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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. 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

  5. A late Jurassic pterosaur (Reptilia, Pterodactyloidea) from northwestern Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Codorniú, Laura; Gasparini, Zulma; Paulina-Carabajal, Ariana

    2006-03-01

    A small to medium-sized pterodactyloid pterosaur (wingspan approximately 1.10 m) from the Upper Jurassic (middle-late Tithonian) marine deposits of the Vaca Muerta Formation of Patagonia (Los Catutos area, central Neuquén Province, Argentina) is reported. The specimen lacks the skull but constitutes a nearly complete postcranial skeleton, which includes cervical and dorsal vertebrae; a few thoracic ribs; both pectoral girdles; the left pelvic girdle; a proximal right wing (humerus, ulna, and radius) and metacarpal IV; a left wing that lacks only wing phalanx four; and both hindlimbs, the right one without the foot. Ontogenetic features suggest that the new fossil corresponds to a relatively mature individual, probably a subadult. Observed characters support its assignment to the Archaeopteroactyloidea, a basal clade within the Pterodactyloidea. This specimen is the second pterosaur from Los Catutos and the most complete Jurassic pterosaur so far known from South America.

  6. ORIGINAL PAPER A Late Jurassic freshwater shark assemblage

    E-print Network

    Schöne, Bernd R.

    isotopes Introduction Hybodontiformes are the extinct sister group to all living sharks, skates, and raysORIGINAL PAPER A Late Jurassic freshwater shark assemblage (Chondrichthyes, Hybodontiformes) from

  7. 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.

  8. Broad-Scale Patterns of Late Jurassic Dinosaur Paleoecology

    PubMed Central

    Noto, Christopher R.; Grossman, Ari

    2010-01-01

    Background There have been numerous studies on dinosaur biogeographic distribution patterns. However, these distribution data have not yet been applied to ecological questions. Ecological studies of dinosaurs have tended to focus on reconstructing individual taxa, usually through comparisons to modern analogs. Fewer studies have sought to determine if the ecological structure of fossil assemblages is preserved and, if so, how dinosaur communities varied. Climate is a major component driving differences between communities. If the ecological structure of a fossil locality is preserved, we expect that dinosaur assemblages from similar environments will share a similar ecological structure. Methodology/Principal Findings This study applies Ecological Structure Analysis (ESA) to a dataset of 100+ dinosaur taxa arranged into twelve composite fossil assemblages from around the world. Each assemblage was assigned a climate zone (biome) based on its location. Dinosaur taxa were placed into ecomorphological categories. The proportion of each category creates an ecological profile for the assemblage, which were compared using cluster and principal components analyses. Assemblages grouped according to biome, with most coming from arid or semi-arid/seasonal climates. Differences between assemblages are tied to the proportion of large high-browsing vs. small ground-foraging herbivores, which separates arid from semi-arid and moister environments, respectively. However, the effects of historical, taphonomic, and other environmental factors are still evident. Conclusions/Significance This study is the first to show that the general ecological structure of Late Jurassic dinosaur assemblages is preserved at large scales and can be assessed quantitatively. Despite a broad similarity of climatic conditions, a degree of ecological variation is observed between assemblages, from arid to moist. Taxonomic differences between Asia and the other regions demonstrate at least one case of ecosystem convergence. The proportion of different ecomorphs, which reflects the prevailing climatic and environmental conditions present during fossil deposition, may therefore be used to differentiate Late Jurassic dinosaur fossil assemblages. This method is broadly applicable to different taxa and times, allowing one to address questions of evolutionary, biogeographic, and climatic importance. PMID:20838442

  9. 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

  10. New Fossil Lepidoptera (Insecta: Amphiesmenoptera) from the Middle Jurassic Jiulongshan Formation of Northeastern China

    PubMed Central

    Zhang, Weiting; Shih, Chungkun; Labandeira, Conrad C.; Sohn, Jae-Cheon; Davis, Donald R.; Santiago-Blay, Jorge A.; Flint, Oliver; Ren, Dong

    2013-01-01

    Background The early history of the Lepidoptera is poorly known, a feature attributable to an inadequate preservational potential and an exceptionally low occurrence of moth fossils in relevant mid-Mesozoic deposits. In this study, we examine a particularly rich assemblage of morphologically basal moths that contribute significantly toward the understanding of early lepidopteran biodiversity. Methodology/Principal Findings Our documentation of early fossil moths involved light- and scanning electron microscopic examination of specimens, supported by various illumination and specimen contrast techniques. A total of 20 moths were collected from the late Middle Jurassic Jiulongshan Formation in Northeastern China. Our principal results were the recognition and description of seven new genera and seven new species assigned to the Eolepidopterigidae; one new genus with four new species assigned to the Mesokristenseniidae; three new genera with three new species assigned to the Ascololepidopterigidae fam. nov.; and one specimen unassigned to family. Lepidopteran assignment of these taxa is supported by apomorphies of extant lineages, including the M1 vein, after separation from the M2 vein, subtending an angle greater than 60 degrees that is sharply angulate at the junction with the r–m crossvein (variable in Trichoptera); presence of a foretibial epiphysis; the forewing M vein often bearing three branches; and the presence of piliform scales along wing veins. Conclusions/Significance The diversity of these late Middle Jurassic lepidopterans supports a conclusion that the Lepidoptera–Trichoptera divergence occurred by the Early Jurassic. PMID:24278142

  11. 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.

  12. A Giant Pliosaurid Skull from the Late Jurassic of England

    PubMed Central

    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

  13. Cycads: Fossil evidence of late paleozoic origin

    USGS Publications Warehouse

    Mamay, S.H.

    1969-01-01

    Plant fossils from Lower Permian strata of the southwestern United States have been interpreted as cycadalean megasporophylls. They are evidently descended from spermopterid elements of the Pennsylvanian Taeniopteris complex; thus the known fossil history of the cycads is extended from the Late Triassic into the late Paleozoic. Possible implications of the Permian fossils toward evolution of the angiosperm carpel are considered.

  14. 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

  15. New fossil Osmylopsychopidae (Neuroptera) from the Early/Middle Jurassic of Kyrgyzstan, Central Asia.

    PubMed

    Khramov, Alexander V; Makarkin, Vladimir N

    2015-01-01

    Four genera and four species of Osmylopsychopidae are described from the Jurassic of Kyrgyzstan, Central Asia: Oligophlebiopsis biramosa gen. et sp. nov. (Early Jurassic of Sogyuty); Osmylopsychoides anteromedialis gen. et sp. nov., Psychostoechotes undulatus gen. et sp. nov. and Osmylopsychostoechus sogulensis gen. et sp. nov. (all from the late Early to early Middle Jurassic of Sai-Sagul). By their poorly-developed outer gradate series of crossveins, these taxa (except O. anteromedialis gen. et sp. nov.) are more similar to Triassic genera than to the Middle/Late Jurassic Osmylopsychopidae (particularly from Daohugou, China). Two isolated hind wings from Sai-Sagul (i.e., Osmylopsychostoechus sp. and Osmylopsychopidae gen. et sp. indet.) are preliminarily assigned to this family. PMID:26701556

  16. 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

  17. 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.

  18. 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.

  19. Complex palaeosol ichnofabrics from Late Jurassic-Early Cretaceous volcaniclastic successions of Central Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Bedatou, Emilio; Melchor, Ricardo N.; Genise, Jorge F.

    2009-06-01

    Late Jurassic-Early Cretaceous volcaniclastic continental deposits from central Patagonia, Argentina were analyzed for an integral characterization of palaeosol ichnofabrics. These units contain complex continental ichnofabrics that were also recorded in other late Jurassic-late Miocene extended volcaniclastic successions from Patagonia. According to a recently proposed method, ichnofabric, pedofabric and original bedding of selected intervals were measured separately in order to determinate the degree in which the deposits are affected by soil features besides the ichnofabrics. Four recurrent ichnofabrics were recognized in studied palaeosols: the Loloichnus, large Taenidium- Beaconites, diffuse boxwork, and Dagnichnus ichnofabrics. The Loloichnus ichnofabric is characterized by sub-vertical Loloichnusbaqueroensis and subordinate, similarly arrenged large Taenidiumbarretti and Beaconitescoronus.L.baqueroensis is a crayfish dwelling structure while large T.barretti and B.coronus are assigned to locomotion of the same organisms. Root traces are additional components of this ichnofabric. The large Taenidium- Beaconites ichnofabric is formed by large, irregular and curved T.barretti and B.coronus and by L.baqueroensis in low proportion. This ichnofabric is also assigned to crayfish activity. The diffuse boxwork ichnofabric is characterized by a pervasive and intricate three-dimensional boxwork of burrows; occasionally joined to subspherical chambers (possible Castrichnus). The diffuse boxwork is interpreted as an earthworm burrow system and the associated chambers are probably for aestivation. Rare and scattered discrete trace fossils in this ichnofabric include L.baqueroensis, T.barretti and B.coronus. The Dagnichnus ichnofabric is formed by Dagnichnustitoi, root traces and, subordinately, Loloichnusbaqueroensis, Cellicalichnusmeniscatus and tangled groups of meniscate burrows. D.titoi and C.meniscatus has been interpreted as crayfish breeding structures and the tangled groups of meniscate burrows are probably related to juvenile crayfish activity. The studied ichnofabrics were formed in weakly to moderately developed palaeosols in lowland areas with frequent reworking of pyroclastic material by unconfined flows. The recognized ichnofabrics show that in Patagonia, for the Late Jurassic-Early Cretaceous times, crayfishes and earthworms were the dominant soil organisms and, along with plants, rapidly colonized deposits exposed subaerially. After sediment deposition and with high soil moisture content or high water table crayfishes probably crawled in moist sediments forming the large Taenidium- Beaconites ichnofabric. With a better drained soil profile or lower water tables, the Loloichnus ichnofabric, representing the dwelling structures of adult crayfishes, overprinted the previous ichnofabric. The diffuse boxwork ichnofabric, usually located in the uppermost portion of palaeosols, correspond to extensive fossil earthworm burrow systems. The Dagnichnus ichnofabric occurs in very weakly developed palaeosols and probably reflects the optimal palaeoenvironmental conditions for breeding crayfish.

  20. The Late Jurassic pterosaur Rhamphorhynchus, a frequent victim of the ganoid fish Aspidorhynchus?

    PubMed

    Frey, Eberhard; Tischlinger, Helmut

    2012-01-01

    Associations of large vertebrates are exceedingly rare in the Late Jurassic Solnhofen Limestone of Bavaria, Southern Germany. However, there are five specimens of medium-sized pterosaur Rhamphorhynchus that lie adjacent to the rostrum of a large individual of the ganoid fish Aspidorhynchus. In one of these, a small leptolepidid fish is still sticking in the esophagus of the pterosaur and its stomach is full of fish debris. This suggests that the Rhamphorhynchus was seized during or immediately after a successful hunt. According to the fossil record, Rhamphorhynchus frequently were accidentally seized by large Aspidorhnychus. In some cases the fibrous tissue of the wing membrane got entangled with the rostral teeth such that the fish was unable to get rid of the pterosaur. Such encounters ended fatally for both. Intestinal contents of Aspidorhynchus-type fishes are known and mostly comprise fishes and in one single case a Homoeosaurus. Obviously Rhamphorhynchus did not belong to the prey spectrum of Aspidorhynchus. PMID:22412850

  1. The Late Jurassic Pterosaur Rhamphorhynchus, a Frequent Victim of the Ganoid Fish Aspidorhynchus?

    PubMed Central

    Frey, Eberhard; Tischlinger, Helmut

    2012-01-01

    Associations of large vertebrates are exceedingly rare in the Late Jurassic Solnhofen Limestone of Bavaria, Southern Germany. However, there are five specimens of medium-sized pterosaur Rhamphorhynchus that lie adjacent to the rostrum of a large individual of the ganoid fish Aspidorhynchus. In one of these, a small leptolepidid fish is still sticking in the esophagus of the pterosaur and its stomach is full of fish debris. This suggests that the Rhamphorhynchus was seized during or immediately after a successful hunt. According to the fossil record, Rhamphorhynchus frequently were accidentally seized by large Aspidorhnychus. In some cases the fibrous tissue of the wing membrane got entangled with the rostral teeth such that the fish was unable to get rid of the pterosaur. Such encounters ended fatally for both. Intestinal contents of Aspidorhynchus-type fishes are known and mostly comprise fishes and in one single case a Homoeosaurus. Obviously Rhamphorhynchus did not belong to the prey spectrum of Aspidorhynchus. PMID:22412850

  2. 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

    ON DINOSAUR BONES FROM THE UPPER JURASSIC MORRISON FORMATION, NORTHEASTERN WYOMING, AND THEIR USE IN VERTEBRATE TAPHONOMY by ? 2008 Kenneth Stephen Bader B.S., University of Kansas, 2003 Submitted to the Department of Geology and the Faculty... of the following thesis: INSECT TRACE FOSSILS ON DINOSAUR BONES FROM THE UPPER JURASSIC MORRISON FORMATION, NORTHEASTERN WYOMING, AND THEIR USE IN VERTEBRATE TAPHONOMY Advisory Committee...

  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. Vertebrate fossils and trace fossils in Upper Jurassic-Lower cretaceous red beds in the Atacama region, Chile

    NASA Astrophysics Data System (ADS)

    Bell, C. M.; Suárez, M.

    Pterosaur, dinosaur, and crocodile bones are recorded here for the first time in Upper Jurassic-Lower Cretaceous red beds in the Atacama region east of Copiapó, Chile. Trace fossils produced by vertebrate animals include the footprints of theropod dinosaurs and the depressions of sandstone laminae interpreted as burrows and foot impressions. The fossils occur in the 1500-meter-thick Quebrada Monardes Formation, which consists predominantly of the aeolian and alluvial deposits of a semi-arid terrestrial environment. Vertebrate fossils are very rare in Chile. Dinosaur bones and footprints have previously been recorded at only seven locations, and pterosaur remains at only one location. The newly discovered dinosaur bones are the oldest to be described in Chile.

  6. Discovery of silicified lacustrine micro-fossils and stromatolites: Triassic-Jurassic Fundy Group, Nova Scotia

    SciTech Connect

    Cameron, B.

    1985-01-01

    A unique assemblage of silicified invertebrate and algal fresh-water lake fossils has been discovered in the Scots Bay Formation at the top of the Triassic-Jurassic Fundy Group of the Fundy Basin in Nova Scotia. This is important because the basins of the eastern North American Triassic-Jurassic rift system have not yielded many invertebrate and algal fossils. These new finds will contribute significantly to evolutionary, paleoecological and biostratigraphic studies of fresh-water Mesozoic deposits. Silicified fossils have been extracted from chert-bearing, mixed carbonate and siliciclastic lithologies. They include ostracodes, gastropods, rare bivalves, charaphytes (algae), stromatolites, and chert nodules cored with well-preserved woody tissues of tree trunks. Possible algal filaments occur in the silicified stromatolites. This association of charaphytes, ostracodes, microscopic gastropods and stromatolites is found in carbonate lakes today. The Scots Bay Formation is probably a near-shore carbonate facies of the more widespread silicilastic lacustrine McCoy Brook Formation. The gastropods and ostracodes, studied by SEM, indicate a Jurassic age for the Scots bay Formation, confirming speculations based on other data.

  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. PMID:26064545

  8. Geological investigations of pre-late Jurassic terranes in the southernmost Andes

    NASA Astrophysics Data System (ADS)

    Forsythe, R. D.

    Pre-Late Jurassic terranes of the Patagonian Archipelago were investigated. Their regional stratigraphic and structural characteristics were surveyed. Their significance in the late Paleozoic to early Mesozoic evolution of South America were determined. Pre-Late Jurassic rocks within the archipelago are distributed in two belts. Within the outer belt the Madre de Dios Archipielago was studied in detail. Pre-Late Jurassic rocks of this area are divisible into three mappable units. These three units are interpreted to be part of a late Paleozoic to early Mesozoic accretionary prism that was located along the ancestral Pacific margin of the South American sector of Gondwana. Within the inner belt, the region of Peninsula Staines was studied in detail. In this region greenschist facies metamorphism and pervasive deformation fabrics prevent stratigraphic subdivision of the terrane. However the lithologies present are correlative with the outer belt suggesting that they also were part of the late Paleozoic to early Mesozoic accretionary prism.

  9. 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.

  10. 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.

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

    SciTech Connect

    Turner-Peterson, C.E.; Fishman, N.S. )

    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.

  12. Vertebrate fossils from late Cenozoic deposits of central Kansas

    E-print Network

    Hibbard, C. W.

    1952-03-20

    PALEONTOLOGICAL CONTRIBUTIONS VERTEBRATA ARTICLE 2 Pages 1-14, Figures 1-14 VERTEBRATE FOSSILS FROM LATE CENOZOIC DEPOSITS OF CENTRAL KANSAS By CLAUDE W. HIBBARD UNIVERS= OF KANSAS PUBLICATIONS MARCH 20, 1952 PRINTED BY FERD VOILAND, JR.. STATE PRINTER TOPEKA.... KANSAS 1952 24-975 UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS VERTEBRATA, ARTICLE 2, PAGES 1-14, FIGLTRES 1-14 VERTEBRATE FOSSILS FROM LATE CENOZOIC DEPOSITS OF CENTRAL KANSAS By CLAUDE W. HIBBARD CONTENTS PAGE 3 Microtus (Pedomys) Ilanensis...

  13. Late Jurassic breakup of the Proto-Caribbean and circum-global circulation across Pangea

    NASA Astrophysics Data System (ADS)

    Baumgartner, Peter O.; Rojas-Agramonte, Yamirka; Sandoval-Gutierrez, Maria; Urbani, Franco; García-Delgado, Dora; Garban, Grony; Pérez Rodríguez, Mireya

    2013-04-01

    Based on earlier plate reconstructions, many authors have postulated a circum-global equatorial current system flowing through the Pangea breakup, the Tethys - Atlantic - Caribbean Seaway, to explain changes in global climate during the Middle and Late Jurassic. While a Toarcian (late Early Jurassic) breakup is well constrained for the Central Atlantic, the place and timing of initial ocean crust formation between the Americas (Gulf of Mexico or Proto-Caribbean?) is still poorly constrained. Ar/Ar ages (190 to 154 Ma) in the Tinaquillo ultramafic complex (NW-Venezuela) have been interpreted as a result of initial Proto-Caribbean rifting. However, the Tinaquillo is clearly a subconinental block and the cited ages age cannot be related with breakup. The Siquisique Ophiolite (NW-Venezuela), long known for the occurrence of Bajocian-early Bathonian ammonite fragments found in interpilow sediments, has previously been interpreted as an early Proto-Caribbean remnant. However, the ammonite fragments were recovered from blocks in a Paleogene tectonic mélange, whereas the main Siquisique ophiolite body seems to be of middle Cretaceous age, based on a few Ar/Ar dates and poorly preserved middle to late Cretaceous radiolarians, which we recovered from black cherts interbedded with volcanics. The best record of Proto-Caribbean rifting and breakup is preserved in the Guaniguanico Terrane of NW-Cuba, which represents a distal Yucatan (N-American) passive margin segment telescoped by Tertiary nappe tectonics. In this terrane middle to upper Oxfordian pelagic limestones encroach on the E-MORB type El Sabalo Basalts which represent the oldest known remnants of oceanic crust clearly identifiable as Proto-Caribbean. Older, syn-rift sediments in the Proto-Caribbean and Gulf of Mexico are known to be deltaic to shallow marine detrital, and evaporitic. Although oceanic crust seemingly started to form in the early Late Jurassic (158 my), recent plate tectonic reconstructions show important obstructions throughout the Late Jurassic and early Cretaceous between the Central Atlantic, the Proto-Caribbean, and the Colombian back-arc basin, which in turn was separated from the Pacific by a mature arc. Hence, the lack of an open ocean connection makes a trans-Pangean, circum-global current system impossible before the Late Jurassic and unlikely during the Late Jurassic-Early Cretaceous. The least restricted passage between the Americas, most favourable to such a circulation, existed during the early Late Cretaceous, when the Caribbean Large Igneous Province was formed and approached its place between the Americas. Ribbon-bedded radiolarite is the most common Jurassic pelagic facies on Tethyan ocean floor and in the entire circum-Pacific realm but, is so far unknown from the Central Atlantic and the Proto-Caribbean. Radiolarite occurrences in ophiolite (s.l.) complexes of the Antilles are interpreted to have a Pacific origin like the Caribbean Plate. An east-west directed global current system would account for the higher fertility radiolarian chert on both extremes of the Tethys - Proto-Caribbean Seaway, but is in contradiction with the low fertility facies in the Central Atlantic. Jurassic-Early Cretaceous pelagic carbonates in the Central Atlantic and the Proto-Caribbean are interpreted as the consequence of more oligotrophic surface waters than those of the adjacent Tethys and Panthalassa. The Central Atlantic was a 'Mediterranean-type' ocean basin, such as the Modern Red Sea. It was (and still is) a carbonate ocean, characterized by an anti-estuarine circulation. By latest Jurassic time, the Western Tethys changed to calcareous low-fertility facies sedimentation, while in the circum-Pacific realm radiolarite sedimentation continued. It is only by Late Cretaceous times that a global homogenisation of facies is observed, such as the pelagic (marly) limestones or 'oceanic red beds'.

  14. Late Jurassic Epiphyton-like cyanobacteria: Indicators of long-term episodic variation in marine bioinduced microbial calcification?

    E-print Network

    Riding, Robert

    Late Jurassic Epiphyton-like cyanobacteria: Indicators of long-term episodic variation in marine February 2014 Accepted 25 February 2014 Available online xxxx Keywords: Calcification Cyanobacteria. Their highly sporadic geological distribution resembles that of marine calcified cyanobacteria, which show

  15. 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

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

    SciTech Connect

    Harker, S.D. Ltd., Aberdeen ); Mantel, K.A. ); Morton, D.J. ); Riley, L.A. )

    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.

  17. 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

  18. 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.

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

    SciTech Connect

    Norwood, E.M.; Brinton, L.

    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.

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

    SciTech Connect

    Norwood, E.M. ); Brinton, L. )

    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.

  1. The Tendaguru formation of southeastern Tanzania, East Africa: An alternating Late Jurassic to Early Cretaceous palaeoenvironment of exceptional status

    NASA Astrophysics Data System (ADS)

    Sames, B.

    2009-04-01

    Dinosaur remains have inspired considerable scientific interest in the Tendaguru formation of southeastern Tanzania during the 20th century; however, this formation is exceptional in many other respects. The Late Jurassic to Early Cretaceous deposits of the Tendaguru formation in the southwestern Tethys are unique because they represent a marginal marine palaeoenvironment with nonmarine faunal and floral content. It is a threefold succession of marginal marine to terrestrial, carbonate-siliciclastic sediments with cyclic character, consisting of three transgressive-regressive cycles. Revisitation of the type locality (the Tendaguru, a hill approximately 60km northwest of the town of Lindi) by a German-Tanzanian expedition in summer 2000 (Heinrich et al., 2001) resulted in a new standard section (hitherto unpublished, the informal terminology is indicated by the use of lower case in Tendaguru formation), a refined environmental model (Aberhan et al., 2002) and many new insights towards its geology (with evidence of event-sedimentation, Bussert and Aberhan, 2004), biostratigraphy and a better understanding of the Tendaguru palaeo-ecosystems and the palaeoclimate. Within the scope of the designation of a new standard section at the type locality, calcareous microfossils (ostracods, charophytes) have been described to supplement the ongoing discussion about the age and palaeoecology of the Tendaguru formation (Sames, 2008). Although only a few unevenly distributed layers across the section produced calcareous microfossils, the results are very promising. A total of 40 ostracode and 2 charophyte taxa could be distinguished. The non-marine part of the ostracod fauna provides an important contribution to the documentation of Purbeck/Wealden-type nonmarine palaeoenvironments and its microfaunas and -floras previously unknown from East Africa. The marine faunal part belongs to a relatively endemic southern (Gondwana) fauna. Together with other fossil groups, the palaeoecological analysis of microfaunal and -floral assemblages confirms that the former subdivision of the Tendaguru formation into three non-marine intercalated with three marine layers should be recognised as generally only, because the formation is much more complex in detail. Application of calcareous microfossils has been demonstrated to make an important contribution to the interpretation of the Tendaguru formation's palaeoenvironment and is considered highly developable in the future. References: Aberhan, M., Bussert, R., Heinrich, W.-D., Schrank, E., Schultka, S., Sames, B., Kriwet, J. and Kapilima, S., 2002. Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania). Mitteilungen aus dem Museum für Naturkunde in Berlin, Geowissenschaftliche Reihe, 5: 19-44. Bussert, R. and Aberhan, M., 2004. Storms and tsunamis: evidence of event sedimentation in the Late Jurassic Tendaguru Beds of southeastern Tanzania. Journal of African Earth Sciences, 39: 549-555. Heinrich, W.-D., Bussert, R., Aberhan, M., Hampe, O., Kapilima, S., Schrank, E., Schultka, S., Maier, G., Msaky, E., Sames, B. and Chami, R., 2001. The German-Tanzanian Tendaguru Expedition 2000. Mitteilungen aus dem Museum für Naturkunde Berlin, Geowissenschaftliche Reihe, 20: 223-237. Sames, B., 2008. Application of Ostracoda and Charophyta from the Late Jurassic to Early Cretaceous Tendaguru formation at Tendaguru, Tanzania (East Africa) - Biostratigraphy, Palaeobiogeography and Palaeoecology. Palaeogeography, Palaeoclimatology, Palaeoecology, 264(3-4): 213-229.

  2. Fish faunas from the Late Jurassic (Tithonian) Vaca Muerta Formation of Argentina: One of the most important Jurassic marine ichthyofaunas of Gondwana

    NASA Astrophysics Data System (ADS)

    Gouiric-Cavalli, Soledad; Cione, Alberto Luis

    2015-11-01

    The marine deposits of the Vaca Muerta Formation (Tithonian-Berriasian) houses one of the most diverse Late Jurassic ichthyofaunas of Gondwana. However, most of the specimens remain undescribed. Jurassic fishes have been recovered from several localities at Neuquén Province (i.e., Picún Leufú, Plaza Huincul, Cerro Lotena, Portada Las Lajas, Los Catutos, and Arroyo Covunco) but also from Mendoza Province (i.e., La Valenciana, Los Molles, and Arroyo del Cajón Grande). Presently, the fish fauna of Los Catutos, near Zapala city (Neuquén Province), has yielded the highest number of specimens, which are taxonomically and morphologically diverse. At Los Catutos locality, the Vaca Muerta Formation is represented by the Los Catutos Member, which is considered the only lithographic limestones known in the Southern Hemisphere. Here, we review the Tithonian fish faunas from the Vaca Muerta Formation. During Late Jurassic times, the actual Argentinian territory could have been a morphological diversification center, at least for some actinopterygian groups. The apparently lower species diversity recorded in marine Jurassic ichthyofaunas of Argentina (and some Gondwanan countries) in comparison with Chilean and European fish faunas could be related to the fish paleontological research history in Gondwana and the low number of detailed studies of most of specimens recorded.

  3. Bulk Geochemical Data of Fossil Wood from the Middle Jurassic Clays of Poland

    NASA Astrophysics Data System (ADS)

    Smolarek, Justyna

    2012-01-01

    Macroscopic observations, microscopic studies and literature data revealed that Middle Jurassic wood from Cz?stochowa area has a different state of preservation, and various types and degrees of mineralization and oxidation. Obtained results of organic matter fractionation illustrate a clear domination of polar fraction in the obtained extracts revealing low thermal maturity stage. Total organic carbon (TOC) values for analysed samples are in a wide range from 1.06% to 68.50%. The highest amount of TOC were measured in not or poorly mineralized wood samples but most of them are mineralized wood fragments, showing the TOC values in the range of 2% - 10%. Percentage content of carbonate in fossil wood constitute in a wide range from less than 1% CaCO3 to above 85% CaCO3. The resulting percentage of the total sulfur content is very varied and do not show convergence with other data such as TOC, carbonate content, etc and is most probable connected with pyritisation range. Unlike the Middle Jurassic clay samples, where long-chain and short-chain n-alkanes occur in similar concentrations, in wood samples always short-chain n-alkanes dominated, in the range from 15 to 23 carbon atoms in molecule. The values of the CPI are generally higher than 1 which indicates the contribution of organic matter derived from higher plant waxes, which are characteristic of e.g. needles from gymnosperm plants. Under the influence of post - diagenetic oxidation in mineralized wood samples distribution of n-alkanes is changing. Diaster-13(17)-enes with 28 and 29 carbon atoms in molecule are present in the wood samples, while those with 29 atoms strongly prevail. Makroskopowe obserwacje, mikroskopowe badania i dane literaturowe wykaza?y, ?e ?rodkowojurajskie drewno z okolic Cz?stochowy ma ró?ny stan zachowania oraz ró?ne rodzaje i stopie? mineralizacji oraz utlenienia. Uzyskane wyniki rozdzia?u frakcyjnego pokazuj? wyra?n? przewag? frakcji polarnej w badanych ekstraktach. Warto?ci TOC dla badanych próbek wahaj? si? w szerokim zakresie od 1,06% do 68,50 %. Najwi?ksza ilo?? TOC wyst?puje w nie zmineralizowanych lub s?abo zmineralizowanych próbkach drewna. Wi?kszo?? próbek to zmineralizowane fragmenty drewna, pokazuj?c warto?ci TOC w zakresie od 2% - 10%. Zawarto?? procentowa w?glanów w badanych próbkach znajduje si? w szerokim zakresie od mniej ni? 1% CaCO3 do ponad 85% CaCO3. Procentowa zawarto?? siarki ca?kowitej jest bardzo zró?nicowana i nie wykazuje zbie?no?ci z innymi danymi, takimi jak TOC czy zawarto?? w?glanów, itp. W odró?nieniu od ?rodkowojurajskich i?ów, gdzie d?ugo?a?cuchowe i krótko?a?cuchowe n-alkany wyst?puj? w podobnych st??eniach , w próbkach drewna zawsze przewy?szaj? nalkanów krótko?a?cuchowe, wyst?puj?ce w zakresie od 15 do 23 atomów w?gla w cz?steczce. Warto?ci wska?nika CPI s? generalnie wy?sze ni? 1, co wskazuje na udzia? materii organicznej pochodz?cej z wosków ro?lin wy?szych. Pod wp?ywem post-diagenetycznego utleniania zmineralizowanych próbek drewna zmienia si? dystrybucja n-alkanów. W badanych próbkach obecne s? diaster-13 (17)-enes o 28 i 29 atomów w?gla w cz?steczce, natomiast te o 29 atomów znacznie przewa?aj?.

  4. Late Jurassic ocean anoxic event: evidence from voluminous sulphide deposition and preservation in the Panthalassa

    PubMed Central

    Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

    2013-01-01

    The historically productive copper-bearing Besshi-type sulphide deposits in the Japanese accretionary complex were formed as volcanogenic massive sulphide deposits on the deep-sea floor of the Panthalassa Ocean. Here we report that eleven typical Besshi-type deposits yielded Re-Os isochron ages around 150?Ma (148.4 ± 1.4?Ma from the composite isochron) in Late Jurassic time. This date coincides with the lowest marine 87Sr/86Sr ratio and highest atmospheric CO2 concentration of the past 300 million years. We infer that intense mid-ocean ridge hydrothermal and volcanic activity in the Late Jurassic produced huge sulphide deposits and large emissions of CO2 gas, leading to global warming and a stratified Panthalassa Ocean with anoxic deep seas that favored preservation of sulphides in the pelagic environment. The emergence of ocean anoxia triggered by seafloor volcanism is also consistent with a positive ?13C excursion and widespread deposition of petroleum source rocks and black shales. PMID:23712471

  5. 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.

  6. Plate tectonic trigger of changes in pCO2 and climate in the Oxfordian (Late Jurassic): Carbon isotope and modeling evidence

    E-print Network

    Gilli, Adrian

    was characterized by significant changes in oceanography and climate and by changes in global carbon cycle as shown of the Late Jurassic. Using a simple carbon cycle model we show that an increase in atmospheric pCO2 starting: carbon isotopes; pCO2; climate; carbon cycle; model simulation 1. Introduction The Late Jurassic carbon

  7. 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.

  8. Evolution of the Carbon Cycle During Major Turning Point in Oceanogaphy in the Late Jurassic.

    NASA Astrophysics Data System (ADS)

    Rais, P.; Louis-Schmid, B.; Bernasconi, S. M.; Weissert, H.

    2005-12-01

    The Late Jurassic was a time of accelerated fragmentation of Pangea resulting in a reorganisation of climate and oceanography. Some of these changes culminated in the Oxfordian as reflected in the Sr-isotope record. The 87/86Sr ratio reach the lowest values of the Mesozoic, indicative for high seafloor spreading and/or low continental weathering rates. Oxygen isotope values suggest that the Late Callovian and the Early Oxfordian were an exceptionally cool time in the Jurassic. The opening Tethyan ocean was chosen for an investigation of the evolution of the global carbon cycle and of changing current patterns along the east-west trending seaway. The carbon isotope curve shows a large-amplitude shift from low values around 1.5‰ (VPDB) in the Early Oxfordian towards values of around 3‰ in the Middle Oxfordian (Transversarium ammonite zone). After these high values, the ratio decreases towards values of 2‰. We used bio- and carbon isotope stratigraphy to correlate the evolution of current intensity based on an expanded reference carbon isotope section from the Vocontian trough (France). Stable carbon isotope records provide a very good tool for correlation between different paleoceanographic settings. Strong oceanic currents sweeping the Tethyan seafloor caused the formation of hardgrounds on sedimentary highs, whereas protected basins act as sedimentary sinks, with high sediment accumulation rates. These hardgrounds are of Late Callovian to Early Oxfordian age. The decrease of current activity corresponds to the top of the condensed sediments and the onset of normal accumulation rates. It coincides with the time of most positive carbon isotope values in the Transversarium ammonite zone. The carbon isotope shift corresponds exactly to the change in current pattern along the northern part of the Tethyan seaway. The synchronous change in carbon cycling and in physical oceanography suggests that there are feedbacks between physical oceanography and carbon cycling. The variations of the carbon isotopic signal reflect the complicated interaction of biological and chemical factors associated with a global oceanic and climate reorganisation.

  9. 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

  10. Thalassemys bruntrutana n. sp., a new coastal marine turtle from the Late Jurassic of Porrentruy (Switzerland), and the paleobiogeography of the Thalassemydidae

    PubMed Central

    Anquetin, Jérémy; Billon-Bruyat, Jean-Paul

    2015-01-01

    Background. The Swiss Jura Mountains are a key region for Late Jurassic eucryptodiran turtles. Already in the mid 19th century, the Solothurn Turtle Limestone (Solothurn, NW Switzerland) yielded a great amount of Kimmeridgian turtles that are traditionally referred to Plesiochelyidae, Thalassemydidae, and Eurysternidae. In the past few years, fossils of these coastal marine turtles were also abundantly discovered in the Kimmeridgian of the Porrentruy region (NW Switzerland). These findings include numerous sub-complete shells, out of which we present two new specimens of Thalassemys (Thalassemydidae) in this study. Methods. We compare the new material from Porrentruy to the type species Th. hugii, which is based on a well preserved specimen from the Solothurn Turtle Limestone (Solothurn, Switzerland). In order to improve our understanding of the paleogeographic distribution of Thalassemys, anatomical comparisons are extended to Thalassemys remains from other European countries, notably Germany and England. Results. While one of the two Thalassemys specimens from Porrentruy can be attributed to Th. hugii, the other specimen represents a new species, Th. bruntrutana n. sp. It differs from Th. hugii by several features: more elongated nuchal that strongly thickens anterolaterally; wider vertebral scales; proportionally longer plastron; broader and less inclined xiphiplastron; wider angle between scapular process and acromion process. Our results show that Th. hugii and Th. bruntrutana also occur simultaneously in the Kimmeridgian of Solothurn as well as in the Kimmeridgian of England (Kimmeridge Clay). This study is an important step towards a better understanding of the paleobiogeographic distribution of Late Jurassic turtles in Europe. PMID:26468437

  11. Late Triassic to middle Jurassic history of the north-central high Atlas, Morocco

    SciTech Connect

    Letsch, D.K.

    1988-02-01

    The Lower and Middle Jurassic (Liassic and Dogger) rocks in the north-central High Atlas and on the adjacent Oran Meseta, Morocco, were deposited on the subsiding margin of the Triassic/Jurassic High Atlas trough. This and the Middle Atlas trough formed as a result of rifting of the Moroccan Meseta and oran Meseta from the Saharan craton during initial stages of the opening of the modern Atlantic. The Tethys seaway flooded these troughs in the early Liassic, resulting in deposition of several thousand meters of liassic and Dogger limestone and marlstone. The deepening-upward Liassic section in the north-central High Atlas reflects the rapid development of the short-lived High Atlas trough, which formed in the Late Triassic-Early Liassic flooding by the Tethys established carbonate tidal flats on the Oran Meseta, a shelf margin at the basin's edge, and slope and basin-floor deposition within the trough. Rapid subsidence of the margin brought slope and basin floor sediments on top of the platform margin as the trough developed. Subsidence slowed toward the end of the Lias, resulting in progradation of the shelf-margin environments. At the end of the Lias, a portion of the margin slid into the basin, followed by debris shed off the slide scar. Continued marlstone and limestone deposition filled the basin during the Dogger, marking the end of rift-related sedimentation in the High Atlas trough.

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

    E-print Network

    Gilli, Adrian

    Strontium and carbon isotope stratigraphy of the Late Jurassic shallow marine limestone in western-Pacific a b s t r a c t Strontium and carbon isotope stratigraphy was applied to a 202 m-thick shallow marine, which was deposited in the western Palaeo-Pacific. Strontium isotopic ratios of rudist specimens suggest

  13. New fossil record of a Jurassic pterosaur from Neuquen Basin, Vaca Muerta Formation, Argentina

    NASA Astrophysics Data System (ADS)

    Codorniú, Laura; Garrido, Alberto

    2013-12-01

    Discoveries of Jurassic pterosaurs in the Southern Hemisphere are extremely unusual. In Argentina, pterosaurs from the Upper Jurassic (Tithonian) have only been found in the Northwest of Patagonia (Neuquén Basin). These come from marine deposits and three specimens have been discovered up to the present. In this paper, we report a new finding from the Neuquén Basin. This material is identified as a tibiotarsus, which probably belonged to an osteologically adult individual and represents a new species of a pterodactyloid pterosaur of medium size. This discovery provides new evidence that at least two different species of pterodactyloid pterosaurs may have coexisted in Los Catutos Member, Vaca Muerta Formation, from the shallow marine deposits of the Neuquén Basin.

  14. Fauna and predator-prey relationships of Ettling, an actinopterygian fish-dominated Konservat-Lagerstätte from the Late Jurassic of southern Germany.

    PubMed

    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

  15. 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

  16. Mid-Late Holocene environmental change in northern Sweden: an investigation using fossil insect remains 

    E-print Network

    Khorasani, Sara

    2013-11-28

    For the first time, Mid-Late Holocene insect fossil assemblages were studied from inland northern Sweden, producing new evidence relating to both natural environmental changes and human impacts. The insect fossil ...

  17. The first fossil spider (Araneae: Palpimanoidea) from the Lower Jurassic (Grimmen, Germany).

    PubMed

    Selden, Paul A; Dunlop, Jason A

    2014-01-01

    The first Lower Jurassic (Lias) spider is described as Seppo koponeni n. gen. & n. sp. from a single female specimen from Grimmen, Germany. It most likely belongs to the Palpimanoidea, on account of the presence of cheliceral peg teeth and other features consistent with palpimanoid families, though its familial placement is uncertain. Its presence in the region at that time concurs with ideas about the more widespread presence of palpimanoids across the world in the early Mesozoic, before the break-up of Pangaea. PMID:25544628

  18. 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.

  19. Evidence of macrophagous teleosaurid crocodylomorphs in the Corallian Group (Oxfordian, Late Jurassic) of the UK

    PubMed Central

    Young, Mark T.; Brusatte, Stephen L.

    2015-01-01

    Teleosaurids were a group of semi-aquatic crocodylomorphs with a fossil record that spanned the Jurassic Period. In the UK, abundant specimens are known from the Oxford Clay Formation (OCF, Callovian to lower Oxfordian), but are very rare in the Kimmeridge Clay Formation (KCF, Kimmeridgian to lower Tithonian), despite their abundance in some contemporaneous deposits in continental Europe. Unfortunately, due to the paucity of material from the intermediate ‘Corallian Gap’ (middle to upper Oxfordian), we lack an understanding of how and why teleosaurid taxic abundance and diversity declined from the OCF to the KCF. The recognition of an incomplete teleosaurid lower jaw from the Corallian of Weymouth (Dorset, UK) begins to rectify this. The vertically oriented dentition, blunt tooth apices, intense enamel ornamentation that shifts to an anastomosed pattern apically, and deep reception pits on the dentary unambiguously demonstrates the affinity of this specimen with an unnamed sub-clade of macrophagous/durophagous teleosaurids (‘Steneosaurus’ obtusidens + Machimosaurus). The high symphyseal tooth count allows us to exclude the specimen from M. hugii and M. mosae, but in absence of more diagnostic material we cannot unambiguously assign DORCM G.3939 to a more specific level. Nevertheless, this specimen represents the first mandibular material referable to Teleosauridae from the poorly sampled middle-upper Oxfordian time-span in the UK. PMID:26713246

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

    SciTech Connect

    Schellekens, J.H. )

    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.

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

    NASA Astrophysics Data System (ADS)

    Hamilton, Thomas D.; Ashley, Gall M.; Reed, Katherine M.; Schweger, Charles E.

    1993-05-01

    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.

  2. Revision of the Late Jurassic crocodyliform Alligatorellus, and evidence for allopatric speciation driving high diversity in western European atoposaurids

    PubMed Central

    Mannion, Philip D.

    2014-01-01

    Atoposaurid crocodyliforms represent an important faunal component of Late Jurassic to Early Cretaceous Laurasian semi-aquatic to terrestrial ecosystems, with numerous spatiotemporally contemporaneous atoposaurids known from western Europe. In particular, the Late Jurassic of France and Germany records evidence for high diversity and possible sympatric atoposaurid species belonging to Alligatorellus, Alligatorium and Atoposaurus. However, atoposaurid taxonomy has received little attention, and many species are in need of revision. As such, this potentially high European diversity within a narrow spatiotemporal range might be a taxonomic artefact. Here we provide a taxonomic and anatomical revision of the Late Jurassic atoposaurid Alligatorellus. Initially described as A. beaumonti from the Kimmeridgian of Cerin, eastern France, additional material from the Tithonian of Solnhofen, south-eastern Germany, was subsequently referred to this species, with the two occurrences differentiated as A. beaumonti beaumonti and A. beaumonti bavaricus, respectively. We provide a revised diagnosis for the genus Alligatorellus, and note a number of anatomical differences between the French and German specimens, including osteoderm morphology and the configuration and pattern of sculpting of cranial elements. Consequently, we restrict the name Alligatorellus beaumonti to include only the French remains, and raise the rank of the German material to a distinct species: Alligatorellus bavaricus. A new diagnosis is provided for both species, and we suggest that a recently referred specimen from a coeval German locality cannot be conclusively referred to Alligatorellus. Although it has previously been suggested that Alligatorellus, Alligatorium and Atoposaurus might represent a single growth series of one species, we find no conclusive evidence to support this proposal, and provide a number of morphological differences to distinguish these three taxa that appear to be independent of ontogeny. Consequently, we interpret high atoposaurid diversity in the Late Jurassic island archipelago of western Europe as a genuine biological signal, with closely related species of Alligatorellus, Alligatorium and Atoposaurus in both French and German basins providing evidence for allopatric speciation, potentially driven by fluctuating highstand sea levels. PMID:25279270

  3. 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

  4. 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 a Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794-8081; b Division of Fossil of fossil primates from the Eocene of Algeria (1) and Egypt (2­4), Africa's role in the early evolution

  5. 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. PMID:26064563

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

    PubMed

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

    2014-11-01

    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. PMID:26064563

  7. Geochemical constraints on the origin of the late Jurassic proto-Caribbean oceanic crust in Hispaniola

    NASA Astrophysics Data System (ADS)

    Viruete, J. Escuder; Pérez-Estaún, A.; Weis, D.

    2009-03-01

    The nature of the oceanic crust produced through rifting and oceanic spreading between North and South America during the Late Jurassic is a key element for the Caribbean plate tectonic model reconstruction. Located in the Cordillera Central of Hispaniola, the Loma La Monja volcano-plutonic assemblage (LMA) is composed of gabbros, dolerites, basalts, and oceanic sediments, as well as metamorphic equivalents, which represent a dismembered fragment of this proto-Caribbean oceanic crust. Petrologic and geochemical data show that the LMA have a relatively broad diversity in composition, which represent the crystallization products of a typical low-pressure tholeiitic fractionation of mid-ocean ridge basalts (MORB)-type parental magmas, ranging from N- to E-MORB. Three geochemical groups have been distinguished in the volcanic sequence: LREE-flat to slightly LREE-enriched basalts of groups II and III occur interlayered in the lower stratigraphic levels; and LREE-depleted basalts of group I in the upper levels. Mantle melt modeling suggests that group III magmas are consistent by mixing within a mantle melt column of low-degree (<1%) melts of a deep garnet lherzolite source and high-degree (>15%) melts of a shallow spinel source, and groups II and I magmas are explained with moderate to high (14-18%) and very high (>20%) fractional melting degrees of a shallower spinel mantle source, respectively. Thus, upward in the volcanic sequence of the LMA, the magmas represent progressively more extensive melting of shallower sources, in a plume-influenced spreading ridge of the proto-Caribbean oceanic crust. Nb/Y versus Zr/Y systematics combined with recent plate tectonic model reconstructions reveal that Caribbean Colombian oceanic plateau fragments in Hispaniola formed through melting of heterogeneous mantle source regions related with distinct plumes during at least from Aptian-Albian (>96 Ma) to Late Campanian.

  8. Architecture and chemostratigraphy of Late Jurassic shallow marine carbonates in NE Japan, western Paleo-Pacific

    NASA Astrophysics Data System (ADS)

    Kakizaki, Yoshihiro; Kano, Akihiro

    2009-02-01

    We used microfacies analysis and carbon isotope stratigraphy to interpret the Late Jurassic (Late Kimmeridgian-Early Tithonian) Koike Limestone Member of northeastern Japan. The distribution of microfacies in the five studied sections allows reconstruction of a carbonate platform generally dipping from south to north. We observed reefal frameworks consisting of corals, stromatoporoids, and microencrusters in the southernmost section. The coral fragments were transported to the north and deposited with fine-grained carbonates in a deeper setting. The northward deepening trend is also supported by the texture of the oncoidal facies, which changes from grainstone in the south to pack-wackestone in the north. We recognized cyclic facies changes in most sections; these are best illustrated by quantitative analysis of rock components in the Koike section, which exposes the most continuous sequence. There, recurring upward-fining cycles consisting of coral floatstone, oncoidal facies, and peloidal wacke-grainstone probably formed in response to decreasing water-energy. The ?13C profile of the Koike Limestone Member shows an increasing trend from 0.72‰ to 1.90‰ but includes several negative excursions. The negative values correspond to facies containing sparry cements and microspar and likely reflect a diagenetic overprint. The range of ?13C values of the lower Koike Limestone Member is 1.0-1.5‰ lower than the average range of the Tethys Ocean values. In the upper member, the ?13C values are within the same range as the Tethys values. The differences in ?13C are potentially explained by a higher rate of marine organic production or organic burial in the Tethys Ocean during the Kimmeridgian.

  9. Dysaerobic trace fossils and ichnofabrics in the upper Jurassic Kimmeridge Clay of southern England

    SciTech Connect

    Wignall, P.B. )

    1991-06-01

    The trace fossil suite from the Kimmeridge Clay is calibrated against an oxygen gradient derived from previous geochemical, lithological and shelly macrofaunal studies. Several soft-bodied trace markers appear to have tolerated lower oxygen tensions than even the hardiest shelly benthic macrofauna-a common occurrence in both recent and ancient dysaerobic settings. Lowest diversity trace fossil assemblages consist of Astacimorphichnus etchesi (new ichnotaxon), a small endostratal pascichnial trace attributed to pioneering polychaete populations. Ekdale and Masons' (1988) contention that fodinichnia dominate the lowest diversity and lowest oxygen settings is not substantiated as the only example of this feeding strategy, Rhizocorallium irregulare, is encountered in moderately diverse trace fossil assemblages associated with a low diversity shelly macrofauna. Upper dysaerobic conditions are characterized by the development of a surface mixed layer and the consequent destruction of fine lamination. Tiering is only developed under normal oxygen conditions with Chondrites as the deepest trace. In contrast to many previous studies, Chondrites is never found in dysaerobic facies.

  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. )

    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. 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.

  12. Regression trees for modeling geochemical data-An application to Late Jurassic carbonates (Ammonitico Rosso)

    NASA Astrophysics Data System (ADS)

    Coimbra, Rute; Rodriguez-Galiano, Victor; Olóriz, Federico; Chica-Olmo, Mario

    2014-12-01

    Research based on ancient carbonate geochemical records is often assisted by multivariate statistical analysis, among others, used for data mining. This contribution reports a complementary approach that can be applied to paleoenvironmental research. The choice to use a machine learning method, here regression trees (RT), relied in the ability to learn complex patterns, integrating multiple types of data with different statistical distributions to obtain a knowledge model of geochemical behavior along a paleo-platform. The Late Jurassic epioceanic deposits under scope are represented by six stratigraphic sections located in SE Spain and on the Majorca Island. The used database comprises a total of 1960 data points corresponding to eight variables (stable C and O isotopes, the elements Ca, Mg, Sr, Fe, Mn and skeletal content). This study uses RT models in which the predictive variables are the geochemical proxies, whilst skeletal content is used as a target variable. The resulting model is data driven, explaining variations in the target variable and providing additional information on the relative importance of each variable to each prediction, as well as its corresponding threshold values. The obtained RT revealed a structured distribution of samples, organized either by stratigraphic section or sets of nearby sections. Averaged estimated skeletal abundance confirmed the initial observations of higher skeletal content for the most distal sections with estimated values from 18% to 27%. In contrast, lower skeletal abundance from 5% to 15% is proposed for the remaining sections. The geochemical variable that best discriminates this major trend is ?18O, at a threshold value of -0.2‰, interpreted as evidence for separation of water-mass properties across the studied areas. Other four variables were considered relevant by the obtained decision tree: C isotopes, Ca, Sr and Mn, providing new insights for further differentiation between sets of samples.

  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. Mollusks of the Upper Jurassic (upper Oxfordian-lower Kimmeridgian) shallow marine Minas Viejas Formation, northeastern Mexico

    NASA Astrophysics Data System (ADS)

    Zell, Patrick; Beckmann, Seija; Stinnesbeck, Wolfgang; Götte, Martin

    2015-10-01

    We present the first systematic description of Late Jurassic (late Oxfordian-early Kimmeridgian) invertebrates from the shallow marine Minas Viejas Formation of northeastern Mexico. The unit was generally considered to be extremely poor in fossils, due to an overall evaporitic character. The collection described here includes three taxa of ammonites, 10 taxa of bivalves and five taxa of gastropods. The fossils were discovered near Galeana and other localities in southern Nuevo León and northeastern San Luis Potosí, in thin-bedded marly limestones intercalated between gypsum units. Due to complex internal deformation of the sediments, fossils used for this study cannot be assigned to precise layers of origin. However, the taxa identified suggest a Late Jurassic (late Oxfordian-early Kimmeridgian) age for these fossil-bearing layers and allow us, for the first time, to assign a biostratigraphic age to Upper Jurassic strata in the region underlying the La Caja and La Casita formations.

  16. [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

  17. 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.

  18. 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.

  19. Carbonate-evaporite sequences of the late Jurassic, southern and southwestern Arabian Gulf

    SciTech Connect

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

    1995-11-01

    The carbonate-evaporite sequences of the Upper Jurassic Arab and overlying Hith formations in the southern and southwestern Arabian Gulf form many supergiant and giant fields that produce from the Arab Formation and are excellent examples of a classic reservoir/seal relationship. The present-day sabkha depositional setting that extends along most of the southern and southwestern coasts of the Arabian Gulf provides an analog to these Upper Jurassic sedimentary rocks. In fact, sabkha-related diagenesis of original grain-supported sediments in the Arab and Hith formations has resulted in five distinct lithofacies that characterize the reservoir/seal relationship: (1) oolitic/peloidal grainstone, (2) dolomitic grainstone, (3) dolomitic mudstone, (4) dolomitized grainstone, and (5) massive anhydrite. Interparticle porosity in grainstones and dolomitic grainstones and intercrystalline porosity in dolomitized rocks provide the highest porosity in the study area. These sediments accumulated in four types of depositional settings: (1) supratidal sabkhas, (2) intertidal mud flats and stromatolitic flats, (3) shallow subtidal lagoons, and (4) shallow open-marine shelves. The diagenetic history of the Arab and Hith formations in the southern and southwestern Arabian Gulf suggests that the anhydrite and much of the dolomitization are a result of penecontemporaneous sabkha diagenesis. The character and timing of the paragenetic events are responsible for the excellent porosity of the Arab Formation and the lack of porosity in the massive anhydrites of the Hith, which together result in the prolific hydrocarbon sequences of these formations.

  20. 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.

  1. Intraplate Late Jurassic deformation and exhumation in western central Argentina: Constraints from surface data and U-Pb detrital zircon ages

    NASA Astrophysics Data System (ADS)

    Naipauer, Maximiliano; García Morabito, Ezequiel; Marques, Juliana C.; Tunik, Maisa; Rojas Vera, Emilio A.; Vujovich, Graciela I.; Pimentel, Marcio P.; Ramos, Victor A.

    2012-02-01

    Intraplate deformation has been described in several tectonic settings and recently in western central Argentina it has been proposed to explain the complex structural patterns developed between Early Jurassic and Cretaceous times along the Huincul deformation zone. We integrate new field data and detrital zircon ages of the exposed portion of the Huincul High that permit us to quantify the significance of this intraplate deformation in the relief generation. A stratigraphic and structural record of a Jurassic pulsed contractional deformation is derived from field surveys. It is documented through multiple unconformities and growth geometries linked to NE and E-W oriented growth structures extensively developed across the studied region. The pattern of zircon ages from the analyzed Late Jurassic successions indicates that they have a clear provenance from sources located along the Huincul deformation zone. The Tordillo Formation outcrops north of the Huincul High have a dominant provenance from the Andean Jurassic arc; while the Quebrada del Sapo Formation, south of the Huincul High, has a significant input from Late Triassic (220-200 Ma) and Late Permian (280-260 Ma) sources of the axial exposures of the Huincul High. Surface data, combined with detrital zircon ages proved to be a powerful method to confirm the presence of an ancient positive element developed within the southern Neuquén basin. Its genesis falls within the early history of the Huincul deformation zone, where several structural features indicate pulses of growth since Early Jurassic times prior to the main Andean contractional cycle that started in the Late Cretaceous. Therefore, these data document for the first time the importance of the early contractional phases in the relief construction in the southern Central Andes, reinforcing previous hypotheses about pre-Andean intraplate deformation concentrated along this extensive east-west oriented basement weakness zone.

  2. Highly extended oceanic lithosphere: The basement and wallrocks for the Late Jurassic Rogue-Chetco oceanic arc, Oregon Klamath Mountains

    SciTech Connect

    Yule, J.D.; Saleeby, J.B.

    1993-04-01

    The superbly preserved, coeval Late Jurassic Rogue-Chetco oceanic arc and Josephine inter-arc basin exposed in the western Jurassic belt of the Oregon Klamath Mountains provide a unique opportunity to (1) directly observe the oceanic lithosphere upon which this oceanic arc was constructed, and (2) gain a better understanding of the pre-accretionary dynamic processes that shape oceanic arc and inter-arc basin lithosphere. Field relations exposed in the Roque, Illinois, and Chetco River areas show that (1) plutonic and volcanic rocks of the Rogue-Chetco arc both intruded and conformably overlapped fragmented composite blocks of oceanic crust and serpentinized, dike-filled depleted mantle rocks; and (2) arc growth occurred during regional oblique extension of the oceanic lithosphere resulting in the extreme fragmentation of oceanic crustal rocks and the local exposure of serpentinized mantle rocks on the sea floor. The Rogue-Chetco overlap sequence consists of rhythmically bedded volcanogenic turbidites, chert, argillite, and local deposits of polymict basal breccias. The clasts which comprise the distinctive basal breccias indicate derivation from a dominantly ophiolitic crust and serpentinized mantle source. Source materials for the basal breccias comprise the basement and wallrocks for the Roque-Chetco arc and consist of (1) rifted fragments of western Paleozoic and Triassic belt rocks (Yule and others, 1991) cut by heterogeneous mafic complexes inferred to represent early Josephine age rifting at approximately 165 Ma, (2) fault bounded blocks of massive gabbro, sheeted mafic dikes, pillow lava and breccia overlain by Callovian age chert, and (3) serpentinized depleted mantle peridotite cut by multiple generation of mafic and intermediate dikes. The basement rock types all share a pervasive brittle fragmentation and hydrothermal alteration history that is conspicuously absent in the arc volcanic and plutonic rocks.

  3. 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].

  4. 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

  5. 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

  6. 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.

  7. Geochronology, geochemistry, and deformation history of Late Jurassic-Early Cretaceous intrusive rocks in the Erguna Massif, NE China: Constraints on the late Mesozoic tectonic evolution of the Mongol-Okhotsk orogenic belt

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Xu, Wen-Liang; Wang, Feng; Zhao, Shuo; Li, Yu

    2015-09-01

    This paper presents new zircon and sphene U-Pb ages, biotite and hornblende 40Ar/39Ar ages, Hf isotopic data, and geochemical data for five Mesozoic plutons in the Erguna Massif of NE China. These data are used to constrain the late Mesozoic tectonic evolution of the Mongol-Okhotsk orogenic belt. This new dating, when combined with previously published ages, indicates that the Late Jurassic-Early Cretaceous (J3-K1) intrusive rocks can be subdivided into three stages that represent periods of magmatism during the Late Jurassic (~ 155 Ma), early Early Cretaceous (~ 137 Ma), and late Early Cretaceous (~ 123 Ma). In addition, the rocks have undergone later deformation recorded by peak ages of ~ 137 and ~ 123 Ma. The Late Jurassic and early Early Cretaceous intrusive rocks in the study area are dominantly syenogranites and are either A-type granites or are classified as alkaline series, suggesting that they formed in an extensional environment. The late Early Cretaceous intrusive rocks in this area are generally monzogranitic and were emplaced as dikes in an extensional environment, along with coeval bimodal volcanics. These data, combined with the presence of regional unconformities in the northern part of Hebei Province and western part of Liaoning Province, and the spatial distribution of coeval volcanic rocks in NE China, suggest the Late Jurassic and early Early Cretaceous magmatisms and the early Early Cretaceous deformation in this area occurred in an extensional environment related to the delamination of a thickened part of the crust after closure of the Mongol-Okhotsk Ocean. In comparison, the late Early Cretaceous deformation and magmatism occurred in an extensional environment related to either delamination of the previously thickened crust related to the Mongol-Okhotsk tectonic regime or the subduction of the Paleo-Pacific Plate, or the combined influence of these two tectonic regimes.

  8. Approaching trophic structure in Late Jurassic neritic shelves: A western Tethys example from southern Iberia

    NASA Astrophysics Data System (ADS)

    Olóriz, Federico; Reolid, Matías; Rodríguez-Tovar, Francisco J.

    2006-11-01

    The palaeoenvironmental conditions and trophic structure of a mid-outer neritic biota (microfossils, mainly forams, and macroinvertebrate assemblages) have been approached in middle Oxfordian-lowermost Kimmeridgian deposits from the Prebetic Zone (Betic Cordillera) in south-eastern Spain. According to relationships between fossil assemblages and lithofacies, a general seaward trend is identified which displays decreasing sedimentation rates and nutrient inputs, but increasing substrate consistency and presumably depth. Midshelf, terrigenous-rich deposits in the External Prebetic relate to the highest sedimentation rates and nutrient availability. These two parameters correlate with the highest content in vagile-benthic, calcareous perforate, epifaunal forams, as well as with potentially deep infaunal forams and infaunal macroinvertebrates. Outer-shelf lumpy deposits in the Internal Prebetic show the lowest sedimentation rates and nutrient availability and the highest records for macro-micro nektonics and planktics. In contrast, vagile-benthic, calcareous perforate epifaunal and potentially deep infaunal forams are scarcer in the midshelf environments. Colonial encrusting forams, benthic microbial communities and sessile benthic macro-invertebrates increase from the middle to outer shelf. Trophic-analysis structuring through the integration of benthic microbial communities, foraminiferal and macroinvertebrate fossil assemblages makes it possible to interpret: (a) a trophic-level frame composed of producers and primary and secondary consumers; (b) a main trophic-group differentiation in suspension-feeders, detritus-feeders, browsers, grazers, carnivores and scavengers; (c) a preliminary approach to food-chain structure supported by suspension-feeders, deposit-feeders and predators (active prey-selection carnivores); and (d) a food-pyramid model, which takes into account both recorded fossils and envisaged —i.e., ecologically inferred-organisms.

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

    SciTech Connect

    Donato, M.M. ); 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.

  10. Dike orientations in the late jurassic independence dike swarm and implications for vertical-axis tectonic rotations in eastern California

    USGS Publications Warehouse

    Hopson, R.F.; Hillhouse, J.W.; Howard, K.A.

    2008-01-01

    Analysis of the strikes of 3841 dikes in 47 domains in the 500-km-long Late Jurassic Independence dike swarm indicates a distribution that is skewed clockwise from the dominant northwest strike. Independence dike swarm azimuths tend to cluster near 325?? ?? 30??, consistent with initial subparallel intrusion along much of the swarm. Dike azimuths in a quarter of the domains vary widely from the dominant trend. In domains in the essentially unrotated Sierra Nevada block, mean dike azimuths range mostly between 300?? and 320??, with the exception of Mount Goddard (247??). Mean dike azimuths in domains in the Basin and Range Province in the Argus, Inyo, and White Mountains areas range from 291?? to 354?? the mean is 004?? in the El Paso Mountains. In the Mojave Desert, mean dike azimuths range from 318?? to 023??, and in the eastern Transverse Ranges, they range from 316?? to 051??. Restoration for late Cenozoic vertical-axis rotations, suggested by paleodeclinations determined from published studies from nearby Miocene and younger rocks, shifts dike azimuths into better agreement with azimuths measured in the tectonically stable Sierra Nevada. This confirms that vertical-axis tectonic rotations explain some of the dispersion in orientation, especially in the Mojave Desert and eastern Transverse Ranges, and that the dike orientations can be a useful if imperfect guide to tectonic rotations where paleomagnetic data do not exist. Large deviations from the main trend of the swarm may reflect (1) clockwise rotations for which there is no paleomagnetic evidence available, (2) dike intrusions of other ages, (3) crack filling at angles oblique or perpendicular to the main swarm, (4) pre-Miocene rotations, or (5) unrecognized domain boundaries between dike localities and sites with paleomagnetic determinations. ?? 2008 The Geological Society of America.

  11. Late Jurassic-Early Cretaceous coal-forming plants of the Bureya Basin, Russian Far East

    NASA Astrophysics Data System (ADS)

    Markevich, V. S.; Bugdaeva, E. V.

    2014-05-01

    The analysis of the composition of fossil palynomorphs from coals and clastic rocks of the Talyndzhan, Dublikan, Soloni, Chagdamyn, and Chemchuko formations of the Bureya coaliferous Basin revealed that the main coal-forming plants during the Talyndzhan and Dublikan time were represented by cyatheaceous ferns, plants similar to Pinaceae, and plants produced Ginkgocycadophytus pollen. In the Soloni time, the boggy plant communities were composed of dominant Cyatheaceae, subordinate Pinaceae, rare Gleichenaceae representatives, and Ginkgocycadophytus-producing plants. During the Chagdamyn time, the main coal-forming role belonged to gleicheniaceous ferns, bryophytes, and lycopsids, while the Chemchuko time was marked by the dominant contribution of Gleicheniaceae, Cyatheaceae, Ginkgocycadophytus, and plants close to Taxodiaceae to the coal formation.

  12. The Aguilar pluton (23°12? S-65°40? W; NW Argentina): Petrological implications on the origin of the Late Jurassic intraplate magmatism in the Central Andes

    NASA Astrophysics Data System (ADS)

    Omarini, Ricardo H.; Gioncada, Anna; Vezzoli, Luigina; Mazzuoli, Roberto; Cristiani, Chiara; Sureda, Ricardo J.

    2013-11-01

    The Late Jurassic Aguilar pluton is located in NW Argentina, about 300-400 Km east of the Tarapacá basin, representing the backarc basin linked to the Jurassic volcanic arc. This small-size and compositionally heterogeneous pluton intruded the metasedimentary rocks of the Ordovician Santa Victoria Group, along the Cobres-Salinas Grandes lineament. A revision of published geochemical data in the light of new field and petrological results, allows us to propose a model concerning the petrogenesis and emplacement mechanisms of Aguilar pluton and to discuss its geodynamic setting. The pluton is mainly composed of metaluminous and nearly peraluminous granitoids, showing the geochemical characteristics of ferroan granites. The volumetrically subordinate mafic rocks are both ne- and hy-normative, and their primary magmas were generated by partial melting of a pristine Proterozoic mantle. Aguilar rocks display a rather limited range in (87Sr/86Sr)i, compared to the entire rift-related plutonic suite, i.e., 0.703198-0.704601, and ?Ndt from -1.06 to 3.82, calculated at 149 Ma. Fractional crystallization of mantle-derived magmas and crustal contamination processes explain the evolution to produce strongly silica-oversaturated magmas, which emplaced in the continental crust. The petrological data indicate that magma emplacement and cooling occurred at rather shallow depth. Multiple injections of magma batches into the magma chamber caused mingling and mixing processes early in the crystallization history. The Aguilar pluton is one of the several igneous complexes whose formation was associated with the extensional tectonics active during Late Jurassic-Early Cretaceous in NW Argentina. Based on the geological position and the igneous rocks affinity, we exclude that the Late Jurassic magmatism was generated in an orogenic setting and envisage that it was linked to the early extensional phase that preceded the Cretaceous continental rifting, related to the break-up of the South America-Africa continents.

  13. A New Non-Pterodactyloid Pterosaur from the Late Jurassic of Southern Germany

    PubMed Central

    Hone, David W. E.; Tischlinger, Helmut; Frey, Eberhard; Röper, Martin

    2012-01-01

    Background The ‘Solnhofen Limestone’ beds of the Southern Franconian Alb, Bavaria, southern Germany, have for centuries yielded important pterosaur specimens, most notably of the genera Pterodactylus and Rhamphorhynchus. Here we describe a new genus of non-pterodactyloid pterosaur based on an extremely well preserved fossil of a young juvenile: Bellubrunnus rothgaengeri (gen. et sp. nov.). Methodology/Principal Findings The specimen was examined firsthand by all authors. Additional investigation and photography under UV light to reveal details of the bones not easily seen under normal lighting regimes was completed. Conclusions/Significance This taxon heralds from a newly explored locality that is older than the classic Solnhofen beds. While similar to Rhamphorhynchus, the new taxon differs in the number of teeth, shape of the humerus and femur, and limb proportions. Unlike other derived non-pterodacytyloids, Bellubrunnus lacks elongate chevrons and zygapophyses in the tail, and unlike all other known pterosaurs, the wingtips are curved anteriorly, potentially giving it a unique flight profile. PMID:22792168

  14. 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.

  15. 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

  16. Provenance of Late Carboniferous to Jurassic sandstones for southern Taimyr, Arctic Russia: A comparison of heavy mineral analysis by optical and QEMSCAN methods

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojing; Pease, Victoria; Omma, Jenny; Benedictus, Aukje

    2015-11-01

    Sandstone framework-grain petrography, optical and QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) heavy mineral analysis carried out on 40 samples collected from east and west southern Taimyr are used to constrain the provenance and tectonic history of Late Carboniferous to Late Jurassic siliciclastic sequences. The tectonic settings of provenance evolved gradually from a mix of volcanic arc and recycled orogen to craton interior. Much of the detritus in the Late Paleozoic to Mesozoic siliciclastic succession came from proximal sources with contributions from multi-type source rocks including acid igneous rocks, basalts, sedimentary rocks and low to medium-grade metamorphic rocks. Carboniferous to Permian sandstones contain low-diversity suites of heavy minerals, including apatite, tourmaline, zircon, rutile, Cr-spinel, monazite and titanite. Cr-spinel indicates probable influx from exposed ophiolitic basement. Abundant euhedral zircon and apatite suggest a volcanic arc source related with Uralian collision. The appearance of garnet in the early Triassic signals the unroofing of a metamorphic source. The abrupt increase of clinopyroxene in Middle to Late Triassic sandstones indicates the influx of detritus from basic rocks related with Siberian Trap magmatism. The decrease of Cr-spinel and an abundance of staurolite in Jurassic samples indicate that unroofing of an ophiolitic source ceased and that stripping of a different thrust sheet containing plenty of staurolite-bearing metamorphic rocks commenced.

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

    SciTech Connect

    Forester, R.M.; Smith, A.J.

    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.

  18. The motion of Adria during the Late Jurassic and Cretaceous: New paleomagnetic results from stable Istria

    NASA Astrophysics Data System (ADS)

    Márton, Em?; ?osovi?, Vlasta; Moro, Alan; Zvocak, Sergej

    2008-06-01

    The motion of Adria, the largest lithospheric fragment in the Central Mediterranean region, has played an important role in the tectonic development of the surrounding mountain chains and even of distant areas, like the Eastern Alps or the Pannonian basin. The available paleomagnetic data were insufficient to constrain this motion, except in a general way. In this paper, new paleomagnetic results are presented from one of the stable parts of Adria which emerge from the Adriatic Sea. The results were obtained on weakly magnetic platform carbonates of the mud-supported type, collected from 21 geographically distributed localities. The results, combined with mean paleomagnetic directions from selected localities from a pioneer study in Istria that were chosen using statistical criteria, were divided into three age groups (Tithonian-Aptian, Albian-Cenomanian, Turonian-Coniacian). The paleomagnetic poles calculated for each of them (Tithonian-Aptian): ?( N) = 47°, ?( E) = 275°, k = 67, ?95 = 9.4°, N = 5; Albian-Cenomanian: ?( N) = 58°, ?( E) = 253°, k = 145, ?95 = 4.3°, N = 9; Turonian-Coniacian: ?( N) = 63°, ?( E) = 261°, k = 50, ?95 = 7.3°, N = 9) reveal a moderate shift during the Cretataceous, which is comparable with that calculated from the African reference poles. However, the Istrian apparent polar wander path is slightly displaced from the African curve, as a consequence of about 10° counterclockwise rotation of Istria, with respect to Africa. This rotation angle is more that 10° smaller than the difference measured for the Mid-Late Eocene between the paleomagnetic direction of platform carbonates from Istria and the African reference direction. This difference may be the consequence of a small clockwise rotation of Istria, with respect to Africa, most probably at the end of Cretaceous.

  19. Oldest fossil flowers of hamamelidaceous affinity, from the Late Cretaceous of New Jersey.

    PubMed Central

    Crepet, W L; Nixon, K C; Friis, E M; Freudenstein, J V

    1992-01-01

    Exceptionally well-preserved staminate inflorescences, pistillate inflorescences, and detached stamens with important phylogenetic and paleoecological implications have been discovered from the Turonian (ca. 88.5-90.4 million years B.P.) Raritan Formation of New Jersey. The fossils have a combination of floral and pollen characters found in various genera of modern entomophilous and anemophilous Hamamelidaceae and anemophilous Platanus (Platanaceae). The floral characters of the fossils, including a sepal cup, staminal tube, and apparently nectariferous staminodes, indicate that this taxon was probably insect pollinated. The juxtaposition of character complexes in an extinct taxon from disparate modern taxa provides an interesting phylogenetic perspective on the origins of Hamamelidaceae and is a striking example of a fossil that is a mosaic of familial level characters relative to modern taxa. Of even broader interest, however, is the occurrence of staminodal nectaries that have structural characters intermediate between the fossil's functional stamens and modern hamamelidaceous petals. This transitional staminode morphology in the context of the other fossil characters suggests a staminodal origin of petals in the hamamelid-rosid lineage. This hypothesis is supported by the apparent staminode position within the fossil flowers where petals are found in modern genera. The character complex of morphologically transitional staminodes, a staminal tube, and sepal cup can be viewed as prehypanthial, lacking only fusion of the staminal tube to the sepal cup. The appearance of the character complex embodied in these flowers during the late mid-Cretaceous may signal the early stages of the relationship between specialized pollinators, such as bees, and the hamamelid-rosid-asterid lineage of angiosperms, arguably one of the most important events in angiosperm radiation. Images PMID:11607328

  20. Inference of pCO2 Levels during the Late Cretaceous Using Fossil Lauraceae

    NASA Astrophysics Data System (ADS)

    Richey, J. D.; Upchurch, G. R.

    2011-12-01

    Botanical estimates of pCO2 for the Late Cretaceous have most commonly used Stomatal Index (SI) in fossil Ginkgo. Recently, SI in fossil Lauraceae has been used to infer changes in pCO2 across the Cenomanian-Turonian boundary, based on the relation between SI and pCO2 in extant Laurus and Hypodaphnis. To provide a broad-scale picture of pCO2 based on fossil Lauraceae, we examined dispersed cuticle of the leaf macrofossil genus Pandemophyllum from: 1) the early to middle Cenomanian of the Potomac Group of Maryland (Mauldin Mountain locality, lower Zone III) and 2) the Maastrichtian of southern Colorado (Raton Basin, Starkville South and Berwind Canyon localities). These samples fall within the Late Cretaceous decline in pCO2 inferred from geochemical modeling and other proxies. SI was calculated from fossil cuticle fragments using ImageJ and counts of up to 56,000 cells per sample, a far greater number of cells than are counted in most studies. CO2 levels were estimated using the relation between SI and CO2 published for Laurus nobilis and Hypodaphnis zenkeri. Early to middle Cenomanian atmospheric pCO2 is estimated at 362-536 parts per million (ppm). This represents the absolute minimum and maximum estimated CO2 levels from the ±95% confidence intervals (CI) of the relation between SI and CO2 for the modern equivalents, and SI ± 1 Standard Deviation (SD) in the fossil genus Pandemophyllum. Late Maastrichtian atmospheric pCO2 is estimated at 358-534 ppm. The Maastrichtian estimates falls within the range of published estimates from other proxies. The Cenomanian estimate, in contrast, is low relative to most other estimates. The 95% confidence intervals of our pCO2 estimates overlap each other and many of the assemblages published by Barclay et al. (2010) for Lauraceae across the Cenomanian-Turonian boundary. This could indicate that 1) pCO2 did not undergo a major long-term decline during the Late Cretaceous, 2) Lauraceae show low sensitivity to high pCO2, or 3) additional sampling is necessary to find the mid-Cretaceous pCO2 maximum inferred by other proxy methods.

  1. 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.

  2. SHRIMP U-Pb zircon geochronology of Mesozoic granitoids from the Bariloche region (Argentina): Implications for the Middle-Late Jurassic evolution of the North Patagonian batholith.

    NASA Astrophysics Data System (ADS)

    Castro, Antonio; Vujovich, Graciela; Fernández, Carlos; Moreno-Ventas, Iñaki; Martino, Roberto; Corretgé, Guillermo; Díaz-Alvarado, Juan; Heredia, Nemesio; Gallastegui, Gloria

    2010-05-01

    A detailed U-Pb geochronological study has been carried out on granitoids of the North Patagonian batholith in the region of Bariloche (Argentina), between 40°30' S and 41°45' S. In this region, the calc-alkaline, subduction-related, granitic bodies of the North Patagonian batholith intruded an Early Jurassic volcano-sedimentary sequence contemporary with the intrusion of the Subcordilleran Patagonian batholith (J1 magmatism), and unconformably overlying a metamorphic Gondwanan basement. All these rocks were affected by the Andean compressional phases during the Cenozoic. U-Pb SHRIMP dating of zircon crystals from 11 samples (109 spots) of diorites, tonalites, granodiorites and granites yielded dates ranging from 173 ± 3 Ma to 150 ± 2 Ma (Aalenian to Tithonian). No significant age differences have been identified among the distinct lithological types. Also no spatial trend emerges from these results, although ages tend to be younger westward in the traverse of the Manso River (? 41° 35' S). Two peaks appear in the probability density plot of zircon ages. Most of the dated zircons are Bajocian-Bathonian (Middle Jurassic, ?169 Ma, J2 magmatism), while a secondary peak is observed at the boundary Oxfordian-Kimmeridgian (Late Jurassic, ? 156 Ma, J3 magmatism). The J2 magmatic period is coeval to the main stage of effusive activity (V2) in the huge volcanic Chon Aike Province, while J3 coincides with the lesser V3 period of volcanism in Chon Aike. These new geochronological data strongly contribute to the knowledge of the first stages of tectonic evolution of the Andean subduction margin in southern South America. Contrary to previous models, it can be proposed that the subduction-related Mesozoic magmatism started well before the Late Jurassic, and that a continuous supply of calc-alkaline magmas dominated the active margin of South America during at least 190 Ma, from the Early Jurassic to nowadays. Therefore, no dramatic time gap can be observed between the Subcordilleran Patagonian batholith and the North Patagonian batholith at the studied area. On the other side, the close age relationship between the North Patagonian batholith and the volcanic rocks of the Chon Aike Province, that, according to previous studies, shows a strong subduction-related geochemical affinity for the V2 and V3 episodes, opens new ways to decipher this poorly known period of Andean subduction and to evaluate the petrogenetical links between plutonic and volcanic rocks in active continental margins.

  3. 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.

  4. Late Pleistocene Nannofossil Assemblages and Time-Averaging in the Fossil Record [IODP Site U1419] 

    E-print Network

    Patrick, Amanda Kacy

    2014-09-21

    stream_source_info PATRICK-THESIS-2015.pdf.txt stream_content_type text/plain stream_size 28140 Content-Encoding UTF-8 stream_name PATRICK-THESIS-2015.pdf.txt Content-Type text/plain; charset=UTF-8 LATE... PLEISTOCENE NANNOFOSSIL ASSEMBLAGES AND TIME- AVERAGING IN THE FOSSIL RECORD [IODP SITE U1419] An Undergraduate Research Scholars Thesis by AMANDA KACY PATRICK Submitted to Honors and Undergraduate Research Texas A&M University in partial...

  5. Late Quaternary Precipitation Seasonality of SW North America Reconstructed from Stable Isotopes in Fossil Packrat Pellets

    NASA Astrophysics Data System (ADS)

    Cole, K. L.; Ironside, K.; Cole, E. A.; Fisher, J.

    2011-12-01

    Stable isotopic values of Carbon 13, Nitrogen 15, Oxygen 18, and Deuterium were measured from modern and fossil packrat pellets from throughout the southwestern United States using a gas isotope ratio mass spectrometer. Late Twentieth Century climate observations were extrapolated to the locations of 41 modern pellet reference samples ranging across Arizona, Utah, Nevada, and California, U.S.A. The reference samples demonstrated correlations between the amount and percent of annual precipitation falling in the winter to early spring (December through April) for ?15N, and percent monsoon precipitation (July through September) for ?D. Isotope values were not well correlated with temperature variables. Isotopes of Carbon and Oxygen were poorly correlated with the climate variables investigated, although previous studies have indicated that ?13C often reflects the abundance of CAM species within the middens as packrats usually feed upon either succulent CAM or C3 conifer species. The modern isotopic values were next compared to series of fossil values from the Grand Canyon, AZ, Glen Canyon, UT, Wupatki National Monument, AZ, and Picacho Peak, CA. Fifty to 100 fossil pellets were ground to dust and homogenized to create a sample from each midden deposit. This sample should represent an average from local plants consumed by the packrat over at least several years. The two most complete series of ?D values, from upper and lower elevations within the Grand Canyon, suggested extremely low monsoon percentages from 23.5 to 18.0 ka (full-glacial Wisconsinan), but higher than current values from 13.7 to 13.0 ka (Alleröd Period) and from 11.7 to 7.6 ka (early Holocene). The increased monsoon amounts during the Alleröd and early Holocene reinforce earlier conclusions based upon plant fossils from these midden series. Fossil series of ?15N values showed fewer clear trends through time. Our results suggest that ?D values from fossil packrat pellets can serve as a valuable complement to plant fossils in reconstructing past precipitation seasonality in the monsoonal deserts of southwestern North America.

  6. 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.

  7. Ribosomal RNA gene fragments from fossilized cyanobacteria identified in primary gypsum from the late Miocene, Italy.

    PubMed

    Panieri, G; Lugli, S; Manzi, V; Roveri, M; Schreiber, B C; Palinska, K A

    2010-03-01

    Earth scientists have searched for signs of microscopic life in ancient samples of permafrost, ice, deep-sea sediments, amber, salt and chert. Until now, evidence of cyanobacteria has not been reported in any studies of ancient DNA older than a few thousand years. Here, we investigate morphologically, biochemically and genetically primary evaporites deposited in situ during the late Miocene (Messinian) Salinity Crisis from the north-eastern Apennines of Italy. The evaporites contain fossilized bacterial structures having identical morphological forms as modern microbes. We successfully extracted and amplified genetic material belonging to ancient cyanobacteria from gypsum crystals dating back to 5.910-5.816 Ma, when the Mediterranean became a giant hypersaline brine pool. This finding represents the oldest ancient cyanobacterial DNA to date. Our clone library and its phylogenetic comparison with present cyanobacterial populations point to a marine origin for the depositional basin. This investigation opens the possibility of including fossil cyanobacterial DNA into the palaeo-reconstruction of various environments and could also be used to quantify the ecological importance of cyanobacteria through geological time. These genetic markers serve as biosignatures providing important clues about ancient life and begin a new discussion concerning the debate on the origin of late Miocene evaporites in the Mediterranean. PMID:20059556

  8. 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.

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

    PubMed

    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

  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. 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.

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

    USGS Publications Warehouse

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

    2004-01-01

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

  13. Late Quaternary paleoclimate of western Alaska inferred from fossil chironomids and its relation to vegetation histories

    USGS Publications Warehouse

    Kurek, Joshua; Cwynar, Les C.; Ager, Thomas A.; Abbott, Mark B.; Edwards, Mary E.

    2009-01-01

    Fossil Chironomidae assemblages (with a few Chaoboridae and Ceratopogonidae) from Zagoskin and Burial Lakes in western Alaska provide quantitative reconstructions of mean July air temperatures for periods of the late-middle Wisconsin (~39,000-34,000 cal yr B.P.) to the present. Inferred temperatures are compared with previously analyzed pollen data from each site summarized here by indirect ordination. Paleotemperature trends reveal substantial differences in the timing of climatic warming following the late Wisconsin at each site, although chronological uncertainty exists. Zagoskin Lake shows early warming beginning at about 21,000 cal yr B.P., whereas warming at Burial Lake begins ~4000 years later. Summer climates during the last glacial maximum (LGM) were on average ~3.5C° below the modern temperatures at each site. Major shifts in vegetation occurred from ~19,000 to 10,000 cal yr B.P. at Zagoskin Lake and from ~17,000 to 10,000 cal yr B.P. at Burial Lake. Vegetation shifts followed climatic warming, when temperatures neared modern values. Both sites provide evidence of an early postglacial thermal maximum at ~12,300 cal yr B.P. These chironomid records, combined with other insect-based climatic reconstructions from Beringia, indicate that during the LGM: (1) greater continentality likely influenced regions adjacent to the Bering Land Bridge and (2) summer climates were, at times, not dominated by severe cold.

  14. 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

  15. 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

  16. 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.

  17. 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.

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

    SciTech Connect

    Goldhammer, R.K. )

    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.

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

    SciTech Connect

    Goldhammer, R.K.

    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.

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

    SciTech Connect

    Sablock, J. . 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.

  1. 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

  2. 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.

  3. Fossil embryos from the Middle and Late Cambrian period of Hunan, south China.

    PubMed

    Dong, Xi-Ping; Donoghue, Philip C J; Cheng, Hong; Liu, Jian-Bo

    2004-01-15

    Comparative embryology is integral to uncovering the pattern and process of metazoan phylogeny, but it relies on the assumption that life histories of living taxa are representative of their antecedents. Fossil embryos provide a crucial test of this assumption and, potentially, insight into the evolution of development, but because discoveries so far lack phylogenetic constraint, their significance is moot. Here we describe a collection of embryos from the Middle and Late Cambrian period (500 million years ago) of Hunan, south China, that preserves stages of development from cleavage to the pre-hatching embryo of a direct-developing animal comparable to living Scalidophora (phyla Priapulida, Kinorhyncha, Loricifera). The latest-stage embryos show affinity to the Lower Cambrian embryo Markuelia, whose life-history strategy contrasts both with the primitive condition inferred for metazoan phyla and with many proposed hypotheses of affinity, all of which prescribe indirect development. Phylogenetic tests based on these embryological data suggest a stem Scalidophora affinity. These discoveries corroborate, rather than contradict, the predictions of comparative embryology, providing direct historical support for the view that the life-history strategies of living taxa are representative of their stem lineages. PMID:14724636

  4. 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.

  5. Stable Iron Isotopes and Microbial Mediation in Red Pigmentation of the Rosso Ammonitico (Mid-Late Jurassic, Verona Area, Italy)

    NASA Astrophysics Data System (ADS)

    Préat, Alain R.; de Jong, Jeroin, 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 ‰, ranging between -1.52 to -0.06‰) 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 ?56Fe values that were systematically lower in the red facies residues (median: -0.84‰, range: -1.46 to +0.26‰) compared to the grey facies residues (median: -0.08 ‰, range: -0.34 to +0.23‰). In addition, the red facies residues were characterized by a lighter ?56Fe 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-Corg 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.

  6. 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

  7. 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.

  8. Fossil shrews from Honduras and their significance for late glacial evolution in body size (Mammalia: Soricidae: Cryptotis)

    USGS Publications Warehouse

    Woodman, N.; Croft, D.A.

    2005-01-01

    Our study of mammalian remains excavated in the 1940s from McGrew Cave, north of Copan, Honduras, yielded an assemblage of 29 taxa that probably accumulated predominantly as the result of predation by owls. Among the taxa present are three species of small-eared shrews, genus Cryptotis. One species, Cryptotis merriami, is relatively rare among the fossil remains. The other two shrews, Cryptotis goodwini and Cryptotis orophila, are abundant and exhibit morpho metrical variation distinguishing them from modern populations. Fossils of C. goodwini are distinctly and consistently smaller than modern members of the species. To quantify the size differences, we derived common measures of body size for fossil C. goodwini using regression models based on modern samples of shrews in the Cryptotis mexicana-group. Estimated mean length of head and body for the fossil sample is 72-79 mm, and estimated mean mass is 7.6-9.6 g. These numbers indicate that the fossil sample averaged 6-14% smaller in head and body length and 39-52% less in mass than the modern sample and that increases of 6-17% in head and body length and 65-108% in mass occurred to achieve the mean body size of the modern sample. Conservative estimates of fresh (wet) food intake based on mass indicate that such a size increase would require a 37-58% increase in daily food consumption. In contrast to C. goodwini, fossil C. orophila from the cave is not different in mean body size from modern samples. The fossil sample does, however, show slightly greater variation in size than is currently present throughout the modern geographical distribution of the taxon. Moreover, variation in some other dental and mandibular characters is more constrained, exhibiting a more direct relationship to overall size. Our study of these species indicates that North American shrews have not all been static in size through time, as suggested by some previous work with fossil soricids. Lack of stratigraphic control within the site and our failure to obtain reliable radiometric dates on remains restrict our opportunities to place the site in a firm temporal context. However, the morphometrical differences we document for fossil C. orophila and C. goodwini show them to be distinct from modern populations of these shrews. Some other species of fossil mammals from McGrew Cave exhibit distinct size changes of the magnitudes experienced by many northern North American and some Mexican mammals during the transition from late glacial to Holocene environmental conditions, and it is likely that at least some of the remains from the cave are late Pleistocene in age. One curious factor is that, whereas most mainland mammals that exhibit large-scale size shifts during the late glacial/postglacial transition experienced dwarfing, C. goodwini increased in size. The lack of clinal variation in modern C. goodwini supports the hypothesis that size evolution can result from local selection rather than from cline translocation. Models of size change in mammals indicate that increased size, such as that observed for C. goodwini, are a likely consequence of increased availability of resources and, thereby, a relaxation of selection during critical times of the year.

  9. Late Jurassic--Early Cretaceous cooling for Late Proterozoic through Early Devonian crystalline rocks from the Bronson Hill anticlinorium, MA--VT: Evidence from apatite fission track analysis

    SciTech Connect

    Roden, M.K. . Dept. of Earth and Environmental Science)

    1993-03-01

    Ten samples of crystalline rocks from the Bronson Hill anticlinorium in north central Massachusetts--south central Vermont yield Mesozoic apatite fission track cooling ages ranging from 98 [+-] 8 to 158 [+-] 24 Ma. Compositionally, the samples include a quartz-phyric rhyolite from the Ammonoosuc Volcanics, a pegmatite from the Kempfield Anticline, a gabbro from the Prescott Intrusive Complex, the Dry Hill and Fourmile Gneisses from the Pelham Dome, Swanzey Gneiss from the Keene Dome, Pauchaug Gneiss from the Warwick Dome, and the Monson Gneiss. Published U-Pb zircon analyses for the same samples yield ages of 613 [+-] 3 Ma for the Dry Hill Gneiss; 454--442 [+-] 3 Ma for the Swanzey, Pauchaug, Monson and Fourmile Gneisses; 453 [+-] 2 Ma for the Ammonoosuc Volcanics; and 407 [+-] 3/[minus]2 Ma for the Prescott Intrusive Complex gabbro (Tucker and Robinson, 1990). Apatite fission track ages are all reset and increase in apparent age eastward from the edge of the Deerfield-Hartford Basin, consistent with published apatite fission track ages from Jurassic sedimentary units within the Deerfield and Northern Hartford Basins. Mean track lengths ranged from 13.4 to 14.4 [mu]m with moderately large standard deviations. These track length distributions suggest relatively slow cooling through the track annealing range of 70--90 C and are consistent with track length distributions for sedimentary samples within the Deerfield and Northern Hartford Basins. The trend of increasing apatite fission track apparent age eastward from the basin margin suggests several interpretations: (1) differential uplift; (2) deeper burial in the basin and adjacent areas; (3) higher heat flow along the basin margin. Zircon fission track analyses are in progress to constrain maximum burial depths and should help differentiate between these models.

  10. 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

  11. Crust/mantle interaction during the construction of an extensional magmatic dome: Middle to Late Jurassic plutonic complex from western Liaoning, North China Craton

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaohui; Yuan, Lingling; Wilde, Simon A.

    2014-09-01

    Differentiating magmatic doming and low-angle normal faulting remains critical for fully understanding the thermal, mechanical and chemical evolution of continental landmasses under extension. This zircon U-Pb dating and geochemical study documents two Middle to Late Jurassic batholiths (Lüshan and Haitangshan) from the Yiwulüshan range of western Liaoning, North China Craton. They consist of a variety of lithologies including gabbro, diorite, granodiorite, monzogranite, together with microgranular magmatic enclaves (MME) and mafic dykes. Synthesizing petrologic, elemental, whole-rock Sr-Nd and zircon Hf isotopic data leads to the characterization of multiple mafic and felsic end-members and their concomitant interaction in building the magmatic dome. A subduction-related metasomatized lithospheric mantle source is fingerprinted by the gabbroic to dioritic rocks with enriched large ion lithophile elements, depleted high field strength elements and heterogeneous isotopic compositions (87Sr/86Sri = 0.70541 to 0.70577, ?Nd(t) = - 1.78 to - 5.54 and zircon ?Hf(t) = - 6.0 to 8.1). One felsic magma end-member of ancient mafic lower crustal parentage is discernable from adakitic granites with high Sr/Y and evolved isotopic composition (87Sr/86Sri = 0.70533 to 0.70792, ?Nd(t) = - 18.8 to - 21.7, zircon ?Hf(t) = - 18.5 to - 28.8), whereas another felsic magma end-member of newly underplated crustal heritage manifests itself from some monzogranites with non-adakitic elemental affinity and juvenile isotopic composition (87Sr/86Sri = 0.70429 to 0.70587, ?Nd(t) = - 4.47 to - 5.87, zircon ?Hf(t) = 4.3 to 1.3). Hybridization processes between mantle-derived mafic magma and ancient crustal-derived felsic magma result in the formation of MME-bearing granodiorites with intermediate isotopic signatures (87Sr/86Sri = 0.70491 to 0.70499, ?Nd(t) = - 15.3 to - 15.8, zircon ?Hf(t) = - 12.7 to - 17.4). Subsequent fractional crystallization of the hybridized magmas endows the differentiated monzogranites with low Sr/Y and highly evolved isotopes (87Sr/86Sri = 0.70496 to 0.70605, ?Nd(t) = - 16.0 to - 18.7, zircon ?Hf(t) = - 14.3 to - 21.5). Apart from distinguishing Middle-Late Jurassic extensional magmatic doming from Early Cretaceous detachment faulting, this complex mafic-felsic magma association encapsulates a multi-level crust/mantle interaction leading to lithospheric thinning and concomitant crustal architectural reorganization in the Yanshan belt during the Late Mesozoic. Near-synchronization of a two-stage extensional pattern in the Yanshan belt and even across NE continental Asia accords well with gravitational collapse and convective removal of lithospheric mantle within an evolved post-collisional to within-plate extensional regime.

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

    SciTech Connect

    Oldow, J.S. . 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.

  13. Atmospheric CO2 from the late Oligocene to early Miocene reconstructed from photosynthesis data and leaf characteristics of fossil plants

    NASA Astrophysics Data System (ADS)

    Grein, Michaela; Oehm, Christoph; Konrad, Wilfried; Utescher, Torsten; Kunzmann, Lutz; Roth-Nebelsick, Anita

    2013-04-01

    In the Cenozoic era, global climate changed from greenhouse to icehouse conditions. During the Oligocene, the comparatively cool phase in the earlier part of the late Oligocene is followed by the Late Oligocene Warming and a major glaciation event at the Oligocene-Miocene transition (Mi-1). Various studies indicate that these climate events were coupled to changes in atmospheric CO2 levels. In this study, atmospheric CO2 from the late Oligocene to the early Miocene was reconstructed by using photosynthesis data and fossil leaf characteristics. We used plant material from various sites located in Germany and Austria comprising fossil leaves of four angiosperm plant species: Platanus neptuni (Platanaceae), Quercus rhenana, Q. praerhenana and Eotrigonobalanus furcinervis (all Fagaceae). A mechanistic-theoretical approach based on stomatal parameters, photosynthesis data and gas exchange parameters was applied to model palaeoatmospheric CO2 levels. Detailed climate data of the considered sites were reconstructed as well since the mechanistic-theoretical approach requires climate data as input parameters for calculating both assimilation rate and transpiration rate. Our results indicate a steady CO2 level of about 400 ppm for all sites and therefore suggest a decoupling of CO2 and cooling/warming events for the considered time slices.

  14. Recent synchronous radiation of a living fossil.

    PubMed

    Nagalingum, N S; Marshall, C R; Quental, T B; Rai, H S; Little, D P; Mathews, S

    2011-11-11

    Modern survivors of previously more diverse lineages are regarded as living fossils, particularly when characterized by morphological stasis. Cycads are often cited as a classic example, reaching their greatest diversity during the Jurassic-Cretaceous (199.6 to 65.5 million years ago) then dwindling to their present diversity of ~300 species as flowering plants rose to dominance. Using fossil-calibrated molecular phylogenies, we show that cycads underwent a near synchronous global rediversification beginning in the late Miocene, followed by a slowdown toward the Recent. Although the cycad lineage is ancient, our timetrees indicate that living cycad species are not much older than ~12 million years. These data reject the hypothesized role of dinosaurs in generating extant diversity and the designation of today's cycad species as living fossils. PMID:22021670

  15. First glimpse into Lower Jurassic deep-sea biodiversity: in situ diversification and resilience against extinction.

    PubMed

    Thuy, Ben; Kiel, Steffen; Dulai, Alfréd; Gale, Andy S; Kroh, Andreas; Lord, Alan R; Numberger-Thuy, Lea D; Stöhr, Sabine; Wisshak, Max

    2014-07-01

    Owing to the assumed lack of deep-sea macrofossils older than the Late Cretaceous, very little is known about the geological history of deep-sea communities, and most inference-based hypotheses argue for repeated recolonizations of the deep sea from shelf habitats following major palaeoceanographic perturbations. We present a fossil deep-sea assemblage of echinoderms, gastropods, brachiopods and ostracods, from the Early Jurassic of the Glasenbach Gorge, Austria, which includes the oldest known representatives of a number of extant deep-sea groups, and thus implies that in situ diversification, in contrast to immigration from shelf habitats, played a much greater role in shaping modern deep-sea biodiversity than previously thought. A comparison with coeval shelf assemblages reveals that, at least in some of the analysed groups, significantly more extant families/superfamilies have endured in the deep sea since the Early Jurassic than in the shelf seas, which suggests that deep-sea biota are more resilient against extinction than shallow-water ones. In addition, a number of extant deep-sea families/superfamilies found in the Glasenbach assemblage lack post-Jurassic shelf occurrences, implying that if there was a complete extinction of the deep-sea fauna followed by replacement from the shelf, it must have happened before the Late Jurassic. PMID:24850917

  16. First glimpse into Lower Jurassic deep-sea biodiversity: in situ diversification and resilience against extinction

    PubMed Central

    Thuy, Ben; Kiel, Steffen; Dulai, Alfréd; Gale, Andy S.; Kroh, Andreas; Lord, Alan R.; Numberger-Thuy, Lea D.; Stöhr, Sabine; Wisshak, Max

    2014-01-01

    Owing to the assumed lack of deep-sea macrofossils older than the Late Cretaceous, very little is known about the geological history of deep-sea communities, and most inference-based hypotheses argue for repeated recolonizations of the deep sea from shelf habitats following major palaeoceanographic perturbations. We present a fossil deep-sea assemblage of echinoderms, gastropods, brachiopods and ostracods, from the Early Jurassic of the Glasenbach Gorge, Austria, which includes the oldest known representatives of a number of extant deep-sea groups, and thus implies that in situ diversification, in contrast to immigration from shelf habitats, played a much greater role in shaping modern deep-sea biodiversity than previously thought. A comparison with coeval shelf assemblages reveals that, at least in some of the analysed groups, significantly more extant families/superfamilies have endured in the deep sea since the Early Jurassic than in the shelf seas, which suggests that deep-sea biota are more resilient against extinction than shallow-water ones. In addition, a number of extant deep-sea families/superfamilies found in the Glasenbach assemblage lack post-Jurassic shelf occurrences, implying that if there was a complete extinction of the deep-sea fauna followed by replacement from the shelf, it must have happened before the Late Jurassic. PMID:24850917

  17. Origin of the volcanic complexes of La Désirade, Lesser Antilles: Implications for tectonic reconstruction of the Late Jurassic to Cretaceous Pacific-proto Caribbean margin

    NASA Astrophysics Data System (ADS)

    Neill, Iain; Gibbs, Jennifer A.; Hastie, Alan R.; Kerr, Andrew C.

    2010-12-01

    La Désirade Island is located on the hanging wall of the present-day Lesser Antilles subduction zone and consists of a suite of Mesozoic igneous rocks capped by Neogene limestone. The basement suite contains Kimmeridgian to Tithonian (~ 153-145 Ma) mafic lava flows and pillow basalts overlain by felsic flows and breccias and intruded by a Mid-Berriasian (~ 144 Ma) trondhjemite pluton and intermediate to felsic dykes. The mafic rocks form a ~ 300 m thick sequence which trace element geochemistry reveals to contain, in stratigraphic order: (1) tholeiites with a very weak subduction signature; (2) calc-alkaline and tholeiitic arc rocks containing pelagic and terrigenous sediment slab-related components and (3) arc tholeiites with a minor subduction signature. The mantle wedge source was depleted and did not contain a significant plume-related component. The overlying felsic rocks show similar trace element patterns and incompatible trace element ratios to the mafic units. Factors such as pelagic sedimentary deposition and re-working, low eruption rates and the presence of MORB-like and felsic rocks are best explained by an origin at a back-arc spreading ridge. This back-arc was most likely in the proto-Caribbean (Colombian Marginal) seaway and was related to east-dipping Andean/Cordilleran subduction. Other sites in the Greater Antilles and Central America older than the ~ 135 Ma westward acceleration of North America appear to corroborate a latest Jurassic-Early Cretaceous east-dipping arc system. The preservation of La Désirade in the fore-arc of the present Antilles arc is consistent with Mid-to-Late Cretaceous inception of west-dipping subduction along the former back-arc axis which had previously given rise to La Désirade.

  18. A contribution to regional stratigraphic correlations of the Afro-Brazilian depression - The Dom João Stage (Brotas Group and equivalent units - Late Jurassic) in Northeastern Brazilian sedimentary basins

    NASA Astrophysics Data System (ADS)

    Kuchle, Juliano; Scherer, Claiton Marlon dos Santos; Born, Christian Correa; Alvarenga, Renata dos Santos; Adegas, Felipe

    2011-04-01

    The Dom João Stage comprises an interval with variable thickness between 100 and 1200 m, composed of fluvial, eolian and lacustrine deposits of Late Jurassic age, based mainly on the lacustrine ostracod fauna (although the top deposits may extend into the Early Cretaceous). These deposits comprise the so-called Afro-Brazilian Depression, initially characterized as containing the Brotas Group of the Recôncavo Basin (which includes the Aliança and the Sergi Formations) and subsequently extended into the Tucano, Jatobá, Camamu, Almada, Sergipe, Alagoas and Araripe Basins in northeastern Brazil, encompassing the study area of this paper. The large occurrence area of the Dom João Stage gives rise to discussions about the depositional connectivity between the basins, and the real extension of sedimentation. In the first studies of this stratigraphic interval, the Dom João Stage was strictly associated with the rift phase, as an initial stage (decades of 1960-70), but subsequent analyses considered the Dom João as an intracratonic basin or pre-rift phase - without any relation to the active mechanics of a tectonic syn-rift phase (decades of 1980-2000). The present work developed an evolutionary stratigraphic and tectonic model, based on the characterization of depositional sequences, internal flooding surfaces, depositional systems arrangement and paleoflow directions. Several outcrops on the onshore basins were used to build composite sections of each basin, comprising facies, architectural elements, depositional systems, stratigraphic and lithostratigraphic frameworks, and paleocurrents. In addition to that, over a hundred onshore and offshore exploration wells were used (only 21 of which are showed) to map the depositional sequences and generate correlation sections. These show the characteristics and relations of the Dom João Stage in each studied basin, and they were also extended to the Gabon Basin. The results indicate that there were two main phases during the Dom João Stage, in which distinctive sedimentary environments were developed, reflecting depositional system arrangements, paleoflow directions were diverse, and continuous or compartmented basins were developed.

  19. Paleomagnetism of Late Jurassic to Early Cretaceous red beds from the Cardamom Mountains, southwestern Cambodia: Tectonic deformation of the Indochina Peninsula

    NASA Astrophysics Data System (ADS)

    Tsuchiyama, Yukiho; Zaman, Haider; Sotham, Sieng; Samuth, Yos; Sato, Eiichi; Ahn, Hyeon-Seon; Uno, Koji; Tsumura, Kosuke; Miki, Masako; Otofuji, Yo-ichiro

    2016-01-01

    Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from the Sihanoukville and Koah Kong areas of the Phuquoc-Kampot Som Basin, southwestern Cambodia. Two high-temperature remanent components with unblocking temperature ranging 650°-670 °C and 670-690 °C were identified. The magnetization direction for the former component (D = 5.2 °, I = 18.5 ° with ?95 = 3.1 ° in situ) reveals a negative fold test that indicates a post-folding secondary nature. However, the latter component, carried by specular hematite, is recognized as a primary remanent magnetization. A tilt-corrected mean direction of D = 43.4 °, I = 31.9 ° (?95 = 3.6 °) was calculated for the primary component at 11 sites, corresponding to a paleopole of 47.7°N, 178.9°E (A95 = 3.6 °). When compared with the 130 Ma East Asian pole, a southward displacement of 6.0 ° ± 3.5 ° and a clockwise rotation of 33.1 ° ± 4.0 ° of the Phuquoc-Kampot Som Basin (as a part of the Indochina Block) with respect to East Asia were estimated. This estimate of the clockwise rotation is ?15° larger than that of the Khorat Basin, which we attribute to dextral motion along the Wang Chao Fault since the mid-Oligocene. The comparison of the herein estimated clockwise rotation with the counter-clockwise rotation reported from the Da Lat area in Vietnam suggests the occurrence of a differential tectonic rotation in the southern tip of the Indochina Block. During the southward displacement of the Indochina Block, the non-rigid lithosphere under its southern tip moved heterogeneously, while the rigid lithosphere under the Khorat Basin moved homogeneously.

  20. 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

    2015-08-01

    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).

  1. 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

  2. Geochemistry and geochronology of the Dongshanwan porphyry Mo-W deposit, Northeast China: Implications for the Late Jurassic tectonic setting

    NASA Astrophysics Data System (ADS)

    Zeng, Qing-Dong; Sun, Yan; Chu, Shao-Xiong; Duan, Xiao-Xia; Liu, Jianming

    2015-01-01

    The Dongshanwan porphyry Mo-W deposit is located in the southern segment of the Da Hinggan Mountains of the eastern segment of the Central Asia Orogenic Belt. More than 95% of the mineralization occurs within the Dongshanwan granite porphyry, with a small part being hosted within quartz veins that crosscut the Late Permian strata. Zircon U-Pb age measurements indicate that the Dongshanwan granite porphyry has a 206Pb/238U age of 151.4 ± 0.8 Ma. Three molybdenite samples from the Dongshanwan deposit were selected for Re-Os isotope measurement to define the mineralization age of the deposit. These yielded Re-Os model ages of 149.3 ± 2.3 to 155.4 ± 3.3 Ma. Based on analyses of major and trace elements and Hf isotopes, the Dongshanwan porphyry is characterized by low Sr and high Y values, exhibiting strong negative Eu anomalies (?Eu = 0.01-0.04), indicating post-collisional (A-type) geochemical characteristics. The Hf isotopic composition of the Dongshanwan porphyry (?Hf(t) = +5.5 to +9.2) indicates that both juvenile crustal sources and depleted mantle contributed to their origin. The regional geological setting, when combined with the geochemistry of the Dongshanwan porphyry, probably indicates that the granite porphyry derives from crustal root melting during lithospheric delamination in northeast China caused by the rollback of the paleo-Pacific plate.

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

    SciTech Connect

    Cowan, D.S. . 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.

  4. Visualizing fossilization using laser ablation-inductively coupled plasma-mass spectrometry maps of trace elements in Late Cretaceous bones

    USGS Publications Warehouse

    Koenig, A.E.; Rogers, R.R.; Trueman, C.N.

    2009-01-01

    Elemental maps generated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) provide a previously unavailable high-resolution visualization of the complex physicochemical conditions operating within individual bones during the early stages of diagenesis and fossilization. A selection of LA-ICP-MS maps of bones collected from the Late Cretaceous of Montana (United States) and Madagascar graphically illustrate diverse paths to recrystallization, and reveal unique insights into geochemical aspects of taphonomic history. Some bones show distinct gradients in concentrations of rare earth elements and uranium, with highest concentrations at external bone margins. Others exhibit more intricate patterns of trace element uptake related to bone histology and its control on the flow paths of pore waters. Patterns of element uptake as revealed by LA-ICP-MS maps can be used to guide sampling strategies, and call into question previous studies that hinge upon localized bulk samples of fossilized bone tissue. LA-ICP-MS maps also allow for comparison of recrystallization rates among fossil bones, and afford a novel approach to identifying bones or regions of bones potentially suitable for extracting intact biogeochemical signals. ?? 2009 Geological Society of America.

  5. Glandulocalyx upatoiensis, a fossil flower of Ericales (Actinidiaceae/Clethraceae) from the Late Cretaceous (Santonian) of Georgia, USA

    PubMed Central

    Schönenberger, Jürg; von Balthazar, Maria; Takahashi, Masamichi; Xiao, Xianghui; Crane, Peter R.; Herendeen, Patrick S.

    2012-01-01

    Background and Aims Ericales are a major group of extant asterid angiosperms that are well represented in the Late Cretaceous fossil record, mainly by flowers, fruits and seeds. Exceptionally well preserved fossil flowers, here described as Glandulocalyx upatoiensis gen. & sp. nov., from the Santonian of Georgia, USA, yield new detailed evidence of floral structure in one of these early members of Ericales and provide a secure basis for comparison with extant taxa. Methods The floral structure of several fossil specimens was studied by scanning electron microscopy (SEM), light microscopy of microtome thin sections and synchrotron-radiation X-ray tomographic microscopy (SRXTM). For direct comparisons with flowers of extant Ericales, selected floral features of Actinidiaceae and Clethraceae were studied with SEM. Key Results Flowers of G. upatoiensis have five sepals with quincuncial aestivation, five free petals with quincuncial aestivation, 20–28 stamens arranged in a single series, extrorse anther orientation in the bud, ventral anther attachment and a tricarpellate, syncarpous ovary with three free styles and numerous small ovules on axile, protruding-diffuse and pendant placentae. The calyx is characterized by a conspicuous indumentum of large, densely arranged, multicellular and possibly glandular trichomes. Conclusions Comparison with extant taxa provides clear evidence for a relationship with core Ericales comprised of the extant families Actinidiaceae, Roridulaceae, Sarraceniaceae, Clethraceae, Cyrillaceae and Ericaceae. Within this group, the most marked similarities are with extant Actinidiaceae and, to a lesser degree, with Clethraceae. More detailed analyses of the relationships of Glandulocalyx and other Ericales from the Late Cretaceous will require an improved understanding of the morphological features that diagnose particular extant groups defined on the basis of molecular data. PMID:22442339

  6. Tectono-stratigraphy and low-grade metamorphism of Late Permian and Early Jurassic accretionary complexes within the Kurosegawa belt, Southwest Japan: Implications for mechanisms of crustal displacement within active continental margin

    NASA Astrophysics Data System (ADS)

    Hara, Hidetoshi; Kurihara, Toshiyuki; Mori, Hiroshi

    2013-04-01

    We characterize the tectono-stratigraphic architecture and low-grade metamorphism of the accretionary complex preserved in the Kurosegawa belt of the Kitagawa district in eastern Shikoku, Southwest Japan, in order to understand its internal structure, tectono-metamorphic evolution, and assessments of displacement of continental fragments within the complex. We report the first ever documented occurrence of an Early Jurassic radiolarian assemblage within the accretionary complex of the Kurosegawa belt that has been previously classified as the Late Permian accretionary complex, thus providing a revised age interpretation for these rocks. The accretionary complex is subdivided into four distinct tectono-stratigraphic units: Late Permian mélange and phyllite units, and Early Jurassic mélange and sandstone units. The stratigraphy of these four units is structurally repeated due to an E-W striking, steeply dipping regional fault. We characterized low-grade metamorphism of the accretionary complex via illite crystallinity and Raman spectroscopy of carbonaceous material. The estimated pattern of low-grade metamorphism showed pronounced variability within the complex and revealed no discernible spatial trends. The primary thermal structure in these rocks was overprinted by later tectonic events. Based on geological and thermal structure, we conclude that continental fragments within the Kurosegawa belt were structurally translated into both the Late Permian and Early Jurassic accretionary complexes, which comprise a highly deformed zone affected by strike-slip tectonics during the Early Cretaceous. Different models have been proposed to explain the initial structural evolution of the Kurosegawa belt (i.e., micro-continent collision and klippe tectonic models). Even if we presuppose either model, the available geological evidence requires a new interpretation, whereby primary geological structures are overprinted and reconfigured by later tectonic events.

  7. 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

  8. 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.

  9. Sedimentology and invertebrate paleontology of Triassic and Jurassic Lacustrine deposits, Culpeper Basin, northern Virginia

    NASA Astrophysics Data System (ADS)

    Gore, P. J. W.

    The Culpeper Basin contains late Triassic and early Jurassic continental sedimentary rocks. Lacustrine rocks are present in the Bull Run Formation, Buckland Formation, and Waterfall formation. The lacustrine rocks were grouped into eight lithofacies using cluster analysis: (1) red massive siltstone or mudstone, (2) gray massive siltsone or mudstone, (3) disrupted graded siltstone and mudstone, (4) laminated mudstone, (5) limestone, (6) black shale, (7) red laminated and cross-laminated siltstone, sandstone, and mudstone, and (8) sandstone. Freshwater invertebrate fossils (conchostracans, notostracans, ostracodes, and pelecypods) which inhabited shallow water are abundant in some lacustrine beds. The Culpeper Basin notostracans (Triops) are the first to be reported from the Triassic of North America. The conchostracans, Cyzicus and Cornia may be useful for correlation in the Culpeper Basin. Cyzicus is present in the Triassic Bull Run Formation. Cornia is present in the Jurassic Waterfall Formation. This is the first report of Cornia from the Newark Supergroup.

  10. A new fossil thryonomyid from the Late Miocene of the United Arab Emirates and the origin of African cane rats

    NASA Astrophysics Data System (ADS)

    Kraatz, Brian P.; Bibi, Faysal; Hill, Andrew; Beech, Mark

    2013-05-01

    Cane rats (Thryonomyidae) are represented today by two species inhabiting sub-Saharan Africa. Their fossil record is predominately African, but includes several Miocene species from Arabia and continental Asia that represent dispersal events from Africa. For example, Paraulacodus indicus, known from the Miocene of Pakistan, is closely related to living Thryonomys. Here we describe a new thryonomyid, Protohummus dango, gen. et sp. nov., from the late Miocene Baynunah Formation of the United Arab Emirates. The new thryonomyid is less derived than " Thryonomys" asakomae from the latest Miocene of Ethiopia and clarifies the origin of crown Thryonomys and the evolutionary transition from Paraulacodus. A phylogenetic analysis shows Protohummus dango to be morphologically intermediate between Paraulacodus spp. and extinct and living Thryonomys spp. The morphological grade and phylogenetic position of Protohummus dango further supports previous biochronological estimates of the age of the Baynunah Formation (ca. 6-8 Ma).

  11. Late Holocene vegetation and historic grazing impacts at Capital Reef National Park reconstructed using fossil packrat middens

    SciTech Connect

    Cole, K.L.

    1995-06-01

    Late Holocene vegetation change from a high desert site in southern Utah was reconstructed using fossil plant macrofossils and pollen from packrat middens. Presettlement middens consistently contained abundant macrofossils of plant species palatable to livestock that are now absent or reduced such as: Ceratoides lanata, Stipa hymenoides, Pinus edulis, and Artemisia spp.. In contrast, species typical of overgrazed range, such as: Chrysothamnus visidiflorus, Sarcobatus vermiculatus, and Gutterezia sarothrae, are now more abundant than prior to the historic introduction of grazing animals. Similar changes are evident in the fossil pollen from the packrat middens. Pine and sagebrush pollen is now far lower than prior to settlement, while Salsola sp. is first recorded following settlement. Ordination of the plant records using Detrended Correspondence Analysis demonstrates that the modem assemblages are substantially different from the presettlement assemblages and that the rates of vegetation change accompanying settlement are far greater than any recorded during the previous 5000 years. These results suggest that the plant communities and rates of vegetation change observed during this century are unlike previous natural communities and rates of vegetation change.

  12. 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.

  13. The Pipe Creek Sinkhole biota, a diverse late tertiary continental fossil assemblage from Grant County, Indiana

    USGS Publications Warehouse

    Farlow, J.O.; Sunderman, J.A.; Havens, J.J.; Swinehart, A.L.; Holman, J.A.; Richards, R.L.; Miller, N.G.; Martin, R.A.; Hunt, R.M., Jr.; Storrs, G.W.; Curry, B. Brandon; Fluegeman, R.H.; Dawson, M.; Flint, M.E.T.

    2001-01-01

    Quarrying in east-central Indiana has uncovered richly fossiliferous unconsolidated sediment buried beneath Pleistocene glacial till. The fossiliferous layer is part of a sedimentary deposit that accumulated in a sinkhole developed in the limestone flank beds of a Paleozoic reef. Plant and animal (mostly vertebrate) remains are abundant in the fossil assemblage. Plants are represented by a diversity of terrestrial and wetland forms, all of extant species. The vertebrate assemblage (here designated the Pipe Creek Sinkhole local fauna) is dominated by frogs and pond turtles, but fishes, birds; snakes and small and large mammals are also present; both extinct and extant taxa are represented. The mammalian assemblage indicates an early Pliocene age (latest Hemphillian or earliest Blancan North American Land Mammal Age). This is the first Tertiary continental biota discovered in the interior of the eastern half of North America.

  14. Dinosaur dynamics in the Jurassic Era

    NASA Astrophysics Data System (ADS)

    Lee, Scott

    2010-04-01

    Dinosaurs were fascinating animals and elicit much excitement in the classroom. Analysis of fossilized dinosaur trackways permits one to estimate the locomotion speeds and accelerations of these extinct beasts. Such analysis allows one to apply Newton's laws of motion to examples from the Jurassic Era.

  15. Late-Holocene fossil rodent middens from the Arica region of northernmost Chile

    USGS Publications Warehouse

    Holmgren, C.A.; Rosello, E.; Latorre, C.; Betancourt, J.L.

    2008-01-01

    Identification of >40 taxa of plant macrofossils in 14 rodent (Abrocoma) middens collected from 2800 to 3590 m elevation at the latitude of Arica, Chile (18??S) provide snapshots of vegetation in the northernmost Atacama Desert over the past 3000 years. Midden floras show considerable stability throughout the late Holocene, which may be due in part to the broad elevational ranges of many perennial species and midden insensitivity to changes in plant community structure. The greatest variability is found in annuals in the Prepuna, a climatically sensitive zone. This variability, however might also arise from the brevity of midden depositional episodes. As the first midden record from the Arica-Parinacota Region (Chile's northernmost administrative region), this study demonstrates the potential for future midden research in this area. ?? 2007 Elsevier Ltd. All rights reserved.

  16. Late-Holocene fossil rodent middens from the Arica region of northernmost Chile

    USGS Publications Warehouse

    Holmgren, C.A.; Rosello, E.; Latorre, C.; Betancourt, J.L.

    2008-01-01

    Identification of >40 taxa of plant macrofossils in 14 rodent (Abrocoma) middens collected from 2800 to 3590 m elevation at the latitude of Arica, Chile (18°S) provide snapshots of vegetation in the northernmost Atacama Desert over the past 3000 years. Midden floras show considerable stability throughout the late Holocene, which may be due in part to the broad elevational ranges of many perennial species and midden insensitivity to changes in plant community structure. The greatest variability is found in annuals in the Prepuna, a climatically sensitive zone. This variability, however might also arise from the brevity of midden depositional episodes. As the first midden record from the Arica-Parinacota Region (Chile's northernmost administrative region), this study demonstrates the potential for future midden research in this area.

  17. 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

  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. 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.

  20. Late Holocene sea level changes and tectonic movements inferred from fossil diatom assemblages in Tainohama, Tokushima prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Chiba, T.; Fujino, S.; Kobori, E.

    2014-12-01

    The average recurrence interval of the interplate earthquakes along the Nankai Trough is estimated from historical literature and archaeological data. However, the details of tectonic movements by past Nankai earthquakes are mostly left unclear from historical literature, therefore, we need to obtain the geological evidence of the tectonic movements. Yuki city, Tokushima prefecture, located in north part of the Nankai Trough, has been subsided and many tsunamis attacked along the coast of the Shikoku islands accompanied by the previous Nankai earthquakes. Therefore, some historical documents and memorial monuments written about the past Nankai earthquakes and tsunamis remain in the city. The study purposed to reveal tectonic movements of the earthquakes from Nankai Trough during the late Holocene at Tainohama in Minami city which is adjacent to the southwest of Yuki city by fossil diatom analysis. We obtained a 700cm long core at a marsh behind a barrier spit probably be not affected directly from sea waves in Tainohama. The core includes more than 13 sand layers in organic-rich muddy or peaty sedimentary succession up to 500cm depth in the core. And the diatom assemblages included in the peat and peaty mud deposits were dominated by fresh and brackish water species, especially Pseudostaurosira brevistriata, P. subsalina and Tabellaria fenestrate. In contrast to the above mentioned sand layers, brackish and marine species, such as Diploneis smithii increased. The diatom assemblages from the organic rich muddy sediments and radiocarbon ages indicate that freshwater marsh or saltmarsh formed in this region during the late Holocene. On the other hand, the sandy layers include the diatoms living in environments where salinities are higher than freshwater or salt marsh, so the assemblages suggest that the sand layers were transported from seaside by past tsunamis. In addition, changes of diatom assemblages in the peaty or peaty mud sediments show increase or decrease of freshwater species, suggesting paleo-sea level changes. The sea level in this area declined gradually to modern sea level from +50cm higher level than modern by eustatic sea level fall during the late Holocene (Sato 2014), thus the fluctuations suggest co-seismic or inter-seismic crustal movements of the past interplate earthquakes along the Nankai Trough.

  1. 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

  2. Submicron-Chemical Speciation of Late Albian, Well-Preserved Fossil Samples from Tlayúa, the Mexican Solenhofen.

    NASA Astrophysics Data System (ADS)

    Marcus, M.; Fakra, S.; Tamura, N.; Alvarado-Ortega, J.; Espinosa-Arruberena, L.; Banfield, J.; Cervini-Silva, J.

    2007-12-01

    The Tlayúa slurry quarry constitutes the most important paleontological locality in the American continent, and constitutes the second most important locality in its genre worldwide. The importance of Tlayúa strives inderives from the fact that a great diversity of marine and terrestrial fossils in perfect state of preservation have been found, with ages surpassing 115 million yrs. Paleomagnetic and biostratigraphic determinations conducted in ammonites and belemnites indicate that the formation of the Tlayúa slurry dates back to the late Albian. One of the most accepted hypothesis for explaining Tlayúa's formation relies on the deposition of sediments and fauna on a shallow platform of a tropical sea. A similar geographic place is located in Solenhofen, Germany, where slurries have been exploited for more than 200 yrs with a production of approximately 500 species. Remarkably, in the Tepexi del Rio region alone for the past 20 yrs more than 5,000 fossil specimens representing more than 200 species have been collected alone. An The exceptional specimen preservation found in Tlayúa has been attributed to restricted circulation of water resulting in an anaerobic and/or hypersaline environment, coupled with the general absence of infaunal species. There were periods when the deposition site supported a rich planktontic community. Large quantities of calcareous ooze were produced, resulting in rapid burial of the organisms. The presence of diagnostic terrestrial and freshwater organisms, including arachnids, insects, lizards, and chelonians, along with typical marine fauna, suggests that Tlayúa lagoon had periodic freshwater inflow, in addition to the strong marine, lagoonal, and reefal influence. Some organisms were transported into the lagoon when the barrier was breached, probably during periods of heavy rains and hurricanes, or during high tides. Additionally, some fishes from Tlayua have been found to have affinities with recent families known to inhabit brackish and freshwater environments. In search for reconstructing paleoenvironments in Tlayúa, fish bone samples from a Pachyrhizodontide specimens, from the telesteos incertae sedis group already extinct, were analyzed using XRFmicro X-ray fluorescence, ? -X-ray diffraction RD, and ??-EXAFSnd XANES/EXAFS. Conducting Ca- EXAFS allowed us to resolve Ca-speciation in CaCO3 matrices. Micro Ca-EXAFSDiffraction and Ca K-edge XANES on bone material confirmed the presence of apatite, not hydroxyapatite consistent with highly-weathered environment. High concentrations of As were found in CaCO3) grains, Mn oxides grains as well as Celestine (SrSO4) grains dispersed in the egg core.

  3. 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.

  4. Triassic and Jurassic rocks at Currie, Nevada Preliminary paleontologic evidence

    SciTech Connect

    Johnson, E.A.; Dubiel, R.F.; Brouwers, E.M. ); Litwin, R.J. ); Ash, S.R. ); Good, S.C. )

    1993-04-01

    A sequence of continental rocks overlies the Lower Triassic Thaynes Formation in a poorly exposed syncline near Currie in northeastern NV. The authors recognize four lithostratigraphic units above the Thaynes near Currie and provide new paleontologic data. In ascending order, unit 1 (120 ft) consists of reddish-brown, very fine grained sandstone. Unit 2 (50 ft) consists of light-gray, trough cross-stratified, coarse-grained, conglomeratic sandstone. Unit 3 (at least 500 ft) consists of green, red, and brown sandstone and mudstone. Unit 4 occurs as isolated outcrops of reddish-orange, fine- to medium-grained sandstone. New fossil evidence, while not definitive, constrain the age of this sequence. Plant megafossils in unit 1 include (1) a specimen with narrow ovate leaves, possibly from an early Mesozoic conifer and (2) abundant fragments of probable Neocalamites. The presence of these fossils and the absence of any angiosperm leaves or wood fragments suggest an early Mesozoic age. Ostracodes in unit 3 are exclusively Darwinula sp., and their association with conchostracans in the absence of younger ostracodes suggests a Triassic age. Finally, two small outcrops, previously mapped as Triassic/Jurassic, contain the gastropods Pilidae indet. and Lymnaea sp., which resemble Late Cretaceous to Paleocene faunas. The sequence is similar to the nearest Lower Mesozoic section on the Colorado Plateau at Cove Fort, Utah, 165 miles to the southeast. The authors' new evidence supports the longstanding correlation of units 1--4 with the Lower Triassic Moenkopi Formation (part), the Shinarump and Petrified Forest Members of the Upper Triassic Chinle Formation, and the Lower Jurassic Navajo Sandstone of the Plateau. These rocks at Currie demonstrate that the Early Mesozoic depositional systems of the Colorado Plateau extended at least this far west and provide constraints on Early Mesozoic tectonism in the eastern Great Basin.

  5. The shape of pterosaur evolution: evidence from the fossil record.

    PubMed

    Dyke, G J; McGowan, A J; Nudds, R L; Smith, D

    2009-04-01

    Although pterosaurs are a well-known lineage of Mesozoic flying reptiles, their fossil record and evolutionary dynamics have never been adequately quantified. On the basis of a comprehensive data set of fossil occurrences correlated with taxon-specific limb measurements, we show that the geological ages of pterosaur specimens closely approximate hypothesized patterns of phylogenetic divergence. Although the fossil record has expanded greatly in recent years, collectorship still approximates a sigmoid curve over time as many more specimens (and thus taxa) still remain undiscovered, yet our data suggest that the pterosaur fossil record is unbiased by sites of exceptional preservation (lagerstätte). This is because as new species are discovered the number of known formations and sites yielding pterosaur fossils has also increased - this would not be expected if the bulk of the record came from just a few exceptional faunas. Pterosaur morphological diversification is, however, strongly age biased: rarefaction analysis shows that peaks of diversity occur in the Late Jurassic and Early Cretaceous correlated with periods of increased limb disparity. In this respect, pterosaurs appear unique amongst flying vertebrates in that their disparity seems to have peaked relatively late in clade history. Comparative analyses also show that there is little evidence that the evolutionary diversification of pterosaurs was in any way constrained by the appearance and radiation of birds. PMID:19210587

  6. The occurrence of an abdominal fauna in an articulated tapir (Tapirus polkensis) from the Late Miocene Gray Fossil Site, Northeastern Tennessee.

    PubMed

    McConnell, Shannon M; Zavada, Michael S

    2013-03-01

    The analysis of samples recovered from the abdominal area of an articulated tapir (Tapirus polkensis) from the Late Miocene (4.5-7 million BP) Gray Fossil Site (GFS) revealed a rich palyno-fauna comprised of about 94% egg/oocyst-like structures and 6% pollen and other palynomorphs. In addition, a group of 6 hickory nuts (Carya) was recovered from the same area suggesting that the samples represent the abdominal contents. The analysis of a sample from immediately outside the tapir produced a sample with 98% pollen and less than 0.5% egg/oocyst-like structures. The size, shape, and general morphology of egg/oocyst-like structures were analyzed with light and scanning electron microscopy and were compared to a variety of intestinal parasites found in extant ungulates, and the Perissodactyla in particular. We also compared fossil structures to the numbers and kind of intestinal parasites recovered from fecal samples from the Baird's tapir (T. bairdii) in Costa Rica and from samples collected from the lowland tapir (T. terrestris) from Ecuador to assess their similarity to our fossil sample. Based on these data, we discuss what role parasites may have played in the biology of T. polkensis during the Late Miocene-Early Pliocene. PMID:23586562

  7. 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

  8. Oxygen and strontium isotopes from fossil shark teeth: Environmental and ecological implications for Late Palaeozoic European basins

    E-print Network

    Schöne, Bernd R.

    Oxygen and strontium isotopes from fossil shark teeth: Environmental and ecological implications online 8 February 2013 Editor: U. Brand Keywords: Oxygen isotopes Strontium isotopes Bioapatite Palaeozoic deposits, therefore their palaeo- ecology is controversial. The oxygen and strontium isotopic

  9. U-Pb zircon ages and geochemistry of Kangareh and Taghiabad mafic bodies in northern Sanandaj-Sirjan Zone, Iran: Evidence for intra-oceanic arc and back-arc tectonic regime in Late Jurassic

    NASA Astrophysics Data System (ADS)

    Azizi, Hossein; Najari, Mohammad; Asahara, Yoshihiro; Catlos, Elizabeth J.; Shimizu, Misa; Yamamoto, Koshi

    2015-10-01

    The northern Sanandaj-Sirjan Zone (SaSZ) in northwestern Iran contains several granitoid and gabbroic bodies that are parallel to the Zagros Suture zone in a northwest-southeast direction. The fine-grained Taghiabad gabbro and coarse-grained Kangareh gabbroic bodies southwest of the Ghorveh in the northern SaSZ were crystallized at 158.0 ± 10.0 Ma and 148.3 ± 3.6 Ma, respectively, based on U-Pb zircon dating. The SiO2 contents of the Kangareh and Taghiabad rocks are similar and range from 45.5 to 51.5 wt.%, and the Al2O3 contents vary from 14 to 24 wt.%, with high Mg number (Mg# = 61-72% and 46-63%, respectively). The Taghiabad body has higher contents of TiO2, Fe2O3, and P2O5 than the Kangareh rocks. The Fe2O3 contents of the Taghiabad rocks vary from 6 to 15 wt.%, whereas those of the Kangareh rocks range from 5 to 9 wt.%. The TiO2 concentrations of the Taghiabad samples are high (1-3 wt.%), and these rocks can be classified as high Ti and Fe rocks. The chemical compositions of the two bodies show some clear differences. Positive ?Nd(t) values (+ 3 to + 8) and low initial 87Sr/86Sr ratios (0.7034 to 0.7054) indicate a depleted mantle source for both bodies. The variation and distribution of trace elements, REEs patterns, and initial 87Sr/86Sr-143Nd/144Nd ratios show that the Kangareh and Taghiabad bodies have high affinities to tholeiitic and alkaline magmatic series. These results suggest an arc and back-arc system regime in an intra-oceanic system than the Andean magmatic type regime for the origin of these bodies in the Middle to Late Jurassic period. These complexes merged with the northern SaSZ during accretion-type continental growth in the Late Jurassic.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. 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.

  17. 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.; Jorstad, R.B.

    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.

  18. 3D morphometric analysis of fossil canid skulls contradicts the suggested domestication of dogs during the late Paleolithic.

    PubMed

    Drake, Abby Grace; Coquerelle, Michael; Colombeau, Guillaume

    2015-01-01

    Whether dogs were domesticated during the Pleistocene, when humans were hunter-gatherers, or during the Neolithic, when humans began to form permanent settlements and engage in agriculture, remains controversial. Recently discovered Paleolithic fossil skulls, Goyet dated 31,680 +/- 250?YBP and Eliseevichi MAE 447/5298 dated 13,905 +/- 55?YBP, were previously identified as dogs. However, new genetic studies contradict the identification of these specimens as dogs, questioning the validity of traditional measurements used to morphologically identify canid fossil skulls. We employ 3D geometric morphometric analyses to compare the cranial morphology of Goyet and Eliseevichi MAE to that of ancient and modern dogs and wolves. We demonstrate that these Paleolithic canids are definitively wolves and not dogs. Compared to mesaticephalic (wolf-like breeds) dog skulls, Goyet and Eliseevichi MAE, do not have cranial flexion and the dorsal surface of their muzzles has no concavity near the orbits. Morphologically, these early fossil canids resemble wolves, and thus no longer support the establishment of dog domestication in the Paleolithic. PMID:25654325

  19. 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.

  20. Occurrences of Chert in Jurassic-Cretaceous Calciturbidites (SW Turkey)

    NASA Astrophysics Data System (ADS)

    Gül, Murat

    2015-10-01

    The Lycian Nappes, containing ophiolite and sedimentary rocks sequences, crop out in the southwest Turkey. The Tavas Nappe is a part of the Lycian Nappes. It includes the Lower Jurassic-Upper Cretaceous calciturbidites. Chert occurrences were observed in the lower part of this calciturbidite. These cherts can be classified on the basis of length, internal structure and host rock. Chert bands are 3.20-35.0min length and 7.0-35.0 cm thick. Chert lenses are 5.0-175.0 cm in length and 1.0-33.0 cm thick. According to its internal structure, granular chert (bladedlarge equitant quartz minerals replaced the big calcite mineral of fossil shell) and porcelanious chert (microcrystalline silica replaced micrite) have been separated. Cherts are generally associated with calcarenite-calcirudite, the others with calcilutite. Micritic calcite patches of cherts point out an uncompleted silicification. The source of silica was dominantly quartz-rich, older, basal rocks and to a lesser extent radiolarians. The coarse-grained calciturbidites act as a way for silica transportation. Some calcite veins (formed during transportation and emplacement of nappes) cut both calciturbidites and cherts. Thus, chert occurrences evolved before emplacement of nappes (the latest Cretaceous-Late Miocene period) during the epigenetic phase.

  1. 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

  2. Fossil vertebrates from Antigua, Lesser Antilles: Evidence for late Holocene human-caused extinctions in the West Indies

    PubMed Central

    Steadman, David W.; Pregill, Gregory K.; Olson, Storrs L.

    1984-01-01

    Vertebrate remains recovered from a limestone fissure filling on Antigua, Lesser Antilles, are associated with radiocarbon dates ranging from 4300 to 2500 yr B.P., contemporaneous with the earliest aboriginal human occupation of the island. Nine taxa of lizards, snakes, birds, bats, and rodents (one-third of the total number of species represented as fossils) are either completely extinct or have never been recorded historically from Antigua. These extinctions came long after any major climatic changes of the Pleistocene and are best attributed to human-caused environmental degradation in the past 3500 yr. Such unnatural influences have probably altered patterns of distribution and species diversity throughout the West Indies, thus rendering unreliable the data traditionally used in ecological and biogeographic studies that consider only the historically known fauna. PMID:16593490

  3. 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.

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

    USGS Publications Warehouse

    Thompson, W.B.; Griggs, C.B.; Miller, N.G.; Nelson, R.E.; Weddle, T.K.; Kilian, T.M.

    2011-01-01

    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??5014C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520+95/??20calyr BP. Ages of shells juxtaposed with the logs are 12,850??6514C yr BP (Mytilus edulis) and 12,800??5514C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000yr. 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. ?? 2011 University of Washington.

  5. 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.

  6. 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.

  7. 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

  8. Jurassic tectonostratigraphic evolution of the Junggar basin, NW China: A record of Mesozoic intraplate deformation in Central Asia

    NASA Astrophysics Data System (ADS)

    Yang, Yong-Tai; Song, Chuan-Chun; He, Sheng

    2015-01-01

    Mesozoic basins in northwest China provide important records for investigating relationships between intraplate deformation in Central Asia and tectonic processes at Asian boundaries. The present study, using well, seismic, outcrop, and thermochronology data in the Junggar Basin and neighboring areas, describes the main features of Jurassic strata in the basin, analyzes the Jurassic evolution of the basin and neighboring mountain belts, and discusses possible mechanisms of Jurassic intraplate deformation in Central Asia. During the Early-Middle Jurassic, episodic uplift of surrounding mountain belts kept the Junggar Basin a contractional closed basin, and alluvial fan, fluvial, delta, and lacustrine depositional environments successively developed from surrounding ranges to the central basin. During the Late Jurassic, the western and central parts of the basin were folded and uplifted, and deposition migrated mainly to the eastern basin. During the latest Jurassic-earliest Cretaceous, pre-Cretaceous strata in the eastern and northeastern Junggar Basin were folded and uplifted, and coarse-grained sediments were transported from surrounding uplifts to the central basin. We suggest that Jurassic episodic deformation events in the Junggar Basin and other areas of Central Asia are related to the Qiangtang collision during the Late Triassic-Early Jurassic, the closure of the western Mongol-Okhotsk Ocean at the Early/Middle Jurassic boundary, a collision of a microcontinent in the Pamir with the southern Asian margin during the late Middle Jurassic-early Late Jurassic, the collision of the Kolyma-Omolon Block with Siberia at the end of the Jurassic, and the subsequent closure of the eastern Mongol-Okhotsk Ocean during the latest Jurassic-earliest Cretaceous.

  9. Jurassic platform development, northwestern Gulf of Mexico

    SciTech Connect

    Moore, C.H. Jr.

    1987-05-01

    Triassic and Early Jurassic rifting set the stage for the subsequent development of carbonate platforms in the Late Jurassic. These platforms formed along the interior margins of salt basins separated from the main ancestral Gulf of Mexico by a series of positive features. A major sea level rise, after deposition of the Louann Salt (late Callovian), drowned the interior salt basins around the margins of the Gulf of Mexico, leading to an anoxic event. Organic-rich sediments of the lower Smackover were deposited as a basin-fill sequence, forming one of the major hydrocarbon source rocks of the region. As sea level rise slowed in the late Oxfordian, carbonate production began to catch up with sea level rise along the basin margins, leading to the initial development of a rimmed carbonate platform. The platform margin was marked by high-energy ooid grainstones, while crustacean pellet muds were deposited in the platform interior. A high-energy ooid-dominated platform (upper Smackover) developed in the late Oxfordian when sea level reached a standstill. During the subsequent Kimmeridgian sea level rise, a second rimmed carbonate platform, the Haynesville, was developed. During the initial rise, grainstones were deposited on the platform margin, while the interior was dominated by evaporites (Buckner) and siliciclastics. As sea level slowed and reached a standstill, the platform margin facies extended shoreward (Gilmer) and a high-energy platform, analogous to the upper Smackover, was formed. The Smackover and Haynesville platforms of the northwestern gulf show a parallel evolution in response to cyclic changes in Upper Jurassic sea level.

  10. Paleomagnetism of Jurassic carbonate rocks from Sardinia: No indication of post-Jurassic internal block rotations

    NASA Astrophysics Data System (ADS)

    Kirscher, U.; Aubele, K.; Muttoni, G.; Ronchi, A.; Bachtadse, V.

    2011-12-01

    Several paleomagnetic studies on Carboniferous and Permian sedimentary and volcanic rocks from Sardinia and Corsica have recently demonstrated (1) the tectonic coherence between southern Corsica and northern Sardinia and (2) significant rotations between individual crustal blocks within Sardinia itself. The geodynamic significance of these rotations, however, is not clearly understood mainly because of uncertainties in defining their timing and causes. In order to contribute to these issues, a pioneering paleomagnetic study on Jurassic carbonates from the Baronie-Supramonte region of eastern-central Sardinia has been extended regionally and stratigraphically. A total of 280 oriented drill cores were taken from 44 sites of Middle and Late Jurassic age in the Nurra, Baronie-Supramonte, Barbagia-Sarcidano, and Sulcis regions. Despite generally weak remanent magnetization intensities, on the order of less than 1 mA/m, thermal and alternating field demagnetizations were successfully applied to define a characteristic remanent magnetization component in about 60% of the samples. Site mean directions show rather good agreement after correction for bedding tilt and yield Middle and Late Jurassic overall mean directions of D = 269.7° and I = 45.0° (?95 = 8.0°, k = 14, and n = 25 sites) and D = 275.5° and I = 50.7° (?95 = 7.2°, k = 45.3, and n = 10 sites). Positive regional and local fold and reversal tests demonstrate the primary character of the natural magnetic remanence, which is carried by magnetite. These results indicate only insignificant amounts (±10°) of post-Jurassic rotations within the island of Sardinia. The resulting Middle and Late Jurassic paleopoles (latitude (Lat) = 16.5°, longitude (Long) = 299.1°, dp = 6.4°, and dm = 10.1° and Lat = 23.4°, Long = 301.2°, dp = 6.5°, and dm = 9.7°), corrected for the opening of (1) the Liguro-Provençal Basin and (2) the Bay of Biscay using rotation parameters from the literature, fall near the coeval segment of the European apparent polar wander path. These results constrain the timing of large differential block rotations found in Late Carboniferous-Permian rocks to a pre-Middle Jurassic age and lead us to exclude tectonics related to the Alpine orogeny for such rotations.

  11. 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. )

    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.

  12. 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

  13. 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.

  14. 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.

  15. Mid to late Holocene sea-surface temperature reconstruction using fossil corals from Kume Island, Ryukyu, Japan

    NASA Astrophysics Data System (ADS)

    Seki, A.; Yokoyama, Y.; Suzuki, A.; Kawakubo, Y.; Okai, T.; Miyairi, Y.; Matsuzaki, H.; Namizaki, N.; Kan, H.

    2012-12-01

    The relative warmth and stability of the Holocene was punctuated by several brief cold events. Although these cold events on a global scale are widely reported, the lack of records from regions such as the East China Sea (ECS) results in an incomplete understanding of the underlying cooling mechanism. Late Quaternary climate anomaly, at around 4.2 ka evidence found in elsewhere, is a time of such abrupt climate change, and mechanisms of this event have not been understood. Here, we present a coral-based paleo-SST (sea-surface temperature) reconstruction from the ECS to unveil Holocene variability in strength of the Kuroshio Western Boundary Current and the East Asian Monsoon (EAM). Our new data confirm that cold conditions prevailed at 3.8 cal kyr BP, and were started after 4.5 cal kyr BP. The timing of this cold event is consistent with previously reported Pulleniatina Minimum Event (PME, 4.5-3.0 ka) (e.g., Ujiié and Ujiié, 1999). While PME had not been resolved seasonality, our high-resolution data clearly indicate a different seasonal response of summer and winter SST . This result provides an important insight into the mechanism of the millennium scale cold event in the ECS, where the region affected by EAM (Seki et al., 2012).

  16. Aalenian-Early Bathonian (Middle Jurassic) radiolarian assemblages in the Tavas nappe within Lycian nappes in the western Taurides (SW Turkey): The first dating of carbonate platform drowning

    NASA Astrophysics Data System (ADS)

    Soycan, Havva; Erdo?an, Kemal; Konak, Ne?at

    2015-05-01

    Stratigraphic sections (Kizilca and Kizilca North) in the Tavas nappe, western Taurides, Turkey records the event of carbonate platform drowning in the western Tethyan realm. Our detailed biostratigraphic study of radiolarians and other microfossils places the important temporal constraints on this event and indicates that drowning occured in the geochronological interval from Early Jurassic (Hettangian-Sinemurian) through to Middle Jurassic (early Bathonian). The basal part of the Kizilca section is represented by platform carbonates with abundant benthic foraminifera and algae of Hettangian-Sinemurian to Pliensbachian age. Toward the upper part of the section, the occurrence of brecciated limestones with some ammonites and belemnites reveals that the drowning event began in the Pliensbachian. The first radiolarian assemblages of early-middle to late Aalenian age were obtained from the overlying units characterized by pelagic limestones and chert alternation. Just after the subsidence of the platform, ribbon chert sedimentation began in the late Aalenian, as indicated by the radiolarians. Successively, early-late Bajocian and latest Bajocian-early Bathonian radiolarian assemblages were obtained from overlying chert with mudstone-silicified mudstones. Similar to that observed in the Kizilca section, the Kizilca North section include successively pelagic limestones, pelagic limestone-chert alternation and chert-mudstone alternation of late Aalenian to early-middle Bajocian age according to radiolarian biostratigraphy. All of these observations indicate that a continuous stratigraphy recorded the drowning event without a large gap from Hettangian-Sinemurian to early Bathonian in the Tavas nappe. This drowning event has close similarities with coeval events in other Tethyan realms in terms of mechanism, facies characteristics and fossil assemblages. Therefore, this study can aid correlation studies of the Tavas nappe with the Jurassic paleogeography worldwide.

  17. Stable isotopes in yellow-bellied marmot (Marmota flaviventris) fossils reveal environmental stability in the late Quaternary of the Colorado Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Reynard, Linda M.; Meltzer, David J.; Emslie, Steven D.; Tuross, Noreen

    2015-03-01

    High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~ 1 cal ka BP. We coupled isotopic and radiocarbon measurements (?18O, ?D, ?15N, ?13C, and 14C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene.

  18. High-resolution ammonite, belemnite and stable isotope record from the most complete Upper Jurassic section of the Bakony Mts (Transdanubian Range, Hungary)

    NASA Astrophysics Data System (ADS)

    F?zy, István; Janssen, Nico M. M.; Price, Gregory D.

    2011-10-01

    This research focuses on the cephalopod fauna and biostratigraphy of the latest Jurassic succession of the Lókút Hill (Bakony Mts, Transdanubia, Hungary). Fossils were collected bed-by-bed from Ammonitico Rosso facies and from the subsequent Biancone type rock. The poorly preserved cephalopods from the lowermost part of the profile, immediately above the radiolarite, may represent a part of the Oxfordian stage. The rich Kimmeridgian ammonite fauna is published for the first time while the formerly illustrated Tithonian fauna is revised. All the successive Kimmeridgian and Early Tithonian Mediterranean ammonite zones can be traced. The highest documented ammonite zone is the Late Tithonian Microcanthum Zone. The beds above yielded no cephalopods. Particular attention was paid to the belemnite fauna of over 120 specimens collected under strict ammonite control. Among the belemnite faunas an Early Tithonian, an early middle Tithonian, a late middle Tithonian, and a latest Tithonian assemblage can be distinguished. Thereby, an association is distinguished in the middle Late Kimmeridgian and one that characterizes the Oxfordian-Kimmeridgian boundary beds. The main difference from previously published belemnite data appears to be that the Hungarian assemblages are impoverished with respect to contemporary faunas from Italy and Spain (Mediterranean Province). An isotopic analysis of the belemnites show that the carbon-isotope data are consistent with carbon-isotope stratigraphies of the Western Tethys and show a decrease in values towards the Jurassic-Cretaceous boundary.

  19. Jurassic hydrocarbon exploration of southern Florida

    SciTech Connect

    Mitchell-Tapping, H.J.

    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.

  20. 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.

  1. 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

  2. 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.

  3. Olsen, P. E., 1986, Discoveryof earliest Jurassic reptile assemblage from Nova Scotia impliescatastrophicend to Triassic: Lamont (Newsletter),v. 12,p. 1-3. Discovery of Earliest Jurassic Reptile Assemblages from Nova Scotia

    E-print Network

    Olsen, Paul E.

    Olsen, P. E., 1986, Discoveryof earliest Jurassic reptile assemblage from Nova Scotia from Nova Scotia: Imply Catastrophic End to the Triassic LateTriassic and EarlyJurassic sediments, tilted, and deeply eroded remnantsare expose6from Nova Scotiato South Carolina and are termed the Newark

  4. A fossil record full of holes: The Phanerozoic history of drilling predation

    NASA Astrophysics Data System (ADS)

    Kowalewski, Michal; Dulai, Alfréd; Fürsich, Franz T.

    1998-12-01

    The evolutionary history of drilling predation, despite a long and rich fossil record (Precambrian Holocene), contains a 120 m.y. gap (Late Triassic Early Cretaceous). Drilled bivalve and brachiopod shells from Jurassic deposits of Hungary, India, and four localities documented in the literature indicate that drillers may have existed continuously throughout the Mesozoic. They may have been descendants of Paleozoic predators, unknown Mesozoic carnivores, or precursors of modern drillers. A literature database suggests three major phases in the Phanerozoic history of drilling predators: (1) the Paleozoic phase (latest Precambrian Carboniferous) dominated by rare to moderately frequent drillings in brachiopods and sessile echinoderms; (2) the Mesozoic phase (Permian Early Cretaceous) with very rare, or even facultative, drillers that had little impact on marine benthic communities, but nevertheless may have been present continuously; and (3) the Cenozoic phase (Late Cretaceous Holocene) dominated by frequent gastropod drillings in mollusks.

  5. Lucas, S.G. and Spielmann, J.A., eds., 2007, The Global Triassic. New Mexico Museum of Natural History and Science Bulletin 41. TRIASSIC-JURASSIC BOUNDARYON THE SOUTHERN MARGIN OFTETHYS

    E-print Network

    McRoberts, Christopher A.

    this period (Late Triassic-Early Jurassic). Numerous tectonic processes were active during the time History and Science Bulletin 41. TRIASSIC-JURASSIC BOUNDARYON THE SOUTHERN MARGIN OFTETHYS: IMPLICATIONS the Triassic­Jurassic boundary in the southern Tethyan margin have been studied in Egypt, Sudan, Jordan

  6. GEOL 102: Historical Geology Overview of Major Groups of Fossil Forming Organisms

    E-print Network

    Holtz Jr., Thomas R.

    1 GEOL 102: Historical Geology Overview of Major Groups of Fossil Forming Organisms Prokaryote cyanobacteria). Unicellular Eukaryote Fossil-formers Diatoms (Jurassic-Quaternary; more abundant in Cenozoic accumulate to form foraminferal ooze, very important index fossils. Some major groups of forams include: o

  7. 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

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

    PubMed

    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

  9. Jurassic faults of southwest Alabama and offshore areas

    SciTech Connect

    Mink, R.M.; Tew, B.H.; Bearden, B.L.; Mancini, E.A. )

    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.

  10. Marquee Fossils

    ERIC Educational Resources Information Center

    Clary, Renee; Wandersee, James

    2008-01-01

    Professors of an online graduate-level paleontology class developed the concept of marquee fossils--fossils that have one or more unique characteristics that capture the attention and direct observation of students. In the classroom, Marquee fossils integrate the geology, biology, and environmental science involved in the study of fossilized

  11. 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

  12. 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

  13. 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

  14. 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.

  15. Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia: Sauropterygia)

    E-print Network

    Benton, Michael

    Functional anatomy and feeding biomechanics of a giant Upper Jurassic pliosaur (Reptilia Abstract Pliosaurs were among the largest predators in Mesozoic seas, and yet their functional anatomy, direct fossil evidence including gut contents, and bite marks. The functional anatomy of the pliosaur

  16. "Fossil" Forecasting.

    ERIC Educational Resources Information Center

    Brody, Michael J.; deOnis, Ann

    2001-01-01

    Presents a density study in which students calculate the density of limestone substrate to determine if the specimen contains any fossils. Explains how to make fossils and addresses national standards. (YDS)

  17. 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.

  18. JURASSIC Retrieval Processing

    NASA Astrophysics Data System (ADS)

    Blank, J.; Ungermann, J.; Guggenmoser, T.; Kaufmann, M.; Riese, M.

    2012-04-01

    The Gimballed Limb Observer for Radiance Imaging in the Atmosphere (GLORIA) is an aircraft based infrared limb-sounder. This presentation will give an overview of the retrieval techniques used for the analysis of data produced by the GLORIA instrument. For data processing, the JUelich RApid Spectral SImulation Code 2 (JURASSIC2) was developed. It consists of a set of programs to retrieve atmospheric profiles from GLORIA measurements. The GLORIA Michelson interferometer can run with a wide range of parameters. In the dynamics mode, spectra are generate with a medium spectral and a very high temporal and spatial resolution. Each sample can contain thousands of spectral lines for each contributing trace gas. In the JURASSIC retrieval code this is handled by using a radiative transport model based on the Emissivity Growth Approximation. Deciding which samples should be included in the retrieval is a non-trivial task and requires specific domain knowledge. To ease this problem we developed an automatic selection program by analysing the Shannon information content. By taking into account data for all relevant trace gases and instrument effects, optimal integrated spectral windows are computed. This includes considerations for cross-influence of trace gases, which has non-obvious consequence for the contribution of spectral samples. We developed methods to assess the influence of spectral windows on the retrieval. While we can not exhaustively search the whole range of possible spectral sample combinations, it is possible to optimize information content using a genetic algorithm. The GLORIA instrument is mounted with a viewing direction perpendicular to the flight direction. A gimbal frame makes it possible to move the instrument 45° to both direction. By flying on a circular path, it is possible to generate images of an area of interest from a wide range of angles. These can be analyzed in a 3D-tomographic fashion, which yields superior spatial resolution along line of site. Usually limb instruments have a resolution of several hundred kilometers. In studies we have shown to get a resolution of 35km in all horizontal directions. Even when only linear flight patterns can be realized, resolutions of ?70km can be obtained. This technique can be used to observe features of the Upper Troposphere Lower Stratosphere (UTLS), where important mixing processes take place. Especially tropopause folds are difficult to image, as their main features need to be along line of flight when using common 1D approach.

  19. Pennsylvanian to Jurassic eolian transportation systems in the western United States

    USGS Publications Warehouse

    Peterson, F.

    1988-01-01

    The direction of sediment transport in eolian sandstones of Pennsylvanian to Jurassic age was interpreted from crossbedding resultants (vector means) obtained from studies of eolian rocks in the western U.S., supplemented by data from the few eolian units of eastern North America. These were compiled from the published or unpublished (theses) literature, from unpublished field data contributed by colleagues, or from measurements made for this study. In addition, new paleogeographic maps were compiled to evaluate the influence of geographic features on the atmospheric circulation patterns that are inferred from the crossbedding studies. Regionally, the crossbedding indicates northeasterly, northerly, or northwesterly winds (present coordinates) from Pennsylvanian through most of Middle Jurassic time. A rather abrupt change in wind directions occurred in late Middle Jurassic time (late part of the Callovian Age) when westerly wind patterns developed. By the Late Jurassic the winds shifted to southwesterly. Calculations of the consistency factor (vector mean strength) made from region-wide analyses of the resultants indicate fairly unidirectional winds from the Pennsylvanian through the Early Jurassic. Middle Jurassic circulation was more varied, judging from crossbedding studies in the lower part of the Entrada Sandstone. Crossbedding in Upper Jurassic eolian rocks of Wyoming and South Dakota yielded a random pattern but Upper Jurassic rocks farther south on the Colorado Plateau and adjoining areas show a return to a fairly unidirectional pattern. Comparing the resultants with their reconstructed paleogeographic setting shows surprisingly little influence of major geographic features on overall circulation patterns. However, the greatest amount of local variation occurred at or near highly indented shorelines where the temperature contrast between land and water produces local wind currents that may vary appreciably from regional circulation patterns. Although they do not cause noticeable horizontal deflections in wind patterns, small and low topographic highs appear to be able to promote the development of a dune field if a source of sand is available and if streams do not enter the growing dune field. ?? 1988.

  20. 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

  1. 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

  2. An arboreal docodont from the Jurassic and mammaliaform ecological diversification

    NASA Astrophysics Data System (ADS)

    Meng, Qing-Jin; Ji, Qiang; Zhang, Yu-Guang; Liu, Di; Grossnickle, David M.; Luo, Zhe-Xi

    2015-02-01

    A new docodontan mammaliaform from the Middle Jurassic of China has skeletal features for climbing and dental characters indicative of an omnivorous diet that included plant sap. This fossil expands the range of known locomotor adaptations in docodontans to include climbing, in addition to digging and swimming. It further shows that some docodontans had a diet with a substantial herbivorous component, distinctive from the faunivorous diets previously reported in other members of this clade. This reveals a greater ecological diversity in an early mammaliaform clade at a more fundamental taxonomic level not only between major clades as previously thought.

  3. 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

  4. Late Quaternary vegetation and environments in the Verkhoyansk Mountains region (NE Asia) reconstructed from a 50-kyr fossil pollen record from

    E-print Network

    Schöne, Bernd R.

    ) reconstructed from a 50-kyr fossil pollen record from Lake Billyakh Stefanie Müller a,*,1 , Pavel E. Tarasova,1 we present a detailed radiocarbon-dated 936 cm long pollen record from Lake Billyakh (65 170 N, 126 of the Arctic Circle. A set of 53 surface pollen samples representing tundra, cold deciduous forest and taiga

  5. 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.

  6. The Fossil RThe Fossil RThe Fossil RThe Fossil RThe Fossil Reporteporteporteporteport Oak Ridge National Laboratory Fossil Energy Program Fall 2003

    E-print Network

    Pennycook, Steve

    The Fossil RThe Fossil RThe Fossil RThe Fossil RThe Fossil Reporteporteporteporteport Oak Ridge National Laboratory Fossil Energy Program Fall 2003 Energy Technology for the Future...and for the World See NPR - page 2 The Fossil Report is published quarterly by Paul Theodore Carlson, Oak Ridge National

  7. The Fossil RThe Fossil RThe Fossil RThe Fossil RThe Fossil Reporteporteporteporteport Oak Ridge National Laboratory Fossil Energy Program Spring 2003

    E-print Network

    Pennycook, Steve

    The Fossil RThe Fossil RThe Fossil RThe Fossil RThe Fossil Reporteporteporteporteport Oak Ridge National Laboratory Fossil Energy Program Spring 2003 Energy Technology for the Future...and for the World Leasing Prctic Leasing Programogramogramogramogram The Fossil Report is published quarterly by Paul T

  8. The Fossil RThe Fossil RThe Fossil RThe Fossil RThe Fossil Reporteporteporteporteport Oak Ridge National Laboratory Fossil Energy Program Fall 2002

    E-print Network

    Pennycook, Steve

    The Fossil RThe Fossil RThe Fossil RThe Fossil RThe Fossil Reporteporteporteporteport Oak Ridge National Laboratory Fossil Energy Program Fall 2002 Energy Technology for the Future...and for the World Hermetic Seal for High-Temperature Electrochemical Application Continuing Resolutions Continuing The Fossil

  9. Applying microCT and 3D visualization to Jurassic silicified conifer seed cones: A virtual advantage over thin-sectioning1

    PubMed Central

    Gee, Carole T.

    2013-01-01

    • Premise of the study: As an alternative to conventional thin-sectioning, which destroys fossil material, high-resolution X-ray computed tomography (also called microtomography or microCT) integrated with scientific visualization, three-dimensional (3D) image segmentation, size analysis, and computer animation is explored as a nondestructive method of imaging the internal anatomy of 150-million-year-old conifer seed cones from the Late Jurassic Morrison Formation, USA, and of recent and other fossil cones. • Methods: MicroCT was carried out on cones using a General Electric phoenix v|tome|x s 240D, and resulting projections were processed with visualization software to produce image stacks of serial single sections for two-dimensional (2D) visualization, 3D segmented reconstructions with targeted structures in color, and computer animations. • Results: If preserved in differing densities, microCT produced images of internal fossil tissues that showed important characters such as seed phyllotaxy or number of seeds per cone scale. Color segmentation of deeply embedded seeds highlighted the arrangement of seeds in spirals. MicroCT of recent cones was even more effective. • Conclusions: This is the first paper on microCT integrated with 3D segmentation and computer animation applied to silicified seed cones, which resulted in excellent 2D serial sections and segmented 3D reconstructions, revealing features requisite to cone identification and understanding of strobilus construction. PMID:25202495

  10. 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. ); Vallier, T. ); Stanley, G.D. Jr. ); Ash, S.R. ); 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.

  11. Ediacara Fossils

    ERIC Educational Resources Information Center

    Science Teacher, 2005

    2005-01-01

    Now, a research team from Virginia Tech and Nanjing Institute of Geology and Paleontology has discovered uniquely well-preserved fossil forms from 550-million-year-old rocks of the Ediacaran Period. The research appears in the Proceedings of the National Academy of Sciences. The discovery of these unusually preserved fossils reveals unprecedented…

  12. 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…

  13. Molecular composition and ultrastructure of Jurassic paravian feathers.

    PubMed

    Lindgren, Johan; Sjövall, Peter; Carney, Ryan M; Cincotta, Aude; Uvdal, Per; Hutcheson, Steven W; Gustafsson, Ola; Lefèvre, Ulysse; Escuillié, François; Heimdal, Jimmy; Engdahl, Anders; Gren, Johan A; Kear, Benjamin P; Wakamatsu, Kazumasa; Yans, Johan; Godefroit, Pascal

    2015-01-01

    Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers. PMID:26311035

  14. Molecular composition and ultrastructure of Jurassic paravian feathers

    PubMed Central

    Lindgren, Johan; Sjövall, Peter; Carney, Ryan M.; Cincotta, Aude; Uvdal, Per; Hutcheson, Steven W.; Gustafsson, Ola; Lefèvre, Ulysse; Escuillié, François; Heimdal, Jimmy; Engdahl, Anders; Gren, Johan A.; Kear, Benjamin P.; Wakamatsu, Kazumasa; Yans, Johan; Godefroit, Pascal

    2015-01-01

    Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers. PMID:26311035

  15. 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

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

    SciTech Connect

    Sabine, C. . 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.

  17. Jurassic Deformation in and Around the Ordos Basin, North China

    NASA Astrophysics Data System (ADS)

    Zhang, Yueqiao; Liao, Changzhen; Shi, Wei; Zhang, Tian; Guo, Fangang

    The Jurassic era was an important period for tectonic development of the East Asia continent in general, and can be divided into two different deformation stages around the Ordos basin in particular. It was under weak extension during the Early to Middle Jurassic, with the stretching direction in N-S to NNE-SSW, and the stretching deformation mainly occurred in zones surrounding the Ordos basin. This extension was possibly associated with intra-continental stress adjustment following the Late Triassic collision between North and South China Blocks along the Qinling ranges. During the Middle to Late Jurassic, the tectonic regime changed in the Ordos basin to multi-directed compressions, with the maximum stress axes oriented in W-E, NW-SE, and NE-SW; the boundary compressional belts with different trends and structural styles were formed around the Ordos basin. The formation of the N-S trending thrust and nappe belt developed along the western margin of the Ordos basin, resulted from the eastward extrusion of the Alashan and Longxi blocks; and the eastern boundary belt is characterized by W-dipping back-thrust reverse faults and associated folds, which is inferred to occur on the frontal hinging wall ramp (HWR) of a westward propagated decollement system beneath the Shanxi faulted uplift. Large-scale thrust and nappe structures and inversion tectonics of the Early to Middle Jurassic grabens along the Daqingshan in the north of the Ordos basin indicate strong N-S crustal shortening and rejuvenation of the Yinshan Range. The boundary structural belts around the Ordos basin well record multi-directed compressions and continental crust thickening during the Middle to Late Jurassic, which were dynamically associated with far-field effects produced by synchronous convergences toward the East Asia continent of three different plates (Siberia, Paleo-Pacific, and Tethys). This multi-directed compressional deformation accelerated hydrocarbon generation and had profound impact on the accumulation and localization of the multi-energy mineral deposits in the Ordos basin.

  18. 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.

  19. 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. ); Thy, P. )

    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.

  20. The age for the fossil-bearing Tabbowa beds in Sri Lanka

    NASA Astrophysics Data System (ADS)

    Chang, S. C.; Dassanayake, S.; Wang, J.

    2014-12-01

    Well-preserved terrestrial fossils, mainly including conifers, cycads and ferns, were discovered from the Tabbowa beds in northwestern Sri Lanka. The high diversity and abundance of plants and insects from these Jurassic sediments provide a unique window to understand floral evolution and plant-insect co-evolution in the Mesozoic. For example, unearthed fossils from the Tabbowa beds indicate that leaf feeding and dwelling insects played a significant role in the Jurassic ecosystem. For another example, feeding and chewing marks on leaves allow studying insect behavior and paleo-ecology. Additionally, the recent discoveries of Otozamites latiphyllus and Otozamites tabbowensis from these sediments provide evidence that Bennettitales, an extinct order of seed plants, widely spread in the Gondwana during the Jurassic period. Although most fossils are yet to be well studied, and only few of the fossil occurrences have been published in western journals, plant fossils from the Tabbowa beds have great potential for substantially increasing our knowledge of Jurassic terrestrial ecosystems. The fossil-bearing Tabbowa beds are mainly composed of sandstone, siltstone, and mudstone with occasional thin bands of nodular limestone. Until now, radio-isotopic age determinations for the fossil-rich Tabbowa beds are lacking. In this study, we investigate the geological and geochronological setting of this area by dating detrital zircons from the Tabbowa beds. The age data will allow testing several hypotheses regarding the plant evolution, the basin development of this region.

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

    SciTech Connect

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

    1985-04-01

    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 platform that prograded seaward with the development of ramps. By the Late Jurassic, a major reef complex had developed at the outer continental shelf. The onset of reef growth can be tentatively dated as 138 Ma by using the J1 reflector dated by the Deep Sea Drilling Project. A well-developed reef-talus deposit can be identified overlying the interface that generates the J1 reflector. A detailed analysis of semblancederived interval velocities in the reef-talus sequence indicates a compressional velocity of 4.3-4.5 km/sec (14,100-14,800 ft/sec) for that interval, which was part of a major barrier reef along the United States eastern margin. After the reef formed, the deep oceanic basin was mostly starved from shelf-derived sediments until the reef died and was buried by clastic sediments. By correlation of our seismic data and COST well information, that in the Baltimore Canyon Trough this reef had terminated by about the end of the Jurassic Period.

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. Fossil Horses

    NASA Astrophysics Data System (ADS)

    MacFadden, Bruce J.

    1994-06-01

    The family Equidae have an extensive fossil record spanning the past 58 million years, and the evolution of the horse has frequently been used as a classic example of long-term evolution. In recent years, however, there have been many important discoveries of fossil horses, and these, in conjunction with such new methods as cladistics, and techniques such as precise geochronology, have allowed us to achieve a much greater understanding of the evolution and biology of this important group. This book synthesizes the large body of data and research relevant to an understanding of fossil horses from several disciplines including biology, geology and paleontology. Using horses as the central theme, the author weaves together in the text such topics as modern geochronology, paleobiogeography, climate change, evolution and extinction, functional morphology, and population biology during the Cenozoic period. This book will be exciting reading for researchers and graduate students in vertebrate paleontology, evolution, and zoology.

  7. 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. . 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.

  8. Taphonomic and paleoenvironmental considerations for the concentrations of macroinvertibrate fossils in the Romualdo Member, Santana Formation, Late Aptian - Early Albian, Araripe Basin, Araripina, NE, Brazil

    NASA Astrophysics Data System (ADS)

    Prado, Ludmila Alves Cadeira Do; Pereira, Priscilla Albuquerque; Sales, Alexandre Magno Feitosa; Barreto, Alcina Magnólia Franca

    2015-10-01

    Benthic macroinvertebrate fossils can be seen towards to the top of the Romualdo Member of the Santana Formation, in the Araripe Basin, Northeast Brazil, and can provide paleoenvironmental and paleobiogeographical information regarding the Cretaceous marine transgression which reached the interior basins in Northeast Brazil. We analyse taphonomic characteristics of macroinvertebrate concentrations of two outcrops (Torrinha and Torre Grande) within the municipality Araripina, Pernambuco, in order to enhance our understanding of the Cretaceous paleoenvironment in the western portion of the Araripe Basin. At the outcrop Torrinha, proximal tempestitic taphofacies were identified. These predominantly consist of ceritid, cassiopid, and later, naticid gastropods as well as undetermined bivalves. Given this lack of variability it can be deduced that there were no significant paleoenvironmental changes during the successive stages tempestitic sedimentation. In the Torre Grande outcrop distal to proximal tempestitic taphofacies were identified from the base to the top respectively pointing to a decrease in paleodepth. Asides from the macroinvertebrates present in Torrinha, there are also echinoids - unequivocal evidence for marine conditions. These occurrences appear to be restricted to Romualdo Member outcrops in the Araripina municipality (the Southeast portion of the Araripe Basin) confirming a previously published hypothesis suggesting that the Cretaceous marine transgression originated from the neighbouring Parnaíba Basin to the west. This study identified marine molluscs of a similar age to those in the Romualdo Member's equivalent rock units in the Parnaíba and Sergipe-Alagoas (SE-AL) basins suggesting a marine connection between these basins and the Araripe Basin during the Early Cretaceous.

  9. Fossil Finds Expand Early Hominid Anatomy.

    ERIC Educational Resources Information Center

    Bower, B.

    1991-01-01

    Hominid fossils found in late 1990 in Ethiopia are reported. A controversy surrounding these remains and those of earlier expeditions, including Lucy, over whether more than one species of hominid are represented is discussed. (CW)

  10. 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

  11. Rhopalomma stefaniae gen. et sp. n., the first ommatid beetle from the Upper Jurassic in Australia (Coleoptera: Archostemata: Ommatidae).

    PubMed

    Ashman, Lauren G; Oberprieler, Rolf G; ?lipi?ski, Adam

    2015-01-01

    The first Upper Jurassic fossil of the family Ommatidae (Coleoptera: Archostemata) from Australia is described and illustrated from a single specimen discovered at the Talbragar Fish Bed. Rhopalomma stefaniae gen. et sp. n. is classified in Ommatidae based on the length and insertion of the antennae, the tuberculate cuticle, the pattern of elytral striae, the complete epipleura and the presence of scutellary strioles. Due to the lack of preservation of crucial characters, Rhopalomma cannot be assigned to a subfamily and is therefore classified as Ommatidae incertae sedis. Rhopalomma fills an important gap in the fossil record of the family, indicating that Ommatidae occurred in Australia from the Lower Jurassic to the present day. Australia is the only place in the world where this family is found in both the fossil record and the living fauna. PMID:26249943

  12. Late Jurassic-Early Cretaceous radiolarian age constraints from the sedimentary cover of the Amasia ophiolite (NW Armenia), at the junction between the Izmir-Ankara-Erzinçan and Sevan-Hakari suture zones

    NASA Astrophysics Data System (ADS)

    Danelian, T.; Asatryan, G.; Galoyan, Gh.; Sahakyan, L.; Stepanyan, J.

    2015-07-01

    The Amasia ophiolite, situated at the northernmost corner of Armenia, is part of the Sevan-Hakari suture zone which links with the Izmir-Ankara-Erzinçan suture zone in northern Turkey. Three new radiolarian assemblages have been extracted from siliceous sedimentary rocks that accumulated on the Amasia ophiolite in an oceanic setting. Two of these assemblages were extracted from red-brownish bedded cherts overlying basaltic lavas; one of these is likely to be middle Oxfordian to early Kimmeridgian in age, while the second correlates with the Berriasian. Similar time-equivalent lava-chert sequences have been dated recently using radiolarians from the Stepanavan, Vedi and Sevan ophiolite units, where they are considered to relate to submarine volcanic activity in the back-arc marginal basin in which the Armenian ophiolites were formed. The third radiolarian assemblage, of late Barremian age, was extracted from a more than 15-m-thick volcaniclastic-chert sequence. The related volcanic activity is likely to have been subaerial and probably relates to the formation of an oceanic volcanic plateau; no Cretaceous subaerial volcanism has been previously recorded in the Lesser Caucasus area.

  13. A new rhamphorhynchid pterosaur (Pterosauria) from Jurassic deposits
    of Liaoning Province, China.

    PubMed

    Lü, Junchang; Pu, Hanyong; Xu, Li; Wei, Xuefang; Chang, Huali; Kundrát, Martin

    2015-01-01

    Compared to pterosaurs from the Early Cretaceous from China, Late Jurassic pterosaurs are relatively rare. A new rhamphorhynchid pterosaur, Orientognathus chaoyngensis gen. et sp. nov., is erected based on an incomplete skeleton from the Upper Jurassic Tuchengzi Formation of Chaoyang, Liaoning Province, China. It is identified by the following characters: the toothless tip of the lower jaw is slightly pointed; the length ratio of wing metacarpal to humerus is 0.38, the ulna is shorter than each wing phalanx and the tibia is nearly equal to femur in length. A phylogenetic analysis recovers Orientognathus chaoyngensis as a rhamphorhynchid pterosaur. Orientognathus chaoyngensis is perhaps the youngest Jurassic pterosaur from western Liaoning Province of China.  PMID:25661600

  14. 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

  15. 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

  16. Biostratigraphic restudy documents Triassic/Jurassic section in Georges Bank COST G-2 well

    SciTech Connect

    Cousminer, H.L.; Steinkraus, W.E.; Hall, R.E.

    1984-04-01

    In 1977, the COST G-2 well as drilled in Georges Bank, 132 mi (212 km) east of Nantucket Island to a total depth of 21,874 ft (6667 m). Biostratigraphic studies of 363 sidewall and conventional cores and 695 cutting samples resulted in a detailed zonation from the Late Jurassic to the present. Restudy of the original samples, as well as new preparations from previously unstudied core material, resulted in revision of the zonation of the Late Jurassic and older section. On the basis of our study of pollen and spores, dinoflagellates, nannofossils, and foraminifers, we revised the age sequence as follows: 5856 ft (1785 m) Late Jurassic (Thithonian); 6000 ft (1829 m) Kimmeridgian; 6420 ft (1957 m) Oxfordian; 6818 ft (2078 m) Callovian; 8200 ft (2499 m) Bathonian; 9677 ft (2950 m) Bajocian; 14567 ft (4440 m) Norian (Late Triassic). Norian dinoflagellate cysts and Tasmanites sp. indicate that intermittent normal marine sedimentation was taking place on Georges Bank as early as Norian time, although most of the Triassic section (+14,500 ft or 4420 m to T.D.) interpreted as having been deposited under evaporitic sabkha-like conditions. The Norian dinoflagellates (Noricysta, Heibergella, Hebecysta, Suessia, Dapcodinium, and Rhombodella) include species common to both Arctic Canada and the Tethyan region, indicating a possible Late Triassic marine connection.

  17. 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

  18. 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

  19. Microfossil evidence for a mid-Jurassic squid egg-laying area in association with the Christian Malford Lagerstätte

    NASA Astrophysics Data System (ADS)

    Hart, Malcolm; de Jonghe, Alex; Duff, Keith; Page, Kevin; Price, Gregory; Smart, Christopher; Wilby, Philip

    2010-05-01

    In the 1840s, during the construction of the Great Western Railway west of Swindon, a number of beautifully preserved coleoids (belemnites and squid-like cephalopods) were found. These famous specimens of Belemnoteuthis and Mastigophora, as well as a number of fish, were eventually described as a fossil lagerstätte under the name of the "Christian Malford Squid Bed". Many of these specimens, which come from the Phaeinum Zone (Callovian) of the Oxford Clay Formation, contain soft tissue, muscle fibres and the content of their ink sacs. In October 2007 the British Geological Survey funded an excavation of the site some ~100 m from the original borrow pits alongside the railway. This pit yielded some new coleoid specimens as well as many ammonites, bivalves and gastropods, all of which are exquisitely preserved. Some of the bedding surfaces recovered are plastered with monospecific assemblages of foraminifera (In the 1840s, during the construction of the Great Western Railway west of Swindon, a number of beautifully preserved coleoids (belemnites and squid-like cephalopods) were found. These famous specimens of Belemnoteuthis and Mastigophora, as well as a number of fish, were eventually described as a fossil lagerstätte under the name of the "Christian Malford Squid Bed". Many of these specimens, which come from the Phaeinum Zone (Callovian) of the Oxford Clay Formation, contain soft tissue, muscle fibres and the content of their ink sacs. In October 2007 the British Geological Survey funded an excavation of the site some ~100 m from the original borrow pits alongside the railway. This pit yielded some new coleoid specimens as well as many ammonites, bivalves and gastropods, all of which are exquisitely preserved. Some of the bedding surfaces recovered are plastered with monospecific assemblages of foraminifera (Epistomina spp.). Our work on borehole core No. 10 (from the same location) has recovered exceptionally large numbers of statoliths, otoliths (fish ‘ear' bones), squid hooks and foraminifera. Statoliths are the small, paired, aragonitic stones found in the heads of modern and fossil coleoids. Jurassic statoliths have yet to be described in any detail as there is only one reference to them in the literature (Clarke, 2003). The exceptional abundance of statoliths and squid hooks recorded in the samples from the core is thought to represent a Jurassic squid-breeding ground which existed for a substantial interval of late Callovian time. The annual spawning of female squids massively enlarges their ovaries and this breaks down the body wall leaving spent individuals to die. The lack of belemnites in the same strata suggests that the animals involved (unknown at present) did not possess a calcified "guard". The highest numbers of statoliths occur over a 3 m thickness of strata with the greatest abundance ~1 m below the Christian Malford Squid Bed. The numbers recorded in this part of the Phaeinum Zone are well above background levels in the rest of the Jurassic in the UK (Malcolm Clarke, pers.com.) where one has to wash several kg of sediment to recover <200 statoliths. The occurrence of abundant, though low diversity, foraminiferal assemblages in the same samples point to an oxic, though possibly stressed, environment. The significant proportion of deformed foraminifera in the assemblages appears to confirm that the environment was less than optimum. CLARKE, M.R. 2003. Potential of statoliths for interpreting coleoid evolution: A brief review. Berliner Paläobiol. Abh., 3, 37-47.

  20. Pump-Probe Microscopic Imaging of Jurassic-Aged Eumelanin

    PubMed Central

    Simpson, Mary Jane; Glass, Keely E.; Wilson, Jesse W.; Wilby, Philip R.; Simon, John D.

    2013-01-01

    Melanins are biological pigments found throughout the animal kingdom that have many diverse functions. Pump-probe imaging can differentiate the two kinds of melanins found in human skin, eumelanin and pheomelanin, the distributions of which are relevant to the diagnosis of melanoma. The long-term stability of the melanin pump-probe signal is central to using this technology to analyze melanin distributions in archived tissue samples to improve diagnostic procedures. This report shows that most of the pump-probe signal from eumelanin derived from a Jurassic cephalopod is essentially identical to that of eumelanin extracted from its modern counterpart, Sepia officinalis. However, additional classes of eumelanin signals found in the fossil reveal that the pump-probe signature is sensitive to iron content, which could be a valuable tool for pathologists who cannot otherwise know the microscopic distributions of iron in melanins. PMID:23847720

  1. Dictyodoru and associated trace fossils from the Palaeozoic of Thuringia

    E-print Network

    Benton, Michael

    Dictyodoru and associated trace fossils from the Palaeozoic of Thuringia MICHAEL J. BENTON Bcnton some of which are fossiliferous. Large tracts yield only deep-sea trace fossil faunas of Late to visit several localities and collect trace fossils (because of the politically sensitive nature of some

  2. Constraints on Phanerozoic paleotemperature and seawater oxygen isotope evolution from the carbonate clumped isotope compositions of Late Paleozoic marine fossils (Invited)

    NASA Astrophysics Data System (ADS)

    Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Pérez-Huerta, A.; Shenton, B.; Yancey, T. E.

    2013-12-01

    A long-standing geoscience controversy has been the interpretation of the observed several per mil increase in the oxygen isotope compositions of marine calcites over the Phanerozoic Eon. Explanations for this trend have included decreasing seawater paleotemperatures, increasing seawater oxygen isotope values, and post-depositional calcite alteration. Carbonate clumped isotope paleothermometry is a useful geochemical tool to test these hypotheses because of its lack of dependence on the bulk isotopic composition of the water from which carbonate precipitated. This technique is increasingly applied to ancient marine invertebrate shells, which can be screened for diagenesis using chemical and microstructural approaches. After several years of clumped isotope analysis of these marine carbonates in a handful of laboratories, a long-term temperature and isotopic trend is emerging, with the results pointing to relatively invariant seawater ?18O and generally decreasing seawater temperatures through the Phanerozoic. Uncertainties remain, however, including the effects of reordering of primary clumped isotope compositions via solid-state diffusion of C and O through the mineral lattice at elevated burial temperatures over hundred million year timescales. To develop a quantitative understanding of such reordering, we present data from laboratory heating experiments of late Paleozoic brachiopod calcite. When combined with kinetic models of the reordering reaction, the results of these experiments suggest that burial temperatures less than ~120 °C allow for preservation of primary brachiopod clumped isotope compositions over geological timescales. Analyses of well-preserved Carboniferous and Permian brachiopods reinforce these results by showing that shells with apparent clumped isotope temperatures of ~150 °C are associated with deep sedimentary burial (>5 km), whereas those with putatively primary paleotemperatures in the 10-30 °C range experienced no more than ~1.5 km of burial. Consideration of the thermal history of samples is essential for identifying the possibility of clumped isotope alteration via C-O bond reordering. Our experimental results further suggest that even nascent reordering (<5-10%) is enough to measurably bias reconstructed paleotemperatures (and calculated seawater oxygen isotope compositions) to higher values. We also investigate the use of electron backscatter diffraction (EBSD), which resolves crystallographic orientation at high spatial resolution, as an alternative method for identifying sub-microstructural diagenesis in calcite. Preliminary results of EBSD on the experimental and natural Paleozoic brachiopod shells will be presented and discussed with respect to their clumped isotope compositions and the Phanerozoic record.

  3. 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.

  4. World petroleum systems with Jurassic source rocks

    SciTech Connect

    Klemme, H.D. )

    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.

  5. 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.

  6. Evidence for GRB Induced Extinctions in the Fossil Record?

    NASA Astrophysics Data System (ADS)

    Kaye, Thomas G.

    2004-09-01

    Particular problems in the fossil record are placed in context with a GRB event causing death by radiation exposure, followed by comet showers from a disruption in the Oort Cloud. The absence of pollen below the iridium layer at the KT and Triassic-Jurassic boundaries, the pattern of extinction on land and in the oceans and divergence times of molecular DNA studies may all have a common root in ionizing radiation.

  7. 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

  8. Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition.

    PubMed

    Benson, Roger B J; Druckenmiller, Patrick S

    2014-02-01

    Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic-Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic-Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic-Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic-Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade-specific factors may have been more important than overarching extrinsic drivers of faunal turnover during the Jurassic-Cretaceous boundary interval. PMID:23581455

  9. Early Jurassic shale chemostratigraphy and UPb ages from the Neuqun Basin (Argentina): Implications for the Toarcian Oceanic Anoxic Event

    E-print Network

    Svensen, Henrik

    Early Jurassic shale chemostratigraphy and U­Pb ages from the Neuquén Basin (Argentina shale section in the Neuquén Basin, Argentina, are presented in order to better constrain the triggering. Chemostratigraphy from a 65 m thick shale-dominated marine section of Late Pliensbachian to Early Toarcian age shows

  10. 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.

  11. Will My Fossil Float?

    ERIC Educational Resources Information Center

    Riesser, Sharon; Airey, Linda

    1993-01-01

    Explains how young students can be introduced to fossils. Suggests books to read and science activities including "Fossils to Eat" where students make fossils from peanut butter, honey, and powdered milk. (PR)

  12. Are the oldest 'fossils', fossils

    NASA Technical Reports Server (NTRS)

    Schopf, J. W.

    1976-01-01

    A comparative statistical study has been carried out on populations of modern algae, Precambrian algal microfossils, the 'organized elements' of the Orgueil carbonaceous meteorite, and the oldest microfossil-like objects now known (spheroidal bodies from the Fig Tree and Onverwacht Groups of the Swaziland Supergroup, South Africa). The distribution patterns exhibited by the more than 3000 m.y.-old Swaziland microstructures bear considerable resemblance to those of the abiotic 'organized elements' but differ rather markedly from those exhibited by younger, assuredly biogenic, populations. Based on these comparisons, it is concluded that the Swaziland spheroids could be, at least in part, of nonbiologic origin; these oldest known fossil-like microstructures should not be regarded as constituting firm evidence of Archean life.

  13. 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

  14. 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.

  15. The late Quaternary dynamics of pines in northern Asia

    E-print Network

    Liu, Kam-biu

    V.Kremenetski.Kam-biuLiuand GlenM.MacDonald Introduction pumila and P. sibinca during glacial periods may have playeda role reflects changes in abundance and geo- graphicrangesthat haveoccurredsincethe end ofthe last glacial period jurassic and Cretaceous Asian pine fossils into extinct pinaceous genera makes the case for an Asian centre

  16. 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.

  17. 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

  18. Paleoclimatology indicators of the Salt Wash member of the Upper Jurassic Morrison Formation near Jensen, Utah

    SciTech Connect

    Medlyn, D.A. . Dept. of Geology); Bilbey, S.A. )

    1993-04-01

    The Upper Jurassic Morrison Formation has yielded one of the richest floras of the so-called transitional conifers'' of the Middle Mesozoic. Recently, a silicified axis of one of these conifers was collected from the Salt Wash member in essentially the same horizon as a previously reported partial Stegosaurus skeleton. In addition, two other axes of conifers were collected in the same immediate vicinity. Paleoecological considerations are extrapolated from the coniferous flora, vertebrate fauna and associated lithologies. Techniques of paleodendrology and relationships of extant/extinct environments are compared. The paleoclimatic conditions of the transitional conifers and associated dinosaurian fossils are postulated.

  19. Mammalian evolution. An arboreal docodont from the Jurassic and mammaliaform ecological diversification.

    PubMed

    Meng, Qing-Jin; Ji, Qiang; Zhang, Yu-Guang; Liu, Di; Grossnickle, David M; Luo, Zhe-Xi

    2015-02-13

    A new docodontan mammaliaform from the Middle Jurassic of China has skeletal features for climbing and dental characters indicative of an omnivorous diet that included plant sap. This fossil expands the range of known locomotor adaptations in docodontans to include climbing, in addition to digging and swimming. It further shows that some docodontans had a diet with a substantial herbivorous component, distinctive from the faunivorous diets previously reported in other members of this clade. This reveals a greater ecological diversity in an early mammaliaform clade at a more fundamental taxonomic level not only between major clades as previously thought. PMID:25678661

  20. Discovery of Jurassic ammonite-bearing series in Jebel Bou Hedma (South-Central Tunisian Atlas): Implications for stratigraphic correlations and paleogeographic reconstruction

    NASA Astrophysics Data System (ADS)

    Bahrouni, Néjib; Houla, Yassine; Soussi, Mohamed; Boughdiri, Mabrouk; Ali, Walid Ben; Nasri, Ahmed; Bouaziz, Samir

    2016-01-01

    Recent geological mapping undertaken in the Southern-Central Atlas of Tunisia led to the discovery of Jurassic ammonite-bearing series in the Jebel Bou Hedma E-W anticline structure. These series represent the Southernmost Jurassic rocks ever documented in the outcrops of the Tunisian Atlas. These series which outcrop in a transitional zone between the Southern Tunisian Atlas and the Chott basin offer a valuable benchmark for new stratigraphic correlation with the well-known Jurassic series of the North-South Axis of Central Tunisia and also with the Jurassic subsurface successions transected by petroleum wells in the study area. The preliminary investigations allowed the identification, within the most complete section outcropping in the center of the structure, of numerous useful biochronological and sedimentological markers helping in the establishment of an updated Jurassic stratigraphic framework chart of South-Western Tunisia. Additionally, the Late Jurassic succession documents syn-sedimentary features such as slumping, erosion and reworking of sediments and ammonite faunas that can be considered as strong witnesses of an important geodynamic event around the Jurassic-Cretaceous boundary. These stratigraphic and geodynamic new data make of the Jurassic of Jebel Bou Hedma a key succession for stratigraphic correlation attempt between Atlas Tunisian series and those currently buried in the Chott basin or outcropping in the Saharan platform. Furthermore, the several rich-ammonite identified horizons within the Middle and Upper Jurassic series constitute reliable time lines that can be useful for both paleogeographic and geodynamic reconstructions of this part of the North African Tethyan margin but also in the refinement of the potential migration routes for ammonite populations from the Maghrebian Southern Tethys to Arabia.

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

    SciTech Connect

    Ross, C.A. ); Moore, G.T.; Hayashida, D.N. )

    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.

  2. The palaeoclimatic significance of Eurasian Giant Salamanders (Cryptobranchidae: Zaissanurus, Andrias) - indications for elevated humidity in Central Asia during global warm periods (Eocene, late Oligocene warming, Miocene Climate Optimum)

    NASA Astrophysics Data System (ADS)

    Vasilyan, Davit; Böhme, Madelaine; Winklhofer, Michael

    2010-05-01

    Cryptobranchids represent a group of large sized (up to 1.8 m) tailed amphibians known since the Middle Jurassic (Gao & Shubin 2003). Two species are living today in eastern Eurasia: Andrias davidianus (China) and A. japonicus (Japan). Cenozoic Eurasian fossil giant salamanders are known with two genera and two or three species from over 30 localities, ranging from the Late Eocene to the Early Pliocene (Böhme & Ilg 2003). The Late Eocene species Zaissanurus beliajevae is restricted to the Central Asian Zaissan Basin (SE-Kazakhstan, 50°N, 85°E), whereas the Late Oligocene to Early Pliocene species Andrias scheuchzeri is distributed from Central Europe to the Zaissan Basin. In the latter basin the species occur during two periods; the latest Oligocene and the late Early to early Middle Miocene (Chkhikvadse 1982). Andrias scheuchzeri is osteological indistinguishable from both recent species, indicating a similar ecology (Westfahl 1958). To investigate the palaeoclimatic significance of giant salamanders we analyzed the climate within the present-day distribution area and at selected fossil localities with independent palaeoclimate record. Our results indicate that fossil and recent Andrias species occur in humid areas where the mean annual precipitation reach over 900 mm (900 - 1.300 mm). As a working hypothesis (assuming a similar ecology of Andrias and Zaissanurus) we interpret occurrences of both fossil Eurasian giant salamanders as indicative for humid palaeoclimatic conditions. Based on this assumption the Late Eocene, the latest Oligocene (late Oligocene warming) and the late Early to early Middle Miocene (Miocene Climatic Optimum) of Central Asia (Zaissan Basin) are periods of elevated humidity, suggesting a direct (positive) relationship between global climate and Central Asian humidity evolution. Böhme M., Ilg A. 2003: fosFARbase, www.wahre-staerke.com/ Chkhikvadze V.M. 1982. On the finding of fossil Cryptobranchidae in the USSR and Mongolia. Vertebrata Hungarica, 21: 63-67. Gao K.-Q., Shubin N.H. 2003. Earliest known crown-group Salamanders. Nature, 422: 424-428. Westphal F. 1958. Die Tertiären und rezenten Eurasiatischen Riesensalamander. Palaeontolographica Abt. A, 110: 20-92.

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

    SciTech Connect

    Johnson, C.R.; Ward, W.C. ); Goldhammer, R.K. )

    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.

  4. Jurassic stratigraphy of the Wiggins Arch, Mississippi

    SciTech Connect

    Rhodes, J.A.; Maxwell, G.B. )

    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.

  5. 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…

  6. 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

  7. Jurassic evolution of the Tien-Shan

    SciTech Connect

    Bebeshev, I.I.

    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.

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

    SciTech Connect

    Algar, S.; Erikson, J.P.

    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.

  9. Basin architecture, salt tectonics, and Upper Jurassic structural styles, DeSoto Canyon Salt basin, northeastern Gulf of Mexico

    SciTech Connect

    MacRae, G.; Watkins, J.S. )

    1993-10-01

    Despite the Gulf of Mexico being a mature hydrocarbon province, the least understood aspects of the basin's geologic history are undoubtedly those concerning pre-Middle Jurassic tectonic events and their implication for the tectonic and sedimentary evolution of the region. Despite awareness of the importance of continental extension during rifting, there are few quantitative studies that show the influence of crustal extension on basin architecture, the distribution of salt, and Late Jurassic sedimentation in the DeSoto Canyon Salt basin, northeastern Gulf of Mexico. Application of simplified isostatic principles using a lithospheric buoyancy model allow quantification of total tectonic subsidence, crustal thickness, crustal extension, and crust type. An average crustal thickness of 25 km and crustal extension [beta] values between 1.4 and 1.8 suggest the sedimentary succession is underlain by moderately stretched and attenuated continental crust. The widespread distribution and geometry of dipping subsalt reflectors, particularly in the shelfal areas, provide evidence for a Late Triassic-Early Jurassic phase of rifting prior to deposition of Middle Jurassic salt. Although deposition occurred in a slowly subsiding, stable marginal setting, salt movement and associated growth faulting are the most significant tectonic elements affecting the stratigraphic and structural development of the overlying strata.

  10. 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. )

    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.

  11. Paleoenvironments of the Jurassic and Cretaceous Oceans: Selected Highlights

    NASA Astrophysics Data System (ADS)

    Ogg, J. G.

    2007-12-01

    There are many themes contributing to the sedimentation history of the Mesozoic oceans. This overview briefly examines the roles of the carbonate compensation depth (CCD) and the associated levels of atmospheric carbon dioxide, of the evolution of marine calcareous microplankton, of major transgressive and regressive trends, and of super-plume eruptions. Initiation of Atlantic seafloor spreading in the Middle Jurassic coincided with an elevated carbonate compensation depth (CCD) in the Pacific-Tethys mega-ocean. Organic-rich sediments that would become the oil wealth of regions from Saudi Arabia to the North Sea were deposited during a continued rise in CCD during the Oxfordian-early Kimmeridgian, which suggests a possible increase in carbon dioxide release by oceanic volcanic activity. Deep-sea deposits in near-equatorial settings are dominated by siliceous shales or cherts, which reflect the productivity of siliceous microfossils in the tropical surface waters. The end-Jurassic explosion in productivity by calcareous microplankton contributed to the lowering of the CCD and onset of the chalk ("creta") deposits that characterize the Tithonian and lower Cretaceous in all ocean basins. During the mid-Cretaceous, the eruption of enormous Pacific igneous provinces (Ontong Java Plateau and coeval edifices) increased carbon dioxide levels. The resulting rise in CCD terminated chalk deposition in the deep sea. The excess carbon was progressively removed in widespread black-shale deposits in the Atlantic basins and other regions - another major episode of oil source rock. A major long-term transgression during middle and late Cretaceous was accompanied by extensive chalk deposition on continental shelves and seaways while the oceanic CCD remained elevated. Pacific guyots document major oscillations (sequences) of global sea level superimposed on this broad highstand. The Cretaceous closed with a progressive sea-level regression and lowering of the CCD that again enabled widespread carbonate deposition in the deep sea.

  12. 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.

  13. 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

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

    PubMed Central

    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

  15. Mysterious Fossils from the Chesapeake Bay Impact Crater and Beyond

    USGS Multimedia Gallery

    Photo of fossil algae (dinocyst). Specimen is about 90 micrometers across.The largest known impact crater in the U.S. lies buried beneath the Virginia Coastal Plain. The late Eocene Chesapeake Bay impact event caused a wide variety of distinctive features, such as fossil algae (dinocysts) that were ...

  16. Trace fossils and sedimentary facies from a Late Cambrian-Early Ordovician tide-dominated shelf (Santa Rosita Formation, northwest Argentina): Implications for ichnofacies models of shallow marine successions

    USGS Publications Warehouse

    Mangano, M.G.; Buatois, L.A.; Acenolaza, G.F.

    1996-01-01

    The Santa Rosita Formation is one the most widely distributed lower Paleozoic units of northwest Argentina. At the Quebrada del Salto Alto section, east of Purmamarca, Jujuy Province, it is represented by four sedimentary facies: thick-bedded planar cross-stratified quartzose sandstones (A), thin-bedded planar cross-stratified quartzose sandstones and mudstones (B), wave-rippled sandstones and bioturbated mudstones (C), and black and greenish gray shales (D). Paleocurrent data, sandstone architecture, and sedimentary structures from facies A and B indicate bipolar/bimodal paleoflows, suggesting the action of tidal currents. The succession is interpreted as that of a tide-dominated shelf, with only secondary influence of wave processes. Trace fossils are restricted to facies B and C. The Cruziana ichnocoenosis is preserved on the soles of thin-bedded planar cross-stratified quartzose sandstones (facies B). This ichnocoenosis consists of Conostichus isp., Cruziana omanica, C. semiplicata, C. cf. tortworthi, Cruziana isp. Helminthopsis abeli, Monomorphichnus bilinearis, M. multilineatus, Palaeophycus tubularis, Rusophycus carbonarius, R. latus, and R. isp. The occurrence of Cruziana semiplicata, C. omanica, C. cf. tortworthi, and Rusophycus latus supports a Late Cambrian-Tremadoc age. Slabbing of Cruziana shows complex interactions between biologic and sedimentologic processes, and suggests a predominance of exhumed traces, washed out and recast by tractive sand deposition. Sandstone soles are densely packed with biogenic structures and exhibit distinctive clusters of Rusophycus isp. that most likely represent trilobite nesting burrows. The Cruziana ichnocoenosis records the resident fauna of a protected, lower intertidal to subtidal interbar setting. The Skolithos ichnocoenosis is represented by high to low density vertical burrows of Skolithos linearis, which extend downwards to the quartzose sandstone soles of facies B and cross the Cruziana ichnocoenosis. The Skolithos ichnocoenosis represents colonization by suspension-feeding organisms following a major change in environmental conditions, related to the migration of lower intertidal to subtidal sandwaves. The Planolites ichnocoenosis consists exclusively of Planolites montanus within mudstones overlying wave-rippled sandstones (facies C). The Planolites ichnocoenosis records opportunistic colonization by infaunal deposit feeders that mined the organic-rich fine-grained sediment during the waning phase of storms that scoured organic detritus from the sea bottom. The section records, from base to top, a Cruziana-Skolithos ichnofacies zone, a Skolithos ichnofacies zone and an unbioturbated zone typified by the thick-bedded cross-stratified quartzose sandstone (facies A). This trend reflects progressively higher energy conditions linked to the establishment of a large sand wave complex. The presence of a mixed Cruziana-Skolithos ichnofacies in the lower interval reflects changes in substrate and energy levels, rather than water depth. Accordingly, contrasting ichnocoenoses from interbars (Cruziana) and sandwaves (Skolithos) must be considered an example of ichnofacies controlled by local parameters instead of general bathymetric trends. Conversely, the vertical replacement of the Cruziana ichnofacies by the Skolithos ichnofacies towards the middle interval of the section reflects the environmental changes associated with the transition between the intertidal and subtidal zones. As overall tidal energy increases from supratidal to subtidal settings, the Skolithos ichnofacies tends to occur seaward of the Cruziana ichnofacies in tide-dominated shallow marine environments. Therefore, onshore-offshore ichnofacies replacement in tide-dominated shallow seas is opposite to that in wave-dominated marine settings.

  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. Position of the Triassic-Jurassic boundary and timing of the end-Triassic extinctions on land: Data from the Moenave Formation on the southern Colorado Plateau, USA

    USGS Publications Warehouse

    Lucas, S.G.; Tanner, L.H.; Donohoo-Hurley, L.; Geissman, J.W.; Kozur, H.W.; Heckert, A.B.; Weems, R.E.

    2011-01-01

    Strata of the Moenave Formation on and adjacent to the southern Colorado Plateau in Utah-Arizona, U.S.A., represent one of the best known and most stratigraphically continuous, complete and fossiliferous terrestrial sections across the Triassic-Jurassic boundary. We present a synthesis of new biostratigraphic and magnetostratigraphic data collected from across the Moenave Formation outcrop belt, which extends from the St. George area in southwestern Utah to the Tuba City area in northern Arizona. These data include palynomorphs, conchostracans and vertebrate fossils (including footprints) and a composite polarity record based on four overlapping magnetostratigraphic sections. Placement of the Triassic-Jurassic boundary in strata of the Moenave Formation has long been imprecise and debatable, but these new data (especially the conchostracans) allow us to place the Triassic-Jurassic boundary relatively precisely in the middle part of the Whitmore Point Member of the Moenave Formation, stratigraphically well above the highest occurrence of crurotarsan body fossils or footprints. Correlation to marine sections based on this placement indicates that major terrestrial vertebrate extinctions preceded marine extinctions across the Triassic-Jurassic boundary and therefore were likely unrelated to the Central Atlantic Magmatic Province (CAMP) volcanism. ?? 2011 Elsevier B.V.

  19. Harris et al., eds., 2006, The Triassic-Jurassic Terrestrial Transition. New Mexico Museum of Natural History and Science Bulletin 37. AN OVERVIEWOFTHE PALEONTOLOGYOFUPPERTRIASSICAND

    E-print Network

    Barnosky, Anthony D.

    490 Harris et al., eds., 2006, The Triassic-Jurassic Terrestrial Transition. New Mexico Museum rocks exposed in Zion National Park in southwestern Utah include fossiliferous units of Late Triassic. These strata were deposited over a period of 275 million years, and record a multitude of environments

  20. Unravelling the collapse mechanisms at a Jurassic caldera of the Chon Aike silicic LIP in Southern Patagonia (47° 15 'S, 71° 40'W), Argentina

    NASA Astrophysics Data System (ADS)

    Sruoga, P.; Japas, S.; Salani, F.; Kleiman, L.; Graffigna, M.

    2008-10-01

    La Peligrosa Caldera is located at Sierra Colorada (47° 15'S, 71° 40' W) in the Chon-Aike silicic LIP. It represents an unique window to understand the eruptive mechanisms that prevailed throughout the ignimbritic flare-up in Southern Patagonia during middle to late Jurassic times. Key pieces of lithologic and structural evidences are taken into account to reconstruct the volcanic structure.

  1. Jurassic Cordilleran dike swarm-shear zones: Implications for the Nevadan orogeny and North American plate motion

    SciTech Connect

    Wolf, M.B.; Saleeby, J.B. )

    1992-08-01

    A cogenetic and coeval tonalitic and mafic dike swarm has been identified within a southern fragment (the Owens Mountain area) of the western Foothills terrane (California). The dikes were mylonitized and transposed (rotated into subparallel orientation) during emplacement, from 155 to 148 Ma (U-Pb zircon data), which coincides in time with the Nevadan orogeny. Steeply southeast-plunging fold axes and S-fold geometries indicate a sinistral-sense of shear, possibly with some dip-slip motion as well. This shear zone may be the southern and possibly deeper extension of the Bear Mountains fault zone. This and other Late Jurassic Cordilleran dike swarms record a complex pattern of sinistral-sense transtension-transpression that developed at the apparent-polar-wander J2 cusp ([approximately] 150 Ma) and during subsequent, rapid, northwestward acceleration of North America. The Late Jurassic Nevadan orogeny is a manifestation of these dramatic changes in magnitude and direction of North American motion.

  2. The Jurassic Bajanzhargalanidae (Insecta: Grylloblattida?): New genera and species, and data on postabdominal morphology.

    PubMed

    Cui, Yingying; Béthoux, Olivier; Klass, Klaus-Dieter; Ren, Dong

    2015-11-01

    The presumed phylogenetic link between extant ice-crawlers (Grylloblattidae = 'crown-Grylloblattida') and fossil species of the taxon concept Grylloblattida sensu Storozhenko (2002) is essentially based on postabdominal morphology. However, the fossil data are limited, and the interpretation is open to debate. Here we investigate a sample of a poorly known fossil 'grylloblattidan' family, the Bajanzhargalanidae, collected from the Daohugou locality (Middle Jurassic, China). We describe Sinonele fangi gen. nov., sp. nov., Sinonele hei gen. nov., sp. nov., Sinonele phasmoides gen. nov., sp. nov., and Sinonele mini gen. nov., sp. nov. Thanks to the abundance and exceptional preservation of the material, we could document wing venation intra-specific variability, provide cues to identify male and female individuals, describe and tentatively interpret various body structures of both sexes, and discuss them with a broad pterygotan phylogenetic perspective. The Bajanzhargalanidae exhibit a puzzling combination of postabdominal characters leaving us inconclusive on their affinities, or lack thereof, with crown-Grylloblattida. Our contribution suggests that a substantial effort will be needed to further investigate postabdominal structures from comparatively ancient fossil insects preserved as rock imprints, because of their broad morphological disparity. PMID:25979677

  3. A golden orb-weaver spider (Araneae: Nephilidae: Nephila) from the Middle Jurassic of China.

    PubMed

    Selden, Paul A; Shih, ChungKun; Ren, Dong

    2011-10-23

    Nephila are large, conspicuous weavers of orb webs composed of golden silk, in tropical and subtropical regions. Nephilids have a sparse fossil record, the oldest described hitherto being Cretaraneus vilaltae from the Cretaceous of Spain. Five species from Neogene Dominican amber and one from the Eocene of Florissant, CO, USA, have been referred to the extant genus Nephila. Here, we report the largest known fossil spider, Nephila jurassica sp. nov., from Middle Jurassic (approx. 165 Ma) strata of Daohugou, Inner Mongolia, China. The new species extends the fossil record of the family by approximately 35 Ma and of the genus Nephila by approximately 130 Ma, making it the longest ranging spider genus known. Nephilidae originated somewhere on Pangaea, possibly the North China block, followed by dispersal almost worldwide before the break-up of the supercontinent later in the Mesozoic. The find suggests that the palaeoclimate was warm and humid at this time. This giant fossil orb-weaver provides evidence of predation on medium to large insects, well known from the Daohugou beds, and would have played an important role in the evolution of these insects. PMID:21508021

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

    PubMed

    Clapham, Matthew E; Bottjer, David J

    2007-08-01

    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

  5. Fossil-energy program

    NASA Astrophysics Data System (ADS)

    McNeese, L. E.

    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 combustor for cogeneration, TVA FBC demonstration plant program technical support, PFBC systems analysis, FBC char utilization improvement, fossil fuel applications assessments, performance assurance system support for fossil energy projects, international energy technology, generalized equilibrium models for liquid and gaseous fuel supplies, instrumentations and controls and fossil energy information center.

  6. Preliminary interpretations of syn- and posttectonic palaeomagnetism of Jurassic sediments from Velebit Mts (Karst Dinarides, Croatia)

    NASA Astrophysics Data System (ADS)

    Werner, Tomasz; Lewandowski, Marek; Vlahovi?, Igor; Veli?, Ivo; Sidorczuk, Magdalena

    2013-04-01

    Velebit Mts, a part of the Adria Microplate, belonged to a NE margin of Gondwana during the Carboniferous and Permian. While Permian is characterised by clastics, post-Permian sedimentation is dominated by a thick sequence of carbonate rocks. Today, the entire sequence, representing a stratigraphic range from Carboniferous to Recent, is in places more than 10,000 m thick. The Early to Late Jurrasic deposits (limestones in seven sites, reduction spots' limestones in one site and mudstones in one site) along the transect in Mali Halan in the southern part of the Velebit Mt. were studied using palaeomagnetic and rock magnetic measurements. Strata in the whole transect dips moderately to SW. Magnetic susceptibility of diamagnetic carbonates is not affected by heating up to 400-500°C. SIRM(T) experiments revealed low temperature (Tub<400°C) Ti poor magnetite and some hematite phase in fresh samples. Heating in air results in excessive growth of new magnetite phase above 600°C. Thermal and AF treatment were performed and were more successful for the Lower Jurassic sites with stronger NRM. It resulted in separation of two ChRM components: "L" with Tub up to 200-250°C and "M" with Tub up to 400-475°C or two coercivity spectra (very soft and harder) in most successfully demagnetized samples. In some samples only soft/LT component was recorded. "M" component for the Lower and Middle Jurassic sites (345/30 in situ) correlates well with results of Marton (2008) for Early Jurassic grainstones in the same area. The tilt corrected data for "M" component fall close to Middle Jurassic segment for APWP for Africa. However site means for " M" component are distributed along the small circle with subhorizontal WNW trending axis. That may be interpreted as pre- to syntectonic remenance recorded during the regional folding. Such mechanism is consistent with paleomagnetic results for remagnetized Permian clastic sediments in Velebit Mts. (Crne Grede and Kosna localities, Lewandowski et al., 2012, AGU Fall Meeting, GP21A-1136). "L" component (of lower accuracy) for Lower/Middle Jurassic sites (in situ) falls close to the Tertiary segment of APWP for Africa as well indicating its post-tectonic secondary origin. For Upper Jurassic sites with lower NRM intensity "L" component seems to be post-tectonic but results for "M" component need to be yet discussed. AMS results for sites are not consistent between sites due to varying contribution of ferro- and diamagnetic phases to magnetic susceptibility in each site.

  7. 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

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

    SciTech Connect

    Anderson, T.H.; Kohn, M. . 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.

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

    SciTech Connect

    Fritsche, A.E. ); Yamashiro, D.A. )

    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.

  10. Upper Jurassic carbonate/evaporite shelf, south Alabama and west Florida

    SciTech Connect

    Moore, B.R.

    1986-05-01

    The association of Upper Jurassic carbonates and evaporites in south Alabama and west Florida defines a brining upward and inward sequence that is indicative of deposition on an increasingly evaporitic marine shelf. Structural features that bound this evaporitic shelf were the Pensacola arch, the South Mississippi platform, and the State Line flexure. Paleo-drainage of the surrounding highlands also affected shelf salinities as fresh waters were funneled into the Covington and Manila Embayments. During the Late Jurassic, marine carbonates and evaporites of the Smackover and Lower Haynesville (Buckner) Formations were deposited over Middle Jurassic Norphlet clastics that accumulated in arid continental and marginal-marine environments. Initially, Smackover carbonate deposition was pervasive across the shallow shelf. Later, as a result of increasing water salinities, contemporaneous precipitation of central-shelf evaporites and basin-edge carbonates occurred. Maximum restriction of the basin and the culmination of subaqueous deposition resulted in the formation of a basin-wide lower Haynesville salt unit. The overlying upper Haynesville strata represents a shift to subaerial environments. Application of a shelf-basin evaporite model explains the spatial and temporal lithologic relationships observed within the study area. Onlap of evaporites over porous carbonates, due to brining-upward processes, suggest that large-scale stratigraphic traps exist within the Smackover Formation in a sparsely explored part of the basin.

  11. 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.

  12. A fossil flora from the Frontier formation of southwestern Wyoming

    USGS Publications Warehouse

    Knowlton, F.H.

    1917-01-01

    This paper deals with a small but important fossil flora, now known to be of Colorado age, from the vicinity of Cumberland, Lincoln County, Wyo. It was for many years thought to be of Jurassic age, and only within the last decade has its stratigraphic position been established. Although small in number of species, this flora offers information bearing on the physical and climatic conditions that prevailed during early Upper Cretaceous time in this region, and, moreover, it furnishes a series of stratigraphic marks that may be used in the recognition of this horizon elsewhere.

  13. Adaptation, plant evolution, and the fossil record

    NASA Technical Reports Server (NTRS)

    Knoll, A. H.; Niklas, K. J.

    1987-01-01

    The importance of adaptation in determining patterns of evolution has become an important focus of debate in evolutionary biology. As it pertains to paleobotany, the issue is whether or not adaptive evolution mediated by natural selection is sufficient to explain the stratigraphic distributions of taxa and character states observed in the plant fossil record. One means of addressing this question is the functional evaluation of stratigraphic series of plant organs set in the context of paleoenvironmental change and temporal patterns of floral composition within environments. For certain organ systems, quantitative estimates of biophysical performance can be made on the basis of structures preserved in the fossil record. Performance estimates for plants separated in time or space can be compared directly. Implicit in different hypotheses of the forces that shape the evolutionary record (e.g. adaptation, mass extinction, rapid environmental change, chance) are predictions about stratigraphic and paleoenvironmental trends in the efficacy of functional performance. Existing data suggest that following the evolution of a significant structural innovation, adaptation for improved functional performance can be a major determinant of evolutionary changes in plants; however, there are structural and development limits to functional improvement, and once these are reached, the structure in question may no longer figure strongly in selection until and unless a new innovation evolves. The Silurian-Devonian paleobotanical record is consistent with the hypothesis that the succession of lowland floodplain dominants preserved in the fossil record of this interval was determined principally by the repeated evolution of new taxa that rose to ecological importance because of competitive advantages conferred by improved biophysical performance. This does not seem to be equally true for Carboniferous-Jurassic dominants of swamp and lowland floodplain environments. In these cases, environmental disruption appears to have been a major factor in shaping the fossil record. This does not mean that continuing adaptation was not important during this interval, but it may indicate that adaptive evolution was strongest in environments other than those best represented in the paleobotanical record.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  15. New species and revisions of Pediciidae (Diptera) from the Middle Jurassic of northeastern China and Russia.

    PubMed

    Gao, Jiaqi; Shih, Chungkun; Kope?, Katarzyna; Krzemi?ski, Wies?aw; Ren, Dong

    2015-01-01

    Two new species of Praearchitipula Kalugina, 1985, P. apprima sp. nov. and P. mirabilis sp. nov., are described and illustrated from the late Middle Jurassic Jiulongshan Formation of Daohugou in eastern Inner Mongolia, China. In addition, we propose to transfer Architipula abnormis Hao & Ren, 2009 (which is from the same locality of Daohugou) from Architipula of Limoniidae to Praearchitipula of Pediciidae: Praearchitipula abnormis (Hao & Ren, 2009) comb. nov. In addition, we propose to transfer Praearchitipula spasskia Kalugina, 1985 to the genus Mesotipula (Limoniidae, Architipulinae). We also suggest treating Praearchitipula lata Kalugina, 1985 as a junior synonym of Praearchitipula notabilis Kalugina, 1985. An emended generic diagnosis of Praearchitipula is provided. PMID:26249421

  16. New species and revisions of Pediciidae (Diptera) from the Middle Jurassic of northeastern China and Russia.

    PubMed

    Gao, Jiaqi; Shih, Chungkun; Kope?, Katarzyna; Krzemi?ski, Wies?aw; Ren, Dong

    2015-01-01

    Two new species of Praearchitipula Kalugina, 1985, P. apprima sp. nov. and P. mirabilis sp. nov., are described and illustrated from the late Middle Jurassic Jiulongshan Formation of Daohugou in eastern Inner Mongolia, China. In addition, we propose to transfer Architipula abnormis Hao & Ren, 2009 (which is from the same locality of Daohugou) from Architipula of Limoniidae to Praearchitipula of Pediciidae: Praearchitipula abnormis (Hao & Ren, 2009) comb. nov. In addition, we propose to transfer Praearchitipula spasskia Kalugina, 1985 to the genus Mesotipula (Limoniidae, Architipulinae). We also suggest treating Praearchitipula lata Kalugina, 1985 as a junior synonym of Praearchitipula notabilis Kalugina, 1985. An emended generic diagnosis of Praearchitipula is provided. PMID:26249400

  17. Andean-scale highlands in the Late Cretaceous Cordillera of the North American western margin

    NASA Astrophysics Data System (ADS)

    Sewall, Jacob O.; Fricke, Henry C.

    2013-01-01

    From the Late Jurassic through the Cretaceous, collision between the North American and Farallon plates drove extensive thin-skinned thrusting and crustal shortening that resulted in substantial relief in the North American Cordillera. The elevation history of this region is tightly linked to the tectonic, climatic and landscape evolution of western North America but is not well constrained. Here we use an atmospheric general circulation model with integrated oxygen isotope tracers (isoCAM3) to predict how isotope ratios of precipitation would change along the North American Cordillera as the mean elevation of orogenic highlands increased from 1200 m to 3975 m. With increases in mean elevation, highland temperatures fall, monsoonal circulation along the eastern front of the Cordillera is enhanced, and wet season (generally spring and summer) precipitation increases. Simulated oxygen isotopic ratios in that precipitation are compared to those obtained from geologic materials (e.g. fossil bivalves, authigenic minerals). Quantification of match between model and data-derived ?18O values suggests that during the Late Cretaceous, the best approximation of regional paleoelevation in western North America is a large orogen on the scale of the modern Andes Mountains with a mean elevation approaching 4000 m and a north-south extent of at least 15° of latitude.

  18. Fossilized bioelectric wire - the trace fossil Trichichnus

    NASA Astrophysics Data System (ADS)

    K?dzierski, M.; Uchman, A.; Sawlowicz, Z.; Briguglio, A.

    2015-04-01

    The trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the oxic-anoxic interface zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus, formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that it is produced by modern large, mat-forming, sulfide-oxidizing bacteria, belonging mostly to Thioploca-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized "electric wire".

  19. Fossilized bioelectric wire - the trace fossil Trichichnus

    NASA Astrophysics Data System (ADS)

    K?dzierski, M.; Uchman, A.; Sawlowicz, Z.; Briguglio, A.

    2014-12-01

    The trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the interface oxic - anoxic zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that produced by modern large, mat-forming, sulphide-oxidizing bacteria, belonging mostly to Trichichnus-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized "electric wire".

  20. Fossilized bioelectric wire – the trace fossil Trichichnus

    PubMed Central

    K?dzierski, M.; Uchman, A.; Sawlowicz, Z.; Briguglio, A.

    2015-01-01

    The trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the oxic–anoxic interface zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus, formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that it is produced by modern large, mat-forming, sulfide-oxidizing bacteria, belonging mostly to Thioploca-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized “electric wire”. PMID:26290671

  1. 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.

  2. 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.

  3. 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

  4. Ecological succession of a Jurassic shallow-water ichthyosaur fall

    PubMed Central

    Danise, Silvia; Twitchett, Richard J.; Matts, Katie

    2014-01-01

    After the discovery of whale fall communities in modern oceans, it has been hypothesized that during the Mesozoic the carcasses of marine reptiles created similar habitats supporting long-lived and specialized animal communities. Here, we report a fully documented ichthyosaur fall community, from a Late Jurassic shelf setting, and reconstruct the ecological succession of its micro- and macrofauna. The early ‘mobile-scavenger’ and ‘enrichment-opportunist’ stages were not succeeded by a ‘sulphophilic stage’ characterized by chemosynthetic molluscs, but instead the bones were colonized by microbial mats that attracted echinoids and other mat-grazing invertebrates. Abundant cemented suspension feeders indicate a well-developed ‘reef stage’ with prolonged exposure and colonization of the bones prior to final burial, unlike in modern whale falls where organisms such as the ubiquitous bone-eating worm Osedax rapidly destroy the skeleton. Shallow-water ichthyosaur falls thus fulfilled similar ecological roles to shallow whale falls, and did not support specialized chemosynthetic communities. PMID:25205249

  5. 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

  6. Fossil Energy Program

    NASA Astrophysics Data System (ADS)

    McNeese, L. E.

    1981-01-01

    Increased utilization of coal and other fossil fuel alternatives as sources of clean energy is reported. The following topics are discussed: coal conversion development, chemical research and development, materials technology, component development and process evaluation studies, technical support to major liquefaction projects, process analysis and engineering evaluations, fossil energy environmental analysis, flue gas desulfurization, solid waste disposal, coal preparation waste utilization, plant control development, atmospheric fluidized bed coal combustor for cogeneration, TVA FBC demonstration plant program technical support, PFBC systems analysis, fossil fuel applications assessments, performance assurance system support for fossil energy projects, international energy technology assessment, and general equilibrium models of liquid and gaseous fuel supplies.

  7. 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.

  8. Molecular and Fossil Evidence on the Origin of Angiosperms

    NASA Astrophysics Data System (ADS)

    Doyle, James A.

    2012-05-01

    Molecular data on relationships within angiosperms confirm the view that their increasing morphological diversity through the Cretaceous reflected their evolutionary radiation. Despite the early appearance of aquatics and groups with simple flowers, the record is consistent with inferences from molecular trees that the first angiosperms were woody plants with pinnately veined leaves, multiparted flowers, uniovulate ascidiate carpels, and columellar monosulcate pollen. Molecular data appear to refute the hypothesis based on morphology that angiosperms and Gnetales are closest living relatives. Morphological analyses of living and fossil seed plants that assume molecular relationships identify glossopterids, Bennettitales, and Caytonia as angiosperm relatives; these results are consistent with proposed homologies between the cupule of glossopterids and Caytonia and the angiosperm bitegmic ovule. Jurassic molecular dates for the angiosperms may be reconciled with the fossil record if the first angiosperms were restricted to wet forest understory habitats and did not radiate until the Cretaceous.

  9. The Quaternary fossil-pollen record and global change

    SciTech Connect

    Grimm, E.C. . Research and Collections Center)

    1993-03-01

    Fossil pollen provide one of the most valuable records of vegetation and climate change during the recent geological past. Advantages of the fossil-pollen record are that deposits containing fossil pollen are widespread, especially in areas having natural lakes, that fossil pollen occurs in continuous stratigraphic sequences spanning millennia, and that fossil pollen occurs in quantitative assemblages permitting a multivariate approach for reconstructing past vegetation and climates. Because of stratigraphic continuity, fossil pollen records climate cycles on a wide range of scales, from annual to the 100 ka Milankovitch cycles. Receiving particular emphasis recently are decadal to century scale changes, possible from the sediments of varved lakes, and late Pleistocene events on a 5--10 ka scale possibly correlating with the Heinrich events in the North Atlantic marine record or the Dansgaard-Oeschger events in the Greenland ice-core record. Researchers have long reconstructed vegetation and climate by qualitative interpretation of the fossil-pollen record. Recently quantitative interpretation has developed with the aid of large fossil-pollen databases and sophisticated numerical models. In addition, fossil pollen are important climate proxy data for validating General Circulation Models, which are used for predicting the possible magnitude future climate change. Fossil-pollen data also contribute to an understanding of ecological issues associated with global climate change, including questions of how and how rapidly ecosystems might respond to abrupt climate change.

  10. Jurassic climate mode governed by ocean gateway.

    PubMed

    Korte, Christoph; Hesselbo, Stephen P; Ullmann, Clemens V; Dietl, Gerd; Ruhl, Micha; Schweigert, Günter; Thibault, Nicolas

    2015-01-01

    The Jurassic (?201-145?Myr ago) was long considered a warm 'greenhouse' period; more recently cool, even 'icehouse' episodes have been postulated. However, the mechanisms governing transition between so-called Warm Modes and Cool Modes are poorly known. Here we present a new large high-quality oxygen-isotope dataset from an interval that includes previously suggested mode transitions. Our results show an especially abrupt earliest Middle Jurassic (?174?Ma) mid-latitude cooling of seawater by as much as 10?°C in the north-south Laurasian Seaway, a marine passage that connected the equatorial Tethys Ocean to the Boreal Sea. Coincidence in timing with large-scale regional lithospheric updoming of the North Sea region is striking, and we hypothesize that northward oceanic heat transport was impeded by uplift, triggering Cool Mode conditions more widely. This extreme climate-mode transition provides a counter-example to other Mesozoic transitions linked to quantitative change in atmospheric greenhouse gas content. PMID:26658694

  11. Jurassic climate mode governed by ocean gateway

    PubMed Central

    Korte, Christoph; Hesselbo, Stephen P.; Ullmann, Clemens V.; Dietl, Gerd; Ruhl, Micha; Schweigert, Günter; Thibault, Nicolas

    2015-01-01

    The Jurassic (?201–145?Myr ago) was long considered a warm ‘greenhouse' period; more recently cool, even ‘icehouse' episodes have been postulated. However, the mechanisms governing transition between so-called Warm Modes and Cool Modes are poorly known. Here we present a new large high-quality oxygen-isotope dataset from an interval that includes previously suggested mode transitions. Our results show an especially abrupt earliest Middle Jurassic (?174?Ma) mid-latitude cooling of seawater by as much as 10?°C in the north–south Laurasian Seaway, a marine passage that connected the equatorial Tethys Ocean to the Boreal Sea. Coincidence in timing with large-scale regional lithospheric updoming of the North Sea region is striking, and we hypothesize that northward oceanic heat transport was impeded by uplift, triggering Cool Mode conditions more widely. This extreme climate-mode transition provides a counter-example to other Mesozoic transitions linked to quantitative change in atmospheric greenhouse gas content. PMID:26658694

  12. 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

  13. 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.

  14. Bird-Like Anatomy, Posture, and Behavior Revealed by an Early Jurassic Theropod Dinosaur Resting Trace

    PubMed Central

    Milner, Andrew R. C.; Harris, Jerald D.; Lockley, Martin G.; Kirkland, James I.; Matthews, Neffra 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 million-year-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. PMID:19259260

  15. Dinosaur ichnofauna of the Upper Jurassic/Lower Cretaceous of the Paraná Basin (Brazil and Uruguay)

    NASA Astrophysics Data System (ADS)

    Francischini, H.; Dentzien–Dias, P. C.; Fernandes, M. A.; Schultz, C. L.

    2015-11-01

    Upper Jurassic and Lower Cretaceous sedimentary layers are represented in the Brazilian Paraná Basin by the fluvio-aeolian Guará Formation and the Botucatu Formation palaeoerg, respectively, overlapped by the volcanic Serra Geral Formation. In Uruguay, the corresponding sedimentary units are named Batoví and Rivera Members (both from the Tacuarembó Formation), and the lava flows constitute the Arapey Formation (also in Paraná Basin). Despite the lack of body fossils in the mentioned Brazilian formations, Guará/Batoví dinosaur fauna is composed of theropod, ornithopod and wide-gauge sauropod tracks and isolated footprints, as well as theropod teeth. In turn, the Botucatu/Rivera dinosaur fauna is represented by theropod and ornithopod ichnofossils smaller than those from the underlying units. The analysis of these dinosaur ichnological records and comparisons with other global Mesozoic ichnofauna indicates that there is a size reduction in dinosaur fauna in the more arid Botucatu/Rivera environment, which is dominated by aeolian dunes. The absence of sauropod trackways in the Botucatu Sandstone fits with the increasingly arid conditions because it is difficult for heavy animals to walk on sandy dunes, as well as to obtain the required amount of food resources. This comparison between the Upper Jurassic and Lower Cretaceous dinosaur fauna in south Brazil and Uruguay demonstrates the influence of aridization on the size of animals occupying each habitat.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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…

  2. Post-Jurassic tectonic evolution of Southeast Asia

    NASA Astrophysics Data System (ADS)

    Zahirovic, Sabin; Seton, Maria; Dietmar Müller, R.; Flament, Nicolas

    2014-05-01

    The accretionary growth of Asia, linked to long-term convergence between Eurasia, Gondwana-derived blocks and the Pacific, resulted in a mosaic of terranes for which conflicting tectonic interpretations exist. Here, we propose solutions to a number of controversies related to the evolution of Sundaland through a synthesis of published geological data and plate reconstructions that reconcile both geological and geophysical constraints with plate driving forces. We propose that West Sulawesi, East Java and easternmost Borneo rifted from northern Gondwana in the latest Jurassic, collided with an intra-oceanic arc at ~115 Ma and subsequently sutured to Sundaland by 80 Ma. Although recent models argue that the Southwest Borneo core accreted to Sundaland at this time, we use volcanic and biogeographic constraints to show that the core of Borneo was on the Asian margin since at least the mid Jurassic. This northward transfer of Gondwana-derived continental fragments required a convergent plate boundary in the easternmost Tethys that we propose gave rise to the Philippine Archipelago based on the formation of latest Jurassic-Early Cretaceous supra-subduction zone ophiolites on Halmahera, Obi Island and Luzon. The Late Cretaceous marks the shift from Andean-style subduction to back-arc opening on the east Asian margin. Arc volcanism along South China ceased by ~60 Ma due to the rollback of the Izanagi slab, leading to the oceanward migration of the volcanic arc and the opening of the Proto South China Sea (PSCS). We use the Apennines-Tyrrhenian system in the Mediterranean as an analogue to model this back-arc. Continued rollback detaches South Palawan, Mindoro and the Semitau continental blocks from the stable east Asian margin and transfers them onto Sundaland in the Eocene to produce the Sarawak Orogeny. The extrusion of Indochina and subduction polarity reversal along northern Borneo opens the South China Sea and transfers the Dangerous Grounds-Reed Bank southward to terminate PSCS south-dipping subduction and culminates in the Sarawak Orogeny on Borneo and ophiolite obduction on Palawan. We account for the regional plate reorganizations related to the initiation of Pacific subduction along the Izu-Bonin-Mariana Arc, the extrusion tectonics resulting from the India-Eurasia collision, and the shift from basin extension to inversion on Sundaland as an indicator of collision between the Australian continent and the active Asian margin. We generate continuously closing and evolving plate boundaries, seafloor age-grids and global plate velocity fields using the open-source and cross-platform GPlates plate reconstruction software. We link our plate motions to numerical mantle flow models in order to predict mantle structure at present-day that can be qualitatively compared to P- and S- wave seismic tomography models. This method allows us to analyse the evolution of the mantle related to Tethyan and Pacific subduction and to test alternative plate reconstructions. This iterative approach can be used to improve plate reconstructions in the absence of preserved seafloor and conjugate passive margins of continental blocks, which may have been destroyed or highly deformed by multiple episodes of accretion along the Asian margins.

  3. 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.

  4. Fossil energy program

    NASA Astrophysics Data System (ADS)

    McNeese, L. E.

    1981-12-01

    Research and development programs in support of the increased utilization of coal and other fossil fuel alternatives as sources of clean energy are reported. The following projects are reported: 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 combustor for cogeneration, TVA FBC demonstration plant program technical support, PFBC systems analysis, FBC char utilization improvement, fossil fuel applications assessments, performance assurance system support for fossil energy projects, international energy technology, generalized equilibrium models for liquid and gaseous fuel supplies, analysis of coal production, and fossil energy information center.

  5. Fossil energy program

    NASA Astrophysics Data System (ADS)

    McNeese, L. E.

    1981-02-01

    The projects reported include those for coal conversion development, chemical research and development, materials technology, component development and process evaluation studies, technical support to major liquefaction projects, process analysis and engineering evaluations, fossil energy environmental analysis, flue gas desulfurization, plant control development, atmospheric fluidized bed coal combustor for cogeneration, TVA, FBC demonstration plant program technical support, and PFBC systems analysis. Fossil fuel application assessments, performance assurance system support for fossil energy projects, international energy technology assessment, and general equilibrium models of liquid and gaseous fuel supplies are presented.

  6. Fossil fuels -- future fuels

    SciTech Connect

    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.

  7. 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.

  8. Salt glands in the Jurassic metriorhynchid Geosaurus: implications for the evolution of osmoregulation in Mesozoic marine crocodyliforms

    NASA Astrophysics Data System (ADS)

    Fernández, Marta; Gasparini, Zulma

    2008-01-01

    The presence of salt-excreting glands in extinct marine sauropsids has been long suspected based on skull morphology. Previously, we described for the first time the natural casts of salt-excreting glands in the head of the Jurassic metriorhynchid crocodyliform Geosaurus araucanensis from the Tithonian of the Vaca Muerta Formation in the Neuquén Basin (Argentina). In the present study, salt-excreting glands are identified in three new individuals (adult, a sub-adult and a juvenile) referable to the same species. New material provides significant information on the salt glands form and function and permit integration of evolutionary scenarios proposed on a physiological basis in extant taxa with evidence from the fossil record. G. araucanensis represents an advanced stage of the basic physiological model to marine adaptations in reptiles. G. araucanensis salt glands were hypertrophied. On this basis, it can be hypothesized that these glands had a high excretory capability. This stage implies that G. araucanensis (like extant pelagic reptiles, e.g. cheloniids) could have maintained constant plasma osmolality even when seawater or osmoconforming prey were ingested. A gradual model of marine adaptation in crocodyliforms based on physiology (freshwater to coastal/estuarine to estuarine /marine to pelagic life) is congruent with the phylogeny of crocodyliforms based on skeletal morphology. The fossil record suggests that the stage of marine pelagic adaptation was achieved by the Early Middle Jurassic. Salt gland size in the juvenile suggests that juveniles were, like adults, pelagic.

  9. The Late Jurassic Tithonian, a greenhouse phase in the Middle JurassicEarly Cretaceous `cool' mode: evidence from the cyclic

    E-print Network

    Husinec, Antun

    (restricted lagoon), fenestral carbonates and microbial laminites (tidal flat). Parasequences in the overall to the base of the tidal flat units capping parasequences) were generally (Veizer et al., 2000) and by the pCO2 plots GEOCARB III of Berner & Kothavala (2001). At the long

  10. 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

  11. 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

  12. JURASSIC CYCLOSTRATIGRAPHY AND PALEONTOLOGY OF THE HARTFORD BASIN

    E-print Network

    Olsen, Paul E.

    A4-1 JURASSIC CYCLOSTRATIGRAPHY AND PALEONTOLOGY OF THE HARTFORD BASIN by Paul E. Olsen and Jessica and temporal context the rich paleontological and biostratigraphically useful assemblages in the aftermath

  13. Fossil energy program

    NASA Astrophysics Data System (ADS)

    McNeese, L. E.

    1981-03-01

    A compendium of monthly progress reports for the ORNL research and development programs that are in support of the increased utilization of coal and other fossil fuel alternatives as sources of clean energy is presented. The projects reported this month include those for coal conversion development, chemical research and development, materials technology, component development and process evaluation, technical support to major liquefaction projects, process analysis; and engineering evaluations, fossil energy environmental analysis, flue gas desulfurization, solid waste disposal, coal preparation and waste utilization, plant control development, atmospheric fluidized bed coal combustor for cogeneration, Tennessee Valley Authority Fluidized Bed Combustion demonstration plant program technical support, PFBC systems analysis, fossil fuel applications assessments, performance assurance system support for fossil energy projects, international energy technology assessment, and generalized equilibrium models of liquid and gaseous fuel supplies.

  14. Evidence of Evolution I. Fossils and the fossil record

    E-print Network

    Dever, Jennifer A.

    radioactive elements · Generally applied to igneous & metamorphic rocks, so what about fossils & sedimentary in the rocks deposited in those Eras. #12;#12;Why is the fossil record incomplete? · fossilization - "lucky in the rock! Accurate method for determining the age of fossils and rocks - Measures the decay of certain

  15. Early evolution and historical biogeography of fishflies (Megaloptera: Chauliodinae): implications from a phylogeny combining fossil and extant taxa.

    PubMed

    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

  16. 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

  17. Zeolites replacing plant fossils in the Denver formation, Lakewood, Colorado.

    USGS Publications Warehouse

    Modreski, P.J.; Verbeek, E.R.; Grout, M.A.

    1984-01-01

    Well-developed crystals of heulandite and stilbite, within fossil wood, occur in sedimentary rocks in Lakewood, Jefferson County. The rocks belong to the Denver formation, a locally fossiliferous deposit of fluvial claystone, siltstone, sandstone and conglomerate, containing some volcanic mudflows (andesitic) of late Cretaceous to Palaeocene age. Altered volcanic glass released Na and Ca into the ground-water and subsequently zeolites were crystallized in the open spaces between grains and within fossil plant structures. Minor pyrite, quartz (jasper), calcite and apatite also occur as replacements of fossil wood. Similar zeolite occurrences in other areas are reviewed.-R.S.M.

  18. 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.

  19. 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

  20. 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)

  1. Cerium anomaly at microscale in fossils.

    PubMed

    Gueriau, Pierre; Mocuta, Cristian; Bertrand, Loïc

    2015-09-01

    Patterns in rare earth element (REE) concentrations are essential instruments to assess geochemical processes in Earth and environmental sciences. Excursions in the "cerium anomaly" are widely used to inform on past redox conditions in sediments. This proxy resources to the specificity of cerium to adopt both the +III and +IV oxidation states, while most rare earths are purely trivalent and share very similar reactivity and transport properties. In practical terms, the level of cerium anomaly is established through elemental point quantification and profiling. All these models rely on a supposed homogeneity of the cerium oxidation state within the samples. However, this has never been demonstrated, whereas the cerium concentration can significantly vary within a sample, as shown for fossils, which would vastly complicate interpretation of REE patterns. Here, we report direct micrometric mapping of Ce speciation through synchrotron X-ray absorption spectroscopy and production of local rare earth patterns in paleontological fossil tissues through X-ray fluorescence mapping. The sensitivity of the approach is demonstrated on well-preserved fishes and crustaceans from the Late Cretaceous (ca. 95 million years (Myr) old). The presence of Ce under the +IV form within the fossil tissues is attributed to slightly oxidative local conditions of burial and agrees well with the limited negative cerium anomaly observed in REE patterns. The [Ce(IV)]/[Ce(tot)] ratio appears remarkably stable at the microscale within each fossil and is similar between fossils from the locality. Speciation maps were obtained from an original combination of synchrotron microbeam X-ray fluorescence, absorption spectroscopy, and diffraction, together with light and electron microscopy. This work also highlights the need for more systematic studies of cerium geochemistry at the microscale in paleontological contexts, in particular across fossil histologies. PMID:26239283

  2. Emplacement of the Jurassic Mirdita ophiolites (southern Albania): evidence from associated clastic and carbonate sediments

    NASA Astrophysics Data System (ADS)

    Robertson, Alastair H. F.; Ionescu, Corina; Hoeck, Volker; Koller, Friedrich; Onuzi, Kujtim; Bucur, Ioan I.; Ghega, Dashamir

    2012-09-01

    Sedimentology can shed light on the emplacement of oceanic lithosphere (i.e. ophiolites) onto continental crust and post-emplacement settings. An example chosen here is the well-exposed Jurassic Mirdita ophiolite in southern Albania. Successions studied in five different ophiolitic massifs (Voskopoja, Luniku, Shpati, Rehove and Morava) document variable depositional processes and palaeoenvironments in the light of evidence from comparable settings elsewhere (e.g. N Albania; N Greece). Ophiolitic extrusive rocks (pillow basalts and lava breccias) locally retain an intact cover of oceanic radiolarian chert (in the Shpati massif). Elsewhere, ophiolite-derived clastics typically overlie basaltic extrusives or ultramafic rocks directly. The oldest dated sediments are calpionellid- and ammonite-bearing pelagic carbonates of latest (?) Jurassic-Berrasian age. Similar calpionellid limestones elsewhere (N Albania; N Greece) post-date the regional ophiolite emplacement. At one locality in S Albania (Voskopoja), calpionellid limestones are gradationally underlain by thick ophiolite-derived breccias (containing both ultramafic and mafic clasts) that were derived by mass wasting of subaqueous fault scarps during or soon after the latest stages of ophiolite emplacement. An intercalation of serpentinite-rich debris flows at this locality is indicative of mobilisation of hydrated oceanic ultramafic rocks. Some of the ophiolite-derived conglomerates (e.g. Shpati massif) include well-rounded serpentinite and basalt clasts suggestive of a high-energy, shallow-water origin. The Berriasian pelagic limestones (at Voskopoja) experienced reworking and slumping probably related to shallowing and a switch to neritic deposition. Mixed ophiolite-derived clastic and neritic carbonate sediments accumulated later, during the Early Cretaceous (mainly Barremian-Aptian) in variable deltaic, lagoonal and shallow-marine settings. These sediments were influenced by local tectonics or eustatic sea-level change. Terrigenous sediment gradually encroached from neighbouring landmasses as the ophiolite was faulted or eroded. An Aptian transgression was followed by regression, creating a local unconformity (e.g. at Boboshtica). A Turonian marine transgression initiated widespread Upper Cretaceous shelf carbonate deposition. In the regional context, the southern Albania ophiolites appear to have been rapidly emplaced onto a continental margin in a subaqueous setting during the Late Jurassic (Late Oxfordian-Late Tithonian). This was followed by gradual emergence, probably in response to thinning of the ophiolite by erosion and/or exhumation. The sedimentary cover of the south Albanian ophiolites is consistent with rapid, relatively short-distance emplacement of a regional-scale ophiolite over a local Pelagonian-Korabi microcontinent.

  3. 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

  4. Calpionellid distribution and microfacies across the Jurassic/ Cretaceous boundary in western Cuba (Sierra de los Órganos)

    NASA Astrophysics Data System (ADS)

    López-Martínez, Rafael; Barragán, Ricardo; Reháková, Daniela; Cobiella-Reguera, Jorge Luis

    2013-06-01

    A detailed bed-by-bed sampled stratigraphic section of the Guasasa Formation in the Rancho San Vicente area of the "Sierra de los Órganos", western Cuba, provides well-supported evidence about facies and calpionellid distribution across the Jurassic/Cretaceous boundary. These new data allowed the definition of an updated and sound calpionellid biozonation scheme for the section. In this scheme, the drowning event of a carbonate platform displayed by the facies of the San Vicente Member, the lowermost unit of the section, is dated as Late Tithonian, Boneti Subzone. The Jurassic/Cretaceous boundary was recognized within the facies of the overlying El Americano Member on the basis of the acme of Calpionella alpina Lorenz. The boundary is placed nearly six meters above the contact between the San Vicente and the El Americano Members, in a facies linked to a sea-level drop. The recorded calpionellid bioevents should allow correlations of the Cuban biozonation scheme herein proposed, with other previously published schemes from distant areas of the Tethyan Domain.

  5. 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

  6. Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution.

    PubMed

    Slack, Kerryn E; Jones, Craig M; Ando, Tatsuro; Harrison, G L Abby; Fordyce, R Ewan; Arnason, Ulfur; Penny, David

    2006-06-01

    Testing models of macroevolution, and especially the sufficiency of microevolutionary processes, requires good collaboration between molecular biologists and paleontologists. We report such a test for events around the Late Cretaceous by describing the earliest penguin fossils, analyzing complete mitochondrial genomes from an albatross, a petrel, and a loon, and describe the gradual decline of pterosaurs at the same time modern birds radiate. The penguin fossils comprise four naturally associated skeletons from the New Zealand Waipara Greensand, a Paleocene (early Tertiary) formation just above a well-known Cretaceous/Tertiary boundary site. The fossils, in a new genus (Waimanu), provide a lower estimate of 61-62 Ma for the divergence between penguins and other birds and thus establish a reliable calibration point for avian evolution. Combining fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, the penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous. This includes a conservative estimate that modern sea and shorebird lineages diverged at least by the Late Cretaceous about 74 +/- 3 Ma (Campanian). It is clear that modern birds from at least the latest Cretaceous lived at the same time as archaic birds including Hesperornis, Ichthyornis, and the diverse Enantiornithiformes. Pterosaurs, which also coexisted with early crown birds, show notable changes through the Late Cretaceous. There was a decrease in taxonomic diversity, and small- to medium-sized species disappeared well before the end of the Cretaceous. A simple reading of the fossil record might suggest competitive interactions with birds, but much more needs to be understood about pterosaur life histories. Additional fossils and molecular data are still required to help understand the role of biotic interactions in the evolution of Late Cretaceous birds and thus to test that the mechanisms of microevolution are sufficient to explain macroevolution. PMID:16533822

  7. 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.

  8. Nature of the Jurassic Magnetic Quiet Zone

    NASA Astrophysics Data System (ADS)

    Tominaga, Masako; Tivey, Maurice A.; Sager, William W.

    2015-10-01

    The nature of the Jurassic Quiet Zone (JQZ), a region of low-amplitude oceanic magnetic anomalies, has been a long-standing debate with implications for the history and behavior of the Earth's geomagnetic field and plate tectonics. To understand the origin of the JQZ, we studied high-resolution sea surface magnetic anomalies from the Hawaiian magnetic lineations and correlated them with the Japanese magnetic lineations. The comparison shows the following: (i) excellent correlation of anomaly shapes from M29 to M42; (ii) remarkable similarity of anomaly amplitude envelope, which decreases back in time from M19 to M38, with a minimum at M41, then increases back in time from M42; and (iii) refined locations of pre-M25 lineations in the Hawaiian lineation set. Based on these correlations, our study presents evidence of regionally and possibly globally coherent pre-M29 magnetic anomalies in the JQZ and a robust extension of Hawaiian isochrons back to M42 in the Pacific crust.

  9. A New Fossil of Necrotauliidae (Insecta: Trichoptera) from the Jiulongshan Formation of China and Its Taxonomic Significance

    PubMed Central

    Liu, Yujia; Zhang, Weiting; Yao, Yunzhi; Ren, Dong

    2014-01-01

    Background Acisarcuatus variradius gen. et sp. nov., an extinct new species representing a new genus, is described from the Middle Jurassic Jiulongshan Formation in Daohugou Village, Inner Mongolia, China. Methodology/Principal Findings In this paper, we revised the diagnosis of Necrotauliidae Handlirsch, 1906. One new genus and species of Necrotauliidae is described. An analysis based on the fossil morphological characters clarified the taxonomic status of the new taxa. Conclusions/Significance New fossil evidence supports the viewpoint that the family Necrotauliidae belongs to the Integripalpia. PMID:25494387

  10. A revised checklist of Nepticulidae fossils (Lepidoptera) indicates an Early Cretaceous origin.

    PubMed

    Doorenweerd, Camiel; Nieukerken, Erik J Van; Sohn, Jae-Cheon; Labandeira, Conrad C

    2015-01-01

    With phylogenetic knowledge of Lepidoptera rapidly increasing, catalysed by increasingly powerful molecular techniques, the demand for fossil calibration points to estimate an evolutionary timeframe for the order is becoming an increasingly pressing issue. The family Nepticulidae is a species rich, basal branch within the phylogeny of the Lepidoptera, characterized by larval leaf-mining habits, and thereby represents a potentially important lineage whose evolutionary history can be established more thoroughly with the potential use of fossil calibration points. Using our experience with extant global Nepticulidae, we discuss a list of characters that may be used to assign fossil leaf mines to Nepticulidae, and suggest useful methods for classifying relevant fossil material. We present a checklist of 79 records of Nepticulidae representing adult and leaf-mine fossils mentioned in literature, often with multiple exemplars constituting a single record. We provide our interpretation of these fossils. Two species now are included in the collective generic name Stigmellites: Stigmellites resupinata (Krassilov, 2008) comb. nov. (from Ophiheliconoma) and Stigmellites almeidae (Martins-Neto, 1989) comb. nov. (from Nepticula). Eleven records are for the first time attributed to Nepticulidae. After discarding several dubious records, including one possibly placing the family at a latest Jurassic position, we conclude that the oldest fossils likely attributable to Nepticulidae are several exemplars representing a variety of species from the Dakota Formation (USA). The relevant strata containing these earliest fossils are now dated at 102 Ma (million years ago) in age, corresponding to the latest Albian Stage of the Early Cretaceous. Integration of all records in the checklist shows that a continuous presence of nepticulid-like leaf mines preserved as compression-impression fossils and by amber entombment of adults have a fossil record extending to the latest Early Cretaceous. PMID:26249403

  11. A field-based analysis of the accuracy of niche models applied to the fossil record

    E-print Network

    Walls, Bradley J.; Stigall, Alycia L.

    2012-04-11

    of ENM methods for Paleozoic brachiopod species. This study represents the first field validation analysis of ENM methods in the fossil record. Previously published species distributions models for 8 Late Ordovician brachiopod species from the Cincinnati...

  12. The Triassic-Jurassic boundary in eastern North America

    NASA Technical Reports Server (NTRS)

    Olsen, P. E.; Comet, B.

    1988-01-01

    Rift basins of the Atlantic passive margin in eastern North America are filled with thousands of meters of continental rocks termed the Newark Supergroup which provide an unprecedented opportunity to examine the fine scale structure of the Triassic-Jurassic mass extinction in continental environments. Time control, vital to the understanding of the mechanisms behind mass extinctions, is provided by lake-level cycles apparently controlled by orbitally induced climate change allowing resolution at the less than 21,000 year level. Correlation with other provinces is provided by a developing high resolution magnetostratigraphy and palynologically-based biostratigraphy. A large number of at least local vertebrate and palynomorph extinctions are concentrated around the boundary with survivors constituting the earliest Jurassic assemblages, apparently without the introduction of new taxa. The palynofloral transition is marked by the dramatic elimination of a relatively high diversity Triassic pollen assemblage with the survivors making up a Jurassic assemblage of very low diversity overwhelmingly dominated by Corollina. Based principally on palynological correlations, the hypothesis that these continental taxonomic transitions were synchronous with the massive Triassic-Jurassic marine extinctions is strongly corroborated. An extremely rapid, perhaps catastrophic, taxonomic turnover at the Triassic-Jurassic boundary, synchronous in continental and marine realms is hypothesized and discussed.

  13. Author's personal copy Rolling bones Taphonomy of Jurassic dinosaur bones inferred from diagenetic

    E-print Network

    Schöne, Bernd R.

    Author's personal copy Rolling bones ­ Taphonomy of Jurassic dinosaur bones inferred from 2010 Accepted 28 January 2011 Available online 4 February 2011 Keywords: Dinosaurs Taphonomy Diagenesis Bone histology Pyrolusite Junggar Basin Dinosaur bones from the Upper Jurassic Shishugou Formation near

  14. Fossil-Fired Boilers

    Energy Science and Technology Software Center (ESTSC)

    1993-09-23

    Boiler Performance Model (BPM 3.0S) is a set of computer programs developed to analyze the performance of fossil-fired utility boilers. The programs can model a wide variety of boiler designs, and can model coal, oil, or natural gas firing. The programs are intended for use by engineers performing analyses of alternative fuels, alternative operating modes, or boiler modifications.

  15. 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.

  16. Supraregional seismites in Triassic - Jurassic boundary strata

    NASA Astrophysics Data System (ADS)

    Lindström, Sofie; Pedersen, Gunver K.; van de Schootbrugge, Bas; Johansson, Leif; Petersen, Henrik I.; Dybkjær, Karen; Weibel, Rikke; Hansen, Katrine H.; Erlström, Mikael; Alwmark, Carl; Nielsen, Lars Henrik; Oschmann, Wolfgang; Tegner, Christian

    2014-05-01

    The end-Triassic mass extinction event (201.564 Ma) was synchronous with the earliest volcanic phase during the emplacement of the Central Atlantic Magmatic Province (CAMP), a large igneous province (LIP) formed during the initial breakup of Pangea. Volcanic degassing of CO2 and other volatile gases, and/or thermogenic methane, from the CAMP is generally regarded as the main cause of the end-Triassic biotic crisis. However, discrepancies in the durations of the ETE (50 Kyrs) and the CAMP volcanism (600 Kyrs) as well as temporal offsets between carbon cycle perturbations and biotic turnovers suggest a more complex scenario that require further studies of the temporal succession of events in Triassic-Jurassic (TJ) boundary strata. Here, we present and examine multiple episodes of soft-sediment deformation (seismite) within uppermost Rhaetian marine and terrestrial strata of Denmark, Sweden and Germany. These seismites are stratigraphically constrained by palynology and C-isotopes to the latest Rhaetian, and are synchronous to the single seismite layer from the UK, which similarly predates the T/J boundary, and has been explained by an extraterrestrial bolide impact. Instead, we argue that the multiple episodes of soft-sediment deformation, interbedded by undisturbed strata, were formed from repeated intense earthquake activity restricted to an interval within the latest Rhaetian bracketed by two negative excursions in ?13C and also containing palynological evidence for deforestation and fern proliferation. The fact that these biotic changes coincide with repeated seismic activity has implications for the end-Triassic extinction and the CAMP scenario. We discuss the temporal position of the seismites in regards to other end-Triassic events, and argue that their supraregional distribution in pre-TJ-boundary strata of NW Europe may be linked to intensified earthquake activity during CAMP emplacement, rather than an extraterrestrial impact.

  17. 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.

  18. Synchrony between the Central Atlantic magmatic province and the TriassicJurassic mass-extinction event?

    E-print Network

    Olsen, Paul E.

    Synchrony between the Central Atlantic magmatic province and the Triassic­Jurassic mass-extinction relationship between the Triassic­Jurassic mass extinction (202 Ma) and Earth's largest sequence of continental, S., 2002. Terrestrial and marine extinction at the Triassic­Jurassic boundary synchronized

  19. 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

  20. Constraints on Upper Jurassic palaeogeography in the Ula Gyda trend

    SciTech Connect

    Mundal, I.; Milton, N.; Robinson, N.

    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.

  1. 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

  2. Giving the early fossil record of sponges a squeeze.

    PubMed

    Antcliffe, Jonathan B; Callow, Richard H T; Brasier, Martin D

    2014-11-01

    Twenty candidate fossils with claim to be the oldest representative of the Phylum Porifera have been re-analysed. Three criteria are used to assess each candidate: (i) the diagnostic criteria needed to categorize sponges in the fossil record; (ii) the presence, or absence, of such diagnostic features in the putative poriferan fossils; and (iii) the age constraints for the candidate fossils. All three criteria are critical to the correct interpretation of any fossil and its placement within an evolutionary context. Our analysis shows that no Precambrian fossil candidate yet satisfies all three of these criteria to be a reliable sponge fossil. The oldest widely accepted candidate, Mongolian silica hexacts from c. 545 million years ago (Ma), are here shown to be cruciform arsenopyrite crystals. The oldest reliable sponge remains are siliceous spicules from the basal Cambrian (Protohertzina anabarica Zone) Soltanieh Formation, Iran, which are described and analysed here in detail for the first time. Extensive archaeocyathan sponge reefs emerge and radiate as late as the middle of the Fortunian Stage of the Cambrian and demonstrate a gradual assembly of their skeletal structure through this time coincident with the evolution of other metazoan groups. Since the Porifera are basal in the Metazoa, their presence within the late Proterozoic has been widely anticipated. Molecular clock calibration for the earliest Porifera and Metazoa should now be based on the Iranian hexactinellid material dated to c. 535 Ma. The earliest convincing fossil sponge remains appeared at around the time of the Precambrian-Cambrian boundary, associated with the great radiation events of that interval. PMID:24779547

  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. Morphological changes in the Jurassic and Cretaceous radiolarians (Nassellaria) at different stratigraphic levels

    NASA Astrophysics Data System (ADS)

    Vishnevskaya, Valentina

    2014-05-01

    Analysis of the geographic and stratigraphic distribution of the genera most famous in the Jurassic - Early Cretaceous family Parvicingulidae Pessagno, 1977 (Rhaetian-Barremian) radiolarians (Nassellaria), which consists of up to 200 species, 17 genera, showed that if high conical its representatives with belt-like cameras and apical horn (Parvicingula, Proparvicingula, Praeparvicingula, Atalantria, Canelonus, Elodium, Darvelus, Nitrader) come from the Pacific paleogeographic province (Vishnevskaya, 2011), and had occupied the Boreal and the Notal (Antarctic-related) regions, the other genera (Mirifusus, Ristola, Tethysetta, Caneta, Svinitzium, Pseudocrolanium, Wrangelium) had a preferential distribution in the Tethyan region and their occurrence associated with temperature optima - beginning of Sinemurian, Aalenian, late Kimmeridgian-Valanginian (Vishnevskaya, 2012), while the extinction coincided with the cooling at the end of the Aptian-Albian. An archaic cyrtids appeared at the beginning of the Jurassic - family Bagotidae Pessagno et Whalen, 1982 (Hettangian-Tithonian), 9 genera, 6 of whom died in the early Toarcian and family Hsuidae Pessagno et Whalen, 1982 (Hettangian-Albian), 10 genera, 6 of which had arisen in the Pliensbachian and evolved rapidly due to a sharp increase in the number of segments, while the Middle Jurassic subspherical morphotypes extinct in the late Callovian. Family Archaeodictyomitridae Pessagno, 1977, 8 genera, which probably gave rise to the modern cyrtids appeared in Hettangian and died in the early Paleocene. The evolution of Cretaceous morphotypes took place due to increasing of the number of divisions. Analysis of the stratigraphic distribution of the genera of cosmopolitan family Xitidae Pessagno, 1977 (Bajocian-Eocene) showed that it includes 13 genera, 11 of which appeared in the Cretaceous. The rapid evolution in the Cretaceous due to short-lived genera Foremanina Empson-Morin (Campanian), Novixitus Pessagno and Tuguriella O'Dogherty, De Wever, Gorican (Late Albian-Turonian) Schaafella Vishnevskaya (Albian-Cenomanian), Clavaxitus Dumitrica (Houterivian - Barremian) can be used as markers of various bioevents (anoxic etc.). Of great interest is the analysis of changes in the morphology of xitoid wall. First xitoid structure appears in the long-lived genera Eoxitus Kozur(Bajocian-Aptian) and Xitus Pessagno (Bathonian-Maastrichtian), which is strictly maintained on all cameras. In the early Cretaceous group of subspherical forms arises: Pseudoxitus Wu et Pessagno (Berriasian-Barremian), Praexitus Dumitrica (Berriasian-Barremian), Neorelumbra Kiessling (Berriasian-Aptian) and Clavaxitus Dumitrica (Hauterivian-Barremian) where xitoid structure varied from coarse to fine that was probably related to adaptation to a dramatic deepening of the oceans at the Jurassic-Cretaceous boundary. The Cretaceous - Paleogene boundary only unxitoid Amphipyndacids survived. This research was supported by the Russian Foundation for Basic Research, project 12-05-00690 and the Presidium Program of the Russian Academy of Sciences "The Origin and Evolution of the Biosphere".

  5. 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.

  6. Jurassic deposits of the southern part of the Irkutsk sedimentary basin

    NASA Astrophysics Data System (ADS)

    Akulov, N. I.; Frolov, A. O.; Mashchuk, I. M.; Akulova, V. V.

    2015-07-01

    This work presents new data on the lithology, paleontology, stratigraphy, and correlation of Jurassic deposits of the Irkutsk coal-bearing basin. According to the detailed analysis of the lithology and paleontology of the reference sections, the Jurassic deposits of the southern part of this basin are subdivided into four formations: Baikal'skaya, Dabatskaya, Cheremkhovskaya, and Prisayanskaya. The Lower Jurassic coarse deposits of the Baikal'skaya Formation are regarded as the most ancient; the Middle Jurassic deposits of the Prisayanskaya Formation are the youngest. The industrial coal-bearing deposits of the Cheremkhovskaya Formation formed in the Early Jurassic, from the Pliensbachian to Toarcian.

  7. 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

  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. Evolutionary dynamics of Pinus taeda L. in the Late Quaternary: An interdisciplinary approach 

    E-print Network

    Al-Rabab'ah, Moh'd Ali

    2004-11-15

    ,000 years (the Late Quaternary; Late Pleistocene through Holocene) in response to climate change and anthropogenic factors. These changes are believed to have caused a significant imprint on the species genetic structure. To test these assertions...) Millions of years ago Holocene 0.01 Pleistocene 2.4 2.5 Pliocene 4.5 7 Miocene 19 26 Oligocene 12 34 Eocene 16 54 Cenozoic Tertiary Paleocene 11 65 Cretaceous 71 136 Jurassic 54 190 Mesozoic Triassic 35 225 * Adopted from...

  10. Hydrocarbon potential of a new Jurassic play, central Tunisia

    SciTech Connect

    Beall, A.O.; Law, C.W.

    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.

  11. Hydrocarbon potential of a new Jurassic play, central Tunisia

    SciTech Connect

    Beall, A.O. ); Law, C.W. )

    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.

  12. Cycles in fossil diversity

    SciTech Connect

    Rohde, Robert A.; Muller, Richard A.

    2004-10-20

    It is well-known that the diversity of life appears to fluctuate during the course the Phanerozoic, the eon during which hard shells and skeletons left abundant fossils (0-542 Ma). Using Sepkoski's compendium of the first and last stratigraphic appearances of 36380 marine genera, we report a strong 62 {+-} 3 Myr cycle, which is particularly strong in the shorter-lived genera. The five great extinctions enumerated by Raup and Sepkoski may be an aspect of this cycle. Because of the high statistical significance, we also consider contributing environmental factors and possible causes.

  13. 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

  14. The cranial osteology of Tyrannoneustes lythrodectikos (Crocodylomorpha: Metriorhynchidae) from the Middle Jurassic of Europe

    PubMed Central

    Young, Mark T.

    2014-01-01

    Tyrannoneustes lythrodectikos is one of numerous metriorhynchid crocodylomorph species known from the Oxford Clay Formation of England (Callovian-Oxfordian; Middle-Late Jurassic). This taxon is of evolutionary importance, as it is the oldest and most basal known macrophagous metriorhynchid. It has a mosaic of plesiomorphic and derived feeding related characteristics, including: teeth with microscopic, poorly formed and non-contiguous denticles; increased tooth apicobasal length; ventrally displaced dentary tooth row (increased gape); reduced dentary tooth count; and a proportionally long mandibular symphysis. However the type specimen, and current referred specimens, all lack a preserved cranium. As such, the craniofacial morphology of this taxon, and its potential feeding ecology, remains poorly understood. Here we describe two skulls and two lower jaws which we refer to T. lythrodectikos. Previously these specimens were referred to ‘Metriorhynchus’ brachyrhynchus. They share with the T. lythrodectikos holotype: the in-line reception pits on the dentary, dorsal margin of the surangular is strongly concave in lateral view, and the most of the angular ventral margin is strongly convex. Based on our description of these specimens, the skull of T. lythrodectikos has three autapomorphies: very long posterior processes of the premaxilla terminating in line with the 4th or 5th maxillary alveoli, deep lateral notches on the lateral surface of the maxillary with reception pits for dentary teeth, and the premaxilla forms the anterior margin of the first maxillary alveoli. Our description of the cranial anatomy of Tyrannoneustes lythrodectikos confirms that some macrophagous characteristics evolved during the Middle Jurassic, and were not exclusive to the clade Geosaurini. Moreover, the skulls further highlight the mosaic nature of Tyrannoneustes lythrodectikos and wide-gape macrophagous evolution in Geosaurinae. PMID:25289192

  15. 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

  16. Sedimentary evolution and palaeogeography of mid-Jurassic deposits of the Central High Atlas, Morocco

    NASA Astrophysics Data System (ADS)

    Ait Addi, Abdellah; Chafiki, Driss

    2013-08-01

    In the axis of the Moroccan Central High Atlas rift basin, Toarcian-Middle Jurassic deposits, excepting the early Toarcian Tagoudite Formation, are represented by two formations - Agoudim and Tazigzaout - comprising clays, marls and limestones. On the margins of the basin, the lateral equivalents of these two formations are dolostone-dominated and show the lithological and environmental characteristics of the Bin El Ouidane Group recognized in the NW part of the Central High Atlas (Beni-Mellal/Azilal area). This group is overlain by clays and limestones of the Tillouguite Formation and by Bathonian red beds (silts, sandstones and conglomerates) of the Anemzi Formation. From the Toarcian to Aalenian (Agoudim Members I and II) the contrasting palaeogeographical evolution is marked by a relatively deep central basin bordered by shallow marine carbonates. The Aalenian-Lower Bajocian interval (Agoudim Member II) contains lenticular biodetritic limestones within hemipelagic deposits. These facies resulted from recurrent faulting (tectonic pulses), which was at the origin of the individualization of a series of ridges and depocentres within the High Atlas trough. During the Bajocian (Agoudim Members III and IV) the palaeogeography became homogeneous across the Central High Atlas and corresponded to a carbonate ramp with coral patch reefs. During the ?Late Bajocian (Tazigzaout Lower Member) a new palaeogeography developed with reappearance of the central depocentres. During the latest Bajocian-earliest Bathonian (Tazigzaout Upper Member) a very homogeneous carbonate ramp was again established. These times of uniform palaeogeography are interpreted as relative stable tectonic periods that were progressive stages leading to the ending of the Toarcian-Middle Jurassic sedimentary cycles in the Central High Atlas rift basin of Morocco.

  17. Embryo fossilization is a biological process mediated by microbial biofilms

    PubMed Central

    Raff, Elizabeth C.; Schollaert, Kaila L.; Nelson, David E.; Donoghue, Philip C. J.; Thomas, Ceri-Wyn; Turner, F. Rudolf; Stein, Barry D.; Dong, Xiping; Bengtson, Stefan; Huldtgren, Therese; Stampanoni, Marco; Chongyu, Yin; Raff, Rudolf A.

    2008-01-01

    Fossilized embryos with extraordinary cellular preservation appear in the Late Neoproterozoic and Cambrian, coincident with the appearance of animal body fossils. It has been hypothesized that microbial processes are responsible for preservation and mineralization of organic tissues. However, the actions of microbes in preservation of embryos have not been demonstrated experimentally. Here, we show that bacterial biofilms assemble rapidly in dead marine embryos and form remarkable pseudomorphs in which the bacterial biofilm replaces and exquisitely models details of cellular organization and structure. The experimental model was the decay of cleavage stage embryos similar in size and morphology to fossil embryos. The data show that embryo preservation takes place in 3 distinct steps: (i) blockage of autolysis by reducing or anaerobic conditions, (ii) rapid formation of microbial biofilms that consume the embryo but form a replica that retains cell organization and morphology, and (iii) bacterially catalyzed mineralization. Major bacterial taxa in embryo decay biofilms were identified by using 16S rDNA sequencing. Decay processes were similar in different taphonomic conditions, but the composition of bacterial populations depended on specific conditions. Experimental taphonomy generates preservation states similar to those in fossil embryos. The data show how fossilization of soft tissues in sediments can be mediated by bacterial replacement and mineralization, providing a foundation for experimentally creating biofilms from defined microbial species to model fossilization as a biological process. PMID:19047625

  18. 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.

  19. Animal Behavior Frozen in Time: Gregarious Behavior of Early Jurassic Lobsters within an Ammonoid Body Chamber

    PubMed Central

    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. 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

  1. Pre-breakup geology of the Gulf of Mexico-Caribbean: Its relation to Triassic and Jurassic rift systems of the region

    SciTech Connect

    Bartok, P. )

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. Fossil Microorganisms in Archaean

    NASA Technical Reports Server (NTRS)

    Astafleva, Marina; Hoover, Richard; Rozanov, Alexei; Vrevskiy, A.

    2006-01-01

    Ancient Archean and Proterozoic rocks are the model objects for investigation of rocks comprising astromaterials. The first of Archean fossil microorganisms from Baltic shield have been reported at the last SPIE Conference in 2005. Since this confeence biomorphic structures have been revealed in Archean rocks of Karelia. It was determined that there are 3 types of such bion structures: 1. structures found in situ, in other words microorganisms even-aged with rock matrix, that is real Archean fossils biomorphic structures, that is to say forms inhabited early formed rocks, and 3. younger than Archean-Protherozoic minerali microorganisms, that is later contamination. We made attempt to differentiate these 3 types of findings and tried to understand of burial of microorganisms. The structures belongs (from our point of view) to the first type, or real Archean, forms were under examination. Practical investigation of ancient microorganisms from Green-Stone-Belt of Northern Karelia turns to be very perspective. It shows that even in such ancient time as Archean ancient diverse world existed. Moreover probably such relatively highly organized cyanobacteria and perhaps eukaryotic formes existed in Archean world.

  4. Sedimentary paleoenvironments of fossil platyrrhine localities, Miocene Pinturas Formation, Santa Cruz Province, Argentina

    USGS Publications Warehouse

    Bown, T.M.

    1990-01-01

    The Pinturas Formation is a pyroclastic and epiclastic aeolian deposit of Miocene age lying discordantly upon Jurassic rocks in the elevated Andean precordillera of northwest Santa Cruz Province, Argentina. The history of development of the Pinturas Formation was significantly affected by the gradual, though sporadic, draping of this aeolian sediment across a profound, slowly filling paleotopography. The Pinturas depositional cycle consisted of: (1) minor aeolian deposition followed by soil formation, and (2) major aeolian deposition followed by intervals of regional erosion. Fluvial action seems to have been almost wholly confined to intraformational erosion, and two significant intraformational erosional unconformities divide the Pinturas Formation into three sequences. The lower sequence is dominated by pyroclastic mudrocks upon which were formed very mature, probably mollic, paleosols; the middle sequence is composed largely of epiclastic sand occurring as barchanoid paleodunes; and the upper sequence consists of massive, poorly bedded pyroclastic mudrocks. Many Pinturas lacunae were reconstructed on the basis of locally preserved strata, and a novel method of holostrome reconstruction using relative paleosol maturities places Pinturas sedimentation in a more accurate temporal light. It also indicates: (1) that the Pinturas sediment accumulation rate increased with time; (2) that regional erosive intervals are correlated directly with major influxes of pyroclastic material; and (3) that the introduction of the Pinturas platyrrhine primates occurred in the sequence:Carlocebus carmenensis, C. intermedius andSoriacebus ameghinorum. Soriacebus adrianae. Pinturas paleosols appear to have formed under moist conditions, and both mature and immature varieties yield a host of ichnofossils. These include the burrows and nests of bees, scarabeid beetles, termites, and at least two different kinds of colonial rodents, in addition to rhizoliths and the calcified boles and root systems of trees. A fossil nest of a nasutitermitine termite in the lower sequence of the formation indicates the presence of tropical forest. Climatic conditions may have been drier during deposition of the barchanoid paleodunes in early late Pinturas time, or the dunes might reflect drier source areas or have simply encroached on areas of highland forest. Fossil mammals are abundant in Pinturas sediments, and attritional concentrations of them were recognized in the upper parts of paleosols and on the floors of erosional scours. Radiometric dates indicate that the fossil mammals (including platyrrhine primates) occurring in the lower and middle parts of the formation may range in age from about 16-6 to younger than 13-3 Ma (million years ago) (Santacrucian and, almost certainly, Friasian land-mammal ages). This age range is somewhat younger than previous estimates, and suggests that the Pinturas faunas correlate broadly with those from the type Santa Cruz Formation, with the presumed position of the type Friasian, and with the base of the marine Gaiman Formation in the lower valley of the Rio Chubut.

  5. 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.

  6. 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.

  7. Peaches Preceded Humans: Fossil Evidence from SW China.

    PubMed

    Su, Tao; Wilf, Peter; Huang, Yongjiang; Zhang, Shitao; Zhou, Zhekun

    2015-01-01

    Peach (Prunus persica, Rosaceae) is an extremely popular tree fruit worldwide, with an annual production near 20 million tons. Peach is widely thought to have origins in China, but its evolutionary history is largely unknown. The oldest evidence for the peach has been Chinese archaeological records dating to 8000-7000?BP. Here, we report eight fossil peach endocarps from late Pliocene strata of Kunming City, Yunnan, southwestern China. The fossils are identical to modern peach endocarps, including size comparable to smaller modern varieties, a single seed, a deep dorsal groove, and presence of deep pits and furrows. These fossils show that China has been a critical region for peach evolution since long before human presence, much less agriculture. Peaches evolved their modern morphology under natural selection, presumably involving large, frugivorous mammals such as primates. Much later, peach size and variety increased through domestication and breeding. PMID:26610240

  8. Peaches Preceded Humans: Fossil Evidence from SW China

    PubMed Central

    Su, Tao; Wilf, Peter; Huang, Yongjiang; Zhang, Shitao; Zhou, Zhekun

    2015-01-01

    Peach (Prunus persica, Rosaceae) is an extremely popular tree fruit worldwide, with an annual production near 20 million tons. Peach is widely thought to have origins in China, but its evolutionary history is largely unknown. The oldest evidence for the peach has been Chinese archaeological records dating to 8000–7000?BP. Here, we report eight fossil peach endocarps from late Pliocene strata of Kunming City, Yunnan, southwestern China. The fossils are identical to modern peach endocarps, including size comparable to smaller modern varieties, a single seed, a deep dorsal groove, and presence of deep pits and furrows. These fossils show that China has been a critical region for peach evolution since long before human presence, much less agriculture. Peaches evolved their modern morphology under natural selection, presumably involving large, frugivorous mammals such as primates. Much later, peach size and variety increased through domestication and breeding. PMID:26610240

  9. Jurassic sedimentary basins in the Central Asian orogenic belt

    SciTech Connect

    Bebeshev, I.I.

    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.

  10. Jurassic and triassic hydrocarbon exploration of southern Florida

    SciTech Connect

    Mitchell-Tapping, H.J.

    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.

  11. Petroleum potential of Lower-Jurassic deposits in Nurolsk megadepression

    NASA Astrophysics Data System (ADS)

    G, Lobova; E, Osipova; V, Isaev; D, Terre

    2015-02-01

    Based on reservoir temperature measurement data from twenty-three reference well cross-sections and paleotemperature modeling, the thermal history of Lower-Jurassic Togur source rock within Nurolsk megadepression and its framing structures have been reconstructed. Plotted maps showed the density distribution of initial accumulated oil resources for Lower J15-J16 formations. Based on performed zoning of reservoirs the areas for priority hydrocarbon prospecting were proposed.

  12. New transitional fossil snakeflies from China illuminate the early evolution of Raphidioptera

    PubMed Central

    2014-01-01

    Background Raphidioptera (snakeflies) is a holometabolous order of the superorder Neuropterida characterized by the narrowly elongate adult prothorax and the long female ovipositor. Mesozoic snakeflies were markedly more diverse than the modern ones are. However, the evolutionary history of Raphidioptera is largely unexplored, as a result of the poorly studied phylogeny among fossil and extant lineages within the order. Results In this paper, we report a new snakefly family, Juroraphidiidae fam. nov., based on exquisitely preserved fossils, attributed to a new species Juroraphidia longicollumgen. et sp. nov., from the Jiulongshan Formation (Middle Jurassic) in Inner Mongolia, China. The new family is characterized by an unexpected combination of plesiomorphic and apomorphic characters of Raphidioptera. Based on our phylogenetic analysis, Juroraphidiidae fam. nov. together with Raphidiomorpha form a monophyletic clade, which is the sister to Priscaenigmatomorpha. The snakefly affinity of Priscaenigmatomorpha is confirmed and another new family, Chrysoraphidiidae fam. nov., is erected in this suborder. Conclusions Juroraphidiidae fam. nov. is determined to be a transitional lineage between Priscaenigmatomorpha and Raphidiomorpha. Diversification of higher snakefly taxa had occurred by the Early Jurassic, suggesting that these insects had already had a long but undocumented history by this time. PMID:24742030

  13. Trace-fossil assemblages with a new ichnogenus in "spotted"

    NASA Astrophysics Data System (ADS)

    Šimo, Vladimír; Tomašových, Adam

    2013-10-01

    Highly-bioturbated "spotted" limestones and marls (Fleckenmergel-Fleckenkalk facies) of the Early Jurassic, which were deposited in broad and recurrent deep-shelf habitats of the Northern Tethys, are characterized by rare benthic carbonate-producing macroinvertebrates. To address this paradox, we analyse trace-fossil assemblages in a ~85 m-thick succession of Pliensbachian spotted deposits (Zliechov Basin, Western Carpathians). They are dominated by infaunal and semi-infaunal deposit-feeders, with 9 ichnogenera and pyritized tubes of the semi-infaunal foraminifer Bathysiphon, being dominated by Chondrites, Lamellaeichnus (new ichnogenus), and Teichichnus. Lamellaeichnus, represented by a horizontal basal cylindrical burrow and an upper row of stacked convex-up gutters, was produced by a mobile deposit-feeder inhabiting shallow tiers because it is crossed by most other trace fossils. We show that the spotty appearance of the deposits is generated by a mixture of (1) dark, organic-rich shallow- and deep-tier traces (TOC = 0.16-0.36), and (2) light grey, organic-poor mottled or structurless sediment (TOC = 0.09-0.22). The higher TOC in shallow-tier burrows of Lamellaeichnus demonstrates that uppermost sediment layers were affected by poor redox cycling. Such conditions imply a limited mixed-layer depth and inefficient nutrient recycling conditioned by hypoxic bottom-waters, allowed by poor circulation and high sedimentation rates in depocenters of the Zliechov Basin. Hypoxic conditions are further supported by (1) dominance of trace-fossils produced by infaunal deposit feeders, (2) high abundance of hypoxiatolerant agglutinated foraminifer Bathysiphon, and (3) high abundance of Chondrites with ~0.5 mm-sized branches. Oxygen-deficient bottom-conditions can thus simultaneously explain the rarity of benthic carbonate-producing macroinvertebrates and high standing abundance of tolerant soft-shell and agglutinated organisms in spotted deposits.

  14. Fossil preservation and the stratigraphic ranges of taxa.

    PubMed

    Foote, M; Raup, D M

    1996-01-01

    The incompleteness of the fossil record hinders the inference of evolutionary rates and patterns. Here, we derive relationships among true taxonomic durations, preservation probability, and observed taxonomic ranges. We use these relationships to estimate original distributions of taxonomic durations, preservation probability, and completeness (proportion of taxa preserved), given only the observed ranges. No data on occurrences within the ranges of taxa are required. When preservation is random and the original distribution of durations is exponential, the inference of durations, preservability, and completeness is exact. However, reasonable approximations are possible given non-exponential duration distributions and temporal and taxonomic variation in preservability. Thus, the approaches we describe have great potential in studies of taphonomy, evolutionary rates and patterns, and genealogy. Analyses of Upper Cambrian-Lower Ordovician trilobite species, Paleozoic crinoid genera, Jurassic bivalve species, and Cenozoic mammal species yield the following results: (1) The preservation probability inferred from stratigraphic ranges alone agrees with that inferred from the analysis of stratigraphic gaps when data on the latter are available. (2) Whereas median durations based on simple tabulations of observed ranges are biased by stratigraphic resolution, our estimates of median duration, extinction rate, and completeness are not biased.(3) The shorter geologic ranges of mammalian species relative to those of bivalves cannot be attributed to a difference in preservation potential. However, we cannot rule out the contribution of taxonomic practice to this difference. (4) In the groups studied, completeness (proportion of species [trilobites, bivalves, mammals] or genera [crinoids] preserved) ranges from 60% to 90%. The higher estimates of completeness at smaller geographic scales support previous suggestions that the incompleteness of the fossil record reflects loss of fossiliferous rock more than failure of species to enter the fossil record in the first place. PMID:11539203

  15. Fossil preservation and the stratigraphic ranges of taxa

    NASA Technical Reports Server (NTRS)

    Foote, M.; Raup, D. M.

    1996-01-01

    The incompleteness of the fossil record hinders the inference of evolutionary rates and patterns. Here, we derive relationships among true taxonomic durations, preservation probability, and observed taxonomic ranges. We use these relationships to estimate original distributions of taxonomic durations, preservation probability, and completeness (proportion of taxa preserved), given only the observed ranges. No data on occurrences within the ranges of taxa are required. When preservation is random and the original distribution of durations is exponential, the inference of durations, preservability, and completeness is exact. However, reasonable approximations are possible given non-exponential duration distributions and temporal and taxonomic variation in preservability. Thus, the approaches we describe have great potential in studies of taphonomy, evolutionary rates and patterns, and genealogy. Analyses of Upper Cambrian-Lower Ordovician trilobite species, Paleozoic crinoid genera, Jurassic bivalve species, and Cenozoic mammal species yield the following results: (1) The preservation probability inferred from stratigraphic ranges alone agrees with that inferred from the analysis of stratigraphic gaps when data on the latter are available. (2) Whereas median durations based on simple tabulations of observed ranges are biased by stratigraphic resolution, our estimates of median duration, extinction rate, and completeness are not biased.(3) The shorter geologic ranges of mammalian species relative to those of bivalves cannot be attributed to a difference in preservation potential. However, we cannot rule out the contribution of taxonomic practice to this difference. (4) In the groups studied, completeness (proportion of species [trilobites, bivalves, mammals] or genera [crinoids] preserved) ranges from 60% to 90%. The higher estimates of completeness at smaller geographic scales support previous suggestions that the incompleteness of the fossil record reflects loss of fossiliferous rock more than failure of species to enter the fossil record in the first place.

  16. 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

  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. Exceptional preservation of fossils in an Upper Proterozoic shale

    NASA Technical Reports Server (NTRS)

    Butterfield, N. J.; Knoll, A. H.; Swett, K.

    1988-01-01

    An exceptionally well-preserved and distinctive assemblage of Late Proterozoic fossils from subtidal marine shales is reported. In addition to the spheromorphic acritarchs and cyanobacteria sheaths routinely preserved in Proterozoic rocks, this assemblage includes multicellular algae, a diverse assortment of morphologically complex protistan vesicles, and probable heterotrophic bacteria. Thus, it provides one of the clearest and most taxonomically varied views of Proterozoic life yet reported.

  19. 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.

  20. 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. )

    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.

  1. Absolute dating of brittle fault movements: Late Permian and late Jurassic extensional fault breccias in western Norway

    E-print Network

    Andersen, Torgeir Bjørge

    breccias in western Norway Elizabeth A. Eide1 *, Trond H. Torsvik1,2 and Torgeir B. Andersen3 1 Geological have utilized two different dating techniques to constrain the ages of fault breccia genesis in a reactivated detach- ment zone in western Norway (Fig. 1). Brittle fault breccias are viable materi- als

  2. Organic molecules as chemical fossils - The molecular fossil record

    NASA Technical Reports Server (NTRS)

    Eglinton, G.

    1983-01-01

    The study of biochemical clues to the early earth and the origin of life is discussed. The methods used in such investigation are described, including the extraction, fractionation, and analysis of geolipids and the analysis of kerogen. The occurrence of molecular fossils in the geological record is examined, discussing proposed precursor-product relationships and the molecular assessment of deep sea sediments, ancient sediments, and crude petroleums. Alterations in the molecular record due to diagenesis and catagenesis are considered, and the use of microbial lipids as molecular fossils is discussed. The results of searches for molecular fossils in Precambrian sediments are assessed.

  3. Genome duplication and the origin of angiosperms

    E-print Network

    Gent, Universiteit

    for a period of 80­90 million years before their appearance. Nevertheless, the existence during the Jurassic through a period of little diversification during the Late Triassic (220 Mya) and Jurassic, either because in the fossil record during the Jurassic [208­145 million years ago (Mya)], with no obvious ancestors

  4. Timing and evolution of Jurassic-Cretaceous granitoid magmatisms in the Mongol-Okhotsk belt and adjacent areas, NE Asia: Implications for transition from contractional crustal thickening to extensional thinning and geodynamic settings

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Guo, Lei; Zhang, Lei; Yang, Qidi; Zhang, Jianjun; Tong, Ying; Ye, Ke

    2015-01-01

    The Mongol-Okhotsk belt and adjacent areas are key areas to study the relationship between the Okhotsk and Paleo-Pacific tectonic regimes and their superposition on the older Paleo-Asian regimes during late Mesozoic times. This paper summarizes the spatial-temporal evolution of Late Mesozoic (Jurassic-Cretaceous) granitoids and related intrusions in these areas, and interprets the magmatic evolution in terms of a transition from contractional crustal thickening to extensional thinning. According to 407 published zircon ages, these granitoids were mainly emplaced during the intervals 200-180 Ma, 180-165 Ma, 165-145 Ma, 145-135 Ma and 135-100 Ma. Jurassic granitoids (200-145 Ma) predominately occur in the Baikal-NE Mongolia (BNEM) and Great Xing'an Range. Early Cretaceous (145-100 Ma) granitoids are mainly occur in the Great Xing'an Range, and display a southward-younging migration. Significantly, Early Cretaceous granitoids also extend into the Trans-Baikal area across the Mongol-Okhotsk suture, far away from the Paleo-Pacific plate margin (in NE China); thus they were more plausibly related to post-orogenic collapse of the Mongol-Okhotsk orogen. From the Late Jurassic to Early Cretaceous, the granitoids evolved compositionally from calc-alkaline and high-K calc-alkaline, I-type, with some adakite-like features, to high-K calc-alkaline and shoshonitic, highly fractionated I-, transitional I-A or, A-type, characterized by a significant decrease in their Sr/Y ratios. This evolution coincided with a tectonic transition from contractional crustal thickening to extensional thinning. Combined with regional geology, we speculate that the Jurassic granitoids were likely derived from melting of the deep-seated, thickened lower continental crustal (LCC) sources, whereas the Cretaceous granitoids produced through crustal melting from an extensional thinning setting. Our results provide a case study demonstrating that the petrogenesis of granitic magmatism was closely associated with crustal tectonics. Early Jurassic granitoids along the Okhotsk belt formed in a subduction/collision setting related to closure of the Mongol-Okhotsk Ocean, whereas Late Jurassic granitoids in the Great Xing'an Range and in the northern North China Craton may have formed in a syn- or post-collisional setting superposed by far-field affects of subduction of the Paleo-Pacific plate. Early Cretaceous granitoids in these areas formed in response to post-orogenic extensional collapse of the Mongol-Okhotsk belt, coupled with back-arc extension related to Paleo-Pacific plate subduction.

  5. Palaeoceanographic and palaeoclimatic reorganization around the MiddleLate Jurassic transition

    E-print Network

    Gilli, Adrian

    limestones is exposed in the Jura mountains and in the Helvetic of the Swiss Alps. These sediments were and nodular limestones were also formed on the Briançonnais High, today outcropping in the middle Penninic nappe pile of the Alps. Hardgrounds record strong and persistent current activity along the northern

  6. High energy transgressive deposits from the Late Jurassic of Wagad, Eastern Kachchh, India

    NASA Astrophysics Data System (ADS)

    Mishra, Diwakar

    2009-03-01

    The whole sedimentary succession (ca 600 m thick) of Wagad area ranging in age from Callovian to Early Kimmeridgian has been divided in to three Formations namely Washtawa, Kanthkot and Gamdau in ascending order. Prograding Kanthkot Formation was frequently interrupted by transgressions. Field and petrographic investigations revealed that the Kanthkot Formation represents three fossiliferous marker beds corresponding to Transgressive sequence I; Transgressive sequence II and Transgressive sequence III. These transgressive sequences are composed of two lithounits: medium to coarse grained/gritty, graded to massive, sheetlike, fossiliferous calcareous sandstone (storm lag unit I) and fossiliferous mudrocks (swell lag unit II). The thickness of the unit I varies from 5 to 75 cm and contains mostly convexly oriented shell fragments and whole shell of Pelecypods, Cephalopods and Brachiopods. Unit II (5-15 cm) is distinguished by sheetlike, massive or laminated, yellowish colour, soft fossiliferous mudrocks. This unit is intercalated with moderately bioturbated sandy siltstone. Unit I is dominant over Unit II in the sequences. Study suggests that the transgressive units were deposited close to wave base by high energy storm flows followed by low energy marine swells during transgression. The intense storms played a major role in the distribution of siliciclastics and nonclastic materials. Storms are evidenced by the occurrence of two distinctly different types of units (storm lags and swell lags). High energy levels are characterized by sand dominated sequence, abundance of reworked sediment particles, high proportion broken shells with convex up orientation and erosional and sharp nature of basal contacts of units together with well preserved bioclasts. Sudden short term changes from high to low energy during transgression are explained by the occurrence of medium to coarse grained siliciclastics interbedded with moderately bioturbated mudrocks. Moderately bedded individual strata, high content of coarse clastics along with polished granule size quartz and abundance of comminuted shells indicate a significant change in depositional setting, possibly closure approach of the source of terrigenous fraction or source uplift. Synrift sedimentation in the present study is documented by an abundance of coarse clastics and an over all aggradational nature of transgressive sequences.

  7. Harper Creek and Cuyamaca Reservoir gneisses, CLMSZ: Late Jurassic plutons of the Peninsular Ranges batholith

    SciTech Connect

    Miller, J.; Girty, G.H.; Girty, M.S. . Dept. of Geological Sciences)

    1993-04-01

    The Cuyamaca Laguna Mountains shear zone (CLMSZ), southern California, has been interpreted to represent east-over-west thrusting resulting from Early Cretaceous arc-continent collision. Near Pine Valley, the western margin of the CLMSZ is underlain by the Harper Creek (HCg) and Cuyamaca Reservoir (CRg) gneisses. U-Pb zircon studies indicate ages of 161 [+-] 17 Ma and 156 [+-] 12 Ma for the Hcg and an age of 158 Ma for the CRg. Geochemically the HCg and CRg are calc-alkaline and peraluminous. Trace element data suggest a magmatic arc setting. Modal and normative mineralogy suggest granodioritic and tonalitic protoliths. Mineral assemblages indicate upper greenschist facies to lower amphibolite grade conditions during deformation. The HCg and CRg were deformed prior to the emplacement of the adjacent 118 [+-] 9 Ma Pine Valley pluton. Structural fabrics described above suggest NE-SW contraction and subvertical extension and are thus compatible with the arc-continent collisional model proposed by earlier workers.

  8. A stratigraphic framework for Late Jurassic Early Cretaceous gas-bearing strata

    E-print Network

    (Monteith A) depositional settings records a continuous progradation of a long-lived depositional system and C are up to 160 m, 100 m and 200 m thick, respectively. Depositional thinning to the northeast Formations de Monteith A, B et C atteignent des épaisseurs de 160 m, de 100 m et de 200 m, respectivement. Au

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

    E-print Network

    Müller, Dietmar

    configuration C. HEINE* AND R. D. MU¨LLER University of Sydney Institute of Marine Science and School have revisited the marine magnetic anomaly record of the Argo and Gascoyne Abyssal Plains of the Scott Plateau, Rowley Terrace and Exmouth/Wombat Plateaus limits this ocean basin to the east, south

  10. Upper Jurassic mafic magmatic rocks of the eastern Klamath Mountains, northern California: remnant of a volcanic arc built on young continental crust

    USGS Publications Warehouse

    Brouxel, M.; Lapierre, H.; Zimmermann, J.-L.

    1989-01-01

    Diabasic and gabbroic dikes intruding the lower Paleozoic Trinity Ophiolite in the Lovers Leap section, Klamath Mountains, California, display strong calc-alkalic petrological and geochemical features. These dikes, of Late Jurassic age (149??6Ma by K/Ar), are petrographically and geochemically similar to the contemporaneous calc-alkalic ultramafic magmatism well developed through the Klamath Mountains. They present negative Nb, Zr, and Ti anomalies typical of subduction-related magmatism and probably belong to a volcanic arc on an active continental margin. Values of ??Nd suggest that no old continental crust underlies the Klamath Mountains. -from Authors

  11. Fossil fuel furnace reactor

    DOEpatents

    Parkinson, William J. (Los Alamos, NM)

    1987-01-01

    A fossil fuel furnace reactor is provided for simulating a continuous processing plant with a batch reactor. An internal reaction vessel contains a batch of shale oil, with the vessel having a relatively thin wall thickness for a heat transfer rate effective to simulate a process temperature history in the selected continuous processing plant. A heater jacket is disposed about the reactor vessel and defines a number of independent controllable temperature zones axially spaced along the reaction vessel. Each temperature zone can be energized to simulate a time-temperature history of process material through the continuous plant. A pressure vessel contains both the heater jacket and the reaction vessel at an operating pressure functionally selected to simulate the continuous processing plant. The process yield from the oil shale may be used as feedback information to software simulating operation of the continuous plant to provide operating parameters, i.e., temperature profiles, ambient atmosphere, operating pressure, material feed rates, etc., for simulation in the batch reactor.

  12. FOSSIL2 energy policy model documentation: FOSSIL2 documentation

    SciTech Connect

    1980-10-01

    This report discusses the structure, derivations, assumptions, and mathematical formulation of the FOSSIL2 model. Each major facet of the model - supply/demand interactions, industry financing, and production - has been designed to parallel closely the actual cause/effect relationships determining the behavior of the United States energy system. The data base for the FOSSIL2 program is large, as is appropriate for a system dynamics simulation model. When possible, all data were obtained from sources well known to experts in the energy field. Cost and resource estimates are based on DOE data whenever possible. This report presents the FOSSIL2 model at several levels. Volumes II and III of this report list the equations that comprise the FOSSIL2 model, along with variable definitions and a cross-reference list of the model variables. Volume III lists the model equations and a one line definition for equations, in a short, readable format.

  13. 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

  14. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.

    E-print Network

    Sieving, Kathryn E.

    . ISSN 0003-0090. Paper, $8.60.--Only a few years ago, the fossil record for the earliest known period in the evo- lution of birds was depressingly meager. From the late Jurassic Archaeopteryx to the late

  15. The taxonomy and taphonomy of fossil spiders from the Crato Formation of Brazil

    E-print Network

    Downen, Matthew Ross

    2014-12-31

    (early to mid-Eocene) in Utah, Colorado, and Wyoming and the Florissant Formation (late Eocene) in Colorado (Meyer, 2003; Smith et al., 2008). Green River Formation fossils used in this study are from the Parachute Creek Member (49–50 Ma), which... 1). In contrast, the Parachute Creek Member of the Green River Formation has been interpreted to reflect an ancient stratified saline lake environment (Cole, 1985). Fossil spiders from this unit display more curled leg orientations than...

  16. 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.

  17. Ancient wet aeolian environments on Earth: Clues to presence of fossil/live microorganisms on Mars

    USGS Publications Warehouse

    Mahaney, W.C.; Milner, M.W.; Netoff, D.I.; Malloch, D.; Dohm, J.M.; Baker, V.R.; Miyamoto, H.; Hare, T.M.; Komatsu, G.

    2004-01-01

    Ancient wet aeolian (wet-sabkha) environments on Earth, represented in the Entrada and Navajo sandstones of Utah, contain pipe structures considered to be the product of gas/water release under pressure. The sediments originally had considerable porosity allowing the ingress of living plant structures, microorganisms, clay minerals, and fine-grained primary minerals of silt and sand size from the surface downward in the sedimentary column. Host rock material is of a similar size and porosity and presumably the downward migration of fine-grained material would have been possible prior to lithogenesis and final cementation. Recent field emission scanning electron microscopy (FESEM) and EDS (energy-dispersive spectrometry) examination of sands from fluidized pipes in the Early Jurassic Navajo Sandstone reveal the presence of fossil forms resembling fungal filaments, some bearing hyphopodium-like structures similar to those produced by modern tropical leaf parasites. The tropical origin of the fungi is consistent with the paleogeography of the sandstone, which was deposited in a tropical arid environment. These fossil fungi are silicized, with minor amounts of CaCO3 and Fe, and in some cases a Si/Al ratio similar to smectite. They exist as pseudomorphs, totally depleted in nitrogen, adhering to the surfaces of fine-grained sands, principally quartz and orthoclase. Similar wet aeolian paleoenvironments are suspected for Mars, especially following catastrophic sediment-charged floods of enormous magnitudes that are believed to have contributed to rapid formation of large water bodies in the northern plains, ranging from lakes to oceans. These events are suspected to have contributed to a high frequency of constructional landforms (also known as pseudocraters) related to trapped volatiles and water-enriched sediment underneath a thick blanket of materials that were subsequently released to the martian surface, forming piping structures at the near surface and constructional landforms at the surface. This constructional process on Mars may help unravel the complex history of some of the piping structures observed on Earth; on Earth, evidence for the constructional landforms has been all but erased and the near-surface piping structures exposed through millions of years of differential erosion and topographic inversion now occur as high-standing promontories. If the features on both Earth and Mars formed by similar processes, especially involving water and other volatiles, and since the piping structures of Earth provided suitable environments for life to thrive in, the martian features in the northern plains should be considered as prime targets for physico/mineral/chemical/microbiological analyses once the astrobiological exploration of the red planet begins in earnest. ?? 2004 Elsevier Inc. All rights reserved.

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

    SciTech Connect

    Bellis, D.; Wolberg, D.L. )

    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.

  19. An Introduction to Fossil Plants

    ERIC Educational Resources Information Center

    Thomas, B. A.

    1976-01-01

    Introduces methods of studying fossil plants and of teaching palaeobotany. Brief accounts are given of different types of preservation and where to find specimens. An annotated bibliography is provided. (Author/SL)

  20. 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)

  1. A Sketch of "paleogeographical Atlas For The Russian Arctic Sector and Svalbard From Vendian To Jurassic Times"

    NASA Astrophysics Data System (ADS)

    Egorov, A. Ju.; Borisova, T. P.; Gerzeva, M. V.; Kononov, M. V.; Kouznetsov, N. B.

    Pyigevsky 7, Moscow, 109017, Russia, kouznikor@mail.ru "AEROGEOLOGIA" company carried out a scientific program "Development of lithological-stratigraphical approach of geodynamical reconstructions for the Russian Arctic sector and Svalbard" during the last decade. A huge volume of new data (geo- logic, lithological, stratigraphical, petrochemical, paleomagnetic, and others) has been gathered for Russian Arctic sector (between 60 degree N, and 20 degree E and 175 degree W) and Svalbard. The data were summarized into the Atlas. The Atlas consists of a geodynamical map (present-day coordinates, scale 1: 6 000 000) and 14 map sets representing the following geological times: (1) - 570 Ma U middle late Vendian time; (2) - 535 Ma U Tommotian stage of early Cambrian; 3) U 520 Ma U Botomian and Tojonian stages of early Cambrian; (4) U 490 Ma U Arenig stage of early Ordovician; (5) U 430 Ma U Llandovery stage of early Silurian; (6) U 412 Ma U Pridoli stage of late Silurian; (7) U 388 Ma U Emsian stage of early Devonian; (8) U 370 Ma U Frasnian stage of late Devonian; (9) U 310 Ma U Moscowian stage of middle Car- boniferous; (10) U 280 Ma - Asselian stage of early Permian; (11) U 244 Ma U Indian stage of early Triassic; (12) U 215 Ma U Norin stage of late Triassic; (13) U 190 Ma U Plinsbachian stage of early Jurassic; (14) U 150 Ma U middle Volgian (Tithoian) stage of late Jurassic. Each set includes a paleogeographical map (present-day coor- dinates, scale 1: 6 000 000) and a plate-tectonic map (paleocoordinates, scale 1: 30 000 000, Polar projection). The positions a continental land-masses relatively a fixed Europe location were defined from summarizing of paleomagnetic, kinematic, paleo- climatic data, and hot spots tracks. The paleogeographical information for continental landmasses located now in Russian Arctic Sector were overlaid on the plate-tectonic reconstructions. Additionally, contours of Laurentia, Amazonia and other large paleo- continents were plotted on the plate-tectonic maps.

  2. Bokan Mountain peralkaline granitic complex, Alexander terrane (southeastern Alaska): evidence for Early Jurassic rifting prior to accretion with North America

    USGS Publications Warehouse

    Dostal, Jaroslav; Karl, Susan M.; Keppie, J. Duncan; Kontak, Daniel J.; Shellnutt, J. Gregory

    2013-01-01

    The circular Bokan Mountain complex (BMC) on southern Prince of Wales Island, southernmost Alaska, is a Jurassic peralkaline granitic intrusion about 3 km in diameter that crosscuts igneous and metasedimentary rocks of the Alexander terrane. The BMC hosts significant rare metal (rare earth elements, Y, U, Th, Zr, and Nb) mineralization related to the last stage of BMC emplacement. U–Pb (zircon) and 40Ar/39Ar (amphibole and whole-rock) geochronology indicates the following sequence of intrusive activity: (i) a Paleozoic basement composed mainly of 469 ± 4 Ma granitic rocks; (ii) intrusion of the BMC at 177 ± 1 Ma followed by rapid cooling through ca. 550 °C at 176 ± 1 Ma that was synchronous with mineralization associated with vertical, WNW-trending pegmatites, felsic dikes, and aegirine–fluorite veins and late-stage, sinistral shear deformation; and (iii) intrusion of crosscutting lamprophyre dikes at >150 Ma and again at ca. 105 Ma. The peralkaline nature of the BMC and the WNW trend of associated dikes suggest intrusion during NE–SW rifting that was followed by NE–SW shortening during the waning stages of BMC emplacement. The 177 Ma BMC was synchronous with other magmatic centres in the Alexander terrane, such as (1) the Dora Bay peralkaline stock and (2) the bimodal Moffatt volcanic suite located ~30 km north and ~100 km SE of the BMC, respectively. This regional magmatism is interpreted to represent a regional extensional event that precedes deposition of the Late Jurassic – Cretaceous Gravina sequence that oversteps the Wrangellia and Alexander exotic accreted terranes and the Taku and Yukon–Tanana pericratonic terranes of the Canadian–Alaskan Cordillera.

  3. 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.

  4. 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.

  5. The legacy of fossil fuels.

    PubMed

    Armaroli, Nicola; Balzani, Vincenzo

    2011-03-01

    Currently, over 80% of the energy used by mankind comes from fossil fuels. Harnessing coal, oil and gas, the energy resources contained in the store of our spaceship, Earth, has prompted a dramatic expansion in energy use and a substantial improvement in the quality of life of billions of individuals in some regions of the world. Powering our civilization with fossil fuels has been very convenient, but now we know that it entails severe consequences. We treat fossil fuels as a resource that anyone anywhere can extract and use in any fashion, and Earth's atmosphere, soil and oceans as a dump for their waste products, including more than 30?Gt/y of carbon dioxide. At present, environmental legacy rather than consistence of exploitable reserves, is the most dramatic problem posed by the relentless increase of fossil fuel global demand. Harmful effects on the environment and human health, usually not incorporated into the pricing of fossil fuels, include immediate and short-term impacts related to their discovery, extraction, transportation, distribution, and burning as well as climate change that are spread over time to future generations or over space to the entire planet. In this essay, several aspects of the fossil fuel legacy are discussed, such as alteration of the carbon cycle, carbon dioxide rise and its measurement, greenhouse effect, anthropogenic climate change, air pollution and human health, geoengineering proposals, land and water degradation, economic problems, indirect effects on the society, and the urgent need of regulatory efforts and related actions to promote a gradual transition out of the fossil fuel era. While manufacturing sustainable solar fuels appears to be a longer-time perspective, alternatives energy sources already exist that have the potential to replace fossil fuels as feedstocks for electricity production. PMID:21290608

  6. 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

  7. 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

  8. THE SKULL AND ENDOCRANIUM OF A LOWER JURASSIC ICHTHYOSAUR BASED ON DIGITAL

    E-print Network

    Benton, Michael

    THE SKULL AND ENDOCRANIUM OF A LOWER JURASSIC ICHTHYOSAUR BASED ON DIGITAL RECONSTRUCTIONS by RYAN (`Hauffiopteryx' typicus) skull from the Toarcian (183­174 Ma, Lower Jurassic) of Straw- berry Bank, England the skull. Other ichthyosaurs may be three dimen- sional, but disarticulated. The Strawberry Bank deposit

  9. Triassic-Jurassic faunal and floral transition in the Fundy Basin, Nova

    E-print Network

    Olsen, Paul E.

    . The Triassic-Jurassic mass extinction may have cleared ecological space for dinosaurian ascent much as the K-T is at least equal in magnitude to that at the more famous Cretaceous-Tertiary boundary (Benton, 1995) (Fig. 1 of the Triassic-Jurassic boundary and subsequent events in the Fundy basin, one of the richest sources for data

  10. 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

  11. 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

  12. 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

  13. Jurassic kimberlites from Picton and Varty Lake, Ontario: Geochemical and stable isotopic characteristics

    NASA Astrophysics Data System (ADS)

    Arima, Makoto; Kerrien, Robert

    1988-07-01

    Micaceous ultramafic dikes of Jurassic age from Picton and Varty Lake, Ontario, consist mineralogically of olivine — phlogopite — serpentine — calcite-spinel. The rocks are characterized by abundant Ba-rich phlogopite (up to 6.5 wt.% BaO) and spinels with a diagnostic “kimberlite trend-1”. Compositionally the dikes are characterized by extreme silica-undersaturation (21 30 wt.% SiO2), primitive Mg/(Mg + FeT) ratios (0.75 0.83), large enrichments of volatile components (CO2 and H2O), and relatively high abundances of both incompatible and compatible trace elements. The dikes exhibit pronounced enrichments of light rare earth elements (LREE) (LaN=320 1330) combined with strongly fractionated patterns (LaN/YbN=45 108). Calcite in the dikes is a primary magmatic phase, from textural relations and C-isotopic compositions ( ? 13C= -4.0 to -8.3‰). A calcite-rich aphanitic phase of the Picton dike is interpreted to be a late stage magmatic differentiate, which possibly involved olivine fractionation. Although the dikes lack most of the macrocrysts generally considered to be important diagnostic minerals of kimberlite magmatism, the geochemical, mineralogical and C- and O-isotopic characteristics collectively indicate that the dikes are evolved varieties of hypabyssal facies kimerlite.

  14. A new neosuchian with Asian affinities from the Jurassic of northeastern Brazil

    NASA Astrophysics Data System (ADS)

    Montefeltro, Felipe C.; Larsson, Hans C. E.; de França, Marco A. G.; Langer, Max C.

    2013-09-01

    Phylogenetic relationships near the origin of extant crocodylians are weakly supported, and this lack of resolution makes for poor estimates of taxonomic and morphological diversity. Previously known taxa are found throughout the Cretaceous in Laurasia and at a few sites from Brazil, Australia, and northern Africa. Here, we report Batrachomimus pastosbonensis gen. et sp. nov. from the Late Jurassic of northeastern Brazil, which is deeply nested within Neosuchia and associated to the Cretaceous Asian paralligatorids. The new taxon predates all other members of Paralligatoridae and its immediate sister group (including Eusuchia) by 30 million years. A nearly complete skull, osteoderms, and limb bones were recovered, and autapomorphies of B. pastosbonensis include a scalloped lateral margin of the rostrum in dorsal view, unsculpted alveolar margin at the caudalmost portion of the maxilla, blunt lateral prongs on the jugal at the base of the postorbital bar, hourglass shaped choanae, and pterygoid choanal septum extended between the palatal shelves of the palatines. The crocodyloid-like skull proportions and the slender, conical teeth suggest an amphibious and piscivorous life history to this 1 m long animal.

  15. JurassicCretaceous low paleolatitudes from the circum-Black Sea region (Crimea and Pontides) due to True Polar Wander

    E-print Network

    Utrecht, Universiteit

    with respect to its core, and it was recently quantified. The period from 195­135 Ma (Early JurassicJurassic­Cretaceous low paleolatitudes from the circum-Black Sea region (Crimea and Pontides) due lower (15°) latitudes from Early Jurassic to Earliest Cretaceous at the position of Adria than suggested

  16. PUBLISHED ONLINE: 13 JULY 2009 | DOI: 10.1038/NGEO577 Floral changes across the Triassic/Jurassic

    E-print Network

    Falkowski, Paul G.

    occurred at the boundary of the Triassic and Jurassic periods, 201.6 million years ago. The loss of marineARTICLES PUBLISHED ONLINE: 13 JULY 2009 | DOI: 10.1038/NGEO577 Floral changes across the Triassic/Jurassic volcanism. Here we present pollen, spore and geochemical analyses across the Triassic/Jurassic boundary from

  17. 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.

  18. Dissimilar diagenetic histories of Jurassic sandstones in the Gulf of Mexico

    SciTech Connect

    Dworkin, S.I. . Dept. of Geology)

    1992-01-01

    Jurassic sandstones from the LA and MS interior salt basins show different diagenetic histories apparent from the style of framework grain modification, the types of cements precipitated, and the timing of cementation. Differences in diagenetic histories can be attributed to the depositional environment of the sandstones as well as the subsequent evolution of the pore fluids. Feldspars within the sandstones in the two basins show contrasting compositions resulting from diagenesis rather than provenance. Sandstones in the LA basin contain feldspars with end-member albite compositions, whereas the feldspars in the MS basin are dominated by end-member K-feldspar compositions. Potassium-rich brines in the MS basin, which provided the chemical stability for those feldspars, were probably generated through the dissolution of deeply buried bittern salts. The paragenetic sequence for the major cementation events in the LA basin sandstones is quartz, ferroan dolomite, calcite, and anhydrite. The order of cement precipitation in the MS basin is K-feldspar, dolomite, quartz, calcite, and anhydrite. The early dolomite in the MS basin has a composition indicative of a seawater origin and is missing from the LA basin because LA basin sandstones were deposited in deep water and thus lacked an efficient pump. Quartz cement in both basins has oxygen isotopic compositions that indicate relatively early emplacement although the timing of this cement in the two basins differs. The origin of silica for the quartz is inferred to be from dissolving feldspars during shallow burial. The presence of ferroan dolomite in the LA basin indicates that the evolution of the pore fluids continued to vary between the basins late in the burial history. Anhydrite cementation occurred in both basins late in the burial history as a result of remobilization of buried calcium sulfate deposits.

  19. 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

  20. Tectonic and eustatic controls on carbonate platforms of the Jurassic High Atlas rift of Morocco

    SciTech Connect

    Crevello, P. )

    1990-05-01

    Stratigraphic studies of Lower and Middle Jurassic carbonates along the southern margin of the High Atlas rift document five major stages of platform development a response to rift tectonics and eustasy. The five stages are as follows. (1) Early Sinemurian marine transgression over Triassic-Liassic continental red beds and basalts lead to the development of regionally extensive, cyclic carbonate platforms. (2) Middle to late Sinemurian marked the initiation of Liassic rifting, with synrift platforms restricted to the rift margin and to localized horsts within the rift axis. Synrift platforms developed diverse depositional systems, with a marked change to rimmed margins flanked by steep slopes and deep (400-500 m) marine basins. Two orders of cyclicity shallowing-upward cycles and bundles of cycles dominated the platform tops. (3) Late Pliensbachian subaerial exposure, resulting in termination of Liassic platform development, was recorded by regressive seaward shifts in facies belts, microkarstification, and deposition of continental red beds across the platforms. (4) Early to middle Toarcian transgression, yielding landward shifts in facies belts on platform tops, was signified by deposition of noncyclic, skeletal carbonate sequences. (5) Middle Toarcian platform drowning was followed by deposition of Toarcian-Aalenian amonite-bearing marine shales (100 m thick) blanketing (downlapping, width source from the south) the southern platform, whereas only a condensed sequence (2-3 m thick) of glauconitic, ammonite-skeletal carbonate strata covered the submerged, isolated, axial rift platform of Jebel Bou Dahar. Prolonged sediment starvation on Bou Dahar combined with depositional onlap of its slope by basin-filling shales (Toarcian to Bajocian) and distal carbonate turbidites (Aalenian), also sourced from the southern margin of the rift, produccd a drowning onlap unconformity.

  1. A Jurassic ceratosaur from China helps clarify avian digital homologies.

    PubMed

    Xu, Xing; Clark, James M; Mo, Jinyou; Choiniere, Jonah; Forster, Catherine A; Erickson, Gregory M; Hone, David W E; Sullivan, Corwin; Eberth, David A; Nesbitt, Sterling; Zhao, Qi; Hernandez, Rene; Jia, Cheng-kai; Han, Feng-lu; Guo, Yu

    2009-06-18

    Theropods have traditionally been assumed to have lost manual digits from the lateral side inward, which differs from the bilateral reduction pattern seen in other tetrapod groups. This unusual reduction pattern is clearly present in basal theropods, and has also been inferred in non-avian tetanurans based on identification of their three digits as the medial ones of the hand (I-II-III). This contradicts the many developmental studies indicating II-III-IV identities for the three manual digits of the only extant tetanurans, the birds. Here we report a new basal ceratosaur from the Oxfordian stage of the Jurassic period of China (156-161 million years ago), representing the first known Asian ceratosaur and the only known beaked, herbivorous Jurassic theropod. Most significantly, this taxon possesses a strongly reduced manual digit I, documenting a complex pattern of digital reduction within the Theropoda. Comparisons among theropod hands show that the three manual digits of basal tetanurans are similar in many metacarpal features to digits II-III-IV, but in phalangeal features to digits I-II-III, of more basal theropods. Given II-III-IV identities in avians, the simplest interpretation is that these identities were shared by all tetanurans. The transition to tetanurans involved complex changes in the hand including a shift in digit identities, with ceratosaurs displaying an intermediate condition. PMID:19536256

  2. Jurassic extension and Alpine inversion of the northern Morocco

    SciTech Connect

    Zizi, M. )

    1993-09-01

    The lower Mesozoic half grabens of northern Morocco form part of an extensional system that is related to the opening of the western Tethys. They appear to be somewhat younger than the Triassic-Jurassic systems associated with the opening the Atlantic Ocean. During the Tertiary and as consequence of the Alpine collision of Africa with Europe, these half graben systems were inverted as shown by the High and the Middle Atlas mountains. Seismic illustrations of similar but smaller inversion structures are available from the Guercif area and the [open quotes]Rides Prerifaines[close quotes] of northern Morocco. These seismic profiles serve as small models for the much larger Atlas Mountains. In the Guercif area, the inversions are limited in scope, but in the [open quotes]Ride Prerifaines[close quotes] are extensive decollement systems that sole out in the Triassic evaporites. These systems evolve into complex thrust faults and associated lateral ramps that are strongly influenced by the configuration of the Jurassic transtensional systems. Significant hydrocarbon accumulation have been known for some time from the [open quotes]Rides Prerifaines.[close quotes] A review of the geometry of the inverted half-graben systems, combined with detailed stratigraphic studies, is likely to lead to the discovery of additional reserves in the area.

  3. Species-specific responses of Late Quaternary megafauna to climate and humans

    E-print Network

    Lorenzen, Eline D.; Nogué s-Bravo, David; Orlando, Ludovic; Weinstock, Jaco; Binladen, Jonas; Marske, Katharine A.; Ugan, Andrew; Borregaard, Michael K.; Gilbert, M. Thomas P.; Nielsen, Rasmus; Ho, Simon Y.W.; Goegel, Ted; Graf, Kelly E.; Byers, David; Stenderup, Jesper T.; Rasmussen, Morten; Campos, Paula F.; Leonard, Jennifer A.; Koepfli, Klaus-Peter; Froese, Duane; Zazula, Grant; Stafford, Thomas W. Jr.; Aaris-Sø rensen, Kim; Batra, Persaram; Haywood, Alan M.; Singarayer, Joy S.; Valdes, Paul J.; Boeskorov, Gennady; Burns, James A.; Davydov, Sergey P.; Haile, James; Jenkins, Dennis L.; Kosintsev, Pavel; Kuznetsova, Tatyana; Lai, Xulong; Martin, Larry D.; McDonald, H. Gregory; Mol, Dick; Meldgaard, Morten; Munch, Kasper; Stephan, Elisabeth; Sablin, Mikhail; Sommer, Robert S.; Sipko, Taras; Scott, Eric; Suchard, Marc A.; Tikhonov, Alexei; Willerslev, Rane; Wayne, Robert K.; Cooper, Alan; Hofreiter, Michael; Sher, Andrei; Shapiro, Beth; Rahbek, Carsten; Willerslev, Eske

    2014-11-17

    Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary remain contentious. We use ancient DNA, species distribution models and the human fossil record...

  4. 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.

  5. Travels with the Fossil Hunters

    NASA Astrophysics Data System (ADS)

    Whybrow, Peter J.

    2000-04-01

    Whether dodging bullets in West Africa, or rabid dogs in Pakistan, surviving yak-butter tea in Tibet, or eating raw fish in China, the life of a globe-trotting fossil hunter is often hazardous and always filled with surprises. Travels with the Fossil Hunters lets readers share the wonder, joys of discovery, and excitement of these intrepid scientists. Packed with more than 100 beautiful, full-color photographs, the volume takes readers on twelve expeditions to remote parts of the world in search of diverse fossil remains, from those of dinosaurs to human ancestors. Each expedition by paleontologists from London's Natural History Museum reveals the problems and challenges of working in extreme conditions, from the deserts of the Sahara and Yemen to the frozen wastes of Antarctica, from the mountains of India to the forests of Latvia. Along the way they also describe the paleontology and geology of the countries they visit and the scientific reasons for their expeditions. With a foreword from Sir David Attenborough and an introduction from Richard Fortey, this fascinating book will appeal to amateur and professional fossil hunters alike and to readers interested in accounts of exotic locales. Peter Whybrow is a research scientist at the Natural History Museum, London. His research interests include Arabian Miocene vertebrates, paleoclimates, paleogeography, and biotic diversity. He is senior editor with A. Hill of Fossil Vertebrates of Arabia (Yale University Press, New Haven, 1999).

  6. Astronomical constraints on the duration of the early Jurassic Hettangian stage and recovery rates following the end-Triassic mass extinction

    E-print Network

    Utrecht, Universiteit

    for the base of the Jurassic period and the duration of lower Jurassic stages largely vary between studiesAstronomical constraints on the duration of the early Jurassic Hettangian stage and recovery rates Available online 10 May 2010 Editor: P. DeMenocal Keywords: Triassic Jurassic cyclostratigraphy astronomical

  7. The central elliptical galaxy in fossil groups and formation of BCGs

    E-print Network

    Habib G. Khosroshahi; Trevor. J. Ponman; Laurence R. Jones

    2006-08-07

    We study the dominant central giant elliptical galaxies in ``Fossil groups'' using deep optical (R-band) and near infrared (Ks-band) photometry. These galaxies are as luminous as the brightest cluster galaxies (BCGs), raising immediate interest in their link to the formation of BCGs and galaxy clusters. However, despite apparent similarities, the dominant fossil galaxies show non-boxy isophotes, in contrast to the most luminous BCGs. This study suggests that the structure of the brightest group galaxies produced in fossil groups are systematically different to the majority of BCGs. If the fossils do indeed form from the merger of major galaxies including late-types within a group, then their disky nature is consistent with the results of recent numerical simulations of semi-analytical models which suggest that gas rich mergers result in disky isophote ellipticals. We show that fossils form a homogeneous population in which the velocity dispersion of the fossil group is tightly correlated with the luminosity of the dominant elliptical galaxy. This supports the scenario in which the giant elliptical galaxies in fossils can grow to the size and luminosity of BCGs in a group environment. However, the boxy structure of luminous BCGs indicate that they are either not formed as fossils, or have undergone later gas-free mergers within the cluster environment.

  8. A fossil hominoid proximal femur from Kikorongo Crater, southwestern Uganda.

    PubMed

    DeSilva, Jeremy; Shoreman, Eleanor; MacLatchy, Laura

    2006-06-01

    The external morphology of a fragmentary right proximal femur from southwestern Uganda is described here. Discovered in the Kikorongo Crater of Queen Elizabeth National Park in 1961, this specimen was informally assigned to Homo sapiens (although never described) and tentatively dated to the late Pleistocene. However, because aspects of the external morphology of the femur align the fossil with the African great apes, we suggest that the Kikorongo femur may be the first postcranial fossil of the genus Pan. Like the African apes, the Kikorongo specimen lacks both an obturator externus groove and an intertrochanteric line. It has a short femoral neck with a circular cross section, and a narrow and deep superior notch. Using resampling statistics and discriminant function analysis, the Kikorongo femur clustered with the genus Pan, as opposed to Gorilla or Homo. However, if the specimen is from Pan, it would be large for this taxon. Furthermore, features that clearly distinguish the external morphology of Plio-Pleistocene hominin proximal femora from African ape femora, such as the shape of the femoral neck in cross section and femoral neck length, have converged in Holocene humans and African apes. Unfortunately, the internal morphology of the femoral neck of the Kikorongo fossil was not discernable. Although we hypothesize that the Kikorongo femur is from the genus Pan, there is such variability in the proximal femora of modern humans that, although it would be an unusual human, it remains possible that this fossil represents H. sapiens. PMID:16620913

  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. The Middle Jurassic basinal deposits of the Surmeh Formation in the Central Zagros Mountains, southwest Iran: Facies, sequence stratigraphy, and controls

    USGS Publications Warehouse

    Lasemi, Y.; Jalilian, A.H.

    2010-01-01

    The lower part of the Lower to Upper Jurassic Surmeh Formation consists of a succession of shallow marine carbonates (Toarcian-Aalenian) overlain by a deep marine basinal succession (Aalenian-Bajocian) that grades upward to Middle to Upper Jurassic platform carbonates. The termination of shallow marine carbonate deposition of the lower part of the Surmeh Formation and the establishment of deep marine sedimentation indicate a change in the style of sedimentation in the Neotethys passive margin of southwest Iran during the Middle Jurassic. To evaluate the reasons for this change and to assess the basin configuration during the Middle Jurassic, this study focuses on facies analysis and sequence stratigraphy of the basinal deposits (pelagic and calciturbidite facies) of the Surmeh Formation, referred here as 'lower shaley unit' in the Central Zagros region. The upper Aalenian-Bajocian 'lower shaley unit' overlies, with an abrupt contact, the Toarcian-lower Aalenian platform carbonates. It consists of pelagic (calcareous shale and limestone) and calciturbidite facies grading to upper Bajocian-Bathonian platform carbonates. Calciturbidite deposits in the 'lower shaley unit' consist of various graded grainstone to lime mudstone facies containing mixed deep marine fauna and platform-derived material. These facies include quartz-bearing lithoclast/intraclast grainstone to lime mudstone, bioclast/ooid/peloid intraclast grainstone, ooid grainstone to packstone, and lime wackestone to mudstone. The calciturbidite layers are erosive-based and commonly exhibit graded bedding, incomplete Bouma turbidite sequence, flute casts, and load casts. They consist chiefly of platform-derived materials including ooids, intraclasts/lithoclasts, peloids, echinoderms, brachiopods, bivalves, and open-ocean biota, such as planktonic bivalves, crinoids, coccoliths, foraminifers, and sponge spicules. The 'lower shaley unit' constitutes the late transgressive and the main part of the highstand systems tract of a depositional sequence and grades upward to platform margin and platform interior facies as a result of late highstand basinward progradation. The sedimentary record of the 'lower shaley unit' in the Central Zagros region reveals the existence of a northwest-southeast trending platform margin during the Middle Jurassic that faced a deep basin, the 'Pars intrashelf basin' in the northeast. The thinning of calciturbidite layers towards the northeast and the widespread Middle Jurassic platform carbonates in the southern Persian Gulf states and in the Persian Gulf area support the existence of a southwest platform margin and platform interior source area. The platform margin was formed as a result of tectonic activity along the preexisting Mountain Front fault associated with Cimmerian continental rifting in northeast Gondwana. Flooding of the southwest platform margin during early to middle Bajocian resulted in the reestablishment of the carbonate sediment factory and overproduction of shallow marine carbonates associated with sea-level highstand, which led to vertical and lateral expansion of the platform and gradual infilling of the Pars intrashelf basin by late Bajocian time. ?? 2010 Springer-Verlag.

  11. Total petroleum systems of the Paleozoic and Jurassic, Greater Ghawar Uplift and adjoining provinces of central Saudi Arabia and northern Arabian-Persian Gulf

    USGS Publications Warehouse

    Pollastro, Richard M.

    2003-01-01

    The greater Paleozoic and Jurassic petroleum systems of the Arabian Peninsula form two of the most prolific petroleum-producing systems in the world. Source rocks of these systems extend throughout the eastern Arabian Peninsula and Arabian-Persian Gulf. Primary elements of these Paleozoic and Jurassic petroleum systems?source, reservoir, and seal rocks?are of great areal extent and exceptional quality. The combination of these regionally extensive, exceptional petroleum-system elements, and the formation of large subtle structural closures prior to, or coincident with, peak oil generation and migration, have produced oil and gas fields with reserve volumes second to none. Two total petroleum systems (TPS), one of Paleozoic age and one of Jurassic age, in the central part of the Arabian Peninsula are identified in this report. The Central Arabia Qusaiba-Paleozoic TPS and the Arabian Sub-Basin Tuwaiq/Hanifa-Arab TPS of Jurassic age encompass the Greater Ghawar Uplift Province (USGS Province 2021) and portions of adjoining geologic provinces. Structures that trap hydrocarbons in these systems are mostly (1) large, gentle anticlines formed from reactivated basement fault blocks, (2) salt domes that resulted from halokinesis, or (3) structural traps resulting from a combination of these two processes. Major tectonic events that created these structures resulted from early Zagros rifting during the Early Triassic and two Alpine tectonic episodes that occurred during the Late Cretaceous and middle to late Tertiary. Hydrocarbons of the Central Arabia Qusaiba-Paleozoic TPS are sourced mainly by organic-rich, so-called ?hot shale? that occurs in the basal part of the Lower Silurian Qusaiba Member of the Qalibah Formation. Oil and gas are produced mainly from sandstones of the Permian Unayzah and Devonian Jauf Formations, and from basal transgressive marine sandstones and cyclic, dolomitic shelf-carbonates of the Late Permian Khuff Formation. Two assessment units (AU) are recognized in the Central Arabia Qusaiba-Paleozoic TPS that are related to type of structural trap and presence of underlying Infracambrian salt: (1) the onshore Central Arch Horst-Block Anticlinal Oil and Gas AU, and (2) the mostly offshore North Gulf Salt Basin Structural Gas AU. The mean total volume of undiscovered resource for the Central Arabia Qusaiba-Paleozoic TPS is estimated at about 108 billion barrels of oil equivalent (BBOE). Oil of the Arabian Sub-Basin Tuwaiq/Hanifa-Arab TPS is sourced by organic-rich, marine carbonates of the Jurassic Tuwaiq Mountain and Hanifa Formations. These source rocks were deposited in two of three intraplatform basins during the Jurassic and, where thermally mature, have generated a superfamily of oils with distinctive geochemical characteristics. Oils were generated and expelled from these source rocks beginning in the Cretaceous at about 75 Ma. Hydrocarbon production is from 3 cyclic carbonate-rock reservoirs of the Arab Formation that are sealed by overlying anhydrite. Several giant and supergiant fields, including the world?s largest oil field at Ghawar, Saudi Arabia, produce mostly from the Arab carbonate-rock reservoirs. Two assessment units are also recognized in the Arabian Sub-Basin Tuwaiq/Hanifa-Arab TPS that are similarly related to structural trap style and presence of underlying Infracambrian salt: (1) an onshore Horst-Block Anticlinal Oil AU, and (2) a mostly offshore Salt-Involved Structural Oil AU. The mean total volume of undiscovered resource for the Arabian Sub-Basin Tuwaiq/Hanifa-Arab TPS is estimated at about 49 billion barrels of oil equivalent (42 billion barrels of oil, 34 trillion feet of gas, and 1.4 billion barrels of natural gas liquids).

  12. Uranium-series disequilibrium data for tooth fragments from the fossil hominid site at Ternifine, Algeria.

    USGS Publications Warehouse

    Szabo, B. J.

    1982-01-01

    I report here analyses of elephant molar-tooth fragments that were submitted by the late K.P.Oakley for uranium-series dating. The tooth fragments were collected by the late C. Arambourg from Pleistocene sand in association with the hominid fossils of Ternifine Man, Algeria. Of the results reported the minimum age of over 360 000 yr BP for the enamel appears to be the most reliable. -Authors

  13. Palaeobiology: Argentinian unhatched pterosaur fossil.

    PubMed

    Chiappe, Luis M; Codorniú, Laura; Grellet-Tinner, Gerald; Rivarola, David

    2004-12-01

    Our knowledge of the eggs and embryos of pterosaurs, the Mesozoic flying reptiles, is sparse. Until now, the recent discovery of an ornithocheirid embryo from 121-million-year-old rocks in China constituted the only reliable evidence of an unhatched pterosaur. Here we describe an embryonic fossil of a different pterosaur from the Early Cretaceous lacustrine deposits of Loma del Pterodaustro (the Lagarcito Formation, which is about 100 million years old) in central Argentina. This new fossil provides insight into the eggshell morphology, early growth and nesting environments of pterosaurs. PMID:15577899

  14. FOSSIL2 energy policy model documentation: FOSSIL2 documentation

    SciTech Connect

    1980-10-01

    This report discusses the structure, derivations, assumptions, and mathematical formulation of the FOSSIL2 model. Each major facet of the model - supply/demand interactions, industry financing, and production - has been designed to parallel closely the actual cause/effect relationships determining the behavior of the United States energy system. The data base for the FOSSIL2 program is large, as is appropriate for a system dynamics simulation model. When possible, all data were obtained from sources well known to experts in the energy field. Cost and resource estimates are based on DOE data whenever possible. This report presents the FOSSIL2 model at several levels. Volumes II and III of this report list the equations that comprise the FOSSIL2 model, along with variable definitions and a cross-reference list of the model variables. Volume II provides the model equations with each of their variables defined, while Volume III lists the equations, and a one line definition for equations, in a shorter, more readable format.

  15. Fossil Group Origins VII. Galaxy substructures in fossil systems

    E-print Network

    Zarattini, S; Aguerri, J A L; Boschin, W; Barrena, R; del Burgo, C; Castro-Rodriguez, N; Corsini, E M; D'Onghia, E; Kundert, A; Méndez-Abreu, J; Sánchez-Janssen, R

    2015-01-01

    Fossil groups are expected to be the final product of galaxy merging within galaxy groups. In simulations, they are predicted to assemble their mass at high redshift. This early formation allows for the innermost $M^\\ast$ galaxies to merge into a massive central galaxy. Then, they are expected to maintain their fossil status because of the few interactions with the large-scale structure. In this context, the magnitude gap between the two brightest galaxies of the system is considered a good indicator of its dynamical status. As a consequence, the systems with the largest gaps should be dynamically relaxed. In order to examine the dynamical status of these systems, we systematically analyze, for the first time, the presence of galaxy substructures in a sample of 12 spectroscopically-confirmed fossil systems with redshift $z \\le 0.25$. We apply a number of tests in order to investigate the substructure in fossil systems in the two-dimensional space of projected positions out to $R_{200}$. Moreover, for a subsam...

  16. 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.

  17. Timescales of orogeny: Jurassic construction of the Klamath Mountains

    NASA Astrophysics Data System (ADS)

    Hacker, Bradley R.; Donato, Mary M.; Barnes, Calvin G.; McWilliams, M. O.; Ernst, W. G.

    1995-06-01

    An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 94YCJ2454, Timescales of orogeny: Jurassic construction of the Klamath Mountains, B.R. Hacker, M.M. Donato, C.G. Barnes, M.O. McWilliams, and W.G. Ernst). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order. Classical interpretations of orogeny were based on relatively imprecise biostratigraphic and isotopic age determinations that necessitated grouping apparently related features that may in reality have been greatly diachronous. Isotopic age techniques now have the precision required to resolve the timing of orogenic events on a scale much smaller than that of entire mountain belts. Forty-five new 40Ar/39Ar ages from the Klamath Mountains illuminate the deformation, metamorphism, magmatism, and sedimentation involved in the Jurassic construction of that orogen, leading to a new level of understanding regarding how preserved orogenic features relate to ancient plate tectonic processes. The new geochronologic relationships show that many Jurassic units of the Klamath Mountains had 200 Ma or older volcanoplutonic basement. Subsequent formation of a large ˜170 Ma arc was followed by contractional collapse of the arc. Collision with a spreading ridge may have led to large-scale NW-SE extension in the central and northern Klamaths from 167 to ˜155 Ma, coincident with the crystallization of voluminous plutonic and volcanic suites. Marked cooling of a large region of the central Klamath Mountains to below ˜350°C at ˜150 Ma may have occurred as the igneous belt was extinguished by subduction of colder material at deeper structural levels. These data demonstrate that the Klamath Mountains—and perhaps other similar orogens—were constructed during areally and temporally variant episodes of contraction, extension, and magmatism that do not fit classical definitions of orogeny.

  18. Diagenetic history of fluvial and lacustrine sandstones of the Hartford Basin (Triassic Jurassic), Newark Supergroup, USA

    NASA Astrophysics Data System (ADS)

    Wolela, A. M.; Gierlowski-Kordesch, E. H.

    2007-04-01

    The early introduction of clays into continental sandstones has been attributed to mechanical infiltration by percolation of clay-rich surface waters into grain framework or cutans formed from pedogenic processes. The discovery of pedogenic mud aggregates as traction-load mud in ancient fluvial deposits suggests that permeability and porosity of terrigenous sandstones can be influenced at deposition and control early diagenetic patterns. This study compares diagenesis in fluvial (subaerially exposed) sandstones with lacustrine (subaqueous) sandstones in a Triassic-Jurassic continental rift basin (Hartford Basin, Newark Supergroup). Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment. The fluvial sandstones in the New Haven Arkose, East Berlin Formation, and Shuttle Meadow Formation of the Hartford Basin are dominated by concretionary calcite and early calcite cement, infiltrated clays (illite-smectite), pedogenic mud aggregates (smectite and illite-smectite), grain coating clays (illite/hematite, illite-chlorite/hematite), quartz overgrowths, late stage carbonate cements (calcite, ferroan calcite), pore-filling clays (illite, kaolinite with minor amounts of smectite, smectite-chlorite, illite-smectite) and hematite. However, pedogenic processes in these fluvial sandstones retarded the development of quartz and feldspar overgrowths, and carbonate authigenesis, as well as the quality of diagenetically enhanced porosity. Dark gray-black lacustrine (subaqueous) sandstones and mudrocks in the East Berlin and Shuttle Meadow Formations are dominated by pyrite, concretionary dolomite and early dolomite cement, radial grain coating clays (smectite-chlorite, illite-smectite), late stage carbonate cements (dolomite, ferroan dolomite, ankerite), albite and pore-filling clays (smectite-chlorite, illite-smectite, illite-chlorite). Clay minerals exist as detrital, mechanically infiltrated, and neoformed clay. The fluvial sandstones in the New Haven Arkose are dominated by illite. The East Berlin and Shuttle Meadow Formations are dominated by illite in the fluvial sequences and smectite-chlorite and illite-smectite in the lacustrine sandstones. Dolomite, ferroan dolomite, and ankerite are restricted to lacustrine sandstones, whereas calcite and ferroan calcite to fluvial sandstones. Albite predominantly precipitated in lacustrine rather than fluvial environments through intergranular dissolution of plagioclase by acidic meteoric water, dissolution of unstable mafic minerals, and sodium-rich brines and evaporites developed from groundwater. Albitization and carbonate cementation are the most pronounced late stage diagenetic processes affecting both types of Hartford sandstones.

  19. Final results on the Jurassic-Cretaceous boundary in the Gresten Klippenbelt (Austria): Macro-, micro-, nannofossils, isotopes, geochemistry, susceptibility, gamma-log and palaeomagnetic data as environmental proxies of the early Penninic Ocean history

    NASA Astrophysics Data System (ADS)

    Lukeneder, A.; Halásová, E.; Kroh, A.; Mayrhofer, S.; Pruner, P.; Reháková, D.; Schnabl, P.; Sprovieri, M.

    2009-04-01

    Jurassic to Lower Cretaceous pelagic sediments are well known to form a major element of the northernmost tectonic units of the Gresten Klippenbelt (Lower Austria). The Penninic Ocean was a side tract of the Central Atlantic Oceanic System intercalated between the European and the Austroalpine plates. Its opening started during the Mid Jurrasic, as rifting of the of the oceanic crust between the European and the Austroalpine plates. The turnover of the deposition on the European shelf (Helvetic Zone) from deep-water siliciclastics into pelagic carbonates is correlated with the deepening of this newly arising ocean. Within the Gresten Klippenbelt Unit, this transition is reflected by the lithostratigraphic boundary between the Tithonian marl-limestone succession and the Berriasian limestones of the Blassenstein Formation. This boundary is well exposed in a newly discovered site at Nutzhof, in the heart of Lower Austria (Kroh and Lukeneder 2009, Lukeneder 2009, Pruner, Schnabl, and Lukeneder 2009, Reháková, Halásová and Lukeneder 2009). Biostratigraphy. According to microfossil (calcareous dinoflagellates, calpionellids) and palaeomagnetic data, the association indicates that the cephalopod-bearing beds of the Nutzhof section belong to the Carpistomiosphaera tithonica-Zone of the Early Tithonian up to the Calpionella Zone of the Middle Berriasian. This interval corresponds to the ammonoid zones from the Early Tithonian Hybonoticeras hybonotum-Zone up to the Middle Berriasian Subthurmannia occitanica-Zone. Ammonoids. Late Jurassic to Early Cretaceous ammonoids were collected at the Nutzhof locality in the eastern part of the Gresten Klippenbelt in Lower Austria. The cephalopod fauna from the Blassenstein Formation, correlated with micro- and nannofossil data from the marly unit and the limestone unit, indicates Early Tithonian to Middle Berriasian age (Hybonoticeras hybonotum Zone up to the Subthurmannia occitanica Zone). According to the correlation of the fossil and magnetostratigraphic data, the entire succession of the Nutzhof section embraces a duration of approx. 8 million years (approx. 150-142 Ma). The deposition of the limestones, marly limestones and marls in this interval occurred during depositionally (e.g. tectonics) unstable conditions.The ammonite fauna comprises 6 different genera, each apparently represented by a single species. The occurrence at the Nutzhof section is dominated by ammonites of the perisphinctid-type. Ammonitina