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1

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

E-print Network

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

Benton, Michael

2

Late Jurassic salamandroid from western Liaoning, China  

PubMed Central

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 (40Ar/39Ar dates of 122–129 Ma), but slightly younger than the Middle Jurassic Daohugou horizon (40Ar/39Ar 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.

2012-01-01

3

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

4

A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago.  

PubMed

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

Göhlich, Ursula B; Chiappe, Luis M

2006-03-16

5

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

6

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

7

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

8

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

E-print Network

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

Benton, Michael

9

Broad-Scale Patterns of Late Jurassic Dinosaur Paleoecology  

PubMed Central

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

Noto, Christopher R.; Grossman, Ari

2010-01-01

10

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

PubMed Central

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

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

2013-01-01

11

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

12

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

13

Late Jurassic salamanders from northern China  

Microsoft Academic Search

With ten extant families, salamanders (urodeles) are one of the three major groups of modern amphibians (lissamphibians). Extant salamanders are often used as a model system to assess fundamental issues of developmental, morphological and biogeographical evolution. Unfortunately, our understanding of these issues has been hampered by the paucity of fossil evidence available to assess the early history of the group.

Ke-Qin Gao; Neil H. Shubin

2001-01-01

14

New discovery of Palaeontinid fossils from the Middle Jurassic in Daohugou, Inner Mongolia (Homoptera, Palaeontinidae)  

Microsoft Academic Search

Three new species of fossil Palaeontinidae are described from Daohugou Village, Inner Mongolia, China: Daohugoucossus shii sp. nov., D. parallelivenius sp. nov., D. lii sp. nov. The diagnosis of Daohugoucossus Wang, Zhang and Fang, 2006 is revised. These materials are the first complete fossil palaeontinids in the Middle Jurassic\\u000a of the world. Based on observation of these new specimens, Sc

Ying Wang; Dong Ren; ChungKun Shih

2007-01-01

15

Repeated flood events and fossil forests at Curio Bay (Middle Jurassic), New Zealand  

Microsoft Academic Search

During the Middle Jurassic, the regional environment of Curio Bay, southeast South Island, New Zealand, was a fluvial plain marginal to volcanic uplands. Intermittent flashy, poorly-confined flood events buried successive conifer forests. With the termination of each flood, soils developed and vegetation was reestablished. In most cases, this developed into coniferous forest. In approximately 40m of vertical section, 10 fossil

Mike Pole

2001-01-01

16

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

E-print Network

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

Cai, Long

17

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

Microsoft Academic Search

The transmission of the tectonic regime from the Paleo-Asian Ocean to the Pacific Ocean during Mesozoic era was reconstructed using the modeling of Late Triassic (T3) and Late Jurassic (J3) stress fields employing two dimensional linear finite element models (2-D FEM). The model at T3 proposes that Qinling-Dabie–Sulu orogens coevally collided and the model J3 proposes that Subei block continued

Guiting Hou; Yanxin Wang; K. R. Hari

2010-01-01

18

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

19

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

20

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. PMID:22412850

Frey, Eberhard; Tischlinger, Helmut

2012-01-01

21

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

NASA Astrophysics Data System (ADS)

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

Bell, C. M.; Suárez, M.

22

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

SciTech Connect

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

Cameron, B.

1985-01-01

23

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

E-print Network

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

Gilli, Adrian

24

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

25

Potential hydrocarbon traps within a late Jurassic strike-slip lacustrine basin of north Spain  

Microsoft Academic Search

Strike-slip basins in northern Spain were initiated during the Late Jurassic in association with crustal stretching that heralded the opening of the Bay of Biscay. One of these basins is the Aguilar basin, which has been studied using outcrop and published well data. The basin subsided rapidly to accumulate up to 800 m of sediment. It extends at least 60

V. Pujalte; S. Robles

1988-01-01

26

Coral reef bioerosion in times of crises - the Late Triassic\\/ Early Jurassic example  

Microsoft Academic Search

A study across the major extinction phase of scleractinians during the Late Triassic\\/Early Jurassic was performed. Samples from seven localities in Austria, Morocco and Iran were quantitatively evaluated for macroborings. Each locality represents a turbid or clear-water environment before and after the 5 million years of crisis. Norian reefs suffered almost no bioerosion in clear water but in a turbid

M. Bertling

27

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

Microsoft Academic Search

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

Roger L. Larson; Thomas W. C. Hilde

1975-01-01

28

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

SciTech Connect

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

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

1989-09-01

29

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

30

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. PMID:24883240

Püntener, Christian; Billon-Bruyat, Jean-Paul

2014-01-01

31

Broad-Scale Patterns of Late Jurassic Dinosaur  

E-print Network

Background: There have been numerous studies on dinosaur biogeographic distribution patterns. However, these distribution data have not yet been applied to ecological questions. Ecological studies of dinosaurs have tended to focus on reconstructing individual taxa, usually through comparisons to modern analogs. Fewer studies have sought to determine if the ecological structure of fossil assemblages is preserved and, if so, how dinosaur communities varied. Climate is a major component driving differences between communities. If the ecological structure of a fossil locality is preserved, we expect that dinosaur assemblages from similar environments will share a similar ecological structure. Methodology/Principal Findings: This study applies Ecological Structure Analysis (ESA) to a dataset of 100+ dinosaur taxa arranged into twelve composite fossil assemblages from around the world. Each assemblage was assigned a climate zone (biome) based on its location. Dinosaur taxa were placed into ecomorphological categories. The proportion of each category creates an ecological profile for the assemblage, which were compared using cluster and principal components analyses. Assemblages grouped according to biome, with most coming from arid or semi-arid/seasonal climates. Differences between assemblages are tied to the proportion of large high-browsing vs. small ground-foraging herbivores, which separates arid from semi-arid and moister environments, respectively. However, the effects of historical, taphonomic, and other environmental factors are still evident.

Christopher R. Noto; Ari Grossman

32

Fossils from the Middle Jurassic of China shed light on morphology of Choristopsychidae (Insecta, Mecoptera).  

PubMed

Choristopsychidae, established by Martynov in 1937 with a single isolated forewing, is a little known extinct family in Mecoptera. Since then, no new members of this enigmatic family have been described. Based on 23 well-preserved specimens with complete body and wings from the Middle Jurassic of northeastern China, we report one new genus and three new species of Choristopsychidae, two new species of the genus Choristopsyche Martynov, 1937: Choristopsyche perfecta sp. n. and Choristopsyche asticta sp. n.; one new species of Paristopsyche gen. n.: Paristopsyche angelineae sp. n.; and re-describe Choristopsyche tenuinervis Martynov, 1937. In addition, we emend the diagnoses of Choristopsychidae and Choristopsyche. Analyzing the forewing length/width ratios of representative species in Mecoptera, we confirm that choristopsychids have the lowest ratio of forewing length/width, meaning broadest forewings. These findings, the first fossil choristopsychids with well-preserved body structure and the first record of Choristopsychidae in China, shed light on the morphology of these taxa and broaden their distribution from Tajikistan to China, while increasing the diversity of Mesozoic Mecoptera in China. PMID:23950679

Qiao, Xiao; Shih, Chung Kun; Petrulevi?ius, Julian F; Dong, Ren

2013-01-01

33

Aromatic hydrocarbons from the Middle Jurassic fossil wood of the Polish Jura  

NASA Astrophysics Data System (ADS)

Aromatic hydrocarbons are present in the fossil wood samples in relatively small amounts. In almost all of the tested samples the dominating aromatic hydrocarbon is perylene and its methyl and dimethyl derivatives. The most important biomarkers present in the aromatic fraction are dehydroabietane, siomonellite and retene, compounds characteristic for conifers. The distribution of discussed compounds is highly variable due to such early diagenetic processes affecting the wood as oxidation and the activity of microorganisms. MPI1 parameter values (methylphenanthrene index) for the majority of the samples are in the range of 0.1 to 0.5, which results in the highly variable values of Rc (converted value of vitrinite reflectance) ranging from 0.45 to 0.70%. Such values suggest that MPI1 parameter is not useful as maturity parameter in case of Middle Jurassic ore-bearing clays, even if measured strictly on terrestrial organic matter (OM). As a result of weathering processes (oxidation) the distribution of aromatic hydrocarbons changes. In the oxidized samples the amount of aromatic hydrocarbons, both polycyclic as well as aromatic biomarkers decreases.

Smolarek, Justyna; Marynowski, Leszek

2013-09-01

34

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

E-print Network

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

Riding, Robert

35

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

36

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

SciTech Connect

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

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

1991-03-01

37

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

38

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

PubMed

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

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

2005-06-01

39

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

40

Late Jurassic deformation in Honduras. Proposals for a revised regional stratigraphy  

NASA Astrophysics Data System (ADS)

The lithostratigraphical subdivision of Mesozoic rocks in Honduras poses problems that are still imperfectly resolved. Observations made by the authors in Honduras between 1988 and 1992, show a clear separation between an older detrital unit, locally known as the Agua Fria Formation which is relatively homogeneous and can be found throughout the so-called Chortis Block, and a younger one composed essentially of cyclic detrital deposition (conglomerates and other molasse type rocks grading into pelites and silstones), usually called red beds ("capas rojas"). The older detrital unit, here called the Honduras Group, is an Early to Middle Jurassic folded and locally metamorphosed unit. The younger unit known as "capas rojas" starts with a molasse type rock which is not metamorphosed and presently have no generic name, and was deposited in extensional basins during a second sedimentary cycle of Early (and younger?) Cretaceous age. Between the two cycles a clear deformation phase took place in the late Jurassic. At La Chacra, near Comayagua in the centre of the country, outcrop conditions and exploration data enabled the observation of a composite section through the lithostratigraphic succession of the two Mesozoic cycles. The following succession was observed from bottom to top: • Schist and conglomerate of the Agua Fria Formation, turned to a near-vertical position, which was intruded by granite and mineralized veins that are considered to have a late magmatic (Late Jurassic) age. • A paleo-erosion surface over the Agua Fria Formation, shown by the presence of discordant weathering phenomena and a palaeosol. • Detrital deposits (calcareous sandstone) and carbonate rocks of the Cretaceous cycle (molasse and red beds of the second cycle), which unconformably overlie the rocks of the first cycle. These observations confirm the existence, in Honduras and throughout the Chortis Block, of two distinct depositional cycles of Mesozoic age that were separated by a major crustal-deformation phase of Late Jurassic age. The same features are known from central Mexico, whence the Chortis Block seems to have come according to generally admitted crustal-block reconstructions of Central America. Early Cretaceous deposits in Honduras fill Cretaceous graben of the central zone. Although superficially resembling the (Triassic-Jurassic) Todos Santos Formation in Mexico and Guatemala, they cannot be compared with this unit because of their different age and origin, and will require better definition and a new name in Honduras.

Viland, J. C.; Henry, B.; Calix, R.; Diaz, C.

1996-07-01

41

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

SciTech Connect

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

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

1996-01-01

42

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

SciTech Connect

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

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

1996-12-31

43

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

NASA Astrophysics Data System (ADS)

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

Sames, B.

2009-04-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

45

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. PMID:23712471

Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

2013-01-01

46

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

PubMed Central

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

Deschamps, Sylvie; Claude, Julien

2014-01-01

47

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

48

Chemo- and biostratigraphy of the Late Jurassic from the Lower Saxony Basin, Northern Germany  

NASA Astrophysics Data System (ADS)

The upper Jurassic (Oxfordian to Tithonian) sediments of the Lower Saxony Basin (Northern Germany) comprises a succession of limestones, marlstones and claystones deposited in a shallow marine to lacustrine epicontinental basin situated between the Tethys and the Sub-Boreal seas. Both, the depositional environment and the palaeogeographically isolated position strongly compromise a chronostratigraphic dating of the regional lithostratigraphical and biostratigraphical units. In order to obtain a stratigraphic standard section for the Late Jurassic of the Lower Saxony Basin we drilled a 325 m long core (Core Eulenflucht 1) covering the lower part of the Berriasian (Wealden 2-3 of the Bückeburg Formation) to the lower Oxfordian (Heersum Formation). A compilation with a section outcropping in an active quarry 2 km north of the drill site resulted in a 340 m long section reaching down to the late Callovian (Ornatenton Formation) . Ammonites have only been described in the lowermost, Callovian part of the section. Investigations of benthic foraminifers, ostracods as well as palynology, however, allowed for a rather detailed biozonation of the core. These data indicate the stratigrapical completeness of the section when compared to the regional stratigraphic data of the Lower Saxony Basin. Due to the lack of ammonites in Late Jurassic part of the section, which would have allowed for a correlation with Tethyan successions, high resolution stable carbon isotope data have been produced from bulk rock carbonate. Even though most of the data derive from shallow marine, rather coarse grained carbonates, such as ooliths and floatstones the resulting carbon isotope curve is surprisingly clean with only little "noise" in the upper part (early Tithonian?) of the measured succession. The curve clearly shows some distinctive features reported from biostratigraphically well-dated carbon isotope records of the Northern Tethys (e.g. Bartolini et al., 2003, Padden et al., 2002, Rais et al., 2007) and the Sub-Boreal (Nunn et al., 2009, Nunn & Price, 2010). Therefore it allows for a correlation of isotope excursions such as the pronounced mid-Oxfordian positive and the two brief negative excursions of the mid-Oxfordian, the broad positive excursion in the late Oxfordian and a general trend towards light values starting at the Kimmeridgian-Tithonian boundary. This results in a chronostratigraphic re-interpretation of the Oxfordian to lower Tithonian litho- and biostratigraphic units in the Lower Saxony Basin, details of which are presented on our poster.

Erbacher, Jochen; Luppold, Friedrich Wilhelm; Heunisch, Carmen; Heldt, Matthias; Caesar, Sebastian

2013-04-01

49

A Jurassic mammal from South America.  

PubMed

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

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

2002-03-14

50

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

SciTech Connect

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

Letsch, D.K.

1988-02-01

51

The Trace Fossil Diplopodichnus from the Lower Jurassic Lacustrine Sediments of Central China and the Isopod Armadillidium vulgare (Pillbug) Lebensspuren as its Recent Analogue  

Microsoft Academic Search

The trace fossil Diplopodichnus isp. was identified in lacustrine siliciclastics of the Lower Jurassic Anyao Formation in the Henan Province, central China. This is the youngest occurrence of this ichnogenus. It is similar to some variants of recent surface traces of the isopod Armadillidium vulgare (pillbug) crawling on soft mud in temporal puddles. Therefore, isopods are suggested to be producers

Alfred Uchman; Bin Hu; Yuanyuan Wang; Huibo Song

2011-01-01

52

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

E-print Network

1 An Investigation of mid to late Holocene fossil insects from raised bogs in the Irish Midlands the results of late Holocene insect fossil analysis from six raised bogs in the Irish Midlands. A distribution patterns in the taphonomy of the insect fossil assemblages, through the development of the bog and across

Sheldon, Nathan D.

53

Impact of methane seeps on the local carbon-isotope record: a case study from a Late Jurassic hemipelagic section  

E-print Network

Impact of methane seeps on the local carbon-isotope record: a case study from a Late Jurassic) with horizontal and vertical extents of up to several metres contain a fauna characteristic of hydrocarbon seep in these seep limestones give evidence for the pres- ence of archaea-performing AOM (Peckmann and Thiel, 2004

Gilli, Adrian

54

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

E-print Network

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

Gilli, Adrian

55

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

NASA Astrophysics Data System (ADS)

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

Hall, Robert

2012-10-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

57

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

E-print Network

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

Khorasani, Sara

2013-11-28

58

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

Microsoft Academic Search

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

RANDALL B. IRMIS

2005-01-01

59

Fauna and predator-prey relationships of ettling, an actinopterygian fish-dominated konservat-lagerstätte from the late jurassic of southern Germany.  

PubMed

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

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

2015-01-01

60

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

PubMed Central

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

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

2015-01-01

61

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

SciTech Connect

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

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

1991-03-01

62

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

PubMed Central

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

Mannion, Philip D.

2014-01-01

63

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

64

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

65

Brachiopods from Late Jurassic-Early Cretaceous hydrocarbon seep deposits, central Spitsbergen, Svalbard.  

PubMed

Late Jurassic-Early Cretaceous (Late Volgian-latest Ryazanian) rhynchonellate brachiopods are described from eight out of 15 hydrocarbon seep deposits in the Slottsmøya Member of the Agardhfjellet Formation in the Janusfjellet to Knorringfjellet area, central Spitsbergen, Svalbard. The fauna comprises rhynchonellides, terebratulides (terebratuloids and loboidothyridoids) and a terebratellidine. The rhynchonellides include: Pseudomonticlarella varia Smirnova; Ptilorhynchia mclachlani sp. nov.; and Ptilorhynchia obscuricostata Dagys. The terebratulides belong to the terebratuloids: Cyrtothyris? sp.; Cyrtothyris aff. cyrta (Walker); Praelongithyris? aff. borealis Owen; and the loboidothyridoids: Rouillieria cf. michalkowii (Fahrenkohl); Rouillieria aff. ovoides (Sowerby); Rouillieria aff. rasile Smirnova; Uralella? cf. janimaniensis Makridin; Uralella? sp.; Pinaxiothyris campestris? Dagys; Placothyris kegeli? Harper et al.; and Seductorithyris septemtrionalis gen. et sp. nov. The terebratellidine Zittelina? sp. is also present. Age determinations for all but one of the brachiopod-bearing seeps are based on associated ammonites. Five of the seep carbonates have yielded Lingularia similis?, and it is the only brachiopod species recorded from two of the seeps. Other benthic invertebrate taxa occurring in the seeps include bivalves, gastropods, echinoderms, sponges, and serpulid and non-serpulid worm tubes. The brachiopod fauna has a strong Boreal palaeobiogeographic signature. Collectively, the Spitsbergen seep rhynchonellate brachiopods exhibit high species richness and low abundance (<100 specimens from 8 seeps). This contrasts markedly with other Palaeozoic---Mesozoic brachiopod-dominated seep limestones where brachiopods are of low diversity (typically monospecific) with a super-abundance of individuals. The shallow water environmental setting for the Spitsbergen seeps supported a diverse shelf fauna, compared to enigmatic Palaeozoic-Mesozoic brachiopod-dominated seeps. PMID:25543805

Sandy, Michael R; Hryniewicz, Krzysztof; Hammer, Øyvind; Nakrem, Hans Arne; Little, Crispin T S

2014-01-01

66

New Late Jurassic palaeomagnetic data from the northern Sichuan basin: implications for the deformation of the Yangtze craton  

NASA Astrophysics Data System (ADS)

Upper Jurassic red sandstones and red siltstones were collected from 67 layers at 12 localities in the Penglaizhen formation. This formation is in the north of Bazhong county (31.8 degN, 106.7 degE) in the Sichuan basin, which is located in the northern part of the Yangtze craton. Thermal demagnetization isolated a high-temperature magnetic component with a maximum unblocking temperature of about 690 degC from 45 layers. The primary nature of the magnetization acquisition is ascertained through the presence of magnetostratigraphic sequences with normal and reversed polarities, as well as positive fold and reversal tests at the 95 per cent confidence level. The tilt-corrected mean direction of 36 layers is D=20.0 deg, I=28.8 deg with ?95=5.8 deg. A Late Jurassic palaeomagentic pole at 64.7 degN, 236.0 degE with A95=7.0 deg is calculated from the palaeomagnetic directions of 11 localities. This pole position agrees with the two other Late Jurassic poles from the northern part of the Yangtze craton. A characteristic Late Jurassic pole is calculated from the three poles (68.6 degN, 236.0 degE with A95=8.0 deg) for the northern part of the Yangtze craton. This pole position is significantly different from that for the southern part of the Yangtze craton. This suggests that the southern part of the Yangtze craton was subjected to southward extrusion by 1700+/-1000 km with respect to the northern part. Intracraton deformation occurred within the Yangtze craton.

Yokoyama, Masahiko; Liu, Yuyan; Otofuji, Yo-ichiro; Yang, Zhenyu

1999-12-01

67

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

SciTech Connect

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

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

1992-03-01

68

Late Paleozoic to Early Jurassic tectonic development of the high Andean Principal Cordillera, El Indio Region, Chile (29 30°S)  

NASA Astrophysics Data System (ADS)

Regional mapping (1:50,000) and U-Pb and K-Ar geochronology in the El Indio region refines the knowledge of the distribution, lithostratigraphy, and age of the sedimentary, volcanic, and intrusive rocks that comprise the regionally extensive Pastos Blancos Group which is equivalent to the Choiyoi Group of the Argentine Frontal Cordillera. The Pastos Blancos Group (which we elevate to Group status herein) includes at least two diachronous volcanic-sedimentary sequences: an older felsic volcanic and volcaniclastic unit, the Guanaco Sonso sequence, that is Permian in age, and a younger bimodal volcanic and volcaniclastic unit, the Los Tilos sequence that is Middle Triassic to Early Jurassic. Sedimentary rocks of the Los Tilos sequence are transitional upward into the overlying Early to Middle Jurassic shallow marine limestones of the Lautaro Formation. Intrusions that make up the regionally extensive Permian to Early Jurassic plutons of the Chollay and Elqui-Limar?´ batholiths that were previously mapped as a single plutonic association, the Ingaguás Complex, include in the El Indio region at least three discrete intrusive units. These include: Early Permian (280-270 Ma) biotite granites, Early to Middle Triassic (242-238 Ma) silica-rich leucocratic granites and rhyolitic porphyries that made up the bulk of the Chollay Batholith, and a younger Late Triassic-Early Jurassic unit (221-200 Ma) of mainly intrusive rhyolitic porphyries, extrusive domes, and subordinate mafic intrusions and both felsic and mafic dikes, which are coeval with volcanic rocks of the Los Tilos sequence. Our data show that latest Paleozoic to Early Jurassic intrusive, volcanic, and sedimentary rocks in the El Indio region of the High Andes of Chile between 29-30°S likely formed during extension driven processes after the cessation of Carboniferous-Early Permian subduction along the western edge of Gondwana. These processes began by Late Permian time, but instead of recording a single and protracted magmatic event, as has been previously suggested, rocks that belong to the Pastos Blancos Group and the Ingaguás Intrusive Complex record at least three discrete periods of silicic to bimodal magmatism which occurred during the Middle Permian to Early Jurassic interval.

Martin, Mark W.; Clavero R, Jorge; Mpodozis M, Constantino

1999-01-01

69

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

70

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

NASA Astrophysics Data System (ADS)

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

Mainali, P.; Rowe, H. D.

2010-12-01

71

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

NASA Astrophysics Data System (ADS)

Strontium and carbon isotope stratigraphy was applied to a 202 m-thick shallow marine carbonate section within the Late Jurassic Bau Limestone at the SSF quarry in northwest Borneo, Malaysia, which was deposited in the western Palaeo-Pacific. Strontium isotopic ratios of rudist specimens suggest that the SSF section was formed between the latest Oxfordian (155.95 Ma) and the Late Kimmeridgian (152.70 Ma), which is consistent with previous biostratigraphy. The ?13Ccarb values of bulk carbonate range from -0.10 to +2.28‰ and generally show an increasing upward trend in the lower part of the section and a decreasing upward trend in the upper part of the section. A comparable pattern is preserved in the ?13Corg isotope record. Limestone samples of the SSF section mainly preserve the initial ?13Ccarb values, except for the interval 84-92 m, where an apparent negative anomaly likely developed as a result of meteoric diagenesis. Comparing with the Tethyan ?13Ccarb profile, a negative anomaly in the lower SSF section can be correlated with the lowered ?13C values around the Oxfordian/Kimmeridgian boundary. In addition, ?13Ccarb values of the Bau Limestone are generally ?1‰ lower than the Tethyan values, but comparable with the values reported from Scotland and Russia, located in Boreal realm during the Late Jurassic. This suggests that either the Tethyan record or the other records have been affected by the ?13C values of regionally variable dissolved inorganic carbon (DIC). The Late Jurassic ?13CDIC values are thought to have been regionally variable as a result of their palaeoceanographic settings. This study shows that ?13C chemostratigraphy of the Palaeo-Pacific region contributes to an improved understanding of global carbon cycling and oceanography during this time period.

Kakizaki, Yoshihiro; Weissert, Helmut; Hasegawa, Takashi; Ishikawa, Tsuyoshi; Matsuoka, Jun; Kano, Akihiro

2013-09-01

72

Late Holocene environmental change in southwest Greenland fossil insect assemblages from Tasiusaq  

E-print Network

in Greenland, do not provide clear evidence for any distinct climatic event during the medieval periodLate Holocene environmental change in southwest Greenland ­ fossil insect assemblages from Tasiusaq Holocene environmental change in southwest Greenland ­ fossil insect assemblages from Tasiusaq. Boreas, 10

Panagiotakopulu, Eva

73

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

E-print Network

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

Rees, Allister

74

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

75

Analysis of gaseous inclusions in fossil resin from a late cretaceous stratigraphic sequence  

NASA Astrophysics Data System (ADS)

It is the purpose of this work to analyze the fluids included in the Fossil Forest fossil resin. The fossil resin samples used in this study were collected from the Fruitland Formation (Campanian-Maastrichtian; 76-72 Ma), a sequence of interbedded coals, drab-colored mudstones and claystones, poorly fissile carbonaceous shales, siltstones and sandstone in the Fossil Forest study area located in the west-central San Juan Basin of New Mexico. The resin is found in association with and included in fossilized taxodiaceous wood. The fluids trapped in Late Cretaceous fossil resin have a higher oxygen content that is found in younger samples. The analytical data are presented in a framework devised to differentiate between trapped paleoatmospheres and gases dissolved in the amber matrix. The data suggest that the Late Cretaceous atmosphere had an O 2 content of at least 24%. The gases trapped in fossil resin most likely are not pristine paleoatmosphere. However, fossil resin can record the composition of the atmosphere over the past 120 m.y., the length of the resin record.

Bellis, Diane; Wolberg, Donald L.

1991-12-01

76

Evidence for gondwanan origins for sassafras (lauraceae)? : late cretaceous fossil wood of antarctica  

Microsoft Academic Search

Sassafrasoxylon gottwaldii sp. nov. is a new taxon for fossil wood with\\u000aa suite of features diagnostic of Sassafras Nees & Eberm. of the Lauraceae.\\u000aThe fossil wood described is from Late Cretaceous (Santonian-\\u000aMaastrichtian) sediments of the northern Antarctica Peninsula region.\\u000aThis new species of Sassafrasoxylon Brezinová et Süss resembles the\\u000aspecies of extant Sassafras in being distinctly ring-porous,

I. J. Poole; Hans G. Richter; Jane E. Francis

2000-01-01

77

Oxygen isotope compositions of Late Jurassic vertebrate remains from lithographic limestones of western Europe: implications for the ecology of fish, turtles, and crocodilians  

Microsoft Academic Search

Oxygen isotopes can be used to reconstruct the palaeoenvironmental conditions in which vertebrates lived, and thereby give an indication of their ecology. This has been done for faunas from the famous Late Jurassic lithographic limestones of Western Europe. Oxygen isotope compositions of phosphate from apatite were measured in aquatic or semiaquatic vertebrate remains (fish, turtles, and crocodilians) deposited in these

Jean-Paul Billon-Bruyat; Christophe Lécuyer; François Martineau; Jean-Michel Mazin

2005-01-01

78

Application of Ostracoda and Charophyta from the Late Jurassic to Early Cretaceous Tendaguru formation at Tendaguru, Tanzania (East Africa) — Biostratigraphy, palaeobiogeography and palaeoecology  

Microsoft Academic Search

Revisitation of the famous Late Jurassic\\/Early Cretaceous dinosaur locality of Tendaguru by a German–Tanzanian expedition in summer 2000 resulted in a new standard section. Micropalaeontologic samples from this section yielded a marine and nonmarine, partially mixed ostracod fauna consisting of 40 taxa and some charophyte gyrogonites and utriculi. A few marine taxa provided biostratigraphic information, although comparable faunas from the

Benjamin Sames

2008-01-01

79

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

E-print Network

isotope stratigraphy is marked by a positive carbon isotope excursion of 3 which has been dated as MiddlePlate tectonic trigger of changes in pCO2 and climate in the Oxfordian (Late Jurassic): Carbon was characterized by significant changes in oceanography and climate and by changes in global carbon cycle as shown

Gilli, Adrian

80

Palaeoenvironment of the Late Triassic (Rhaetian) and Early Jurassic (Hettangian) Mecsek Coal Formation (south Hungary): implications from macro- and microfloral assemblages  

Microsoft Academic Search

The changes in early Mesozoic land plant communities, their vegetation patterns and vegetation dynamics are still only poorly\\u000a understood, mainly because of the lack of integrated studies on fossil plant macroremains and palynomorphs. The Early Jurassic\\u000a represents a major recovery phase of marine and terrestrial ecosystems after one of the biggest mass extinction events in\\u000a Earth’s history at the end

Annette E. Götz; Katrin Ruckwied; Maria Barbacka

2011-01-01

81

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

82

Algal fossils from a late precambrian, hypersaline lagoon.  

PubMed

Organically preserved algal microfossils from the Ringwood evaporite deposit in the Gillen Member of the Bitter Springs Formation (late Precambrian of central Australia) are of small size, low diversity, and probable prokaryotic affinities. These rather primitive characteristics appear to reflect the stressful conditions that prevailed in a periodically stagnant, hypersaline lagoon. This assemblage (especially in comparison with the much more diverse assemblages preserved in the Loves Creek Member of the same formation) illustrates the potential utility of Proterozoic microbiotas for basin analysis and local stratigraphic correlation and demonstrates the need to base evolutionary considerations and Precambrian intercontinental biostratigraphy on biotas that inhabited less restricted environments. PMID:17790847

Oehler, D Z; Oehler, J H; Stewart, A J

1979-07-27

83

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

E-print Network

A fossil primate of uncertain affinities from the earliest late Eocene of Egypt Erik R. Seifferta,1 Primates, Duke Lemur Center, Durham, NC 27705; c Department of Ecology and Evolution, Stony Brook but is considerably larger than other primate taxa known from the same paleocommunity. The species bears an odd mosaic

Boyer, Doug M.

84

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

85

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

PubMed Central

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

Srivastava, Gaurav; Mehrotra, R.C.

2014-01-01

86

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

SciTech Connect

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

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

1993-04-01

87

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

88

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

PubMed Central

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

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

2013-01-01

89

Page 1 of 45 Gigantism among Late Jurassic limulids: new ichnological evidence from  

E-print Network

the Late Devonian to the Oligocene (Table 1). Although Fernández and Pazos (2013) mentioned the relative geological record (Piekowski and Niedwiedzki, 2009; Gaillard, 2011; Diedrich, 2011; Fernández and Pazos, 2013

90

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

91

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

E-print Network

was an important period in the evo- lution of Testudinata and encompasses the origin of many clades stratigraphic range of turtles (i.e. Testudinata sensu Joyce et al., 2004) extends from the Triassic is Odontochelys semitestacea from the Late Triassic of Guizhou, China, which is 220 myr old (Li et al. 2008), some

Benton, Michael

92

A Jurassic mammal from South America  

Microsoft Academic Search

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

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

2002-01-01

93

Fossils  

NSDL National Science Digital Library

This Topic in Depth begins with a Web site from the Royal Ontario Museum called Fossils!-Behind the Scenes at the Museum (1). It gives a light-hearted but informative introduction to what fossils are and how they're formed, collected, and identified. Next, the University of California Museum of Paleontology offers the Web site Learning From the Fossil Record (2), which contains several learning resources and lesson plans. Topics covered include Determining Age of Rocks and Fossils, Fossilization and Adaptation: Activities in Paleontology, and Microfossils. The third site is a US Geological Survey publication entitled Fossils, Rocks, and Time (3). Visitors can learn about succession, geologic time, and other relevant facts about how fossils are studied. The University of Arizona Department of Geosciences maintains the next site, which is entitled Petrified Wood (4). It provides information on Petrified Forest National Park, an interactive look at the process of petrification, and more. Offered by the Museum Victoria, the fifth site, Dating Rocks and Fossils (5), explains the difference between relative and absolute (radiometric) dating. It also includes a chart that gives the various isotopes used, their half-life, daughter isotope, and geologic application. The next site, provided by the BBC and their Walking With Dinosaurs series, is called Fossil Detectives (6). The site describes why dinosaur fossils are so rare, where the best place to find them is, how their age is estimated, and other interesting information that can be found on this page and the rest of the site. Next, from the Florida Museum of Natural History comes the Fossil Preparation and Conservation (7) Web site. A more in-depth and technical description of fossil preparation is presented, including the use of cosolidants, adhesives, and various tools. The last site is from the University of Kentucky Paleontological Society called Photographs of Fossils Found on KPS Fieldtrips (8). As you would expect, the site contains a large categorized list of fossils, each briefly described and linked to its respective photograph.

2002-01-01

94

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

95

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

96

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. PMID:22792168

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

2012-01-01

97

Petrosal anatomy and inner ear structures of the Late Jurassic Henkelotherium (Mammalia, Cladotheria, Dryolestoidea): insight into the early evolution of the ear region in cladotherian mammals  

PubMed Central

The petrosal anatomy and inner ear structure of Jurassic cladotherian mammals represent the ancestral morphological conditions (groundplan) from which modern therian mammals (marsupials and placentals) have evolved. We present the reconstruction of the petrosal and inner ear features of the Late Jurassic dryolestoid mammal Henkelotherium guimarotae from high-resolution computed tomography and three-dimensional imaging analysis. This study of Henkelotherium revealed a combination of derived and primitive features, including: cladotherian apomorphies, such as the promontorial sulcus for the internal carotid artery and reduced lateral trough; trechnotherian characters, such as an enclosed cochlear canaliculus for the perilymphatic duct, post-promontorial tympanic sinus and caudal tympanic process; in addition to plesiomorphic mammalian features, such as the cavum supracochleare and prootic canal. The inner ear of Henkelotherium shows a division between the utricle and saccule, a cochlear canal coiled through at least 270°, a distinctive primary bony lamina for the basilar membrane, and a secondary bony lamina. The development of the primary and secondary bony laminae in the cochlear canal is suggested here to be correlated with the concurrent coiling of the bony canal and membranous duct of the inner ear cochlea, apomorphies of the more inclusive cladotherian clade that also represent the ancestral morphotype of modern therian mammals. Because these features are crucial for high-frequency hearing in extant therian mammals, their early appearance in Late Jurassic cladotherians suggests a more ancient origination for high-frequency hearing in mammalian history than previously thought. PMID:19438763

Ruf, Irina; Luo, Zhe-Xi; Wible, John R; Martin, Thomas

2009-01-01

98

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

99

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

SciTech Connect

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

Robinson, J.P.

1993-04-01

100

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. PMID:23301008

Camens, Aaron Bruce; Carey, Stephen Paul

2013-01-01

101

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

SciTech Connect

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

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

1995-10-01

102

Inference of pCO2 Levels during the Late Cretaceous Using Fossil Lauraceae  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

103

What Fossils Tell Us about the Evolution of the Neocortex  

Microsoft Academic Search

The story of the brain's evolution is told by casts of the cranial cavities of extinct species. These endocasts document much of the evolution of the mammalian brain during the past 65 million years, the Cenozoic era. A single late Jurassic fossil (Simpson, 1927; Jerison, 1973) had extended the known evidence to about 150 million years ago (mya), and other

Harry J Jerison

104

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. PMID:23028723

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

2012-01-01

105

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.

106

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

NASA Astrophysics Data System (ADS)

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

Fedonkin, Mikhail A.; Waggoner, Benjamin M.

1997-08-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

108

Northward subduction of Bangong-Nujiang Tethys: Insight from Late Jurassic intrusive rocks from Bangong Tso in western Tibet  

NASA Astrophysics Data System (ADS)

New zircon LA-ICPMS U-Pb age data, whole-rock major and trace elements, and zircon Hf isotopic data of intrusive rocks from Larelaxin and Caima plutons in the southern margin of the Western Qiangtang subterrane provide important evidence of northward subduction of the Bangong-Nujiang Tethyan Ocean lithosphere. Host granitoids including quartz diorites, granodiorites, and syenogranites and associated mafic varieties including gabbroic enclaves, dioritic dikes and enclaves, and quartz dioritic enclaves are investigated in this study. Five host granitoid samples are dated at 163-160 Ma, and one dioritic dike and three dioritic enclave samples are dated at 162-158 Ma, which indicates that these rocks were contemporaneous. The quartz diorites and granodiorites are normal calc-alkaline I-type granitoids. The syenogranites are characterized by high SiO2 (74-77 wt.%) and differentiation index (DI = 92-97) and marked depletion in Ba, Nb, Ta, Sr, P, Ti, and Eu, thus indicating that they are highly fractionated I-type granitoids. The host granitoids exhibit uniform zircon ?Hf(t) values (- 1.4 to + 1.9). Considering the current data and their negative whole-rock ?Nd(t) values (- 4.7 to - 3.5) reported in recent studies, these rocks can be interpreted to have resulted from the partial melting of ancient mafic lower crust with varying contributions from mantle-derived or juvenile crust-derived components. One gabbroic enclave sample exhibits high Al2O3 (18.3 wt.%), low MgO (3.3 wt.%), high TiO2 (1.4 wt.%), and high Nb (24 ppm) and is geochemically similar to high-alumina basalt (HAB) and high-Nb basalt (HNB). This indicates that the gabbroic enclave originated from the partial melting of mantle wedge peridotite that was metasomatized by slab melting and subsequently experienced significant fractional crystallization of olivine and clinopyroxene. The dioritic dike and enclave samples yield ?Hf(t) values (- 1.6 to + 3.1) similar to those of the host granitoids. They most likely originated from magma mixing between mantle-derived and crust-derived melts at or close to the Moho. The intrusive rocks with geochemical diversity of the Larelaxin and Caima plutons from Bangong Tso in western Tibet can be interpreted to have resulted from melting, assimilation, storage, and homogenization (a MASH process) above subduction zones, thus indicating that the Bangong-Nujiang Tethyan Ocean lithosphere was subducted northward beneath the Western Qiangtang subterrane during the Late Jurassic.

Li, Shi-Min; Zhu, Di-Cheng; Wang, Qing; Zhao, Zhi-Dan; Sui, Qing-Lin; Liu, Sheng-Ao; Liu, Dong; Mo, Xuan-Xue

2014-09-01

109

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

110

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

111

Fossil birds from the Late Cretaceous Los Alamitos Formation, Río Negro Province, Argentina  

NASA Astrophysics Data System (ADS)

In this note we report new avian remains from the Late Cretaceous Los Alamitos Formation (Campanian-Maastrichtian) at the Los Alamitos locality, Río Negro Province, Argentina. Isolated remains referable to indeterminate Aves, ?Patagopterygiformes, indeterminate Ornithurae, cf. Hesperornithes and cf. Neornithes are described and discussed. The new genus and species Alamitornis minutus is erected to include a minute-sized and gracile bird, probably related to the non-volant ratite-like bird Patagopteryx. If correctly identified, the record of Hesperornithes may be the first for this group in the Southern Hemisphere. The Los Alamitos paleoavifauna represents one of the most diverse fossil bird assemblage from the Mesozoic of Gondwana known to date.

Agnolin, Federico L.; Martinelli, Agustín G.

2009-02-01

112

Plagiogranite magmatism in the frontal part of Pekulney segment of Late Jurassic-Early Cretaceous Pekulney-Zolotogorskaya paleoarc  

NASA Astrophysics Data System (ADS)

PLAGIOGRANITE MAGMATISM IN THE FRONTAL PART OF PEKULNEY SEGMENT OF LATE JURASSIC-EARLY CRETACEOUS PEKULNEY-ZOLOTOGORSKAYA PALEOARC M.V.Luchitskaya (1), O.L.Morozov (1), S.A.Palandzhyan (2) (1) Geological Institute, Russian Academy of Sciences, Russia, Moscow, (2) Institute of Lithosphere of Marginal and Inner Seas, Russian Academy of Sciences, Russia, Moscow luchitskaya@geo.tv-sign.ru/Fax: (095) 2310443 Pekulney-Zolotogorskaya system of Central Chukotka is located at the junction of Verkhoynsk-Chukotka Mesozoides and Koryak-Kamchatka accretionary region. In the fold-and-thrust structure of its Pekulney segment autochthone, allochthone and neoautochthone are reconstructed. Autochtone is J3-K1 volcano-plutonic island arc complex and its pre-Mz heterogeneous basement (Pz3-Mz1 volcano-plutonic complex and Precambrian (?) metabasite-gabbroic complex). Allochtone is composed of J2-K1 siliceous-volcanic complex (a fragment of an oceanic basin crust) and K1 terrigeneous-tuffaceous-siliceous complex, formed on the inner trench slope). Neoautochthone is composed of post-K1h formations, overlying with unconfirmity the deformed complexes of different age and genesis. Plagiogranites are located at the contact of slices composed of J2-K1 siliceous-volcanic deposits and K1 terrigeneous-tuffaceous-siliceous complex. They form dikes in the matrix of terrigeneous-tuffaceous-siliceous complex and in the rocks of siliceous-volcanic complex and are also observed as a different size fragments in the former. Part of plagiogranites is dinamothermally metamorphosed together with host siliceous-volcanic deposits. The age of plagiogranites is post-K1nc according to geological data. Plagiogranites are low-K, low-Al rocks, K/Na=0.07-0.46. They fall in the trondhjemites field on the Ab-An-Or diagram and follow gabbro-trondhjemite trend. They fall in VAG field in the Rb Y+Nb diagram and in the supra-subduction related rocks field in the (Nb/Zr)n Zr diagram. ORG-normalized patterns are characterized by Ta, Nb negative anomalies. REE patterns of plagiogranites comprise two groups: more fractionated with positive Eu-anomaly and less fractionated with negative one. The latter have adakite-like Sr/Y ratios. The structure of Pekulney segment of paleoarc in K1 time, structural position of plagiogranites, permanent character of their intrusion and their geochemistry, allow to suppose two models of plagiogranite melts formation: melting of metabasite complexes in the pre-Mz heterogeneous arc basement and fractional crystallization of tholeiite-basalt melts. Acid melts migrated throuh accretional structure in the arc frontal part. Geochemical modelling using REE show that these two paths of plagiogranite formation may took place. Supported by RFBR grant N 01-05-64469.

Luchitskaya, M. V.; Morozov, O. L.; Palandzhyan, S. A.

2003-04-01

113

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

NASA Astrophysics Data System (ADS)

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 ˜3.5 °C 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.

2009-05-01

114

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

115

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

116

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

E-print Network

Late Pleistocene fossil find in Svalbard: the oldest remains of a polar bear (Ursus maritimus in Svalbard, a well preserved subfossil left mandible of a polar bear (Ursus maritimus Phipps, 1774--suggests that it is of Eemian­Early Weich- selian age: 130­110 Ky old. This makes the find the oldest remains of a polar bear

Ingólfsson, �lafur

117

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

Microsoft Academic Search

Late Holocene vegetation change from a high desert site in southern Utah was reconstructed using fossil plant macrofossils and pollen from packrat middens. Presettlement middens consistently contained abundant macrofossils of plant species palatable to livestock that are now absent or reduced such as: Ceratoides lanata, Stipa hymenoides, Pinus edulis, and Artemisia spp.. In contrast, species typical of overgrazed range, such

1995-01-01

118

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

119

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

120

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

121

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)

1996-12-31

122

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

123

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

Microsoft Academic Search

The late Triassic period is recognized as one of the five major mass extinctions in the fossil record. All these important intervals in earth history are associated with excursions in C-isotope records thought to have been caused by perturbations in the global carbon cycle. The nature and causes of C-isotopic events across the Triassic–Jurassic (T–J) transition however, are poorly understood.

Micha Ruhl; Wolfram M. Kürschner; Leopold Krystyn

2009-01-01

124

Three new Jurassic euharamiyidan species reinforce early divergence of mammals.  

PubMed

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

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

2014-10-30

125

Stratigraphy of the Jurassic system in northern Egypt  

SciTech Connect

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

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

1988-08-01

126

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

127

Echinate fossil pollen of Asteraceae from the Late Oligocene of Patagonia: an assessment of its botanical affinity  

Microsoft Academic Search

The Late Oligocene Mutisiapollis telleriae, which is the oldest echinate fossil pollen of Asteraceae from Patagonia, was tentatively related to the subfamily Mutisioideae.\\u000a A detailed comparison of M. telleriae with extant asteraceous pollen indicates strong similarities with both Mutisioideae (in particular the Gongylolepis type)\\u000a and Carduoideae (some genera of Carduinae) subfamilies. This morphotype, as an example of the exceptional diversity

María Cristina Tellería; Viviana Barreda; Luis Palazzesi; Liliana Katinas

2010-01-01

128

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

PubMed

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

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

2008-08-01

129

Bennettitalean foliage in the Rhaetian–Bajocian (latest Triassic–Middle Jurassic) floras of Scania, southern Sweden  

Microsoft Academic Search

This comprehensive macromorphological and cuticular study of bennettitalean foliage from the Rhaetian–Bajocian (Late Triassic–Middle Jurassic) floras of the former mining districts of Scania, southern Sweden, has necessitated revision of several morphotaxa reported widely across Laurasia from the mid-Mesozoic. More than 25000 fossil specimens from 42 localities in Scania were assessed, of which 732 yielded bennettitalean foliage remains. Fifty-one foliage taxa

Christian Pott; Stephen McLoughlin

2009-01-01

130

Transtensional tectonics induced by oblique reactivation of previous lithospheric anisotropies during the Late Triassic to Early Jurassic rifting in the Neuquén basin: Insights from analog models  

NASA Astrophysics Data System (ADS)

The goal of this study was to determine the main factors that controlled the kinematic evolution and the structural architecture developed during the Late Triassic to Early Jurassic rifting that led to the opening of the Neuquén basin in the southwestern sector of Gondwana. We carried out a series of analog models to simulate an extensional system with a bent geometry similar to the northeastern border of the basin. In different experiments, we varied the extension direction between NNE (N10°E) and NE (N45°E) orientations, inducing rift systems with different degrees of obliquity in each sector of the extended area. We compared the kinematic evolution and the final structural architecture observed in the experiments with data from two selected representative areas of the basin: (1) the Atuel depocenter, situated in the northern Andean sector, and (2) the Entre Lomas area, situated in the northeastern Neuquén Embayment. In both cases, the good match between the field and subsurface data and the results of the analog models supports a NNE orientation of the regional extension (N30°E-N20°E) during the synrift stage. Our experimental results suggest that lithospheric weakness zones of NNW to NW trend could have controlled and localized the extension in the Neuquén basin. These previous anisotropies were linked to the sutures and rheological contrasts generated during the collision of terranes against the southwestern margin of Gondwana during the Paleozoic, as well as further modifications of the thermo-mechanical state of the lithosphere during the Late Paleozoic to Early Mesozoic evolution.

Bechis, Florencia; Cristallini, Ernesto O.; Giambiagi, Laura B.; Yagupsky, Daniel L.; Guzmán, Cecilia G.; García, Víctor H.

2014-09-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

132

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

SciTech Connect

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

Roden, M.K. (Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Earth and Environmental Science)

1993-03-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

134

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

PubMed Central

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

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

2014-01-01

135

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

136

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

137

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

SciTech Connect

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

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

1993-04-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

139

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

140

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

PubMed Central

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

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

2012-01-01

141

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

142

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

143

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

144

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

145

Surculichnus bifurcauda n. igen., n. isp., a trace fossil from Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, USA, attributed to notostracan crustaceans based on neoichnological experimentation  

Microsoft Academic Search

New trace fossils found in the Late Pleistocene glaciolacustrine varves of the Connecticut River Valley, Vermont, USA represent the first known notostracan presence in glacial Lake Hitchcock. These unique trace fossils warrant a new ichnogenus and ichnospecies Surculichnus bifurcauda. The New England Varve Chronology (NEVC) constrains the initial presence of S. bifurcauda at ?13.3–13.2 kyr. The morphology of S. bifurcauda correlates

Richard J. Knecht; Jacob S. Benner; D. Christopher Rogers; John C. Ridge

2009-01-01

146

Fossil Plant Relative Abundances Indicate Sudden Loss of Late Triassic Biodiversity in East Greenland  

Microsoft Academic Search

The pace of Late Triassic (LT) biodiversity loss is uncertain, yet it could help to decipher causal mechanisms of mass extinction. We investigated relative abundance distributions (RADs) of six LT plant assemblages from the Kap Stewart Group, East Greenland, to determine the pace of collapse of LT primary productivity. RADs displayed not simply decreases in the number of taxa, but

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

2009-01-01

147

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

148

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

SciTech Connect

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

Cole, K.L. [Univ. of Minnesota, St. Paul, MN (United States)

1995-06-01

149

Four new species of hangingflies (Insecta, Mecoptera, Bittacidae) from the Middle Jurassic of northeastern China  

PubMed Central

Abstract Two new species of Mongolbittacus Petrulevi?ius, Huang & Ren, 2007, Mongolbittacus speciosus sp. n. and Mongolbittacus oligophlebius sp. n., and two new species of Exilibittacus Yang, Ren & Shih, 2012, Exilibittacus foliaceus sp. n. and Exilibittacus plagioneurus sp. n., in the family Bittacidae, are described and illustrated based on five well-preserved fossil specimens. These specimens were collected from the late Middle Jurassic Jiulongshan Formation of Daohugou, Inner Mongolia, China. These new findings enhance our understanding of the morphological characters of early hangingflies and highlight the diversity of bittacids in the Mid Mesozoic ecosystems. PMID:25610337

Liu, Sulin; Shih, Chungkun; Ren, Dong

2014-01-01

150

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

151

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

USGS Publications Warehouse

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

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

2008-01-01

152

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

USGS Publications Warehouse

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

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

2008-01-01

153

Plant and insect fossils at Norwood in south-central Minnesota: A record of late-glacial succession*1  

NASA Astrophysics Data System (ADS)

The Norwood site in Sibley Co., Minnesota, contains 1.6 m of silt resting on till and overlain by peat. The base of the peat has been radiocarbon dated at 12,400 ± 60 and the top at 11,200 ± 250 yr B.P. The pollen, plant macrofossils, and insect remains in the basal silt consist of boreal species inhabiting open environments, but not tundra. No modern analogue exists for the insect assemblage, which includes elements of boreal forest, tundra-forest, and western affinities. The transition from an unstable open environment to a stable coniferous forest is reflected by both plant and insect fossils and is interpreted as a successional rather than a climatic event. During this time of significant biologic change, the climate is inferred to have been relatively uniform, with temperatures similar to those presently existing in the boreal forest south of the tundra-forest transition zone. The geologic and ecologic succession at Norwood is generally similar to that presently associated with ice stagnation of the Klutlan Glacier in the Yukon Territory. Localized successional sequences similar to those at Norwood are conceived to have occurred repeatedly during the melting of the Laurentide ice, and thus the proposed model has potentially broad application to the interpretation of late-glacial sequences.

Ashworth, Allan C.; Schwert, Donald P.; Watts, William A.; Wright, H. E.

1981-07-01

154

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

Microsoft Academic Search

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

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

1985-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

156

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. PMID:21062504

2010-01-01

157

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

158

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. PMID:23349701

Srivastava, Gaurav; Mehrotra, Rakesh C.

2013-01-01

159

Triassic and Jurassic rocks at Currie, Nevada Preliminary paleontologic evidence  

SciTech Connect

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

Johnson, E.A.; Dubiel, R.F.; Brouwers, E.M. (Geological Survey, Denver, CO (United States)); Litwin, R.J. (Geological Survey, Reston, VA (United States)); Ash, S.R. (Weber State Coll., Ogden, UT (United States)); Good, S.C. (State Univ. Coll., Cortland, NY (United States))

1993-04-01

160

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. PMID:20352090

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

2010-01-01

161

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

PubMed

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

McConnell, Shannon M; Zavada, Michael S

2013-03-01

162

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.

163

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

164

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

E-print Network

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

Schöne, Bernd R.

165

Petrology of a Jurassic cold seep carbonate mound, Great Valley Group, northern California  

SciTech Connect

Ancient sites of chemosynthetic marine invertebrate communities have been increasingly described from the stratigraphic record. Fossil cold seeps are best identified by the stratigraphically restricted co-occurrence of anomalous carbonates and fossils of organisms that in modern environments are chemosymbiotic. A Late Jurassic (Tithonian) age fossil seep site is preserved in deep-water turbidites of the Stony Creek Formation (Great Valley Group). Two low-relief carbonate mounds contain an abundant and diverse fossil macrofauna including taxa whose modern counterparts are chemosymbiotic, as well as several associate taxa. Two broad carbonate fabric types are present: a bioturbated, peloidal, fossiliferous micrite with abundant flecks of organic matter and several wavy laminated marine cements. The micrite and cements are either irregularly interlayered on distinctly separated by corrosion surfaces coated with iron oxides that may mark pulses of H[sub 2]S-rich fluids to the seep. Petrographic observations indicate the following idealized paragenetic sequence: deposition of micrite, with contemporaneous biotic activity; corrosion event, with preferential preservation of some peloids; precipitation of pyrite on some corrosion surfaces and concentration of insoluble siltstone linings where corrosion has opened vugs; precipitation of blocky yellow calcite cement with organic-rich inclusions in void spaces and around peloids; growth of clear to gray, botryoidal to fibrous cement; and precipitation of late, clear calcite spar. Similar fabrics and abundant tube-like structures are present in another Great Valley carbonate lens of Early Cretaceous (Albian-Aptian) age exposed on the Cold Fork of Cottonwood Creek near Red Bluff, California. Detailed integration of petrological studies of these fabrics with stable isotope studies and fossil faunal distributions provide a powerful approach for understanding the history of development and individual fossil seeps.

Campbell, K.A.; Bottjer, D.J. (Univ. of Southern California, Los Angeles, CA (United States). Dept. of Geological Sciences)

1992-01-01

166

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

Microsoft Academic Search

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

Enrique Fucks; Marina Aguirre; Cecilia M. Deschamps

2005-01-01

167

A large and complete Jurassic geothermal field at Claudia, Deseado Massif, Santa Cruz, Argentina  

NASA Astrophysics Data System (ADS)

Late Jurassic geothermal deposits at Claudia, Argentinean Patagonia, are among the largest (40 km2) and most varied in the Deseado Massif, a 60,000 km2 volcanic province hosting precious metals (Au, Ag) mineralization generated during diffuse back arc spreading and opening of the South Atlantic Ocean. Both siliceous sinter and travertine occur in the same stratigraphic sequence. Deposits range from those interpreted as fluvially reworked hydrothermal silica gels, to extensive apron terraces, to a clustering of high-temperature subaerial vent mounds. Paleoenvironmentally diagnostic textures of sinters include wavy laminated, bubble mat and nodular fabrics, and for travertines comprise fossil terracette rims, wavy laminated, bubble mat, spherulitic, oncoidal, and peloidal fabrics. Of special note is the presence of relatively large (to 25 cm high), inferred subaqueous "Conophyton" structures in travertines, which serve as analogs for some Precambrian stromatolites and imply the presence of relatively deep pools maintained by voluminous spring discharges. The Claudia geothermal field is geographically and geologically linked to the Cerro Vanguardia epithermal project (total resource of ~ 7.8 million ounces Au equivalent) via proximity, similar veins, and structural linkages, making it an especially large and relevant prospect for the region. The combined Claudia-Cerro Vanguardia hydrothermal system likely represents a fortuitous alignment of focused fluid flow and structure conducive to forming a giant epithermal ore deposit, with respect to size, ore concentration and potentially duration, in the Late Jurassic of Patagonia.

Guido, Diego M.; Campbell, Kathleen A.

2014-04-01

168

Jurassic Reef Park  

NSDL National Science Digital Library

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

Reinhold Leinfelder

169

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

170

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

PubMed

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

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

2015-01-01

171

The cranial anatomy of the Early Jurassic turtle Kayentachelys aprix  

Microsoft Academic Search

The fossil turtle Kayentachelys aprix is known from Early Jurassic sediments of the Kayenta Formation, Arizona, USA. The detailed description of this taxon's cranium offered in this paper demonstrates that this turtle presents a mixture of primitive and derived character states. Among others, the presence of an interpterygoid vacuity, a basipterygoid process, a prootic that is exposed in ventral view,

JULIANA STERLI; WALTER G. JOYCE

172

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

PubMed Central

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

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

2014-01-01

173

Triassic/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama  

SciTech Connect

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

Hutley, J.K.

1985-02-01

174

Jurassic crustal deformation in west-central part of Colorado Plateau  

SciTech Connect

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

Peterson, F.

1985-05-01

175

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

176

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. PMID:16593490

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

1984-01-01

177

The systematics and paleobiogeographic significance of Sub-Boreal and Boreal ammonites (Aulacostephanidae and Cardioceratidae) from the Upper Jurassic of the Bohemian Massif  

NASA Astrophysics Data System (ADS)

Upper Jurassic marine deposits are either rarely preserved due to erosion or buried under younger sediments in the Bohemian Massif. However, fossil assemblages from a few successions exposed in northern Bohemia and Saxony and preserved in museum collections document the regional composition of macro-invertebrate assemblages and thus provide unique insights into broad-scale distribution and migration pathways of ammonites during the Late Jurassic. In this paper, we focus on the systematic revision of ammonites from the Upper Oxfordian and Lower Kimmeridgian deposits of northern Bohemia and Saxony. The ammonites belong to two families (Aulacostephanidae and Cardioceratidae) of high paleobiogeographic and stratigraphic significance. Six genera belong to the family Aulacostephanidae (Prorasenia, Rasenia, Eurasenia, Rasenioides, Aulacostephanus, Aulacostephanoides) and one genus belongs to the family Cardioceratidae (Amoeboceras). They show that the Upper Jurassic deposits of the northern Bohemian Massif belong to the Upper Oxfordian and Lower Kimmeridgian and paleobiogeographically correspond to the German-Polish ammonite branch with the geographical extent from the Polish Jura Chain to the Swabian and Franconian Alb. Therefore, the occurrences of ammonites described here imply that migration pathway connecting the Polish Jura Chain with habitats in southern Germany was located during the Late Oxfordian and Early Kimmeridgian in the Bohemian Massif.

Hrbek, Jan

2014-10-01

178

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

179

Triassic and Jurassic radiolarians from sedimentary blocks of ophiolite mélange in the Avala Gora area (Belgrade surroundings, Serbia)  

NASA Astrophysics Data System (ADS)

Blocks of cherty rocks and Aptychus Limestone embedded into ophiolite mélange south of Avala Gora (Serbia) contain radiolarians of different ages. We distinguished here Late Jurassic (middle Oxfordianearly Tithonian), Middle-Late Jurassic (Bathonian-early Tithonian), and Middle Triassic (early Ladinian) radiolarian assemblages. The respective stratigraphic data suggest that the ophiolite mélange was formed after the early Tithonian.

Bragin, N. Yu.; Bragina, L. G.; Djeri?, N.; Tolji?, M.

2011-12-01

180

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

Microsoft Academic Search

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

Yongdong Wang

2002-01-01

181

Sequence stratigraphy of Jurassic strata in the lower Surat Basin succession, Queensland  

Microsoft Academic Search

The principles of non-marine sequence stratigraphy were applied to the Jurassic strata in the lower part of the Surat Basin, in order to better determine the depositional history of the basin and highlight potential reservoir and source rocks. The lithostratigraphic units in the Early-early Late Jurassic interval can be divided into three supersequences: J, K and L. Each supersequence consists

K. L. Hoffmann; J. M. Totterdell; O. Dixon; G. A. Simpson; A. T. Brakel; A. T. Wells; J. L. Mckellar

2009-01-01

182

Jurassic crustal deformation in west-central part of Colorado Plateau  

Microsoft Academic Search

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

1985-01-01

183

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

184

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

185

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

E-print Network

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

Hesselbo, Stephen P.

186

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

188

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

PubMed Central

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

Wang, Qi; Shih, Chungkun; Ren, Dong

2013-01-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

190

Paleontology, sedimentology and paleoenvironment of a new fossiliferous locality of the Jurassic Cañadón Asfalto Formation, Chubut Province, Argentina  

NASA Astrophysics Data System (ADS)

A new Late Jurassic assemblage of “conchostracans”, ostracods, bivalves and caddisfly cases from the locality “Estancia La Sin Rumbo”, Chubut Province (Patagonia, Argentina) is recorded. The fossils occur in the upper part of an outcropping 45 m thick volcaniclastic lacustrine sequence of yellowish tuffs and tuffites of the Puesto Almada Member, which is the upper member of the Cañadón Asfalto Formation with U/Pb age of 161 ± 3 Ma. The sequence represents one sedimentary cycle composed of a (lower) hemicycle of expansion and a (higher) hemicycle of contraction of the water body. The invertebrates lived in small freshwater bodies during the periods of expansion of the lake. The occurrence of a great number of small spinicaudatans, associated with mud-cracks, is evidence of dry climatic conditions and suggests several local mortality events. The spinicaudatan record of the fushunograptid-orthestheriid (component of the Eosestheriopsis dianzhongensis fauna) and the presence of Congestheriella rauhuti Gallego and Shen, suggest a Late Jurassic (Oxfordian to Tithonian) age. Caddisfly cases are recorded for the first time in the Cañadón Asfalto Basin.

Gallego, Oscar F.; Cabaleri, Nora G.; Armella, Claudia; Volkheimer, Wolfgang; Ballent, Sara C.; Martínez, Sergio; Monferran, Mateo D.; Silva Nieto, Diego G.; Páez, Manuel A.

2011-02-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

192

The Nd-isotopic composition of late Cretaceous bathyal-abyssal seawater from fossil fish skeletal debris  

NASA Astrophysics Data System (ADS)

There is currently very little proxy data available for determining the inter-ocean mixing of deep-water masses during the Cretaceous, and thus uncertainty remains as to the importance of deep-water circulation in latitudinal heat transport and bottom-water oxygenation for that time. A solution lies in exploiting a geochemical water-mass tracer, such as the neodymium (Nd) isotopic composition of seawater. It has been shown that the distinct differences in the Nd-isotopic composition observed in modern deep and intermediate waters have persisted since the early Cenozoic, but currently our knowledge of the Cretaceous oceans is poor. Most of the existing Nd-isotope data for the Cretaceous are from shallow-water masses on the continental shelves of the Tethyan and Atlantic Oceans. It has previously been shown that biogenic apatites record the Nd-isotopic composition of bottom-waters during an early diagenetic reaction at the sediment-water interface. We present Nd-isotope data from fish-teeth and skeletal debris picked from deep-ocean sediments recovered by DSDP and ODP drilling in the North and South Atlantic, Indian and Pacific Oceans. The sites chosen for this study were all deposited at bathyal-abyssal water depths. In conjunction with other recent studies, our data establish that the Pacific Ocean has likely maintained a constant range of Nd-isotopic values between ~-5 and -3 since at least 135 Ma. The data from the North Atlantic, South Atlantic and proto-Indian Ocean show that bottom-waters in these basins had relatively radiogenic Nd-isotopic compositions for much of the mid-Cretaceous (~-8 to ~-5), before shifting to less radiogenic values (<-9) between 85 and 75 Ma. A recently published study from Demerara Rise (MacLeod et al. 2008) revealed the existence there of a large positive Nd-isotope excursion during OAE2, which we see no evidence for elsewhere suggesting that the excursion most likely resulted from mixing of locally-sourced bottom-waters with bottom-waters from the rest of the deep North Atlantic. We interpret the Late Cretaceous shift in our data as reflecting either a decrease in the influence of Pacific waters via circum-equatorial surface currents, or as an increase in the contribution of a deep-water mass with a highly radiogenic value. The values attained by this shift suggest a Late Cretaceous age for the establishment of the Cenozoic Nd-isotope pattern. However, this shift did not occur at the transition in the Turonian to more oxygenated sedimentation in the North Atlantic, thereby leaving unanswered the question of whether ocean circulation changes and shifting tectonic gateways were responsible for the oxygenation event. MacLeod, K.G., et al., 2008, Nd isotopic excursion across Cretaceous ocean anoxic event 2 (Cenomanian-Turonian) in the tropical North Atlantic, Geology, 36, 811-814.

Robinson, S. A.; Vance, D.

2009-04-01

193

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

PubMed

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

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

2013-12-01

194

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

PubMed Central

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

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

2013-01-01

195

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

196

Jurassic epithermal Au–Ag deposits of Patagonia, Argentina  

Microsoft Academic Search

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

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

1997-01-01

197

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

198

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

199

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

200

Fossil Fondue  

NSDL National Science Digital Library

To understand how fossils are formed, students model the process of fossilization by making fossils using small toy figures and melted chocolate. They extend their knowledge to the many ways that engineers aid in the study of fossils, including the development of tools and technologies for determining the physical and chemical properties of fossilized organisms, and how those properties tell a story of our changing world.

Integrated Teaching And Learning Program

201

Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event  

PubMed

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

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

2000-07-27

202

4th Grade Fossils  

NSDL National Science Digital Library

Introduction to Fossils What is a fossil What is a Fossil? Body and Trace Fossils Body and Trace Fossils Life of a Vertebrate fossil Life of a Vertebrate Fossil Finding Fossils Finding Fossils How fossils are found How fossils are formed Age of Fossils Age of Fossils in Sedimentary Rock Fossils found in Utah Fossils found in Utah Where fossils are found in Utah Where fossils are found in Utah Utah County Map Utah County Map ...

richrigby

2010-01-26

203

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

E-print Network

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

Olsen, Paul E.

204

Fossil primates 1 Fossil primates  

E-print Network

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

Delson, Eric

205

Fossil humans 1 Fossil humans  

E-print Network

Fossil humans 1 Fossil humans All prehistoric skeletal remains of humans which are archeologically or fossilization of bone, and regardless of whether the remains may be classed as Homo sapi- ens sapiens of the Neanderthal speci- men in 1856. Fossil human remains have come prin- cipally from Europe, Asia, China, Java

Delson, Eric

206

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

E-print Network

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

Holtz Jr., Thomas R.

207

Discovering Fossils: Fossil Tools & Resources  

NSDL National Science Digital Library

Fossil enthusiasts Roy Shephard and Luci Algar combined their professional skills in media and education to develop this informative and entertaining website. Designed to be educational and accessible to children, this site presents a wide variety of information about fossils. The site contains a nice collection of images and diagrams; and includes a fossils guide for beginners, information on preparing fossils, a collection of fossil myths, information on ammonites, and more. The site also contains a Games & Activities section for teachers and students, a glossary of fossil terms, a neat diagram depicting the evolution of life on our planet, and even some free fossil desktop images.

208

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

Microsoft Academic Search

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

Michael E. Schudack

1999-01-01

209

An evaluation of fossil tip-dating versus node-age calibrations in tetraodontiform fishes (Teleostei: Percomorphaceae).  

PubMed

Time-calibrated phylogenies based on molecular data provide a framework for comparative studies. Calibration methods to combine fossil information with molecular phylogenies are, however, under active development, often generating disagreement about the best way to incorporate paleontological data into these analyses. This study provides an empirical comparison of the most widely used approach based on node-dating priors for relaxed clocks implemented in the programs BEAST and MrBayes, with two recently proposed improvements: one using a new fossilized birth-death process model for node dating (implemented in the program DPPDiv), and the other using a total-evidence or tip-dating method (implemented in MrBayes and BEAST). These methods are applied herein to tetraodontiform fishes, a diverse group of living and extinct taxa that features one of the most extensive fossil records among teleosts. Previous estimates of time-calibrated phylogenies of tetraodontiforms using node-dating methods reported disparate estimates for their age of origin, ranging from the late Jurassic to the early Paleocene (ca. 150-59Ma). We analyzed a comprehensive dataset with 16 loci and 210 morphological characters, including 131 taxa (95 extant and 36 fossil species) representing all families of fossil and extant tetraodontiforms, under different molecular clock calibration approaches. Results from node-dating methods produced consistently younger ages than the tip-dating approaches. The older ages inferred by tip dating imply an unlikely early-late Jurassic (ca. 185-119Ma) origin for this order and the existence of extended ghost lineages in their fossil record. Node-based methods, by contrast, produce time estimates that are more consistent with the stratigraphic record, suggesting a late Cretaceous (ca. 86-96Ma) origin. We show that the precision of clade age estimates using tip dating increases with the number of fossils analyzed and with the proximity of fossil taxa to the node under assessment. This study suggests that current implementations of tip dating may overestimate ages of divergence in calibrated phylogenies. It also provides a comprehensive phylogenetic framework for tetraodontiform systematics and future comparative studies. PMID:25462998

Arcila, Dahiana; Alexander Pyron, R; Tyler, James C; Ortí, Guillermo; Betancur-R, Ricardo

2015-01-01

210

Jurassic Polar Movement Relative to North America  

Microsoft Academic Search

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

ANY C. E. HELSLEY

1972-01-01

211

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

212

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. PMID:23536443

Toljagi?, Olja; Butler, Richard J.

2013-01-01

213

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

214

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

PubMed Central

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

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

2009-01-01

215

"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

216

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

PubMed

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

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

2015-01-01

217

Amount of subsidence during a late Holocene earthquake—evidence from fossil tidal marsh foraminifera at Vancouver Island, west coast of Canada  

Microsoft Academic Search

Fossil foraminifera in intertidal deposits beneath a marsh near Tofino on west-central Vancouver Island, British Columbia, provide a basis for estimating the amount of subsidence during a large earthquake less than 400 years ago. We compared the fossil foraminiferal assemblages with present-day assemblages along a surveyed transect across the marsh, and we estimated paleo-elevation by means of both subjective and

Jean-Pierre Guilbault; John J. Clague; Martine Lapointe

1995-01-01

218

Seismic evidence for the presence of Jurassic oceanic crust in the1 central Gulf of Cadiz (SW Iberian margin)2  

E-print Network

. The narrow oceanic basin would38 have formed during an oblique rifting and seafloor spreading episode between40 spreading in the North Atlantic at the Tithonian (late Jurassic-earliest Cretaceous). The41

Paris-Sud XI, Université de

219

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

SciTech Connect

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

Not Available

1992-01-01

220

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. PMID:19019789

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

2008-01-01

221

Finding Fossils  

NSDL National Science Digital Library

This OLogy activity serves as a kid-friendly how-to manual about searching for fossils. In Not Just Any Rock Will Do, kids learn that fossils "hide out" in sedimentary rock and see examples of shale and sandstone. Do's and Don'ts for Fossil Hunters gives kids practical tips and a list of fossil-hunting supplies. In Fossils You May Find, there are photos of common invertebrate, vertebrate, and plant fossils to guide kids. Paleontology Clubs and Web Sites lists resources to help kids determine where to hunt for fossils. In Keeping a Field Journal, kids are shown a sample journal entry that points out the types of information they should record.

222

Fossils 1: Fossils and Dinosaurs  

NSDL National Science Digital Library

This lesson will go beyond naming dinosaurs and give students a broad understanding of how we know about the great beasts. This lesson focuses on what we have learned and can learn from fossils. The follow-up lesson, Dinosaurs Fossils - Uncovering the Facts, explores what information can be discerned by comparing fossils to living organisms.

Science Netlinks

2001-10-20

223

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

224

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

225

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

226

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.

227

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

228

Pennsylvanian to Jurassic eolian transportation systems in the western United States  

USGS Publications Warehouse

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

Peterson, F.

1988-01-01

229

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

PubMed

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

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

2012-01-01

230

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

231

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

232

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. PMID:22615359

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

233

An arboreal docodont from the Jurassic and mammaliaform ecological diversification.  

PubMed

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

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

2015-02-13

234

Fossil spiders.  

PubMed

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

Selden, Paul A; Penney, David

2010-02-01

235

Fossil Fuels  

NSDL National Science Digital Library

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

Iowa Public Television. Explore More Project

2004-01-01

236

Triassic-Jurassic Flora of Poland; Floristical Support of Climatic Changes  

NASA Astrophysics Data System (ADS)

Plant macroremains from five boreholes in Poland were studied. Two of them (Huta OP-1 and Studzianna) from the northern margin of the Holy Cross Mountains, yielded several taxa. In the other three boreholes determinable fos-sil plants were sporadic, albeit important. Most of the taxa from the Huta OP-1 and Studzianna boreholes are typi-cal of the European Early Jurassic (Hettangian and Sinemurian). Both localities, although close to one another, show incertae sedis, Desmiophyllum harrisii phytes and conifers (a new species incertae sedis, Desmiophyllum harrisii Barbacka et Pacyna is herein proposed), which would suggest rather wet and warm conditions. This flora is typical of the European Province of the Euro-Sinian Region. In Studzianna the Siberian elements dominate, gymnosperms, mainly Czekanowskiales, which in-dicate a drier and colder environment. The palaeobotanical data correspond to the results of clay mineral studies, in particular the kaolinite/illite ratio in the source formations. The kaolinite content confirms a decrease in temperature and a reduction in rainfall in the late Early Hettangian and the latest Hettangian in the area.

Barbacka, Maria; Pacyna, Grzegorz; Feldman-Olszewska, Anna; Ziaja, Jadwiga; Bodor, Emese

2014-12-01

237

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

NASA Technical Reports Server (NTRS)

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

Pessagno, E. A., Jr.

1971-01-01

238

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

PubMed Central

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

Gee, Carole T.

2013-01-01

239

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. PMID:20974956

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

2010-01-01

240

Chondrites: A Trace Fossil Indicator of Anoxia in Sediments  

Microsoft Academic Search

The trace fossil Chondrites, a highly branched burrow system of unknown endobenthic deposit feeders, occurs in all types of sediment, including those deposited under anaerobic conditions. In some cases, such as the Jurassic Posidonienschiefer Formation of Germany, Chondrites occurs in black, laminated, carbonaceous sediment that was deposited in chemically reducing conditions. In other cases, such as numerous oxic clastic and

Richard G. Bromley; A. A. Ekdale

1984-01-01

241

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

E-print Network

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

Olsen, Paul E.

242

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

SciTech Connect

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

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

1992-08-01

243

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.

244

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

245

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

SciTech Connect

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

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

1993-04-01

246

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

247

Bird Fossils  

NSDL National Science Digital Library

A fossil of a small, feathered animal, Longisquama insignis, that lived approximately 220 million years ago (Ma) in what is now Central Asia, was re-discovered recently in the dusty drawers of a Moscow museum collection. This discovery has rocked the paleontological world because the fossil exhibits feather impressions, making it possibly the world's oldest known bird. Archaeopteryx, thought until now to be the oldest true bird, is from a limestone deposit in Germany dated at approximately 145 Ma. This new fossil discovery fires the debate over whether birds are descended from dinosaurs, or branched off from an earlier group of reptiles. This week's In The News takes a look at scientists' latest understanding of the reptile-bird evolutionary transition, and the surrounding controversies.

248

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”. PMID:21738409

Zinovyev, Evgeniy

2011-01-01

249

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

SciTech Connect

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

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

1991-02-01

250

Jurassic-Cretaceous continental margin of Southeastern Russia: Outcrop sequence stratigraphy, sedimentation and tectonics  

Microsoft Academic Search

Data on the composition and distribution of the sedimentary complexes of the Late Mesozoic continental margin of Southeastern Russia and their boundaries permit reconstruction of the tectonic evolution stages using different units of outcrop sequence stratigraphy separated by unconformities. Four siliciclastic megasequences extending from the Bureya ancient massif (microcontinent) to Sakhalin have been recorded within the Jurassic-Cretaceous continental margin of

Kirillova

2009-01-01

251

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

PubMed

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

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

2014-10-24

252

Upper Jurassic depositional systems and hydrocarbon potential of southeast Mississippi  

SciTech Connect

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

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

1987-09-01

253

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

SciTech Connect

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

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

1994-04-01

254

Middle Jurassic sand reservoirs of Tazovskoe field (West Siberia)  

NASA Astrophysics Data System (ADS)

Perspectives of Tazovskoe field Jurassic strata development are associated with lithological and mineralogical characteristics of reservoirs, which are the main reserve of the region, because of the high rate of depletion of the most prolific Cenomanian gas pools. Tazovskoye field is multibedded and is unique in terms of hydrocarbon reserves. Middle Jurassic strata occur everywhere and are represented by rocks of the Tyumenskaya formation, comprising layers J2 - J5. The producing horizons are composed of sandstones, sandy siltstones, cemented by shaly-carbonate cement mass. According to laboratory data, the Jurassic reservoirs are characterized by a wide range of porosity (up to 22.5%) and mainly low permeability (up to 2 mD), except for a few samples of J3 reservoir with permeability up to 100-150 mD. Test objects were the core samples taken from 7 intervals of the well T-83 and logging data from 4 intervals of wells 73, 93 in the Tazovskoye field. Depth and core recovery from T-83 well of the Tazovskoye field are shown in Table 1. Total linear core recovery from the Jurassic strata was 79.4 m. Late Bajocian-Bathonian alluvial-lacustrine strata compose the first regressive cycle of sedimentation in the Tazovskoye field. They are represented by alternating thin sandy, siltstone-sandy, siltstone, shaly-siltstone, siltstone-shaly, and shaly rocks with coal interbeds. They include three main productive formations: J2, J3 and J4. Above in the vertical section, the Upper Jurassic rocks occur, while lower, basal strata of the Callovian stage overlay them with a distinct unconformity. In the Upper Jurassic time, the main transgression phase of the Jurassic period occurred over the whole territory of the Western Siberia. These strata are built by non-uniform alternating sandstones, siltstones and shales with coal interbeds of the continental genesis (alluvial-lacustrine); The reservoirs contain cyclites that as a rule have binary structure, less often - ternary structure: the lower element of cyclites is represented by sandy and siltstone-sandy strata formed in a channel and in a point-bar, the upper element of cyclites is represented by siltstone, siltstone-shaly, shaly, and carbonaceous-shaly strata formed in the floodplain or in lacustrine-boggy sedimentation environment; The producing strata of J2-J4 formations are characterized in general by moderate porosity (11-17%) and low permeability (1 mD); This genetic type of the Middle Jurassic reservoirs is typical throughout the Pur-Taz petroleum region, as well is possible for the Nadym-Pur petroleum region, except for the most eastern areas of Nadym, where these rocks have flysch nature, and therefore one can predict their presence in adjacent fields, where the Jurassic reservoirs are not discovered yet.Core recoveries from T83 well;

Kurasov, I. A.

2012-12-01

255

Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event  

Microsoft Academic Search

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

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

2000-01-01

256

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

SciTech Connect

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

Rogers, R.

1987-09-01

257

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

Microsoft Academic Search

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

B. L. Nikitenko

2008-01-01

258

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

Microsoft Academic Search

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

B. L. Nikitenko

2008-01-01

259

Fossil Fuels  

NSDL National Science Digital Library

The Department of Energy Web site Fossil Fuels is billed as an energy education site mainly for older kids, but can be enjoyed by adult kids as well. The site gives an introduction to energy, and then a more detailed look at the acquisition and uses of coal, oil, and gas. The good descriptions, illustrations, and animations, along with the frequent questions page and glossary of related terms, combine to give a clear and enlightening overview of the subject.

260

Annual monsoon rains recorded by Jurassic dunes.  

PubMed

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

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

2001-07-01

261

Rulers of the Jurassic Seas  

NSDL National Science Digital Library

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

Motani, Ryosuke.

2000-01-01

262

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

PubMed

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

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

2015-01-01

263

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

264

Describing Fossils  

NSDL National Science Digital Library

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

Judy Massare

265

Strategies for assessing EarlyMiddle (PliensbachianAalenian) Jurassic  

E-print Network

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

266

Amphibious flies and paedomorphism in the Jurassic period.  

PubMed

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

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

2013-03-01

267

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

SciTech Connect

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

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

1984-04-01

268

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

269

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

270

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

271

World petroleum systems with Jurassic source rocks  

SciTech Connect

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

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

1993-11-08

272

Jurassic-Neocomian biostratigraphy, North Slope, Alaska  

SciTech Connect

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

Mickey, M.B.; Haga, H.

1985-04-01

273

Mineralization of soft-part anatomy and invading microbes in the horseshoe crab Mesolimulus from the Upper Jurassic Lagerstätte 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. PMID:15817437

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

2005-01-01

274

Are the oldest 'fossils', fossils  

NASA Technical Reports Server (NTRS)

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

Schopf, J. W.

1976-01-01

275

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

276

Will My Fossil Float?  

ERIC Educational Resources Information Center

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

Riesser, Sharon; Airey, Linda

1993-01-01

277

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

Microsoft Academic Search

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

Alan Channing; Alba Zamuner; Dianne Edwards; Diego Guido

2011-01-01

278

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; den Bogaard, Paul; Hoernle, Kaj; Werner, Reinhard; Whittaker, Joanne M.; Müller, R. Dietmar

2012-05-01

279

Anomalies in global carbon cycling and extinction at the Triassic/Jurassic boundary: evidence from a marine  

E-print Network

. Introduction The Late Triassic was a period of intense biological change involving both marine and nonAnomalies in global carbon cycling and extinction at the Triassic/Jurassic boundary: evidence from This study investigates whether the end-Triassic biotic crisis was coupled with a perturbation of the marine

Gilli, Adrian

280

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

281

NEW METHODS TO DOCUMENT FOSSILS FROM LITHOGRAPHIC LIMESTONES OF SOUTHERN GERMANY AND LEBANON  

Microsoft Academic Search

We present different documentation methods tested on fossil specimens from Solnhofen-type lithographic limestones (Upper Jurassic, southern Germany) and from the related deposits from the Upper Cretaceous of Lebanon. One of the principles is composite imaging. This combines image fusion, i.e., coalescing several images of the same area but at different focal planes, resulting in a single image of high depth

Carolin Haug; Joachim T. Haug; Dieter Waloszek; Andreas Maas; Roger Frattigiani; Stefan Liebau

282

Jurassic igneous-related metallogeny of southwestern North America  

E-print Network

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

Barton, Mark D.

283

Deductions from Fossil Preservtion  

NSDL National Science Digital Library

Students will view fossils, sometimes with supporting illustrations, and answer questions about them via deductive reasoning. The exercise is highly interactive, with the instructor providing hints and helpful questions. The questions concern ways in which fossil preservation reveals information about things like what kind of organism the fossil represents, how that organism lived, and how the fossil came into being.

Steven Stanley

284

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

SciTech Connect

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

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

1995-08-01

285

Early Jurassic mafic magmatism in the Lesser Xing'an-Zhangguangcai Range, NE China, and its tectonic implications: Constraints from zircon U-Pb chronology and geochemistry  

NASA Astrophysics Data System (ADS)

LA-ICP-MS zircon U-Pb dating and geochemical data have been obtained from five representative mafic-ultramafic intrusions in the Lesser Xing'an-Zhangguangcai Range, NE China, with the aim of improving our understanding of the Mesozoic tectonic evolution in the region, and in particular, determining the time of initiation of the circum-Pacific tectonic system. The selected zircons exhibit striped absorption in cathodoluminescence (CL) images and have high Th/U ratios (0.20-3.16), indicating a magmatic origin. The zircon U-Pb dates indicate that most of these magmatic zircons (other than a few relics that were captured and entrained in the magma) formed in the late Early Jurassic (186-182 Ma), and not as previously supposed in the Middle Caledonian. The five mafic-ultramafic plutons are composed of olivine-gabbro, hornblendite, gabbro, hornblende-gabbro, and gabbro-diorite. The olivine-gabbro and hornblendite display cumulate textures, implying that fractional crystallization of olivine and plagioclase took place during magma evolution. These mafic-ultramafic igneous rocks have SiO2 = 37.3%-55.7%, MgO = 3.05%-13.3%, Al2O3 = 11.8%-23.8%, Mg# = 42-69 [Mg# = 100Mg / (Mg + Fe2 +total)], and ?Eu = 0.88-1.32, and they display three types of rare earth element (REE) distribution patterns: right-slipped, flat patterns, or dome-like. The trace element spider diagrams show that the rocks are enriched in large ion lithophile elements (LILEs) such as Ba, K, and Sr, and depleted in high field strength elements (HFSEs) such as Nb, Ta, Zr, and Hf. The zircons have ?Hf (186-182 Ma) = + 2.7 to + 12.0, and TDM1 = 366-732 Ma. The geochemical data indicate that the Early Jurassic mafic magma originated in an extensional environment from the partial melting of a depleted mantle wedge that had been metasomatized by fluids released from a fossil subducted slab. These data, combined with information on the spatial variation of coeval igneous rocks, indicate that the formation of the Early Jurassic mafic-ultramafic rocks in the Lesser Xing'an-Zhangguangcai Range was related to the subduction of the Paleo-Pacific Plate beneath the Eurasian continent, and this event would mark the beginning of the circum-Pacific tectonic system.

Yu, Jie-Jiang; Wang, Feng; Xu, Wen-Liang; Gao, Fu-Hong; Pei, Fu-Ping

2012-06-01

286

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

PubMed

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

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

2011-11-01

287

Early Jurassic Insects from the Newark Supergroup, Northeastern  

E-print Network

13 Early Jurassic Insects from the Newark Supergroup, Northeastern United States Phillip Huber, Nicholas G. McDonald, and Paul E. Olsen F ossil insects from the Early Jurassic (Hettan- gian in this chapter constitutes the only record of Jurassic insects from North America. Lower Mesozoic sedimentary

Olsen, Paul E.

288

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

289

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

E-print Network

This journal is q 2011 The Royal Society Received 28 February 2011 Accepted 30 March 2011 7Palaeontology A golden orb-weaver spider (Araneae: Nephilidae: Nephila) from the Middle Jurassic of China Paul A. Selden1,2,3,*, ChungKun Shih1 and Dong Ren1,* 1College... but not as elongate as in those extant Nephila in which it is more than twice as long as wide (e.g. N. pilipes) [18]. The body length of the fossil is comparable to that in Nephila plumipes, N. clavipes and N. edulis, species which also retain tibial setal tufts...

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

2011-04-20

290

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

E-print Network

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

Bermingham, Eldredge

291

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

292

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

293

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

SciTech Connect

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

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

1992-01-01

294

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

295

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

296

Jurassic stratigraphy of the Wiggins Arch, Mississippi  

SciTech Connect

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

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

1993-09-01

297

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. PMID:12495489

Kano, Yasunori; Chiba, Satoshi; Kase, Tomoki

2002-01-01

298

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

SciTech Connect

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

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

1991-03-01

299

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

300

Petrology and structure of Pwemain to Jurassic rocks near Yreka, Klamath Mountains, California  

NASA Astrophysics Data System (ADS)

Rocks of the western Paleozoic and Triasic Belt (TrPz belt) of Irwin (1966) in the north eastern Klamath Mountains of California can be subdivided into the same lithotectonic units (terranes) recognized in the southern and central Klamath Mountains. In descending structural order, these are the Fort Jones, North Fork, Salmon River, Havfork and Marble Mountains terranes of Blake and others (1982). Stratigraphic and petrologic regions are consistent with the North Fork, Salmon River and eastern Hayford terranes evolved in close proximity to each other since their origin in Permian time. Faunal and sedimentological evidence suggest that the North Fork terrane was probably at least hundreds of kilometers distant from North America in Permian time, but was close to the continent by early Jurassic time. The structural and metamorphic history of the terranes is consistent with assembly of the TrPz belt in a single, evolving middle and late Jurassic arc/subduction system.

Mortimer, N.

301

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

SciTech Connect

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

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

1995-04-01

302

Transitional Tetrapod Fossil  

NSDL National Science Digital Library

In this video segment from NOVA: Judgment Day: Intelligent Design on Trial, learn about the discovery of a well-preserved transitional fossil and how such transitional fossils support the theory of evolution.

Foundation, Wgbh E.

2007-11-01

303

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

304

Mysterious Fossils from the Chesapeake Bay Impact Crater and Beyond  

USGS Multimedia Gallery

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

305

Follow a Fossil  

NSDL National Science Digital Library

The Follow a Fossil Web site is presented by the Denver Museum of Nature and Science. It documents the prospecting, evacuation, preparation, curation, research, and exhibiting of vertebrate, invertebrate, and plant fossils. The site is simple and effective, giving a good introduction to the process of finding and using fossils for learning about the past.

2000-01-01

306

New integrated stratigraphic data from Hungary and a global carbon isotope stack across the Jurassic-Cretaceous boundary  

NASA Astrophysics Data System (ADS)

Late Jurassic-Early Cretaceous carbon isotope stratigraphies derived from measured sections in the Bakony and the Gerecse Mts. (Hungary), constrained by ammonite, belemnite and calpionellid biostratigraphy together with magnetostratigraphy are presented. We evaluate whether a consistent pattern in carbon (and oxygen) isotope variation can be established, particularly with respect to the Jurassic-Cretaceous boundary. We also assess the possible controls on carbon isotope variation and the correlation potential. Oxygen isotopes point to warming through this interval. We observe a decrease in carbon isotopes through the Late Jurassic, consistent with carbon isotope stratigraphies of the Western Tethys. A change to more positive carbon isotope values in the Early Cretaceous is manifest in the Valanginian Weissert event, potentially reflecting a change to increasingly nutrient-rich conditions and enhanced carbon cycling. Biostratigraphic and magnetostratigraphic data allow us to accurately place the low point seen in the carbon isotope curve within these schemes. Locally a carbon isotope minimum appears in the upper part of magneto subzone M19n2n and towards the middle of calpionellid Zone B (i.e. the Alpina Subzone), but not resolved in the carbon isotope stack from across Tethys and the Atlantic. Aside from the well-defined Valanginian event, chemostratigraphic correlation across the Jurassic-Cretaceous boundary using the carbon isotope record is challenging due to relatively stable carbon isotope values resulting in a curve with a slope too slight.

Price, Gregory; F?zy, István; Pálfy, József

2014-05-01

307

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

SciTech Connect

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

MacRae, G.; Watkins, J.S. (Texas A M Univ., College Station, TX (United States))

1993-10-01

308

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

SciTech Connect

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

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

1991-03-01

309

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

310

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

311

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

312

Fossilized bioelectric wire - the trace fossil Trichichnus  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

313

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

314

Fossil Mapping of Utah  

NSDL National Science Digital Library

Fossils are evidence of living organisms from the past and are usually preserved in sedimentary rocks. A fossil may be an impression left in sediments, the preserved remains of an organism, or a trace mark showing that an organism once existed. Fossils are usually made from the hard parts of an organism because soft parts decay quickly. Fossils provide clues to Earth's history. They provide evidence that can be used to make inferences about past environments. Fossils can be compared to one another, to living organisms, and to organisms that lived long ago. Students will understand how fossils are formed, where they may be found in Utah, and how they can be used to make inferences. Research locations where fossils are found in Utah and construct a simple fossil map. 4th Grade Utah Core Curriculum, Science Benchmark, Standard 4, Objective 1, UEN TASK Congratulations. You have all become Paleontologists. You study fossils and it is your job to map the fossils of Utah for the State. Students will be divided into 4 groups. Each group will be given a Utah County Map. Each group will focus on one category ...

Ramsey

2009-11-18

315

A fossil flora from the Frontier formation of southwestern Wyoming  

USGS Publications Warehouse

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

Knowlton, F.H.

1917-01-01

316

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

PubMed Central

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

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

2011-01-01

317

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

Microsoft Academic Search

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

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

2011-01-01

318

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

E-print Network

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

Barnosky, Anthony D.

319

Morphology, fossils, divergence timing, and the phylogenetic relationships of Gavialis.  

PubMed

Although morphological data have historically favored a basal position for the Indian gharial (Gavialis gangeticus) within Crocodylia and a Mesozoic divergence between Gavialis and all other crocodylians, several recent molecular data sets have argued for a sister-group relationship between Gavialis and the Indonesian false gharial (Tomistoma schlegelii) and a divergence between them no earlier than the Late Tertiary. Fossils were added to a matrix of 164 discrete morphological characters and subjected to parsimony analysis. When morphology was analyzed alone, Gavialis was the sister taxon of all other extant crocodylians whether or not fossil ingroup taxa were included, and a sister-group relationship between Gavialis and Tomistoma was significantly less parsimonious. In combination with published sequence and restriction site fragment data, Gavialis was the sister taxon of all other living crocodylians, but the position of Tomistoma depended on the inclusion of fossil ingroup taxa; with or without fossils, preferred morphological and molecular topologies were not significantly different. Fossils closer to Gavialis than to Tomistoma can be recognized in the Late Cretaceous, and fossil relatives of Tomistoma are known from the basal Eocene, strongly indicating a divergence long before the Late Tertiary. Comparison of minimum divergence time from the fossil record with different measures of molecular distance indicates evolutionary rate heterogeneity within Crocodylia. Fossils strongly contradict a post-Oligocene divergence between Gavialis and any other living crocodylian, but the phylogenetic placement of Gavialis is best viewed as unresolved. PMID:11975331

Brochu, C A

1997-09-01

320

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

NASA Astrophysics Data System (ADS)

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

Tuchkova, M. I.

2003-04-01

321

Tectonic implications of paleomagnetic data from Early Jurassic Dunlap Formation, west-central Nevada  

SciTech Connect

Improved understanding of the kinematics of Mesozoic convergence in the western Basin and Range province is possible by paleomagnetic evaluation of rotations of layered rocks, as has been demonstrated in other fold/thrust belts. Hematitic clastic and shallow marine carbonate strata of the Early Jurassic Dunlap Formation were deposited within and around a successor basin formed after accretion of a Permian arc terrane. Because of their hematitic nature, Dunlap Formation strata may contain a magnetization which survived Late Cretaceous remagnetization. The authors have sampled eleven localities in upper and lower plates of major east-west oriented thrusts, from the western Excelsior to the southern Cedar Mountains. Site sample magnetizations (RM) are usually well-grouped, single component in character, and of normal polarity. They infer, by fold and conglomerate tests, a penecontemporaneous Early Jurassic age of RM acquisition. AF and thermal demagnetization and rock magnetic tests indicate that the RM resides largely in hematite. After simple correction for local tilt, locality mean inclinations are not statistically different from those expected for the craton for Early Jurassic time. Latitudinal translation relative to the craton, since RM acquisition, is not indicated. Locally, mean declinations, on the other hand, are often statistically discordant and imply considerable clockwise rotation of strata during thrust impingement.

Callian, J.T.; Geissman, J.W.; Oldow, J.S.

1985-01-01

322

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

SciTech Connect

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

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

1991-02-01

323

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

SciTech Connect

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

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

1993-04-01

324

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

SciTech Connect

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

Moore, B.R.

1986-05-01

325

Correlation of the Jurassic-Cretaceous siliceous-volcanogenic sediments in northwestern surroundings of the Pacific (Koryak Upland)  

NASA Astrophysics Data System (ADS)

In distribution areas of the Pekul’neiveem and Chirynai formations customary distinguishable in the Koryak Upland, complicated tectonostratigraphic units are composed of alternating thrust sheets of different lithologic composition and age, which are juxtaposed because of widespread thrust faulting, as is proved by the radiolarian analysis. Nineteen radiolarian assemblages of different age are first established here in the Lower Jurassic-Hauterivian succession of siliceous-volcanogenic sediments. In the Lower Jurassic interval, the lower and upper Hettangian, lower and upper Sinemurian, and Pliensbachian beds are recognized. Paleontological characterization is also presented for the Aalenian (or Toarcian?-Aalenian), upper Bajocian, lower and upper Bathonian, and Callovian beds of the Middle Jurassic. Within the Upper Jurassic, the Oxfordian-early Kimmeridgian, late Kimmeridgian-early Tithonian, Tithonian, and late Tithonian-early Berriasian radiolarian assemblages are distinguished. The late Berriasian-early Valanginian, middle-late Valanginian, and Hauterivian radiolarian assemblages are first recognized or compositionally revised. Radiolarians and lithofacies data are used to correlate the tectonostratigraphic units and individualize the jasper-alkali basaltic (lower Hettangian), chert-terrigenous (Hettangian-Sinemurian), jasper-cherty (Pliensbachian-Aalenian), jasper (Bajocian-Hauterivian), jasper-basaltic (upper Bajocian-Valanginian), Fe-Ti basaltic (upper Bajocian-Bathonian), tuffitejasper-basaltic (Bathonian-Hauterivian), and terrigenous-volcanogenic (Bajocian-Valanginian) sequences. The correlation results are extrapolated into other continental areas flanking the Pacific, i.e., to the western Kamchatka, northern and northwestern coastal areas of the Sea of Okhotsk, where the analogous radiolarian assemblages are characteristic of comparable allochthonous units of terrigenous-siliceous-volcanogenic sediments.

Vishnevskaya, V. S.; Filatova, N. I.

2008-12-01

326

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

PubMed Central

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

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

2011-01-01

327

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

PubMed

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

Clapham, Matthew E; Bottjer, David J

2007-08-01

328

Fossil Energy Website  

NSDL National Science Digital Library

This site serves as a gathering point for US Department of Energy (USDOE) materials related to fossil energy. Well-organized and easily navigated, the Fossil Energy Website hosts a wealth of resources, including fossil energy news, related USDOE budget information, an events calendar, in-depth explorations of selected issues, speeches and testimony, technical reports, statistics, and an overview of fossil energy-related global activities, among others. Additional resources include regulatory information, a news headlines ticker, a free email update service, related links, and professional notices.

329

Plant Fossil Record  

NSDL National Science Digital Library

The International Organization of Palaeobotany (IOP) manages the Plant Fossil Record (PFR) database. The recently released version of the database, PFR2.2, offers descriptive details of most plant fossil genera and modern genera with fossil species. Based on "the scientific literature ... or museum collections," the database is organized into five sections: Genera (references for plant fossil genera published mostly before 1985), Descriptions (containing descriptive details of "the type specimens of more than 10,000 extinct plant genera"), Taxonomy (an "informal system of vascular plant classification" based on published schemes), Occurrences (distribution information and references), and Palaeo Maps.

330

Fossil Energy Program  

NASA Astrophysics Data System (ADS)

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

McNeese, L. E.

1981-01-01

331

Modes of fossil preservation  

USGS Publications Warehouse

The processes of geologic preservation are important for understanding the organisms represented by fossils. Some fossil differences are due to basic differences in organization of animals and plants, but the interpretation of fossils has also tended to be influenced by modes of preservation. Four modes of preservation generally can be distinguished: (1) Cellular permineralization ("petrifaction") preserves anatomical detail, and, occasionally, even cytologic structures. (2) Coalified compression, best illustrated by structures from coal but characteristic of many plant fossils in shale, preserves anatomical details in distorted form and produces surface replicas (impressions) on enclosing matrix. (3) Authigenic preservation replicates surface form or outline (molds and casts) prior to distortion by compression and, depending on cementation and timing, may intergrade with fossils that have been subject to compression. (4) Duripartic (hard part) preservation is characteristic of fossil skeletal remains, predominantly animal. Molds, pseudomorphs, or casts may form as bulk replacements following dissolution of the original fossil material, usually by leaching. Classification of the kinds of preservation in fossils will aid in identifying the processes responsible for modifying the fossil remains of both animals and plants. ?? 1975.

Schopf, J.M.

1975-01-01

332

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

333

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

PubMed

Decompression syndrome (caisson disease or the "the bends") resulting in avascular necrosis has been documented in mosasaurs, sauropterygians, ichthyosaurs, and turtles from the Middle Jurassic to Late Cretaceous, but it was unclear that this disease occurred as far back as the Triassic. We have examined a large Triassic sample of ichthyosaurs and compared it with an equally large post-Triassic sample. Avascular necrosis was observed in over 15% of Late Middle Jurassic to Cretaceous ichthyosaurs with the highest occurrence (18%) in the Early Cretaceous, but was rare or absent in geologically older specimens. Triassic reptiles that dive were either physiologically protected, or rapid changes of their position in the water column rare and insignificant enough to prevent being recorded in the skeleton. Emergency surfacing due to a threat from an underwater predator may be the most important cause of avascular necrosis for air-breathing divers, with relative frequency of such events documented in the skeleton. Diving in the Triassic appears to have been a "leisurely" behavior until the evolution of large predators in the Late Jurassic that forced sudden depth alterations contributed to a higher occurrence of bends. PMID:22573359

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

2012-06-01

334

Ovule-bearing organs of Ginkgo ginkgoidea (Tralau) comb. nov., and associated leaves from the Middle Jurassic of Scania, South Sweden  

Microsoft Academic Search

Fossil seeds originally described as Allicospermum ginkgoideum from the Middle Jurassic Mariedal Formation of Eriksdal, Scania, Sweden, are re-examined together with several new seeds and ovule-bearing organs discovered from the same locality and horizon. The ovule-bearing organs consist of a peduncle furcating into two (to three?) pedicels, each with a single sessile ovule supported by a cup-shaped collar. Ovules are

Xiao-Ju Yang; Else Marie Friis; Zhi-Yan Zhou

2008-01-01

335

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 Willem.

2001-01-01

336

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

USGS Publications Warehouse

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

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

2010-01-01

337

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

338

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.

339

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.

Anthony Martin

340

"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.

Peg Yacobucci

341

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

342

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

343

Architectural studies of Jurassic-Cretaceous fluvial units, Colorado Plateau  

SciTech Connect

A sixfold hierarchy of architectural elements and bounding surfaces evolved from outcrop studies of three fluvial units: Westwater Canyon member (WCM), Morrison Formation, Upper Jurassic; Torrivio sandstone member (TSM), Gallup Sandstone, Upper Cretaceous, northwestern New Mexico; and Kayenta Formation (KF), Lower Jurassic, southwestern Colorado. This hierarchy is discussed.

Miall, A.D.; Bromley, M.H.; Cowan, E.J.; Turner-Peterson, C.E.

1989-03-01

344

PARTITOMORPHITAE, A NEW SUBGROUP OF TRIASSIC AND JURASSIC ACRITARCHS  

Microsoft Academic Search

Three new genera of acritarchs are described: Rugidinium, comprising two new species, R. ornatum and ,R. undulatum, from the Bajocian (Jurassic) of Canada; Thuledinium, represented by a single species, T. groenlandicum , from the Callovian (Jurassic) of Greenland; and Teichertodinium, represented by a single species, T. triassicum, from the Triassic (Anisian) of Pakistan. All three genera share the charac^ teristics

STANLEY A. J. POCOCK; WILLIAM A. S. SARJEANT

345

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

E-print Network

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

McRoberts, Christopher A.

346

Massive dissociation of gas hydrate during a Jurassic  

E-print Network

.............................................................................................................................................. In the Jurassic period, the Early Toarcian oceanic anoxic event (about 183 million years ago) is associated hydrate during a Jurassic oceanic anoxic event Stephen P. Hesselbo*, Darren R. Gro¨cke*, Hugh C. Jenkyns together, these 13 C curves depict a period of gradual rise in isotopic values which is interrupted

Hesselbo, Stephen P.

347

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. PMID:23844257

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

2013-01-01

348

Ecological succession of a Jurassic shallow-water ichthyosaur fall  

PubMed Central

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

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

2014-01-01

349

Late pleistocene passerine birds from Sonora, Mexico  

Microsoft Academic Search

Songbirds (Passeriformes) have a very limited fossil record in spite of making up more than one-half of the world's 10,000 living species of birds. From the late Pleistocene fossil site of Térapa in east-central Sonora, Mexico, the identifiable fossils of songbirds consist exclusively of species of Icteridae. The seven extant species (Red-winged Blackbird Agelaius phoeniceus, Yellow-headed Blackbird Xanthocephalus xanthocephalus, Brewer's

Jessica A. Oswald; David W. Steadman

2011-01-01

350

Mesozoic units in SE Rhodope (Bulgaria): new structural and petrologic data and geodynamic implications for the Early Jurassic to Mid-Cretaceous evolution of the Vardar ocean basin  

NASA Astrophysics Data System (ADS)

In the southeastern Rhodope, both in southern Bulgaria and northern Greece, Mesozoic low-grade to non-metamorphic units, together with similar units in the eastern Vardar zone, were designated as the Circum-Rhodope Belt (CRB) that fringes the Rhodope high-grade metamorphic complex. In the Bulgarian southeastern Rhodope, Mesozoic units show a complicated tectono-stratigraphy underlaid by amphibolite-facies basement units. The basement sequence includes a lower orthogneiss unit with eclogite and meta-ophiolite lenses overlain by an upper marble-schist unit, presumably along a SSW-directed detachment fault as indicated by shear sense indicators. The Mesozoic sequence starts with greenschist units at the base, overlaying the basement along the tectonic contact. Mineral assemblages such as actinolite-chlorite-white mica ± garnet in schists and phyllites indicate medium greenschist facies metamorphism. Kinematic indicators in the same unit demonstrate a top-to-the NNW and NNE shear deformation coeval with metamorphism, subparallel to NW-SE to NE-SW trending mineral elongation lineation and axis of NW vergent small-scale folds. The greenschist unit is overlain by tectonic or depositional contact of melange-like unit that consists of diabases with Lower Jurassic radiolarian chert interlayers, Upper Permian siliciclastics and Middle-Upper Triassic limestones found as blocks in olistostromic member, embedded in Jurassic-Lower Cretaceous turbiditic matrix. The uppermost sedimentary-volcanogenic unit is represented by andesito-basalt lavas and gabbro-diorites, interbedded with terrigeneous-marl and tufaceous sediments that yield Upper Cretaceous (Campanian) fossils, related to the Late Cretaceous back-arc magmatic activity to the north in Sredna Gora zone. Petrologic and geochemical data indicates sub-alkaline and tholeiitic character of the greenschists and ophiolitic basaltic lavas, and the latter are classified as low-K and very low-Ti basalts with some boninitic affinity. Immobile trace element discrimination of both rock types constrains the volcanic (oceanic)-arc origin. They generally show low total REE concentrations (LREE>HREE) with enrichment of LIL elements relative to the HFS elements, and also very low Nb and relatively high Ce content consistent with an island-arc tectonic setting. We consider that the Meliata-Maliac ocean northern passive margin could be the source provenance for the Upper Permian clastics and Middle-Upper Triassic limestone blocks within the olistostromic melange-like unit, whereas turbidites and magmatic blocks may originate in an island arc-accretionary complex that relates to the southward subduction of the Maliac ocean under the supra-subduction back-arc Vardar ocean/island arc system. These new structural and petrologic data allow to precise the tectonic setting of the Mesozoic units and their geodynamic context in the frame of the Early Jurassic to Late Cretaceous evolution of the Vardar ocean.

Bonev, N.; Stampfli, G.

2003-04-01

351

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

352

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. PMID:11095754

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

2000-01-01

353

The Quaternary fossil-pollen record and global change  

SciTech Connect

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

Grimm, E.C. (Illinois State Museum, Springfield, IL (United States). Research and Collections Center)

1993-03-01

354

BEETLE RECORDS Late Tertiary and Early Quaternary  

E-print Network

B BEETLE RECORDS Contents Overview Late Tertiary and Early Quaternary Middle Pleistocene of Europe of London, Surrey, UK ª 2007 Elsevier B.V. All rights reserved. The study of fossil beetles (Coleoptera of the world, most recently to Australia, New Zealand, and Japan. Fossil beetle research has led to many

Sheldon, Nathan D.

355

Late Mesozoic tectonics of Central Asia based on paleomagnetic evidence  

Microsoft Academic Search

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

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

2010-01-01

356

Early Jurassic deformation in the Pine Forest Range, northwest Nevada, and implications for Cordilleran tectonics  

NASA Astrophysics Data System (ADS)

Triassic and Jurassic rocks in the Black Rock Desert of northwest Nevada comprise part of the Mesozoic volcanic arc successions found throughout the westernmost U.S. Cordillera. Detailed structural studies in the Pine Forest Range, located in the western Black Rock Desert, provide new insight into the Jurassic structural history of this part of the Mesozoic arc system. Regional Jurassic deformation and metamorphism in the Pine Forest Range affected a thick (˜10.5 km) section of lower(?) Paleozoic through Triassic strata that were tilted after deformation and are now exposed in approximately cross-sectional view. At high stratigraphic levels, deformation produced a slaty cleavage and relatively open folds, both of which are concentrated in rheologically incompetent rock types, and was accompanied by metamorphism at low grade. At deeper stratigraphic levels, the regional foliation intensifies and becomes more pervasive, folds tighten, and metamorphic grade increases through greenschist into amphibolite grade. At the deepest stratigraphic levels, the rocks are amphibolite grade L-S tectonites with a pronounced mylonitic fabric. The ˜2 km-thick-zone of mylonites is interpreted as a ductile shear zone that formed when the stratigraphic section was still upright, whereas the less deformed, younger rocks are interpreted to occupy the upper plate of the shear zone and to record a strain gradient away from the shear zone. A variety of structural and regional relations indicate that the shear zone is a ductile thrust fault along which younger rocks moved to the northwest (in present-day coordinates) with respect to older rocks. The timing of regional Jurassic deformation and metamorphism is constrained by relations in and around two plutons dated by the U-Pb zircon method. The 201±1 Ma Big Creek pluton was intruded as a sill-like body along the upper levels of the shear zone and is associated with a variety of features indicating syntectonic intrusion, including internal textural features in plutonic rocks and metamorphic changes in wall rocks with proximity to the pluton. The 185±1 Ma Theodore pluton which intrudes across part of the shear zone has a thermal aureole which statically overprints the shear zone fabric. Deformation was thus ongoing at 201 Ma and over by 185 Ma. The Early Jurassic age of regional shortening deformation in the Pine Forest Range contrasts with the Middle to Late Jurassic (˜170-150 Ma) age of regional shortening documented in many other parts of the Mesozoic arc system, including the Klamath Mountains, Sierra Nevada, and Mojave Desert regions of California. It also contrasts with the record of Early Jurassic extensional tectonism documented in the Sierra Nevada, Mojave Desert, and western Arizona segments of the Mesozoic arc system. These conflicting relations indicate a complex tectonic evolution for the Jurassic U.S. Cordillera plate margin and lend support to the idea that disparate parts of this plate margin were juxtaposed along younger strike-slip faults.

Wyld, Sandra J.

1996-06-01

357

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

358

Fossil energy program  

NASA Astrophysics Data System (ADS)

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

McNeese, L. E.

1981-02-01

359

Fossil Identification Project  

NSDL National Science Digital Library

Students attend a class fieldtrip where over five locations across Tennessee representing three different geological time periods (Ordovician, Devonian, and Cretaceous) are visited. The students are required to collect 20 different taxa (5 of which must be unique to each student) and then using the knowledge they have gained in labs identify their taxa to species level. They must make a powerpoint presentation summarizing the paleocological and paleoclimatological information gained about each locality through the collection of the fossil taxa. The activity helps familiarize students with the geology of Tennessee and field collection of fossils in addition to lab identification of fossils.

Lobegeier, Melissa

360

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

361

Jurassic-Early Cretaceous Gondwanan homoxylous woods: a nomenclatural revision of the genera with taxonomic notes.  

PubMed

The homoxylous fossil woods occurring in the Gondwanan continents of South America, Australia, Africa, India and Antarctica during the Jurassic and Early Cretaceous period are considered here. Original descriptions of the genera and wherever possible, the type material, have been consulted. Applying the rules of the International Code of Botanical Nomenclature, the generic names of the homoxylous woods have been revised from a nomenclatural point of view. According to this review, out of 31 generic names used for woods from the given time interval and area, 6 are illegitimate later nomenclatural synonyms, 1 is a later homonym, and 5 can be considered as taxonomical synonyms. Moreover, 9 genera have been used erroneously. We propose one new generic name (Protaxodioxylon n. gen.) and elsewhere we will propose for conservation, with a conserved type one of the illegitimate names and one of the taxonomic synonyms. As a result, we consider that there are only eighteen generic names correctly quoted for the Jurassic-Early Cretaceous of Gondwana, and we provide a taxonomic key for the corresponding genera. This revision is the first step in systematically comparing northern and southern hemisphere woods. PMID:11179718

Bamford, M K.; Philippe, M

2001-04-01

362

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

363

An enormous Jurassic turtle bone bed from the Turpan Basin of Xinjiang, China  

NASA Astrophysics Data System (ADS)

A spectacular new terrestrial Konzentratlagerstätte is introduced from the Turpan Basin of Xinjiang, China that probably belongs to the late Middle Jurassic Qigu Formation. It contains a mass accumulation of "xinjiangchelyid" turtles preliminarily identified as Annemys sp. In the zone with the highest turtle concentration, complete and articulated turtle skeletons are tightly packed at a density of up to 36 turtles per square meter. The fossiliferous layer is thickened here and shows an erosional base. This high concentration zone outcrops approximately 10 m in length and shows no decrease in turtle density after exposing 2 m of the layer into the hillside. Adjacent is a more expansive zone of at least 10 m by 30 m. In this region, the fossiliferous layer is evenly thick, and approximately five, fully disarticulated turtles are present per square meter. A conservatively estimated 1,800 turtles may, therefore, have been deposited at this site. It is likely that these aquatic turtles gathered in a retreating water hole in a riverine environment during a drought, much as some aquatic turtles will do today, but perished when the habitat dried up completely. A following catastrophic rainfall event caused a debris flow, possibly channelized in a dry river bed, which transported complete turtles, disarticulated turtles, and mudstone clasts and deposited them after a short distance. This taphonomic model is consistent with previous environmental reconstructions of the Turpan Basin during the late Middle Jurassic in predicting the episodic breakdown of regional monsoonal circulation resulting in a seasonally dry climate with severe episodic droughts.

Wings, Oliver; Rabi, Márton; Schneider, Jörg W.; Schwermann, Leonie; Sun, Ge; Zhou, Chang-Fu; Joyce, Walter G.

2012-11-01

364

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

365

A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds.  

PubMed

The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle-Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China) has challenged the pivotal position of Archaeopteryx, regarded from its discovery to be the most basal bird. Removing Archaeopteryx from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of Archaeopteryx; (3) it places Troodontidae as the sister-group to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle-Late Jurassic period. PMID:23719374

Godefroit, Pascal; Cau, Andrea; Dong-Yu, Hu; Escuillié, François; Wenhao, Wu; Dyke, Gareth

2013-06-20

366

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

367

Fossil energy program  

NASA Astrophysics Data System (ADS)

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

McNeese, L. E.

1981-03-01

368

Fossilized Dinosaur Bones  

NSDL National Science Digital Library

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

369

The Great Fossil Find  

NSDL National Science Digital Library

On an imaginary fossil hunt, learners "find" (remove from envelope) paper "fossils" of some unknown creature, only a few at a time. Each time, they attempt to reconstruct the creature, and each time their interpretation tends to change as new pieces are "found." Use this as an introduction to the nature of science inquiry -- scientists don't always have all the information, scientists must form interpretations of the information, scientists must work together to come to consensus about interpretations.

Steve Rendak

1999-01-01

370

Evidence of Evolution I. Fossils and the fossil record  

E-print Network

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

Dever, Jennifer A.

371

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

372

The earliest fossil record of the animals and its significance.  

PubMed

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

Budd, Graham E

2008-04-27

373

The First Metriorhynchid Crocodylomorph from the Middle Jurassic of Spain, with Implications for Evolution of the Subclade Rhacheosaurini  

PubMed Central

Background Marine deposits from the Callovian of Europe have yielded numerous species of metriorhynchid crocodylomorphs. While common in English and French Formations, metriorhynchids are poorly known from the Iberian Peninsula. Twenty years ago an incomplete, but beautifully preserved, skull was discovered from the Middle Callovian of Spain. It is currently the oldest and best preserved metriorhynchid specimen from the Iberian Peninsula. Until now it has never been properly described and its taxonomic affinities remained obscure. Methodology/Principal Findings Here we present a comprehensive description for this specimen and in doing so we refer it to a new genus and species: Maledictosuchus riclaensis. This species is diagnosed by numerous autapomorphies, including: heterodont dentition; tightly interlocking occlusion; lachrymal anterior process excludes the jugal from the preorbital fenestra; orbits longer than supratemporal fenestrae; palatine has two non-midline and one midline anterior processes. Our phylogenetic analysis finds Maledictosuchus riclaensis to be the basal-most known member of Rhacheosaurini (the subclade of increasingly mesopelagic piscivores that includes Cricosaurus and Rhacheosaurus). Conclusions/Significance Our description of Maledictosuchus riclaensis shows that the craniodental morphologies that underpinned the success of Rhacheosaurini in the Late Jurassic and Early Cretaceous, as a result of increasing marine specialization to adaptations for feeding on fast small-bodied prey (i.e. divided and retracted external nares; reorientation of the lateral processes of the frontal; elongate, tubular rostrum; procumbent and non-carinated dentition; high overall tooth count; and dorsolaterally inclined paroccipital processes), first appeared during the Middle Jurassic. Rhacheosaurins were curiously rare in the Middle Jurassic, as only one specimen of Maledictosuchus riclaensis is known (with no representatives discovered from the well-sampled Oxford Clay Formation of England). As such, the feeding/marine adaptations of Rhacheosaurini did not confer an immediate selective advantage upon the group, and it took until the Late Jurassic for this subclade to dominate in Western Europe. PMID:23372699

Parrilla-Bel, Jara; Young, Mark T.; Moreno-Azanza, Miguel; Canudo, José Ignacio

2013-01-01

374

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

375

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

376

Structure and kinematics along a segment of the Mojave-Sonora megashear: A strike-slip fault that truncates the Jurassic continental magmatic arc of southwestern North America  

NASA Astrophysics Data System (ADS)

Similarities between crystalline crust and overlying pre-Jurassic cover in northwestern Sonora, Mexico, and in the Inyo Mountains-Death Valley region, California, are attributed to left-lateral displacement along the Mojave-Sonora megashear, a Late Jurassic transform fault related to the opening of the Gulf of Mexico. Three exposures of mylonitic rocks extending 25 km along the postulated fault occur within Sierra de Los Tanques, Sonora, Mexico. The exposures 13 km southwest of Sonoita reveal a tripartite assemblage of (1) Jurassic volcanic and volcaniclastic strata to the northeast, (2) an axial zone of mylonitic rocks, and (3) masses of granitic rocks and compositionally banded quartzo-feldspathic gneiss of Proterozoic (?) and Late Triassic age to the southwest. Mylonitic foliation in rocks within the axial zone strikes northwesterly, and lineations plunge shallowly. Microstructues record left-lateral shear. Shallow thrusts, folded mylonite, and steeply dipping mylonitic foliation with downdip mineral lineation record transpression. Triassic and Precambrian crystalline rocks are emplaced above shallow thrusts onto ductilly deformed Jurassic rocks northeast of the principal fault. In the central and northwestern exposures, pervasively foliated and lineated rocks are cut by weakly foliated Cretaceous granite that also may contain inclusions of mylonite. The northwesterly strike of steep foliation, left-lateral kinematics, and relationships with Cretaceous intrusive rocks preclude correlation with episodes of Cretaceous contraction and Tertiary extension that are recognized in the southwestern United States. The fault is interpreted to have formed in the Late Jurassic and records a change in tectonic setting from arc magmatism to rifting and basin development.

Campbell, Patricia A.; Anderson, Thomas H.

2003-12-01

377

Chronology and paleohydrology of late Quaternary high lake levels in the Manyara basin (Tanzania) from isotopic data ( 18O, 13C, 14C, {Th}/{U}) on fossil stromatolites  

NASA Astrophysics Data System (ADS)

Superimposed phases of stromatolite buildup are observed on the eastern margin of Lake Manyara and depict a paleoshoreline at about 20 m above modern lake level. Radiocarbon and {Th}/{U} measurements permitted the dating of the last two phases of stromatolite formation at ca. 90,000 yr and between 27,000 and 23,000 yr B.P., respectively. The {Th}/{U} chronology is based on the decay of a strong 230Th-excess (over 234U) inherited with the detrital particles cemented into the stromatolites. The various generations of stromatolites show comparable stable carbon and oxygen isotope contents and are located at the same paleolake stabilization levels. This indicates that stringent hydrological conditions are necessary for the development of the encrusting benthic microbial communities responsible for stromatolite formation. A comparison with similar stromatolitic units from the nearby Lake Natron-Lake Magadi basin shows that such conditions occurred during only a few of the late Quaternary humid episodes known in eastern Africa and that they are different in each basin. Stromatolites do not necessarily represent all high lake levels that Lake Manyara experienced during the late Pleistocene and Holocene.

Casanova, Joel; Hillaire-Marcel, Claude

1992-09-01

378

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

379

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. PMID:22792287

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

2012-01-01

380

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

381

Circum-Arctic mantle structure and long-wavelength topography since the Jurassic  

NASA Astrophysics Data System (ADS)

circum-Arctic is one of the most tectonically complex regions of the world, shaped by a history of ocean basin opening and closure since the Early Jurassic. The region is characterized by contemporaneous large-scale Cenozoic exhumation extending from Alaska to the Atlantic, but its driving force is unknown. We show that the mantle flow associated with subducted slabs of the South Anuyi, Mongol-Okhotsk, and Panthalassa oceans have imparted long-wavelength deflection on overriding plates. We identify the Jurassic-Cretaceous South Anuyi slab under present-day Greenland in seismic tomography and numerical mantle flow models. Under North America, we propose the "Farallon" slab results from Andean-style ocean-continent convergence around ~30°N and from a combination of ocean-continent and intraoceanic subduction north of 50°N. We compute circum-Arctic dynamic topography through time from subduction-driven convection models and find that slabs have imparted on average <1-16 m/Myr of dynamic subsidence across the region from at least 170 Ma to ~50 Ma. With the exception of Siberia, the main phase of circum-Arctic dynamic subsidence has been followed either by slowed subsidence or by uplift of <1-6 m/Myr on average to present day. Comparing these results to geological inferences suggest that subduction-driven dynamic topography can account for rapid Middle to Late Jurassic subsidence in the Slave Craton and North Slope (respectively, <15 and 21 m/Myr, between 170 and 130 Ma) and for dynamic subsidence (<7 m/Myr, ~170-50 Ma) followed by dynamic uplift (<6 m/Myr since 50 Ma) of the Barents Sea region. Combining detailed kinematic reconstructions with geodynamic modeling and key geological observations constitutes a powerful tool to investigate the origin of vertical motion in remote regions.

Shephard, G. E.; Flament, N.; Williams, S.; Seton, M.; Gurnis, M.; Müller, R. D.

2014-10-01

382

Fossil Fuels: Capstone  

NSDL National Science Digital Library

This lesson summarizes our dependency upon fossil fuels, pointing out that there are very few aspects of our daily life that are not impacted by their use. The discussion centers around whether these fuels could be replaced and makes the point that there is a significant percentage of them which is used to manufacture products and is not simply burned for energy. The lesson includes an activity in which students use an online calculator to estimate how much of each fossil fuel they are responsible for consuming each year.

John Pratte

383

Dinoflagellata: Fossil Record  

NSDL National Science Digital Library

Information on this page pertains to dinoflagellates, the fossil record of which may extend into the Precambrian. Spherical organic-walled microfossils known as acritarchs, some of which may be dinoflagellate hystrichospheres, first appear in rocks about 1.8 billion years old. Exactly what the acritarchs were is not known with certainty; they probably included a number of clades of eukaryotic algae, and are thus a form taxon, including all those spore-like fossils which have not been conclusively assigned to another group.

384

Science Sampler: Fossil detectives  

NSDL National Science Digital Library

Middle school students are transformed into Fossil detectives as they examine the fossil record and use evidence about paleo-environments to develop an understanding of structure and function in living systems and changes over time in Earths history. In this enrichment activity, students work in teams to research an assigned geologic time period. They determine available habitats, food sources and types (animal, plant; woody, herbaceous, etc.), cover sources, methods of getting food, defense, and reproduction that would allow an animal to live in the assigned paleoenvironment. In culmination of their efforts, students create a diorama to display their findings.

Bourdeau, Virginia

2006-07-01

385

Fossil reptilian gelatins.  

PubMed

1. Studies have been made of products obtained by treating several reptilian fossil bones with dilute formic acid. 2. Their amounts and compositions have been compared with those of similarly treated fresh and Pleistocene bones. 3. Fewer and small peptides are obtained from the older fossils but in only one instance was the composition significantly different from that of the total protein. 4. For the collagenous proteins aspartic acid was the most readily freed by hydrolysis; for these older proteins it is alanine. 5. Unlike the Pleistocene proteins, the chromatograms from these older proteins have always had peaks in the position of beta-alanine, and usually others of unidentified origin. PMID:318304

Wyckoff, R W; Davidson, F D

1979-01-01

386

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.

2014-04-14

387

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

388

The Origin of the Jurassic Quiet Zone -new insights from Hawaiian Jurassic magnetic anomalies (Invited)  

NASA Astrophysics Data System (ADS)

Marine magnetic anomalies recorded in oceanic crust, have played a central role in documenting Earth's magnetic field history as compiled in the geomagnetic polarity timescale (GPTS). The oldest part of the marine record is the Jurassic Quiet Zone (JQZ) (pre-M29 chrons) which is known to be a period when field intensity was low, while reversal rate was high. The origin and character of the JQZ has been the subject of marine magnetic studies over past 20 years in the western Pacific where the oldest and arguably best preserved Jurassic magnetic anomalies create three Jurassic lineation sets (Japanese, Hawaiian, and Phoenix). The Japanese JQZ sequence was extensively investigated by an aeromagnetic and 2 deeptow magnetometer surveys, revealing (i) the presence of lineated anomalies older than M29; (ii) a GPTS record extending from M29 to M44 with a tie to ODP Hole 801C and (iii) remarkably fast reversals that decrease in intensity back in time until M38. Prior to M38 there is a low amplitude zone (LAZ) in anomalies lasting until M42, when both anomaly amplitude and a lineated character reappears around Hole 801C. Recently collected (2011) high quality seasurface marine magnetic anomaly data from the Hawaiian lineations show changes in magnetic anomaly shape and amplitude that are similar in to the Japanese lineations, suggesting that the anomalies record globally coherent geomagnetic field behavior for the Jurassic. Specifically, the strong similarity of anomaly patterns between the Japanese and Hawaiian sequences from M19 to M38 supports the remarkably dynamic geomagnetic field behavior of fast reversals and changing intensity, confirming a proposed record of the GPTS sequence for M29 to M38. While the LAZ in the Hawaiian sequence is not as clear as in the Japanese lineations, we believe we can correlate the earlier M42-M44 sequence between the two sets of lineations. The slower spreading rate in the Hawaiian lineations may contribute to this lack of resolution of the LAZ and result in a less clear recording of anomalies. We present models to investigate if this is simply a lack of spatial resolution or if there are indeed different processes active within the Hawaiian sequence such as seamount/plateau formation and crustal construction.

Tominaga, M.; Tivey, M.; Sager, W. W.

2013-12-01

389

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

390

Fossil Evidence of Bipedalism  

NSDL National Science Digital Library

This video segment adapted from NOVA shows how scientists use the fossil record to trace when early human ancestors and related species began walking on two legs instead of four, and to determine whether they were more apelike or human in appearance.

2010-03-10

391

Therapod Fossil Hunt Dispatch  

NSDL National Science Digital Library

This online article reports on the finding of a dromaeosaur fossil, the best specimen to date to show that feathers existed long before modern birds and flight. The research was a collaboration between the American Museum of Natural History and the Geological Museum of China.

392

Fossils and Minerals  

NSDL National Science Digital Library

This site from the Black Hills Institute features information about different types of fossils, minerals, meteorites, and geology in general. Each topic has a brief description, with links to a more detailed explanation. Various samples and books are abailable for purchase on the site.

Research, Inc. B.

393

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

394

Fossil Halls: Vertebrate Evolution  

NSDL National Science Digital Library

Part of a larger virtual tour of the Museum's famed Fossil Halls, this Web site has an interactive cladogram with 20 clickable evolutionary branching points. It shows vertebrate evolution for the following three AMNH halls: Hall of Vertebrate Origins, Hall of Dinosaurs and Hall of Mammals and Their Extinct Relatives.

395

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. PMID:24223138

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

2013-01-01

396

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. PMID:22308330

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

2012-01-01

397

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. PMID:22628475

Pol, Diego; Rauhut, Oliver W. M.

2012-01-01

398

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

399

A new arboreal haramiyid shows the diversity of crown mammals in the Jurassic period.  

PubMed

A major unsolved problem in mammalian evolution is the origin of Allotheria, including Multituberculata and Haramiyida. Multituberculates are the most diverse and best known Mesozoic era mammals and ecologically resemble rodents, but haramiyids are known mainly from isolated teeth, hampering our search for their phylogenetic relationships. Here we report a new haramiyid from the Jurassic period of China, which is, to our knowledge the largest reported so far. It has a novel dentition, a mandible resembling advanced multituberculates and postcranial features adapted for arboreal life. Our phylogenetic analysis places Haramiyida within crown Mammalia, suggesting the origin of crown Mammalia in the Late Triassic period and diversification in the Jurassic, which contrasts other estimated divergence times of crown Mammalia. The new haramiyid reveals additional mammalian features of the group, helps to identify other haramiyids represented by isolated teeth, and shows again that, regardless of various phylogenetic scenarios, a complex pattern of evolution involving many convergences and/or reversals existed in Mesozoic mammals. PMID:23925244

Zheng, Xiaoting; Bi, Shundong; Wang, Xiaoli; Meng, Jin

2013-08-01

400

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

PubMed Central

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

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

2014-01-01

401

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

402

Geochemical evolution of Jurassic diorites from the Bristol Lake region, California, USA, and the role of assimilation  

Microsoft Academic Search

Late Jurassic dioritic plutons from the Bristol Lake region of the eastern Mojave Desert share several geochemical attributes with high-alumina basalts, continental hawaiite basalts, and high-K are andesites including: high K2O concentrations; high Al2O3 (16–19 weight %); elevated Zr\\/TiO2; LREE (light-rare-earth-element) enrichment (La\\/YbCN=6.3–13.3); and high Nb. Pearce element ratio analysis supported by petrographic relations demonstrates that P, Hf, and Zr

Edward D. Young; Joseph L. Wooden; Yuch-Ning Shieh; Daniel Farber

1992-01-01

403

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

404

A fossil record of colonization and response of lacustrine fish populations to climate change  

Microsoft Academic Search

To study fish species colonization and the response of populations to climate change, we reexamined a well- preserved late Pleistocene to early Holocene fossil fish assemblage from lake deposits on the Missouri Coteau, North Dakota. The fossil fishes in the assemblage include complete specimens of yellow perch (Perca flavescens), brassy minnow (Hybognathus hankinsoni), blacknose shiner (Notropis heterolepis), banded killifish (Fundulus

Michael G. Newbrey; Allan C. Ashworth

2004-01-01

405

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

406

The Triassic-Jurassic boundary in eastern North America  

NASA Technical Reports Server (NTRS)

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

Olsen, P. E.; Comet, B.

1988-01-01

407

Paleozoic to Jurassic terrane accretion along the northeastern margin of Tibet plateau  

NASA Astrophysics Data System (ADS)

The Tibet plateau is considered to have been constructed by a number of basement terranes accreted to the Eurasian margin during Paleozoic to Mesozoic times, and accretion is interpreted to have progressed southwards. The northern margin, exposed in Altyn and Qilian Mountains, is generally considered as an Lower Paleozoic orogen including previously subducted ultra-high successions (Yin and Harrison, 2000; Xiao et al., 2009). Previous tectonic models of the Qaidam block and adjacent mountain ranges at the northeastern margin of the Tibet plateau ass