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1

Late Jurassic salamandroid from western Liaoning, China.  

PubMed

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

Gao, Ke-Qin; Shubin, Neil H

2012-03-12

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.

Gao, Ke-Qin; Shubin, Neil H.

2012-01-01

3

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

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

New discovery on dinosaur fossils from Early Jurassic, Sichuan, China  

Microsoft Academic Search

An early and primitive sauropod dinosaur,Gongxianosaurus shibeiensis (gen. et sp. nov.), from Lower Jurassic Dongyuemiao Member of Ziliujing Formation in Shibei Village, Gongxian County, Sichuan\\u000a Province, China is described, which is among Gongxian dinosaur fossils discovered in 1997. Except for skull incomplete, fossils\\u000a were well-preserved. It has concurrently some features of both sauropod and prosauropds. It is an intermediate type

Yaonan Luo; Changsheng Wang

1999-01-01

6

Evidence for Late Jurassic release of methane from gas hydrate  

Microsoft Academic Search

Four Late Jurassic carbonate successions deposited in the Tethys-Atlantic Ocean record a negative carbon isotope excursion of at least 20\\/00. The excursion is present in both organic and carbonate carbon records and is comparable in magnitude and duration to isotopic changes during the late Paleocene thermal maximum. Our results indicate that during the Late Jurassic, long considered a warm greenhouse

Maureen Padden; Helmut Weissert; Marc de Rafelis

2001-01-01

7

Earliest evolution of multituberculate mammals revealed by a new Jurassic fossil.  

PubMed

Multituberculates were successful herbivorous mammals and were more diverse and numerically abundant than any other mammal groups in Mesozoic ecosystems. The clade also developed diverse locomotor adaptations in the Cretaceous and Paleogene. We report a new fossil skeleton from the Late Jurassic of China that belongs to the basalmost multituberculate family. Dental features of this new Jurassic multituberculate show omnivorous adaptation, and its well-preserved skeleton sheds light on ancestral skeletal features of all multituberculates, especially the highly mobile joints of the ankle, crucial for later evolutionary success of multituberculates in the Cretaceous and Paleogene. PMID:23950536

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

2013-08-16

8

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

9

A high-resolution three-dimensional reconstruction of a fossil forest (Upper Jurassic Shishugou Formation, Junggar Basin, Northwest China)  

Microsoft Academic Search

This study focuses on the three-dimensional (3D) reconstruction of an Late Jurassic fossil forest based on a fossil assemblage\\u000a located in the Shishugou Formation near Jiangjunmiao, north-eastern Junggar Basin, Xinjiang Uygur Autonomous Region, Northwest\\u000a China. On the basis of tree stumps found in growth position together with published data on megaplant fossils, seeds and spores,\\u000a a high-resolution digital computer model,

Juliane K Hinz; Ian Smith; Hans-Ulrich Pfretzschner; Oliver Wings; Ge Sun

2010-01-01

10

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

11

Direct evidence of hybodont shark predation on Late Jurassic ammonites.  

PubMed

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

Vullo, Romain

2011-03-31

12

A Giant Pliosaurid Skull from the Late Jurassic of England  

PubMed Central

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

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

2013-01-01

13

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

14

A new insect trace fossil in Jurassic wood from Patagonia, Argentina  

Microsoft Academic Search

A new trace fossil assigned to insect activity in wood is described from the Jurassic Petrified Forest of Jaramillo in Santa Cruz Province (Argentina). Dekosichnus meniscatus n. ichnogen. n. ichnosp. is the second known Jurassic trace occurring in permineralized wood. The boring system is composed of longitudinal tunnels connected by tangential tunnels. The system is connected to the exterior by

Jorge F. Genise; Patricia L. Hazeldine

1995-01-01

15

Upper Jurassic Fossils from Ellsworth Land, West Antarctica, and notes on upper Jurassic Biogeography of the South Pacific Region  

Microsoft Academic Search

Fossils from Lyon Nunataks (74° 52? S, 74° 02? W) are described: Conodicoelites spp., Rotularia sp. indet., indet. pectinacean: cf. Entolium, and Variamussium lyonensis sp. nov. Upper Jurassic (?Lower Kimmeridgian) age. The Conodicoelites spp. have strong affinities with those of the New Zealand Lower Kimmeridgian. Ammonites, belemnites, and Inoceramus, all with strong Indo-Pacific affinities, are present in the Kimmeridgian and

G. R. Stevens

1967-01-01

16

Ultrastructure of early jurassic fossil plant cuticles: Pachypteris gradinarui Popa.  

PubMed

Exceptional preservation of extinct Pachypteris extra-epidermal cuticle enabled the first detailed statistical measurements of its ultrastructure using transmission electron microscopy. Pachypteris is a leaf genus of the Mesozoic belonging to seed fern foliage of the order Corystospermales. The species studied in this paper is Pachypteris gradinarui Popa [Rev. Palaeobot. Palynol. 111 (2000) 31], based on fossils which are Early Jurassic in age (Hettangian-Sinemurian, approximately 205-190 million years old). Both the upper and the lower cuticles were thoroughly examined, including the detail of the stomatal complexes and epidermal cells. The data obtained from our TEM analysis, together with the confidence intervals, were very useful to give precise description of the cuticles as they distinguished between upper and lower epidermal and stomatal cell types. Moreover a combination of characters was used to develop the first dichotomous key based on ultrastructural characters, i.e. not only the total thickness of the cuticle but also details and proportions of A cuticle proper and B cuticular layer. Comparisons with ultrastructures known from other Pachypteris species show that the influence of space and time, diagenetic processes, and/or processes related to technical procedures, seem to be minimal within this genus. Detailed studies of this type may be very useful for further comparisons among other species and at higher taxonomical ranks. PMID:15261746

Guignard, G; Popa, M E; Barale, G

2004-08-01

17

A basal tyrannosauroid dinosaur from the Late Jurassic of China.  

PubMed

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

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

2006-02-01

18

Ice age at the Middle–Late Jurassic transition?  

Microsoft Academic Search

A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (?18O values of shark tooth enamel) indicates a severe cooling at the Middle–Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1–3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale

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

2003-01-01

19

Short communication A new fossil genus of Mesosciophilidae (Diptera, Nematocera) with two new species from the Middle Jurassic of Inner Mongolia, China  

Microsoft Academic Search

A new genus within the family Mesosciophilidae, Jurasciophila gen. nov., with two new species, J. curvula gen. et sp. nov. and J. lepida gen. et sp. nov., are described and illustrated. They are established based on fossil specimens with bodies and complete wings. All of them were collected from the late Middle Jurassic Jiulongshan Formation of Daohugou in southeastern Inner

Tingting Li; Dong Ren

20

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

21

Giant late Jurassic sabkhas of Arabian Tethys  

Microsoft Academic Search

THE discovery that anhydrite-gypsusm evaporites with characteristic textures are forming today in the shallow subsurface of supratidal coastal sabkhas and in continental sabkhas from Arabia1,2 has revolutionised the interpretation of ancient evaporite sucessions. Several ancient evaporite basins, of great economic importance, lately regarded as former hypersaline lagoons or barred basins, have been recently re-interpreted as the deposits of former prograding

M. R. Leeder; R. Zeidan

1977-01-01

22

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

Microsoft Academic Search

Pre-Late Jurassic terranes of the Patagonian Archipelago were investigated. Their regional stratigraphic and structural characteristics were surveyed. Their significance in the late Paleozoic to early Mesozoic evolution of South America were determined. Pre-Late Jurassic rocks within the archipelago are distributed in two belts. Within the outer belt the Madre de Dios Archipielago was studied in detail. Pre-Late Jurassic rocks of

R. D. Forsythe

1981-01-01

23

Global Jurassic tetrapod biochronology  

Microsoft Academic Search

Jurassic tetrapod fossils are known from all of the continents, and their distribution documents a critical paleobiogeographic juncture in tetrapod evolution - the change from cosmopolitan Pangean tetrapod faunas to the provincialized faunas that characterize the late Mesozoic and Cenozoic. Two global tetrapod biochronological units (faunachrons) have been named for the Early Jurassic - Wassonian and Dawan - and reflect

Spencer G. LUCAS

24

Fossil plant evidence for Early and Middle Jurassic paleoenvironmental changes in Lanzhou area, Northwest China  

Microsoft Academic Search

Estimating the paleoclimate changes through CO2 levels has become a promising area of geological research. This paper focuses on analysis of fossil Ginkgo in continuous sedimentary series in northwestern China using plant anatomy and organic geochemistry approaches. The CO2 variation curve during Early and Middle Jurassic is reconstructed based on the stomatal ratio method, which is consistent with the estimated

Bai-Nian Sun; San-Ping Xie; De-Fei Yan; Pei-Yun Cong

2008-01-01

25

Aspects of Late Triassic/Early Jurassic and Middle Jurassic fluvial sedimentation in the Viking Graben area, North Sea.  

National Technical Information Service (NTIS)

The Viking Graben of the North Sea is the site of the economically important Brent hydrocarbon province. This dissertation focuses on the nature of non-marine and coastal plain deposits of Late Triassic - Early Jurassic (Statfjord Formation) and Middle Ju...

A. Ryseth

1994-01-01

26

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

27

Porosity controls in Late Jurassic algal reefs, Mississippi salt basin  

SciTech Connect

Reefs associated with high-rise salt structures that were active during Late Jurassic deposition (Smackover-Haynesville) have been the target of numerous deep tests in the Mississippi Salt basin. One such test, in Wayne County, Mississippi, encountered a 24-m reef. The reef exhibited no porosity or permeability, while sequences above (21 m) and below (24 m) were dolomitized, porous, and permeable. The reef sequence consists of a facies mosaic of encrusting to columnar massive red coralline algae, laminated to stromatolitic blue-green algae(.) with associated pelleted internal sediments and other features characteristic of modern framework reefs. The reef complex exhibits a strong early marine diagenetic overprint consisting of bladed to fibrous magnesian calcite(.) cements and botryoidal masses of magnesian calcite or aragonite. The lack of discernible freshwater diagenesis and the nature of the reef framework seem to indicate deeper water conditions for reef development and subsequent early diagenesis. The associated dolomites have relict texture indicating that they were originally grainstones, perhaps derived from the reef itself. In the reef sequence, the geologic setting (relatively deep water), early marine cementation, and encrusting nature of the reef-formers produced a non-porous rock which was not susceptible to early dolomitization. However, the associated porous grainstones allowed active circulation of dolomitizing fluids (marine water.), leading to total dolomitization and a favorable reservoir facies.

Heydari, E.; Moore, C.H.

1987-05-01

28

Middle to Late Jurassic Tectonic Evolution of the Klamath Mountains, California-Oregon  

NASA Astrophysics Data System (ADS)

The geochronology, stratigraphy, and spatial relationships of Middle and Late Jurassic terranes of the Klamath Mountains strongly suggest that they were formed in a single west-facing magmatic arc built upon older accreted terranes. A Middle Jurassic arc complex is represented by the volcanic rocks of the western Hayfork terrane and consanguineous dioritic to peridotitic plutons. New U/Pb zircon dates indicate that the Middle Jurassic plutonic belt was active from 159 to 174 Ma and is much more extensive than previously thought. This plutonic belt became inactive just as the 157 Ma Josephine ophiolite, which lies west and structurally below the Middle Jurassic arc, was generated. Late Jurassic volcanic and plutonic arc rocks (Rogue Formation and Chetco intrusive complex) lie outboard and structurally beneath the Josephine ophiolite; U/Pb and K/Ar age data indicate that this arc complex is coeval with the Josephine ophiolite. Both the Late Jurassic arc complex and the Josephine ophiolite are overlain by the "Galice Formation," a Late Jurassic flysch sequence, and are intruded by 150 Ma dikes and sills. The following tectonic model is presented that accounts for the age and distribution of these terranes: a Middle Jurassic arc built on older accreted terranes undergoes rifting at 160 Ma, resulting in formation of a remnant arc/back-arc basin/island arc triad. This system collapsed during the Late Jurassic Nevadan Orogeny (150 Ma) and was strongly deformed and stacked into a series of east-dipping thrust sheets. Arc magmatism was active both before and after the Nevadan Orogeny, but virtually ceased at 140 Ma.

Harper, Gregory D.; Wright, James E.

1984-12-01

29

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

Microsoft Academic Search

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

Amy C. Henrici

1998-01-01

30

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

Microsoft Academic Search

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

Matthew T. Carrano; Jorge Velez-Juarbe

2006-01-01

31

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

32

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

PubMed Central

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

Lukashevich, Elena D.; Przhiboro, Andrey A.

2011-01-01

33

Latest Jurassic-early Cretaceous events and the ''late Cimmerian unconformity'' in North Sea area  

Microsoft Academic Search

Several regional or local unconformities occur in the latest Jurassic-Early Cretaceous sequences of the North Sea and adjacent areas. Each may have been identified locally as the ''late Cimmerian unconformity,'' a supposed major break at the base of the Valhall Formation (or Rodby Formation where the Valhall is locally absent). Although a major hiatus (or a condensed sequence) may occur

P. F. Rawson; L. A. Riley

1982-01-01

34

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

35

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

PubMed Central

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

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

2012-01-01

36

Fossil evidence on evolution of inner ear cochlea in Jurassic mammals  

PubMed Central

The coiled cochlea is a key evolutionary innovation of modern therian mammals. We report that the Late Jurassic mammal Dryolestes, a relative to modern therians, has derived bony characteristics of therian-like innervation, but its uncoiled cochlear canal is less derived than the coiled cochlea of modern therians. This suggests a therian-like innervation evolved before the fully coiled cochlea in phylogeny. The embryogenesis of the cochlear nerve and ganglion in the inner ear of mice is now known to be patterned by neurogenic genes, which we hypothesize to have influenced the formation of the auditory nerve and its ganglion in Jurassic therian evolution, as shown by their osteological correlates in Dryolestes, and by the similar base-to-apex progression in morphogenesis of the ganglion in mice, and in transformation of its canal in phylogeny. The cochlear innervation in Dryolestes is the precursory condition in the curve-to-coil transformation of the cochlea in mammalian phylogeny. This provides the timing of the evolution, and where along the phylogeny the morphogenetic genes were co-opted into patterning the cochlear innervation, and the full coiling of the cochlea in modern therians.

Luo, Zhe-Xi; Ruf, Irina; Schultz, Julia A.; Martin, Thomas

2011-01-01

37

Fossil evidence on evolution of inner ear cochlea in Jurassic mammals.  

PubMed

The coiled cochlea is a key evolutionary innovation of modern therian mammals. We report that the Late Jurassic mammal Dryolestes, a relative to modern therians, has derived bony characteristics of therian-like innervation, but its uncoiled cochlear canal is less derived than the coiled cochlea of modern therians. This suggests a therian-like innervation evolved before the fully coiled cochlea in phylogeny. The embryogenesis of the cochlear nerve and ganglion in the inner ear of mice is now known to be patterned by neurogenic genes, which we hypothesize to have influenced the formation of the auditory nerve and its ganglion in Jurassic therian evolution, as shown by their osteological correlates in Dryolestes, and by the similar base-to-apex progression in morphogenesis of the ganglion in mice, and in transformation of its canal in phylogeny. The cochlear innervation in Dryolestes is the precursory condition in the curve-to-coil transformation of the cochlea in mammalian phylogeny. This provides the timing of the evolution, and where along the phylogeny the morphogenetic genes were co-opted into patterning the cochlear innervation, and the full coiling of the cochlea in modern therians. PMID:20667879

Luo, Zhe-Xi; Ruf, Irina; Schultz, Julia A; Martin, Thomas

2010-07-28

38

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

39

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

40

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

Microsoft Academic Search

Niirnberg, D. and Mtiller, R.D., 1991. The tectonic evolution of the South Atlantic from Late Jurassic to present. Tectonophysics, 191: 21-53. An improved tectonic database for the South Atlantic has been compiled by combining magnetic anomaly, Geosat altimetry, and onshore geologic data. We used this database to obtain a revised plate-kinematic model. Starting with a new fit-reconstruction for the continents

Dirk N; R. Dietmar Miiller

1991-01-01

41

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

2013-07-26

42

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

PubMed Central

Abstract 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.

Qiao, Xiao; Shih, Chung Kun; Petrulevicius, Julian F.; Dong, Ren

2013-01-01

43

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

44

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

45

Hettangian (Early Jurassic) plant fossils from Puale Bay (Peninsular terrane, Alaska)  

Microsoft Academic Search

Middle Hettangian (Early Jurassic) plant macrofossils from the Kamishak Formation at Puale Bay, Alaska occur mainly as leaves and leafy shoots found together with ammonites that allow precise biostratigraphic age assignment. This new locality is the first in the Jurassic of Alaska where the plant material shows preserved cuticle. Four species of three genera are identified representing three different gymnosperm

Maria Barbacka; József Pálfy; Paul L. Smith

2006-01-01

46

Geophysical Evidence for a Possible Late Jurassic Mantle Plume in the Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Gravity, magnetic and seismic refraction data reveal a prominent basement structure beneath the Keathley Canyon area of the western Gulf of Mexico. Several seismic refraction profiles acquired near and over the structure indicate depths to its crest range from 10.5 to 12 km, rising from basement depths of 14 to 16 km below sea level. Because of the presence of extensive salt features, seismic reflection data are unable to accurately image the structure but several reflection profiles indicate the existence of a basement high in the area. A positive free-air gravity anomaly associated with this basement structure extends 200 km from 93.9o W, 26.4o N along a roughly WNW-ESE directed path to 91.7o W, 25.9o N where it turns northeastward. Bathymetric and seismic reflection data indicate the gravity anomaly is not produced by seafloor topography or shallow sedimentary sources, but can be attributed to the basement relief documented. Its amplitude and wavelength decrease to the ESE, from 70 mGal and 100 km wavelength to 35 mGal and 40 km wavelength. A positive magnetic anomaly with a 130 nT amplitude and 30 km wavelength coincides with the WNW end of the free air gravity anomaly. It extends to the ESE in a similar manner to the gravity anomaly, but its amplitude decays more rapidly. Most models for the formation of the Gulf of Mexico basin culminate in a late Jurassic-early Cretaceous phase of seafloor spreading as the Yucatan Block rotates counterclockwise away from North America. The shape of the free air gravity anomaly over the deep basement structure defines a geometry that is similar to those produced by other hotspot tracks, such as the New England Seamounts, Rio Grande Rise or Vitoria-Trindade seamount chain. The WNW-ESE direction is broadly consistent with motion of North America in the hotspot reference frame at the time of basin formation. Such an interpretation suggests that a minor mantle plume may have been active during spreading and played a significant role in the development of the basin. We consider the westerly end of the gravity anomaly to roughly delineate the ocean-continent boundary beneath >15 km of sediments off the Texas coast. At its eastern end, the gravity anomaly turns northeastward and may correspond to the location of a fossil sea floor spreading center.

Bird, D. E.; Hall, S. A.; Casey, J. F.; Burke, K.

2001-12-01

47

Contrasting styles of Late Jurassic syn-rift turbidite sedimentation: a comparative study of the Magnus and Oseberg areas, northern North Sea  

Microsoft Academic Search

Contrasting types of sediment gravity flow and hemipelagite deposition are recorded by the Late Jurassic syn-rift successions in the Magnus and Oseberg areas in the northern North Sea. In both areas the Late Jurassic rift interval was characterized by recurrent tectonic phases. During the Late Oxfordian to Early Volgian, the Penguin halfgraben in the Magnus area received a significant amount

R. Ravnås; R. J. Steel

1997-01-01

48

Isotopic signals from late Jurassic-early Cretaceous (Volgian-Valanginian) subArctic belemnites, Yatria River, Western Siberia  

Microsoft Academic Search

This contribution presents the first detailed oxygen and carbon isotope record from the latest Jurassic-early Cretaceous interval of the Yatria River, subpolar Urals, Siberia. Isotopic compositions have been determined on well-preserved belemnite samples from the genera Lagonibelus, Cylindroteuthis and Acroteuthis. These new data indicate a shift to lower temperatures from the late Volgian into the late Valanginian, with some warmer

G. D. P RICE; J. M UTTERLOSE; Drake Circus

2004-01-01

49

Fossil woods from the Late Cretaceous Aachen Formation  

Microsoft Academic Search

Silicified fossil woods from the Late Cretaceous (Santonian) Aachen Formation of northeast Belgium, southernmost Netherlands and adjacent Germany were investigated. Gymnosperms dominate this assemblage: Taxodioxylon gypsaceum, T. cf. gypsaceum, T. cf. albertense (all Taxodiaceae), Dammaroxylon aachenense sp. nov. (Araucariaceae), Pinuxylon sp. (Pinaceae), and Scalaroxylon sp. (Cycad or Cycadeoid). Angiosperms are minor constituents: Nyssoxylon sp. (Nyssaceae?, Cornaceae?), Mastixioxylon symplocoides sp. nov.

Jacques J. F. Meijer

2000-01-01

50

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

PubMed

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

Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

2013-01-01

51

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

PubMed Central

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

Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

2013-01-01

52

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

53

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

54

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

55

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

56

Ammonite faunas and palaeobiogeography of the Himalayan belt during the Jurassic: Initiation of a Late Jurassic austral ammonite fauna  

Microsoft Academic Search

New data obtained in Nepal and Spiti (India) on stratigraphy and Jurassic ammonite faunas form the basis for a new biogeographical interpretation of the peri-Gondwanan faunas. Faunas of the same ages from New Guinea, New Zealand, Antarctica and South America are also considered.From the upper Bathonian up to the Tithonian-Berriasian, six main successive assemblages are distinguished in Nepal and are

Raymond Enay; Elie Cariou

1997-01-01

57

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

Microsoft Academic Search

Our understanding of Cretaceous climate and environments has been hampered by the lack of data from high latitudes. This study presents new isotopic data from a late Jurassic-early Cretaceous (Volgian-Hauterivian) interval from the Yatria River, subpolar Urals, Western Siberia. The succession consists of ~70 m of highly fossiliferous silty claystones. These were deposited, during the early Cretaceous, on the southern

G. D. Price; J. Mutterlose

2003-01-01

58

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

59

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

60

Late Permian–Middle Jurassic lithospheric thinning in Peru and Bolivia, and its bearing on Andean-age tectonics  

Microsoft Academic Search

Integrated studies and revisions of sedimentary basins and associated magmatism in Peru and Bolivia (8–22°S) show that this part of western Gondwana underwent rifting during the Late Permian–Middle Jurassic interval. Rifting started in central Peru in the Late Permian and propagated southwards into Bolivia until the Liassic\\/Dogger, along an axis that coincides with the present Eastern Cordillera. Southwest of this

Thierry Sempere; Gabriel Carlier; Pierre Soler; Michel Fornari; V??ctor Carlotto; Javier Jacay; Oscar Arispe; Didier Néraudeau; José Cárdenas; Silvia Rosas; Néstor Jiménez

2002-01-01

61

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

62

Latest Jurassic-early Cretaceous events and the ''late Cimmerian unconformity'' in North Sea area  

SciTech Connect

Several regional or local unconformities occur in the latest Jurassic-Early Cretaceous sequences of the North Sea and adjacent areas. Each may have been identified locally as the ''late Cimmerian unconformity,'' a supposed major break at the base of the Valhall Formation (or Rodby Formation where the Valhall is locally absent). Although a major hiatus (or a condensed sequence) may occur at basin margins or above structural highs, over most of the North Sea the base of the Valhall Formation is isochronous, and conformable with underlying sediments. It is detected on seismic reflection profiles because it represents a widespread facies change marking the late Ryazanian transgression. Most of the unconformities and associated sedimentary and/or biologic events are of eustatic origin and, even in the tectonically active areas of the North Sea, the effects of eustatic sea level changes were never completely masked by local tectonics. Thus, in the modeling of individual oil fields, the possibility of sedimentary breaks occurring can be predicted in part by reference to regional or eustatic events.

Rawson, P.F. (Queen Mary College, London, United Kingdom); Riley, L.A.

1982-12-01

63

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

Microsoft Academic Search

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

Peter M. Galton

2010-01-01

64

Sequence stratigraphy and paleo-oceanography of an open-marine mixed carbonate\\/siliciclastic succession (Late Jurassic, Southern Germany)  

Microsoft Academic Search

Summary  The Late Jurassic epicontinental sea of South Germany protruded far to the North forming a wide bay which was rimmed by shallow-water\\u000a platforms (Swiss and French Jura). This wide shelf is characterized by extensive downslope mud accumulations including siliceous\\u000a sponge buildups. The bioherms are aligned along the more pericontinental parts of this shelf, which graded to the South into\\u000a the

Thomas C. Brachert

1992-01-01

65

Oncoid-dwelling foraminifera from Late Jurassic shallow-water carbonates of the Northern Calcareous Alps (Austria and Germany)  

Microsoft Academic Search

Oncoidal limestones with different oncoid types are ubiquitous in back-reef open-lagoonal and, to a minor amount, in closed-lagoonal\\u000a facies of the Late Jurassic Plassen Carbonate Platform of the Northern Calcareous Alps. A common feature of the oncoids from\\u000a moderately to well-agitated open-lagoonal habitats are incorporated small trochospiral benthic foraminifers, tentatively assigned\\u000a to trochamminids, switched between individual micritic layers. Their life

Felix Schlagintweit; Hans-Jürgen Gawlick

2009-01-01

66

Lowland-upland migration of sauropod dinosaurs during the Late Jurassic epoch.  

PubMed

Sauropod dinosaurs were the largest vertebrates ever to walk the Earth, and as mega-herbivores they were important parts of terrestrial ecosystems. In the Late Jurassic-aged Morrison depositional basin of western North America, these animals occupied lowland river-floodplain settings characterized by a seasonally dry climate. Massive herbivores with high nutritional and water needs could periodically experience nutritional and water stress under these conditions, and thus the common occurrence of sauropods in this basin has remained a paradox. Energetic arguments and mammalian analogues have been used to suggest that migration allowed sauropods access to food and water resources over a wide region or during times of drought or both, but there has been no direct support for these hypotheses. Here we compare oxygen isotope ratios (?(18)O) of tooth-enamel carbonate from the sauropod Camarasaurus with those of ancient soil, lake and wetland (that is, 'authigenic') carbonates that formed in lowland settings. We demonstrate that certain populations of these animals did in fact undertake seasonal migrations of several hundred kilometres from lowland to upland environments. This ability to describe patterns of sauropod movement will help to elucidate the role that migration played in the ecology and evolution of gigantism of these and associated dinosaurs. PMID:22031326

Fricke, Henry C; Hencecroth, Justin; Hoerner, Marie E

2011-10-26

67

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

SciTech Connect

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

Montgomery, H.A.

1985-01-01

68

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

69

Episodes of Middle to Late Jurassic Arc Development in the Klamath Mountains, California and Oregon  

NASA Astrophysics Data System (ADS)

The sequence of tectonostratigraphic terranes in the Klamath Mountains provides a rich history of arc magmatism that spans at least 400 m.y. The Middle to Late Jurassic record can be organized into episodes that consist of arc formation and development, contractional deformation (thrusting), plutonism that lacks significant crustal influence, and younger plutonism (with accompanying extension?) with widespread crustal assimilation and/or anatexis. The first episode began with formation of the Middle Jurassic western Hayfork arc (WH; 179 to 171 Ma). It is characterized by water-rich calc-alkaline andesite, but ranges from basalt to dacite. WH magmatism ended with a regional thrusting event. Following thrusting, within uncertainty of dating, plutons of the Ironside Mountain suite (IM) were emplaced. They show a distinctive decrease in Mg/(Mg+Fe), a paucity of early hydrous phases, and increases in LILE. Neither the WH nor IM rocks show evidence for significant crustal contribution. The period 169 to 162 Ma was characterized by regional metamorphism and emplacement of small calc-alkaline plutons. Then from 162 to 159 Ma, large calc-alkaline to calcic plutons were emplaced (Wooley Creek suite). All plutons of this age show isotopic evidence for crustal anatexis and/or assimilation. Scarce 159 Ma garnet-bearing andesitic dikes suggest equilibration at circa 800 MPa, with a crustal thickness of at least 30 km. Wooley Creek magmatism was coeval with outboard growth of the supra-subduction zone Josephine ophiolite (166 to 159 Ma). Extension associated with ophiolite formation may have increased the flux of mafic magma necessary for crustal melting in the Wooley Creek suite. The next episode began with development of the Rogue/Chetco arc along the outboard margin of the Josephine ophiolite (155 to 160 Ma). This arc was generally similar to the WH arc, with water-rich, calc-alkaline magmatism. Collapse and underthrusting of the Josephine ophiolite-Rogue arc assemblage beneath inboard terranes occurred from 155 to 150 Ma; this contractional deformation was the Nevadan orogeny. Thrusting was followed by renewed calcic and calc-alkaline plutonism from 150 to 146 Ma, some of which was similar to the dry, LILE-rich IM suite. These plutons are also similar to the IM in that they show little evidence for interaction with crustal rocks. In contrast, tonalitic to granodioritic plutonism from 145 to 136 Ma requires primarily crustal sources, specifically the underthrust rocks of the Josephine-Rogue assemblage. Each episode began with arc magmatism that ended in contractional deformation. Contraction was followed by localized emplacement of mantle-derived plutons. Later magmatism was partly crustal in origin and, at least in the case of the Wooley Creek suite, associated with extension. This suggests that the time lag between post-arc contraction and emplacement of crustally-derived magmas reflects the time necessary for fresh, mantle-derived magma to heat the lower crust to its solidus.

Barnes, C. G.; Allen, C. M.; Snoke, A. W.

2003-12-01

70

Middle to Late Jurassic basin evolution and sandstone reservoir distribution in the Danish Central Trough. A contribution to the EFP-90 project: Upper Jurassic sandstone reservoirs in the Danish Central Trough.  

National Technical Information Service (NTIS)

During the Middle and Late Jurassic, long-term eustatic sea-level rise and halfgraben subsidence in the Danish Central Trough resulted in a major transgression. Deposition of widespread alluvial plain sediments in the Soegne Basin and Tail End Graben was ...

P. N. Johannessen J. Andsbjerg

1992-01-01

71

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

NASA Astrophysics Data System (ADS)

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

Price, G. D.; Mutterlose, J.

2003-04-01

72

Late Jurassic seismic sequences, Inner Moray Firth, U. K. North Sea: Do local influences invalidate a key segment of Exxon's sea-level chart  

Microsoft Academic Search

Exxon workers used seismic reflector terminations in the Late Jurassic of the Inner Moray Firth (IMF) to define seven sequence boundaries within the late Oxfordian-Berriasian marine interval. The seven are incorporated in their global chart showing relative changes of coastal onlap and eustatic sea level because it was considered that data from the IMF showed no evidence that tectonics caused

1991-01-01

73

Paleoenvironmental controls on the morphology and abundance of the coccolith Watznaueria britannica (Late Jurassic, southern Germany)  

Microsoft Academic Search

The coccolithophore species Watznaueria britannica is dominant in Middle-Upper Jurassic calcareous nannofossil assemblages and presents morphological variation, including different coccolith size, shape and length of the central area and of the bridge. Six morphotypes can be recognized in the polarizing light microscope. The aim of this work is to better understand the morphological variability of W. britannica and determine if

Fabienne Giraud; Bernard Pittet; Emanuela Mattioli; Vanessa Audouin

2006-01-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

75

The Josephine Ophiolite—Remains of a Late Jurassic marginal basin in northwestern California  

NASA Astrophysics Data System (ADS)

The Josephine Ophiolite is a fully developed ophiolite exposed in the western Jurassic belt of the Klamath Mountains. The ophiolite is overlain by a thick flysch sequence derived from both an active volcanic arc and the continental margin. Many lines of evidence favor genesis of the ophiolite in an immature marginal basin by back-arc spreading rather than at a mid-ocean spreading center.

Harper, Gregory D.

1980-07-01

76

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

National Technical Information Service (NTIS)

Climate change plays an important role in determining as possible long term hydrological performance of the potential high level nuclear waste repository within Yucca Mountain, Nevada. Preliminary study of late-glacial fossil ostracodes from 'marsh deposi...

R. M. Forester A. J. Smith

1995-01-01

77

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

Microsoft Academic Search

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

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

2010-01-01

78

Patch reef development in the florigemma Bank Member (Oxfordian) from the Deister Mts (NW Germany): a type example for Late Jurassic coral thrombolite thickets  

Microsoft Academic Search

Small reefal bioconstructions that developed in lagoonal settings are widespread in a few horizons of the Late Jurassic (Oxfordian) succession of the Korallenoolith Formation, exposed southwest of Hannover, Northwest Germany. Especially the florigemma-Bank Member, “sandwiched” between oolite shoal deposits, exposes a high variety of build-ups, ranging from coral thrombolite patch reefs, to biostromes and to coral meadows. The reefs show

Carsten Helm; Immo Schülke

2006-01-01

79

Shallow-water marl-limestone alternations in the Late Jurassic of western France: Cycles, storm event deposits or both?  

NASA Astrophysics Data System (ADS)

The contribution of event deposits to various basin fills can be very significant, higher than 90% in some cases. Events may lead to the formation of marl-limestone alternations, which can also result from cyclic changes in sea level or climate, for example. The marl-limestone alternations of the Late Jurassic of western France contain abundant coarse-grained accumulations that resemble storm deposits described in other western European successions. The detailed analysis of facies evolution and hierarchical, high-frequency stacking pattern of depositional sequences of the Phare de Chassiron section (Ile d'Oléron, western France) allows the controls on marl-limestone formation to be defined. This section contains nearshore and shallow-marine mud deposits that were exposed to high-energy events. Elementary, small-, and medium-scale depositional sequences are defined. The stacking-pattern and the duration of these sequences suggest an orbital control on sedimentation. Precession (20 ka) cycles notably controlled the formation of elementary sequences that correspond to marl-limestone alternations. The deposition of marly or carbonate mud occurred in this storm-dominated system because of muddy sea beds, the gentle slope of the shelf, and the great amount of particles in suspension, which reduced water energy resulting from storms. Sediment supply was also sufficient to limit bioturbation and favour the preservation of numerous storm deposits. The production of carbonate mud was localised on positive structures and partly controlled by Milankovitch-scale sea-level cycles. Transport by storms of carbonate mud to the adjacent marly depressions during high carbonate production periods led to the formation of calcareous beds. Marl-limestone alternations in the Late Jurassic of western France therefore result from the combined effects of cyclic changes in carbonate production and high-energy, episodic events.

Colombié, Claude; Schnyder, Johann; Carcel, Damien

2012-10-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

81

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

82

Tectonic evolution of the Transbaikal region (Siberia) from Late Jurassic to Present. Implications for the Mongol-Okhotsk orogeny.  

NASA Astrophysics Data System (ADS)

The Transbaikal region extends over several hundreds of kilometres east of the Baikal Rift System. It is characterized by a number of sub-parallel Mesozoic grabens or half grabens generally filled with late Jurassic to Early Cretaceous clastic sediments interbedded with coal layers (1). Similar basins occur on an even larger area spanning from the Transbaikal region down to Korea implying a large-scale extensional process affecting most of the Amuria plate during the Mesozoic. In the Transbaikal region, the normal faults controlling the edges of the Mesozoic basins are generally superimposed to Palaeozoic ductile shear zones implying a strong localisation of the extensional deformation on inherited structures. Recent studies, associated to our own fieldwork demonstrated that some of the faults were again activated (2), still as extensional faults, during the Tertiary or Quaternary, and that some of them are presently active. The closure of the Mongol-Okhotsk ocean separating the Siberian plate from the Amurian block during the Mesozoic corresponds to a major event in the growth process of the East Asian continent. The oceanic suture zone is situated on the southern edge of the Transbaikal region and its roughly SW-NE direction is parallel to the basins (3). The timing of the closure of the Mongol-Okhotsk ocean is still highly debated: while sedimentological and tectonic data suggest that the oceanic closure and the following collision occurred in early Middle Jurassic (4), paleomagnetic studies advocate for a Early Cretaceous collision (5). Furthermore, several other questions remain on the localization, the size and the fate of the relief that most probably formed during the collision between the Amuria block and the Siberian craton. In order to answer those questions we used low temperature thermochronology data associated to tectonic, sedimentology and palinology to investigate the evolution of the Transbaikal grabens from Mesozoic to Present. Tectonic and thermochronology data provide evidences of exhumation and erosion along the eastern edge of the Siberian craton during the Middle Jurassic as well as a potential continuum of deformation between the Mesozoic extension and the initiation of the Baikal Rift System (6). Sedimentology and palinology reveals that the sediments deposited in the Transbaikal basin did not registered large-scale compressive deformation during or after their Late Jurassic - Early Cretaceous deposition and that they do not correspond to the dismantling of a strong compressive relief. (1) Tsekhovsky and Leonov, (2007), Lithology and Min. Res., 42, doi:10.1134/S0024490207040037 (2) Lunina and Gladkov, (2009), Geotectonics, doi:10.1134/S0016852109010051 (3) Zorin, (1999), Tectonophysics, 306, pp. 33-56 (4) Ermikov, (1994), Bull. Cent. Rech. Explor. Prod. Elf Aquitaine, 18, pp.123-134 (5) Metelkin et al., (2010), Gondwana Research, doi:10.1016/j.gr.2009.12.008 (6) Jolivet et al., (2009), Tectonics, doi:10.1029/2008TC002404

Jolivet, M.; Arzhannikova, A.; Arzhannikov, S.; Chauvet, A.; Vassallo, R.; Kulagina, N.; Akulova, V.

2012-04-01

83

The late Middle Pleistocene hominin fossil record of eastern Asia: synthesis and review.  

PubMed

Traditionally, Middle Pleistocene hominin fossils that cannot be allocated to Homo erectus sensu lato or modern H. sapiens have been assigned to different specific taxa. For example, in eastern Asia, these hominin fossils have been classified as archaic, early, or premodern H. sapiens. An increasing number of Middle Pleistocene hominin fossils are currently being assigned to H. heidelbergensis. This is particularly the case for the African and European Middle Pleistocene hominin fossil record. There have been suggestions that perhaps the eastern Asian late Middle Pleistocene hominins can also be allocated to the H. heidelbergensis hypodigm. In this article, I review the current state of the late Middle Pleistocene hominin fossil record from eastern Asia and examine the various arguments for assigning these hominins to the different specific taxa. The two primary conclusions drawn from this review are as follows: 1) little evidence currently exists in the eastern Asian Middle Pleistocene hominin fossil record to support their assignment to H. heidelbergensis; and 2) rather than add to the growing list of hominin fossil taxa by using taxonomic names like H. daliensis for northeast Asian fossils and H. mabaensis for Southeast Asian fossils, it is better to err on the side of caution and continue to use the term archaic H. sapiens to represent all of these hominin fossils. What should be evident from this review is the need for an increase in the quality and quantity of the eastern Asian hominin fossil data set. Fortunately, with the increasing number of large-scale multidisciplinary paleoanthropological field and laboratory research projects in eastern Asia, the record is quickly becoming better understood. PMID:21086528

Bae, Christopher J

2010-01-01

84

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

85

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.

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

2013-01-01

86

Late Jurassic extension in the Bisbee basin: Marine and volcanic strata of the Chiricahua Mountains, Arizona  

SciTech Connect

Upper Jurassic strata in the northeastern Chiricahua Mountains provide unambiguous stratigraphic and geographic links between the Chihuahua trough of north-central Mexico and the Bisbee basin of southeastern Arizona. Approximately 1,800 m of limestone, shale, and mafic volcanic rocks overlie the Glance Conglomerate and underlie fluvial redbeds of the Lower Cretaceous Morita Formation. Basal strata are alluvial-fan and sabkha deposits. A thick (150 m), ammonite-bearing black shale interval above the sabkha deposits indicates an abrupt increase of water depths; deepening was accompanied initially by emplacement of subaerial basalt flows and subsequently by deposition of basaltic tuff and pillow lava. Ammonites are present both below and above the tuff and indicate its exclusively subaqueous origin. Arkosic deltaic deposits above the tuff were derived from Precambrian rocks of the footwall block to the northeast. At least 200 m of mafic subaerial flows, previously regarded as mid-Tertiary, overlie the deltaic deposits. The existence of a depleted mantle source beneath the Bisbee basin at 150 Ma suggests a unique tectonic setting that combined backarc and Gulf of Mexico extension.

Lawton, T.F.; McMillan, N.J. (New Mexico State Univ., Las Cruces, NM (United States)); Cameron, K.L. (Univ. of California, Santa Cruz, CA (United States). Earth Sciences Board)

1993-04-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

88

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

89

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

90

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  

Microsoft Academic Search

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

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

2011-01-01

91

Late Hettangian-Early Sinemurian (Jurassic) ammonite biochronology of the Western Cordillera, United States  

Microsoft Academic Search

A faunal succession based on ammonoids is established for the Late Hettangian to Early Sinemurian interval in the Western Cordillera, United States. The faunal sequence consisting of one zone and four informal biochronologic units termed assemblages is given as follows: Paracaloceras morganense assemblage, Badouxia oregonensis assemblage, Canadensis Zone, Metophioceras trigonatum assemblage and Coroniceras involutum assemblage. The succession correlates with the

David G. Taylor

1998-01-01

92

Late Jurassic coral\\/microbial reefs from the northern Paris Basin — facies, palaeoecology and palaeobiogeography  

Microsoft Academic Search

During the late middle Oxfordian, patch reefs grew on the northern margin of the Paris Basin. According to the facies analysis of the reef and inter-reef sediments, the environment was a warm, clear and agitated sea with highly episodic sedimentation. The bioherms were a short-lived phenomenon during the third phase of regional reefal development. Sequence stratigraphically, they are associated with

Markus Bertling; Enzo Insalaco

1998-01-01

93

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

94

Paleoceanographic and paleoclimatic controls on ooid mineralogy of the Smackover Formation, Mississippi salt basin: Implications for Late Jurassic seawater composition  

SciTech Connect

The Late Jurassic Smackover Formation in the Mississippi salt basin consists of two 150 m thick shoaling-upward cycles, each capped by ooid grainstones. During deposition of the lower cycle, originally calcite ooids formed on the seaward side of the basin and former aragonite ooids were precipitated on the landward side. In the upper cycle, originally calcite ooids were precipitated on both the seaward and the landward sides of the basin. Because kinetic variables are incapable of totally preventing aragonite formation the authors suggest that Smackover calcite ooids were precipitated from seawater with low carbonate saturation state (possibly undersaturated relative to aragonite). The shift from seaward calcite to landward aragonite ooids in the lower cycle was controlled by a shoreward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in the carbonate saturation state in response to decreasing dissolved CO[sub 2] and increasing CO[sub 3][sup 2[minus

Heydari, E.; Moore, C.H. (Louisiana State Univ., Baton Rouge, LA (United States))

1994-01-01

95

Fossil Crustacea of the Late Pleistocene Port Morant Formation, west Port Morant Harbour, southeastern Jamaica  

Microsoft Academic Search

The Late Pleistocene Port Morant Formation of southeast Jamaica is particularly rich in fossil marine crustaceans. A new locality on the west side of Port Morant Harbour, parish of St. Thomas, has yielded decapods including the callianassids Lepidophthalmus jamaicense? (Schmitt ), Neocallichirus peraensis Collins et al. and Neocallichirus? sp.; anomurans Petrochirus bahamensis (Herbst) and Paguristes sp. cf. P. lymanni A.

J. S. H. Collins; S. K. Donovan; T. A. Stemann

2009-01-01

96

A fossil plant organ with unusual internal structure from the Late Carboniferous of New South Wales  

Microsoft Academic Search

An unusual plant fossil of unknown affinities is reported from the Late Carboniferous of New South Wales. Burdekinia multiseptata gen. et sp. nov. is known from a straplike organ, externally rather featureless, but characterised by a distinctive internal structure of regular transverse sphenopsid-like partitions which form rectangular sections. These sections are filled with a lattice-work of about six parallel rows

W. B. K. Holmes

1996-01-01

97

Fossil hyrax dung and evidence of Late Pleistocene and Holocene vegetation types in the Namib Desert  

Microsoft Academic Search

Pollen was derived from fossil dung of herbivorous hyraxes, deposited in a rock shelter on the highest mountain in Namibia, Dâures or Brandberg, situated on the Namib Desert margin. Radiocarbon dating ranging in age between modern times and 30 000 yr BP showed it represents the first empirical pollen evidence of continental palaeovegetation during the Late Pleistocene along the western

Louis Scott; Eugene Marais; George A. Brook

2004-01-01

98

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

99

Fossil organic carbon fluxes released by chemical and mechanical weathering. Jurassic marls of Draix experimental watersheds, France  

Microsoft Academic Search

Fate of Fossil Organic Carbon (FOC), originating from sedimentary rock weathering, is a major unknown into carbon cycle. Generally considered as degradable and as a CO2 source for the atmosphere, its occurrence was highlighted by numerous studies in various pools, such as rivers, soils and recent sediments, indicating a potential resistance to weathering. This work focuses on annual FOC fluxes

Y. Graz; C. di-Giovanni; Y. Copard; M. Boussafir; F. Laggoun-Défarge; N. Mathys; F. Rey; S. Sizaret

2009-01-01

100

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

PubMed Central

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

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

2012-01-01

101

Fossil Spores, Pollen, and Fishes from Connecticut Indicate Early Jurassic Age for Part of the Newark Group  

Microsoft Academic Search

Palynologically productive localities have been found in the United States throughout the Newark Group basins, most of which had previously been assumed to be barren. Rich palynoflorules dominated by coniferous pollen of Circulina-Classopollis type, and well-preserved fossil fishes, including possible new semionotids, have been found in the Hartford basin. Palynological data indicate that the Newark Group has considerable time-stratigraphic range:

Bruce Cornet; Alfred Traverse; Nicholas G. McDonald

1973-01-01

102

Building of the deepest crust at a fossil slow-spreading centre (Pineto gabbroic sequence, Alpine Jurassic ophiolites)  

NASA Astrophysics Data System (ADS)

This work presents new field and petrological data on a poorly known lower crustal section from the Alpine Jurassic ophiolites, the Pineto gabbroic sequence from Corsica (France). The Pineto gabbroic sequence is estimated to be ~1.5 km thick and mainly consists of clinopyroxene-rich gabbros to gabbronorites near its stratigraphic top and of troctolites and minor olivine gabbros in its deeper sector. The sequence also encloses olivine-rich troctolite and mantle peridotite bodies at different stratigraphic heights. The composition and the lithological variability of the Pineto gabbroic sequence recall those of the lower crustal sections at slow- and ultra-slow-spreading ridges. The gabbroic sequence considered in this study is distinct in the high proportion of troctolites and olivine gabbros, which approximately constitute 2/3 of the section. In particular, the lower sector of the Pineto gabbroic sequence shows the existence of large-scale fragments of the deepest oceanic crust displaying a highly primitive bulk composition. The mineral chemical variations document that the origin and the evolution of the Pineto gabbroic rocks were mostly constrained by a process of fractional crystallisation. The clinopyroxenes from the olivine gabbros and the olivine-rich troctolites also record the infiltration of olivine-dissolving, Cr2O3-rich melts that presumably formed within the mantle, into replacive dunite bodies. Cooling rates of the troctolites and the olivine gabbros were evaluated using the Ca in olivine geospeedometer. We obtained high and nearly constant values of -2.2 to -1.7 °C/year log units, which were correlated with the building of the Pineto gabbroic sequence through multiple gabbroic intrusions intruded into a cold lithospheric mantle.

Sanfilippo, Alessio; Tribuzio, Riccardo

2013-04-01

103

a Plate-Tectonic Model for Late Jurassic Ophiolite Genesis, Nevadan Orogeny and Forearc Initiation, Northern California  

NASA Astrophysics Data System (ADS)

Recently published age and structural data allow the reconciliation of previously conflicting models for Late Jurassic genesis of the Josephine, Smartville and Coast Range ophiolites, and the Nevadan orogeny in the Klamath Mountains and Sierra Nevada. The resulting model is consistent with the mode of initiation, location and geometry of the Great Valley forearc basin, and with the lack of a significant forearc basin west of the Klamath Mountains. The Coast Range ophiolite formed by backarc spreading west of an east-facing intraoceanic arc. Soon thereafter, a remnant arc was calved off the west side of this arc, and the Smartville ophiolite formed by backarc (interarc) spreading. During this time, the Sierran phase of the Nevadan orogeny began as the intraoceanic arc encountered the west-facing continental-margin arc of North America. An east-west-trending calcalkaline dike swarm in the Sierra Nevada foothills may mark the trajectory of the colliding arcs at the initiation of the collision. Simultaneously, a new subduction zone was initiated west of the collision (suture) zone, and this new trench propagated southward, thus trapping the Coast Range ophiolite in the new forearc area south of the Klamath area. Intense deformation in the Sierran region resulted from this collision, and both magmatic arcs became inactive as the last remnant of intervening oceanic crust was subducted. Continued westward relative movement of the North American arc was permitted north of the Sierra Nevada owing to the lack of a colliding intraoceanic arc. The result was the westward rifting of the continental-margin arc by intraarc spreading, which formed the Josephine ophiolite in the Klamath area. The Klamath phase of the Nevadan orogeny resulted from contraction of the west-facing intraoceanic arc and Josephine backarc basin beneath the continental margin. Basal sediments of the Great Valley forearc basin were derived primarily from the sutured arc/ophiolite terranes, and were deposited on top of the Coast Range ophiolite, the southern edge of the Klamaths, and the western side of the Sierra Nevada. A new (late Mesozoic) magmatic arc was superposed across the previously accreted terranes, and formed the primary sediment source for the Cretaceous forearc basin.

Ingersoll, Raymond V.; Schweickert, Richard A.

1986-10-01

104

Fossils  

NSDL National Science Digital Library

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

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))

1996-01-01

122

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

PubMed

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

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

2009-06-19

123

Fossil pollen records reveal a late rise of open-habitat ecosystems in Patagonia.  

PubMed

The timing of major turnovers in terrestrial ecosystems of the Cenozoic Era has been largely interpreted from the analysis of the assumed feeding preference of extinct mammals. For example, the expansion of open-habitat ecosystems (grasslands or savannas) is inferred to have occurred earlier in Patagonia than elsewhere because of the early advent of high-crowned teeth (hypsodont) mammals ?26?Ma ago. However, the plant fossil record from Patagonia implies another evolutionary scenario. Here we show that the dominance of key open-habitat species--amaranths, Ephedra, asters and grasses--occurred during the last 10?Ma, about 15?Ma later than previously inferred using feeding/habitat ecology of extinct mammals. This late rise of open-landscapes in southern South America brings into question whether the expansion of open-habitat vegetation could have been the prime factor of high-crowned mammal diversification. PMID:23250424

Palazzesi, Luis; Barreda, Viviana

2012-01-01

124

Thermal evolution of Tethyan surface waters during the Middle-Late Jurassic: Evidence from ?18O values of marine fish teeth  

NASA Astrophysics Data System (ADS)

Oxygen isotope compositions of phosphate from vertebrate tooth enamel were measured to determine the evolution of tropical sea surface (<˜200 m depth) temperatures in the western Tethys during the Middle-Late Jurassic. On the basis of a high-resolution stratigraphic framework with a 1 Myr time resolution, vertebrate teeth were sampled on Aalenian to Portlandian isochrons over the Anglo-Paris Basin. Asteracanthus sharks and Pycnodontidae teleosteans, identified as sea surface dwellers, have enamel with ?18O values that range from 18.5 to 22.3‰. Thermal variations of tropical surface waters, with amplitudes of a few degrees per few million years, suggest that Middle to Late Jurassic climates were quite variable. Assuming a seawater ?18O value of 0‰ for surface tropical waters in the absence of polar ice caps, temperatures increased from 25 to 29°C from the mid-Bajocian to mid-Bathonian. During the middle to late Bathonian, a strong geographic zonation in isotopic compositions is observed between the eastern and western parts of the basin. High ?18O values of fish tooth enamel (up to 22.3‰) could reflect the arrival of a cold water current from the Arctic during the opening of the North Sea rift. An apparent large drop of temperatures from 28 to 21°C is identified at the Callovian-Oxfordian boundary over no more than ?2-3 Myr. This cooling is compatible with previous paleobotanical and geochemical studies and can be precisely correlated with the migration of boreal ammonites into the Tethyan domain. Because isotopic sea surface temperatures are probably too low to be compatible with tropical climatic conditions, the ?18O value of seawater could have been >0‰ owing to limited growth of continental ice during the early middle Oxfordian. The resulting sea level fall is estimated to be at least 50 m and is compatible with a global regression stage. The middle Oxfordian thermal minimum is followed by a new warming stage of 3-4°C from the middle to the late Oxfordian.

LéCuyer, Christophe; Picard, StéPhanie; Garcia, Jean-Pierre; Sheppard, Simon M. F.; Grandjean, Patricia; Dromart, Gilles

2003-09-01

125

Provenance of fluvial sandstones at the start of late Jurassic Early Cretaceous rifting in the Cameros Basin (N. Spain)  

NASA Astrophysics Data System (ADS)

The Cameros Basin (Iberian Chain, Central Spain) developed during the latest Jurassic Early Cretaceous in an extensional regime characterized by high rates of subsidence. Its sedimentary fill has been subdivided into eight depositional sequences (DS) mainly composed of continental sediments. DS 1 and DS 2 represent the first rifting stage (Tera Group, Tithonian). The purpose of this study is to characterize the Tera Group in the eastern part of the basin based on provenance criteria derived from fluvial sandstones. In this area of the basin, the Tera Group can be subdivided into three formations: the Ágreda Formation, the Magaña Formation and the Sierra de Matute Formation. These formations are composed of alluvial-fan deposits, meandering fluvial sediments and lacustrine palustrine mudstones. A quantitative petrographic study indicated the presence of three main petrofacies in the Tera Group. The close correlation between petrofacies and lithostratigraphic units indicates that sandstone composition is a powerful tool for deciphering the tectonic processes active during the initial rift stages of the Cameros Basin. Petrofacies 1 is sedimentolithic (mean: Qm54F3Lt43) and represents erosion of the Jurassic marine pre-rift substratum (mainly Kimmeridgian limestones) during deposition of the DS 1 alluvial fan deposits (Ágreda Fm.). Petrofacies 2 is quartzofeldspathic, and can be subdivided into Petrofacies 2A, with an average composition of Qm84F15Lt1 and Petrofacies 2B, whose average composition is Q71F23Lt6. Petrofacies 2 was generated by the erosion of low to medium-grade metamorphic terranes and plutonic source rocks. It characterizes the Magaña Fm. (DS 2). Petrofacies 3 is quartzolithic (mean: Qm67F16Lt17), and is attributed to tectonic reactivation of the basin. This petrofacies characterizes the Sierra de Matute Fm. (DS 2). Thus, the provenance evolution of this basin is characterized by erosion of the pre-rift sedimentary substratum, followed by unroofing of the basement, as recorded in other ancient and modern rifted basins.

González-Acebrón, Laura; Arribas, José; Mas, Ramón

2007-11-01

126

THE ALFRED LEEDS FOSSIL VERTEBRATE COLLECTION OF THE NATIONAL MUSEUM OF IRELAND—NATURAL HISTORY  

Microsoft Academic Search

Alfred nicholson Leeds (1847-1917) is famous among vertebrate palaeontologists for amassing an invaluable collection of fossil vertebrates from the Middle Jurassic aged 'Oxford Clay' deposits of the Peterborough district in the UK, throughout the late nineteenth and early twentieth centuries. Part of his collection was acquired by the national Museum of Ireland— natural History in november 1893 but has not

Ricardo Araújo; Adam S. Smith; Jeff Liston

2008-01-01

127

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

PubMed Central

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

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

2007-01-01

128

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

Microsoft Academic Search

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

Fade Gong; Istvan Karsai

2010-01-01

129

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

PubMed Central

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

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

2010-01-01

130

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

131

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

132

Late Jurassic paleogeographic evolution of the Andean back-arc basin: New constrains from the Lagunillas Formation, northern Chile (27°30?-28°30?S)  

NASA Astrophysics Data System (ADS)

The Late Jurassic Lagunillas Formation exposed between 27°30? and 28°30?S in the northern Chilean Andes comprises two members: a lower sedimentary member, and an upper volcanic member. This unit was deposited during a significant palaeogeographic change related to a major relative sea-level fall that took place in the Andean back-arc basin between 18° and 44°S. The sedimentary member of the Lagunillas Formation consists of a prograding succession in which distal sheetflood alluvial deposits interbedded with aeolian sandstones predominate in the lower part whereas channelized conglomerates, characteristic of more proximal alluvial fan deposition, become progressively more abundant to the top. U-Pb geochronology on detrital zircons indicate maximum depositional ages for the Lagunillas Formation at the Kimmerigdian/Tithonian boundary (150.8 ± 4.0 Ma). These results constitute the first age data for this or correlative units in Chile and indicate correlation of the Lagunillas Formation with the continental Tordillo Formation in the Neuquén basin. Provenance studies by clast count analyses and U-Pb ages in detrital zircons suggest a temporal variation in the sources of the clastic material. At the beginning of the deposition, fine-grained detritus would have been supplied mainly from the Mesozoic magmatic arc located to the west of the basin, but also from Late Paleozoic units probably located to the east. As deposition proceeded, most of the material was being supplied by Paleozoic to Neoproterozoic ("Grenvillian") units. Mesoproterozoic cratonic units, likely located further east, were exposed and eroded at the end of the deposition, prior to the onset of volcanism in the back-arc.

Oliveros, Verónica; Labbé, Mariana; Rossel, Pablo; Charrier, Reynaldo; Encinas, Alfonso

2012-08-01

133

Seismic Images and Magnetic Evidence of The Late Jurassic To Early Cretaceous Africa-eurasia Plate Boundary Off SW Iberia  

NASA Astrophysics Data System (ADS)

During the last decades numerous studies have investigated the structure of the West Iberia non-volcanic continental margin. However, the nature of the crust off SW Iberia is still poorly understood, because of sparse geophysical and geological data coverage. Here we present a 275-km-long multichannel seismic reflection profile, line AR01, acquired in E-W direction across the Horseshoe Abyssal Plain, to partially fill the gap of information in the margin. Line AR01 runs across the inferred plate boundary between the Iberian and the African plates during the opening of the Central Atlantic Ocean. The boundary separates crust formed during or soon after continental rifting of the SW Iberian margin from normal seafloor spreading oceanic crust of the Central Atlantic Ocean. Line AR01 has been processed and pre-stack depth migrated to show the tectonic structure of the crust across the paleo plate boundary. A zone of large basements highs bounded by landward-dipping reflections that penetrate to depths of 15-18 km, marks a change in the character of the basement structure and relief from east to west. In this study we integrate pre-stack depth migration images of line AR01 with potential field data to show that the change in basement structure occurs across the fossil plate boundary separating African oceanic crust of the M series (M22-M16) to the west from the transitional crust of the Iberian margin to the east.

Rovere, M.; Ranero, C. R.; Zitellini, N.; Sartori, R.; Torelli, L.

134

Seismic images and magnetic signature of the Late Jurassic to Early Cretaceous Africa-Eurasia plate boundary off SW Iberia  

NASA Astrophysics Data System (ADS)

Over the last two decades numerous studies have investigated the structure of the west Iberia continental margin, a non-volcanic margin characterized by a broad continent-ocean transition (COT). However, the nature and structure of the crust of the segment of the margin off SW Iberia is still poorly understood, because of sparse geophysical and geological data coverage. Here we present a 275-km-long multichannel seismic reflection (MCS) profile, line AR01, acquired in E-W direction across the Horseshoe Abyssal Plain, to partially fill the gap of information along the SW Iberia margin. Line AR01 runs across the inferred plate boundary between the Iberian and the African plates during the opening of the Central Atlantic ocean. The boundary separates crust formed during or soon after continental rifting of the SW Iberian margin from normal seafloor spreading oceanic crust of the Central Atlantic ocean. Line AR01 has been processed and pre-stack depth migrated to show the tectonic structure of the crust across the palaeo plate boundary. This boundary is characterized by a 30-40-km-wide zone of large basements highs related to landward-dipping reflections, which penetrate to depths of 13-15 km, and it marks a change in the character of the basement structure and relief from east to west. In this study, we have used pre-stack depth migrated images, the velocity model of line AR01 and magnetic data available in the area to show that the change in basement structure occurs across the fossil plate boundary, separating African oceanic crust of the M series (M21-M16) to the west from the transitional crust of the Iberian margin to the east.

Rovere, M.; Ranero, C. R.; Sartori, R.; Torelli, L.; Zitellini, N.

2004-08-01

135

From Back-Arc Drifting to Arc Accretion: the Late Jurassic-Early Cretaceous Evolution of the Guerrero Terrane in Central Mexico (Sierra de Guanajuato)  

NASA Astrophysics Data System (ADS)

Three paleogeographic scenarios have been proposed for the Mesozoic volcano-sedimentary successions that compose the Guerrero terrane, western Mexico. In the "type 1" scenario the Guerrero terrane is an exotic Pacific arc accreted to nuclear Mexico by the consumption of a pre-Cretaceous oceanic basin, named Arperos Basin. The "type 2" scenario considers the Guerrero terrane as a fringing multi-arc system, accreted by the closure of relatively small pre-Cretaceous oceanic basins at multiple subduction zones with varying polarities. Alternatively, in the "type 3" scenario the Guerrero terrane is interpreted as a North American west-facing para-autochthonous arc, which drifted into the paleo-Pacific domain by the opening of the Cretaceous back-arc oceanic Arperos Basin, and subsequently accreted back to the Mexican mainland. In order to test these reconstructions and understand the dynamics of the arc accretion, we present here a combined study that includes sandstone provenance, U-Pb geochronology, and structural data from the Arperos Basin in the Sierra de Guanajuato, central Mexico. Our data document that the Arperos Basin developed in a back-arc setting, and evolved from continental to oceanic conditions from the Late Jurassic to the Early Cretaceous. Sandstone provenance analysis shows an asymmetric distribution of the infill sources for the Arperos Basin: continent-recycled sedimentary rocks were deposited along its north-eastern side, whereas magmatic arc-recycled clastic rocks developed at its south-western side. Such an asymmetric distribution closely fits with sedimentological models proposed for present-day continent-influenced back-arc basins. Based on these evidences, we favor a "type 3" scenario for the Guerrero terrane, which is then considered to represent a detached slice of the Mexican leading-edge that drifted in the paleo-Pacific domain during Late Jurassic-lower Early Cretaceous back-arc extension, and subsequently accreted back to the Mexican craton prior to the Aptian. The accretion of the Guerrero terrane produced a ~80 km-wide suture belt that is represented by a complex pile of tectonic nappes. The lowermost nappes are composed of the Arperos Basin successions and are piled up with a top-to-the SW tectonic transport, whereas the uppermost nappes contain the arc succession and show a top-to-the E transport. We interpret this double vergence pile as the result of a two-stage evolution of the arc-mainland collision. Initially, the oceanic substrate of the Arperos Basin was subducted beneath the Mexican craton, producing the accretion and top-to-the SW piling up of the basin infill. Once the oceanic floor was consumed, the arc overthrust to the E the previously accreted basin nappes and locked the subduction process.

Martini, M.; Solari, L.; Centeno-García, E.; Mori, L.; Camprubi, A.

2011-12-01

136

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

137

Implications of trace fossil assemblages from Late Paleozoic Glaciomarine Talchir Formation, Raniganj Basin, India  

Microsoft Academic Search

The trace fossil assemblages of the ice-marginal shallow marine sediments of the Talchir Formation (Permo-Carboniferous), Raniganj Basin, India, record the adverse effect of extreme climatic conditions on biota. The glaciomarine Talchir succession starts with glacial sediments near the base and gradually passes to storm-laid shallow marine sediments up-section. The fine-grained storm sediments host abundant trace fossils. Although the studied ichnites

Biplab Bhattacharya; H. N. Bhattacharya

2007-01-01

138

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

139

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

Microsoft Academic Search

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

David Penney; Paul A. Selden

2006-01-01

140

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

Microsoft Academic Search

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

Zhong-Wu Lan; Zhong-Qiang Chen

141

Behaviour of nuclides and U-series disequilibrium in clayey sediments: application to the Late Jurassic record from the eastern Paris basin  

NASA Astrophysics Data System (ADS)

We present a record of U-series disequilibrium covering the Callovo-Oxfordian-Thitonian times of the Late Jurassic carbonated platform from the eastern part of the Paris basin. The Callovo-Oxfordian clayey layer is the potential host rock for reconnaissance work carried out by Andra (e.g., Agence Nationale de Gestion des Déchets Radioactifs) in eastern France, the objective of which is the designing and building of an underground research laboratory to study the aptitude of the clay-marl Callovo-Oxfordian layer for the storage of radioactive wastes. We analyse U and Th trace elements on both the labile fraction (extracted by cold HCl) and the total bulk sediments. The Th contents are extremely low in the Oxfordian shelf reef carbonates (<10 ppb) with respect to the Kimmeridgian-Tithonian clayey marls and the Callovian-Oxfordian argilites (up to 10 ppm). In contrast, the uranium contents are much more homogenous (1 ppm ±0.8) along the section. With respect to bulk concentrations, the nuclide contents in the labile component are particularly low in the Callovian-Oxfordian argilites. This behaviour suggests that given the extremely low permeability of the rock, any groundwater circulation of solutes could only have taken place by diffusion - a very slow mechanism that favours water-rock interactions. For U-series analyses (measured by alpha-spectrometry), a total of 43 bulk-rock samples were preferentially microdrilled from the fine-grained lithologies, although the heterogeneity of carbonate facies within sections necessitated occasional sampling of coarser grained lithologies. Within the carbonate-rich part (Oxfordian to Tithonian) of the section, the 234U/238U ratios slightly fluctuate from secular equilibrium and are interpreted as preferential 234U-solution processes related to groundwater circulation. Preferential removal of 234U in this zone is also indicated by some 230Th/234U activity ratios higher than unity. In contrast, most of the samples from the Callovian-Oxfordian argilites plot on or close to the secular equilibrium line. The observed isotopic disequilibriums from samples taken on either side of the interface between the clay formation and the carbonated country rock, are mainly related to a 234U deficiency relative to 230Th and correspond to bulk U-solution.

Casanova, J.; Négrel, Ph.; Innocent, C.; Brulhet, J.

2003-04-01

142

Vertebrate fossils from the Adamantina Formation (Late Cretaceous), Prata Paleontological District, Minas Gerais State, Brazil  

Microsoft Academic Search

In this contribution is given a preliminary up-to-date annotated list of all fossil vertebrates from the Turonian–Santonian Adamantina Formation, Bauru Group where it occurs in the Prata Paleontological District which is located 45 km to the west of Prata in Minas Gerais State, Brazil. The Adamantina Formation is reddish sandstone in the Triângulo Mineiro region. These fluviolacustrine sediments were deposited in

Carlos Roberto A. Candeiro; Adriano R. Santos; Thomas H. Rich; Thiago S. Marinho; Emerson C. Oliveira

143

Vertebrate fossils from the Adamantina Formation (Late Cretaceous), Prata paleontological district, Minas Gerais State, Brazil  

Microsoft Academic Search

In this contribution is given a preliminary up-to-date annotated list of all fossil vertebrates from the Turonian–Santonian Adamantina Formation, Bauru Group where it occurs in the Prata paleontological district which is located 45 km to the west of Prata in Minas Gerais State, Brazil. The Adamantina Formation is a reddish sandstone in the Triângulo Mineiro region. These fluviolacustrine sediments were deposited

Carlos Roberto A. Candeiro; Adriano R. Santos; Thomas H. Rich; Thiago S. Marinho; Emerson C. Oliveira

2006-01-01

144

Oldest Fossil Flowers of Hamamelidaceous Affinity, from the Late Cretaceous of New Jersey  

Microsoft Academic Search

Exceptionally well-preserved staminate inflorescences, pistillate inflorescences, and detached stamens with important phylogenetic and paleoecological implications have been discovered from the Turonian (ca. 88.5-90.4 million years B.P.) Raritan Formation of New Jersey. The fossils have a combination of floral and pollen characters found in various genera of modern entomophilous and anemophilous Hamamelidaceae and anemophilous Platanus (Platanaceae). The floral characters of the

William L. Crepet; Kevin C. Nixon; Else Marie Friis; John V. Freudenstein

1992-01-01

145

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

Microsoft Academic Search

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

Olaf Elicki

2005-01-01

146

Fossil Coral Snapshots of ENSO and Tropical Pacific Climate Over the Late Holocene  

Microsoft Academic Search

Following on previous work, we present new 30 to 150-yr long reconstructions of ENSO activity and mean climate in the central tropical Pacific over the last several millennia based on the oxygen isotopic composition of fossil corals from the Line Island chain. Three recent field trips to Palmyra (2N, 162W), Fanning (4N, 160W), and Christmas (2N, 157W) islands yielded over

K. M. Cobb; C. D. Charles; H. Cheng; R. L. Edwards

2005-01-01

147

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

NASA Astrophysics Data System (ADS)

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

Gore, P. J. W.

148

The Middle-Late Jurassic forced regression and disconformity in central Portugal: eustatic, tectonic and climatic effects on a carbonate ramp system  

Microsoft Academic Search

Successions across the Middle-Upper Jurassic disconformity in the Lusitanian Basin (west-central Portugal) are highly varied, and were probably developed on a large westward-inclined hangingwall of a half-graben. The disconformity is preceded by a complex forced regression showing marked variations down the ramp, and provides an example of the effects of rapid, relative sea-level falls on carbonate ramp systems. In the

ANA C. AZER; E EDO; V. P AUL W RIGHTand M IGUEL

149

The Late Cretaceous environment of the Arctic: A quantitative reassessment based on plant fossils  

Microsoft Academic Search

Late Cretaceous megafossil floras from the palaeo-Arctic of northeastern Russia and northern Alaska are reviewed in respect of their age, composition, structure and floral dynamics. Palaeofloral correlations and comparisons are made between the two regions. Nine angiosperm-rich, predominantly Cenomanian to Coniacian, floras from the palaeo-Arctic are re-evaluated using Climate Leaf Analysis Multivariate Program (CLAMP) calibrated using a global gridded (0.5°×0.5°)

Robert A. Spicer; Alexei B. Herman

2010-01-01

150

Triassic\\/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama  

Microsoft Academic Search

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,

Hutley

1985-01-01

151

Shallow marine syn-rift sedimentation: Middle Jurassic Pelion Formation, Jameson Land, East Greenland  

Microsoft Academic Search

The Middle Jurassic Pelion Formation - Fossilbjerget Formation couplet of Jameson Land, East Greenland, is a well-exposed example of the Middle Jurassic inshore-offshore successions char- acteristic of the rifted seaways in the Northwest European - North Atlantic region. Early Jurassic deposition took place under relatively quiet tectonic conditions following Late Permian - earli- est Triassic and Early Triassic rift phases

Michael Engkilde; Finn Surlyk

152

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

153

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

154

Harvestmen (arachnida: opiliones) from the middle Jurassic of China.  

PubMed

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. PMID:19495718

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

2009-06-03

155

Fossil record of holococcoliths and selected hetero-holococcolith associations from the Mediterranean (Holocene–late Pleistocene): Evaluation of carbonate diagenesis and palaeoecological–palaeocenographic implications  

Microsoft Academic Search

The Holocene–late Pleistocene distribution of holococcoliths, is quantified by light microscopy from cores from the Western Mediterranean, the Aegean Sea and eight eastern Mediterranean cores recovering sapropel S1. The diversity of fossil holococcoliths is much lower than is seen in the plankton, indicating selective preservation. However the holococcolith phases of Syracosphaera pulchra and Helicosphaera carteri are abundantly preserved allowing a

Daniela Crudeli; Jeremy R. Young; Elisabetta Erba; Markus Geisen; Patrizia Ziveri; Gert J. de Lange; Caroline P. Slomp

2006-01-01

156

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

157

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

158

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

159

The Terrestrial Fossil Organic Matter Record of Global Carbon Cycling: A Late Paleozoic through Early Mesozoic Perspective  

NASA Astrophysics Data System (ADS)

The carbon isotope composition of terrestrial fossil organic matter (?13Corg) has been widely used as a proxy of global carbon cycling and to reconstruct perturbations to the ocean-atmosphere carbon budget. The degree to which terrestrial ?13Corg records local to regional environmental conditions versus the evolution of the global carbon cycle has been highly debated. The high-resolution (104 to 106 m.y.) terrestrial ?13Corg record presented here defines a long-term trend through the latest Devonian to Late Triassic that reveals significant and systematic variations that track independently inferred changes in climate, paleo-atmospheric pCO2, and major restructuring in paleotropical flora. This newly derived record is based on 350 carbon isotope analyses of compressed and permineralized plants, cuticle, charcoal and coal (including vitrinite and fusinite) collected from paleo-wetland mudstones and claystones, claystone-filled abandoned fluvial channels, floodplain mudstones, and ephemeral lacustrine deposits at paleo-tropical to paleo-temperate latitudes. Morphologic and geochemical analysis of contemporaneous paleosols and fluvial-alluvial deposits allow for correlation of terrestrial ?13Corg values to reconstructed paleo-environmental conditions. Terrestrial ?13Corg values of contemporaneous fossil organic matter exhibit systematic inter- and intra-basinal variation of up to 2‰ associated with differences in paleo-precipitation and burial history, and geomorphic position within depositional basins and paleo-fluvial systems. Variation in ?13Corg by organic matter type is minimal to less than 1.5‰; specifically, charcoal ?13Corg values overlap to are slightly less negative than those of thermally less mature organic components analyzed. Overall, variation within contemporaneous populations is significantly less than defined by the long-term terrestrial ?13Corg record. Moreover, paleo-floral pi/pa ratios, an established proxy of water-use efficiency of plant growth, estimated from measured terrestrial ?13Corg values and contemporaneous marine carbonate ?13C values define a relatively consistent and narrow range (0.45 to 0.6) throughout the 150 million year interval within each depositional basin, regardless of landscape or stratigraphic position. Their narrow range in conjunction with the statistically significant long-term ?13Corg trend indicates that local to regional environmental effects on ?13Corg were secondary to extrabasinal influences such as the carbon isotopic composition of the paleo-atmosphere. This suggests that the long-term terrestrial ?13Corgrecord archives first-order variations in atmospheric ?13C throughout the Late Paleozoic and Early Mesozoic.

Montanez, I. P.

2006-12-01

160

Wollemi pine: Living fossil from jurassic landscape  

Microsoft Academic Search

As recently as 1994, the dinosaur of the plant kingdom, Wollemi pine (Wollemi nobilis) has been discovered in its site of origin, the Wollemi National Park, 150 km from the city of Sydney, Australia. This giant\\u000a grows to a height of 40m with a trunk diameter of over 1m. All possible steps have been taken to conserve this giant in

N S Leela

2003-01-01

161

High-resolution correlation of the late Triassic (Raetian) to the early Jurassic (Toarcian) between Pelagic sequence of Panthalassa and terrestrial sequence of Pangea using Milankovitch cycles  

NASA Astrophysics Data System (ADS)

Milankovitch forcing is one of the main drivers of cyclic climate changes, and cyclicities of Milankovitch cycles recorded in sedimentary rhythms would give a clue to establish the astronomically calibrated age model. Bedded cherts consist of rhythmical alternations of a chert bed and a shale bed, which are considered to have been formed as a result of cyclic changes in accumulation rate of biogenic SiO2 under extremely slow and continuous accumulation of pelagic clay. Although Milankovitch cycle origin of bedded chert was suggested by several arthors (e.g. Hori et al., 1993), such an origin has been still unproved. Ikeda et al. (2008) demonstrated the Milankovitch cycle origin of the middle Triassic bedded chert based on the similarities in the hierarchy of dominant cyclicities and the nature of amplitude modulation between Milankovitch cycles and the chert bed thickness cycles. However, because the errors of age determinations in the middle Triassic bedded chert are too large, we could not orbitally tune the bedded chert sequence to the astronomical time scale. In this study, we extend our research to the upper Triassic (Raetian) to lower Jurassic (Toarcian) bedded chert sequence and demonstrate its Milankovitch cycle origin. The Triassic/Jurassic (T/J) boundary was recognized as a radiolarian faunal turnover (Carter & Hori, 2005). Because the astronomically calibrated cyclostratigraphy was already established using the upper Triassic (Carnian) to lower Jurassic (Hettangian) lacustrine sequences of Pangea including the T/J boundary horizon (e.g. Olsen & Kent, 1999; Whiteside et al., 2007), we could compare our bedded chert sequence with them. We conducted geologic survey at Katsuyama section (e.g. Carter & Hori, 2005), in Inuyama area, central Japan. The average duration of ca. 20 ky for a chert-shale couplet based on radiolarian biostratigraphy is consistent with the assumption that a chert-shale couplet represents a precession cycle. Spectral analysis of bed number series of chert bed thickness revealed ca. 5, 20, and 200beds cycles that correspond to ca. 100, 400, and ca. 3500 ky eccentricity cycles, respectively. The similarity in the hierarchy of dominant periodicities between Milankovitch cycles and chert bed thickness cycles strongly support the idea that the cyclicities in thickness of a chert bed of upper Triassic to lower Jurassic bedded chert sequence were paced by Milankovitch cycles. We try to import the astronomically calibrated cyclostratigraphy for the lacustrine sequence in Newark basin (Olsen & Kent, 1999; Whiteside et al., 2007) into the bedded chert sequence in Inuyama by using the T/J boundary as a datum level. This correlation suggests that the radiolarian faunal turnover in Panthalassa is almost synchronous (~ ca. 100 ky) with the faunal and floral turnover in Pangea. Such a cyclostratigraphic correlation between pelagic bedded chert sequence and terrestrial lacustrine sequence will also provide useful information on the detailed process and mechanism of environmental changes at the T/J boundary and its relation with mass extinction.

Ikeda, M.; Tada, R.; Sakuma, H.

2009-12-01

162

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

163

Transitional fossil earwigs - a missing link in Dermaptera evolution  

PubMed Central

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

2010-01-01

164

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

NASA Astrophysics Data System (ADS)

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

Geissman, John W.; Harlan, Stephen S.

2004-07-01

165

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

167

The Jurassic of the Circum-Pacific  

NASA Astrophysics Data System (ADS)

In this work, sixty specialists assembled to discuss the regional occurrences of Jurassic rocks around the Pacific rim. The tectonic setting, stratigraphical sequences, and fossil assemblages of the region are covered in detail; regional biozones based on palynonorphs, protistans, plants and invertebrates are defined; and super-regional standard zones based on ammonites are established. Numerous tables are used to document and illustrate intra- and intercontinental circum-Pacific correlations, and a large atlas illustrates more than 1,000 circum-Pacific index fossils.

Westermann, Gerd E. G.

1993-03-01

168

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

Microsoft Academic Search

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

Christine E. Turner; Fred Peterson

2004-01-01

169

Jurassic Park Safety Audit  

NSDL National Science Digital Library

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

2007-09-18

170

Jurassic Reef Park  

NSDL National Science Digital Library

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

171

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.

Leinfelder, Reinhold

172

Correlation of the major late Jurassic —early Tertiary low- and highstand cycles of south-west Egypt and north-west Sudan  

NASA Astrophysics Data System (ADS)

The mainly continental deposits of northwest Sudan and south-west Egypt have been correlated with coeval shallow marine and marine deposits in northern Egypt along a north-south running cross-section, based on surface and subsurface data. The palaeodepth curve of northern Egypt illustrates the gradual seal-level rise, reaching its maximum during the Late Cretaceous with conspicuous advances during the Aptian and late Cenomanian. A general highstand is also recorded during the Campanian-Maastrichtian in north-west Sudan. A detailed facies correlation is given for the Aptian and late Cenomanian highstand in western Egypt. The correlation of the Cenomanian Bahariya and Maghrabi formations displays short-term relative sealevel fluctuations. The interpretation illustrates the extensiveness of related erosional processes in the hinterland, partly intensified by temporarily uplift of the Uweinat-Aswan High in the south. Regional uplift and constant erosion took place in south-west Egypt during Coniacian and Santonian times. The regional stratigraphic gaps and uncertain interpretation of the Bahariya Uplift are induced by the influence of the Trans-African Lineament, especially during the Late Cretaceous. Low-stand fluvial sheet sandstones characterized by non-cyclic sequence development and high facies stability occur, especially in the Neocomian and early Turonian. During the Barremian and Albian, fluvial architecture changes to more cyclic fluvial sequences and increasing soil formation, due to increasing subsidence, more humid climatic conditions and the generally rising sea level, culminating in the extensive shallow marine Abu Ballas and Maghrabi formations.

Wycisk, Peter

1994-12-01

173

Florida: A Jurassic transform plate boundary  

NASA Astrophysics Data System (ADS)

Magnetic, gravity, seismic, and deep drill hole data integrated with plate tectonic reconstructions substantiate the existence of a transform plate boundary across southern Florida during the Jurassic. On the basis of this integrated suite of data the pre-Cretaceous Florida-Bahamas region can be divided into the pre-Jurassic North American plate, Jurassic marginal rift basins, and a broad Jurassic transform zone including stranded blocks of pre-Mesozoic continental crust. Major tectonic units include the Suwannee basin in northern Florida containing Paleozoic sedimentary rocks, a central Florida basement complex of Paleozoic age crystalline rock, the west Florida platform composed of stranded blocks of continental crust, the south Georgia rift containing Triassic sedimentary rocks which overlie block-faulted Suwannee basin sedimentary rocks, the Late Triassic-Jurassic age Apalachicola rift basin, and the Jurassic age south Florida, Bahamas, and Blake Plateau marginal rift basins. The major tectonic units are bounded by basement hinge zones and fracture zones (FZ). The basement hinge zone represents the block-faulted edge of the North American plate, separating Paleozoic and older crustal rocks from Jurassic rifted crust beneath the marginal basins. Fracture zones separate Mesozoic marginal sedimentary basins and include the Blake Spur FZ, Jacksonville FZ, Bahamas FZ, and Cuba FZ, bounding the Blake Plateau, Bahamas, south Florida, and southeastern Gulf of Mexico basins. The Bahamas FZ is the most important of all these features because its northwest extension coincides with the Gulf basin marginal fault zone, forming the southern edge of the North American plate during the Jurassic. The limited space between the North American and the South American/African plates requires that the Jurassic transform zone, connecting the Central Atlantic and the Gulf of Mexico spreading systems, was located between the Bahamas and Cuba FZ's in the region of southern Florida. Our plate reconstructions combined with chronostratigraphic and lithostratigraphic information for the Gulf of Mexico, southern Florida, and the Bahamas indicate that the gulf was sealed off from the Atlantic waters until Callovian time by an elevated Florida-Bahamas region. Restricted influx of waters started in Callovian as a plate reorganization, and increased plate separation between North America and South America/Africa produced waterways into the Gulf of Mexico from the Pacific and possibly from the Atlantic.

Klitgord, Kim D.; Popenoe, Peter; Schouten, Hans

1984-09-01

174

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.

175

Early Adaptive Radiation of Birds: Evidence from Fossils from Northeastern China  

Microsoft Academic Search

Late Jurassic and Early Cretaceous birds from northeastern China, including many complete skeletons of Confuciusornis, provide evidence for a fundamental dichotomy in the class Aves that may antedate the temporal occurrence of the Late Jurassic Archaeopteryx. The abundance of Confuciusornis may provide evidence of avian social behavior. Jurassic skeletal remains of an ornithurine bird lend further support to the idea

Lianhai Hou; Larry D. Martin; Zhonghe Zhou; Alan Feduccia

1996-01-01

176

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

177

Fossil Vertebrates from Antigua, Lesser Antilles: Evidence for Late Holocene Human-Caused Extinctions in the West Indies  

Microsoft Academic Search

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

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

1984-01-01

178

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

179

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

180

The Terrestrial Fossil Organic Matter Record of Global Carbon Cycling: A Late Paleozoic through Early Mesozoic Perspective  

Microsoft Academic Search

The carbon isotope composition of terrestrial fossil organic matter (delta13Corg) has been widely used as a proxy of global carbon cycling and to reconstruct perturbations to the ocean-atmosphere carbon budget. The degree to which terrestrial delta13Corg records local to regional environmental conditions versus the evolution of the global carbon cycle has been highly debated. The high-resolution (104 to 106 m.y.)

I. P. Montanez

2006-01-01

181

Cold episodes inside Jurassic times: is the carbonate deposition engine controlling atmospheric CO2?  

Microsoft Academic Search

The calculated history of Phanerozoic CO2 suggests a rather constantly warm Mesozoic (Berner and Kothavala, 2001). This result is in disagreement with recent findings suggesting the occurrence of short (several 105 years) glacial episodes during the Jurassic, particularly at the Middle-Late Jurassic transition (Dromart et al., 2003). This climatic event is linked to perturbations in the carbonate production, with a

Y. Godderis; Y. Donnadieu; G. Dromart; R. T. Pierrehumbert

2006-01-01

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

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

184

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

185

Fossil bee nests, coleopteran pupal chambers and tuffaceous paleosols from the Late Cretaceous Laguna Palacios Formation, Central Patagonia (Argentina)  

Microsoft Academic Search

The Late Cretaceous Laguna Palacios Formation in Central Patagonia (San Jorge Basin), southern South America, is composed of tuffaceous deposits supplied by periodical volcanic ash falls partly reworked by rivers, on broad plains. Variations in ash-fall rates allowed the formation of stacked, mature paleosols, which are one of the most characteristic features of this formation. The mature paleosols show well-developed

Jorge F. Genise; Juan C. Sciutto; José H. Laza; Mirta G. González; Eduardo S. Bellosi

2002-01-01

186

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.

Wang, Qi; Shih, Chungkun; Ren, Dong

2013-01-01

187

The view from the Lincoln Cave: mid- to late Pleistocene fossil deposits from Sterkfontein hominid site, South Africa.  

PubMed

The Lincoln-Fault cave system lies adjacent to the Sterkfontein Cave system in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa. Lincoln Cave contains a mid- to late Pleistocene fossiliferous deposit which has been dated using uranium series methods to between 252,600+/-35,600 and 115,300+/-7,700 years old. Although speleologists presumed that there was no connection between the Lincoln Cave and Sterkfontein Cave systems, results of excavations conducted in 1997 suggest a link between the deposits. Detailed comparisons of artifacts, fauna, hominid material, and a statistical correspondence analysis (CA) of the macromammalian fauna in the deposits strongly support this hypothesis. The recovery of Early Acheulean-type artifacts from the Lincoln Cave suggests that older artifacts eroded out of Sterkfontein Member 5 West and were redeposited into the younger Lincoln Cave deposits. The close physical proximity of these deposits, and the nature of the material recovered from them, indicates that the material was probably redeposited via a link between the two cave systems. Although faunal mixing is present, it is possible to say that large carnivorans become more scarce at Sterkfontein during the mid- to late Pleistocene, while small canids and felids appear to become more abundant, indicating that large and small carnivorans probably varied their use of the site through time. This may also reflect an increasing presence of humans in the Sterkfontein area during the mid- to late Pleistocene. PMID:17624409

Reynolds, S C; Clarke, R J; Kuman, K A

2007-07-10

188

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

Microsoft Academic Search

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

John W. Geissman; Stephen S. Harlan

2004-01-01

189

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

190

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

191

Jurassic hydrocarbon exploration of southern Florida  

SciTech Connect

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

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

1994-09-01

192

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; Malnis, Paula Santi; Correa, Gustavo A; Abelin, Diego; Alcober, Oscar

2013-10-16

193

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

194

New sedimentological, bio-, and magnetostratigraphic data on the Jurassic-Cretaceous boundary interval of Eastern Crimea (Feodosiya)  

NASA Astrophysics Data System (ADS)

The first compiled composite section comprises continuous succession of upper Tithonian-lower Berriasian strata (Jacobi Zone) from different isolated outcrops of the Feodosiya area. Based on new magnetostratigraphic and sedimentological data, the paleomagnetic section is correlated with succession of M20r, M19n, M19r, M18b chrons and M18n.1r Subchron ("Brodno"). The thorough complex bio- and magnetostratigraphic correlation of the upper Tithonian-lower Berriasian interval (Jacobi Zone) carried out through the Western Tethys and Eastern Paratethys provided grounds for first defining age analogs of the Durangites Zone in the Crimean Mountains and specifying location of the boundary between the Jurassic and Cretaceous systems, as well as for determining late Tithonian age of strata in the Dvuyakornaya Bay section barren of fossils.

Guzhikov, A. Yu.; Arkad'ev, V. V.; Baraboshkin, E. Yu.; Bagaeva, M. I.; Piskunov, V. K.; Rud'ko, S. V.; Perminov, V. A.; Manikin, A. G.

2012-05-01

195

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

196

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

197

Mexican Fossil Mammals, Who, Where and When?  

Microsoft Academic Search

Although the earliest report of a fossil mammal from Mexico dates from 1799, our knowledge of the group is still poor. The\\u000a Mexican mammalian fossil record is biased towards the large-sized taxa and younger ages.\\u000a \\u000a The mammalian record in Mexico ranges from the Jurassic to the Quaternary. Most of the Cenozoic epochs, except for the Paleocene,\\u000a have mammal bearing deposits.

Marisol Montellano-Ballesteros; Eduardo Jimenez-Hidalgo

198

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

199

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

200

The Late Pleistocene-Holocene community development in Central and SE-Europe in direct fossil record: scope of the approach, common patterns and inter-regional differences.  

NASA Astrophysics Data System (ADS)

The information provided by modern instrumental approaches (molecular phylogeography, ancient DNA analyses, large scale radiocarbon datings etc.) refined the knowledge on Late Quaternary faunal development and range history of particular taxa in essential way. Nevertheless, the direct fossil record remains still an essential substrate in study of that topics, and to reveal all the information, that it may provide, and integrate it with the outputs of the other approaches presents one of the essential aim of the present meeting. Unfortunately, the immediate use of fossil record for the paleoecologic and paleobiogeographic inferences is often limited by its fragmentarity (both in temporal and spatial respects), taphonomic influences and/or locally specific post-sedimentary effects which all may bias it in a considerable degree. Hence, each particular record is to be carefully reexamined in respect to all factor which may bias it - unfortunately, often it is not too easy to respond that task, particularly when the record is retrived from secondary sources. It should also be remembered that the records representing narrow time slices without a robust lithostratigraphic context do not provide any information on the historical and contextual setting of the respective faunal situation. Such information that is essential for reconstructions of paleobiogeography of community development and similar locally-sensitive phenomena can only be retrived from the continuous sedimentary series which establish the sequence of particular faunal events by direct superposition. A sufficiently dense network of such series provides than a possibility of direct inter-regional comparisons and a high resolution information on the paleobiogeography of the Late Pleistocene-Holocene rearrangements of mammalian communities, local variation in history of particular species and its community context. We illustrate productivity of such approach on with aid of the fossil record obtained from continuous sedimentary sequences from different regions of Czech Republic and Slovakia (850 community samples, 29,800 MNI) and neighbouring countries of Central Europe. Despite common general trends we demonstrated stricking local and regional specificities. Among other they include (a) continuous survival of several woodland elements (Clethrionomys glareolus, Sorex araneus, Micotus subterraneus, Microtus agrestis) throughout Weichselian (including LGM) in the Carpathians, (b) prolonged survival of the glacial elements Ochotona pusilla and Microtus gregalis in Pannonian basin and (c) Dicrostonyx gulielmi in the Carpathian foredeep, contrasting to (d) the early disappearance of them in S-Germany and Bohemia, and (e) similar difference were found also in other cenologic traits. While the glacial communities were nearly homogenous in their structure throughout whole the region, the Holocene development produced a considerable faunal provincialism, which was the most pronounced during Boreal. In contrast to central Europe, the available sequences from the SE-Europe and Asia Minor show only minute faunal changes during the Vistulian and Holocene, no essential rearrangements in community structure were observed (at least as the core species are concerned) and except for Lagurus no glacial immigrant did invade the region. At the same time a degree of local provincialism was continuously high and, in a regional scale, it continuously exceeded that of the Boreal central Europe.

Horacek, Ivan; Lozek, Vojen

2010-05-01

201

Jurassic salt tectonism within Mt. Enterprise fault system, Rusk County, Texas  

SciTech Connect

A synthesis of seismic, bore-hole, and gravity data in southeastern Rusk County, Texas, indicates that faulting within the Mt. Enterprise fault system was the result of Jurassic salt tectonism. Faults were developed in response to salt movement and subsequent collapse of the overlying section into areas of salt withdrawal, resulting in the formation of a graben containing no Louann Salt. An abnormally thick Bossier Formation within the graben indicates a Late Jurassic age for significant structural deformation within the fault zone. The potential exists for numerous untested traps within the Jurassic section associated with salt-generated structures along the Mt. Enterprise fault system.

Ferguson, J.D.

1985-02-01

202

JURASSIC Retrieval Processing  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

203

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

NASA Astrophysics Data System (ADS)

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

Korte, Christoph; Hesselbo, Stephen P.

2011-12-01

204

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

PubMed

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

2009-03-01

205

Marquee Fossils  

ERIC Educational Resources Information Center

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

Clary, Renee; Wandersee, James

2008-01-01

206

Marquee Fossils  

ERIC Educational Resources Information Center

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

Clary, Renee; Wandersee, James

2008-01-01

207

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

Microsoft Academic Search

BackgroundThe 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 FindingsA new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et

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

2009-01-01

208

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

209

Upper Jurassic of east Texas, a stratigraphic sedimentologic reevaluation  

Microsoft Academic Search

The Smackover-Haynesville of east Texas has long been modeled as a simple progradational carbonate-evaporite ramp. Recent data indicate that the conventional ramp model for this sequence should be abandoned in favor of an evolving rimmed shelf to platform model, forming in response to changes in rate of relative sea level rise during the Late Jurassic. Evidence for Smackover-Haynesville shelves include:

C. H. Moore; K. McGillis; S. Stewart; S. Wilkinson; G. Harwood

1985-01-01

210

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.

211

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

212

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

213

"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

214

Direct chemical evidence for eumelanin pigment from the Jurassic period  

PubMed Central

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

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

2012-01-01

215

Direct chemical evidence for eumelanin pigment from the Jurassic period.  

PubMed

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

2012-05-21

216

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 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

217

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

218

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

NASA Astrophysics Data System (ADS)

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

Selden, Paul A.; Huang, Diying

2010-05-01

219

Fossil fuels  

Microsoft Academic Search

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

Herman Daly

1994-01-01

220

Swimming styles in Jurassic ichthyosaurs  

Microsoft Academic Search

Postcranial axial anatomy of six Jurassic ichthyosaurs is described and used to define a generalized pattern of regional anatomy with four structural units (neck, trunk, tail stock, fluke). Functional interpretation of each unit predicts a generalized swimming mode that used a laterally compressed, laterally oscillating caudal fluke as the propulsive organ. Fluke displacement was accomplished by the undulation of a

Emily A. Buchholtz

2001-01-01

221

A Jurassic mammaliaform and the earliest mammalian evolutionary adaptations.  

PubMed

The earliest evolution of mammals and origins of mammalian features can be traced to the mammaliaforms of the Triassic and Jurassic periods that are extinct relatives to living mammals. Here we describe a new fossil from the Middle Jurassic that has a mandibular middle ear, a gradational transition of thoracolumbar vertebrae and primitive ankle features, but highly derived molars with a high crown and multiple roots that are partially fused. The upper molars have longitudinal cusp rows that occlude alternately with those of the lower molars. This specialization for masticating plants indicates that herbivory evolved among mammaliaforms, before the rise of crown mammals. The new species shares the distinctive dental features of the eleutherodontid clade, previously represented only by isolated teeth despite its extensive geographic distribution during the Jurassic. This eleutherodontid was terrestrial and had ambulatory gaits, analogous to extant terrestrial mammals such as armadillos or rock hyrax. Its fur corroborates that mammalian integument had originated well before the common ancestor of living mammals. PMID:23925238

Zhou, Chang-Fu; Wu, Shaoyuan; Martin, Thomas; Luo, Zhe-Xi

2013-08-01

222

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

SciTech Connect

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

May, S.R.

1985-01-01

223

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

224

Paleogeography of Jurassic fragments in the Caribbean  

NASA Astrophysics Data System (ADS)

Jurassic rocks of the Caribbean are a sampling of 100 million years of Farallon Plate history with fragments originating at diverse paleolatitudes and from varied tectonic settings. Fragments with clear paleogeographic signatures are components of the basement complexes of Duarte in Hispaniola, Bermeja in Puerto Rico and La Désirade off Guadeloupe. Paleolatitudinally sensitive radiolarian faunas document origination of Duarte as equatorial, La Désirade as higher latitude, and various Bermeja cherts as both equatorial and higher latitude. Red ribbon chert of Duarte and Bermeja of the same age, physical appearance, and lithological association are probably dismembered components of the same slab of Pacific crust. La Désirade red ribbon chert is slightly younger than the Duarte and Bermeja red ribbon chert and was deposited at higher latitude. Bermeja tuffaceous chert is also of higher latitude and probably had an arc-proximal origin. On the basis of modeled plate trajectories in the Pacific, the origin of various cherts from different paleolatitudes that end up in the same location requires different arrival times at the trench between North and South America. Based on radiolarian paleobiogeography plus indications of origin at a spreading ridge and ignoring the poorly constrained, modeled trajectories for the Late Jurassic, at least one of the higher latitude fragments may have originated in the southern hemisphere. The accumulation of multifarious chert, greenstone, and other ocean floor components was accomplished by offscraping strata transported to the subduction zone along the eastern Pacific margin and warehousing this material in an accretionary complex prior to entry of the Caribbean Plate into the gap between North and South America.

Montgomery, Homer; Pessagno, Emile A.; Lewis, John F.; Schellekens, Johannes

1994-06-01

225

Biogeochemistry of the Triassic-Jurassic Boundary  

NASA Astrophysics Data System (ADS)

New biostratigraphic and biogeochemical data are presented from Triassic-Jurassic (Tr-J) boundary sections at Kennecott Point, Queen Charlotte Islands (QCI), Canada, Muller Canyon, Nevada, USA, and Marokopa Beach, New Zealand. The New Zealand record shows two negative excursions in ?13Corg of approximately 2‰ associated with the Tr-J transition. The QCI and Nevada boundary sections show a consistent isotopic trend indicative of multiple major perturbations to the carbon cycle: one negative excursion in ?13Corg of 2‰ at the boundary and one positive excursion of 3 to 5‰ following the boundary. The post-Tr-J boundary positive excursion is especially prominent in boundary sections from QCI, where the high organic content of the black shales makes the rocks suitable for a survey of lipid biomarkers. New GC-MS data are presented from this locality, revealing changes in the distribution and abundance of alkanes, hopanes, and steranes across the Tr-J transition. Litho-, bio- and chemostratigraphy from these boundary localities do not support a single impact cause for the late Triassic extinctions, although impact events such as the Manicouagan may well have exerted significant stress on a biosphere still recovering from the Permian-Triassic mass extinction. The data support the idea of a degraded late Triassic environment persisting for millions of years and characterized by low atmospheric oxygen and high carbon dioxide associated with Central Atlantic Magmatic Province volcanism. Global warming and sea level change may have led to destabilization of seafloor methane hydrates and runaway greenhouse conditions.

Williford, K. H.; Ward, P. D.; Garrison, G. H.

2006-12-01

226

Fossil Find  

NSDL National Science Digital Library

In this classroom activity, middle school students simulate a "dinosaur dig." The activity opens with background information for teachers about fossils. Working in groups, students excavate fossil sites created in advance by the teacher, or other group of students, and try to reconstruct a chicken skeleton. The activity closes with a two-page student worksheet that directs students to diagram the fossil site and includes probing questions to help them decode their findings.

227

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

228

Finding Fossils  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2007-01-01

229

Shelf-to-basin resedimented carbonates of the southern margin of the Jurassic central high Atlas trough, Morocco  

Microsoft Academic Search

The Central High Atlas Mountains occupy the site of an Early to Middle Jurassic east-west-trending seaway known as the Central High Atlas trough. Late Triassic-Early Jurassic continental rifting, combined with a transtensional structural regime, formed a system of pull-apart basins comprising the trough. A thick sequence of carbonate shelf-to-basin-plain deposits filled the trough and were later uplifted and exposed during

B. H. Hazlett; J. E. Warme

1988-01-01

230

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

231

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

232

Fossil Crinoids  

Microsoft Academic Search

Crinoids have graced the oceans for more than 500 million years. Among the most attractive fossils, crinoids had a key role in the ecology of marine communities through much of the fossil record, and their remains are prominent rock forming constituents of many limestones. This is the first comprehensive volume to bring together their form and function, classification, evolutionary history,

Hans Hess; William I. Ausich; Carlton E. Brett; Michael J. Simms

2003-01-01

233

Fossil Crinoids  

Microsoft Academic Search

Crinoids have graced the oceans for more than 500 million years. Among the most attractive fossils, crinoids had a key role in the ecology of marine communities through much of the fossil record, and their remains are prominent rock forming constituents of many limestones. This is the first comprehensive volume to bring together their form and function, classification, evolutionary history,

Hans Hess; William I. Ausich; Carlton E. Brett; Michael J. Simms

1999-01-01

234

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

235

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

236

Fossil Crinoids  

NASA Astrophysics Data System (ADS)

Crinoids have graced the oceans for more than 500 million years. Among the most attractive fossils, crinoids had a key role in the ecology of marine communities through much of the fossil record, and their remains are prominent rock forming constituents of many limestones. This is the first comprehensive volume to bring together their form and function, classification, evolutionary history, occurrence, preservation and ecology. The main part of the book is devoted to assemblages of intact fossil crinoids, which are described in their geological setting in twenty-three chapters ranging from the Ordovician to the Tertiary. The final chapter deals with living sea lilies and feather stars. The volume is exquisitely illustrated with abundant photographs and line drawings of crinoids from sites around the world. This authoritative account recreates a fascinating picture of fossil crinoids for paleontologists, geologists, evolutionary and marine biologists, ecologists and amateur fossil collectors.

Hess, Hans; Ausich, William I.; Brett, Carlton E.; Simms, Michael J.

2003-01-01

237

Fossil Crinoids  

NASA Astrophysics Data System (ADS)

Crinoids have graced the oceans for more than 500 million years. Among the most attractive fossils, crinoids had a key role in the ecology of marine communities through much of the fossil record, and their remains are prominent rock forming constituents of many limestones. This is the first comprehensive volume to bring together their form and function, classification, evolutionary history, occurrence, preservation and ecology. The main part of the book is devoted to assemblages of intact fossil crinoids, which are described in their geological setting in twenty-three chapters ranging from the Ordovician to the Tertiary. The final chapter deals with living sea lilies and feather stars. The volume is exquisitely illustrated with abundant photographs and line drawings of crinoids from sites around the world. This authoritative account recreates a fascinating picture of fossil crinoids for paleontologists, geologists, evolutionary and marine biologists, ecologists and amateur fossil collectors.

Hess, Hans; Ausich, William I.; Brett, Carlton E.; Simms, Michael J.

1999-10-01

238

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.

Project, Iowa P.

2004-01-01

239

Biogeography and migration routes of large mammal faunas in South–East Asia during the Late Middle Pleistocene: focus on the fossil and extant faunas from Thailand  

Microsoft Academic Search

Thailand has long held a key position in South–East Asia because of its location at the boundary of the Indochinese and Sundaic provinces, the major biogeographical regions of South–East Asia. These provinces are distinct climatically, floristically and faunistically. The present-day limit between them is located at the Kra Isthmus, in peninsular Thailand.Previous studies of the Javanese large mammal fossil faunas

C Tougard

2001-01-01

240

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

241

Diverse subaerial and sublacustrine hot spring settings of the Cerro Negro epithermal system (Jurassic, Deseado Massif), Patagonia, Argentina  

NASA Astrophysics Data System (ADS)

The Late Jurassic (~ 150 Ma) Cerro Negro volcanic-epithermal-geothermal system (~ 15 km2 area), Deseado Massif, Patagonia, Argentina, includes two inferred volcanic emission centers characterized by rhyolitic domes linked along NW-SE regional faults that are associated with deeper level Au/Ag mineralization to the NW, and with shallow epithermal quartz veins and mainly travertine surface hot spring manifestations to the SE. Some travertines are silica-replaced, and siliceous and mixed silica-carbonate geothermal deposits also are found. Five hot spring-related facies associations were mapped in detail, which show morphological and textural similarities to Pleistocene-Recent geothermal deposits at Yellowstone National Park (U.S.A.), the Kenya Rift Valley, and elsewhere. They are interpreted to represent subaerial travertine fissure ridge/mound deposits (low-flow spring discharge) and apron terraces (high-flow spring discharge), as well as mixed silica-carbonate lake margin and shallow lake terrace vent-conduit tubes, stromatolitic mounds, and volcano-shaped cones. The nearly 200 mapped fossil vent-associated deposits at Cerro Negro are on a geographical and numerical scale comparable with subaerial and sublacustrine hydrothermal vents at Mammoth Hot Springs, and affiliated with Yellowstone Lake, respectively. Overall, the Cerro Negro geothermal system yields paleoenvironmentally significant textural details of variable quality, owing to both the differential preservation potential of particular subaerial versus subaqueous facies, as well as to the timing and extent of carbonate diagenesis and silica replacement of some deposits. For example, the western fault associated with the Eureka epithermal quartz vein facilitated early silicification of the travertine deposits in the SE volcanic emission center, thereby preserving high-quality, microbial macro- and micro-textures of this silica-replaced "pseudosinter." Cerro Negro provides an opportunity to reconstruct paleogeographic, paleohydrologic and paleoenvironmental associations in a well-exposed, extensive and diverse fossil geothermal system. This Late Jurassic hydrothermal deposit will likely contribute to a better understanding of the impact of depositional and post-depositional history on the development and long-term preservation potential of Lagerstätte in epithermal settings and, more generally, in extreme environments of the geological record.

Guido, Diego M.; Campbell, Kathleen A.

2012-06-01

242

Sedimentology and palaeontology of upper Karoo aeolian strata (Early Jurassic) in the Tuli Basin, South Africa  

Microsoft Academic Search

The Karoo Supergroup in the Tuli Basin (South Africa) consists of a sedimentary sequence composed of four stratigraphic units, namely the Basal, Middle and Upper units, and Clarens Formation. The units were deposited in continental settings from approximately Late Carboniferous to Middle Jurassic. This paper focuses on the Clarens Formation, which was examined in terms of sedimentary facies and palaeo-environments

Emese M. Bordy; Octavian Catuneanu

2002-01-01

243

Mesosaurus Fossil Site  

NSDL National Science Digital Library

This article describes the occurrence and habits of Mesosaurus, a small marine reptile that lived during the late Carboniferous and early Permian periods, as seen at a site in Namibia. Topics include the distribution of Mesosaurus fossils in both African and South American rock formations (evidence of continental drift), the shallow sea habitats in which Mesosuarus existed 280 to 320 million years ago, and some of its postulated living habits.

244

Fossils 1: Fossils and Dinosaurs  

NSDL National Science Digital Library

In this lesson, students will understand what can be learned from fossils and in doing so, realize the difference between fact and theory. This lesson is the first of a two-part series on fossils. These lessons will go beyond naming dinosaurs and give students a broad understanding of how we know about the great beasts. They will start to acquire knowledge of the fossil record in preparation for learning about evolution and natural selection, concepts they will study in high school. This particular lesson focuses on what we have learned and can learn from fossils. In the first part, students will discuss what we know about horses. They will then do the same for a Stegosaurus. Another part of the lesson briefly covers how fossils are formed.

245

Extinction trajectories of benthic organisms across the Triassic–Jurassic boundary  

Microsoft Academic Search

We analysed diversity and abundance patterns of benthic organisms across the Triassic–Jurassic (T-J) boundary based on the Paleobiology Database (PBDB), which compiles palaeontological collection data on a global scale. While Sepkoski's [Sepkoski, J.J. Jr., 2002. A compendium of fossil marine animal genera. Bulletins of American Paleontology 363, 1–563] compendium on the stratigraphic ranges of marine animal genera suggests that the

Wolfgang Kiessling; Martin Aberhan; Benjamin Brenneis; Peter J. Wagner

2007-01-01

246

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

247

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

248

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

249

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

250

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.

251

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

SciTech Connect

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

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

1983-03-01

252

Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton  

SciTech Connect

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

van Houten, F.B.

1980-06-01

253

Upper Jurassic of east Texas, a stratigraphic sedimentologic reevaluation  

SciTech Connect

The Smackover-Haynesville of east Texas has long been modeled as a simple progradational carbonate-evaporite ramp. Recent data indicate that the conventional ramp model for this sequence should be abandoned in favor of an evolving rimmed shelf to platform model, forming in response to changes in rate of relative sea level rise during the Late Jurassic. Evidence for Smackover-Haynesville shelves include: (1) thick high-energy carbonates along the basin margin in the Smackover and throughout the Haynesville, (2) low-energy pellet-dominated lagoonal carbonates, evaporites, and evaporitic siliciclastics occurring landward of, and interfingering with, the Smackover and Haynesville basin-margin carbonate barriers, (3) deeper water, open-marine low-energy limestones with black shales seaward of the basin-margin barriers (Smackover-Gilmer undifferentiated), and (4) the Gilmer shale forms a siliciclastic wedge seaward of the Haynesville basin margin and its zero isopach defines the Kimmeridgian shelf margin. The Smackover and Haynesville seem to represent 2 distinct sedimentologic cycles, with each cycle reflecting an initial relative sea level rise during which a rimmed shelf and lagoon are developed, and a terminal sea level standstill during which the shelf evolved into a high-energy platform. Although these sedimentologic patterns seem compatible with accepted Jurassic sea level curves, they may also reflect differential basin-margin subsidence combined with variable carbonate production rates. Finally, the shelf-platform model more clearly defines future exploration strategies for Smackover-Haynesville targets in east Texas and perhaps across the Gulf of Mexico, if eustatic sea level changes were the dominant causative factor for shelf development in the Late Jurassic.

Moore, C.H.; McGillis, K.; Stewart, S.; Wilkinson, S.; Harwood, G.

1985-02-01

254

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

PubMed Central

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

Zinovyev, Evgeniy

2011-01-01

255

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

PubMed

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

Zinovyev, Evgeniy

2011-05-20

256

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

257

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

2013-02-20

258

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.

259

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

260

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

261

Jurassic Rhynchonellids: Internal Structures and Taxonomic Revisions.  

National Technical Information Service (NTIS)

Jurassic brachiopods of the order Rhynchonellida are classified according to modern concepts and techniques, with special attention to internal structures. They are grouped into 6 families and 16 subfamilies of which three are new: the Acanthorhynchiinae,...

X. Y. Shi R. E. Grant

1993-01-01

262

Middle–Upper Jurassic (Upper Callovian–Lower Kimmeridgian) stable isotope and elemental records of the Russian Platform: Indices of oceanographic and climatic changes  

NASA Astrophysics Data System (ADS)

New isotope (?18O, ?13C) and elemental (Mg/Ca, Sr/Ca) data of well-preserved belemnite rostra, ammonite and gastropod shells from the Middle Oxfordian–Lower Kimmerdgian (Densiplicatum–Kitchini zones) of the Russian Platform are presented. This record is supplemented with published data from the Upper Callovian–Lower Kimmeridgian interval (Athleta–Kitchini zones). Significant differences in average temperatures calculated from ?18O values of particular fossil groups (5–15 °C) show the thermal gradient and the presence of cold bottom waters in the Middle Russian Sea during the Late Callovian–Middle Oxfordian. An Upper Oxfordian–lowermost Kimmeridgian decrease in ?18O values and an increase in Sr/Ca ratios of cylindroteuthid belemnite rostra likely reflect a warming of the bottom waters of ca. 3.5 °C. The gradual Late Oxfordian–earliest Kimmeridgian warming is followed by an abrupt temperature rise of 3–6 °C that occurred at the transition of the Early Kimmeridgian Bauhini and Kitchini chrons.The occurrences of cold bottom waters and of (Sub)Mediterranean ammonites and belemnites in the Middle Russian Sea at the Middle–Late Jurassic transition are regarded as a result of the opening of seaways during a sea level highstand. The bottom waters are considered to have been formed in the cool Boreal Sea. The subsequent retreats of the cold bottom waters and of the (Sub)Mediterranean cephalopods from the Middle Russian Sea in the Late Oxfordian are explained by the restriction of water circulation during a sea-level fall. The Early Kimmeridgian rise of bottom temperatures of the sea is linked to a global climate warming. The data presented do not support a major cooling of the Arctic and a consequent glaciation in this region at the Middle–Late Jurassic transition. Since occurrences of cold water masses are diachronous in different European basins, the observed variations in sea water temperatures are interpreted as a result of changes in marine currents and water circulation.?13C values of belemnite rostra from the Russian Platform are scattered but show the long-term Upper Callovian–Middle Oxfordian positive excursion consistent with the previously published isotope records of the Boreal Realm and terrestrial organic matter.

Wierzbowski, Hubert; Rogov, Mikhail A.; Matyja, Bronis?aw A.; Kiselev, Dmitry; Ippolitov, Alexei

2013-08-01

263

Fossil Finds Expand Early Hominid Anatomy.  

ERIC Educational Resources Information Center

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

Bower, B.

1991-01-01

264

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

266

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.

267

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

PubMed

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

2005-03-22

268

The Fossil Record of Feather Evolution in the Mesozoic  

Microsoft Academic Search

SYNOPSIS. The oldest known feathers from the Late Jurassic are already modern in form and microscopic detail. Because these oldest examples are assignable to an extinct branch (Sauriurae) of the basal avian dichotomy, their features must have been established at a significantly earlier date. The skin of a wide variety of di- nosaurs is now known and is unlikely to

Larry D. Martin; Stephan A. Czerkas

2000-01-01

269

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

Microsoft Academic Search

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

Peter N. Johannessen

270

High-resolution ammonite and carbon isotope stratigraphy across the Triassic–Jurassic boundary at New York Canyon (Nevada)  

Microsoft Academic Search

The Triassic–Jurassic boundary is generally considered as one of the major extinctions in the history of Phanerozoic. The high-resolution ammonite correlations and carbon isotope marine record in the New York Canyon area allow to distinguish two negative carbon excursions across this boundary with different paleoenvironmental meanings. The Late Rhaetian negative excursion is related to the extinction and regressive phase. The

Jean Guex; Annachiara Bartolini; Viorel Atudorei; David Taylor

2004-01-01

271

Gas play opportunities in deeper Jurassic sequences of the Neuquen basin embayment, Argentina  

Microsoft Academic Search

We have defined new gas plays at around 4000 m depth near the giant Loma La Lata gas field. The plays, in lower Jurassic sandstones, were developed using a different approach in stratigraphic signatures as well as deformation styles. Two initial rifting stages led to the Triassic-Early Liassic volcanoclastic deposition (Precuyo s.l.) into a suite of discrete half-grabens. The late

F. Fernandez-Seveso; D. E. Figueroa; H. Rodriguez

1996-01-01

272

Facies and palaeoecology of Upper Jurassic (Middle Oxfordian) coral reefs in England  

Microsoft Academic Search

Summary  This study documents the facies and fauna of Late Jurassic (Middle Oxfordian) coral reefs in England. Sedimentological and\\u000a palaeoecological analysis of these reefs distinguishes three generic reef types: (1) small reef patches and thickets associated\\u000a with siliciclastic deposits; (2) small reef patches and thickets associated with siliciclastic-free bioclastic grainstones\\u000a and packstones; and (3) biostromal units associated with deep water facies.

Enzo Insalaco

1999-01-01

273

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

Microsoft Academic Search

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

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

1983-01-01

274

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

275

A review of polyphase karstification in extensional tectonic regimes: Jurassic and Cretaceous examples, Betic Cordillera, southern Spain  

Microsoft Academic Search

Five karstification phases are recognized and analysed in the Mesozoic carbonate sequences of the External and Internal Subbetic (Betic Cordilleras, southern Spain). These phases are related to important stratigraphic discontinuities in the following ages: (1) Intra-Carixian, (2) Early–Middle Jurassic boundary, (3) late Bathonian–early Callovian, (4) Intra-Kimmeridgian, and (6) late Albian. The importance of each karstification phase is variable according to

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

1999-01-01

276

Chondrites: A Trace Fossil Indicator of Anoxia in Sediments  

NASA Astrophysics Data System (ADS)

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 carbonate units throughout the geologic column, Chondrites typically represents the last trace fossil in a bioturbation sequence. This indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters.

Bromley, Richard G.; Ekdale, A. A.

1984-05-01

277

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

Microsoft Academic Search

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

Richard J. F. Jenkins

1995-01-01

278

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

279

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

280

Jurassic carbonate reservoirs of the Amu Darya Basin, Uzbekistan and Turkmenistan  

SciTech Connect

The Amu Darya Basin is a world class hydrocarbon province. Current reserves estimates are 220 TCF of gas and 800 MMbbl of oil and condensate, 50% of which is reservoired in Late Jurassic carbonates. Exploration opportunities still exist in large parts of the basin which are relatively undrilled. Within the 100-600m thick carbonate sequence, reservoir facies include reefs, shelf grainstones and turbidite fares. The major seal are Kimmeridgian - Tithonian evaporates which are up to 1600m thick in the basin centre. Stratigraphic trapping is common and often enhanced by structural modifications. The reservoirs are in communication with a major gas-prone Early-Middle Jurassic source rock. Oil-prone source rocks are thought to occur in basinal sediments which are coeval with the Late Jurassic reservoirs. Carbonate sedimentation commenced during the Late Jurassic with the development of a ramp complex. This evolved into a rimmed shelf with barrier and pinnacle reefs. Several cycles of relative sea-level change (largely eustatic?) influence the carbonate ramp/shelf systems and effect the distribution of reservoir facies. Numerous empirical observations by VNIGNI scientists on carbonate successions have enabled them to develop mathematically calculated indices for facies and reservoir prediction, which have been applied successfully in the Amu Darya Basin. Reservoir quality in the limestones is strongly controlled by primary facies. Reefs and shelf grainstones display the best reservoir characteristics. Whilst many facies have good total porosity, it is only the reef and grainstone belts where connected porosity (with pore throats greater than 10um) becomes effective. Burial cements are rare. Freshwater solution and cementation has often improved or preserved primary porosity.

Shein, V.S.; Fortunatova, N.K. [VNIGNI, Moscow (Russian Federation); Neilson, J.E. [Carbonate Reservoirs Ltd., Aberdeen (United Kingdom)] [and others

1995-08-01

281

Comparison of the Jurassic and Cretaceous sedimentary cycles of Somalia and Madagascar: implications for the Gondwana breakup  

NASA Astrophysics Data System (ADS)

The Jurassic and Cretaceous sedimentary history of northern Somalia and the Morondava Basin of south-western Madagascar have been studied. Both regions display an independent facial development; however, a comparison of the sequential evolution of the Mesozoic sedimentary successions in these two presently widely separated areas reveals a surprisingly high level of similarity, which probably reflects major events during the disintegration of Eastern Gondwana during the Jurassic and Cretaceous. Although in Jurassic times the onset of transgressions and regressions in both areas compares well with eustatic development, major deviations in combination with the tectonic activities of different degrees are observed in the Early and Late Cretaceous synchronously in both regions. Transgressions are observed in Toarcian, Bajocian (not dated in northern Somalia), Callovian, Valanginian (Madagascar only), Aptian and Campanian times. Tectonism is noted before the Aptian and Campanian transgressions in northern Somalia and the Morondava Basin of south-western Madagascar.

Luger, Peter; Gröschke, M.; Bussmann, M.; Dina, A.; Mette, W.; Uhmann, A.; Kallenbach, H.

1994-12-01

282

The conservation of A Jurassic Ichthyosaur  

Microsoft Academic Search

Examination of a Jurassic ichthyosaur, prepared for wall display in the nineteenth century and currently in storage in the National Museums and Galleries of Wales (NMGW), revealed extensive deterioration of the plaster mount caused by movement of the wooden frame. During the project to create a new stable support, it was found that the specimen had undergone significant reconstruction when

Caroline Buttler; Alison Stooshnov

2002-01-01

283

Tectonism and eustasy in the Jurassic  

Microsoft Academic Search

Intensive orogenic activity and vulcanicity during the Jurassic was largely confined to the circum-Pacific geosynclinal belt and the Caucasus-Crimea region of the Tethyan Belt. Notable vulcanicity also occurred within the stable shield regions of Africa, Australia and Antarctica. There was an increase of tectonic activity throughout the course of the period, reaching its climax at or near the close with

A. Hallam

1969-01-01

284

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…

Peacock, Alan

2007-01-01

285

Origin of the Pacific Jurassic quiet zone  

Microsoft Academic Search

Understanding the marine magnetic anomaly record is critical for constructing realistic geodynamo models of global geomagnetic field, polarity reversal mechanisms, and long-term geomagnetic field behavior. One of the least understood portions of the marine magnetic anomaly record is also the oldest part of the record, the Jurassic quiet zone (JQZ), where anomalies become weak and difficult to correlate. The reason

Maurice A. Tivey; William W. Sager; Sang-Mook Lee; Masako Tominaga

2006-01-01

286

Oldest fossil basidiomycete clamp connections  

Microsoft Academic Search

A rachis of the fossil filicalean fern Botryopteris antiqua containing abundant septate hyphae with clamp connections is preserved in a late Visean (Mississippian; ~330 Ma) chert from\\u000a Esnost (Autun Basin) in central France. Largely unbranched tubular hyphae pass from cell to cell, but may sometimes produce\\u000a a branch from a clamp connection. Other clamp-bearing hyphae occur clustered in individual cells or

Michael Krings; Nora Dotzler; Jean Galtier; Thomas N. Taylor

2011-01-01

287

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

2011-11-02

288

Paleotectonic controls on deposition of upper Upper Jurassic La Casita Formation, east-central Chihuahua, Mexico  

SciTech Connect

Surface mapping of the basal Mesozoic La Casita Formation (upper Upper Jurassic) in east-central Chihuahua, Mexico, indicates initial Mesozoic sedimentation occurred in a segmented, interconnected subbasin of the Chihuahua trough. La Casite Formation (1200 m thick) is a tectonostratigraphic unit resting with angular unconformity on the Lower Permian Plomosas Formation. It consists primarily of siliciclastic material with sporadic interbedded limestones. The dominant lithofacies, approximately 1000 m thick, consists of turbiditic sandstone units (10-20 m) alternating with thicker, monotonous shale sequences. In the mapped area (approximately 30 km/sup 2/), flute cast measurements indicate flows from both the northeast (N20/degree/E) and southwest (S58/degree/W). Turbiditic sandstone units appear to pinch out and/or interfinger as they extend from the north and south into the central portion of the area. The initial opening of the Chihuahua trough is often associated with Late Jurassic block faulting, related to development of the ancestral Gulf of Mexico. Synrift depositional sequences of a similar age have been described in southern Coahuila, northern Zacatecas, and western Chiapas, Mexico. The subbasin (graben ) examined here may be ascribed a paleoposition near the western edge of the early Chihuahua trough. The western boundary of the early trough may have comprised a series of these subbasins, forming a cuspate or serrated coastline. Late Jurassic ammonites recovered from this and other localities along the length of the Chihuahua trough suggest that the subbasins were interconnected by means of an eastern continuous seaway.

Roberts, D.C.

1989-03-01

289

Late Oxfordian to Late Kimmeridgian carbonate deposits of NW Switzerland (Swiss Jura): Stratigraphical and palaeogeographical implications in the transition area between the Paris Basin and the Tethys  

NASA Astrophysics Data System (ADS)

Geological sections of the shallow-water, carbonate-dominated sedimentary system of the Late Jurassic Reuchenette Formation in northwestern Switzerland have been studied between the southern Jura Mountains and the Tabular Jura. The largest sections show a characteristic cyclic stacking pattern. Up to now, the age of these sediments (including the type-section) linking the Boreal and Tethyan realms, was biostratigraphically poorly constrained. In the Tabular Jura five 3rd order sequences can be assigned to the Planula- to Eudoxus-Zone (Late Oxfordian to Late Kimmeridgian) using index-fossils (ammonites and ostracodes; [Jank M., 2004, New insights into the development of the Late Jurassic Reuchenette Formation of NW Switzerland (Late Oxfordian to Late Kimmeridgian, Jura Mountains). Dissertationen aus dem Geologisch-Paläontologischen Institut der Universität Basel, 32, 121 pp.]). This time control and several new outcrops, in combination with mineralostratigraphical and lithological marker beds, allow the correlation and dating of the thickest sections of the Reuchenette Formation and thus serve to improve the previously estimated ages of their sequence boundaries. The variability of stacking pattern and facies between sections also reveals distinctive changes in facies evolution, related to Late Palaeozoic basement structures and synsedimentary subsidence. These structures acted as important controlling factors for the sediment distribution of the Reuchenette Formation besides the sea level fluctuations. The interplay of sea level changes and synsedimentary subsidence is outlined by lateral thickness variations and shifting depositional environments. A close examination of these changes also sheds much light on the nature of platform topography in the transition area between the Paris Basin in the north and the Tethys in the south, or more generally between the Boreal and Tethyan realms. During the Planula- to Divisum-time-intervals the study area was a flat platform with a more or less uniform facies distribution, which connected the above-mentioned realms. During the Divisum-to Acanthicum-time-intervals this platform changed into a pronounced basin-and-swell morpoholgy, with specific depositional environments and “separated” the Paris Basin from the Tethys.

Jank, Markus; Meyer, Christian A.; Wetzel, Andreas

2006-05-01

290

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

PubMed Central

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.

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

2010-01-01

291

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

NASA Astrophysics Data System (ADS)

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

Bretshtein, Yu. S.

2009-06-01

292

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

293

Paleoenvironments of the Jurassic and Cretaceous Oceans: Selected Highlights  

NASA Astrophysics Data System (ADS)

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

Ogg, J. G.

2007-12-01

294

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

295

Pelahatchie: the geologist's Jurassic problem child  

Microsoft Academic Search

An unusually high-pressure oil well was tested from the Norphlet sand of Jurassic age in Rankin County, Miss. This 17,000-ft well had been drilled in the same 40-acre tract as the original Lower Cretaceous discovery well of Pelahatchie field. This field is situated in the updip belt of Lower Cretaceous oil production and in the downdip belt of Smackover production.

Karges

1968-01-01

296

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

USGS Publications Warehouse

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

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

2011-01-01

297

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.

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

2011-01-01

298

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

PubMed

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

2011-04-20

299

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

300

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

301

Non-destructive multiple approaches to interpret the preservation of plant fossils: implications for calcium-rich permineralizations  

Microsoft Academic Search

Permineralized fossil coniferous woods from the Pliocene of Dunarobba, Umbria, Italy, and the Jurassic of Swindon, Wiltshire, England, were studied using non-destructive techniques on uncoated polished thin sections to elucidate their preservational history. Specimens were observed using transmitted light, polarized light, reflected light under oil, and cathodoluminescence. Selected areas were studied using a variable pressure SEM in backscattered electron mode.

ANDREW C. S COTT; E. C OLLINSON

302

Dolomitization patterns in Jurassic-Cretaceous dissolution-collapse breccias of Mainalon Mountain (Tripolis Unit, Central Peloponnesus-Greece)  

Microsoft Academic Search

Along the Jurassic-Cretaceous dolomitic beds of the Tripolis Unit in the Mainalon Mt. and the surrounding areas, products\\u000a of a widespread breccias have been recognized. This brecciation extended through at least two stages, early- and late diagenetic,\\u000a respectively. The first brecciation stage is considered to have taken place penecontemporaneously or soon after the deposition\\u000a related with desiccation processes and\\/or small-scale

Fonti Pomoni Papaioanou; Zafiris Carotsieris

1993-01-01

303

Black shales on the basin margin: a model based on examples from the Upper Jurassic of the Boulonnais, northern France  

Microsoft Academic Search

Organic-rich shales were deposited during two phases of relative sea-level rise in the Kimmeridgian (Late Jurassic) basin margin sections of the Boulonnais (N. France). Pyrite framboid analysis indicates that bottom waters were euxinic during substantial periods of organic-rich shale formation, and Th\\/U ratios and degree of pyritisation of Fe suggest severe oxygen-restriction, whilst palaeoecological and sedimentological evidence suggests that seafloor

P. B Wignall; R Newton

2001-01-01

304

Mesozoic sequence of Fuerteventura (Canary Islands): Witness of Early Jurassic sea-floor spreading in the central Atlantic  

Microsoft Academic Search

The Fuerteventura Jurassic sedimentary succession consists of oceanic and clastic de- posits, the latter derived from the southwest- ern Moroccan continental margin. Normal mid-oceanic-ridge basalt (N-MORB) flows and breccias are found at the base of the se- quence and witness sea-floor spreading events in the central Atlantic. These basalts were ex- truded in a postrift environment (post-late Pliensbachian). We propose

Christian Steiner; Alice Hobson; Philippe Favre; Gérard M. Stampfli; Jean Hernandez

1998-01-01

305

Great Jurassic thrust sheets in Beishan (North Mountains)—Gobi areas of China and southern Mongolia  

NASA Astrophysics Data System (ADS)

Jurassic thrust sheets with minimum displacements of 120 180 km have been discovered within the ‘Hercynian-Indosinian’ orogenic belt of the Beishan of China and south Gobi area. The thrusts strike E-W, extend over 1200 km in length, and carried Meso-Proterozoic massive dolomitic limestones over strata ranging from NeoProterozoic (Cryogenian and Terminal Proterozoic) to Lower-Middle Jurassic. Slip-linear plots based on kinematic indicators, such as slickenlines and groove lineations, fiber lineations and ‘drag folds’ adjacent to the fault surface, vergence of folds and imbricated thrusts in the upper plate, indicate northward movement in the Beishan area to the west and southward movement in the South Gobi area to the east. The two major thrust faults, the Beishan thrust and South Gobi thrust, are presumably separated by a major tear fault, the Ruo Shui fault. The major thrust faults were later deformed into a series of E-W antiforms and synforms and the sheets are separated, due to erosion, into a number of klippen mainly located on synforms of the major faults. The Yagan metamorphic core complex, which is a result of an extensional event that postdates the thrust event, yields an40Ar-39Ar plateau age of 155.1 +- 10 Ma, and RbSr isochron age of 153 +- 6.2 Ma. The thrust sheets formed during the late Middle Jurassic, long after the closure of any oceans in the study area previously reported for this region, and are ascribed to a phase of intracontinental deformation. The closing of the Jurassic Tethys or retroarc deformation behind an active continental margin at the southern edge of Asia, prior to the Tethyan collision, or/and the closing of Mongolo-Okhotsk oceans might be responsible for this event.

Zheng, Y.; Zhang, Q.; Wang, Y.; Liu, R.; Wang, S. G.

1996-09-01

306

Theropod Fossil Hunt Dispatch  

NSDL National Science Digital Library

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

307

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

Microsoft Academic Search

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

Cajus Diedrich

2011-01-01

308

Reevaluation of upper Jurassic Morrison Formation, Western Interior  

Microsoft Academic Search

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

Mantzios

1989-01-01

309

A New Interpretation of the Oldest Fossil Bee (Hymenoptera: Apidae)  

Microsoft Academic Search

The oldest fossil bee, '' Trigona'' prisca (Apidae: Meliponini), in Late Cretaceous (Maas- trichtian) amber from New Jersey, is redescribed and figured. Differences between T. prisca and extant Trigona are noted and the fossil is transferred into a new genus, Cretotrigona. An exploratory cladistic analysis of the Meliponini is undertaken and Cretotrigona supported as sister to the African genus Dactylurina.

MICHAEL S. ENGEL

2000-01-01

310

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

311

Is It a Fossil?  

NSDL National Science Digital Library

This formative assessment item is used to uncover students' ideas about fossils before a lesson has begun. Students will determine whether examples are fossils, and what sort of inferences can be made about prior environments because of fossils. This probe is aligned with the National Science Education Standards. Resources are provided along with instructional suggestions.

Fries-Gaither, Jessica

312

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

PubMed Central

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

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

2011-01-01

313

The Jurassic of Denmark and Greenland: key elements in the reconstruction of the North Atlantic Jurassic rift system  

Microsoft Academic Search

The Jurassic succession of Denmark is largely confined to the subsurface with the exception of exposures on the island of Bornholm in the Baltic Sea. In East Greenland, in contrast, the Jurassic is extensively exposed. Comparison of basin evolution in the two regions, which now occur on two separate plates, thus relies on highly different datasets. It is possible nevertheless

Finn Surlyk; Jon R. Ineson

2003-01-01

314

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

315

Fossils of Kentucky  

NSDL National Science Digital Library

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

316

Types of Fossils  

NSDL National Science Digital Library

The word fossil, derived from a Latin word meaning 'something dug up', refers to the preserved remains or traces of ancient life. Careful study of these remains can answer questions about life and evolution, and provide information about the history of Earth itself; for example, revealing that a tropical sea was present where only a desert exists today. This interactive feature explores the kinds of things we can learn from several types of fossils that scientists study. Viewers can see examples of body fossils (shells, bones, etc.), trace fossils (tracks, burrows, etc.), and an example of a fossil which has attributes of both.

317

Fossil-energy program  

NASA Astrophysics Data System (ADS)

The increased utilization of coal and other fossil fuel alternatives as sources of clean energy is reported. The projects reported include: coal conversion development, chemical research and development, materials technology, component development and process evaluation, technical support to major liquefaction, process analysis and engineering evaluations, fossil energy environmental analysis, environmental control technology, coal preparation waste utilization, atmospheric fluidized bed coal combustor for cogeneration, TVA FBC demonstration plant program technical support, PFBC systems analysis, FBC char utilization improvement, fossil fuel applications assessments, performance assurance system support for fossil energy projects, international energy technology, generalized equilibrium models for liquid and gaseous fuel supplies, instrumentations and controls and fossil energy information center.

McNeese, L. E.

1982-01-01

318

Upper Triassic-Lower Jurassic salt basin southeast of the Grand Banks  

NASA Astrophysics Data System (ADS)

A grid of multichannel seismic reflection (MCS) profiles has been used to delineate and map a large, apparently tectonically controlled basin and associated diapiric province beneath the continental slope and rise southeast of the Grand Banks of Newfoundland. The depocenter, for which we propose the name Salar basin, is defined both landward and seaward by pronounced hinges in acoustic basement. It is approximately 400 km long, 35-70 km wide, and covers an area of approximately 20,000 km2. The southern end of the basin is marked by the intersection of the Southeast Newfoundland Ridge with the South Bank High on the Grand Banks, and the northern end is bounded by the southwestern margin of Flemish Cap. The Salar basin generally parallels the much smaller Carson basin, which lies beneath the Grand Banks immediately to the west, and it merges with this basin north of 45°22'N. Based upon correlation with contiguous deposits sampled by drilling in the Carson basin, we infer piercements filling the Salar basin to be mobilized Late Triassic-Early Jurassic evaporites, probably predominantly halite. A consequent early Mesozoic age for the Salar basin implies a multi-stage rifting history for the Newfoundland Basin, as has been documented for the adjacent Grand Banks. Initial extension, which probably formed the Salar basin's bounding basement hinge zones, occurred in Late Triassic-Early Jurassic time, and was associated with rifting of North America from Africa and extension in western Europe. The presence of early Mesozoic evaporites in a basin southeast of the Grand Banks suggests development of a significant, but shallow and restricted, seaway between the Grand Banks and the Iberian peninsula, probably connected northward with coeval salt provinces of northwestern Europe. A second rift phase related to separation of Iberia and the Grand Banks affected the Grand Banks and Salar basin in Late Jurassic to Early Cretaceous time, after a period of epeirogenic subsidence during the Early and Middle Jurassic. Uplift associated with this extension led to the development of the widespread ``U'' (Avalon) unconformity across the Grand Banks, the Salar basin and the Newfoundland Basin out to the J-Anomaly and may have induced the first halokinesis in the Salar basin. The second rift phase culminated in the initiation of seafloor spreading in mid-Early Cretaceous (Aptian) time at a location now marked by the J-Anomaly.

Austin, James A.; Tucholke, Brian E.; Uchupi, Elazar

1989-04-01

319

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

PubMed Central

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

Clapham, Matthew E.; Bottjer, David J.

2007-01-01

320

Kinematics of Jurassic ultra-slow spreading in the Piemonte Ligurian ocean  

NASA Astrophysics Data System (ADS)

The geological record of the western and northern Mediterranean region (Apennines, Alps, Carpathians) contains relics of an ocean basin of Jurassic age known as the Piemonte-Ligurian (PL), Alpine or Alpine Tethys ocean. We here reconstruct the age, direction and amount of extension in the PL basin by analyzing the differences in spreading rates based on marine magnetic anomalies and fracture zones in the Central Atlantic ocean between Africa and North America, and the North Atlantic Ocean between Iberia and North America. The difference in spreading rate must have been accommodated between Iberia and Adria, which we assume to be rigidly attached to the African plate in the late Jurassic. We compute a maximum of ˜450 km of WSW-ENE extension between Iberia and Africa, largely between ˜170 and ˜150 Ma. Relative Adria (Africa)-Europe motion predicts up to 670 km of extension at the longitude of the western Alps - distributed over the PL and Valaisan basins - decreasing to ˜315 km along the easternmost boundary of the PL basin formed by the Tornquist-Tesseyre line. We note that the Africa-Europe plate boundary in the late Jurassic was probably not discretely localized along the Tornquist-Tesseyre line, but distributed over several fault zones including the Severin oceanic basin to the west of the Moesian platform; the 315 km of PL extension in the east should hence be considered a maximum. It is unknown to what extent PL extension was accommodated by genuine ocean spreading, but full spreading rates in the western PL basin were slow, no more than 20 mm/yr. This ultraslow spreading is consistent with characteristics of western Mediterranean ophiolites, including exposure of upper mantle rocks at the sea floor, the alternation of volcanic and avolcanic segments, and the petrologic features of the pertinent magmas and peridotites.

Vissers, Reinoud L. M.; van Hinsbergen, Douwe J. J.; Meijer, Paul Th.; Piccardo, Giovanni B.

2013-10-01

321

Systematic Palaeontology (Vertebrate Palaeontology) A basal sauropod dinosaur from the Early Jurassic of Morocco  

Microsoft Academic Search

Continental strata of Early Jurassic age are seldom exposed, and little is known of the history of sauropod dinosaurs prior to the Middle Jurassic radiation of neosauropods. Well-preserved skeletons and skulls have not been recovered from strata older than the Middle Jurassic. Here we report, in the Early Jurassic of the Moroccan High Atlas, the discovery of the skeleton, including

Ronan Allain; Najat Aquesbi; Jean Dejax; Christian Meyer; Michel Monbaron; Christian Montenat; Philippe Richir; Mohammed Rochdy; Dale Russell; Philippe Taquet

322

U/Pb zircon and baddeleyite ages for the Palisades and Gettysburg sills of the northeastern United States: Implications for the age of the Triassic/Jurassic boundary  

NASA Astrophysics Data System (ADS)

Zircons extracted from the Palisades and Gettysburg sills and baddeleyite from the Palisades sill yield consistent U-Pb ages of 201 ±1 Ma. These sills are likely related to the lowermost basalt flows of the Late Triassic-Early Jurassic Newark Supergroup rift basins of the eastern margin of North America (because of the geochemical similarity of their high-Ti quartz tholeiites and because drilling suggests that the Palisades sill directly fed some of the lowermost flows). Because the lowermost flows of the Newark Supergroup are paleonto-logically assigned to the lowermost Hettangian, the 201 ±1 Ma age of the sills should be slightly younger than the age of the Triassic/Jurassic boundary. Our data support the age of 204 ±4 Ma assigned the Triassic/Jurassic boundary and suggest that recent K-Ar dating for the Hettangian flows of the Newark Supergroup, which yielded an average age of 190 ±3 Ma, is about 5% low.

Dunning, G. R.; Hodych, J. P.

1990-08-01

323

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

PubMed Central

Background A new dinosaur tracksite from ?Middle Jurassic sediments of the Irhazer Group on the plains of Agadez (Rep. Niger, northwest Africa) revealed extraordinarily well preserved didactyl tracks of a digitigrade bipedal trackmaker. The distinct morphology of the pes imprints indicates a theropod trackmaker from a paravian maniraptoran closely related to birds. Methodology/Principal Findings The early age and the morphological traits of the tracks allow for description of the new ichnotaxon Paravipus didactyloides. A total of 120 tracks are assigned to 5 individual trackways. The ‘medium-sized’ tracks with an average footprint length of 27.5 cm and footprint width of 23.1 cm are deeply imprinted into the track bearing sandstone. Conclusions/Significance A comparison with other didactyl tracks gives new insights into the foot morphology of advanced maniraptoran theropods and contributes to knowledge of their evolutionary history. The new ichnotaxon takes an important position in the ichnological fossil record of Gondwana and the mid-Jurassic biota worldwide, because it is among the earliest known records of paravian maniraptorans and of didactyl theropod tracks from Africa.

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

2011-01-01

324

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

325

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

NASA Astrophysics Data System (ADS)

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

Sewall, Jacob O.; Fricke, Henry C.

2013-01-01

326

High resolution stratigraphy of the Jurassic-Cretaceous boundary interval in the Gresten Klippenbelt (Austria)  

NASA Astrophysics Data System (ADS)

The key objective of investigation of hemipelagic sediments from the Gresten Klippenbelt (Blassenstein Formation, Ultrahelvetic paleogeographic realm) was to shed light on environmental changes around the Jurassic-Cretaceous (J/K) boundary on the northern margin of the Penninic Ocean. This boundary is well exposed in a newly discovered site at Nutzhof. Around the critical interval including the boundary, this new outcrop bears a rich microplanktonic assemblage characterized by typical J/K (Tithonian/Berriasian) boundary faunas. The Nutzhof section is located in the Gresten Klippenbelt (Lower Austria) tectonically wedged into the deep-water sediments of the Rhenodanubian Flysch Zone. In Late Jurassic-Early Cretaceous time the Penninic Ocean was a side tract of the proto-North Atlantic Oceanic System, intercalated between the European and the Austroalpine plates. Its opening started during the Early Jurassic, induced by sea floor spreading, followed by Jurassic-Early Cretaceous deepening of the depositional area of the Gresten Klippenbelt. These tectonically induced paleogeographic changes are mirrored in the lithology and microfauna that record a deepening of the depositional environment from Tithonian to Berriasian sediments of the Blassenstein Formation at Nutzhof. The main lithological change is observed in the Upper Tithonian Crassicollaria Zone, in Chron M20N, whereas the J/K boundary can be precisely fixed at the Crassicollaria-Calpionella boundary, within Chron M19n.2n. The lithological turnover of the deposition from more siliciclastic pelagic marl-limestone cycles into deep-water pelagic limestones is correlated with the deepening of the southern edge of the European continent at this time. Within the Gresten Klippenbelt Unit, this transition is reflected by the lithostratigraphic boundary between siliciclastic-bearing marl-limestone sedimentation in the uppermost Jurassic and lowermost Cretaceous limestone formation, both within the Blassenstein Formation. The cephalopod fauna (ammonites, belemnites, aptychi) and crinoids from the Blassenstein Formation, correlated with calcareous microfossil and nannofossil data combined with isotope and paleomagnetic data, indicate the Tithonian to middle Berriasian (Hybonoticeras hybonotum Zone up to the Subthurmannia occitanica Zone; M17r-M21r). The succession of the Nutzhof section thus represents deposition of a duration of approximately 7 Myr (ca. 150-143 Ma). The deposition of the limestone, marly limestone and marls in this interval occurred during tectonically unstable conditions reflected by common allodapic material. Along with the integrated biostratigraphic, geochemical and isotopic analysis, the susceptibility and gamma-ray measurements were powerful stratigraphic tools and important for the interpretation of the paleogeographic setting. Two reverse magneto-subzones, Kysuca and Brodno, were detected within magnetozones M20n and M19n, respectively.

Lukeneder, Alexander; Halásová, Eva; Kroh, Andreas; Mayrhofer, Susanne; Pruner, Petr; Reháková, Daniela; Schnabl, Petr; Sprovieri, Mario; Wagreich, Michael

2010-10-01

327

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

2013-05-29

328

Geology, fossil fuel potential and environmental concerns of the Caspian Sea  

Microsoft Academic Search

The fossil fuel producing areas of the Caspian region consists primarily of two basins, the Precaspian and South Caspian basins, both containing sediments in excess of 20km. The South Caspian Basin, a remnant of Tethys, was formed commencing in the Early-Middle Jurassic as a result of opening of back-arc basins behind volcanic arcs. The PreCaspian Basin extends onshore onto Kazakhstan

P. Rabinowitz; M. Yusifov; J. Arnoldi

2003-01-01

329

Morphological variation in fossil crayfish of the Jehol biota, Liaoning Province, China and its texonomic discrimination  

Microsoft Academic Search

Twelve morphological characteristics in 61 fossil crayfish specimens, which came from the Upper Jurassic Yixian Formation,\\u000a are discussed respectively in the present paper. A study of these new and better preserved materials allows us to add to and\\u000a revise the original description for Family Cricoidoscelosidae. In our collection, no modifications of the second pleopod of\\u000a the males have yet been

Yanbin Shen; Frederick R. Schram; Rod S. Taylor

2001-01-01

330

Occurrence of fossil organic matter in modern environments: Optical, geochemical and isotopic evidence  

Microsoft Academic Search

This study relates to the input and fate of fossil organic matter (FOM) in the modern environment, and focuses on two experimental watersheds overlying Jurassic marls: Le Laval and Le Brusquet (1km2 in area), located near Digne, Alpes-de-Haute-Provence, France. Considering that FOM delivery is mainly a result of different processes affecting sedimentary rocks [(bio)chemical and mechanical weathering], samples from different

Y. Graz; C. Di-Giovanni; Y. Copard; M. Elie; P. Faure; F. Laggoun Defarge; J. Lévèque; R. Michels; J. E. Olivier

2011-01-01

331

Middle Jurassic Radiolaria from a siliceous argillite block in a structural melange zone near Viqueque, Timor Leste: Paleogeographic implications  

NASA Astrophysics Data System (ADS)

Thin-bedded siliceous argillite forming a large block within a structural melange zone at Viqueque, Timor Leste, has yielded a Middle Jurassic (late Bathonian–early Callovian) radiolarian assemblage belonging to Unitary Association Zone 7. Fifty-five species are recognized and illustrated, forming the most diverse radiolarian fauna yet documented from the Jurassic of Timor. The fauna shows little similarity in species content to the few other assemblages previously listed from the Middle or Late Jurassic of Timor, and also has few species in common with faunas known elsewhere in the region from Rotti, Sumatra, South Kalimantan, and Sula. Based on lithofacies similarities and age, the siliceous argillite succession in the melange block at Viqueque is included in the Noni Group originally described as the lower part of the Palelo Series in West Timor. In terms of lithofacies, the Noni Group is distinct from other stratigraphic units known in Timor. It may be associated with volcanic rocks but age relationships are uncertain, although some of the radiolarian cherts in the Noni Group in West Timor have been reported to include tuffaceous sediment. The deep-water character of the siliceous hemipelagite-pelagite facies, the probable volcanic association, and an age close to that of continental breakup in the region suggest deposition in a newly rifted Indian Ocean. In Timor's tectonostratigraphic classification scheme, the Noni Group is here placed in the "Indian Ocean Megasequence".

Haig, David W.; Bandini, Alexandre Nicolas

2013-10-01

332

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

USGS Publications Warehouse

The presence of Cretaceous detrital zircon in Upper Jurassic strata of the Great Valley Group may require revision of the lower Great Valley Group chronostratigraphy, with significant implications for the Late Jurassic-Cretaceous evolution of the continental margin. Samples (n = 7) collected from 100 km along strike in the purported Tithonian strata of the Great Valley Group contain 20 Cretaceous detrital zircon grains, based on sensitive high-resolution ion microprobe age determinations. These results suggest that Great Valley Group deposition was largely Cretaceous, creating a discrepancy between biostratigraphy based on Buchia zones and chronostratigraphy based on radiometric age dates. These results extend the duration of the Great Valley Group basal unconformity, providing temporal separation between Great Valley forearc deposition and creation of the Coast Range Ophiolite. If Great Valley forearc deposition began in Cretaceous time, then sediment by passed the developing forearc in the Late Jurassic, or the Franciscan subduction system did not fully develop until Cretaceous time. In addition to these constraints on the timing of deposition, pre-Mesozoic detrital zircon age signatures indicate that the Great Valley Group was linked to North America from its inception. ?? 2006 Geological Society of America.

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

2006-01-01

333

Tiny Fossil Sheds Light on Mammalian Evolution  

NSDL National Science Digital Library

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

De Nie, Michael W.

2001-01-01

334

Black shales of Jurassic Newark basin  

SciTech Connect

Rock cores have exposed the complete Jurassic section of the Newark basin, including three sedimentary formations of fluvial origin. Within the Feltville, Towaco, and Boonton formations, 16 lacustrine/fan units range in thickness from 1 to 15 m. Each unit contains one black shale facies, although lower units of the Towaco contain multiple fining-upward sequences ending with truncated deep-water shale. Additional thinner gray sandstone facies in each formation occur at the margin of lacustrine units located farther southwest, in the paleodrainage direction of the Newark basin. Most microlaminated black shale shows evidence of turbidity flows. Freshly broken pieces of black shale and adjacent sandstones also have a strong organic odor.

Fedosh, M.S.

1986-05-01

335

Origin of the Pacific Jurassic quiet zone  

NASA Astrophysics Data System (ADS)

Understanding the marine magnetic anomaly record is critical for constructing realistic geodynamo models of global geomagnetic field, polarity reversal mechanisms, and long-term geomagnetic field behavior. One of the least understood portions of the marine magnetic anomaly record is also the oldest part of the record, the Jurassic quiet zone (JQZ), where anomalies become weak and difficult to correlate. The reason for the existence of the JQZ is unclear. It has been suggested that the JQZ is a true polarity superchron, similar to the Cretaceous normal superchron. Continental magnetostratigraphic studies have suggested that the JQZ is a period of rapid polarity reversal, of low field intensity, or both. We show results of a deep-tow survey of Pacific Jurassic crust that confirms the existence of magnetic anomalies within the JQZ. We tie Ocean Drilling Program Hole 801C (167.4 Ma) into the record and show that seafloor-spreading magnetic anomalies are present around the hole and extend to 170 Ma crust. We find a rise in reversal rate with increasing age with reversal rates over 10 rev/m.y. at 160 Ma and at 167 Ma. Anomaly amplitudes decrease in the record from 155 Ma until 162 Ma, where low-amplitude anomalies are difficult to correlate. Prior to 167 Ma, anomalies regain amplitude and remain strong until the end of our record at 170 Ma. The JQZ thus appears to be a combination of low-amplitude magnetic anomalies combined with rapid field fluctuations, which could be due to either intensity or polarity changes.

Tivey, Maurice A.; Sager, William W.; Lee, Sang-Mook; Tominaga, Masako

2006-09-01

336

Fossil Shapes Extension Activity  

NSDL National Science Digital Library

In this activity students view photographs of 12 fossils and try to draw pictures of what the organisms looked like while they were alive. They then slice up fruit in various ways to get an idea of the difficulty of identifying an organism when only some of the hard parts may be exposed along a bedding surface, making it difficult to determine the true shape of the fossil, let alone the organism the fossil represents.

Greb, Stephen

337

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

338

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.

339

The Primate Fossil Record  

NASA Astrophysics Data System (ADS)

The Primate Fossil Record is a profusely illustrated, up-to-date, and comprehensive treatment of primate paleontology that captures the complete history of the discovery and interpretation of primate fossils. Each chapter emphasizes three key components of the record of primate evolution: history of discovery, taxonomy of the fossils, and evolution of the adaptive radiations they represent. The volume objectively summarizes the many intellectual debates surrounding the fossil record and provides a foundation of reference information on the last two decades of astounding discoveries and worldwide field research for physical anthropologists, paleontologists, and evolutionary biologists.

Hartwig, Walter Carl

2002-05-01

340

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.

341

Downhole magnetic measurements of ODP Hole 801C: Implications for Pacific oceanic crust and magnetic field behavior in the Middle Jurassic  

NASA Astrophysics Data System (ADS)

Downhole horizontal and vertical magnetic field measurements within the 474 m thick Jurassic crustal section drilled at ODP Hole 801C in the western Pacific show anomalies that are "in phase," indicating that this site formed in the southern hemisphere and moved across the paleoequator to its present location at 18.6°N. The inclination computed from the horizontal and vertical anomaly logging data varies significantly downhole and can be explained by progressive rotation of the lava sequence as it is buried during accretion. This is compatible with the observed dips in the Formation Micro Scanner (FMS) data, which show up to 42° of rotation toward the fossil spreading axis. We restore the magnetic inclination to prerotated values and obtain an estimated pretilt inclination of 39.9° ± 6.6°, corresponding to a paleolatitude of 22.7° ± 5°S. The magnetic logging data document six polarity units within the drilled volcanic extrusive crust. The upper 132 m thick logged section of lavas contains four polarity units, which apparently formed 7 Myr after the formation of the underlying basement. The lower 212 m logged section of the hole is reversely magnetized with an intervening normal polarity zone. More than one reversal downhole would indicate a rapid reversal rate given the time it takes to form the extrusive section of oceanic crust: ˜45,000 years at a fast spreading rate of 66 km/Myr. Previous results from a contemporaneous section in Spain suggest rapid reversals throughout the late Bajocian-early Bathonian Stage (170-165 Ma). Nevertheless, the complicated formation history prevents quantification of the geomagnetic reversal rate for the 801C crustal section.

Tivey, Maurice; Larson, Roger; Schouten, Hans; Pockalny, Rob

2005-04-01

342

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.

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

2013-01-01

343

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

344

Fossil Dig Site  

NSDL National Science Digital Library

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

Museum, Chicago C.

2011-01-01

345

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

346

Becoming a Fossil  

NSDL National Science Digital Library

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

2005-01-01

347

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

348

Trace Fossil Image Database  

NSDL National Science Digital Library

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

Martin, Anthony; University, Emory

349

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

350

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

NASA Astrophysics Data System (ADS)

A review of the prebreakup geology of west central Pangea, comprising northern South America, the Gulf of Mexico, and West Africa, combined with a study of the Mesozoic rift trends of the region confirms a relation between the rift systems and the underlying older grain of deformation. The prebreakup analysis focuses attention on the Precambrian, early Paleozoic, and late Paleozoic tectonic events affecting the region and assumes a Pindell fit. Two late Precambrian orogenic belts are observed in west central Pangea. Along the northern South American margin and Yucatan a paleo northeast trending Pan-African aged fold belt is documented. A second system is observed along West Africa extending from the High Atlas to the Mauritanides and Rockelides. Similar aged orogenies in the Appalachians are compared. During the late Paleozoic, renewed orogenic activity, associated with the Gondwana-Laurentia suture, affected large segments of west central Pangea. The general trend of the system is northeast-southwest and essentially parallels the Guayana craton and West African and eastern North American cratons. Mesozoic rifling closely followed either the Precambrian trends or the late Paleozoic orogenic belt. The Triassic component focused along the western portions of the Gulf of Mexico continuing into eastern Mexico and western South America. The Jurassic rift trend followed along the separation between Yucatan and northern South America. At Lake Maracaibo the Jurassic rift system eventually overlaps the Triassic rifts. The Jurassic rift resulted in the "Hispanic Corridor" that permitted Tethyan and Pacific marine faunas to mix at a time when the Gulf of Mexico underwent continental sedimentation.

Bartok, Peter

1993-01-01

351

Fossil energy program  

NASA Astrophysics Data System (ADS)

Research and development programs in support of the increased utilization of coal and other fossil fuel alternatives as sources of clean energy are reported. The following projects are reported: coal conversion development, chemical research and development, materials technology, component development and process evaluation, technical support to major liquefaction, process analysis and engineering evaluations, fossil energy environmental analysis, environmental control technology, coal preparation waste utilization, atmospheric fluidized bed coal combustor for cogeneration, TVA FBC demonstration plant program technical support, PFBC systems analysis, FBC char utilization improvement, fossil fuel applications assessments, performance assurance system support for fossil energy projects, international energy technology, generalized equilibrium models for liquid and gaseous fuel supplies, analysis of coal production, and fossil energy information center.

McNeese, L. E.

1981-12-01

352

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

PubMed Central

The Triassic–Jurassic boundary (Tr–J; ?201 Ma) is marked by a doubling in the concentration of atmospheric CO2, rising temperatures, and ecosystem instability. This appears to have been driven by a major perturbation in the global carbon cycle due to massive volcanism in the Central Atlantic Magmatic Province. It is hypothesized that this volcanism also likely delivered sulphur dioxide (SO2) to the atmosphere. The role that SO2 may have played in leading to ecosystem instability at the time has not received much attention. To date, little direct evidence has been presented from the fossil record capable of implicating SO2 as a cause of plant extinctions at this time. In order to address this, we performed a physiognomic leaf analysis on well-preserved fossil leaves, including Ginkgoales, bennettites, and conifers from nine plant beds that span the Tr–J boundary at Astartekløft, East Greenland. The physiognomic responses of fossil taxa were compared to the leaf size and shape variations observed in nearest living equivalent taxa exposed to simulated palaeoatmospheric treatments in controlled environment chambers. The modern taxa showed a statistically significant increase in leaf roundness when fumigated with SO2. A similar increase in leaf roundness was also observed in the Tr–J fossil taxa immediately prior to a sudden decrease in their relative abundances at Astartekløft. This research reveals that increases in atmospheric SO2 can likely be traced in the fossil record by analyzing physiognomic changes in fossil leaves. A pattern of relative abundance decline following increased leaf roundness for all six fossil taxa investigated supports the hypothesis that SO2 had a significant role in Tr–J plant extinctions. This finding highlights that the role of SO2 in plant biodiversity declines across other major geological boundaries coinciding with global scale volcanism should be further explored using leaf physiognomy.

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

2013-01-01

353

The fossil pollen record of Araceae  

Microsoft Academic Search

The fossil record of Araceae pollen beginning in the late Early Cretaceous and peaking in the Paleocene\\/Eocene is very sparse\\u000a up to now, consisting of three highly distinctive types: zona-aperturate pollen of the Monstera or Gonatopus type (very similar to Proxapertites operculatus), an ulcerate-spiny type typical for Limnobiophyllum, and a polyplicate, omniaperturate pollen type (an ephedroid pollen with non-gnetalean affinities)

M. Hesse; R. Zetter

2007-01-01

354

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

PubMed

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. PMID:20711558

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

2010-08-14

355

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

356

Fossil fuels -- future fuels  

SciTech Connect

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

NONE

1998-03-01

357

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

358

Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander  

NASA Astrophysics Data System (ADS)

The paleomagnetism of the approximately 147 Ma (Tithonian) Brushy Basin Member of the Morrison Formation was analyzed to obtain a Late Jurassic paleomagnetic pole for North America. A total of 200 samples were collected from 25 sedimentary horizons (sites) at Norwood Hill in southwest Colorado. At Montezuma Creek in southeast Utah, 184 samples were collected from 26 sites. Detailed thermal demagnetization (up to nine temperature steps between 600 C and 680 C) and principal component analysis were required to confidently isolate characteristic remanent magnetization (ChRM) directions carried by hematite. Demagnetization behavior for many horizons is erratic and does not allow isolation of a high unblocking-temperature ChRM. Data selection criteria required sample ChRM directions to be defined by three or more thermal demagnetization steps and maximum angular deviations of sample ChRM directions to be less than or equal to 20 deg. Eight sites from the Norwood Hill location and 10 sites from the Montezuma Creek location passed these criteria. The 18 site-mean virtual geomagnetic poles yield a paleomagnetic pole position from the Brushy Basin Member of 68.3 deg N, 156.2 deg E (A(sub 95) = 4.8 deg, K = 53). This pole position is within 2 deg of the paleomagnetic pole which Steiner and Helsley (1975a) reported for the 'upper' Morrison Formation at Norwood Hill, Colorado. A second paleomagnetic pole was calculated after excluding sites with site-mean alpha(sub 95) is greater than 20 deg and sites with fewer than three samples that passed the above selection criteria. This additional editing did not significantly change the paleomagnetic pole position at the 95% confidence level. Along with other paleomagnetic poles from the continental interior the paleomagnetic data from the Brushy Basin Member of the Morrison Formation are interpreted to indicate that the Late Jurassic part of the North American apparent polar wander path progresses from a late Middle Jurassic (approximately 160 Ma) position at approximately 60 deg N, 135 deg E toward the mid-Cretaceous pole position at 72 deg N, 191 deg E.

Bazard, David R.; Butler, Robert F.

1994-04-01

359

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

360

The African Plate: A history of oceanic crust accretion and subduction since the Jurassic  

NASA Astrophysics Data System (ADS)

We present a model for the Jurassic to Present evolution of plate boundaries and oceanic crust of the African plate based on updated interpretation of magnetic, gravity and other geological and geophysical data sets. Location of continent ocean boundaries and age and geometry of old oceanic crust (Jurassic and Cretaceous) are updated in the light of new data and models of passive margin formation. A new set of oceanic palaeo-age grid models constitutes the basis for estimating the dynamics of oceanic crust through time and can be used as input for quantifying the plate boundary forces that contributed to the African plate palaeo-stresses and may have influenced the evolution of intracontinental sedimentary basins. As a case study, we compute a simple model of palaeo-stress for the Late Cretaceous time in order to assess how ridge push, slab pull and horizontal mantle drag might have influenced the continental African plate. We note that the changes in length of various plate boundaries (especially trenches) do not correlate well with absolute plate motion, but variations in the mean oceanic crust age seem to be reflected in acceleration or deceleration of the mean absolute plate velocity.

Gaina, Carmen; Torsvik, Trond H.; van Hinsbergen, Douwe J. J.; Medvedev, Sergei; Werner, Stephanie C.; Labails, Cinthia

2013-09-01

361

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

362

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

PubMed Central

Direct animal behavior can be inferred from the fossil record only in exceptional circumstances. The exceptional mode of preservation of ammonoid shells in the Posidonia Shale (Lower Jurassic, lower Toarcian) of Dotternhausen in southern Germany, with only the organic periostracum preserved, provides an excellent opportunity to observe the contents of the ammonoid body chamber because this periostracum is translucent. Here, we report upon three delicate lobsters preserved within a compressed ammonoid specimen of Harpoceras falciferum. We attempt to explain this gregarious behavior. The three lobsters were studied using standard microscopy under low angle light. The lobsters belong to the extinct family of the Eryonidae; further identification was not possible. The organic material of the three small lobsters is preserved more than halfway into the ammonoid body chamber. The lobsters are closely spaced and are positioned with their tails oriented toward each other. The specimens are interpreted to represent corpses rather than molts. The lobsters probably sought shelter in preparation for molting or against predators such as fish that were present in Dotternhausen. Alternatively, the soft tissue of the ammonoid may have been a source of food that attracted the lobsters, or it may have served as a long-term residency for the lobsters (inquilinism). The lobsters represent the oldest known example of gregariousness amongst lobsters and decapods in the fossil record. Gregarious behavior in lobsters, also known for extant lobsters, thus developed earlier in earth's history than previously known. Moreover, this is one of the oldest known examples of decapod crustaceans preserved within cephalopod shells.

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

2012-01-01

363

Sequence and seismic stratigraphy of the Jurassic strata in northeastern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

The Upper Jurassic section in the northeastern Gulf of Mexico includes the Norphlet and Smackover Formations (Oxfordian), considered as one of the most prolific oil and gas producers in the area, the Haynesville Formation (Kimmeridgian), and the Cotton Valley Group (Tithonian to Berriasian/Lower Valanginian). The study area, located in the onshore-offshore southwest Alabama, consists of mixed siliciclastic and carbonate deposits representing continental, marginal marine, and marine environments. Well log, core and two-dimensional reflection seismic data were used to provide a sequence stratigraphic framework for the Jurassic section through identification of transgressive-regressive sequences and their associated key stratigraphic surfaces. Three transgressive-regressive (T-R) sequences were identified in the Upper Jurassic-Lower Cretaceous strata onshore Alabama, using well log and limited core data. In the offshore area, four transgressive-regressive sequences were recognized on well logs. Stratigraphic analysis of the reflection seismic data yielded three T-R sequences. Sequence boundaries and marine flooding events were identified on seismic sections through interpretation of reflection termination patterns of seismic reflectors. The reflection seismic data were eventually integrated with well log data using check-shot surveys and synthetic seismogram. The recognized transgressive-regressive sequences have utility for regional stratigraphic correlation of the Jurassic sediments across the northern Gulf of Mexico. The Oxfordian (Smackover), the Late Kimmeridgian (Haynesville), and the Berriasian (Cotton Valley) marine flooding events have potential for global correlation. Sequence boundaries and marine flooding surfaces were identified as major events in the geohistory of the northern Gulf of Mexico. Several approaches to sequence stratigraphy have been established. The three most popular approaches are the depositional sequence, the genetic stratigraphic sequence, and the T-R sequence. The T-R approach is thought to have the greatest utility in the study area. An evaluation of the merits and limitations of each approach was performed considering a number of factors such as applicability to the study area, compatibility with the basic definition of a sequence, complexity and amount of terminology associated with each approach, type of available data, geographic location and geologic setting of the study area, and nature of stratigraphic section in question.

Obid, Jamal A.

364

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.

365

Minerals and Fossils  

NSDL National Science Digital Library

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

Mineraltown.com

366

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

367

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

PubMed Central

Fishflies (Corydalidae: Chauliodinae) are one of the main groups of the basal holometabolous insect order Megaloptera, with ca. 130 species distributed worldwide. A number of genera from the Southern Hemisphere show remarkably disjunctive distributions and are considered to be the austral remnants or “living fossils” of Gondwana. Hitherto, the evolutionary history of fishflies remains largely unexplored due to limited fossil record and incomplete knowledge of phylogenetic relationships. Here we describe two significant fossil species of fishflies, namely Eochauliodes striolatus gen. et sp. nov. and Jurochauliodes ponomarenkoi Wang & Zhang, 2010 (original designation for fossil larvae only), from the Middle Jurassic of Inner Mongolia, China. These fossils represent the earliest fishfly adults. Furthermore, we reconstruct the first phylogenetic hypothesis including all fossil and extant genera worldwide. Three main clades within Chauliodinae are recognized, i.e. the Dysmicohermes clade, the Protochauliodes clade, and the Archichauliodes clade. The phylogenetic and dispersal-vicariance (DIVA) analyses suggest Pangaean origin and global distribution of fishflies before the Middle Jurassic. The generic diversification of fishflies might have happened before the initial split of Pangaea, while some Gondwanan-originated clades were likely to be affected by the sequential breakup of Pangaea. The modern fauna of Asian fishflies were probably derived from their Gondwanan ancestor but not the direct descendents of the Mesozoic genera in Asia.

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

2012-01-01

368

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

PubMed

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

2012-07-06

369

Fossil energy program  

NASA Astrophysics Data System (ADS)

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

McNeese, L. E.

1981-12-01

370

The Great Fossil Find  

NSDL National Science Digital Library

In this imaginary fossil hunt, students learn about the uncertainty of science and the fact that, as new evidence is revealed, ideas may change. As they follow a script read by the teacher, students find (remove from envelope) paper fossils of some unknown creature, 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.

371

Burial depth and post-Early Cretaceous uplift of Lower-Middle Jurassic strata in the Fennoscandian Border Zone based on organic maturity  

Microsoft Academic Search

The burial depth and the magnitude of Late Cretaceous - Early Cenozoic and Neogene-Pleistocene uplift of Lower-Middle Jurassic strata in the Fennoscandian Border Zone are estimated from mea- surements of huminite reflectance and comparison with a regional coalification gradient. The regional coalification curve is constructed by plotting uplift-corrected sample depths against more than 300 huminite\\/vitrinite reflectance values from Upper Triassic

Henrik I. Petersen; Lars H. Nielsen; Torben Bidstrup; Erik Thomsen

2003-01-01

372

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

373

A cratonic Middle Jurassic paleopole: Callovian-Oxfordian stillstand (J-2 cusp), rotation of the Colorado Plateau, and Jurassic North American apparent polar wander  

NASA Astrophysics Data System (ADS)

Paleomagnetic results have been obtained from two sequences of the upper Middle Jurassic (upper Callovian) Summerville Formation which are located on the North American craton (north central New Mexico). The thicker of the two sections (Trujillo) exhibits a well-defined dual-polarity remanence, forming a magnetostratigraphy of at least 12 relatively short polarity intervals. The high reversal frequency is consistent with that recorded by the oceanic crust at this time. The second section (Romeroville) is thin, gypsiferous, and poorly indurated; consequently, only a short interval (5 m) was successfully sampled. The characteristic magnetization was wholly normal polarity. In the rapid reversals of the thicker section, that thickness of normal polarity is unique and thus forms the basis of magnetostratigraphic correlation between the two sections. A cratonic late Middle Jurassic paleomagnetic pole at 148.2°E, 57.3°N (k = 30.3, ?95 = 6.0°) was obtained from the larger Trujillo sequence. Despite large confidence limits, the small sample population of the Romeroville sequence displayed the same pole. Throughout the western United States, the Summerville Formation is overlain with little or no discordance by the Morrison Formation, although the two stratigraphic units are commonly reported to be separated by an unconformity, designated J-5. The New Mexico paleopoles of the Summerville and overlying lower Morrison Formations are statistically identical at the 95% confidence level; a similar situation exists between Summerville and lower Morrison paleopoles of the Colorado Plateau. The presence of the same geomagnetic field direction in both the Summerville and the lower Morrison Formations suggests that the J-5 unconformity which separates them may encompass little time, perhaps representing only a minor break in deposition. The two newly investigated Summerville sites are located east of the Rio Grande Rift, hence representative of the North American craton; their paleopoles are displaced counterclockwise relative to those of the Colorado Plateau, and in amounts consistent with other coeval craton-Colorado Plateau pole pairs. Together, six coeval paleopoles indicate that the Colorado Plateau has rotated clockwise by about 9.0 ± 3° since Late Pennsylvanian time. The cratonic Summerville paleopole also removes the uncertainty over the Jurassic North American apparent polar wander path. The statistically identical Summerville and lower Morrison paleopoles form a substantial data set, five paleopoles, which indicate that NA APW traced a path roughly along 60° latitude. The five paleopoles stand in stark contrast to the paleopole from the slightly older (5-8 Ma) Moat Volcanics. Spreading rates in the central Atlantic do not allow NA plate motion that would include both paleopoles positions. Because the weight of the data, five paleopoles from widely spaced localities and different tectonic blocks, the Moat Volcanics pole cannot be representative of North America in the Middle Jurassic.

Steiner, Maureen B.

2003-06-01

374

Timing of the North-South China collision from new middle to late Mesozoic paleomagnetic data from the North China Block  

NASA Astrophysics Data System (ADS)

We collected paleomagnetic samples from 43 sites of Middle and Upper Jurassic and Cretaceous rocks along a 250 km wide east-west trending belt located north of the suture between the North and South China Blocks. In each case, laboratory treatment isolates dual polarity, antipodal magnetizations that are demonstrably pre-folding. The paleomagnetic poles show very good coherence with coeval poles from other localities from the North China Block (NCB), suggesting the apparent polar wander path (APWP) from the NCB is not distorted by post-Middle Jurassic local vertical axis block rotations. A comparison of the NCB APWP with that from the South China Block suggests that collision continued after the Early Jurassic and ended no later than the Late Jurassic. A cusp in the NCB APWP coincides with a marked angular unconformity that separates Middle Jurassic from Upper Jurassic and younger sediments. Together, these observations indicate that the scissor-like collision and associated deformation ceased at the Middle to Late Jurassic boundary (˜159 Ma). The time of rapid (1°/Ma) relative angular velocity between the two plates (225 to 190 Ma) coincides with a peak in U-Pb and Ar-Ar dates obtained from metamorphic rocks in the suture. The combined Late Jurassic and Cretaceous paleomagnetic data from both blocks suggest that the united China plate traveled 2000 km north relative to Eurasia during the Late Jurassic before docking in the Cretaceous. This younger collision event is also marked by a cusp on the Cretaceous part of the Eurasian APWP.

Gilder, Stuart; Courtillot, Vincent

1997-08-01

375

Strategies for assessing Early{Middle (Pliensbachian{Aalenian) Jurassic cyclochronologies  

Microsoft Academic Search

There are a number of fundamental problems in assessing the astronomically forced cyclostratigraphy of the Jurassic Period. First, Jurassic geochronology is not well constrained, due to a general scarcity of radiometric dates, inferior precision of the existing ones, and large inaccuracies in stratigraphic constraints. These problems are particularly troublesome in the Early to Middle Jurassic cyclic carbonates of the Colle

J. P ark

1999-01-01

376

Low intensity of the geomagnetic field in early Jurassic time  

USGS Publications Warehouse

From a large collection of Jurassic continental tholeiites cropping out in Europe and Africa, we selected 90 samples for paleointensity determinations. Twenty-eight well-clustered paleointensity estimates were obtained from two European dikes that were emplaced during Early Jurassic time: the Kerforne dike at Brenterc'h in Brittany (northwestern France) and the Messejana dike on the Iberian Peninsula (Spain and Portugal). Virtual dipole moments calculated from both magmatic units are similar and only about one-third of present-day values. -from Authors

Perrin, M.; Prevot, M.; Mankinen, E. A.

1991-01-01

377

The second Jurassic dinosaur rush and the dawn of dinomania.  

PubMed

During the second Jurassic dinosaur rush museum paleontologists raced to display the world's first mounted sauropod dinosaur. The American Museum of Natural History triumphed in 1905 when its Brontosaurus debuted before an admiring crowd of wealthy New Yorkers. The Carnegie Museum of Natural History in Pittsburgh, the Field Columbian Museum in Chicago and other institutions were quick to follow with their own sauropod displays. Thereafter, dinomania spread far and wide, and big, showpiece dinosaurs became a museum staple. This brief but intensely competitive period of acquisitiveness fostered important Jurassic dinosaur revisions and crucial innovations in paleontological field and lab techniques. PMID:20667597

Brinkman, Paul D

2010-07-29

378

Trace Fossil Analysis  

NASA Astrophysics Data System (ADS)

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

Hasiotis, Stephen T.

2009-05-01

379

Fossilization of feathers  

NASA Astrophysics Data System (ADS)

Scanning electron microscopy of feathers has revealed evidence that a bacterial glycocalyx (a network of exocellular polysaccharide fibers) played a role in promoting their fossilization in some cases. This mode of preservation has not been reported in other soft tissues. The majority of fossil feathers are preserved as carbonized traces. More rarely, bacteria on the surface are replicated by authigenic minerals (bacterial autolithification). The feathers of Archaeopteryx are preserved mainly by imprintation following early lithification of the substrate and decay of the feather. Lacustrine settings provide the most important taphonomic window for feather preservation. Preservation in terrestrial and normal-marine settings involves very different processes (in amber and in authigenically mineralized coprolites, respectively). Therefore, there may be a significant bias in the avian fossil record in favor of inland water habitats.

Davis, Paul G.; Briggs, Derek E. G.

1995-09-01

380

The Fossil Record  

NSDL National Science Digital Library

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

Wu, Lisa

381

Fossil energy program  

NASA Astrophysics Data System (ADS)

Progress is reported for the period July 1 through September 30 for the Oak Ridge National Laboratory research and development projects that are carried out in support of the increased utilization of coal and other fossil fuels as sources of clean energy. These projects are supported by various parts of DOE including Fossil Energy, Basic Energy Sciences, Office of Health and Environmental Research, Office of Environmental Compliance and Overview, Economic Regulatory Administration, Power Research Institute, and by the Tennessee Valley Authority and the EPA Office of Research and Development through interagency agreements

McNeese, L. E.

1981-01-01

382

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

2006-01-01

383

What is a Fossil?  

NSDL National Science Digital Library

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

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

2004-01-01

384

A Remarkable New Family of Jurassic Insects (Neuroptera) with Primitive Wing Venation and Its Phylogenetic Position in Neuropterida  

PubMed Central

Background Lacewings (insect order Neuroptera), known in the fossil record since the Early Permian, were most diverse in the Mesozoic. A dramatic variety of forms ranged in that time from large butterfly-like Kalligrammatidae to minute two-winged Dipteromantispidae. Principal Findings We describe the intriguing new neuropteran family Parakseneuridae fam. nov. with three new genera and 15 new species from the Middle Jurassic of Daohugou (Inner Mongolia, China) and the Early/Middle Jurassic of Sai-Sagul (Kyrgyzstan): Parakseneura undula gen. et sp. nov., P. albomacula gen. et sp. nov., P. curvivenis gen. et sp. nov., P. nigromacula gen. et sp. nov., P. nigrolinea gen. et sp. nov., P. albadelta gen. et sp. nov., P. cavomaculata gen. et sp. nov., P. inflata gen. et sp. nov., P. metallica gen. et sp. nov., P. emarginata gen. et sp. nov., P. directa gen. et sp. nov., Pseudorapisma jurassicum gen. et sp. nov., P. angustipenne gen. et sp. nov., P. maculatum gen. et sp. nov. (Daohugou); Shuraboneura ovata gen. et sp. nov. (Sai-Sagul). The family comprises large neuropterans with most primitive wing venation in the order indicated by the presence of ScA and AA1+2, and the dichotomous branching of MP, CuA, CuP, AA3+4, AP1+2. The phylogenetic position of Parakseneuridae was investigated using a phylogenetic analysis of morphological scoring for 33 families of extinct and extant Neuropterida combined with DNA sequence data for representatives of all extant families. Parakseneuridae were recovered in a clade with Osmylopsychopidae, Prohemerobiidae, and Ithonidae. Conclusions/Significance The presence of the presumed AA1+2 in wings of Parakseneuridae is a unique plesiomorphic condition hitherto unknown in Neuropterida, the clade comprising Neuroptera, Megaloptera, Raphidioptera. The relative uncertainty of phylogenetic position of Parakseneuridae and the majority of other families of Neuroptera reflects deficient paleontological data, especially from critical important periods for the order, earliest Triassic and latest Triassic/earliest Jurassic.

Yang, Qiang; Makarkin, Vladimir N.; Winterton, Shaun L.; Khramov, Alexander V.; Ren, Dong

2012-01-01

385

Depositional and compositional controls on sandstone diagenesis, the Tetori Group (Middle Jurassic Early Cretaceous), central Japan  

NASA Astrophysics Data System (ADS)

The Tetori Group is a representative Middle Jurassic to Lower Cretaceous deposit in the northern central part of Honshu, Japan. The Tetori Group is divided into the Kuzuryu, Itoshiro and Akaiwa Subgroups with decreasing age. It consists mainly of a marine sequence in the lower part (Kuzuryu Subgroup) and non-marine sequence in the upper part (Akaiwa Subgroup) with transitional sequence in the middle part (Itoshiro Subgroup). Diagenesis of Tetori Group sandstones comprises compaction, cementation and replacement. Early diagenetic events include mechanical compaction, and pore-filling cementation of calcite, siderite, dolomite and formation of kaolinite. Late diagenesis includes formation of quartz cement and albitization of feldspar, and formation of illite, chlorite, calcite, ankerite and pyrite. Among the diagenetic minerals, carbonate forms the major cement in Tetori Group sandstones. Calcite of each subgroup is subdivided into two or three types based on cathodoluminescence. Tetori Group sandstones of marine, fresh-water, and mixed depositional environments are characterized by distinct chemical compositions of early diagenetic calcites. Late diagenesis seems to have been mainly influenced by detrital compositions of the sequence, burial temperatures and partially hydrothermal processes. Especially, late diagenetic carbonate and authigenic clay minerals seem to have formed mainly from ions released from clay mineral transformations in the adjacent shales. Based on the illite crystallinity (IC), the Kuzuryu Subgroup exhibits higher diagenetic grades than the overlying Itoshiro and Akaiwa Subgroups, indicating that the diagenesis of the Tetori Group was mainly affected by depth of burial.

Kim, Jin Cheul; Lee, Yong Il; Hisada, Ken-Ichiro

2007-03-01

386

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

NASA Astrophysics Data System (ADS)

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

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

1991-06-01

387

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

Microsoft Academic Search

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

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

1998-01-01

388

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

2006-03-13

389

A dinosaur ichnocoenosis from the middle jurassic of Yorkshire, UK  

Microsoft Academic Search

An assemblage of dinosaur tracks from the undersurface of a sandstone bed in the Saltwick Formation (Middle Jurassic) of Yorkshire shows a range of morphological types, preservational variants and behavioral styles. The tracks are combinations of transmitted prints and underprints and include three distinct trackways. One trackway was made by an animal walking on exposed damp sand, another was left

M. A. Whyte; M. Romano

2001-01-01

390

Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton  

Microsoft Academic Search

Nonmarine to paralic detrital deposits accumulated in six large basins between Algeria and the Arabo-Nubian shield during major regression in latest Jurassic and Early Cretaceous time. The Ghadames Sirte (north-central Libya), and Northern (Egypt) basins lay along the cratonic margin of northeastern Africa. The Murzuk, Kufra, and Southern (Egypt) basins lay in the south within the craton. Data for reconstructing

van Houten

1980-01-01

391

Upper Jurassic depositional systems and hydrocarbon potential of southeast Mississippi  

Microsoft Academic Search

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

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

1987-01-01

392

Hydrothermal venting of greenhouse gases triggering Early Jurassic global warming  

Microsoft Academic Search

The climate change in the Toarcian (Early Jurassic) was characterized by a major perturbation of the global carbon cycle. The event lasted for approximately 200,000 years and was manifested by a global warming of ?6 °C, anoxic conditions in the oceans, and extinction of marine species. The triggering mechanisms for the perturbation and environmental change are however strongly debated. Here, we present

Henrik Svensen; Sverre Planke; Luc Chevallier; Anders Malthe-Sørenssen; Fernando Corfu; Bjørn Jamtveit

2007-01-01

393

The ammonite succession in the Middle Jurassic o£ East Greenland  

Microsoft Academic Search

The ammonite sequence in the Middle Jurassic of central East Greenland is the most complete and detailed known in the Arctic so far, and has become a standard of reference for the whole of the Boreal Faunal Province. It is made up of some 37 distinguishable assemblages that characterize a time-ordered succession of discrete faunal horizons. This succession has been

JOHN H. CALLOMON

1993-01-01

394

Evolutionary size increase and longevity in Jurassic bivalves and ammonites  

Microsoft Academic Search

A study of the relationship between the rate of increase of size and generic or specific longevity in Jurassic ammonites and bivalves shows that taxa which increase more rapidly become extinct more quickly. The results, which can be interpreted stochastically, make it possible to distinguish two modes of evolution respectively involving an increase and decrease in size.

A. Hallam

1975-01-01

395

Exploration in Jurassic of North Mafla, eastern Gulf of Mexico  

Microsoft Academic Search

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

Kemmer

1987-01-01

396

Let the Volgian stage stay in the Jurassic  

Microsoft Academic Search

In 1996 the Volgian Stage was divided into the Jurassic and Cretaceous units, removed from the Geological Time Scale, and substituted by the Tithonian Stage according to the guidelines of the Interdepartmental Stratigraphic Committee of the Russian Federation (ISC RF). Consequently, the Upper Volgian Substage including three zones (five subzones) was placed into the Berriasian Stage (the Cretaceous) proceeding from

V. A. Zakharov; M. A. Rogov

2008-01-01

397

Basic aspects of Jurassic landscape development in southeastern central Asia  

SciTech Connect

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

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

1986-11-01

398

Spatial Response of Mammals to Late Quaternary Environmental Fluctuations  

Microsoft Academic Search

Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quatemary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar

Russell W. Graham; Ernest L. Lundelius Jr.; Mary Ann Graham; Erich K. Schroeder; Rickard S. Toomey III; Elaine Anderson; Anthony D. Barnosky; James A. Burns; Charles S. Churcher; Donald K. Grayson; R. Dale Guthrie; C. R. Harington; George T. Jefferson; Larry D. Martin; H. Gregory McDonald; Richard E. Morlan; Holmes A. Semken Jr.; S. David Webb; Lars Werdelin; Michael C. Wilson; M. C. Wilson

1996-01-01

399

Fossilization of Acidophilic Microorganisms  

Microsoft Academic Search

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

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

2010-01-01

400

Fossil Halls: Virtual Tours  

NSDL National Science Digital Library

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

401

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.

Foundation, Wgbh E.

2010-04-05

402

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.

403

Advanced fossil energy utilization  

SciTech Connect

This special issue of Fuel is a selection of papers presented at the symposium ‘Advanced Fossil Energy Utilization’ co-sponsored by the Fuels and Petrochemicals Division and Research and New Technology Committee in the 2009 American Institute of Chemical Engineers (AIChE) Spring National Meeting Tampa, FL, on April 26–30, 2009.

Shekhawat, D.; Berry, D.; Spivey, J.; Pennline, H.; Granite, E.

2010-01-01

404

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

405

A Fossil Buttercup  

Microsoft Academic Search

WHEN we examine a catalogue of fossil plants, such as that for North America recently published by Knowlton, we are struck by the enormous number of recorded species, and readily receive the impression that the flora of former ages is quite well known. It is only when we make a more critical investigation that we perceive the great gap in

T. D. A. Cockerell

1922-01-01

406

Structural development of the Jurassic Magnetic Quiet Zone off Morocco and identification of Middle Jurassic magnetic lineations  

Microsoft Academic Search

Geophysical investigations carried out during two Meteor cruises have revealed weak linear magnetic anomalies in those parts of the Jurassic Magnetic Quiet Zone (JMQZ) off Morocco that are not affected by Cenozoic igneous activity. The linear magnetic anomalies are not correlated with variations in relief or structure of oceanic crust. Using the reversal sequence M25-M41, the anomalies of the JMQZ

H. A. Roeser; C. Steiner; B. Schreckenberger; M. Block

2002-01-01

407

New turtle egg fossil from the Upper Cretaceous of the Laiyang Basin, Shandong Province, China.  

PubMed

A new type of turtle egg fossil was established: Emydoolithus laiyangensis oogen. et oosp. nov.. Based on its elliptical morphological shape, rigid eggshells, and eggshell characteristics, it is different from other types of round chelonian egg fossils. It is the second chelonian egg fossil found in Cretaceous in China. This discovery shows the Laiyang ecosystem in Late Cretaceous is more diversified than previously thought. PMID:23538955

Wang, Qiang; Wang, Xiaolin; Zhao, Zikui; Zhang, Jialiang; Jiang, Shunxing

2013-03-01

408

Centering on Fossils and Dinosaurs.  

ERIC Educational Resources Information Center

|Describes a set of 10 activities which introduce mainstreamed junior high school students to concepts relating to fossils and dinosaurs. Provides students with opportunities for learning the concepts of change and adaptation, as well as fossil facts and terminology. (TW)|

Coble, Charles R.; McCall, Gregory K.

1986-01-01

409

Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers  

Microsoft Academic Search

Penguin feathers are highly modified in form and function, but there have been no fossils to inform their evolution. A giant penguin with feathers was recovered from the late Eocene (~36 million years ago) of Peru. The fossil reveals that key feathering features, including undifferentiated primary wing feathers and broad body contour feather shafts, evolved early in the penguin lineage.

Julia A. Clarke; Daniel T. Ksepka; Rodolfo Salas-Gismondi; Ali J. Altamirano; Matthew D. Shawkey; Liliana D'Alba; Jakob Vinther; Thomas J. DeVries; Patrice Baby

2010-01-01

410

Ediacaran fossils from the Miette Group, Rocky Mountains, British Columbia, Canada  

Microsoft Academic Search

The discovery of metazoan fossils in the upper part of the Hadrynian Miette Group (Windermere Supergroup) extends the range of the cosmopolitan Ediacara fauna (late Vendian) to a new region, and brings to six the number of genera now known in western North America. The fossils, provisionally identified as Cyclomedusa davidi?, Irridinitus sp., and Protodipleurosoma sp., occur in a greenish-gray,

H. J. Hofmann; E. W. Mountjoy; M. W. Teitz

1985-01-01

411

Adhesive grass spikelet with mammalian hair in Dominican amber: First fossil evidence of epizoochory  

Microsoft Academic Search

Discovery of a female spikelet of the grass genusPharus (Gramineae: Bambusoideae: Phareae) in association with mammalian hair in Dominican Republic amber provides the first fossil evidence of epizoochory. Hooked macrohairs on the lemma of the spikelet show that morphological modifications in grasses for dispersal by attachment to the surface of animals were present in the Late Eocene. The fossil also

G. O. Poinar; J. T. Columbus

1992-01-01

412

Teacher's Domain: Fun with Fossils  

NSDL National Science Digital Library

Fossils provide a valuable record of the plant and animal life and environmental conditions from millions, even billions of years ago. In this lesson, students create their own fossils, and then use multimedia resources to learn how real fossils form and what scientists can learn from them. They should understand that fossils provide evidence of plants and animals that lived long ago, as well as the environmental conditions at that time. Instructions, a materials list, and links to multimedia resources are provided.

2005-01-01

413

REVIEW Developmental Evolution of Metazoan Bodyplans: The Fossil Evidence  

Microsoft Academic Search

Evidence from the fossil record, developmental biology and metazoan phylogeny demonstrates that the rapid origination of major metazoan bodyplans during the late Neoproterozoic and earliest Cambrian was intimately associated with a series of innovations in developmental control mechanisms that included the Hox gene cluster. The interval between about 565 Ma (million years ago) and 530 Ma evidently includes the protostome-deuterostome

James W. Valentine; Douglas H. Erwin; David Jablonski

414

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

Microsoft Academic Search

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

David J. Mossman; Lucy M. Force

1969-01-01

415

Combined oxygen- and carbon-isotope records through the Early Jurassic: multiple global events and two modes of carbon-cycle/temperature coupling  

NASA Astrophysics Data System (ADS)

The Jurassic comprises some 55 million years of Earth history. However, within the Jurassic, only one major environmental change (hyperthermal) event is really well known - the Early Toarcian Oceanic Anoxic Event (OAE) at ~183 Ma - and until very recently the extent to which the accompanying environmental changes were global has been strongly debated. Nevertheless, partly as a result of the international effort to define Global Stratotype Sections and Points (GSSPs), much more is now being discovered about environmental changes taking place at and around the other Jurassic Age (Stage) boundaries, to the extent that meaningful comparisons between these events can begin to be made. Here we present new carbon and oxygen isotope data from mollusks (bivalves and belemnites) and brachiopods collected through the marine Early Jurassic succession of NE England, including the Sinemurian-Plienbachian boundary GSSP. All materials have been screened by chemical analysis and scanning electron microscopy to check for diagenetic alteration. Analysis of carbon isotopes from marine calcite is supplemented by analysis of carbon-isotope values from fossil wood collected through the same section. It is demonstrated that both long-term and short-term carbon-isotope shifts from the UK Early Jurassic represent global changes in carbon cycle balances. The Sinemurian-Pliensbachian boundary event is an event of global significance and shows several similarities to the Toarcian OAE (relative sea-level change, carbon-isotope signature), but also some significant contrasts (oxygen-isotope based paleotemperatures which provide no evidence for warming). Significant contrast in oxygen- and carbon-isotope co-variation also occurs on a long timescale. There appear to be two modes in the co-variation of carbon and oxygen isotopes through this time interval: mo