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1

Late Jurassic salamandroid from western Liaoning, China.  

PubMed

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

Gao, Ke-Qin; Shubin, Neil H

2012-04-10

2

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

Microsoft Academic Search

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

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

2009-01-01

3

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

NASA Astrophysics Data System (ADS)

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.

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

2006-03-01

4

A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago  

Microsoft Academic Search

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

Ursula B. Göhlich; Luis M. Chiappe

2006-01-01

5

Direct evidence of hybodont shark predation on Late Jurassic ammonites  

NASA Astrophysics Data System (ADS)

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.

Vullo, Romain

2011-06-01

6

Late Jurassic plutonism in the southwest U.S. Cordillera  

USGS Publications Warehouse

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.

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

2008-01-01

7

A Giant Pliosaurid Skull from the Late Jurassic of England  

PubMed Central

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).

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

2013-01-01

8

Cycads: Fossil evidence of late paleozoic origin  

USGS Publications Warehouse

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.

Mamay, S. H.

1969-01-01

9

A basal tyrannosauroid dinosaur from the Late Jurassic of China.  

PubMed

The tyrannosauroid fossil record is mainly restricted to Cretaceous sediments of Laurasia, although some very fragmentary Jurassic specimens have been referred to this group. Here we report a new basal tyrannosauroid, Guanlong wucaii gen. et sp. nov., from the lower Upper Jurassic of the Junggar Basin, northwestern China. G. wucaii is the oldest known tyrannosauroid and shows several unexpectedly primitive pelvic features. Nevertheless, the limbs of G. wucaii share several features with derived coelurosaurs, and it possesses features shared by other coelurosaurian clades. This unusual combination of character states provides an insight into the poorly known early radiation of the Coelurosauria. Notably, the presumed predatory Guanlong has a large, fragile and highly pneumatic cranial crest that is among the most elaborate known in any non-avian dinosaur and could be comparable to some classical exaggerated ornamental traits among vertebrates. PMID:16467836

Xu, Xing; Clark, James M; Forster, Catherine A; Norell, Mark A; Erickson, Gregory M; Eberth, David A; Jia, Chengkai; Zhao, Qi

2006-02-01

10

ENIGMATIC TRACE FOSSILS FROM THE AEOLIAN LOWER JURASSIC CLARENS FORMATION, SOUTHERN AFRICA  

Microsoft Academic Search

The Lower Jurassic aeolienites of the Clarens Formation in southern Africa con- tain unique sedimentary structures that are unlikely to be non-biogenic. They are also unlike any known modern or ancient trace fossils. Here, some enigmatic, horizontal, regularly-oriented sedimentary structures are described, which occur in association with other trace fossils as well as features that were previously interpreted as nests

Emese M. Bordy

2008-01-01

11

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

USGS Publications Warehouse

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.

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

2006-01-01

12

Potential ZnS fossilization of gastropods (Middle Jurassic claystones from Central Poland)  

NASA Astrophysics Data System (ADS)

The rich fossil fauna in the Middle Jurassic claystones that crop out in the Krakow-Czestochowa Upland is extensively replaced by sulfide minerals, mainly pyrite. Sphalerite (ZnS) is rare and restricted to the internal casts of gastropods, often together with framboidal and euhedral pyrite and calcite. Scanning electron microscopy-energy dispersive spectrometer study was undertaken to explain this curious association. The results show that although direct infilling of the carbonate shell, similar to processes occurring during pyritization, is probable, it does not explain all textures observed. We propose that the carbonate shells were initially infilled by calcite and iron sulfides and sphalerite subsequently replaced the calcite casts. Preferential occurrence of ZnS in gastropods could result from accumulation of higher concentration of zinc during the organisms’ life. After death, this Zn was introduced into the carbonate making gastropods more prone to ZnS replacement. Formation of ZnS casts was probably a late diagenetic event as zinc content of the surrounding sediment does not appear to influence sphalerite formation.

Szczepanik, Patrycja; Sawlowicz, Zbigniew

2008-09-01

13

Ice age at the Middle-Late Jurassic transition?  

NASA Astrophysics Data System (ADS)

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

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

2003-08-01

14

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

NASA Astrophysics Data System (ADS)

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.

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

2009-06-01

15

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

PubMed Central

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.

Frey, Eberhard; Tischlinger, Helmut

2012-01-01

16

The conchostracan subgenus Orthestheria (Migransia) from the Tacuarembó Formation (Late Jurassic-?Early Cretaceous, Uruguay) with notes on its geological age  

NASA Astrophysics Data System (ADS)

Conchostracans from the Tacuarembó Formation s.s. of Uruguay are reassigned to the subgenus Orthestheria (Migransia) Chen and Shen. They show more similarities to genera of Late Jurassic age in the Congo Basin and China than to those of Early Cretaceous age. On the basis of the character of the conchostracans, we suggest that the Tacuarembó Formation is unlikely to be older than Late Jurassic. It is probably Kimmeridgian, but an Early Cretaceous age cannot be excluded. This finding is consistent with isotopic dating of the overlying basalts, as well as the age range of recently described fossil freshwater sharks.

Yanbin, Shen; Gallego, Oscar F.; Martínez, Sergio

17

Fossil insect eggs on Lower Jurassic plant remains from Bavaria (Germany)  

Microsoft Academic Search

Imprints of fossil insect eggs (oviposition slits of endophytic eggs) on Lower Jurassic plants from Franconia (Bavaria, Germany) are described. Two forms can be distinguished. Form A (2.5–3 mm long, 0.5–0.7 mm wide) is comparable to Hysterites friesii Nathorst 1876, who described it on Podozamites leaves (Coniferales) and considered it to be fungal remains. The present oviposition slits are, however,

Johanna H. A. van Konijnenburg-van Cittert; Stefan Schmeißner

1999-01-01

18

Chasing the Late Jurassic APW Monster Shift in Ontario Kimberlites  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

19

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

SciTech Connect

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.

Salvador, A.

1987-04-01

20

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

NASA Astrophysics Data System (ADS)

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

Li, Hong-Yan; Huang, Xiao-Long

2013-07-01

21

New Late Jurassic and Middle Carboniferous Paleomagnetic Results from the Junggar Basin, NW China  

NASA Astrophysics Data System (ADS)

The Junggar Basin of northwestern China, often considered to be the southeast extremity of the Kazakhstan Block, sits in a complicated region squeezed between the Tarim Basin on the south, the Kazakhstan Block on the west, and Siberia to the northeast. New paleomagnetic data from several Late Jurassic and Middle Carboniferous rock units from the Junggar Basin suggest that the Junggar basin was close to Tarim Basin but quite far south away from Kazakhstan and Siberia. We have obtained preliminary paleomagnetic results from Late Jurassic and Middle Carboniferous rocks sampled over a large area in eastern Junggar basin. After removal of a low-temperature component that resembles both Tertiary and present field directions and fails fold test, a stable high temperature characteristic component (ChRM) remains in Late Jurassic sandstone Shishu and Xishanyao Formations, and Middle Carboniferous red sandstone and andesite Bataimayiruishan Formation. The ChRM has both normal and reversed magnetic polarities and passes local fold tests at high levels of confidence. The corresponding paleopoles place Junggar basin at paleolatitudes of 34.6 N and 19.5N in Late Jurassic and Middle Carboniferous time, respectively, suggesting that Junggar basin and its northern neighboring blocks (Kazakhstan and Siberia) have not maintained their relative positions since Middle Carboniferous.

Finn, D. R.; Zhao, X.; Li, J.

2009-12-01

22

New Chironomidae (Diptera) with elongate proboscises from the Late Jurassic of Mongolia  

PubMed Central

Abstract Four new species of Chironomidae with well-developed elongate proboscises are described from a Late Jurassic site Shar Teg in SW Mongolia. These are named Cretaenne rasnicyni sp. n., Podonomius blepharis sp. n., Podonomius macromastix sp. n., ?Podonomius robustus sp. n.

Lukashevich, Elena D.; Przhiboro, Andrey A.

2011-01-01

23

A new species of Theriosuchus (Atoposauridae, Crocodylomorpha) from the Late Jurassic (Kimmeridgian) of Guimarota, Portugal  

Microsoft Academic Search

A new species of an atoposaurid crocodilian, Theriosuchus guimarotae, is described from the Late Jurassic (Kimmeridgian) of Portugal. Theriosuchus guimarotae can be distinguished from other species of Theriosuchus by a lateral surface of squamosal bevelled ventrally; a rounded, caudally projecting and dorsally sculptured caudolateral corner of the squamosal; a premaxillomaxillary suture aligned caudomedially in dorsal aspect; a minimum space between

Daniela Schwarz; Steven W. Salisbury

2005-01-01

24

A New Rhynchocephalian from the Late Jurassic of Germany with a Dentition That Is Unique amongst Tetrapods  

PubMed Central

Background Rhynchocephalians, the sister group of squamates (lizards and snakes), are only represented by the single genus Sphenodon today. This taxon is often considered to represent a very conservative lineage. However, rhynchocephalians were common during the late Triassic to latest Jurassic periods, but rapidly declined afterwards, which is generally attributed to their supposedly adaptive inferiority to squamates and/or Mesozoic mammals, which radiated at that time. New finds of Mesozoic rhynchocephalians can thus provide important new information on the evolutionary history of the group. Principle Findings A new fossil relative of Sphenodon from the latest Jurassic of southern Germany, Oenosaurus muehlheimensis gen. et sp. nov., presents a dentition that is unique amongst tetrapods. The dentition of this taxon consists of massive, continuously growing tooth plates, probably indicating a crushing dentition, thus representing a previously unknown trophic adaptation in rhynchocephalians. Conclusions/Significance The evolution of the extraordinary dentition of Oenosaurus from the already highly specialized Zahnanlage generally present in derived rhynchocephalians demonstrates an unexpected evolutionary plasticity of these animals. Together with other lines of evidence, this seriously casts doubts on the assumption that rhynchocephalians are a conservative and adaptively inferior lineage. Furthermore, the new taxon underlines the high morphological and ecological diversity of rhynchocephalians in the latest Jurassic of Europe, just before the decline of this lineage on this continent. Thus, selection pressure by radiating squamates or Mesozoic mammals alone might not be sufficient to explain the demise of the clade in the Late Mesozoic, and climate change in the course of the fragmentation of the supercontinent of Pangaea might have played a major role.

Rauhut, Oliver W. M.; Heyng, Alexander M.; Lopez-Arbarello, Adriana; Hecker, Andreas

2012-01-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

26

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

NASA Astrophysics Data System (ADS)

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'.

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

2013-04-01

27

A taxonomic review of the Late Jurassic eucryptodiran turtles from the Jura Mountains (Switzerland and France)  

PubMed Central

Background. Eucryptodiran turtles from the Late Jurassic (mainly Kimmeridgian) deposits of the Jura Mountains (Switzerland and France) are among the earliest named species traditionally referred to the Plesiochelyidae, Thalassemydidae, and Eurysternidae. As such, they are a reference for the study of Late Jurassic eucryptodires at the European scale. Fifteen species and four genera have been typified based on material from the Late Jurassic of the Jura Mountains. In the past 50 years, diverging taxonomic reassessments have been proposed for these turtles with little agreement in sight. In addition, there has been a shift of focus from shell to cranial anatomy in the past forty years, although most of these species are only represented by shell material. As a result, the taxonomic status of many of these 15 species remains ambiguous, which prevents comprehensive comparison of Late Jurassic turtle assemblages throughout Europe and hinders description of new discoveries, such as the new assemblage recently unearthed in the vicinity of Porrentruy, Switzerland. Methods. An exhaustive reassessment of the available material provides new insights into the comparative anatomy of these turtles. The taxonomic status of each of the 15 species typified based on material from the Late Jurassic of the Jura Mountains is evaluated. New diagnoses and general descriptions are provided for each valid taxon. Results. Six out of the 15 available species names are recognized as valid: Plesiochelys etalloni, Craspedochelys picteti, Craspedochelys jaccardi, Tropidemys langii, Thalassemys hugii, and ‘Thalassemys’ moseri. The intraspecific variability of the shell of P. etalloni is discussed based on a sample of about 30 relatively complete specimens from Solothurn, Switzerland. New characters are proposed to differentiate P. etalloni, C. picteti, and C. jaccardi, therefore rejecting the previously proposed synonymy of these forms. Based partly on previously undescribed specimens, the plastral morphology of Th. hugii is redescribed. The presence of lateral plastral fontanelles is notably revealed in this species, which calls into question the traditional definitions of the Thalassemydidae and Eurysternidae. Based on these new data, Eurysternum ignoratum is considered a junior synonym of Th. hugii. The Eurysternidae are therefore only represented by Solnhofia parsonsi in the Late Jurassic of the Jura Mountains. Finally, ‘Th.’ moseri is recognized as a valid species, although a referral to the genus Thalassemys is refuted.

Puntener, Christian; Billon-Bruyat, Jean-Paul

2014-01-01

28

Late Jurassic low latitude of Central Iran: paleogeographic and tectonic implications  

NASA Astrophysics Data System (ADS)

The individual blocks forming present-day Central Iran are now comprised between the Zagros Neo-Tethys suture to the south and the Alborz Palaeo-Tethys suture to the north. At the end of the Palaeozoic, the Iranian blocks rifted away from the northern margin of Gondwana as consequence of the opening of the Neo-Tethys, and collided with Eurasia during the Late Triassic, giving place to the Eo-Cimmerian orogeny. From then on, the Iranian block(s) should have maintained European affinity. Modern generations of apparent polar wander paths (APWPs) show the occurrence in North American and African coordinates of a major and rapid shift in pole position (=plate shift) during the Middle-Late Jurassic. This so-called monster polar shift is predicted also for Eurasia from the North Atlantic plate circuit, but Jurassic data from this continent are scanty and problematic. Here, we present paleomagnetic data from the Kimmeridgian-Tithonian (Upper Jurassic) Garedu Formation of Iran. Paleomagnetic component directions of primary (pre-folding) age indicate a paleolatitude of deposition of 10°N ± 5° that is in excellent agreement with the latitude drop predicted for Iran from APWPs incorporating the Jurassic monster polar shift. We show that paleolatitudes calculated from these APWPs, used in conjunction with simple zonal climate belts, better explain the overall stratigraphic evolution of Iran during the Mesozoic.

Mattei, Massimo; Muttoni, Giovanni; Cifelli, Francesca

2014-05-01

29

Late Triassic to Late Jurassic evolution of the Adriatic Carbonate Platform and Budva Basin, Southern Montenegro  

NASA Astrophysics Data System (ADS)

Southeastern Montenegro is the only part of the Adriatic Carbonate Platform (AdCP) that bears record of its evolution from a ramp, through a distally steepened ramp to a platform. In this paper we present the sequence stratigraphy of the Late Triassic to Late Jurassic rocks from this part of Tethys for the first time in the literature. We discovered and described three new facies: hardground and cerebroid oolites of the Livari Supersequence, and black pebble conglomerate of the Tejani Supersequence. The mid-ramp and lower ramp cherty oolite, wackestone and mudstone facies of the Livari Supersequence, as well as Oolite Conglomerate facies of the Stari Bar Supersequence were partially or completely reinterpreted. The Middle and Late Triassic rifting separated the AdCP from the other South Tethyan carbonate platforms and created the intraplatform Budva Basin. The AdCP evolved through three morphologic stages: a detached ramp (Livari Supersequence; Rhaetian-Early Toarcian), a distally steepened ramp (Tejani Supersequence; Early Toarcian-Middle Callovian) and an accretionary rimmed platform (Stari Bar Supersequence; Oxfordian to Neogene). The Rhaetian regression is marked by a regional unconformity surface that represents a type S sequence boundary at the base of the Livari Supersequence. Lowstand Wedge of the Halobia Limestone was the oldest sediment in the Budva Basin. TST and HST of the Livari Supersequence include: supratidal and intertidal inner ramp sediments, ooid shoals, and cyclic shallowing-up parasequences of the mid-ramp. Sedimentation rates were high in the inner ramp, while Budva Basin received relatively thin accumulation of siliceous plankton. A brief exposure of supratidal flats and ooid bars represents a type P sequence boundary between the Livari and the Tejani Supersequences, which was flooded by the Early Toarcian transgression. TST and HST of the Tejani Supersequence consist of supratidal, lagoon, and shoal sediments in the inner ramp, and deeper water carbonates of the mid- and outer ramp. Highstand shedding of the sediment from the steepened ramp left thick deposits in the Budva Basin. The Bathonian regression is marked by a regional unconformity that represents a type S sequence boundary between the Tejani and Stari Bar Supersequences. Stari Bar Oolite Conglomerate is a Lowstand Wedge of the Stari Bar Supersequence. The Middle Callovian transgression induced aggradation of ooid shoals deep into the platform interior. Oxfordian coral reefs created a rimmed platform and restricted export of the shallow carbonates into the Budva Basin.

?adjenovi?, Damjan; Kilibarda, Zoran; Radulovi?, Novo

2008-02-01

30

Jurassic volcaniclastic – basaltic andesite – dolerite sequence in Tasmania: new age constraints for fossil plants from Lune River  

Microsoft Academic Search

Jurassic plants excavated from a 12 × 5 m site, at Lune River, southern Tasmania, include an araucarian tree and numerous pteridophytes, belonging to the orders Osmundales, Filicales and Bennettitales. The fossils occur in 2 – 3 m of immature volcanilithic sandstone beds. The sandstone consists primarily of clasts from granitic basement rocks underlying much of southeast Tasmania and mafic clasts containing feldspathic microliths, and primary,

K. Bromfield; C. F. Burrett; R. A. Leslie; S. Meffre

2007-01-01

31

Mammals from the Late Jurassic Qigu Formation in the Southern Junggar Basin, Xinjiang, Northwest China  

Microsoft Academic Search

Five mammalian taxa based on teeth and jaw fragments are reported from a bonebed of the Late Jurassic (Oxfordian) Qigu Formation\\u000a at the Liuhuanggou site in the southern Junggar Basin. The mammals recovered to date comprise a new eleutherodontid haramiyid,\\u000a the docodonts Dsungarodon and Tegotherium, an undetermined amphilestid triconodont, and a new species of the stem zatherian Nanolestes and represent

Thomas Martin; Alexander O. Averianov; Hans-Ulrich Pfretzschner

2010-01-01

32

A Late Jurassic freshwater shark assemblage (Chondrichthyes, Hybodontiformes) from the southern Junggar Basin, Xinjiang, Northwest China  

Microsoft Academic Search

A low-diversity hybodont assemblage from the Late Jurassic (Oxfordian) Qigu Formation at Liuhuanggou in the southern Junggar\\u000a Basin includes the remains of three taxa based on isolated teeth, two of which represent new species of a hitherto unknown\\u000a genus: Hybodus sp. cf. H. huangnidanensis Wang, 1977, Jiaodontus montaltissimus gen. et sp. nov., and Jiaodontus vedenemus gen. et sp. nov. H.

Stefanie Klug; Thomas Tütken; Oliver Wings; Hans-Ulrich Pfretzschner; Thomas Martin

2010-01-01

33

Late Jurassic Squamata and possible Choristodera from the Junggar Basin, Xinjiang, Northwest China  

Microsoft Academic Search

Screen washing at the Liuhuanggou locality, a fossiliferous bone bed within the early Late Jurassic Qigu Formation, 40 km\\u000a southwest of the city of Urumqi, yielded two lizard jaw fragments with teeth and two lizard osteoderm fragments, which together\\u000a reveal the presence of Paramacellodidae. The same locality also yielded four tentative choristoderan jaw and tooth fragments.\\u000a This find is the first

Annette Richter; Oliver Wings; Hans-Ulrich Pfretzschner; Thomas Martin

2010-01-01

34

The eroded Late Jurassic Kurbnesh carbonate platform in the Mirdita Ophiolite Zone of Albania and its bearing on the Jurassic orogeny of the Neotethys realm  

Microsoft Academic Search

Several Late Jurassic (Kimmeridgian?-Tithonian) to Early Cretaceous (Late Berriasian-Valanginian) shallow-water carbonate\\u000a clasts of different facies are contained in mass-flow deposits in a pelagic sequence in the Kurbnesh area of central Albania.\\u000a These clasts are used to reconstruct shallow-water carbonate platforms, which formed on top of the radiolaritic-ophiolitic\\u000a wildflysch (ophiolitic mélange) of the Mirdita Zone. Stratigraphic interpretation of the platform carbonates

Felix Schlagintweit; Hans-Jürgen Gawlick; Sigrid Missoni; Lirim Hoxha; Richard Lein; Wolfgang Frisch

2008-01-01

35

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

USGS Publications Warehouse

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.

Bishop, M. G.

1999-01-01

36

Conflicting tectonics? Contraction and extension at middle and upper crustal levels along the Cordilleran Late Jurassic arc, southeastern California  

NASA Astrophysics Data System (ADS)

Effects of mid-Mesozoic contraction followed closely in time by extension are present in mid- to upper-crustal plutonic rocks in the Chuckwalla Mountains of the eastern Transverse Ranges, California. Late Jurassic movement along a steeply dipping, right-lateral mylonitic shear zone is bracketed between 159 and 147 Ma via U-Pb dated plutons. Depth of emplacement vs. time data based on hornblende geobarometry and U-Pb geochronology of Mesozoic plutons indicate that a period of dramatic uplift affected the Chuckwalla Mountains during the Late Jurassic, contrasting sharply with data from the (then) nearby San Gabriel Mountains. Subsequent latest Jurassic extensional tectonics is suggested by alkalic plutonism, nearly synchronous intrusion of the Late Jurassic Independence dike swarm, and possibly by deposition of the McCoy Mountains Formation. We conclude that both contraction and extension were significant at upper- and mid-crustal depths in the Chuckwalla Mountains region during the Late Jurassic, and speculate that the combined influence of oblique convergence and the opening of the Gulf of Mexico may have caused the contrasting and nearly contemporaneous tectonic modes.

Davis, Mark J.; Farber, Daniel L.; Wooden, Joe L.; Lawford Anderson, J.

1994-03-01

37

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

PubMed

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 (87)Sr/(86)Sr 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 ?(13)C excursion and widespread deposition of petroleum source rocks and black shales. PMID:23712471

Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

2013-01-01

38

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

PubMed Central

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.

Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

2013-01-01

39

Stable isotope composition of calcite fossils and bulk carbonate as a proxy for the reconstruction of Jurassic marine environments  

NASA Astrophysics Data System (ADS)

Changes in global ocean productivity may be studied by means of carbon isotope analyses of marine carbonates. The analyses of the isotopic composition of carbonate oxygen are a basis for seawater temperature reconstructions, which are indicative of environmental and climatic changes. In this study we use carbon and oxygen isotope composition for the evaluation of the environmental changes in the Pieniny Klippen Basin (PKB) during the Jurassic. PKB is a narrow and long structure separating the Outer and Central Carpathians. The sample set includes the stratigraphically well-dated bulk carbonates and calcite fossils from several outcrops in Polish, Slovakian and Ukrainian parts of the PKB. Sample screening for the state of preservation was conducted using cathodoluminescence microscopy and optical emission spectrometry method. The aims of the project are: (i) to reconstruct the evolution of sea water temperatures using the oxygen isotope composition and Mg/Ca and Sr/Ca ratios of the belemnite rostra; (ii) to trace the secular changes in the carbonate carbon isotope composition in order to present temporal variations in ?13C values of Jurassic bulk carbonates and belemnite rostra; (iii) to compare the obtained ?13C curves with the previously reported records of the isotope composition of carbonate carbon. Preliminary results of the study show that: (i) a negative excursion of the bulk carbonate ?13C curve during the Toarcian may correspond to the Toarcian Oceanic Anoxic Event; (ii) high Middle Oxfordian ?13C values of bulk carbonate and calcite fossils correspond to the global positive isotope excursion in carbonate carbon; (iii) for Upper Jurassic belemnite ?18O values range from -0.8 to 0.4 ‰VPDB what implies temperatures of 13 ± 2°C.

Arabas, A. Z.

2012-12-01

40

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

41

Enigmatic Fossil Footprints from the Sundance Formation (Upper Jurassic) of Bighorn Canyon National Recreation Area, Wyoming  

Microsoft Academic Search

The Sundance Formation (Middle-Upper Jurassic) of Wyoming is well known for pterosaur footprints. Two new partial trackways from the upper Sundance Formation of the Bighorn Canyon National Recreation Area (BICA) of north-central Wyoming are enigmatic. The trackways are preserved in rippled, flaser bedded, glauconitic sand and mud. The deposits were laid down in tidal flats, behind barrier islands, along the

Jerald D. Harris; Kenneth J. Lacovara

2004-01-01

42

The significance of dropstones in a tropical lacustrine setting, eastern Cameros Basin (Late Jurassic–Early Cretaceous, Spain)  

Microsoft Academic Search

Outsized clasts (mainly white quartzite pebbles) are found in carbonate deposits of the Enciso Group exposed on the northern border of the Cameros rift basin (Late Jurassic–Early Cretaceous, northern Spain). In the Arnedillo section, all the stones are enclosed in micrite, which was assumed deposited in littoral to open lacustrine environments, with minor inputs of deltaic sandstones. The clasts are

Stéfan Doublet; Jean-Pierre Garcia

2004-01-01

43

Turtle egg pseudomorphs from the Late Jurassic of Schamhaupten, Germany Schildkroteneier-Pseudomorphe aus dem Oberjura von Schamhaupten (Deutschland)  

Microsoft Academic Search

The shell of a turtle, tentatively identified as a eurysternid, was recovered from a Late Jurassic limestone concretion found near the village of Schamhaupten, Germany. Transverse sections through the body cavity revealed four spherical crystalline objects that are embedded in a micritic matrix and surrounded by a thin calcareous crust that superficially resembles inside-out turtle eggshell. Although various hypotheses can

WALTER G. JOYCE; DARLA K. ZELENITSKY

44

Trace fossils from Jurassic lacustrine turbidites of the Anyao Formation (central China) and their environmental and evolutionary significance  

USGS Publications Warehouse

The Lower Jurassic Anyao Formation crops out near Jiyuan city, western Henan Province, central China. It is part of the infill of the nonmarine early Mesozoic Jiyuan-Yima Basin. In the Jiyuan section, this unit is about 100 m thick and consists of laterally persistent, thin and thick-bedded turbidite sandstones and mudstones displaying complete and base- or top-absent Bouma sequences, and thickbedded massive sandstones. The Anyao Formation records sedimentation within a lacustrine turbidite system developed in a pull-apart basin. Processes involved include high and low density turbidity currents, sometimes affected by liquefaction or fluidization. Facies analysis suggests that this succession is formed by stacked aggradational turbidite lobes. The absence of thick mudstone packages indicates that background sedimentation was subordinate to high frequency turbidite deposition. The Anyao Formation hosts a moderately diverse ichnofauna preserved as hypichnial casts on the soles of thin-bedded turbidite sandstones. The ichnofauna consists of Cochlichnus anguineus, Helminthoidichnites tenuis, Helminthopsis abeli, H. hieroglyphica, Monomorphichnus lineatus, Paracanthorhaphe togwunia, Tuberculichnus vagans, Vagorichnus anyao, tiny grazing trails, and irregularly branching burrows. Vagorichnus anyao occurs not only as a discrete trace, but also as a compound ichnotaxon intergrading with Gordia marina and Tuberculichnus vagans. Both predepositional and post-depositional traces are present on the soles of turbidites. This ichnofauna comprises both feeding and grazing traces produced by a deposit-feeding lacustrine benthic biota. Crawling traces are rare. Although certain ichnofossils (e.g. V. anyao, P. togwunia) show overall similarities with deep-sea agrichnia, they differ in reflecting remarkably less specialized feeding strategies, displaying overcrossing between specimens (and to a lesser extent, self-crossing), and in the case of V. anyao recording post-turbidite burrowing activity. The development of less specialized strategies than those displayed by deep-marine ichnofaunas may be related to less stable conditions, typical of lake settings. Oxygenation, energy, sedimentation rate (both event and background), food supply, soft-sediment deformation and erosion rate have mainly influenced trace-fossil distribution. Turbidity currents would have ensured oxygen (as well as food) supply to deep lake settings, thus allowing the establishment of a moderately diverse biota. Biogenic structures were mostly confined to the outer, low energy areas. High sedimentation rates and strong erosion precluded preservation of ichnofossils in inner lobe settings. The Anyao ichnofauna is of significance in furthering knowledge of the colonization of deep lakes throughout the stratigraphic record and in identification of additional nonmarine ichnofacies. The analyzed ichnofauna resembles late Paleozoic lacustrine assemblages described from different localities around the world and is regarded as a Mesozoic example of the Mermia ichnofacies. However, when compared with Paleozoic assemblages, the Anyao ichnofauna shows a clear dominance of burrows over surface trails, deeper burrowing penetration, larger size, and presence of relatively more complex structures. The high burrow/surface trail ratio may be indicative of lower preservation potential in the latter, thus reflecting a tap-honomic overprint. In contrast to the Paleozoic examples, the establishment of a relatively well-developed lacustrine infauna may have precluded preservation of surface trails. Burrower activity probably obliterated biogenic structures formed close to the sediment-water interface. ?? 1996 OPA (Overseas Publishers Association) Amsterdam B.V. Published in The Netherlands by Harwood Academic Publishers GmbH.

Buatois, L. A.; Mangano, M. G.; Wu, X.; Zhang, G.

1996-01-01

45

New fossil Praeaulacinae wasps (Insect: Hymenoptera: Evanioidea: Praeaulacidae) from the Middle Jurassic of China.  

PubMed

A new genus with a new species, Archaulacus probus gen. et sp. nov., and two new species, Praeaulacus subrhombeus sp. nov., P. tenellus sp. nov., belonging to the subfamily Praeaulacinae (Praeaulacidae) are described and illustrated. The specimens were collected from the Middle Jurassic of Jiulongshan Formation at Daohugou in Inner Mongolia, China. Archaulacus gen. nov. differs from other genera of Praeaulacinae in having the first abscissa of Rs of the fore wing subvertical to R and 2m-cu slightly basad of 2r-m. This is the first time that these characters are reported for the Praeaulacinae. Based on new information provided by the new species, an updated key to the known species of Praeaulacus is provided. PMID:24943440

Li, Longfeng; Shih, Chungkun; Ren, Dong

2014-01-01

46

A new Late Jurassic species of the rare synechodontiform shark, Welcommia (Chondrichthyes, Neoselachii)  

Microsoft Academic Search

A new Jurassic species of the very rare and incompletely known synechodontiform shark, Welcommia, is described. The new species, Welcommia cappettai, is represented only by a single tooth, precluding reconstruction of its dentition in detail. Nevertheless, this specimen\\u000a provides sufficient information and characteristics to establish its taxonomic status. Welcommia cappettai n. sp. occurs in the middle Oxfordian (Upper Jurassic) of

Stefanie KlugJurgen Kriwet; Jürgen Kriwet

2010-01-01

47

Late Paleozoic to Jurassic tectonic evolution of the Bogda area (northwest China): Evidence from detrital zircon U-Pb geochronology  

NASA Astrophysics Data System (ADS)

Since the Cenozoic, the Tian Shan is rejuvenated by crustal shortening related to the ongoing India-Asia collision. However, the tectonic process prior to the Cenozoic remains ambiguous, especially in the Bogda area of the eastern Tian Shan. The continuous Late Paleozoic-Mesozoic sequences in the Bogda area record abundant information about the basin-mountain interaction. U-Pb (LA-ICP-MS) dating of detrital zircons from seven sandstone samples from Permian to Jurassic was used to investigate the changes of provenance and basin-mountain interaction in the Bogda area. During the Permian, proximal and synchronous pyroclastic materials were the major source. The Late Paleozoic magmatic belt in the North Tian Shan (NTS) had gradually become one of the main sources by the Late Permian, which implies the uplift and exhumation in the NTS area. This is interpreted in terms of near-source sedimentation in basin developing in a post-orogenic extension setting. The large range of U-Pb ages of detrital zircons observed in the Early-Middle Jurassic sediments encompasses most of the available sources implying a wide drainage pattern developing on a rather flat topography. Re-emergence of the Early Permian peak in the spectrum implies that the Bogda Mountains has existed as a gentle positive relief and began to provide materials to the submountain regions. The southern Junggar Basin extended towards to the south and evolved as a passively subsiding basin from the Middle Triassic to the Middle Jurassic. However, the synchronous pyroclastic (tuff) and the exhumed late Paleozoic detrital materials from the uplifted Bogda Mountains were the major component of the Upper Jurassic sediments. Associated to the conglomerate in the Kalaza Formation, the basin-range evolution entered a compression uplift stage. The basin pattern evolution of the Bogda area is consistent with that of the southern Junggar Basin.

Tang, Wenhao; Zhang, Zhicheng; Li, Jianfeng; Li, Ke; Chen, Yan; Guo, Zhaojie

2014-06-01

48

Conflicting tectonics? Contraction and extension at middle and upper crustal levels along the Cordilleran Late Jurassic arc, southeastern California  

Microsoft Academic Search

Effects of mid-Mesozoic contraction followed closely in time by extension are present in mid- to upper-crustal plutonic rocks in the Chuckwalla Mountains of the eastern Transverse Ranges, California. Late Jurassic movement along a steeply dipping, right-lateral mylonitic shear zone is bracketed between 159 and 147 Ma via U-Pb dated plutons. Depth of emplacement vs. time data based on hornblende geobarometry

Mark J. Davis; Daniel L. Farber; Joe L. Wooden; J. Lawford Anderson

1994-01-01

49

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

PubMed Central

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

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

2006-01-01

50

Sedimentological evolution, diagenesis and hydrocarbon potentiality of late Jurassic carbonates, Eastern Region, Yemen Arab Republic  

SciTech Connect

On the basis of the lateral and vertical distribution of the lithofacies identified within the Late Jurassic Amran sequence (Thoma Member) in Jabal Al-Balaq area, Marib, Y.A.R., three megafacies were recognized. Proceeding from the shore landwards they are: Ooid bank, including barriers such as reefs and carbonate sand shoals adjacent to the margin of a shallow platform having intertidal to subtidal agitated water, the bank being composed of skeletal packstone, oolitic grainstone and oncolitic packstone; Shelf lagoon, behind the shoal, characterized by less turbulent pelletoidal wackestone, sandy mudstone and algal stromatolite (boundstone); Alluvial coastal plain, including tidal sand flat of the marine shoreline-intertidal area, where cross-bedded sandstone and alluvial fan toe conglomerate were deposited. The apparent small-scale facies variations which are the result of the allocyclic tectonically controlled sea level fluctuations, reflect a complex interfingering of the depositional environments and the resulting rock types. The paragenetic sequence of the post-depositional processes within the siliciclastics inferred is: iron oxide cementation, authigenic growth of mica clays, generation of pressure solution and compaction, and generation of quartz overgrowths. It is indicated that the compaction process followed the neomorphism and cementation within the carbonates.

El-anbaawy, M.I.H.; Al-thour, K.A. (Dept. of Geology, Faculty of Science, Cairo Univ., Giza (EG))

1989-01-01

51

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

PubMed

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

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

2012-07-17

52

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

PubMed Central

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

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

2012-01-01

53

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

NASA Astrophysics Data System (ADS)

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.

Kakizaki, Yoshihiro; Kano, Akihiro

2009-02-01

54

Tectonic and magmatic evolution of a fossil (Ultra-)Slow Spreading Ocean: the study case of the Jurassic Ligurian Tethys.  

NASA Astrophysics Data System (ADS)

The Jurassic Ligurian Tethys oceanic basin has been recognized as the fossil analogue of modern (Ultra- )Slow Spreading Ridges. Stratigraphic and structural studies on the Western Alpine - Northern Apennine (AA) ophiolites, that are remnants of the lithosphere of the ancient basin, evidence that the basin was characterized by the sea-floor exposure on mantle peridotites, discontinuously covered by MORB volcanites and pelagic sediments (i.e. radiolarion cherts). The related passive margins were typically not-volcanic. Palaeogeographic restorations indicate that exhumed sub-continental mantle was exposed at the ocean- continent transition (OCT) zones, frequently associated to continental crust material and pelagic sediments. These exhumed sub-continental lithospheric peridotites were equilibrated under spinel-facies conditions, preserving diffuse structural relicts of precursor garnet, and show widespread spinel(-garnet)-pyroxenites bands. Sm-Nd isotope data on Cpx from these peridotites indicate DMM affinity and Proterozoic model ages, that have been interpreted as early accretion to, and long residence in, the sub-continental lithosphere. OCT peridotites frequently show strong localized deformation along km-scale shear zones that were formed during lithosphere extension leading to the oceanic opening. Isotope data indicate that mantle exhumation during lithosphere extension was already active during Triassic times and was most probably accomodated by a network of lithosphere-scale shear zones. Lithospheric thinning caused asthenosphere adiabatic upwelling and decompression melting along the axial zone of the extensional system. The asthenospheric MORB melts infiltrated by porous flow and percolated through the overlying extending lithospheric mantle causing significant melt-peridotite interaction. The pristine lithospheric mantle was tranformed to strongly pyroxene-depleted (i.e. reactive and replacive peridotites) or plagioclase-enriched (i.e. impregnated and refertilized peridotites) rock types. Isotope data indicate that asthenosphere melting and lithosphere melt percolation started during Early Jurassic times and the pristine lithospheric peridotites were isotopically equilibrated with the percolating melts, attaining MORB isotopic signatures. Melt impregnation (i.e. interstitial crystallization) caused significant melt entrapment in the extending lithosphere: accordingly, the rift evolution of the continental system, from rifting to drifting to formation of the passive margins was significantly not-volcanic (but not a-magmatic). Ongoing extension caused complete failure of the continental crust and peridotites from the sub-continental mantle were exposed to the sea-floor. Sub-continental peridotites were exhumed and exposed at the sea- floor close to the continental margins, whereas the strongly modified peridotites formed by melt-rock interaction were exhumed and exposed at more internal oceanic settings of the basin. Present knowledge indicates that none of the known AA ophiolitic peridotites from the Jurassic Ligurian Tethys can be recognized as simple refractory residua after Jurassic asthenosphere partial melting. This could indicate that the Ligurian Tethys never reached a complete oceanic stage, where magmatic rocks and mantle refractory residua should be almost coeval and cogenetic.

Piccardo, G. B.

2008-12-01

55

Bioerosional structures and pseudoborings from Late Jurassic and Late Cretaceous-Paleocene shallow-water carbonates (Northern Calcareous Alps, Austria and SE France) with special reference to cryptobiotic foraminifera  

Microsoft Academic Search

Examples of bioerosional processes (boring patterns) are described from shallow-water limestones of the Late Jurassic Plassen\\u000a Carbonate Platform (PCP) and the Late Cretaceous to Paleocene Gosau Group of the Northern Calcareous Alps, Austria. Some micro-\\/macro-borings\\u000a can be related to distinct ichnotaxa, others are classified in open nomenclature. In the Alpine Late Jurassic, bioerosional\\u000a structures recorded from clasts in mass-flows allow

Felix Schlagintweit

2008-01-01

56

Late Pliensbachian (Early Jurassic) Cold Seep Carbonates: Methane Release Prior to the Toarcian Oceanic Anoxic Event  

NASA Astrophysics Data System (ADS)

We present evidence for methane seepage during the Early Jurassic (~ 185 Ma) in the form of newly discovered extensive occurrences of carbonate concretions that resemble the subsurface plumbing system of better known Cenozoic to Recent examples of cold seep carbonates. Columnar carbonate concretions of up to 1 m in length that are perpendicular to bedding, occur abundantly in the Upper Pliensbachian (upper Amaltheus margaritatus Zone, gibbosus Subzone) in outcrops in the vicinity of Riviere-sur-Tarn, southern France. Stable isotope analyses of these nodules show depleted ?13C values that decrease from the rim to the center from -18.8 to -25.7‰ (V-PDB), but normal marine ?18O values (-1.8‰). Computer tomographic (CT) scanning of the columnar concretions show one or more central canals that are lined or filled entirely with pyrite and late diagenetic minerals. Septarian cracks are also filled with secondary calcite and/or siderite. Based on our preliminary geochemical and sedimentological observations we suggest that these concretions formed as a combination of the anaerobic oxidation of methane (AOM) and sulfate reduction within the sediment. Previously, these concretions with one, two or more central tubes have been ascribed to the activity of an enigmatic organism, possibly with annelid or arthropod affinities, known as Tisoa siphonalis. Our results suggest tisoan structures are abiogenic. Interestingly, Tisoa siphonalis has been described from many locations in the Grands Causses Basin in southern France, and from northern France and Luxemburg, always occurring at the same stratigraphic level. Upper Pliensbachian cold seep carbonates thus possibly cover an area of several thousand square kilometers, largely distributed across the basin centres of the NW European epicontinental seaway. Our findings may have far reaching implications for understanding the Toarcian Oceanic Anoxic Event, which is interpreted to bear the hallmarks of catastrophic methane release from gas hydrates in the form of a pronounced negative C-isotope excursion. Carbon isotope analyses of Late Pliensbachian bulk carbonate (matrix) samples show clearly decreasing C-isotope values across the margaritatus Zone and reach -3‰ within the uppermost Pliensbachian spinatum Zone. We attribute this decrease to seeping fluids that led to induration and diagenesis. Isotope analyses of coeval belemnite rostra do not document such a negative C-isotope trend with values remaining stable around +2‰. Hence, if methane was seeping prior to the Toarcian OAE, it appears not to have imprinted global carbon reservoirs.

van de Schootbrugge, B.; Harazim, D.; Sorichter, K.; Fiebig, J.; Zanella, F.; Oschmann, W.; Rosenthal, Y.

2008-12-01

57

Overview of Mesozoic crocodylomorphs from the Junggar Basin, Xinjiang, Northwest China, and description of isolated crocodyliform teeth from the Late Jurassic Liuhuanggou locality  

Microsoft Academic Search

Lacustrine and fluvial Jurassic and Cretaceous sediments in the Junggar Basin yielded at least five crocodylomorph taxa. The\\u000a Middle and Late Jurassic Shishugou Formation has produced the crocodylomorph Junggarsuchus sloani, the holotype specimen of the middle-sized, amphibious goniopholidid Sunosuchus junggarensis, and remains of the shartegosuchid crocodyliform Nominosuchus matutinus. The contemporary Qigu Formation has also yielded Sunosuchus. Two crocodyliforms have been

Oliver Wings; Daniela Schwarz-Wings; Hans-Ulrich Pfretzschner; Thomas Martin

2010-01-01

58

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  

Microsoft Academic Search

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

Peter D. Ward; Geoffrey H. Garrison; James W. Haggart; David A. Kring; Michael J. Beattie

2004-01-01

59

The generation of high Sr/Y plutons following Late Jurassic arc-arc collision, Blue Mountains province, NE Oregon  

NASA Astrophysics Data System (ADS)

High Sr/Y plutons (Sr/Y > 40) occupy large areas in ancient and modern orogenic belts, yet considerable controversy exists regarding mechanisms of their generation, the tectonic settings in which they form, and their relationship to contractional deformation through time. In the Blue Mountains province (NE Oregon), a suite of Late Jurassic (148-145 Ma), high Sr/Y plutons intrude Middle Jurassic (162-157 Ma), low Sr/Y (< 40) arc-related lavas and plutons in the Dixie Butte area immediately after widespread Late Jurassic arc-arc collision (159-154 Ma). Early, pre- to syn-kinematic low Sr/Y lavas and plutons (162-157 Ma) have flat to slightly enriched light rare earth element (REE) abundances, low Sr (< 400 ppm) and Sr/Y values (< 40), and strongly positive initial epsilon Hf values (+ 10.1 to + 12.3: 2? weighted average). Ce/Y values from basalts and gabbros yield a maximum crustal thickness of ~ 23 km. These geochemical and isotopic features suggest derivation from a depleted-mantle source and/or shallow-level (? 40 km) melting of pre-existing island arc crust with little to no evolved crustal input. In contrast, post-kinematic high Sr/Y plutons (148-145 Ma) are more compositionally restricted (tonalite-trondhjemite-granodiorite) and display depleted heavy REE abundances, an absence of Eu anomalies, elevated Sr (> 600 ppm) and Sr/Y values (> 40), and positive initial epsilon Hf values (+ 10.5 to + 7.8: 2? weighted average). These geochemical and isotopic results are consistent with geochemical models suggesting derivation from partial melting of island arc crust in the presence of a plagioclase-poor to absent, clinopyroxene + hornblende + garnet-bearing source (depths > 35-40 km). We propose that the transition from low Sr/Y to high Sr/Y magmatism resulted from orogenic thickening of island arc crust in the Dixie Butte area during Late Jurassic arc-arc collision between the Olds Ferry and Wallowa island arcs at 159-154 Ma. This fundamental change in crustal structure influenced post-orogenic magmatism and resulted in a relatively brief (~ 3 myr: 148-145 Ma) episode of high Sr/Y magmatism. Other high Sr/Y plutons occur throughout the US sector of the western North American Cordillera (e.g., Salmon River suture zone, Klamath Mountains, Peninsular Ranges) and closely follow major contractional events involving arc-arc and arc-continent collisions.

Schwartz, Joshua J.; Johnson, Kenneth; Miranda, Elena A.; Wooden, Joseph L.

2011-09-01

60

Late Jurassic ultramaphic lamprophyres with kimberlitic affinity in the allochthonous Batain nappes of Eastern Oman  

NASA Astrophysics Data System (ADS)

Carbonatite, alkaline volcanic rocks and ultramafic lamprophyres with kimberlitic affinities have been recently discovered in the allochthonous Batain nappes of Eastern Oman. The main bodies of the ultramafic lamprophyres occur in a diatreme at the coast of the Asseelah village, northeastern Oman. The second major outcrops of ultramafic lamprophyres occur as several 6 km long dykes at the Bomethra area. The diatreme consists of heterogeneous deposits dominated by 'diatreme facies' volcaniclastic rocks. These include accretionary and armoured carbonate lapilli, and carbonate-dominated tuffs, all of which intrude late Jurassic to early Cretaceous cherts and shales of the Wahra Formation. The Asseelah ultramafic rocks may be classified as either aillikite and/or carbonatite with kimberlitic affinity. Garnet (G0), chromite, phlogopite, ilmenite, zircon, apatite, rutile, corundum, and sillimanite have been recovered from heavy mineral concentrates. Zircon grains extracted from the diatreme rocks have a mean age of 137 + 1 Ma (95 % confidence, MSWD = 0.49). The trace element patterns of the zircon gains are typical of kimberlitic to carbonatitic rocks and their Hf isotope ratio (176Hf/177Hf = 0.28286 + 1, å Hf = 6.2) is typical of kimberlitic zircons of early Cretaceous. The lamprophyric dyke swarms of the Bomethra area comprise macrocrystic, spinel and phlogopite bearing hybabyssall facies calcite aillikites/damtjernites with pelletal lapilli and globular segregationary textures. The main dyke extends in length up to 6 km and ranges in width between 1 and 30 meters with two main blows 300-500 m in width. The petrography, mineralogy, trace element and isotopic composition of the dyke rocks are comparable to aillikites and damtjernites with kimberlitic affinity. Kimberlite indicator minerals include chromite, Cr-diopside, G4 garnet, and picroilmenite. The Asseelah and the Bomethra ultramafic rocks are enriched in light REE and have a high modal proportion of Ti-Al rich phlogopite, suggesting that they were derived from a source region which has experienced melt-depletion followed by metasomatic enrichment. This enrichment of the source region could be a consequence of the upward percolation of an alkaline melts that penetrated the base of the subcontinental lithosphere during the break-up of Gondwanaland. There is no obvious age difference (137 Ma; U-Pb zircon dating of Asseelah rocks and 150- 162 Ma; Ar-Ar age dating of Bomethra rocks) between these various rocks, so the initial magmas were formed around the same time. These ages correlate with large-scale tectonic events recorded in the early Indian Ocean at 140-160 Ma. The magmatism is probably a distal effect of the breakup of Gondwana, during and/or after the rift-to-drift transition that led to the opening of the Indian Ocean. The magmas in the Batain area are petrogenetically related and appear to have originated in a single event, possibly triggered by the arrival of the hot material beneath the Batain lithosphere that had been recently metasomatised and is related spatially and compositionally to mantle upwelling associated with the rifting.

Nasir, S. J.

2009-05-01

61

Petrology and geochemistry of the Late Jurassic calc-alkaline series associated to Middle Jurassic ophiolites in the South Apuseni Mountains (Romania)  

Microsoft Academic Search

Abstract In the South Apuseni Mountains (SAM), Romania, Jurassic calc-alkaline magmatic series occur in association with Jurassic ophiolites within a narrow belt that marks the boundary,between,the Eurasian and Adria Paleozoic conti- nental margins. This association of magmatic series has been previously reported,as a single ophiolitic sequence,by many authors. Calc-alkaline rocks include volcanic and intrusive rocks and, along with associated ophiolites,

Ionel Nicolae; Emilio Saccani

2003-01-01

62

Early Jurassic to Late Cretaceous evolution of Zoophycos in the French Subalpine Basin (southeastern France)  

Microsoft Academic Search

The complex and enigmatic trace fossil Zoophycos is recorded worldwide, from Cambrian to Holocene. The possible evolution of the ichnofossil has already been proposed by some authors, but their works concerned the very large group of trace fossils related to Zoophycos (structures that could be assigned potentially to several ichnogenera) recorded in several depositional basins. This paper focuses on the

D Olivero

2003-01-01

63

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

National Technical Information Service (NTIS)

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. Preliminary study of late-glacial fossil ostracodes from 'marsh deposi...

R. M. Forester A. J. Smith

1995-01-01

64

Inferring ecological disturbance in the fossil record: A case study from the late Oligocene of Ethiopia  

Microsoft Academic Search

Environmental disturbances profoundly impact the structure, composition, and diversity of modern forest communities. A review of modern studies demonstrates that important characteristics used to describe fossil angiosperm assemblages, including leaf margin type, plant form, plant diversity, insect herbivore diversity and specialization, and variation in herbivory among plant species, differ between early and late successional forests. Therefore, sequences of fossil floras

Ellen D. Currano; Bonnie F. Jacobs; Aaron D. Pan; Neil J. Tabor

2011-01-01

65

The conchostracan subgenus Orthestheria (Migransia) from the Tacuarembó Formation (Late Jurassic–?Early Cretaceous, Uruguay) with notes on its geological age  

Microsoft Academic Search

Conchostracans from the Tacuarembó Formation s.s. of Uruguay are reassigned to the subgenus Orthestheria (Migransia) Chen and Shen. They show more similarities to genera of Late Jurassic age in the Congo Basin and China than to those of Early Cretaceous age. On the basis of the character of the conchostracans, we suggest that the Tacuarembó Formation is unlikely to be

Shen Yanbin; Oscar F Gallego; Sergio Mart??nez

2004-01-01

66

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

PubMed

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

Hendrickx, Christophe; Mateus, Octávio

2014-01-01

67

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

68

Late Jurassic lungfishes (Dipnoi) from Uruguay, with comments on the systematics of Gondwanan ceratodontiforms  

Microsoft Academic Search

We describe herein the only known fossil dipnoans from Uruguay, recovered from continental deposits of Kimmeridgian–?early Cretaceous age (Batoví Member of the Tacuarembó Formation). The material includes several tooth plates referred herein to “Ceratodus” tiguidiensisTabaste, 1963 (the current generic assignment being either Arganodus or Asiatoceratodus), and one to Ceratodus africanusHaug, 1905. “C.” tiguidiensis was so far only recorded in the

Matías Soto; Daniel Perea

2010-01-01

69

Frond-like fossils from the base of the late Precambrian Wilpena Group, South Australia  

Microsoft Academic Search

Late Precambrian metazoan fossils are at present known from at least 23 different regions in Africa, Asia, Australia, Europe and North America1. The Ediacara fossil assemblage2,3 occurs widely in the Flinders Ranges, South Australia, near the base of the Rawnsley quartzite of the Pound Subgroup. This complex of soft-bodied organisms includes medusoid coelenterates, soft corals related to pennatulids, segmented worms,

Ian A. Dyson

1985-01-01

70

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

NASA Astrophysics Data System (ADS)

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.

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

2006-11-01

71

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

72

Plate tectonic trigger of changes in pCO 2 and climate in the Oxfordian (Late Jurassic): Carbon isotope and modeling evidence  

Microsoft Academic Search

The transition from the Middle to the Late Jurassic was characterized by significant changes in oceanography and climate and by changes in global carbon cycle as shown in the C-isotope record. A prominent mid-Oxfordian positive excursion in bulk carbonate carbon isotope values (?13Ccarb) with an amplitude of more than 1‰ has been documented from many sections in the Northern Tethys

Beat Louis-Schmid; Pauline Rais; Philippe Schaeffer; Stefano M. Bernasconi; Helmut Weissert

2007-01-01

73

Paleomagnetism of middle-late Jurassic sediments from Poland and implications for the polarity of the geomagnetic field  

NASA Astrophysics Data System (ADS)

Paleomagnetic data for the middle-late Jurassic sediments from nine localities of Krakow-Czestochowa Upland belonging to stable Europe and from three valleys of the Lower Subtatric Nappe belonging to mobile Europe are presented. The majority of the rocks investigated comprising limestones, stromatolites and radiolarites were found to be normally magnetized. Natural remanent magnetizations (NRM) of reversed polarity were found in limestones and stromatolites of middle Callovian age from the stable region and in one exposure of Oxfordian radiolarites from the mobile region. Along one of the middle Callovian sections studied the NRM direction of the specimens changed from R to N. The mean paleomagnetic pole positions obtained for the Krakow-Czestochowa Upland (lat. 72.3° N, long. 150.4°E, ? 95 = 7.3° and for the Lower Subtatric Nappe (lat. 71.7 N, long. 132.2° E, ? 95 = 4.3° ) are consistent with the data for stable Europe (lat. 74.7 °N, long. 147.1 °E, ? 95 = 5.0° ). The paleomagnetic results presented do not reveal any major relative rotations either within the Lower Subtatric Nappe or between this area and the Krakow-Czestochowa Upland. The reversed directions of NRM observed indicate the existence of a period of reversed field direction in the Middle Callovian and perhaps also in the Oxfordian.

Ka¸dzia?ko-Hofmokl, M.; Kruczyk, J.

1987-07-01

74

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

PubMed Central

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.

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

2012-01-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

76

Motion of Iberia since the Late Jurassic: Results from detailed aeromagnetic measurements in the Newfoundland Basin  

NASA Astrophysics Data System (ADS)

A detailed aeromagnetic survey carried out in the Newfoundland Basin shows well developed seafloor spreading anomalies 24 to 34. Comparison of these anomalies with the corresponding anomalies in the Northeast Atlantic suggests asymmetric spreading from anomalies 31 to 34, with slower spreading in the Newfoundland Basin. Anomaly M0 is a very weak anomaly in the Newfoundland Basin compared to south of the Newfoundland Fracture Zone where it forms a prominent low within the large amplitude "J" anomaly. A similar behaviour of this anomaly is observed off Iberia. In the Newfoundland Basin it does not continue as far as the Flemish Cap but terminates in the vicinity of the Newfoundland Seamounts. The position of this anomaly as obtained here differs from previous identifications. The shapes of magnetic lineations in the Newfoundland Basin are significantly different from the corresponding lineations off Iberia. This has been interpreted as arising from shifts in the plate boundary between Africa and Eurasia during the time when Iberia was moving as part of the African plate. By combining the present data with other detailed survey data to the north we have been able to derive a plate kinematic solution for Iberia which shows that from the middle Cretaceous to the Late Eocene Iberia moved as part of the African plate and then as an independent plate until the Late Oligocene. Since then it has been moving as part of the Eurasian plate. During these times the boundary between Eurasia and Africa jumped successively from the Bay of Biscay accretion axis to the King's Trough-North Spanish Trough lineament to the Azores-Gibraltar Fracture Zone. The kinematic solution for Iberia so derived, from chron M0 to the present, not only explains the formation of some prominent bathymetric features in the oceanic regions, such as King's Trough, but equally well the formation of geological features on land, such as the Pyrenees. The difficulties in deriving a kinematic solution for Iberia for times earlier than chron M0 are discussed and a speculative position of Iberia at the time of its initial separation from the Grand Banks of Newfoundland is proposed. Furthermore, with the availability of a well-constrained model for the motion of Iberia, it should now be possible to relate more accurately the relative motions among Eurasia, Iberia and Africa to the history of the Mediterranean region.

Srivastava, S. P.; Roest, W. R.; Kovacs, L. C.; Oakey, G.; Lévesque, S.; Verhoef, J.; Macnab, R.

1990-12-01

77

Fossils  

NSDL National Science Digital Library

Students discover the science of paleontology and the fossilization process. Why should we study fossils? Use your KWL chart to record information you have learned and anything else you want to know about. First read about the fossils of birds and what we learn from them. Then discover the Fossilization Process. Find out if there are still new dinosaurs to be discovered. Watch paleontologists hunt for ...

Tassihj

2009-10-21

78

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

PubMed Central

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.

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

2012-01-01

79

Giant fossil coelacanths of the Late Cretaceous in the eastern United States  

NASA Astrophysics Data System (ADS)

Remains of giant fossil coelacanth fish are relatively common in Upper Cretaceous strata (late Santonian to early Campanian age) in Alabama and Georgia. These are penecontemporaneous with the youngest reported fossil coelacanths from any global location and ˜135 m.y. younger than the last coelacanth fish reported from North America. A coelacanth coronoid fragment from New Jersey, apparently from the same taxon, is of latest Campanian or Maastrichtian age and is the youngest known definite coelacanth fossil. The species reconstructs to 3.5 m, which is as large as any known coelacanth. The name Megalocoelacanthus dobiei is proposed for this new coelacanth, which is also the last known member of the Glade that includes the extant Latimeria.

Schwimmer, David R.; Stewart, J. D.; Dent Williams, G.

1994-06-01

80

Fossils  

NSDL National Science Digital Library

4th Grade Science Standard 4: Students will understand how fossils are formed, where they may be found in Utah, and how they can be used to make inferences. DISCOVERING FOSSILS!!

81

The significance of dropstones in a tropical lacustrine setting, eastern Cameros Basin (Late Jurassic-Early Cretaceous, Spain)  

NASA Astrophysics Data System (ADS)

Outsized clasts (mainly white quartzite pebbles) are found in carbonate deposits of the Enciso Group exposed on the northern border of the Cameros rift basin (Late Jurassic-Early Cretaceous, northern Spain). In the Arnedillo section, all the stones are enclosed in micrite, which was assumed deposited in littoral to open lacustrine environments, with minor inputs of deltaic sandstones. The clasts are found in fine-grained lacustrine sediments either as isolated stones or as loosely packed elongated clusters occasionally associated with quartz sands and gravels. The mean size of the clasts is 40 mm (range: 3-100 mm); they are polished, well-rounded, and lack any faceting or striae. Lithology suggests that the clasts were potentially supplied by three stratigraphic formations cropping out in the catchment area of the Cameros lake. The occurrence of outsized stones within featureless micrite indicative of low-energy conditions involves a hydrodynamic paradox which can only be resolved by their vertical or oblique emplacement in the host sediment as dropstones. The lack of mass-flow deposits in the Enciso Group precludes gravitational processes and suggests deposition from a rafting agent. Icebergs and stone-swallowing animals are the main transport agents identified in continental settings. Here, stone swallowing is rejected as the transport mechanism because the stones are loosely packed and are never associated with skeletal remains. Ice rafting is also rejected because of the low density of clusters, and the absence of faceting and striations which characterize glacial sediments. Furthermore, the sub-tropical position of Iberia, the absence of surrounding high relief, and global climatic models for the Aptian corroborate the absence of a glaciolacustrine environment. Consequently, we propose wood rafting as an alternative depositional mechanism for dropstones in non-glacial lacustrine environments. Although no direct evidence has yet been found (i.e. stones enclosed in the roots of rafted woods), several data support our interpretation. First, the occurrence of isolated stones and loosely packed elongated clusters is consistent with the fall of single stones or the disintegration of clods embedded among tree roots. The occurrence of large rafted conifer trunks in lacustrine deposits of the Enciso Group indicates that they may have rafted small clusters of stones from the catchment area into the lake. If wood rafting is a possible depositional mechanism, the occurrence of dropstones is consequently not a sound criterion for inferring the existence of glacial conditions in lacustrine environments. The reliability of wood-rafted dropstones in lacustrine settings as an indicator of paleoclimate is also discussed.

Doublet, Stéfan; Garcia, Jean-Pierre

2004-01-01

82

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

Microsoft Academic Search

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

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

2007-01-01

83

An abelisauroid (Dinosauria: Theropoda) from the Early Jurassic of the High Atlas Mountains, Morocco, and the radiation of ceratosaurs  

Microsoft Academic Search

The fossil record of abelisauroid carnivorous dinosaurs was previously restricted to Cretaceous sediments of Gondwana and probably Europe. The discovery of an incomplete specimen of a new basal abelisauroid, Berberosaurus liassicus, gen. et sp. nov., is reported from the late Early Jurassic of Moroccan High Atlas Mountains. Phylogenetic analysis recovers Ceratosauroidea and Coelophysoidea as sister lineages within Ceratosauria, and Berberosaurus

Ronan Allain; Ronald Tykoski; Najat Aquesbi; Nour-Eddine Jalil; Michel Monbaron; Dale Russell; Philippe Taquet

2007-01-01

84

Contemporaneous trace and body fossils from a late Pleistocene Lakebed in Victoria, Australia, allow assessment of bias in the fossil record.  

PubMed

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

Camens, Aaron Bruce; Carey, Stephen Paul

2013-01-01

85

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

PubMed Central

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

Camens, Aaron Bruce; Carey, Stephen Paul

2013-01-01

86

Fossils  

NSDL National Science Digital Library

Paleontologists seldom have the good fortune to find a complete set of remains of an ancient organism that is wholly intact. For instance, the discovery of a frozen woolly mammoth carcass, preserved hair and all, was a truly rare event. More common are discoveries of incomplete remains, such as bones, teeth, or hair, and trace fossils, such as footprints or leaf impressions, which indicate an organism once existed even though its actual remains have not been found. This slide presentation reveals the variety of forms that fossils take, as well as examples of the kinds of life whose remains have been preserved. A background essay and discussion questions are included.

2011-05-17

87

Laramide Magmatism in the SW US as a Consequence of Lithospheric Thinning and Thermal Structure Created by Late Jurassic Continental Rifting  

NASA Astrophysics Data System (ADS)

Spatial and temporal patterns of Late Cretaceous-Early Cenozoic magmatism in Arizona, New Mexico, west Texas, and northern Mexico demonstrate that arc-like magmatism was prevalent up to 1000 km east of the Farallon-North America trench. Prior to the Late Cretaceous, Mesozoic magmatism was focused in the Sierra Nevada region, with widespread peraluminous intrusions throughout the Cordilleran interior. As early as 80 Ma, however, magmatism shifted far inboard and persisted as late as 50 Ma. Early models for this phenomenon relate an eastward sweep of magmatism to the progressively decreasing subduction angle of the Farallon plate. This model is no longer tenable, for several reasons. 1) Investigation of shallow-angle subduction worldwide demonstrates that magmatism ceases as the subduction angle decreases; modern shallow-angle subduction zones are nearly devoid of active volcanoes. 2) Thermochemical models for melting in subduction zones require both metasomatism of the mantle wedge by slab-derived fluids and convection of the hydrated mantle wedge downward until it reaches its solidus temperature. These processes are minimized or precluded by elimination of the mantle wedge during low-angle subduction. 3) Advances in the quality and quantity of geochronologic data suggest that the locus of magmatism shifted abruptly from near-trench to far inboard, rather than sweeping gradually eastward as previously thought. We propose that Laramide magmatism in the SW US and northern Mexico was not caused by subduction processes, although the igneous rocks have arc-like geochemical characteristics. Instead, we suggest that Laramide magmatism was controlled by the mantle structure inherited from the preceding tectonic event. During Late Jurassic time, southwestern North America experienced extension, resulting in the Border continental rift. The Border rift is defined by thick accumulations of fault-bounded alluvial and marine strata intercalated with rhyolitic ash-flow tuffs and asthenosphere-derived basalts. Border rift basalts have been documented in Kimmeridgian/Tithonian marine and terrigenous strata in the Chiricahua Mountains of SE AZ, in Upper Jurassic strata in the Little Hatchet Mountains of SW NM, and as allochthonous blocks in diapiric Upper Jurassic salts in the La Popa basin of NE Mexico. Because the paleogeographic extent of the Border rift coincides with the region of Laramide magmatism, we interpret Laramide magmatism as the result of dehydration of the Farallon slab and subsequent mantle melting as the slab entered hot asthenospheric mantle emplaced to shallow depths during Border rift extension. Partial melts of metasomatized mantle experienced crustal contamination during ascent, resulting in Laramide igneous rocks with continental arc-like geochemical signatures.

McMillan, N. J.; Lawton, T. F.; Cowee, C.

2003-12-01

88

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)

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.

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

2014-05-01

89

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

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.

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

2004-01-01

90

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

PubMed

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

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

2010-03-01

91

Central Appalachian Valley and Ridge Province Cenozoic igneous activity and its relation in space and time with the Late Jurassic rift-to-drift-related alkalic dikes  

NASA Astrophysics Data System (ADS)

A Swarm of Late Jurassic alkalic intrusions, geographically limited mainly to the Augusta County in western Virginia has been studied geochemically. These dykes were emplaced along a northwest-southeast cross-strike basement fracture zone during Mesozoic extension. However, not all igneous rocks in Virginia are Jurassic; published K-Ar ages already suggested an Eocene age activity around Monterey, VA. We systematically sampled and studied these rocks geochemically and used the Ar-Ar dating technique to define a more precise age for this youngest volcanic activity East of the Mississippi. The younger igneous bodies have traditionally been interpreted as intrusive bodies representing old plumbing systems of eroded volcanic centers. This hypothesis is based on studies of aphanitic to porphyritic and occasionally vesicular hard rocks from quarries and road cuts. Pyroclastic deposits have mainly been neglected during theses earlier studies. However additional petrographic studies of volcanic sediments are able to shed light not only on the volcanic nature of these pyroclastic rocks but also on eruption mechanisms and magma crust interactions. Our petrographic studies indicate that these volcanic sediments contain different clasts of igneous and sedimentary country rocks (sandstones and limestones of different formations), fresh glass shards and crystals of predominantly pyroxene, hornblende and micas. A previously unmapped, massive, m-thick andesitic pyroclastic deposit has been studied in detail to shed light on the formation of theses volcanic sediments. Field relations and observations (e.g. denser rock fragments are enriched in the lower part of the sequence and bedding is largely parallel to the present topography) are consistent with a massive welded ignimbrite. As a result, surface erosion after the eruption must be less significant than previously believed and some rocks are clearly volcanic in nature. Petrogenetically the Jurassic magmas are much more alkalic and particularly K-rich, and thus have all the characteristics of delamination magmas. This confirms that delamination seems a substantial process during the rift to drift transition. After Jurassic delamination of lithosphere below Virginia hot geochemically depleted asthenosphere was transformed into lithosphere by lithospherization. This newly formed lithosphere has later been the mantle source of the Cenozoic volcanic activity. As a result, the suggested geodynamic model is not only important to the petrology community but also to understand the local geomorphology, seismicity and presence of hot springs.

Meyer, R.; Schultz, L.; Hendriks, B. W.; Harbor, D. J.; Connors, C. D.

2011-12-01

92

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

SciTech Connect

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.

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

1996-01-01

93

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)

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.

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

2013-12-01

94

A paleomagnetic study from the Late Jurassic volcanics (155Ma), North China: Implications for the width of Mongol-Okhotsk Ocean  

NASA Astrophysics Data System (ADS)

Existing paleomagnetic studies have demonstrated that the North China Block (NCB) and Amuria(AMU) should have formed a single entity since the late Permian, and then as one block completed the collision with the South China Block (SCB) during the middle Jurassic to late Jurassic. Jurassic-Cretaceous collision of an amalgamated NCB-AMU with Siberia Block (SIB) is widely believed to have accompanied closure of a Mongolo-Okhotsk sea more than 800-1000 km north of the Yanshan Belt. However, the final amalgamation of this United East Asia Block (UEAB, including AMU, NCB and SCB) and the SIB is not well defined. A new paleomagnetic study has been carried out on the Tiaojishan Formation effusives in the Chengde area, North China Block (NCB). The age of the Tiaojishan Formation volcanics was recently dated from 153 Ma to 161 Ma by U-Pb and 40Ar-39Ar. A total of 154 samples from 16 sites within the Tiaojishan Formation was collected. Rock magnetic experiments are designed to identify the magnetic minerals within the rocks. Isothermal Remanent Magnetization (IRM) and three-axis thermal demagnetization of IRMs were conducted in the Paleomagnetic Laboratory of the Institute of Geomechanics in Beijing. Fields of 2.4 T, 0.4 T and 0.12 T were applied along the Z, Y and X axes of the specimens, respectively. Then, stepwise thermal demagnetization up to 680°C was performed. IRM were measured using the IM-10 impulse magnetizer and the JR-6 magnetometer. These experiments indicate that magnetite is the main magnetic carrier in the Tiaojishan Formation, but hematite probably exists in some parts of the rocks. All samples were subsequently subjected to progressive thermal demagnetization up to 600°C or 680°C in 12-14 steps using an ASC-Scientific TD-48 thermal demagnetizer with an interval residual field lower than 10 nT. The Natural Remanent Magnetization (NRM) were measured on a JR-6 spinner magnetometer due to their high NRM intensities. Detailed stepwise thermal demagnetization allows us to isolate two components from 77 oriented drill-core samples. A low-temperature component identified in most samples falls close to the present local Earth field direction. Characteristic remanent directions obtained from high-temperature pass-reversal test yield a pole position at 240.3°E, 59.9°N with ?95=6.8°. Combined with coeval paleopoles obtained from the Siberia Block (SIB), these results show a significant paleolatitude displacement between the NCB and SIB, which indicates that the Mongol-Okhotsk Ocean was still open with ~3000 km width in its eastern part at ca. 155 Ma.

Pei, J.; Sun, Z.; Liu, J.; Yang, Z.; Zhao, Y.

2011-12-01

95

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

USGS Publications Warehouse

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.

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

2009-01-01

96

A coral-microbialite patch reef from the late jurassic ( florigemma Bank, Oxfordian) of NW Germany (Süntel mountains)  

Microsoft Academic Search

Summary  Anin situ Oxfordian patch reef from the Süntel hills (florigemma-Bank, Korallenoolith, NW-Germany) is described. It is composed of an autochthonous reef core overlain by a ‘parautochthonous’\\u000a biostrome. The exposed reefal area amounts to about 20 m in lateral and up to 4 m in vertical direction. Nearly all major\\u000a marine reefal fossil associations from the Tethyal realm are present.\\u000a \\u000a In

Carsten Helm; Immo Schülke

1998-01-01

97

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

PubMed

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

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

98

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

Microsoft Academic Search

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

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

2003-01-01

99

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

PubMed Central

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.

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

100

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

Microsoft Academic Search

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,

Michal Kowalewski; Alfréd Dulai; Franz T. Fürsich

1998-01-01

101

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

102

Vitis seeds (Vitaceae) from the late Neogene Gray Fossil Site, northeastern Tennessee, U.S.A  

Microsoft Academic Search

This study focuses on morphometric and systematic analyses of the fossil Vitis seeds, recovered from the Gray Fossil Site (7–4.5Ma, latest Miocene–earliest Pliocene), northeastern Tennessee, U.S.A. A multivariate analysis based on eleven measured characters from 76 complete fossil seeds recognizes three morphotaxa. Further comparisons with both selected modern and fossil vitaceous specimens confirm that these morphotaxa represent three new species,

Fade Gong; Istvan Karsai

2010-01-01

103

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

NASA Astrophysics Data System (ADS)

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.

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

2008-08-01

104

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

PubMed Central

Paleontological work carried out over the last 3 decades has established that three major primate groups were present in the Eocene of Africa—anthropoids, adapiforms, and advanced strepsirrhines. Here we describe isolated teeth of a previously undocumented primate from the earliest late Eocene (?37 Ma) of northern Egypt, Nosmips aenigmaticus, whose phylogenetic placement within Primates is unclear. Nosmips is smaller than the sympatric adapiform Afradapis but is considerably larger than other primate taxa known from the same paleocommunity. The species bears an odd mosaic of dental features, combining enlarged, elongate, and molariform premolars with simple upper molars that lack hypocones. Phylogenetic analysis across a series of different assumption sets variously places Nosmips as a stem anthropoid, a nonadapiform stem strepsirrhine, or even among adapiforms. This phylogenetic instability suggests to us that Nosmips likely represents a highly specialized member of a previously undocumented, and presumably quite ancient, endemic African primate lineage, the subordinal affinities of which have been obscured by its striking dental autapomorphies. Discriminant functions based on measurements of lower molar size and topography reliably classify extant prosimian primates into their correct dietary groups and identify Nosmips and Afradapis as omnivores and folivores, respectively. Although Nosmips currently defies classification, this strange and unexpected fossil primate nevertheless provides additional evidence for high primate diversity in northern Africa ?37 million years ago and further underscores the fact that our understanding of early primate evolution on that continent remains highly incomplete.

Seiffert, Erik R.; Simons, Elwyn L.; Boyer, Doug M.; Perry, Jonathan M. G.; Ryan, Timothy M.; Sallam, Hesham M.

2010-01-01

105

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

SciTech Connect

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.

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

1993-04-01

106

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

Microsoft Academic Search

Neotropical rainforests have a very poor fossil record, making hypotheses concerning their origins difficult to evaluate. Never- theless, some of their most important characteristics can be pre- served 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

S. L. Wing; Fabiany Herrera; C. A. Jaramillo; Carolina Gomez-Navarro; P. Wilf; Conrad C. Labandeira

2009-01-01

107

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

SciTech Connect

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.

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

1993-04-01

108

Palaeogeography and relative sea-level history forcing eco-sedimentary contexts in Late Jurassic epicontinental shelves (Prebetic Zone, Betic Cordillera): An ecostratigraphic approach  

NASA Astrophysics Data System (ADS)

The analysis of macroinvertebrate and foraminiferal assemblages from Upper Jurassic (Middle Oxfordian to Lower Kimmeridgian) epicontinental shelf deposits in the Prebetic (Betic Cordillera, southern Spain) reveals the influence of environmental changes. They are expressed as selected parameters in palaeogeographic and stratigraphic trends (litho- and microfacies, faunal composition, taphonomy), which are interpreted in the context of relative sea-level histories. Middle Oxfordian to early Kimmeridgian (Transversarium to Planula Chrones) rocks and faunal assemblages in comparatively distal sectors (distal shelf) show lower sedimentation rates (lumpy lithofacies), and higher proportions of ammonoids, planktic foraminifera, corrasion degree, microboring and encrustation. Landwards, towards the mid-shelf, eco-sedimentary conditions resulted in spongiolithic limestones and marl-limestone rhythmites with local development of microbial-sponge buildups. Greater distance from shore during relative sea-level highs accords with greater: (1) stratigraphic condensation; (2) abundance in ammonoids, planktic foraminifera and nubeculariids; and (3) degrees of corrasion, microboring and encrustation. These trends in faunal composition and taphonomy agree with backstepping phases, increasing ecospace and a longer exposition of shelly remains on the sea bottom. Decreasing distance from shore during relative sea-level lows relates to opposite trends, as evidenced by: (4) increasing terrigenous input and decreasing stratigraphic condensation; (5) impoverishment in ammonoids and planktic foraminifera; and (6) diminution of corrasion, microboring and encrustation. Phases of forestepping/progradation and aggradation, a reduction of ecospace for nekto-planktic organisms, and comparatively rapid burial of shell remains are interpreted to force the recorded trends. An ecostratigraphic approach is used here to correlate and characterise sea-level changes, applying high resolution stratigraphy to sections where the identification of relevant surfaces is more difficult. The changes in distance from shore and ecospace, triggered by relative sea-level fluctuations, are considered prime factors forcing trade-offs in faunal communities of the studied fossil assemblages. Ecostratigraphy was used as a template for the characterization, correlation and interpretation of relative sea-levels and associated sedimentary packages in a time span from just above the Milankovitch band to the million-year scale.

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

2012-02-01

109

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

USGS Publications Warehouse

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.

Woodman, N.; Croft, D.A.

2005-01-01

110

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

PubMed

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

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

111

Recent synchronous radiation of a living fossil.  

PubMed

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

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

2011-11-11

112

The Pipe Creek Sinkhole Biota, a Diverse Late Tertiary Continental Fossil Assemblage from Grant County, Indiana  

Microsoft Academic Search

Quarrying in east-central Indiana has uncovered richly fossiliferous unconsol- idated 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

JAMES O. FARLOW; JACK A. SUNDERMAN; JONATHAN J. HAVENS; ANTHONY L. SWINEHART; J. ALAN HOLMAN; RONALD L. RICHARDS; NORTON G. MILLER; ROBERT A. MARTIN; ROBERT M. HUNT; GLENN W. STORRS; B. BRANDON CURRY; RICHARD H. FLUEGEMAN; MARY R. DAWSON; MARY E. T. FLINT

2001-01-01

113

New Data on the Late Neandertals: Direct Dating of the Belgian Spy Fossils  

Microsoft Academic Search

In Eurasia, the period between 40,000 and 30,000 BP saw the replacement of Neandertals by anatomically modern humans (AMH) during and after the Middle to Upper Paleolithic transition. The human fossil record for this period is very poorly defined with no overlap between Neandertals and AMH on the basis of direct dates. Four new 14 C dates were obtained on

Patrick Semal; Hélène Rougier; Isabelle Crevecoeur; Cécile Jungels; Damien Flas; Anne Hauzeur; Bruno Maureille; Mietje Germonpré; Hervé Bocherens; Stéphane Pirson; Laurence Cammaert; Nora De Clerck; Anne Hambucken; Thomas Higham; Michel Toussaint; Johannes van der Plicht

2009-01-01

114

First fossil Huttoniidae (Arthropoda: Chelicerata: Araneae) in late Cretaceous Canadian amber  

Microsoft Academic Search

The first fossils of the extant New Zealand spider family Huttoniidae are described from Cretaceous (Campanian) amber from Alberta and Manitoba, Canada. The specimens are juveniles and poorly preserved, but the following combination of characters permits identification as huttoniids: general habitus, carapace without a raised cephalic region or fovea, eight eyes in two rows of four, three-clawed tarsus (with tiny

David Penney; Paul A. Selden

2006-01-01

115

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

Microsoft Academic Search

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

Zhong-Wu Lan; Zhong-Qiang Chen

116

Molecular Fossil Record of Elevated Methane Levels in Late Pleistocene Coastal Waters  

Microsoft Academic Search

Accumulating evidence suggests that methane has been released episodically from hydrates trapped in sea floor sediments during many intervals of rapid climate warming. Here we show that sediments from the Santa Barbara Basin deposited during warm intervals in the last glacial period contain molecular fossils that are diagnostic of aerobic and anaerobic methanotrophs. Sediment intervals with high abundances of these

Kai-Uwe Hinrichs; Laura R. Hmelo; Sean P. Sylva

2003-01-01

117

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

USGS Publications Warehouse

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.

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

2009-01-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

119

Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf  

NASA Astrophysics Data System (ADS)

We evaluate the available palaeontological and geochemical proxy data from bivalves, bryozoans, silicoflagellates, diatoms and cetaceans for sea surface temperature (SST) regimes around the nearshore Antarctic coast during the late Neogene. These fossils can be found in a number of shallow marine sedimentary settings from three regions of the Antarctic continent, the northern Antarctic Peninsula, the Prydz Bay region and the western Ross Sea. Many of the proxies suggest maximum spring-summer SSTs that are warmer than present by up to 5 °C, which would result in reduced seasonal sea ice. The evidence suggests that the summers on the Antarctic shelf during the late Neogene experienced most of the warming, while winter SSTs were little changed from present. Feedbacks from changes in summer sea ice cover may have driven much of the late Neogene ocean warming seen in stratigraphic records. Synthesized late Neogene and earliest Quaternary Antarctic shelf proxy data are compared to the multi-model SST estimates of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Despite the fragmentary geographical and temporal context for the SST data, comparisons between the SST warming in each of the three regions represented in the marine palaeontological record of the Antarctic shelf and the PlioMIP climate simulations show a good concordance.

Clark, Nicola A.; Williams, Mark; Hill, Daniel J.; Quilty, Patrick G.; Smellie, John L.; Zalasiewicz, Jan; Leng, Melanie J.; Ellis, Michael A.

2013-08-01

120

Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf.  

PubMed

We evaluate the available palaeontological and geochemical proxy data from bivalves, bryozoans, silicoflagellates, diatoms and cetaceans for sea surface temperature (SST) regimes around the nearshore Antarctic coast during the late Neogene. These fossils can be found in a number of shallow marine sedimentary settings from three regions of the Antarctic continent, the northern Antarctic Peninsula, the Prydz Bay region and the western Ross Sea. Many of the proxies suggest maximum spring-summer SSTs that are warmer than present by up to 5 °C, which would result in reduced seasonal sea ice. The evidence suggests that the summers on the Antarctic shelf during the late Neogene experienced most of the warming, while winter SSTs were little changed from present. Feedbacks from changes in summer sea ice cover may have driven much of the late Neogene ocean warming seen in stratigraphic records. Synthesized late Neogene and earliest Quaternary Antarctic shelf proxy data are compared to the multi-model SST estimates of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Despite the fragmentary geographical and temporal context for the SST data, comparisons between the SST warming in each of the three regions represented in the marine palaeontological record of the Antarctic shelf and the PlioMIP climate simulations show a good concordance. PMID:23828612

Clark, Nicola A; Williams, Mark; Hill, Daniel J; Quilty, Patrick G; Smellie, John L; Zalasiewicz, Jan; Leng, Melanie J; Ellis, Michael A

2013-08-01

121

New data on the late Neandertals: direct dating of the Belgian Spy fossils.  

PubMed

In Eurasia, the period between 40,000 and 30,000 BP saw the replacement of Neandertals by anatomically modern humans (AMH) during and after the Middle to Upper Paleolithic transition. The human fossil record for this period is very poorly defined with no overlap between Neandertals and AMH on the basis of direct dates. Four new (14)C dates were obtained on the two adult Neandertals from Spy (Belgium). The results show that Neandertals survived to at least approximately 36,000 BP in Belgium and that the Spy fossils may be associated to the Lincombian-Ranisian-Jerzmanowician, a transitional techno-complex defined in northwest Europe and recognized in the Spy collections. The new data suggest that hypotheses other than Neandertal acculturation by AMH may be considered in this part of Europe. PMID:19003923

Semal, Patrick; Rougier, Hélène; Crevecoeur, Isabelle; Jungels, Cécile; Flas, Damien; Hauzeur, Anne; Maureille, Bruno; Germonpré, Mietje; Bocherens, Hervé; Pirson, Stéphane; Cammaert, Laurence; De Clerck, Nora; Hambucken, Anne; Higham, Thomas; Toussaint, Michel; van der Plicht, Johannes

2009-04-01

122

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

PubMed

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

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

2009-11-01

123

Late Pleistocene Climates of Beringia, Based on Analysis of Fossil Beetles  

Microsoft Academic Search

Thirty-one fossil beetle assemblages from central and eastern Beringia (Alaska, the Yukon Territory, and the now-submerged Bering Land Bridge) have yielded seasonal temperature estimates for the interval 43,550–9250 14C yr before present (yr B.P.). Estimates of the mean temperature of the warmest (TMAX) and coldest (TMIN) months were derived by the Mutual Climatic Range method. Assemblages from northern and western

Scott A. Elias

2000-01-01

124

NEW LATE MIOCENE ELEPHANTOID (MAMMALIA: PROBOSCIDEA) FOSSILS FROM LEMUDONG'O, KENYA  

Microsoft Academic Search

The late Miocene marked a time of significant geographic dispersal and radiation for many mammalian taxa within Africa, including the proboscidean lineages. The ,6.1 Ma site of Lemudong'o, Kenya, yielded two elephantoid specimens. The first is a mandibular fragment with the third molar. This specimen represents a primitive member of the Anancus kenyensis lineage, with similarities to a specimen from

HARUO SAEGUSA; LESLEA J. HLUSKO

125

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)

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).

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

2013-05-01

126

Two new fossil vertebrate localities in the Santa Cruz Formation (late early early middle Miocene, Argentina), ˜51° South latitude  

NASA Astrophysics Data System (ADS)

Two new fossil vertebrate localities are described from the Santa Cruz Formation (late early - early middle Miocene) of coastal Patagonia. They are noteworthy because they are the lowest stratigraphically of any precisely recorded in coastal Santa Cruz Province and they contain a rich fauna including many partially articulated skeletons undisturbed by collecting. Thus, they offer the potential for taphonomic analysis and paleocommunity reconstruction. The latter is particularly intriguing because the fauna document the Miocene Climatic Optimum at >51° South latitude. Together with several previously documented sites in this region, it offers a potential window into the nature of mammalian communities farther south than any other in the world during this time and documents the farthest south distribution of primates.

Kay, Richard F.; Vizcaíno, Sergio F.; Bargo, M. Susana; Perry, Jonathan M. G.; Prevosti, Francisco J.; Fernicola, Juan Carlos

2008-03-01

127

New data on Late Vendian problematic fossils from the genus Harlaniella  

NASA Astrophysics Data System (ADS)

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.

Ivantsov, A. Yu.

2013-11-01

128

Mass mutations of insects at the Jurassic\\/Cretaceous boundary?  

Microsoft Academic Search

Diverse fossil insect assemblages near the Jurassic\\/ Cretaceous transition from the Shar-Teg in Mongolia comprise frequent deformed species. These (first known) mass fossil animal deformities, expressed as fusions of veins changing the wing geometry, probably represent heritable mutations. They accumulated as a result of a changed structure of selective pressure, and are unique in showing how individual variations may be

PETER VRŠANSKÝ

2005-01-01

129

Late Pleistocene Climates of Beringia, Based on Analysis of Fossil Beetles  

NASA Astrophysics Data System (ADS)

Thirty-one fossil beetle assemblages from central and eastern Beringia (Alaska, the Yukon Territory, and the now-submerged Bering Land Bridge) have yielded seasonal temperature estimates for the interval 43,550-9250 14C yr before present (yr B.P.). Estimates of the mean temperature of the warmest (TMAX) and coldest (TMIN) months were derived by the Mutual Climatic Range method. Assemblages from northern and western sites show a mid-Wisconsin interstadial TMAX warming from 35,000-30,000 yr B.P.; this warming is less pronounced in assemblages for interior regions. There is little or no beetle evidence for the spread of coniferous forest in eastern Beringia during this interstade, except for in parts of the Yukon Territory. During the last glacial maximum TMAX values were depressed by about 2°-2.5°C in Arctic regions of Beringia, and by about 4°C in the interior; TMIN values were about 8°C colder in both regions. TMAX and TMIN values rose rapidly at northern sites after 12,000 yr B.P. Seasonal temperatures peaked at 11,000 yr B.P., just as the Bering Land Bridge was inundated. This was followed by a sharp climatic cooling between 11,000 and 10,000 yr B.P., the equivalent of a Younger Dryas cooling in eastern Beringia.

Elias, Scott A.

2000-03-01

130

Geodynamic Implications of Jurassic Ophiolites Associated with Island-Arc Volcanics, South Apuseni Mountains, Western Romania  

Microsoft Academic Search

The South Apuseni Mountains are located in the inner zone of the Carpathian belt. This area is characterized by a complex assemblage of nappes, in which Jurassic igneous associations are well represented. New geological and geochemical data on these igneous associations document the occurrence of Middle Jurassic ophiolites overlain by Late Jurassic calc-alkaline volcanic rocks.The ophiolite sequence is characterized by:

Valerio Bortolotti; Michele Marroni; Ionel Nicolae; Luca Pandolfi; Gianfranco Principi; Emilio Saccani

2002-01-01

131

Charcoal and fossil wood from palaeosols, sediments and artificial structures indicating Late Holocene woodland decline in southern Tibet (China)  

NASA Astrophysics Data System (ADS)

Charcoal and fossil wood taken from palaeosols, sediments and artificial structures were analysed in order to evaluate the regional pedoanthracological potential and to obtain information on Holocene environmental changes, particularly on possible past tree occurrences in southern Tibet. This research was initiated by the question to what extent this area is influenced by past human impact. Even recent evaluations have perceived the present treeless desertic environment of southern Tibet as natural, and the previous Holocene palaeoenvironmental changes detected were predominantly interpreted to be climate-determined. The material analysed - comprising a total of 53 botanical spectra and 55 radiocarbon datings from 46 sampling sites (c. 3500-4700 m a.s.l.) - represents the largest systematically obtained data set of charcoal available from Tibet so far. 27 taxa were determined comprising trees, (dwarf-) shrubs and herbs as well as grasses. The predominant tree taxa were Juniperus, Hippophae, Salix and Betula. According to their present-day occurrence in the region, the genera Juniperus and Hippophae can be explicitly attributed to tree species. Further, less frequently detected tree taxa were Populus, Pinus, Quercus, Taxus and Pseudotsuga. Charcoal of Juniperus mainly occurred on southern exposures, whereas Betula was associated with northern exposures. In contrast, the (partly) phreatophytic taxa Hippophae and Salix showed no prevalent orientation. The distribution of radiocarbon ages on charcoal revealed a discontinuous record of burning events cumulating in the Late Holocene (c. 5700-0 cal BP). For southern Tibet, these results indicated a Late Holocene vegetation change from woodlands to the present desertic pastures. As agrarian economies in southern and south-eastern Tibet date back to c. 3700 and 5700 cal BP, respectively, and the present-day climate is suitable for tree growth up to c. 4600 m a.s.l., we concluded that the Late Holocene loss or thinning out of woodlands had been primarily caused by humans.

Kaiser, Knut; Opgenoorth, Lars; Schoch, Werner H.; Miehe, Georg

2009-07-01

132

2D Geochemical Characterisation of Late Carboniferous Concretions: Constraints for 3D Fossil Preservation  

NASA Astrophysics Data System (ADS)

Because of their potential to perfectly preserve fossils in three dimensions, concretions and nodules from various stratigraphic positions and different geological settings have been the subject of intense investigations in the past. The results of these studies aided to elucidate the fine- and ultrastructure of fossilised materials, and gave detailed insights into the anatomy of many plants and animals of the geological past. Nodules have been described as concretionary bodies which are formed by the precipitation of authigenic minerals. They are sometimes monomineralic and homogenous, but polymineralic nodules are characterised by concentric zones of different mineralogical compositions (such as chert, barite, phosphates or manganiferous ores) around a mostly biogenic core. Several factors have been recognised which are thought to play an important role for the formation of nodules. These include [1] the availability of nucleating materials, [2] presence of metals in the water column and sediment, [3] favourable tectonic and physiographic features, [4] favourable sediment-water interface, [5] low rate of sedimentation, [6] presence of nutrient rich bottom water mass and [7] an oxidizing/reducing environment. Up to now, no consistent generic model has been proposed to address the complex geochemical interactions between these factors in the course of nodule formation. With the aim, to describe the different geochemical reactions that lead to nodule generation and hence fossil preservation, a ferromanganese nodule was extracted from the Upper Carboniferous sequences at Broadhaven, Pembrokshire, UK. The geology of this area consists of cyclothems, which contain cyclic sequences of limestones, sandstones and shales. Within this sequence, the nodules are located in the shale beds. The extracted ferromanganese nodule was cut in half using a diamond rock saw and is 7.1 cm in height and 9.8 cm in width. For the analysis of major and trace elements a Niton XL3t X-ray fluorescence instrument was used. A grid of 3mm by 3mm was then drawn onto the cut surface of the nodule in graphite pencil. A graphite pencil was chosen as graphite (Carbon) is too light to interfere with the incident x-ray beam of the XRF. A total of 1052 data points produced by this grid formed the points at which the XRF analysis was undertaken. Elements analysed were Ag, Al, As, Ba, Ca, Cl, Cd, Cr, Cs, Cu, Fe, Hg, K, Mn, Nb, Ni, P, Pd, Rb, S, Sb, Sc, Se, Si, Sn, Sr, Te, Th, Ti, U, V, Zn and Zr. This geochemical data has been modelled into 2D contour maps and 3D elevation models which have shown significant and systematic enrichments (Ag, As, Ba, Ca, Cd, Cr, Cs, Fe, Hg, Mn, Ni, P, S, Sb, Si, Sn, Sr, Te, Th, U, V, Zn) and depletions (Al, Cl, Cu, K, Nb, Pd, Rb, Sc, Se, Ti, Zr) of elements across the extent of the nodule. The geochemical data obtained were used to establish the types of geochemical reduction/oxidation-reactions that were involved during the formation of the nodule. A new model, based on non-linear disequilibrium quasi-Belousov-Zhabotinsky reactions, for nodule formation is presented and will be discussed.

Howell, C. P.; Montenari, M.

2012-04-01

133

Identification of organic matter sources in sulfidic late Holocene Antarctic fjord sediments from fossil rDNA sequence analysis  

NASA Astrophysics Data System (ADS)

The 18S ribosomal DNA (rDNA) isolated from sulfidic Holocene sediments and particulate organic matter in the water column of the stratified Small Meromictic Basin (SMB) in Ellis Fjord (eastern Antarctica) was analyzed to identify possible biological sources of organic matter. Previous work had shown that the sediments contained numerous diatom frustules and high contents of a highly branched isoprenoid (HBI) C25:2 alkene (which is a specific biomarker of certain species of the diatom genera Navicula, Haslea, Pleurosigma, or Rhizosolenia), so we focused our search on preserved fossil 18S rDNA of diatoms using sensitive polymerase chain reaction (PCR) approaches. We did not find diatom-derived fossil 18S rDNA using general eukaryotic primers, and even when we used primers selective for diatom 18S rDNA, we only identified a Chaetoceros phylotype, which is known to form cysts in the SMB but is not a likely source of the C25:2 HBI. When we used PCR/denaturing gradient gel electrophoresis methods specific to phylotypes within the HBI-biosynthesizing genera, we were able to identify three phylotypes in the sediments related to HBI-producing strains of the genera Haslea and Navicula. The ancient DNA data thus provided a limited, but valuable, view of the diversity of late Holocene primary producers with a particular bias to specific components of the biota that were better preserved such as the Chaetoceros cysts. This use of paleogenetics also revealed unexpected possible sources of organic matter such as novel stramenopiles for which no specific lipid biomarkers are known and thus would not have been identified based on traditional lipid stratigraphy alone.

Coolen, Marco J. L.; Volkman, John K.; Abbas, Ben; Muyzer, Gerard; Schouten, Stefan; Sinninghe Damsté, Jaap S.

2007-06-01

134

A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah  

PubMed Central

Background Basal sauropodomorphs, or ‘prosauropods,’ are a globally widespread paraphyletic assemblage of terrestrial herbivorous dinosaurs from the Late Triassic and Early Jurassic. In contrast to several other landmasses, the North American record of sauropodomorphs during this time interval remains sparse, limited to Early Jurassic occurrences of a single well-known taxon from eastern North America and several fragmentary specimens from western North America. Methodology/Principal Findings On the basis of a partial skeleton, we describe here a new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah, Seitaad ruessi gen. et sp. nov. The partially articulated skeleton of Seitaad was likely buried post-mortem in the base of a collapsed dune foreset. The new taxon is characterized by a plate-like medial process of the scapula, a prominent proximal expansion of the deltopectoral crest of the humerus, a strongly inclined distal articular surface of the radius, and a proximally and laterally hypertrophied proximal metacarpal I. Conclusions/Significance Phylogenetic analysis recovers Seitaad as a derived basal sauropodomorph closely related to plateosaurid or massospondylid ‘prosauropods’ and its presence in western North America is not unexpected for a member of this highly cosmopolitan clade. This occurrence represents one of the most complete vertebrate body fossil specimens yet recovered from the Navajo Sandstone and one of the few basal sauropodomorph taxa currently known from North America.

Sertich, Joseph J. W.; Loewen, Mark A.

2010-01-01

135

Transitional fossil earwigs - a missing link in Dermaptera evolution  

PubMed Central

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.

2010-01-01

136

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

137

An overview of the dinosaur fossil record from Chile  

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

138

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

Microsoft Academic Search

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

N. L. Baghai; R. B. Jorstad

1995-01-01

139

First fossil record of Alphonsea Hk. f. & T. (Annonaceae) from the Late Oligocene sediments of Assam, India and comments on its phytogeography.  

PubMed

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

Srivastava, Gaurav; Mehrotra, Rakesh C

2013-01-01

140

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

PubMed Central

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

Srivastava, Gaurav; Mehrotra, Rakesh C.

2013-01-01

141

Tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau, USA  

Microsoft Academic Search

Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic–Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point

Spencer G. Lucas; Lawrence H. Tanner

2007-01-01

142

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

NASA Astrophysics Data System (ADS)

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

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

1987-08-01

143

Jurassic Park Safety Audit  

NSDL National Science Digital Library

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

2007-09-18

144

New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic-Cretaceous Boundary  

PubMed Central

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.

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

2012-01-01

145

Triassic and Jurassic structural development along the Tornquist Zone, Denmark  

NASA Astrophysics Data System (ADS)

In the Danish area the old crustal weakness zone, the Tornquist Zone, was repeatedly reactivated during the Triassic and Jurassic/Early Cretaceous, causing minor dextral movements along the major boundary faults. These tectonic events were minor as compared to the tectonic events of the Late Carboniferous/Early Permian and the Late Cretaceous/Early Tertiary, although a dynamic structural and stratigraphical analysis indicate that the zone was highly active compared to the surrounding areas. During the Middle to Late Permian the area was exposed to erosion and became a peneplane. A regional Triassic subsidence produces seismic onlap towards the northeast, where the youngest Triassic sediment is found, supercropping the Precambrian basement. During mainly the Early Triassic, several of the major Early Permian faults became reactivated, probably with dextral strike-slip along the Børglum Fault. The Jurassic-Early Cretaceous subsidence became restricted primarily to the area between the two main faults in the Tornquist Zone, the Grenå-Helsingborg Fault and the Børglum Fault. This restricted basin development indicates a change in the regional stress field that seems to have come into existence during the transition between the Triassic and the Jurassic. The subsidence in the Middle Jurassic and the Late Jurassic-Early Cretaceous follows the Early Jurassic pattern with local subsidence in the Tornquist Zone, but even more restricted to the zone. The subsidence seems to have decreased in the Middle Jurassic; hereafter subsidence increased again during Late Jurassic/Early Cretaceous times. A set of small faults were generated during the Mesozoic internally in the Tornquist Zone. This fault pattern indicates a broad transfer of strike-slip/oblique-slip motion from the Grenå-Helsingborg Fault to the Børglum Fault.

Mogensen, Tommy E.

1995-12-01

146

Fossil Halls: Timelines  

NSDL National Science Digital Library

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

147

Skull of a Jurassic ankylosaur (Dinosauria)  

Microsoft Academic Search

The origin and early evolution of many major dinosaur groups are poorly known because specimens are rare. One of these groups, the Ankylosauria, or armour-plated dinosaurs, is best known from well-preserved specimens from the Upper Cretaceous period of Asia and North America. Here we describe a well-preserved skull of an earlier, Late Jurassic ankylosaur, which will be important in clarifying

Kenneth Carpenter; Clifford Miles; Karen Cloward

1998-01-01

148

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)

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.

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

2013-12-01

149

Early to Middle Jurassic palaeoenvironmental changes: High resolution ?13C and ?18O records from the UK  

NASA Astrophysics Data System (ADS)

Low-Mg-calcite fossils, such as bivalves, belemnites and brachiopods, and bulk rocks have been extensively utilized to reconstruct past seawater chemistry and paleoenviron¬mental changes. Recent work on major bioevents demonstrated that particularly higher resolution stable isotope records are necessary to reveal short-term paleoenviron¬mental fluctuations and, in addition, to discover its causes. Here we present a new high resolution carbon and oxygen isotope dataset generated from low-Mg-calcite fossils, fossil wood and bulk rocks collected from Early to Middle Jurassic marine successions of the UK. In addition to the well know carbon isotope fluctuations across the Toarcian Oceanic Anoxic Event (OAE), further ?13C perturbations have been obtained from the analyzed samples: (1) a positive trend in the earliest Sinemurian (Conybeari zone), negative excursions in the (2) Sinemurian Bucklandi zone and (3) at the Sinemurian-Pliensbachian boundary (upper raricostatum and lower jamesoni zones), and (4) a positive excursion in the Late Pliensbachian margaritatus zone. At the Sinemurian-Pliensbachian boundary a positive ?18O shift occurs during the negative ?13C excursion, suggesting most likely bottom water cooling as a result of the Early Pliensbachian transgression. Two additional cooling events, (1) in the Late Pliensbachian and (2) during the Aalenian-Bajocian, are discovered by positive oxygen isotope trends. The cool Late Pliensbachian shallow sea-floor is in agreement with previous inference of partial icehouse conditions at that time. More uncertain are potential icehouse interludes during the Aalenian-Bajocian interval. The new isotope datasets show partly a strong similarity between the positions of the global warming/cooling events within transgressive/regressive phases of second-order depositional sequences though the Early to Middle Juras¬sic supporting the idea that second-order depositional se¬quences are a result of eustatic sea-level changes at that time.

Korte, C.; Hesselbo, S.; Ullmann, C. V.; Ruhl, M.; Thibault, N.

2013-12-01

150

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

Microsoft Academic Search

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

Matthew C. Mihlbachler

2003-01-01

151

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

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.

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

1995-10-01

152

New stratigraphic markers in the late Pleistocene Palouse loess: novel fossil gastropods, absolute age constraints and non-aeolian facies  

Microsoft Academic Search

Four stratigraphic sections in the southern part of the Columbia Basin preserve a sequence of aeolian and non-aeolian sediments ranging in age from 9Æ43 to >47Æ0 14C ka based on accelerator mass spectrometry radiocarbon dating of fossil molluscs, geochemistry of Cascade Mountain-sourced tephra and association with formally recognized pedostratigraphic units (the Washtucna and Old Maid Coulee soils). Study sections are

PATRICK K. S PENCER; NGELA N. KNAPP; Nick Eyles

2009-01-01

153

Jurassic mimicry between a hangingfly and a ginkgo from China  

PubMed Central

A near-perfect mimetic association between a mecopteran insect species and a ginkgoalean plant species from the late Middle Jurassic of northeastern China recently has been discovered. The association stems from a case of mixed identity between a particular plant and an insect in the laboratory and the field. This confusion is explained as a case of leaf mimesis, wherein the appearance of the multilobed leaf of Yimaia capituliformis (the ginkgoalean model) was accurately replicated by the wings and abdomen of the cimbrophlebiid Juracimbrophlebia ginkgofolia (the hangingfly mimic). Our results suggest that hangingflies developed leaf mimesis either as an antipredator avoidance device or possibly as a predatory strategy to provide an antiherbivore function for its plant hosts, thus gaining mutual benefit for both the hangingfly and the ginkgo species. This documentation of mimesis is a rare occasion whereby exquisitely preserved, co-occurring fossils occupy a narrow spatiotemporal window that reveal likely reciprocal mechanisms which plants and insects provide mutual defensive support during their preangiospermous evolutionary histories.

Wang, Yongjie; Labandeira, Conrad C.; Shih, Chungkun; Ding, Qiaoling; Wang, Chen; Zhao, Yunyun; Ren, Dong

2012-01-01

154

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

Microsoft Academic Search

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

Diego M. Guido; Kathleen A. Campbell

2011-01-01

155

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

Microsoft Academic Search

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

GAO Ke-Qin; REN Dong

156

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

157

Palaeo-climatic information from isotopic signatures of fossil teeth in Late Pleistocene from Arkoudospilia Cave (Aridea, N. Greece)  

NASA Astrophysics Data System (ADS)

The O and C isotopic composition of enamel carbonate hydroxy-apatite in the teeth of certain animals reflects the oxygen isotope composition of the water they ingest. The isotopic composition of meteoric water is well-correlated with mean annual temperature so that there is potential for recovering palaeo-temperature of the regions where the animals lived. Analyses were made on enamel from fossil teeth of Ursus Ingressus from Arkoudospilia Cave in Northern Greece. Analyses were made also on modern teeth of Ursus from different areas in Greece. Oxygen and deuterium isotopic analyses of water were also made. Although the preservation of primary oxygen isotopic composition of enamel carbonate hydroxy-apatite was more difficult to assess, however the isotopic signals seem to have utility for the paleoenvironmental reconstructions of the studied area.

Dotsika, Elissavet; Tsoukala, Evangelia; Zisi, Nikoleta; Poutoukis, Dimitrios; Psomiadis, David

2010-05-01

158

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

PubMed Central

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.

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

1984-01-01

159

The role of true polar wander on the Jurassic palaeoclimate  

NASA Astrophysics Data System (ADS)

From the Late Carboniferous until the Middle Jurassic, continents were assembled in a quasi-rigid supercontinent called Pangea. The first palaeomagnetic data of South America indicated that the continent remained stationary in similar present-day latitudes during most of the Mesozoic and even the Palaeozoic. However, new palaeomagnetic data suggest that such a scenario is not likely, at least for the Jurassic. In order to test the stationary versus the dynamic-continent model, we studied the Jurassic apparent polar wander paths of the major continents, that is, Eurasia, Africa and North America that all in all show the same shape and chronology of the tracks with respect to those from South America. We thus present a master path that could be useful for the Jurassic Pangea. One of the most remarkable features observed in the path is the change in pole positions at ~197 Ma (Early Jurassic), which denotes the cessation of the counter-clockwise rotation of Pangea and commencement of a clockwise rotation that brought about changes in palaeolatitude and orientation until the end of the Early Jurassic (185 Ma). Here, we analyse a number of phenomena that could have triggered the polar shift between 197 and 185 Ma and conclude that true polar wander is the most likely. In order to do this, we used Morgan's (Tectonophysics 94:123-139, 1983) grid of hotspots and performed "absolute" palaeogeographical reconstructions of Pangea for the Late Triassic and Jurassic. The palaeolatitudes changes that we observe from our palaeomagnetic data are very well sustained by diverse palaeoclimatic proxies derived from geological and palaeoecological data at this time of both the southern and northern hemispheres.

Iglesia Llanos, María Paula; Prezzi, Claudia Beatriz

2013-04-01

160

Early Jurassic black shales: Global anoxia or regional "Dead Zones"?  

NASA Astrophysics Data System (ADS)

The so-called "Schwarzer Jura" or "Black Jurassic" in Germany is informally used to designate a series of organic-rich sediments that roughly span the Early Jurassic (201.6 - 175.6 Myr), and which culminate in the Toarcian Oceanic Anoxic Event. Based on organic and inorganic geochemical as well as (micro)palaeontological data from several recently drilled cores, black shales deposited directly following the end-Triassic extinction (201.6 Ma) during the Hettangian are extremely similar to Toarcian black shales. Both events are characterized by laminated black shales that contain high amounts of the biomarker isorenieratane, a fossilized pigment derived from green sulphur bacteria. Furthermore, the two intervals show similar changes in phytoplankton assemblages from chromophyte (red) to chlorophyte (green) algae. Combined, the evidence suggests that photic zone euxinia developed repeatedly during the Early Jurassic, making wide swaths of shelf area inhospitable to benthic life. In the oceans today such areas are called "Dead Zones" and they are increasing in number and extent due to the combined effects of man-made eutrophication and global warming. During the Early Jurassic, regional anoxic events developed in response to flood basalt volcanism, which triggered global warming, increased run-off, and changes in ocean circulation. The patchiness of Early Jurassic anoxia allows comparisons to be made with present-day "Dead Zones", while at the same time ocean de-oxygenation in the past may serve to predict future perturbations in the Earth system.

van de Schootbrugge, B.; Payne, J.; Wignall, P.

2012-12-01

161

Jurassic hydrocarbon exploration of southern Florida  

SciTech Connect

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.

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

1994-09-01

162

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

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.

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

2011-01-01

163

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

164

New method to estimate paleoprecipitation using fossil amphibians and reptiles and the middle and late Miocene precipitation gradients in Europe  

NASA Astrophysics Data System (ADS)

Existing methods for determining paleoprecipitation are subject to large errors (±350 400 mm or more using mammalian proxies), or are restricted to wet climate systems due to their strong facies dependence (paleobotanical proxies). Here we describe a new paleoprecipitation tool based on an indexing of ecophysiological groups within herpetological communities. In recent communities these indices show a highly significant correlation to annual precipitation (r2 = 0.88), and yield paleoprecipitation estimates with average errors of ±250 280 mm. The approach was validated by comparison with published paleoprecipitation estimates from other methods. The method expands the application of paleoprecipitation tools to dry climate systems and in this way contributes to the establishment of a more comprehensive paleoprecipitation database. This method is applied to two high-resolution time intervals from the European Neogene: the early middle Miocene (early Langhian) and the early late Miocene (early Tortonian). The results indicate that both periods show significant meridional precipitation gradients in Europe, these being stronger in the early Langhian (threefold decrease toward the south) than in the early Tortonian (twofold decrease toward the south). This pattern indicates a strengthening of climatic belts during the middle Miocene climatic optimum due to Southern Hemisphere cooling and an increased contribution of Arctic low-pressure cells to the precipitation from the late Miocene onward due to Northern Hemisphere cooling.

Böhme, M.; Ilg, A.; Ossig, A.; Küchenhoff, H.

2006-06-01

165

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

SciTech Connect

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.

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

1990-05-01

166

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)

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.

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

2012-04-01

167

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)

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.

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

2011-10-01

168

Jurassic faults of southwest Alabama and offshore areas  

SciTech Connect

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.

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

1991-03-01

169

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

PubMed Central

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

Toljagic, Olja; Butler, Richard J.

2013-01-01

170

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

PubMed

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

Toljagic, Olja; Butler, Richard J

2013-06-23

171

Jurassic Park: Adventure in Learning.  

ERIC Educational Resources Information Center

Describes using the movie "Jurassic Park" as a foundation for a middle school interdisciplinary unit involving science, math, language arts, history, and geography. Suggested books and activities are presented. (PR)

Shams, Marcia; Boteler, Trina

1993-01-01

172

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

Microsoft Academic Search

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

Yildirim Dilek; Peter Thy; Eldridge M. Moores

1991-01-01

173

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

PubMed Central

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

Guinot, Guillaume; Adnet, Sylvain; Cappetta, Henri

2012-01-01

174

JURASSIC Retrieval Processing  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

175

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

176

Shallow marine carbon and oxygen isotope and elemental records indicate icehouse-greenhouse cycles during the Early Jurassic  

NASA Astrophysics Data System (ADS)

For much of the Mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences. We present a carbon and oxygen isotope and elemental record for part of the Early Jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the Cleveland Basin, UK. The invertebrate isotope record is supplemented with carbon isotope data from fossil wood, which samples atmospheric carbon. New data elucidate two major global carbon isotope events, a negative excursion of ˜2‰ at the Sinemurian-Pliensbachian boundary, and a positive excursion of ˜2‰ in the Late Pliensbachian. The Sinemurian-Pliensbachian boundary event is similar to the slightly younger Toarcian Oceanic Anoxic Event and is characterized by deposition of relatively deepwater organic-rich shale. The Late Pliensbachian strata by contrast are characterized by shallow marine deposition. Oxygen isotope data imply cooling locally for both events. However, because deeper water conditions characterize the Sinemurian-Pliensbachian boundary in the Cleveland Basin the temperature drop is likely of local significance; in contrast a cool Late Pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions. Both the large-scale, long-term and small-scale, short-duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy. Isotope events and the sea level cycles are concluded to reflect processes of global significance, supporting the idea of an Early Jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 Ma.

Korte, Christoph; Hesselbo, Stephen P.

2011-12-01

177

A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles  

PubMed Central

The discovery of a new stem turtle from the Middle Jurassic (Bathonian) deposits of the Isle of Skye, Scotland, sheds new light on the early evolutionary history of Testudinata. Eileanchelys waldmani gen. et sp. nov. is known from cranial and postcranial material of several individuals and represents the most complete Middle Jurassic turtle described to date, bridging the morphological gap between basal turtles from the Late Triassic–Early Jurassic and crown-group turtles that diversify during the Late Jurassic. A phylogenetic analysis places the new taxon within the stem group of Testudines (crown-group turtles) and suggests a sister-group relationship between E. waldmani and Heckerochelys romani from the Middle Jurassic of Russia. Moreover, E. waldmani also demonstrates that stem turtles were ecologically diverse, as it may represent the earliest known aquatic turtle.

Anquetin, Jeremy; Barrett, Paul M.; Jones, Marc E.H.; Moore-Fay, Scott; Evans, Susan E.

2008-01-01

178

Sun and shade leaves? Cuticle ultrastructure of Jurassic Komlopteris nordenskioeldii (Nathorst) Barbacka  

Microsoft Academic Search

An ultrastructural transmission electron microscope (TEM) study of fossil leaf cuticles from the Jurassic pteridosperm Komlopteris nordenskioeldii (Nathorst) Barbacka from the Mecsek Mountains (South Hungary) was conducted. Remnants of cuticles of leaves originating from so-called “sun and shade” environments were sectioned with a diamond knife, transversally as well as longitudinally. Although the present study showed a simple type of cuticle

G Guignard; K Bóka; M Barbacka

2001-01-01

179

Calsoyasuchus valliceps, a new crocodyliform from the Early Jurassic Kayenta Formation of Arizona  

Microsoft Academic Search

We describe a new fossil crocodyliform archosaur from the Early Jurassic Kayenta Formation of the Navajo Nation that is surprisingly derived for so ancient a specimen. High-resolution X-ray CT analysis reveals that its long snout houses an extensive system of pneumatic paranasal cavities. These are among the most distinctive features of modern crocodylians, yet the evolutionary history of this unique

Ronald S. Tykoski; Timothy B. Rowe; Richard A. Ketcham; Matthew W. Colbert

2002-01-01

180

Diversity and paleogeographic distribution of Early Jurassic plesiosaurs  

NASA Astrophysics Data System (ADS)

Early Jurassic plesiosaurs, a group of extinct marine reptiles, were one of the first groups to be described in the history of vertebrate paleontology. Nevertheless, the paleogeographic distribution and the taxonomic diversity of these forms are still unclear, particularly because most descriptions and taxonomic attributions were realized during the mid 19th to early 20th century. Here we investigate the paleodiversity and paleogeographic distribution of Early Jurassic plesiosaurs using an extensive taxonomic and anatomical revision of most known Early Jurassic specimens. We also present an examination of the biostratigraphic and sedimentological framework of deposits in which these specimens were discovered, in order to decipher whether their fossil record reflects primary paleobiological trends or taphonomic/discovery biases. Early Jurassic Plesiosaur diversity appears to reach its maximum during the Toarcian (falciferum-bifrons ammonite zones). Nevertheless, the inclusion of ghost lineages into the diversity curves indicates that this pattern likely reflects discovery and taphonomical biases rather than primary biodiversity trends. Indeed, most strata where numerous plesiosaurs species were discovered correspond to sediments that were deposited under poorly-oxygenated conditions and exploited at least in a semi-industrial way during the 1800's-1950's. The Lower Jurassic fossiliferous localities that yielded identifiable plesiosaur species are only found in Western Europe (England, Germany, and France). In Europe, the Toarcian stage is the only interval where more than one fossiliferous locality is known (the Hettangian, Sinemurian and Pliensbachian stages being each represented by only one locality where specimens are identifiable at the species level). The different Toarcian fossiliferous sites of Europe do not bear any single common taxon, suggesting a high degree of endemism in Early Jurassic plesiosaurs. Nevertheless, these sites are fundamentally diachronous at the ammonite zone level; this absence of shared taxa might hence reflect temporal changes rather than paleogeographic trends. Further data are required to determine whether if this pattern is a consequence of truly limited paleobiogeographic ranges or the result of high rates of turnover. In addition, future fossil discoveries and refinements of the phylogenetic relationships are required to precise the evolution of this diversity at a higher stratigraphic resolution, and hence determine how plesiosaurs responded to severe environmental change that punctuated this period (i.e. Early Hettangian and Early Toarcian mass extinction events).

Vincent, Peggy; Suan, Guillaume

2010-05-01

181

A palynological investigation across the Jurassic-Cretaceous boundary on the south-east flanks of Mount Hermon, Israel  

Microsoft Academic Search

The disconformable contact across the Jurassic-Cretaceous boundary on the south-east flanks of Mount Hermon, Israel was studied palynologically. The youngest Jurassic sediments (Beer-Sheva and Haluza Formation J6-J7) are of late Oxfordian age. Miospores, probably of (?late) Berriasian age, were discovered within sediments in a volcanic sequence, the E’Shatr sequence, above the contact, and are considered to be the oldest Cretaceous

Brian H. Conway

1996-01-01

182

Rare earth, major and trace elements in Jurassic manganese shales of the Northern Calcareous Alps: hydrothermal versus hydrogenous origin of stratiform manganese deposits  

Microsoft Academic Search

Summary  ¶The rare earth, major and trace element geochemistry of Jurassic deep marine manganese shales allow insight into their environment\\u000a of deposition. We present data of 24 samples from the Northern Calcareous Alps (Eastern Alps), collected from Late Jurassic\\u000a strata of the Tennengebirge and from Early Jurassic strata of the Karwendel Mts. Whereas major and trace element geochemistry\\u000a is controlled by

G. Rantitsch; F. Melcher; Th. Meisel; Th. Rainer

2003-01-01

183

Direct chemical evidence for eumelanin pigment from the Jurassic period  

PubMed Central

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.

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

184

"Fossil" Forecasting.  

ERIC Educational Resources Information Center

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)

Brody, Michael J.; deOnis, Ann

2001-01-01

185

Fossil fuels  

Microsoft Academic Search

The recovery, handling and combustion of fossil fuels is damaging the environment. This damage may ultimately cause many plant and animal species to become extinct. If we continue to increase our use of fossil fuels for energy production, humanity may ultimately become one of the species that perish. This is an overwhelming reason to stop the use of fossil fuels

Herman Daly

1994-01-01

186

Paleomagnetism of Jurassic volcanic rocks in southeastern Arizona and North American Jurassic apparent polar wander  

SciTech Connect

The Corral Canyon sequence in the Patagonia Mountains is a 650 meter thick homoclinal sequence consisting of interbedded volcaniclastic red-beds, welded ash-flow tuff, and lavas. Rb/Sr isotopic analysis of eight whole rock tuff samples yields an isochron age of 171 +/- 3 Ma. Welded tuffs in the Corral Canyon sequence possess a stable, primary magnetization carried in both magnetite and hematite that defines a paleomagnetic pole at 61.8/sup 0/N, 116.0/sup 0/E. Paleomagnetic study of the Canelo Hills volcanics welded tuff member also yields a stable, primary magnetization throughout a stratigraphic thickness of 600 meters. Various aspects of the paleomagnetic data indicate that discordance of the Canelo Hills volcanics pole is probably due to acquisition of remanent magnetization during a period of non-dipole behavior of the geomagnetic field. Dispersion of paleomagnetic directions suggests that the welded tuff member represents at most two cooling units and can be interpreted as a caldera-fill sequence. A revised Jurassic APW path differs significantly from available paths and has important implications for North American plate motion and paleolatitude. The spatio-temporal progression of reliable Jurassic paleopoles, in conjunction with Triassic and Early Cretaceous poles, is well described by paleomagnetic Euler pole analysis. The APW path is divided into three tracks, separated by two cusps. These cusps represent changes in the direction of North American absolute plate motion and can be correlated with global plate motion and intraplate deformation events at approximately 200-210 Ma and 150 Ma. Finally, the APW path presented herein predicts more southerly Late Triassic and Jurassic paleolatitudes for North America than have been suggested by previous authors.

May, S.R.

1985-01-01

187

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

PubMed Central

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.

McElwain, J. C.

1998-01-01

188

The depth of pelagic deposits in the Tethyan Jurassic and the use of corals: an example from the Apennines  

NASA Astrophysics Data System (ADS)

Assessing the palaeobathymery of pelagic deposits is rather speculative, as proof through lithology or fossils significant for depth estimates is sparse. This is unfortunate as the bathymetric history of pelagic successions allows to conceive the evolution of continental margins and oceanic basins. Discoveries in coral biology bring an unexpected impact on basin analysis. Evidence strongly suggests that pennular corals, fossil and modern, constitute a zooxanthellate group with an outstanding specialization in colonizing deeper parts of the marine photic zone. This adaptation includes light amplification by autofluorescent pigmented cells, and particular feeding, witnessed by peculiar gastric ducts and skeletal features. Such corals occur in the Umbria-Marche and Sabina Apennines on top of Late Jurassic submarine highs and at basin margins. Values of palaeodepth relative to pelagic deposits are provided by corals and other environmental data. Because depth reconstruction involves classical Tethyan facies, such as Ammonitico Rosso, Aptychus limestone and radiolarian cherts, we must note that these results do not meet with actualistic models relying on carbonate dissolution for estimating depth. Deposits viewed as bathyal to abyssal could also have accumulated within, or just below, the photic zone. Thus, a new insight opens on Mesozoic bathymetries, regarding vast areas (Middle East to Caribbean) and on subjects ranging from platform drowning to regional extension styles.

Gill, Gabriel A.; Santantonio, Massimo; Lathuilière, Bernard

2004-04-01

189

Boron-containing organic pigments from a Jurassic red alga  

PubMed Central

Organic biomolecules that have retained their basic chemical structures over geological periods (molecular fossils) occur in a wide range of geological samples and provide valuable paleobiological, paleoenvironmental, and geochemical information not attainable from other sources. In rare cases, such compounds are even preserved with their specific functional groups and still occur within the organisms that produced them, providing direct information on the biochemical inventory of extinct organisms and their possible evolutionary relationships. Here we report the discovery of an exceptional group of boron-containing compounds, the borolithochromes, causing the distinct pink coloration of well-preserved specimens of the Jurassic red alga Solenopora jurassica. The borolithochromes are characterized as complicated spiroborates (boric acid esters) with two phenolic moieties as boron ligands, representing a unique class of fossil organic pigments. The chiroptical properties of the pigments unequivocally demonstrate a biogenic origin, at least of their ligands. However, although the borolithochromes originated from a fossil red alga, no analogy with hitherto known present-day red algal pigments was found. The occurrence of the borolithochromes or their possible diagenetic products in the fossil record may provide additional information on the classification and phylogeny of fossil calcareous algae.

Wolkenstein, Klaus; Gross, Jurgen H.; Falk, Heinz

2010-01-01

190

The Jurassic of Svalbard, Sedimentology, Stratigraphy and Paleontology  

NASA Astrophysics Data System (ADS)

During the Mesozoic the landmass now known as Svalbard drifted from 45oN to 65oN. The average global temperature was significantly higher, disabling the formation of icecaps at the poles, resulting in a higher sea-level. At the time the location now known as Svalbard was covered by a shallow ocean and mostly marine, organic rich, black shales, interrupted by possibly deltaic sediments were deposited. These sediments are rich in invertebrate fossils. A general description of the Agardhfjellet formation, spanning the middle to upper Jurassic, was made by Dypvik in 1991. Wierzbowski (1989) described some ammonites in detail from the Kimmeridgian. It is not known if the fauna extends further up or down in the formation. Since 2004 the Museum of Natural History of Oslo has been active in Spitsbergen Svalbard. Extensive and detailed sedimentological and stratigraphic research was never conducted as the focus lay on vertebrate fossils. A detailed sedimentological analysis, description and correlation to other Jurassic Formations (such as the Kimmeridge Shales, Hekkingen Formation and draupne Formation) is essential to better understand the circumstances where the black organic-rich shales (a highly potential source rock) were deposited in and to be able to predict their occurrences. Included in this description is taxonomy, taphonomy and the stratigraphic development of invertebrate fauna to pinpoint the age of the sediments.

Koevoets, Maayke; Hammer, Øyvind

2014-05-01

191

Fossil formation  

NSDL National Science Digital Library

The National Science Education Standards Life Science Content Standard mentions that fossils indicate extinct species and contribute to an understanding of evolution and diversity. The Earth and Space Sciences Content Standard tells us they provide clues about past environments. But what is a fossil? How does it form? The processes can be complex. An understanding of fossil formation will enable accurate student conceptions of related science concepts including methods of science in geology, paleontology, and evolution.

University, Staff A.

2008-03-07

192

Fossil Excavation  

NSDL National Science Digital Library

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

193

Finding Fossils  

NSDL National Science Digital Library

This activity (located on page 4 of the PDF) is a full inquiry investigation to determine the age of fossils based on where they are discovered. Groups of learners will dig for fossils embedded in a cake of multiple layers, carefully excavating each stratum and eventually preparing a chart from their notes for discussion with the group. The two main lessons from this exercise are that fossils from different layers come from different eras and that multiple interpretations of incomplete fossil evidence are possible. Relates to linked video, DragonflyTV GPS: Baby Dinosaurs.

Twin Cities Public Television, Inc.

2007-01-01

194

Fossil Fuels.  

ERIC Educational Resources Information Center

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…

Crank, Ron

195

Fossil Horses  

Microsoft Academic Search

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,

Bruce J. MacFadden

1994-01-01

196

Ediacara Fossils  

ERIC Educational Resources Information Center

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…

Science Teacher, 2005

2005-01-01

197

Prolific Overton field gas reservoirs within large transverse oolite shoals, Upper Jurassic Haynesville, Eastern Margin East Texas basin  

Microsoft Academic Search

Late Triassic rifting along a northeast-southwest spreading center in east Texas resulted in basement highs along the eastern margin of the East Texas basin that became sites of extensive ooid shoal deposition during Late Jurassic time. Reservoirs within oolite facies at Overton field contain over 1 tcf of natural gas. These large shoals, each approximately 15 mi (24 km) long

T. E. Covington; R. G. Lighty; W. M. Ahr

1985-01-01

198

Fossil Hunt  

NSDL National Science Digital Library

This activity is structured to allow students to experience one of the largest puzzles in science, the fossil record. Students will be encouraged to ask questions about the nature of science as they experience a simulated fossil hunt. They will be asked to reconstruct a book that has been literally destroyed, just as the fossil record has been changed by billions of years of geological processes. They will gain insight into the academic processes of piecing together bits and pieces of information. This site includes background information, a list of materials, introduction and description of the activity, and suggestions for evaluation.

199

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

PubMed Central

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.

Dong, Fei; Shih, Chungkun; Ren, Dong

2014-01-01

200

Ichnology of Lower Jurassic beach deposits in the Shemshak Formation at Shahmirzad, southeastern Alborz Mountains, Iran  

Microsoft Academic Search

A 19 m thick package of well-sorted lowermost Jurassic (Hettangian-Lower Sinemurian?) sandstones within the Shemshak Formation\\u000a of the southeastern Alborz Mountains displays features characteristic of foreshore to upper shoreface environments such as\\u000a tabular bedding, low-angle lamination, trough cross-stratification, parting lineation, and oscillation ripples. In contrast\\u000a to most other beach successions recorded in the literature the sandstones contain a trace fossil assemblage

Franz T. Fürsich; Markus Wilmsen; Kazem Seyed-Emami

2006-01-01

201

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

PubMed

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

Dong, Fei; Shih, Chungkun; Ren, Dong

2014-01-01

202

A remarkable new genus of Tettigarctidae (Insecta, Hemiptera, Cicadoidea) from the Middle Jurassic of northeastern China.  

PubMed

Tianyuprosbole zhengi, a remarkable new genus and species of Tettigarctidae (Insecta, Hemiptera, Cicadoidea), is described based on a whole-bodied fossil from the Middle Jurassic of Daohugou, northeastern China. The new species possesses a tegmen similar to that of Cicadoprosbole, the type genus of Cicadoprosbolinae, and has an exceedingly expanded pronotum as the extant genus Tettigarcta. This specimen provides new insights in the evolution and taxonomy of tettigarctids. PMID:24870657

Chen, Jun; Wang, Bo; Zhang, Haichun; Wang, Xiaoli

2014-01-01

203

Fossil Halls  

NSDL National Science Digital Library

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

204

In search of the first flower: A jurassic angiosperm, archaefructus, from northeast china  

PubMed

Angiosperm fruiting axes were discovered from the Upper Jurassic of China. Angiosperms are defined by carpels enclosing ovules, a character demonstrated in this fossil. This feature is lacking in other fossils reported to be earliest angiosperms. The fruits are small follicles formed from conduplicate carpels helically arranged. Adaxial elongate stigmatic crests are conspicuous on each carpel. The basal one-third of the axes bore deciduous organs of uncertain affinities. No scars of subtending floral organs are present to define the individual fertile parts as floral units, but the leaf-like structures subtending each axis define them as flowers. These fruiting axes have primitive characters and characters not considered primitive. PMID:9831557

Sun; Dilcher; Zheng; Zhou

1998-11-27

205

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

Microsoft Academic Search

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

1994-01-01

206

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

Microsoft Academic Search

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

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

2011-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

208

Jurassic-Cretaceous low paleolatitudes from the circum-Black Sea region (Crimea and Pontides) due to True Polar Wander  

NASA Astrophysics Data System (ADS)

In a recent study, paleomagnetic and paleoenvironmental data from Adria (as part of the African plate) suggest a trend toward much lower (˜ 15°) latitudes from Early Jurassic to Earliest Cretaceous at the position of Adria than suggested by the apparent polar wander (APW) paths. The smoothing of existing (APW) paths has most likely caused this low-latitude episode to be overlooked. In this study, we test if the low paleolatitudes in the Jurassic to Early Cretaceous can also be found in Eurasia, i.e. Crimea (Ukraine) and the Pontides (Turkey) that are situated in the present-day Black Sea region. Our Eurasian data suggest the same low Late Jurassic to Early Cretaceous paleolatitudes as shown for Africa. The Jurassic to Lower Cretaceous time span is characterized by Tethys subduction between the African and Eurasian continents and these subduction zones likely functioned as an anchor in the mantle. Therefore, we regard it unlikely that both the African and Eurasian plates moved by > 1500 km south and subsequently north with respect to the mantle, as suggested by the paleomagnetic results. True polar wander (TPW) provides a mechanism that rotates the Earth's crust and mantle with respect to its core, and it was recently quantified. The period from 195-135 Ma (Early Jurassic to Earliest Cretaceous) is subject to clockwise TPW, which could well explain our results. We conclude that TPW rather than plate tectonics is the cause of low Late Jurassic to Early Cretaceous African and Eurasian paleolatitudes in the eastern Mediterranean area.

Meijers, Maud J. M.; Langereis, Cor G.; van Hinsbergen, Douwe J. J.; Kaymakc?, Nuretdin; Stephenson, Randell A.; Alt?ner, Demir

2010-08-01

209

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

PubMed Central

Abstract 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”.

Zinovyev, Evgeniy

2011-01-01

210

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

PubMed

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

Zinovyev, Evgeniy

2011-01-01

211

Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva  

PubMed Central

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

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

2014-01-01

212

A Jurassic eutherian mammal and divergence of marsupials and placentals.  

PubMed

Placentals are the most abundant mammals that have diversified into every niche for vertebrates and dominated the world's terrestrial biotas in the Cenozoic. A critical event in mammalian history is the divergence of eutherians, the clade inclusive of all living placentals, from the metatherian-marsupial clade. Here we report the discovery of a new eutherian of 160?Myr from the Jurassic of China, which extends the first appearance of the eutherian-placental clade by about 35?Myr from the previous record, reducing and resolving a discrepancy between the previous fossil record and the molecular estimate for the placental-marsupial divergence. This mammal has scansorial forelimb features, and provides the ancestral condition for dental and other anatomical features of eutherians. PMID:21866158

Luo, Zhe-Xi; Yuan, Chong-Xi; Meng, Qing-Jin; Ji, Qiang

2011-08-25

213

Plutonic rocks of Jurassic age in the Alaska-Aleutian Range batholith: chemical variation and polarity.  

USGS Publications Warehouse

Plutonic rocks of Jurassic age exposed on the Pacific side of this batholith form a compositionally continuous calc-alkaline suite that ranges from hornblende gabbro to quartz monzonite. Tonalite and quartz diorite are the dominant rock types. Trend-surface analysis of 102 samples indicates that the direction of slope of the trend is approximately normal to the Jurassic magmatic arc. K2O and SiO2 increase towards the E-SE and the other oxides towards the W-NW. If the chemical trends reflect the approximate geometry of a palaeo-subduction zone, the polarity of the Jurassic magmatic arc is to the NW, i.e. subduction was directed towards the SE. Thus the palaeo-subduction zone is on the opposite side of the arc from the position that has generally been assumed, indicating that the Jurassic plutonic rocks were not generated in response to classical Andean-type convergent plate margins. The magmatic arc may have been formed in an intra-ocean environment and subsequently has been rafted northwards and accreted to this part of the N Pacific rim during the late Mesozoic. Middle and Upper Jurassic clastics underlying Cook Inlet to the SE and derived from the magmatic arc are classified as back-arc deposits, rather than as an arc-trench gap sequence.-L.C.H.

Reed, B. I.; Miesch, A. T.; Lanphere, M. A.

1983-01-01

214

Fossil Horses  

NASA Astrophysics Data System (ADS)

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.

MacFadden, Bruce J.

1994-06-01

215

Diversity dynamics and mass extinctions of the Early–Middle Jurassic foraminifers: A record from the Northwestern Caucasus  

Microsoft Academic Search

The Early–Middle Jurassic foraminiferal assemblages of the Northwestern Caucasus, including a total of 315 species and 68 genera, were analysed to establish the principal diversity patterns at substage level of resolution. An overall conclusion is that the number of species varied significantly in contrast to the number of genera. The most diversified were Late Sinemurian–Pliensbachian, Late Toarcian–Early Aalenian, and Late

Dmitry A. Ruban; Jaros?aw Tyszka

2005-01-01

216

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

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

217

Fossil Algæ  

Microsoft Academic Search

IN a review of Saporta's work on ``Fossil Algæ'' in NATURE (vol. xxvii. p. 514) there are certain opinions brought forward which ought not to be passed by without some remarks. At first it should be stated that Saporta, while still insisting upon the vegetable nature of his so-called ``algæ,'' does not only defend his views about those doubtful bodies

A. G. Nathorst

1883-01-01

218

Fossil Finds Expand Early Hominid Anatomy.  

ERIC Educational Resources Information Center

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)

Bower, B.

1991-01-01

219

Ocean circulation during the Middle Jurassic in the presence/absence of a circumglobal current system  

NASA Astrophysics Data System (ADS)

Pangea breakup started in the Early Jurassic by the formation of the Central Atlantic and its connection with the Neotethys. By the Middle Jurassic, rifting between North and South America may have opened a first marine proto-Caribbean passage. However, the oldest known proto-Caribbean ocean crust is only of early Late Jurassic age. Based on earlier plate tectonic reconstructions featuring a wide open proto-Caribbean seaway, the existence of a circumglobal equatorial current system has been suggested by many authors as a possible physical mechanism for increasing the poleward ocean heat transport, and hence, producing the reduced meridional temperature gradient documented for the Middle Jurassic. Models with increased atmospheric pCO2, estimated to be between 1 and 7 times pre-industrial values in the Jurassic, generate elevated temperatures both in the tropics and in polar regions, but do not reduce the meridional gradient. A different mechanism needs to be considered in order to reproduce such reduced meridional temperature gradient. A possibility is enhanced poleward heat transport through the ocean. However, this hypothesis has been questioned by Late Jurassic simulations with a specified, reduced meridional gradient, which showed that the required ocean heat transport is much smaller than in present-day simulations. We investigate the critical role of a Tethyan-Atlantic-proto-Caribbean passage with respect to the Middle Jurassic ocean circulation by means of coupled ocean/sea-ice numerical models based on detailed plate reconstructions of the oceanic realms. We perform numerical experiments with an open/closed western boundary of the proto-Caribbean basin and we discuss the water properties, the gyre transport and the overturning meridional circulation for these different bathymetric configurations. For an open western boundary, we find a trans-Pangean circumglobal current of the order of 1 Sv, that flows in the upper 300 m along the northern margin of the Central Atlantic and proto-Caribbean basins. We discuss the consequences of such a modest current on the global ocean circulation and on water stratification/low upwelling rates in the Central Atlantic. We compare the predicted effects with a revised analysis of Middle Jurassic oceanic sedimentary records from the proto-Caribbean and the Central Atlantic.

Brunetti, Maura; Baumgartner, Peter O.; Vérard, Christian; Hochard, Cyril

2013-04-01

220

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

Microsoft Academic Search

The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are

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

1987-01-01

221

A new chronology for the late Triassic to early Jurassic  

Microsoft Academic Search

Throughout geological history of life, a small number of mass extinctions have forever changed the path of evolution. The two main mechanisms that account for these dramatic events are asteroid impacts and massive volcanic eruptions of Large Igneous Provinces (LIP’s). The interplay between mass-extinctions, LIP emplacement, extra-terrestrial causes, and perturbations in the carbon cycle belongs to the most significant, fascinating

M. H. L. Deenen

2010-01-01

222

Testing Iberian kinematics at Jurassic-Cretaceous times  

NASA Astrophysics Data System (ADS)

reconstructions of Iberia at the Mesozoic are still a matter of debate. The incompatibility between kinematic models and paleomagnetic data older than 120 Ma is a major problem for which no cause has yet been determined. Here we use a new method to investigate the origin of this misfit. We solve the inverse problem of finding the Euler poles that fit paleomagnetic poles with the Global Apparent Polar Wander Path (GAPWP) and then test their implications on Iberian reconstructions. We show that Iberian poles from the Early Cretaceous (mean poles for 123 and 130 Ma) are incompatible with the GAPWP, bringing into question their validity. Contrarily, Late Jurassic data (mean pole at 151 Ma) are compatible with the GAPWP and, thus, can be considered reliable. Based on these results, we propose a new magnetic reconstruction of Iberia and surrounding plates at ~150 Ma (M22 anomaly). This work provides new constraints for the kinematic evolution of Iberia during Jurassic-Cretaceous. However, the development of a detailed and consensual model for the kinematic evolution of Iberia is dependent on the acquisition of new, high-quality paleomagnetic data and a reevaluation of seafloor magnetic anomalies.

Neres, M.; Miranda, J. M.; Font, E.

2013-09-01

223

Isotopic constraints on the petrogenesis of jurassic plutons, Southeastern California  

USGS Publications Warehouse

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.

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

1998-01-01

224

Magnetostratigraphy of a Marine Triassic-Jurassic Boundary Section, Kennecott Point, Queen Charlotte Islands: Implications for the Temporal Correlation of a 'Big Five' Mass Extinction Event  

Microsoft Academic Search

Several causes have been proposed for Triassic-Jurassic (T-J) boundary extinctions, including global ocean anoxia\\/euxinia, an impact event, and\\/or eruption of the massive Central Atlantic Magmatic Province (CAMP), but poor intercontinental correlation makes testing these difficult. Sections at Kennecott Point, Queen Charlotte Islands, British Columbia span the late Norian through Rhaetian (Triassic) and into the earliest Hettangian (Jurassic) and provide the

I. A. Hilburn; J. L. Kirschvink; P. D. Ward; J. W. Haggart; T. D. Raub

2008-01-01

225

Constraining the Jurassic extent of Greater India: Tectonic evolution of the West Australian margin  

NASA Astrophysics Data System (ADS)

Alternative reconstructions of the Jurassic northern extent of Greater India differ by up to several thousand kilometers. We present a new model that is constrained by revised seafloor spreading anomalies, fracture zones and crustal ages based on drillsites/dredges from all the abyssal plains along the West Australian margin and the Wharton Basin, where an unexpected sliver of Jurassic seafloor (153 Ma) has been found embedded in Cretaceous (95 My old) seafloor. Based on fracture zone trajectories, this NeoTethyan sliver must have originally formed along a western extension of the spreading center that formed the Argo Abyssal Plain, separating a western extension of West Argoland/West Burma from Greater India as a ribbon terrane. The NeoTethyan sliver, Zenith and Wallaby plateaus moved as part of Greater India until westward ridge jumps isolated them. Following another spreading reorganization, the Jurassic crust resumed migrating with Greater India until it was re-attached to the Australian plate ˜95 Ma. The new Wharton Basin data and kinematic model place strong constraints on the disputed northern Jurassic extent of Greater India. Late Jurassic seafloor spreading must have reached south to the Cuvier Abyssal Plain on the West Australian margin, connected to a spreading ridge wrapping around northern Greater India, but this Jurassic crust is no longer preserved there, having been entirely transferred to the conjugate plate by ridge propagations. This discovery constrains the major portion of Greater India to have been located south of the large-offset Wallaby-Zenith Fracture Zone, excluding much larger previously proposed shapes of Greater India.

Gibbons, Ana D.; Barckhausen, Udo; van den Bogaard, Paul; Hoernle, Kaj; Werner, Reinhard; Whittaker, Joanne M.; Müller, R. Dietmar

2012-05-01

226

Mineralization of soft-part anatomy and invading microbes in the horseshoe crab Mesolimulus from the Upper Jurassic Lagerst?tte of Nusplingen, Germany  

PubMed Central

A remarkable specimen of Mesolimulus from the Upper Jurassic (Kimmeridgian) of Nusplingen, Germany, preserves the musculature of the prosoma and associated microbes in three dimensions in calcium phosphate (apatite). The musculature of Mesolimulus conforms closely to that of modern horseshoe crabs. Associated with the muscles are patches of mineralized biofilm with spiral and coccoid forms. This discovery emphasizes the potential of soft-bodied fossils as a source for increasing our knowledge of the diversity of fossil microbes in particular settings.

Briggs, Derek E.G; Moore, Rachel A; Shultz, Jeffrey W; Schweigert, Gunter

2005-01-01

227

The space-time relationship of taxonomic diversity and morphological disparity in the Middle Jurassic ammonite radiation  

Microsoft Academic Search

The Middle Jurassic ammonite radiation (from the late Aalenian to the end of the mid-Bathonian) is traced using combined analyses of morphological disparity and taxonomic diversity. The global signals of disparity and diversity are compared. These signals are then broken down by paleogeographical provinces to detect any heterogeneity in the radiation. An examination of the global signals reveals three biodiversity

Sébastien Moyne; Pascal Neige

2007-01-01

228

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

Microsoft Academic Search

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

Peter N. Johannessen

229

The Jurassic–Lower Cretaceous Byers Group, South Shetland Islands, Antarctica: revised stratigraphy and regional correlations  

Microsoft Academic Search

The Byers Group, exposed in the western South Shetland Islands, is a thick (at least 2.7 km) succession recording Late Jurassic–Early Cretaceous sedimentation and volcanism on the Pacific flank of the Antarctic Peninsula magnetic arc. At least 1.3 km of marine clastic rocks are overlain by 1.4 km of non-marine strata. Penecontemporaneous, mainly intrusive, igneous rocks are present in much

B. Hathway; S. A. Lomas

1998-01-01

230

Paleomagnetic evidence for Jurassic deformation of the McCoy Mountains Formation, southeastern California and southwestern Arizona  

Microsoft Academic Search

The Mesozoic McCoy Mountains Formation is a 7.3-km-thick deformed clastic sequence exposed in six mountain ranges in southeastern California and southwestern Arizona. Interbedded with Jurassic volcanic rocks at its base, the McCoy Mountains Formation had been assigned a Cretaceous age based upon fossil angiosperm wood found in the upper third of the section. Characteristic natural remanent magnetism (NRM) from 145

Lucy E. Harding; Robert F. Butler; Peter J. Coney

1983-01-01

231

Types of morphogenesis of the dermal skeleton in fossil sharks  

Microsoft Academic Search

Four types of morphogenesis of the dermal skeleton can be distinguished. They differ with regard to scale growth, scale replacement\\u000a and insertion of new scales during ontogeny. Three of the types occur exclusively in fossil sharks and have been found in\\u000a only a few articulate specimens. In only one case (Jurassic hybodontids) it is possible to trace the phyletic transition

Wolf-Ernst Reif

1978-01-01

232

The girdles of the oldest fossil turtle, Proterochersis robusta, and the age of the turtle crown  

PubMed Central

Background Proterochersis robusta from the Late Triassic (Middle Norian) of Germany is the oldest known fossil turtle (i.e. amniote with a fully formed turtle shell), but little is known about its anatomy. A newly prepared, historic specimen provides novel insights into the morphology of the girdles and vertebral column of this taxon and the opportunity to reassess its phylogenetic position. Results The anatomy of the pectoral girdle of P. robusta is similar to that of other primitive turtles, including the Late Triassic (Carnian) Proganochelys quenstedti, in having a vertically oriented scapula, a large coracoid foramen, a short acromion process, and bony ridges that connect the acromion process with the dorsal process, glenoid, and coracoid, and by being able to rotate along a vertical axis. The pelvic elements are expanded distally and suturally attached to the shell, but in contrast to modern pleurodiran turtles the pelvis is associated with the sacral ribs. Conclusions The primary homology of the character “sutured pelvis” is unproblematic between P. robusta and extant pleurodires. However, integration of all new observations into the most complete phylogenetic analysis that support the pleurodiran nature of P. robusta reveals that this taxon is more parsimoniously placed along the phylogenetic stem of crown Testudines. All current phylogenetic hypotheses therefore support the basal placement of this taxon, imply that the sutured pelvis of this taxon developed independently from that of pleurodires, and conclude that the age of the turtle crown is Middle Jurassic.

2013-01-01

233

The problems and potential of using animal fossils and trace fossils in terminal Proterozoic biostratigraphy  

Microsoft Academic Search

Despite the discovery of soft-bodied megascopic fossils of late Neoproterozoic age at numerous localities world-wide, there has been slow acceptance of their potential for intercontinental correlation. The stratigraphic thickness of sediments separating individual occurrences of such fossils from the base of the Cambrian is very varied. Basic questions have also been posed as to the classification of the organisms represented

Richard J. F. Jenkins

1995-01-01

234

Discovery of Middle Jurassic mammals from Siberia  

Microsoft Academic Search

Mammal remains from the Middle Jurassic (Bathonian) Berezovsk Quarry on the south of Krasnoyarsk Territory, West Siberia, Russia are referred to Docodonta indet. (two edentulous fragmentary dentaries) and Mammalia indet. (a sin? gle?rooted tooth). The dentaries exemplify a unique combination of plesiomorphic characters found among stem mam? mals only in Docodonta and Morganucodon: well developed Meckel's groove, trough for postdentary

ALEXANDER O. AVERIANOV; ALEXEY V. LOPATIN; PAVEL P. SKUTSCHAS; NIKOLAI V. MARTYNOVICH; SERGEI V. LESHCHINSKIY; ANTON S. REZVYI; SERGEI A. KRASNOLUTSKII; ALEXEY V. FAYNGERTZ

235

Jurassic evolution of the Tien-Shan  

SciTech Connect

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.

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

1994-09-01

236

Discovering the "-Ologies" on the Jurassic Coast  

ERIC Educational Resources Information Center

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…

Peacock, Alan

2007-01-01

237

Jurassic and Cretaceous Geological History of Cuba  

Microsoft Academic Search

The Mesozoic rocks of Cuba are a key element in reconstructing the geological history of the Mesoamerican (Gulf of Mexico and the Caribbean) area. Four different Jurassic-Cretaceous sections are recorded in Cuba, including three from tectonostratigraphic terranes. From north to south they include the following: (1) a portion of the Mesozoic passive margin of North America, with outstanding zonality, especially

Jorge L. Cobiella-Reguera

2000-01-01

238

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

SciTech Connect

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.

Medlyn, D.A. (Utah State Univ., Logan, UT (United States). Dept. of Geology); Bilbey, S.A. (Utah Field House of Natural History State Park, Vernal, UT (United States))

1993-04-01

239

Upper Jurassic and Lower Cretaceous sedimentary sequence, Baltimore Canyon trough, US Atlantic margin  

SciTech Connect

The extent and character of Upper Jurassic and Lower Cretaceous rock units in the Baltimore Canyon Trough are revealed by geologic data from 29 exploratory wells. These data, released to the public in 1982, have been used previously to define regional rock-stratigraphic units. In this study, four detailed stratigraphic cross sections were constructed to show rock-unit correlations based on lithology and electric logs. Thin-section photomicrographs document the mineralogic composition of these units. Most of the Upper Jurassic section consists primarily of Mic Mac gray shale and siltstone with minor amounts of very fine to medium-grained quartzarenite, red-brown shale, and lignite. This interval also contains some anomalously thick sandstones and siltstones, which are generally limited to the north and have been tentatively assigned to the Mohawk unit. These sandstones are mostly medium to coarse-grained, calcite-cemented quartzarenites. Upper Jurassic Abenaki limestone as much as 2210 ft (675 m) thick was penetrated by most of the eastern wells. The limestone is mostly wackestone to grainstone, with varying amounts of oolites and fossils. Thick-bedded sandstones characterize the Lower Cretaceous Mississauga unit. These sandstones are mostly fine to medium-grained, calcite-cemented quartzarenites. The overlying Naskapi unit consists of calcareous shale. Thick sandstone beds dominate the uppermost Logan Canyon unit, which consists mostly of fine to coarse-grained, calcite-cemented quartz arenite.

Libby-French, J.

1984-12-01

240

Fossil energy review  

SciTech Connect

The Fossil Energy Review provides an update of key events in the Department of Energy's Fossil Energy Program. This issue contains topics relating to: clean coal technology; fossil energy research; and petroleum reserves. (JEF)

Not Available

1989-01-01

241

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

PubMed

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

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

2010-02-01

242

Petromagnetic and paleomagnetic study of Jurassic sedimentary rocks of the southeast of Russia  

NASA Astrophysics Data System (ADS)

In the present paper the new petro- and paleomagnetic data on the Jurassic terrigenous complexes of the Mesozoic sedimentary basins of the Amur River region, Trans Baikal region, and Yakutia are presented. The magnetic properties of the sedimentary rocks of coastal-marine (paleo-shelf) and lake genesis are investigated in the contemporary intracontinental riftogenic Mesozoic superimposed troughs of the Siberian and Amur plates: the Chulmansk, the Unda-Dainsk, the Sredne-Amur, the Amuro-Zeisk, and the Verkhne-Bureinsk troughs. The statistically significant differences in the magnetic (anisotropic) characteristics of continental and marine deposits were inferred. The correlation of the scalar and tensor characteristics of magnetic susceptibility anisotropy and the parameters of its linearity, which depend indirectly on the intensity of the folding, is established. The preferential directions of regional stress during the fold formation are determined based on the analysis of the distribution of the axes of the tensor ellipsoid of the magnetic susceptibility anisotropy. The Jurassic positions of the paleomagnetic pole, which are close to the Mesozoic section of the trajectory of its apparent motion for the North Chinese plate and which differ from the Jurassic poles of the Siberian plate, are defined more accurately. The intraplate rotations of geoblocks within the limits of the amalgamated to the end of the Jurassic-to the beginning of the Cretaceous terrains as a part of the Amur tectonic plate are inferred. The calculated coordinates of the paleomagnetic pole indicate the larger than the present-day difference of the latitudinal positions of the southern part of the Siberian plate, and also of the Amur and North Chinese plates in the Early-Middle Jurassic time. This can be indicative of the fact that the total width of the shallow residual basins of the Paleo-Asian Ocean, which separated the geoblocks indicated in the Early-Middle Jurassic, attained the first thousands of kilometers, and/or such a difference in the paleolatitudes reflects the total value of the shortening (crowding) of the crust during the accretion and the fold formation. The time of the completion of the accretion of the terrains of the Amur and the North-Chinese plates and their attachment to the Siberian plate is not earlier than the end of the Late Jurassic-the beginning of the Cretaceous.

Bretshtein, Yu. S.

2009-06-01

243

Astronomically tuned geomagnetic polarity timescale for the Late Triassic  

Microsoft Academic Search

Cycle stratigraphic and magnetostratigraphic analyses of a ~5000-m-thick composite section obtained by scientific coring in the Newark rift basin of eastern North America provide a high-resolution astronomically calibrated geomagnetic polarity timescale (GPTS) spanning over 30 m.y. of the Late Triassic and earliest Jurassic. Only normal polarity is found in ~1000 m of interbedded volcanics and continental sediments of earliest Jurassic

Dennis V. Kent; Paul E. Olsen

1999-01-01

244

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

NASA Astrophysics Data System (ADS)

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

Evans, S. E.; Wang, Y.

2007-06-01

245

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

PubMed

More than one century after its original description by Marsh in 1877, we report in this paper the first uncontroversial evidence of a member of the genus Stegosaurus out of North America. The specimen consists of a partial skeleton from the Upper Jurassic of Portugal, herein considered as Stegosaurus cf. ungulatus. The presence of this plated dinosaur in the upper Kimmeridgian-lower Tithonian Portuguese record and synchronic levels of the Morrison Formation of North America reinforces previous hypothesis of a close relationship between these two areas during the Late Jurassic. This relationship is also supported by geotectonic evidences indicating high probability of an episodic corridor between the Newfoundland and Iberian landmasses. Together, Portuguese Stegosaurus discovery and geotectonic inferences could provide a scenario with episodical faunal contact among North Atlantic landmasses during the uppermost Kimmeridgian-lowermost Tithonian (ca. 148-153 Ma ago). PMID:17187254

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

2007-05-01

246

Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva.  

PubMed

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

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

2014-01-01

247

Triassic-Jurassic atmospheric CO2 spike.  

PubMed

I question the claim by Tanner et al. that atmospheric CO2 levels remained constant across the Triassic-Jurassic boundary on the grounds of problems with stratigraphic completeness and contamination with atmospheric methane. Because methanogenic CH4 has a light isotope composition and oxidizes readily to CO2, methane-clathrate dissociation and oxidation events cannot be detected by palaeobarometers that use the carbon-isotope composition of palaeosol carbonate. PMID:11807543

Retallack, Gregory J

2002-01-24

248

Palynostratigraphy and vegetation history of the Triassic-Jurassic transition in East Greenland  

NASA Astrophysics Data System (ADS)

Plant macrofossils from East Greenland provide vital information on the response of terrestrial vegetation to major environmental change at the Triassic-Jurassic transition (Tr-J; 200 Ma). However, owing to the lack of a robust stratigraphic correlation between the exact horizons containing plant macrofossils in East Greenland ('plant beds') and Tr-J boundary sections in well-studied areas such as Europe, it is difficult to fit the results of palaeoecological investigations in East Greenland into the wider picture of Tr-J biotic change. Recent work has highlighted major differences in the types of plants represented in sporomorph assemblages and macrofossil assemblages from the plant beds in East Greenland, but the taphonomic processes responsible for these differences remain poorly explained. Additionally, the exact nature of Tr-J vegetation change as recorded by sporomorphs from the plant beds is somewhat unclear. In order to address these issues we have undertaken a palynological study of a Tr-J boundary section at Astartekløft, East Greenland. We have generated an updated palynostratigraphic scheme and vegetation history for this locality and have integrated these with existing carbon isotope records. Samples for palynological analysis were collected from precisely the same stratigraphic horizons as plant macrofossils from Astartekløft, allowing the results of palaeoecological analyses based on macrofossils at this locality to be directly compared with palaeoecological analyses of other fossil organisms in different regions. Our analyses highlight four local sporomorph assemblage zones that are compositionally distinct from each other at Astartekløft. The extremely low abundance of Classopollis pollen in all samples, and the pronounced decline in Ricciisporites tuberculatus in the Late Rhaetian are particularly striking features of the sporomorph record of Tr-J vegetation at Astartekløft. Plants with small stature that do not shed fronds by abscission, such as lycopods and ferns, are under-represented as macrofossils. Plants that may have been deciduous or had a canopy habit, such as conifers and ginkgos, dominate macrofossil assemblages where present. Plants that may have been pollinated by insects are under-represented in the sporomorph record. Correlation of Astartekløft and a marine Tr-J boundary section at St Audrie's Bay provides no support for the idea that extinction and diversity loss in terrestrial ecosystems preceded biotic change in marine ecosystems at the Tr-J. Instead, the available data support suggestions that the onset of the Tr-J biotic crisis was synchronous in terrestrial and marine environments.

Mander, L.; Kürschner, W. M.; McElwain, J. C.

2012-04-01

249

Fossils, Rocks, and Time  

NSDL National Science Digital Library

This on-line book, published by the United States Geological Survey (USGS), discusses the use of fossils in determining the age of rocks. The publication covers how to place events in correct temporal order, a description of the geologic time scale, the use of fossils to indicate rock ages, the law of fossil succession, index fossils, and radioactive dating.

250

Major adaptive radiation in neritopsine gastropods estimated from 28S rRNA sequences and fossil records.  

PubMed Central

A well-supported phylogeny of the Neritopsina, a gastropod superorder archaic in origin, radiated ecologically and diverse in morphology, is reconstructed based on partial 28S rRNA sequences. The result (Neritopsidae (Hydrocenidae (Helicinidae + Neritiliidae) (Neritidae + Phenacolepadidae))) is highly congruent with the fossil records and the character distribution of reproductive tracts in extant taxa. We suggest that the Neritopsina originated in subtidal shallow waters, invaded the land and became fully terrestrial at least three times in different clades, by the extinct Dawsonellidae in the Late Palaeozoic and by the Helicinidae and Hydrocenidae in the Mesozoic. Invasion of fresh- and brackish waters is prevalent among the Neritopsina as the Jurassic and freshwater ancestory is most probable for helicinids. The Phenacolepadidae, a group exclusively inhabiting dysoxic environments, colonized deep-sea hydrothermal vents and seeps in the Late Cretaceous or Early Cenozoic. Submarine caves have served as refuges for the archaic Neritopsidae since the Early to Middle Cenozoic, and the marine neritopsine slug Titiscania represents a highly specialized but relatively recent offshoot of this family. The Neritiliidae is another clade to be found utilizing submarine caves as shelter by the Oligocene; once adapted to the completely dark environment, but some neritiliids have immigrated to surface freshwater habitats.

Kano, Yasunori; Chiba, Satoshi; Kase, Tomoki

2002-01-01

251

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

252

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

SciTech Connect

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.

Wolf, M.B.; Saleeby, J.B. (California Inst. of Technology, Pasadena, CA (United States))

1992-08-01

253

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

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.

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

2011-01-01

254

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)

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.

Vasilyan, Davit; Böhme, Madelaine; Winklhofer, Michael

2010-05-01

255

Reevaluation of upper Jurassic Morrison Formation, Western Interior  

Microsoft Academic Search

Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic

Mantzios

1989-01-01

256

Sequence stratigraphy of the Jurassic of the Danish Central Graben  

Microsoft Academic Search

A sequence stratigraphic framework is established for the Jurassic of the Danish Central Graben based primarily on petrophysical log data, core sedimentology and biostratigraphic data from about 50 wells. Regional seismic lines are used to assist in the correlation of some wells and in the con- struction of isochore maps. In the Lower Jurassic (Hettangian-Pliensbachian) succession, five sequences have been

Jan Andsbjerg; Karen Dybkjær

257

Calcareous tempestites in pelagic facies (Jurassic, Betic Cordilleras, Southern Spain)  

NASA Astrophysics Data System (ADS)

Calcareous tempestite levels interbedded with Ammonitico Rosso and other related pelagic facies have been recognized. The previously described examples of calcareous tempestites in pelagic facies are scarce. The studied outcrops are Middle and Late Jurassic in age and correspond to ancient sediments in the Southern Iberian Continental Paleomargin. These outcrops are now included in a notably deformed geological unit (External Subbetic) in the External Zones of the Betic Cordillera. The calcareous tempestites are calcarenite and calcisiltite beds, grainstone and packstone with peloids and bioclasts (mainly 'filaments' and Saccocoma), showing an internal structure with hummocky cross-stratification. The deposits are thought to be formed by tropical storms and hurricanes and their recurrence intervals have been estimated (200 ka in average). The presence of these calcareous tempestite levels and the symmetrical wave-ripples on the top of the beds are two important arguments in favour of a palaeobathymetric interpretation of related pelagic sediments in the sense that the deposition occurred below, but near to the storm wave base, and that calcareous tempestites are episodic resedimentation, mainly coincident with relative sea-level falls (lowstand phases), in which major storm waves affect the sea bottom.

Molina, J. M.; Ruiz-Ortiz, P. A.; Vera, J. A.

1997-03-01

258

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

PubMed Central

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.

Carabajal, Ariana Paulina; Sterli, Juliana; Muller, Johannes; Hilger, Andre

2013-01-01

259

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

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.

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

1996-01-01

260

A report on biocompounds from palm fossil of India  

PubMed Central

The occurrence of a large number of fossil woods having resemblance in anatomical features with the modern palm genus, Phoenix L in Deccan Intertrappean fossil flora of Maastrichtian-Danian age (i. e. Late Cretaceous and Earliest Tertiary (65-67 my)) indicates the most primitive record of date palm. Present discovery of biocompounds from fossil wood of Phoenix collected from Deccan Intertrappean having affinity with the biocompounds known from modern plant further exemplify the earliest documentation of Phoenix in Indian peninsula.

Sharma, Dinesh Chandra; Khan, Mohd Sajid; Khan, M Salman; Srivastava, Rashmi; Srivastava, Ashwini Kumar; Shukla, Ritu

2014-01-01

261

Make a Fossil!  

NSDL National Science Digital Library

In this activity, make your own fossils using a shell, preferably with an interesting texture and strong edges. Use Plaster of Paris to create a mold fossil. This activity guide includes a step-by-step instructional video.

Center, Saint L.

2013-01-17

262

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

Microsoft Academic Search

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

Cajus Diedrich

2011-01-01

263

Mass Extinctions in the Marine Fossil Record  

Microsoft Academic Search

A new compilation of fossil data on invertebrate and vertebrate families indicates that four mass extinctions in the marine realm are statistically distinct from background extinction levels. These four occurred late in the Ordovician, Permian, Triassic, and Cretaceous periods. A fifth extinction event in the Devonian stands out from the background but is not statistically significant in these data. Background

David M. Raup; J. John Sepkoski

1982-01-01

264

Overcoming Fossilized English.  

ERIC Educational Resources Information Center

Causes of language fossilization and ways to overcome it are considered. Fossilization is the relatively permanent incorporation of incorrect linguistic forms into a person's second language competence. The discussion is focused on fossilization of incorrect syntactical rules, based on experiences with learners of English as a second language at…

Graham, Janet G.

265

Jurassic-Cretaceous (Bathonian to Cenomanian) palynology and stratigraphy of the West Tiba-1 borehole, northern Western Desert, Egypt  

NASA Astrophysics Data System (ADS)

Land-derived pollen and spores and marine dinoflagellate cysts were extracted from the Jurassic and Cretaceous sediments of the West Tiba-1 borehole, northern Western Desert, Egypt, On the basis of the recovered palynomorphs, of known stratigraphical significance, the following stages were assessed: Bathonian-Oxfordian (Middle-Late Jurassic) and Hauterivian, Aptian-Early Albian, Late Albian-Early Cenomanian, Early Cenomanian and Late Cenomanian (Early-Middle Cretaceous). No palynomorphs diagnostic for the Berriasian, Valanginian and Barremian stages (Early Cretaceous) were depicted. Based on the nature and composition of the identified palynomorph content, five informal palynomorph assemblage zones were recognised. These are: the Gonyaulacysta jurassica-Korystocysta kettonensis Assemblage Zone (PI, Bathonian-Oxfordian), Ephedripites-Aequitriradites verrucosus Assemblage Zone (PII, Hauterivian), Afropollis jardinus-Duplexisporites generalis-Tricolpites Assemblage Zone (PIIl, Aptian-Early Albian), Nyssapollenites-Elaterosporites Assemblage Zone (PIV, Late Albian-Early Cenomanian) and Assemblage Zone PV (Early-Late Cenomanian). The latter zone was differentiated into two subzones, namely the Classopollis brasiliensis-Elaterosporites klaszii Assemblage Subzone (PVa, Early Cenomanian) and Afropollis kahramanensis-Triporates Assemblage Subzone (PVb, Late Cenomanian). The time stratigraphy of the studied interval was revised. The occurrences and types of the dinoflagellate cysts, extracted from the studied succession, reflect a general shallow (shelf) marine pal?oenvironment.

Mahmoud, Magdy S.; Moawad, Abdel-Rahim M. M.

2000-02-01

266

A new long-proboscid genus of Pseudopolycentropodidae (Mecoptera) from the Middle Jurassic of China and its plant-host specializations  

PubMed Central

Abstract We describe a new genus and species of Mecoptera with siphonate mouthparts, Sinopolycentropus rasnitsyni gen. et sp. n., assigned to the family Pseudopolycentropodidae Handlirsch, 1925. The specimen was collected from late Middle Jurassic nonmarine strata of the Jiulongshan Formation in Inner Mongolia, northeastern China. The new material provides additional evidence for an early diversification of pseudopolycentropodids that was ongoing during the Middle Jurassic. This diversity also adds to the variety of known pseudopolycentropodids with tubular proboscides that apparently fed on ovulate fluids produced by Mesozoic gymnosperms.

Shih, ChungKun; Yang, Xiaoguang; Labandeira, Conrad C.; Ren, Dong

2011-01-01

267

Aestivation in the fossil record: evidence from ichnology.  

PubMed

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

Hembree, Daniel I

2010-01-01

268

Fossils of Kentucky  

NSDL National Science Digital Library

Information on Kentucky fossils is organized by type, age, and region. General fossil facts are given, and there are out-of-print technical reports available at this site. A fossil identification key helps users identify unknown fossils by shape or by descriptive terms. A Geologic and Paleontologic Cookbook offers directions for creating edible models that illustrate prehistoric and other Earth Science concepts (such as trilobite cookies and layer-cake geology). There are links to more K-12 activities and other fossil websites.

269

Post-Jurassic tectonic evolution of Southeast Asia  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

270

Adaptation, plant evolution, and the fossil record  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

271

Didactyl Tracks of Paravian Theropods (Maniraptora) from the ?Middle Jurassic of Africa  

PubMed Central

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.

Mudroch, Alexander; Richter, Ute; Joger, Ulrich; Kosma, Ralf; Ide, Oumarou; Maga, Abdoulaye

2011-01-01

272

A giant spider from the Jurassic of China reveals greater diversity of the orbicularian stem group  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

273

Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace  

USGS Publications Warehouse

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.

Milner, A. R. C.; Harris, J. D.; Lockley, M. G.; Kirkland, J. I.; Matthews, N. A.

2009-01-01

274

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

PubMed Central

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.

Milner, Andrew R. C.; Harris, Jerald D.; Lockley, Martin G.; Kirkland, James I.; Matthews, Neffra A.

2009-01-01

275

Middle Jurassic to early Cretaceous igneous rocks along eastern North American continental margin  

SciTech Connect

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.

Jansa, L.F.; Pe-Piper, G.

1988-03-01

276

Jurassic granitoid magmatism in the Dinaride Neotethys: geochronological constraints from detrital minerals  

NASA Astrophysics Data System (ADS)

Three independent single-grain geochronometers applied to detrital minerals from Central Dinaride sediments constrain the timing of felsic magmatism that associated the Jurassic evolution of the Neotethys. The Lower Cretaceous clastic wedge of the Bosnian Flysch, sourced from the Dinaride ophiolitic thrust complex, yields magmatic monazite and zircon grains with dominant age components of 164 ± 3 Ma and 152 ± 10 Ma, respectively. A unique tephra horizon within the Mesozoic Adriatic Carbonate Platform was dated at 148 ± 11 Ma by apatite fission track analysis. These consistent results suggest that leucocractic melt generation in the Central Dinaride segment of the Neotethys culminated in Middle to Late Jurassic times, coeval with and slightly post-dating sub-ophiolitic sole metamorphism. Monazite growth and explosive volcanism call for supra-subduction zone processes at the convergent Neotethyan plate margin. This is in accordance with the geochemical diversity of the peraluminous to metaluminous plagiogranite and other granitoid bodies investigated so far suggesting the addition of crustal components (especially Th, LREE, Zr, Hf) to their source magmas (e.g. Bébien et al., 1997; Aigner-Torres and Koller, 1999, Anders et al., 2005). Temporal framework of the supra-subduction zone processes was restricted to a <30 Ma duration by the early Mid-Jurassic onset of subduction and the latest Jurassic completion of ophiolite obduction. New compilation of geochronological data demonstrates that such Jurassic felsic rocks, either intruding mafic/ultramafic lithologies or interfingering with ophiolite mélange deposits, are widespread in the entire Dinaride-Hellenide orogen. In the Dinarides, supra-subduction zone processes played a more important role than considered in previous tectonic reconstructions. References Aigner-Torres, M. and Koller, F., 1999. Nature of the magma source of the Szarvask? Complex, NE Hungary: Petrological and geochemical constraints. Ofioliti, 24, 1-12. Anders, B., Reischmann, T., Poller, U. and Kostopoulos, D., 2005. Age and origin of granitic rocks of the eastern Vardar Zone, Greece: new constraints on the evolution of the Internal Hellenides. Journal of the Geological Society, 162, 857-870. Bébien, J., Dautaj, N., Shallo, M., Turku, I. and Barbarin, B., 1997. Diversité des plagiogranites ophiolitiques: l'example albanais. Comptes Rendus de ?Academie des Sciences, sér. IIa, 324, 875-882.

Mikes, T.; Baresel, B.; Kronz, A.; Frei, D.; Dunkl, I.; Tolosana-Delgado, R.; von Eynatten, H.

2009-04-01

277

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

PubMed Central

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.

Clapham, Matthew E.; Bottjer, David J.

2007-01-01

278

Middle Jurassic stratigraphy in the southwestern part of the Republic of Tatarstan  

NASA Astrophysics Data System (ADS)

Data on the structure of the Middle Jurassic marine deposits in the vicinity of Ulyanovsk (sections of the Tarkhanovskaya Pristan-Dolinovka profile) are generalized with due regard for ammonites, bivalves, and microfossils occurring in sediments. Outcrops of the Tarkhanovskaya Pristan site represent the northernmost Bajocian section of the Russian Platform, where ammonites of Tethyan origin are identified. As is established, the pre-Callovian sand-clay sequence formerly attributed to the Bathonian includes the Garantiana beds of the upper Bajocian in its middle part. The multidisciplinary biostratigraphic-sedimentological research showed that downwarping of the Ulyanovsk-Saratov basin and origin of the Simbirsk Bay of the Tethyan marginal sea commenced in the Bajocian Age. The identified fossils of the upper Bajocian and lower and upper Callovian are cited in paleontological plates of this work.

Mitta, V. V.; Kostyleva, V. V.; Glinskikh, L. A.; Shurygin, B. N.; Starodubtseva, I. A.

2014-01-01

279

Does the Great Valley Group contain Jurassic strata? Reevaluation of the age and early evolution of a classic forearc basin  

USGS Publications Warehouse

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.

Surpless, K. D.; Graham, S. A.; Covault, J. A.; Wooden, J. L.

2006-01-01

280

Seismic stratigraphy and structural setting of Early Jurassic to Mid-Cretaceous sedimentary rocks in southern Neuquen basin, Argentina  

SciTech Connect

The structural evolution of the Neuquen, or Huincul, dorsal and its effect on sedimentation and stratigraphy is interpreted from seismic and well data in the southern Neuquen basin, a Mesozoic back-arc basin located in west-central Argentina, Seismic cross sections reveal that dominantly marine Jurassic sediments began filling the basin as a series of thick, discontinuous, progradational packages. Transpressional forces during the Late Jurassic Araucanian phase resulted in the formation of an extensive east-northeast-trending anticlinal structure in the southern Neuquen basin, known as the Huincul dorsal, which is important as a structural trap for hydrocarbons. Regional regression and erosion during this phase resulted in a pronounced angular unconformity, readily identifiable throughout the southern basin. The subsequent deposition of Late Jurassic to mid-Cretaceous sediments is seen on seismic cross sections as a series of low-angle, laterally continuous reflectors. Reactivation of the Huincul dorsal occurred during the mid-Cretaceous Mirano phase. Due to uplift and regression during this phase, a low-angle erosional unconformity, although often subtle, can be observed on several seismic cross sections. Uplift and deformation of the Huincul dorsal originated in basement along dominantly northward-dipping, high-angle thrust faults with up to 2000 m of vertical offset. The initial uplift and compressional deformation of the Andean Cordillera began in the mid-Cretaceous to the west of the Neuquen basin. This resulted in a final stage of primarily continental sedimentation, lasting through the Tertiary.

Harder, M.W.; Allen, R.B.

1987-05-01

281

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

NASA Astrophysics Data System (ADS)

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.

Sewall, Jacob O.; Fricke, Henry C.

2013-01-01

282

Main phytostratigraphic boundaries in the Jurassic deposits of Western Siberia  

NASA Astrophysics Data System (ADS)

The study of the large collections of plant remains gained from cores of numerous boreholes drilled in Western Siberia made it possible to determine the taxonomic composition of the Jurassic flora of this region, the stages of its evolution, and the sequence of floral assemblages, which characterize the regional stratigraphic horizons indirectly correlated via series of parallel faunal, microfaunal, spore and pollen zonal scales with a general stratigraphic scale. The compositions of floral assemblages was established in the Hettangian-lower part of the upper Pliensbachian, upper part of the upper Pliensbachian, lower Toarcian, upper Toarcian, Aalenian, Bajocian, Bathonian, and Callovian-Oxfordian sediments. Criteria were elaborated to substantiate the Triassic-Jurassic and Lower-Middle Jurassic boundaries. Lithologically and biostrati-graphically, the Middle-Upper Jurassic boundary is poorly expressed.

Mogutcheva, N. K.

2014-05-01

283

Tiny Fossil Sheds Light on Mammalian Evolution  

NSDL National Science Digital Library

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

De Nie, Michael W.

2001-01-01

284

Late Cretaceous-Eocene marginal seas in the Black Sea-Caspian region: Paleotectonic reconstructions  

Microsoft Academic Search

A series of seven reconstructions is presented to illustrate the evolution of marginal seas in the Black Sea-South Caspian\\u000a segment of the margin of the Tethys Ocean from the Late Jurassic to the middle Eocene. After Middle Jurassic inversion and\\u000a until the Aptian Age, no marginal (backarc) basins were formed in the region, while the Pontides-Rhodope margin developed\\u000a in the

V. G. Kaz’min; N. F. Tikhonova

2006-01-01

285

Molecular and Fossil Evidence on the Origin of Angiosperms  

NASA Astrophysics Data System (ADS)

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.

Doyle, James A.

2012-05-01

286

Organic Walled Phytoplankton Response to Changes in Early Jurassic Paleoceanography  

NASA Astrophysics Data System (ADS)

The Early Jurassic is considered to be a watershed phase in the evolution of two groups of photosynthetic phytoplankton taxa, i.e. coccolithophorids and thecate dinoflagellates. Both groups are important primary producers in the contemporary ocean. Especially the Upper Pliensbachian has caught our attention, since this interval shows rapid diversification of phytoplankton and directly precedes the Toarcian Oceanic Anoxic Event. The aim of this study is to understand long term changes in paleoceanography leading to the Toarcian OAE and affecting evolution and radiation of cyst producing dinoflagellates. For this purpose an integrated geochemical (?13Ccarb, ?13Corg, TOC, HI) and palynological study was performed on the Mochras Borehole (Wales, UK). The appearance of the missing link Liasidium variabile during the Middle Sinemurian marks the onset of a long term (U. Sin.- L. Pliensb.) ?13Ccarb increase from 0%{tiny 0} - +4%{tiny 0} and increase in TOC (>2%). Prior to this dinocyst diversity is extremely low. The Upper Pliensbachian to Lower Toarcian shows decreasing ?13Ccarb and background TOC (<0.5%) values coincidental with a rapid diversification of cold water species. During the Toarcian OAE phytoplankton is entirely dominated by prasinophytes (green algae), which have their highest abundance in conjunction with very negative ?13Ccarb and ?13Corg isotope values. The Upper Pliensbachian represents a major turning point in the radiation and evolution of thecate dinoflagellates related to changes in ocean circulation/chemistry that preconditioned shelf areas for the Toarcian OAE. We suggest the Late Pliensbachian was generally cold leading to the southward spread of cool Boreal water, increased mixing and oxygenation of bottom waters. These conditions appear to have been more advantageous to phytoplankton with benthic resting stages than the adverse anoxic, stratified and warm conditions that prevailed during the Early Pliensbachian and Early Toarcian.

van de Schootbrugge, B.; Bailey, T. R.; Katz, M. E.; Wright, J. D.; Feist-Burkhardt, S.

2003-04-01

287

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

USGS Publications Warehouse

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.

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

1996-01-01

288

Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns.  

PubMed

Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed "living fossils" has remained unchanged over at least 180 million years-a paramount example of evolutionary stasis. PMID:24653037

Bomfleur, Benjamin; McLoughlin, Stephen; Vajda, Vivi

2014-03-21

289

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

NASA Astrophysics Data System (ADS)

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.

Fernández, Marta; Gasparini, Zulma

2008-01-01

290

Rapid compositional change and significant loss of plant species diversity among Triassic-Jurassic palynofloras in East Greenland  

NASA Astrophysics Data System (ADS)

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.

Mander, Luke; Kürschner, Wolfram; McElwain, Jennifer

2010-05-01

291

Prolific Overton field gas reservoirs within large transverse oolite shoals, Upper Jurassic Haynesville, Eastern Margin East Texas basin  

SciTech Connect

Late Triassic rifting along a northeast-southwest spreading center in east Texas resulted in basement highs along the eastern margin of the East Texas basin that became sites of extensive ooid shoal deposition during Late Jurassic time. Reservoirs within oolite facies at Overton field contain over 1 tcf of natural gas. These large shoals, each approximately 15 mi (24 km) long and 3 mi (4.8 km) wide, trend north-south as a group and northeast-southwest individually. They are oblique to the basin margin but parallel with Jurassic diffracted tidal currents within the East Texas embayment. Modern Bahamian ooid shoals of similar size, trend, and depositional setting occur at the terminus of the deep Tongue-Of-The-Ocean platform reentrant. Overton field reservoirs are in ooid grainstone shoal facies and in transitional shoal margins of skeletal-oolitic-peloidal grainstones and packstones. Adjacent nonreservoir facies are peloidal-skeletal-siliciclastic wackestones and mudstones. Early diagenesis of grainstone reservoir facies included meteoric dissolution and grain stabilization, resulting in abundant chalky intraparticle porosity and equant and bladed calcite cements filling interparticle porosity. Subsequent burial diagenesis resulted in intense solution compaction and coarse equant calcite and saddle crystal dolomite that occluded remaining interparticle porosity. Whole-rock trace element analysis indicates greatest diagenetic flushing (less magnesium, strontium) in porous zones. Stable isotopes for grains and cements show strong overprint of later burial diagenesis, with greater depletion of delta/sup 18/O in reservoir facies. However, hydrocarbons were emplaced prior to late cementation, and unlike other Jurassic Gulf Coast reservoirs, deep burial diagenesis provided no late-stage formation of porosity.

Glynn, W.G.; Covington, T.E.; Lighty, R.G.; Ahr, W.M.

1985-02-01

292

Sustainable Fossil Fuels  

Microsoft Academic Search

More and more people believe we must quickly wean ourselves from fossil fuels - oil, natural gas and coal - to save the planet from environmental catastrophe, wars and economic collapse. Professor Jaccard argues that this view is misguided. We have the technological capability to use fossil fuels without emitting climate-threatening greenhouse gases or other pollutants. The transition from conventional

Mark Jaccard

293

"It's Alive!" Fossil Activity  

NSDL National Science Digital Library

The first lab activity for the course is called "PaleontologyâPast, Present, and Future". In addition to discussing several documents related to present and future research directions in the field, students review a brief timeline of the historical development of paleontology as a science. Then they get their first opportunity to work directly with fossils. Students are presented with a set of fossil specimens in boxes (with no identifying labels). Each student selects one fossil of their own. They are asked to make and record very close, detailed observations of the specimen, and to sketch the fossil. Then they are told to "think like it's 1600." Someone has brought this object, taken out of the local rocks, for the student to investigate. The student must write a "proof" that this fossil was obviously once alive, and is not just an interesting mineral or rock formation. They can use their observations, compare the specimen to other objects with which they're familiar, resort to pure logic, or apply any other avenue of argumentation they think will help make their case. Note: In the next lab, on fossil preservation and taphonomy, the students revisit their fossil specimen, and determine its mode of preservation. Indeed, the student's "pet fossil" could be used throughout the course to illustrate various components of the course content.

Yacobucci, Peg

294

Becoming a Fossil  

NSDL National Science Digital Library

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

2005-01-01

295

Trace Fossil Image Database  

NSDL National Science Digital Library

This database from Emory University consists of images and basic information concerning trace fossils photographed by Anthony Martin. Included in this information is the formation, age, and locality of the specimen if known. Many of the images were originally photographed while in the field, and each type of trace fossil has numerous examples to browse through.

Martin, Anthony; University, Emory

296

Restoring Fossil Creek  

ERIC Educational Resources Information Center

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…

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

2004-01-01

297

Fossil Dig Site  

NSDL National Science Digital Library

In this activity (located on page 5 of PDF), learners work in groups to create dig sites for display. Learners arrange dry, uncooked pasta "bones" to resemble dinosaur fossils on a foam tray of wet soil. Use this activity to introduce learners to dinosaur anatomy, dig sites, fossils, and paleontology in general.

Museum, Chicago C.

2011-01-01

298

Dinosaur Footprints & Fossils  

NSDL National Science Digital Library

In this activity, early learners simulate fossil prints in play dough or clay. Using plastic dinosaur feet to make footprints on their âmudâ (much as dinosaurs walked around their habitat) and harvest items (leaves, corn, twigs, acorns) to make impressions, learners simulate fossil prints. This resource includes open-ended discussion questions to encourage reflection.

Omsi

2004-01-01

299

Make a Model Fossil  

NSDL National Science Digital Library

This activity is a combination outdoor/indoor lab where students will collect natural materials from the environment and use them to create both a mold and cast model of a fossil. Students will learn how a fossil is formed and why scientists use models to help them understand how things work and develop.

300

Stratigraphy of Upper Jurassic Morrison and Lower Cretaceous Cloverly formations of Big Horn basin, northern Wyoming  

SciTech Connect

The Morrison and Cloverly Formations in the Big Horn basin of northern Wyoming and southern Montana are part of a distal edge of a westward-thickening clastic wedge of sediment deposited in an elongate intracontinental basin in the western North American craton. These formations reflect orogenic and volcanic activity in the western Cordillera during Late Jurassic and the subsequent eastward migration of volcanic centers during Early Cretaceous. The Morrison Formation (Upper Jurassic) conformably overlies the Jurassic marine Sundance Formation and consists of light olive-green, lenticular, calcareous siltstones and mudstones interbedded with white to buff or yellowish green, massive and cross laminated, calcareous quartz-arenites. The Cloverly Formation (Lower Cretaceous) consists of three members: the Pryor Conglomerate, and Little Sheep Mudstone, and the Himes; it overlies the Morrison Formation both conformably and unconformably. Both the Morrison and Cloverly Formations are characterized by high ratios of overbank fines relative to coarse channel sands. It has been assumed, but not documented by detailed sedimentologic study, that the deposits were part of an aggrading alluvial flood plain complex dotted by seasonal lakes and swamps and crossed by braided rivers. This model deviates from most modern braided systems which are characterized by rapid lateral mobility and the lack of fine-grained overbank material. The large ratio of fine-grained siltstones and mudstones to coarser grained sandstones can be explained by a number of processes, the most probable being rapid overbank aggradation as a result of a large influx of windblown volcanic material from vents to the west.

Kvale, E.P.; Vondra, C.F.

1983-08-01

301

Increased Atmospheric SO2 Detected from Changes in Leaf Physiognomy across the Triassic-Jurassic Boundary Interval of East Greenland  

PubMed Central

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.

Bacon, Karen L.; Belcher, Claire M.; Haworth, Matthew; McElwain, Jennifer C.

2013-01-01

302

Eumetazoan fossils in terminal Proterozoic phosphorites?  

PubMed Central

Phosphatic sedimentary rocks preserve a record of early animal life different from and complementary to that provided by Ediacaran fossils in terminal Proterozoic sandstones and shales. Phosphorites of the Doushantuo Formation, South China, contain eggs, egg cases, and stereoblastulae that document animals of unspecified phylogenetic position; small fossils containing putative spicules may specifically record the presence of sponges. Microfossils recently interpreted as the preserved gastrulae of cnidarian and bilaterian metazoans can alternatively be interpreted as conventional algal cysts and/or egg cases modified by diagenetic processes known to have had a pervasive influence on Doushantuo phosphorites. Regardless of this interpretation, evidence for Doushantuo eumetazoans is provided by millimeter-scale tubes that display tabulation and apical budding characteristic of some Cnidaria, especially the extinct tabulates. Like some Ediacaran remains, these small, benthic, colonial fossils may represent stem-group eumetazoans or stem-group cnidarians that lived in the late Proterozoic ocean.

Xiao, Shuhai; Yuan, Xunlai; Knoll, Andrew H.

2000-01-01

303

Relative importance of the Hercynian and post-Jurassic tectonic phases in the Saharan platform: a palaeomagnetic study of Jurassic sills in the Reggane Basin (Algeria)  

NASA Astrophysics Data System (ADS)

In the intracontinental domain of the northwestern Saharan platform, the deformation of the Palaeozoic sedimentary cover is mainly attributed to a far-field effect of the Hercynian orogeny having occurred at the African-Laurusian plate boundary in the Late Carboniferous to Early Permian times. However, geological observations from different parts of Africa and Arabia provide evidence that several minor but widespread tectonic events occurred later, particularly during the Cretaceous. Contrary to elsewhere in the northwestern part of Africa, in the Reggane Basin, outcropping doleritic sills of Early Jurassic age are intruded in folded Palaeozoic sediments of Devonian to Carboniferous ages deposited before the Hercynian orogeny. In this favourable situation, a palaeomagnetic study of the Liassic dolerite is able to provide information on the tectonic history of the surrounding area independently from geological observations. The present study aims to quantify the relative proportion of tilting related to, respectively, the Hercynian and a post-intrusion phase, using a fold test based on the small circle analysis. This method proved to be very efficient to unravel these tectonic events. It shows that, in the studied area, the folds were initiated during the Hercynian phase, but mainly amplified during the post-intrusion phase which turned out to be the dominant one. In the Reggane Basin, the age of this second event is not geologically well constrained between probably Late Jurassic and Early Cretaceous. It could be the far-field effect of either the Cimmerian phase (~140 Ma) or more likely the Austrian tectonic phase (Late Barremian, ~125 Ma). The Late Barremian tectonic episode corresponds to a major event: the break-up of Western Gondwana, which led to the separation of Africa from South America and to the incipient fragmentation of the African plate into three major blocks. The conclusion drawn from the palaeomagnetic study in the Reggane Basin is consistent with the geological observations and representative of the intraplate Cretaceous deformations recorded in many other places in Africa. It emphasizes once again that stresses can be transferred far from the plate boundaries, into the continental plate interiors.

Smith, B.; Derder, M. E. M.; Henry, B.; Bayou, B.; Yelles, A. K.; Djellit, H.; Amenna, M.; Garces, M.; Beamud, E.; Callot, J. P.; Eschard, R.; Chambers, A.; Aifa, T.; Ait Ouali, R.; Gandriche, H.

2006-10-01

304

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

305

Problematic microscopic trace (?) fossils, Oligocene, Slovakia  

NASA Astrophysics Data System (ADS)

Meioscopic to microscopic capsules found in reddish, probably marine or brackish shales (Oligocene, Pannonian Basin; South Slovakia) are interpreted as possible trace fossils. They may represent burrows of meioscopic in-fauna. Ferruginous walls of the capsules appeared very probably as late as during diagenesis; however, the (possibly organic) matrix had to exist before the diagenetic processes. Other discussed explanations (inorganic "ironstones"; coprolites) are not plausible.

Mikuláš, R.; Boorová, D.; Holcová, K.

2013-05-01

306

Polarity Zones and Apparent Polar Wander at the Jurassic /Cretaceous Boundary in the Southern Alps, Italy  

NASA Astrophysics Data System (ADS)

The magnetic and nannofossil stratigraphies of several sections spanning the Jurassic/Cretaceous (J/K) boundary have been studied in the Lombardian Basin (Torre de Busi, Colle di Sogno) and Trento Plateau (Colme di Vignole, Foza). The magnetic stratigraphies span the CM16R (late Berriasian) to the CM22 (Kimmeridgian/Tithonian boundary) interval corresponding to the 138-150 Ma interval spanning the J/K boundary (142 Ma). In Lombardy, the facies transition from "Rosso ad Aptici" (siliceous limestone) to Maiolica (pelagic limestone) occurs in the latest Tithonian (CM19N-CM20N), just prior to the J/K boundary, closely synchronous with the transition from Rosso Ammonitico to Maiolica on the Trento Plateau. The identification of polarity zones is based on polarity-zone pattern fit, and the previously established correlations of polarity chrons to nannofossil events/zones. The apparent polar wander path (APWP) for each section is calibrated based on the magnetic stratigraphy and lies close to an estimated African APWP of the same age, implying very little rotation of the Lombardian and Trento plateau regions of the Southern Alps relative to Africa since latest Jurassic time. Our objective is to produce a calibrated APWP (polar wander by polarity chron), and thereby improve the definition of the Adria APWP in this interval of relatively rapid apparent polar wander.

Channell, J. E.; Muttoni, G.; Casellato, C.; Erba, E.

2007-12-01

307

A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs  

PubMed Central

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.

Pol, Diego; Rauhut, Oliver W. M.

2012-01-01

308

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

PubMed Central

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.

Klompmaker, Adiel A.; Fraaije, Rene H. B.

2012-01-01

309

Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus  

PubMed Central

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.

Reisz, Robert R.; Evans, David C.; Roberts, Eric M.; Sues, Hans-Dieter; Yates, Adam M.

2012-01-01

310

Forever Love: The Hitherto Earliest Record of Copulating Insects from the Middle Jurassic of China  

PubMed Central

Background Mating behaviors have been widely studied for extant insects. However, cases of mating individuals are particularly rare in the fossil record of insects, and most of them involved preservation in amber while only in rare cases found in compression fossils. This considerably limits our knowledge of mating position and genitalia orientation during the Mesozoic, and hinders our understanding of the evolution of mating behaviors in this major component of modern ecosystems. Principal Finding Here we report a pair of copulating froghoppers, Anthoscytina perpetua sp. nov., referable to the Procercopidae, from the Middle Jurassic of northeastern China. They exhibit belly-to-belly mating position as preserved, with male's aedeagus inserting into the female's bursa copulatrix. Abdominal segments 8 to 9 of male are disarticulated suggesting these segments were twisted and flexed during mating. Due to potential taphonomic effect, we cannot rule out that they might have taken side-by-side position, as in extant froghoppers. Genitalia of male and female, based on paratypes, show symmetric structures. Conclusions/Significance Our findings, consistent with those of extant froghoppers, indicate froghoppers' genitalic symmetry and mating position have remained static for over 165 million years.

Li, Shu; Shih, Chungkun; Wang, Chen; Pang, Hong; Ren, Dong

2013-01-01

311

Paleogeographic Reconstructions in the Mediterranean - A Paleomagnetic Study of Jurassic Sediments From Sardinia  

NASA Astrophysics Data System (ADS)

The paleogeography and tectonic history of the Corsica-Sardinia block and the opening of the Liguro-Provençal ocean since Oligocene times is based on a wealth of geologic, geophysical, and paleomagnetic studies and relatively well understood (Gattacceca et al. 2007, Vigliotti and Langenheim 1995). Conversely, the paleogeography of Sardinia and the surrounding regions during the Mesozoic is much less clear due to the absence of paleomagnetic data, except for a single study on Jurassic sediments from eastern Sardinia (Horner and Lowrie 1981). Consequently, pre-Oligocene deformations of Sardinia remain virtually undated. Recent paleomagnetic studies of dykes of Late Carboniferous and Permian age as well as Permian sediments have revealed significant counterclockwise rotations between Northern, Central and Southern Sardinia (Emmer et al., 2005). The geodynamic context these rotational movements are related to, however, is still far from being clear. In an attempt to contribute to better time constraints for tectonic motions within Sardinia, a total of 208 oriented core samples from 24 sites of predominantly Jurassic age have been collected from the Nurra region (1), the Gulf of Orosei (2) and the Tacchi region (3). Unfortunately, samples taken from the northwest of Sardinia (1) proved to be too weakly magnetized and did not yield any stable directions. Primary directions of magnetization, passing the reversal test, were recovered from regions (2) and (3), yielding overall mean directions of D=284.8°, I=46.6° (N=36, ?95=9.9, k=32.1) and D=267.0°, I=49.9° (N=68, ?95=12.3, k=13.5) for the Gulf of Orosei and the Tacchi region, respectively. Taking into account error limits, these directions are not significantly different from each other and confirm and expand the limited data set of Horner and Lowrie (1981). Based on these new results, we conclude that no post-Jurassic deformation has affected the region. This suggests that the counterclockwise rotations previously observed in Permian rocks by Emmer et al. must be pre-Jurassic in age and cannot be related to subduction rollback tectonics during the Oligocene to Miocene as suggested by Helbig et al. (2006).

Aubele, K.; Bachtadse, V.; Muttoni, G.

2009-05-01

312

Supraregional seismites in Triassic - Jurassic boundary strata  

NASA Astrophysics Data System (ADS)

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.

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

313

The “van Zijl” Jurassic geomagnetic reversal revisited  

NASA Astrophysics Data System (ADS)

We have collected two new detailed records of what could be the second oldest well documented reversal, the "van Zijl" Jurassic (˜180 Ma) reversal recorded in the thick basalt sequences of the Karoo large igneous province in Lesotho and South Africa. Sections yielded 10 and 8 independent transitional paleomagnetic directions respectively over two continuous 130 m and 160 m sequences. The corresponding VGP reversing paths share a number of consistent features and are integrated with a third record at Bushmen's Pass from Prévot et al. (2003) to yield a single reversal path with: 1- a large directional jump with no transitional poles between 45°S and 45°N in the first, main phase of the reversal, 2- a large elongated loop (multiple hairpin) to the SE with poles going down to ˜20° latitudes in the second phase of the reversal, and 3- a rebound before finally settling in normal polarity. We have measured relative paleo-intensities on a set of carefully selected samples. Intensity was low prior to the directional changes and recovery to the following normal polarity was progressive. Transitional intensity is 80 to 90% lower than full polarity values. There is no significant increase in intensity at the time of transitional directional clusters. Our results are consistent with a weak non-dipolar reversing field, with faster and larger directional secular variation as the equator is crossed by VGPs. They tend to vindicate the notion of a short duration of the directional reversal, though one cannot draw global conclusions from a record limited to essentially a single location.

Moulin, Maud; Courtillot, Vincent; Fluteau, FréDéRic; Valet, Jean-Pierre

2012-03-01

314

Survival of Theriosuchus (Mesoeucrocodylia: Atoposauridae) in a Late Cretaceous archipelago: a new species from the Maastrichtian of Romania  

NASA Astrophysics Data System (ADS)

Small terrestrial non-eusuchian mesoeucrocodylians are common components of Cretaceous assemblages of Gondwanan provinces with notosuchians and araripesuchids as flagship taxa in South America, Africa and Madagascar, well into the Late Cretaceous. On the other hand, these are exceedingly rare in Laurasian landmasses during the Late Cretaceous. Small terrestrial mesoeucrocodylians from Europe were often referred to the genus Theriosuchus, a taxon with stratigraphic range extending from the Late Jurassic to the late Early Cretaceous. Theriosuchus is abundantly reported from various European localities, although Asiatic and possibly North American members are also known. It has often been closely associated with the first modern crocodilians, members of the Eusuchia, because of the presence of procoelous vertebrae, a widespread key character diagnosing the Eusuchia. Nevertheless, the relationships of Theriosuchus have not been explored in detail although one species, Theriosuchus pusillus, has been extensively described and referred in numerous works. Here, we describe a new basal mesoeucrocodylian, Theriosuchus sympiestodon sp. nov. from the Maastrichtian of the Ha?eg Basin, Romania, suggesting a large temporal gap (about 58 myr) in the fossil record of the genus. Inclusion of the new taxon, along with Theriosuchus guimarotae, in a phylogenetic analysis confirms its referral to the genus Theriosuchus, within a monophyletic atoposaurid clade. Although phylogenetic resolution within this clade is still poor, the new taxon appears, on morphological grounds, to be most closely related to T. pusillus. The relationships of Atoposauridae within Mesoeucrocodylia and especially to Neosuchia are discussed in light of the results of the present contribution as well as from recent work. Our results raise the possibility that Atoposauridae might not be regarded as a derived neosuchian clade anymore, although further investigation of the neosuchian interrelationships is needed. Reports of isolated teeth referable to a closely related taxon from the Upper Cretaceous of Romania and France, together with the presence of Doratodon and Ischyrochampsa, indicate a previously unsuspected diverse assemblage of non-eusuchian mesoeucrocodylians in the Late Cretaceous European archipelago.

Martin, Jeremy E.; Rabi, Márton; Csiki, Zoltán

2010-09-01

315

Reappraisal of Displacement of Northern Cordilleran Terranes Since the Triassic and Jurassic  

NASA Astrophysics Data System (ADS)

Triassic-Jurassic paleomagnetic data from the Cordillera of Canada had initially indicated displacements of about 1000 km from the south. Later, as a result of revisions in the APW path for North America, it was contended that there had been no such displacements. The Cordilleran data are from Wrangellia (Nicolai/Karmutsen (225 Ma) and Bonanza (195 Ma) formations) and Stikinia (Hazelton (195-180 Ma) and Stuhinni (~210 Ma) formations). These are two largest exotic superterranes in the Cordillera. Data all are from massive lavas (mainly) or diabase sills whose bedding attitudes are well controlled and whose magnetizations are believed to record accurately the field direction. On the other hand, several of the APW paths determined from North America that were sometimes used for reference are dominated by results from sedimentary rocks, which recently published work using directional distributions and anisotropy measurements has demonstrated are commonly affected by inclination flattening, for example, Late Triassic and Early Jurassic sedimentary rocks in rift basins of eastern North America. When corrected for inclination flattening, sedimentary data agree with inclinations from coeval igneous rocks when these data are available, for example, 200 Ma CAMP volcanics, but don't support the J1 cusp, previously a cornerstone of many APW paths for North America. In order to avoid possible shallow bias in latitude determinations, we make a special effort to avoid errors arising from inclination-flattening in sedimentary rocks by (1) using only data from sedimentary rocks that have been corrected for inclination-flattening, and by rejecting all other sedimentary data, and (2) incorporating igneous data from all other major continents. Relative to present geography the global APW path relative to North America begins in Mongolia in the Early Triassic, trends north-northwest towards the estuary of the Ob River by the end of the Early Jurassic, where it lingers before rapidly moving to the vicinity of Nunivak Island by the end of the Jurassic (and then boomerangs to the Cretaceous standstill position in the Chukchi Sea). Cordilleran magnetizations always have inclinations that are shallower than expected from the reference path. There is therefore no ambiguity about the sense of displacements - they are always from the south relative to cratonic North America. However, within these structurally disrupted terranes, only individual poles and not their paths can be constructed and there are uncertainties in relating individual results to the global polarity time-scale, and so we cannot say, from the paleomagnetic evidence alone, whether the terranes were in the southern or the northern hemisphere during the early Mesozoic. Assuming the closest (northern hemisphere) position, all the Cordilleran terrane strata nevertheless give displacements of about 1000 km or more. The Nicolai of Alaska yields a displacement of ~2500 km which reflects the strong northward motion of SE Alaska in the Tertiary. We believe this settles the debate: Triassic and Jurassic rocks of Wrangellia and Stikinia all have been displaced significantly from the south. Notable also are the strong anticlockwise rotations of 40°-60° from the Nicolai (Triassic), Bonanza and Hazelton (Jurassic), which have been observed also by Enkin throughout the stratigraphy of the Skeena fold- belt of central Stikinia. The Karmutsen (Triassic) of Vancouver Island shows a huge 150° anticlockwise rotation, perhaps a composite of several deformation phases.

Kent, D. V.; Irving, E.

2008-12-01

316

Fossil Halls: Curator Videos  

NSDL National Science Digital Library

Part of a larger virtual tour of the Museum's famed Fossil Halls, this Web site has links to a library of 22 videos highlighting specific exhibits in the hall. The videos are available in broadband and dial-up versions.

317

Advances in Fossil Energy.  

National Technical Information Service (NTIS)

The Morgantown Technology Center is a US Department of Energy fossil fuel research center. It is reponsible for conducting research and development to extract, convert, and utilize coal, oil, and gas in an environmentally acceptable manner. METC performs ...

1984-01-01

318

Minerals and Fossils  

NSDL National Science Digital Library

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

Mineraltown.com

319

Fossil energy program  

NASA Astrophysics Data System (ADS)

The progress made during the period from July 1 through September 30 for the Oak Ridge National Laboratory research and development projects in support of the increased utilization of coal and other fossil fuels as sources of clean energy is reported. The following topics are discussed: coal conversion development, chemical research and development, materials technology, fossil energy materials program, liquefaction projects, component development, process analysis, environmental control technology, atmospheric fluidized bed combustion, underground coal gasification, coal preparation and waste utilization.

McNeese, L. E.

1981-12-01

320

Facies changes in the Triassic–Jurassic boundary interval in an intraplatform basin succession at Cs?vár (Transdanubian Range, Hungary)  

Microsoft Academic Search

A continuous, pelagic marine Triassic–Jurassic boundary section is exposed in newly excavated trenches in the surroundings of Cs?vár, NE of Budapest, Hungary. In the late Triassic, this area was located close to the offshore margin of the Dachstein carbonate platform system that was segmented by intraplatform basins. Based on detailed facies analysis of the Rhaetian–Hettangian platform foreslope–basin succession, a long-term

János Haas

2004-01-01

321

Revisiting Early-Middle Jurassic igneous activity in the Nanling Mountains, South China: Geochemistry and implications for regional geodynamics  

NASA Astrophysics Data System (ADS)

Early-Middle Jurassic igneous rocks (190-170 Ma) are distributed in an E-W-trending band within the Nanling Tectonic Belt, and have a wide range of compositions but are only present in limited volumes. This scenario contrasts with the uniform but voluminous Middle-Late Jurassic igneous rocks (165-150 Ma) in this area. The Early-Middle Jurassic rocks include oceanic-island basalt (OIB)-type alkali basalts, tholeiitic basalts and gabbros, bimodal volcanic rocks, syenites, A-type granites, and high-K calc-alkaline granodiorites. Geochemical and isotopic data indicate that alkaline and tholeiitic basalts and syenites were derived from melting of the asthenospheric mantle, with asthenosphere-derived magmas mixing with variable amounts of magmas derived from melting of metasomatized lithospheric mantle. In comparison, A-type granites in the study area were probably generated by shallow dehydration-related melting of hornblende-bearing continental crustal rocks that were heated by contemporaneous intrusion of mantle-derived basaltic magmas, and high-K calc-alkaline granodiorites resulted from the interaction between melts from upwelling asthenospheric mantle and the lower crust. The Early-Middle Jurassic magmatic event is spatially variable in terms of lithology, geochemistry, and isotopic systematics. This indicates that the deep mantle sources of the magmas that formed these igneous rocks were significantly heterogeneous, and magmatism had a gradual decrease in the involvement of the asthenospheric mantle from west to east. These variations in composition and sourcing of magmas, in addition to the spatial distribution and the thermal structure of the crust-mantle boundary during this magmatic event, indicates that these igneous rocks formed during a period of rifting after the Indosinian Orogeny rather than during subduction of the paleo-Pacific oceanic crust.

Ye, Hai-Min; Mao, Jian-Ren; Zhao, Xi-Lin; Liu, Kai; Chen, Dan-Dan

2013-08-01

322

Early Evolution and Historical Biogeography of Fishflies (Megaloptera: Chauliodinae): Implications from a Phylogeny Combining Fossil and Extant Taxa  

PubMed Central

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.

Liu, Xingyue; Wang, Yongjie; Shih, Chungkun; Ren, Dong; Yang, Ding

2012-01-01

323

Jurassic-Cretaceous palynomorphs, palynofacies, and petroleum potential of the Sharib-1X and Ghoroud-1X wells, north Western Desert, Egypt  

NASA Astrophysics Data System (ADS)

Palynomorph and palynofacies analyses have been performed on 93 cutting samples from the Jurassic Masajid Formation and Cretaceous Alam El Bueib, Alamein, Dahab, Kharita, and Bahariya formations in the Sharib-1X and Ghoroud-1X wells, north Western Desert, Egypt. Two palynological biozones are proposed for the studied interval of the Sharib-1X well: the Systematophora penicillata-Escharisphaeridia pocockii Assemblage Zone (Middle to Late Jurassic) and the Cretacaeiporites densimurus-Elateroplicites africaensis-Reyrea polymorpha Assemblage Zone (mid-Cretaceous: late Albian to early Cenomanian). Spore coloration and visual kerogen analysis are used to assess the thermal maturation and source rock potential. Mature oil prone to overmature gas prone source rocks occur in the studied interval of the Sharib-1X well, whereas highly mature to overmature gas prone source rocks occur in the studied interval of the Ghoroud-1X well. Palynofacies and palynomorph assemblages in both wells reflect shallow marine conditions throughout the Jurassic and the late Albian and early Cenomanian. During these times, warm and dry climatic conditions prevailed. The Cretaceous palynomorph assemblages of the Sharib-IX well correlate with the Albian-Cenomanian Elaterates Province of Herngreen et al. (1996).

Zobaa, Mohamed K.; El Beialy, Salah Y.; El-Sheikh, Hassan A.; El Beshtawy, Mohamed K.

2013-02-01

324

The "van Zijl" Jurassic geomagnetic reversal revisited  

NASA Astrophysics Data System (ADS)

In 1962, van Zijl and colleagues published the first record of one of the oldest reversals available in some detail. This was a Jurassic reversal recorded in the basaltic sequence of the Lesotho, part of the Karoo large igneous province. In 2003, Prévot and colleagues provided a second more accurate record (Bushmen's Pass section - BP). We have recently obtained two other detailed records from two sections (Naude's Nek NN and Oxbow-Moteng Pass OM). The reversal is therefore now recorded in some detail in three sections which are up to 200km away from each other (the age being at ~180Ma). The reversal is recorded as 23 transitional directions over 130m in NN. When lava flows having recorded the (statistically) same direction to within a few degrees, which likely belong to the same cooling unit, are regrouped (directional groups or DG), we are left with 10 independent directions. There are 13 transitional directions over 160m in OM, and 8 distinct, independent directions. And in the BP section, there are 35 transitional directions over 200m, and 21 independent directions. The three records are remarkably similar and at the same time complementary. They can be used to retrace the VGP reversal path in a unique and robust way. Directions display 4 strong clusters which are interpreted as times of slow secular variation and/or fast extrusion rate of the lava. The path jumps from transitional reversed to transitional normal directions with no intermediate directions between 30°S and 30°N (once the path has been restored to proper geographical coordinates applicable to the ~180Ma reconstruction of the continents). We have applied several techniques to determine the evolution of relative paleo-intensities during the reversal; all these methods converge to the same conclusion, with intensities lower by a factor close to 10 between the core of the reversal and the time when full normal polarity has been regained, with intermediate intensities just before and after the core of the reversal. These observations are consistent with fast and large secular variation at a time when field intensity was the weakest and field geometry the least dipolar. The question which remains is how complete is this record? At the same time, the fact that it has been recorded in such a consistent way in three very remote sections would argue in favor of a positive answer, though the large extent and volume of Karoo cooling units may argue to the contrary...

Courtillot, V.; Moulin, M.; fluteau, F.; Valet, J. M.

2011-12-01

325

Fossil Simulation in the Classroom  

ERIC Educational Resources Information Center

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)

Hoehn, Robert G.

1977-01-01

326

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

USGS Publications Warehouse

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.

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

1984-01-01

327

A report on biocompounds from palm fossil of India.  

PubMed

The occurrence of a large number of fossil woods having resemblance in anatomical features with the modern palm genus, Phoenix L in Deccan Intertrappean fossil flora of Maastrichtian-Danian age (i. e. Late Cretaceous and Earliest Tertiary (65-67 my)) indicates the most primitive record of date palm. Present discovery of biocompounds from fossil wood of Phoenix collected from Deccan Intertrappean having affinity with the biocompounds known from modern plant further exemplify the earliest documentation of Phoenix in Indian peninsula. PMID:24966541

Sharma, Dinesh Chandra; Khan, Mohd Sajid; Khan, M Salman; Srivastava, Rashmi; Srivastava, Ashwini Kumar; Shukla, Ritu

2014-01-01

328

Paleointensity of the Earth's magnetic field in the Jurassic: New results from a Thellier study of the Lesotho Basalt, southern Africa  

NASA Astrophysics Data System (ADS)

Thellier paleointensity experiments carried out on the Jurassic (180 m.y. old) Karoo basalt, Lesotho, southern Africa, provided paleointensity estimates for 40 samples from 10 distinct lava flows with reversed magnetization. Mean paleointensity was found to be equal to 24.2 ± 11.3 ?T (standard deviation), with a minimum of 12 ?T and a maximum of 41.3 ?T. This corresponds to a mean virtual dipole moment (VDM) of 4.6±2.0×1022 Am2. The between-flow dispersion is ascribed to paleosecular variation, which thus would approach up to 40% of the mean paleointensity, as is observed from the published paleointensity data set covering last 20 m.y. This result yields further evidence for the period of low geomagnetic field in Jurassic to Early Cretaceous time (Mesozoic Dipole Low). A symmetrical intensity versus time pattern is suggested for this time interval, with a minimum VDM of 3×1022 Am2 in Late Jurassic and substantially higher (˜ 4.5×1022 Am2) VDMs in Early to Middle Jurassic and Early Cretaceous, respectively.

Kosterov, Andrei A.; PréVot, Michel; Perrin, Mireille; Shashkanov, Vladimir A.

1997-11-01

329

Trace Fossil Analysis  

NASA Astrophysics Data System (ADS)

Today, the study of trace fossils—ichnology—is an important subdiscipline of geology at the interface of paleontology and sedimentology, mostly because of the efforts of Adolf Seilacher. His ability to synthesize various aspects of ichnology and produce a hierarchy of marine ichna and sedimentary facies has made ichnology useful worldwide in interpreting paleodiversity, rates of sedimentation, oxygenation of bottom water and sediment pore water, and depositional energy. Seilacher's book Trace Fossil Analysis provides a glimpse into the mind, methodology, and insights of the father of modern ichnology, generated from his course notes as a professor and a guest lecturer. The title sounds misleading—readers looking for up-to-date principles and approaches to trace fossil analysis in marine and continental strata will be disappointed. In his preface, however, Seilacher clearly gives direction for the use of his text: “This is a course book—meaning that it is intended to confer not knowledge, but skill.” Thus, it is not meant as a total compilation of all trace fossils, ichnotaxonomy, ichnological interpretations, applications, or the most relevant and up-to-date references. Rather, it takes the reader on a personal journey, explaining how trace fossils are understood in the context of their three-dimensional (3-D) morphology and sedimentary facies.

Hasiotis, Stephen T.

2009-05-01

330

Jurassic magnetostratigraphy, 4. Early Callovian through Middle Oxfordian of the Krakow Uplands (Poland)  

NASA Astrophysics Data System (ADS)

A magnetic polarity pattern has been constructed for the Early Callovian through Middle Oxfordian stages of the Jurassic from several ammonite-rich magnetostratigraphy sections within the Krakow-Czestochowa-Wielun region of southern Poland. These overlapping sections encompass portions of every ammonite from the late-Early Callovian through late-Middle Oxfordian; however, the presence of several hiatuses and condensed intervals within the shallow-marine to pelagic sediments preclude reliable identification of the complete polarity pattern. The mean Callovian-Oxfordian pole from these sites is at 74.3°N, 200.3°E (? 95 = 4.7°). The Callovian through Early Oxfordian is dominated by reversed polarity with a minimum of five normal-polarity zones. The early-Middle Oxfordian is predominantly of normal polarity, and the late-Middle Oxfordian is characterized by reversed polarity, with several relatively brief normal-polarity episodes. The Callovian and Oxfordian stages appear to average a minimum of two magnetic polarity reversals per million years. This reversal frequency is similar to the average Tertiary record, but is less than the reported spacing of Callovian and Oxfordian magnetic anomalies in the Pacific.

Ogg, James G.; Steiner, Maureen B.; Wieczorek, Jozef; Hoffmann, Mariusz

1991-06-01

331

The Fossil Record  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 9-12. It centers around fossils found in the Burgess Shale in western Canada. Topics include body shapes of fossils found, the movement of organisms from oceans to land, and whether organisms existed that did not fossilize. This part of geologic history began in the Cambrian Sea about 540 million years ago. The resource includes objectives, materials, procedures, discussion questions, evaluation ideas, extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

Wu, Lisa

332

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

NASA Astrophysics Data System (ADS)

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".

Vishnevskaya, Valentina

2014-05-01

333

Exploration in Jurassic of North Mafla, eastern Gulf of Mexico  

Microsoft Academic Search

Exploration in North Mafla focuses on general categories of prospects, potential reservoirs and their associated facies, and seismic modeling of available well control. Jurassic prospects in North Mafla can be classified into four general categories: (1) basement-related structures: (2) closures associated with the Pensacola-Destin peripheral fault trend, (3) salt anticlines, and (4) prospects associated with the interregional structural highs. Each

Kemmer

1987-01-01

334

Basic aspects of Jurassic landscape development in southeastern central Asia  

SciTech Connect

Based on detailed lithofacies and mineralogical-petrographic studies of the Jurassic terrigenous-carbonate-salt-bearing formations and of changes in characteristics of the basic cycles horizontally and vertically, five paleolandscape development stages have been identified. Each corresponds to a given time interval and geotectonic phase. Paleogeographic charts were constructed for each of the stages. They trace landscape changes in space and time.

Timofeev, P.P.; Bebeshev, I.I.; Makarov, Yu.V.

1986-11-01

335

Organic Walled Phytoplankton Response to Changes in Early Jurassic Paleoceanography  

Microsoft Academic Search

The Early Jurassic is considered to be a watershed phase in the evolution of two groups of photosynthetic phytoplankton taxa, i.e. coccolithophorids and thecate dinoflagellates. Both groups are important primary producers in the contemporary ocean. Especially the Upper Pliensbachian has caught our attention, since this interval shows rapid diversification of phytoplankton and directly precedes the Toarcian Oceanic Anoxic Event. The

B. van de Schootbrugge; T. R. Bailey; M. E. Katz; J. D. Wright; S. Feist-Burkhardt

2003-01-01

336

Triassic-Jurassic Mass Extinction: Evidence for Bolide Impact?  

Microsoft Academic Search

The Triassic-Jurassic (TJ) mass extinction event is one of the most severe in geologic history and is one of the five largest in the Phanerozoic with as many as 80% of the species lost. It is also one of the most poorly understood. Only a few geologic sections have been identified for the TJ extinction and most of those are

R. Perry; L. Becker; J. Haggart; R. Poreda

2003-01-01

337

A NEW SAUROPOD FROM THE JURASSIC OF PATAGONIA 1  

Microsoft Academic Search

Thanks to the excellent works of Lydekker and Huene, based principally on the materials which form part of the collections of the Museum of La Plata and were published in its Anales, the Cretaceous Argentine dinosaurs, especially the Saurischia, are known, if not completely, at least satisfactorily. In contrast, of the Jurassic representatives of these reptiles in our territory until

Angel Cabrera

338

What is a Fossil?  

NSDL National Science Digital Library

In this activity about dinosaurs, learners explore how and why fossils form. First, learners are introduced to dinosaur fossils by reading the book "Bones, Bones, Dinosaur Bones" by Byron Barton. Then, learners make impressions in clay using a seashell, pennies, dinosaur teeth and other items. Next, learners make dinosaur tracks in the clay as they "walk" plastic models across the soft clay. Learners also use sponges pre-cut in the shape of dinosaur feet to make more tracks. This activity is featured on page 29 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

339

FossilPlot  

NSDL National Science Digital Library

This spreadsheet application allows users to make graphs of the diversity and stratigraphic ranges of Phanerozoic marine animals. FossilPlot uses the compendium of marine animal genera compiled by J.J. Sepkoski and his associates at the University of Chicago, from 'A compendium of fossil marine animal genera', found in Bulletins of American Paleontology, v. 363, p. 1-560. The application operates in Microsoft Excel for PC or Mac, and is free for users to download. A slide show on how to use the application (also downloadable) is provided.

340

Hydrocarbon potential of a new Jurassic play, central Tunisia  

SciTech Connect

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.

Beall, A.O. (Arthur O. Beall International E P, Houston, TX (United States)); Law, C.W. (Geomath, Houston, TX (United States))

1996-01-01

341

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

PubMed

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

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

2006-06-01

342

Earliest Marine beds in the Jurassic sedimentary record near the Huajuapan-Petlalcingo region, southern Mexico and their paleogeographic implications  

NASA Astrophysics Data System (ADS)

A paleogeographic model of Jurassic-Cretaceous is presented, the study area is the region near Huajuapan de Leon in the Mixteca Terrane, Mexico where a sedimentary successions constituted by interlayered terrestrial and marine beds, provides evidence of transgression and regression episodes. The sediments in the study zone were deposited over a Paleozoic metamorphic basement, the Acatlan Complex. The stratigraphic features in the Middle Jurassic of the terrestrial beds indicate a depositional elements varying from alluvial fans to floodplains and channel deposits, represented by conglomerates, sandy conglomerates and sandstones. After, in the same epoch (Bajocian and Bathonian age) a transgression coming from the Pacific Ocean covered the region. A transitional zone between continental and marine sediments is situated between Tezoatlan and Petlalcingo, the actual cross section consists in the earliest marine beds: limestones interlayered with terrestrial beds. Fossil contents in this beds indicate an age between the Oxfordian and the Tithonian. During this period of transgression the paleogeography was dominated by a small bay with shallow waters connected in the south with the Pacific Ocean, represented principally by limestone and dolomite units. At the end of the transgression, volcanic episodes occurred and the land emerged again. The sedimentary beds were later affected by tectonic activity that produced a normal fault near Zapotitlan, putting the metamorphic basement in contact with the sedimentary sequence.

Contla, D.

2008-12-01

343

The "terminal Triassic catastrophic extinction event" in perspective: a review of carboniferous through Early Jurassic terrestrial vertebrate extinction patterns  

USGS Publications Warehouse

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.

Weems, R. E.

1992-01-01

344

Cement stratigraphy in Triassic and Jurassic limestones of the Weserbergland (northwestern Germany)  

NASA Astrophysics Data System (ADS)

Cement stratigraphy of the Korallenoolith (Oxfordian) and Trochitenkalk (Upper Muschelkalk) Formations, southern Lower Saxony Hills of Germany, is based on investigation of 232 carbonate samples by cathodoluminescence (CL). This enables subdivision of cements into four main generations: Generation 1, consisting of fine columnar, equant and syntaxial cements with blotchy CL and/or microdolomite inclusions, that is interpreted as originally submarine Mg calcitic precipitate. Generation 2, found in Jurassic samples only. These cements show intrinsic to non-luminescent CL with thin bright orange subzones and they are interpreted as meteoric phreatic calcites. Generation 3.1, characterized by zoned calcites with variable CL colours. These cements precipitated under shallow burial conditions, in a phreatic environment during an incipient stage of late diagenesis. Generation 3.2, with relatively uniform orange CL, indicative of precipitation in a stable chemical environment. This cement generation is interpreted as late diagenetic deep burial calcites. Generation 3.3, partially strongly zoned and with a characteristically intense CL contrast. It has been identified in only 17 of the 82 Trochitenkalk samples. Deformation twins end within this generation, indicating a post-tectonic genesis for the subsequent younger cement zones. The cements were probably precipitated in a near-surface environment characterized by reducing or variable Eh conditions. Generation 4, consisting of calcites that show intrinsic CL with bright orange subzones comparable to generation 2, but lacking deformation twins. These cements are interpreted as post-tectonic late diagenetic products of a meteoric phreatic environment. Based on detailed CL petrography, fifteen diagenetic events (three calcite cements, three dolomite generations, three fissure generations, two stages of dedolomitization, aragonite dissolution, matrix recrystallization and two stages of HMC ? LMC transformation) can be distinguished and timed relative to cement zonation. The progressively decreasing ?18O values for cement generations 1 to 3.2 likely reflect increasing temperatures caused by burial. The low ?18C values of cement generation 4 are probably a reflection of a meteoric diagenetic environment. A time—burial—cementation pathway can be modelled combining CL patterns, cement isotopic data and the subsidence history of the study area. The main features of this model are: (1) Generation 1 cements are submarine precipitates and their age therefore coincides with sedimentation. (2) Cement generation 3.1 of the Trochitenkalk commenced precipitation at a depth of about 120 m, reached during Late Triassic time. In case this minimum depth is also the formation depth of generation 3.1 in the Korallenoolith Formation, then precipitation of these cements started during Late Jurassic time. (3) Cement generation 3.2 of both the Trochitenkalk and the Korallenoolith Formation, precipitated at assumed depths > 1000 m, reached during the Doggerian and at the time of Jurassic/Cretaceous transition, respectively. (4) Cement generation 4 precipitated after the sediments had undergone telogenesis, and must thus be younger than the Intra-Senonian (Sub-Hercynian) tectonic phase and possibly even younger than the Paleocene tectonic pulse (Laramian Phase).

Bruckschen, P.; Neuser, R. D.; Richter, D. K.

1992-12-01

345

Fossil Halls: Virtual Tours  

NSDL National Science Digital Library

Part of a larger online look at the Museum's famed Fossil Halls, this Web site has an overview of the halls' many highlights and four QuickTime virtual tours:Hall of Saurischian Dinosaurs, Hall of Ornithischian Dinosaurs, Hall of Primitive Mammals, and Hall of Advanced Mammals.

346

Fossil Halls: Cladistics  

NSDL National Science Digital Library

Part of a larger virtual tour of the Museum's famed Fossil Halls, this Web site has an overview explaining the cladistic method of scientific analysis as well as how to read cladograms. It answers the following questions: What is the best way to reconstruct evolutionary history? What is a cladogram? What is an advanced feature? Why use cladistics?

347

Fossilization of Acidophilic Microorganisms  

Microsoft Academic Search

This study examines fossil microorganisms found in iron-rich deposits in an extreme acidic environment, the Tinto River in SW Spain. Both electron microscopy (SEM and TEM) and non-destructive in situ microanalytical techniques (EDS, EMP and XPS) were used to determine the role of permineralization and encrustation in preserving microorganisms forming biofilms in the sediments. Unicellular algae were preserved by silica

Virginia Souza-Egipsy; Angeles Aguilera; Eva Mateo-Martí; José Angel Martín-Gago; Ricardo Amils

2010-01-01

348

Rethinking Fossil Fuels  

NSDL National Science Digital Library

Climate change and fossil fuel use are connected. It would serve the world well to: begin a moratorium on coal-fired power plants; explore and use renewable energy; insist on immediate action from world governments; and penalize industries putting excess CO2 into the atmosphere.

James Hansen (NASA Goddard Institute for Space Studies;)

2008-09-09

349

Late Permian to Late Triassic palaeomagnetic data from Iran: constraints on the migration of the Iranian block through the Tethyan Ocean and initial destruction of Pangaea  

Microsoft Academic Search

A palaeomagnetic study of Late Permian to early Jurassic rocks from the Alborz and Sanandaj-Sirjan zones in Iran and a compilation of selected palaeopoles from the Carboniferous to the present provide an updated history of the motion of the Iranian block within the Tethys Ocean. The Iran assemblage, part of Gondwana during the Palaeozoic, rifted away by the end of

J. Besse; F. Torcq; Y. Gallet; L. E. Ricou; L. Krystyn; A. Saidi

1998-01-01

350

Late paraphrenia.  

PubMed

This article reviews the historical development of the concept of late paraphrenia. Studies that attempt to define symptoms, demographics, and risk factors for late-onset paranoid disorders are reviewed. Differences between late-onset schizophrenia and early-onset schizophrenia are highlighted. Current research on potential brain abnormalities in these disorders is examined critically. PMID:7659602

Addonizio, G C

1995-06-01

351

Sustainability of Fossil Fuels  

NASA Astrophysics Data System (ADS)

For a sustainable world economy, energy is a bottleneck. Energy is at the basis of a modern, technological society, but unlike materials it cannot be recycled. Energy or more precisely "negentropy" (the opposite of entropy) is always consumed. Thus, one either accepts the use of large but finite resources or must stay within the limits imposed by dilute but self-renewing resources like sunlight. The challenge of sustainable energy is exacerbated by likely growth in world energy demand due to increased population and increased wealth. Most of the world still has to undergo the transition to a wealthy, stable society with the near zero population growth that characterizes a modern industrial society. This represents a huge unmet demand. If ten billion people were to consume energy like North Americans do today, world energy demand would be ten times higher. In addition, technological advances while often improving energy efficiency tend to raise energy demand by offering more opportunity for consumption. Energy consumption still increases at close to the 2.3% per year that would lead to a tenfold increase over the course of the next century. Meeting future energy demands while phasing out fossil fuels appears extremely difficult. Instead, the world needs sustainable or nearly sustainable fossil fuels. I propose the following definition of sustainable under which fossil fuels would well qualify: The use of a technology or resource is sustainable if the intended and unintended consequences will not force its abandonment within a reasonable planning horizon. Of course sustainable technologies must not be limited by resource depletion but this is only one of many concerns. Environmental impacts, excessive land use, and other constraints can equally limit the use of a technology and thus render it unsustainable. In the foreseeable future, fossil fuels are not limited by resource depletion. However, environmental concerns based on climate change and other environmental effects of injecting excess carbon into the environment need to be eliminated before fossil fuels can be considered sustainable. Sustainable fossil fuel use would likely rely on abundant, low-grade hydrocarbons like coal, tar, and shale. It would require a closed cycle approach in which carbon is extracted from the ground, processed for its energy content, and returned into safe and stable sinks for permanent disposal. Such sequestration technologies already exist and more advanced approaches that could maintain access to fossil energy for centuries are on the drawing boards. I will review these options and outline a pathway towards a zero emission fossil fuel based economy that could provide energy at prices comparable to those of today for several centuries. A successful implementation will depend not only on technological advances but also on the development of economic institutions that allow one to pay for the required carbon management. If done correctly the markets will decide whether renewable energy, or sustainable fossil energy provides a better choice.

Lackner, K. S.

2002-05-01

352

Exceptional preservation of fossils in an Upper Proterozoic shale.  

PubMed

Late Proterozoic organisms must have been diverse and widely distributed, but in general their fossil record is both taxonomically and environmentally limited. Exceptional preservation of Proterozoic fossils is not unknown, but it is usually associated with silicified carbonates from restricted peritidal or playa lake environments. We report here an exceptionally well preserved and distinctive assemblage of Late Proterozoic fossils from subtidal marine shales. In addition to the sphaeromorphic acritarchs and cyanobacterial sheaths routinely preserved in Proterozoic rocks, this assemblage includes multicellular algae ('seaweeds'), 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. PMID:11542151

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

1988-08-01

353

Jurassic palaeoenvironmental change and the broader context of the Toarcian Oceanic Anoxic Event  

NASA Astrophysics Data System (ADS)

Of Jurassic palaeoenvironmental change events, the Toarcian Oceanic Anoxic Event (T-OAE) stands out as being potentially the premier 'supergreenhouse' episode. In addition to clear carbon-isotope signatures, a range of other isotopic, elemental, sedimentological and palaeontological anomalies have been described by multiple authors over the last three decades. The T-OAE palaeoenvironmental changes clearly affected both marine and non-marine settings. Nevertheless, over recent years there has been continued controversy concerning the magnitude, the areal extent, and the causes of this environmental perturbation, largely as a result of early concentration of research efforts in marine sections from the European domain. Many proxy records of environmental change have now been generated from new locations with a global distribution, and also from more extended stratigraphic intervals. Such studies confirm both the global impact of the T-OAE on a multitude of Earth systems and also the unique magnitude of change represented by the event. On the other hand it is also becoming clear that several other times in the Jurassic are likewise characterised by repeated global carbon-cycle perturbations and associated palaeoenvironmental changes, these greater in magnitude than anything experienced by the planet during the Cenozoic. Of particular significance are a major black shale event at the Sinemurian-Pliensbachian boundary and also another within the Sinemurian. More uncertain are putative 'ice house' interludes in the Late Pliensbachian and during the Aalenian and Bajocian. New high-resolution and stratigraphically extensive elemental and isotopic datasets are now allowing us to place all these events firmly in a chronological context, and to determine relationships to other Earth system events such as LIPs more accurately.

Hesselbo, Stephen; Korte, Christoph; Ullmann, Clemens

2013-04-01

354

Early Permian to Middle Jurassic rifting and sedimentation in East Africa and Madagascar  

NASA Astrophysics Data System (ADS)

Pre-drift sediments of Madagascar (Early Permian-Middle Jurassic) have been studied palynologically. These studies resulted in a more precise dating of individual stratigraphic units and the recognition of minor and major breaks in the succession. Palynostratigraphic and physical evidence of unconformities have been used to subdivide the pre-drift sediments into depositional cycles and to infer rifting events. A comparison with equivalent strata of Mozambique, Tanzania, Kenya, Ethiopia and Somalia shows a general correspondence and provides additional information for the construction of a generalized framework for the East African/Madagascan region which demonstrates the relationships between rifting and sedimentation and elucidates the prehistory of the break-up of Gondwana into a western and eastern fragment during the Middle Jurassic. The predrift succession of East Africa/Madagascar can be subdivided into two major sequences, a Karoo sequence (cycles 1 5, Asselian-early Smithian) and a transitional sequence (cycles 6 9, Ladinian-early Bajocian). The two sequences are separeted by a late Scythian to Anisian hiatus which indicates extensive uplift and erosion before a major rifting event initiated the resumption of sedimentation in the Ladinian. This Middle Triassic event marks the transition from the intracratonic rift stage to the pericratonic basin stage and correlates with a significant event in the Pangaean history, the transition from final coalescence to initial dispersal. The onset of the southward drift of Madagascar is believed to have occurred about 60 Ma later near the Aalenian-Bajocian boundary, contemporaneous with or immediately after the deposition of syntectonic sediments of cycle 9.

Hankel, O.

1994-12-01

355

A survey of paleozoic microbial fossils in chert  

Microsoft Academic Search

Non-acritarch, microbial fossils from Paleozoic marine cherts exhibit generally poor preservation with rare exceptional preservation. Microbial microfossils were discovered in 11 out of 17 stromatolitic and non-stromatolitic Paleozoic units containing replacement cherts from the continental United States. Many microfossils likely have a cyanobacterial affinity having both coccoid and filamentous morphotypes. Examined units range in age from Middle Cambrian to Late

Kenneth J Tobin

2004-01-01

356

Quaternary fossil fish from the Kibish Formation, Omo Valley, Ethiopia  

Microsoft Academic Search

The late Quaternary Kibish Formation of the Omo Valley, southwestern Ethiopia, preserves environments reflecting a history of fluctuations in the level of nearby Lake Turkana over the past 200,000 years. The Kibish Formation has yielded a diverse mammalian fauna (as well as birds and crocodiles), stone tools, and the oldest anatomically modern Homo sapiens. Fish, the most common vertebrate fossils

Josh Trapani

2008-01-01

357

Permian fossils from the Greenhills group, Bluff, Southland, New Zealand  

Microsoft Academic Search

Rare fossils including the gastropod Peruvispira aff. imbricata Waterhouse and the bivalve Atomodesma aff. marwicki Waterhouse indicate a late Lower Permian age for the middle part of the Greenhills Group. Plerophyllum aff. timorense Gerth occurs in a lower horizon of the Greenhills Group. Bands of marble containing shell prisms, rare radiolarians, and other microfossils occur in the upper part of

David J. Mossman; Lucy M. Force

1969-01-01

358

Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem - A synthesis  

USGS Publications Warehouse

A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early and Middle Kimmeridgian eolian deposits and Late Kimmeridgian alkaline, saline wetland/lacustrine deposits demonstrate that dryness persisted throughout the Kimmeridgian. Tithonian-age coal reflects lower evaporation rates associated with a slight cooling trend, but not a significant climate change. With a subtropical high over the Paleo-Pacific Ocean and atmospheric circulation generally toward the east, moisture carried by prevailing winds "rained out" progressively eastward, leaving the continental interior-and the Morrison depositional basin-dry. Within the basin, high evaporation rates associated with the southerly paleolatitude and greenhouse effects added to the dryness. Consequently, the two main sources of water-groundwater and surface water-originated outside the basin, through recharge of regional aquifers and streams that originated in the western uplands. Precipitation that fell west of the basin recharged aquifers that underlay the basin and discharged in wetlands and lakes in the distal, low-lying part of the basin. Precipitation west of the basin also fed intermittent and scarce perennial streams that flowed eastward. The streams were probably "losing" streams in their upstream reaches, and contributed to a locally raised water table. Elsewhere in the basin, where the floodplain intersected the water table, small lakes dotted the landscape. Seasonal storms, perhaps in part from the Paleo-Gulf of Mexico, brought some precipitation directly to the basin, although it was also subjected to "rain out" en route. Thus, meteoric input to the basin was appreciably less than groundwater and surface water contributions. The terrestrial Morrison ecosystem, which can be likened to a savannah, expanded with the northward retreat of the Late Jurassic Western Interior Seaway. The ecosystem was a complex mosaic, the components of which shifted through time. Riparian environments probably were the most diverse parts of the ecosystem, where a multi-storeyed canopy supported a diverse fauna, from insects to dinosaurs. Equable conditions also existed in wetlands, lakes, and elsewhere on the floodplain when seasonal rainfall brought an herbaceous groundcover to life. Eolian environments and alkaline, saline wetlands were inhospitable to life.Large herbivorous dinosaurs were adapted to this semi-arid landscape. Their size was an adaptive asset based on considerations of food requirements associated with a low metabolism and was also an advantage for migration during drought. Some of the large sauropods were adapted to browsing the higher vegetation associated with riparian environments; others to grazing the herbaceous groundcover on the floodplain and charophytes in the wetlands. The extensive distal wetlands may, in fact, have been refugia for some of these herbivores during the dry season and droughts. Extended periods of drought account for some of the dinosaur death assemblages; yet, the ecosystem could also sustain the most unusual life forms that ever roamed the Earth. ?? 2004 Elsevier B.V. All rights reserved.

Turner, C. E.; Peterson, F.

2004-01-01

359

Florissant Fossil Beds National Monument  

NSDL National Science Digital Library

This National Park Service (NPS) website contains details about Florissant Fossil Beds National Monument in Colorado. It includes details about the geological history of the monument, fossils found there, history of the area, flora and fauna, and other details. There is an education page containing curricula for K-12 classes for teaching paleontology. It contains labs, activities, games, vocabulary and fossil identification information.

360

Apatite Fission-Track Analysis of the Middle Jurassic Todos Santos Formation from Chiapas, Mexico.  

NASA Astrophysics Data System (ADS)

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

Abdullin, Fanis; Solé, Jesús; Shchepetilnikova, Valentina; Solari, Luigi; Ortega-Obregón, Carlos

2014-05-01

361

X-ray tomography as a non-destructive tool for evaluating the preservation of primary isotope signatures and mineralogy of Mesozoic fossils  

NASA Astrophysics Data System (ADS)

The stable isotope compositions of carbonate and phosphate components in fossil teeth and bone are widely used to infer information on paleoclimate and the physiology of extinct organisms. Recently the potential for measuring the body temperatures of extinct vertebrates from analyses of 13C-18O bond ordering in fossil teeth has been demonstrated (Eagle et al. 2010). The interpretation of these isotopic signatures relies on an assessment of the resistance of fossil bioapatite to alteration, as diffusion within, and partial recrystallization, or replacement of the original bioapatite will lead to measured compositions that represent mixtures between primary and secondary phases and/or otherwise inaccurate apparent temperatures. X-ray computed tomography (CT) allows 3-D density maps of teeth to be made at micron-scale resolution. Such density maps have the potential to record textural evidence for alteration, recrystallization, or replacement of enamel. Because it is non-destructive, CT can be used prior to stable isotope analysis to identify potentially problematic samples without consuming or damaging scientifically significant specimens. As a test, we have applied CT to tooth fragments containing both dentin and enamel from Late Jurassic sauropods and a Late Cretaceous theropod that yielded a range of clumped isotope temperatures from anomalously high ˜60oC to physiologically plausible ?40oC. This range of temperatures suggests partial, high-temperature modification of some specimens, but possible preservation of primary signals in others. Three-dimensional CT volumes generated using General Electric Phoenix|x-ray CT instruments were compared with visible light and back-scattered electron images of the same samples. The tube-detector combination used for the CT study consisted of a 180 kV nanofocus transmission tube coupled with a 127 micron pixel pitch detector ( ˜3-12? m voxel edges), allowing us to clearly map out alteration zones in high contrast, while reducing edge effects and beam hardening artifacts. CT images of these teeth show a range of replacement textures. One tooth -- thought to be the least altered -- shows only localized positive density anomalies near fractures, while a second -- thought to be highly altered -- contains high-density replacement mineralization. A third tooth -- one suspected of possible partial alteration -- shows a network of rectilinear density anomalies in the enamel similar to 2-D transmitted light and back-scattered electron images. This may represent recrystallization or replacement of the primary bioapatite. Unlike 2-D imaging techniques, 3-D volumes can be used to quickly and easily make quantitative measurements of the volumes of altered and unaltered materials: For example, in the enamel of sample 3, we observe a ratio of high density to low density material of ˜ 3:2.

Santillan, J. D.; Boyce, J. W.; Eagle, R.; Martin, T.; Tuetken, T.; Eiler, J.

2010-12-01

362

Sun and shade leaves? Cuticle ultrastructure of Jurassic Komlopteris nordenskioeldii (Nathorst) Barbacka.  

PubMed

An ultrastructural transmission electron microscope (TEM) study of fossil leaf cuticles from the Jurassic pteridosperm Komlopteris nordenskioeldii (Nathorst) Barbacka from the Mecsek Mountains (South Hungary) was conducted. Remnants of cuticles of leaves originating from so-called "sun and shade" environments were sectioned with a diamond knife, transversally as well as longitudinally. Although the present study showed a simple type of cuticle in this pteridosperm, differences were observed in the occurrence of its components, such as electron lucent amorphous material and various densities of granules, which give rise to different zones. The included fibrilous elements appeared to be made of aggregated and aligned granules, equivalent in size and electron density to nearby non-fibrilous granular regions. The combinations of these ultrastructural features allow distinctions between four types of cuticle: sun upper, sun lower, shade upper and shade lower. Considering the distinction made earlier in two types of cuticle and supposed to be related to sun and shade on the basis of macroscopical and microscopical features, four types only on the basis of differences in thickness, the present study reinforces the distinctions with ultrastructural microcharacteristics. As this study shows the variations in ultrastructure of cuticle among the four types, the differences observed may reveal the great sensitivity of some plants to environment. At the same time, it points out the importance, in ultrastructural studies of cuticles, of studying a number of samples for one taxon. PMID:11389914

Guignard, G; Bóka, K; Barbacka, M

2001-04-01

363

Geologic study and engineering review of Jurassic Smackover Formation of Thomasville field, Rankin County, Mississippi  

SciTech Connect

The Jurassic (Oxfordian) Smackover Formation in Thomasville field, Rankin County, Mississippi, produces sour gas from deep (19,000 + ft), geopressured (> 0.88 psi/ft) siliciclastics that are interbedded with nonreservoir carbonates. The siliciclastics are moderately to moderately well-sorted, fine to medium-grained subarkosic sandstones. They are characterized by low average porosities (7.0%) and permeabilities (0.35 md) resulting from both diagenetic and primary textural controls. Secondary and altered primary porosity are present. Permeability is reduced by several diagenetic events, including the formation of anthraxolite and authigenic fibrous illite. Smackover carbonate ramp deposition was interrupted in Thomasville by the periodic influx of siliciclastics. Siliciclastics were delivered to the basin of deposition by ancestral drainage systems and distributed on the ramp by current and storm processes. They are interpreted to be shallow marine (beach and bar), inner shelf (sand waves and storm deposits), and outer shelf to upper basinal (storm and turbidite channels) deposits based on sedimentary structures, trace fossils, and lateral and vertical facies association with the interbedded carbonates. The carbonates indicate a shoaling-upward sequence, with outer shelf and upper basinal mudstones and wackestones at the base grading upward through shelf packstones, high-energy ooid grainstone shoals, and asphalt intertidal mudstones to grainstones. Rock properties and interpretations of the depositional environments were based on core and drill-cutting analyses. These analyses supplemented the use of computer-enhanced wireline logs to establish rock-log calibrations, correlation markers, structural growth, and reservoir continuity.

Shew, R.D.; Garner, M.M.

1986-09-01

364

Fossil Age Estimation Model  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2006-01-01

365

Restoring Fossil Creek  

NSDL National Science Digital Library

As part of an ongoing environmental project and partnership with a local university, high school students monitor changes to Fossil Creek in Arizona. Components of the project include fish behavior studies, responses to fishing, water chemistry measurements, aquatic invertebrate studies, photographic recording, riparian habitat transects, and small mammal trapping transects. The data collected will ultimately provide an invaluable annual record for students, working scientists, and the wider community as changes are monitored over time.

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

2004-07-01

366

Fossil Microbes on Mars?  

NSDL National Science Digital Library

This online article, from Cosmic Horizons: Astronomy at the Cutting Edge, reports on the controversial discovery of Martian meteorite ALH84001. In 1996, a team of scientists led by David McKay of NASAâs Johnson Space Flight Center announced that they had discovered evidence for microscopic fossil life in this meteorite from Mars. From the start, the evidence was both fascinating and controversial, and to this day it remains so.

367

Frisco City sand: New Jurassic reservoir in southwest Alabama  

Microsoft Academic Search

The first commercial production of hydrocarbons from the Jurassic Haynesville Formation in southwestern Alabama was from the Frisco City field. The field currently produces 57.8° API gravity oil on 160-ac well spacing from a depth of approximately 12,000 ft. Perforations are in the Frisco City sand interval, in the lower part of the Haynesville Formation. Average porosity is 15% and

S. D. Mann; R. M. Mink; B. L. Bearden; R. D. Jr. Schneeflock

1989-01-01

368

Jurassic sedimentary basins in the Central Asian orogenic belt  

SciTech Connect

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.

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

1995-05-01

369

New paleomagnetic data from Jurassic Sediments from Sardinia  

NASA Astrophysics Data System (ADS)

The dynamic history of the Corso-Sardinian microplate since Oligocene times is well defined based on numerous geologic, geophysical and paleomagnetic studies (e.g. Vigliotti and Langenheim 1995), especially the counter clockwise rotation and the associated opening of the Liguro-Provençal ocean (Gattacceca et al., 2007). In the early 80’s Horner and Lowrie (1981) published paleomagnetic results from Jurassic and Triassic carbonates from the Orosei region, eastern Sardinia. Although these data are of rather poor quality they nevertheless indicate a two step rotational history of the microplate. Horner and Lowrie concluded that a cw rotation of ~70° -90° is required in order to compensate the opening of the Liguro-Provençal ocean and to restore Sardinia into its pre-Oligocene position. However these results are of very limiting regional spread and do not allow to test the structural integrity of the island for post-Jurassic times. Data for the Permian basins and the Carboniferous dyke swarms indicate large rotations between Northern, Central and Southern Sardinia (Emmer et al., 2005). In order to better constrain the timing of these movements a detailed paleomagnetic study was undertaken covering all areas of Sardinia where Jurassic rocks have been identified. A total of 367 samples from 46 sites was subjected to stepwise thermal and AF demagnetization experiments, yielding well defined characteristic directions of magnetization. The primary character of this magnetization is supported by positive fold and reversal tests. The resulting mean direction, based on 31 sites (?_95=8.4°) is D = 273.6° and I=+43.0° (Sardinian coordinates) is in very good agreement with the older data published by Horner and Lowrie (1981). Furthermore it indicates that no internal rotation of post-Jurassic age affected the island. This result has important implications for the interpretation of the paleomagnetically identified rotations for Permian basins and Permo- Carboniferous dyke swarms of Sardinia.

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

2009-12-01

370

Carbon cycle changes during the Triassic-Jurassic transition  

Microsoft Academic Search

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

M. Ruhl

2010-01-01

371

Magnetostratigraphy of the Lower Jurassic (Hettangian-Sinemurian)  

NASA Astrophysics Data System (ADS)

Magnetostratigraphy and correlation to the Geomagnetic Polarity Time Scale (GPTS) constitute a standard dating tool in Earth Sciences. When integrated with biostratigraphy and especially cyclostratigraphy, magnetostratigraphy allows high-resolution correlations all over the world, because paleomagnetic polarity reversals can geologically be seen as globally synchronous events. It is therefore the stratigraphic tool of choice to perform correlations between continental and marine realms. An integrated astronomical time scale, which has been achieved for most of the Neogene and is in progress for the Palaeogene and Mesozoic, provides high resolution and accuracy. The Geologic Time Scale (GTS) for the Early Jurassic is far less robust (Gradstein et al., 2004, 2012) because magnetostratigraphic records of marine Hettangian and Sinemurian successions are rare and equivocal (Gallet et al., 1990; Yang et al., 1996). Consequently, the Global Stratotype Section and Points (GSSP's) for the Hettangian (Kuhjoch; Austria) and Sinemurian (East Quantoxhead; UK) are mainly defined on biostratigraphic (ammonite) arguments (Hillebrandt et al., 2007; Bloos and Page, 2002). Cyclostratigraphic analyses from the Lower Jurassic marine successions at St. Audrie's Bay and East Quantoxhead located on the west Somerset coast on the southern side of the Bristol Channel Basin (UK) resulted in an independent astronomical framework for the Hettangian Stage, allowing to locate the stratigraphic position of the marine de?ned Triassic-Jurassic and Hettangian-Sinemurian boundary in the continental realm (Ruhl et al., 2010). We will present the magnetostratigraphy of the Hettangian and lower Sinemurian successions of St. Audrie's Bay and East Quantoxhead, which will be used to evaluate the marine-continental correlations in the recovery interval following the end-Triassic mass extinction and to develop a more robust GPTS for the Lower Jurassic.

Hüsing, Silja Katherine; Abels, Hemmo; Deenen, Martijn; Ruhl, Micha; Krijgsman, Wout

2013-04-01

372

Reevaluation of upper Jurassic Morrison Formation, Western Interior  

SciTech Connect

Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic features. Similar depositional setting has been observed in the Morrison Formation in the Bighorn basin, Wyoming, where pedogenic features suggest a distal floodplain setting with low-sinuosity channels cutting through. In both localities the dominant clay mineral is illite. The upper Brushy Basin member in the Colorado Plateau is composed mostly of gray and purpose mudstones rich in montmorillonite. Devitrified tuff beds and bentonite occur in certain levels throughout the unit. Pedogenic features are not conspicuously developed. The Lower Cretaceous Clovery Formation in the Bighorn basin, Wyoming, is strikingly similar in terms of lithological aspects. The depositional environment is interpreted in both localities as a playa deposit. A great variety of nodules is present such as silcretes, septaria, and silica-carbonate nodules. Radiometric dating of bentonites in central Utah revealed that the upper Brushy Basin member is Early Cretaceous in age. Field and geochemical data support these conclusions and aid the understanding of the exact nature of the depositional basin, environments, stratigraphy, and paleotectonics of the Upper Jurassic-Lower Cretaceous interval in the Western Interior.

Mantzios, C.

1989-03-01

373

The Paleoenvironment of Anaerobic Sediments in the Late Mesozoic South Atlantic Ocean.  

National Technical Information Service (NTIS)

Laminated dark calcareous oozes/chalks/limestones as well as clayey and marly mudstones/claystones with high organic carbon contents were deposited during Jurassic, Early and Late Cretaceous times in the Atlantic, Pacific and Indian Oceans. In the South A...

J. Thiede T. H. van Andel

1976-01-01

374

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

SciTech Connect

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.

Bartok, P. (EGEP Consultores, Caracus (Venezuela))

1993-02-01

375

Lower-Middle Jurassic paleomagnetic data from the Mae Sot area (Thailand): Paleogeographic evolution and deformation history of Southeastern Asia  

NASA Astrophysics Data System (ADS)

We have carried out a paleomagnetic study (12 sites, 85 samples) of Early-Middle Jurassic limestones and sandstones from the Mae Sot area of western Thailand. This area is part of the Shan-Thai-Malay (STM) block, and its geological characteristics have led some authors to suggest a Late Jurassic accretion of this region against the rest of Indochina along the Changning-Menglian zone, the latter sometimes being interpreted as a Mesozoic suture. The high-temperature (or high-coercivity) component isolated yields a paleodirection at D = 359.8 °, I = 31.4 ° (? 95 = 5.0 °). The primary nature of the magnetization acquisition is ascertained at a site with reversed polarity and a positive fold test (at the 95% confidence level). Comparison of the Mae Sot paleolatitude and another one from the STM with those recently published for the Simao and Khorat blocks show no significant difference at the 95% level, showing that the STM was situated close to, or had already accreted with, the Simao or Khorat blocks in the Early-Middle Jurassic. Comparison of the latitudes from these blocks with those from China indicates a relative southward motion of 8 ± 4° of Indochina as a single entity relative to China. Most rotations of these regions relative to China are found to be clockwise (between 14 and 75°). These rotations, and most prominently the 1200 ± 500 km post-Cretaceous left-lateral motion inferred for the Red River Fault, provide quantitative estimates of the large amount of extrusion of Indochina with respect to the rest of Asia.

Yang, Z. Y.; Besse, J.; Sutheetorn, V.; Bassoullet, J. P.; Fontaine, H.; Buffetaut, E.

1995-12-01

376

The Upper Triassic to Middle Jurassic strata and floras of the Junggar Basin, Xinjiang, Northwest China  

Microsoft Academic Search

The Upper Triassic to Middle Jurassic strata are well exposed and basically continuous in the Junggar Basin of Xinjiang, Northwest\\u000a China. The Upper Triassic strata include the Huangshanjie Formation (lacustrine facies mainly) and Haojiagou Formation (fluvial\\u000a to fluvial-swamp facies). The Lower Jurassic consists of the coal-bearing Badaowan Formation (fluvial swamp facies) and Sangonghe\\u000a Formation (lacustrine facies mainly). The Middle Jurassic

Ge Sun; Yuyan Miao; Volker Mosbrugger; Abdul R. Ashraf

2010-01-01

377

Fluvial sedimentology of an Upper Jurassic petrified forest assemblage, Shishu Formation, Junggar Basin, Xinjiang, China  

Microsoft Academic Search

McKnight, C. L.. Graham, S A.. Carroll. A. R.. Gan. Q., Dilcher, D. L, Min Zhao and Yun Hal Liang. 1990 Fluvial sedimeutology of au Upper JurassIC petflfied forest assemblage. Shishu Formation. Junggar Basm, Xinjiang, Chma. Palaeogeogr.. PalaeoclImatol. Palueoecol., 79' 1-9. A remarkable petflfied forest assemblage is preserved 10 the Upper Jurassic Shishu FonnatlOn of the northeastern Junggar basin. Xmjiang

Cleavy L. McKnight; S. A. Graham; A. R. Carrollb; Q GAN; D DILCHER; M ZHAO; Y HAILIANG

1990-01-01

378

Jurassic magmatic bodies of mountainous Crimea in the Bodrak River catchment (Southwestern Crimea)  

Microsoft Academic Search

The synthetic (geological and petrochemical) study of Jurassic magmatic bodies in the catchment of the Bodrak River (mountainous\\u000a Crimea) is conducted. Their structural position and a Middle Jurassic age were determined. The magmatic bodies of mountainous\\u000a Crimea were compared to those of the Lozovskaya zone. The study considers the geodynamic settings of the Middle Jurassic magmatism\\u000a in mountainous Crimea.

A. V. Latyshev; D. I. Panov

2008-01-01

379

Cycles in fossil diversity  

SciTech Connect

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.

Rohde, Robert A.; Muller, Richard A.

2004-10-20

380

Interpreting Fossil Assemblages  

NSDL National Science Digital Library

Students are provided several fossiliferous samples to analyze in detail. I provide more than they need to snalyze so everyone in the class can be working. I give a range of specimens of different geologic ages, diversities, abundances, taxonomic compositions, depositional environments and taphonomic grades. The goal is for the students to identify all of the different fossil types to the lowest taxonomic level. I provide some that are well preserved and some that are highly fragmented making identification difficult. Next, students are tasked with assigning an age range of the sample by combining the age ranges of individual taxa, and make taphonomic descriptions and paleoecological analyses.

Boyer, Diana

381

A Fossil Thermometer  

NSDL National Science Digital Library

In this activity, students calculate temperatures during a time in the geologic record when rapid warming occurred using a well known method called 'leaf-margin analysis.' Students determine the percentage of the species that have leaves with smooth edges, as opposed to toothed, or jagged, edges. Facsimiles of fossil leaves from two collection sites are examined, categorized, and the data is plugged into an equation to provide an estimate of paleotemperature for two sites in the Bighorn Basin. It also introduces students to a Smithsonian scientist who worked on the excavation sites and did the analysis.

Institution, Smithsonian; Institute, Smithsonian

382

Middle Jurassic (Bajocian and Bathonian) dinosaur megatracksites, Bighorn Basin, Wyoming, USA  

USGS Publications Warehouse

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.

Kvale, E. P.; Johnson, G. D.; Mickelson, D. L.; Keller, K.; Furer, L.; Archer, A.

2001-01-01

383

Two new carnivores from an unusual late Tertiary forest biota in eastern North America  

Microsoft Academic Search

Late Cenozoic terrestrial fossil records of North America are biased by a predominance of mid-latitude deposits, mostly in the western half of the continent. Consequently, the biological history of eastern North America, including the eastern deciduous forest, remains largely hidden. Unfortunately, vertebrate fossil sites from this vast region are rare, and few pertain to the critically important late Tertiary period,

Steven C. Wallace; Xiaoming Wang

2004-01-01

384

Subduction erosion of the Jurassic Talkeetna-Bonanza arc and the Mesozoic accretionary tectonics of western North America  

USGS Publications Warehouse

The Jurassic Talkeetna volcanic arc of south-central Alaska is an oceanic island arc that formed far from the North American margin. Geochronological, geochemical, and structural data indicate that the arc formed above a north-dipping subduction zone after ca. 201 Ma. Magmatism migrated northward into the region of the Talkeetna Mountains ca. 180 Ma. We interpret this magmatism as the product of removal of the original forearc while the arc was active, mainly by tectonic erosion. Rapid exhumation of the arc after ca. 160 Ma coincided with the sedimentation of the coarse clastic Naknek Formation. This exhumation event is interpreted to reffect collision of the Talkeetna arc with either the active margin of North America or the Wrangellia composite terrane to the north along a second north-dipping subduction zone. The juxtaposition of accreted trench sedimentary rocks (Chugach terrane) against the base of the Talkeetna arc sequence requires a change from a state of tectonic erosion to accretion, probably during the Late Jurassic (before 150 Ma), and definitely before the Early Cretaceous (ca. 125 Ma). The change from erosion to accretion probably reflects increasing sediment flux to the trench due to collision ca. 160 Ma. ?? 2005 Geological Society of America.

Clift, P. D.; Pavlis, T.; DeBari, S. M.; Draut, A. E.; Rioux, M.; Kelemen, P. B.

2005-01-01

385

Unearthing Important Fossils  

NSDL National Science Digital Library

Over the past several weeks, a flurry of dinosaur and other fossil discoveries have reached the mainstream news. From the two 530-million-year-old fish-like creatures that could be the earliest known vertebrates found in China, to the bones of two dinosaurs in Madagascar that may be the oldest dinosaurs ever found, to the "60-ton giraffe-like creature" (3) found in Oklahoma (called Sauroposeidon proteles, or "thunder lizard"), paleontologists are immersed in discovery. The significance of the first discovery is triggering excitement among paleontologists, worldwide. In particular, the discovery of the two "fish-like" fossils in China (to be published in this week's journal Nature) indicates that fish (i.e., vertebrates) evolved much earlier than previously thought and that "the rates of evolution in the oceans during the Cambrian period must have been exceptionally fast" (1). This week's In The News discusses some of the recently unveiled discoveries and provides background information and resources on vertebrate paleontology.

Payne, Laura X.

386

Fossil Microorganisms in Archaean  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

387

The tectonic evolution of the South Atlantic from Late Jurassic to present  

NASA Astrophysics Data System (ADS)

An improved tectonic database for the South Atlantic has been compiled by combining magnetic anomaly, Geosat altimetry and onshore geologic data. We used this database to obtain a revised plate-kinematic model. Starting with a new fit-reconstruction for the continents around the South Atlantic, we present a high-resolution isochron map from Chron M4 to present. Fit reconstructions of South America and Africa that require rigid continental plates result in substantial misfits either in the southern South Atlantic or in the equatorial Atlantic. To achieve a fit without gaps, we assume a combination of complex rift and strike-slip movements: (1) along the South American Parana-Chacos Basin deformation zone, (2) within marginal basins in South America (Salado, Colorado Basin) and (3) along the Benue Trough/Niger Rift system in Africa. These faults are presumed to have been active before or during the breakup of the continents. Our model describes a successive "unzipping" of rift zones starting in the southern South Atlantic. Between 150 Ma (Tithonian) and approximately 130 Ma (Hauterivian), rifting propagated to 38 °S, causing tectonic movements within the Colorado and Salado basins. Subsequently, between 130 Ma and Chron M4 (126.5 Ma), the tip of the South Atlantic rift moved to 28 °S, resulting in intracontinental deformation along the Parana-Chacos Basin deformation zone. Between Chron M4 and Chron MO (118.7 Ma) rifting propagated into the Benue Trough and Niger Rift, inducing rift and strike-slip motion. After Chron MO, the equatorial Atlantic began to open, while rifting and strike-slip motion still occurred in the Benue Trough and Niger Rift. Since Chron 34 (84 Ma), the opening of the South Atlantic is characterized by simple divergence of two rigid continental plates.

Nürnberg, Dirk; Müller, R. Dietmar

1991-05-01