has important implications for paleoclimatic interpretation. Late Jurassic climate was apparently much more arid than had previously been thought. In fact, sedimentologic evidence suggests that the lake basin was typically dry for extended periods and enjoyed only brief wet intervals. This conclusion has important consequences for environmental interpretation of the habitat that was favorable for large herbivorous dinosaurs, which thrived in the Late Jurassic. -from Authors

  20. Fossilization of nanobes studied by transmission electron microscopy and constraints related to their population - recent and late quaternary reefbanks (San Salvador Island, the Bahamas; Heron Island, Australia)

    NASA Astrophysics Data System (ADS)

    Hladil, J.; Gemperle, A.; Carew, J. L.; Bosak, P.; Slavik, L.; Pruner, P.; Charvatova, K.; Mylroie, J. E.; Jell, J. S.

    2003-04-01

    SEM analyses of rocks from Blow Hole Cave and The Gulf sections (San Salvador Island, Bahamas) found that ca 90-95% of peloids (and minor parts of other particles and cements) are substantially rebuilt into tiny corpuscles of ovoid, rotund cylindrical or slightly bent shapes (50-80 × 60-120 nm). About 20-30% of them form short and branched chains. These fabrics resemble `accumulations of ant eggs', have 40-60% fine porosity, correspond to better morpho-definitions of nanobes (cons. by R.L. Folk, 2002), and put a new light on micritization processes. The rocks strongly rebuilt by nanobes negatively correlate with magnetic susceptibility, but slightly contribute to NGR (uranium, gamma-ray spectrometry). In spite of strongly negative correlation to magnetic horizons, the nanobes are also present there, but to a lesser extent. The suspensions with nanobes (extracted by pump from the pores of rocks preserved in glutaraldehyde) exhibit a variety of preservation stages - from amorphous organics to completely fossilized corpuscles (studied by TEM). Early stages of fossilization are characterized by a gradually increasing amount of very fine crystalline inclusions, which are triangular to tetragonal in shape, and 3-15 nm long (mean size ˜ 6 nm). The TEM diffractograms provided data about face-centered cubic structures of B1 type (NaCl-like), with strongest 2nd and 3rd reflections on 0.240 and 0.170 nm and mean lattice parameter of 0.4813 nm. The substance was clearly identified as CaO. The difference to 0.4802 nm (ICDD data for pure CaO) is explained by effects of impurities Sr (+) > Fe, Mn (-). The number of CaO inclusions fluctuates from a few to 5 × 104 / ? {m3}. The CaO nucleation is possible in natural necrotic high-pH low-Eh organic coagulates; but presence of glutaraldehyde can facilitate the process. Other fossilization stages show unstable amorphous to crystalline calcium carbonate, homogeneous aragonite and calcite, and calcite replacing aragonite along sharp boundaries. The X-ray diffraction data suggest that calcite prevails. The massive nanobe population corresponds to early stages of emergence of banks (according to diagenetic and microbial successions). The short-term nanobe bloom had to be concurrent with early fungal growth in corroded rock micropores. However, the residual nanobe populations survived a die off of the early bloom of nannobes and are still alive (˜ 3 × 103 /{mm3}). A small number of nanobes are spread by endolithic cyanobacteria even in situations, that are not favorable for expansion of nanobe populations (examples from the Heron Island, Australia). / Project A3013209 "Weathering products".

  1. Middle Jurassic strata link Wallowa, Olds Ferry, and Izee terranes in the accreted Blue Mountains island arc, northeastern Oregon

    SciTech Connect

    White, J.D.L. (Dalhousie Univ., Halifax, Nova Scotia (Canada)); Vallier, T. (Geological Survey, Menlo Park, CA (United States)); Stanley, G.D. Jr. (Univ. of Montana, Missoula (United States)); Ash, S.R. (Weber State Univ., Odgen, UT (United States)); White, D.L.

    1992-08-01

    Middle Jurassic strata atop the Wallowa terrane in northeastern Oregon link the Wallowa, Izee, and Olds Ferry terranes as related elements of a single long-lived and complex oceanic feature, the Blue Mountains island arc. Middle Jurassic strata in the Wallowa terrane include a dacitic ash-flow deposit and contain fossil corals and bivalves of North American affinity. Plant fossils in fluvial sandstones support a Jurassic age and indicate a seasonal temperate climate. Corals in a transgressive sequence traditionally overlying the fluvial units are of Bajocian age and are closely related to endemic varieties of the Western Interior embayment. They are unlike Middle Jurassic corals in other Cordilleran terranes; their presence suggests that the Blue Mountains island arc first approached the North American craton at high paleolatitudes in Middle Jurassic time. The authors consider the Bajocian marine strata and underlying fluvial volcaniclastic units to be a basin-margin equivalent of the Izee terrane, a largely Middle Jurassic (Bajocian) succession of basinal volcaniclastic and volcanic rocks known to overlie the Olds Ferry and Baker terranes.

  2. Sub-fossil beetle assemblages associated with the "mammoth fauna" in the Late Pleistocene localities of the Ural Mountains and West Siberia.

    PubMed

    Zinovyev, Evgeniy

    2011-01-01

    The distribution of beetles at the end of the Middle Pleninglacial (=terminal Quaternary) was examined based on sub-fossil material from the Ural Mountains and Western Siberia, Russia. All relevant localities of fossil insects have similar radiocarbon dates, ranging between 33,000 and 22,000 C14 years ago. Being situated across the vast territory from the southern Ural Mountains in the South to the middle Yamal Peninsula in the North, they allow latitudinal changes in beetle assemblages of that time to be traced. These beetles lived simultaneously with mammals of the so-called "mammoth fauna" with mammoth, bison, and wooly rhinoceros, the often co-occurring mega-mammalian bones at some of the sites being evidence of this. The beetle assemblages found between 59° and 57°N appear to be the most interesting. Their bulk is referred to as a "mixed" type, one which includes a characteristic combination of arcto-boreal, boreal, steppe and polyzonal species showing no analogues among recent insect complexes. These peculiar faunas seem to have represented a particular zonal type, which disappeared since the end of the Last Glaciation to arrive here with the extinction of the mammoth biota. In contrast, on the sites lying north of 60°N, the beetle communities were similar to modern sub-arctic and arctic faunas, yet with the participation of some sub-boreal steppe components, such as Poecilus ravus Lutshnik and Carabus sibiricus Fischer-Waldheim. This information, when compared with our knowledge of synchronous insect faunas from other regions of northern Eurasia, suggests that the former distribution of beetles in this region could be accounted for both by palaeo-environmental conditions and the impact of grazing by large ruminant mammals across the so-called "mammoth savannas". PMID:21738409

  3. Fossil Identification

    NSDL National Science Digital Library

    Connie Soja, Colgate University, csoja@colgate.edu

    This activity asks students to identify examples of types of fossils amongst the exhibits at the Museum of the Earth at the Paleontological Research Institution in Ithaca, New York. Students will build on their understanding of the history of life, paleontology, taphonomy, ichnology, and paleoecologyâespecially reefs.

  4. Strontium isotopic variations in Jurassic and Cretaceous seawater

    NASA Astrophysics Data System (ADS)

    Jones, Charles E.; Jenkyns, Hugh C.; Coe, Angela L.; Stephen, Hesselbo P.

    1994-07-01

    A high-resolution seawater strontium isotope curve has been generated through the analysis of well-dated and well-preserved belemnites and oysters from the Middle and Upper Jurassic and the Lower Cretaceous of Great Britain. Analysis of Fe and Mn concentrations in these fossils has yielded criteria for eliminating samples that are diagenetically altered. The strontium isotope curve remains relatively flat through the Aalenian and early Bajocian, rapidly descends through the late Bajocian and Bathonian, and reaches a minimum in the Callovian and Oxfordian. It then begins a rapid increase in the Kimmeridgian and Portlandian that continues through much of the early Cretaceous. The curve levels off in the Barremian, suddenly dips downwards in the Aptian, and recovers gradually through the Albian. The strontium isotopic variations are sufficiently large and the data are presented with sufficient stratigraphic detail to allow precise correlation to the classic ammonite zones and lithologic sections of Great Britain using the techniques of strontium isotope stratigraphy. Model results indicate that much of the variation in seawater 87Sr /86Sr between 120 and 40 Ma can be explained by changing the intensity of mid-ocean ridge hydrothermal fluxes proportionally to estimated mid-ocean ridge crustal generation rates. It is also possible that the variations during the rest of the Mesozoic and the Permian are primarily reflections of changing hydrothermal inputs. The model results have several important implications. First, they provide an example in which the variations in the strontium isotope curve are not necessarily driven by changes in fluvial inputs. Second, they suggest that from at least the Aptian through the Eocene variations in continental weathering were minimal. This heightens the importance of the rapid rise in seawater 87Sr /86Sr beginning ~ 40 Ma as a significant transition to an extended period of increasing fluvial 87Sr fluxes continuing to the present. Finally, the results suggest that several documented short-term excursions towards lower 87Sr /86Sr in the latest Triassic, Pliensbachian-Toarcian, Callovian-Oxfordian, Aptian-Albian, and Cenomanian-Turonian are interpretable as pulses of seafloor hydrothermal activity. If so, the strontium isotope record offers a means of constraining the timing, duration, and magnitude of known or proposed hydrothermal events in the geological record.

  5. Late Pleistocene sediments and fossils near the mouth of Mad River, Humboldt County, California: Facies analysis, sequence development, and possible age correlation

    SciTech Connect

    Harvey, E.W. (Ohio State Univ., Columbus, OH (United States). Dept. of Geological Sciences)

    1994-04-01

    Study of late Pleistocene-age sediments near the mouth of the Mad River revealed a sequence of nearshore marine and shallow bay deposits. This sequence, bounded by unconformities, is informally named the Mouth of Mad unit. The Mouth of mad unit can be divided into four distinct depositional facies at the study site. The lowest facies are the Nearshore Sand and Estuarine Mud, which lie unconformably on a paleosol. The sand facies grades upward into a high-energy, interbedded Nearshore Sand and Gravel facies containing storm and rip-channel deposits. Above the sand and gravel is a Strand-Plain Sand facies. This sand is overlain by a laterally variable sequence of shell-rich Bay facies. The bay deposits can be further divided into five subfacies: (1) a Bioturbated Sand; (2) a Lower Tidal Flat Mud; (3) a Mixed Sand and Mud; (4) an oyster-rich Bay Mud; and (5) an Upper Tidal Flat Mud. The bay sequence is overlain unconformably by younger late Pleistocene-age marine terrace deposits. The depositional environments represented by these facies progress from a shoreline estuary to nearshore deposits, above storm wave base, and slowly back to shoreline and finally shallow bay conditions. The Mouth of Mad unit represents a transgressive-regressive sequence, involving the development of a protective spit. The uppermost mud within the Mouth of Mad unit has been dated, using thermoluminescence age estimation, at 176 [+-] 33 ka, placing it in the late Pleistocene. The Mouth of Mad unit appears to be younger than the fossiliferous deposits at Elk Head, Crannell Junction, Trinidad Head, Moonstone Beach, and the Falor Formation near Maple Creek, and possibly time equivalent with gravel deposits exposed at the western end of School Road in McKinleyville.

  6. 56 SCIENCE SCOPE Fossil sharks: Learning

    E-print Network

    Bermingham, Eldredge

    , that particular area was cov- ered with water. Plate tectonics Scientific evidence indicates that the positions of continents have changed over geologic time as a result of plate tectonics. These Earth move- ments have Fossils tell important stories about plate tectonics. Re- lated fossils are often discovered at varied

  7. Jurassic plutons in the Desolation wilderness, northern Sierra Nevada batholith, California: A new segment in the Jurassic magmatic arc

    SciTech Connect

    Sabine, C. (Desert Research Inst., Reno, NV (United States). Quaternary Sciences Center)

    1993-04-01

    A 164[+-]7 Ma U-P zircon date establishes a Middle- to Late-Jurassic age for the Pyramid Peak granite and synplutonic dioritoids and hybrid rocks that comprise the Crystal Range suite, located southwest of Lake Tahoe. A Jurassic age is also assigned to the Keiths Dome quartz monzonite and the Desolation Valley and Camper Flat granodiorites (Loomis', 1983, Early Granitic Group) which are distinctly older than surrounding Cretaceous granitoids. The Keiths Dome quartz monzonite, the oldest pluton of the group, may be as old as 180 Ma and is distinguished by ductile shear zones and recrystallization textures which indicate an episode of deformation not undergone by other plutons. The Camper flat and Desolation Valley granodiorites are the youngest plutons of the group. ENE-trending microdiorite dikes filled extensional fractures, perpendicular to the direction of shortening, in all Jurassic plutons but on none of the Cretaceous bodies. Jurassic plutons may help constrain ages of metasedimentary and metavolcanic rocks and associated structures in the Mount Tallac roof pendant. The Pyramid Peak granite intrudes the Sailor Canyon Formation which bears Late Pliensbachian ammonites (Fisher, 1990), and the Keiths Dome quartz monzonite intrudes the overlying Tuttle Lake Formation and transects faults and shear zones in the pendant. Initial Sr isotope ratios for the Pyramid Peak granite range between 0.705427 and 0.706874, spanning the 0.706 value taken by some to mark the western limit of sialic lower crust. Data suggest an isotopically mixed source containing mantle and crustal components. Such an environment is not inconsistent with a passive continental margin where mafic magma invades rifted continental crust.

  8. An 80 million year oceanic redox history from Permian to Jurassic pelagic sediments of the Mino-Tamba terrane, SW Japan, and the origin of four mass extinctions

    Microsoft Academic Search

    Paul B. Wignall; David P. G. Bond; Kiyoko Kuwahara; Yoshitaka Kakuwa; Robert J. Newton; Simon W. Poulton

    2010-01-01

    Fabric and pyrite framboid size analysis of Permian to Jurassic samples from the Mino-Tamba terrane of Japan provide an 80myr redox history from the Panthalassa Ocean. Fully oxygenated conditions dominated but were punctuated by three phases of anoxia (euxinia) during the Permo-Triassic boundary, the late Early Triassic (Spathian Stage) and the late Early Jurassic (Toarcian Stage). A Permo-Triassic superanoxic event

  9. Episodic dike intrusions in the northwestern Sierra Nevada, California: Implications for multistage evolution of a Jurassic arc terrane

    SciTech Connect

    Dilek, Y.; Moores, E.M. (Univ. of California, Davis (USA)); Thy, P. (NASA, Houston, TX (USA))

    1991-02-01

    In the northwestern Sierra Nevada, California, volcanic and plutonic rocks of the Smartville and Slate Creek complexes, both fragments of a Jurassic arc terrane, are tectonically juxtaposed against ophiolitic and marine rocks that represent late Paleozoic-early Mesozoic oceanic basement. This oceanic basement is intruded by Early Jurassic dikes that are coeval with hypabyssal and plutonic rocks within the Smartville and Slate Creek complexes. These dikes have geochemical characteristics reflecting a depleted and metasomatized source, as commonly observed in modern fore-arc settings and incipient volcanic arcs, and are interpreted to be the conduits for the Early Jurassic arc volcanism, which was built on and across the disrupted oceanic basement. Late Jurassic sheeted dikes intruding the Smartville complex have basaltic compositions compatible with an intra-arc or back-arc origin and indicate that a spreading event occurred within the arc in early Late Jurassic time. These interpretations support models for a complex multistage evolution via episodic magmatism and deformation within a singly ensimatic Jurassic arc terrane west of the North American continent.

  10. Response to Comment on "A Jurassic ornithischian dinosaur from Siberia with both feathers and scales".

    PubMed

    Godefroit, Pascal; Sinitsa, Sofia M; Dhouailly, Danielle; Bolotsky, Yuri L; Sizov, Alexander V; McNamara, Maria E; Benton, Michael J; Spagna, Paul

    2014-10-24

    Lingham-Soliar questions our interpretation of integumentary structures in the Middle-Late Jurassic ornithischian dinosaur Kulindadromeus as feather-like appendages and alternatively proposes that the compound structures observed around the humerus and femur of Kulindadromeus are support fibers associated with badly degraded scales. We consider this hypothesis highly unlikely because of the taphonomy and morphology of the preserved structures. PMID:25342796

  11. Sea-level change and facies development across potential Triassic-Jurassic boundary horizons, SW Britain

    Microsoft Academic Search

    STEPHEN P. H ESSELBO; S T UA; RT A. RO; S U R LY K

    2004-01-01

    The Late Triassic to Early Jurassic aged succession of SW Britain (the Penarth and lower Lias Groups) comprises mudstone, sandstone and limestone strata deposited in a variety of marine to non-marine environments. Faunal and floral characteristics of these successions have led to the proposal that one location in SW England, St Audrie's Bay, should serve as the Global Stratotype Section

  12. Carbon?Cycle Perturbation in the Middle Jurassic and Accompanying Changes in the Terrestrial Paleoenvironment

    Microsoft Academic Search

    2003-01-01

    Carbon-isotope analyses of fossil wood from the Middle Jurassic Ravenscar Group, Yorkshire, NE England, reveal a significant excursion toward light isotopic values (d 13 C change of 3t o4‰) at about the Aalenian-Bajocian boundary (?174 Ma). A positive carbon isotopic excursion is also shown for the middle Bajocian (?170 Ma) but is less clearly defined. These isotopic patterns are very

  13. Two new species of Trichoceridae from the Middle Jurassic Jiulongshan Formation of Inner Mongolia, China

    PubMed Central

    Dong, Fei; Shih, Chungkun; Ren, Dong

    2014-01-01

    Abstract Two new species, Eotrichocera (Archaeotrichocera) longensis sp. n. and Eotrichocera (Archaeotrichocera) amabilis sp. n. of Trichoceridae are described based on a combination of the following characters: Sc ending proximad of the forking of R2, shape of d cell and A2 rather short and bending sharply toward posterior margin. These fossil specimens were collected from the Middle Jurassic Jiulongshan Formation of Daohugou in Inner Mongolia, China. PMID:24899858

  14. Palynological age determination for Dorcheat and Hosston Formations - Jurassic-Cretaceous boundary in northern Louisiana

    SciTech Connect

    Rogers, R.

    1987-09-01

    Forty-four core samples from three wells drilled into the Dorcheat and Hosston formations in northern Louisiana were examined for fossil palynomorphs. These samples were obtained from the four beds of the Dorcheat formation, and from the lower two beds of the Hosston Formation. A diverse terrestrial and marine palynoflora containing stratigraphically significant species indicates that the cored section of strata spans the Jurassic-Cretaceous boundary.

  15. Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event

    Microsoft Academic Search

    Stephen P. Hesselbo; Darren R. Gröcke; Hugh C. Jenkyns; Christian J. Bjerrum; Paul Farrimond; Helen S. Morgans Bell; Owen R. Green

    2000-01-01

    In the Jurassic period, the Early Toarcian oceanic anoxic event (about 183 million years ago) is associated with exceptionally high rates of organic-carbon burial, high palaeotemperatures and significant mass extinction. Heavy carbon-isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon, which is isotopically light. In contrast, examples of light carbon-isotope

  16. Upper Jurassic depositional systems and hydrocarbon potential of southeast Mississippi

    SciTech Connect

    Meendsen, F.C.; Moore, C.H.; Heydari, E.; Sassen, R.

    1987-09-01

    Upper Jurassic sedimentation in southeast Mississippi was controlled by eustatic sea level fluctuations and locally modified by salt tectonism and basement structure. This study, using conventional core data and geophysical logs, indicates that a stable carbonate platform developed along the updip margin of the Mississippi interior salt basin. The basin was partially barred from the main Gulf of Mexico water mass by the Wiggins uplift, and became evaporitic during the Late Jurassic. Moldic, intercrystalline, and vuggy dolomite porosity is developed on the crests of intermediate and high-amplitude salt highs and on the Wiggins uplift. Jurassic source rocks are lower Smackover laminated lime mudstones. Migration into adjacent reservoirs postdated formation of porosity and the growth of salt anticlines, the most common trap type. A large potential Norphlet-Smackover gas play extends along the southern flank of the Wiggins uplift. Salt anticlines within the interior basin remain viable targets. Small oil discoveries should continue in stratigraphic traps, subtle salt structures, and basement blocks on the platform.

  17. Describing Fossils

    NSDL National Science Digital Library

    Judy Massare

    Students are given a description of a fossil brachiopod, from the literature, along with a one-page handout describing the basic morphology of brachiopods. Students work independently to make a scale drawing of the fossil described (brachial valve, pedicle valve, anterior view, lateral view). They have access to textbooks (Moore, Laliker & Fisher; Clarkson), the Treatise volume, and the internet to get information on morphological terms. This takes about an hour, after which I display all of the diagrams on the wall along with the photographs from the paper from which the description was extracted. We discuss some of the differences and where problems arose in interpreting the description. I emphasize the importance of an accurate drawing or photograph to accompany a description. Students are then given a different brachiopod specimen and asked to produce a written description (pedicle-valve, brachial valve, anterior view, lateral view) of their fossil similar to the one that they readâi.e. using all of the appropriate terms. They are told that other students will be trying to match their description to their specimen. I collect all of the descriptions, edit them (remove portions that use incorrect terminology or inappropriate), and produce a handout of all of the descriptions. At the next class, students are given the descriptions and asked to match descriptions to specimens. They do this independently outside of class. The specimens are made available in the lab room for several days. I add a couple of 'extra' specimens (without description) so that it is not a process of elimination.

  18. The Early Jurassic to Aalenian paleobiogeography of the Arctic realm: Implication of microbenthos (Foraminifers and Ostracodes)

    Microsoft Academic Search

    B. L. Nikitenko

    2008-01-01

    Stages in evolution of the Early Jurassic to Aalenian foraminifers and ostracodes are established based on the analyzed diversity dynamics of respective microfauna associations. Evolution of foraminifers is divided in two, the Hettangian-initial early Toarcian and the late early Toarcian-Aalenian stages, while the identical first stage in evolution of ostracodes has been followed by the late early Toarcian-Callovian stage. During

  19. The Early Jurassic to Aalenian paleobiogeography of the Arctic realm: Implication of microbenthos (Foraminifers and Ostracodes)

    Microsoft Academic Search

    B. L. Nikitenko

    2008-01-01

    Stages in evolution of the Early Jurassic to Aalenian foraminifers and ostracodes are established based on the analyzed diversity\\u000a dynamics of respective microfauna associations. Evolution of foraminifers is divided in two, the Hettangian-initial early\\u000a Toarcian and the late early Toarcian-Aalenian stages, while the identical first stage in evolution of ostracodes has been\\u000a followed by the late early Toarcian-Callovian stage. During

  20. Increased fire activity at the Triassic/Jurassic boundary in Greenland due to climate-driven floral change

    NASA Astrophysics Data System (ADS)

    Belcher, Claire M.; Mander, Luke; Rein, Guillermo; Jervis, Freddy X.; Haworth, Matthew; Hesselbo, Stephen P.; Glasspool, Ian J.; McElwain, Jennifer C.

    2010-06-01

    One of the largest mass extinctions of the past 600 million years (Myr) occurred 200Myr ago, at the Triassic/Jurassic boundary. The major floral and faunal turnovers have been linked to a marked increase in atmospheric carbon dioxide levels, probably resulting from massive volcanism in the Central Atlantic Magmatic Province. Future climate change predictions suggest that fire activity may increase, in part because higher global temperatures are thought to increase storminess. Here we use palaeontological reconstructions of the fossil flora from East Greenland to assess forest flammability along with records of fossil charcoal preserved in the rocks to show that fire activity increased markedly across the Triassic/Jurassic boundary. We find a fivefold increase in the abundance of fossil charcoal in the earliest Jurassic, which we attribute to a climate-driven shift from a prevalence of broad-leaved taxa to a predominantly narrow-leaved assemblage. Our fire calorimetry experiments show that narrow leaf morphologies are more flammable than broad-leaved morphologies. We suggest that the warming associated with increased atmospheric carbon dioxide levels favoured a dominance of narrow-leaved plants, which, coupled with more frequent lightening strikes, led to an increase in fire activity at the Triassic/Jurassic boundary.

  1. Annual monsoon rains recorded by Jurassic dunes.

    PubMed

    Loope, D B; Rowe, C M; Joeckel, R M

    2001-07-01

    Pangaea, the largest landmass in the Earth's history, was nearly bisected by the Equator during the late Palaeozoic and early Mesozoic eras. Modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality, but direct evidence for annual rainfall periodicity has been lacking. In the Mesozoic era, about 190 million years ago, thick deposits of wind-blown sand accumulated in dunes of a vast, low-latitude desert at Pangaea's western margin. These deposits are now situated in the southwestern USA. Here we analyse slump masses in the annual depositional cycles within these deposits, which have been described for some outcrops of the Navajo Sandstone. Twenty-four slumps, which were generated by heavy rainfall, appear within one interval representing 36 years of dune migration. We interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains, with the other four having been the result of winter storms. The slumped lee faces of these Jurassic dunes therefore represent a prehistoric record of yearly rain events. PMID:11452305

  2. UV Light Reveals the Diversity of Jurassic Shell Colour Patterns: Examples from the Cordebugle Lagerstätte (Calvados, France)

    PubMed Central

    Caze, Bruno; Merle, Didier; Schneider, Simon

    2015-01-01

    Viewed under UV light the diverse and exceptionally well-preserved molluscs from the Late Jurassic Cordebugle Konservat Lagerstätte (Calvados, Normandy, France) reveal fluorescent fossil shell colour patterns predating the oldest previously known instance of such patterns by 100 Myr. Evidently, residual colour patterns are observable in Mesozoic molluscs by application of this non-destructive method, provided the shells are not decalcified or recrystallized. Among 46 species which are assigned to twelve gastropod families and eight bivalve families, no less than 25 species yielded positive results. Out of nine colour pattern morphologies that have been distinguished six occur in gastropods and three in bivalves. The presence of these variant morphologies clearly indicates a significant pre-Cenozoic diversification of colour patterns, especially in gastropods. In addition, the occurrence of two distinct types of fluorescence highlights a major difference in the chemical composition of the pigments involved in colour pattern formation in gastropods. This discovery enables us to discriminate members of higher clades, i.e. the Vetigastropoda emitting red fluorescence from the Caenogastropoda and Heterobranchia emitting whitish-beige to yellow fluorescence. Consequently, fluorescent colour patterns may help to allocate part of the numerous enigmatic Mesozoic gastropod taxa to their correct systematic position. PMID:26039592

  3. UV Light Reveals the Diversity of Jurassic Shell Colour Patterns: Examples from the Cordebugle Lagerstätte (Calvados, France).

    PubMed

    Caze, Bruno; Merle, Didier; Schneider, Simon

    2015-01-01

    Viewed under UV light the diverse and exceptionally well-preserved molluscs from the Late Jurassic Cordebugle Konservat Lagerstätte (Calvados, Normandy, France) reveal fluorescent fossil shell colour patterns predating the oldest previously known instance of such patterns by 100 Myr. Evidently, residual colour patterns are observable in Mesozoic molluscs by application of this non-destructive method, provided the shells are not decalcified or recrystallized. Among 46 species which are assigned to twelve gastropod families and eight bivalve families, no less than 25 species yielded positive results. Out of nine colour pattern morphologies that have been distinguished six occur in gastropods and three in bivalves. The presence of these variant morphologies clearly indicates a significant pre-Cenozoic diversification of colour patterns, especially in gastropods. In addition, the occurrence of two distinct types of fluorescence highlights a major difference in the chemical composition of the pigments involved in colour pattern formation in gastropods. This discovery enables us to discriminate members of higher clades, i.e. the Vetigastropoda emitting red fluorescence from the Caenogastropoda and Heterobranchia emitting whitish-beige to yellow fluorescence. Consequently, fluorescent colour patterns may help to allocate part of the numerous enigmatic Mesozoic gastropod taxa to their correct systematic position. PMID:26039592

  4. Rulers of the Jurassic Seas

    NSDL National Science Digital Library

    Motani, Ryosuke.

    2000-01-01

    Available free from Scientific American's Website, this article takes a thorough and fascinating look at the marine reptiles known as Ichthyosaurs that lived during the Mesozoic Era. The text covers recent discoveries about the evolution of Ichthyosaurs from land dwelling reptiles, including limb adaptations. Highlights of the article are special sections about ichthyosaur eyes and diet, and color illustrations and diagrams. The text contains hyperlinks to related pages (Britannica.com, Tree of Life, American Cetacean Society, etc.). "Rulers of the Jurassic Seas" is a good read for students of paleontology or marine science.

  5. Jurassic Park Institute: Dino Lab

    NSDL National Science Digital Library

    Created as a "science-based and educationally focused program," the Jurassic Park Institute (JPI) aims to provide "kids, families, educators and scientists with the ultimate resource for dinosaur learning and fun." As would be expected from a project of Universal Studios, the JPI Dino Lab Web site is packed with cool computer animation and other multimedia features. Visitors to this site become virtual dinosaur paleontologists, interpreting discoveries and solving problems along the way. Educators can register for JPI Dino Lab's free Teacher Resources, which includes lesson plans, assessment tools, and teaching strategy tips. This site is best accessed with a high-speed connection.

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

    SciTech Connect

    van Houten, F.B.

    1980-06-01

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

  7. Amphibious flies and paedomorphism in the Jurassic period.

    PubMed

    Huang, Diying; Nel, André; Cai, Chenyang; Lin, Qibin; Engel, Michael S

    2013-03-01

    The species of the Strashilidae (strashilids) have been the most perplexing of fossil insects from the Jurassic period of Russia and China. They have been widely considered to be ectoparasites of pterosaurs or feathered dinosaurs, based on the putative presence of piercing and sucking mouthparts and hind tibio-basitarsal pincers purportedly used to fix onto the host's hairs or feathers. Both the supposed host and parasite occur in the Daohugou beds from the Middle Jurassic epoch of China (approximately 165 million years ago). Here we analyse the morphology of strashilids from the Daohugou beds, and reach markedly different conclusions; namely that strashilids are highly specialized flies (Diptera) bearing large membranous wings, with substantial sexual dimorphism of the hind legs and abdominal extensions. The idea that they belong to an extinct order is unsupported, and the lineage can be placed within the true flies. In terms of major morphological and inferred behavioural features, strashilids resemble the recent (extant) and relict members of the aquatic fly family Nymphomyiidae. Their ontogeny are distinguished by the persistence in adult males of larval abdominal respiratory gills, representing a unique case of paedomorphism among endopterygote insects. Adult strashilids were probably aquatic or amphibious, shedding their wings after emergence and mating in the water. PMID:23426262

  8. Strategies for assessing EarlyMiddle (PliensbachianAalenian) Jurassic

    E-print Network

    cyclostratigraphy of the Jurassic Period. First, Jurassic geochronology is not well constrained, due to a generalStrategies for assessing Early­Middle (Pliensbachian­Aalenian) Jurassic cyclochronologies By Linda in stratigraphic constraints. These problems are particularly troublesome in the Early to Middle Jurassic cyclic

  9. Parasites in the Fossil Record: A Cretaceous Fauna with Isopod-Infested Decapod Crustaceans, Infestation Patterns through Time, and a New Ichnotaxon

    PubMed Central

    Klompmaker, Adiël A.; Artal, Pedro; van Bakel, Barry W. M.; Fraaije, René H. B.; Jagt, John W. M.

    2014-01-01

    Parasites are common in modern ecosystems and are also known from the fossil record. One of the best preserved and easily recognisable examples of parasitism in the fossil record concerns isopod-induced swellings in the branchial chamber of marine decapod crustaceans. However, very limited quantitative data on the variability of infestation percentages at the species, genus, and family levels are available. Here we provide this type of data for a mid-Cretaceous (upper Lower Cretaceous, upper Albian) reef setting at Koskobilo, northern Spain, on the basis of 874 specimens of anomurans and brachyurans. Thirty-seven specimens (4.2%), arranged in ten species, are infested. Anomurans are more heavily infested than brachyurans, variability can be high within genera, and a relationship may exist between the number of specimens and infestation percentage per taxon, possibly suggesting host-specificity. We have also investigated quantitative patterns of infestation through geological time based on 88 infested species (25 anomurans, 55 brachyurans, seven lobsters, and one shrimp), to show that the highest number of infested species can be found in the Late Jurassic, also when corrected for the unequal duration of epochs. The same Late Jurassic peak is observed for the percentage of infested decapod species per epoch. This acme is caused entirely by infested anomurans and brachyurans. Biases (taphonomic and otherwise) and causes of variability with regard to the Koskobilo assemblage and infestation patterns through time are discussed. Finally, a new ichnogenus and -species, Kanthyloma crusta, are erected to accommodate such swellings or embedment structures (bioclaustrations). PMID:24667587

  10. New Fossil Evidence on the Sister-Group of Mammals and Early Mesozoic Faunal Distributions

    NASA Astrophysics Data System (ADS)

    Shubin, Neil H.; Crompton, A. W.; Sues, Hans-Dieter; Olsen, Paul E.

    1991-03-01

    Newly discovered remains of highly advanced mammal-like reptiles (Cynodontia: Tritheledontidae) from the Early Jurassic of Nova Scotia, Canada, have revealed that aspects of the characteristic mammalian occlusal pattern are primitive. Mammals and tritheledontids share an homologous pattern of occlusion that is not seen in other cynodonts. The new tritheledontids represent the first definite record of this family from North America. The extreme similarity of North American and African tritheledontids supports the hypothesis that the global distribution of terrestrial tetrapods was homogeneous in the Early Jurassic. This Early Jurassic cosmopolitanism represents the continuation of a trend toward increased global homogeneity among terrestrial tetrapod communities that began in the late Paleozoic.

  11. Was There a Jurassic Intra-Oceanic Arc in the Yarlung Zangbo Tethyan System?

    NASA Astrophysics Data System (ADS)

    Xu, J. F.; Kang, Z. Q.; Chen, J. L.; Wang, G. Q.; Wang, B. D.

    2014-12-01

    It is still disputed topic on subduction history of the Neo-Tethys in the south Tibet. Aitchison et al. ( J. Geol. 2007, 115, 197-213) and Jain (Current Science, 2014, 106, 254-266) suggested that the there was a Jurassic intra-oceanic arc developed within the Neo-Tethys. However, Zhang et al. (JAES, 2013, 80, 34-55) documented that this arc should be a continental margin arc. Present study reports new geochronology and geochemistry of the Sangri Group volcanic rocks which has been believed to be typical products of the Neo-Tethys subduction in the south Tibet. The Sangri Group volcanic rocks are distributed along the southern edge of the Lhasa Terrane on the northern side of the Indus-Yarlung Zangbo suture zone. It consists of the Mamuxia and Bima formations and has long been considered to be Late Jurassic to Early Cretaceous in age. We have obtained for the first time zircon LA-ICP-MS U-Pb ages for the Bima Formation volcanic rocks in Sangri County, Tibet. Two samples yield zircon U-Pb ages of 195 ± 3 Ma and 189 ± 3 Ma, respectively. These data suggest that the volcanic rocks formed during the Early Jurassic and not the Late Jurassic-Early Cretaceous as previously reported. The volcanic rocks of the Bima Formation are composed dominantly of basalt and andesite enriched in LILEs and LREEs and depleted in HFSEs, showing typical characteristics of arc volcanic rocks. They also show positive ?Nd (t) (3.19-7.02) values and low initial 87Sr/86Sr (0.703182-0.705489) ratios, similar to the MORB of the Indus-Yarlung Zangbo ophiolites, indicating that the volcanic rocks were derived from a depleted mantle wedge. The magmas of the Bima Formation volcanic rocks were thus generated by the northward subduction of Neo-Tethys as early as 195 Ma. Considering they were coeval with Late Triassic-Early Jurassic felsic intrusions within the Gangdese arc, we conclude two possibilities of the early Jurassic magmatic arc: (1) it was initiated at a juvenile continental margin arc during Late Triassic-Early Jurassic, (2) Sangri group volcanic rocks represented a remnant of an intra-oceanic arc in the Tethyan system, then emplaced into the southern margin of Lhasa terrane. Here we favor the second possibility but further investigation is necessary.

  12. Authigenic sericite record of a fossil geothermal system: the Offenburg trough, central Black Forest, Germany

    Microsoft Academic Search

    Olaf Brockamp; Norbert Clauer; Michael Zuther

    2003-01-01

    A fossil geothermal area is hosted by the Carboniferous, Permian and Bunter sandstones of the Offenburg intramontane trough in the central Black Forest. The hydrothermal alteration is identified on the basis of newly formed sericites, which appear as pseudomorphs after feldspar and filling of pore spaces. According to K–Ar dating of sericite, serititization occurred about 145 Ma ago (Jurassic). On the

  13. The first half of tetrapod evolution, sampling proxies, and fossil record quality Michael J. Benton a,

    E-print Network

    Benton, Michael

    : Tetrapoda Amniota Diversification Devonian Carboniferous Permian Triassic Jurassic The first half Permian, and showing major diversity declines in the late Moscovian, Early Permian, Wordian, lower Wuchiapingian, end-Permian, lower Anisian, lower Ladinian, Late Triassic (lower Norian to upper Rhaetian), end

  14. The Jurassic-early Cretaceous Ilo batholith of southern coastal Peru: geology, geochronology and geochemistry

    NASA Astrophysics Data System (ADS)

    Boekhout, Flora; Sempere, Thierry; Spikings, Richard; Schaltegger, Urs

    2010-05-01

    The Ilo batholith (17°00 - 18°30 S) crops out in an area of about 20 by 100 km, along the coast of southern Peru. This batholith is emplaced into the ‘Chocolate‘ Formation of late Permian to middle Jurassic age, which consists of more than 1000 m of basaltic and andesitic lavas, with interbedded volcanic agglomerates and breccias. The Ilo Batholith is considered to be a rarely exposed fragment of the Jurassic arc in Peru. Our aim is to reconstruct the magmatic evolution of this batholith, and place it within the context of long-lasting magma genesis along the active Andean margin since the Paleozoic. Sampling for dating and geochemical analyses was carried out along several cross sections through the batholith that were exposed by post-intrusion eastward tilting of 20-30°. Sparse previous work postulates early to middle Jurassic and partially early Cretaceous emplacement, on the basis of conventional K/Ar and 40Ar/39Ar dating methods in the Ilo area. Twenty new U-Pb zircon ages (LA-ICP-MS and CA-ID-TIMS) accompanied by geochemical data suggests the Ilo batholith formed via the amalgamation of middle Jurassic and early Cretaceous, subduction-related plutons. Preliminary Hf isotope studies reveal a primitive mantle source for middle Jurassic intrusions. Additional Sr, Nd and Hf isotope analyses are planned to further resolve the source regions of different pulses of plutonic activity. We strongly suggest that batholith emplacement was at least partly coeval with the emplacement of the late Permian to middle Jurassic Chocolate Formation, which was deposited in an extensional tectonic regime. Our age results and geochemical signature fit into the scheme of episodic emplacement of huge amounts of subduction related magmatism that is observed throughout the whole Andean event, particularly during the middle Jurassic onset of the first Andean cycle (southern Peru, northern Chile and southern Argentina). Although the exact geodynamic setting remains to be precisely defined, these events can be linked to extensional episodes during the breakup of Pangea, which commenced at 230-220 Ma along the western South American margin, with a period of rifting, and culminated in the Jurassic with arc and back-arc extension.

  15. E QUISETUM THERMALE SP. NOV. (EQUISETALES) FROM THE JURASSIC SAN AGUST Í N HOT SPRING DEPOSIT, PATAGONIA: ANATOMY, PALEOECOLOGY, AND INFERRED PALEOECOPHYSIOLOGY 1

    Microsoft Academic Search

    Alan Channing; Alba Zamuner; Dianne Edwards; Diego Guido

    2011-01-01

    • Premise of the study : Dated molecular phylogenies suggest a Cenozoic origin for the crown group of Equisetum . but compression fossil equisetaleans that are morphologically indistinguishable from extant Equisetum and recently discovered anatomically preserved examples strongly suggest an earlier Mesozoic initial diversifi cation. • Methods : In situ samples of Equisetum thermale sp. nov. from the Upper Jurassic

  16. World petroleum systems with Jurassic source rocks

    SciTech Connect

    Klemme, H.D. (Geo Basins Ltd., Bondville, VT (United States))

    1993-11-08

    Fourteen petroleum systems with Upper Jurassic source rocks contain one quarter of the world's discovered oil and gas. Eleven other systems with Lower and Middle Jurassic source rocks presently have a minor but significant amount of discovered oil and gas. The purpose of this article is to review the systems geologically, describe their location in space and time on a continental scale, estimate their relative petroleum system recovery efficiencies, and outline the effect their essential elements and processes have on their petroleum plumbing.

  17. Jurassic-Neocomian biostratigraphy, North Slope, Alaska

    SciTech Connect

    Mickey, M.B.; Haga, H.

    1985-04-01

    The foraminiferal and palynological biostratigraphy of subsurface Jurassic and Neocomian (Early Cretaceous) age strata from the North Slope were investigated to better define biostratigraphic zone boundaries and to help clarify the correlation of the stratigraphic units in the National Petroleum Reserve in Alaska (NPRA). Through use of micropaleontologic data, eight principal biostratigraphic units have been identified. The Neocomian and Jurassic strata have each been subdivided into four main units.

  18. Sr-isotope stratigraphy of the Upper Jurassic of central Portugal (Lusitanian Basin) based on oyster shells

    NASA Astrophysics Data System (ADS)

    Schneider, Simon; Fürsich, Franz T.; Werner, Winfried

    2009-12-01

    Strontium isotope stratigraphy was performed on oyster shells from the Late Jurassic of the Lusitanian Basin (central Portugal). This represents the first approach to obtain numerical ages for these strata. The new chronostratigraphic data provide a more precise age determination of several units. After a basin-wide hiatus sedimentation in the Late Jurassic is proven in the Cabo Mondego and Cabaços formations to resume as early as the Middle Oxfordian. The Alcobaça formation can be placed in the latest Late Oxfordian to Late Kimmeridgian, while data from the upper part of the Abadia Formation indicate an Early to Late Kimmeridgian age. The Farta Pao formation ranges from the latest Kimmeridgian to the latest Tithonian. The largely synchronous Sobral, Arranhó I, and Arranhó II members are overlain by the late Early to Late Tithonian Freixial Member. The brief, local carbonate incursion of the Arranhó I member marks the Kimmeridgian-Tithonian boundary. Oysters are shown once more to be suitable for strontium isotope studies. Their calcitic shells are often unaffected by diagenesis. In particular for marginal marine Jurassic and Cretaceous strata, where belemnites are usually absent, oysters may serve as a valuable tool for isotope stratigraphy.

  19. Sedimentology and sequence stratigraphy of paralic and shallow marine Upper Jurassic sandstones in the northern Danish Central Graben

    Microsoft Academic Search

    Peter N. Johannessen

    Paralic and shallow marine sandstones were deposited in the Danish Central Graben during Late Jurassic rifting when half-grabens were developed and the overall eustatic sea level rose. During the Kimmeridgian, an extensive plateau area consisting of the Heno Plateau and the Gertrud Plateau was situated between two highs, the Mandal High to the north, and the combined Inge and Mads

  20. Highly specialized mammalian skulls from the Late Cretaceous of South America.

    PubMed

    Rougier, Guillermo W; Apesteguía, Sebastián; Gaetano, Leandro C

    2011-11-01

    Dryolestoids are an extinct mammalian group belonging to the lineage leading to modern marsupials and placentals. Dryolestoids are known by teeth and jaws from the Jurassic period of North America and Europe, but they thrived in South America up to the end of the Mesozoic era and survived to the beginnings of the Cenozoic. Isolated teeth and jaws from the latest Cretaceous of South America provide mounting evidence that, at least in western Gondwana, dryolestoids developed into strongly endemic groups by the Late Cretaceous. However, the lack of pre-Late Cretaceous dryolestoid remains made study of their origin and early diversification intractable. Here we describe the first mammalian remains from the early Late Cretaceous of South America, including two partial skulls and jaws of a derived dryolestoid showing dental and cranial features unknown among any other group of Mesozoic mammals, such as single-rooted molars preceded by double-rooted premolars, combined with a very long muzzle, exceedingly long canines and evidence of highly specialized masticatory musculature. On one hand, the new mammal shares derived features of dryolestoids with forms from the Jurassic of Laurasia, whereas on the other hand, it is very specialized and highlights the endemic, diverse dryolestoid fauna from the Cretaceous of South America. Our specimens include only the second mammalian skull known for the Cretaceous of Gondwana, bridging a previous 60-million-year gap in the fossil record, and document the whole cranial morphology of a dryolestoid, revealing an unsuspected morphological and ecological diversity for non-tribosphenic mammals. PMID:22051679

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

    E-print Network

    Bermingham, Eldredge

    The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system Keywords: Amazon basin Amazon River Late Miocene Paleogeography Paleoecology fossil vertebrates palinology

  2. Isotopic constraints on the petrogenesis of jurassic plutons, Southeastern California

    USGS Publications Warehouse

    Mayo, D.P.; Anderson, J.L.; Wooden, J.L.

    1998-01-01

    The 165 Ma Eagle Mountain intrusion is a heterogeneous, enclave-bearing, metaluminous remnant of the Cordilleran Jurassic arc that cuts regionally metamorphosed pre-Mesozoic rocks in the southeastern Mojave Desert of California. The main phase of the intrusion consists of granodiorite to tonalite host facies, diorite mixed facies, and homogeneous monzogranite facies. The host facies contains microdiorite enclaves interpreted as intermingled masses of mafic magma. Late-phase leucogranite stocks cut the main phase. Mineral equilibria indicate emplacement at ???6.5 km depth, with solidus temperatures ranging from 760??C for diorite to 700??C for felsic granodiorite. Although uniform radiogenic-isotope compositions (Sri = 0.7085, ???Ndi = -9.4) suggest derivation from a single source, no known source has the composition required. A hybrid source is proposed, consisting of various proportions of juvenile mantle and recycled lower crust. Calculations indicate that the source of the Eagle Mountain intrusion comprised >60% juvenile mantle and <40% recycled crust. On the basis of their isotopic compositions, other mafic Jurassic plutons in the region were derived from sources containing different proportions of mantle and crustal components.

  3. Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece

    USGS Publications Warehouse

    Aiello, I.W.; Hagstrum, J.T.; Principi, G.

    2008-01-01

    Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and the nature of a Tethys-wide change from biosiliceous to biocalcareous (mainly nannofossil) deposition at the beginning of Cretaceous time, have remained open questions. Previous paleomagnetic analyses of Jurassic red radiolarian cherts in the Italian Apennines indicate that radiolarian deposition occurred at low peri-equatorial latitudes, similar to modern day deposition of radiolarian-rich sediments within equatorial zones of high biologic productivity. To test this result for other sectors of the Mediterranean region, we undertook paleomagnetic study of Mesozoic (mostly middle to upper Jurassic) red radiolarian cherts within the Aegean region on the Peloponnesus and in continental Greece. Sampled units are from the Sub-Pelagonian Zone on the Argolis Peninsula, the Pindos-Olonos Zone on the Koroni Peninsula, near Karpenissi in central Greece, and the Ionian Zone in the Varathi area of northwestern Greece. Thermal demagnetization of samples from all sections removed low-temperature viscous and moderate-temperature overprint magnetizations that fail the available fold tests. At Argolis and Koroni, however, the cherts carry a third high-temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests. We interpret the high-temperature component to be the primary magnetization acquired during chert deposition and early diagenesis. At Kandhia and Koliaky (Argolis), the primary declinations and previous results indicate clockwise vertical-axis rotations of ??? 40?? relative to "stable" Europe. Due to ambiguities in hemispheric origin (N or S) and thus paleomagnetic polarity, the observed declinations could indicate either clockwise (CW) or counterclockwise (CCW) vertical-axis rotations. Thus at Adriani (Koroni), the primary declinations indicate either CW or CCW rotations of ??? 95?? or ??? 84??, depending on paleomagnetic polarity and age. The primary inclinations for all Peloponnesus sites indicate peri-equatorial paleolatitudes similar to those found for coeval radiolarian cherts exposed in other Mediterranean orogenic belts. Our new paleomagnetic data support the interpretation that Mesozoic radiolarites within the Tethys Ocean were originally deposited along peri-equatorial belts of divergence and high biologic productivity. ?? 2007 Elsevier B.V. All rights reserved.

  4. An earwig in Late Cretaceous Vendean amber (Dermaptera)

    E-print Network

    Engel, Michael S.; Perrichot, Vincent

    2014-12-01

    A new fossil earwig nymph is described and figured from the Late Cretaceous (Cenomanian to Santonian) amber of Vendée, northwestern France. Vendeenympha gravesi n. gen. and sp., is distinguished from previously recorded nymphs in other French fossil...

  5. Chronostratigraphy and hydrocarbon habitat associated with the Jurassic carbonates of Abu Dhabi, United Arab Emirates

    SciTech Connect

    Alsharahan, A.S.; Whittle, G.L.

    1995-08-01

    Deposition of Jurassic epeiric shelf carbonates and evaporates were controlled by epeirogenic movement and sea level fluctuations which formed an excellent combination of source rocks, reservoirs and seats in Abu Dhabi. At the end of the Triassic, a relative drop in sea level, caused by eustatic sea level lowering in conjunction with minor tectonic uplift, resulted in non-deposition or erosion. In the Toarcian, deposition of carbonates and terrigenous, clastics produced the Marrat Formation. In the mid-Aalenian, a drop in sea level eroded much of the Marrat and some of the Triassic in offshore U.A.E. The deposition of the Hamlah Formation followed, under neritic, well-oxygenated conditions. The Middle Jurassic was characterized by widespread, normal marine shelf carbonates which formed the cyclic Izhara and Araej formations (reservoirs). In the Upper Jurassic, the carbonate shelf became differentiated into a broad shelf with a kerogen-rich intrashelf basin, formed in response to a eustatic rise coupled with epeirogenic downwarping and marine flooding. The intrashelf basin fill of muddy carbonate sediments constitutes the Diyab Formation and its onshore equivalent, the Dukhan Formation (source rocks). In the late Upper Jurassic, the climate became more arid and cyclic deposition of carbonates and evaporates prevailed, forming alternating peritidal anhydrite, dolomite and limestone in the Arab Formation (reservoir). Arid conditions continued into the Tithonian, fostering the extensive anhydrite of the Hith Formation (seal) in a sabkha/lagoonal setting on the shallow peritidal platform, the final regressive supratidal stage of this major depositional cycle.

  6. Jurassic igneous-related metallogeny of southwestern North America

    E-print Network

    Barton, Mark D.

    Jurassic igneous-related metallogeny of southwestern North America Mark D. Barton*, James D Jurassic magmatism and related hydrothermal systems formed across much of southwestern North America, advanced argillic, metallogeny, magmatism, southwestern North America INTRODUCTION The Great Basin

  7. The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962

    E-print Network

    The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962: cranial 27 August 2010 The cranial anatomy of the Lower Jurassic ornithischian dinosaur Heterodontosaurus commonly seen in basal archosaurs and saurischian dinosaurs). Evidence for tooth replacement (which has

  8. Theropod Fossil Hunt Dispatch

    NSDL National Science Digital Library

    This site outlines the step by step progression as a rare fossil is found, authenticated and identified. Follow along as a paleontologist pursues a well-preserved fossil of Sinosauropteryx, a feathered dromaeosaur. The site is enhanced with several photographs.

  9. Quaternary fossil fauna of South Canterbury, South Island, New Zealand

    Microsoft Academic Search

    T. H. Worthy

    1997-01-01

    This study documents the Late Quaternary fossil fauna from 59 fossil sites in the South Canterbury downlands, South Island, New Zealand. Twenty?seven sites were predator accumulations attributed to laughing owls, two were accumulated by falcons, two were swamp sites, and the rest were pitfalls or rockshelter deposits. A total of 60 indigenous species of birds, one bat, three rodents, one

  10. Post-Cimmerian (Jurassic-Cenozoic) paleogeography and vertical axis tectonic rotations of Central Iran and the Alborz Mountains

    NASA Astrophysics Data System (ADS)

    Mattei, Massimo; Cifelli, Francesca; Muttoni, Giovanni; Rashid, Hamideh

    2015-04-01

    According to previous paleomagnetic analyses, the northward latitudinal drift of Iran related to the closure of the Paleo-Tethys Ocean resulted in the Late Triassic collision of Iran with the Eurasian plate and Cimmerian orogeny. The post-Cimmerian paleogeographic and tectonic evolution of Iran is instead less well known. Here we present new paleomagnetic data from the Upper Jurassic Bidou Formation of Central Iran, which we used in conjunction with published paleomagnetic data to reconstruct the history of paleomagnetic rotations and latitudinal drift of Iran during the Mesozoic and Cenozoic. Paleomagnetic inclination values indicate that, during the Late Jurassic, the Central-East-Iranian Microcontinent (CEIM), consisting of the Yazd, Tabas, and Lut continental blocks, was located at low latitudes close to the Eurasian margin, in agreement with the position expected from apparent polar wander paths (APWP) incorporating the so-called Jurassic massive polar shift, a major event of plate motion occurring in the Late Jurassic from 160 Ma to 145-140 Ma. At these times, the CEIM was oriented WSW-ENE, with the Lut Block bordered to the south by the Neo-Tethys Ocean and to the southeast by the Neo-Sistan oceanic seaway. Subsequently, the CEIM underwent significant counter-clockwise (CCW) rotation during the Early Cretaceous. This rotation may have resulted from the northward propagation of the Sistan rifting-spreading axis during Late Jurassic-Early Cretaceous, or to the subsequent (late Early Cretaceous?) eastward subduction and closure of the Sistan oceanic seaway underneath the continental margin of the Afghan Block. No rotations of, or within, the CEIM occurred during the Late Cretaceous-Oligocene, whereas a second phase of CCW rotation occurred after the Middle-Late Miocene. Both the Late Jurassic-Early Cretaceous and post Miocene CCW rotations are confined to the CEIM and do not seem to extend to other tectonic regions of Iran. Finally, an oroclinal bending mechanism is proposed for the origin of the curved Alborz Mountains, which acquired most of its curvature in the last 8 Myr.

  11. Face-to-Fossil

    NSDL National Science Digital Library

    This Web article is part of OLogy, where kids can collect virtual trading cards and create projects with them. Here they meet Deena Soris, who interviews the fossil of a Protoceratops. The more-than-20 questions answered by this dinosaur fossil cover topics such as what were you like when you were alive and how did you become a fossil.

  12. Aestivation in the fossil record: evidence from ichnology.

    PubMed

    Hembree, Daniel I

    2010-01-01

    Aestivation is a physiological and behavioral response to high temperature or low moisture conditions. Therefore, it is typically not considered to be capable of being preserved in the fossil record. However, most aestivating organisms produce a burrow to protect themselves from the harmful environmental conditions that trigger aestivation. These structures can be preserved in the rock record as trace fossils. While trace fossils are abundant in the continental fossil record, few are definitively associated with aestivation. Interpreting aestivation behavior from fossil burrows requires a detailed examination and interpretation of the surrounding sedimentary rocks and comparisons with taxonomically and ecologically similar extant organisms. Currently, only four types of aestivation structures are recognized in the fossil record: Pleistocene earthworm chambers, Devonian to Cretaceous lungfish burrows, Permian lysorophid burrows, and Permian to Triassic dicynodont burrows. The trace fossil evidence suggests that aestivation evolved independently among continental organisms in several clades during the middle to late Paleozoic. PMID:20069413

  13. A juvenile lizard specimen with well-preserved skin impressions from the Upper Jurassic/Lower Cretaceous of Daohugou, Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Evans, S. E.; Wang, Y.

    2007-06-01

    Lizards are now relatively well known from the Yixian Formation of northeastern China. In this study, we describe a juvenile lizard from a fossil horizon at Daohugou, Inner Mongolia. These beds predate the Yixian Formation, and are probably Late Jurassic or earliest Cretaceous in age. The new specimen thus documents the first lizard material from the Daohugou locality and is the earliest lizard skeleton from China. Comparisons with developmental stages of modern lizards suggest the Daohugou lizard is a hatchling. Although tiny, the specimen is notable in preserving exquisite skin impressions showing the variation in scalation across the body, the shape and position of the cloacal outlet, and details of the manus and pes. These are the earliest recorded lepidosaurian skin traces. In its general proportions and the possession of paired frontals, the small Daohugou lizard resembles both the Yixian taxon Yabeinosaurus tenuis and the questionable Jeholacerta formosa, but it differs from the latter in scalation and, based on other characters, may be distinct from both.

  14. TriassicJurassic boundary events: Problems, progress, possibilities 1. Problems

    E-print Network

    McRoberts, Christopher A.

    As for most geological period boundaries, the Triassic­Jurassic (T­J) transition, 200 million years agoEditorial Triassic­Jurassic boundary events: Problems, progress, possibilities 1. Problems to reconstruct past events, a physical record of their passing is essential. Here again the Triassic­Jurassic

  15. Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America.

    PubMed

    Butler, Richard J; Galton, Peter M; Porro, Laura B; Chiappe, Luis M; Henderson, Donald M; Erickson, Gregory M

    2010-02-01

    The extremes of dinosaur body size have long fascinated scientists. The smallest (<1 m length) known dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65-75 cm in total body length and 0.5-0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade. PMID:19846460

  16. Latest Jurassic ammonoid provinces: Paleoecological implications using a general circulation model

    SciTech Connect

    Ross, C.A. (Chevron, Houston, TX (United States)); Moore, G.T.; Hayashida, D.N. (Chevron Oil Field Research Co., La Habra, CA (United States))

    1992-01-01

    The Lake Permian-early Mesozoic megacontinent Pangea was progressively fragmented by two rift systems that propagated westward out of the Tethys Sea and a third more persistent rift system that connected the Boreal and Tethys seas. By the late Tithonian, these major rift systems produced interconnected oceanic seaways that divided Pangea into four continental segments: North America, Eur-Asia, and northern and southern Gondwana. Increased rates of sea-floor spreading during the Jurassic reduced the volumetric capacity of ocean basins and produced a sea level rise through the period that culminated in the Lake Jurassic. The extensive marine shelf margins and epeiric seas hosted a widely distributed and diverse ammonoid fauna. By the early Tithonian, faunal communication existed between the northwestern Tethys Sea and the eastern Panthalassa Ocean through the proto-Gulf of Mexico. By the late Tithonian, faunal similarities indicate the opening of the proto-Indian Ocean so that northern and southern Gondwana had become separate continents. A region of the equatorial Tethys that includes most of the present Arabian Peninsular contains neuritic platform facies but lacks ammonoids. In high northern latitudes, cool to cold water faunas formed a Boreal Realm which extended westward across northern North America, Europe, and Siberia during middle and late Tithonian. Late Kimmeridgian and Tithonian ammonoid distributions when compared with Late Jurassic paleoclimate simulations show likely causal relationships with sea surface water temperatures and upwelling, and possibly shed light on the temperature limitations of ammonoids. Results from modeled seasonal sea surface temperature, sea ice distribution, precipitation-evaporation, and wind-driven upwelling permit the evaluation and quantification of paleoenvironmental factors favorable as well as pernicious for ammonoid distribution.

  17. Living-fossil coccolithophore survivors of the Cretaceous-Paleogene mass extinction

    NASA Astrophysics Data System (ADS)

    Hagino, K.; Young, J. R.; Bown, P. R.; Godrijan, J.; Kogame, K.; Kulhanek, D. K.; Horiguchi, T.

    2012-12-01

    Calcareous nannofossils (coccolithophores and other associated fossils), diversified greatly through the middle-late Mesozoic, but around 90% of these species became extinct at the K/Pg event. Although the specific cause of this mass extinction is still uncertain, the record of extinction and survivorship of nannoplankton has informed our understanding of the rates of extinction and recovery, and nature of survivorship in the plankton ecosystem. Recently we found living cells of a coccolithophore, which morphologically and structurally resembles the Mesozoic genus Cyclagelosphaera, from coastal-neritic waters of Tottori, Japan and of Rovinj, Croatia. Cyclagelosphaera is a characteristic Mesozoic genus that appeared in the middle Jurassic. It survived the K/Pg event, briefly flourished in post K/Pg oceans, with other K/Pg survivors, but disappeared from the fossil record in the Eocene. Bibliographic study has revealed that our specimens correspond to a living species Tergestiella adriatica, which was discovered from offshore Rovinji in 1934 but has never since been reported. Molecular phylogenetic studies of T. adriatica based on SSU rDNA sequences show that T. adriatica branched from the base of the clade of other living coccolithophores. This result suggests that T. adriatica diverged from the ancestor of other coccolithophores before the diversification of other taxa and supports the inference that T. adriatica is a direct descendent of Mesozoic Cyclagelosphaera rather than a homoeomorph. Floristic studies of living coccolithophores show that T. adriatica coexists with Braarudosphaera bigelowii, another K/Pg survivor, in the coastal area of Tottori, Japan. In both Mesozoic and Cenozoic oceans, calcareous nannoplankton are typically open-ocean dwellers, but a few taxa are confined to coastal waters. Curiously, all three extant coccolithophores with Mesozoic fossil records are coastal, meanwhile the other extant taxa with Cenozoic fossil records are oceanic. Our observation of T. adriatica and B. bigelowii from coastal environments provides evidence that coastal coccolithophores survived the K/Pg event selectively, and reinforces the hypothesis that calcareous plankton were almost completely eliminated from oceanic environments. The clearance of Mesozoic oceanic taxa likely allowed the temporary flourishing of coastal survivors in open ocean until the evolution of new specialist open ocean taxa. This selectivity may indicate that ocean acidification was a contributory factor in the K/Pg extinctions.

  18. Mechanisms for high-frequency cyclicity in the Upper Jurassic limestone of northeastern Mexico

    SciTech Connect

    Johnson, C.R.; Ward, W.C. (Univ. of New Orleans, LA (United States)); Goldhammer, R.K. (Exxon Production Research, Houston, TX (United States))

    1991-03-01

    The 520 m of Upper Jurassic Zuloaga Limestone exposed in the Sierra de Bunuelos in southern Coahuila comprise 118 cycles of peritidal carbonate rock deposited on a gently dipping ramp. Field studies with Fischer plots and time-series analysis suggest that a Milankovitchian glacioeustasy mechanism is inadequate to describe the Zuloaga cycles. Autocyclic progradation may have been the major influence on depositional cyclicity. Depositional cycles in the Zuloaga Formation typically are a few meters thick and asymmetric with subtidal wackestone and packstone grading upward into subtidal grainstone or into intertidal stromatolites. Width of the carbonate ramp is estimated to have been about 150 km. Sedimentation rates for these peritidal carbonate environments apparently exceeded subsidence rates inasmuch as most of the carbonate platform remained near sea level during Zuloaga deposition. The area was tectonically quiescent during the late Jurassic. Autocyclic shoreline progradation is a feasible mechanism for producing the high-frequency cycles, as suggested by (1) poor correlation with predicted Milankovitch periodicity shown by time-series analysis, (2) little evidence of subaerial exposure, (3) development of complete peritidal cycles, (4) general progradational sequences within each third-order unit, and (5) absence of polar glaciation during Late Jurassic.

  19. Bennettitales from the Grisethorpe Bed (Middle Jurassic) at Cayton Bay, Yorkshire, UK.

    PubMed

    Crane, Peter R; Herendeen, Patrick S

    2009-01-01

    Middle Jurassic fossil plants from the Grisethorpe Bed at Cayton Bay and Grisethorpe Bay, Yorkshire, UK, are preserved in a soft claystone, and plant mesofossils recovered by sieving reveal excellent details of external structure. Studies of these mesofossils complement previous work on macrofossils from the Grisethorpe Bed and allow the plant fossils in this classic flora to be studied in a similar way to those preserved in Cretaceous mesofloras. Bennettitales, a key group in discussions of how angiosperms may be related to other seed plants, are especially well represented among mesofossils from the Grisethorpe Bed. Abundant bennettitalean leaves, scale leaves, and fragments of pollen and ovulate organs provide new information on these extinct plants. In particular, a specimen of Williamsoniella coronata (presumed aborted) shows only weak differentiation between interseminal scales and ovules and provides further evidence of homology between these structures. PMID:21628189

  20. Applications of fossil resin studies to an understanding of depositional and paleoenvironments

    Microsoft Academic Search

    D. Bellis; D. L. Wolberg

    1989-01-01

    Fossil resins are polymerized terpene (isoprenoid) acids. Because of their complexity and resulting variability, isoprenoids have been useful for their information content and geochemical signatures. Fossil resin occurs throughout a 304-ft continuous core and correlated outcrops from the Late Cretaceous Fruitland Formation in the Fossil Forest study area, San Juan basin, New Mexico, in associated with coal, sandstone, shale, and

  1. Correlation of the Jurassic through Oligocene Stratigraphic Units of Trinidad and Northeastern Venezuela

    SciTech Connect

    Algar, S. [Enterprise Oil, London (United Kingdom); Erikson, J.P. [Univ. of California, Davis, CA (United States)

    1995-04-01

    The Jurassic through Oligocene stratigraphies of Trinidad and the Serrenia del Interior of eastern Venezuela exhibit many similarities because of their proximity on the passive continental margins of northeastern South America. A slightly later subsidence in eastern Venezuela, and the generally deeper-water sedimentation in Trinidad, is interpreted to be the result of a serration of the original rift margin, producing an eastern Venezuela promontory and Trinidadian re-entrant. We interpret these serrations to be the result of oblique (NW-SE) spreading of North and South America during Middle and late Jurassic time. The stratigraphies of northeastern Venezuela and Trinidad contrast in the Hauterivan-Albian interval, with dynamic shallow shelf environments prevailing in the Serrenia del Interior and deeper marine submarine-fan deposition in Trinidad. Both areas develop middle to Upper Cretaceous source rocks during a time of eustatic sea level high and widespread oceanic anoxia. 15 refs., 4 fig.

  2. New evidence of shared dinosaur across Upper Jurassic Proto-North Atlantic: Stegosaurus from Portugal

    NASA Astrophysics Data System (ADS)

    Escaso, Fernando; Ortega, Francisco; Dantas, Pedro; Malafaia, Elisabete; Pimentel, Nuno L.; Pereda-Suberbiola, Xabier; Sanz, José Luis; Kullberg, José Carlos; Kullberg, María Carla; Barriga, Fernando

    2007-05-01

    More than one century after its original description by Marsh in 1877, we report in this paper the first uncontroversial evidence of a member of the genus Stegosaurus out of North America. The specimen consists of a partial skeleton from the Upper Jurassic of Portugal, herein considered as Stegosaurus cf. ungulatus. The presence of this plated dinosaur in the upper Kimmeridgian-lower Tithonian Portuguese record and synchronic levels of the Morrison Formation of North America reinforces previous hypothesis of a close relationship between these two areas during the Late Jurassic. This relationship is also supported by geotectonic evidences indicating high probability of an episodic corridor between the Newfoundland and Iberian landmasses. Together, Portuguese Stegosaurus discovery and geotectonic inferences could provide a scenario with episodical faunal contact among North Atlantic landmasses during the uppermost Kimmeridgian-lowermost Tithonian (ca. 148-153 Ma ago).

  3. Jurassic stratigraphy of the Wiggins Arch, Mississippi

    SciTech Connect

    Rhodes, J.A.; Maxwell, G.B. (Mobil Oil Company, Houston, TX (United States))

    1993-09-01

    Mobil and Shell jointly explored the Wiggins arch area in southern Mississippi from 1985 to 1991. The effort concentrated on the Jurassic Norphlet and Smackover formations. Two wells were drilled into Paleozoic crystalline rocks and one well into the Pine Hill formation. Two of these wells were located on the southern side of the Wiggins arch and provide significant data for interpreting Jurassic stratigraphy. The Mobil No. 1 U.S.A. well encountered a complete Jurassic section, but with some significantly different facies than those encountered by wells to the north. A granite wash section is the equivalent to the Frisco City formation previously only found 100 mi to the north-northeast. All 300 ft of Smackover is crystalline dolomite. The Norphlet section is entirely granite wash. The Pine Hill anhydrite is unusually thick and interpreted to be equivalent to the Louann Salt. Correlations to other wells on the Wiggins arch, particularly the Conoco No. 1 Higgins, indicate that the Jurassic can be divided into three transgressive events separated by the Norphlet/Pine Hill and Frisco City/Buckner regressive events.

  4. Jurassic evolution of the Tien-Shan

    SciTech Connect

    Bebeshev, I.I. [Geological Institute, Moscow (Russian Federation)

    1994-09-01

    Complex studies led to identification of three stages in Jurassic deposits. The stages reflect development periods of the studied deposits. Each stage is represented by a paleogeographic map that indicates the evolution of ancient landforms in the Tien-Shan region in time and space.

  5. The Early Jurassic Ornithischian Dinosaurian Ichnogenus Anomoepus

    E-print Network

    Olsen, Paul E.

    Jurassic footprint genus produced by a relatively small, gracile orni- thischian dinosaur. It has, Edward Hitchcock described the first of what we now recognize as dinosaur tracks from Early Juras- sic.1 and 19.2). Because skeletons of dinosaur feet were not known at the time, he naturally attributed

  6. Discovering the "-Ologies" on the Jurassic Coast

    ERIC Educational Resources Information Center

    Peacock, Alan

    2007-01-01

    The Jurassic Coast is Britain's only natural World Heritage site, a tangible time-line that takes one through 185 million years of history in 95 miles of coast. It provides individuals with a world-famous educational resource and an unrivalled outdoor classroom that has played a key role in the study of earth sciences. The author is keen to ignite…

  7. Deep burial dolomitization driven by plate collision: Evidence from strontium-isotopes of Jurassic Arab IV dolomites from offshore Qatar

    SciTech Connect

    Vahrenkamp, V.C.; Taylor, S.R. (Shell Research, Rijswijk (Netherlands))

    1991-03-01

    The use of strontium-isotope ratios of dolomites to constrain timing and mechanism of diagenesis has been investigated on Jurassic Arab IV dolomites from offshore Qatar. Reservoir quality is determined by two types of dolomites, which were differentiated geochemically (cathodoluminescence, fluid inclusions, and carbon and oxygen stable isotopes): (1) stratigraphically concordant sucrosic dolomites with high porosity formed during early near-surface diagenesis (Jurassic) and (2) stratigraphically discordant cylindrical bodies of massive, porosity-destroying dolomites formed late during deep burial diagenesis (Eocene-Pliocene). Detailed Sr-isotope analysis of dolomites from the Arab IV confirms an Early Jurassic age of the sucrosic, high porosity dolomites ({sup 87}Sr/{sup 86}SR = 0.70707 for NBS 987 = 0.71024) with magnesium and strontium being derived from Jurassic seawater. Late Tertiary compressional orogeny of the Zagros belt to the north is proposed to have caused large-scale squeezing of fluids from the pore system of sedimentary rocks. A regional deep fluid flow system developed dissolving infra-Cambrian evaporites upflow and causing large-scale deep burial dolomitization downflow.

  8. Jurassic hydrocarbon seep-carbonates in the High Atlas Basin (Morocco)

    NASA Astrophysics Data System (ADS)

    Bodin, Stephane; Kothe, Tim; Rose, Johannes; Krencker, Francois-Nicolas; Kabiri, Lahcen

    2015-04-01

    In the central High Atlas Basin of Morocco, the occurrence of Jurassic hydrocarbon seeps is observed in two distinct horizons: (1) the uppermost Polymorphum ammonite zone (Lower Toarcian) and (2) the Sauzei (eq. Propiquans) ammonite zone (Lower Bajocian). The Toarcian seep-carbonates are made of 5 - 6cm in diameter, half-spherical concretions that surround two vertical and closely spaced tubes, parallel to each other. Each tube is less than 1cm in diameter and filled with late diagenetic cements. The tubes are interpreted as burrow trace fossil. The concretions are embedded within an organic-matter rich interval and resemble to the Tisoa siphonalis concretions described in the upper Pliensbachian of Western Europe. Carbon isotope values decrease from the rim to the center of the concretion (from 1 to -7 per mil) whereas oxygen isotope values remain stable around -7 per mil. The C-isotope values of the concretion rim are similar to the bulk carbon isotope values of the embedding rocks. The most negative C-isotope values indicate that the carbon source of the carbonate precipitated in the centre of the concretion is likely sourced from the organoclastic sulfate reduction zone. The Bajocian seep-carbonates are observed within the dark calcareous mudstone of the Sauzei zone. One peculiarly well-exposed seep system shows the presence of a plumbing system leading to a 20cm thick carbonate crust showing the occasional occurrence of chimney structures on its upper part. The high abundance of serpulids clusters within the carbonate crust shows that it was precipitated at the water-sediment interface. The pipe structures of the plumbing system are composed of an external micritic rim enclosing a central tube that can be up to 12cm large. A complex, multi-phased infilling is observed in the inner part of the pipe and separated from the rim by a millimetric pyritized crust. Carbon isotope values are comprised between -20 per mil and -8 per mil for the micritic rim, whereas the infilling carbonate have values ranging from -12 per mil to 1 per mil. As for the Toarcian carbonate seep, the source of the carbon is therefore likely situated within the organoclastic sulfate reduction zone. Both seep-carbonate intervals are interpreted to be the consequence of early diagenetic processes affecting organic-rich sediments, and therefore a local signature of enhanced organic matter burial.

  9. Syntectonic emplacement of the Middle Jurassic Concón Mafic Dike Swarm, Coastal Range, central Chile (33° S)

    NASA Astrophysics Data System (ADS)

    Creixell, Christian; Parada, Miguel Ángel; Roperch, Pierrick; Morata, Diego; Arriagada, César; de Arce, Carlos Pérez

    2006-10-01

    The Concón Mafic Dike Swarm (CMDS) consists of basaltic to andesitic dikes emplaced into deformed Late Paleozoic granitoids during the development of the Jurassic arc of central Chile. The dikes are divided into an early group of thick dikes (5-12 m) and a late group of thin dikes (0.5-3 m). Two new amphibole 40Ar/ 39Ar dates obtained from undeformed and deformed dikes, constrain the age of emplacement and deformation of the CMDS between 163 and 157 Ma. Based on radiometric ages, field observations, AMS studies and petrographic data, we conclude that the emplacement of the CMDS was syntectonic with the Jurassic arc extension and associated with sinistral displacements along the NW-trending structures that host the CMDS. The common occurrence of already deformed and rotated xenoliths in the dikes indicates that deformation in the granitoids started previously. The early thick dikes and country rocks appear to have been remagnetized during the exhumation of deep-seated coastal rocks in the Early Cretaceous (around 100 Ma). The remanent magnetization in late thin dikes is mainly retained by small amounts of low-Ti magnetite at high temperature and pyrrhotite at low temperature. The magnetization in these dikes appears to be primary in origin. Paleomagnetic results from the thin dikes also indicate that the whole area was tilted ˜ 23° to the NNW during cooling of the CMDS. The NNW-SSE extension vectors deduced from the paleomagnetic data and internal fabric of dikes are different with respect to extension direction deduced for the Middle-Late Jurassic of northern Chile, pointing to major heterogeneities along the margin of the overriding plate during the Mesozoic or differences in the mechanisms driving extension during such period.

  10. Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva.

    PubMed

    Chen, Jun; Wang, Bo; Engel, Michael S; Wappler, Torsten; Jarzembowski, Edmund A; Zhang, Haichun; Wang, Xiaoli; Zheng, Xiaoting; Rust, Jes

    2014-01-01

    The reconstruction of ancient insect ectoparasitism is challenging, mostly because of the extreme scarcity of fossils with obvious ectoparasitic features such as sucking-piercing mouthparts and specialized attachment organs. Here we describe a bizarre fly larva (Diptera), Qiyia jurassica gen. et sp. nov., from the Jurassic of China, that represents a stem group of the tabanomorph family Athericidae. Q. jurassica exhibits adaptations to an aquatic habitat. More importantly, it preserves an unusual combination of features including a thoracic sucker with six radial ridges, unique in insects, piercing-sucking mouthparts for fluid feeding, and crocheted ventral prolegs with upward directed bristles for anchoring and movement while submerged. We demonstrate that Q. jurassica was an aquatic ectoparasitic insect, probably feeding on the blood of salamanders. The finding reveals an extreme morphological specialization of fly larvae, and broadens our understanding of the diversity of ectoparasitism in Mesozoic insects.DOI: http://dx.doi.org/10.7554/eLife.02844.001. PMID:24963142

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

    PubMed Central

    Clapham, Matthew E.; Bottjer, David J.

    2007-01-01

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

  12. Tiny Fossil Sheds Light on Mammalian Evolution

    NSDL National Science Digital Library

    de Nie, Michael Willem.

    2001-01-01

    In the most recent issue of Science, a team of American and Chinese scientists announced the discovery of the fossil of a tiny shrew-like creature that lived 195 million years ago, 45 million years before previously discovered mammals. Found in 1985 in Yunnan province, China, the fossil was originally believed to be merely a bone fragment because of its small size. It has now been named Hadrocodium wui, ("Fullhead"), and could possibly be the direct ancestor of all living mammals. Hadrocodium was an insectivore, eating worms and small insects. Though it weighed only two grams (the weight of a paper clip), Hadrocodium had a considerably larger brain than most known mammals from the early Jurassic period. The tiny skull also possesses three other key traits that are characteristic of the transition from mammal-like animals to true mammals: a three-bone middle ear separated from the jaw, matching upper and lower teeth, and a powerful jaw hinge. Readers can begin learning more about this discovery with the Science article. Additional coverage is provided by Discovery news, the BBC, National Geographic, ABC News, and CNN.

  13. Fossil-energy program

    Microsoft Academic Search

    L. E. McNeese

    1982-01-01

    The increased utilization of coal and other fossil fuel alternatives as sources of clean energy is reported. The projects reported include: coal conversion development, chemical research and development, materials technology, component development and process evaluation, technical support to major liquefaction, process analysis and engineering evaluations, fossil energy environmental analysis, environmental control technology, coal preparation waste utilization, atmospheric fluidized bed coal

  14. Restoring Fossil Creek

    ERIC Educational Resources Information Center

    Flaccus, Kathleen; Vlieg, Julie; Marks, Jane C.; LeRoy, Carri J.

    2004-01-01

    Fossil Creek had been dammed for the past 90 years, and plans were underway to restore the stream. The creek runs through Central Arizona and flows from the high plateaus to the desert, cutting through the same formations that form the Grand Canyon. This article discusses the Fossil Creek monitoring project. In this project, students and teachers…

  15. Becoming a Fossil

    NSDL National Science Digital Library

    2005-01-01

    This text and accompanying video provide an overview of how fossils are formed and preserved. A video clip from the NOVA television program, 'In Search of Human Origins', shows how the famous early hominid 'Lucy' might have died and been fossiliized, and points out the rare set of circumstances that must occur for an organism to be fossilized. Questions for discussion are included.

  16. A New Sauropodomorph Dinosaur from the Early Jurassic of Patagonia and the Origin and Evolution of the Sauropod-type Sacrum

    Microsoft Academic Search

    Diego Pol; Alberto Garrido; Ignacio A. Cerda; Andrew Allen Farke

    2011-01-01

    BackgroundThe origin of sauropod dinosaurs is one of the major landmarks of dinosaur evolution but is still poorly understood. This drastic transformation involved major skeletal modifications, including a shift from the small and gracile condition of primitive sauropodomorphs to the gigantic and quadrupedal condition of sauropods. Recent findings in the Late Triassic–Early Jurassic of Gondwana provide critical evidence to understand

  17. Bacteria: Fossil Record

    NSDL National Science Digital Library

    This description of the fossil record of bacteria focuses on one particular group of bacteria, the cyanobacteria or blue-green algae, which have left a fossil record that extends far back into the Precambrian. The oldest cyanobacteria-like fossils known are nearly 3.5 billion years old and are among the oldest fossils currently known. Cyanobacteria are larger than most bacteria and may secrete a thick cell wall. More importantly, cyanobacteria may form large layered structures, called stromatolites (if more or less dome-shaped) or oncolites (if round). The site also refers to pseudomorphs of pyrite and siderite, and a group of bacteria known as endolithic. Two links are available for more information. One provides information on the discovery of possible remains of bacteria-like organisms on a meteorite from Mars and the other has a research report on fossilized filamentous bacteria and other microbes, found in Cretaceous amber.

  18. Grazing trails formed by soldier fly larvae (Diptera: Stratiomyidae) and their paleoenvironmental and paleoecological implications for the fossil record

    USGS Publications Warehouse

    Mangano, M.G.; Buatois, L.A.; Claps, G.L.

    1996-01-01

    Recent trails formed by soldier fly larvae (Diptera: Stratiomyidae) were examined in a shallow pond in the floodplain of a braided river in Jujuy Province, northwestern Argentina. Collected specimens were identified as Stratiomys convexa van der Wulp. Simple, irregularly meandering trails were produced across the surface of a muddy-silty substrate. Since soldier fly larvae extend their caudal respiratory tube to the water-air interface, they are restricted to extremely shallow water. The presence of benthic algal remains within the mouthparts of the larvae suggests a feeding habit of algal grazing. If preserved, these trails would be included in the ichnogenus Helminthopsis, a common element in ancient freshwater ichnofaunas. Helminthopsis preserved in pond and lacustrine margin deposits younger than Late Jurassic is regarded as one possible trace fossil analogue of the trails documented herein. Additionally, it is suggested that larvae of many aquatic Diptera with similar ecologic restrictions are potential tracemakers of Helminthopsis and other simple trails in these environments, particularly in post-Paleozoic deposits. Studies of modern shallow aquatic habitats and reexamination of the ichnologic record stress the importance of fly larvae as tracemakers in lake margin and pond ecosystems. Ecologic requirements of soldier fly larvae make them inappropriate analogues of Helminthopsis tracemakers in deeper water, lacustrine settings. ?? 1996 OPA (Overseas Publishers Association) Amsterdam B.V. Published in The Netherlands by Harwood Academic Publishers GmbH.

  19. Two new species of Sinosmylites Hong (Neuroptera, Berothidae) from the Middle Jurassic of China, with notes on Mesoberothidae

    PubMed Central

    Makarkin, Vladimir N.; Yang, Qiang; Ren, Dong

    2011-01-01

    Abstract Two new species of the genus Sinosmylites Hong are described from the Middle Jurassic locality at Daohugou (Inner Mongolia, China): Sinosmylites fumosus sp. n. and Sinosmylites rasnitsyni sp. n. This is the oldest known occurrence of the family Berothidae. The berothid affinity of this genus is confirmed by examination of the hind wing venation characteristic of the family. The Late Triassic family Mesoberothidae may represent an early group of Berothidae. PMID:22259277

  20. Upper Jurassic tidal flat megatracksites of Germany—coastal dinosaur migration highways between European islands, and a review of the dinosaur footprints

    Microsoft Academic Search

    Cajus Diedrich

    2011-01-01

    Dinosaur tracks occur at three vertebrate tracksites in north-western Germany, in the acanthicum\\/mutabilis ammonoid biozone of the basal Upper Kimmeridgian (Upper Jurassic, KIM 3-4 cycle, 152.70-152.10 Ma). The trackbeds are mud-cracked,\\u000a siliciclastic, tidal sand flat biolaminates, overlain by paleosol beds. Channels contain rare fossils of sauropod, ornithopod\\u000a and pterosaur bones as well as shark and plant remains. Large sauropod tracks of

  1. Post-sedimentation transformations of Lower-Middle Jurassic sandstones of Great Caucases

    NASA Astrophysics Data System (ADS)

    Tuchkova, M. I.

    2003-04-01

    POST-SEDIMENTATION TRANSFORMATIONS OF LOWER-MIDDLE JURASSIC SANDSTONES OF GREAT CAUCASES M.I. Tuchkova Geological Institute Russian Academy of Sciences, Moscow, Russia tuchkova@geo.tv-sign.ru/ /Fax: (095) 2310443 Generalization of author’s and literature data is based on the analysis of sandstones cement and structure, composition and politypism of clay minerals and index of mica crystallinity. Fore zones of sandstone transformations are distinguished for Lower-Middle Jurassic sedimentary complexes of Great Caucases: 1) zone of neogenic chlorite and muscovite (index of crystallinity IC=1.0-2.0 mm) with wide development of epidote; solubility, blastic and spinulose structures, 2) zone of neogenic chlorite and sericite (IC=2.0-3.0 mm); solubility and spinulose structures, 3) zone of neogenic hydromica (IC=2.5-3.5 mm), kaolinite and/or montmorillonite minerals with microstylolite, conformal and conformal-regenerational contacts between grains, 4) zone of kaolinite and/or montmorillonite, mixed-layered and chlorite minerals with carbonate cement of pores filling, ferugination and conformal and microstylolite contacts between grains. Index of crystallinity of mica mineral IC=3.5-5.5 mm. In modern geological structure the region with most intensive transformations (zone 1) is traced in sandstones of here and there preserved Sinemurian-Lower Pliensbachian and Toarcian deposits in the belt of Jurassic deposits of the southern slope of Great Caucases. The extent of rock transformation increases northward and southward from the axial zone of Great Caucases. Represented zonality doesn’t depend on deposits thickness and doesn’t coincide with stratigraphycal borders. Post-sedimentation zonality of Jurassic deposits originated as a result of stress during the period of folding at the end of Middle and the beginning of Late Jurassic following the thrusting of northern flank of Great Caucases basin onto its axial part. The rocks of lowest part of Jurassic deposits of the southern slope, observed at the base of tectonically imbricated slices, were affected maximum transformations. They weren’t including in the subduction zone, but were only near this zone, so full sequence (up to metamorphism) of their transformations is not observed. The work was funded by RFBR, grant 02-05-64477.

  2. Reconstruction of Jurassic paleogeography of part of southwestern North America: Some relevant factors

    SciTech Connect

    Anderson, T.H.; Kohn, M. (Univ. of Pittsburgh, PA (United States). Dept. of Geology and Planetary Science)

    1993-04-01

    A tectonic restoration has been initiated with the objective of reconstructing the paleogeography of the middle Jurassic volcanic and plutonic belt in part of southwestern North America west and southwest of the Colorado Plateau. Consideration of displacements of stratigraphic or tectonostratigraphic elements related to a structure or a system of structures include: (1) strike-slip translation along faults of the San Andreas system, especially those affecting rocks of the western Mojave desert region; (2) tertiary extensions west of the perimeter of the Colorado Plateau; (3) cretaceous contraction recorded by supracrustal rocks; (4) cretaceous lateral displacement, specifically as recorded by the Mojave-Snowy Lake fault; and (5) Late Jurassic lateral displacement along the Mojave-Sonora megashear. Cretaceous and Jurassic magmatic rocks are assumed to have formed about zones of subduction near the margins of converging plates. These rocks generally form crudely linear bands which may be used to monitor regional translations. Other linear elements useful in recording regional strain are facies lines and terrane boundaries, especially those related to steep lateral faults.

  3. Jurassic through Oligocene pre-basin stratigraphy in the Santa Maria basin area, California

    SciTech Connect

    Fritsche, A.E. (California State Univ., Northridge, CA (United States)); Yamashiro, D.A. (Groundwater Technology, Inc., Tempe, AZ (United States))

    1991-02-01

    Compilation from published records of 30 pre-Miocene stratigraphic columns in the Santa Maria basin area of California (west of the Sur-Nacimiento fault and north of the Santa Ynez fault) reveals two basement units and 22 overlying sedimentary units. This article displays the stratigraphic columns and includes descriptions and environmental interpretations of the 24 rock units. The basement rocks include an Upper Jurassic ophiolite sequence and the Lower Jurassic through Upper Cretaceous Franciscan Complex. Most of the 22 sedimentary units were deposited along a subduction-type margin prior to development of the late Tertiary Santa Maria basin. Overlying and generally in fault contact with the basement rocks are four Upper Jurassic through Lower Cretaceous units that were deposited in basin plain and out continental margin environments. Unconformably overlying these units are eight Upper Cretaceous units that were deposited in a wide range of environments that ranged from trench, slope, and submarine fan up through shelf and nonmarine fluvial environments. Lower Tertiary units onlap unconformably onto the Cretaceous rocks and were deposited only in the southernmost part of the area. These rocks include lower Eocene basin plain and outer submarine fan deposits; middle Eocene mid-fan and slope deposits; upper Eocene inner fan, shelf, shoreface, and foreshore deposits; and Oligocene shoreface, foreshore, and nonmarine fluvial deposits.

  4. The earliest mollusc dominated seep fauna from the Early Jurassic of Argentina

    NASA Astrophysics Data System (ADS)

    Kaim, Andrzej; Jenkins, Robert; Parent, Horacio; Garrido, Alberto; Moriya, Kazuhiro

    2015-04-01

    The earliest mollusc dominated seep fauna from the Early Jurassic of Argentina Andrzej Kaim, Robert G. Jenkins, Horacio Parent, Alberto C. Garrido The hydrocarbon seep deposits are known from Early Jurassic of Argentina since the report of Gomez-Perez (2003). The latter author identified very negative ?13C values (down to -33) and several fabrics typical for seep carbonates. Nevertheless she identified no macrofaunal assemblages apart from worm tubes. We re-visited the locality of Gomez-Perez (named here La Elina) and we were able to collect several molluscs associated with the seep carbonate. The most common and diversified are molluscs and worm tubes. We identified at least three species of gastropods, including the oldest-known species of neomphalids, lucinid and protobranch bivalves and numerous ammonoids. Unlike another known Early Jurassic seep from Oregon and the only Late Triassic seep (also from Oregon) there are no brachiopods associated with this seep. Therefore we consider the seep at La Elina as the oldest seep of modern aspect where the fauna is dominated by molluscs and not brachiopods.

  5. Fossil fuels -- future fuels

    SciTech Connect

    NONE

    1998-03-01

    Fossil fuels -- coal, oil, and natural gas -- built America`s historic economic strength. Today, coal supplies more than 55% of the electricity, oil more than 97% of the transportation needs, and natural gas 24% of the primary energy used in the US. Even taking into account increased use of renewable fuels and vastly improved powerplant efficiencies, 90% of national energy needs will still be met by fossil fuels in 2020. If advanced technologies that boost efficiency and environmental performance can be successfully developed and deployed, the US can continue to depend upon its rich resources of fossil fuels.

  6. Sedimentology of the Madumabisa Mudstone Formation (Late Permian), Lower Karoo Group, mid-Zambezi Valley Basin, southern Zambia

    NASA Astrophysics Data System (ADS)

    Nyambe, Imasiku A.; Dixon, Owen

    2000-04-01

    Sediments of the Upper Carboniferous to Lower Jurassic Karoo Supergroup (˜ 4.5 km thick) were deposited in the mid-Zambezi Valley Basin, southern Zambia. The Upper Palæozoic Lower Karoo Group in this area ends with a Late Permian sedimentary unit called the Madumabisa Mudstone Formation. The formation is 700 m thick and comprises four lithofacies grouped into two facies assemblages, collectively interpreted as lacustrine deposits. Sediments of a massive mudrock facies assemblage were deposited from suspension, probably from sediment-laden rivers entering a lake. Concretionary calcilutite beds probably mark the positions of palæosediment-water interfaces where calcite was precipitated. A laminated mudrock facies assemblage is attributed to lacustrine deposition from inflowing rivers at the lake margins and shallow parts of the lake. Repeated thickening-upward cycles are evidence of upward shallowing, interrupted by events of more abrupt deepening. Sandstone interbeds are interpreted as fluvial deposits laid down during low lake stands, with cross-lamination and asymmetrical ripples indicating current rather than wave deposition. A fossil assemblage of ostracods, bivalves, gastropods, fish scales, the alga Botryococcus sp. and fossil burrows is consistent with a lacustrine origin for the formation.

  7. Late Mesozoic tectonics of Central Asia based on paleomagnetic evidence

    Microsoft Academic Search

    Dmitry V. Metelkin; Valery A. Vernikovsky; Alexey Yu. Kazansky; Michael T. D. Wingate

    2010-01-01

    This paper presents paleomagnetic data for Late Mesozoic (Middle Jurassic to end-Cretaceous) rocks of the Siberian platform (Verkhoyansk Trough) and its southwestern margin (Transbaikalian basins and Minusa Trough). We determine a series of key paleomagnetic poles for 165, 155, 135, 120, and 75Ma, which define the Mesozoic apparent polar wander path (APWP) for Siberia. This quantitative approach provides the opportunity

  8. Fossilized Dinosaur Bones

    NSDL National Science Digital Library

    This slide show presents images of dinosaur bones and shows paleotologists at work excavating and preserving these fossils, the best evidence remaining of these long-lost creatures. A background essay and discussion questons are included.

  9. Minerals and Fossils

    NSDL National Science Digital Library

    mineraltown.com

    This site is dedicated to rock and mineral collecting. It contains information for worldwide mineral and fossil collectors with articles, mineral photos, videos, a search engine and free classified ads.

  10. Relationship of voluminous ignimbrites to continental arc plutons: Petrology of Jurassic ignimbrites and contemporaneous plutons in southern California

    USGS Publications Warehouse

    Fohey-Breting, N. K.; Barth, A.P.; Wooden, J.L.; Mazdab, F.K.; Carter, C.A.; Schermer, E.R.

    2010-01-01

    Volcanism was broadly associated in both space and time with Mesozoic plutonism in the Cordillera continental margin arc, but the precise petrogenetic relationships between volcanic rocks and adjacent zoned plutons are not known. Igneous rocks in a tilted crustal section in California include four laterally extensive Jurassic ash flow tuffs from 550 to >1100 m thick underlain at deeper structural levels by Jurassic plutons. Zircon geochronology confirms previous correlations of individual tuffs, suggesting ignimbrites with eruptive volumes up to 800 km3 were deposited both during the apparent Early Jurassic plutonic lull as well as contemporaneous with solidification of regionally widespread Middle and Late Jurassic plutons. The tuffs are weakly to strongly porphyritic (5 to 55% phenocrysts) monotonous intermediate porphyritic dacite to low-silica rhyolite and show strong bulk rock chemical affinity to contemporaneous plutons. Trace element compositions of zircons from the tuffs and contemporaneous plutonic rocks record large and consistent differences in Hf/Zr and REE over similar ranges in Ti abundances, supporting bulk compositional similarities and illuminating similarities and variations in thermal histories despite the effects of hydrothermal alteration. ?? 2009 Elsevier B.V. All rights reserved.

  11. The bivalve mollusc genus Limatula: A list of described species and a review of living and fossil species in the Southwest Pacific

    Microsoft Academic Search

    C. A. Fleming

    1978-01-01

    About 150 named fossil and living species of Limidae grouped in the genus Limatula Searles Wood are listed. They range from Jurassic (perhaps Triassic) to Recent and are now distributed in all oceans and seas from the Arctic to the Antarctic. The genus has not previously been subdivided, but its phylogenetic and biogeographic history can only be approached by recognizing

  12. Fossil Age Estimation Model

    NSDL National Science Digital Library

    Twin Cities Public Television, Inc.

    2006-01-01

    In this activity (page 1 of the PDF), learners will model how paleontologists estimate the age of fossil discoveries by extracting “fossil” playing cards from newspapers stacked in chronological order. Learners identify the “age” of the card based on the “evidence” (printed date) in the surrounding pages. They then create a data table and graph and analyze their findings. Use this activity to introduce learners to paleontology and geology. Relates to the linked video, DragonflyTV GPS: Dinosaurs.

  13. The earliest fossil record of the animals and its significance.

    PubMed

    Budd, Graham E

    2008-04-27

    The fossil record of the earliest animals has been enlivened in recent years by a series of spectacular discoveries, including embryos, from the Ediacaran to the Cambrian, but many issues, not least of dating and interpretation, remain controversial. In particular, aspects of taphonomy of the earliest fossils require careful consideration before pronouncements about their affinities. Nevertheless, a reasonable case can now be made for the extension of the fossil record of at least basal animals (sponges and perhaps cnidarians) to a period of time significantly before the beginning of the Cambrian. The Cambrian explosion itself still seems to represent the arrival of the bilaterians, and many new fossils in recent years have added significant data on the origin of the three major bilaterian clades. Why animals appear so late in the fossil record is still unclear, but the recent trend to embrace rising oxygen levels as being the proximate cause remains unproven and may even involve a degree of circularity. PMID:18192192

  14. Neuroanatomy of the Marine Jurassic Turtle Plesiochelys etalloni (Testudinata, Plesiochelyidae)

    PubMed Central

    Carabajal, Ariana Paulina; Sterli, Juliana; Müller, Johannes; Hilger, André

    2013-01-01

    Turtles are one of the least explored clades regarding endocranial anatomy with few available descriptions of the brain and inner ear of extant representatives. In addition, the paleoneurology of extinct turtles is poorly known and based on only a few natural cranial endocasts. The main goal of this study is to provide for the first time a detailed description of the neuroanatomy of an extinct turtle, the Late Jurassic Plesiochelysetalloni, including internal carotid circulation, cranial endocast and inner ear, based on the first digital 3D reconstruction using micro CT scans. The general shape of the cranial endocast of P. etalloni is tubular, with poorly marked cephalic and pontine flexures. Anteriorly, the olfactory bulbs are clearly differentiated suggesting larger bulbs than in any other described extinct or extant turtle, and indicating a higher capacity of olfaction in this taxon. The morphology of the inner ear of P. etalloni is comparable to that of extant turtles and resembles those of slow-moving terrestrial vertebrates, with markedly low, short and robust semicircular canals, and a reduced lagena. In P. etalloni the arterial pattern is similar to that found in extant cryptodires, where all the internal carotid branches are protected by bone. As the knowledge of paleoneurology in turtles is scarce and the application of modern techniques such as 3D reconstructions based on CT scans is almost unexplored in this clade, we hope this paper will trigger similar investigations of this type in other turtle taxa. PMID:23844257

  15. Upper Jurassic ramp carbonate and associated evaporite, Neuquen Province, Argentina

    SciTech Connect

    Nickelsen, B.H.; Merrill, D.A.

    1986-05-01

    The Oxfordian La Manga Limestone (10-65 m) and overlying Auquilco Gypsum (315 m maximum thickness) crop out along the west flank of the Neuquen basin, Neuquen Province, Argentina (36/sup 0/40/sup 0/S lat.). The contact with the underlying Lotena Sandstone is gradational, and both formations are cut by the Late Jurassic Araucanian angular unconformity. Seven lithofacies have been identified within sections measured through the entire interval along the northeast to southwest trending, 30-km long Sierra de la Vaca Muerta ridge (38/sup 0/30'-39/sup 0/S). The La Manga Limestone is interpreted as a temperate ramp carbonate that developed over the Lotena Formation siliciclastic shelf. Interpretations of lithofacies from southwest to northeast are: behind-barrier subtidal lagoon with washovers; coral and red algae biostromes; ooid and peloid sand shoals; downslope wackestone and packstone mud mounds; and deep-water carbonate turbidites. A minor regression separates La Manga and Auquilco Formations. Lithofacies of the Auquilco Formation indicate a shallowing-up sequence comprised of initially deep (hundreds of meters) subaqueous evaporite deposition followed by shallow, subtidal carbonate peloidal and shell fragment grainstones and evaporites. Thickness of the subaqueous evaporite gives an order of magnitude estimate of Auquilco basin depths of a few hundred meters at most. The Neuquen basin has an intermediate proportion of carbonate in comparison to relatively carbonate-poor basins to the south and carbonate-rich basins to the north.

  16. Fossil Simulation in the Classroom

    ERIC Educational Resources Information Center

    Hoehn, Robert G.

    1977-01-01

    Describes classroom science demonstrations and experiments that simulate the process of fossil formation. Lists materials, procedures and suggestions for successful activities. Includes ten student activities (coral fossils, leaf fossils, leaf scars, carbonization, etc.). Describes a fossil game in which students work in pairs. (CS)

  17. 004118:a0001 Fossil Record

    E-print Network

    Benton, Michael

    004118:a0001 Fossil Record Michael J Benton, University of Bristol, Bristol, UK Fossils life. 004118:s0001 Introduction 004118:p0001 Fossils are the remains of plants and animals that once lived. The common image of a fossil is an ancient shell or bone that has been turned to rock

  18. Architectural studies of Jurassic-Cretaceous fluvial units, Colorado Plateau

    SciTech Connect

    Miall, A.D.; Bromley, M.H.; Cowan, E.J.; Turner-Peterson, C.E.

    1989-03-01

    A sixfold hierarchy of architectural elements and bounding surfaces evolved from outcrop studies of three fluvial units: Westwater Canyon member (WCM), Morrison Formation, Upper Jurassic; Torrivio sandstone member (TSM), Gallup Sandstone, Upper Cretaceous, northwestern New Mexico; and Kayenta Formation (KF), Lower Jurassic, southwestern Colorado. This hierarchy is discussed.

  19. Massive dissociation of gas hydrate during a Jurassic

    E-print Network

    Hesselbo, Stephen P.

    .............................................................................................................................................. In the Jurassic period, the Early Toarcian oceanic anoxic event (about 183 million years ago) is associated hydrate during a Jurassic oceanic anoxic event Stephen P. Hesselbo*, Darren R. Gro¨cke*, Hugh C. Jenkyns together, these 13 C curves depict a period of gradual rise in isotopic values which is interrupted

  20. Ornithopod dinosaur tracks from the Lower Jurassic of Queensland

    Microsoft Academic Search

    Richard A. Thulborn

    1994-01-01

    Natural casts of seven small footprints have been identified on a single weathered block derived from the Precipice Sandstone (Lower Jurassic) of the Carnarvon Gorge, southeastern Queensland. The footprints are attributed to ornithopod dinosaurs and are referred to the ichnogenus Anomoepus. They appear to be most similar to the ichnospecies Anomoepus gracillimus, originally defined on footprints from the Lower Jurassic

  1. Reevaluation of upper Jurassic Morrison Formation, Western Interior

    Microsoft Academic Search

    Mantzios

    1989-01-01

    Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic

  2. Early Evolution and Historical Biogeography of Fishflies (Megaloptera: Chauliodinae): Implications from a Phylogeny Combining Fossil and Extant Taxa

    PubMed Central

    Liu, Xingyue; Wang, Yongjie; Shih, Chungkun; Ren, Dong; Yang, Ding

    2012-01-01

    Fishflies (Corydalidae: Chauliodinae) are one of the main groups of the basal holometabolous insect order Megaloptera, with ca. 130 species distributed worldwide. A number of genera from the Southern Hemisphere show remarkably disjunctive distributions and are considered to be the austral remnants or “living fossils” of Gondwana. Hitherto, the evolutionary history of fishflies remains largely unexplored due to limited fossil record and incomplete knowledge of phylogenetic relationships. Here we describe two significant fossil species of fishflies, namely Eochauliodes striolatus gen. et sp. nov. and Jurochauliodes ponomarenkoi Wang & Zhang, 2010 (original designation for fossil larvae only), from the Middle Jurassic of Inner Mongolia, China. These fossils represent the earliest fishfly adults. Furthermore, we reconstruct the first phylogenetic hypothesis including all fossil and extant genera worldwide. Three main clades within Chauliodinae are recognized, i.e. the Dysmicohermes clade, the Protochauliodes clade, and the Archichauliodes clade. The phylogenetic and dispersal-vicariance (DIVA) analyses suggest Pangaean origin and global distribution of fishflies before the Middle Jurassic. The generic diversification of fishflies might have happened before the initial split of Pangaea, while some Gondwanan-originated clades were likely to be affected by the sequential breakup of Pangaea. The modern fauna of Asian fishflies were probably derived from their Gondwanan ancestor but not the direct descendents of the Mesozoic genera in Asia. PMID:22792287

  3. Didactyl Tracks of Paravian Theropods (Maniraptora) from the ?Middle Jurassic of Africa

    PubMed Central

    Mudroch, Alexander; Richter, Ute; Joger, Ulrich; Kosma, Ralf; Idé, Oumarou; Maga, Abdoulaye

    2011-01-01

    Background A new dinosaur tracksite from ?Middle Jurassic sediments of the Irhazer Group on the plains of Agadez (Rep. Niger, northwest Africa) revealed extraordinarily well preserved didactyl tracks of a digitigrade bipedal trackmaker. The distinct morphology of the pes imprints indicates a theropod trackmaker from a paravian maniraptoran closely related to birds. Methodology/Principal Findings The early age and the morphological traits of the tracks allow for description of the new ichnotaxon Paravipus didactyloides. A total of 120 tracks are assigned to 5 individual trackways. The ‘medium-sized’ tracks with an average footprint length of 27.5 cm and footprint width of 23.1 cm are deeply imprinted into the track bearing sandstone. Conclusions/Significance A comparison with other didactyl tracks gives new insights into the foot morphology of advanced maniraptoran theropods and contributes to knowledge of their evolutionary history. The new ichnotaxon takes an important position in the ichnological fossil record of Gondwana and the mid-Jurassic biota worldwide, because it is among the earliest known records of paravian maniraptorans and of didactyl theropod tracks from Africa. PMID:21339816

  4. Jurassic-Early Cretaceous Gondwanan homoxylous woods: a nomenclatural revision of the genera with taxonomic notes.

    PubMed

    Bamford, M K.; Philippe, M

    2001-04-01

    The homoxylous fossil woods occurring in the Gondwanan continents of South America, Australia, Africa, India and Antarctica during the Jurassic and Early Cretaceous period are considered here. Original descriptions of the genera and wherever possible, the type material, have been consulted. Applying the rules of the International Code of Botanical Nomenclature, the generic names of the homoxylous woods have been revised from a nomenclatural point of view. According to this review, out of 31 generic names used for woods from the given time interval and area, 6 are illegitimate later nomenclatural synonyms, 1 is a later homonym, and 5 can be considered as taxonomical synonyms. Moreover, 9 genera have been used erroneously. We propose one new generic name (Protaxodioxylon n. gen.) and elsewhere we will propose for conservation, with a conserved type one of the illegitimate names and one of the taxonomic synonyms. As a result, we consider that there are only eighteen generic names correctly quoted for the Jurassic-Early Cretaceous of Gondwana, and we provide a taxonomic key for the corresponding genera. This revision is the first step in systematically comparing northern and southern hemisphere woods. PMID:11179718

  5. A giant spider from the Jurassic of China reveals greater diversity of the orbicularian stem group

    NASA Astrophysics Data System (ADS)

    Selden, Paul A.; Shih, ChungKun; Ren, Dong

    2013-12-01

    A large female spider, Nephila jurassica, was described from Middle Jurassic strata of north-east China and placed in the modern genus Nephila (family Nephilidae) on the basis of many morphological similarities, but, as with many ancient fossils, the single specimen lacked synapomorphies of the family (Selden et al. 2011). In order to test the placement within the nephilid phylogenetic tree, Kuntner et al. (2013) calibrated the molecular phylogeny using N. jurassica in three different scenarios based on inferred mitochondrial substitution rates. They concluded that N. jurassica fitted better as a stem orbicularian than a nephilid. Now, a giant male spider has been discovered at the same locality that yielded N. jurassica. The two sexes are considered conspecific based on their similar morphological features, size, and provenance. The male cannot be accommodated in Nephilidae because of its pedipalp morphology, so the new genus Mongolarachne and family Mongolarachnidae are erected for the species. Comparison with possibly related families show that Mongolarachnidae is most likely on the orbicularian stem, close to other cribellate orbicularians (e.g., Deinopoidea), which suggests a greater diversity of cribellate orbicularians during the Middle Jurassic.

  6. Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace

    USGS Publications Warehouse

    Milner, A.R.C.; Harris, J.D.; Lockley, M.G.; Kirkland, J.I.; Matthews, N.A.

    2009-01-01

    Background: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. Methodology/Principal Findings: Here we describe a well-preserved theropod trackway in a Lower Jurassic (???198 millionyear- old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. Conclusions/Significance: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.

  7. Middle Jurassic to early Cretaceous igneous rocks along eastern North American continental margin

    SciTech Connect

    Jansa, L.F.; Pe-Piper, G.

    1988-03-01

    Late Middle Jurassic and Early Cretaceous mafic dikes, sills, flows, and local volcaniclastic sediments are intercalated within continental shelf sediments from the Baltimore Canyon Trough northward to the Grand Banks of Newfoundland. The igneous rocks on the eastern North American margin are mainly alkali basalts of intraplate affinity. The late Middle Jurassic igneous activity was of short duration, at about 140 Ma, and was restricted to Georges Bank where it led to construction of several volcanic cones. The main period of igneous activity was concentrated at about 120 Ma in the Aptian/Berremian. The activity consists of dike swarms in Baltimore Canyon, occasional dikes on the Scotian Shelf, and the growth of stratovolcanoes on the Scotian Shelf and Grand Banks. Younger dikes (approx. 95 Ma) also are present on the Grand Banks. With regard to oil exploration on the continental margin, care must be taken to properly identify igneous and volcaniclastic rocks on mechanical logs, drill cuttings, and cores. Reflection seismic profiles can be used to map the areal extent of sills, flows, and low-angle dikes, which commonly show distinctive seismic responses. However, steeply dipping dikes generally produce little, if any, seismic response. Isotopic-age determinations of igneous rocks, combined with biostratigraphic-age determinations of adjacent strata, are invaluable for stratigraphic correlation, establishing chronology of seismic sequences, and analysis of basin sedimentation and tectonic history. 9 figures, 2 tables.

  8. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds.

    PubMed

    Godefroit, Pascal; Cau, Andrea; Dong-Yu, Hu; Escuillié, François; Wenhao, Wu; Dyke, Gareth

    2013-06-20

    The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle-Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China) has challenged the pivotal position of Archaeopteryx, regarded from its discovery to be the most basal bird. Removing Archaeopteryx from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of Archaeopteryx; (3) it places Troodontidae as the sister-group to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle-Late Jurassic period. PMID:23719374

  9. The bivalve Anopaea (Inoceramidae) from the Upper Jurassic–lowermost Cretaceous of Mexico

    NASA Astrophysics Data System (ADS)

    Zell, Patrick; Crame, J. Alistair; Stinnesbeck, Wolfgang; Beckmann, Seija

    2015-07-01

    In Mexico, the Upper Jurassic to lowermost Cretaceous La Casita and coeval La Caja and La Pimienta formations are well-known for their abundant and well-preserved marine vertebrates and invertebrates. The latter include conspicuous inoceramid bivalves of the genus Anopaea not formally described previously from Mexico. Anopaea bassei (Lecolle de Cantú, 1967), Anopaea cf. stoliczkai (Holdhaus, 1913), Anopaea cf. callistoensis Crame and Kelly, 1995 and Anopaea sp. are rare constituents in distinctive Tithonian-lower Berriasian levels of the La Caja Formation and one Tithonian horizon of the La Pimienta Formation. Anopaea bassei was previously documented from the Tithonian of central Mexico and Cuba, while most other members of Anopaea described here are only known from southern high latitudes. The Mexican assemblage also includes taxa which closely resemble Anopaea stoliczkai from the Tithonian of India, Indonesia and the Antarctic Peninsula, and Anopaea callistoensis from the late Tithonian to ?early Berriasian of the Antarctic Peninsula. Our new data expand the palaeogeographical distribution of the high latitude Anopaea to the Gulf of Mexico region and substantiate faunal exchange, in the Late Jurassic-earliest Cretaceous, between Mexico and the Antarctic Realm.

  10. Does the Great Valley Group contain Jurassic strata? Reevaluation of the age and early evolution of a classic forearc basin

    USGS Publications Warehouse

    Surpless, K.D.; Graham, S.A.; Covault, J.A.; Wooden, J.L.

    2006-01-01

    The presence of Cretaceous detrital zircon in Upper Jurassic strata of the Great Valley Group may require revision of the lower Great Valley Group chronostratigraphy, with significant implications for the Late Jurassic-Cretaceous evolution of the continental margin. Samples (n = 7) collected from 100 km along strike in the purported Tithonian strata of the Great Valley Group contain 20 Cretaceous detrital zircon grains, based on sensitive high-resolution ion microprobe age determinations. These results suggest that Great Valley Group deposition was largely Cretaceous, creating a discrepancy between biostratigraphy based on Buchia zones and chronostratigraphy based on radiometric age dates. These results extend the duration of the Great Valley Group basal unconformity, providing temporal separation between Great Valley forearc deposition and creation of the Coast Range Ophiolite. If Great Valley forearc deposition began in Cretaceous time, then sediment by passed the developing forearc in the Late Jurassic, or the Franciscan subduction system did not fully develop until Cretaceous time. In addition to these constraints on the timing of deposition, pre-Mesozoic detrital zircon age signatures indicate that the Great Valley Group was linked to North America from its inception. ?? 2006 Geological Society of America.

  11. Middle Jurassic Radiolaria from a siliceous argillite block in a structural melange zone near Viqueque, Timor Leste: Paleogeographic implications

    NASA Astrophysics Data System (ADS)

    Haig, David W.; Bandini, Alexandre Nicolas

    2013-10-01

    Thin-bedded siliceous argillite forming a large block within a structural melange zone at Viqueque, Timor Leste, has yielded a Middle Jurassic (late Bathonian-early Callovian) radiolarian assemblage belonging to Unitary Association Zone 7. Fifty-five species are recognized and illustrated, forming the most diverse radiolarian fauna yet documented from the Jurassic of Timor. The fauna shows little similarity in species content to the few other assemblages previously listed from the Middle or Late Jurassic of Timor, and also has few species in common with faunas known elsewhere in the region from Rotti, Sumatra, South Kalimantan, and Sula. Based on lithofacies similarities and age, the siliceous argillite succession in the melange block at Viqueque is included in the Noni Group originally described as the lower part of the Palelo Series in West Timor. In terms of lithofacies, the Noni Group is distinct from other stratigraphic units known in Timor. It may be associated with volcanic rocks but age relationships are uncertain, although some of the radiolarian cherts in the Noni Group in West Timor have been reported to include tuffaceous sediment. The deep-water character of the siliceous hemipelagite-pelagite facies, the probable volcanic association, and an age close to that of continental breakup in the region suggest deposition in a newly rifted Indian Ocean. In Timor's tectonostratigraphic classification scheme, the Noni Group is here placed in the "Indian Ocean Megasequence".

  12. The Fossil Record

    NSDL National Science Digital Library

    Lisa Wu

    This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 9-12. It centers around fossils found in the Burgess Shale in western Canada. Topics include body shapes of fossils found, the movement of organisms from oceans to land, and whether organisms existed that did not fossilize. This part of geologic history began in the Cambrian Sea about 540 million years ago. The resource includes objectives, materials, procedures, discussion questions, evaluation ideas, extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

  13. High resolution stratigraphy of the Jurassic-Cretaceous boundary interval in the Gresten Klippenbelt (Austria)

    NASA Astrophysics Data System (ADS)

    Lukeneder, Alexander; Halásová, Eva; Kroh, Andreas; Mayrhofer, Susanne; Pruner, Petr; Reháková, Daniela; Schnabl, Petr; Sprovieri, Mario; Wagreich, Michael

    2010-10-01

    The key objective of investigation of hemipelagic sediments from the Gresten Klippenbelt (Blassenstein Formation, Ultrahelvetic paleogeographic realm) was to shed light on environmental changes around the Jurassic-Cretaceous (J/K) boundary on the northern margin of the Penninic Ocean. This boundary is well exposed in a newly discovered site at Nutzhof. Around the critical interval including the boundary, this new outcrop bears a rich microplanktonic assemblage characterized by typical J/K (Tithonian/Berriasian) boundary faunas. The Nutzhof section is located in the Gresten Klippenbelt (Lower Austria) tectonically wedged into the deep-water sediments of the Rhenodanubian Flysch Zone. In Late Jurassic-Early Cretaceous time the Penninic Ocean was a side tract of the proto-North Atlantic Oceanic System, intercalated between the European and the Austroalpine plates. Its opening started during the Early Jurassic, induced by sea floor spreading, followed by Jurassic-Early Cretaceous deepening of the depositional area of the Gresten Klippenbelt. These tectonically induced paleogeographic changes are mirrored in the lithology and microfauna that record a deepening of the depositional environment from Tithonian to Berriasian sediments of the Blassenstein Formation at Nutzhof. The main lithological change is observed in the Upper Tithonian Crassicollaria Zone, in Chron M20N, whereas the J/K boundary can be precisely fixed at the Crassicollaria-Calpionella boundary, within Chron M19n.2n. The lithological turnover of the deposition from more siliciclastic pelagic marl-limestone cycles into deep-water pelagic limestones is correlated with the deepening of the southern edge of the European continent at this time. Within the Gresten Klippenbelt Unit, this transition is reflected by the lithostratigraphic boundary between siliciclastic-bearing marl-limestone sedimentation in the uppermost Jurassic and lowermost Cretaceous limestone formation, both within the Blassenstein Formation. The cephalopod fauna (ammonites, belemnites, aptychi) and crinoids from the Blassenstein Formation, correlated with calcareous microfossil and nannofossil data combined with isotope and paleomagnetic data, indicate the Tithonian to middle Berriasian (Hybonoticeras hybonotum Zone up to the Subthurmannia occitanica Zone; M17r-M21r). The succession of the Nutzhof section thus represents deposition of a duration of approximately 7 Myr (ca. 150-143 Ma). The deposition of the limestone, marly limestone and marls in this interval occurred during tectonically unstable conditions reflected by common allodapic material. Along with the integrated biostratigraphic, geochemical and isotopic analysis, the susceptibility and gamma-ray measurements were powerful stratigraphic tools and important for the interpretation of the paleogeographic setting. Two reverse magneto-subzones, Kysuca and Brodno, were detected within magnetozones M20n and M19n, respectively.

  14. Science Sampler: Fossil detectives

    NSDL National Science Digital Library

    Virginia Bourdeau

    2006-07-01

    Middle school students are transformed into Fossil detectives as they examine the fossil record and use evidence about paleo-environments to develop an understanding of structure and function in living systems and changes over time in Earths history. In this enrichment activity, students work in teams to research an assigned geologic time period. They determine available habitats, food sources and types (animal, plant; woody, herbaceous, etc.), cover sources, methods of getting food, defense, and reproduction that would allow an animal to live in the assigned paleoenvironment. In culmination of their efforts, students create a diorama to display their findings.

  15. Dinoflagellata: Fossil Record

    NSDL National Science Digital Library

    Information on this page pertains to dinoflagellates, the fossil record of which may extend into the Precambrian. Spherical organic-walled microfossils known as acritarchs, some of which may be dinoflagellate hystrichospheres, first appear in rocks about 1.8 billion years old. Exactly what the acritarchs were is not known with certainty; they probably included a number of clades of eukaryotic algae, and are thus a form taxon, including all those spore-like fossils which have not been conclusively assigned to another group.

  16. Fossilized excreta associated to dinosaurs in Brazil

    NASA Astrophysics Data System (ADS)

    Souto, P. R. F.; Fernandes, M. A.

    2015-01-01

    This work provides an updated register of the main occurrences of fossilized excreta (coprolites and urolites) associated with dinosaurs found in the Brazil. The goal is to provide a relevant guide to the interpretation of the environment in the context of Gondwana. In four geographic areas, the excreta are recovered from Cretaceous sedimentary deposits in outcrops of the Bauru and São Luis basins and the Upper Jurassic aeolian deposits of the Parana Basin in the state of São Paulo. The coprolites were analyzed by X-ray diffraction and X-ray fluorescence methods. The results of these analyses reveal compositions that differ from the surrounding matrix, indicating a partial substitution of the organic material due to the feeding habits of the producers. Additionally, we describe the urolite excavations in epirelief and hyporelief, the result of gravitational flow the impact from urine jets on sand. These are associated with ornithopod and theropod dinosaur footprints preserved in the aeolian flagstones of the Botucatu Formation, Parana Basin.

  17. Rethinking Fossil Fuels

    NSDL National Science Digital Library

    James Hansen (NASA Goddard Institute for Space Studies; )

    2008-09-09

    Climate change and fossil fuel use are connected. It would serve the world well to: begin a moratorium on coal-fired power plants; explore and use renewable energy; insist on immediate action from world governments; and penalize industries putting excess CO2 into the atmosphere.

  18. Fossil-energy

    NASA Astrophysics Data System (ADS)

    1981-08-01

    Progress in the following areas of fossil energy is reported: physiochemical cleaning and recovery of fine coal; a systematic investigation of the organosulfur components in coal; microstructures of coal; rapid analysis of mineral content in coal; coal blending experiments; performance characteristics of heavy media cyclones using fly ash derived heavy media; briquetting solvent treated coal; and coal preparation and testing.

  19. Fossil Halls: Vertebrate Evolution

    NSDL National Science Digital Library

    Part of a larger virtual tour of the Museum's famed Fossil Halls, this Web site has an interactive cladogram with 20 clickable evolutionary branching points. It shows vertebrate evolution for the following three AMNH halls: Hall of Vertebrate Origins, Hall of Dinosaurs and Hall of Mammals and Their Extinct Relatives.

  20. Fossil Evidence of Bipedalism

    NSDL National Science Digital Library

    2010-03-10

    This video segment adapted from NOVA shows how scientists use the fossil record to trace when early human ancestors and related species began walking on two legs instead of four, and to determine whether they were more apelike or human in appearance.

  1. Fossil Halls: Cladistics

    NSDL National Science Digital Library

    Part of a larger virtual tour of the Museum's famed Fossil Halls, this Web site has an overview explaining the cladistic method of scientific analysis as well as how to read cladograms. It answers the following questions: What is the best way to reconstruct evolutionary history? What is a cladogram? What is an advanced feature? Why use cladistics?

  2. Advanced fossil energy utilization

    SciTech Connect

    Shekhawat, D.; Berry, D.; Spivey, J.; Pennline, H.; Granite, E.

    2010-01-01

    This special issue of Fuel is a selection of papers presented at the symposium ‘Advanced Fossil Energy Utilization’ co-sponsored by the Fuels and Petrochemicals Division and Research and New Technology Committee in the 2009 American Institute of Chemical Engineers (AIChE) Spring National Meeting Tampa, FL, on April 26–30, 2009.

  3. Classification of Fossil Microplankton

    Microsoft Academic Search

    C. Downie; G. L. Williams; W. A. S. SARJEANT

    1961-01-01

    IT is becoming increasingly desirable that a definite decision be made as to whether the fossil organicshelled microplankton (dinoflagellates, hystrichospheres, and genera of presumed microplankton incertae sedis) should be classed, for nomenclatural purposes, in the animal or in the plant kingdom. The dinoflagellates, a group of unicellular organisms some of which contain chlorophyll, are clearly algae, while others contain no

  4. Rapid compositional change and significant loss of plant species diversity among Triassic-Jurassic palynofloras in East Greenland

    NASA Astrophysics Data System (ADS)

    Mander, Luke; Kürschner, Wolfram; McElwain, Jennifer

    2010-05-01

    The Triassic-Jurassic (Tr-J; 200Ma) transition coincides with the eruption of massive flood basalts associated with the opening of the Atlantic Ocean. This is thought to have lead to a fourfold increase in palaeoatmospheric carbon dioxide, a consequent rise in global temperatures of between 3 and 6 degrees Celsius, and a rise in atmospheric pollutants such as sulphur dioxide. Recent work has employed either plant macrofossils (mostly leaves) or sporomorphs (pollen and spores) to reconstruct the response of terrestrial vegetation to this episode of major environmental change. Investigations of the macrofossil record at Astartekloft in East Greenland indicate a rapid loss of plant diversity in the Late Rhaetian, culminating in an 80% species turnover at the Tr-J boundary interval. However, evidence for such catastrophic diversity loss is conspicuously absent from the sporomorph record. This fossil group indicates that the Tr-J boundary interval in central and northwest Europe is characterized by compositional change and a transient shift from gymnosperm forests to fern-dominated vegetation. In order to address this uncertainty regarding Tr-J vegetation change according to macrofossils versus sporomorphs, we present an analysis of sporomorph diversity and compositional change across the Tr-J at Astartekloft, East Greenland. Sporomorph diversity was estimated using individual and sample-based rarefaction techniques, and compositional differences between sporomorph samples were assessed using non-metric multidimensional scaling. These analyses reveal that sporomorph assemblages from the Tr-J boundary interval at Astartekloft are between 23 and 27% less taxonomically diverse than other Triassic assemblages, and that this interval is characterized by a dramatic shift in the composition of the standing vegetation. These results are statistically significant and are also unrelated to changes in the environment of deposition. These results indicate that the magnitude of plant diversity loss across the Tr-J in East Greenland is apparently greater in the macrofossil record than the sporomorph record. Comparison of these results with taphonomic work on the representation of different groups of plants in macrofossil and sporomorph records at Astartekloft is used to understand this discrepancy.

  5. Structure and kinematics along a segment of the Mojave-Sonora megashear: A strike-slip fault that truncates the Jurassic continental magmatic arc of southwestern North America

    NASA Astrophysics Data System (ADS)

    Campbell, Patricia A.; Anderson, Thomas H.

    2003-12-01

    Similarities between crystalline crust and overlying pre-Jurassic cover in northwestern Sonora, Mexico, and in the Inyo Mountains-Death Valley region, California, are attributed to left-lateral displacement along the Mojave-Sonora megashear, a Late Jurassic transform fault related to the opening of the Gulf of Mexico. Three exposures of mylonitic rocks extending 25 km along the postulated fault occur within Sierra de Los Tanques, Sonora, Mexico. The exposures 13 km southwest of Sonoita reveal a tripartite assemblage of (1) Jurassic volcanic and volcaniclastic strata to the northeast, (2) an axial zone of mylonitic rocks, and (3) masses of granitic rocks and compositionally banded quartzo-feldspathic gneiss of Proterozoic (?) and Late Triassic age to the southwest. Mylonitic foliation in rocks within the axial zone strikes northwesterly, and lineations plunge shallowly. Microstructues record left-lateral shear. Shallow thrusts, folded mylonite, and steeply dipping mylonitic foliation with downdip mineral lineation record transpression. Triassic and Precambrian crystalline rocks are emplaced above shallow thrusts onto ductilly deformed Jurassic rocks northeast of the principal fault. In the central and northwestern exposures, pervasively foliated and lineated rocks are cut by weakly foliated Cretaceous granite that also may contain inclusions of mylonite. The northwesterly strike of steep foliation, left-lateral kinematics, and relationships with Cretaceous intrusive rocks preclude correlation with episodes of Cretaceous contraction and Tertiary extension that are recognized in the southwestern United States. The fault is interpreted to have formed in the Late Jurassic and records a change in tectonic setting from arc magmatism to rifting and basin development.

  6. Increased Atmospheric SO2 Detected from Changes in Leaf Physiognomy across the Triassic–Jurassic Boundary Interval of East Greenland

    PubMed Central

    Bacon, Karen L.; Belcher, Claire M.; Haworth, Matthew; McElwain, Jennifer C.

    2013-01-01

    The Triassic–Jurassic boundary (Tr–J; ?201 Ma) is marked by a doubling in the concentration of atmospheric CO2, rising temperatures, and ecosystem instability. This appears to have been driven by a major perturbation in the global carbon cycle due to massive volcanism in the Central Atlantic Magmatic Province. It is hypothesized that this volcanism also likely delivered sulphur dioxide (SO2) to the atmosphere. The role that SO2 may have played in leading to ecosystem instability at the time has not received much attention. To date, little direct evidence has been presented from the fossil record capable of implicating SO2 as a cause of plant extinctions at this time. In order to address this, we performed a physiognomic leaf analysis on well-preserved fossil leaves, including Ginkgoales, bennettites, and conifers from nine plant beds that span the Tr–J boundary at Astartekløft, East Greenland. The physiognomic responses of fossil taxa were compared to the leaf size and shape variations observed in nearest living equivalent taxa exposed to simulated palaeoatmospheric treatments in controlled environment chambers. The modern taxa showed a statistically significant increase in leaf roundness when fumigated with SO2. A similar increase in leaf roundness was also observed in the Tr–J fossil taxa immediately prior to a sudden decrease in their relative abundances at Astartekløft. This research reveals that increases in atmospheric SO2 can likely be traced in the fossil record by analyzing physiognomic changes in fossil leaves. A pattern of relative abundance decline following increased leaf roundness for all six fossil taxa investigated supports the hypothesis that SO2 had a significant role in Tr–J plant extinctions. This finding highlights that the role of SO2 in plant biodiversity declines across other major geological boundaries coinciding with global scale volcanism should be further explored using leaf physiognomy. PMID:23593262

  7. Increased atmospheric SO? detected from changes in leaf physiognomy across the Triassic-Jurassic boundary interval of East Greenland.

    PubMed

    Bacon, Karen L; Belcher, Claire M; Haworth, Matthew; McElwain, Jennifer C

    2013-01-01

    The Triassic-Jurassic boundary (Tr-J; ?201 Ma) is marked by a doubling in the concentration of atmospheric CO2, rising temperatures, and ecosystem instability. This appears to have been driven by a major perturbation in the global carbon cycle due to massive volcanism in the Central Atlantic Magmatic Province. It is hypothesized that this volcanism also likely delivered sulphur dioxide (SO2) to the atmosphere. The role that SO2 may have played in leading to ecosystem instability at the time has not received much attention. To date, little direct evidence has been presented from the fossil record capable of implicating SO2 as a cause of plant extinctions at this time. In order to address this, we performed a physiognomic leaf analysis on well-preserved fossil leaves, including Ginkgoales, bennettites, and conifers from nine plant beds that span the Tr-J boundary at Astartekløft, East Greenland. The physiognomic responses of fossil taxa were compared to the leaf size and shape variations observed in nearest living equivalent taxa exposed to simulated palaeoatmospheric treatments in controlled environment chambers. The modern taxa showed a statistically significant increase in leaf roundness when fumigated with SO2. A similar increase in leaf roundness was also observed in the Tr-J fossil taxa immediately prior to a sudden decrease in their relative abundances at Astartekløft. This research reveals that increases in atmospheric SO2 can likely be traced in the fossil record by analyzing physiognomic changes in fossil leaves. A pattern of relative abundance decline following increased leaf roundness for all six fossil taxa investigated supports the hypothesis that SO2 had a significant role in Tr-J plant extinctions. This finding highlights that the role of SO2 in plant biodiversity declines across other major geological boundaries coinciding with global scale volcanism should be further explored using leaf physiognomy. PMID:23593262

  8. Paleomagnetism of Jurassic dolerites from Northern Victoria Land, Antarctica - Onset of rapid Jurassic pole shift?

    NASA Astrophysics Data System (ADS)

    Kirscher, U.; Bachtadse, V.; Petersen, N.; Rolf, C.; Lemna, O. S.

    2014-12-01

    Flood basalts (Kirkpatrick) and sills (Ferrar) of the Transantarctic mountains (183Ma) have been studied paleomagnetically in detail in the 60's to 90's of the 1900's yielding two groups of paleopole positions plotting at ~55°S (A) or at ~80°S (B). Group A poles have been interpreted to reflect the Early Jurassic Earth magnetic field but the significance of Group B poles is less clear. Here we report new data from the Kirkpatrick basalts at Gair Mesa (73.47°S; 162.87°E), where about 800 stratigraphic meters including 23 volcanic flows were sampled. After removal of a steep magnetic overprint straight linear segments trending toward the origin of the projection plane are identified in 151 samples from 22 sites. All characteristic directions are of normal polarity and interpreted to be carried by magnetite. The resulting mean pole plots at 66.4°S; 227.7°E, A95=6.2°, k = 25.7 similar to group B poles. Reflecting light microscopy suggests that the original magnetization has survived low temperature alteration. Since secular variation has been averaged (Sb=15.9°) we argue that the Gair Mesa basalts have recorded the time averaged geomagnetic field during early to mid Jurassic times. Hence, we conclude that both groups A and B are of primary origin and consequently speculate that group B paleopoles might reflect the onset of the recently postulated Jurassic pole shift.

  9. Prebreakup geology of the Gulf of Mexico-Caribbean: Its relation to Triassic and Jurassic rift systems of the region

    NASA Astrophysics Data System (ADS)

    Bartok, Peter

    1993-01-01

    A review of the prebreakup geology of west central Pangea, comprising northern South America, the Gulf of Mexico, and West Africa, combined with a study of the Mesozoic rift trends of the region confirms a relation between the rift systems and the underlying older grain of deformation. The prebreakup analysis focuses attention on the Precambrian, early Paleozoic, and late Paleozoic tectonic events affecting the region and assumes a Pindell fit. Two late Precambrian orogenic belts are observed in west central Pangea. Along the northern South American margin and Yucatan a paleo northeast trending Pan-African aged fold belt is documented. A second system is observed along West Africa extending from the High Atlas to the Mauritanides and Rockelides. Similar aged orogenies in the Appalachians are compared. During the late Paleozoic, renewed orogenic activity, associated with the Gondwana-Laurentia suture, affected large segments of west central Pangea. The general trend of the system is northeast-southwest and essentially parallels the Guayana craton and West African and eastern North American cratons. Mesozoic rifling closely followed either the Precambrian trends or the late Paleozoic orogenic belt. The Triassic component focused along the western portions of the Gulf of Mexico continuing into eastern Mexico and western South America. The Jurassic rift trend followed along the separation between Yucatan and northern South America. At Lake Maracaibo the Jurassic rift system eventually overlaps the Triassic rifts. The Jurassic rift resulted in the "Hispanic Corridor" that permitted Tethyan and Pacific marine faunas to mix at a time when the Gulf of Mexico underwent continental sedimentation.

  10. Centering on Fossils and Dinosaurs.

    ERIC Educational Resources Information Center

    Coble, Charles R.; McCall, Gregory K.

    1986-01-01

    Describes a set of 10 activities which introduce mainstreamed junior high school students to concepts relating to fossils and dinosaurs. Provides students with opportunities for learning the concepts of change and adaptation, as well as fossil facts and terminology. (TW)

  11. A comparative study of frontal bone morphology among Pleistocene hominin fossil groups

    Microsoft Academic Search

    Sheela Athreya

    2009-01-01

    Features of the frontal bone that are conventionally used to distinguish among fossil hominin groups were quantitatively examined. Fifty-five fossil crania dating from the early to the late Pleistocene were analyzed. Using a modified pantograph, outlines of the frontal bone were collected along the midsagittal and two parasagittal planes. The profile from nasion to bregma, as well as two profiles

  12. An assessment of the contribution of fossil cave deposits to the Quaternary paleontological record

    Microsoft Academic Search

    Christopher N. Jass; Christian O. George

    2010-01-01

    Mammal-bearing cave deposits are an important part of the Quaternary fossil record, but the exact nature of the contribution that caves make to the fossil record is a research area that is largely unexplored. To explore this issue, late Pleistocene species representation in cave versuses non-cave deposits was examined. Additionally, this study examined how fossiliferous cave deposits influence perceptions of

  13. A fossil record of colonization and response of lacustrine fish populations to climate change

    Microsoft Academic Search

    Michael G. Newbrey; Allan C. Ashworth

    2004-01-01

    To study fish species colonization and the response of populations to climate change, we reexamined a well- preserved late Pleistocene to early Holocene fossil fish assemblage from lake deposits on the Missouri Coteau, North Dakota. The fossil fishes in the assemblage include complete specimens of yellow perch (Perca flavescens), brassy minnow (Hybognathus hankinsoni), blacknose shiner (Notropis heterolepis), banded killifish (Fundulus

  14. FOSSIL ROVE BEETLES FROM PLEISTOCENE CALIFORNIA ASPHALT DEPOSITS (COLEÓPTERA: STAPHYLINIDAE)

    Microsoft Academic Search

    IAN MOORE; SCOTT E. MILLER

    Three species of Staphylinidae are known as fossils from Late Pleisto- cene asphalt deposits in California: 1 species oí Aleochara from the Carpin- tería asphalt deposit in Santa Barbara County and 2 species of Philonthus from the McKittrick asphalt deposit in Kern County. No Staphylinid frag- ments identifiable to genus have yet been recovered from the Rancho La Brea asphalt

  15. NEW TURTLES (CHELONIA) FROM THE LATE EOCENE THROUGH LATE MIOCENE OF THE PANAMA CANAL BASIN

    E-print Network

    Bermingham, Eldredge

    NEW TURTLES (CHELONIA) FROM THE LATE EOCENE THROUGH LATE MIOCENE OF THE PANAMA CANAL BASIN EDWIN@ncsu.edu.; ,jbourque@flmnh.ufl.edu.; ,jbloch@flmnh.ufl.edu.; and 2 Smithsonian Tropical Research Institute, Panama, AA 34002- 0948, Panama, ,jaramilloc@si.edu. ABSTRACT--Four distinct fossil turtle assemblages (Chelonia

  16. Fossil energy materials needs assessment

    Microsoft Academic Search

    R. T. King; R. R. Judkins

    1980-01-01

    An assessment of needs for materials of construction for fossil energy systems was prepared by Oak Ridge National Laboratories staff members who conducted a literature search and interviewed various individuals and organizations that are active in the area of fossil energy technology. Critical materials problems associated with fossil energy systems are identified. Background information relative to the various technologies is

  17. Circum-Arctic mantle structure and long-wavelength topography since the Jurassic

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Flament, N.; Williams, S.; Seton, M.; Gurnis, M.; Müller, R. D.

    2014-10-01

    The circum-Arctic is one of the most tectonically complex regions of the world, shaped by a history of ocean basin opening and closure since the Early Jurassic. The region is characterized by contemporaneous large-scale Cenozoic exhumation extending from Alaska to the Atlantic, but its driving force is unknown. We show that the mantle flow associated with subducted slabs of the South Anuyi, Mongol-Okhotsk, and Panthalassa oceans have imparted long-wavelength deflection on overriding plates. We identify the Jurassic-Cretaceous South Anuyi slab under present-day Greenland in seismic tomography and numerical mantle flow models. Under North America, we propose the "Farallon" slab results from Andean-style ocean-continent convergence around ~30°N and from a combination of ocean-continent and intraoceanic subduction north of 50°N. We compute circum-Arctic dynamic topography through time from subduction-driven convection models and find that slabs have imparted on average <1-16 m/Myr of dynamic subsidence across the region from at least 170 Ma to ~50 Ma. With the exception of Siberia, the main phase of circum-Arctic dynamic subsidence has been followed either by slowed subsidence or by uplift of <1-6 m/Myr on average to present day. Comparing these results to geological inferences suggest that subduction-driven dynamic topography can account for rapid Middle to Late Jurassic subsidence in the Slave Craton and North Slope (respectively, <15 and 21 m/Myr, between 170 and 130 Ma) and for dynamic subsidence (<7 m/Myr, ~170-50 Ma) followed by dynamic uplift (<6 m/Myr since 50 Ma) of the Barents Sea region. Combining detailed kinematic reconstructions with geodynamic modeling and key geological observations constitutes a powerful tool to investigate the origin of vertical motion in remote regions.

  18. Stratigraphy of Upper Jurassic Morrison and Lower Cretaceous Cloverly formations of Big Horn basin, northern Wyoming

    SciTech Connect

    Kvale, E.P.; Vondra, C.F.

    1983-08-01

    The Morrison and Cloverly Formations in the Big Horn basin of northern Wyoming and southern Montana are part of a distal edge of a westward-thickening clastic wedge of sediment deposited in an elongate intracontinental basin in the western North American craton. These formations reflect orogenic and volcanic activity in the western Cordillera during Late Jurassic and the subsequent eastward migration of volcanic centers during Early Cretaceous. The Morrison Formation (Upper Jurassic) conformably overlies the Jurassic marine Sundance Formation and consists of light olive-green, lenticular, calcareous siltstones and mudstones interbedded with white to buff or yellowish green, massive and cross laminated, calcareous quartz-arenites. The Cloverly Formation (Lower Cretaceous) consists of three members: the Pryor Conglomerate, and Little Sheep Mudstone, and the Himes; it overlies the Morrison Formation both conformably and unconformably. Both the Morrison and Cloverly Formations are characterized by high ratios of overbank fines relative to coarse channel sands. It has been assumed, but not documented by detailed sedimentologic study, that the deposits were part of an aggrading alluvial flood plain complex dotted by seasonal lakes and swamps and crossed by braided rivers. This model deviates from most modern braided systems which are characterized by rapid lateral mobility and the lack of fine-grained overbank material. The large ratio of fine-grained siltstones and mudstones to coarser grained sandstones can be explained by a number of processes, the most probable being rapid overbank aggradation as a result of a large influx of windblown volcanic material from vents to the west.

  19. Jurassic play pattern in Mississippi comes into focus

    Microsoft Academic Search

    1969-01-01

    A fast-moving play across Central Mississippi has shoved its production to an all time high. Buttressed with new oil from deep-lying Jurassic formations, the state expects to climb above 170,000 bpd. Providing this additional crude are 29 new fields, most all of them found in the last 4 yr. Jurassic production accounts for nearly 30% of Mississippi's total oil output.Current

  20. The largest fossil rodent

    PubMed Central

    Rinderknecht, Andrés; Blanco, R. Ernesto

    2008-01-01

    The discovery of an exceptionally well-preserved skull permits the description of the new South American fossil species of the rodent, Josephoartigasia monesi sp. nov. (family: Dinomyidae; Rodentia: Hystricognathi: Caviomorpha). This species with estimated body mass of nearly 1000?kg is the largest yet recorded. The skull sheds new light on the anatomy of the extinct giant rodents of the Dinomyidae, which are known mostly from isolated teeth and incomplete mandible remains. The fossil derives from San José Formation, Uruguay, usually assigned to the Pliocene–Pleistocene (4–2?Myr ago), and the proposed palaeoenvironment where this rodent lived was characterized as an estuarine or deltaic system with forest communities. PMID:18198140

  1. Bibliography of Fossil Vertebrates

    NSDL National Science Digital Library

    1997-01-01

    The Society of Vertebrate Paleontology (SVP), one of most reputable American paleontological societies, sponsors this online edition of its Bibliography of Fossil Vertebrates. The database, which currently covers the years 1509-1958 and 1981-1993 with approximately 112,000 references, is searchable by author, subject, taxon, language, editor, and journal book or volume title. A help page with query instructions for the somewhat finicky search engine is provided.

  2. Restoring Fossil Creek

    NSDL National Science Digital Library

    Carri J. LeRoy

    2004-07-01

    As part of an ongoing environmental project and partnership with a local university, high school students monitor changes to Fossil Creek in Arizona. Components of the project include fish behavior studies, responses to fishing, water chemistry measurements, aquatic invertebrate studies, photographic recording, riparian habitat transects, and small mammal trapping transects. The data collected will ultimately provide an invaluable annual record for students, working scientists, and the wider community as changes are monitored over time.

  3. Schewel and Schipper 1 FOSSIL FREIGHT: HOW MUCH FOSSIL FUEL DOES IT TAKE TO MOVE FOSSIL1

    E-print Network

    Kammen, Daniel M.

    Schewel and Schipper 1 FOSSIL FREIGHT: HOW MUCH FOSSIL FUEL DOES IT TAKE TO MOVE FOSSIL1 FUEL?2 #12;Schewel and Schipper 2 Abstract1 This paper asks as the question: how much fossil fuel does it take to move fossil fuel inside the U.S.? An2 understanding of this "fossil freight", which takes up

  4. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus

    PubMed Central

    Reisz, Robert R.; Evans, David C.; Roberts, Eric M.; Sues, Hans-Dieter; Yates, Adam M.

    2012-01-01

    The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding. PMID:22308330

  5. Forever Love: The Hitherto Earliest Record of Copulating Insects from the Middle Jurassic of China

    PubMed Central

    Li, Shu; Shih, Chungkun; Wang, Chen; Pang, Hong; Ren, Dong

    2013-01-01

    Background Mating behaviors have been widely studied for extant insects. However, cases of mating individuals are particularly rare in the fossil record of insects, and most of them involved preservation in amber while only in rare cases found in compression fossils. This considerably limits our knowledge of mating position and genitalia orientation during the Mesozoic, and hinders our understanding of the evolution of mating behaviors in this major component of modern ecosystems. Principal Finding Here we report a pair of copulating froghoppers, Anthoscytina perpetua sp. nov., referable to the Procercopidae, from the Middle Jurassic of northeastern China. They exhibit belly-to-belly mating position as preserved, with male's aedeagus inserting into the female's bursa copulatrix. Abdominal segments 8 to 9 of male are disarticulated suggesting these segments were twisted and flexed during mating. Due to potential taphonomic effect, we cannot rule out that they might have taken side-by-side position, as in extant froghoppers. Genitalia of male and female, based on paratypes, show symmetric structures. Conclusions/Significance Our findings, consistent with those of extant froghoppers, indicate froghoppers' genitalic symmetry and mating position have remained static for over 165 million years. PMID:24223138

  6. A new arboreal haramiyid shows the diversity of crown mammals in the Jurassic period.

    PubMed

    Zheng, Xiaoting; Bi, Shundong; Wang, Xiaoli; Meng, Jin

    2013-08-01

    A major unsolved problem in mammalian evolution is the origin of Allotheria, including Multituberculata and Haramiyida. Multituberculates are the most diverse and best known Mesozoic era mammals and ecologically resemble rodents, but haramiyids are known mainly from isolated teeth, hampering our search for their phylogenetic relationships. Here we report a new haramiyid from the Jurassic period of China, which is, to our knowledge the largest reported so far. It has a novel dentition, a mandible resembling advanced multituberculates and postcranial features adapted for arboreal life. Our phylogenetic analysis places Haramiyida within crown Mammalia, suggesting the origin of crown Mammalia in the Late Triassic period and diversification in the Jurassic, which contrasts other estimated divergence times of crown Mammalia. The new haramiyid reveals additional mammalian features of the group, helps to identify other haramiyids represented by isolated teeth, and shows again that, regardless of various phylogenetic scenarios, a complex pattern of evolution involving many convergences and/or reversals existed in Mesozoic mammals. PMID:23925244

  7. The African Plate: A history of oceanic crust accretion and subduction since the Jurassic

    NASA Astrophysics Data System (ADS)

    Gaina, Carmen; Torsvik, Trond H.; van Hinsbergen, Douwe J. J.; Medvedev, Sergei; Werner, Stephanie C.; Labails, Cinthia

    2013-09-01

    We present a model for the Jurassic to Present evolution of plate boundaries and oceanic crust of the African plate based on updated interpretation of magnetic, gravity and other geological and geophysical data sets. Location of continent ocean boundaries and age and geometry of old oceanic crust (Jurassic and Cretaceous) are updated in the light of new data and models of passive margin formation. A new set of oceanic palaeo-age grid models constitutes the basis for estimating the dynamics of oceanic crust through time and can be used as input for quantifying the plate boundary forces that contributed to the African plate palaeo-stresses and may have influenced the evolution of intracontinental sedimentary basins. As a case study, we compute a simple model of palaeo-stress for the Late Cretaceous time in order to assess how ridge push, slab pull and horizontal mantle drag might have influenced the continental African plate. We note that the changes in length of various plate boundaries (especially trenches) do not correlate well with absolute plate motion, but variations in the mean oceanic crust age seem to be reflected in acceleration or deceleration of the mean absolute plate velocity.

  8. The late early Miocene Sabine River

    SciTech Connect

    Manning, E. (Louisiana State Univ., Baton Rouge (USA))

    1990-09-01

    Work on a new late early Miocene vertebrate fossil site, in a paleochannel deposit of the upper Carnahan Bayou Member of the lower Fleming Formation, has revealed unexpected data on the course and nature of the Sabine River of that time. Screen washing for smaller vertebrate remains at the site, just west of the Sabine River in Newton County, central eastern Texas, has resulted in the recovery of early Permian, Early Cretaceous, Late Cretaceous (Maestrichtian), Paleocene/Eocene, late Eocene, and Oligocene/Miocene fossils, in addition to the main early Miocene fauna. The reworked fossils, as well as distinctive mineral grains, show that the late early Miocene Sabine River was connected to the Texas/Oklahoma/Arkansas boundary section of the Red River, as well as to rivers draining the southern Ouachita Mountains. These rivers must have joined the Texas/Louisiana boundary section of the Sabine River somewhere in northwest Louisiana at that time. This suggests that the Louisiana section of the present Red River pirated the Texas/Oklahoma/Arkansas boundary section of the river some time after the early Miocene. The preservation of recognizable fossils transported hundreds of miles in a large river itself requires explanation. It is speculated here that the late early Miocene Sabine River incorporated a large amount of the then recently deposited volcanic ash from the Trans-Pecos Volcanic Field. Montmorillonite clay from the altered volcanic ash would have made the river very turbid, which could have allowed coarse sand-sized particles to be carried in the suspended load of the river, rather than in its bed load (where they would have been destroyed by the rolling chert gravel). Additional evidence for such long-distance fossil transport in the late early Miocene rivers of the western Gulf Coastal Plain comes from the abundant Cretaceous fossils of the upper Oakville Formation of southeast Texas and the Siphonina davisi zone of the southeast Texas subsurface.

  9. Geochemical evolution of Jurassic diorites from the Bristol Lake region, California, USA, and the role of assimilation

    Microsoft Academic Search

    Edward D. Young; Joseph L. Wooden; Yuch-Ning Shieh; Daniel Farber

    1992-01-01

    Late Jurassic dioritic plutons from the Bristol Lake region of the eastern Mojave Desert share several geochemical attributes with high-alumina basalts, continental hawaiite basalts, and high-K are andesites including: high K2O concentrations; high Al2O3 (16–19 weight %); elevated Zr\\/TiO2; LREE (light-rare-earth-element) enrichment (La\\/YbCN=6.3–13.3); and high Nb. Pearce element ratio analysis supported by petrographic relations demonstrates that P, Hf, and Zr

  10. Fossilized Dinosaur Teeth Adaptations

    NSDL National Science Digital Library

    Rick Crosslin

    2004-01-01

    In this activity, learners use models of fossilized dinosaur teeth to understand how dinosaur teeth were used. Learners specifically research Tyrannosaurus rex and Triceratops horridus dinosaurs and determine that Triceratops teeth work the way pliers and scissors operate, and T. rex teeth are like sharp knives. Learners match and sort dinosaurs by the type and use of their teeth. This activity is featured on pp.14-18 (part of a lesson that begins on p.7) of the "Dinosphere" unit of study for grades 3-5.

  11. Paleointensity of the Earth's magnetic field in the Jurassic: New results from a Thellier study of the Lesotho Basalt, southern Africa

    NASA Astrophysics Data System (ADS)

    Kosterov, Andrei A.; PréVot, Michel; Perrin, Mireille; Shashkanov, Vladimir A.

    1997-11-01

    Thellier paleointensity experiments carried out on the Jurassic (180 m.y. old) Karoo basalt, Lesotho, southern Africa, provided paleointensity estimates for 40 samples from 10 distinct lava flows with reversed magnetization. Mean paleointensity was found to be equal to 24.2 ± 11.3 ?T (standard deviation), with a minimum of 12 ?T and a maximum of 41.3 ?T. This corresponds to a mean virtual dipole moment (VDM) of 4.6±2.0×1022 Am2. The between-flow dispersion is ascribed to paleosecular variation, which thus would approach up to 40% of the mean paleointensity, as is observed from the published paleointensity data set covering last 20 m.y. This result yields further evidence for the period of low geomagnetic field in Jurassic to Early Cretaceous time (Mesozoic Dipole Low). A symmetrical intensity versus time pattern is suggested for this time interval, with a minimum VDM of 3×1022 Am2 in Late Jurassic and substantially higher (˜ 4.5×1022 Am2) VDMs in Early to Middle Jurassic and Early Cretaceous, respectively.

  12. Fossil plant self assessment

    SciTech Connect

    Bozgo, R.H. [Consolidated Edison Company of New York, Inc., New York, NY (United States); Maguire, B.A. [VPA Corp., Reston, VA (United States)

    1996-07-01

    The increasingly competitive environment of the electric utility business is focusing utilities attention on reducing the cost of electricity generation. By using benchmark indicators, gains are being sought in plant material condition with corresponding improvements in operating efficiency and capacity factor as well as reductions in Operating and Maintenance (O&M) costs. In designing a process for improvement, Consolidated Edison Company of New York, Inc. (Con Edison) plant managers were asked to review and approve objectives and criteria for Fossil Plant Operations. The program methods included optimizing work processes (including material condition, maintenance programs, work control systems, and personnel performance); team building techniques to foster personnel buy-in of the process; and long term cultural change to insure an ongoing continuous improvement process with measurable results. The program begins with a self assessment of each plant based upon the approved Objectives and Criteria. The Criteria and Review Approaches (CRAs) are established by senior management and the review team. The criteria cover Management, Operations, Maintenance, and Support Functions including Technical Support, Training and Qualification, Environmental Compliance, Chemistry, and Safety and Emergency Preparedness. The Assessment is followed by a review of corrective action plans and an interim corrective action review. Annual Assessments are planned to ensure continuous improvement. Emphasis is placed on progress made in maintenance at the fossil stations.

  13. Growth dynamics and ecology of Upper Jurassic mounds, with comparisons to Mid-Palaeozoic mounds

    NASA Astrophysics Data System (ADS)

    Schmid, Dieter U.; Leinfelder, Reinhold R.; Nose, Martin

    2001-12-01

    The Mid-Palaeozoic, including the Late Jurassic, was a time of both widespread coral reef growth and pronounced mound formation. A comparison of mound features and their general setting highlights, despite all differences, general similarities in overall growth dynamics. Mound formation was frequently driven by discontinuous patterns, particularly by background sedimentation. In many examples, episodes of mound stabilisation by early lithification, growth of microbolite crusts and winnowing of fines was followed by growth episodes of benthic fauna under reduced to negligible background sedimentation. This pattern of variable sedimentation and organic buildups may have occurred in different orders and magnitudes, inducing a fractal pattern in some mound complexes. A composite approach in estimating growth rates of mounds demonstrates that high-frequency oscillations necessary for growth of most mounds might have ranged from a few thousand years to 4th and 5th order Milankovich cycles that were superimposed by autocyclic factors.

  14. Fossils 2: Uncovering the Facts

    NSDL National Science Digital Library

    Science Netlinks

    2001-10-20

    In Fossils and Dinosaurs, the first lesson of this two lesson series, students learned the differences between facts and ideas that are extrapolated from fossil evidence. This lesson allows students to go through an 'interview' with the remains of a Protoceratops. In preparation for the interview, students first brainstorm the questions they would like answers to, and then narrow their questions to those that can be answered by studying the Protoceratops fossils.

  15. Furculae in the Late Triassic theropod dinosaur Coelophysis bauri

    Microsoft Academic Search

    Larry F. Rinehart; Spencer G. Lucas; Adrian P. Hunt

    2007-01-01

    Furculae have been identified in many dinosaurs and are synapomorphic in some clades (e.g., dromaeosaurids). All coelophysid\\u000a dinosaurs exceptCoelophysis bauri have been shown to possess furculae. To date, the oldest well-documented furculae have been those of the Early Jurassic coelophysids,Coelophysis kayentakatae andCoelophysis rhodesiensis. The confirmation of furculae in Apachean-agedC. bauri further documents appearance of these elements in the Late Triassic

  16. Late Cenozoic intraplate faulting in eastern Australia

    NASA Astrophysics Data System (ADS)

    Babaahmadi, Abbas; Rosenbaum, Gideon

    2014-12-01

    The intensity and tectonic origin of late Cenozoic intraplate deformation in eastern Australia is relatively poorly understood. Here we show that Cenozoic volcanic rocks in southeast Queensland have been deformed by numerous faults. Using gridded aeromagnetic data and field observations, structural investigations were conducted on these faults. Results show that faults have mainly undergone strike-slip movement with a reverse component, displacing Cenozoic volcanic rocks ranging in ages from ?31 to ?21 Ma. These ages imply that faulting must have occurred after the late Oligocene. Late Cenozoic deformation has mostly occurred due to the reactivation of major faults, which were active during episodes of basin formation in the Jurassic-Early Cretaceous and later during the opening of the Tasman and Coral Seas from the Late Cretaceous to the early Eocene. The wrench reactivation of major faults in the late Cenozoic also gave rise to the occurrence of brittle subsidiary reverse strike-slip faults that affected Cenozoic volcanic rocks. Intraplate transpressional deformation possibly resulted from far-field stresses transmitted from the collisional zones at the northeast and southeast boundaries of the Australian plate during the late Oligocene-early Miocene and from the late Miocene to the Pliocene. These events have resulted in the hitherto unrecognized reactivation of faults in eastern Australia.

  17. U-Pb geochronology of detrital zircon from Upper Jurassic synorogenic turbidites, Galice Formation, and related rocks, western Klamath Mountains: Correlation and Klamath Mountains provenance

    NASA Astrophysics Data System (ADS)

    Miller, M. Meghan; Saleeby, Jason B.

    1995-09-01

    Synorogenic turbidites of the Upper Jurassic Galice Formation overlie a variety of basement terranes within the western Klamath Mountains along the Oregon-California border, including the early Late Jurassic ophiolite assemblages, ensimatic arc deposits, and sedimentary terranes. U-Pb analyses of 68 multiple grain fractions from 11 samples of detrital zircon support the correlation of Galice Formation on these various basement terranes, although some new complexities in provenance are revealed. With one exception, upper intercept ages range from 1509-3+3 to 1675-8+8 Ma. Least squares regression of all fractions yields an upper intercept age of 1583±1 Ma, indicating the importance of an ultimately continental, recycled, and generally well-mixed sedimentary source. Early Mesozoic lower intercept ages range between 183-2+2 and 263-3+4 and average 215±1 Ma. Results from Galice cover on sedimentary basement show significantly older 2.1 Ga Precambrian component, however, that may be locally derived from pre-Late Jurassic basement rocks that are rich in recycled sedimentary debris. Existing isotopic data from older, zircon-bearing Klamath units further indicate that Galice detritus was derived from immediate source terranes within the Klamath Mountains. Reworking of fragile limestone clasts from the biogeographically distinctive eastern Klamath terrane (McCloud Limestone) into Galice Formation substrate also supports early paleogeographic ties between terranes. Thus the tectonic setting of the Late Jurassic Nevadan orogeny in the Klamath Mountains is tightly constrained by original paleogeographic ties between subterranes of the western belt and by provenance ties to terranes to the east. Ultimately continent-derived clastic debris and other distinctive tracers were recycled within this long-lived ensimatic convergent margin system.

  18. Strategies for assessing Early{Middle (Pliensbachian{Aalenian) Jurassic cyclochronologies

    Microsoft Academic Search

    J. P ark

    1999-01-01

    There are a number of fundamental problems in assessing the astronomically forced cyclostratigraphy of the Jurassic Period. First, Jurassic geochronology is not well constrained, due to a general scarcity of radiometric dates, inferior precision of the existing ones, and large inaccuracies in stratigraphic constraints. These problems are particularly troublesome in the Early to Middle Jurassic cyclic carbonates of the Colle

  19. Geological model of the Jurassic section in the State of Kuwait

    SciTech Connect

    Yousif, S.; Nouman, G.

    1995-11-01

    Until the end of the seventies, the knowledge of Jurassic Geology in the State of Kuwait was very limited, since only one deep well was drilled and bottomed in the Triassic sediments. Few scattered wells partially penetrated the Jurassic sequence. During the eighties, appreciable number of wells were drilled through the Jurassic, and added a remarkable volume of information. consequently it was necessary to analyze the new data, in order to try to construct a geological model for the Jurassic in the State of Kuwait. This paper includes a number of isopach maps explaining the Jurassic depositional basin which also helps in trying to explain the Jurassic basin in the Arabian Gulf basin. Structural evolution of the Jurassic sequence indicated an inversion of relief when compared with the Cretaceous sequence. In fact, the main Cretaceous arches were sites of sedimentation troughs during the Jurassic period. This fact marks a revolution in the concepts for the Jurassic oil exploration. One of the very effective methods of the definition of the Jurassic structures is the isopaching of the Gotnia Formation. Najmah, Sargelu and Marrat Formations include the main Jurassic reservoirs which were detected as a result of the exploration activities during the eighties. Selective stratigraphic and structural cross sections have been prepared to demonstrate and explain the nature of the Jurassic sediments.

  20. Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription of Iguanodonichnus frenki)

    E-print Network

    Benton, Michael

    Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription studied Upper Jurassic dinosaur unit in South America, the Ban~os del Flaco Formation, Chile. Keywords: Chile; Dinosaur footprints; Parabrontopodus; Sauropod; Upper Jurassic Resu´men En el presente

  1. Fossil turbulence and fossil turbulence waves can be dangerous

    E-print Network

    Carl H Gibson

    2012-11-25

    Turbulence is defined as an eddy-like state of fluid motion where the inertial-vortex forces of the eddies are larger than any other forces that tend to damp the eddies out. By this definition, turbulence always cascades from small scales where vorticity is created to larger scales where turbulence fossilizes. Fossil turbulence is any perturbation in a hydrophysical field produced by turbulence that persists after the fluid is no longer turbulent at the scale of the perturbation. Fossil turbulence patterns and fossil turbulence waves preserve and propagate energy and information about previous turbulence. Ignorance of fossil turbulence properties can be dangerous. Examples include the Osama bin Laden helicopter crash and the Air France 447 Airbus crash, both unfairly blamed on the pilots. Observations support the proposed definitions, and suggest even direct numerical simulations of turbulence require caution.

  2. Fossil arthropods in Late Cretaceous Vendean amber (northwestern France)

    E-print Network

    2014-12-01

    . 8 Opiliones indet. 1 Entognatha Collembola indet. 1 Insecta Blattaria indet. 1 Coleoptera Ptinidae 2 indet. 2 Dermaptera Neodermaptera* 1 Diptera Cecidomyiidae 4 Ceratopogonidae* 10 Chironomidae 5 Dolichopodidae* 1 Anisopodidae...

  3. A Remarkable New Family of Jurassic Insects (Neuroptera) with Primitive Wing Venation and Its Phylogenetic Position in Neuropterida

    PubMed Central

    Yang, Qiang; Makarkin, Vladimir N.; Winterton, Shaun L.; Khramov, Alexander V.; Ren, Dong

    2012-01-01

    Background Lacewings (insect order Neuroptera), known in the fossil record since the Early Permian, were most diverse in the Mesozoic. A dramatic variety of forms ranged in that time from large butterfly-like Kalligrammatidae to minute two-winged Dipteromantispidae. Principal Findings We describe the intriguing new neuropteran family Parakseneuridae fam. nov. with three new genera and 15 new species from the Middle Jurassic of Daohugou (Inner Mongolia, China) and the Early/Middle Jurassic of Sai-Sagul (Kyrgyzstan): Parakseneura undula gen. et sp. nov., P. albomacula gen. et sp. nov., P. curvivenis gen. et sp. nov., P. nigromacula gen. et sp. nov., P. nigrolinea gen. et sp. nov., P. albadelta gen. et sp. nov., P. cavomaculata gen. et sp. nov., P. inflata gen. et sp. nov., P. metallica gen. et sp. nov., P. emarginata gen. et sp. nov., P. directa gen. et sp. nov., Pseudorapisma jurassicum gen. et sp. nov., P. angustipenne gen. et sp. nov., P. maculatum gen. et sp. nov. (Daohugou); Shuraboneura ovata gen. et sp. nov. (Sai-Sagul). The family comprises large neuropterans with most primitive wing venation in the order indicated by the presence of ScA and AA1+2, and the dichotomous branching of MP, CuA, CuP, AA3+4, AP1+2. The phylogenetic position of Parakseneuridae was investigated using a phylogenetic analysis of morphological scoring for 33 families of extinct and extant Neuropterida combined with DNA sequence data for representatives of all extant families. Parakseneuridae were recovered in a clade with Osmylopsychopidae, Prohemerobiidae, and Ithonidae. Conclusions/Significance The presence of the presumed AA1+2 in wings of Parakseneuridae is a unique plesiomorphic condition hitherto unknown in Neuropterida, the clade comprising Neuroptera, Megaloptera, Raphidioptera. The relative uncertainty of phylogenetic position of Parakseneuridae and the majority of other families of Neuroptera reflects deficient paleontological data, especially from critical important periods for the order, earliest Triassic and latest Triassic/earliest Jurassic. PMID:23028608

  4. Constraints on Upper Jurassic palaeogeography in the Ula Gyda trend

    SciTech Connect

    Mundal, I.; Milton, N.; Robinson, N. [BP Norge, Stavanger (Norway)

    1995-08-01

    BP Norway`s semi-regional 3D database in the Central Trough covers an area of nearly 3000 sq.km. around BP Norway`s two producing fields, Ula and Gyda, and includes strategic acreage within tie-back distance to the fields. Prospectivity in the Ula Gyda trend involves complex salt influenced structures and localized Upper Jurassic depositional systems. The objective of this paper is to demonstrate how the understanding of the semi-regional structures and salt tectonics helped constrain the interpretation of the Upper Jurassic palaeogeography. The control of basement structures (Permian) on cover structures (Upper Jurassic/Base Cretaceous) through Zechstein Salt was interpreted using the 3D semi-regional dataset. Analogue sandbox experiments from the Austin Geodynamics Laboratory provide support for the complex structures which were interpreted on the 3D seismic data. Sandbox models mimic the interpreted monoclinal drape of the Triassic and Jurassic section over the critical basin bounding fault in the Base Zechstein. Structural cells can be identified with the help of the salt isochore. The understanding of the relationship between structural development and salt distribution was a major control on the interpretation. This interpretation coupled with the Upper Jurassic reservoir distribution from well data provided the primary evidence for the gross depositional environment maps which were used in prospect evaluation in the area. 3D visualization and shaded relief displays of the interpreted horizons and isochores played a significant part in developing an understanding of the interplay between the deeper structures and the likely Upper Jurassic palaeogeography and depocentres.

  5. The fossil record of cnidarian medusae

    Microsoft Academic Search

    Graham A. Young; James W. Hagadorn

    2010-01-01

    Fossils of cnidarian medusae are extremely rare, although reports of fossil “medusoids,” most of which do not represent medusae, are rather common. Our previous inability to distinguish these fossils has hampered attempts to investigate patterns and processes within the medusozoan fossil record. Here we describe criteria for the recognition of bona fide fossil medusae and use them to assess the

  6. Annual monsoon rains recorded by Jurassic dunes

    Microsoft Academic Search

    David B. Loope; Clinton M. Rowe; R. Matthew Joeckel

    2001-01-01

    Pangaea, the largest landmass in the Earth's history, was nearly bisected by the Equator during the late Palaeozoic and early Mesozoic eras. Modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality, but direct evidence for annual rainfall periodicity has been lacking. In the Mesozoic era, about 190million years ago,

  7. The second Jurassic dinosaur rush and the dawn of dinomania.

    PubMed

    Brinkman, Paul D

    2010-09-01

    During the second Jurassic dinosaur rush museum paleontologists raced to display the world's first mounted sauropod dinosaur. The American Museum of Natural History triumphed in 1905 when its Brontosaurus debuted before an admiring crowd of wealthy New Yorkers. The Carnegie Museum of Natural History in Pittsburgh, the Field Columbian Museum in Chicago and other institutions were quick to follow with their own sauropod displays. Thereafter, dinomania spread far and wide, and big, showpiece dinosaurs became a museum staple. This brief but intensely competitive period of acquisitiveness fostered important Jurassic dinosaur revisions and crucial innovations in paleontological field and lab techniques. PMID:20667597

  8. The "terminal Triassic catastrophic extinction event" in perspective: a review of carboniferous through Early Jurassic terrestrial vertebrate extinction patterns

    USGS Publications Warehouse

    Weems, R.E.

    1992-01-01

    A catastrophic terminal Triassic extinction event among terrestrial vertebrates is not supported by available evidence. The current model for such an extinction is based on at least eight weak or untenable assumptions: (1) a terminal Triassic extinction-inducing asteroid impact occurred, (2) a terminal Triassic synchronous mass extinction of terrestrial vertebrates occurred, (3) a concurrent terminal Triassic marine extinction occurred, (4) all terrestrial vertebrate families have similar diversities and ecologies, (5) changes in familial diversity can be gauged accurately from the known fossil record, (6) extinction of families can be compared through time without normalizing for changes in familial diversity through time, (7) extinction rates can be compared without normalizing for differing lengths of geologic stages, and (8) catastrophic mass extinctions do not select for small size. These assumptions have resulted in unsupportable and (or) erroneous conclusions. Carboniferous through Early Jurassic terrestrial vertebrate families mostly have evolution and extinction patterns unlike the vertebrate evolution and extinction patterns during the terminal Cretaceous event. Only the Serpukhovian (mid Carboniferous) extinction event shows strong analogy to the terminal Cretaceous event. Available data suggest no terminal Triassic extinction anomaly, but rather a prolonged and nearly steady decline in the global terrestrial vertebrate extinction rate throughout the Triassic and earliest Jurassic. ?? 1992.

  9. Long bone histology of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan.

    PubMed

    Skutschas, Pavel; Stein, Koen

    2015-04-01

    Kokartus honorarius from the Middle Jurassic (Bathonian) of Kyrgyzstan is one of the oldest salamanders in the fossil record, characterized by a mixture of plesiomorphic morphological features and characters shared with crown-group salamanders. Here we present a detailed histological analysis of its long bones. The analysis of a growth series demonstrates a significant histological maturation during ontogeny, expressed by the progressive appearance of longitudinally oriented primary vascular canals, primary osteons, growth marks, remodelling features in primary bone tissues, as well as progressive resorption of the calcified cartilage, formation of endochondral bone and development of cartilaginous to bony trabeculae in the epiphyses. Apart from the presence of secondary osteons, the long bone histology of Kokartus is very similar to that of miniaturized temnospondyls, other Jurassic stem salamanders, miniaturized seymouriamorphs and modern crown-group salamanders. We propose that the presence of secondary osteons in Kokartus honorarius is a plesiomorphic feature, and the loss of secondary osteons in the long bones of crown-group salamanders as well as in those of miniaturized temnospondyls is the result of miniaturization processes. Hitherto, all stem salamander long bong histology (Kokartus, Marmorerpeton and 'salamander A') has been generally described as having paedomorphic features (i.e. the presence of Katschenko's Line and a layer of calcified cartilage), these taxa were thus most likely neotenic forms. The absence of clear lines of arrested growth and annuli in long bones of Kokartus honorarius suggests that the animals lived in an environment with stable local conditions. PMID:25682890

  10. Zoidogamy in fossil gymnosperms

    PubMed Central

    Poort, Ruud J.; Visscher, Henk; Dilcher, David L.

    1996-01-01

    This year is the centenary of the surprising discovery in 1896 of zoidogamy in extant cycadophytes and Ginkgo. But by coincidence, also in the same year, the concept of prepollen was introduced. The morphology of prepollen was considered justification for the probable production of motile antherozoids in extinct gymnosperms. In this paper, the history of the prepollen concept is briefly outlined. It is emphasized that, in addition to well-known examples in pteridosperms and cordaitaleans, a prepollen condition also occurred among late Paleozoic conifers. Images Fig. 2 PMID:16594095

  11. Termite Traces on Bones from the Late Pleistocene of Argentina

    Microsoft Academic Search

    Lucas Horacio Pomi; Eduardo Pedro Tonni

    2011-01-01

    Insect activity during the late Cenozoic of the Pampean Region (Argentina) has been recorded mainly as fossil nests of ants, termites, flies and beetles. We present new evidence of insect activity based on the presence of traces on bones from a late Pleistocene site in the Quequén Grande Basin. Potential tracemakers were evaluated by comparing these scratches with both modern

  12. Hydrothermal venting of greenhouse gases triggering Early Jurassic global warming

    Microsoft Academic Search

    Henrik Svensen; Sverre Planke; Luc Chevallier; Anders Malthe-Sørenssen; Fernando Corfu; Bjørn Jamtveit

    2007-01-01

    The climate change in the Toarcian (Early Jurassic) was characterized by a major perturbation of the global carbon cycle. The event lasted for approximately 200,000 years and was manifested by a global warming of ?6 °C, anoxic conditions in the oceans, and extinction of marine species. The triggering mechanisms for the perturbation and environmental change are however strongly debated. Here, we present

  13. Let the Volgian stage stay in the Jurassic

    Microsoft Academic Search

    V. A. Zakharov; M. A. Rogov

    2008-01-01

    In 1996 the Volgian Stage was divided into the Jurassic and Cretaceous units, removed from the Geological Time Scale, and substituted by the Tithonian Stage according to the guidelines of the Interdepartmental Stratigraphic Committee of the Russian Federation (ISC RF). Consequently, the Upper Volgian Substage including three zones (five subzones) was placed into the Berriasian Stage (the Cretaceous) proceeding from

  14. MEGASPORES FROM THE JURASSIC OF THE ISLAND OF BORNHOLM, DENMARK

    Microsoft Academic Search

    HELGE GRY

    An account is given of the lithology, areal extent and depositional history of the Jurassic sediments and a preliminary description is given of the megaspore content of the sediments (excluding new species). The deltaic deposits below the marine Lias y horizon are Lias a in age and the deltaic deposits above this horizon are referred to the Dogger.

  15. Combined oxygen- and carbon-isotope records through the Early Jurassic: multiple global events and two modes of carbon-cycle/temperature coupling

    NASA Astrophysics Data System (ADS)

    Hesselbo, S. P.; Korte, C.

    2010-12-01

    The Jurassic comprises some 55 million years of Earth history. However, within the Jurassic, only one major environmental change (hyperthermal) event is really well known - the Early Toarcian Oceanic Anoxic Event (OAE) at ~183 Ma - and until very recently the extent to which the accompanying environmental changes were global has been strongly debated. Nevertheless, partly as a result of the international effort to define Global Stratotype Sections and Points (GSSPs), much more is now being discovered about environmental changes taking place at and around the other Jurassic Age (Stage) boundaries, to the extent that meaningful comparisons between these events can begin to be made. Here we present new carbon and oxygen isotope data from mollusks (bivalves and belemnites) and brachiopods collected through the marine Early Jurassic succession of NE England, including the Sinemurian-Plienbachian boundary GSSP. All materials have been screened by chemical analysis and scanning electron microscopy to check for diagenetic alteration. Analysis of carbon isotopes from marine calcite is supplemented by analysis of carbon-isotope values from fossil wood collected through the same section. It is demonstrated that both long-term and short-term carbon-isotope shifts from the UK Early Jurassic represent global changes in carbon cycle balances. The Sinemurian-Pliensbachian boundary event is an event of global significance and shows several similarities to the Toarcian OAE (relative sea-level change, carbon-isotope signature), but also some significant contrasts (oxygen-isotope based paleotemperatures which provide no evidence for warming). Significant contrast in oxygen- and carbon-isotope co-variation also occurs on a long timescale. There appear to be two modes in the co-variation of carbon and oxygen isotopes through this time interval: mode 1 shows positive correlation and may be explained by conventional sources and sinks for carbon-dioxide; mode 2, representing negative correlation, is more difficult to explain but appears to dominate. Additionally, we show that estimates of carbon dioxide change through the Early Jurassic based on ??13C values from the stratigraphically extended Mochras Farm core are unlikely to be correct.

  16. The youngest Ediacaran fossils from southern Africa.

    PubMed

    Narbonne, G M; Saylor, B Z; Grotzinger, J P

    1997-11-01

    Discovery of fossils of the Ediacara biota near the top of the Spitzkopf Member at farm Swanpunt extends the known range of these remains in Namibia more than 600 m to near the sub-Cambrian unconformity. The fossiliferous beds occur approximately 100 m above a volcanic ash dated at 543 +/- 1 Ma, and thus may be the youngest Proterozoic Ediacara-type fossils reported anywhere in the world. Fossils are preserved within and on the tops of dm-thick beds of storm-deposited sandstone at two stratigraphic levels; the environment is interpreted as open marine, generally calm but with episodic disruptions by storm waves, and probably within the euphotic zone. The presence of Pteridinium carolinaense (St. Jean), which is also known from the classic sections in Ediacara and the White Sea among others, reinforces evidence from geochronology and chemostratigraphy that the Swartpunt section is terminal Neoproterozoic in age. The new genus and species Swartpuntia germsi is a large, multifoliate frond that exhibits at least three quilted petaloids. Macroscopically, Swartpuntia resembles Pteridinium and Ediacara-type fronds such as Charniodiscus traditionally interpreted as Cnidaria, whereas microscopically it exhibits segmentation that is remarkably similar to that of the putative worm Dickinsonia. Combination of diagnostic characters of these supposedly disparate groups in a single species suggests that many species of quilted Ediacaran organisms were more similar to each other than they were to any modern groups, and provides support for the concept of the "Vendobionta" as a late Neoproterozoic group of mainly multifoliate organisms with a distinctive quilted segmentation. PMID:11541433

  17. Hydrocarbon potential of a new Jurassic play, central Tunisia

    SciTech Connect

    Beall, A.O. (Arthur O. Beall International E P, Houston, TX (United States)); Law, C.W. (Geomath, Houston, TX (United States))

    1996-01-01

    A largely unrecognized Jurassic Sag Basin has been identified in central Tunisia, proximal to the Permo-Carboniferous flexure delineating the northern boundary of the Saharan platform of north Africa. The northwestern margin of the Sag is delineated by an extensive region of salt-cored anticlines and localized salt diapirs extending north and west. Due to lack of deep drilling, delineation of the Sag is largely based on regional gravity data. Subsidence of the Jurassic Sag Basin is characterized by rapid expansion of Jurassic sediments from 400 m. of tidal flat and shelf carbonate at the western outcrop to over 2000 meters of tidal flat and basinal carbonate and shale within the basin center, a five-fold expansion. Rapid loading of the basin continued into Lower Cretaceous time, marked by lateral flowage of Triassic salt into pronounced structural trends. Published source rock data and interpreted subsurface well data provided the basis for GENEX 1-D hydrocarbon generation and expulsion modeling of the Sag. Middle Jurassic black source shales typically contain Type II and Type III kerogens with T.O.C.'s ranging up to 4 percent. Modeling results indicate that middle Jurassic shales are presently mature for liquid generation within portions of the Sag, with maximum generation taking place during the Tertiary. Potential hydrocarbon generation yields, based on 60 meters of mature source shale, are 20,000 BOE/acre for gas and 75,000 BOE/acre for liquids. Prospects within the region could contain an estimated potential reserve of several T.C.F. or over 1 billion barrels of oil.

  18. Hydrocarbon potential of a new Jurassic play, central Tunisia

    SciTech Connect

    Beall, A.O. [Arthur O. Beall International E& P, Houston, TX (United States); Law, C.W. [Geomath, Houston, TX (United States)

    1996-12-31

    A largely unrecognized Jurassic Sag Basin has been identified in central Tunisia, proximal to the Permo-Carboniferous flexure delineating the northern boundary of the Saharan platform of north Africa. The northwestern margin of the Sag is delineated by an extensive region of salt-cored anticlines and localized salt diapirs extending north and west. Due to lack of deep drilling, delineation of the Sag is largely based on regional gravity data. Subsidence of the Jurassic Sag Basin is characterized by rapid expansion of Jurassic sediments from 400 m. of tidal flat and shelf carbonate at the western outcrop to over 2000 meters of tidal flat and basinal carbonate and shale within the basin center, a five-fold expansion. Rapid loading of the basin continued into Lower Cretaceous time, marked by lateral flowage of Triassic salt into pronounced structural trends. Published source rock data and interpreted subsurface well data provided the basis for GENEX 1-D hydrocarbon generation and expulsion modeling of the Sag. Middle Jurassic black source shales typically contain Type II and Type III kerogens with T.O.C.`s ranging up to 4 percent. Modeling results indicate that middle Jurassic shales are presently mature for liquid generation within portions of the Sag, with maximum generation taking place during the Tertiary. Potential hydrocarbon generation yields, based on 60 meters of mature source shale, are 20,000 BOE/acre for gas and 75,000 BOE/acre for liquids. Prospects within the region could contain an estimated potential reserve of several T.C.F. or over 1 billion barrels of oil.

  19. Animal behavior frozen in time: gregarious behavior of Early Jurassic lobsters within an ammonoid body chamber.

    PubMed

    Klompmaker, Adiël A; Fraaije, René H B

    2012-01-01

    Direct animal behavior can be inferred from the fossil record only in exceptional circumstances. The exceptional mode of preservation of ammonoid shells in the Posidonia Shale (Lower Jurassic, lower Toarcian) of Dotternhausen in southern Germany, with only the organic periostracum preserved, provides an excellent opportunity to observe the contents of the ammonoid body chamber because this periostracum is translucent. Here, we report upon three delicate lobsters preserved within a compressed ammonoid specimen of Harpoceras falciferum. We attempt to explain this gregarious behavior. The three lobsters were studied using standard microscopy under low angle light. The lobsters belong to the extinct family of the Eryonidae; further identification was not possible. The organic material of the three small lobsters is preserved more than halfway into the ammonoid body chamber. The lobsters are closely spaced and are positioned with their tails oriented toward each other. The specimens are interpreted to represent corpses rather than molts. The lobsters probably sought shelter in preparation for molting or against predators such as fish that were present in Dotternhausen. Alternatively, the soft tissue of the ammonoid may have been a source of food that attracted the lobsters, or it may have served as a long-term residency for the lobsters (inquilinism). The lobsters represent the oldest known example of gregariousness amongst lobsters and decapods in the fossil record. Gregarious behavior in lobsters, also known for extant lobsters, thus developed earlier in earth's history than previously known. Moreover, this is one of the oldest known examples of decapod crustaceans preserved within cephalopod shells. PMID:22412846

  20. Jurassic hot spring deposits of the Deseado Massif (Patagonia, Argentina): Characteristics and controls on regional distribution

    NASA Astrophysics Data System (ADS)

    Guido, Diego M.; Campbell, Kathleen A.

    2011-06-01

    The Deseado Massif, Santa Cruz Province, Argentinean Patagonia, hosts numerous Middle to Late Jurassic age geothermal and epithermal features represented by siliceous and calcareous chemical precipitates from hot springs (sinters and travertines, respectively), hydrothermal breccias, quartz veins, and widespread hydrothermal silicification. They indicate pauses in explosive volcanic activity, marking the final stages in the evolution of an extensive Jurassic (ca. 178-151 Ma) volcanic complex set in a diffuse extensional back-arc setting heralding the opening of the Atlantic Ocean. Published paleo-hot spring sites for the Deseado Massif, plus additional sites identified during our recent field studies, reveal a total of 23 locations, five of which were studied in detail to determine their geologic and facies associations. They show structural, lithologic, textural and biotic similarities with Miocene to Recent hot spring systems from the Taupo and Coromandel volcanic zones, New Zealand, as well as with modern examples from Yellowstone National Park, U.S.A. These comparisons aid in the definition of facies assemblages for Deseado Massif deposits - proximal, middle apron and distal siliceous sinter and travertine terraces and mounds, with preservation of many types of stromatolitic fabrics - that likely were controlled by formation temperature, pH, hydrodynamics and fluid compositions. Locally the mapped hot spring deposits largely occur in association with reworked volcaniclastic lacustrine and/or fluvial sediments, silicic to intermediate lava domes, and hydrothermal mineralization, all of which are related to local and regional structural lineaments. Moreover, the numerous geothermal and significant epithermal (those with published minable resources) deposits of the Deseado Massif geological province mostly occur in four regional NNW and WNW hydrothermal-structural belts (Northwestern, Northern, Central, and Southern), defined here by alignment of five or more hot spring deposits and confirmed as structurally controlled by aeromagnetic data. The Northern and Northwestern belts, in particular, concentrate most of the geothermal and epithermal occurrences. Hence, Jurassic hydrothermal fluid flow was strongly influenced by the most dominant and long-active geological boundaries in the region, the outer limits of the Deseado Massif 'horst' itself.

  1. Dating Fossil Pollen: A Simulation.

    ERIC Educational Resources Information Center

    Sheridan, Philip

    1992-01-01

    Describes a hands-on simulation in which students determine the age of "fossil" pollen samples based on the pollen types present when examined microscopically. Provides instructions for the preparation of pollen slides. (MDH)

  2. Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis

    NASA Astrophysics Data System (ADS)

    Turner, Christine E.; Peterson, Fred

    2004-05-01

    A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early and Middle Kimmeridgian eolian deposits and Late Kimmeridgian alkaline, saline wetland/lacustrine deposits demonstrate that dryness persisted throughout the Kimmeridgian. Tithonian-age coal reflects lower evaporation rates associated with a slight cooling trend, but not a significant climate change. With a subtropical high over the Paleo-Pacific Ocean and atmospheric circulation generally toward the east, moisture carried by prevailing winds "rained out" progressively eastward, leaving the continental interior—and the Morrison depositional basin—dry. Within the basin, high evaporation rates associated with the southerly paleolatitude and greenhouse effects added to the dryness. Consequently, the two main sources of water—groundwater and surface water—originated outside the basin, through recharge of regional aquifers and streams that originated in the western uplands. Precipitation that fell west of the basin recharged aquifers that underlay the basin and discharged in wetlands and lakes in the distal, low-lying part of the basin. Precipitation west of the basin also fed intermittent and scarce perennial streams that flowed eastward. The streams were probably "losing" streams in their upstream reaches, and contributed to a locally raised water table. Elsewhere in the basin, where the floodplain intersected the water table, small lakes dotted the landscape. Seasonal storms, perhaps in part from the Paleo-Gulf of Mexico, brought some precipitation directly to the basin, although it was also subjected to "rain out" en route. Thus, meteoric input to the basin was appreciably less than groundwater and surface water contributions. The terrestrial Morrison ecosystem, which can be likened to a savannah, expanded with the northward retreat of the Late Jurassic Western Interior Seaway. The ecosystem was a complex mosaic, the components of which shifted through time. Riparian environments probably were the most diverse parts of the ecosystem, where a multi-storeyed canopy supported a diverse fauna, from insects to dinosaurs. Equable conditions also existed in wetlands, lakes, and elsewhere on the floodplain when seasonal rainfall brought an herbaceous groundcover to life. Eolian environments and alkaline, saline wetlands were inhospitable to life. Large herbivorous dinosaurs were adapted to this semi-arid landscape. Their size was an adaptive asset based on considerations of food requirements associated with a low metabolism and was also an advantage for migration during drought. Some of the large sauropods were adapted to browsing the higher vegetation associated with riparian environments; others to grazing the herbaceous groundcover on the floodplain and charophytes in the wetlands. The extensive distal wetlands may, in fact, have been refugia for some of these herbivores during the dry season and droughts. Extended periods of drought account for some of the dinosaur death assemblages; yet, the ecosystem could also sustain the most unusual life forms that ever roamed the Earth.

  3. Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem - A synthesis

    USGS Publications Warehouse

    Turner, C.E.; Peterson, F.

    2004-01-01

    A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early and Middle Kimmeridgian eolian deposits and Late Kimmeridgian alkaline, saline wetland/lacustrine deposits demonstrate that dryness persisted throughout the Kimmeridgian. Tithonian-age coal reflects lower evaporation rates associated with a slight cooling trend, but not a significant climate change. With a subtropical high over the Paleo-Pacific Ocean and atmospheric circulation generally toward the east, moisture carried by prevailing winds "rained out" progressively eastward, leaving the continental interior-and the Morrison depositional basin-dry. Within the basin, high evaporation rates associated with the southerly paleolatitude and greenhouse effects added to the dryness. Consequently, the two main sources of water-groundwater and surface water-originated outside the basin, through recharge of regional aquifers and streams that originated in the western uplands. Precipitation that fell west of the basin recharged aquifers that underlay the basin and discharged in wetlands and lakes in the distal, low-lying part of the basin. Precipitation west of the basin also fed intermittent and scarce perennial streams that flowed eastward. The streams were probably "losing" streams in their upstream reaches, and contributed to a locally raised water table. Elsewhere in the basin, where the floodplain intersected the water table, small lakes dotted the landscape. Seasonal storms, perhaps in part from the Paleo-Gulf of Mexico, brought some precipitation directly to the basin, although it was also subjected to "rain out" en route. Thus, meteoric input to the basin was appreciably less than groundwater and surface water contributions. The terrestrial Morrison ecosystem, which can be likened to a savannah, expanded with the northward retreat of the Late Jurassic Western Interior Seaway. The ecosystem was a complex mosaic, the components of which shifted through time. Riparian environments probably were the most diverse parts of the ecosystem, where a multi-storeyed canopy supported a diverse fauna, from insects to dinosaurs. Equable conditions also existed in wetlands, lakes, and elsewhere on the floodplain when seasonal rainfall brought an herbaceous groundcover to life. Eolian environments and alkaline, saline wetlands were inhospitable to life.Large herbivorous dinosaurs were adapted to this semi-arid landscape. Their size was an adaptive asset based on considerations of food requirements associated with a low metabolism and was also an advantage for migration during drought. Some of the large sauropods were adapted to browsing the higher vegetation associated with riparian environments; others to grazing the herbaceous groundcover on the floodplain and charophytes in the wetlands. The extensive distal wetlands may, in fact, have been refugia for some of these herbivores during the dry season and droughts. Extended periods of drought account for some of the dinosaur death assemblages; yet, the ecosystem could also sustain the most unusual life forms that ever roamed the Earth. ?? 2004 Elsevier B.V. All rights reserved.

  4. Apatite Fission-Track Analysis of the Middle Jurassic Todos Santos Formation from Chiapas, Mexico.

    NASA Astrophysics Data System (ADS)

    Abdullin, Fanis; Solé, Jesús; Shchepetilnikova, Valentina; Solari, Luigi; Ortega-Obregón, Carlos

    2014-05-01

    The Sierra de Chiapas (SCH), located in the south of Mexico, is a complex geological province that can be divided on four different lithological or tectonic areas: (1) the Chiapas Massif Complex (CMC); (2) the Central Depression; (3) the Strike-slip Fault Province, and (4) the Chiapas Fold-and-thrust Belt. The CMC mostly consists of Permian granitoids and meta-granitoids, and represents the basement of the SCH. During the Jurassic period red beds and salt were deposited on this territory, related to the main pulse of rifting and opening of the Gulf of Mexico. Most of the Cretaceous stratigraphy contains limestones and dolomites deposited on a marine platform setting during the postrift stage of the Gulf of Mexico rift. During the Cenozoic Era took place the major clastic sedimentation along the SCH. According the published low-temperature geochronology data (Witt et al., 2012), SCH has three main phases of thermo-tectonic history: (1) slow exhumation between 35 and 25 Ma, that affected mainly the basement (CMC) and is probably related to the migration of the Chortís block; (2) fast exhumation during the Middle-Late Miocene caused by strike-slip deformation that affects almost all Chiapas territory; (3) period of rapid cooling from 6 to 5 Ma, that affects the Chiapas Fold-and-thrust Belt, coincident with the landward migration of the Caribbean-North America plate boundaries. The two last events were the most significant on the formation of the present-day topography of the SCH. However, the stratigraphy of the SCH shows traces of the existence of earlier tectonic events. This study presents preliminary results of apatite fission-track (AFT) dating of sandstones from the Todos Santos Formation (Middle Jurassic). The analyses are performed with in situ uranium determination using LA-ICP-MS (e.g., Hasebe et al., 2004). The AFT data indicate that this Formation has suffered high-grade diagenesis (probably over 150 ºC) and the obtained cooling ages, about 70-60 Ma, correspond to a Late Cretaceous event. This tectonic event is contemporaneous with a startup of the Laramide Orogeny occurred in North America. The constructed time-temperature paths show the rapid cooling during the Middle-Late Miocene (15-10 Ma), like other published data. References: Hasebe et al. (2004) Chemical Geology, 207, 135-145 Witt et al. (2012) Tectonics, 31, TC6001, doi:10.1029/2012TC003141

  5. Pre-breakup geology of the Gulf of Mexico-Caribbean: Its relation to Triassic and Jurassic rift systems of the region

    SciTech Connect

    Bartok, P. (EGEP Consultores, Caracus (Venezuela))

    1993-02-01

    A review of the pre-breakup geology of west-central Pangea, comprised of northern South America, Gulf of Mexico and West Africa, combined with a study of the Mesozoic rift trends of the region confirms a relation between the rift systems and the underlying older grain of deformation. The pre-breakup analysis focuses attention on the Precambrian, Early Paleozoic and Late Paleozoic tectonic events affecting the region and assumes a Pindell fit. Two Late Precambrian orogenic belts are observed in the west central Pangea. Along the northern South American margin and Yucatan a paleo northeast trending Pan-African aged fold belt is documented. A second system is observed along West Africa extending from the High Atlas to the Mauritanides and Rockelides. During the Late Paleozoic, renewed orogenic activity, associated with the Gondwana/Laurentia suture, affected large segments of west central Pangea. The general trend of the system is northeast-southwest and essentially parallels the Gyayana Shield, West African, and eastern North American cratons. Mesozoic rifting closely followed either the Precambrian trends or the Late Paleozoic orogenic belt. The Triassic component focuses along the western portions of the Gulf of Mexico continuing into eastern Mexico and western South America. The Jurassic rift trend followed along the separation between Yucatan and northern South America. At Lake Maracaibo the Jurassic rift system eventually overlaps the Triassic rifts. The Jurassic rift resulted in the [open quotes]Hispanic Corridor[close quotes] that permitted Tethyan and Pacific marine faunas to mix at a time when the Gulf of Mexico underwent continental sedimentation.

  6. Synchronous wildfire activity rise and mire deforestation at the triassic-jurassic boundary.

    PubMed

    Petersen, Henrik I; Lindström, Sofie

    2012-01-01

    The end-Triassic mass extinction event (?201.4 million years ago) caused major faunal and floral turnovers in both the marine and terrestrial realms. The biotic changes have been attributed to extreme greenhouse warming across the Triassic-Jurassic (T-J) boundary caused by massive release of carbon dioxide and/or methane related to extensive volcanism in the Central Atlantic Magmatic Province (CAMP), resulting in a more humid climate with increased storminess and lightning activity. Lightning strikes are considered the primary source of wildfires, producing charcoal, microscopically recognized as inertinite macerals. The presence of polycyclic aromatic hydrocarbons (PAHs) of pyrolytic origin and allochthonous charcoal in siliciclastic T-J boundary strata has suggested widespread wildfire activity at the time. We have investigated largely autochthonous coal and coaly beds across the T-J boundary in Sweden and Denmark. These beds consist of predominantly organic material from the in situ vegetation in the mires, and as the coaly beds represent a substantial period of time they are excellent environmental archives. We document a remarkable increase in inertinite content in the coal and coaly beds across the T-J boundary. We show estimated burning temperatures derived from inertinite reflectance measurements coupled with palynological data and conclude that pre-boundary late Rhaetian mire wildfires included high-temperature crown fires, whereas latest Rhaetian-Sinemurian mire wildfires were more frequent but dominated by lower temperature surface fires. Our results suggest a major change in the mire ecosystems across the T-J boundary from forested, conifer dominated mires to mires with a predominantly herbaceous and shrubby vegetation. Contrary to the overall regional vegetation for which onset of recovery commenced in the early Hettangian, the sensitive mire ecosystem remained affected during the Hettangian and did not start to recover until around the Hettangian-Sinemurian boundary. Decreasing inertinite content through the Lower Jurassic suggests that fire activity gradually resumed to considerable lower levels. PMID:23077574

  7. Jurassic through Oligocene paleogeography of the Santa Maria basin area, California

    SciTech Connect

    Fritsche, A.E. (California State Univ., Northridge (United States)); Yamashiro, D.A. (Groundwater Technology, Inc., Tempe, AZ (United States))

    1991-02-01

    Compilation from published reports indicates that the paleogeographic history of the Santa Maria basin area of California (west of the Sur-Nacimiento fault and north of the Santa Ynez Fault) began in the Early Jurassic in an area for to the south with the creation of a spreading-center ophiolite sequence. As the ophiolite rocks moved relatively away from the spreading center, they were covered by Lower Jurassic through Lower Cretaceous basin plain and prograding outer continental margin deposits. During this time, right-lateral movement along faults that were located to the east was transporting the area relatively northward toward its present location. A mild tectonic event in the middle of the Cretaceous caused formation of a parallel unconformity. Renewed subsidence in the Late Cretaceous brought deposition in trench, slope, sandy submarine fan, shelf, and ultimately in the eastern part of the area, delta and fluvial environments. During the ensuing Laramide orogeny, significant deformation raised the entire area above sea level and erosion created a major angular unconformity. During the early Tertiary, most of the Santa Maria basin area remained elevated as a forearc highland. The present-day east-west-trending area south of the Santa Ynez River fault was at the time oriented north-south. During the Eocene, this portion of the area was submerged and became a forearc basin that was located to the east of the forearc ridge that served as a source of sediment. The basin filled through the Eocene and Oligocene with submarine fan, sloe, shelf, coastal, and finally fluvial deposits. In the medial Miocene, these forearc basin rocks were rotated clockwise into their present position along the southern margin of the basin and the upper Tertiary Santa maria basin was formed.

  8. Cold episodes inside Jurassic times: is the carbonate deposition engine controlling atmospheric CO2?

    NASA Astrophysics Data System (ADS)

    Godderis, Y.; Donnadieu, Y.; Dromart, G.; Pierrehumbert, R. T.

    2006-12-01

    The calculated history of Phanerozoic CO2 suggests a rather constantly warm Mesozoic (Berner and Kothavala, 2001). This result is in disagreement with recent findings suggesting the occurrence of short (several 105 years) glacial episodes during the Jurassic, particularly at the Middle-Late Jurassic transition (Dromart et al., 2003). This climatic event is linked to perturbations in the carbonate production, with a general contraction of the latitudinal extent of carbonate platform occurrence. By the end of the early Callovian, the carbonate production on platform located in the mid-latitudes (above 25° lat, W-Europe and E-Africa) was completely shutdown, and transferred to the equatorial area (e.g. Arabian Peninsula). Finally, low latitude platform also endure a short shut down of production in the latest Callovian. The ultimate causes of these perturbations in the carbonate production are not known, but might be related to regional processes. In this contribution, we explore their impact on the global carbon cycle, atmospheric CO2 and climate. The numerical model used is the GEOCLIM model (Donnadieu et al., 2006), which couples a global geochemical cycle model to the climatic general circulation model FOAM. The model is forced with geological evidences of the timing of the evolution of carbonate production in the mid and low latitudes. We found that, when carbonate production is progressively reduced in the mid-latitudes, and finally transiently shut down everywhere, global climate gets transiently cooler by more than 5°C, coevally with an atmospheric CO2 drop by 600 ppmv (from 900 ppmv in the early Callovian, down to 300 ppmv at the Callovian-Oxfordian boundary). This pronounced glacial episode lasts about 500 kyr, followed by a rapid climatic recovery. Perturbations in the carbonate production might thus result in huge climatic changes in the geological past, at a timescale just below 106 years, explaining rapid glacial episodes.

  9. Synchronous Wildfire Activity Rise and Mire Deforestation at the Triassic–Jurassic Boundary

    PubMed Central

    Petersen, Henrik I.; Lindström, Sofie

    2012-01-01

    The end-Triassic mass extinction event (?201.4 million years ago) caused major faunal and floral turnovers in both the marine and terrestrial realms. The biotic changes have been attributed to extreme greenhouse warming across the Triassic–Jurassic (T–J) boundary caused by massive release of carbon dioxide and/or methane related to extensive volcanism in the Central Atlantic Magmatic Province (CAMP), resulting in a more humid climate with increased storminess and lightning activity. Lightning strikes are considered the primary source of wildfires, producing charcoal, microscopically recognized as inertinite macerals. The presence of polycyclic aromatic hydrocarbons (PAHs) of pyrolytic origin and allochthonous charcoal in siliciclastic T–J boundary strata has suggested widespread wildfire activity at the time. We have investigated largely autochthonous coal and coaly beds across the T–J boundary in Sweden and Denmark. These beds consist of predominantly organic material from the in situ vegetation in the mires, and as the coaly beds represent a substantial period of time they are excellent environmental archives. We document a remarkable increase in inertinite content in the coal and coaly beds across the T–J boundary. We show estimated burning temperatures derived from inertinite reflectance measurements coupled with palynological data and conclude that pre-boundary late Rhaetian mire wildfires included high-temperature crown fires, whereas latest Rhaetian–Sinemurian mire wildfires were more frequent but dominated by lower temperature surface fires. Our results suggest a major change in the mire ecosystems across the T–J boundary from forested, conifer dominated mires to mires with a predominantly herbaceous and shrubby vegetation. Contrary to the overall regional vegetation for which onset of recovery commenced in the early Hettangian, the sensitive mire ecosystem remained affected during the Hettangian and did not start to recover until around the Hettangian–Sinemurian boundary. Decreasing inertinite content through the Lower Jurassic suggests that fire activity gradually resumed to considerable lower levels. PMID:23077574

  10. Trace fossil evidence from the Adigrat Sandstone for an Ordovician glaciation in Eritrea, NE Africa

    NASA Astrophysics Data System (ADS)

    Kumpulainen, R. A.; Uchman, A.; Woldehaimanot, B.; Kreuser, T.; Ghirmay, S.

    2006-08-01

    Trace fossils are described here from the Adigrat Sandstone formation of hitherto uncertain Palaeozoic-Mesozoic age in south-central Eritrea. The formation is subdivided into a lower unit, the Adi MaEkheno Member, and an upper informal unit, Member 2. The formation was deposited on the locally mudcracked top of the glacigenic Edaga Arbi Beds, suggesting that these two rock units were formed in a very short time interval. The Adi MaEkheno Member and the lower part of Member 2 contain trace fossils Arthrophycus alleghaniensis (Harlan), Arthrophycus ?brongniartii (Harlan), Didymaulichnus lyelli (Rouault), Palaeophycus tubularis Hall, Taenidium isp., thin winding ridges, winding ridges and furrows, simple cylinders, and 'stellate' forms. A. alleghaniensis is distinctively of Ordovician-Silurian (?Early Devonian) age. The trace fossil association belongs to the Cruziana ichnofacies that indicates a shallow marine environment between the normal and storm wave bases. The trace fossil data and stratigraphic relationships indicate that the Adigrat Sandstone formation and the Edaga Arbi Beds in Eritrea are Ordovician-Silurian in age. The Edaga Arbi Beds are correlated with other Upper Ordovician (Hirnantian) glacial units in northern Africa and the Arabian Peninsula, lending these beds the status of a marker unit in the Lower Palaeozoic stratigraphy of the Horn of Africa. The Jurassic "Adigrat Sandstone" in central-west and eastern Ethiopia cannot be correlated with the Adigrat Sandstone formation in its type area and in Eritrea.

  11. Applications of fossil resin studies to an understanding of depositional and paleoenvironments

    SciTech Connect

    Bellis, D.; Wolberg, D.L. (New Mexico Bureau of Mines and Mineral Resources, Socorro (USA))

    1989-09-01

    Fossil resins are polymerized terpene (isoprenoid) acids. Because of their complexity and resulting variability, isoprenoids have been useful for their information content and geochemical signatures. Fossil resin occurs throughout a 304-ft continuous core and correlated outcrops from the Late Cretaceous Fruitland Formation in the Fossil Forest study area, San Juan basin, New Mexico, in associated with coal, sandstone, shale, and petrified wood. Fourier transformation infrared (FTIR) spectra of resin from throughout the sequence reveal oxidative and chemical variation. FTIR spectra of resin incorporated in petrified wood differ from those of resin exposed to the paleoatmosphere in the same individual tree. This study was initiated to complement previous studies related to analyses of fluid inclusions in fossil resin and to elucidate reactions between the resin matrix and possible atmospheric inclusions. It was done in conjunction with extensive trace-element, palynological, and mineralogical analyses. Understanding the biogeochemistry of fossil resin may elucidate the origin, diagenesis, and depositional environment of smaller concentrations of isoprenoids.

  12. Technology Treaties and Fossil-Fuels Extraction

    Microsoft Academic Search

    Jon Strand

    2007-01-01

    We consider some unintended effects of a technology treaty to increase the (stochastic) possibility of developing an energy alternative to fossil fuels which, when available, makes fossil fuels redundant. One implication of such a treaty is to increase the incentives for fossil-fuels producers to extract fossil fuels existing in given quantity more rapidly, under competition when the equilibrium price path

  13. The avian fossil record in Insular Southeast Asia and its implications for avian biogeography and palaeoecology

    PubMed Central

    2014-01-01

    Excavations and studies of existing collections during the last decades have significantly increased the abundance as well as the diversity of the avian fossil record for Insular Southeast Asia. The avian fossil record covers the Eocene through the Holocene, with the majority of bird fossils Pleistocene in age. Fossil bird skeletal remains represent at least 63 species in 54 genera and 27 families, and two ichnospecies are represented by fossil footprints. Birds of prey, owls and swiftlets are common elements. Extinctions seem to have been few, suggesting continuity of avian lineages since at least the Late Pleistocene, although some shifts in species ranges have occurred in response to climatic change. Similarities between the Late Pleistocene avifaunas of Flores and Java suggest a dispersal route across southern Sundaland. Late Pleistocene assemblages of Niah Cave (Borneo) and Liang Bua (Flores) support the rainforest refugium hypothesis in Southeast Asia as they indicate the persistence of forest cover, at least locally, throughout the Late Pleistocene and Holocene. PMID:24688871

  14. Rise and demise of the Bahama-Grand Banks gigaplatform, northern margin of the Jurassic proto-Atlantic seaway

    USGS Publications Warehouse

    Poag, C. Wylie

    1991-01-01

    An extinct, > 5000-km-long Jurassic carbonate platform and barrier reef system lies buried beneath the Atlantic continental shelf and slope of the United States. A revised stratigraphic framework, a series of regional isopach maps, and paleogeographic reconstructions are used to illustrate the 42-m.y. history of this Bahama-Grand Banks gigaplatform from its inception in Aalenian(?) (early Middle Jurassic) time to its demise and burial in Berriasian-Valanginian time (early Early Cretaceous). Aggradation-progradation rates for the gigaplatform are comparable to those of the familiar Capitan shelf margin (Permian) and are closely correlated with volumetric rates of siliciclastic sediment accumulation and depocenter migration. Siliciclastic encroachment behind the carbonate tracts appears to have been an important impetus for shelf-edge progradation. During the Early Cretaceous, sea-level changes combined with eutrophication (due to landward soil development and seaward upwelling) and the presence of cooler upwelled waters along the outer shelf appear to have decimated the carbonate producers from the Carolina Trough to the Grand Banks. This allowed advancing siliciclastic deltas to overrun the shelf edge despite a notable reduction in siliciclastic accumulation rates. However, upwelling did not extend southward to the Blake-Bahama megabank, so platform carbonate production proceeded there well into the Cretaceous. Subsequent stepwise carbonate abatement characterized the Blake Plateau Basin, whereas the Bahamas have maintained production to the present. The demise of carbonate production on the northern segments of the gigaplatform helped to escalate deep-water carbonate deposition in the Early Cretaceous, but the sudden augmentation of deep-water carbonate reservoirs in the Late Jurassic was triggered by other agents, such as global expansion of nannoplankton communities. ?? 1991.

  15. Magnetostratigraphic dating of the proposed Rhaetian GSSP at Steinbergkogel (Upper Triassic, Austria): Implications for the Late Triassic time scale

    E-print Network

    Utrecht, Universiteit

    by cyclostratigraphic control on the marine Pizzo Mondello (Italy) section, where a combination of long period The Late Triassic period is characterized by increasingenvironmental stress that eventually culminated and Rhaetian stages. The GSSP defining the base of the Hettangian (base Jurassic) was formally accepted by ICS

  16. Global biogeography of scaly tree ferns (Cyatheaceae): evidence for Gondwanan

    E-print Network

    . Fossil evidence shows that the lineage originated in the Late Juras- sic period. We reconstructed large Markov chain Monte Carlo framework using beast. Results Cyatheaceae originated in the Late Jurassic

  17. An organic record of terrestrial ecosystem collapse and recovery at the Triassic-Jurassic boundary in East Greenland

    NASA Astrophysics Data System (ADS)

    Williford, Kenneth H.; Grice, Kliti; Holman, Alexander; McElwain, Jennifer C.

    2014-02-01

    Terrestrial ecosystem collapse at the end of the Triassic Period coincided with a major mass extinction in the marine realm and has been linked to increasing atmospheric carbon dioxide, global warming, and fire activity. Extractable hydrocarbons in samples from the fluvial Triassic-Jurassic boundary section at Astartekløft, East Greenland were analyzed to investigate the molecular and isotopic organic record of biotic and environmental change during this event. Carbon isotopic compositions of individual plant wax lipids show a >4‰ negative excursion coinciding with peak extinction and a further decrease of 2‰ coinciding with peak pCO2 as estimated from the stomatal indices of fossil Gingkoales. An increase of ˜30‰ in the hydrogen isotopic compositions of the same plant wax lipids coincides with ecosystem collapse, suggesting that the biotic crisis was accompanied by strong hydrologic change. Concentrations of polycyclic aromatic hydrocarbons related to combustion also increase together with abrupt plant diversity loss and peak with fossil charcoal abundance and maximum plant turnover, supporting the role of fire in terrestrial extinctions. Anomalously high concentrations of a monoaromatic diterpenoid related to gymnosperm resin derivatives (and similar to dehydroabietane) occur uniquely in samples from the boundary bed, indicating that environmental stress factors leading to peak plant extinction stimulated increased resin production, and that plant resin derivatives may be effective biomarkers of terrestrial ecosystem stress.

  18. Fossil Leaves and Fossil Leaf n-Alkanes: Reconstructing the First Closed Canopied Rainforests

    NASA Astrophysics Data System (ADS)

    Graham, H. V.; Freeman, K. H.

    2013-12-01

    Although the age and location is disputed, the rise of the first closed-canopy forest is likely linked with the expansion of angiosperms in the late Cretacous or early Cenozoic. The carbon isotope 'canopy effect' reflects the extent of canopy closure, and is well documented in ?13C values of the leaves and leaf lipids in modern forests. To test the extent of canopy closure among the oldest documented angiosperm tropical forests, we analyzed isotopic characteristics of leaf fossils and leaf waxes from the Guaduas and Cerrejón Formations. The Guaduas Fm. (Maastrichtian) contains some of the earliest angiosperm fossils in the Neotropics, and both leaf morphology and pollen records at this site suggest an open-canopy structure. The Cerrejón Fm. (Paleocene) contains what are believed to be the first recorded fossil leaves from a closed-canopy forest. We analyzed the bulk carbon isotope content (?13Cleaf) of 199 fossil leaves, as well as the n-alkane concentration and chain-length distribution, and ?13C of alkanes (?13Clipid) of 73 fossil leaves and adjacent sediment samples. Fossil leaves are dominated by eudicots and include ten modern plant families (Apocynaceae, Bombaceae, Euphorbaceae, Fabaceae, Lauraceae, Malvaceae, Meliaceae, Menispermaceae, Moraceae, Sapotaceae). We interpreted extent of canopy coverage based on the range of ?13Cleaf values. The narrow range of ?13C values in leaves from the Guaduas Fm (2.7‰) is consistent with an open canopy. A significantly wider range in values (6.3‰) suggests a closed-canopy signature for site 0315 of the Cerrejón Fm,. In contrast, at Site 0318, a lacustrine deposit, leaves had a narrow range (3.3‰) in ?13C values, and this is not consistent with a closed-canopy, but is consistent with leaf assemblages from a forest edge. Leaves that accumulate in lake sediments tend to be biased toward plants living at the lake edge, which do not experience closed-canopy conditions, and do not express the isotopic characteristics associated with canopy effect. A biomass flux-weighted model of alkane chain-length distribution and ?13Cleaf indicate n-alkanes extracted from bulk rock are consistent with inputs integrated over time from plants represented by fossil leaves. In a modern rainforest, we found leaf lipid amounts markedly higher in the shaded and moist understory, consistent with studies that show alkanes proffer fungal protection. Shade tolerance is associated with higher plant orders and, consistent with this, literature data for modern plants from 30 plant orders shows alkane production in asterids and rosids is 2 to 3 times greater than in basal angiosperms or gymnosperms. The lower clades tend to contain greater amounts of terpenoids and novel benzylisoquinoline alkaloids, rather than alkanes. For our three fossil floras, alkane abundance is strongly influenced by depositional setting, with preservation best in the lacustrine setting. Within each site, abundance patterns are potentially influenced by both taxonomic affiliation and by canopy structure as measured by ?13Cleaf values, and such relationships shed light on the combined influences of plant evolution, canopy structure and the function of biochemical resources on the geochemical record of the first rainforests.

  19. Jurassic Magmatism and Tectonics of the North American Cordillera

    NASA Astrophysics Data System (ADS)

    Boettcher, Stefan

    The relationship of Jurassic magmatic arc rocks to the tectonic evolution of the North American Cordilleran continental margin is a principle theme of Geological Society of America Special Paper 299. The volume gives readers a comprehensive view of the early stages of magmatic arc evolution on a continental margin and is a tribute to the contributions of Richard Lee Armstrong, whose pioneering studies provide a framework for current geologic investigations of the North American Cordillera.

  20. Astronomical pacing of methane release in the Early Jurassic period

    Microsoft Academic Search

    David B. Kemp; Angela L. Coe; Anthony S. Cohen; Lorenz Schwark

    2005-01-01

    A pronounced negative carbon-isotope (delta13C) excursion of ~5-70\\/00 (refs 1-7) indicates the occurrence of a significant perturbation to the global carbon cycle during the Early Jurassic period (early Toarcian age, ~183 million years ago). The rapid release of 12C-enriched biogenic methane as a result of continental-shelf methane hydrate dissociation has been put forward as a possible explanation for this observation.

  1. Jurassic sedimentary basins in the Central Asian orogenic belt

    SciTech Connect

    Bebeshev, I.I. [Geological Institute, Moscow (Russian Federation)

    1995-05-01

    The principal stages of development of Jurassic sedimentary basins (from their origin to the end of their existence) in the Central Asian orogenic belt are considered. The interrelations of the basins with the surrounding paleorises are investigated. Paleogeographic maps are compiled representing the evolution of paleolandscapes and revealing their interrelations in space and time for each stage. Areas with the highest prospects for coal are found.

  2. Jurassic and triassic hydrocarbon exploration of southern Florida

    SciTech Connect

    Mitchell-Tapping, H.J. [Retog, Inc., DeSoto, TX (United States)

    1994-12-31

    The Triassic and Jurassic of South Florida have been overlooked as a viable exploration target because of lack of data and plate tectonics application. In Florida {open_quotes}basement{close_quotes} is defined as crystalline, igneous, metamorphic and unmetamorphosed sediments of Paleozoic age. Age-dating of zircons has shown that the Florida lower Paleozoic terrain is not akin to that of North America but is part of the West African Guinean Shield. Pre-Atlantic reconstruction of the Gulf of Mexico in this study suggests that there was a Florida connection to Yucatan-Cuba-Africa during the Triassic. This reconstruction also shows that Jurassic rocks that are well known in the Northern Gulf Coast should have been deposited in similar depositional environments in southern Florida. Deep drilling on the Florida peninsula has confirmed this hypothesis. By using plate tectonic reconstruction based on the rifting of the North Atlantic Ocean and evidence from petrology of basement samples from deep wells, together with petrographic analyses of Jurassic sedimentary rocks, a Smackover-equivalent exploration play can be developed. Petrographic and petrophysical analysis of wells that have encountered Jurassic marine shales, anhydrite, dolomite, carbonate, and clastic sedimentary rocks has determined that they were deposited in shallow-water subtidal to supratidal environments. Excellent gas shows, oil stain in pores, and high TOC values in marine shales indicate that there are accumulations of hydrocarbon present. Application of analogous Gulf Coast Smackover stratigraphic models to this area, based on petrology and hydrogeology, should reduce risk and help define productive oil and gas reservoirs.

  3. Origin of crude oil in eastern Gulf Coast: Upper Jurassic, Upper Cretaceous, and lower Tertiary source rocks

    SciTech Connect

    Sassen, R.

    1988-02-01

    Analysis of rock and crude oil samples suggests that three source rocks have given rise to most crude oil in reservoirs of the eastern Gulf Coast. Carbonate source rocks of the Jurassic Smackover Formation are characterized by algal-derived kerogen preserved in an anoxic and hypersaline environment, resulting in crude oils with distinct compositions. Migration commenced during the Cretaceous, explaining the emplacement of Smackover-derived crude oil in Jurassic and in some Cretaceous reservoirs. Upper Cretaceous clastic and carbonate source rocks are also present. Much crude oil in Upper Cretaceous reservoirs has been derived from organic-rich marine shales of the Tuscaloosa Formation. These shales are characterized by algal and higher plant kerogen, resulting in distinct crude oil compositions. Migration commenced during the Tertiary, but was mostly focused to Upper Cretaceous reservoirs. Lower Tertiary shales, including those of the Wilcox Formation, are quite organic-rich and include downdip marine facies characterized by both algal and higher plant kerogen. Crude oils in lower Tertiary reservoirs are dissimilar to crude oils from deeper and older source rocks. Migration from lower Tertiary shales commenced during the late Tertiary and charged Tertiary reservoirs. Although most crude oil in the eastern Gulf Coast has been emplaced by short-range migration, often with a strong vertical component, some long-range lateral migration (> 100 km) has occurred along lower Tertiary sands. The framework of crude oil generation and migration onshore has important implications with respect to origin of crude oil in the Gulf of Mexico.

  4. Tectonic evolution of the Selkirk fan, southeastern Canadian Cordillera: A composite Middle Jurassic-Cretaceous orogenic structure

    NASA Astrophysics Data System (ADS)

    Gibson, H. Daniel; Brown, Richard L.; Carr, Sharon D.

    2008-12-01

    The eastward transition from penetrative ductile deformation, metamorphism, and plutonism in the hinterland of the southern Canadian Cordillera to the ``thin-skinned'' deformation of the foreland represents a significant change in tectonic style and process. The transition is also marked by a zone of structural divergence across which SW vergent hinterland structures pass into NE vergent foreland structures. The Selkirk fan within the Selkirk Mountains of the southern Canadian Cordillera is considered a type locality for this zone. This structure trends SE-NW for more than 120 km in greenschist to upper amphibolite facies rocks that have at least three generations of superposed deformation. The kinematic development of the Selkirk fan has been controversial, but its age generally has been inferred to be Middle to Late Jurassic. However, new U-Th-Pb dates obtained by ID-TIMS and SHRIMP indicate a more protracted history. The data demonstrate that a protofan developed in the Middle Jurassic (172-167 Ma) and that the west flank of the fan was exhumed to upper crustal levels at this time. Conversely, the eastern flank was progressively buried to >25 km depth and pervasively overprinted by Cretaceous deformation (104-84 Ma) and Cretaceous-Paleocene metamorphism (144-56 Ma). A new tectonic model is proposed to reconcile the composite nature and protracted development (>100 Ma) of the Selkirk fan within an orogenic system that evolved in response to periods of terrane accretion on the western margin of the North American craton.

  5. Middle Jurassic (Bajocian and Bathonian) dinosaur megatracksites, Bighorn Basin, Wyoming, USA

    USGS Publications Warehouse

    Kvale, E.P.; Johnson, G.D.; Mickelson, D.L.; Keller, K.; Furer, L.; Archer, A.

    2001-01-01

    Two previously unknown rare Middle Jurassic dinosaur megatracksites are reported from the Bighorn Basin of northern Wyoming in the Western Interior of the United States. These trace fossils occur in carbonate units once thought to be totally marine in origin, and constitute the two most extensive Middle Jurassic dinosaur tracksites currently known in North America. The youngest of these occurs primarily along a single horizon at or near the top of the "basal member" of the "lower" Sundance Formation, is mid-Bathonian in age, and dates to ??? 167 ma. This discovery necessitates a major change in the paleogeographic reconstructions for Wyoming for this period. The older tracksites occur at multiple horizons within a 1 m interval in the middle part of the Gypsum Spring Formation. This interval is uppermost Bajocian in age and dates to ??? 170 ma. Terrestrial tracks found, to date, have been all bipedal tridactyl dinosaur prints. At least some of these prints can be attributed to the theropods. Possible swim tracks of bipedal dinosaurs are also present in the Gypsum Spring Formation. Digitigrade prints dominate the Sundance trackways, with both plantigrade and digitigrade prints being preserved in the Gypsum Spring trackways. The Sundance track-bearing surface locally covers 7.5 square kilometers in the vicinity of Shell, Wyoming. Other tracks occur apparently on the same horizon approximately 25 kilometers to the west, north of the town of Greybull. The Gypsum Spring megatracksite is locally preserved across the same 25 kilometer east-west expanse, with the Gypsum Spring megatracksite more extensive in a north-south direction with tracks occurring locally across a 100 kilometer extent. Conservative estimates for the trackway density based on regional mapping in the Sundance tracksite discovery area near Shell suggests that over 150, 000 in situ tracks may be preserved per square kilometer in the Sundance Formation in this area. Comparable estimates have not been made for other areas. Similarities between the two megatracksites include their formation and preservation in upper intertidal to supratidal sediments deposited under at least seasonally arid conditions. Microbial mat growth on the ancient tidal flats apparently initiated the preservation of these prints.

  6. Reevaluation of upper Jurassic Morrison Formation, Western Interior

    SciTech Connect

    Mantzios, C.

    1989-03-01

    Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic features. Similar depositional setting has been observed in the Morrison Formation in the Bighorn basin, Wyoming, where pedogenic features suggest a distal floodplain setting with low-sinuosity channels cutting through. In both localities the dominant clay mineral is illite. The upper Brushy Basin member in the Colorado Plateau is composed mostly of gray and purpose mudstones rich in montmorillonite. Devitrified tuff beds and bentonite occur in certain levels throughout the unit. Pedogenic features are not conspicuously developed. The Lower Cretaceous Clovery Formation in the Bighorn basin, Wyoming, is strikingly similar in terms of lithological aspects. The depositional environment is interpreted in both localities as a playa deposit. A great variety of nodules is present such as silcretes, septaria, and silica-carbonate nodules. Radiometric dating of bentonites in central Utah revealed that the upper Brushy Basin member is Early Cretaceous in age. Field and geochemical data support these conclusions and aid the understanding of the exact nature of the depositional basin, environments, stratigraphy, and paleotectonics of the Upper Jurassic-Lower Cretaceous interval in the Western Interior.

  7. U/Pb zircon and baddeleyite ages for the Palisades and Gettysburg sills of the northeastern United States: Implications for the age of the Triassic/Jurassic boundary

    SciTech Connect

    Dunning, G.R.; Hodych, J.P. (Memorial Univ. of Newfoundland, St. John's (Canada))

    1990-08-01

    Zircons extracted from the Palisades and Gettysburg sills and baddeleyite from the Palisades sill yield consistent U-Pb ages of 201 {plus minus} 1 Ma. These sills are likely related to the lowermost basalt flows of the Late Triassic-Early Jurassic Newark Supergroup rift basins of the eastern margin of North America (because of the geochemical similarity of their high-Ti quartz tholeiites and because drilling suggests that the Palisades sill directly fed some of the lowermost flows). Because the lowermost flows of the Newark Supergroup are paleontologically assigned to the lowermost Hettangian, the 201 {plus minus} 1 Ma age of the sills should be slightly younger than the age of the Triassic/Jurassic boundary. Our data support the age of 204 {plus minus} 4 Ma assigned the Triassic/Jurassic boundary and suggest that recent K-Ar dating for the Hettangian flows of the Newark Supergroup, which yielded an average age of 190 {plus minus} 3 Ma, is about 5% low.

  8. The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquén Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana

    NASA Astrophysics Data System (ADS)

    Leanza, H. A.; Mazzini, A.; Corfu, F.; Llambías, E. J.; Svensen, H.; Planke, S.; Galland, O.

    2013-03-01

    New radiometric U-Pb ages obtained on zircon crystals from Early Jurassic ash layers found within beds of the Chachil Limestone at its type locality in the Chachil depocentre (southern Neuquén Basin) confirm a Pliensbachian age (186.0 ± 0.4 Ma). Additionally, two ash layers found in limestone beds in Chacay Melehue at the Cordillera del Viento depocentre (central Neuquén Basin) gave Early Pliensbachian (185.7 ± 0.4 Ma) and earliest Toarcian (182.3 ± 0.4 Ma) U-Pb zircon ages. Based on these new datings and regional geological observations, we propose that the limestones cropping out at Chacay Melehue are correlatable with the Chachil Limestone. Recent data by other authors from limestones at Serrucho creek in the upper Puesto Araya Formation (Valenciana depocentre, southern Mendoza) reveal ages of 182.16 ± 0.6 Ma. Based on these new evidences, we consider the Chachil Limestone an important Early Jurassic stratigraphic marker, representing an almost instantaneous widespread flooding episode in western Gondwana. The unit marks the initiation in the Neuquén Basin of the Cuyo Group, followed by widespread black shale deposition. Accordingly, these limestones can be regarded as the natural seal of the Late Triassic -earliest Jurassic Precuyano Cycle, which represents the infill of halfgrabens and/or grabens related to a strong extensional regime. Paleontological evidence supports that during Pliensbachian-earliest Toarcian times these limestones were deposited in western Gondwana in marine warm water environments.

  9. Molecules and fossils reveal punctuated diversification in Caribbean “faviid” corals

    PubMed Central

    2012-01-01

    Background Even with well-known sampling biases, the fossil record is key to understanding macro-evolutionary patterns. During the Miocene to Pleistocene in the Caribbean Sea, the fossil record of scleractinian corals shows a remarkable period of rapid diversification followed by massive extinction. Here we combine a time-calibrated molecular phylogeny based on three nuclear introns with an updated fossil stratigraphy to examine patterns of radiation and extinction in Caribbean corals within the traditional family Faviidae. Results Concatenated phylogenetic analysis showed most species of Caribbean faviids were monophyletic, with the exception of two Manicina species. The time-calibrated tree revealed the stem group originated around the closure of the Tethys Sea (17.0?Ma), while the genus Manicina diversified during the Late Miocene (8.20?Ma), when increased sedimentation and productivity may have favored free-living, heterotrophic species. Reef and shallow water specialists, represented by Diploria and Favia, originate at the beginning of the Pliocene (5 – 6?Ma) as the Isthmus of Panama shoaled and regional productivity declined. Conclusions Later origination of the stem group than predicted from the fossil record corroborates the hypothesis of morphological convergence in Diploria and Favia genera. Our data support the rapid evolution of morphological and life-history traits among faviid corals that can be linked to Mio-Pliocene environmental changes. PMID:22831179

  10. Controls on strain localisation in the Middle to Late Jurassic North Sea rift system 

    E-print Network

    Gill, Caroline E

    2005-01-01

    Extensional fault propagation and linkage play an important role in the structural and sedimentological development of rift basins. In this study, use of 85,000km² 3D seismic data provides a new and unique opportunity ...

  11. Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia

    Microsoft Academic Search

    Oliver W. M. Rauhut; Kristian Remes; Regina Fechner; Gerardo Cladera; Pablo Puerta

    2005-01-01

    Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark

  12. Geology Fieldnotes: Fossil Butte National Monument, Wyoming

    NSDL National Science Digital Library

    Fossil Butte National Monument preserves a 50-million year old bed of Eocene limestone that contains one of the richest fossil deposits in the world. Site features include park geology information, photographs of fossils, related links, visitor information, multimedia resources, and resources for teaching geology with National Park examples. The park geology section discusses the Monument's geologic history and fossil beds, focusing on the conditions that created the fossil-rich region and on the history of fossil collection in the area. A map of the Monument is also included.

  13. Fossil mammals and paleoenvironments in the Omo-Turkana Basin.

    PubMed

    Bobe, René

    2011-01-01

    Although best known for its fossil hominins, the Omo-Turkana Basin of Kenya and Ethiopia is the source of one of the best records of vertebrate evolution from the Late Cenozoic of Africa. Located near the heart of the East African Rift Valley, the basin serves as an important frame of reference for the continent. The fossil record from this region plays a key role in our efforts to understand the environmental and ecological context of human evolution in Africa. The Omo-Turkana faunal data shed light on key questions of human evolution: What kinds of environments did early humans inhabit? How did these environments change over time? What is the relationship between faunal change in East Africa and broader patterns of climatic change? PMID:22170694

  14. Evolution and the Fossil Record

    E-print Network

    Kammer, Thomas

    .) · Charles Darwin, 1859: The Origin of Species by Natural Selection. #12;Artificial Selection vs. Natural Anatomy of Fossilized organisms #12;Natural Selection · Natural selection, a creative force, is one Selection: Dog breeds produced by artificial selection #12;Natural Selection: Key Points · 3 facts lead

  15. Biological fossil CO 2 mitigation

    Microsoft Academic Search

    Evan Hughes; John R Benemann

    1997-01-01

    Over ten times more CO2 is fixed by plants into biomass, and annually released by decomposers and food chains, than is emitted to the atmosphere due to the burning of fossil fuels. Human activity is already directly and indirectly affecting almost half of the terrestrial biological C cycle. Management of even a small fraction of the biological C cycle would

  16. Fossil Reptiles of Great Britain

    E-print Network

    Benton, Michael

    Fossil Reptiles of Great Britain M.J. Benton and P.S. Spencer Department of Geology, University CONSERVATION REVIEW SERIES The comparatively small land area of Great Britain contains an unrivalled sequence by generations of leading geologists, thus giving Britain a unique status in the development of the science. Many

  17. Fossil Identification and Classification Lab

    NSDL National Science Digital Library

    Ralph Willoughby

    Students pick, sort, box, and identify fossils (mostly mollusks but also bryozoa, arthropods, cnidaria, and annelids) from richly fossiliferous, clastic marine sediment, compile a faunal list,compare the fauna with modern taxa, and make evaluate a paleogeographic model for the taxa found.

  18. Progress of Fossil Fuel Science

    Microsoft Academic Search

    M. F. Demirbas

    2007-01-01

    Coal is the most abundant and widely distributed fossil fuel. More than 45% of the world's electricity is generated from coal, and it is the major fuel for generating electricity worldwide. The known coal reserves in the world are enough for more than 215 years of consumption, while the known oil reserves are only about 39 times of the world's

  19. Fossil/modern mole phylogeny

    NSDL National Science Digital Library

    This study is introduced at the beginning of class, and runs throughout the quarter. Students are first given a paper describing a morphological phylogeny of modern moles. The first few weeks' labs teach the students basic phylogenetic methods and the aspects of skeletal morphology needed to understand the character descriptions. Students in groups of 2 or 3 are assigned a set of characters from a particular region of the skeleton (i.e. humerus, lower teeth, skull, etc.). Those groups are responsible for learning to distinguish those characters on a representative group of modern specimens (for which the character codings are already available in the paper they have) and then coding those characters for a number of fossil taxa. The fossils are either described in papers posted on the course website or are represented by specimens held in the instructor's research lab. Students are responsible for finding time to come in and work with the specimens. The next to last lab of the quarter is concerned with analyzing data within each group, for the class as a whole, for fossil taxa alone, and for fossil and modern taxa. Students then write up the results of their analyses for their term project due at the end of the quarter.

  20. Synthetic soup ground trace fossils

    NSDL National Science Digital Library

    Clint Cowan

    This is a lab exercise where students make synthetic trace fossils (using fishing lures) that was presented as a scientific study: BIOGENIC SEDIMENTARY STRUCTURES PRODUCED BY WORMS IN SOUPY, SOFT MUDS: OBSERVATIONS FROM THE CHATTANOOGA SHALE (UPPER DEVONIAN) AND EXPERIMENTS, by VADEC LOBZA AND JURGEN SCHIEBER, JOURNAL OF SEDIMENTARY RESEARCH, VOL. 69, NO. 5, SEPTEMBER, 1999, P. 1041â1049

  1. Mitochondrial genomes as living 'fossils'.

    PubMed

    Small, Ian

    2013-01-01

    The huge variation between mitochondrial genomes makes untangling their evolutionary histories difficult. Richardson et al. report on the remarkably unaltered 'fossil' genome of the tulip tree, giving us many clues as to how the mitochondrial genomes of flowering plants have evolved over the last 150 million years, and raising questions about how such extraordinary sequence conservation can be maintained. PMID:23587103

  2. Jurassic-Paleogene intraoceanic magmatic evolution of the Ankara Mélange, north-central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Sarifakioglu, E.; Dilek, Y.; Sevin, M.

    2014-02-01

    Oceanic rocks in the Ankara Mélange along the Izmir-Ankara-Erzincan suture zone (IAESZ) in north-central Anatolia include locally coherent ophiolite complexes (? 179 Ma and ? 80 Ma), seamount or oceanic plateau volcanic units with pelagic and reefal limestones (96.6 ± 1.8 Ma), metamorphic rocks with ages of 256.9 ± 8.0 Ma, 187.4 ± 3.7 Ma, 158.4 ± 4.2 Ma, and 83.5 ± 1.2 Ma indicating northern Tethys during the late Paleozoic through Cretaceous, and subalkaline to alkaline volcanic and plutonic rocks of an island arc origin (? 67-63 Ma). All but the arc rocks occur in a shale-graywacke and/or serpentinite matrix, and are deformed by south-vergent thrust faults and folds that developed in the middle to late Eocene due to continental collisions in the region. Ophiolitic volcanic rocks have mid-ocean ridge (MORB) and island arc tholeiite (IAT) affinities showing moderate to significant large ion lithophile elements (LILE) enrichment and depletion in Nb, Hf, Ti, Y and Yb, which indicate the influence of subduction-derived fluids in their melt evolution. Seamount/oceanic plateau basalts show ocean island basalt (OIB) affinities. The arc-related volcanic rocks, lamprophyric dikes and syenodioritic plutons exhibit high-K shoshonitic to medium- to high-K calc-alkaline compositions with strong enrichment in LILE, rare earth elements (REE) and Pb, and initial ?Nd values between +1.3 and +1.7. Subalkaline arc volcanic units occur in the northern part of the mélange, whereas the younger alkaline volcanic rocks and intrusions (lamprophyre dikes and syenodioritic plutons) in the southern part. The late Permian, Early to Late Jurassic, and Late Cretaceous amphibole-epidote schist, epidote-actinolite, epidote-chlorite and epidote-glaucophane schists represent the metamorphic units formed in a subduction channel in the northern Neotethys. The Middle to Upper Triassic neritic limestones spatially associated with the seamount volcanic rocks indicate that the northern Neotethys was an open ocean with its MORB-type oceanic lithosphere by the early Triassic (or earlier). The latest Cretaceous-early Paleocene island arc volcanic, dike and plutonic rocks with subalkaline to alkaline geochemical affinities represent intraoceanic magmatism that developed on and across the subduction-accretion complex above a N-dipping, southward-rolling subducted lithospheric slab within the northern Neotethys. The Ankara Mélange thus exhibits the record of ? 120-130 million years of oceanic magmatism in geological history of the northern Neotethys.

  3. New species of Late Eocene dermestid beetles (Coleoptera, Dermestidae) from the Rovno and Baltic ambers

    Microsoft Academic Search

    R. D. Zhantiev

    2006-01-01

    Fossil beetles of the family Dermestidae are reviewed. Three new species are described: Dermestes progenitor and Megatoma electra from the Baltic amber and Dermestes vetustus from the Rovno amber (Late Eocene).

  4. Continental deposits, magnetostratigraphy and vertebrate paleontology, late Neogene of Eastern Spain

    Microsoft Academic Search

    N. Opdyke; P. Mein; E. Lindsay; A. Perez-Gonzales; E. Moissenet; V. L. Norton

    1997-01-01

    Eleven sections have been sampled for magnetostratigraphy in the fossil mammal-productive late Neogene basins of eastern Spain. The characteristic direction of magnetization was determined through progressive thermal and alternating field demagnetization. It was possible to correlate the magnetozones from the various sections to the GPTS as well as to the fossil MN zones within the sediment. The MN zone boundaries

  5. Geology, fossil fuel potential and environmental concerns of the Caspian Sea

    NASA Astrophysics Data System (ADS)

    Rabinowitz, P.; Yusifov, M.; Arnoldi, J.

    2003-04-01

    The fossil fuel producing areas of the Caspian region consists primarily of two basins, the Precaspian and South Caspian basins, both containing sediments in excess of 20km. The South Caspian Basin, a remnant of Tethys, was formed commencing in the Early-Middle Jurassic as a result of opening of back-arc basins behind volcanic arcs. The PreCaspian Basin extends onshore onto Kazakhstan and Russia and commenced its complicated geological evolution in the Middle Devonian. These basins are presently producing oil and gas in excess of one million barrels per day and two trillion cubic feet per day, respectively. They contain oil and gas reserves that are comparable to those of most other of the world's fossil fuel producing regions, excluding the Middle East. It is anticipated that within a decade these basins will produce over three million barrels of oil and four trillion cubic feet of gas per day. We review the economic, environmental, and geopolitical concerns with respect to exploration and recovery of the region’s fossil fuels. For one, the presence of mud volcanoes, gas hydrates, and earthquakes are a hazard for installation of oil platforms and other facilities. Pollution, attributed in large part to the fossil fuel industry, has created health and other environmental problems such as mass die-off of the Caspian seal, and in part to the large decrease in sturgeon population. Other important environmental concerns include the relatively rapid changes in sea level and desertification of the surrounding regions. There are also important legal questions with respect to ownership of resources beneath the seafloor. In addition, the transportation routes (pipelines) of fossil fuels that are anticipated to be recovered over the next decades have yet to be fully determined. Despite many of the political uncertainties, significant advances have been made in the short time since the breakup of the Soviet Union fueling optimism for the future of the region.

  6. Post-Middle Oligocene origin of paleomagnetic rotations in Upper Permian to Lower Jurassic rocks from northern and southern Peru

    NASA Astrophysics Data System (ADS)

    Gilder, Stuart; Rousse, Sonia; Farber, Daniel; McNulty, Brendan; Sempere, Thierry; Torres, Victor; Palacios, Oscar

    2003-05-01

    We report paleomagnetic data from 28 sites of Upper Permian to Lower Jurassic strata from northern and southern Peru. In northern Peru (6°S), a stable magnetic component from six Permo-Triassic sites passes fold and reversal tests. The overall mean pole agrees well with Late Permian to Triassic poles from cratonal South America, suggesting this part of Peru has experienced neither significant rotation nor latitudinal transport since the Permo-Triassic. In southern Peru (13 to 16°S), thermal demagnetization isolates stable magnetic components in 16 of 22 Upper Permian to Lower Jurassic sites collected along the transition between the Altiplano and the Eastern Cordillera. These 16 sites are rotated 14 to 147° counterclockwise and pass an inclinations-only fold test. Within the same structural zone, three other Permo-Triassic sites as well as 10 Paleocene sites also show important counterclockwise rotations [Roperch and Carlier, J. Geophys. Res. 97 (1992) 17233-17249; Butler et al., Geology 23 (1995) 799-802]. The large magnitude and exclusively counterclockwise sense of rotation suggest that the tectonic regime included an important sinistral shear component. No correlation exists between rotation amount and rock age, suggesting the rotations are post-Paleocene in age. Because the rotations occur along the fringe of the Eastern Cordillera, they were likely produced during its structural formation, hence from the Late Oligocene to Present. Sinistral shear acting in the northern part of the Bolivian Orocline appears much more pronounced than that north of the Abancay Deflection, which likely arises from differences in convergence obliquity.

  7. Climate change impacts on continental weathering through the Middle Jurassic to Lower Cretaceous of Sverdrup Basin, Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Galloway, Jennifer; Grasby, Stephen; Swindles, Graeme; Dewing, Keith

    2014-05-01

    Jurassic to Cretaceous strata of Sverdrup Basin, Canadian Arctic Archipelago, contain marine and non-marine successions that can be studied to reconstruct ancient paleoclimates and paleoenvironments that are poorly understood in high-latitude regions. We use element geochemistry integrated with palynology to study a continuous Aalenian to Albian-aged succession preserved in the Hoodoo Dome H-37 oil and gas well located on southern Ellef Ringnes Island near the centre of Sverdrup Basin. Cluster analysis (stratigraphically constrained incremental sum of squares; CONISS) is used to delineate four geochemical zones that are broadly coeval with major changes in palyno-assemblages interpreted to reflect changes in regional paleoclimate. Zone 1 (late Aalenian to Bathonian) is characterized by palynomorphs associated with humid and warm climate conditions. The chemical alteration index (CAI) is high in this interval, expected under this a humid and warm climate. A transition to a seasonally arid and warm climate occurred in the Bathonian and persisted until the Kimmeridgian or Valanginian (Zone 2). This interval is characterized by decreased chemical weathering, indicated by a drop in CAI. The onset of Zone 3 (Kimmeridgian or Valanginian to late Barremian or early Aptian) occurs during a transition to humid and cool climate conditions and is associated with a period of regional uplift and rifting. Zone 3 is marked by a substantial and progressive drop in CAI, indicating a transition from a weathering to transport-dominated system, possibly associated with landscape destabilization. Reduced tectonic activity in Zone 4 (early Aptian to early or mid Albian) shows a return to active chemical weathering, possibly associated with landscape stabilization, suggested by a continued increase in pollen from upland coniferous taxa. The geochemical and palynological records of Middle Jurassic to Lower Cretaceous strata of the Hoodoo Dome H-37 oil and gas well show close correlation, indicating long-term linkages of terrestrial plant communities and weathering processes.

  8. Geochemical evolution of Jurassic diorites from the Bristol Lake region, California, USA, and the role of assimilation

    USGS Publications Warehouse

    Young, E.D.; Wooden, J.L.; Shieh, Y.-N.; Farber, D.

    1992-01-01

    Late Jurassic dioritic plutons from the Bristol Lake region of the eastern Mojave Desert share several geochemical attributes with high-alumina basalts, continental hawaiite basalts, and high-K are andesites including: high K2O concentrations; high Al2O3 (16-19 weight %); elevated Zr/TiO2; LREE (light-rare-earth-element) enrichment (La/YbCN=6.3-13.3); and high Nb. Pearce element ratio analysis supported by petrographic relations demonstrates that P, Hf, and Zr were conserved during differentiation. Abundances of conserved elements suggest that dioritic plutons from neighboring ranges were derived from similar parental melts. In the most voluminous suite, correlated variations in elemental concentrations and (87Sr/86Sr)i indicate differentiation by fractional crystallization of hornblende and plagioclase combined with assimilation of a component characterized by abundant radiogenic Sr. Levenberg-Marquardt and Monte Carlo techniques were used to obtain optimal solutions to non-linear inverse models for fractional crystallization-assimilation processes. Results show that the assimilated material was chemically analogous to lower crustal mafic granulites and that the mass ratio of contaminant to parental magma was on the order of 0.1. Lack of enrichment in 18O with differentiation is consistent with the model results. Elemental concentrations and O, Sr, and Nd isotopic data point to a hydrous REE-enriched subcontinental lithospheric source similar to that which produced some Cenozoic continental hawaiites from the southern Cordillera. Isotopic compositions of associated granitoids suggest that partial melting of this subcontinental lithosphere may have been an important process in the development of the Late Jurassic plutonic arc of the eastern Mojave Desert. ?? 1992 Springer-Verlag.

  9. Fossil biotas from the Okanagan Highlands, southern British Columbia and northeastern Washington State: climates and ecosystems across an Eocene landscape1

    Microsoft Academic Search

    David R. Greenwood; S. Bruce Archibald; Rolf W. Mathewes; Patrick T. Moss

    The late Early to early Middle Eocene Okanagan Highlands fossil sites, spanning 1000 km north-south (northeastern Washington State, southern British Columbia) provide an opportunity to reconstruct biotic communities across a broad upland landscape during the warmest part of the Cenozoic. Plant taxa from these fossil sites are charac- teristic of the modern eastern North American deciduous forest zone, principally the

  10. New fossil dermestid beetles (Coleoptera: Dermestidae) from the Baltic amber - III

    Microsoft Academic Search

    Jakub PROKOP; Andreas HERRMANN

    2006-01-01

    New representatives of dermestid beetles are described from the Late Eocene to Early Oligocene inclusions of the Baltic amber, i. e. Anthrenus (Nathrenus) kerneggeri sp. nov., Attagenus balticus sp. nov., A. obesus sp. nov., Evorinea amberica sp. nov. and Phradonoma ambericum sp. nov. Taxonomy, new species, description, fossil, Coleoptera, Dermestidae, Tertiary, Eocene, Oligocene, Baltic amber

  11. Hunting Invertebrate Fossils in the Classroom

    NSDL National Science Digital Library

    Jon Garbisch

    This activity is designed to provide a general knowledge about paleontology and its intimate relationship to sedimentary geology. It will introduce the student to fossils with an emphasis on the invertebrate phyla. As a result of this activity students will acquire a general knowledge of fossils and paleontology, be able to identify the major invertebrate groups commonly found in the fossil record, and learn how fossils tell us about the history of the earth.

  12. A new Bathonian (Middle Jurassic) microvertebrate site, within the Chipping Norton Limestone Formation at Hornsleasow Quarry,

    E-print Network

    Benton, Michael

    A new Bathonian (Middle Jurassic) microvertebrate site, within the Chipping Norton Limestone. & DARTNALL, D. L. 1992. A new Bathonian (Middle Jurassic) microvertebrate site within the Chipping Norton the palaeokarst and overlying soils (with their indigenous flora and fauna) suggest a period of emergence

  13. Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation in the Fundy basin

    E-print Network

    Olsen, Paul E.

    Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation] characterized the Triassic as perhaps the most arid period of the Phanerozoic, citing evidence for widespread,5] and the apparent expan- sion of deserts in the Triassic and Early Jurassic to an extent not since repeated [6

  14. NEW INFORMATION ON SEGISAURUS HALLI, A SMALL THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ARIZONA

    E-print Network

    Hutchinson, John

    NEW INFORMATION ON SEGISAURUS HALLI, A SMALL THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ARIZONA, a small Early Jurassic dinosaur and the only theropod known from the Navajo Sandstone. Our study unknown in dinosaurs), seemingly solid centra and limb bones (atypical for theropods), and accessory

  15. A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom

    E-print Network

    Cambridge, University of

    A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom ROGER dinosaur from the Middle Jurassic of Warwickshire, United Kingdom. Acta Palaeontologica Polonica 55 (1): 35-bodied theropod dinosaur, distinct from the contemporaneous Megalosaurus bucklandii. Cruxicheiros newmanorum gen

  16. The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye

    E-print Network

    Benton, Michael

    The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye M. J right tibia of a carnivorous dinosaur is reported from the Lower Jurassic Broadford Beds Formation characteristic features of the ceratosaur theropods, a group of medium-sized predatory dinosaurs that were

  17. Paleogeographic evidence on the Jurassic tectonic history of the Pontides: new paleomagnetic data from the Sakarya continent and Eastern Pontides

    Microsoft Academic Search

    Mualla Cengiz Çinku

    2011-01-01

    The Jurassic paleogeographic position of the Pontides is not well studied because of insufficient paleomagnetic data. For this reason, a paleomagnetic study was carried out in order to constrain the paleolatitudinal drift of the Turkish blocks during the Jurassic period. A total of 32 sites were sampled from volcanic and volcanoclastic rocks of the Lower\\/Middle Jurassic Kelkit formation (Eastern Pontides),

  18. Paleogeographic evidence on the Jurassic tectonic history of the Pontides: new paleomagnetic data from the Sakarya continent and Eastern Pontides

    Microsoft Academic Search

    Mualla Cengiz Cinku

    2010-01-01

    The Jurassic paleogeographic position of the Pontides is not well studied because of insufficient paleomagnetic data. For this reason, a paleomagnetic study was carried out in order to constrain the paleolatitudinal drift of the Turkish blocks during the Jurassic period. A total of 32 sites were sampled from volcanic and volcanoclastic rocks of the Lower\\/Middle Jurassic Kelkit formation (Eastern Pontides),

  19. Lake-mire deposition, earthquakes and wildfires along a basin margin fault; Rønne Graben, Middle Jurassic, Denmark

    Microsoft Academic Search

    Lars Henrik Nielsen; Henrik I. Petersen; Karen Dybkjær; Finn Surlyk

    2010-01-01

    Regional uplift of structural highs took place in the greater North Sea region in early Middle Jurassic times, resulting in a change from marine shelf deposition in the Early Jurassic to widespread emergence, erosion and localized deposition in grabens. The Middle Jurassic Bagå Formation exposed on the island of Bornholm in the Baltic Sea was deposited in the Rønne Graben,

  20. First occurrence of Brachiosaurus (Dinosauria: Sauropoda) from Brachiosaurus (Dinosauria: Sauropoda) from Brachiosaurus the Upper Jurassic Morrison Formation of Oklahoma

    Microsoft Academic Search

    MATTHEW F. BONNAN; MATHEW J. WEDEL

    The giant sauropod Brachiosaurus is one of the rarest sauropods from the Upper Jurassic of North America. The Brachiosaurus is one of the rarest sauropods from the Upper Jurassic of North America. The Brachiosaurus genus has previously been reported from Colorado, Utah, and Wyoming. OMNH 01138 is a sauropod metacarpal of unusual proportions from the Upper Jurassic Morrison Formation of

  1. Scleractinian Fossil Corals as Archives of Seawater ?26Mg

    NASA Astrophysics Data System (ADS)

    Gothmann, A. O.; Higgins, J. A.; Adkins, J. F.; Stolarski, J.; Bender, M. L.

    2014-12-01

    The recovery of environmental signatures from coral skeletons is often made difficult by 'vital effects', which cause skeletal chemistry to deviate from the expected composition of aragonite in equilibrium with seawater. Recent studies show that Mg isotopes in scleractinian corals are subject to vital effects, which appear as a departure of the ?26Mg coral temperature dependence from that of inorganic aragonite [1]. However, different from the case for Mg/Ca or ?44Ca in coral, the magnitude of the observed Mg-isotope vital effect is small (on the order of 0.1 ‰ or less). In addition, measurements of different species of modern coral show similar fractionations, suggesting that coral ?26Mg is not species dependent [2]. Together, these observations indicate that corals should faithfully record the seawater Mg-isotope composition, and that vital effects will not bias reconstructions. We measured Mg isotopes in a set of extremely well-preserved fossil scleractinian corals, ranging in age from Jurassic through Recent, to reconstruct past seawater ?26Mg. Well-preserved fossil corals of similar age show a range in ?26Mg of ~0.2 ‰, pointing to the presence of vital effects. However, our results show little variability in the ?26Mg of fossil corals across different geologic ages, suggesting that seawater ?26Mg has remained relatively constant throughout the Cenozoic and Mesozoic. This pattern has implications for our understanding of the mechanisms driving secular variations in seawater Mg/Ca. In particular, our data imply that dolomitization rates have not changed enough during the Mesozoic and Cenozoic to account for secular variations in seawater Mg/Ca. Our coral ?26Mg record agrees with a Cenozoic record from bulk foraminifera, further supporting the faithfulness of the coral archive. However, both of these records disagree with a third Cenozoic Mg-isotope record, derived from species-specific planktic forams [3]. [1] Saenger, C. et al. (2014) Chem. Geol. 360-361, 105-117. [2] Wombacher, F. et al. (2011) Geochim. Cosmochim. Acta 75, 5797-5818. [3] Pogge von Strandmann, P.A.E. et al. (2014) Biogeosciences Discuss. 11, 7451-7484.

  2. Book reviews Just looking at fossils

    E-print Network

    Tullberg, Birgitta

    Book reviews Just looking at fossils A review by F. Boero Evolutionary Patterns. Growth, Form and Tempo in the Fossil Record. J. B. Jackson, S. Lidgard, F. McKinney (Eds), 2001. University of Chicago on human evolution based on fossils is one example of this pattern. There are groups of organisms, however

  3. Fossil: A Robust Relational Learner Johannes Furnkranz

    E-print Network

    Fürnkranz, Johannes

    Fossil: A Robust Relational Learner Johannes F¨urnkranz juffi@ai.univie.ac.at Austrian Research in this paper describes Fossil, an ILP system that uses a search heuristic based on statistical correlation, Fossil's stopping criterion depends on a search heuristic that estimates the utility of literals

  4. Using extant morphological variation to understand fossil

    E-print Network

    Ackermann, Rebecca Rogers

    Using extant morphological variation to understand fossil relationships: a cautionary tale Rebecca of insights that are pertinent to how we evaluate relationships among our fossil human ancestors. Here I summarize four such insights. I then use a fossil hominid example to illustrate how our understanding

  5. Major Radiations in the Evolution of Caviid Rodents: Reconciling Fossils, Ghost Lineages, and Relaxed Molecular Clocks

    PubMed Central

    Pérez, María Encarnación; Pol, Diego

    2012-01-01

    Background Caviidae is a diverse group of caviomorph rodents that is broadly distributed in South America and is divided into three highly divergent extant lineages: Caviinae (cavies), Dolichotinae (maras), and Hydrochoerinae (capybaras). The fossil record of Caviidae is only abundant and diverse since the late Miocene. Caviids belongs to Cavioidea sensu stricto (Cavioidea s.s.) that also includes a diverse assemblage of extinct taxa recorded from the late Oligocene to the middle Miocene of South America (“eocardiids”). Results A phylogenetic analysis combining morphological and molecular data is presented here, evaluating the time of diversification of selected nodes based on the calibration of phylogenetic trees with fossil taxa and the use of relaxed molecular clocks. This analysis reveals three major phases of diversification in the evolutionary history of Cavioidea s.s. The first two phases involve two successive radiations of extinct lineages that occurred during the late Oligocene and the early Miocene. The third phase consists of the diversification of Caviidae. The initial split of caviids is dated as middle Miocene by the fossil record. This date falls within the 95% higher probability distribution estimated by the relaxed Bayesian molecular clock, although the mean age estimate ages are 3.5 to 7 Myr older. The initial split of caviids is followed by an obscure period of poor fossil record (refered here as the Mayoan gap) and then by the appearance of highly differentiated modern lineages of caviids, which evidentially occurred at the late Miocene as indicated by both the fossil record and molecular clock estimates. Conclusions The integrated approach used here allowed us identifying the agreements and discrepancies of the fossil record and molecular clock estimates on the timing of the major events in cavioid evolution, revealing evolutionary patterns that would not have been possible to gather using only molecular or paleontological data alone. PMID:23144757

  6. The conservation and use of fossil vertebrate sites: British fossil reptile sites

    E-print Network

    Benton, Michael

    The conservation and use of fossil vertebrate sites: British fossil reptile sites Michael J. Benton and William A. Wimbledon BENTON. M. J. & W. A. WIMBLEDON. 19R5. The conservation and use of fossil vertebrate sites: British fossil reptile sites. Proc. Geol. Ass., 96 (I). 1-0. Over a thousand sites in Britain

  7. Fossil groups of galaxies: Are they groups? Are they fossils?

    NASA Astrophysics Data System (ADS)

    Dupke, Renato de Alencar; Miller, Eric; de Oliveira, Claudia Mendes; Sodre, Laerte; Rykoff, Eli; de Oliveira, Raimundo Lopes; Proctor, Rob

    2010-11-01

    Fossil groups present a puzzle to current theories of structure formation. Despite the low number of bright galaxies, their high velocity dispersions and high TX indicate cluster-like potential wells. Measured concentration parameters seem very high indicating early formation epochs in contradiction with the observed lack of large and well defined cooling cores. There are very few fossil groups with good quality X-ray data and their idiosyncrasies may enhance these apparent contradictions. The standard explanation for their formation suggests that bright galaxies within half the virial radii of these systems were wiped out by cannibalism forming the central galaxy. Since dry mergers, typically invoked to explain the formation of the central galaxies, are not expected to change the IGM energetics significantly, thus not preventing the formation of cooling cores, we investigate the scenario where recent gaseous (wet) mergers formed the central galaxy injecting energy and changing the chemistry of the IGM in fossil groups. We show a test for this scenario using fossil groups with enough X-ray flux in the Chandra X-ray Observatory archive by looking at individual metal abundance ratio distributions near the core. Secondary SN II powered winds would tend to erase the dominance of SN IA ejecta in the core of these systems and would help to erase previously existing cold cores. Strong SN II-powered galactic winds resulting from galaxy merging would be trapped by their deep potential wells reducing the central enhancement of SN Ia/SN II iron mass fraction ratio. The results indicate that there is a decrement in the ratio of SN Ia to SN II iron mass fraction in the central regions of the systems analyzed, varying from 99±1% in the outer regions to 85±2% within the cooling radius (Figure 1) and would inject enough energy into the IGM preventing central gas cooling. The results are consistent with a scenario of later formation epoch for fossil groups, as they are defined, when compared to galaxy clusters and normal groups.

  8. INSECT TRACE FOSSILS ON DINOSAUR BONES FROM THE UPPER JURASSIC MORRISON FORMATION, NORTHEASTERN WYOMING, AND THEIR USE IN VERTEBRATE TAPHONOMY

    E-print Network

    Bader, Kenneth Stephen

    2008-08-21

    relatively complete skeleton and the right manus and left pes of a large brachiosaur KUVP 129724 ?Bigfoot? CU Skeleton (2002) BIOPSI ?Big Hand? Dinosauria: Sauropoda Unidentified Diplodocid, possibly Barosaurus or Diplodocus Less than 30% of a... 129713); Nic Mik, a juvenile Camarasaurus (KUVP 129714); and a hypsilophodont, possibly Othnielia (KUVP 129715). Another adult Camarasaurus, Annabelle (KUVP 129716); a small diplodocid, Elmo (KUVP 129717); the left pes of a large brachiosaur, Bigfoot...

  9. Inter-layered clay stacks in Jurassic shales

    NASA Technical Reports Server (NTRS)

    Pye, K.; Krinsley, D. H.

    1983-01-01

    Scanning electron microscopy in the backscattered electron mode is used together with energy-dispersive X-ray microanalysis to show that Lower Jurassic shales from the North Sea Basin contain large numbers of clay mineral stacks up to 150 microns in size. Polished shale sections are examined to determine the size, shape orientation, textural relationships, and internal compositional variations of the clays. Preliminary evidence that the clay stacks are authigenic, and may have formed at shallow burial depths during early diagenesis, is presented.

  10. Is Myanmar jadeitite of Jurassic age? A result from incompletely recrystallized inherited zircon

    NASA Astrophysics Data System (ADS)

    Yui, Tzen-Fu; Fukoyama, Mayuko; Iizuka, Yoshiyuki; Wu, Chao-Ming; Wu, Tsai-Way; Liou, J. G.; Grove, Marty

    2013-02-01

    Zircons from two Myanmar jadeitite samples were separated for texture, mineral inclusion, U-Pb dating and trace element composition analyses. Three types of zircons, with respect to U-Pb isotope system, were recognized. Type I zircons are inherited ones, yielding an igneous protolith age of 160 ± 1 Ma; Type II zircons are metasomatic/hydrothermal ones, giving a (minimum) jadeitite formation age of 77 ± 3 Ma; and Type III zircons are incompletely recrystallized ones, with non-coherent and geologically meaningless ages from 153 to 105 Ma. These Myanmar jadeitites would therefore have formed through whole-sale metasomatic replacement processes. Compared with Type I zircons, Type II zircons show typical metasomatic/hydrothermal geochemical signatures, with low Th/U ratio (< 0.1), small Ce anomaly (Ce/Ce* = < 5) and low ?REE content (40-115 ppm). Type III zircons, however, commonly have the above geochemical signatures straddle in between Type I and Type II zircons. It is shown that the resetting rates of various trace element compositions and U-Pb isotope system of inherited zircons are not coupled "in phase" in response to zircon recrystallization during jadeitite formation. The observed abnormally low Th/U ratio and small Ce anomaly of some Type I zircons, as well as the lack of negative Eu anomaly of all Type I zircons, should be suspected to be of secondary origin. In extreme cases, incompletely recrystallized zircons may show typical metasomatic/hydrothermal geochemical signatures, but leave U-Pb isotope system partially reset or even largely unchanged. Such zircons easily lead to incorrect age interpretation, and hence erroneous geological implication. The Myanmar jadeitites, based on the present study, might have formed during the Late Cretaceous subduction before the beginning of India-Asia continental collision at Paleocene. Previously proposed Late Jurassic ages for Myanmar jadeitites are suggested as results rooted on data retrieved from incompletely recrystallized inherited zircons.

  11. An explanation for conflicting records of Triassic–Jurassic plant diversity

    PubMed Central

    Mander, Luke; Kürschner, Wolfram M.; McElwain, Jennifer C.

    2010-01-01

    Macrofossils (mostly leaves) and sporomorphs (pollen and spores) preserve conflicting records of plant biodiversity during the end-Permian (P-Tr), Triassic–Jurassic (Tr-J), and end-Cretaceous (K-T) mass extinctions. Estimates of diversity loss based on macrofossils are typically much higher than estimates of diversity loss based on sporomorphs. Macrofossils from the Tr-J of East Greenland indicate that standing species richness declined by as much as 85% in the Late Triassic, whereas sporomorph records from the same region, and from elsewhere in Europe, reveal little evidence of such catastrophic diversity loss. To understand this major discrepancy, we have used a new high-resolution dataset of sporomorph assemblages from Astartekløft, East Greenland, to directly compare the macrofossil and sporomorph records of Tr-J plant biodiversity. Our results show that sporomorph assemblages from the Tr-J boundary interval are 10–12% less taxonomically diverse than sporomorph assemblages from the Late Triassic, and that vegetation composition changed rapidly in the boundary interval as a result of emigration and/or extirpation of taxa rather than immigration and/or origination of taxa. An analysis of the representation of different plant groups in the macrofossil and sporomorph records at Astartekløft reveals that reproductively specialized plants, including cycads, bennettites and the seed-fern Lepidopteris are almost absent from the sporomorph record. These results provide a means of reconciling the macrofossil and sporomorph records of Tr-J vegetation change, and may help to understand vegetation change during the P-Tr and K-T mass extinctions and around the Paleocene–Eocene Thermal Maximum. PMID:20713737

  12. An explanation for conflicting records of Triassic-Jurassic plant diversity.

    PubMed

    Mander, Luke; Kürschner, Wolfram M; McElwain, Jennifer C

    2010-08-31

    Macrofossils (mostly leaves) and sporomorphs (pollen and spores) preserve conflicting records of plant biodiversity during the end-Permian (P-Tr), Triassic-Jurassic (Tr-J), and end-Cretaceous (K-T) mass extinctions. Estimates of diversity loss based on macrofossils are typically much higher than estimates of diversity loss based on sporomorphs. Macrofossils from the Tr-J of East Greenland indicate that standing species richness declined by as much as 85% in the Late Triassic, whereas sporomorph records from the same region, and from elsewhere in Europe, reveal little evidence of such catastrophic diversity loss. To understand this major discrepancy, we have used a new high-resolution dataset of sporomorph assemblages from Astartekløft, East Greenland, to directly compare the macrofossil and sporomorph records of Tr-J plant biodiversity. Our results show that sporomorph assemblages from the Tr-J boundary interval are 10-12% less taxonomically diverse than sporomorph assemblages from the Late Triassic, and that vegetation composition changed rapidly in the boundary interval as a result of emigration and/or extirpation of taxa rather than immigration and/or origination of taxa. An analysis of the representation of different plant groups in the macrofossil and sporomorph records at Astartekløft reveals that reproductively specialized plants, including cycads, bennettites and the seed-fern Lepidopteris are almost absent from the sporomorph record. These results provide a means of reconciling the macrofossil and sporomorph records of Tr-J vegetation change, and may help to understand vegetation change during the P-Tr and K-T mass extinctions and around the Paleocene-Eocene Thermal Maximum. PMID:20713737

  13. Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.

    PubMed

    Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B; Cohen, Serge X; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

    2014-01-01

    The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809

  14. Water mass exchange and variations in seawater temperature in the NW Tethys during the Early Jurassic: Evidence from neodymium and oxygen isotopes of fish teeth and belemnites

    NASA Astrophysics Data System (ADS)

    Dera, Guillaume; Pucéat, Emmanuelle; Pellenard, Pierre; Neige, Pascal; Delsate, Dominique; Joachimski, Michael M.; Reisberg, Laurie; Martinez, Mathieu

    2009-08-01

    Oxygen and neodymium isotope analyses performed on biostratigraphically well-dated fish remains recovered from the Hettangian to Toarcian of the Paris Basin were used to reconstruct variations of Early Jurassic seawater temperature and to track oceanographic changes in the NW Tethys. Our results indicate a strong correlation between ?18O trends recorded by fish remains and belemnites, confirming the paleoenvironmental origin of oxygen isotope variations. Interestingly, temperatures recorded by pelagic fishes and nektobenthic belemnites and bottom dwelling fishes are comparable during the Late Pliensbachian sea-level lowstand but gradually differ during the Early Toarcian transgressive episode, recording a difference in water temperatures of ~ 6 °C during the Bifrons Zone. This could suggest that the surface-bottom water temperature difference was not large enough during regressive phases to be recorded by organisms living near the lower and upper part of the water column. The globally unradiogenic Nd budget of Euro-boreal waters through the Early Jurassic suggests that these waters were strongly affected by continental neodymium input from surrounding emerged areas and that exchange with more radiogenic waters from the Tethys and Panthalassa oceans remained limited. This supports the existence of a southward directed current in the Euro-boreal area for most of the Early Jurassic. The only exception is observed at the Early-Late Pliensbachian transition where a positive ?Nd excursion is recorded, suggesting northward influx of low-latitude Tethyan or Panthalassan waters which may have contributed to the warming of NW Tethyan seawater recorded at this time. The absence of a marked negative excursion in ?Nd concomitant with a negative ?18O shift recorded during the Falciferum Zone (Exaratum Subzone) argues against the influence of less radiogenic Arctic water influxes with low ?18O values during this interval. Instead, we suggest that enhanced freshwater inputs related to increasing weathering rates could have contributed to the large ?18O shift recorded by marine organisms, especially in Euro-boreal contexts.

  15. Clustering fossils in solid inflation

    NASA Astrophysics Data System (ADS)

    Akhshik, Mohammad

    2015-05-01

    In solid inflation the single field non-Gaussianity consistency condition is violated. As a result, the long tenor perturbation induces observable clustering fossils in the form of quadrupole anisotropy in large scale structure power spectrum. In this work we revisit the bispectrum analysis for the scalar-scalar-scalar and tensor-scalar-scalar bispectrum for the general parameter space of solid. We consider the parameter space of the model in which the level of non-Gaussianity generated is consistent with the Planck constraints. Specializing to this allowed range of model parameter we calculate the quadrupole anisotropy induced from the long tensor perturbations on the power spectrum of the scalar perturbations. We argue that the imprints of clustering fossil from primordial gravitational waves on large scale structures can be detected from the future galaxy surveys.

  16. Clustering Fossils in Solid Inflation

    E-print Network

    Akhshik, Mohammad

    2014-01-01

    In solid inflation the single field non-Gaussianity consistency condition is violated. As a result, the long tensor perturbation induces observable clustering fossils in the form of quardupole anisotropy in large scale structure power spectrum. In this work we revisit the bispectrum analysis for the scalar-scalar-scalar and tensor-scalar-scalar for the general parameter space of solid. We consider the parameter space of the model in which the level of non-Gaussianity generated is consistent with Planck constraints. Specializing to this allowed range of model parameter, we calculate the quadrupole anisotropy induced from the long tensor perturbations on the power spectrum of scalar perturbations. We argue that imprints of clustering fossil from primordial gravitational waves on large scale structures can be detected from the future galaxy surveys.

  17. Clustering Fossils in Solid Inflation

    E-print Network

    Mohammad Akhshik

    2014-09-10

    In solid inflation the single field non-Gaussianity consistency condition is violated. As a result, the long tensor perturbation induces observable clustering fossils in the form of quardupole anisotropy in large scale structure power spectrum. In this work we revisit the bispectrum analysis for the scalar-scalar-scalar and tensor-scalar-scalar for the general parameter space of solid. We consider the parameter space of the model in which the level of non-Gaussianity generated is consistent with Planck constraints. Specializing to this allowed range of model parameter, we calculate the quadrupole anisotropy induced from the long tensor perturbations on the power spectrum of scalar perturbations. We argue that imprints of clustering fossil from primordial gravitational waves on large scale structures can be detected from the future galaxy surveys.

  18. The paleoenvironment of anaerobic sediments in the Late Mesozoic South Atlantic Ocean

    Microsoft Academic Search

    Jörn Thiede; Tjeerd H. van Andel

    1977-01-01

    Laminated dark calcareous oozes\\/chalks\\/limestones as well as clayey and marly mudstones\\/claystones with high organic carbon contents were deposited during Jurassic, Early and Late Cretaceous times in the Atlantic, Pacific and Indian Oceans. In the South Atlantic, this sedimentary facies has been encountered only in drill sites close to the American and African continental margins. The reconstructed paleogeography of the South

  19. Dinosaur body temperatures determined from isotopic (¹³C-¹?O) ordering in fossil biominerals.

    PubMed

    Eagle, Robert A; Tütken, Thomas; Martin, Taylor S; Tripati, Aradhna K; Fricke, Henry C; Connely, Melissa; Cifelli, Richard L; Eiler, John M

    2011-07-22

    The nature of the physiology and thermal regulation of the nonavian dinosaurs is the subject of debate. Previously, arguments have been made for both endothermic and ectothermic metabolisms on the basis of differing methodologies. We used clumped isotope thermometry to determine body temperatures from the fossilized teeth of large Jurassic sauropods. Our data indicate body temperatures of 36° to 38°C, which are similar to those of most modern mammals. This temperature range is 4° to 7°C lower than predicted by a model that showed scaling of dinosaur body temperature with mass, which could indicate that sauropods had mechanisms to prevent excessively high body temperatures being reached because of their gigantic size. PMID:21700837

  20. Scaling relations in fossil galaxy groups

    E-print Network

    Habib G. Khosroshahi; Trevor J. Ponman; Laurence R. Jones

    2007-02-04

    Using Chandra X-ray observations and optical imaging and spectroscopy of a flux-limited sample of 5 fossil groups, supplemented by additional systems from the literature, we provide the first detailed study of the scaling properties of fossils compared to normal groups and clusters. In general, all the fossils we study show regular and symmetric X-ray emission, indicating an absence of recent major group mergers. We confirm that, for a given optical luminosity of the group, fossils are more X-ray luminous than non-fossil groups. Fossils, however, fall comfortably on the conventional L_X-T_X relation of galaxy groups and clusters, suggesting that their X-ray luminosity and their gas temperature are both boosted, arguably, as a result of their early formation. This is supported by other scaling relations including the L_X-sigma and T_X-sigma relations in which fossils show higher X-ray luminosity and temperature for a given group velocity dispersion. We find that mass concentration in fossils is higher than in non-fossil groups and clusters. In addition, the M_X-T_X relation suggests that fossils are hotter, for a given total gravitational mass, both consistent with an early formation epoch for fossils. We show that the mass-to-light ratio in fossils is rather high but not exceptional, compared to galaxy groups and clusters. The entropy of the gas in low mass fossils appears to be systematically lower than that in normal groups, which may explain why the properties of fossils are more consistent with an extension of cluster properties. We conclude that the cuspy potential raises the luminosity and temperature of the IGM in fossils. However, this works in conjunction with lower gas entropy, which may arise from less effective preheating of the gas.