Sample records for early cretaceous cauvery

  1. Rainfall seasonality on the Indian subcontinent during the Cretaceous greenhouse.

    PubMed

    Ghosh, Prosenjit; Prasanna, K; Banerjee, Yogaraj; Williams, Ian S; Gagan, Michael K; Chaudhuri, Atanu; Suwas, Satyam

    2018-05-31

    The Cretaceous greenhouse climate was accompanied by major changes in Earth's hydrological cycle, but seasonally resolved hydroclimatic reconstructions for this anomalously warm period are rare. We measured the δ 18 O and CO 2 clumped isotope Δ 47 of the seasonal growth bands in carbonate shells of the mollusc Villorita cyprinoides (Black Clam) growing in the Cochin estuary, in southern India. These tandem records accurately reconstruct seasonal changes in sea surface temperature (SST) and seawater δ 18 O, allowing us to document freshwater discharge into the estuary, and make inferences about rainfall amount. The same analytical approach was applied to well-preserved fossil remains of the Cretaceous (Early Maastrichtian) mollusc Phygraea (Phygraea) vesicularis from the nearby Kallankuruchchi Formation in the Cauvery Basin of southern India. The palaeoenvironmental record shows that, unlike present-day India, where summer rainfall predominates, most rainfall in Cretaceous India occurred in winter. During the Early Maastrichtian, the Indian plate was positioned at ~30°S latitude, where present-day rainfall and storm activity is also concentrated in winter. The good match of the Cretaceous climate and present-day climate at ~30°S suggests that the large-scale atmospheric circulation and seasonal hydroclimate patterns were similar to, although probably more intense than, those at present.

  2. Petroleum source-rock potentials of the cretaceous transgressive-regressive sedimentary sequences of the Cauvery Basin

    NASA Astrophysics Data System (ADS)

    Chandra, Kuldeep; Philip, P. C.; Sridharan, P.; Chopra, V. S.; Rao, Brahmaji; Saha, P. K.

    The present work is an attempt to contribute to knowledge on the petroleum source-rock potentials of the marine claystones and shales of basins associated with passive continental margins where the source-rock developments are known to have been associated with the anoxic events in the Mesozoic era. Data on three key exploratory wells from three major depressions Ariyallur-Pondicherry, Thanjavur and Nagapattinam of the Cauvery Basin are described and discussed. The average total organic carbon contents of the transgressive Pre-Albian-Cinomanian and Coniacian/Santonian claystones/shales range from 1.44 and 1.16%, respectively. The transgressive/regressive Campanian/Maastrichtian claystones contain average total organic carbon varying from 0.62 to 1.19%. The kerogens in all the studied stratigraphic sequences are classified as type-III with Rock-Eval hydrogen indices varying from 30 to 275. The nearness of land masses to the depositional basin and the mainly clastic sedimentation resulted in accumulation and preservation of dominantly type-III kerogens. The Pre-Albian to Cinomanian sequences of peak transgressive zone deposited in deep marine environments have kerogens with a relatively greater proportion of type-II components with likely greater contribution of planktonic organic matters. The global anoxic event associated with the Albian-Cinomanian marine transgression, like in many other parts of the world, has pervaded the Cauvery Basin and favoured development of good source-rocks with type-III kerogens. The Coniacian-Campanian-Maastrichtian transgressive/regressive phase is identified to be relatively of lesser significance for development of good quality source-rocks.

  3. Silicon biogeochemical processes in a large river (Cauvery, India)

    NASA Astrophysics Data System (ADS)

    Kameswari Rajasekaran, Mangalaa; Arnaud, Dapoigny; Jean, Riotte; Sarma Vedula, V. S. S.; Nittala, S. Sarma; Sankaran, Subramanian; Gundiga Puttojirao, Gurumurthy; Keshava, Balakrishna; Cardinal, Damien

    2016-04-01

    Silicon (Si), one of the key nutrients for diatom growth in ocean, is principally released during silicate weathering on continents and then exported by rivers. Phytoplankton composition is determined by the availability of Si relative to other nutrients, mainly N and P, which fluxes in estuarine and coastal systems are affected by eutrophication due to land use and industrialization. In order to understand the biogeochemical cycle of Si and its supply to the coastal ocean, we studied a tropical monsoonal river from Southern India (Cauvery) and compare it with other large and small rivers. Cauvery is the 7th largest river in India with a basin covering 85626 sq.km. The major part of the basin (˜66%) is covered by agriculture and inhabited by more than 30 million inhabitants. There are 96 dams built across the basin. As a consequence, 80% of the historical discharge is diverted, mainly for irrigation (Meunier et al. 2015). This makes the Cauvery River a good example of current anthropogenic pressure on silicon biogeochemical cycle. We measured amorphous silica contents (ASi) and isotopic composition of dissolved silicon (δ30Si-DSi) in the Cauvery estuary, including freshwater end-member and groundwater as well as along a 670 km transect along the river course. Other Indian rivers and estuaries have also been measured, including some less impacted by anthropogenic pressure. The average Cauvery δ30Si signature just upstream the estuary is 2.21±0.15 ‰ (n=3) which is almost 1‰ heavier than the groundwater isotopic composition (1.38±0.03). The δ30Si-DSi of Cauvery water is also almost 1‰ heavier than the world river supply to the ocean estimated so far and 0.4‰ heavier than other large Indian rivers like Ganges (Frings et al 2015) and Krishna. On the other hand, the smaller watersheds (Ponnaiyar, Vellar, and Penna) adjacent to Cauvery also display heavy δ30Si-DSi. Unlike the effect of silicate weathering, the heavy isotopic compositions in the river

  4. Tribosphenic mammal from the North American Early Cretaceous.

    PubMed

    Cifelli, R L

    1999-09-23

    The main groups of living mammals, marsupials and eutherians, are presumed to have diverged in the Early Cretaceous, but their early history and biogeography are poorly understood. Dental remains have suggested that the eutherians may have originated in Asia, spreading to North America in the Late Cretaceous, where an endemic radiation of marsupials was already well underway. Here I describe a new tribosphenic mammal (a mammal with lower molar heels that are three-cusped and basined) from the Early Cretaceous of North America, based on an unusually complete specimen. The new taxon bears characteristics (molarized last premolar, reduction to three molars) otherwise known only for Eutheria among the tribosphenic mammals. Morphometric analysis and character comparisons show, however, that its molar structure is primitive (and thus phylogenetically uninformative), emphasizing the need for caution in interpretation of isolated teeth. The new mammal is approximately contemporaneous with the oldest known Eutheria from Asia. If it is a eutherian, as is indicated by the available evidence, then this group was far more widely distributed in the Early Cretaceous than previously appreciated. An early presence of Eutheria in North America offers a potential source for the continent's Late Cretaceous radiations, which have, in part, proven difficult to relate to contemporary taxa in Asia.

  5. Mid Holocene Evidence of High Energy Events in the Geological Record: Sedimentary Deposits from Cauvery Delta Coast, SE Coast of India.

    NASA Astrophysics Data System (ADS)

    Karthikeyan, A.; Seshachalam, S.; Jonathan, M. P.; Roy, P. D.

    2014-12-01

    The Cauvery Basin is one of the important sedimentary basins of southern India and provides information on geological processes since the Cretaceous. Most of the studies in the basin have been carried out on the sediments representing Cretaceous with less emphasis on the Quaternary period with marine high energy event. In the present study, we present the sedimentological and micro fauna assemblages in the 150 cm long trench from the Kameshwaram village, Nagapattinam District, South East Coast of India, in order to reconstruct the past event. OSL and Carbon dating of sand layer sediments from the Cauvery Basin provide the first proxy-record of marine event from the region over the Mid Holocene. A multi proxy approach using trench sediments from Cauvery Delta Coast, East coast of Tamil Nadu provides a high resolution record of high energy event. The dating of the event layer indicates 6 and 8 kyrs also below the layer shell layer was preserved, the radio carbon date of the shell layer was 6545 BC. A combination of sedimentological parameters of grain size, sorting, geochemical analysis (XRF) of Fe, Mn, Ti, Cr, Cu, Ni, Sr, Zr and foraminifera species like Ammonia beccarri, Ammonia dentate and Asterorotalia trispinosa were identified. The sediment layers have thinning-up sequences and it starts from 130 cm to the bottom of the layer 150 cm which included shell debris, and rip-up clasts. In addition, characteristic variations in elemental content at the bottom units of Zr, Ti, Ca is showing higher concentration, which is an indicator of high-energy depositional event often associated with an increase in Ti (2.08 % to 16.016 %) and Sr (116 ppm to 275 ppm). Ca on the other hand suggests a marine influence and Fe, Mn, Cr, Ni values are showing lower concentration indicating that the high marine energy event had inundated the Nagapattinam district in SE coast of India. Based on the multiproxy evidences, we conclude that this could be a major marine event during the Mid

  6. A New Hadrosauroid Dinosaur from the Early Late Cretaceous of Shanxi Province, China

    PubMed Central

    Wang, Run-Fu; You, Hai-Lu; Xu, Shi-Chao; Wang, Suo-Zhu; Yi, Jian; Xie, Li-Juan; Jia, Lei; Li, Ya-Xian

    2013-01-01

    Background The origin of hadrosaurid dinosaurs is far from clear, mainly due to the paucity of their early Late Cretaceous close relatives. Compared to numerous Early Cretaceous basal hadrosauroids, which are mainly from Eastern Asia, only six early Late Cretaceous (pre-Campanian) basal hadrosauroids have been found: three from Asia and three from North America. Methodology/Principal Findings Here we describe a new hadrosauroid dinosaur, Yunganglong datongensis gen. et sp. nov., from the early Late Cretaceous Zhumapu Formation of Shanxi Province in northern China. The new taxon is represented by an associated but disarticulated partial adult skeleton including the caudodorsal part of the skull. Cladistic analysis and comparative studies show that Yunganglong represents one of the most basal Late Cretaceous hadrosauroids and is diagnosed by a unique combination of features in its skull and femur. Conclusions/Significance The discovery of Yunganglong adds another record of basal Hadrosauroidea in the early Late Cretaceous, and helps to elucidate the origin and evolution of Hadrosauridae. PMID:24204734

  7. A new hadrosauroid dinosaur from the early late cretaceous of Shanxi Province, China.

    PubMed

    Wang, Run-Fu; You, Hai-Lu; Xu, Shi-Chao; Wang, Suo-Zhu; Yi, Jian; Xie, Li-Juan; Jia, Lei; Li, Ya-Xian

    2013-01-01

    The origin of hadrosaurid dinosaurs is far from clear, mainly due to the paucity of their early Late Cretaceous close relatives. Compared to numerous Early Cretaceous basal hadrosauroids, which are mainly from Eastern Asia, only six early Late Cretaceous (pre-Campanian) basal hadrosauroids have been found: three from Asia and three from North America. Here we describe a new hadrosauroid dinosaur, Yunganglong datongensis gen. et sp. nov., from the early Late Cretaceous Zhumapu Formation of Shanxi Province in northern China. The new taxon is represented by an associated but disarticulated partial adult skeleton including the caudodorsal part of the skull. Cladistic analysis and comparative studies show that Yunganglong represents one of the most basal Late Cretaceous hadrosauroids and is diagnosed by a unique combination of features in its skull and femur. The discovery of Yunganglong adds another record of basal Hadrosauroidea in the early Late Cretaceous, and helps to elucidate the origin and evolution of Hadrosauridae.

  8. The origin and early evolution of metatherian mammals: the Cretaceous record.

    PubMed

    Williamson, Thomas E; Brusatte, Stephen L; Wilson, Gregory P

    2014-01-01

    Metatherians, which comprise marsupials and their closest fossil relatives, were one of the most dominant clades of mammals during the Cretaceous and are the most diverse clade of living mammals after Placentalia. Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. Metatherians were widespread over Laurasia during the Cretaceous, with members present in Asia, Europe, and North America by the early Late Cretaceous. In particular, they were taxonomically and morphologically diverse and relatively abundant in the Late Cretaceous of western North America, where they have been used to examine patterns of biogeography, macroevolution, diversification, and extinction through the Late Cretaceous and across the Cretaceous-Paleogene (K-Pg) boundary. Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary.

  9. A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah

    USGS Publications Warehouse

    Kirkland, J.I.; Zanno, L.E.; Sampson, S.D.; Clark, J.M.; DeBlieux, D.D.

    2005-01-01

    Therizinosauroids are an enigmatic group of dinosaurs known mostly from the Cretaceous period of Asia, whose derived members are characterized by elongate necks, laterally expanded pelves, small, leaf-shaped teeth, edentulous rostra and mandibular symphyses that probably bore keratinized beaks. Although more than a dozen therizinosauroid taxa are known, their relationships within Dinosauria have remained controversial because of fragmentary remains and an unusual suite of characters. The recently discovered 'feathered' therizinosauroid Beipiaosaurus from the Early Cretaceous of China helped to clarify the theropod affinities of the group. However, Beipiaosaurus is also poorly represented. Here we describe a new, primitive therizinosauroid from an extensive paucispecific bonebed at the base of the Cedar Mountain Formation (Early Cretaceous) of east-central Utah. This new taxon represents the most complete and most basal therizinosauroid yet discovered. Phylogenetic analysis of coelurosaurian theropods incorporating this taxon places it at the base of the clade Therizinosauroiden, indicating that this species documents the earliest known stage in the poorly understood transition from carnivory to herbivory within Therizinosauroidea. The taxon provides the first documentation, to our knowledge, of therizinosauroids in North America during the Early Cretaceous.

  10. Late Cretaceous-Early Palaeogene tectonic development of SE Asia

    NASA Astrophysics Data System (ADS)

    Morley, C. K.

    2012-10-01

    The Late Cretaceous-Early Palaeogene history of the continental core of SE Asia (Sundaland) marks the time prior to collision of India with Asia when SE Asia, from the Tethys in the west to the Palaeo-Pacific in the east, lay in the upper plate of subduction zones. In Myanmar and Sumatra, subduction was interrupted in the Aptian-Albian by a phase of arc accretion (Woyla and Mawgyi arcs) and in Java, eastern Borneo and Western Sulawesi by collision of continental fragments rifted from northern Australia. Subsequent resumption of subduction in the Myanmar-Thailand sector explains: 1) early creation of oceanic crust in the Andaman Sea in a supra-subduction zone setting ~ 95 Ma, 2) the belt of granite plutons of Late Cretaceous-Early Palaeogene age (starting ~ 88 Ma) in western Thailand and central Myanmar, and 3) amphibolite grade metamorphism between 70 and 80 Ma seen in gneissic outcrops in western and central Thailand, and 4) accretionary prism development in the Western Belt of Myanmar, until glancing collision with the NE corner of Greater India promoted ophiolite obduction, deformation and exhumation of marine sediments in the early Palaeogene. The Ranong strike-slip fault and other less well documented faults, were episodically active during the Late Cretaceous-Palaeogene time. N to NW directed subduction of the Palaeo-Pacific ocean below Southern China, Vietnam and Borneo created a major magmatic arc, associated with rift basins, metamorphic core complexes and strike-slip deformation which continued into the Late Cretaceous. The origin and timing of termination of subduction has recently been explained by collision of a large Luconia continental fragment either during the Late Cretaceous or Palaeogene. Evidence for such a collision is absent from the South China Sea well and seismic reflection record and here collision is discounted. Instead relocation of the subducting margin further west, possibly in response of back-arc extension (which created the Proto

  11. The origin and early evolution of metatherian mammals: the Cretaceous record

    PubMed Central

    Williamson, Thomas E.; Brusatte, Stephen L.; Wilson, Gregory P.

    2014-01-01

    Abstract Metatherians, which comprise marsupials and their closest fossil relatives, were one of the most dominant clades of mammals during the Cretaceous and are the most diverse clade of living mammals after Placentalia. Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. Metatherians were widespread over Laurasia during the Cretaceous, with members present in Asia, Europe, and North America by the early Late Cretaceous. In particular, they were taxonomically and morphologically diverse and relatively abundant in the Late Cretaceous of western North America, where they have been used to examine patterns of biogeography, macroevolution, diversification, and extinction through the Late Cretaceous and across the Cretaceous-Paleogene (K-Pg) boundary. Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary. PMID:25589872

  12. A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan

    PubMed Central

    Kusuhashi, Nao; Tsutsumi, Yukiyasu; Saegusa, Haruo; Horie, Kenji; Ikeda, Tadahiro; Yokoyama, Kazumi; Shiraishi, Kazuyuki

    2013-01-01

    We here describe a new Early Cretaceous (early Albian) eutherian mammal, Sasayamamylos kawaii gen. et sp. nov., from the ‘Lower Formation’ of the Sasayama Group, Hyogo Prefecture, Japan. Sasayamamylos kawaii is characterized by a robust dentary, a distinct angle on the ventral margin of the dentary at the posterior end of the mandibular symphysis, a lower dental formula of 3–4 : 1 : 4 : 3, a robust lower canine, a non-molariform lower ultimate premolar, and a secondarily reduced entoconid on the molars. To date, S. kawaii is the earliest known eutherian mammal possessing only four premolars, which demonstrates that the reduction in the premolar count in eutherians started in the late Early Cretaceous. The occurrence of S. kawaii implies that the relatively rapid diversification of eutherians in the mid-Cretaceous had already started by the early Albian. PMID:23536594

  13. A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan.

    PubMed

    Kusuhashi, Nao; Tsutsumi, Yukiyasu; Saegusa, Haruo; Horie, Kenji; Ikeda, Tadahiro; Yokoyama, Kazumi; Shiraishi, Kazuyuki

    2013-05-22

    We here describe a new Early Cretaceous (early Albian) eutherian mammal, Sasayamamylos kawaii gen. et sp. nov., from the 'Lower Formation' of the Sasayama Group, Hyogo Prefecture, Japan. Sasayamamylos kawaii is characterized by a robust dentary, a distinct angle on the ventral margin of the dentary at the posterior end of the mandibular symphysis, a lower dental formula of 3-4 : 1 : 4 : 3, a robust lower canine, a non-molariform lower ultimate premolar, and a secondarily reduced entoconid on the molars. To date, S. kawaii is the earliest known eutherian mammal possessing only four premolars, which demonstrates that the reduction in the premolar count in eutherians started in the late Early Cretaceous. The occurrence of S. kawaii implies that the relatively rapid diversification of eutherians in the mid-Cretaceous had already started by the early Albian.

  14. Early Cretaceous greenhouse pumped higher taxa diversification in spiders.

    PubMed

    Shao, Lili; Li, Shuqiang

    2018-05-24

    The Cretaceous experienced one of the most remarkable greenhouse periods in geological history. During this time, ecosystem reorganizations significantly impacted the diversification of many groups of organisms. The rise of angiosperms marked a major biome turnover. Notwithstanding, relatively little remains known about how the Cretaceous global ecosystem impacted the evolution of spiders, which constitute one of the most abundant groups of predators. Herein, we evaluate the transcriptomes of 91 taxa representing more than half of the spider families. We add 23 newly sequenced taxa to the existing database to obtain a robust phylogenomic assessment. Phylogenetic reconstructions using different datasets and methods obtain novel placements of some groups, especially in the Synspermiata and the group having a retrolateral tibial apophysis (RTA). Molecular analyses indicate an expansion of the RTA clade at the Early Cretaceous with a hunting predatory strategy shift. Fossil analyses show a 7-fold increase of diversification rate at the same period, but this likely owes to the first occurrences spider in amber deposits. Additional analyses of fossil abundance show an accumulation of spider lineages in the Early Cretaceous. We speculate that the establishment of a warm greenhouse climate pumped the diversification of spiders, in particular among webless forms tracking the abundance of insect prey. Our study offers a new pathway for future investigations of spider phylogeny and diversification. Copyright © 2018. Published by Elsevier Inc.

  15. Fossil evidence of avian crops from the Early Cretaceous of China

    PubMed Central

    Zheng, Xiaoting; Martin, Larry D.; Zhou, Zhonghe; Burnham, David A.; Zhang, Fucheng; Miao, Desui

    2011-01-01

    The crop is characteristic of seed-eating birds today, yet little is known about its early history despite remarkable discoveries of many Mesozoic seed-eating birds in the past decade. Here we report the discovery of some early fossil evidence for the presence of a crop in birds. Two Early Cretaceous birds, the basal ornithurine Hongshanornis and a basal avian Sapeornis, demonstrate that an essentially modern avian digestive system formed early in avian evolution. The discovery of a crop in two phylogenetically remote lineages of Early Cretaceous birds and its absence in most intervening forms indicates that it was independently acquired as a specialized seed-eating adaptation. Finally, the reduction or loss of teeth in the forms showing seed-filled crops suggests that granivory was possibly one of the factors that resulted in the reduction of teeth in early birds. PMID:21896733

  16. Water quality in select regions of Cauvery Delta River basin, southern India, with emphasis on monsoonal variation.

    PubMed

    Solaraj, Govindaraj; Dhanakumar, Selvaraj; Murthy, Kuppuraj Rutharvel; Mohanraj, Rangaswamy

    2010-07-01

    Delta regions of the Cauvery River basin are one of the significant areas of rice production in India. In spite of large-scale utilization of the river basin for irrigation and drinking purposes, the lack of appropriate water management has seemingly deteriorated the water quality due to increasing anthropogenic activities. To assess the extent of deterioration, physicochemical characteristics of surface water were analyzed monthly in select regions of Cauvery Delta River basin, India, during July 2007 to December 2007. Total dissolved solids, chemical oxygen demand, and phosphate recorded maximum levels of 1,638, 96, and 0.43 mg/l, respectively, exceeding the permissible levels at certain sampling stations. Monsoonal rains in Cauvery River basin and the subsequent increase in river flow rate influences certain parameters like dissolved solids, phosphate, and dissolved oxygen. Agricultural runoff from watershed, sewage, and industrial effluents are suspected as probable factors of water pollution.

  17. The Early Cretaceous Sulfur Isotope Record: New Data, Revised Ages, and Updated Modeling

    NASA Astrophysics Data System (ADS)

    Kristall, B.; Hurtgen, M.; Sageman, B. B.; Jacobson, A. D.

    2015-12-01

    The Early Cretaceous is a time of significant transformation with the continued break-up of Pangea, the emplacement of several LIPs, and a climatic shift from a cool greenhouse to a warm greenhouse. The timing of these major events and their relationship to seawater geochemistry (as recorded in isotope records) is critical for understanding changes in global biogeochemical cycles during this time. Within this context, recent revisions to the Cretaceous portion of the geologic timescale necessitate a reevaluation of the Cretaceous S isotope record as recorded in marine barite (Paytan et al., 2004). We present a revised Early Cretaceous S isotope record and present new δ34Sbarite data that extend the record further back in time and provide more detail during two major S isotope shifts of the Early Cretaceous. The new data maintain the major ~5‰ negative shift but raise questions on the timing and structure of this perturbation. Furthermore, recently updated estimates for global rates of marine microbial sulfate reduction (MSR) (Bowles et al., 2014) and sulfate burial during the Phanerozoic (Halevy et al., 2012) require notable revisions in the fluxes and isotopic values used to model the global S cycle. We present a revised global S cycle box model and reconstruct the evolution of the Early Cretaceous S isotope record primarily through perturbations in volcanic and hydrothermal fluxes (e.g., submarine LIPs). Changes to the weathering and pyrite burial fluxes and the global integrated fractionation factor for MSR are also used to modulate, balance, and smooth the LIP-driven perturbation. The massive evaporite burial during the Late Aptian post dates the major -5‰ shift and has little affect on the modeled S isotope composition of seawater sulfate, despite causing a major drop in sulfate concentration. The S cycle box model is coupled to a Sr cycle box model to provide additional constraints on the magnitude and timing of perturbations within the S isotope record.

  18. The Wandering Indian Plate and Its Changing Biogeography During the Late Cretaceous-Early Tertiary Period

    NASA Astrophysics Data System (ADS)

    Chatterjee, Sankar; Scotese, Christopher

    Palaeobiogeographic analysis of Indian tetrapods during the Late Cretaceous-Early Tertiary time has recognized that both vicariance and geodispersal have played important roles in producing biogeographic congruence. The biogeographic patterns show oscillating cycles of geodispersal (Late Cretaceous), followed by congruent episodes of vicariance and geodispersal (Early Eocene), followed by another geodispersal event (Middle Eocene). New biogeographic synthesis suggests that the Late Cretaceous Indian tetrapod fauna is cosmopolitan with both Gondwanan and Laurasian elements. Throughout most of the Cretaceous, India was separated from the rest of Gondwana, but in the latest Cretaceous it reestablished contact with Africa through Kohistan-Dras (K-D) volcanic arc, and maintained biotic link with South America via Ninetyeast Ridge-Kerguelen-Antarctica corridor. These two geodispersal routes allowed exchanges of "pan-Gondwana" terrestrial tetrapods from Africa, South America, and Madagascar. During that time India also maintained biotic connections with Laurasia across the Neotethys via Kohistan-Dras Arc and Africa. During the Palaeocene, India, welded to the K-D Arc, rafted like a "Noah's Ark" as an island continent and underwent rapid cladogenesis because of allopatric speciation. Although the Palaeocene fossil record is blank, Early Eocene tetrapods contain both endemic and cosmopolitan elements, but Middle Eocene faunas have strong Asian character. India collided with Asia in Early and Middle Eocene time and established a new northeast corridor for faunal migration to facilitate the bidirectional "Great Asian Interchange" dispersals.

  19. Fossil evidence for a herbaceous diversification of early eudicot angiosperms during the Early Cretaceous

    PubMed Central

    Jud, Nathan A.

    2015-01-01

    Eudicot flowering plants comprise roughly 70% of land plant species diversity today, but their early evolution is not well understood. Fossil evidence has been largely restricted to their distinctive tricolpate pollen grains and this has limited our understanding of the ecological strategies that characterized their primary radiation. I describe megafossils of an Early Cretaceous eudicot from the Potomac Group in Maryland and Virginia, USA that are complete enough to allow reconstruction of important life-history traits. I draw on quantitative and qualitative analysis of functional traits, phylogenetic analysis and sedimentological evidence to reconstruct the biology of this extinct species. These plants were small and locally rare but widespread, fast-growing herbs. They had complex leaves and they were colonizers of bright, wet, disturbance-prone habitats. Other early eudicot megafossils appear to be herbaceous rather than woody, suggesting that this habit was characteristic of their primary radiation. A mostly herbaceous initial diversification of eudicots could simultaneously explain the heretofore sparse megafossil record as well as their rapid diversification during the Early Cretaceous because the angiosperm capacity for fast reproduction and fast evolution is best expressed in herbs. PMID:26336172

  20. Fossil evidence for a herbaceous diversification of early eudicot angiosperms during the Early Cretaceous.

    PubMed

    Jud, Nathan A

    2015-09-07

    Eudicot flowering plants comprise roughly 70% of land plant species diversity today, but their early evolution is not well understood. Fossil evidence has been largely restricted to their distinctive tricolpate pollen grains and this has limited our understanding of the ecological strategies that characterized their primary radiation. I describe megafossils of an Early Cretaceous eudicot from the Potomac Group in Maryland and Virginia, USA that are complete enough to allow reconstruction of important life-history traits. I draw on quantitative and qualitative analysis of functional traits, phylogenetic analysis and sedimentological evidence to reconstruct the biology of this extinct species. These plants were small and locally rare but widespread, fast-growing herbs. They had complex leaves and they were colonizers of bright, wet, disturbance-prone habitats. Other early eudicot megafossils appear to be herbaceous rather than woody, suggesting that this habit was characteristic of their primary radiation. A mostly herbaceous initial diversification of eudicots could simultaneously explain the heretofore sparse megafossil record as well as their rapid diversification during the Early Cretaceous because the angiosperm capacity for fast reproduction and fast evolution is best expressed in herbs. © 2015 The Author(s).

  1. Morphologically Specialized Termite Castes and Advanced Sociality in the Early Cretaceous.

    PubMed

    Engel, Michael S; Barden, Phillip; Riccio, Mark L; Grimaldi, David A

    2016-02-22

    A hallmark of animals that are eusocial, or those with advanced sociality, is reproductive specialization into worker and queen castes. In the most derived societies, these divisions are essentially fixed and in some arthropods, include further specialization--a tripartite system with a soldier caste that defends the colony. Eusociality has originated numerous times among insects but is believed to have appeared first in the termites (Isoptera), in the Early Cretaceous. However, all termites known from the Cretaceous have, until now, only been winged reproductives (alates and dealates); the earliest soldiers and definitive workers were known from just the Miocene (ca. 17-20 million years ago [mya]). Here, we report six termite species preserved in Early Cretaceous (ca. 100 mya) amber from Myanmar, one described as Krishnatermes yoddha gen. et sp. nov., comprising the worker/pseudergate, winged reproductive, and soldier, and a second species, Gigantotermes rex gen. et sp. nov., based on one of the largest soldier termites yet known. Phylogenetic analysis indicates that Krishnatermes are in the basal "Meiatermes-grade" of Cretaceous termites. Workers/pseudergates of another four species are briefly described, but not named. One of these workers/pseudergates reveals that ants--the most serious enemies of modern termites--lived in close proximity to termites in the Burmese paleofauna. These discoveries demonstrate the Mesozoic antiquity of specialized termite caste systems and corroborate that among all social species, termites probably had the original societies. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26-30 °C) existed from this interval (∼160 Ma) to the Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian-Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (∼26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite δ18O 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.

  3. A complete skull of an early cretaceous sauropod and the evolution of advanced titanosaurians.

    PubMed

    Zaher, Hussam; Pol, Diego; Carvalho, Alberto B; Nascimento, Paulo M; Riccomini, Claudio; Larson, Peter; Juarez-Valieri, Rubén; Pires-Domingues, Ricardo; da Silva, Nelson Jorge; Campos, Diógenes de Almeida

    2011-02-07

    Advanced titanosaurian sauropods, such as nemegtosaurids and saltasaurids, were diverse and one of the most important groups of herbivores in the terrestrial biotas of the Late Cretaceous. However, little is known about their rise and diversification prior to the Late Cretaceous. Furthermore, the evolution of their highly-modified skull anatomy has been largely hindered by the scarcity of well-preserved cranial remains. A new sauropod dinosaur from the Early Cretaceous of Brazil represents the earliest advanced titanosaurian known to date, demonstrating that the initial diversification of advanced titanosaurians was well under way at least 30 million years before their known radiation in the latest Cretaceous. The new taxon also preserves the most complete skull among titanosaurians, further revealing that their low and elongated diplodocid-like skull morphology appeared much earlier than previously thought.

  4. Early cretaceous dinosaurs from the sahara.

    PubMed

    Sereno, P C; Wilson, J A; Larsson, H C; Dutheil, D B; Sues, H D

    1994-10-14

    A major question in Mesozoic biogeography is how the land-based dinosaurian radiation responded to fragmentation of Pangaea. A rich fossil record has been uncovered on northern continents that spans the Cretaceous, when continental isolation reached its peak. In contrast, dinosaur remains on southern continents are scarce. The discovery of dinosaurian skeletons from Lower Cretaceous beds in the southern Sahara shows that several lineages of tetanuran theropods and broad-toothed sauropods had a cosmopolitan distribution across Pangaea before the onset of continental fragmentation. The distinct dinosaurian faunas of Africa, South America, and Asiamerica arose during the Cretaceous by differential survival of once widespread lineages on land masses that were becoming increasingly isolated from one another.

  5. A New Sail-Backed Styracosternan (Dinosauria: Ornithopoda) from the Early Cretaceous of Morella, Spain.

    PubMed

    Gasulla, José Miguel; Escaso, Fernando; Narváez, Iván; Ortega, Francisco; Sanz, José Luis

    2015-01-01

    A new styracosternan ornithopod genus and species is here described based on a partial postcranial skeleton and an associated dentary tooth of a single specimen from the Arcillas de Morella Formation (Early Cretaceous, late Barremian) at the Morella locality, (Castellón, Spain). Morelladon beltrani gen. et sp. nov. is diagnosed by eight autapomorphic features. The set of autapomorphies includes: very elongated and vertical neural spines of the dorsal vertebrae, midline keel on ventral surface of the second to fourth sacral vertebrae restricted to the anterior half of the centrum, a posterodorsally inclined medial ridge on the postacetabular process of the ilium that meets its dorsal margin and distal end of the straight ischial shaft laterally expanded, among others. Phylogenetic analyses reveal that the new Iberian form is more closely related to its synchronic and sympatric contemporary European taxa Iguanodon bernissartensis and Mantellisaurus atherfieldensis, known from Western Europe, than to other Early Cretaceous Iberian styracosternans (Delapparentia turolensis and Proa valdearinnoensis). The recognition of Morelladon beltrani gen. et sp. nov. indicates that the Iberian Peninsula was home to a highly diverse medium to large bodied styracosternan assemblage during the Early Cretaceous.

  6. Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska

    USGS Publications Warehouse

    Bundtzen, Thomas K.; Miller, Marti L.; Goldfarb, Richard J.; Miller, Lance D.

    1997-01-01

    Placer gold and precious metal-bearing lode deposits of southwestern Alaska lie within a region 550 by 350 km, herein referred to as the Kuskokwim mineral belt. This mineral belt has yielded 100,240 kg (3.22 Moz) of gold, 12, 813 kg (412,000 oz) of silver, 1,377,412 kg (39,960 flasks) of mercury, and modest amounts of antimony and tungsten derived primarily from the late Cretaceous-early Tertiary igneous complexes of four major types: (1) alkali-calcic, comagmatic volcanic-plutonic complexes and isolated plutons, (2) calc-alkaline, meta-aluminous reduced plutons, (3) peraluminous alaskite or granite-porphyry sills and dike swarms, and (4) andesite-rhyolite subaerial volcanic rocks.About 80 percent of the 77 to 52 Ma intrusive and volcanic rocks intrude or overlie the middle to Upper Cretaceous Kuskokwim Group sedimentary and volcanic rocks, as well as the Paleozoic-Mesozoic rocks of the Nixon Fork, Innoko, Goodnews, and Ruby preaccretionary terranes.The major precious metal-bearing deposit types related to Late Cretaceous-early Tertiary igneous complexes of the Kuskokwim mineral belt are subdivided as follows: (1) plutonic-hosted copper-gold polymetallic stockwork, skarn, and vein deposits, (2) peraluminous granite-porphory-hosted gold polymetallic deposits, (3) plutonic-related, boron-enriched silver-tin polymetallic breccia pipes and replacement deposits, (4) gold and silver mineralization in epithermal systems, and (5) gold polymetallic heavy mineral placer deposits. Ten deposits genetically related to Late Cretaceous-early Tertiary intrusions contain minimum, inferred reserves amounting to 162,572 kg (5.23 Moz) of gold, 201,015 kg (6.46 Moz) silver, 12,160 metric tons (t) of tin, and 28,088 t of copper.The lodes occur in veins, stockworks, breccia pipes, and replacement deposits that formed in epithermal to mesothermal temperature-pressure conditions. Fluid inclusion, isotopic age, mineral assemblage, alteration assemblage, and structural data indicate that

  7. Isotopic evidence for continental ice sheet in mid-latitude region in the supergreenhouse Early Cretaceous

    PubMed Central

    Yang, Wu-Bin; Niu, He-Cai; Sun, Wei-Dong; Shan, Qiang; Zheng, Yong-Fei; Li, Ning-Bo; Li, Cong-Ying; Arndt, Nicholas T.; Xu, Xing; Jiang, Yu-Hang; Yu, Xue-Yuan

    2013-01-01

    Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ18O values of −18.12‰ to −13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ18O value close to mantle values, the extremely negative δ18O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ18O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period. PMID:24061068

  8. A nearly modern amphibious bird from the Early Cretaceous of northwestern China.

    PubMed

    You, Hai-Lu; Lamanna, Matthew C; Harris, Jerald D; Chiappe, Luis M; O'connor, Jingmai; Ji, Shu-An; Lü, Jun-Chang; Yuan, Chong-Xi; Li, Da-Qing; Zhang, Xing; Lacovara, Kenneth J; Dodson, Peter; Ji, Qiang

    2006-06-16

    Three-dimensional specimens of the volant fossil bird Gansus yumenensis from the Early Cretaceous Xiagou Formation of northwestern China demonstrate that this taxon possesses advanced anatomical features previously known only in Late Cretaceous and Cenozoic ornithuran birds. Phylogenetic analysis recovers Gansus within the Ornithurae, making it the oldest known member of the clade. The Xiagou Formation preserves the oldest known ornithuromorph-dominated avian assemblage. The anatomy of Gansus, like that of other non-neornithean (nonmodern) ornithuran birds, indicates specialization for an amphibious life-style, supporting the hypothesis that modern birds originated in aquatic or littoral niches.

  9. Assessment of potential shale gas resources of the Bombay, Cauvery, and Krishna-Godavari Provinces, India, 2011

    USGS Publications Warehouse

    ,

    2012-01-01

    Using a performance-based geologic assessment methodology, the U.S. Geological Survey estimated a technically recoverable mean volume of 6.1 trillion cubic feet of potential shale gas in the Bombay, Cauvery, and Krishna-Godavari Provinces of India.

  10. Low ecological disparity in Early Cretaceous birds

    PubMed Central

    Mitchell, Jonathan S.; Makovicky, Peter J.

    2014-01-01

    Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (= pygostylians) from the Jehol Biota (≈ 125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem. PMID:24870044

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

    USGS Publications Warehouse

    Bishop, M.G.

    1999-01-01

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

  12. Paleomagnetic tests for tectonic reconstructions of the Late Jurassic-Early Cretaceous Woyla Group, Sumatra

    NASA Astrophysics Data System (ADS)

    Advokaat, Eldert; Bongers, Mayke; van Hinsbergen, Douwe; Rudyawan, Alfend; Marshal, Edo

    2017-04-01

    SE Asia consists of multiple continental blocks, volcanic arcs and suture zones representing remnants of closing ocean basins. The core of this mainland is called Sundaland, and was formed by accretion of continental and arc fragments during the Paleozoic and Mesozoic. The former positions of these blocks are still uncertain but reconstructions based on tectonostratigraphic, palaeobiogeographic, geological and palaeomagnetic studies indicate the continental terranes separated from the eastern margin of Gondwana. During the mid-Cretaceous, more continental and arc fragments accreted to Sundaland, including the intra-oceanic Woyla Arc now exposed on Sumatra. These continental fragments were derived from Australia, but the former position of the Woyla Arc is unconstrained. Interpretations on the former position of the Woyla Arc fall in two end-member groups. The first group interprets the Woyla Arc to be separated from West Sumatra by a small back-arc basin. This back arc basin opened in the Late Jurassic, and closed mid-Cretaceous, when the Woyla Arc collided with West Sumatra. The other group interprets the Woyla Arc to be derived from Gondwana, at a position close to the northern margin of Greater India in the Late Jurassic. Subsequently the Woyla Arc moved northwards and collided with West Sumatra in the mid-Cretaceous. Since these scenarios predict very different plate kinematic evolutions for the Neotethyan realm, we here aim to place paleomagnetic constraints on paleolatitudinal evolution of the Woyla Arc. The Woyla Arc consists mainly of basaltic to andesitic volcanics and dykes, and volcaniclastic shales and sandstones. Associated limestones with volcanic debris are interpreted as fringing reefs. This assemblage is interpreted as remnants of an Early Cretaceous intra-oceanic arc. West Sumatra exposes granites, surrounded by quartz sandstones, shales and volcanic tuffs. These sediments are in part metamorphosed. This assemblage is interpreted as a Jurassic-Early

  13. EVOLUTION. A four-legged snake from the Early Cretaceous of Gondwana.

    PubMed

    Martill, David M; Tischlinger, Helmut; Longrich, Nicholas R

    2015-07-24

    Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana. Copyright © 2015, American Association for the Advancement of Science.

  14. New Crocodyliform specimens from Recôncavo-Tucano Basin (Early Cretaceous) of Bahia, Brazil.

    PubMed

    Souza, Rafael G DE; Campos, Diogenes A

    2018-04-16

    In 1940, L.I. Price and A. Oliveira recovered four crocodyliform specimens from the Early Cretaceous Bahia Supergroup (Recôncavo-Tucano Basin). In the present work, we describe four different fossil specimens: an osteoderm, a fibula, a tibia, and some autopodial bones. No further identification besides Mesoeucrocodylia was made due to their fragmentary nature and the reduced number of recognized synapomorphies for more inclusive clades. With exception of the fibula, all other specimens have at least one particular feature, which with new specimens could represent new species. The new specimens described here increase the known diversity of Early Cretaceous crocodyliforms from Brazil. This work highlights the great fossiliferous potential of Recôncavo-Tucano Basin with regard to crocodyliform remains.

  15. Changes to Cretaceous surface fire behaviour influenced the spread of the early angiosperms.

    PubMed

    Belcher, Claire M; Hudspith, Victoria A

    2017-02-01

    Angiosperms evolved and diversified during the Cretaceous period. Early angiosperms were short-stature weedy plants thought to have increased fire frequency and mortality in gymnosperm forest, aiding their own expansion. However, no explorations have considered whether the range of novel fuel types that diversified throughout the Cretaceous also altered fire behaviour, which should link more strongly to mortality than fire frequency alone. We measured ignitability and heat of combustion in analogue Cretaceous understorey fuels (conifer litter, ferns, weedy and shrubby angiosperms) and used these data to model palaeofire behaviour. Variations in ignition, driven by weedy angiosperms alone, were found to have been a less important feedback to changes in Cretaceous fire activity than previously estimated. Our model estimates suggest that fires in shrub and fern understories had significantly greater fireline intensities than those fuelled by conifer litter or weedy angiosperms, and whilst fern understories supported the most rapid fire spread, angiosperm shrubs delivered the largest amount of heat per unit area. The higher fireline intensities predicted by the models led to estimates of enhanced scorch of the gymnosperm canopy and a greater chance of transitioning to crown fires. Therefore, changes in fire behaviour driven by the addition of new Cretaceous fuel groups may have assisted the angiosperm expansion. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  16. Modern mammal origins: evolutionary grades in the Early Cretaceous of North America.

    PubMed

    Jacobs, L L; Winkler, D A; Murry, P A

    1989-07-01

    Major groups of modern mammals have their origins in the Mesozoic Era, yet the mammalian fossil record is generally poor for that time interval. Fundamental morphological changes that led to modern mammals are often represented by small samples of isolated teeth. Fortunately, functional wear facets on teeth allow prediction of the morphology of occluding teeth that may be unrepresented by fossils. A major step in mammalian evolution occurred in the Early Cretaceous with the evolution of tribosphenic molars, which characterize marsupials and placentals, the two most abundant and diverse extant groups of mammals. A tooth from the Early Cretaceous (110 million years before present) of Texas tests previous predictions (based on lower molars) of the morphology of upper molars in early tribosphenic dentitions. The lingual cusp (protocone) is primitively without shear facets, as expected, but the cheek side of the tooth is derived (advanced) in having distinctive cusps along the margin. The tooth, although distressingly inadequate to define many features of the organism, demonstrates unexpected morphological diversity at a strategic stage of mammalian evolution and falsifies previous claims of the earliest occurrence of true marsupials.

  17. Modern mammal origins: evolutionary grades in the Early Cretaceous of North America.

    PubMed Central

    Jacobs, L L; Winkler, D A; Murry, P A

    1989-01-01

    Major groups of modern mammals have their origins in the Mesozoic Era, yet the mammalian fossil record is generally poor for that time interval. Fundamental morphological changes that led to modern mammals are often represented by small samples of isolated teeth. Fortunately, functional wear facets on teeth allow prediction of the morphology of occluding teeth that may be unrepresented by fossils. A major step in mammalian evolution occurred in the Early Cretaceous with the evolution of tribosphenic molars, which characterize marsupials and placentals, the two most abundant and diverse extant groups of mammals. A tooth from the Early Cretaceous (110 million years before present) of Texas tests previous predictions (based on lower molars) of the morphology of upper molars in early tribosphenic dentitions. The lingual cusp (protocone) is primitively without shear facets, as expected, but the cheek side of the tooth is derived (advanced) in having distinctive cusps along the margin. The tooth, although distressingly inadequate to define many features of the organism, demonstrates unexpected morphological diversity at a strategic stage of mammalian evolution and falsifies previous claims of the earliest occurrence of true marsupials. Images PMID:2740336

  18. A Diplodocid Sauropod Survivor from the Early Cretaceous of South America

    PubMed Central

    Gallina, Pablo A.; Apesteguía, Sebastián; Haluza, Alejandro; Canale, Juan I.

    2014-01-01

    Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation) of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere. PMID:24828328

  19. A diplodocid sauropod survivor from the early cretaceous of South America.

    PubMed

    Gallina, Pablo A; Apesteguía, Sebastián; Haluza, Alejandro; Canale, Juan I

    2014-01-01

    Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation) of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere.

  20. Closure of the Mongol-Okhotsk Ocean as Constrained by Late Permian to Early Cretaceous Paleomagnetic Data from the Suture Zone

    NASA Astrophysics Data System (ADS)

    Cogne, J.; Kravchinsky, V.; Gilder, S.; Hankard, F.

    2005-12-01

    The Paleozoic Mongol-Okhotsk Ocean separated the Siberian craton to the north from a landmass composed of Amuria, Tarim, Qaidam, Tibet and the North and South China blocks to the south. Based on a comparison of paleomagnetic data from the NCB with the Eurasian apparent polar wander path, this ocean closed by the beginning of the Cretaceous. We present here a review of recent paleomagnetic studies of Late Permian to Early Cretaceous formations from the Transbaikal area of south Siberia, coming from localities situated on both sides of the Mongol-Okhotsk suture zone. The main conclusions that we draw from these studies are as follows. (1) A Late Permian ~4500 km latitude difference indeed existed between Amuria and the Siberia blocks at 110°E longitude. (2) In Middle-Late Jurassic times, a 1700 to 2700 km paleolatitudinal gap still existed between the two blocks. This contradicts geological interpretations of a Middle Jurassic closure of the ocean at this longitude. (3) Consistency of Early Cretaceous paleolatitudes from both sides of the suture demonstrates the closure of the ocean at that time. Altogether, these suggest a quite fast closure between the Middle Jurassic and the Early Cretaceous, at about 15±11 cm/yr. Finally, all pre-Late Cretaceous paleomagnetic poles appear to be distributed along small-circles centered on site localities. We think this is due to continued deformation acting in the Mongol-Okhotsk suture region related to suturing. Conversely, the post-Early Cretaceous rotations may be related to Tertiary deformation under the effect of the India-Asia collision.

  1. Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis.

    PubMed

    Pan, Yanhong; Zheng, Wenxia; Moyer, Alison E; O'Connor, Jingmai K; Wang, Min; Zheng, Xiaoting; Wang, Xiaoli; Schroeter, Elena R; Zhou, Zhonghe; Schweitzer, Mary H

    2016-12-06

    Microbodies associated with feathers of both nonavian dinosaurs and early birds were first identified as bacteria but have been reinterpreted as melanosomes. Whereas melanosomes in modern feathers are always surrounded by and embedded in keratin, melanosomes embedded in keratin in fossils has not been demonstrated. Here we provide multiple independent molecular analyses of both microbodies and the associated matrix recovered from feathers of a new specimen of the basal bird Eoconfuciusornis from the Early Cretaceous Jehol Biota of China. Our work represents the oldest ultrastructural and immunological recognition of avian beta-keratin from an Early Cretaceous (∼130-Ma) bird. We apply immunogold to identify protein epitopes at high resolution, by localizing antibody-antigen complexes to specific fossil ultrastructures. Retention of original keratinous proteins in the matrix surrounding electron-opaque microbodies supports their assignment as melanosomes and adds to the criteria employable to distinguish melanosomes from microbial bodies. Our work sheds new light on molecular preservation within normally labile tissues preserved in fossils.

  2. Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis

    PubMed Central

    Pan, Yanhong; Zheng, Wenxia; Moyer, Alison E.; O’Connor, Jingmai K.; Zheng, Xiaoting; Wang, Xiaoli; Schroeter, Elena R.; Zhou, Zhonghe; Schweitzer, Mary H.

    2016-01-01

    Microbodies associated with feathers of both nonavian dinosaurs and early birds were first identified as bacteria but have been reinterpreted as melanosomes. Whereas melanosomes in modern feathers are always surrounded by and embedded in keratin, melanosomes embedded in keratin in fossils has not been demonstrated. Here we provide multiple independent molecular analyses of both microbodies and the associated matrix recovered from feathers of a new specimen of the basal bird Eoconfuciusornis from the Early Cretaceous Jehol Biota of China. Our work represents the oldest ultrastructural and immunological recognition of avian beta-keratin from an Early Cretaceous (∼130-Ma) bird. We apply immunogold to identify protein epitopes at high resolution, by localizing antibody–antigen complexes to specific fossil ultrastructures. Retention of original keratinous proteins in the matrix surrounding electron-opaque microbodies supports their assignment as melanosomes and adds to the criteria employable to distinguish melanosomes from microbial bodies. Our work sheds new light on molecular preservation within normally labile tissues preserved in fossils. PMID:27872291

  3. Dolomitization in Late Jurassic-Early Cretaceous Platform Carbonates (Berdiga Formation), Ayralaksa Yayla (Trabzon), NE Turkey

    NASA Astrophysics Data System (ADS)

    Yıldız, Merve; Ziya Kırmacı, Mehmet; Kandemir, Raif

    2017-04-01

    ABSTRACT Pontides constitute an E-W trending orogenic mountain belt that extends about 1100 km along the northern side of Turkey from the immediate east of Istanbul to the Georgian border at the east. Tectono-stratigraphically, the Pontides are divided into three different parts: Eastern, Central, and Western Pontides. The Eastern Pontides, including the studied area, comprise an area of 500 km in length and 100 km in width, extending along the southeast coast of the Black Sea from the Kizilirmak and Yesilirmak Rivers in the vicinity of Samsun to the Little Caucasus. This area is bordered by the Eastern Black Sea basin to the north and the Ankara-Erzincan Neotethyan suture zone to the south. The Late Jurassic-Early Cretaceous platform carbonates are widely exposed in E-W direction in the Eastern Pontides (NE Turkey). The Platform carbonates shows varying lithofacies changing from supratidal to platform margin reef laterally and vertically, and was buried until the end of Late Cretaceous. The studied Ayralaksa Yayla (Trabzon, NE Turkey) area comprises one of the best typical exposures of formation in northern zone of Eastern Pontides. In this area, the lower parts of the formation are pervasively dolomitized by fabric-destructive and fabric-preserving replacement dolomite which are Ca-rich and nonstoichiometric (Ca56-66Mg34-44). Replacement dolomites (Rd) are represented by D18O values of -19.0 to -4.2 (VPDB), D13C values of 4.4 to 2.1 \\permil (VPDB) and 87Sr/86Sr ratios of 0.70889 to 0.70636. Petrographic and geochemical data indicate that Rd dolomites are formed prior to compaction at shallow-moderate burial depths from Late Jurassic-Early Cretaceous seawater and/or partly modified seawater as a result of water/rock interaction and they were recrystallized at elevated temperatures during subsequent burial. In the subsequent diagenetic process during the Late Cretaceous when the region became a magmatic arc, as a result of interaction with Early Jurassic volcanic

  4. Early cretaceous topographic growth of the Lhasaplano, Tibetan plateau: Constraints from the Damxung conglomerate

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Gang; Hu, Xiumian; Garzanti, Eduardo; Ji, Wei-Qiang; Liu, Zhi-Chao; Liu, Xiao-Chi; Wu, Fu-Yuan

    2017-07-01

    Constraining the timing of early topographic growth on the Tibetan plateau is critical for any models of India-Asia collision, Himalayan orogeny and subsequent plateau development in the Cenozoic. Stratigraphic, sedimentological and provenance analysis of the Lower Cretaceous red-beds of the Damxung Conglomerate provide new key information to reconstruct the paleogeography and the tectonic evolution of the Lhasa terrane at the time. The over 700-m-thick Damxung Conglomerate documents distal alluvial fan to braidplain sedimentation passing upward to proximal alluvial fan sedimentation. Deposition began near sea level, as documented by limestone beds occurring at the base of the unit. Zircon U-Pb dating of interbedded tuff layers constrain deposition age at ca. 111 Ma. Abundance of volcanic clasts, Cretaceous U-Pb ages and Hf isotopes of detrital zircons yielding mainly negative ɛHf(t) values together with paleocurrent data indicate an active volcanic source located in the North Lhasa subterrane. Pre-Mesozoic-aged zircon, recycled quartz and (meta) sedimentary rock fragments increase up-section, indicating progressive erosional exhumation of the Paleozoic sedimentary/metasedimentary basement. The Damxung Conglomerate thus records a significant uplift and unroofing stage in the source region, implying initial topographic growth on the Lhasa terrane at early Albian time. Early Cretaceous topographic growth on the Lhasa terrane is supported by the stratigraphic record in the Linzhou basin, the Xigaze forearc basin and the southern Nima basin. In contrast, marine strata in the central-western Lhasa terrane lasted until the early Cenomanian (ca. 96 Ma), indicating diachronous marine regression on the Lhasa terrane from east to west.

  5. Middle Jurassic - Early Cretaceous rifting on the Chortis Block in Honduras: Implications for proto-Caribbean opening (Invited)

    NASA Astrophysics Data System (ADS)

    Rogers, R. D.; Emmet, P. A.

    2009-12-01

    Regional mapping integrated with facies analysis, age constraints and airborne geophysical data reveal WNW and NE trends of Middle Jurassic to Early Cretaceous basins which intersect in southeast Honduras that we interpret as the result of rifting associated with the breakup of the Americas and opening of the proto-Caribbean seaway. The WNW-trending rift is 250 km long by 90 km wide and defined by a basal 200 to 800 m thick sequence of Middle to Late Jurassic fluvial channel and overbank deposits overlain by transgressive clastic shelf strata. At least three sub-basins are apparent. Flanking the WNW trending rift basins are fault bounded exposures of the pre-Jurassic continental basement of the Chortis block which is the source of the conglomeratic channel facies that delineate the axes of the rifts. Cretaceous terrigenous strata mantle the exposed basement-cored rift flanks. Lower Cretaceous clastic strata and shallow marine limestone strata are dominant along this trend indicating that post-rift related subsidence continued through the Early Cretaceous. The rifts coincide with a regional high in the total magnetic intensity data. We interpret these trends to reflect NNE-WSW extension active from the Middle Jurassic through Early Cretaceous. These rifts were inverted during Late Cretaceous shortening oriented normal to the rift axes. To the east and at a 120 degree angle to the WNW trending rift is the 300 km long NE trending Guayape fault system that forms the western shoulder of the Late Jurassic Agua Fria rift basin filled by > 2 km thickness of clastic marine shelf and slope strata. This NE trending basin coincides with the eastern extent of the surface exposure of continental basement rocks and a northeast-trending fabric of the Jurassic (?) metasedimentary basement rocks. We have previously interpreted the eastern basin to be the Jurassic rifted margin of the Chortis block with the Guayape originating as a normal fault system. These two rifts basin intersect

  6. Characterization of minerals in natural and manufactured sand in Cauvery River belt, Tamilnadu, India

    NASA Astrophysics Data System (ADS)

    Gnanasaravanan, S.; Rajkumar, P.

    2013-05-01

    The present study investigates the characterization of minerals in the River Sand (R - Sand) and the Manufactured sand (M-Sand) through FTIR spectroscopic studies. The R - Sand is collected from seven different locations in Cauvery River and M - Sand is collected from eight different manufactures around the Cauvery River belt in Salem, Erode, Tirupur and Namakkal districts of Tamilnadu, India. To extend the effectiveness of the analysis, the samples were subjected to grain size separation to classify the bulk samples into different grain sizes. All the samples were analyzed using FTIR spectrometer. The number of minerals identified with the help of FTIR spectra in overall (bulk) samples of R - Sand is 14 and of M - Sand is 13. The number has been increased while going for grain size separation, i.e., from 14 to 31 for R - Sand and from 13 to 20 for M - Sand. Among all minerals, quartz plays a major role. The relative distribution and the crystallinity nature of quartz have been discussed based on the extinction co-efficient and the crystallinity index values computed. There is no major variation found in M - Sand while going for grain size separation.

  7. Inversion of the Erlian Basin (NE China) in the early Late Cretaceous: Implications for the collision of the Okhotomorsk Block with East Asia

    NASA Astrophysics Data System (ADS)

    Guo, Zhi-Xin; Shi, Yuan-Peng; Yang, Yong-Tai; Jiang, Shuan-Qi; Li, Lin-Bo; Zhao, Zhi-Gang

    2018-04-01

    A significant transition in tectonic regime from extension to compression occurred throughout East Asia during the mid-Cretaceous and has stimulated much attention. However, the timing and driving mechanisms of the transition remain disputed. The Erlian Basin, a giant late Mesozoic intracontinental petroliferous basin located in the Inner Mongolia, Northeast China, contains important sedimentary and structural records related to the mid-Cretaceous compressional event. The stratigraphical, sedimentological and structural analyses reveal that a NW-SE compressional inversion occurred in the Erlian Basin between the depositions of the Lower Cretaceous Saihan and Upper Cretaceous Erlian formations, causing intense folding of the Saihan Formation and underlying strata, and the northwestward migration of the depocenters of the Erlian Formation. Based on the newly obtained detrital zircon U-Pb data and previously published paleomagnetism- and fossil-based ages, the Saihan and Erlian formations are suggested as latest Aptian-Albian and post-early Cenomanian in age, respectively, implying that the inversion in the Erlian Basin occurred in the early Late Cretaceous (Cenomanian time). Apatite fission-track thermochronological data record an early Late Cretaceous cooling/exhuming event in the basin, corresponding well with the aforementioned sedimentary, structural and chronological analyses. Combining with the tectono-sedimentary evolutions of the neighboring basins of the Erlian Basin, we suggest that the early Late Cretaceous inversional event in the Erlian Basin and the large scale tectonic transition in East Asia shared the common driving mechanism, probably resulting from the Okhotomorsk Block-East Asia collisional event at about 100-89 Ma.

  8. Early Cretaceous Archaeamphora is not a carnivorous angiosperm

    PubMed Central

    Wong, William Oki; Dilcher, David Leonard; Labandeira, Conrad C.; Sun, Ge; Fleischmann, Andreas

    2015-01-01

    Archaeamphora longicervia H. Q. Li was described as an herbaceous, Sarraceniaceae-like pitcher plant from the mid Early Cretaceous Yixian Formation of Liaoning Province, northeastern China. Here, a re-investigation of A. longicervia specimens from the Yixian Formation provides new insights into its identity and the morphology of pitcher plants claimed by Li. We demonstrate that putative pitchers of Archaeamphora are insect-induced leaf galls that consist of three components: (1) an innermost larval chamber; (2) an intermediate zone of nutritive tissue; and (3) an outermost wall of sclerenchyma. Archaeamphora is not a carnivorous, Sarraceniaceae-like angiosperm, but represents insect-galled leaves of the previously reported gymnosperm Liaoningocladus boii G. Sun et al. from the Yixian Formation. PMID:25999978

  9. Early Cretaceous Umkomasia from Mongolia: implications for homology of corystosperm cupules.

    PubMed

    Shi, Gongle; Leslie, Andrew B; Herendeen, Patrick S; Herrera, Fabiany; Ichinnorov, Niiden; Takahashi, Masamichi; Knopf, Patrick; Crane, Peter R

    2016-06-01

    Corystosperms, a key extinct group of Late Permian to Early Cretaceous plants, are important for understanding seed plant phylogeny, including the evolution of the angiosperm carpel and anatropous bitegmic ovule. Here, we describe a new species of corystosperm seed-bearing organ, Umkomasia mongolica sp. nov., based on hundreds of three-dimensionally preserved mesofossils from the Early Cretaceous of Mongolia. Individual seed-bearing units of U. mongolica consist of a bract subtending an axis that bifurcates, with each fork (cupule stalk) bearing a cupule near the tip. Each cupule is formed by the strongly reflexed cupule stalk and two lateral flaps that partially enclose an erect seed. The seed is borne at, or close to, the tip of the reflexed cupule stalk, with the micropyle oriented towards the stalk base. The corystosperm cupule is generally interpreted as a modified leaf that bears a seed on its abaxial surface. However, U. mongolica suggests that an earlier interpretation, in which the seed is borne directly on an axis (shoot), is equally likely. The 'axial' interpretation suggests a possible relationship of corystosperms to Ginkgo. It also suggests that the cupules of corystosperms may be less distinct from those of Caytonia than has previously been supposed. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  10. Structure and rheology of the lithosphere below southeastern margin of India and Sri Lanka, and its conjugate segment of the east Antarctica: Implications on early breakup history and margin formation

    NASA Astrophysics Data System (ADS)

    Rao Gangumalla, Srinivasa; Radhakrishna, Munukutla

    2014-05-01

    The eastern continental margin of India has evolved as a consequence of rifting and breakup between India and east Antarctica during the early Cretaceous. Plate reconstruction models for the breakup of eastern Gondwanaland by many earlier workers have unambiguously placed the southeast margin of Sri Lanka and India together as a conjugate segment with the east Antarctica margin that extends from Gunnerus Ridge in the west to western Enderby basin in the east. In this study, we present results of integrated analysis of gravity, geoid, magnetic and seismic data from these two conjugate portions in order to examine the lithosphere structure and early seafloor spreading, style of breakup, continent-ocean boundary (COB) and rheological characteristics at these margins. The interpreted COB lies at a distance of 55-140 km on the side of southeast margin of Sri Lanka and India, whereas, it lies at a distance of 190-550 km on the side of east Antarctica margin. The seismic profiles and the constrained potential field models across these two segments do not show the existence of seaward dipping reflector sequences or magmatic underplating suggesting that these segments have not encountered major magmatic activity. While, significant crustal thinning/stretching is observed at the east Antarctic margin, the Cauvery offshore had experienced limited stretching with faulted Moho interface. Further, the conspicuous residual geoid low in the Cauvery offshore basin is inferred to be due to a continental crustal block. The modelled Lithosphere-Astenosphere Boundary (LAB) in these two margins is located around 110-120 km depth with slightly thicker lithosphere at the east Antarctica margin. In addition, the interpretation of magnetic anomalies provided structure of the oceanic crust generated through seafloor spreading processes with age and magnetization data constrained from the identified magnetic anomalies in the respective margins. Using the Bouguer coherence method, we computed

  11. Vertebrate assemblages from the early Late Cretaceous of southeastern Morocco: An overview

    NASA Astrophysics Data System (ADS)

    Cavin, L.; Tong, H.; Boudad, L.; Meister, C.; Piuz, A.; Tabouelle, J.; Aarab, M.; Amiot, R.; Buffetaut, E.; Dyke, G.; Hua, S.; Le Loeuff, J.

    2010-07-01

    Fossils of vertebrates have been found in great abundance in the continental and marine early Late Cretaceous sediments of Southeastern Morocco for more than 50 years. About 80 vertebrate taxa have so far been recorded from this region, many of which were recognised and diagnosed for the first time based on specimens recovered from these sediments. In this paper, we use published data together with new field data to present an updated overview of Moroccan early Late Cretaceous vertebrate assemblages. The Cretaceous series we have studied encompasses three Formations, the Ifezouane and Aoufous Formations, which are continental and deltaic in origin and are often grouped under the name "Kem Kem beds", and the Akrabou Formation which is marine in origin. New field observations allow us to place four recognised vertebrate clusters, corresponding to one compound assemblage and three assemblages, within a general temporal framework. In particular, two ammonite bioevents characterise the lower part of the Upper Cenomanian ( Calycoceras guerangeri Zone) at the base of the Akrabou Formation and the upper part of the Lower Turonian ( Mammites nodosoides Zone), that may extend into the Middle Turonian within the Akrabou Formation, and allow for more accurate dating of the marine sequence in the study area. We are not yet able to distinguish a specific assemblage that characterises the Ifezouane Formation when compared to the similar Aoufous Formation, and as a result we regard the oldest of the four vertebrate "assemblages" in this region to be the compound assemblage of the "Kem Kem beds". This well-known vertebrate assemblage comprises a mixture of terrestrial (and aerial), freshwater and brackish vertebrates. The archosaur component of this fauna appears to show an intriguingly high proportion of large-bodied carnivorous taxa, which may indicate a peculiar trophic chain, although collecting biases alter this palaeontological signal. A small and restricted assemblage, the

  12. The Cauvery river basin in southern India: major challenges and possible solutions in the 21st century.

    PubMed

    Vanham, D; Weingartner, R; Rauch, W

    2011-01-01

    India is facing major challenges in its water resources management (WRM) sector. Water shortages are attributed to issues such as an explosion in population, rapid urbanization and industrialization, environmental degradation and inefficient water use, all aggravated by changing climate and its impacts on demand, supply and water quality. This paper focuses on the contemporary and future situation in the Cauvery river basin in Southern India, shared by different states, predominantly Karnataka and Tamil Nadu. As water issues largely fall under the authority of the states, inter-state water disputes have a long tradition in the Cauvery river basin. Future changes in precipitation during the two monsoon seasons will only increase these tensions. Both states depend on the arrival of these monsoon rains to water their crops and to replenish the groundwater. The paper identifies the major challenges and general possible solutions for sustainable WRM within the river basin. It synthesises the relevant literature, describes practices that should be addressed in the scope of integrated WRM--including water availability increase and demand management--and stresses the need for further quantitative analyses.

  13. Post-early cretaceous landform evolution along the western margin of the banca~nnia trough, western nsw

    USGS Publications Warehouse

    Gibson, D.L.

    2000-01-01

    Previously undated post-Devonian sediments outcropping north of Fowlers Gap station near the western margin of the Bancannia Trough are shown by plant macro- and microfossil determinations to be of Early Cretaceous (most likely Neocomian and/or Aptian) age, and thus part of the Eromanga Basin. They are assigned to the previously defined Telephone Creek Formation. Study of the structural configuration of this unit and the unconformably underlying Devonian rocks suggests that the gross landscape architecture of the area results from post-Early Cretaceous monoclinal folding along blind faults at the western margin of the trough, combined with the effects of differential erosion. This study shows that, while landscape evolution in the area has been dynamic, the major changes that have occurred are on a geological rather than human timescale.

  14. Polyphase exhumation in the western Qinling Mountains, China: Rapid Early Cretaceous cooling along a lithospheric-scale tear fault and pulsed Cenozoic uplift

    PubMed Central

    Heberer, Bianca; Anzenbacher, Thomas; Neubauer, Franz; Genser, Johann; Dong, Yunpeng; Dunkl, István

    2014-01-01

    The western sector of the Qinling–Dabie orogenic belt plays a key role in both Late Jurassic to Early Cretaceous “Yanshanian” intracontinental tectonics and Cenozoic lateral escape triggered by India–Asia collision. The Taibai granite in the northern Qinling Mountains is located at the westernmost tip of a Yanshanian granite belt. It consists of multiple intrusions, constrained by new Late Jurassic and Early Cretaceous U–Pb zircon ages (156 ± 3 Ma and 124 ± 1 Ma). Applying various geochronometers (40Ar/39Ar on hornblende, biotite and K-feldspar, apatite fission-track, apatite [U–Th–Sm]/He) along a vertical profile of the Taibai Mountain refines the cooling and exhumation history. The new age constraints record the prolonged pre-Cenozoic intracontinental deformation as well as the cooling history mostly related to India–Asia collision. We detected rapid cooling for the Taibai granite from ca. 800 to 100 °C during Early Cretaceous (ca. 123 to 100 Ma) followed by a period of slow cooling from ca. 100 Ma to ca. 25 Ma, and pulsed exhumation of the low-relief Cretaceous peneplain during Cenozoic times. We interpret the Early Cretaceous rapid cooling and exhumation as a result from activity along the southern sinistral lithospheric scale tear fault of the recently postulated intracontinental subduction of the Archean/Palaeoproterozoic North China Block beneath the Alashan Block. A Late Oligocene to Early Miocene cooling phase might be triggered either by the lateral motion during India–Asia collision and/or the Pacific subduction zone. Late Miocene intensified cooling is ascribed to uplift of the Tibetan Plateau. PMID:27065503

  15. Reanalysis of Wupus agilis (Early Cretaceous) of Chongqing, China as a Large Avian Trace: Differentiating between Large Bird and Small Non-Avian Theropod Tracks

    PubMed Central

    Xing, Lida; Buckley, Lisa G.; McCrea, Richard T.; Lockley, Martin G.; Zhang, Jianping; Piñuela, Laura; Klein, Hendrik; Wang, Fengping

    2015-01-01

    Trace fossils provide the only records of Early Cretaceous birds from many parts of the world. The identification of traces from large avian track-makers is made difficult given their overall similarity in size and tridactyly in comparison with traces of small non-avian theropods. Reanalysis of Wupus agilis from the Early Cretaceous (Aptian-Albian) Jiaguan Formation, one of a small but growing number of known avian-pterosaur track assemblages, of southeast China determines that these are the traces of a large avian track-maker, analogous to extant herons. Wupus, originally identified as the trace of a small non-avian theropod track-maker, is therefore similar in both footprint and trackway characteristics to the Early Cretaceous (Albian) large avian trace Limiavipes curriei from western Canada, and Wupus is reassigned to the ichnofamily Limiavipedidae. The reanalysis of Wupus reveals that it and Limiavipes are distinct from similar traces of small to medium-sized non-avian theropods (Irenichnites, Columbosauripus, Magnoavipes) based on their relatively large footprint length to pace length ratio and higher mean footprint splay, and that Wupus shares enough characters with Limiavipes to be reassigned to the ichnofamily Limiavipedidae. The ability to discern traces of large avians from those of small non-avian theropods provides more data on the diversity of Early Cretaceous birds. This analysis reveals that, despite the current lack of body fossils, large wading birds were globally distributed in both Laurasia and Gondwana during the Early Cretaceous. PMID:25993285

  16. An extraterrestrial trigger for the Early Cretaceous massive volcanism? Evidence from the paleo-Tethys Ocean.

    PubMed

    Tejada, M L G; Ravizza, G; Suzuki, K; Paquay, F S

    2012-01-01

    The Early Cretaceous Greater Ontong Java Event in the Pacific Ocean may have covered ca. 1% of the Earth's surface with volcanism. It has puzzled scientists trying to explain its origin by several mechanisms possible on Earth, leading others to propose an extraterrestrial trigger to explain this event. A large oceanic extraterrestrial impact causing such voluminous volcanism may have traces of its distal ejecta in sedimentary rocks around the basin, including the paleo-Tethys Ocean which was then contiguous with the Pacific Ocean. The contemporaneous marine sequence at central Italy, containing the sedimentary expression of a global oceanic anoxic event (OAE1a), may have recorded such ocurrence as indicated by two stratigraphic intervals with (187)Os/(188)Os indicative of meteoritic influence. Here we show, for the first time, that platinum group element abundances and inter-element ratios in this paleo-Tethyan marine sequence provide no evidence for an extraterrestrial trigger for the Early Cretaceous massive volcanism.

  17. An extraterrestrial trigger for the Early Cretaceous massive volcanism? Evidence from the paleo-Tethys Ocean

    PubMed Central

    Tejada, M. L. G.; Ravizza, G.; Suzuki, K.; Paquay, F. S.

    2012-01-01

    The Early Cretaceous Greater Ontong Java Event in the Pacific Ocean may have covered ca. 1% of the Earth's surface with volcanism. It has puzzled scientists trying to explain its origin by several mechanisms possible on Earth, leading others to propose an extraterrestrial trigger to explain this event. A large oceanic extraterrestrial impact causing such voluminous volcanism may have traces of its distal ejecta in sedimentary rocks around the basin, including the paleo-Tethys Ocean which was then contiguous with the Pacific Ocean. The contemporaneous marine sequence at central Italy, containing the sedimentary expression of a global oceanic anoxic event (OAE1a), may have recorded such ocurrence as indicated by two stratigraphic intervals with 187Os/188Os indicative of meteoritic influence. Here we show, for the first time, that platinum group element abundances and inter-element ratios in this paleo-Tethyan marine sequence provide no evidence for an extraterrestrial trigger for the Early Cretaceous massive volcanism. PMID:22355780

  18. New Evidence for opening of the Black Sea; U-Pb analysis of detrital zircons and paleocurrent measurements of the Early Cretaceous turbidites

    NASA Astrophysics Data System (ADS)

    Akdoğan, Remziye; Okay, Aral I.; Sunal, Gürsel; Tari, Gabor; Kylander-Clark, Andrew R. C.

    2015-04-01

    Shelf to submarine turbidite fan deposits of the Early Cretaceous crop out over a large area along the southern coast of the Black Sea. Early Cretaceous turbidites have a thickness of over 2000 meters in the Central Pontides. The shelf of this turbidite basin, represented by shallow marine clastics and carbonates, crops out along the Black Sea coast between Zonguldak and Amasra. Paleocurrent directions in the Lower Cretaceous turbidites were measured in 90 localities using mostly flute and groove casts and to a lesser extend cross-beds. At the eastern part of the basin, the paleocurrents were from north to south. It is scattered in the west of the basin, however, the main paleocurrent directions were from the north. Detrital zircons were analyzed using LA-ICP-MS in eleven samples from the turbiditic sandstones and two samples from the shelf sandstones. Four samples are from the western part (two samples from shelf sediments), four samples from the central part and five samples from the eastern part of the Lower Cretaceous basin. 1085 of 1348 zircon analyses are concordant with rates of 95-105% and the zircon ages range between 141 ± 4 Ma (Berriasian) and 3469 ± 8 Ma (Paleoarchean). 22% of the detrital zircon ages are Paleoproterozoic, 20% Archean, 16% Carboniferous, 13% Neoproterozoic, 8% Permian, 6% Triassic, 5% Mesoproterozoic and 11% other ages. In the western part of the basin the Carboniferous zircons constitute the main population with a less dominant peak at Ordovician, Cambrian and Late Neoproterozoic. The zircons from the center of the basin show scattered distribution with dominant populations in the Triassic, Permian, Carboniferous, Silurian, Paleoproterozoic, Early Neoproterozoic-Late Mesoproterozoic, and minor peak at Late Neoarchean. On the other hand, zircons from the eastern most part of the basin, show dominant peaks in the Paleoproterozoic, Mesoarchean and Permian with minor peaks in Triassic, Carboniferous and Silurian. Anatolia and the Balkans

  19. Pinaceae-like reproductive morphology in Schizolepidopsis canicularis sp. nov. from the Early Cretaceous (Aptian-Albian) of Mongolia.

    PubMed

    Leslie, Andrew B; Glasspool, Ian; Herendeen, Patrick S; Ichinnorov, Niiden; Knopf, Patrick; Takahashi, Masamichi; Crane, Peter R

    2013-12-01

    Seed cone scales assigned to the genus Schizolepidopsis are widespread in Late Triassic to Cretaceous Eurasian deposits. They have been linked to the conifer family Pinaceae based on associated vegetative remains, but their exact affinities are uncertain. Recently discovered material from the Early Cretaceous of Mongolia reveals important new information concerning Schizolepidopsis cone scales and seeds, and provides support for a relationship between the genus and extant Pinaceae. Specimens were collected from Early Cretaceous (probable Aptian-Albian) lignite deposits in central Mongolia. Lignite samples were disaggregated, cleaned in hydrofluoric acid, and washed in water. Specimens were selected for further study using light and electron microscopy. Schizolepidopsis canicularis seed cones consist of loosely arranged, bilobed ovulate scales subtended by a small bract. A single inverted seed with an elongate micropyle is borne on each lobe of the ovulate scale. Each seed has a wing formed by the separation of the adaxial surface of the ovulate scale. Schizolepidopsis canicularis produced winged seeds that formed in a manner that is unique to Pinaceae among extant conifers. We do not definitively place this species in Pinaceae pending more complete information concerning its pollen cones and vegetative remains. Nevertheless, this material suggests that Schizolepidopsis may be important for understanding the early evolution of Pinaceae, and may potentially help reconcile the appearance of the family in the fossil record with results based on phylogenetic analyses of molecular data.

  20. Peculiar macrophagous adaptations in a new Cretaceous pliosaurid

    PubMed Central

    Arkhangelsky, Maxim S.; Stenshin, Ilya M.; Uspensky, Gleb N.; Zverkov, Nikolay G.

    2015-01-01

    During the Middle and Late Jurassic, pliosaurid plesiosaurs evolved gigantic body size and a series of craniodental adaptations that have been linked to the occupation of an apex predator niche. Cretaceous pliosaurids (i.e. Brachaucheninae) depart from this morphology, being slightly smaller and lacking the macrophagous adaptations seen in earlier forms. However, the fossil record of Early Cretaceous pliosaurids is poor, concealing the evolution and ecological diversity of the group. Here, we report a new pliosaurid from the Late Hauterivian (Early Cretaceous) of Russia. Phylogenetic analyses using reduced consensus methods recover it as the basalmost brachauchenine. This pliosaurid is smaller than other derived pliosaurids, has tooth alveoli clustered in pairs and possesses trihedral teeth with complex serrated carinae. Maximum-likelihood ancestral state reconstruction suggests early brachauchenines retained trihedral teeth from their ancestors, but modified this feature in a unique way, convergent with macrophagous archosaurs or sphenacodontoids. Our findings indicate that Early Cretaceous marine reptile teeth with serrated carinae cannot be unequivocally assigned to metriorhynchoid crocodylomorphs. Furthermore, they extend the known diversity of dental adaptations seen in Sauropterygia, the longest lived clade of marine tetrapods. PMID:27019740

  1. Assessment of undiscovered oil and gas resources of the Assam, Bombay, Cauvery, and Krishna-Godavari Provinces, South Asia, 2011

    USGS Publications Warehouse

    Klett, T.R.; Schenk, Christopher J.; Wandrey, Craig J.; Charpentier, Ronald R.; Cook, Troy A.; Brownfield, Michael E.; Pitman, Janet K.; Pollastro, Richard M.

    2012-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated volumes of undiscovered, technically recoverable, conventional petroleum resources for the Assam, Bombay, Cauvery, and Krishna–Godavari Provinces, South Asia. The estimated mean volumes are as follows: (1) Assam Province, 273 million barrels of crude oil, 1,559 billion cubic feet of natural gas, and 43 million barrels of natural gas liquids; (2) Bombay Province, 1,854 million barrels of crude oil, 15,417 billion cubic feet of natural gas, and 498 million barrels of natural gas liquids; (3) Cauvery Province, 941 million barrels of crude oil, 25,208 billion cubic feet of natural gas, and 654 million barrels of natural gas liquids; and (4) Krishna–Godavari Province, 466 million barrels of crude oil, 37,168 billion cubic feet of natural gas, and 484 million barrels of natural gas liquids. The totals for the four provinces are 3,534 million barrels of crude oil, 79,352 billion cubic feet of natural gas, and 1,679 million barrels of natural gas liquids.

  2. A temporary pond in the Early Cretaceous of southern England: palaeoclimatic implications of nonmarine "Purbeck-Wealden" ostracod faunas

    NASA Astrophysics Data System (ADS)

    Horne, D. J.

    2009-04-01

    Excavation of the partial skeleton of an Iguanodon from the Upper Weald Clay (Barremian, Early Cretaceous) at Smokejacks Brickworks near Ockley, Surrey, UK included detailed sampling for micropalaeontological and palynological and studies (Nye et al., 2008). Rich and well-preserved non-marine assemblages of pollen and spores include early angiosperms as well as freshwater green algae. Taphonomic analyses show the ostracod assemblages to be autochthonous thanatocoenoses, indicative of local environment at the time of deposition. Using a palaeobiological approach, the ostracods and palynomorphs demonstrate temporary / ephemeral freshwater conditions at the time when the Iguanodon died and the carcase was buried. Ostracod "faunicycles" in "Purbeck-Wealden" deposits may represent salinity variations in non-marine water-bodies, influenced by the balance between precipitation and evaporation, and/or the relative abundance of permanent and temporary waterbodies in the landscape; many assemblages resulted from post-mortem mixing, perhaps during flood events (Horne, 2002). Faunal alternations may therefore reflect shifts of the boundary between warm temperate and paratropical climate in the Early Cretaceous of NW Europe. The previously rejected suggestion that such assemblage variations record Milankovitch cyclicity deserves to be reconsidered, as does the possibility that they reflect changes on sub-Milankovitch timescales. Climate variability may have influenced the differential evolutionary success of sexual, mixed and parthenogenetic reproductive strategies in nonmarine ostracods. Latitudinally restricted distribution patterns and wind dispersal of resting eggs offer potential for inferring global climate patterns from ostracod palaeobiogeography, although dispersal by large animals (e.g., crocodiles, pterosaurs) is likely to have confused any aeolian transport patterns. References Horne, D. J. 2002. Ostracod biostratigraphy and palaeoecology of the Purbeck Limestone

  3. A gravid lizard from the Cretaceous of China and the early history of squamate viviparity

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Evans, Susan E.

    2011-09-01

    Although viviparity is most often associated with mammals, roughly one fifth of extant squamate reptiles give birth to live young. Phylogenetic analyses indicate that the trait evolved more than 100 times within Squamata, a frequency greater than that of all other vertebrate clades combined. However, there is debate as to the antiquity of the trait and, until now, the only direct fossil evidence of squamate viviparity was in Late Cretaceous mosasauroids, specialised marine lizards without modern equivalents. Here, we document viviparity in a specimen of a more generalised lizard, Yabeinosaurus, from the Early Cretaceous of China. The gravid female contains more than 15 young at a level of skeletal development corresponding to that of late embryos of living viviparous lizards. This specimen documents the first occurrence of viviparity in a fossil reptile that was largely terrestrial in life, and extends the temporal distribution of the trait in squamates by at least 30 Ma. As Yabeinosaurus occupies a relatively basal position within crown-group squamates, it suggests that the anatomical and physiological preconditions for viviparity arose early within Squamata.

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

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

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

  5. Late Jurassic-Early Cretaceous continental convergence and intracontinental orogenesis in East Asia: A synthesis of the Yanshan Revolution

    NASA Astrophysics Data System (ADS)

    Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Cui, Jianjun; Chen, Xuanhua; Zhang, Shuanhong; Miao, Laicheng; Li, Jianhua; Shi, Wei; Li, Zhenhong; Huang, Shiqi; Li, Hailong

    2015-12-01

    The basic tectonic framework of continental East Asia was produced by a series of nearly contemporaneous orogenic events in the late Middle Jurassic to Early Cretaceous. Commonly, the Late Mesozoic orogenic processes were characterized by continent-continent collision, large-scale thrusting, strike-slip faulting and intense crustal shortening, crustal thickening, regional anatexis and metamorphism, followed by large-scale lithospheric extension, rifting and magmatism. To better understand the geological processes, this paper reviews and synthesizes existing multi-disciplinary geologic data related to sedimentation, tectonics, magmatism, metamorphism and geochemistry, and proposes a two-stage tectono-thermal evolutionary history of East Asia during the late Middle Jurassic to Early Cretaceous (ca. 170-120 Ma). In the first stage, three orogenic belts along the continental margins were formed coevally at ca. 170-135 Ma, i.e., the north Mongol-Okhotsk orogen, the east paleo-Pacific coastal orogen, and the west Bangong-Nujiang orogen. Tectonism related to the coastal orogen caused extensive intracontinental folding and thrusting that resulted in a depositional hiatus in the Late Jurassic, as well as crustal anatexis that generated syn-kinematic granites, adakites and migmatites. The lithosphere of the East Asian continent was thickened, reaching a maximum during the latest Jurassic or the earliest Cretaceous. In the second stage (ca. 135-120 Ma), delamination of the thickened lithosphere resulted in a remarkable (>120 km) lithospheric thinning and the development of mantle-derived magmatism, mineralization, metamorphic core complexes and rift basins. The Middle Jurassic-Early Cretaceous subduction of oceanic plates (paleo-Pacific, meso-Tethys, and Mongol-Okhotsk) and continent-continent collision (e.g. Lhasa and Qiangtang) along the East Asian continental margins produced broad coastal and intracontinental orogens. These significant tectonic activities, marked by

  6. Early Cretaceous bimodal volcanic rocks in the southern Lhasa terrane, south Tibet: Age, petrogenesis and tectonic implications

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Ding, Lin; Liu, Zhi-Chao; Zhang, Li-Yun; Yue, Ya-Hui

    2017-01-01

    Limited geochronological and geochemical data from Early Cretaceous igneous rocks of the Gangdese Belt have resulted in a dispute regarding the subduction history of Neo-Tethyan Ocean. To approach this issue, we performed detailed in-situ zircon U-Pb and Hf isotopic, whole-rock elemental and Sr-Nd isotopic analyses on Late Mesozoic volcanic rocks exposed in the Liqiongda area, southern Lhasa terrane. These volcanic rocks are calc-alkaline series, dominated by basalts, basaltic andesites, and subordinate rhyolites, with a bimodal suite. The LA-ICPMS zircon U-Pb dating results of the basaltic andesites and rhyolites indicate that these volcanic rocks erupted during the Early Cretaceous (137-130 Ma). The basaltic rocks are high-alumina (average > 17 wt.%), enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs), showing subduction-related characteristics. They display highly positive zircon εHf(t) values (+ 10.0 to + 16.3) and whole-rock εNd(t) values (+ 5.38 to + 7.47). The silicic suite is characterized by low Al2O3 (< 15.4 wt.%), Mg# (< 40), and TiO2 (< 0.3 wt.%) abundances; enriched and variable concentrations of LILEs and REEs; and strongly negative Eu anomalies (Eu/Eu* = 0.08-0.19), as well as depleted Hf isotopic compositions (εHf(t) = + 4.9 to + 16.4) and Nd isotopic compositions (εNd(t) = + 5.26 to + 6.71). Consequently, we envision a process of basaltic magmas similar to that of MORB extracted from a source metasomatized by slab-derived components for the petrogenesis of mafic rocks, whereas the subsequent mafic magma underplating triggered partial melting of the juvenile crust to generate acidic magma. Our results confirm the presence of Early Cretaceous volcanism in the southern Lhasa terrane. Combined with the distribution of the contemporary magmatism, deformation style, and sedimentary characteristics in the Lhasa terrane, we favor the suggestion that the Neo

  7. A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs

    PubMed Central

    Fischer, Valentin; Appleby, Robert M.; Naish, Darren; Liston, Jeff; Riding, James B.; Brindley, Stephen; Godefroit, Pascal

    2013-01-01

    Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed. PMID:23676653

  8. Composition and depositional environment of concretionary strata of early Cenomanian (early Late Cretaceous) age, Johnson County, Wyoming

    USGS Publications Warehouse

    Merewether, E.A.; Gautier, Donald L.

    2000-01-01

    Unusual, concretion-bearing mudrocks of early Late Cretaceous age, which were deposited in an early Cenomanian epeiric sea, have been recognized at outcrops in eastern Wyoming and in adjoining areas of Montana, South Dakota, Nebraska, and Colorado. In Johnson County, Wyo., on the western flank of the Powder River Basin, these strata are in the lower part of the Belle Fourche Member of the Frontier Formation. At a core hole in south-central Johnson County, they are informally named Unit 2. These strata are about 34 m (110 ft) thick and consist mainly of medium- to dark-gray, noncalcareous, silty shale and clayey or sandy siltstone; and light-gray to grayish-red bentonite. The shale and siltstone are either bioturbated or interlaminated; the laminae are discontinuous, parallel, and even or wavy. Several ichnogenera of deposit feeders are common in the unit but filter feeders are sparse. The unit also contains marine and continental palynomorphs and, near the top, a few arenaceous foraminifers. No invertebrate macrofossils have been found in these rocks. Unit 2 conformably overlies lower Cenomanian shale in the lowermost Belle Fourche Member, informally named Unit 3, and is conformably overlain by lower and middle Cenomanian shale, siltstone, and sandstone within the member, which are informally named Unit 1. The mineral and chemical composition of the three Cenomanian units is comparable and similar to that of shale and siltstone in the Upper Cretaceous Pierre Shale, except that these units contain more SiO2 and less CaO, carbonate carbon, and manganese. Silica is generally more abundant and CaO is generally less abundant in river water than in seawater. The composition of Unit 2 contrasts significantly with that of the underlying and overlying units. Unit 2 contains no pyrite and dolomite and much less sulfur than Units 1 and 3. Sulfate is generally less abundant in river water than in seawater. Unit 2 also includes sideritic and calcitic concretions, whereas Units

  9. Inter-Basin Water Transfer Impact Assessment on Environment of Pennar to Cauvery Link Canal

    NASA Astrophysics Data System (ADS)

    Rajesh, S. V. J. S. S.; Prakasa Rao, B. S.; Niranjan, K.

    2016-07-01

    Owing to its striking differences in its climatic conditions, India is frequently facing with extremities such as heavy rain fall in some regions where as some other regions endure little rainfall. The regions receiving heavy precipitation are facing floods resulting in huge amount of water runs into the sea. Contrarily, the regions, without adequate rainfall are suffering from persistent droughts. To overcome such disparities in the distribution of water, National Water Development Agency (NWDA) put a proposal to transfer water through link canals between rivers. The current study is limited to two river basins, Pennar and Cauvery. The present study is confined to Pennar (somasila) to Cauvery (Grand Anicut) whose length is 483 km. The study consist of10 km. buffer on either side of the canal and it occupies 17,215.68 sq. km. out of these 10,105.96 sq.km.is proposed command area which falls in Chittoor, Chengalpattu, North Arcott and South Arcott districts. Using IRS-P6, LISS-III data the characteristics of the rocks, lineaments, drainage, settlements and land use/land cover are mapped for better analysis and the environmental impact. The study indicated that Current fallow land of 5340.14 km2 and 6307.98 km2 of cropland will be brought under cultivation which is more than what is NWDA estimated land that will be benefited. The canal will provide water for irrigation and drinking to 4597 villages and 244 villages to be rehabilitated. 119 culverts/canal bridges and 24 aqueducts have to be constructed across the canal.

  10. The emergence of modern type rain forests and mangroves and their traces in the palaeobotanical record during the Late Cretaceous and early Tertiary

    NASA Astrophysics Data System (ADS)

    Mohr, Barbara; Coiffard, Clément

    2014-05-01

    The origin of modern rain forests is still very poorly known. This ecosystem could have potentially fully evolved only after the development of relatively high numbers of flowering plant families adapted to rain forest conditions. During the early phase of angiosperm evolution in the early Cretaceous the palaeo-equatorial region was located in a seasonally dry climatic belt, so that during this phase, flowering plants often show adaptations to drought, rather than to continuously wet climate conditions. Therefore it is not surprising that except for the Nymphaeales, the most basal members of extant angiosperm families have members that do not necessarily occur in the continuously wet tropics today. However, during the late Early Cretaceous several clades emerged that later would give rise to families that are typically found today mostly in (shady) moist places in warmer regions. This is especially seen among the monocotyledons, a group of the mesangiosperms, that developed in many cases large leaves often with very specific venation patterns that make these leaves very unique and well recognizable. Especially members of three groups are here of interest: the arum family (Araceae), the palms (Arecaceae) and the Ginger and allies (Zingiberales). The earliest fossil of Araceae are restricted to low latitudes during the lower Cretaceous. Arecaceae and Zingiberales do not appear in the fossil record before the early late Cretaceous and occur at mid latitudes. During the Late Cretaceous, Araceae are represented at mid latitudes by non-tropical early diverging members and at low latitudes by derived rainforest members. Palms became widespread during the Late Cretataceous and also Nypa, a typical element of tropical to subtropical mangrove environments evolved during this time period. During the Paleocene Arecaceae appear to be restricted to lower latitudes as well as Zingiberales. All three groups are again widespread during the Eocene, reaching higher latitudes and

  11. New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography

    PubMed Central

    Poropat, Stephen F.; Mannion, Philip D.; Upchurch, Paul; Hocknull, Scott A.; Kear, Benjamin P.; Kundrát, Martin; Tischler, Travis R.; Sloan, Trish; Sinapius, George H. K.; Elliott, Judy A.; Elliott, David A.

    2016-01-01

    Australian dinosaurs have played a rare but controversial role in the debate surrounding the effect of Gondwanan break-up on Cretaceous dinosaur distribution. Major spatiotemporal gaps in the Gondwanan Cretaceous fossil record, coupled with taxon incompleteness, have hindered research on this effect, especially in Australia. Here we report on two new sauropod specimens from the early Late Cretaceous of Queensland, Australia, that have important implications for Cretaceous dinosaur palaeobiogeography. Savannasaurus elliottorum gen. et sp. nov. comprises one of the most complete Cretaceous sauropod skeletons ever found in Australia, whereas a new specimen of Diamantinasaurus matildae includes the first ever cranial remains of an Australian sauropod. The results of a new phylogenetic analysis, in which both Savannasaurus and Diamantinasaurus are recovered within Titanosauria, were used as the basis for a quantitative palaeobiogeographical analysis of macronarian sauropods. Titanosaurs achieved a worldwide distribution by at least 125 million years ago, suggesting that mid-Cretaceous Australian sauropods represent remnants of clades which were widespread during the Early Cretaceous. These lineages would have entered Australasia via dispersal from South America, presumably across Antarctica. High latitude sauropod dispersal might have been facilitated by Albian–Turonian warming that lifted a palaeoclimatic dispersal barrier between Antarctica and South America. PMID:27763598

  12. New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography.

    PubMed

    Poropat, Stephen F; Mannion, Philip D; Upchurch, Paul; Hocknull, Scott A; Kear, Benjamin P; Kundrát, Martin; Tischler, Travis R; Sloan, Trish; Sinapius, George H K; Elliott, Judy A; Elliott, David A

    2016-10-20

    Australian dinosaurs have played a rare but controversial role in the debate surrounding the effect of Gondwanan break-up on Cretaceous dinosaur distribution. Major spatiotemporal gaps in the Gondwanan Cretaceous fossil record, coupled with taxon incompleteness, have hindered research on this effect, especially in Australia. Here we report on two new sauropod specimens from the early Late Cretaceous of Queensland, Australia, that have important implications for Cretaceous dinosaur palaeobiogeography. Savannasaurus elliottorum gen. et sp. nov. comprises one of the most complete Cretaceous sauropod skeletons ever found in Australia, whereas a new specimen of Diamantinasaurus matildae includes the first ever cranial remains of an Australian sauropod. The results of a new phylogenetic analysis, in which both Savannasaurus and Diamantinasaurus are recovered within Titanosauria, were used as the basis for a quantitative palaeobiogeographical analysis of macronarian sauropods. Titanosaurs achieved a worldwide distribution by at least 125 million years ago, suggesting that mid-Cretaceous Australian sauropods represent remnants of clades which were widespread during the Early Cretaceous. These lineages would have entered Australasia via dispersal from South America, presumably across Antarctica. High latitude sauropod dispersal might have been facilitated by Albian-Turonian warming that lifted a palaeoclimatic dispersal barrier between Antarctica and South America.

  13. Lower Cretaceous Puez key-section in the Dolomites - towards the mid-Cretaceous super-greenhouse

    NASA Astrophysics Data System (ADS)

    Lukeneder, A.; Halásová, E.; Rehákova, D.; Józsa, Š.; Soták, J.; Kroh, A.; Jovane, L.; Florindo, F.; Sprovieri, M.; Giorgioni, M.; Lukeneder, S.

    2012-04-01

    Investigations on different fossil groups in addition to isotopic, paleomagnetic and geochemical analysis are combined to extract the Early Cretaceous history of environmental changes, as displayed by the sea level and climate changes. Results on biostratigraphy are integrated with other dating methods as magnetostraigraphy, correlation and cyclostratigraphy. The main investigation topics of the submitted project within the above-described framework are the biostratigraphic (Lukeneder and Aspmair, 2006, 2012), palaeoecological (Lukeneder, 2008, 2012), palaeobiogeographic, lithostratigraphic (Lukeneder, 2010, 2011), cyclostratigraphic and magnetostratigraphic development of the Early Cretaceous in the Puez area. The main sections occur in expanded outcrops located on the southern margin of the Puez Plateau, within the area of the Puez-Geisler Natural Park, in the northern part of the Dolomites (South Tyrol, North Italy). The cephalopod, microfossil and nannofossil faunas and floras from the marly limestones to marls here indicates Hauterivian to Albian/Cenomanian age. Oxygen isotope values from the Lower Cretaceous Puez Formation show a decreasing trend throughout the log, from -1.5‰ in the Hauterivian to -4.5‰ in the Albian/Cenomanian. The decreasing values mirror an increasing trend in palaeotemperatures from ~ 15-18°C in the Hauterivian up to ~25-30 °C in the Albian/Cenomanian. The trend probably indicates the positive shift in temperature induced by the well known Mid Cretaceous Ocean warming (e.g., Super-Greenhouse). The cooperative project (FWF project P20018-N10; 22 international scientists): An integrative high resolution project. Macro- and microfossils, isotopes, litho-, cyclo-, magneto-and biostratigraphy as tools for investigating the Lower Cretaceous within the Dolomites (Southern Alps, Northern Italy) -The Puez area as a new key region of the Tethyan Realm), is on the way since 2008 by the Natural History Museum in Vienna and the 'Naturmuseum S

  14. Apatite fission-track thermochronometric constraints on the exhumation and evolution of the southeastern Indian (Tamil Nadu) passive margin and the role of structural inheritance

    NASA Astrophysics Data System (ADS)

    De Grave, Johan; Glorie, Stijn; Singh, Tejpal; Van Ranst, Gerben; Nachtergaele, Simon

    2017-04-01

    After rifting from Gondwana in the Late Jurassic - Early Cretaceous, and subsequent opening of the Indian Ocean basin, the continental margins of India developed into typical passive margins. Extensional tectonic forces and thermal subsidence gave rise to the formation of both on-shore and off-shore basins along the southeastern passive margin of the Indian continent, along the Tamil Nadu coast. There, basins such as the Cauvery and Krishna-Godavari basin, accumulated Meso- and Cenozoic (Early Cretaceous to recent) detrital sediments coming off the rifted blocks and the Tamil Nadu hinterland. In places, deep rift basins have accumulated up to over 3000 m of sediments. The continental basement of Tamil Nadu is chiefly composed of metamorphic rocks of the Archean to Palaeoproterozoic Eastern Dharwar Craton and the coeval Southern Granulite Terrane (e.g. Peucat et al., 2013). Several crustal scale shear zones crosscut this assemblage and at least some are considered to represent Gondwanan sutures (Santosh et al., 2012). Smaller, younger granitoid plutons intrude the basement at several locations and most of these are of Late Neoproterozoic age (Glorie et al., 2014). In this work metamorphic basements rocks and the younger granitoids were sampled for a apatite fission-track (AFT) thermochronometric study. A North-South profile from Chennai to Thanjavur mainly transects the Salem block of the Southern Granulite Terrane, and crosscuts several crustal scale shear zones, such as the Cauvery, Salem-Attur and Gangavalli shear zones. Apatites from over 30 samples were used in this study. AFT ages all range between about 190 and 120 Ma (Jurassic - Early Cretaceous). These mainly represent the slow, shallow exhumation of the basement during the rift and early drift phase of the Indian plate from Gondwana. AFT mean track lengths vary between 11 and 13 µm and are typical of slowly exhumed basement. Thermal history modelling (using the QTQt software by Gallagher, 2012) confirms

  15. Origin of Cretaceous phosphorites from the onshore of Tamil Nadu, India

    NASA Astrophysics Data System (ADS)

    Purnachandra Rao, V.; Kessarkar, Pratima M.; Nagendra, R.; Babu, E. V. S. S. K.

    2007-12-01

    Cretaceous phosphorites from the onshore of Tamil Nadu have been investigated for their origin and compared with those in the offshore. Cretaceous phosphorites occur as light brown to yellowish brown or white nodules in Karai Shale of the Uttatur Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus of the nodules consists of light and dark coloured laminae, phosphate peloids/coated grains and detrital particles interspersed between the laminae. Scanning electron microscope (SEM) studies reveal trapping and binding activity of microbial filaments. A mat structure with linearly arranged microbial filaments and hollow, cell-based coccoid cyanobacterial mat are present. Nodules contain abundant carbonate fluorapatite, followed by minor calcite, quartz and feldspar. The P2O5 content of the phosphorites ranges from 18 to 26%. The CaO/P2O5, Sr and F contents are higher than that of pure carbonate fluorapatite. Concentrations of Si, Al, K, Fe, and Ti are low. We suggest that the nuclei of the nodules represent phosphate clasts related to phosphate stromatolites formed at intertidal conditions. At high energy levels the microbial mats were disintegrated into phosphate clasts, coated with carbonate and then reworked into Karai Shale. On the other hand, Quaternary phosphorites occur as irregular to rounded, grey coloured phosphate clasts at water depths between 180 and 320m on the continental shelf of Tamil Nadu. They exhibit grain-supported texture. Despite Quaternary in age, they also resemble phosphate stromatolites of intertidal origin and reworked as phosphate clasts onto the shelf margin depressions. Benthic microbial mats probably supplied high phosphorus to the sediments. Availability of excess phosphorus seems to be a pre-requisite for the formation of phosphate stromatolites.

  16. The early evolution of feathers: fossil evidence from Cretaceous amber of France

    PubMed Central

    Perrichot, Vincent; Marion, Loïc; Néraudeau, Didier; Vullo, Romain; Tafforeau, Paul

    2008-01-01

    The developmental stages of feathers are of major importance in the evolution of body covering and the origin of avian flight. Until now, there were significant gaps in knowledge of early morphologies in theoretical stages of feathers as well as in palaeontological material. Here we report fossil evidence of an intermediate and critical stage in the incremental evolution of feathers which has been predicted by developmental theories but hitherto undocumented by evidence from both the recent and the fossil records. Seven feathers have been found in an Early Cretaceous (Late Albian, ca 100 Myr) amber of western France, which display a flattened shaft composed by the still distinct and incompletely fused bases of the barbs forming two irregular vanes. Considering their remarkably primitive features, and since recent discoveries have yielded feathers of modern type in some derived theropod dinosaurs, the Albian feathers from France might have been derived either from an early bird or from a non-avian dinosaur. PMID:18285280

  17. CRETACEOUS CLIMATE SENSITIVITY STUDY USING DINOSAUR & PLANT PALEOBIOGEOGRAPHY

    NASA Astrophysics Data System (ADS)

    Goswami, A.; Main, D. J.; Noto, C. R.; Moore, T. L.; Scotese, C.

    2009-12-01

    The Early Cretaceous was characterized by cool poles and moderate global temperatures (~16° C). During the mid and late Cretaceous, long-term global warming (~20° - 22° C) was driven by increasing levels of CO2, rising sea level (lowering albedo) and the continuing breakup of Pangea. Paleoclimatic reconstructions for four time intervals during the Cretaceous: Middle Campanian (80 Ma), Cenomanian/Turonian (90 Ma), Early Albian (110 Ma) and Barremian-Hauterivian (130Ma) are presented here. These paleoclimate simulations were prepared using the Fast Ocean and Atmosphere Model (FOAM). The simulated results show the pattern of the pole-to-Equator temperature gradients, rainfall, surface run-off, the location of major rivers and deltas. In order to investigate the effect of potential dispersal routes on paleobiogeographic patterns, a time-slice series of maps from Early - Late Cretaceous were produced showing plots of dinosaur and plant fossil distributions. These Maps were created utilizing: 1) plant fossil localities from the GEON and Paleobiology (PBDB) databases; and 2) dinosaur fossil localities from an updated version of the Dinosauria (Weishampel, 2004) database. These results are compared to two different types of datasets, 1) Paleotemperature database for the Cretaceous and 2) locality data obtained from GEON, PBDB and Dinosauria database. Global latitudinal mean temperatures from both the model and the paelotemperature database were plotted on a series of latitudinal graphs along with the distributions of fossil plants and dinosaurs. It was found that most dinosaur localities through the Cretaceous tend to cluster within specific climate belts, or envelopes. Also, these Cretaceous maps show variance in biogeographic zonation of both plants and dinosaurs that is commensurate with reconstructed climate patterns and geography. These data are particularly useful for understanding the response of late Mesozoic ecosystems to geographic and climatic conditions that

  18. Early environmental effects of the terminal Cretaceous impact

    NASA Technical Reports Server (NTRS)

    Gilmour, Iain; Wolbach, Wendy S.; Anders, Edward

    1988-01-01

    The environmental aftereffects of the terminal Cretaceous impact are examined on the basis of the carbon and nitrogen geochemistry in the basal layer of the K-T boundary clay at Woodside Creek, New Zealand. It is shown that organic carbon and nitrogen at this level are enriched by 15 and 20 times Cretaceous values, respectively. Also, it is found that the N abundances and, to a lesser extent, the organic C abundances are closely correlated with the Ir abundances. The changes in carbon and nitrogen content through the basal layer are outlined, focusing on the possible environmental conditions which could have caused enrichment. In addition, consideration is given to the soot and pyrotoxin content. Possible scenarios for the K-T event and the importance of selective extinction are discussed.

  19. Early Cretaceous adakitic magmatism in central eastern China controlled by ridge subduction

    NASA Astrophysics Data System (ADS)

    Ling, M.; Luo, Z.; Sun, W.

    2017-12-01

    Early Cretaceous adakites are widely distributed in central eastern China, e.g., Lower Yangtze River Belt (LYRB), Dabie orogen and south Tan-Lu Fault (STLF) area. Adakite from the LYRB is closely associated with mineralization, while adakites from Dabie orogen and STLF are ore barren. Their origins, however, remain controversial. Detailed geochemical comparison between these adakites indicates that the LYRB adakite are formed by partial melting of oceanic crust, i.e., slab melting, whereas those from Dabie orogen and STLF (e.g., Guandian pluton) have origin of lower continental crust (LCC) 1,2. Base on the distribution of igneous rocks, e.g., adakite, A-type granite and Nb-enriched basalts, as well as other lines of evidence, ridge subduction of the Pacific and Izanagi plates was proposed to explain the genesis of Cretaceous magmatism and associated mineralization in the LYRB 1. Ridge subduction is a special plate tectonic process that can provide both physical erosion and thermal erosion 3. Flat subduction of a spreading ridge will result in strong physical subduction-related erosion, and trigger destruction (e.g., in the Dabie orogen) or delamination (e.g., in the STLF) of the thickened LCC. Subsequently, ridge subduction, accompanied by opening of a slab window, will facilitate partial melting of the LCC by thermal erosion. References: 1. Ling, M. X. et al. Cretaceous ridge subduction along the Lower Yangtze river belt, eastern China. Econ. Geol. 104, 303-321, doi:10.2113/gsecongeo.104.2.303 (2009). 2. Ling, M. X., Wang, F. Y., Ding, X., Zhou, J. B. & Sun, W. D. Different origins of adakites from the Dabie Mountains and the Lower Yangtze River Belt, eastern China: Geochemical constraints. International Geology Review 53, 727-740 (2011). 3. Ling, M. X. et al. Destruction of the North China Craton Induced by Ridge Subductions. Journal of Geology 121, 197-213 (2013).

  20. Early Cretaceous ice rafting and climate zonation in Australia

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Frakes, L.A.; Alley, N.F.; Deynoux, M.

    1995-07-01

    Lower Cretaceous (Valanginian to Albian) strata of the southwestern Eromanga and Carpentaria basins of central and northern Australia, respectively, provide evidence of strongly seasonal climates at high paleolatitudes. These include dispersed clasts (lonestones) in fine sediments and pseudomorphs of calcite after ikaite (glendonites), the latter being known to form only at temperatures below about 7{degrees}C. Rafting is regarded as the transport mechanism for clasts up to boulder size (lonestones) enclosed within dark mudrocks; this interpretation rests on rare occurrences of penetration by clasts into substrate layers. Driftwood and large floating algae are eliminated as possible rafts because fossil wood ismore » found mainly concentrated in nearshore areas of the basins and large algal masses have not been observed. Rafting by icebergs is considered unlikely in view of the global lack of tillites and related glacial deposits of this age. Our interpretation is that seasonal ice, formed in winter along stream courses and strandlines, incorporated clasts which, during the melt season, were dropped into muddy sediments in both basins. Eromanga fine-sediment and concentrations of large clasts and associated sand lenses, both lying above local erosion surfaces. In the Carpentaria Basin, local dumping of sediment from raft surfaces resulted in accumulation of pods of small clasts. Three zones can be identified for the Early Cretaceous climate of eastern Australia: (1) a very cold southern region, at latitudes above about 72{degrees} S, characterized by meteoric waters possibly originating as Antarctic glacial meltwaters; (2) a zone of strongly seasonal climates, with freezing winters and warm summers, between about 72{degrees} and 53{degrees} S.Lat.; and (3) a mid-latitude zone (below about 50{degrees} S. Lat.), where freezing temperatures were not common. 60 refs., 7 figs.« less

  1. Fossil evidence for Cretaceous escalation in angiosperm leaf vein evolution.

    PubMed

    Feild, Taylor S; Brodribb, Timothy J; Iglesias, Ari; Chatelet, David S; Baresch, Andres; Upchurch, Garland R; Gomez, Bernard; Mohr, Barbara A R; Coiffard, Clement; Kvacek, Jiri; Jaramillo, Carlos

    2011-05-17

    The flowering plants that dominate modern vegetation possess leaf gas exchange potentials that far exceed those of all other living or extinct plants. The great divide in maximal ability to exchange CO(2) for water between leaves of nonangiosperms and angiosperms forms the mechanistic foundation for speculation about how angiosperms drove sweeping ecological and biogeochemical change during the Cretaceous. However, there is no empirical evidence that angiosperms evolved highly photosynthetically active leaves during the Cretaceous. Using vein density (D(V)) measurements of fossil angiosperm leaves, we show that the leaf hydraulic capacities of angiosperms escalated several-fold during the Cretaceous. During the first 30 million years of angiosperm leaf evolution, angiosperm leaves exhibited uniformly low vein D(V) that overlapped the D(V) range of dominant Early Cretaceous ferns and gymnosperms. Fossil angiosperm vein densities reveal a subsequent biphasic increase in D(V). During the first mid-Cretaceous surge, angiosperm D(V) first surpassed the upper bound of D(V) limits for nonangiosperms. However, the upper limits of D(V) typical of modern megathermal rainforest trees first appear during a second wave of increased D(V) during the Cretaceous-Tertiary transition. Thus, our findings provide fossil evidence for the hypothesis that significant ecosystem change brought about by angiosperms lagged behind the Early Cretaceous taxonomic diversification of angiosperms.

  2. Early to mid Cretaceous vegetation of northern Gondwana - the onset of angiosperm radiation and climatic implications

    NASA Astrophysics Data System (ADS)

    Coiffard, Clément; Mohr, Barbara

    2014-05-01

    Early Cretaceous Northern Gondwana seems to be the cradle of many early flowering plants, especially mesangiosperms that include magnoliids and monocots and basal eudicots. So far our knowledge was based mostly on dispersed pollen and small flowering structures. New fossil finds from Brazil include more complete plants with attached roots, leaves and flowers. Taxonomic studies show that these fossils belonged to clades which are, based on macroscopic characters and molecular data, also considered to be rather basal, such as several members of Nymphaeales, Piperales, Laurales, Magnoliales, monocots (Araliaceae) and Ranunculales. Various parameters can be used in order to understand the physiology and habitat of these plants. Adaptations to climate and habitat are partly mirrored in their root anatomy (evidence of tap roots), leaf size and shape, leaf anatomy including presence of glands, and distribution of stomata. An important ecophysiolocical parameter is vein density as an indicator for the plants' cabability to pump water, and the stomatal pore index, representing the proportion of stomatal pore area on the leaf surface, which is related to the water vapor resistance of the leaf epidermis. During the mid-Cretaceous leaf vein density started to surpass that of gymnosperms, one factor that made angiosperms very successful in conquering many kinds of new environments. Using data on these parameters we deduce that during the late Early to mid Cretaceous angiosperms were already diverse, being represented as both herbs, with aquatic members, such as Nymphaeles, helophytes (e.g. some monocots) and plants that may have grown in shady locations. Other life forms included shrubs and perhaps already small trees (e.g. Magnoliales). These flowering plants occupied various habitats, ranging from xeric (e.g. some Magnoliales) to mesic and shady (e.g. Piperales) or aquatic (e.g. Araceae, Nymphaeales). Overall, it seems that several of these plants clearly exhibited some

  3. Novel Insect Leaf-Mining after the End-Cretaceous Extinction and the Demise of Cretaceous Leaf Miners, Great Plains, USA

    PubMed Central

    Donovan, Michael P.; Wilf, Peter; Labandeira, Conrad C.; Johnson, Kirk R.; Peppe, Daniel J.

    2014-01-01

    Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg) boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma) in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia. PMID:25058404

  4. Early Cretaceous paleomagnetic and geochronologic results from the Tethyan Himalaya: Insights into the Neotethyan paleogeography and the India-Asia collision.

    PubMed

    Ma, Yiming; Yang, Tianshui; Bian, Weiwei; Jin, Jingjie; Zhang, Shihong; Wu, Huaichun; Li, Haiyan

    2016-02-17

    To better understand the Neotethyan paleogeography, a paleomagnetic and geochronological study has been performed on the Early Cretaceous Sangxiu Formation lava flows, which were dated from ~135.1 Ma to ~124.4 Ma, in the Tethyan Himalaya. The tilt-corrected site-mean characteristic remanent magnetization (ChRM) direction for 26 sites is Ds = 296.1°, Is = -65.7°, ks = 51.7, α95 = 4.0°, corresponding to a paleopole at 5.9°S, 308.0°E with A95 = 6.1°. Positive fold and reversal tests prove that the ChRM directions are prefolding primary magnetizations. These results, together with reliable Cretaceous-Paleocene paleomagnetic data observed from the Tethyan Himalaya and the Lhasa terrane, as well as the paleolatitude evolution indicated by the apparent polar wander paths (APWPs) of India, reveal that the Tethyan Himalaya was a part of Greater India during the Early Cretaceous (135.1-124.4 Ma) when the Neotethyan Ocean was up to ~6900 km, it rifted from India sometime after ~130 Ma, and that the India-Asia collision should be a dual-collision process including the first Tethyan Himalaya-Lhasa terrane collision at ~54.9 Ma and the final India-Tethyan Himalaya collision at ~36.7 Ma.

  5. Similarity and Differences of Cretaceous Magmatism in the Arctic Region

    NASA Astrophysics Data System (ADS)

    Peyve, A. A.

    2018-03-01

    The paper considers Cretaceous magmatism at the continental margin of the Arctic Region. It is shown that Cretaceous igneous rocks of this region are rather heterogeneous in age, composition, and geodynamic formation setting. This differentiates them from rocks of typical large igneous provinces (LIPs). Local areas of magmatic activity, their substantial remoteness them from one another, and significant distinctions in age, composition of rocks, and formation conditions prevent us from unreservedly combining all occurrences of Cretaceous magmatism at the continental margin of the Arctic Region into a common igneous province. The stage of tholeiitic magmatism in the Svalbard Archipelago, Franz Josef Land, Arctic Canada, and the Alpha-Mendeleev Rise, which can be considered an LIP, began in the Early Cretaceous and continued for a long time, at least until the Campanian. The magmatism apparently had a plume source and was caused by extension during opening of the Canada Basin. Tholeiitic magmatism gave way to the alkaline magmatism stage from the Campanian to the onset of the Paleocene, related to continental rifting at the initial stage of formation of Eurasian Basin in the Arctic Region. No convincing evidence for a genetic link between Early Cretaceous tholeiitic and Late Cretaceous alkaline magmatism is known at present, nor for the alkaline magmatism belonging to a plume source.

  6. Early-mid-Cretaceous evolution in Tethyan reef communities and sea level

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Scott, R.W.

    1988-01-01

    The replacement of corals by rudists in Early Cretaceous reefal communities spanned a 30-m.y. period when sea level rose and drowned continental shelves. During this time corals formed communities in the deeper parts of reefs and rudists occupied the shallow, high-energy habitats. By Aptian time rudists dominated reefs that fringed interior shelf basins and corals formed reefs with rudists on the outer shelf margins. By late Albian coral communities had virtually disappeared, presumably because of complex environmental changes and cycles of organic productivity. Two important events of eustatic sea level rise are represented by unconformities separating carbonate depositional sequences onmore » the Arabian platform that correlate with sequence boundaries on the Gulf Coast platform. Graphic correlation techniques test the synchroneity of these events. A composite standard time scale dates these sea level rises at 115.8 Ma and 94.6 Ma; a third, intra-Albian event at 104.3 Ma is present in many places and may also be eustatic. Associated with these sea level rises were apparent changes in ocean water chemistry as evidenced by changes in isotopes and trace elements, where diagenetic effects can be discounted. During this time the climate became more humid and atmospheric CO/sub 2/ increased. The concomitant environmental changes in the oceanic conditions presumably stressed the deeper coral communities on reefs. The emergence of rudists as reef contributors had a profound effect on Late Cretaceous depositional conditions and the development of hydrocarbon reservoirs.« less

  7. Early-mid-Cretaceous evolution in Tethyan reef communities and sea level

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Scott, R.W.

    1988-02-01

    The replacement of corals by rudists in Early Cretaceous reefal communities spanned a 30-m.y. period when sea level rose and drowned continental shelves. During this time corals formed communities in the deeper parts of reefs and rudists occupied the shallow, high-energy habitats. By Aptian time rudists dominated reefs that fringed interior shelf basins and corals formed reefs with rudists on the outer shelf margins. By late Albian coral communities had virtually disappeared, presumably because of complex environmental changes and cycles of organic productivity. Two important events of eustatic sea level rise are represented by unconformities separating carbonate depositional sequences onmore » the Arabian platform that correlate with sequence boundaries on the Gulf Coast platform. Graphic correlation techniques test the synchroneity of these events. A composite standard time scale dates these sea level rises at 115.8 Ma and 94.6 Ma; a third, intra-Albian event at 104.3 Ma is present in many places and may also be eustatic. Associated with these sea level rises were apparent changes in ocean water chemistry as evidenced by changes in isotopes and trace elements, where diagenetic effects can be discounted. During this time the climate became more humid and atmospheric CO/sub 2/ increased. The concomitant environmental changes in the oceanic conditions presumably stressed the deeper coral communities on reefs. The emergence of rudists as reef contributors had a profound effect on Late Cretaceous depositional conditions and the development of hydrocarbon reservoirs.« less

  8. Plant-arthropod interaction in the Early Cretaceous (Berriasian) of the Araripe Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Pires, Etiene Fabbrin; Sommer, Margot Guerra

    2009-02-01

    Plant-arthropod interactions provide the first relevant data for addressing evidence of phytophagy for an assemblage of coniferous silicified woods from the pre-rift phase in the Araripe Basin, Brazil. A complex system of borings, sometimes filled with small, oval to hexagonal coprolites, allow inferences to be made about the activities of termites (Isoptera). Previous dendrological data indicated that the climate during the Early Cretaceous on the landmasses of the northern Afro-Brazilian Depression was dry and savanna like, where termite borings were common. Features of wood preservation demonstrate that the damage was probably caused by herbivores, not detritivores.

  9. Exploring Early Angiosperm Fire Feedbacks using Coupled Experiments and Modelling Approaches to Estimate Cretaceous Palaeofire Behaviour

    NASA Astrophysics Data System (ADS)

    Belcher, Claire; Hudpsith, Victoria

    2016-04-01

    Using the fossil record we are typically limited to exploring linkages between palaeoecological changes and palaeofire activity by assessing the abundance of charcoals preserved in sediments. However, it is the behaviour of fires that primarily governs their ecological effects. Therefore, the ability to estimate variations in aspects of palaeofire behaviour such as palaeofire intensity and rate of spread would be of key benefit toward understanding the coupled evolutionary history of ecosystems and fire. The Cretaceous Period saw major diversification in land plants. Previously, conifers (gymnosperms) and ferns (pteridophytes) dominated Earth's ecosystems until flowering plants (angiosperms) appear in the fossil record of the Early Cretaceous (~135Ma). We have created surface fire behaviour estimates for a variety of angiosperm invasion scenarios and explored the influence of Cretaceous superambient atmospheric oxygen levels on the fire behaviour occurring in these new Cretaceous ecosystems. These estimates are then used to explore the hypothesis that the early spread of the angiosperms was promoted by the novel fire regimes that they created. In order to achieve this we tested the flammability of Mesozoic analogue fuel types in controlled laboratory experiments using an iCone calorimeter, which measured the ignitability as well as the effective heat of combustion of the fuels. We then used the BehavePlus fire behaviour modelling system to scale up our laboratory results to the ecosystem scale. Our results suggest that fire-angiosperm feedbacks may have occurred in two phases: The first phase being a result of weedy angiosperms providing an additional easily ignitable fuel that enhanced both the seasonality and frequency of surface fires. In the second phase, the addition of shrubby understory fuels likely expanded the number of ecosystems experiencing more intense surface fires, resulting in enhanced mortality and suppressed post-fire recruitment of gymnosperms

  10. Relative sea level changes during the Cretaceous in Israel

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Flexer, A.; Rosenfeld, A.; Lipson-Benitah, S.

    1986-11-01

    Detailed lithologic, microfaunal, and biometric investigations, using relative abundances, diversity indexes, and duration charts of ostracods and foraminifera, allowed the recognition of sea level changes during the Cretaceous of Israel. Three major transgressive-regressive sedimentation cycles occur on the northwest margins of the Arabian craton. These cycles are the Neocomian-Aptian, which is mostly terrigenous sediments; the Albian-Turonian, which is basin marls and platform carbonates; and the Senonian, which is uniform marly chalks. The cycles are separated by two major regional unconformities, the Aptian-Albian and Turonian-Coniacian boundaries. The sedimentary cycles are related to regional tectonic and volcanic events and eustatic changes. Themore » paleodepth curve illustrates the gradual sea level rise, reaching its maximum during the Late Cretaceous, with conspicuous advances during the late Aptian, late Albian-Cenomanian, early Turonian, early Santonian, and early Campanian. Major lowstands occur at the Aptian-Albian, Cenomanian-Turonian, Turonian-Coniacian, and Campanian-Maastrichtian boundaries. This model for Israel agrees well with other regional and global sea level fluctuations. Four anoxic events (black shales) accompanying transgressions correspond to the Cretaceous oceanic record. They hypothesize the presence of mature oil shales in the present-day eastern Mediterranean basin close to allochthonous reef blocks detached from the Cretaceous platform. 11 figures.« less

  11. Phylogenetic diversification of Early Cretaceous seed plants: The compound seed cone of Doylea tetrahedrasperma.

    PubMed

    Rothwell, Gar W; Stockey, Ruth A

    2016-05-01

    Discovery of cupulate ovules of Doylea tetrahedrasperma within a compact, compound seed cone highlights the rich diversity of fructification morphologies, pollination biologies, postpollination enclosure of seeds, and systematic diversity of Early Cretaceous gymnosperms. Specimens were studied using the cellulose acetate peel technique, three-dimensional reconstructions (in AVIZO), and morphological phylogenetic analyses (in TNT). Doylea tetrahedrasperma has bract/fertile short shoot complexes helically arranged within a compact, compound seed cone. Complexes diverge from the axis as a single unit and separate distally into a free bract tip and two sporophylls. Each sporophyll bears a single, abaxial seed, recurved toward the cone axis, that is enveloped after pollinaton by sporophyll tissue, forming a closed cupule. Ovules are pollinated by bisaccate grains captured by micropylar pollination horns. The unique combination of characters shown by D. tetrahedrasperma includes the presence of cupulate seeds borne in conifer-like compound seed cones, an ovuliferous scale analogue structurally equivalent to the ovulate stalk of Ginkgo biloba, gymnospermous pollination, and nearly complete enclosure of mature seeds. These features characterize the Doyleales ord. nov., clearly distinguish it from the seed fern order Corystospermales, and allow for recognition of another recently described Early Cretaceous seed plant as a second species in genus Doylea. A morphological phylogenetic analysis highlights systematic relationships of the Doyleales ord. nov. and emphasizes the explosive phylogenetic diversification of gymnosperms that was underway at the time when flowering plants may have originated and/or first began to radiate. © 2016 Botanical Society of America.

  12. Late Cretaceous-Early Eocene Climate Change Linked to Tectonic Eevolution of Neo-Tethyan Subduction Systems

    NASA Astrophysics Data System (ADS)

    Jagoutz, O. E.; Royden, L.; Macdonald, F. A.

    2015-12-01

    In this presentation we demonstrate that the two tectonic events in the late Cretaceous-Early Tertiary triggered the two distinct cooling events that followed the Cretaceous Thermal Maximum (CTM). During much of the Cretaceous time, the northern Neo Tethyan ocean was dominated by two east-west striking subduction system. Subduction underneath Eurasia formed a continental arc on the southern margin of Eurasia and intra oceanic subduction in the equatorial region of the Neo Tethys formed and intra oceanic arc. Beginning at ~85-90 Ma the western part of the TTSS collided southward with the Afro-Arabian continental margin, terminating subduction. This resulted in southward obduction of the peri-Arabian ophiolite belt, which extends for ~4000 km along strike and includes the Cypus, Semail and Zagros ophiolites. At the same time also the eastern part of the TTS collided northwards wit Eurasia. After this collisional event, only the central part of the subduction system remained active until it collided with the northern margin of the Indian continent at ~50-55 Ma. The collision of the arc with the Indian margin, over a length of ~3000 km, also resulted in the obduction of arc material and ophiolitic rocks. Remnants of these rocks are preserved today as the Kohistan-Ladakh arc and ophiolites of the Indus-Tsangpo suture zone of the Himalayas. Both of these collision events occurred in the equatorial region, near or within the ITCZ, where chemical weathering rates are high and are contemporaneous with the onset of the global cooling events that mark the end of the CTM and the EECO. The tectonic collision events resulted in a shut down of subduction zone magmatism, a major CO2 source and emplacement of highly weatherable basaltic rocks within the ITCZ (CO2 sink). In order to explore the effect of the events in the TTSS on atmospheric CO2, we model the potential contribution of subduction zone volcanism (source) and ophiolite obduction (sink) to the global atmospheric CO2

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

    PubMed

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

    2015-05-27

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

  14. Early Cretaceous Shallow-Water Platform Carbonates of the Bolkar Mountains, Central Taurides - South Turkey: Facies Analysis and Depositional Environments

    NASA Astrophysics Data System (ADS)

    Solak, Cemile; Taslı, Kemal; Koç, Hayati

    2016-10-01

    The study area comprises southern non-metamorphic part of the Bolkar Mountains which are situated in southern Turkey, eastern part of the Central Taurides. The studied five outcrops form geologically parts of the tectonostratigraphic units called as allochthonous Aladag Unit and autochthonous Geyikdagi Unit. The aim of this study is to describe microfacies and depositional environments of the Bolkar Mountains Early Cretaceous shallow- water platform carbonates. The Lower Cretaceous is represented by continuous thick- bedded to massive dolomite sequence ranging from 100 to 150 meters thick, which only contains locally laminated limestone intercalations in the Yüğlük section and thick to very thick-bedded uniform limestones ranging from approximately 50 to 120 meters, consist of mainly laminated- fenestral mudstone, peloidal-intraclastic grainstone-packstone, bioclastic packstone- wackestone, benthic foraminiferal-intraclastic grainstone-packstone, ostracod-fenestral wackestone-mudstone, dasycladacean algal packstone-wackestone and ooidal grainstone microfacies. Based on a combination sedimantological data, facies/microfacies and micropaleontological (predominantly dasycladacean algae and diverse benthic foraminifera) analysis, it is concluded that Early Cretaceous platform carbonates of the Bolkar Mountains reflect a tidally affected tidal-flat and restricted lagoon settings. During the Berriasian- Valanginian unfavourable facies for benthic foraminifera and dolomitization were predominate. In the Hauterivian-early Aptian, the effect of dolomitization largely disappeared and inner platform conditions still prevailed showing alternations of peritidal and lagoon facies, going from peritidal plains (representing various sub-environments including supratidal, intertidal area, tidal-intertidal ponds and ooid bars) dominated by ostracod and miliolids, to dasycladacean algae-rich restricted lagoons-subtidal. These environments show a transition in the vertical and

  15. Early Cretaceous MORB-type basalt and A-type rhyolite in northern Tibet: Evidence for ridge subduction in the Bangong-Nujiang Tethyan Ocean

    NASA Astrophysics Data System (ADS)

    Fan, Jian-Jun; Li, Cai; Sun, Zhen-Ming; Xu, Wei; Wang, Ming; Xie, Chao-Ming

    2018-04-01

    New zircon U-Pb ages, major- and trace-element data, and Hf isotopic compositions are presented for bimodal volcanic rocks of the Zhaga Formation (ZF) in the western-middle segment of the Bangong-Nujiang suture zone (BNSZ), northern Tibet. The genesis of these rocks is described, and implications for late-stage evolution of the Bangong-Nujiang Tethyan Ocean (BNTO) are considered. Detailed studies show that the ZF bimodal rocks, which occur as layers within a typical bathyal to abyssal flysch deposit, comprise MORB-type basalt that formed at a mid-ocean ridge, and low-K calc-alkaline A-type rhyolite derived from juvenile crust. The combination of MORB-type basalt, calc-alkaline A-type rhyolite, and bathyal to abyssal flysch deposits in the ZF leads us to propose that they formed as a result of ridge subduction. The A-type ZF rhyolites yield LA-ICP-MS zircon U-Pb ages of 118-112 Ma, indicating formation during the Early Cretaceous. Data from the present study, combined with regional geological data, indicate that the BNTO underwent conversion from ocean opening to ocean closure during the Late Jurassic-Early Cretaceous. The eastern segment of the BNTO closed during this period, while the western and western-middle segments were still at least partially open and active during the Early Cretaceous, accompanied by ridge subduction within the Bangong-Nujiang Tethyan Ocean.

  16. An enigmatic crocodyliform tooth from the bauxites of western Hungary suggests hidden mesoeucrocodylian diversity in the Early Cretaceous European archipelago

    PubMed Central

    Rabi, Márton; Makádi, László

    2015-01-01

    Background. The Cretaceous of southern Europe was characterized by an archipelago setting with faunas of mixed composition of endemic, Laurasian and Gondwanan elements. However, little is known about the relative timing of these faunal influences. The Lower Cretaceous of East-Central Europe holds a great promise for understanding the biogeographic history of Cretaceous European biotas because of the former proximity of the area to Gondwana (as part of the Apulian microcontinent). However, East-Central European vertebrates are typically poorly known from this time period. Here, we report on a ziphodont crocodyliform tooth discovered in the Lower Cretaceous (Albian) Alsópere Bauxite Formation of Olaszfalu, western Hungary. Methods. The morphology of the tooth is described and compared with that of other similar Cretaceous crocodyliforms. Results. Based on the triangular, slightly distally curved, constricted and labiolingually flattened crown, the small, subequal-sized true serrations on the carinae mesially and distally, the longitudinal fluting labially, and the extended shelves along the carinae lingually the tooth is most similar to some peirosaurid, non-baurusuchian sebecosuchian, and uruguaysuchid notosuchians. In addition, the paralligatorid Wannchampsus also possesses similar anterior teeth, thus the Hungarian tooth is referred here to Mesoeucrocodylia indet. Discussion. Supposing a notosuchian affinity, this tooth is the earliest occurrence of the group in Europe and one of the earliest in Laurasia. In case of a paralligatorid relationship the Hungarian tooth would represent their first European record, further expanding their cosmopolitan distribution. In any case, the ziphodont tooth from the Albian bauxite deposit of western Hungary belongs to a group still unknown from the Early Cretaceous European archipelago and therefore implies a hidden diversity of crocodyliforms in the area. PMID:26339542

  17. Early Cretaceous paleomagnetic and geochronologic results from the Tethyan Himalaya: Insights into the Neotethyan paleogeography and the India-Asia collision

    NASA Astrophysics Data System (ADS)

    Ma, Yiming; Yang, Tianshui; Bian, Weiwei; Jin, Jingjie; Zhang, Shihong; Wu, Huaichun; Li, Haiyan

    2016-02-01

    To better understand the Neotethyan paleogeography, a paleomagnetic and geochronological study has been performed on the Early Cretaceous Sangxiu Formation lava flows, which were dated from ~135.1 Ma to ~124.4 Ma, in the Tethyan Himalaya. The tilt-corrected site-mean characteristic remanent magnetization (ChRM) direction for 26 sites is Ds = 296.1°, Is = -65.7°, ks = 51.7, α95 = 4.0°, corresponding to a paleopole at 5.9°S, 308.0°E with A95 = 6.1°. Positive fold and reversal tests prove that the ChRM directions are prefolding primary magnetizations. These results, together with reliable Cretaceous-Paleocene paleomagnetic data observed from the Tethyan Himalaya and the Lhasa terrane, as well as the paleolatitude evolution indicated by the apparent polar wander paths (APWPs) of India, reveal that the Tethyan Himalaya was a part of Greater India during the Early Cretaceous (135.1-124.4 Ma) when the Neotethyan Ocean was up to ~6900 km, it rifted from India sometime after ~130 Ma, and that the India-Asia collision should be a dual-collision process including the first Tethyan Himalaya-Lhasa terrane collision at ~54.9 Ma and the final India-Tethyan Himalaya collision at ~36.7 Ma.

  18. Crustal architecture and tectonic evolution of the Cauvery Suture Zone, southern India

    NASA Astrophysics Data System (ADS)

    Chetty, T. R. K.; Yellappa, T.; Santosh, M.

    2016-11-01

    The Cauvery suture zone (CSZ) in southern India has witnessed multiple deformations associated with multiple subduction-collision history, with incorporation of the related accretionary belts sequentially into the southern continental margin of the Archaean Dharwar craton since Neoarchean to Neoproterozoic. The accreted tectonic elements include suprasubduction complexes of arc magmatic sequences, high-grade supracrustals, thrust duplexes, ophiolites, and younger intrusions that are dispersed along the suture. The intra-oceanic Neoarchean-Neoproterozoic arc assemblages are well exposed in the form of tectonic mélanges dominantly towards the eastern sector of the CSZ and are typically subjected to complex and multiple deformation events. Multi-scale analysis of structural elements with detailed geological mapping of the sub-regions and their structural cross sections, geochemical and geochronological data and integrated geophysical observations suggest that the CSZ is an important zone that preserves the imprints of multiple cycles of Precambrian plate tectonic regimes.

  19. Dinosaur trackways from the early Late Cretaceous of western Cameroon

    NASA Astrophysics Data System (ADS)

    Martin, Jeremy E.; Menkem, Elie Fosso; Djomeni, Adrien; Fowe, Paul Gustave; Ntamak-Nida, Marie-Joseph

    2017-10-01

    Dinosaur trackways have rarely been reported in Cretaceous strata across the African continent. To the exception of ichnological occurrences in Morocco, Tunisia, Niger and Cameroon, our knowledge on the composition of Cretaceous dinosaur faunas mostly relies on skeletal evidence. For the first time, we document several dinosaur trackways from the Cretaceous of the Mamfe Basin in western Cameroon. Small and medium-size tridactyl footprints as well as numerous large circular footprints are present on a single horizon showing mudcracks and ripple marks. The age of the locality is considered Cenomanian-Turonian and if confirmed, this ichnological assemblage could be younger than the dinosaur footprints reported from northern Cameroon, and coeval with or younger than skeletal remains reported from the Saharan region. These trackways were left in an adjacent subsiding basin along the southern shore of the Benue Trough during a time of high-sea stand when the Trans-Saharan Seaway was already disconnecting West Africa from the rest of the continent. We predict that other similar track sites may be occurring along the margin of the Benue Trough and may eventually permit to test hypotheses related to provincialism among African dinosaur faunas.

  20. One hundred million year old ergot: psychotropic compounds in the Cretaceous?

    USDA-ARS?s Scientific Manuscript database

    A fungal sclerotium similar to sclerotia of the genus Claviceps, commonly known as ergot, was found infecting a grass kernel in Early Cretaceous Myanmar amber. This represents the first fossil record of ergot dating as far back as the Cretaceous period. The fungus, described as Palaeoclaviceps para...

  1. A Ceratopsian Dinosaur from the Lower Cretaceous of Western North America, and the Biogeography of Neoceratopsia

    PubMed Central

    Farke, Andrew A.; Maxwell, W. Desmond; Cifelli, Richard L.; Wedel, Mathew J.

    2014-01-01

    The fossil record for neoceratopsian (horned) dinosaurs in the Lower Cretaceous of North America primarily comprises isolated teeth and postcrania of limited taxonomic resolution, hampering previous efforts to reconstruct the early evolution of this group in North America. An associated cranium and lower jaw from the Cloverly Formation (?middle–late Albian, between 104 and 109 million years old) of southern Montana is designated as the holotype for Aquilops americanus gen. et sp. nov. Aquilops americanus is distinguished by several autapomorphies, including a strongly hooked rostral bone with a midline boss and an elongate and sharply pointed antorbital fossa. The skull in the only known specimen is comparatively small, measuring 84 mm between the tips of the rostral and jugal. The taxon is interpreted as a basal neoceratopsian closely related to Early Cretaceous Asian taxa, such as Liaoceratops and Auroraceratops. Biogeographically, A. americanus probably originated via a dispersal from Asia into North America; the exact route of this dispersal is ambiguous, although a Beringian rather than European route seems more likely in light of the absence of ceratopsians in the Early Cretaceous of Europe. Other amniote clades show similar biogeographic patterns, supporting an intercontinental migratory event between Asia and North America during the late Early Cretaceous. The temporal and geographic distribution of Upper Cretaceous neoceratopsians (leptoceratopsids and ceratopsoids) suggests at least intermittent connections between North America and Asia through the early Late Cretaceous, likely followed by an interval of isolation and finally reconnection during the latest Cretaceous. PMID:25494182

  2. Late Jurassic-Early Cretaceous episodic development of the Bangong Meso-Tethyan subduction: Evidence from elemental and Sr-Nd isotopic geochemistry of arc magmatic rocks, Gaize region, central Tibet, China

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Xiu; Li, Zhi-Wu; Yang, Wen-Guang; Zhu, Li-Dong; Jin, Xin; Zhou, Xiao-Yao; Tao, Gang; Zhang, Kai-Jun

    2017-03-01

    The Bangong Meso-Tethys plays a critical role in the development of the Tethyan realm and the initial elevation of the Tibetan Plateau. However, its precise subduction polarity, and history still remain unclear. In this study, we synthesize a report for the Late Jurassic-Early Cretaceous two-phase magmatic rocks in the Gaize region at the southern margin of the Qiangtang block located in central Tibet. These rocks formed during the Late Jurassic-earliest Cretaceous (161-142 Ma) and Early Cretaceous (128-106 Ma), peaking at 146 Ma and 118 Ma, respectively. The presence of inherited zircons indicates that an Archean component exists in sediments in the shallow Qiangtang crust, and has a complex tectonomagmatic history. Geochemical and Sr-Nd isotopic data show that the two-phase magmatic rocks exhibit characteristics of arc magmatism, which are rich in large-ion incompatible elements (LIIEs), but are strongly depleted in high field strength elements (HFSEs). The Late Jurassic-earliest Cretaceous magmatic rocks mixed and mingled among mantle-derived mafic magmas, subduction-related sediments, or crustally-derived felsic melts and fluids, formed by a northward and steep subduction of the Bangong Meso-Tethys ocean crust. The magmatic gap at 142-128 Ma marks a flat subduction of the Meso-Tethys. The Early Cretaceous magmatism experienced a magma MASH (melting, assimilation, storage, and homogenization) process among mantle-derived mafic magmas, or crustally-derived felsic melts and fluids, as a result of the Meso-Tethys oceanic slab roll-back, which triggered simultaneous back-arc rifting along the southern Qiangtang block margin.

  3. Composition, Age, and Origin of Cretaceous Granitic Magmatism on the Eastern Chukchi Peninsula

    NASA Astrophysics Data System (ADS)

    Luchitskaya, M. V.; Sokolov, S. D.; Pease, V.; Miller, E.; Belyatsky, B. V.

    2018-05-01

    New geochronological and isotopic geochemical data are given, which make it possible to recognize two types of granitic rocks on the eastern Chukchi Peninsula. Early Cretaceous Tkachen and Dolina granitic plutons with zircon ages (U-Pb SIMS) of 119-122 and 131-136 Ma are related to the first type. They cut through Devonian-Lower Carboniferous basement rocks and are overlain by the Aptian-Albian Etelkuyum Formation. Basal units of the latter contain fragments of granitic rocks. Late Cretaceous Provideniya and Rumilet granitic plutons, which contain zircons with ages of 94 and 85 Ma (U-Pb SIMS), respectively, belong to the second type. They cut through volcanic-sedimentary rocks of the Etelkuyum and Leurvaam formations pertaining to the Okhotsk-Chukotka Volcanic Belt. In petrographic and geochemical features, the Early Cretaceous granitic rocks of the Tkachen Pluton are commensurable with I-type granites, while Late Cretaceous granite of the Rumilet Pluton is comparable to A2-type granite. The Sr-Nd isotopic data provide evidence that from the Early Cretaceous Tkachen and Dolina plutons to the Late Cretaceous Provideniya and Rumilet plutons, the degree of crustal assimilation of suprasubduction mantle-derived melts increases up to partial melting of heterogeneous continental crust enriched in rubidium. An unconformity and various degrees of secondary alteration of volcanic-sedimentary rocks have been established in the Okhotsk-Chukotka Volcanic Belt, and this was apparently caused by transition of the tectonic setting from suprasubduction to a transform margin with local extension.

  4. Assessment of bacterial community composition in response to uranium levels in sediment samples of sacred Cauvery River.

    PubMed

    Suriya, Jayaraman; Chandra Shekar, Mootapally; Nathani, Neelam Mustakali; Suganya, Thangaiyan; Bharathiraja, Subramanian; Krishnan, Muthukalingan

    2017-01-01

    Global industrialization is a major cause of effluent discharge from industries up to alarming concentrations. Especially, uranium concentrations in water bodies are of great concern, as its radioactivity significantly affects the persistent diversity of microbiota. Recently, continuous application of pesticides in the agricultural lands and accumulation of quartz that enter the Cauvery River has significantly increased the concentration of uranium (U) and other heavy metals. To perceive the impact of uranium on bacterial diversity in Cauvery River, sediment samples collected from polluted (UP) site with 32.4 Bq/K of U concentration and control (UNP) site were scrutinized for bacterial diversity through metagenomic analysis of the V3 region of 16S rDNA by Illumina sequencing. Taxonomic assignment revealed that the unpolluted sample was dominated by Bacteroidetes (27.7 %), and Firmicutes (25.9 %), while sediment sample from the highly polluted site revealed abundance of Proteobacteria (47.5 %) followed by Bacteroidetes (22.4 %) and Firmicutes (14.6 %). Among Proteobacteria, Gammaproteobacteria was the most prevalent group followed by alpha, delta, epsilon, and beta in the uranium-polluted sample. Rare and abundant species analysis revealed that species like Idiomarina loihiensis was abundant in the pollutant sample; however, it was rare (<0.1 %) in the sample from pristine environment. Similarly, the species distribution in both the samples varied, with the bacteria potentially active in redox activity and biosorption potential dominating in the polluted sample. Outcomes of the present study demonstrated the impact of uranium and metal accumulation on the bacterial communities and further confirmed the promising candidature of specific bacterial species as bioindicators of contamination.

  5. Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, north Cascade Range, Washington and British Columbia

    USGS Publications Warehouse

    Haugerud, R.A.; Van Der Heyden, P.; Tabor, R.W.; Stacey, J.S.; Zartman, R.E.

    1991-01-01

    The Skagit Gneiss Complex forms a more-or-less continuous terrane within the North Cascade Range. The complex comprises abundant plutons intruded at mid-crustal depths into a variety of metamorphosed supracrustal rocks of both oceanic and volcanic-arc origin. U-Pb zircon ages from gneissis plutons within and near the Skagit Gneiss Complex indicate magmatic crystallziations between 75 and 60 Ma. Deformation, recrystallization, and migmatization in part postdate intrusion of the 75-60 Ma plutons. This latest Cretaceous and earliest Tertiary plutonism and migmatization may reflect thermal relaxation following early Late Cretaceous orogeny. The complex was ductilely extended northwest-southeast shortly after intrusion of granite dikes at ~45 Ma, but before emplacement of the earliest (~34 Ma) plutons of the Cascade arc. -from Authors

  6. Reappraisal of Europe’s most complete Early Cretaceous plesiosaurian: Brancasaurus brancai Wegner, 1914 from the “Wealden facies” of Germany

    PubMed Central

    Hornung, Jahn J.; Kear, Benjamin P.

    2016-01-01

    The holotype of Brancasaurus brancai is one of the most historically famous and anatomically complete Early Cretaceous plesiosaurian fossils. It derived from the Gerdemann & Co. brickworks clay pit near Gronau (Westfalen) in North Rhine-Westphalia, northwestern Germany. Stratigraphically this locality formed part of the classic European “Wealden facies,” but is now more formally attributed to the upper-most strata of the Bückeberg Group (upper Berriasian). Since its initial description in 1914, the type skeleton of B. brancai has suffered damage both during, and after WWII. Sadly, these mishaps have resulted in the loss of substantial information, in particular many structures of the cranium and limb girdles, which are today only evidenced from published text and/or illustrations. This non-confirmable data has, however, proven crucial for determining the relationships of B. brancai within Plesiosauria: either as an early long-necked elasmosaurid, or a member of the controversial Early Cretaceous leptocleidid radiation. To evaluate these competing hypotheses and compile an updated osteological compendium, we undertook a comprehensive examination of the holotype as it is now preserved, and also assessed other Bückeberg Group plesiosaurian fossils to establish a morphological hypodigm. Phylogenetic simulations using the most species-rich datasets of Early Cretaceous plesiosaurians incorporating revised scores for B. brancai, together with a second recently named Bückeberg Group plesiosaurian Gronausaurus wegneri (Hampe, 2013), demonstrated that referral of these taxa to Leptocleididae was not unanimous, and that the topological stability of this clade is tenuous. In addition, the trait combinations manifested by B. brancai and G. wegneri were virtually identical. We therefore conclude that these monotypic individuals are ontogenetic morphs and G. wegneri is a junior synonym of B. brancai. Finally, anomalies detected in the diagnostic features for other

  7. Early Cretaceous terrestrial ecosystems in East Asia based on food-web and energy-flow models

    USGS Publications Warehouse

    Matsukawa, M.; Saiki, K.; Ito, M.; Obata, I.; Nichols, D.J.; Lockley, M.G.; Kukihara, R.; Shibata, K.

    2006-01-01

    In recent years, there has been global interest in the environments and ecosystems around the world. It is helpful to reconstruct past environments and ecosystems to help understand them in the present and the future. The present environments and ecosystems are an evolving continuum with those of the past and the future. This paper demonstrates the contribution of geology and paleontology to such continua. Using fossils, we can make an estimation of past population density as an ecosystem index based on food-web and energy-flow models. Late Mesozoic nonmarine deposits are distributed widely on the eastern Asian continent and contain various kinds of fossils such as fishes, amphibians, reptiles, dinosaurs, mammals, bivalves, gastropods, insects, ostracodes, conchostracans, terrestrial plants, and others. These fossil organisms are useful for late Mesozoic terrestrial ecosystem reconstruction using food-web and energy-flow models. We chose Early Cretaceous fluvio-lacustrine basins in the Choyr area, southeastern Mongolia, and the Tetori area, Japan, for these analyses and as a potential model for reconstruction of other similar basins in East Asia. The food-web models are restored based on taxa that occurred in these basins. They form four or five trophic levels in an energy pyramid consisting of rich primary producers at its base and smaller biotas higher in the food web. This is the general energy pyramid of a typical ecosystem. Concerning the population densities of vertebrate taxa in 1 km2 in these basins, some differences are recognized between Early Cretaceous and the present. For example, Cretaceous estimates suggest 2.3 to 4.8 times as many herbivores and 26.0 to 105.5 times the carnivore population. These differences are useful for the evaluation of past population densities of vertebrate taxa. Such differences may also be caused by the different metabolism of different taxa. Preservation may also be a factor, and we recognize that various problems occur in

  8. Oxidation state inherited from the magma source and implications for mineralization: Late Jurassic to Early Cretaceous granitoids, Central Lhasa subterrane, Tibet

    NASA Astrophysics Data System (ADS)

    Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; McInnes, Brent I. A.; Li, JinXiang; Zhao, JunXing

    2018-03-01

    Arc magmas are more oxidized than mid-ocean ridge basalts; however, there is continuing debate as to whether this higher oxidation state is inherited from the source magma or developed during late-stage magmatic differentiation processes. Well-constrained Late Jurassic to Early Cretaceous arc-related intermediate to felsic rocks derived from distinct magma sources provide us with a good opportunity to resolve this enigma. A series of granitoids from the western Central Lhasa subterrane were analyzed for whole-rock magnetic susceptibility, Fe2O3/FeO ratios, and trace elements in zircon. Compared to Late Jurassic samples (1.8 ± 2.0 × 10-4 emu g-1 oe-1, Fe3+/Fetotal = 0.32 ± 0.07, zircon Ce4+/Ce3+* = 15.0 ± 13.4), Early Cretaceous rocks show higher whole-rock magnetic susceptibility (5.8 ± 2.5 × 10-4 emu g-1 oe-1), Fe3+/Fetotal ratios (0.43 ± 0.04), and zircon Ce4+/Ce3+* values (23.9 ± 22.3). In addition, positive correlations among whole-rock magnetic susceptibility, Fe3+/Fetotal ratios, and zircon Ce4+/Ce3+* reveal a slight increase in oxidation state from fO2 = QFM to NNO in the Late Jurassic to fO2 = ˜NNO in the Early Cretaceous. Obvious linear correlation between oxidation indices (whole-rock magnetic susceptibility, zircon Ce4+/Ce3+*) and source signatures (zircon ɛHf(t), TDM C ages) indicates that the oxidation state was predominantly inherited from the source with only a minor contribution from magmatic differentiation. Thus, the sources for both the Late Jurassic and Early Cretaceous rocks were probably influenced by mantle wedge-derived magma, contributing to the increased fO2. Compared to ore-forming rocks at giant porphyry Cu deposits, the relatively low oxidation state (QFM to NNO) and negative ɛHf(t) (-16 to 0) of the studied granitoids implies relative infertility. However, this study demonstrates two potential fast and effective indices ( fO2 and ɛHf(t)) to evaluate the fertility of granitoids for porphyry-style mineralization. In an

  9. Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica.

    PubMed

    Barreda, Viviana D; Palazzesi, Luis; Tellería, Maria C; Olivero, Eduardo B; Raine, J Ian; Forest, Félix

    2015-09-01

    The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76-66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60-50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general.

  10. Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica

    PubMed Central

    Barreda, Viviana D.; Palazzesi, Luis; Tellería, Maria C.; Olivero, Eduardo B.; Raine, J. Ian; Forest, Félix

    2015-01-01

    The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76–66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60–50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general. PMID:26261324

  11. Diverse dinosaur-dominated ichnofaunas from the Potomac Group (Lower Cretaceous) Maryland

    USGS Publications Warehouse

    Stanford, Ray; Lockley, Martin G.; Weems, Robert E.

    2007-01-01

    Until recently fossil footprints were virtually unknown from the Cretaceous of the eastern United States. The discovery of about 300 footprints in iron-rich siliciclastic facies of the Patuxent Formation (Potomac Group) of Aptian age is undoubtedly one of the most significant Early Cretaceous track discoveries since the Paluxy track discoveries in Texas in the 1930s. The Patuxent tracks include theropod, sauropod, ankylosaur and ornithopod dinosaur footprints, pterosaur tracks, and miscellaneous mammal and other vertebrate ichnites that collectively suggest a diversity of about 14 morphotypes. This is about twice the previous maximum estimate for any known Early Cretaceous vertebrate ichnofauna. Among the more distinctive forms are excellent examples of hypsilophodontid tracks and a surprisingly large mammal footprint. A remarkable feature of the Patuxent track assemblage is the high proportion of small tracks indicative of hatchlings, independently verified by the discovery of a hatchling-sized dinosaur. Such evidence suggests the proximity of nest sites. The preservation of such small tracks is very rare in the Cretaceous track record, and indeed throughout most of the Mesozoic.This unusual preservation not only provides us with a window into a diverse Early Cretaceous ecosystem, but it also suggests the potential of such facies to provide ichnological bonanzas. A remarkable feature of the assemblage is that it consists largely of reworked nodules and clasts that may have previously been reworked within the Patuxent Formation. Such unusual contexts of preservation should provide intriguing research opportunities for sedimentologists interested in the diagenesis and taphonomy of a unique track-bearing facies.

  12. New type of kinematic indicator in bed-parallel veins, Late Jurassic-Early Cretaceous Vaca Muerta Formation, Argentina: E-W shortening during Late Cretaceous vein opening

    NASA Astrophysics Data System (ADS)

    Ukar, Estibalitz; Lopez, Ramiro G.; Gale, Julia F. W.; Laubach, Stephen E.; Manceda, Rene

    2017-11-01

    In the Late Jurassic-Early Cretaceous Vaca Muerta Formation, previously unrecognized yet abundant structures constituting a new category of kinematic indicator occur within bed-parallel fibrous calcite veins (BPVs) in shale. Domal shapes result from localized shortening and thickening of BPVs and the intercalation of centimeter-thick, host-rock shale inclusions within fibrous calcite beef, forming thrust fault-bounded pop-up structures. Ellipsoidal and rounded structures show consistent orientations, lineaments of interlayered shale and fibrous calcite, and local centimeter-scale offset thrust faults that at least in some cases cut across the median line of the BPV and indicate E-W shortening. Continuity of crystal fibers shows the domal structures are contemporaneous with BPV formation and help establish timing of fibrous vein growth in the Late Cretaceous, when shortening directions were oriented E-W. Differences in the number of opening stages and the deformational style of the different BPVs indicate they may have opened at different times. The new domal kinematic indicators described in this study are small enough to be captured in core. When present in the subsurface, domal structures can be used to either infer paleostress orientation during the formation of BPVs or to orient core in cases where the paleostress is independently known.

  13. Lead isotope compositions of Late Cretaceous and early Tertiary igneous rocks and sulfide minerals in Arizona: Implications for the sources of plutons and metals in porphyry copper deposits

    USGS Publications Warehouse

    Bouse, R.M.; Ruiz, J.; Titley, S.R.; Tosdal, R.M.; Wooden, J.L.

    1999-01-01

    Porphyry copper deposits in Arizona are genetically associated with Late Cretaceous and early Tertiary igneous complexes that consist of older intermediate volcanic rocks and younger intermediate to felsic intrusions. The igneous complexes and their associated porphyry copper deposits were emplaced into an Early Proterozoic basement characterized by different rocks, geologic histories, and isotopic compositions. Lead isotope compositions of the Proterozoic basement rocks define, from northwest to southeast, the Mojave, central Arizona, and southeastern Arizona provinces. Porphyry copper deposits are present in each Pb isotope province. Lead isotope compositions of Late Cretaceous and early Tertiary plutons, together with those of sulfide minerals in porphyry copper deposits and of Proterozoic country rocks, place important constraints on genesis of the magmatic suites and the porphyry copper deposits themselves. The range of age-corrected Pb isotope compositions of plutons in 12 Late Cretaceous and early Tertiary igneous complexes is 206Pb/204Pb = 17.34 to 22.66, 207Pb/204Pb = 15.43 to 15.96, and 208Pb/204Pb = 37.19 to 40.33. These Pb isotope compositions and calculated model Th/U are similar to those of the Proterozoic rocks in which the plutons were emplaced, thereby indicating that Pb in the younger rocks and ore deposits was inherited from the basement rocks and their sources. No Pb isotope differences distinguish Late Cretaceous and early Tertiary igneous complexes that contain large economic porphyry copper deposits from less rich or smaller deposits that have not been considered economic for mining. Lead isotope compositions of Late Cretaceous and early Tertiary plutons and sulfide minerals from 30 metallic mineral districts, furthermore, require that the southeastern Arizona Pb province be divided into two subprovinces. The northern subprovince has generally lower 206Pb/204Pb and higher model Th/U, and the southern subprovince has higher 206Pb/204Pb and

  14. Cretaceous gastropods: contrasts between tethys and the temperate provinces.

    USGS Publications Warehouse

    Sohl, N.F.

    1987-01-01

    During the Cretaceous Period, gastropod faunas show considerable differences in their evolution between the Tethyan Realm (tropical) and the Temperate Realms to the north and south. Like Holocene faunas, prosobranch, gastropods constitute the dominant part of Cretaceous marine snail faunas. Entomotaeneata and opisthobranchs usually form all of the remainder. In Tethyan faunas the Archaeogastropoda form a consistent high proportion of total taxa but less than the Mesogastropoda throughout the period. In contrast, the Temperate faunas beginning in Albian times show a decline in percentages of archaeogastropod taxa and a significant increase in the Neogastropoda, until they constitute over 50 percent of the taxa in some faunas. The neogastropods never attain high diversity in the Cretaceous of the Tethyan Realm and are judged to be of Temperate Realm origin. Cretaceous Tethyan gastropod faunas are closely allied to those of the 'corallien facies' of the Jurassic and begin the period evolutionarily mature and well diversified. Three categories of Tethyan gastropods are analyzed. The first group consists of those of Jurassic ancestry. The second group orginates mainly during the Barremian and Aptian, reaches a climax in diversification during middle Cretaceous time, and usually declines during the latest Cretaceous. The third group originates late in the Cretaceous and consists of taxa that manage to either survive the Cretaceous-Tertiary crisis or give rise to forms of prominence among Tertiary warm water faunas. Temperate Realm gastropod faunas are less diverse than those of Tethys during the Early Cretaceous. They show a steady increase in diversity, primarily among the Mesogastropoda and Neogastropoda. This trend culminates in latest Cretaceous times when the gastropod assemblages of the clastic provinces of the inner shelf contain an abundance of taxa outstripping that of any other part of the Cretaceous of either realm. Extinction at the Cretaceous

  15. Palaeomagnetic time and space constraints of the Early Cretaceous Rhenodanubian Flysch zone (Eastern Alps)

    NASA Astrophysics Data System (ADS)

    Dallanave, Edoardo; Kirscher, Uwe; Hauck, Jürgen; Hesse, Reinhard; Bachtadse, Valerian; Wortmann, Ulrich Georg

    2018-06-01

    The Rhenodanubian Flysch zone (RDF) is a Lower Cretaceous-lower Palaeocene turbidite succession extending for ˜500 km from the Danube at Vienna to the Rhine Valley (Eastern Alps). It consists of calcareous and siliciclastic turbidite systems deposited in a trench abyssal plain. The age of deposition has been estimated through micropalaeontologic dating. However, palaeomagnetic studies constraining the age and the palaeolatitude of deposition of the RDF are still missing. Here, we present palaeomagnetic data from the Early Cretaceous Tristel and Rehbreingraben Formations of the RDF from two localities in the Bavarian Alps (Rehbrein Creek and Lainbach Valley, southern Germany), and from the stratigraphic equivalent of the Falknis Nappe (Liechtenstein). The quality of the palaeomagnetic signal has been assessed by either fold test (FT) or reversal test (RT). Sediments from the Falknis Nappe are characterized by a pervasive syntectonic magnetic overprint as tested by negative FT, and are thus excluded from the study. The sediments of the Rehbreingraben Formation at Rehbrein Creek, with positive RT, straddle magnetic polarity Chron M0r and the younger M΄-1r΄ reverse event, with an age of ˜127-123 Ma (late Barremian-early Aptian). At Lainbach Valley, no polarity reversals have been observed, but a positive FT gives confidence on the reliability of the data. The primary palaeomagnetic directions, after correction for inclination shallowing, allow to precisely constrain the depositional palaeolatitude of the Tristel and Rehbreingraben Formations around ˜28°N. In a palaeogeographic reconstruction of the Alpine Tethys at the Barremian/Aptian boundary, the RDF is located on the western margin of the Briançonnais terrain, which was separated from the European continent by the narrow Valais Ocean.

  16. Recent advances in the cretaceous stratigraphy of Korea

    NASA Astrophysics Data System (ADS)

    Chang, Ki-Hong; Suzuki, Kazuhiro; Park, Sun-Ok; Ishida, Keisuke; Uno, Koji

    2003-06-01

    A subrounded, accidental, zircon grain from a rhyolite sample of the Oknyobong Formation has shown an U-Pb CHIME isochron age, 187 Ma, implying its derivation from a Jurassic felsic igneous rock. Such a lower limit of the geologic age of the Oknyobong Formation, combined with its pre-Kyongsang upper limit, constrains that the Oknyobong Formation belongs to the Jasong Synthem (Late Jurassic-early Early Cretaceous) typified in North Korea. The Jaeryonggang Movement terminated the deposition of the Jasong Synthem and caused a shift of the depocenter from North Korea to the Kyongsang Basin, Southeast Korea. The Cretaceous-Paleocene Kyongsang Supergroup of the Kyongsang Basin is the stratotype of the Kyongsang Synthem, an unconformity-bounded unit in the Korean Peninsula. The unconformity at the base of the Yuchon Volcanic Group is a local expression of the interregionally recognizable mid-Albian tectonism; it subdivides the Kyongsang Synthem into the Lower Kyongsang Subsynthem (Barremian-Early Albian) and the Upper Kyongsang Subsynthem (Late Albian-Paleocene). The latter is unconformably overlain by Eocene and younger strata. The Late Permian to Early Jurassic radiolarian fossils from the chert pebbles of the Kumidong and the Kisadong conglomerates of the Aptian-Early Albian Hayang Group of the Kyongsang Basin are equivalent with those of the cherts that constitute the Jurassic accretionary prisms in Japan, the provenance of the chert pebbles in the Kyongsang Basin. Bimodal volcanisms throughout the history of the Kyongsang Basin is exemplified by the felsic Kusandong Tuff erupted abruptly and briefly in the Late Aptian when semi-coeval volcanisms were of intermediate and mafic compositions. The mean paleomagnetic direction shown by the Kusandong Tuff is in good agreement with the Early Cretaceous directions known from North China, South China and Siberia Blocks.

  17. Diatom life cycles and ecology in the Cretaceous.

    PubMed

    Jewson, David H; Harwood, David M

    2017-06-01

    The earliest known diatom fossils with well-preserved siliceous frustules are from Lower Cretaceous neritic marine deposits in Antarctica. In this study, we analyzed the cell wall structure to establish whether their cell and life cycles were similar to modern forms. At least two filamentous species (Basilicostephanus ornatus and Archepyrgus melosiroides) had girdle band structures that functioned during cell division in a similar way to present day Aulacoseira species. Also, size analyses of cell diameter indicated that the cyclic process of size decline and size restoration used to time modern diatom life cycles was present in five species from the Lower Cretaceous (B. ornatus, A. melosiroides, Gladius antiquus, Ancylopyrgus reticulatus, Kreagra forfex) as well as two species from Upper Cretaceous deposits (Trinacria anissimowii and Eunotogramma fueloepi) from the Southwest Pacific. The results indicate that the "Diatom Sex Clock" was present from an early evolutionary stage. Other ecological adaptations included changes in mantle height and coiling. Overall, the results suggest that at least some of the species in these early assemblages are on a direct ancestral line to modern forms. © 2017 Phycological Society of America.

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

    PubMed

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

    2011-11-02

    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.

  19. High Arctic paleoenvironmental and Paleoclimatic changes in the Mid-Cretaceous

    NASA Astrophysics Data System (ADS)

    Herrle, Jens; Schröder-Adams, Claudia; Selby, David; Du Vivier, Alice; Flögel, Sascha; McAnena, Alison; Davis, William; Pugh, Adam; Galloway, Jennifer; Hofmann, Peter; Wagner, Thomas

    2014-05-01

    the OAE2 period which shades a new light on temperature gradients during different climate states of the Cretaceous. In contrast, to the Late Cenomanian to Early Turonian the distinct occurrence of several widespread glendonite beds in the Late Aptian to Early Albian support cool bottom waters of about 0°C in the Arctic Sverdrup Basin, consistent with much lower TEX86-SST ~28°C, McAnena et al., 2013) and bottom water temperatures (6°C, Huber et al., 2011) in the low latitude North Atlantic. This supports the global character of the proposed Late Aptian cold snap (Kemper, 1987; Herrle & Mutterlose, 2003; Mutterlose et al. 2009; McAnena et al. 2013) and perhaps a northern hemisphere high-latitude intermediate bottom water source. References Du Vivier, A.C.D., Selby, D., Sageman, B.B., Jarvis, I., Gröcke, D.R., Voigt, S., 2014. Marine 187Os/188Os isotope stratigraphy reveals the interaction of volcanism and ocean circulation during Oceanic Anoxic Event 2. EPSL 389, 23-33. Föllmi, K.B., 2012. Early Cretaceous life, climate and anoxia. Cretaceous Research 35, 230-257. Hay, W.W., 2008. Evolving ideas about the Cretaceous climate and ocean circulation. Cretaceous Research 29, 725-753. Hay, W.W., 2011. Can humans force a return to a "Cretaceous" climate? Sedimentary Geology 235, 5-26. Herrle, J.O. , Mutterlose, J., 2003. Calcareous nannofossils from the Aptian - early Albian of SE France: Paleoecological and biostratigraphic implications. Cretaceous Research 24, 1-22. Huber, B.T., MacLeod, K.G., Gröcke, D.R., Kucera, M., 2011. Paleotemperature and paleosalinity inferences and chemostratigraphy across the Aptian/Albian boundary in the subtropical North Atlantic. Paleoceanography 26, PA4221 doi:10.1029/2011PA002178. McAnena, A., Flögel, S., Hofmann, P., Herrle, J.O., Griesand, A., Pross, J., Talbot, H.M., Rethemeyer, J., Wallmann, K., Wagner, T., 2013. Atlantic cooling associated with a marine biotic crisis during the mid-Cretaceous period. Nature Geoscience 6, 558

  20. Early cretaceous platform-margin configuration and evolution in the central Oman mountains, Arabian peninsula

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pratt, B.R.; Smewing, J.D.

    1993-02-01

    The Hajar Supergroup (Middle Permian-Lower Cretaceous) of northeastern Oman records rifting and development of a passive margin along the edge of the Arabian platform facing Neo-Tethys. The Jurassic and Lower Cretaceous part, comprising the Sahtan, Kahmah, and Wasia groups, was deposited during the maximum extent of the broad epicontinental sea landward of this margin. These limestone units reach a total of 1500 m in thickness and correlate with the hydrocarbon reservoirs of the Arabian Peninsula. The trace of the Jurassic and Cretaceous margin in northeastern Oman followed a zigzag series of rift segments, resulting in promontories and reentrants that changedmore » in position through time in response to the configuration and differential motion of underlying rift blocks. Synsedimentary normal faulting occurred locally in the Middle Jurassic, whereas in the Late Jurassic, the margin was eroded from variable uplift of up to 300 m before subsiding to below storm wave base. This uplift may have been caused by compression from oceanic crust that obducted along the southeastern side of the platform. The Lower Cretaceous succession in the central Oman Mountains and adjacent subsurface began with regional drowning around the Jurassic-Cretaceous boundary. The succession in the east (Saih Hatat) records a single regressive sequence, ending in the progradation of the shallow-water carbonate platform by the Cenomanian. However, the succession in the west (Jebel Akhdar and interior) is dominated by shallow-water carbonate facies, but punctuated by a second regional drowning in the late Aptian. A third, Late Cretaceous drowning terminated deposition of the Wasia Group in the Turonian and was caused by convergence of oceanic crust and foreland basic formation. The record of tectonic behavior of carbonate platforms has important implications for the development of hydrocarbon source rocks and porosity. 68 refs., 11 figs., 1 tab.« less

  1. Flight aerodynamics in enantiornithines: Information from a new Chinese Early Cretaceous bird

    PubMed Central

    Liu, Di; Serrano, Francisco; Habib, Michael; Zhang, Yuguang; Meng, Qinjing

    2017-01-01

    We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yixian Formation of eastern Inner Mongolia, China. Although morphologically similar to Cathayornithidae and other small-sized enantiornithines from China’s Jehol Biota, many morphological features indicate that it represents a new species, here named Junornis houi. The new fossil displays most of its plumage including a pair of elongated, rachis-dominated tail feathers similarly present in a variety of other enantiornithines. BMNHC-PH-919 represents the first record of a Jehol enantiornithine from Inner Mongolia, thus extending the known distribution of these birds into the eastern portion of this region. Furthermore, its well-preserved skeleton and wing outline provide insight into the aerodynamic performance of enantiornithines, suggesting that these birds had evolved bounding flight—a flight mode common to passeriforms and other small living birds—as early as 125 million years ago. PMID:29020077

  2. Flight aerodynamics in enantiornithines: Information from a new Chinese Early Cretaceous bird.

    PubMed

    Liu, Di; Chiappe, Luis M; Serrano, Francisco; Habib, Michael; Zhang, Yuguang; Meng, Qinjing

    2017-01-01

    We describe an exquisitely preserved new avian fossil (BMNHC-PH-919) from the Lower Cretaceous Yixian Formation of eastern Inner Mongolia, China. Although morphologically similar to Cathayornithidae and other small-sized enantiornithines from China's Jehol Biota, many morphological features indicate that it represents a new species, here named Junornis houi. The new fossil displays most of its plumage including a pair of elongated, rachis-dominated tail feathers similarly present in a variety of other enantiornithines. BMNHC-PH-919 represents the first record of a Jehol enantiornithine from Inner Mongolia, thus extending the known distribution of these birds into the eastern portion of this region. Furthermore, its well-preserved skeleton and wing outline provide insight into the aerodynamic performance of enantiornithines, suggesting that these birds had evolved bounding flight-a flight mode common to passeriforms and other small living birds-as early as 125 million years ago.

  3. Late Cretaceous- Cenozoic history of deciduousness and the terminal Cretaceous event.

    USGS Publications Warehouse

    Wolfe, J.A.

    1987-01-01

    Deciduousness in mesic, broad-leaved plants occurred in disturbed, middle-latitude environments during the Late Cretaceous. Only in polar environments in the Late Cretaceous was the deciduous element dominant, although of low diversity. The terminal Cretaceous event resulted in wide-spread selection for plants of deciduous habit and diversification of deciduous taxa, thus leaving a lasting imprint on Northern Hemisphere vegetation. Various environmental factors have played important roles in subsequent diversification of mesic, broad-leaved deciduous taxa and in origination and decline of broad-leaved deciduous forests. Low diversity and rarity of mesic deciduous plants in the post-Cretaceous of the Southern Hemisphere indicate that the inferred 'impact winter' of the terminal Cretaceous event had little effect on Southern Hemisphere vegetation and climate. -Author

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  5. Elemental and Sr-Nd isotopic geochemistry of Cretaceous to Early Paleogene granites and volcanic rocks in the Sikhote-Alin Orogenic Belt (Russian Far East): implications for the regional tectonic evolution

    NASA Astrophysics Data System (ADS)

    Zhao, Pan; Jahn, Bor-ming; Xu, Bei

    2017-09-01

    The Sikhote-Alin Orogenic Belt in Russian Far East is an important Late Mesozoic to Early Cenozoic accretionary orogen related to the subduction of the Paleo-Pacific Plate. This belt was generated by successive accretion of terranes made of accretionary prisms, turbidite basins and island arcs to the continental margin of northeastern Asia (represented by the Bureya-Jiamusi-Khanka Block) from Jurassic to Late Cretaceous. In order to study the tectonic and crustal evolution of this orogenic belt, we carried out zircon U-Pb dating, and whole-rock elemental and Sr-Nd isotopic analyses on granites and volcanic rocks from the Primorye region of southern Sikhote-Alin. Zircon dating revealed three episodes of granitoid emplacement: Permian, Early Cretaceous and Late Cretaceous to Early Paleogene. Felsic volcanic rocks (mainly rhyolite, dacite and ignimbrite) that overlay all tectonostratigraphic terranes were erupted during 80-57 Ma, postdating the accretionary process in the Sikhote-Alin belt. The Cretaceous-Paleogene magmatism represents the most intense tectonothermal event in the Sikhote-Alin belt. Whole-rock major and trace elemental data show arc-like affinity for granitoids and volcanic rocks, indicating that they were likely generated in a supra-subduction setting. Their initial 87Sr/86Sr ratios range from 0.7048 to 0.7114, and εNd(t) values vary from +1.7 to -3.8 (mostly < 0). Thus, the elemental and Sr-Nd isotopic data suggest that the felsic magmas were generated by partial melting of source rocks comprising mantle-derived juvenile component and recycled crustal component. In addition to the occurrence in the Sikhote-Alin orogenic belt, Cretaceous to Early Paleogene magmatic rocks are also widespread in NE China, southern Korean peninsula, Japanese islands and other areas of Russian Far East, particularly along the coastal regions of the Okhotsk and Bering Seas. These rocks constitute an extended magmatic belt along the continental margin of NE Asia. The

  6. Evolution of volcanically-induced palaeoenvironmental changes leading to the onset of OAE1a (early Aptian, Cretaceous)

    NASA Astrophysics Data System (ADS)

    Keller, Christina E.; Hochuli, Peter A.; Giorgioni, Martino; Garcia, Therese I.; Bernasconi, Stefano M.; Weissert, Helmut

    2010-05-01

    During the Cretaceous, several major volcanic events occurred that initiated climate warming, altered marine circulation and increased marine productivity, which in turn often resulted in the widespread black shale deposits of the Oceanic Anoxic Events (OAE). In the sediments underlying the early Aptian OAE1a black shales, a prominent negative carbon isotope excursion is recorded. Its origin had long been controversial (e.g. Arthur, 2000; Jahren et al., 2001) before recent studies attributed it to the Ontong Java volcanism (Méhay et al., 2009; Tejada et al., 2009). Therefore the negative C-isotope excursion covers the interval between the time, when volcanic activity became important enough to be recorded in the C-isotope composition of the oceans to the onset of widespread anoxic conditions (OAE1a). We chose this interval at the locality of Pusiano (N-Italy) to study the effect of a volcanically-induced increase in pCO2 on the marine palaeoenvironment and to observe the evolving palaeoenvironmental conditions that finally led to OAE1a. The Pusiano section (Maiolica Formation) was deposited at the southern continental margin of the alpine Tethys Ocean and has been bio- and magnetostratigraphically dated by Channell et al. (1995). We selected 18 samples from 12 black shale horizons for palynofacies analyses. Palynofacies assemblages consist of several types of particulate organic matter, providing information on the origin of the organic matter (terrestrial/marine) and conditions during deposition (oxic/anoxic). We then linked the palynofacies results to high-resolution inorganic and organic C-isotope values and total organic carbon content measurements. The pelagic Pusiano section consists of repeated limestone-black shale couplets, which are interpreted to be the result of changes in oxygenation of bottom waters. Towards the end of the negative C-isotope excursion we observe enhanced preservation of the fragile amorphous organic matter resulting in increased

  7. New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia

    PubMed Central

    Hocknull, Scott A.; White, Matt A.; Tischler, Travis R.; Cook, Alex G.; Calleja, Naomi D.; Sloan, Trish; Elliott, David A.

    2009-01-01

    Background Australia's dinosaurian fossil record is exceptionally poor compared to that of other similar-sized continents. Most taxa are known from fragmentary isolated remains with uncertain taxonomic and phylogenetic placement. A better understanding of the Australian dinosaurian record is crucial to understanding the global palaeobiogeography of dinosaurian groups, including groups previously considered to have had Gondwanan origins, such as the titanosaurs and carcharodontosaurids. Methodology/Principal Findings We describe three new dinosaurs from the late Early Cretaceous (latest Albian) Winton Formation of eastern Australia, including; Wintonotitan wattsi gen. et sp. nov., a basal titanosauriform; Diamantinasaurus matildae gen. et sp. nov., a derived lithostrotian titanosaur; and Australovenator wintonensis gen. et sp. nov., an allosauroid. We compare an isolated astragalus from the Early Cretaceous of southern Australia; formerly identified as Allosaurus sp., and conclude that it most-likely represents Australovenator sp. Conclusion/Significance The occurrence of Australovenator from the Aptian to latest Albian confirms the presence in Australia of allosauroids basal to the Carcharodontosauridae. These new taxa, along with the fragmentary remains of other taxa, indicate a diverse Early Cretaceous sauropod and theropod fauna in Australia, including plesiomorphic forms (e.g. Wintonotitan and Australovenator) and more derived forms (e.g. Diamantinasaurus). PMID:19584929

  8. On the age of the Jurassic-Cretaceous boundary

    NASA Astrophysics Data System (ADS)

    Lena, Luis; Ramos, Victor; Pimentel, Marcio; Aguirre-Urreta, Beatriz; Naipauer, Maximiliano; Schaltegger, Urs

    2017-04-01

    Calibrating the geologic time is of utmost importance to understanding geological and biological processes throughout Earth history. The Jurassic-Cretaceous boundary has proven to be one of the most problematic boundaries to calibrate in the geologic time. The present definition of the Jurassic-Cretaceous boundary still remains contentious mainly because of the dominant endemic nature of the flora and fauna in stratigraphic sections, which hinders an agreement on a GSSP. Consequently, an absolute and precise age for the boundary is yet to meet an agreement among the community. Additionally, integrating chemical, paleomagnetic or astronomical proxies to aid the definition of the boundary has also proven to be difficult because the boundary lacks any abrupt geochemical changes or recognizable geological events. However, the traditional Berriasella jacobi Subzone is disregarded as a primary marker and the use of calpionellids has been gaining momentum for defining the boundary. The Jurassic Cretaceous boundary in the Vaca Muerta Fm. in the Nuequen Basin of the Andes is a potential candidate for the boundary stratotype because of its high density of ammonites, nannofossils and interbedded datable horizons. Consequently, the Jurassic-Cretaceous boundary is very well defined in the Vaca Muerta Fm. On the basis of both ammonites and nannofossils. Here we present new high-precision U-Pb age determinations from two volcanic ash beds that bracket the age of the Jurassic-Cretaceous boundary: 1) ash bed LLT_14_9, with a 206Pb/238U age of 139.7 Ma, which is 2 meters above Jurassic-Cretaceous boundary based on the Argetiniceras noduliferum (Early Berriasian ) and Substeueroceras Koeneni (Late Tithonian) ammonites zone; and 2) bed LLT_14_10, with an age of 140.1 Ma, located 3m below the J-K boundary based on last occurrence of the nannofossils N. kamptneri minor and N. steinmanni minor. Therefore, we propose that the age of the Jurassic-Cretaceous boundary should be close to 140

  9. Mycophagous rove beetles highlight diverse mushrooms in the Cretaceous

    PubMed Central

    Cai, Chenyang; Leschen, Richard A. B.; Hibbett, David S; Xia, Fangyuan; Huang, Diying

    2017-01-01

    Agaricomycetes, or mushrooms, are familiar, conspicuous and morphologically diverse Fungi. Most Agaricomycete fruiting bodies are ephemeral, and their fossil record is limited. Here we report diverse gilled mushrooms (Agaricales) and mycophagous rove beetles (Staphylinidae) from mid-Cretaceous Burmese amber, the latter belonging to Oxyporinae, modern members of which exhibit an obligate association with soft-textured mushrooms. The discovery of four mushroom forms, most with a complete intact cap containing distinct gills and a stalk, suggests evolutionary stasis of body form for ∼99 Myr and highlights the palaeodiversity of Agaricomycetes. The mouthparts of early oxyporines, including enlarged mandibles and greatly enlarged apical labial palpomeres with dense specialized sensory organs, match those of modern taxa and suggest that they had a mushroom feeding biology. Diverse and morphologically specialized oxyporines from the Early Cretaceous suggests the existence of diverse Agaricomycetes and a specialized trophic interaction and ecological community structure by this early date. PMID:28300055

  10. New Age of Fishes initiated by the Cretaceous-Paleogene mass extinction

    NASA Astrophysics Data System (ADS)

    Sibert, Elizabeth C.; Norris, Richard D.

    2015-07-01

    Ray-finned fishes (Actinopterygii) comprise nearly half of all modern vertebrate diversity, and are an ecologically and numerically dominant megafauna in most aquatic environments. Crown teleost fishes diversified relatively recently, during the Late Cretaceous and early Paleogene, although the exact timing and cause of their radiation and rise to ecological dominance is poorly constrained. Here we use microfossil teeth and shark dermal scales (ichthyoliths) preserved in deep-sea sediments to study the changes in the pelagic fish community in the latest Cretaceous and early Paleogene. We find that the Cretaceous-Paleogene (K/Pg) extinction event marked a profound change in the structure of ichthyolith communities around the globe: Whereas shark denticles outnumber ray-finned fish teeth in Cretaceous deep-sea sediments around the world, there is a dramatic increase in the proportion of ray-finned fish teeth to shark denticles in the Paleocene. There is also an increase in size and numerical abundance of ray-finned fish teeth at the boundary. These changes are sustained through at least the first 24 million years of the Cenozoic. This new fish community structure began at the K/Pg mass extinction, suggesting the extinction event played an important role in initiating the modern "age of fishes."

  11. New Age of Fishes initiated by the Cretaceous-Paleogene mass extinction.

    PubMed

    Sibert, Elizabeth C; Norris, Richard D

    2015-07-14

    Ray-finned fishes (Actinopterygii) comprise nearly half of all modern vertebrate diversity, and are an ecologically and numerically dominant megafauna in most aquatic environments. Crown teleost fishes diversified relatively recently, during the Late Cretaceous and early Paleogene, although the exact timing and cause of their radiation and rise to ecological dominance is poorly constrained. Here we use microfossil teeth and shark dermal scales (ichthyoliths) preserved in deep-sea sediments to study the changes in the pelagic fish community in the latest Cretaceous and early Paleogene. We find that the Cretaceous-Paleogene (K/Pg) extinction event marked a profound change in the structure of ichthyolith communities around the globe: Whereas shark denticles outnumber ray-finned fish teeth in Cretaceous deep-sea sediments around the world, there is a dramatic increase in the proportion of ray-finned fish teeth to shark denticles in the Paleocene. There is also an increase in size and numerical abundance of ray-finned fish teeth at the boundary. These changes are sustained through at least the first 24 million years of the Cenozoic. This new fish community structure began at the K/Pg mass extinction, suggesting the extinction event played an important role in initiating the modern "age of fishes."

  12. High resolution chronology of late Cretaceous-early Tertiary events determined from 21,000 yr orbital-climatic cycles in marine sediments

    NASA Technical Reports Server (NTRS)

    Herbert, Timothy D.; Dhondt, Steven

    1988-01-01

    A number of South Atlantic sites cored by the Deep Sea Drilling Project (DSDP) recovered late Cretaceous and early Tertiary sediments with alternating light-dark, high-low carbonate content. The sedimentary oscillations were turned into time series by digitizing color photographs of core segments at a resolution of about 5 points/cm. Spectral analysis of these records indicates prominent periodicity at 25 to 35 cm in the Cretaceous intervals, and about 15 cm in the early Tertiary sediments. The absolute period of the cycles that is determined from paleomagnetic calibration at two sites is 20,000 to 25,000 yr, and almost certainly corresponds to the period of the earth's precessional cycle. These sequences therefore contain an internal chronometer to measure events across the K/T extinction boundary at this scale of resolution. The orbital metronome was used to address several related questions: the position of the K/T boundary within magnetic chron 29R, the fluxes of biogenic and detrital material to the deep sea immediately before and after the K/T event, the duration of the Sr anomaly, and the level of background climatic variability in the latest Cretaceous time. The carbonate/color cycles that were analyzed contain primary records of ocean carbonate productivity and chemistry, as evidenced by bioturbational mixing of adjacent beds and the weak lithification of the rhythmic sequences. It was concluded that sedimentary sequences that contain orbital cyclicity are capable of providing resolution of dramatic events in earth history with much greater precision than obtainable through radiometric methods. The data show no evidence for a gradual climatic deterioration prior to the K/T extinction event, and argue for a geologically rapid revolution at this horizon.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  14. Evolution of Cupido and Coahuila carbonate platforms, early Cretaceous, northeastern Mexico

    USGS Publications Warehouse

    Lehmann, Christoph; Osleger, David A.; Montañez, Isabel P.; Sliter, William V.; Arnaud Vanneau, Annie; Banner, Jay L.

    1999-01-01

    middle Albian time. Restriction of the platform interior dissipated by middle to late Albian time with the deposition of peloidal, miliolid-rich packstones and grainstones of the Aurora Formation. The Coahuila platform was drowned during latest Albian to early Cenomanian time, and the deep-water laminites of the Cuesta del Cura Formation were deposited.This study fills in a substantial gap in the Cretaceous paleogeography of the eastern Gulf of Mexico coast, improving regional correlations with adjacent hydrocarbon-rich platforms. The enhanced temporal relations and chronology of events recorded in the Cupido and Coahuila platforms significantly improve global correlations with coeval, economically important platforms worldwide, perhaps contributing to the determination of global versus regional controls on carbonate platform evolution during middle Cretaceous time.

  15. Snakefly diversity in Early Cretaceous amber from Spain (Neuropterida, Raphidioptera)

    PubMed Central

    la Fuente, Ricardo Pérez-de; Peñalver, Enrique; Delclòs, Xavier; Engel, Michael S.

    2012-01-01

    Abstract The Albian amber from Spain presently harbors the greatest number and diversity of amber adult fossil snakeflies (Raphidioptera). Within Baissopteridae, Baissoptera? cretaceoelectra sp. n., from the Peñacerrada I outcrop (Moraza, Burgos), is the first amber inclusion belonging to the family and described from western Eurasia, thus substantially expanding the paleogeographical range of the family formerly known from the Cretaceous of Brazil and eastern Asia. Within the family Mesoraphidiidae, Necroraphidia arcuata gen. et sp. n. and Amarantoraphidia ventolina gen. et sp. n. are described from the El Soplao outcrop (Rábago, Cantabria), whereas Styporaphidia? hispanica sp. n. and Alavaraphidia imperterrita gen. et sp. n. are describedfrom Peñacerrada I. In addition, three morphospecies are recognized from fragmentary remains. The following combinations are restored: Yanoraphidia gaoi Ren, 1995, stat. rest., Mesoraphidia durlstonensis Jepson, Coram and Jarzembowski, 2009, stat. rest., and Mesoraphidia heteroneura Ren, 1997, stat. rest. The singularity of this rich paleodiversity could be due to the paleogeographic isolation of the Iberian territory and also the prevalence of wildfires during the Cretaceous. PMID:22787417

  16. Assessment of potential shale oil and tight sandstone gas resources of the Assam, Bombay, Cauvery, and Krishna-Godavari Provinces, India, 2013

    USGS Publications Warehouse

    Klett, Timothy R.; Schenk, Christopher J.; Wandrey, Craig J.; Brownfield, Michael E.; Charpentier, Ronald R.; Tennyson, Marilyn E.; Gautier, Donald L.

    2014-01-01

    Using a well performance-based geologic assessment methodology, the U.S. Geological Survey estimated a technically recoverable mean volume of 62 million barrels of oil in shale oil reservoirs, and more than 3,700 billion cubic feet of gas in tight sandstone gas reservoirs in the Bombay and Krishna-Godavari Provinces of India. The term “provinces” refer to geologically defined units assessed by the USGS for the purposes of this report and carries no political or diplomatic connotation. Shale oil and tight sandstone gas reservoirs were evaluated in the Assam and Cauvery Provinces, but these reservoirs were not quantitatively assessed.

  17. Reinterpreting the Early Cretaceous Sulfur Isotope Records: Implications for the Evolution of Seawater Chemistry

    NASA Astrophysics Data System (ADS)

    Mills, J. V.; Gomes, M. L.; Sageman, B. B.; Jacobson, A. D.; Hurtgen, M. T.

    2013-12-01

    The geologic record of the Cretaceous is punctuated by several periods of high organic carbon burial interpreted to represent global Ocean Anoxic Events (OAEs). In addition to the short-term (<1-Myr) changes in carbon (C) cycling associated with OAEs, evidence from a number of geochemical proxies has been interpreted to represent large-scale changes in ocean chemistry during the period. Specifically, the sulfur (S) isotope composition of early Cretaceous seawater sulfate as recorded in marine barite exhibits an ~5 permil shift in d34Ssulfate that persists for ~15Myr before returning to pre-excursion values. Superimposed upon this long-term shift in S-isotopes is OAE1a, the second major anoxic event recognized in the Cretaceous. Two hypotheses have been proposed to explain this S isotope perturbation: (1) massive evaporite deposition associated with rifting during the opening of the South Atlantic and a corresponding decrease in pyrite burial rates and (2) increased inputs of volcanic-derived S due to extensive LIP-volcanism. While there is geologic evidence for both evaporite deposition and enhanced hydrothermal activity, the relative influence of these potential driving factors remains largely unconstrained. Variation in the strontium (Sr) isotope composition of marine carbonates provides a tool for distinguishing between these influences. We examine the S isotope composition of carbonate-associated sulfate (CAS) spanning the Barremian through Aptian from Resolution Guyot (ODP Site 866) and compare the S isotope record to time equivalent records of carbon and strontium isotopes. Correlative changes in the C, S, and Sr cycles are observed: an ~5 permil shift in d34Ssulfate, which begins at the onset of OAE1a and continues after the positive d13Ccarb excursion, is accompanied by a contemporaneous, parallel shift in 87Sr/86Sr to unradiogenic values. The tight coupling observed between S and Sr throughout the interval is highly suggestive of a common driving mechanism

  18. Geochemical characteristics of Cretaceous carbonatites from Angola

    NASA Astrophysics Data System (ADS)

    Alberti, A.; Castorina, F.; Censi, P.; Comin-Chiaramonti, P.; Gomes, C. B.

    1999-12-01

    The Early Cretaceous (138-130 Ma) carbonatites and associated alkaline rocks of Angola belong to the Paraná-Angola-Etendeka Province and occur as ring complexes and other central-type intrusions along northeast trending tectonic lineaments, parallel to the trend of coeval Namibian alkaline complexes. Most of the Angolan carbonatite-alkaline bodies are located along the apical part of the Moçamedes Arch, a structure representing the African counterpart of the Ponta Grossa Arch in southern Brazil, where several alkaline-carbonatite complexes were also emplaced in the Early Cretaceous. Geochemical and isotopic (C, 0, Sr and Nd) characteristics determined for five carbonatitic occurrences indicate that: (1) the overall geochemical composition, including the OC isotopes, is within the range of the Early and Late Cretaceous Brazilian occurrences from the Paraná Basin; (2) the La versus {La}/{Yb} relationships are consistent with the exsolution of CO i2-rich melts from trachyphonolitic magmas; and (3) the {143Nd}/{144Nd} and {87Sr}/{86Sr} initial ratios are similar to the initial isotopic ratios (129 Ma) of alkaline complexes in northwest Namibia. In contrast, the Lupongola carbonatites have a distinctly different {143Nd}/{144Nd} initial ratio, suggesting a different source. The Angolan carbonatites have SrNd isotopic compositions ranging from bulk earth to time-integrated depleted sources. Since those from eastern Paraguay (at the western fringe of the Paraná-Angola-Etendeka Province) and Brazil appear to be related to mantle-derived melts with time-integrated enriched or B.E. isotopic characteristics, it is concluded that the carbonatites of the Paraná-Angola-Etendeka Province have compositionally distinct mantle sources. Such mantle heterogeneity is attributed to 'metasomatic processes', which would have occurred at ca 0.6-0.7 Ga (Angola, northwest Namibia and Brazil) and ca 1.8 Ga (eastern Paraguay), as suggested by Nd-model ages.

  19. Identification of a New Hesperornithiform from the Cretaceous Niobrara Chalk and Implications for Ecologic Diversity among Early Diving Birds

    PubMed Central

    Bell, Alyssa; Chiappe, Luis M.

    2015-01-01

    The Smoky Hill Member of the Niobrara Chalk in Kansas (USA) has yielded the remains of numerous members of the Hesperornithiformes, toothed diving birds from the late Early to Late Cretaceous. This study presents a new taxon of hesperornithiform from the Smoky Hill Member, Fumicollis hoffmani, the holotype of which is among the more complete hesperornithiform skeletons. Fumicollis has a unique combination of primitive (e.g. proximal and distal ends of femur not expanded, elongate pre-acetabular ilium, small and pyramidal patella) and derived (e.g. dorsal ridge on metatarsal IV, plantarly-projected curve in the distal shaft of phalanx III:1) hesperornithiform characters, suggesting it was more specialized than small hesperornithiforms like Baptornis advenus but not as highly derived as the larger Hesperornis regalis. The identification of Fumicollis highlights once again the significant diversity of hesperornithiforms that existed in the Late Cretaceous Western Interior Seaway. This diversity points to the existence of a complex ecosystem, perhaps with a high degree of niche partitioning, as indicated by the varying degrees of diving specializations among these birds. PMID:26580402

  20. Identification of a New Hesperornithiform from the Cretaceous Niobrara Chalk and Implications for Ecologic Diversity among Early Diving Birds.

    PubMed

    Bell, Alyssa; Chiappe, Luis M

    2015-01-01

    The Smoky Hill Member of the Niobrara Chalk in Kansas (USA) has yielded the remains of numerous members of the Hesperornithiformes, toothed diving birds from the late Early to Late Cretaceous. This study presents a new taxon of hesperornithiform from the Smoky Hill Member, Fumicollis hoffmani, the holotype of which is among the more complete hesperornithiform skeletons. Fumicollis has a unique combination of primitive (e.g. proximal and distal ends of femur not expanded, elongate pre-acetabular ilium, small and pyramidal patella) and derived (e.g. dorsal ridge on metatarsal IV, plantarly-projected curve in the distal shaft of phalanx III:1) hesperornithiform characters, suggesting it was more specialized than small hesperornithiforms like Baptornis advenus but not as highly derived as the larger Hesperornis regalis. The identification of Fumicollis highlights once again the significant diversity of hesperornithiforms that existed in the Late Cretaceous Western Interior Seaway. This diversity points to the existence of a complex ecosystem, perhaps with a high degree of niche partitioning, as indicated by the varying degrees of diving specializations among these birds.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  2. Palaeogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: palaeotopographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chaboureau, A. C.; Guillocheau, F.; Robin, C.; Rohais, S.; Moulin, M.; Aslanian, D.

    2012-04-01

    The tectonic and sedimentary evolution of the Early Cretaceous rift of the central segment of the South Atlantic Ocean is debated. Our objective is to better constraint the timing of its evolution by drawing palaeogeographic and deformation maps. Eight palaeogeographic and deformations maps were drawn from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollens) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains that have a different history in terms of deformation and palaeogeography. The southern domain includes Namibe, Santos and Campos Basins. The northern domain extends from Espirito Santo and North Kwanza Basins, in the South, to Sergipe-Alagoas and North Gabon Basins to the North. Extension started in the northern domain during Late Berriasian (Congo-Camamu Basin to Sergipe-Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain. This is time of emplacement of the Parana-Etendeka Trapp (Late Hauterivian-Early Barremian). Extension started in this southern domain during Early Barremian. The brittle extensional period is shorter in the South (5-6 Ma, Barremian to base Aptian) than in the North (19 to 20 Myr, Upper Berriasian to Base Aptian). From Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower one, organic-rich with no more highs. The lake migrates southward in two steps, until Valanginian at the border between the northern and southern domains, until Early Barremian, North of Walvis Ridge. The Sag phase is of Middle to Late Aptian age. In the southern domain, the transition between the brittle rift and the sag phase is continuous. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age, possible period of mantle exhumation. Marine

  3. Late Cretaceous origin of the rice tribe provides evidence for early diversification in Poaceae.

    PubMed

    Prasad, V; Strömberg, C A E; Leaché, A D; Samant, B; Patnaik, R; Tang, L; Mohabey, D M; Ge, S; Sahni, A

    2011-09-20

    Rice and its relatives are a focal point in agricultural and evolutionary science, but a paucity of fossils has obscured their deep-time history. Previously described cuticles with silica bodies (phytoliths) from the Late Cretaceous period (67-65 Ma) of India indicate that, by the latest Cretaceous, the grass family (Poaceae) consisted of members of the modern subclades PACMAD (Panicoideae-Aristidoideae-Chloridoideae-Micrairoideae-Arundinoideae-Danthonioideae) and BEP (Bambusoideae-Ehrhartoideae-Pooideae), including a taxon with proposed affinities to Ehrhartoideae. Here we describe additional fossils and show that, based on phylogenetic analyses that combine molecular genetic data and epidermal and phytolith features across Poaceae, these can be assigned to the rice tribe, Oryzeae, of grass subfamily Ehrhartoideae. The new Oryzeae fossils suggest substantial diversification within Ehrhartoideae by the Late Cretaceous, pushing back the time of origin of Poaceae as a whole. These results, therefore, necessitate a re-evaluation of current models for grass evolution and palaeobiogeography.

  4. Hydrocarbons related to early Cretaceous source rocks, reservoirs and seals, trapped in northeastern Neuqun basin, Argentina

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gulisano, C.; Minniti, S.; Rossi, G.

    1996-08-01

    The Jurassic-Cretaceous backarc Neuqun Basin, located in the west central part of Argentina, is currently the most prolific oil basin of the country. The primary objective of this study is to evaluate an Early Cretaceous to Tertiary petroleum system in the northeastern portion of the basin, where oil and gas occurrences (e.g., Puesto Hernandez, Chihuido de la Sierra Negra, El Trapial and Filo Morado oil fields, among others) provide 82 MMBO/yr comprising 67% of the basin oil production and 31% of Argentina. The source rocks are represented by two thick sections of basinal kerogen type I and II organic-rich shales,more » deposited during transgressive peaks (Agrio Formation), with TOC content up to 5.1%. Lowstand sandstones bodies, 10 to 100 m thick, are composed of eolian and fluvial facies with good reservoir conditions (Avil and Troncoso Sandstones). The seals are provided by the organic-rich shales resting sharply upon the Avil Sandstone and a widespread Aptian-Albian evaporitic event (Huitrin Formation) on top of the Troncoso reservoir. Tertiary structural traps (duplex anticlines) are developed in the outer foothills, whereas structural, combined and stratigraphic traps are present in the adjacent stable structural platform. Oil-to-source rock and oil-to-oil correlation by chromatographic and biomarker fingerprints, carbon isotopic composition and the geological evidences support the proposed oil system.« less

  5. A long-lived Late Cretaceous-early Eocene extensional province in Anatolia? Structural evidence from the Ivriz Detachment, southern central Turkey

    NASA Astrophysics Data System (ADS)

    Gürer, Derya; Plunder, Alexis; Kirst, Frederik; Corfu, Fernando; Schmid, Stefan M.; van Hinsbergen, Douwe J. J.

    2018-01-01

    Central Anatolia exposes previously buried and metamorphosed, continent-derived rocks - the Kırşehir and Afyon zones - now covering an area of ∼300 × 400 km. So far, the exhumation history of these rocks has been poorly constrained. We show for the first time that the major, >120 km long, top-NE 'Ivriz' Detachment controlled the exhumation of the HP/LT metamorphic Afyon Zone in southern Central Anatolia. We date its activity at between the latest Cretaceous and early Eocene times. Combined with previously documented isolated extensional detachments found in the Kırşehir Block, our results suggest that a major province governed by extensional exhumation was active throughout Central Anatolia between ∼80 and ∼48 Ma. Although similar in dimension to the Aegean extensional province to the east, the Central Anatolian extensional province is considerably older and was controlled by a different extension direction. From this, we infer that the African slab(s) that subducted below Anatolia must have rolled back relative to the Aegean slab since at least the latest Cretaceous, suggesting that these regions were underlain by a segmented slab. Whether or not these early segments already corresponded to the modern Aegean, Antalya, and Cyprus slab segments remains open for debate, but slab segmentation must have occurred much earlier than previously thought.

  6. Palaeomagnetism of lower cretaceous tuffs from Yukon-Kuskokwim delta region, western Alaska

    USGS Publications Warehouse

    Globerman, B.R.; Coe, R.S.; Hoare, J.M.; Decker, J.

    1983-01-01

    During the past decade, the prescient arguments1-3 for the allochthoneity of large portions of southern Alaska have been corroborated by detailed geological and palaeomagnetic studies in south-central Alaska 4-9 the Alaska Peninsula10, Kodiak Island11,12 and the Prince William Sound area13 (Fig. 1). These investigations have demonstrated sizeable northward displacements for rocks of late Palaeozoic, Mesozoic, and early Tertiary age in those regions, with northward motion at times culminating in collision of the allochthonous terranes against the backstop of 'nuclear' Alaska14,15. A fundamental question is which parts of Alaska underwent significantly less latitudinal translation relative to the 'stable' North American continent, thereby serving as the 'accretionary nucleus' into which the displaced 'microplates'16 were eventually incorporated17,18? Here we present new palaeomagnetic results from tuffs and associated volcaniclastic rocks of early Cretaceous age from the Yukon-Kuskokwin delta region in western Alaska. These rocks were probably overprinted during the Cretaceous long normal polarity interval, although a remagnetization event as recent as Palaeocene cannot be ruled out. This overprint direction is not appreciably discordant from the expected late Cretaceous direction for cratonal North America. The implied absence of appreciable northward displacement for this region is consistent with the general late Mesozoic-early Tertiary tectonic pattern for Alaska, based on more definitive studies: little to no poleward displacement for central Alaska, though substantially more northward drift for the 'southern Alaska terranes' (comprising Alaska Peninsula, Kodiak Island, Prince William Sound area, and Matunuska Valley) since late Cretaceous to Palaeocene time. ?? 1983 Nature Publishing Group.

  7. The late Cretaceous Arman flora of Magadan oblast, Northeastern Russia

    NASA Astrophysics Data System (ADS)

    Herman, A. B.; Golovneva, L. B.; Shczepetov, S. V.; Grabovsky, A. A.

    2016-12-01

    The Arman flora from the volcanogenic-sedimentary beds of the Arman Formation is systematically studied using materials from the Arman River basin and the Nelkandya-Khasyn interfluve (Magadan oblast, Northeastern Russia). Seventy-three species of fossil plants belonging to 49 genera are described. They consist of liverworts, horsetails, ferns, seed ferns, cycadaleans, bennettitaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms of uncertain systematic affinity, and angiosperms. The Arman flora shows a unique combination, with relatively ancient Early Cretaceous ferns and gymnosperms occurring alongside younger Late Cretaceous plants, primarily angiosperms. The similarity of the Arman flora to the Penzhina and Kaivayam floras of northwestern Kamchatka and the Tylpegyrgynai flora of the Pekul'nei Ridge allows the Arman flora to be dated as Turonian and Coniacian (Late Cretaceous), which is corroborated by isotopic (U-Pb and 40Ar/39Ar) age determination for the plant-bearing layers.

  8. Cosmic Genes in the Cretaceous-Tertiary transition

    NASA Astrophysics Data System (ADS)

    Wallis, M. K.

    2003-07-01

    It is proposed that genes coding for Aib-polypeptides arose early on in the K/T transition, presumed from the Earth's accretion of interplanetary (comet) dust. Aib-fungi flourished because of the evolutionary advantage of novel antibiotics. The stress on Cretaceous biology led directly and indirectly to mass species extinctions, including many dinosaur species, in the epoch preceding the Chicxulub impact.

  9. Early dolomitization in the Lower Cretaceous shallow-water carbonates of Southern Apennines (Italy): Clues about palaeoclimatic fluctuations in western Tethys

    NASA Astrophysics Data System (ADS)

    Vinci, Francesco; Iannace, Alessandro; Parente, Mariano; Pirmez, Carlos; Torrieri, Stefano; Giorgioni, Maurizio

    2017-12-01

    A multidisciplinary study of the dolomitized bodies present in the Lower Cretaceous platform carbonates of Mt. Faito (Southern Apennines - Italy) was carried out in order to explore the connection between early dolomite formation and fluctuating climate conditions. The Berriasian-Aptian investigated succession is 466 m thick and mainly consists of shallow-water lagoonal limestones with frequent dolomite caps. The dolomitization intensity varies along the succession and reaches its peak in the upper Hauterivian-lower Barremian interval, where it is present a completely dolomitized interval about 100-m-thick. Field relations, petrography, mineralogy, and geochemistry of the analyzed dolomite bodies allowed identifying two populations of early dolomites, a fine-medium crystalline (FMdol) and a coarse crystalline dolomite (Cdol), both interpreted as the product of mesohaline water reflux. According to our interpretation, FMdol precipitated from concentrated brines in the very early stage of the reflux process, producing typical sedimentary features as dolomite caps. In the successive step of the process, the basin-ward 'latent' reflux precipitated Cdol from less concentrated brines. A peculiar feature of the studied succession is the great consistency between stratigraphic distribution of dolomite bodies and their geochemical signature. The completely dolomitized Hauterivian-Barremian interval, in fact, is characterized by geochemical values suggesting an origin from distinctly saltier brines. Considering that the observed near-surface dolomitization process is controlled by physical and chemical parameters reflecting the paleoenvironmental and paleoclimatic conditions during dolomite formation, we propose that the stratigraphically controlled dolomitization intensity reflects periodic fluctuations in the salinity of dolomitizing fluid, in turn controlled by long-term climate oscillations. The present work highlights that the stratigraphic distribution of early

  10. Early Cretaceous to Paleocene North American Drainage Reorganization and Sediment Routing from Detrital Zircons: Significance to the Alberta Oil Sands and Gulf of Mexico Petroleum Provinces

    NASA Astrophysics Data System (ADS)

    Blum, M. D.

    2014-12-01

    Detrital zircons (DZs) represent a powerful tool for reconstructing continental paleodrainage. This paper uses new DZ data from Lower Cretaceous strata of the Alberta foreland basin, and Upper Cretaceous and Cenozoic strata of the Gulf of Mexico passive margin, to reconstruct paleodrainage and sediment routing, and illustrate significance to giant hydrocarbon systems. DZ populations from the Lower Cretaceous Mannville Group of Alberta and Saskatchewan infer a continental-scale river system that routed sediment from the eastern 2/3rds of North America to the Boreal Sea. Aptian McMurray Formation fluvial sands were derived from a drainage sourced in the Appalachians that was similar in scale to the modern Amazon. Albian fluvial sandstones of the Clearwater and Grand Rapids Formations were derived from the same Appalachian-sourced drainage area, which had expanded to include tributaries from the Cordilleran arc of the northwest US and southwest Canada. DZ populations from the Gulf of Mexico coastal plain complement this view, showing that only the southern US and Appalachian-Ouachita cordillera was integrated with the Gulf through the Late Cretaceous. However, by the Paleocene, drainage from the US Western Cordillera to the Appalachians had been routed to the Gulf of Mexico, establishing the template for sediment routing that persists today. The paleodrainage reorganization and changes in sediment routing described above played key roles in establishment of the Alberta oil sands and Gulf of Mexico as giant petroleum provinces. Early Cretaceous routing of a continental-scale fluvial system to the Alberta foreland provided large and contiguous fluvial point-bar sand bodies that became economically viable reservoirs, whereas mid- to late Cretaceous drainage reorganization routed greatly increased sediment loads to the Gulf of Mexico, which loaded the shelf, matured source rocks, and drove the gravitational and salt tectonics that helped establish the working hydrocarbon

  11. Environmental drivers of crocodyliform extinction across the Jurassic/Cretaceous transition

    PubMed Central

    Mannion, Philip D.; Upchurch, Paul

    2016-01-01

    Crocodyliforms have a much richer evolutionary history than represented by their extant descendants, including several independent marine and terrestrial radiations during the Mesozoic. However, heterogeneous sampling of their fossil record has obscured their macroevolutionary dynamics, and obfuscated attempts to reconcile external drivers of these patterns. Here, we present a comprehensive analysis of crocodyliform biodiversity through the Jurassic/Cretaceous (J/K) transition using subsampling and phylogenetic approaches and apply maximum-likelihood methods to fit models of extrinsic variables to assess what mediated these patterns. A combination of fluctuations in sea-level and episodic perturbations to the carbon and sulfur cycles was primarily responsible for both a marine and non-marine crocodyliform biodiversity decline through the J/K boundary, primarily documented in Europe. This was tracked by high extinction rates at the boundary and suppressed origination rates throughout the Early Cretaceous. The diversification of Eusuchia and Notosuchia likely emanated from the easing of ecological pressure resulting from the biodiversity decline, which also culminated in the extinction of the marine thalattosuchians in the late Early Cretaceous. Through application of rigorous techniques for estimating biodiversity, our results demonstrate that it is possible to tease apart the complex array of controls on diversification patterns in major archosaur clades. PMID:26962137

  12. Water Resource Planning Under Future Climate and Socioeconomic Uncertainty in the Cauvery River Basin in Karnataka, India

    PubMed Central

    Conway, Declan; Dessai, Suraje; Stainforth, David A.

    2018-01-01

    Abstract Decision‐Making Under Uncertainty (DMUU) approaches have been less utilized in developing countries than developed countries for water resources contexts. High climate vulnerability and rapid socioeconomic change often characterize developing country contexts, making DMUU approaches relevant. We develop an iterative multi‐method DMUU approach, including scenario generation, coproduction with stakeholders and water resources modeling. We apply this approach to explore the robustness of adaptation options and pathways against future climate and socioeconomic uncertainties in the Cauvery River Basin in Karnataka, India. A water resources model is calibrated and validated satisfactorily using observed streamflow. Plausible future changes in Indian Summer Monsoon (ISM) precipitation and water demand are used to drive simulations of water resources from 2021 to 2055. Two stakeholder‐identified decision‐critical metrics are examined: a basin‐wide metric comprising legal instream flow requirements for the downstream state of Tamil Nadu, and a local metric comprising water supply reliability to Bangalore city. In model simulations, the ability to satisfy these performance metrics without adaptation is reduced under almost all scenarios. Implementing adaptation options can partially offset the negative impacts of change. Sequencing of options according to stakeholder priorities into Adaptation Pathways affects metric satisfaction. Early focus on agricultural demand management improves the robustness of pathways but trade‐offs emerge between intrabasin and basin‐wide water availability. We demonstrate that the fine balance between water availability and demand is vulnerable to future changes and uncertainty. Despite current and long‐term planning challenges, stakeholders in developing countries may engage meaningfully in coproduction approaches for adaptation decision‐making under deep uncertainty. PMID:29706676

  13. Water Resource Planning Under Future Climate and Socioeconomic Uncertainty in the Cauvery River Basin in Karnataka, India.

    PubMed

    Bhave, Ajay Gajanan; Conway, Declan; Dessai, Suraje; Stainforth, David A

    2018-02-01

    Decision-Making Under Uncertainty (DMUU) approaches have been less utilized in developing countries than developed countries for water resources contexts. High climate vulnerability and rapid socioeconomic change often characterize developing country contexts, making DMUU approaches relevant. We develop an iterative multi-method DMUU approach, including scenario generation, coproduction with stakeholders and water resources modeling. We apply this approach to explore the robustness of adaptation options and pathways against future climate and socioeconomic uncertainties in the Cauvery River Basin in Karnataka, India. A water resources model is calibrated and validated satisfactorily using observed streamflow. Plausible future changes in Indian Summer Monsoon (ISM) precipitation and water demand are used to drive simulations of water resources from 2021 to 2055. Two stakeholder-identified decision-critical metrics are examined: a basin-wide metric comprising legal instream flow requirements for the downstream state of Tamil Nadu, and a local metric comprising water supply reliability to Bangalore city. In model simulations, the ability to satisfy these performance metrics without adaptation is reduced under almost all scenarios. Implementing adaptation options can partially offset the negative impacts of change. Sequencing of options according to stakeholder priorities into Adaptation Pathways affects metric satisfaction. Early focus on agricultural demand management improves the robustness of pathways but trade-offs emerge between intrabasin and basin-wide water availability. We demonstrate that the fine balance between water availability and demand is vulnerable to future changes and uncertainty. Despite current and long-term planning challenges, stakeholders in developing countries may engage meaningfully in coproduction approaches for adaptation decision-making under deep uncertainty.

  14. Water Resource Planning Under Future Climate and Socioeconomic Uncertainty in the Cauvery River Basin in Karnataka, India

    NASA Astrophysics Data System (ADS)

    Bhave, Ajay Gajanan; Conway, Declan; Dessai, Suraje; Stainforth, David A.

    2018-02-01

    Decision-Making Under Uncertainty (DMUU) approaches have been less utilized in developing countries than developed countries for water resources contexts. High climate vulnerability and rapid socioeconomic change often characterize developing country contexts, making DMUU approaches relevant. We develop an iterative multi-method DMUU approach, including scenario generation, coproduction with stakeholders and water resources modeling. We apply this approach to explore the robustness of adaptation options and pathways against future climate and socioeconomic uncertainties in the Cauvery River Basin in Karnataka, India. A water resources model is calibrated and validated satisfactorily using observed streamflow. Plausible future changes in Indian Summer Monsoon (ISM) precipitation and water demand are used to drive simulations of water resources from 2021 to 2055. Two stakeholder-identified decision-critical metrics are examined: a basin-wide metric comprising legal instream flow requirements for the downstream state of Tamil Nadu, and a local metric comprising water supply reliability to Bangalore city. In model simulations, the ability to satisfy these performance metrics without adaptation is reduced under almost all scenarios. Implementing adaptation options can partially offset the negative impacts of change. Sequencing of options according to stakeholder priorities into Adaptation Pathways affects metric satisfaction. Early focus on agricultural demand management improves the robustness of pathways but trade-offs emerge between intrabasin and basin-wide water availability. We demonstrate that the fine balance between water availability and demand is vulnerable to future changes and uncertainty. Despite current and long-term planning challenges, stakeholders in developing countries may engage meaningfully in coproduction approaches for adaptation decision-making under deep uncertainty.

  15. A new lineage of Cretaceous jewel wasps (Chalcidoidea: Diversinitidae).

    PubMed

    Haas, Michael; Burks, Roger A; Krogmann, Lars

    2018-01-01

    Jewel wasps (Hymenoptera: Chalcidoidea) are extremely species-rich today, but have a sparse fossil record from the Cretaceous, the period of their early diversification. Three genera and three species, Diversinitus attenboroughi gen. & sp. n. , Burminata caputaeria gen. & sp. n. and Glabiala barbata gen. & sp. n. are described in the family Diversinitidae fam. n., from Lower Cretaceous Burmese amber. Placement in Chalcidoidea is supported by the presence of multiporous plate sensilla on the antennal flagellum and a laterally exposed prepectus. The new taxa can be excluded from all extant family level chalcidoid lineages by the presence of multiporous plate sensilla on the first flagellomere in both sexes and lack of any synapomorphies. Accordingly, a new family is proposed for the fossils and its probable phylogenetic position within Chalcidoidea is discussed. Morphological cladistic analyses of the new fossils within the Heraty et al. (2013) dataset did not resolve the phylogenetic placement of Diversinitidae, but indicated its monophyly. Phylogenetically relevant morphological characters of the new fossils are discussed with reference to Cretaceous and extant chalcidoid taxa. Along with mymarid fossils and a few species of uncertain phylogenetic placement, the newly described members of Diversinitidae are among the earliest known chalcidoids and advance our knowledge of their Cretaceous diversity.

  16. Macrofossil extinction patterns at Bay of Biscay Cretaceous-Tertiary boundary sections

    NASA Technical Reports Server (NTRS)

    Ward, Peter D.; Macleod, Kenneth

    1988-01-01

    Researchers examined several K-T boundary cores at Deep Sea Drilling Project (DSDP) core repositories to document biostratigraphic ranges of inoceramid shell fragments and prisms. As in land-based sections, prisms in the deep sea cores disappear well before the K-T boundary. Ammonites show a very different extinction pattern than do the inoceramids. A minimum of seven ammonite species have been collected from the last meter of Cretaceous strata in the Bay of Biscay basin. In three of the sections there is no marked drop in either species numbers or abundance prior to the K-T boundary Cretaceous strata; at the Zumaya section, however, both species richness and abundance drop in the last 20 m of the Cretaceous, with only a single ammonite specimen recovered to date from the uppermost 12 m of Cretaceous strata in this section. Researchers conclude that inoceramid bivalves and ammonites showed two different times and patterns of extinction, at least in the Bay of Biscay region. The inoceramids disappeared gradually during the Early Maestrichtian, and survived only into the earliest Late Maestrichtian. Ammonites, on the other hand, maintained relatively high species richness throughout the Maestrichtian, and then disappeared suddenly, either coincident with, or immediately before the microfossil extinction event marking the very end of the Cretaceous.

  17. Petrogenesis and tectonic implications of Early Cretaceous volcanic rocks from Lingshan Island in the Sulu Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Meng, Yuanku; Santosh, M.; Li, Rihui; Xu, Yang; Hou, Fanghui

    2018-07-01

    The Dabie-Sulu orogenic belt in eastern China marks the boundary between the Yangtze Block and the North China Block. Here we investigate a suite of volcanic rocks from Lingshan Island in the Sulu belt comprising rhyolite, trachyte, trachyandesite and basaltic trachyandesite. We present petrological, geochemical and zircon Usbnd Pb ages and Hfsbnd O isotope data with a view to gain insights on the petrogenesis and tectonic implications. SHRIMP II analyses of zircon grains from the rhyolite yield 206Pb/238U age of 127.6 ± 1.3 Ma and LA-MC-ICP-MS dating show 126.3 ± 1.2 Ma and 127.3 ± 1.1 Ma, together constraining the eruption time as Early Cretaceous. LA-MC-ICP-MS analyses of zircon grains from the andesitic rocks yield 206Pb/238U ages of 129.0 ± 1.6 Ma, 129.8 ± 1.5 Ma and 130.9 ± 1.0 Ma. Geochemically, the rhyolite shows shoshonitic features with low MgO and Cr, but high Na2O + K2O. The zircon grains from these rocks yield negative εHf(t) values and low δ18O values, and these together with the presence of Neoproterozoic inherited zircons suggest that the magma source involved melting of the Yangtze crust. The andesitic rocks, including basaltic trachyandesite, trachyandesite and trachyte, show a wide range of SiO2, Mg# values, and Cr, enriched in LILE and LREE, depleted in HFSE (Nb, Ta and Ti), and have significantly negative zircon εHf(t) values, suggesting derivation from subcontinental lithosphere mantle that was metasomatized by felsic melts. Our results, integrated with those from previous studies suggest heterogeneous magma involving the mixing of mantle and crustal sources within an extensional setting in the Early Cretaceous.

  18. New fossil ants in French Cretaceous amber (Hymenoptera: Formicidae)

    NASA Astrophysics Data System (ADS)

    Perrichot, Vincent; Nel, André; Néraudeau, Didier; Lacau, Sébastien; Guyot, Thierry

    2008-02-01

    Recent studies on the ant phylogeny are mainly based on the molecular analyses of extant subfamilies and do not include the extinct, only Cretaceous subfamily Sphecomyrminae. However, the latter is of major importance for ant relationships, as it is considered the most basal subfamily. Therefore, each new discovery of a Mesozoic ant is of high interest for improving our understanding of their early history and basal relationships. In this paper, a new sphecomyrmine ant, allied to the Burmese amber genus Haidomyrmex, is described from mid-Cretaceous amber of France as Haidomyrmodes mammuthus gen. and sp. n. The diagnosis of the tribe Haidomyrmecini is emended based on the new type material, which includes a gyne (alate female) and two incomplete workers. The genus Sphecomyrmodes, hitherto known by a single species from Burmese amber, is also reported and a new species described as S. occidentalis sp. n. after two workers remarkably preserved in a single piece of Early Cenomanian French amber. The new fossils provide additional information on early ant diversity and relationships and demonstrate that the monophyly of the Sphecomyrminae, as currently defined, is still weakly supported.

  19. Global research on the Cretaceous

    NASA Astrophysics Data System (ADS)

    Ginsburg, Robert N.

    Cretaceous Resources, Events and Rhythms, a new international research effort on the global aspects of Cretaceous sedimentary geology, is underway. This Global Sedimentary Geology Project (GSGP) is organized by the Commission on Global Sedimentary Geology of the International Union of Geological Sciences (IUGS). The GSGP secretariat is at the University of Miami, Florida (Fisher Island, Miami Beach, FL 33139, tel. 305-672-1840, RNGINSBURG/KOSMOS).Cretaceous time was selected for this pilot research project because Cretaceous sea levels and climates can provide a vision of Earth in its “greenhouse state,” because there is an established geochronology for the era's wide-spread deposits, and because there are extensive resources of hydrocarbons, coal, bauxite and other minerals in Cretaceous rocks.

  20. Significance of the giant Lower Cretaceous paleoweathering event

    NASA Astrophysics Data System (ADS)

    Thiry, Médard; Ricordel-Prognon, Caroline; Schmitt, Jean-Michel

    2010-05-01

    Weathering profiles typically develop at the interface with the atmosphere, and thus, record the fluctuations in the paleoatmosphere's chemistry and climatic conditions. Consequently they are one of the main archives to upgrade our understanding on paleoclimate and the Earth's environmental history. In this presentation, we will focus on the linking between paleoatmosphere compositions, weathering rates, and their impact on the subsequent sedimentary records. Distribution of the Lower Cretaceous lateritic weathering facies. During the Early Cretaceous, sea level drops and wide exondations lead to development of deep "lateritic" weathering profiles. Thick kaolinitic weathering profiles occured on the Hercynian basements and diverse kaolinitic and ferruginous weathering products covered the Jurassic limestone platforms. This major lateritic event is not restricted to Europe but also well know in North-America (up to Canada), South-America (down to Argentina), and in Australia. Moreover, recent paleomagnetic and radiometric datations revealed that numerous kaolinitic and ferruginous formations, which classically were ascribed to Tertiary ages, date back to the Lower Cretaceous period (Thiry et al., 2006). Additionally, the Bonherz iron ore deposits in the paleokarsts of the Jurassic limestone plateform of the Paris Basin also have to be reconsidered as of Cretaceous age, probably as well as the Tertiary age of the Swiss and Bavarian Jura Bonherz. Paleoclimatic interpretation. During a long time, the interpretation of these paleoweathering features has been a major palaeoclimatic argument. The spreading out of deep kaolinitic weathering profiles (from the Scandinavian and Canadian shields to southern Argentina and Australia, which was still situated close to Antarctica at that time) has lead to considerations, that during this period a warm and wet climate prevailed globally, with very little latitudinal differentiation. These paleoclimatic interpretations stand in

  1. Evidence of cretaceous to recent West African intertropical vegetation from continental sediment spore-pollen analysis

    NASA Astrophysics Data System (ADS)

    Salard-Cheboldaeff, M.; Dejax, J.

    The succession of spore-pollen assemblages during the Cretaceous and Tertiary, as defined in each of the basin from Senegal to Angola, gives the possibility to consider the intertropical African flora evolution for the past 120 M.a. During the Early Cretaceous, xeric-adapted gymnosperms and various ferns were predominant the flora which nevertheless comprises previously unknown early angiosperm pollen. During the Middle Cretaceous, gymnospers were gradually replaced by angiosperms; these became more and more abundant, along with the diversification of new genera and species. During the Paleocene, the radiation of the monocotyledons (mainly that of the palm-trees) as well as a greater diversification among the dicotyledons and ferms are noteworthy. Since gymnosperms had almost disappeared by the Eocene, the diversification of the dicotyledons went on until the neogene, when all extinct pollen types are already present. These important modifications of the vegetation reflect evolutionary trends as well as climatic changes during the Cretaceous: the climate, firstly hot, dry and perhaps arid, did probably induced salt deposition, and later became gradually more humid under oceanic influences which arose in connection with the Gondwana break-up.

  2. Europatitan eastwoodi, a new sauropod from the lower Cretaceous of Iberia in the initial radiation of somphospondylans in Laurasia

    PubMed Central

    2017-01-01

    The sauropod of El Oterillo II is a specimen that was excavated from the Castrillo de la Reina Formation (Burgos, Spain), late Barremian–early Aptian, in the 2000s but initially remained undescribed. A tooth and elements of the axial skeleton, and the scapular and pelvic girdle, represent it. It is one of the most complete titanosauriform sauropods from the Early Cretaceous of Europe and presents an opportunity to deepen our understanding of the radiation of this clade in the Early Cretaceous and study the paleobiogeographical relationships of Iberia with Gondwana and with other parts of Laurasia. The late Barremian–early Aptian is the time interval in the Cretaceous with the greatest diversity of sauropod taxa described in Iberia: two titanosauriforms, Tastavinsaurus and Europatitan; and a rebbachisaurid, Demandasaurus. The new sauropod Europatitan eastwoodi n. gen. n. sp. presents a series of autapomorphic characters in the presacral vertebrae and scapula that distinguish it from the other sauropods of the Early Cretaceous of Iberia. Our phylogenetic study locates Europatitan as the basalmost member of the Somphospondyli, clearly differentiated from other clades such as Brachiosauridae and Titanosauria, and distantly related to the contemporaneous Tastavinsaurus. Europatitan could be a representative of a Eurogondwanan fauna like Demandasaurus, the other sauropod described from the Castrillo de la Reina Formation. The presence of a sauropod fauna with marked Gondwananan affinities in the Aptian of Iberia reinforces the idea of faunal exchanges between this continental masses during the Early Cretaceous. Further specimens and more detailed analysis are needed to elucidate if this Aptian fauna is caused by the presence of previously unnoticed Aptian land bridges, or it represents a relict fauna from an earlier dispersal event. PMID:28674644

  3. Leaf Assemblages across the Cretaceous-Tertiary Boundary in the Raton Basin, New Mexico and Colorado

    NASA Astrophysics Data System (ADS)

    Wolfe, Jack A.; Upchurch, Garland R., Jr.

    1987-08-01

    Analyses of leaf megafossil and dispersed leaf cuticle assemblages indicate that major ecologic disruption and high rates of extinction occurred in plant communities at the Cretaceous-Tertiary boundary in the Raton Basin. In diversity increase, the early Paleocene vegetational sequence mimics normal short-term ecologic succession, but on a far longer time scale. No difference can be detected between latest Cretaceous and early Paleocene temperatures, but precipitation markedly increased at the boundary. Higher survival rate of deciduous versus evergreen taxa supports occurrence of a brief cold interval (<1 year), as predicted in models of an “impact winter.”

  4. Isotopic composition of low-latitude paleoprecipitation during the Early Cretaceous

    USGS Publications Warehouse

    Suarez, M.B.; Gonzalez, Luis A.; Ludvigson, Greg A.; Vega, F.J.; Alvarado-Ortega, J.

    2009-01-01

    The response of the hydrologic cycle in global greenhouse conditions is important to our understanding of future climate change and to the calibration of global climate models. Past greenhouse conditions, such as those of the Cretaceous, can be used to provide empirical data with which to evaluate climate models. Recent empirical studies have utilized pedogenic carbonates to estimate the isotopic composition of meteoric waters and calculate precipitation rates for the AptianAlbian. These studies were limited to data from mid(35??N) to high (75??N) paleolatitudes, and thus future improvements in accuracy will require more estimates of meteoric water compositions from numerous localities around the globe. This study provides data for tropical latitudes (18.5??N paleolatitude) from the Tlayua Formation, Puebla, Mexico. In addition, the study confirms a shallow nearshore depositional environment for the Tlayua Formation. Petrographic observations of fenestral fabrics, gypsum crystal molds, stromatolitic structures, and pedogenic matrix birefringence fabric support the interpretation that the strata represent deposition in a tidal flat environment. Carbonate isotopic data from limestones of the Tlayua Formation provide evidence of early meteoric diagenesis in the form of meteoric calcite lines. These trends in ??18O versus ??13C were used to calculate the mean ??18O value of meteoric water, which is estimated at -5.46 ?? 0.56??? (Vienna Standard Mean Ocean Water [VSMOW]). Positive linear covariant trends in oxygen and carbon isotopic values from some horizons were used to estimate evaporative losses of vadose groundwater from tropical exposure surfaces during the Albian, and the resulting values range from 8% to 12%. However, the presence of evaporative mineral molds indicates more extensive evaporation. The added tropical data improve latitudinal coverage of paleoprecipitation ??18O estimates. The data presented here imply that earlier isotope mass balance models most

  5. 118-115 Ma magmatism in the Tethyan Himalaya igneous province: Constraints on Early Cretaceous rifting of the northern margin of Greater India

    NASA Astrophysics Data System (ADS)

    Chen, Sheng-Sheng; Fan, Wei-Ming; Shi, Ren-Deng; Liu, Xiao-Han; Zhou, Xue-Jun

    2018-06-01

    Understanding the dynamics of Large Igneous Provinces (LIPs) is critical to deciphering processes associated with rupturing continental lithosphere. Microcontinental calving, the rifting of microcontinents from mature continental rifted margins, is particularly poorly understood. Here we present new insights into these processes from geochronological and geochemical analyses of igneous rocks from the Tethyan Himalaya. Early Cretaceous mafic dikes are widely exposed in the eastern and western Tethyan Himalaya, but no such rocks have been reported from the central Tethyan Himalaya. Here we present an analysis of petrological, geochronological, geochemical, and Sr-Nd-Hf-Os isotopic data for bimodal magmatic rocks from the center-east Tethyan Himalaya. Zircon U-Pb dating yields six weighted-mean concordant 206Pb/238U ages of 118 ± 1.2 to 115 ± 1.3 Ma. Mafic rocks display MORB-like compositions with flat to depleted LREE trends, and positive εNd(t) (+2.76 to +5.39) and εHf(t) (+8.0 to +11.9) values. The negative Nb anomalies and relatively high 187Os/188Os ratios (0.15-0.19) of these rocks are related to variable degrees (up to 10%) of crustal contamination. Geochemical characteristics indicate that mafic rocks were generated by variable degrees (2-20%) of partial melting of spinel lherzolites in shallow depleted mantle. Felsic rocks are enriched in Th and LREE, with negative Nb anomalies and decoupling of Nd (εNd(t) = -13.39 to -12.78) and Hf (εHf(t) = -4.8 to -2.0), suggesting that they were derived mainly from garnet-bearing lower continental crust. The geochemical characteristics of the bimodal magmatic associations are comparable to those of associations that form in a continental rift setting. Results indicate that Early Cretaceous magmatism occurred across the whole Tethyan Himalaya, named here as the "Tethyan Himalaya igneous province". Separation of the Tethyan Himalaya from the Indian craton may have occurred during ongoing Early Cretaceous extension

  6. The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia

    PubMed Central

    Salisbury, Steven W; Molnar, Ralph E; Frey, Eberhard; Willis, Paul M.A

    2006-01-01

    While the crocodyliform lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms—members of Eusuchia—do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98–95 Myr ago; Albian–Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms—a shift that may be linked to the subsequent rapid diversification of Eusuchia 20 Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana. PMID:16959633

  7. Altered carbon cycling and coupled changes in Early Cretaceous weathering patterns: Evidence from integrated carbon isotope and sandstone records of the western Tethys

    NASA Astrophysics Data System (ADS)

    Wortmann, Ulrich Georg; Herrle, Jens Olaf; Weissert, Helmut

    2004-03-01

    In this study we investigate if a major perturbation of the Early Cretaceous carbon cycle was accompanied by altered weathering and erosion rates. The large Aptian carbon isotope anomaly records the response of the biosphere to widespread volcanic activity and probably resulting changes in atmospheric pCO2 levels. Elevated pCO2 levels should also result in an accelerated hydrological cycle and increased silicate weathering, creating a negative feedback loop removing CO2 from the atmosphere. We propose to interpret the widespread occurrence of quartz sandstones in the Tethys-Atlantic seaway as a result of altered weathering and erosion rates in the wake of the Aptian carbon cycle excursion. We challenge the traditional notion that these are 'flysch' deposits associated with Early Cretaceous orogenic movements in the western Tethys. We propose that these sandstones were most likely part of a large conveyor belt system, acting along the Iberian and European margin of the Tethys seaway. Using chemostratigraphic correlations, we show that the activity of this system was only short-lived and coeval with changes in coastal ecology and the Aptian carbon cycle perturbations. We tentatively relate the existence of this system to a transient climate regime, characterized by fluctuating pCO2 levels.

  8. Assessing the duration of drowning episodes during the Early Cretaceous

    NASA Astrophysics Data System (ADS)

    Godet, A.; Föllmi, K. B.

    2013-12-01

    Drowning unconformities are stratigraphic key surfaces in the history of carbonate platforms. They mostly consist in the deposition of deep marine facies on top of shallow marine limestones. Although large-scale depositional geometries mimic lowstand systems track architecture, these sedimentary turnovers are developed in relation with major sea level rise, inducing an increase in the rate of creation of accommodation space that outpaces the capacity of carbonate to keep up. This so-called paradox of carbonate platform drowning implies that other parameters than purely eustatic fluctuations are involved in the demise of shallow marine ecosystems. Worldwide and at different time during Earth history, in-depth studies of drowning unconformities revealed that changes in nutrient input, clastic delivery, temperature, or a combination of them may be responsible for a decrease in light penetration in the water column and the progressive suffocation and poisoning of photosynthetic carbonate producers. The examination of such case examples from various stratigraphic intervals and palaeogeographical settings thus helps in identifying and hierarchizing potential triggering mechanisms for drowning unconformities. This is complemented by new data from Early Cretaceous successions from the Helvetic Alps. During this time period, the Helvetic carbonate platform developed along the northern Tethyan margin using both photozoan and heterozoan communities. Phases of healthy production were interrupted by several drowning episodes. The latter are marked in the sedimentary record by condensation and associated phosphogenesis and glauconitisation. From the earliest Valanginian to the early to late Barremian, three drowning unconformities reflect the intermittent installation of a more humid climate and subsequent enhanced trophic conditions, which first induced a switch from photozoan to heterozoan communities and then to long-lasting drowning phases. The latter encompass several sea

  9. Geomagnetic Reversals of the Late Jurassic and Early Cretaceous Captured in a North China Core

    NASA Astrophysics Data System (ADS)

    Kuhn, T.; Fu, R. R.; Kent, D. V.; Olsen, P. E.

    2016-12-01

    The Tuchengzi formation in North China nominally spans nearly 20 million years of the Late Jurassic and Early Cretaceous, an interval during which age calibration of the Geomagnetic Polarity Time Scale (GPTS) based on seafloor magnetic anomalies is poorly known. The overlying Yixian formation is of special paleontological interest due to an abundance of spectacularly preserved macrofossils of feathered non-avian dinosaurs, birds, mammals, and insects. Scarce fossils in the Tuchengzi, sparse accurate radiometric dates on both the Tuchengzi and overlying Yixian formation, and scant previous paleomagnetic studies on these formations motivated our application of magnetostratigraphy as a geochronological tool. We constructed a geomagnetic reversal sequence from the upper 142m of a 200m core extracted in Liaoning Province at Huangbanjigou spanning the lower Yixian Formation and the unconformably underlying Tuchengzi Formation. Thermal demagnetization up to 680°C in steps of 25-50°C revealed predominantly normal overprints consistent with the modern day field with unblocking temperatures between 125°C and as high as 550°C, as well as normal and reverse characteristic components with unblocking temperatures between 500°C and 680°C. Going up from the base of the core, there is a reverse polarity magnetozone >6m thick, followed by a 5m normal magnetozone, a 10m reverse magnetozone, a 25m normal magnetozone, and a 6m reverse magnetozone truncated by the Yixian-Tuchengzi unconformity. Above the unconformity, all 81m of core were normal. These results indicate that a meaningful polarity stratigraphy can be recovered from the Tuchengzi and Yixian formations that will be invaluable for correlations across the Tuchengzi and potentially the Yixian formations, which span thousands of square kilometers and vary in thickness by many hundreds of meters. The results also demonstrate that, in combination with accurate and precise radiometric dates, the Tuchengzi Formation has the

  10. Chitinase genes (CHIAs) provide genomic footprints of a post-Cretaceous dietary radiation in placental mammals

    PubMed Central

    Emerling, Christopher A.

    2018-01-01

    The end-Cretaceous extinction led to a massive faunal turnover, with placental mammals radiating in the wake of nonavian dinosaurs. Fossils indicate that Cretaceous stem placentals were generally insectivorous, whereas their earliest Cenozoic descendants occupied a variety of dietary niches. It is hypothesized that this dietary radiation resulted from the opening of niche space, following the extinction of dinosaurian carnivores and herbivores. We provide the first genomic evidence for the occurrence and timing of this dietary radiation in placental mammals. By comparing the genomes of 107 placental mammals, we robustly infer that chitinase genes (CHIAs), encoding enzymes capable of digesting insect exoskeletal chitin, were present as five functional copies in the ancestor of all placental mammals, and the number of functional CHIAs in the genomes of extant species positively correlates with the percentage of invertebrates in their diets. The diverse repertoire of CHIAs in early placental mammals corroborates fossil evidence of insectivory in Cretaceous eutherians, with descendant lineages repeatedly losing CHIAs beginning at the Cretaceous/Paleogene (K/Pg) boundary as they radiated into noninsectivorous niches. Furthermore, the timing of gene loss suggests that interordinal diversification of placental mammals in the Cretaceous predates the dietary radiation in the early Cenozoic, helping to reconcile a long-standing debate between molecular timetrees and the fossil record. Our results demonstrate that placental mammal genomes, including humans, retain a molecular record of the post-K/Pg placental adaptive radiation in the form of numerous chitinase pseudogenes. PMID:29774238

  11. Paleobotany of Livingston Island: The first report of a Cretaceous fossil flora from Hannah Point

    USGS Publications Warehouse

    Leppe, M.; Michea, W.; Muñoz, C.; Palma-Heldt, S.; Fernandoy, F.

    2007-01-01

    This is the first report of a fossil flora from Hannah Point, Livingston Island, South Shetland Islands, Antarctica. The fossiliferous content of an outcrop, located between two igneous rock units of Cretaceous age are mainly composed of leaf imprints and some fossil trunks. The leaf assemblage consists of 18 taxa of Pteridophyta, Pinophyta and one angiosperm. The plant assemblage can be compared to other Early Cretaceous floras from the South Shetland Islands, but several taxa have an evidently Late Cretaceous affinity. A Coniacian-Santonian age is the most probable age for the outcrops, supported by previous K/Ar isotopic studies of the basalts over and underlying the fossiliferous sequence

  12. Facies architecture and paleohydrology of a synrift succession in the Early Cretaceous Choyr Basin, southeastern Mongolia

    USGS Publications Warehouse

    Ito, M.; Matsukawa, M.; Saito, T.; Nichols, D.J.

    2006-01-01

    The Choyr Basin is one of several Early Cretaceous rift basins in southwestern Mongolia that developed in specific regions between north-south trending fold-and-thrust belts. The eastern margin of the basin is defined by high-angle normal and/or strike-slip faults that trend north-to-south and northeast-to-southwest and by the overall geometry of the basin, which is interpreted to be a half graben. The sedimentary succession of the Choyr Basin documents one of the various types of tectono-sedimentary processes that were active in the rift basins of East Asia during Early Cretaceous time. The sedimentary infill of the Choyr Basin is newly defined as the Khalzan Uul and Khuren Dukh formations based on detailed mapping of lateral and vertical variations in component lithofacies assemblages. These two formations are heterotopic deposits and constitute a third-order fluvio-lacustrine sequence that can be divided into transgressive and highstand systems tracts. The lower part of the transgressive systems tract (TST) is characterized by sandy alluvial-fan and braided-river systems on the hanging wall along the western basin margin, and by a gravelly alluvial-fan system on the footwall along the eastern basin margin. The alluvial-fan and braided-river deposits along the western basin margin are fossiliferous and are interpreted to have developed in association with a perennial fluvial system. In contrast, alluvial-fan deposits along the eastern basin margin do not contain any distinct faunas or floras and are interpreted to have been influenced by a high-discharge ephemeral fluvial system associated with fluctuations in wetting and drying paleohydrologic processes. The lower part of the TST deposit fines upward to siltstone-dominated flood-plain and ephemeral-lake deposits that constitute the upper part of the TST and the lower part of the highstand systems tract (HST). These mudstone deposits eventually reduced the topographic irregularities typical of the early stage of

  13. Revised nomenclature, definitions, and correlations for the Cretaceous formations in USGS-Clubhouse Crossroads #1, Dorchester County, South Carolina

    USGS Publications Warehouse

    Gohn, Gregory S.

    1992-01-01

    and definitions of the Cape Fear, Middendorf, Black Creek, and Peedee Formations originally used for the core by Gohn and others and Hazel and others are substantially changed herein. In addition, the Black Creek Formation of the core is raised in rank to become the Black Creek Group, which consists of two newly defined formations (Cane Acre and Coachman) and two newly recognized formations previously described in outcrop (Bladen and Donoho Creek). Four subsurface formations that are not known in outcrop are newly defined in the core (Beech Hill, Clubhouse, Shepherd Grove, and Caddin). The revised stratigraphy of the Cretaceous section in the Clubhouse Crossroads #1 core, from base to top, is as follows: Beech Hill Formation (Cenomanian?), Clubhouse Formation (late Cenomanian? and Turonian), Cape Fear Formation (late Turonian? to early Santonian), Middendorf Formation (middle Santonian), Shepherd Grove Formation (late Santonian and early Campanian), Caddin Formation (early Campanian), Cane Acre Formation (middle Campanian, Black Creek Group), Coachman Formation (middle to late Campanian, Black Creek Group), Bladen Formation (late Campanian, Black Creek Group), Donoho Creek Formation (early Maastrichtian, Black Creek Group), and Peedee Formation (late early Maastrichtian to middle or late Maastrichtian).

  14. Petrogenesis of the late Early Cretaceous granodiorite - Quartz diorite from eastern Guangdong, SE China: Implications for tectono-magmatic evolution and porphyry Cu-Au-Mo mineralization

    NASA Astrophysics Data System (ADS)

    Jia, Lihui; Mao, Jingwen; Liu, Peng; Li, Yang

    2018-04-01

    Comprehensive petrological, zircon U-Pb dating, Hf-O isotopes, whole rock geochemistry and Sr-Nd isotopes data are presented for the Xinwei and Sanrao intrusions in the eastern Guangdong Province, Southeast (SE) China, with an aim to constrain the petrogenesis, tectono-magmatic evolution and evaluate the implication for porphyry Cu-Au-Mo mineralization. The Xinwei intrusion is composed of granodiorite and quartz diorite, whilst the Sanrao intrusion consists of granodiorite. Zircon U-Pb ages show that both intrusions were emplaced at ca. 106-102 Ma. All rocks are metaluminous to weakly peraluminous, high-K calc-alkaline in composition, and they are characterized by LREEs enrichment, depletion in Nb, Ta, P, and Ti, and strongly fractionated LREEs to HREEs. The initial 87Sr/86Sr ratios range from 0.7055 to 0.7059, and εNd(t) values range from -3.9 to -3.0. Together with the relatively high εHf(t) values (-3.2 to 3.3) and low δ18O values (4.9‰ to 6.6‰), these data suggest that the Xinwei and Sanrao intrusions were derived from a mixed source: including the mantle-derived mafic magmas and lower continental crustal magmas. Fractional crystallization played an important role in the magmatic evolution of the Xinwei and Sanrao intrusions. The elemental and isotopic compositions of the Xinwei and Sanrao intrusions, as well as the high water content and oxidation state of their parental magmas, are similar to those of the ore-bearing granodiorites of the Luoboling porphyry Cu-Mo deposit in the Fujian Province, neighbouring east to the Guangdong Province, indicating that the late Early Cretaceous granodioritic intrusions in the eastern Guangdong Province may also have Cu-Au-Mo mineralization potential. The late Early Cretaceous magmatic event is firstly reported in eastern Guangdong, and represents a positive response of large-scale lithosphere extension and thinning, triggered by the changing subduction direction of the Paleo-Pacific plate from oblique subduction to

  15. Neodymium isotope evolution of NW Tethyan upper ocean waters throughout the Cretaceous

    NASA Astrophysics Data System (ADS)

    Pucéat, Emmanuelle; Lécuyer, Christophe; Reisberg, Laurie

    2005-08-01

    Neodymium isotope compositions of twenty-four fish teeth, nineteen from the NW Tethys and five from different locations within the Tethys, are interpreted to reflect the evolution of Tethyan upper ocean water composition during the Cretaceous and used to track changes in erosional inputs to the NW Tethys and in oceanic circulation throughout the Cretaceous. The rather high ɛNd (up to - 7.6) of the NW Tethyan upper ocean waters recorded from the Late Berriasian to the Early Aptian and the absence of negative excursions during this interval support the presence of a permanent westward flowing Tethys Circumglobal Current (TCC). This implies that temperature variations during this time period, inferred from the oxygen isotope analysis of fish tooth enamel, were not driven by changes in surface oceanic currents, but rather by global climatic changes. The results presented here represent a significant advance over previously published Cretaceous seawater Nd isotope records. Our newly acquired data now allow the identification of two stages of low ɛNd values in the NW Tethys, during the Early Albian-Middle Albian interval (down to - 10) and the Santonian-Early Campanian (down to - 11.4), which alternate with two stages of higher ɛNd values (up to - 9) during the Late Albian-Turonian interval and the Maastrichtian. Used in conjunction with the oxygen isotope record, the fluctuations of ɛNd values can be related to major climatic, oceanographic, and tectonic events that appeared in the western Tethyan domain.

  16. Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: remagnetization, compaction, or terrane translation?

    NASA Astrophysics Data System (ADS)

    Smith, Douglas P.; Busby, Cathy J.

    1993-10-01

    Paleomagnetic data from Albian to Turonian sedimentary rocks on Cedros Island, Mexico (28.2° N, 115.2° W) support the interpretation that Cretaceous rocks of western Baja California have moved farther northward than the 3° of latitude assignable to Neogene oblique rifting in the Gulf of California. Averaged Cretaceous paleomagnetic results from Cedros Island support 20 ± 10° of northward displacement and 14 ± 7° of clockwise rotation with respect to cratonic North America. Positive field stability tests from the Vizcaino terrane substantiate a mid-Cretaceous age for the high-temperature characteristic remanent magnetization in mid-Cretaceous strata. Therefore coincidence of characteristic magnetization directions and the expected Quaternary axial dipole direction is not due to post mid-Cretaceous remagnetization. A slump test performed on internally coherent, intrabasinal slump blocks within a paleontologically dated olistostrome demonstrates a mid-Cretaceous age of magnetization in the Valle Group. The in situ high-temperature natural remanent magnetization directions markedly diverge from the expected Quaternary axial dipole, indicating that the characteristic, high-temperature magnetization was acquired prior to intrabasinal slumping. Early acquisition of the characteristic magnetization is also supported by a regional attitude test involving three localities in coherent mid-Cretaceous Valle Group strata. Paleomagnetic inclinations in mudstone are not different from those in sandstone, indicating that burial compaction did not bias the results toward shallow inclinations in the Vizcaino terrane.

  17. Evidence of reworked Cretaceous fossils and their bearing on the existence of Tertiary dinosaurs

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Eaton, J.G.; Kirkland, J.I.; Doi, K.

    The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Cannonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as there is a mixture of marine and freshwater taxa. These taxa have not been recorded elsewhere after the Cretaceous and are not known from the Cannonball Formation. Early Eocene localities at Raven Ridge, Utah, similarly contain teeth of Cretaceous marine and freshwater fish, dinosaurs, and Eocene mammals. The Cretaceous teeth are wellmore » preserved, variably abraded, and serve to cast doubts on criteria recently used to claim that dinosaur teeth recovered from the Paleocene of Montana are not reworked. Another Eocene locality in the San Juan Basin has produced an Eocene mammalian fauna with diverse Cretaceous marine sharks. Neither the nature of preservation nor the degree of abrasion could be used to distinguish reworked from contemporaneous material. The mixed environments represented by the fish taxa and recognition of the extensive pre-Tertiary extinction of both marine and freshwater fish were employed to recognize reworked specimens.« less

  18. Post Cretaceous cooling trend documented in the gastropods (Turritella Sp.) from the Cenozoic startigraphic successions of India

    NASA Astrophysics Data System (ADS)

    Banerjee, Y.; Ghosh, P.; Halder, K.; Malarkodi, N.; Pathak, P.

    2017-12-01

    The aftermath of the Himalyan orogeny and subsequent cooling is documented in the deep sea sedimentary record from the Oceanic realm (1). Here we attempt to reconstruct the temperature pattern based on marine gastropods i.e. Turritella sp. which became abundant during the post Cretaceous period and have successfully been used for the reconstruction of climate by measuring the stable isotopic composition (2,3,4). Well preserved specimens of Cretaceous Turritella from the Rajamundry Infratrappean beds and those from the Miocene, Holocene succession of Kutch, western India were analysed along with specimen from the modern time scale (also from Kutch). The Cretaceous, early to mid Miocene, early Holocene and modern shells recorded δ13C variability from 0.36 to 4.94‰, -1.83 to -4.83‰, -3.26 to 0.40‰, -1.47 to -4.70‰ respectively suggesting drop in the productivity during mid Miocene and subsequent period of rapid growth. The Variability in terms of δ18O ranges from -2.28 to -4.99‰, -2.66 to -7.06‰, -2.86 to 0.96‰, -1.05 to -3.23‰ for the Cretaceous, early to mid Miocene, early Holocene and modern shells respectively. Corbula sp. collected from the same strata with that of the early to mid Holocene Turritella showed a similar δ13C and δ18O values denoting similar environmental condition during deposition. Absence of any significant correlation between δ13C vs δ18O support equilibrium precipitation of shell growth bands. We used Epstein oxygen isotope thermometry to derive temperature from the oxygen isotope of carbonate and adopted water isotopic composition (1‰ for the Cretaceous and -0.7‰ for the Miocene) from the literature. Our observation captured an overall cooling trend from the Cretaceous to the Holocene time period (especially in between mid Miocene to Holocene) and a subsequent warming trend in modern time. Validation with other thermometry method will be displayed at the time of presentation. References: [1] Zachos et al., 2001

  19. Geoligical outline of the Lower Cretaceous Bahia Supergroup, Brazil

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fonseca, J.I.

    1966-01-01

    The report area encompasses about 41,200 sq km covered by over 6,000 m of Lower Cretaceous sediments deposited in fresh to brackish water environment. These sediments, the Bahia Supergroup, represent most of the sedimentary section of the Almada, Reconcavo, Tucano and Jatoba basins. The Reconcavo basin is a half-graben filled with Lower Cretaceous rocks which tilt regionally to the SE. The sediments deposited in this basin were distorted by 2 major periods of deformation. As the result of the application of these systems of tensional forces, the sediments were broken into a complicated system of normal faults. Most of themore » oil production in Brazil, about 91,000 bpd, comes from the Reconcavo basin. During a great part of the Early Cretaceous the Reconcavo and Almada basins probably were connected with the Alagoas-Sergipe basin by the continental shelf. The continental drift theory may explain the presence of these fresh water sediments in the coast line and in the continental shelf of the Bahia and Alagoas-Sergipe states. This offshore area is very prospective and may contribute, in the future, with substantial quantities of hydrocarbons. (14 refs.)« less

  20. Biotic association and palaeoenvironmental reconstruction of the "Loma del Pterodaustro" fossil site (Early Cretaceous, Argentina)

    USGS Publications Warehouse

    Chiappe, L.; Rivarola, D.; Cione, A.; Fregenal-Martinez, M.; Sozzi, H.; Buatois, L.; Gallego, O.; Laza, J.; Romero, E.; Lopez-Arbarello, A.; Buscalioni, A.; Marsicano, C.; Adamonis, S.; Ortega, F.; McGehee, S.; Di, Iorio O.

    1998-01-01

    A sedimentological analysis of the basal section of the Early Cretaceous, lacustrine Lagarcito Formation at "Loma del Pterodaustro" (San Luis, Argentina) and a summary of its biological components are presented. Three sedimentological facies can be recognized in the basal sequence of the Lagarcito Formation. Fossil remains are particularly abundant in laminated claystones of a facies interpreted as deposits formed in offshore areas of the lake. The preservation of delicate structures allows recognition of these deposits as a Konservat Lagersta??tte. Up to now, rocks at "Loma del Pterodaustro" have yielded plants, conchostracans, semionotid and pleuropholid fishes, pterodactyloid pterosaurs, and a variety of invertebrate traces. The chronology of the Lagarcito Formation is discussed and it is concluded that this unit is of Albian age. The palaeoenvironment of deposition of the basal sequence of the Lagarcito Formation at "Loma del Pterodaustro" is interpreted as a perennial, shallow lake developed within an alluvial plain, under semiarid climatic conditions.

  1. The Sredne-Amursky basin: A migrating cretaceous depocenter for the Amur river, eastern Siberia

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Light, M.; Maslanyj, M.; Davidson, K.

    1993-09-01

    Recently acquired seismic, well, and regional geological data imply favorable conditions for the accumulation of oil and gas in the 20,000 km[sup 2] Sredne-Amursky basin. Major graben and northeast-trending sinistral wrench-fault systems are recognized in the basin. Lower and Upper Cretaceous sediments are up to 9000 and 3000 m thick, respectively. Paleogeographic reconstructions imply that during the Late Triassic-Early Cretaceous the Sredne-Amursky basin was part of a narrow marine embayment (back-arc basin), which was open to the north. During the Cretaceous, the region was part of a foreland basin complicated by strike-slip, which produced subsidence related to transtension during obliquemore » collision of the Sikhote-Alin arc with Eurasian margin. Contemporaneous uplift also related to this collision migrated from south to north and may have sourced northward-directed deltas and alluvial fans, which fed northward into the closing back-arc basin between 130 and 85 Ma. The progradational clastic succession of the Berriasian-Albian and the Late Cretaceous fluvial, brackish water and paralic sediments within the basin may be analogous to the highly productive late Tertiary clastics of the Amur River delta in the northeast Sakhalin basin. Cretaceous-Tertiary lacustrine-deltaic sapropelic shales provide significant source and seal potential and potential reservoirs occur in the Cretaceous and Tertiary. Structural plays were developed during Cretaceous rifting and subsequent strike-slip deformation. If the full hydrocarbon potential of the Sredne-Amursky basin is to be realized, the regional appraisal suggests that exploration should be focused toward the identification of plays related to prograding Cretaceous deltaic depositional systems.« less

  2. Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction.

    PubMed

    Field, Daniel J; Bercovici, Antoine; Berv, Jacob S; Dunn, Regan; Fastovsky, David E; Lyson, Tyler R; Vajda, Vivi; Gauthier, Jacques A

    2018-06-04

    The fossil record and recent molecular phylogenies support an extraordinary early-Cenozoic radiation of crown birds (Neornithes) after the Cretaceous-Paleogene (K-Pg) mass extinction [1-3]. However, questions remain regarding the mechanisms underlying the survival of the deepest lineages within crown birds across the K-Pg boundary, particularly since this global catastrophe eliminated even the closest stem-group relatives of Neornithes [4]. Here, ancestral state reconstructions of neornithine ecology reveal a strong bias toward taxa exhibiting predominantly non-arboreal lifestyles across the K-Pg, with multiple convergent transitions toward predominantly arboreal ecologies later in the Paleocene and Eocene. By contrast, ecomorphological inferences indicate predominantly arboreal lifestyles among enantiornithines, the most diverse and widespread Mesozoic avialans [5-7]. Global paleobotanical and palynological data show that the K-Pg Chicxulub impact triggered widespread destruction of forests [8, 9]. We suggest that ecological filtering due to the temporary loss of significant plant cover across the K-Pg boundary selected against any flying dinosaurs (Avialae [10]) committed to arboreal ecologies, resulting in a predominantly non-arboreal post-extinction neornithine avifauna composed of total-clade Palaeognathae, Galloanserae, and terrestrial total-clade Neoaves that rapidly diversified into the broad range of avian ecologies familiar today. The explanation proposed here provides a unifying hypothesis for the K-Pg-associated mass extinction of arboreal stem birds, as well as for the post-K-Pg radiation of arboreal crown birds. It also provides a baseline hypothesis to be further refined pending the discovery of additional neornithine fossils from the Latest Cretaceous and earliest Paleogene. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Giant Upper Cretaceous oysters from the Gulf coast and Caribbean

    USGS Publications Warehouse

    Sohl, Norman F.; Kauffman, Erle G.

    1964-01-01

    Two unusually massive ostreid species, representing the largest and youngest Mesozoic members of their respective lineages, occur in Upper Cretaceous sediment of the gulf coast and Caribbean areas. Their characteristics and significance, as well as the morphologic terminology of ostreids in general, are discussed. Crassostrea cusseta Sohl and Kauffman n. sp. is the largest known ostreid from Mesozoic rocks of North America; it occurs sporadically in the Cusseta Sand and rarely in the Blufftown Formation of the Chattahoochee River region in Georgia and Alabama. It is especially notable in that it lacks a detectable posterior adductor muscle scar on large adult shells. C. cusseta is the terminal Cretaceous member of the C. soleniscus lineage in gulf coast sediments; the lineage continues, however, with little basic modification, throughout the Cenozoic, being represented in the Eocene by C. gigantissima (Finch) and probably, in modern times, by C. virginica (Gmelin). The C. soleniscus lineage is the first typically modern crassostreid group recognized in the Mesozoic. Arctostrea aguilerae (Böse) occurs in Late Campanian and Early Maestrichtian sediments of Alabama, Mississippi, Texas(?), Mexico, and Cuba. The mature shell of this species is larger and more massive than that of any other known arctostreid. Arctostrea is well represented throughout the Upper Jurassic and Cretaceous of Europe, but in North America, despite the great numbers and diversity of Cretaceous oysters, only A. aguilerae and the Albian form A. carinata are known. The presence of A. aquilerae in both the Caribbean and gulf coast faunas is exceptional, as the Late Cretaceous faunas of these provinces are generally distinct and originated in different faunal realms.

  4. A new dinosaur ichnotaxon from the Lower Cretaceous Patuxent Formation of Maryland and Virginia

    USGS Publications Warehouse

    Stanford, Ray; Weems, Robert E.; Lockley, Martin G.

    2004-01-01

    In recent years, numerous dinosaur footprints have been discovered on bedding surfaces within the Lower Cretaceous Patuxent Formation of Maryland and Virginia. Among these, distinctive small tracks that display a combination of small manus with five digit impressions and a relatively much larger pes with four toe impressions evidently were made by animals belonging to the ornithischian family Hypsilophodontidae. These tracks differ from any ornithischian ichnotaxon previously described. We here name them Hypsiloichnus marylandicus and provide a description of their diagnostic characteristics. Although hypsilophodontid skeletal remains have not been found in the Patuxent, their skeletal remains are known from Lower Cretaceous strata of similar age in both western North America and Europe. Therefore, it is not surprising to find that an Early Cretaceous representative of this family also existed in eastern North America.

  5. Extreme Morphogenesis and Ecological Specialization among Cretaceous Basal Ants.

    PubMed

    Perrichot, Vincent; Wang, Bo; Engel, Michael S

    2016-06-06

    Ants comprise one lineage of the triumvirate of eusocial insects and experienced their early diversification within the Cretaceous [1-9]. Their ecological success is generally attributed to their remarkable social behavior. Not all ants cooperate in social hunting, however, and some of the most effective predatory ants are solitary hunters with powerful trap jaws [10]. Recent evolutionary studies predict that the early branching lineages of extant ants formed small colonies of ground-dwelling, solitary specialist predators [2, 5, 7, 11, 12], while some Cretaceous fossils suggest group recruitment and socially advanced behavior among stem-group ants [9]. We describe a trap-jaw ant from 99 million-year-old Burmese amber with head structures that presumably functioned as a highly specialized trap for large-bodied prey. These are a cephalic horn resulting from an extreme modification of the clypeus hitherto unseen among living and extinct ants and scythe-like mandibles that extend high above the head, both demonstrating the presence of exaggerated morphogenesis early among stem-group ants. The new ant belongs to the Haidomyrmecini, possibly the earliest ant lineage [9], and together these trap-jaw ants suggest that at least some of the earliest Formicidae were solitary specialist predators. With their peculiar adaptations, haidomyrmecines had a refined ecology shortly following the advent of ants. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Evidence for Proterozoic and late Cretaceous-early Tertiary ore-forming events in the Coeur d'Alene district, Idaho and Montana

    USGS Publications Warehouse

    Leach, D.L.; Hofstra, A.H.; Church, S.E.; Snee, L.W.; Vaughn, R.B.; Zartman, R.E.

    1998-01-01

    New 40Ar/39Ar age spectra on sericite and lead isotope data on tetrahedrite, siderite, galena, bournonite, and stibnite, together with previously published isotopic, geochemical, and geologic studies provide evidence for two major vein-forming events in the Coeur d'Alene district and surrounding area of the Belt basin. The data suggest that the zinc- and lead-rich veins (e.g., Bunker Hill and Star-Morning mines) formed in the Proterozoic (1.0 Ga), whereas the silver-rich veins (e.g., Silver belt mines), antimony veins (e.g., US Antimony mine), and gold-bearing quartz veins (Murry subdistrict) formed in Late Cretaceous to early Tertiary time.

  7. Preliminary source rock evaluation and hydrocarbon generation potential of the early Cretaceous subsurface shales from Shabwah sub-basin in the Sabatayn Basin, Western Yemen

    NASA Astrophysics Data System (ADS)

    Al-Matary, Adel M.; Hakimi, Mohammed Hail; Al Sofi, Sadam; Al-Nehmi, Yousif A.; Al-haj, Mohammed Ail; Al-Hmdani, Yousif A.; Al-Sarhi, Ahmed A.

    2018-06-01

    A conventional organic geochemical study has been performed on the shale samples collected from the early Cretaceous Saar Formation from the Shabwah oilfields in the Sabatayn Basin, Western Yemen. The results of this study were used to preliminary evaluate the potential source-rock of the shales in the Saar Formation. Organic matter richness, type, and petroleum generation potential of the analysed shales were assessed. Total organic carbon content and Rock- Eval pyrolysis results indicate that the shale intervals within the early Cretaceous Saar Formation have a wide variation in source rock generative potential and quality. The analysed shale samples have TOC content in the range of 0.50 and 5.12 wt% and generally can be considered as fair to good source rocks. The geochemical results of this study also indicate that the analysed shales in the Saar Formation are both oil- and gas-prone source rocks, containing Type II kerogen and mixed Types II-III gradient to Type III kerogen. This is consistent with Hydrogen Index (HI) values between 66 and 552 mg HC/g TOC. The temperature-sensitive parameters such as vitrinite reflectance (%VRo), Rock-Eval pyrolysis Tmax and PI reveal that the analysed shale samples are generally immature to early-mature for oil-window. Therefore, the organic matter has not been altered by thermal maturity thus petroleum has not yet generated. Therefore, exploration strategies should focus on the known deeper location of the Saar Formation in the Shabwah-sub-basin for predicting the kitchen area.

  8. Two early eudicot fossil flowers from the Kamikitaba assemblage (Coniacian, Late Cretaceous) in northeastern Japan

    DOE PAGES

    Takahashi, Masamichi; Herendeen, Patrick S.; Xiao, Xianghui

    2017-05-11

    Two new fossil taxa referable to the basal eudicot grade are described from the Kamikitaba locality (ca. 89 MYBP, early Coniacian: Late Cretaceous) in the Ashizawa Formation (Asamigawa Member) of Futaba Group in northeastern Japan. These charcoalified mesofossils exhibit well-preserved three-dimensional structure and were analyzed using synchrotron-radiation X-ray microtomography (SRXTM) at the Advanced Photon Source (APS) to document the composition and internal structure. Cathiaria japonica sp. nov. is represented by infructescence segments that consist of an axis bearing three to four fruits. The capsular fruits are sessile and dehiscent and consist of a gynoecium subtended by a bract. No perianthmore » parts are present. The gynoecium is monocarpellate containing two pendulous seeds. The carpel is ascidiate in the lower half and conduplicate in the upper part, style is deflected abaxially with a dorsiventral suture and a large, obliquely decurrent stigma. Pollen grains are tricolpate with a reticulate exine. The morphological features of Cathiaria are consistent with an assignment to the Buxaceae s. l. (including Didymelaceae). Archaeostella verticillata gen. et sp. nov. is represented by flowers that are small, actinomorphic, pedicellate, bisexual, semi-inferior, and multicarpellate. The floral receptacle is cup shaped with a perigynous perianth consisting of several tepals inserted around the rim. The androecium comprises ca. 120 stamens with clear differentiation into anther and filament. The anthers are basifixed and tetrasporangiate. The gynoecium consists of a whorl of ten conduplicate, laterally connate but distally distinct carpels with a conspicuous dorsal bulge, including a central cavity. The styles are short, becoming recurved with a ventrally decurrent stigma. The fruit type is a follicle. Seeds are ca. 10 per carpel, marginal, pendulous from the broad, oblique summit of the locule. Seeds are small, spindle-shaped, with a chalazal extension

  9. Two early eudicot fossil flowers from the Kamikitaba assemblage (Coniacian, Late Cretaceous) in northeastern Japan

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Takahashi, Masamichi; Herendeen, Patrick S.; Xiao, Xianghui

    Two new fossil taxa referable to the basal eudicot grade are described from the Kamikitaba locality (ca. 89 MYBP, early Coniacian: Late Cretaceous) in the Ashizawa Formation (Asamigawa Member) of Futaba Group in northeastern Japan. These charcoalified mesofossils exhibit well-preserved three-dimensional structure and were analyzed using synchrotron-radiation X-ray microtomography (SRXTM) at the Advanced Photon Source (APS) to document the composition and internal structure. Cathiaria japonica sp. nov. is represented by infructescence segments that consist of an axis bearing three to four fruits. The capsular fruits are sessile and dehiscent and consist of a gynoecium subtended by a bract. No perianthmore » parts are present. The gynoecium is monocarpellate containing two pendulous seeds. The carpel is ascidiate in the lower half and conduplicate in the upper part, style is deflected abaxially with a dorsiventral suture and a large, obliquely decurrent stigma. Pollen grains are tricolpate with a reticulate exine. The morphological features of Cathiaria are consistent with an assignment to the Buxaceae s. l. (including Didymelaceae). Archaeostella verticillata gen. et sp. nov. is represented by flowers that are small, actinomorphic, pedicellate, bisexual, semi-inferior, and multicarpellate. The floral receptacle is cup shaped with a perigynous perianth consisting of several tepals inserted around the rim. The androecium comprises ca. 120 stamens with clear differentiation into anther and filament. The anthers are basifixed and tetrasporangiate. The gynoecium consists of a whorl of ten conduplicate, laterally connate but distally distinct carpels with a conspicuous dorsal bulge, including a central cavity. The styles are short, becoming recurved with a ventrally decurrent stigma. The fruit type is a follicle. Seeds are ca. 10 per carpel, marginal, pendulous from the broad, oblique summit of the locule. Seeds are small, spindle-shaped, with a chalazal extension

  10. Geological history of the Cretaceous ophiolitic complexes of northwestern South America (Colombian Andes)

    NASA Astrophysics Data System (ADS)

    Bourgois, Jacques; Toussaint, Jean-François; Gonzalez, Humberto; Azema, Jacques; Calle, Bernardo; Desmet, Alain; Murcia, Luis A.; Acevedo, Alvaro P.; Parra, Eduardo; Tournon, Jean

    1987-12-01

    The Western Cordillera of Colombia was formed by intense alpine-type nappe-forming folding and thrusting. The Cretaceous (80-120 Ma B.P.) tholeiitic material of the Western Cordilleran nappes has been obducted onto the Paleozoic and Precambrian polymetamorphic micaschists and gneiss of the Central Cordillera. Near Yarumal, the Antioquia batholith (60-80 Ma B.P.) intrudes both obducted Cretaceous oceanic material and the polymetamorphic basement rock of the Central Cordillera. Therefore, nappe emplacement and obduction onto the Central Cordillera occurred during Late Senonian to Early Paleocene. The nappes travelled from northwest to southeast so that the highest unit, the Rio Calima nappe therefore has the most northwestern source, whereas the lowest units originated from a more southeastward direction. Sedimentological analysis of the volcanoclastic and sandy turbidite material from each unit suggests a marginal marine environment. During Cretaceous times the opening of this marginal sea, from now on called the "Colombia marginal basin", probably originated by detachment of a block from the South American continent related to the Farallon-South America plate convergence. In the Popayan area (southern Colombia), the Central Cordilleran basement exhibits glaucophane schist facies metamorphism. This high pressure low temperature metamorphism is of Early Cretaceous (125 Ma B.P.) age and is related to an undated metaophiolitic complex. The ophiolitic material originating from the Western Cordilleran is thrust over both the blueschist belt and the metaophiolitic complex. These data suggest that the "Occidente Colombiano" suffered at least two phases of ophiolitic obduction during Mesozoic time.

  11. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-12-01

    The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ13Corg excursions and global warming during OAE1b.

  12. Early Cretaceous stratigraphy, paleontology, and sedimentary tectonics in Paris overthrust foredeep (western Wyoming and southeastern Idaho) compared with Quaternary features of indo-gangetic plain

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dorr, J.A. Jr.

    1983-08-01

    Fluviatile clastics of the nonmarine, early Cretaceous Gannett and Wayan groups were deposited on wet alluvial megafans and on intervening interfan piedmont slopes which declined eastward into more poorly drained lowlands from a western highland source area uplifted episodically by movements of the Paris overthrust. Lacustrine episodes of deposition intercalated Peterson and Draney limestones with Gannett fluvial clastics. Westward marine transgressions (Skull Creek, Mowry) intercalated mixed lacustrine and brackish facies (Smiths and Cokedale formations) into Wayan fluviatile clastics. Newly discovered fossil vertebrate and invertebrate materials (all fragmentary but identifiable) include: Gannett Group - large reptiles including turtles; Thomas Fork Formationmore » - freshwater gastropods and unionid pelecypods, gastroliths, two types of turtles, large reptilian fragments (dinosaur), and abundant dinosaur eggshell fragments; Wayan Formation - perennially aquatic snails, turtles, unidentifiable large reptiles, two types of crocodilians, an iguanodontid dinosaur (Tenontosaurus), an ankylosaurian dinosaur, a large ornithopod dinosaur, gastroliths, abundant and ubiquitous dinosaur eggshell fragments (numerous types and sizes), and miscellaneous unidentifiable small vertebrate bone fragments. A census of analogous modern reptile reproductive behaviors supports the conclusion that the Wayan, and probably also the Gannett, alluvial fan environments were used as upland breeding grounds by dinosaurs and perhaps other reptiles. Comparison of these Early Cretaceous data with observations on the tectonic setting, sedimentology, and biology of the Quaternary indo-gangetic plain suggests many close analogies between the two sedimentary tectonic settings.« less

  13. Stratigraphic framework and evolution of the Cretaceous continental sequences of the Bauru, Sanfranciscana, and Parecis basins, Brazil

    NASA Astrophysics Data System (ADS)

    Batezelli, Alessandro; Ladeira, Francisco Sergio Bernardes

    2016-01-01

    With the breakup of the supercontinent Gondwana, the South American Plate has undergone an intense process of tectonic restructuring that led to the genesis of the interior basins that encompassed continental sedimentary sequences. The Brazilian Bauru, Sanfranciscana and Parecis basins during Late Cretaceous have had their evolution linked to this process of structuring and therefore have very similar sedimentary characteristics. The purpose of this study is to establish a detailed understanding of alluvial sedimentary processes and architecture within a stratigraphic sequence framework using the concept of the stratigraphic base level or the ratio between the accommodation space and sediment supply. The integration of the stratigraphic and facies data contributed to defining the stratigraphic architecture of the Bauru, Sanfranciscana and Parecis Basins, supporting a model for continental sequences that depicts qualitative changes in the sedimentation rate (S) and accommodation space (A) that occurred during the Cretaceous. This study discusses the origin of the unconformity surfaces (K-0, K-1 and K-1A) that separate Sequences 1, 2A and 2B and the sedimentary characteristics of the Bauru, Sanfranciscana and Parecis Basins from the Aptian to the Maastrichtian, comparing the results with other Cretaceous Brazilian basins. The lower Cretaceous Sequence 1 (Caiuá and Areado groups) is interpreted as a low-accommodation systems tract compound by fluvial and aeolian systems. The upper Cretaceous lacustrine, braided river-dominated alluvial fan and aeolian systems display characteristics of the evolution from high-to low-accommodation systems tracts (Sequences 2A and 2B). Unconformity K-0 is related to the origin of the Bauru Basin itself in the Early Cretaceous. In Sanfranciscana and Parecis basins, the unconformity K-0 marks the contact between aeolian deposits from Lower Cretaceous and Upper Cretaceous alluvial systems (Sequences 1 and 2). Unconformity K-1, which was

  14. Integrated geophysical and geological study and petroleum appraisal of Cretaceous plays in the Western Gulf of Gabes, Tunisia

    NASA Astrophysics Data System (ADS)

    Dkhaili, Noomen; Bey, Saloua; El Abed, Mahmoud; Gasmi, Mohamed; Inoubli, Mohamed Hedi

    2015-09-01

    An integrated study of available seismic and calibrated wells has been conducted in order to ascertain the structural development and petroleum potential of the Cretaceous Formations of the Western Gulf of Gabes. This study has resulted in an understanding of the controls of deep seated Tethyan tectonic lineaments by analysis of the Cretaceous deposits distribution. Three main unconformities have been identified in this area, unconformity U1 between the Jurassic and Cretaceous series, unconformity U2 separating Early from Late Cretaceous and known as the Austrian unconformity and the major unconformity U3 separating Cretaceous from Tertiary series. The seismic analysis and interpretation have confirmed the existence of several features dominated by an NE-SW extensive tectonic regime evidenced by deep listric faults, asymmetric horst and graben and tilted blocks structures. Indeed, the structural mapping of these unconformities, displays the presence of dominant NW-SE fault system (N140 to N160) bounding a large number of moderate sized basins. A strong inversion event related to the unconformity U3 can be demonstrated by the mapping of the unconformities consequence of the succession of several tectonic manifestations during the Cretaceous and post-Cretaceous periods. These tectonic events have resulted in the development of structural and stratigraphic traps further to the porosity and permeability enhancement of Cretaceous reservoirs.

  15. Tectonic Mechanism for the Mid-Cretaceous - Early Paleogene Intraplate Magmatism from the Gulf of Mexico to Northwestern Canada

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Murphy, M. A.; Snow, J. E.; van Wijk, J.; Cannon, J. M.; Parsons, C.

    2017-12-01

    Tectonic mechanisms have remained controversial for a number of intraplate igneous suites of mid-Cretaceous - early Paleogene age across North America. They span the northern Gulf of Mexico (GoM), through Arkansas and Kansas in the US, to Saskatchewan and Northwestern Territories in Canada, resembling a belt that is located 1000+ km inboard from, and aligned sub-parallel to, the western margin of North America. The northern GoM magmatism is characterized by lamproites, carbonatites, nephelinites, with other alkaline rocks, whereas the rest igneous provinces are dominated by kimberlites. Their geochemical signatures, in general, point to a sub-lithospheric mantle origin. Hypotheses that explain the tectonic origin of these magmatic rocks include: (1) hotspots and mantle plumes, (2) edge-driven convection, (3) lithospheric reactivation, and (4) low-angle subduction. Evaluation based on our integration of published geological and geophysical data shows that contradictions exist in each model between observations and predictions. To explain this plate-scale phenomenon, we propose that the Farallon slab may have stagnated within or around the mantle transition zone during the Early Cretaceous, with its leading edge reaching ca. 1600 km inland beneath the North American plate. Dehydration and decarbonation of the slab produces sporadic, dense, low-degree partial melts at the mantle transition zone depths. As the slab descends into the lower mantle, Rayleigh-Taylor instabilities are induced at slab edges, causing passive upwelling that brings alkali-rich carbonate silicate melts to the base of the overriding plate. Subsequently, the North American lithosphere with varying thicknesses, discontinuities, and compositions interacts with the rising partial melts, generating a spectrum of igneous rocks. Fragments of the once-stagnated slab may still be detectable in the lower mantle beneath eastern US in seismic tomography models. This study highlights a profound plate

  16. Molecular and Paleontological Evidence for a Post-Cretaceous Origin of Rodents

    PubMed Central

    Wu, Shaoyuan; Wu, Wenyu; Zhang, Fuchun; Ye, Jie; Ni, Xijun; Sun, Jimin; Edwards, Scott V.; Meng, Jin; Organ, Chris L.

    2012-01-01

    The timing of the origin and diversification of rodents remains controversial, due to conflicting results from molecular clocks and paleontological data. The fossil record tends to support an early Cenozoic origin of crown-group rodents. In contrast, most molecular studies place the origin and initial diversification of crown-Rodentia deep in the Cretaceous, although some molecular analyses have recovered estimated divergence times that are more compatible with the fossil record. Here we attempt to resolve this conflict by carrying out a molecular clock investigation based on a nine-gene sequence dataset and a novel set of seven fossil constraints, including two new rodent records (the earliest known representatives of Cardiocraniinae and Dipodinae). Our results indicate that rodents originated around 61.7–62.4 Ma, shortly after the Cretaceous/Paleogene (K/Pg) boundary, and diversified at the intraordinal level around 57.7–58.9 Ma. These estimates are broadly consistent with the paleontological record, but challenge previous molecular studies that place the origin and early diversification of rodents in the Cretaceous. This study demonstrates that, with reliable fossil constraints, the incompatibility between paleontological and molecular estimates of rodent divergence times can be eliminated using currently available tools and genetic markers. Similar conflicts between molecular and paleontological evidence bedevil attempts to establish the origination times of other placental groups. The example of the present study suggests that more reliable fossil calibration points may represent the key to resolving these controversies. PMID:23071573

  17. Cretaceous shelf-sea chalk deposits

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hattin, D.E.

    1988-01-01

    The word ''chalk'' is linked etymologically to the Cretaceous, but chalky facies neither dominate that system nor are confined to it. As used commonly, the term ''chalk'' refers to a variety of marine limestone that is white to light gray very fine grained, soft and friable, porous, and composed predominantly of calcitic skeletal remains, especially those derived from coccolithophores. No simple definition suffices to embrace all Cretaceous chalks, which include sandy, marly, shelly, phospatic, glauconitic, dolomitic, pyritic and organic-rich lithotypes. Most of the world's exposed Cretaceous chalk deposits were formed at shelf depths rather than in the deep sea. Cretaceousmore » shelf-sea chalks are developed most extensively in northern Europe, the U.S. Gulf Coastal Plain and Western Interior, and the Middle East, with lesser occurrences alo in Australia. Most Cretaceous shelf-sea chalks formed in the temperature zones, and in relatively deep water. Cretaceous chalks deposited on well-oxygenated sea floors are bioturbated and massive where deficient in terrigenous detritus, or bioturbated and rhythmically interbedded with argillaceous units where influx of terrigenous detritus varied systematically with climate changes. Accumulation of sufficient pelagic mud to form vast deposits of Cretaceous shelf-sea chalk required (1) sustained high productivity of calareous plankton, (2) extensive development of stable shelf and continental platform environments, (3) highstands of seal level, (4) deficiency of aragonitic skeletal material in chalk-forming sediments, and (5) low rates of terrigenous detrital influx. These conditions were met at different times in different places, even within the same general region.« less

  18. The clasts of Cretaceous marls in the conglomerates of the Konradsheim Formation (Pöchlau quarry, Gresten Klippen Zone, Austria)

    NASA Astrophysics Data System (ADS)

    Ślączka, Andrzej; Gasiñski, M. Adam; Bąk, Marta; Wessely, Godfrid

    2009-04-01

    Investigations were carried out on foraminiferids and radiolaria from redeposited clasts within the conglomerates of the Konradsheim Formation (Gresten Klippen Zone) in the area of the Pöchlau hill, east of Maria Neustift. These shales and marls are of Middle to Late Jurassic and Early Cretaceous age. In the latter clasts, foraminiferal assemblages with Tritaxia ex gr. gaultina as well as radiolaria species Angulobracchia portmanni Baumgartner, Dictyomitra communis (Squinabol), Hiscocapsa asseni (Tan), Pseudodictyomitra lodogaensis Pessagno, Pseudoeucyrtis hanni (Tan), Rhopalosyringium fossile (Squinabol) were found. In one block from the uppermost part of the sequence there is an assemblage with Caudammina (H) gigantea, Rotalipora appenninica and Globotruncana bulloides. However, the brecciated character of this block and occurrence near a fault suggest that it was probably wedged into the conglomerates of the Konradsheim Formation during tectonic movements. In pelitic siliceous limestones below the Konradsheim Limestone radiolarian assemblages of Middle Callovian to Early Tithonian age were found. They enable correlation with the Scheibbsbach Formation. In a marly sequence, above the conglomeratic limestone, the foraminiferal assemblages contain taxa from mid-Cretaceous up to Paleocene. The present biostratigraphic investigation confirmed the previous stratigraphic assignments and imply clearly that the sedimentation of deposits similar to the Konradsheim Formation also occurred at the end of the Early Cretaceous and deposition of conglomeratic limestones within the Gresten Klippen Zone, and especially within the Konradsheim Formation, was repeated several times during the Late Jurassic and Early Cretaceous.

  19. Hydrocarbon potential of Early Cretaceous lacustrine sediments from Bima Formation, Yola Sub-basin, Northern Benue Trough, NE Nigeria: Insight from organic geochemistry and petrology

    NASA Astrophysics Data System (ADS)

    Sarki Yandoka, Babangida M.; Abdullah, Wan Hasiah; Abubakar, M. B.; Adegoke, Adebanji Kayode; Maigari, A. S.; Haruna, A. I.; Yaro, Usman Y.

    2017-05-01

    The Early Cretaceous lacustrine sediments from Bima Formation in the Yola Sub-basin, Northern Benue Trough, northeastern Nigeria were studied based on organic geochemistry and petrology. This is in other to provide information on hydrocarbon generation potential; organic matter type (quality), richness (quantity), origin/source inputs, redox conditions (preservation) and thermal maturation in relation to thermal effect of Tertiary volcanics. The total organic carbon (TOC) contents ranges from 0.38 to 0.86 wt % with extractable organic matter (EOM) below 1000 ppm and pyrolysis S2 yield values from 0.16 to 0.68 mg/g, suggesting poor to fair source rock richness. Based on kerogen pyrolysis and microscopy coupled with biomarker parameters, the organic matters contain Type I (lacustrine algae), Type III (terrestrially derived land-plants) and Type IV kerogens deposited in a mixed lacustrine-terrestrial environment under suboxic to relatively anoxic conditions. This suggest potential occurrence of Early Cretaceous lacustrine sediments (perhaps Lower Cretaceous petroleum system) in Yola Sub-basin of the Northern Benue Trough as present in the neighbouring basins of Chad, Niger and Sudan Republics that have both oil and gas generation potential within the same rift trend (WCARS). Vitrinite reflectance (%Ro) and Tmax values of the lacustrine shales ranges from 1.12 to 2.32 VRo% and 448-501 °C, respectively, indicating peak-late to post-maturity stage. This is supported by the presence of dark brown palynomorphs, amorphous organic matter and phytoclasts as well as inertinite macerals. Consequently, the organic matters in the lacustrine shales of Bima Formation in the Yola Sub-basin appeared as a source of oil (most likely even waxy) and gas prone at a relatively deeper part of the basin. However, the high thermal maturity enhanced the organic matters and most of the hydrocarbons that formed in the course of thermal maturation were likely expelled to the reservoir rock units

  20. Petroleum system elements within the Late Cretaceous and Early Paleogene sediments of Nigeria's inland basins: An integrated sequence stratigraphic approach

    NASA Astrophysics Data System (ADS)

    Dim, Chidozie Izuchukwu Princeton; Onuoha, K. Mosto; Okeugo, Chukwudike Gabriel; Ozumba, Bertram Maduka

    2017-06-01

    Sequence stratigraphic studies have been carried out using subsurface well and 2D seismic data in the Late Cretaceous and Early Paleogene sediments of Anambra and proximal onshore section of Niger Delta Basin in the Southeastern Nigeria. The aim was to establish the stratigraphic framework for better understanding of the reservoir, source and seal rock presence and distribution in the basin. Thirteen stratigraphic bounding surfaces (consisting of six maximum flooding surfaces - MFSs and seven sequence boundaries - SBs) were recognized and calibrated using a newly modified chronostratigraphic chart. Stratigraphic surfaces were matched with corresponding foraminiferal and palynological biozones, aiding correlation across wells in this study. Well log sequence stratigraphic correlation reveals that stratal packages within the basin are segmented into six depositional sequences occurring from Late Cretaceous to Early Paleogene age. Generated gross depositional environment maps at various MFSs show that sediment packages deposited within shelfal to deep marine settings, reflect continuous rise and fall of sea levels within a regressive cycle. Each of these sequences consist of three system tracts (lowstand system tract - LST, transgressive system tract - TST and highstand system tract - HST) that are associated with mainly progradational and retrogradational sediment stacking patterns. Well correlation reveals that the sand and shale units of the LSTs, HSTs and TSTs, that constitute the reservoir and source/seal packages respectively are laterally continuous and thicken basinwards, due to structural influences. Result from interpretation of seismic section reveals the presence of hanging wall, footwall, horst block and collapsed crest structures. These structural features generally aid migration and offer entrapment mechanism for hydrocarbon accumulation. The combination of these reservoirs, sources, seals and trap elements form a good petroleum system that is viable

  1. A lower Cretaceous (Valanginian) seed cone provides the earliest fossil record for Picea (Pinaceae).

    PubMed

    Klymiuk, Ashley A; Stockey, Ruth A

    2012-06-01

    Sequence analyses for Pinaceae have suggested that extant genera diverged in the late Mesozoic. While the fossil record indicates that Pinaceae was highly diverse during the Cretaceous, there are few records of living genera. This description of an anatomically preserved seed cone extends the fossil record for Picea A. Dietrich (Pinaceae) by ∼75 Ma. The specimen was collected from the Apple Bay locality of Vancouver Island (Lower Cretaceous, Valanginian) and is described from anatomical sections prepared using cellulose acetate peels. Cladistic analyses of fossil and extant pinaceous seed cones employed parsimony ratchet searches of an anatomical and morphological matrix. This new seed cone has a combination of characters shared only with the genus Picea A. Dietr. and is thus described as Picea burtonii Klymiuk et Stockey sp. nov. Bisaccate pollen attributable to Picea is found in the micropyles of several ovules, corroborating the designation of this cone as an early spruce. Cladistic analyses place P. burtonii with extant Picea and an Oligocene representative of the genus. Furthermore, our analyses indicate that Picea is sister to Cathaya Chun et Kuang, and P. burtonii helps to establish a minimum date for this node in hypotheses of conifer phylogeny. As an early member of the extant genus Picea, this seed cone extends the fossil record of Picea to the Valanginian Stage of the Early Cretaceous, ca. 136 Ma, thereby resolving a ghost lineage predicted by molecular divergence analyses, and offers new insight into the evolution of Pinaceae.

  2. Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater.

    PubMed

    Sanford, Ward E; Doughten, Michael W; Coplen, Tyler B; Hunt, Andrew G; Bullen, Thomas D

    2013-11-14

    High-salinity groundwater more than 1,000 metres deep in the Atlantic coastal plain of the USA has been documented in several locations, most recently within the 35-million-year-old Chesapeake Bay impact crater. Suggestions for the origin of increased salinity in the crater have included evaporite dissolution, osmosis and evaporation from heating associated with the bolide impact. Here we present chemical, isotopic and physical evidence that together indicate that groundwater in the Chesapeake crater is remnant Early Cretaceous North Atlantic (ECNA) sea water. We find that the sea water is probably 100-145 million years old and that it has an average salinity of about 70 per mil, which is twice that of modern sea water and consistent with the nearly closed ECNA basin. Previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical, isotopic and palaeontological analyses of solid materials in deep sediment cores. In contrast, our study identifies ancient sea water in situ and provides a direct estimate of its age and salinity. Moreover, we suggest that it is likely that remnants of ECNA sea water persist in deep sediments at many locations along the Atlantic margin.

  3. Mating and aggregative behaviors among basal hexapods in the Early Cretaceous.

    PubMed

    Sánchez-García, Alba; Peñalver, Enrique; Delclòs, Xavier; Engel, Michael S

    2018-01-01

    Among the many challenges in paleobiology is the inference and reconstruction of behaviors that rarely, if ever, leave a physical trace on the environment that is suitable for fossilization. Of particular significance are those behaviors tied to mating and courtship, individual interactions critical for species integrity and continuance, as well as those for dispersal, permitting the taxon to expand its distribution as well as access new habitats in the face of local or long-term environmental change. In this context, two recently discovered fossils from the Early Cretaceous amber of Spain (ca. 105 mya) give a detailed view of otherwise fleeting ethologies in Collembola. These occurrences are phylogenetically spaced across the class, and from species representing the two major clades of springtails-Symphypleona and Entomobryomorpha. Specifically, we report unique evidence from a symphypleonan male (Pseudosminthurides stoechus Sánchez-García & Engel, 2016) with modified antennae that may have functioned as a clasping organ for securing females during mating on water's surface, and from an aggregation of entomobryomorphan individuals (Proisotoma communis Sánchez-García & Engel, 2016) purportedly representing a swarming episode on the forest floor. We demonstrate that the mating behavioral repertoire in P. stoechus, which is associated with considerable morphological adaptations, likely implied elaborate courtship and maneuvering for guarantee sperm transfer in an epineustic species. These discoveries reveal significant behaviors consistent with modern counterparts and a generalized stasis for some ancient hexapod ethologies associated with complex mating and courtship and social or pre-social aggregations, so critical to specific constancy and dispersal.

  4. Mating and aggregative behaviors among basal hexapods in the Early Cretaceous

    PubMed Central

    Sánchez-García, Alba; Peñalver, Enrique; Delclòs, Xavier

    2018-01-01

    Among the many challenges in paleobiology is the inference and reconstruction of behaviors that rarely, if ever, leave a physical trace on the environment that is suitable for fossilization. Of particular significance are those behaviors tied to mating and courtship, individual interactions critical for species integrity and continuance, as well as those for dispersal, permitting the taxon to expand its distribution as well as access new habitats in the face of local or long-term environmental change. In this context, two recently discovered fossils from the Early Cretaceous amber of Spain (ca. 105 mya) give a detailed view of otherwise fleeting ethologies in Collembola. These occurrences are phylogenetically spaced across the class, and from species representing the two major clades of springtails—Symphypleona and Entomobryomorpha. Specifically, we report unique evidence from a symphypleonan male (Pseudosminthurides stoechus Sánchez-García & Engel, 2016) with modified antennae that may have functioned as a clasping organ for securing females during mating on water’s surface, and from an aggregation of entomobryomorphan individuals (Proisotoma communis Sánchez-García & Engel, 2016) purportedly representing a swarming episode on the forest floor. We demonstrate that the mating behavioral repertoire in P. stoechus, which is associated with considerable morphological adaptations, likely implied elaborate courtship and maneuvering for guarantee sperm transfer in an epineustic species. These discoveries reveal significant behaviors consistent with modern counterparts and a generalized stasis for some ancient hexapod ethologies associated with complex mating and courtship and social or pre-social aggregations, so critical to specific constancy and dispersal. PMID:29466382

  5. Ascaulocardium armatum (Morton 1833), new genus (Late Cretaceous): the ultimate variation on the bivalve paradigm.

    USGS Publications Warehouse

    Pojeta, J.; Sohl, N.F.

    1987-01-01

    Cretaceous clavagellid pelecypods are a poorly known group, and have previously received little study. Ascaulocardium armatum is conchologically the most complex burrowing pelecypod known. From the study of living clavagellids, it is possible to interpret the various tubes extending outward from the adventitious crypt of A. armatum as devices for hydraulic burrowing and deposit feeding. The conchologically complex A. armatum occurs near the beginning of the history of the Clavagellidae, and does not seem to have given rise to any younger species. Ascaulocardium armatum is known only from the Upper Cretaceous rocks (Santonian-Maastrichtian) of the east Gulf and Atlantic Coastal Plains of the United States of America, as is probably the genus Ascaulocardium. All known Cretaceous clavagellids are burrowing species having a free right valve, and this is the ancestral mode of life of the Clavagellidae. Clavagellids that have a boring habit are a more recent evolutionary development, as are burrowing species having both juvenile valves cemented to the crypt. Clavagellids probably evolved from Jurassic-Early Cretaceous pholadomyids. Almost all Cretaceous clavagellids occur outside the Tethyan Zoogeographic Realm; this distribution is in marked contrast to the modern distribution of the family. Living species mostly inhabit clear, shallow seas in subtropical to tropical shelf areas. - Authors

  6. Eobowenia gen. nov. from the Early Cretaceous of Patagonia: indication for an early divergence of Bowenia?

    PubMed

    Coiro, Mario; Pott, Christian

    2017-04-07

    Even if they are considered the quintessential "living fossils", the fossil record of the extant genera of the Cycadales is quite poor, and only extends as far back as the Cenozoic. This lack of data represents a huge hindrance for the reconstruction of the recent history of this important group. Among extant genera, Bowenia (or cuticles resembling those of extant Bowenia) has been recorded in sediments from the Late Cretaceous and the Eocene of Australia, but its phylogenetic placement and the inference from molecular dating still imply a long ghost lineage for this genus. We re-examine the fossil foliage Almargemia incrassata from the Lower Cretaceous Anfiteatro de Ticó Formation in Patagonia, Argentina, in the light of a comparative cuticular analysis of extant Zamiaceae. We identify important differences with the other member of the genus, viz. A. dentata, and bring to light some interesting characters shared exclusively between A. incrassata and extant Bowenia. We interpret our results to necessitate the erection of the new genus Eobowenia to accommodate the fossil leaf earlier assigned as Almargemia incrassata. We then perfom phylogenetic analyses, including the first combined morphological and molecular analysis of the Cycadales, that indicate that the newly erected genus could be related to extant Bowenia. Eobowenia incrassata could represent an important clue for the understanding of evolution and biogeography of the extant genus Bowenia, as the presence of Eobowenia in Patagonia is yet another piece of the biogeographic puzzle that links southern South America with Australasia.

  7. Cretaceous polar climates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ziegler, A.M.; Horrell, M.A.; Lottes, A.L.

    1988-02-01

    The Cretaceous, like most Phanerozoic periods, was characterized by ice-free poles. Some still argue that the glaciers and sea ice were there, and that the tillites, etc, have been eroded or remain undiscovered. However, diverse floras, dense forests, and coal-forming cypress swamps, and dinosaurs, crocodilians, and lungfish are known from areas that were certainly at 75/degree/-80/degree/ north and south paleolatitude in the Cretaceous, implying that the coastal basins did not experience hard freezes. No deep marine connections to the North Pole existed in the Cretaceous, so oceanic polar heat transport can be discounted. However, the five north-south trending epeiric ormore » rift-related seaways that connected or nearly connected the Tethys to the Arctic would have dampened the seasonal temperature cycle, bring maritime climates deep into the North American and Eurasian continents and, more importantly, would have served as an energy source and channel for winter storms, much as the Gulf Stream does today. Cyclones have a natural tendency to move poleward, because of the increase in the Coriolis Parameter, and they transport both sensible and latent heat. The coastal regions of the relatively warm polar ocean in the Cretaceous would have received continuous precipitation during the winter because cyclones would be entering from as many as five directions. Coastal rainfall would also have been abundant in the summer but for a different reason; the land-sea temperature profile would reverse, with the warm land surface drawing in moisture, while clear ice-free conditions over the ocean would allow for solar warming.« less

  8. Cretaceous polar climates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ziegler, A.M.; Horrell, M.A.; Lottes, A.L.

    1988-01-01

    The Cretaceous, like most Phanerozooic periods, was characterized by ice-free poles. Some still argue that the glacier and sea ice were there, and that the tillites, etc, have been eroded or remain undiscovered. However, diverse floras, dense forests, coal-forming cypress swamps, and dinosaurs, crocodilians, and lungfish are known from areas that were certainly at 75/sup 0/-80/sup 0/ north and south paleolatitude in the Cretaceous, implying that the coastal basins did not experience hard freezes. No deep marine connections to the North Pole existed in the Cretaceous, so oceanic polar heat transport can be discounted. However, the five north-south trending epeiricmore » or rift-related seaways that connected or nearly connected the Tethys to the Arctic would have dampened the seasonal temperature cycle, bringing maritime climates deep into the North American and Eurasian continents and, more importantly, would have served as an energy source and channel for winter storms, much as the Gulf Stream does today. Cyclones have a natural tendency to move poleward, because of the increase in the Coriolis Paramteter, and they transport both sensible and latent heat. The coastal regions of the relatively warm polar ocean in the Cretaceous would have received continuous precipitation during the winter because cyclones would be entering from as many as five directions. Coastal rainfall would also have been abundant in the summer but for a different reason; the land-sea temperature profile would reverse, with the warm land surface drawing in moisture, while clear ice-free conditions over the ocean would allow for solar warming.« less

  9. Linkages Between Cretaceous Forearc and Retroarc Basin Development in Southern Tibet

    NASA Astrophysics Data System (ADS)

    Orme, D. A.; Laskowski, A. K.

    2015-12-01

    Integrated provenance and subsidence analysis of forearc and retroarc foreland basin strata were used to reconstruct the evolution of the southern margin of Eurasia during the Early to Late Cretaceous. The Cretaceous-Eocene Xigaze forearc basin, preserved along ~600 km of the southern Lhasa terrane, formed between the Gangdese magmatic arc and accretionary complex as subduction of Neo-Tethyan oceanic lithosphere accommodated the northward motion and subsequent collision of the Indian plate. Petrographic similarities between Xigaze forearc basin strata and Cretaceous-Eocene sedimentary rocks of the northern Lhasa terrane, interpreted as a retroarc foreland basin, were previously interpreted to record N-S trending river systems connecting the retro- and forearc regions during Cretaceous time. New sandstone petrographic and U-Pb detrital zircon provenance analysis of Xigaze forearc basin strata support this hypothesis. Qualitative and statistical provenance analysis using cumulative distribution functions and Kolmogorov-Smirnov (K-S) tests show that the forearc basin was derived from either the same source region as or recycled from the foreland basin. Quartz-rich sandstones with abundant carbonate sedimentary lithic grains and rounded, cobble limestone clasts suggests a more distal source than the proximal Gangdese arc. Therefore, we interpret that the northern Lhasa terrane was a significant source of Xigaze forearc detritus and track spatial and temporal variability in the connection between the retro- and forearc basin systems during the Late Cretaceous. A tectonic subsidence curve for the Xigaze forearc basin shows a steep and "kinked" shape similar to other ancient and active forearc basins. Initial subsidence was likely driven by thermal relaxation of the forearc ophiolite after emplacement while additional periods of rapid subsidence likely result from periods of high flux magmatism in the Gangdese arc and changes in plate convergence rate. Comparison of the

  10. Large-scale removal of lithosphere underneath the North China Craton in the Early Cretaceous: Geochemical constraints from volcanic lavas in the Bohai Bay Basin

    NASA Astrophysics Data System (ADS)

    Sun, Jing; Liu, Zheng; Zhang, Shuai; Li, Xiaoguang; Qi, Jiafu

    2017-11-01

    Cratons are generally considered as the most stable tectonic units on the Earth. Rare magmatism, seismic activity, and intracrustal ductile deformation occur in them. However, several cratons experienced entirely different fates, including the North China Craton (NCC), and were subsequently destroyed. Geodynamic mechanisms and timing of the cratonic destruction are strongly debated. In this paper, we investigate a suite of Mesozoic intermediate to felsic volcanic rocks which are collected from boreholes in the Liaohe Depression of the Bohai Bay Basin the eastern NCC. These volcanic rocks have Precambrian basement-like Sr-Nd isotopic characteristics, consistent with derivation from the lower continental crust underneath the NCC. The Late Jurassic ( 165 Ma) intermediate volcanic rocks don't exhibit markedly negative Eu anomalies, which require a source beyond the plagioclase stability field. And the low heavy rare earth elements (HREEs) contents of these samples indicate that their source has garnet as residue. The Early Cretaceous ( 122 Ma) felsic volcanic rocks are depleted in HREEs but with remarkable Eu anomalies, suggesting that their source have both garnet and plagioclase. The crust thicknesses, estimated from the geochemistry of the intermediate and felsic rocks, are ≥ 50 km at 165 Ma and 30-50 km at 122 Ma, respectively. The crustal thinning is attributed to lithospheric delamination beneath the NCC. Our results combined with previous studies imply that the large-scale lithospheric removal occurred in the Early Cretaceous, between 140 and 120 Ma.

  11. North American nonmarine climates and vegetation during the Late Cretaceous

    USGS Publications Warehouse

    Wolfe, J.A.; Upchurch, G.R.

    1987-01-01

    Analyses of physiognomy of Late Cretaceous leaf assemblages and of structural adaptations of Late Cretaceous dicotyledonous woods indicate that megathermal vegetation was an open-canopy, broad-leaved evergreen woodland that existed under low to moderate amounts of rainfall evenly distributed through the year, with a moderate increase at about 40-45??N. Many dicotyledons were probably large, massive trees, but the tallest trees were evergreen conifers. Megathermal climate extended up to paleolatitude 45-50??N. Mesothermal vegetation was at least partially an open, broad-leaved evergreen woodland (perhaps a mosaic of woodland and forest), but the evapotranspirational stress was less than in megathermal climate. Some dicotyledons were large trees, but most were shrubs or small trees; evergreen conifers were the major tree element. Some mild seasonality is evidenced in mesothermal woods; precipitational levels probably varied markedly from year to year. Northward of approximately paleolatitude 65??N, evergreen vegetation was replaced by predominantly deciduous vegetation. This replacement is presumably related primarily to seasonality of light. The southern part of the deciduous vegetation probably existed under mesothermal climate. Comparisons to leaf and wood assemblages from other continents are generally consistent with the vegetational-climatic patterns suggested from North American data. Limited data from equatorial regions suggest low rainfall. Late Cretaceous climates, except probably those of the Cenomanian, had only moderate change through time. Temperatures generally appear to have warmed into the Santonian, cooled slightly into the Campanian and more markedly into the Maastrichtian, and then returned to Santonian values by the late Maastrichtian. The early Eocene was probably warmer than any period of the Late Cretaceous. Latitudinal temperature gradients were lower than at present. For the Campanian and Maastrichtian, a gradient of about 0.3??C/1

  12. Cretaceous Small Scavengers: Feeding Traces in Tetrapod Bones from Patagonia, Argentina

    PubMed Central

    de Valais, Silvina; Apesteguía, Sebastián; Garrido, Alberto C.

    2012-01-01

    Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem. PMID:22253800

  13. Dinosaurs and the Cretaceous Terrestrial Revolution

    PubMed Central

    Lloyd, Graeme T; Davis, Katie E; Pisani, Davide; Tarver, James E; Ruta, Marcello; Sakamoto, Manabu; Hone, David W.E; Jennings, Rachel; Benton, Michael J

    2008-01-01

    The observed diversity of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125–80 Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR. PMID:18647715

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

    PubMed Central

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

    2012-01-01

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

  15. Early Cretaceous Ductile Deformation of Marbles from the Western Hills of Beijing, North China Craton

    NASA Astrophysics Data System (ADS)

    Feng, H.; Liu, J.

    2017-12-01

    During the Early Cretaceous tectonic lithosphere extension, the pre-mesozoic rocks from the Western Hills in the central part of the North China Craton suffered from weak metamorphism but intense shear deformation. The prominent features of the deformation structures are the coexisting layer-parallel shear zones and intrafolia folds, and the along-strike thickness variations of the marble layers from the highly sheared Mesoproterozoic Jing'eryu Formation. Platy marbles are well-developed in the thinner layers, while intrafolia folds are often observed in the thicker layers. Most folds are tight recumbent folds and their axial planes are parallel to the foliations and layerings of the marbles. The folds are A-type folds with hinges being always paralleling to the stretching lineations consistently oriented at 130°-310° directions throughout the entire area. SPO and microstructural analyses of the sheared marbles suggest that the thicker layers suffered from deformations homogeneously, while strain localization can be distinguished in the thinner layers. Calcite twin morphology and CPO analysis indicate that the deformation of marbles from both thinner and thicker layers happened at temperatures of 300 to 500°C. The above analysis suggests that marbles in the thicker layers experienced a progressive sequence of thermodynamic events: 1) regional metamorphism, 2) early ductile deformation dominated by relatively higher temperature conditions, during which all the mineral particles elongated and oriented limitedly and the calcite grains are deformed mainly by mechanical twinning, and 3) late superimposition of relatively lower temperature deformation and recrystallization, which superposed the early deformation, and made the calcites finely granulated, elongated and oriented by dynamical recrystallization along with other grains. Marbles from the thinner layers, however, experienced a similar, but different sequence of thermo-dynamic events, i.e. regional

  16. New toothed flying reptile from Asia: close similarities between early Cretaceous pterosaur faunas from China and Brazil.

    PubMed

    Wang, Xiaolin; Kellner, Alexander W A; Jiang, Shunxing; Cheng, Xin

    2012-04-01

    Despite the great increase in pterosaur diversity in the last decades, particularly due to discoveries made in western Liaoning (China), very little is known regarding pterosaur biogeography. Here, we present the description of a new pterosaur from the Jiufotang Formation that adds significantly to our knowledge of pterosaur distribution and enhances the diversity of cranial anatomy found in those volant creatures. Guidraco venator gen. et sp. nov. has an unusual upward-directed frontal crest and large rostral teeth, some of which surpass the margins of the skull and lower jaw when occluded. The new species is closely related to a rare taxon from the Brazilian Crato Formation, posing an interesting paleobiogeographic problem and supporting the hypothesis that at least some early Cretaceous pterosaur clades, such as the Tapejaridae and the Anhangueridae, might have originated in Asia. The association of the new specimen with coprolites and the cranial morphology suggest that G. venator preyed on fish.

  17. A new specimen of Manchurochelys manchoukuoensis from the Early Cretaceous Jehol Biota of Chifeng, Inner Mongolia, China and the phylogeny of Cretaceous basal eucryptodiran turtles

    PubMed Central

    2014-01-01

    Background Manchurochelys manchoukuoensis is an emblematic turtle from the Cretaceous Yixian Formation of Liaoning, China, a geological rock unit that is famous for yielding perfectly preserved skeletons of fossil vertebrates, including that of feathered dinosaurs. Manchurochelys manchoukuoensis was one of the first vertebrates described from this fauna, also known as the Jehol Biota. The holotype was lost during World War II and only one additional specimen has been described since. Manchurochelys manchoukuoensis is a critical taxon for unraveling the phylogenetic relationships of Cretaceous pancryptodires from Asia, a group that is considered to be of key importance for the origin of crown-group hidden-neck turtles (Cryptodira). Results A new specimen of Manchurochelys manchoukuoensis is described here from the Jiufotang Formation of Qilinshan, Chifeng, Inner Mongolia, China. This is the third specimen described and expands the range of this taxon from the Yixian Formation of the Fuxin-Yixian Basin in Liaoning to the Jiufotang Formation of the Chifeng-Yuanbaoshan Basin. A possible temporal extension of the range is less certain. The new finding adds to our understanding of the morphology of this taxon and invites a thorough revision of the phylogeny of Macrobaenidae, Sinemydidae, and closely allied forms. Conclusions Our comprehensive phylogenetic analyses of Cretaceous Asian pancryptodires yielded two main competing hypotheses: in the first these taxa form a paraphyletic grade, whereas in the second they form a monophyletic clade. The inclusion of problematic tree changing taxa, such as Panpleurodires (stem + crown side-neck turtles) has a major influence on the phylogenetic relationships of Sinemydidae and closely allied forms. Manchurochelys manchoukuoensis nests within Sinemydidae together with Sinemys spp. and Dracochelys bicuspis in the majority of our analyses. PMID:24707892

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

    NASA Astrophysics Data System (ADS)

    Ogg, J. G.

    2007-12-01

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

  19. Identification of saline water intrusion in part of Cauvery deltaic region, Tamil Nadu, Southern India: using GIS and VES methods

    NASA Astrophysics Data System (ADS)

    Gnanachandrasamy, G.; Ramkumar, T.; Venkatramanan, S.; Chung, S. Y.; Vasudevan, S.

    2016-06-01

    We use electrical resistivity data arrayed in a 2715 km2 region with 30 locations to identify the saline water intrusion zone in part of Cauvery deltaic region, offshore Eastern India. From this dataset we are able to derive information on groundwater quality, thickness of aquifer zone, structural and stratigraphic conditions relevant to groundwater conditions, and permeability of aquifer systems. A total of 30 vertical electrode soundings (VES) were carried out by Schlumberger electrode arrangement to indicate complete lithology of this region using curve matching techniques. The electrical soundings exhibited that H and HK type curves were suitable for 16 shallow locations, and QH, KQ, K, KH, QQ, and HA curves were fit for other location. Low resistivity values suggested that saline water intrusion occurred in this region. According to final GIS map, most of the region was severely affected by seawater intrusion due to the use of over-exploitation of groundwater.The deteriorated groundwater resources in this coastal region should raise environmental and health concerns.

  20. Biotic and environmental dynamics through the Late Jurassic-Early Cretaceous transition: evidence for protracted faunal and ecological turnover.

    PubMed

    Tennant, Jonathan P; Mannion, Philip D; Upchurch, Paul; Sutton, Mark D; Price, Gregory D

    2017-05-01

    The Late Jurassic to Early Cretaceous interval represents a time of environmental upheaval and cataclysmic events, combined with disruptions to terrestrial and marine ecosystems. Historically, the Jurassic/Cretaceous (J/K) boundary was classified as one of eight mass extinctions. However, more recent research has largely overturned this view, revealing a much more complex pattern of biotic and abiotic dynamics than has previously been appreciated. Here, we present a synthesis of our current knowledge of Late Jurassic-Early Cretaceous events, focusing particularly on events closest to the J/K boundary. We find evidence for a combination of short-term catastrophic events, large-scale tectonic processes and environmental perturbations, and major clade interactions that led to a seemingly dramatic faunal and ecological turnover in both the marine and terrestrial realms. This is coupled with a great reduction in global biodiversity which might in part be explained by poor sampling. Very few groups appear to have been entirely resilient to this J/K boundary 'event', which hints at a 'cascade model' of ecosystem changes driving faunal dynamics. Within terrestrial ecosystems, larger, more-specialised organisms, such as saurischian dinosaurs, appear to have suffered the most. Medium-sized tetanuran theropods declined, and were replaced by larger-bodied groups, and basal eusauropods were replaced by neosauropod faunas. The ascent of paravian theropods is emphasised by escalated competition with contemporary pterosaur groups, culminating in the explosive radiation of birds, although the timing of this is obfuscated by biases in sampling. Smaller, more ecologically diverse terrestrial non-archosaurs, such as lissamphibians and mammaliaforms, were comparatively resilient to extinctions, instead documenting the origination of many extant groups around the J/K boundary. In the marine realm, extinctions were focused on low-latitude, shallow marine shelf-dwelling faunas

  1. Structural anatomy of a dismembered ophiolite suite from Gondwana: The Manamedu complex, Cauvery suture zone, southern India

    NASA Astrophysics Data System (ADS)

    Chetty, T. R. K.; Yellappa, T.; Nagesh, P.; Mohanty, D. P.; Venkatasivappa, V.; Santosh, M.; Tsunogae, T.

    2011-08-01

    Detailed geological and structural mapping of the Manamedu ophiolite complex (MOC), from the south-eastern part of the Cauvery suture zone (CSZ) within the Gondwana collisional suture in southern India reveals the anatomy of a dismembered ophiolite succession comprising pyroxenite actinolite-hornblendite, hornblendite, gabbro-norite, gabbro, anorthosite, amphibolite, plagiogranite, mafic dykes, and associated pelagic sediments such as chert-magnetite bands and carbonate horizons. The magmatic foliation trajectory map shows inward dipping foliations and a variety of fold structures. Structural cross-sections of the MOC reveal gentle inward dips with repetition and omission of different lithologies often marked by curvilinear hinge lines. The succession displays imbricate thrust sheets and slices of dismembered ophiolite suites distributed along several localities within the CSZ. The MOC can be interpreted as a deformed large duplex structure associated with south-verging back thrust system, consistent with crustal-scale 'flower structure'. The nature and distribution of ophiolitic rocks in the CSZ suggest supra-subduction zone setting associated with the lithospheric subduction of the Neoproterozoic Mozambique Ocean, followed by collision and obduction during the final stage of amalgamation of the Gondwana supercontinent in the end Precambrian.

  2. Modelling the interactions between vegetation and climate from the Cretaceous to the Eocene

    NASA Astrophysics Data System (ADS)

    Loptson, Claire; Lunt, Dan; Francis, Jane

    2013-04-01

    The climates during the Cretaceous (~144 to 66 Ma) and the early Eocene (~56 to 48 Ma) were much warmer than the present day. Atmospheric CO2 levels for these past climates have a large uncertainty associated with them, but were possibly as high as 2000 to 3000 ppm for the early Eocene (Beerling and Royer, 2011; Lowenstein and Demicco, 2006) and maximum values are thought to range from 800 to 1800 ppm during the Cretaceous (Royer et al., 2012). Current modelling efforts have had great difficulty in replicating the shallow latitudinal temperature gradient indicated by proxy data for these time periods (e.g. Heinemann et al., 2009; Winguth et al., 2010; Shellito et al., 2009). Mechanisms that can result in such a low temperature gradient have not been found (Winguth et al., 2010; Beerling et al., 2011; Sloan and Morrill, 1998), but a contributing factor could be that not all climate feedbacks are included in these models. Vegetation feedbacks have been shown to be especially important (e.g. Otto-Bliesner and Upchurch, 1997; Bonan, 2008) so by including a more accurate representation of vegetation in the climate model, the model-data discrepancies may be reduced. A fully coupled atmosphere-ocean GCM, HadCM3L, coupled to a dynamic global vegetation model (TRIFFID), was used to simulate the climate and the predicted vegetation distributions for and the early Eocene and 12 different time slices representing different ages throughout the Cretaceous at 4x pre-industrial CO2. The only difference in the way these simulations were set up are different boundary conditions that are specific to that time period, e.g. different solar constants and paleogeographies. This allows a direct comparison between the time slices. We present the changes in climate, and therefore vegetation, during the Cretaceous due to changes in these boundary conditions alone, with a focus on Antarctica. Additional Eocene simulations were also carried out with a) fixed globally-uniform vegetation and b

  3. Mid-Cretaceous aeolian desert systems in the Yunlong area of the Lanping Basin, China: Implications for palaeoatmosphere dynamics and paleoclimatic change in East Asia

    NASA Astrophysics Data System (ADS)

    Li, Gaojie; Wu, Chihua; Rodríguez-López, Juan Pedro; Yi, Haisheng; Xia, Guoqing; Wagreich, Michael

    2018-02-01

    The mid-Cretaceous constitutes a period of worldwide atmospheric and oceanic change associated with slower thermohaline circulation and ocean anoxic events, possible polar glaciations and by a changing climate pattern becoming controlled by a zonal planetary wind system and an equatorial humid belt. During the mid-Cretaceous, the subtropical high-pressure arid climate belt of the planetary wind system controlled the palaeolatitude distribution of humid belts in Asia as well as the spatial distribution of rain belts over the massive continental blocks at mid-low latitudes in the southern and northern hemispheres. Additionally, the orographic effect of the Andean-type active continental margin in East Asia hindered the transportation of ocean moisture to inland regions. With rising temperatures and palaeoatmospheric conditions dominated by high pressure systems, desert climate environments expanded at the inland areas of East Asia including those accumulated in the mid-Cretaceous of the Simao Basin, the Sichuan Basin, and the Thailand's Khorat Basin, and leading the Late Cretaceous erg systems in the Xinjiang Basin and Jianghan Basin. This manuscript presents evidences that allow to reinterpret previously considered water-laid sediments to be accumulated as windblown deposits forming part of extensive erg (sandy desert) systems. Using a multidisciplinary approach including petrological, sedimentological and architectural observations, the mid-Cretaceous (Albian-Turonian) Nanxin Formation from the Yunlong region of Lanping Basin, formerly considered to aqueous deposits is here interpreted as representing aeolian deposits, showing local aeolian-fluvial interaction deposits. The palaeowind directions obtained from the analysis of aeolian dune cross-beddings indicates that inland deserts were compatible with a high-pressure cell (HPC) existing in the mid-low latitudes of East Asia during the mid-Cretaceous. Compared with the Early Cretaceous, the mid-Cretaceous had

  4. Evidence for high salinity of Early Cretaceous sea water from the Chesapeake Bay crater

    USGS Publications Warehouse

    Sanford, Ward E.; Doughten, Michael W.; Coplen, Tyler B.; Hunt, Andrew G.; Bullen, Thomas D.

    2013-01-01

    High salinity groundwater more than 1000 metres deep in the Atlantic Coastal Plain of the United States has been documented in several locations1,2, most recently within the 35 million-year-old Chesapeake Bay impact crater3,4,5. Suggestions for the origin of increased salinity in the crater have included evaporite dissolution6, osmosis6, and evaporation from heating7 associated with the bolide impact. Here we present chemical, isotopic and physical evidence that together indicate that groundwater in the Chesapeake crater is remnant Early Cretaceous North Atlantic (ECNA) seawater. We find that the seawater is likely 100-145 million years old and that it has an average salinity of about 70 per mil, which is twice that of modern seawater and consistent with the nearly closed ECNA basin8. Previous evidence for temperature and salinity levels of ancient oceans have been estimated indirectly from geochemical, isotopic and paleontological analyses of solid materials in deep sediment cores. In contrast, our study identifies ancient seawater in situ and provides a direct estimate of its age and salinity. Moreover, we suggest that it is likely that remnants of ECNA seawater persist in deep sediments at many locations along the Atlantic margin.

  5. Cretaceous plutonic rocks in the Donner Lake-Cisco Grove area, northern Sierra Nevada, California

    USGS Publications Warehouse

    Kulow, Matthew J.; Hanson, Richard E.; Girty, Gary H.; Girty, Melissa S.; Harwood, David S.

    1998-01-01

    The northernmost occurrences of extensive, glaciated exposures of the Sierra Nevada batholith occur in the Donner Lake-Cisco Grove area of the northern Sierra Nevada. The plutonic rocks in this area, which are termed here the Castle Valley plutonic assemblage, crop out over an area of 225 km2 and for the most part are shown as a single undifferentiated mass on previously published geological maps. In the present work, the plutonic assemblage is divided into eight separate intrusive units or lithodemes, two of which each consist of two separate plutons. Compositions are dominantly granodiorite and tonalite, but diorite and granite form small plutons in places. Spectacular examples of comb layering and orbicular texture occur in the diorites. U-Pb zircon ages have been obtained for all but one of the main units and range from ~120 to 114 Ma, indicating that the entire assemblage was emplaced in a narrow time frame in the Early Cretaceous. This is consistent with abundant field evidence that many of the individual phases were intruded penecontemporaneously. The timing of emplacement correlates with onset of major Cretaceous plutonism in the main part of the Sierra Nevada batholith farther south. The emplacement ages also are similar to isotopic ages for gold-quartz mineralization in the Sierran foothills west of the study area, suggesting a direct genetic relationship between the voluminous Early Cretaceous plutonism and hydrothermal gold mineralization.

  6. Total petroleum systems of the Bonaparte Gulf Basin area, Australia; Jurassic, Early Cretaceous-Mesozoic; Keyling, Hyland Bay-Permian; Milligans-Carboniferous, Permian

    USGS Publications Warehouse

    Bishop, M.G.

    1999-01-01

    The Bonaparte Gulf Basin Province (USGS #3910) of northern Australia contains three important hydrocarbon source-rock intervals. The oldest source-rock interval and associated reservoir rocks is the Milligans-Carboniferous, Permian petroleum system. This petroleum system is located at the southern end of Joseph Bonaparte Gulf and includes both onshore and offshore areas within a northwest to southeast trending Paleozoic rift that was initiated in the Devonian. The Milligans Formation is a Carboniferous marine shale that sources accumulations of both oil and gas in Carboniferous and Permian deltaic, marine shelf carbonate, and shallow to deep marine sandstones. The second petroleum system in the Paleozoic rift is the Keyling, Hyland Bay-Permian. Source rocks include Lower Permian Keyling Formation delta-plain coals and marginal marine shales combined with Upper Permian Hyland Bay Formation prodelta shales. These source-rock intervals provide gas and condensate for fluvial, deltaic, and shallow marine sandstone reservoirs primarily within several members of the Hyland Bay Formation. The Keyling, Hyland Bay-Permian petroleum system is located in the Joseph Bonaparte Gulf, north of the Milligans-Carboniferous, Permian petroleum system, and may extend northwest under the Vulcan graben sub-basin. The third and youngest petroleum system is the Jurassic, Early Cretaceous-Mesozoic system that is located seaward of Joseph Bonaparte Gulf on the Australian continental shelf, and trends southwest-northeast. Source-rock intervals in the Vulcan graben sub-basin include deltaic mudstones of the Middle Jurassic Plover Formation and organic-rich marine shales of the Upper Jurassic Vulcan Formation and Lower Cretaceous Echuca Shoals Formation. These intervals produce gas, oil, and condensate that accumulates in, shallow- to deep-marine sandstone reservoirs of the Challis and Vulcan Formations of Jurassic to Cretaceous age. Organic-rich, marginal marine claystones and coals of the

  7. Provenance of a large Lower Cretaceous turbidite submarine fan complex on the active Laurasian margin: Central Pontides, northern Turkey

    NASA Astrophysics Data System (ADS)

    Akdoğan, Remziye; Okay, Aral I.; Sunal, Gürsel; Tari, Gabor; Meinhold, Guido; Kylander-Clark, Andrew R. C.

    2017-02-01

    The Pontides formed the southern active margin of Laurasia during the Mesozoic. They became separated from mainland Laurasia during the Late Cretaceous, with the opening of the Black Sea as an oceanic back-arc basin. During the Early Cretaceous, a large submarine turbidite fan complex developed in the Central Pontides. The turbidites cover an area of 400 km by 90 km with a thickness of more than 2 km. We have investigated the provenance of these turbidites-the Çağlayan Formation-using paleocurrent measurements, U-Pb detrital zircon ages, REE abundances of dated zircons and geochemistry of detrital rutile grains. 1924 paleocurrent measurements from 96 outcrop stations indicate flow direction from northwest to southeast in the eastern part of the Çağlayan Basin and from north-northeast to west-southwest in the western part. 1194 detrital zircon ages from 13 Lower Cretaceous sandstone samples show different patterns in the eastern, central and western parts of the basin. The majority of the U-Pb detrital zircon ages in the eastern part of the basin are Archean and Paleoproterozoic (61% of all zircon ages, 337 grains); rocks of these ages are absent in the Pontides and present in the Ukrainian Shield, which indicates a source north of the Black Sea. In the western part of the basin the majority of the zircons are Carboniferous and Neoproterozoic (68%, 246 grains) implying more local sources within the Pontides. The detrital zircons from the central part show an age spectrum as mixture of zircons from western and eastern parts. Significantly, Jurassic and Early Cretaceous zircons make up less than 2% of the total zircon population, which implies lack of a coeval magmatic arc in the region. This is compatible with the absence of the Lower Cretaceous granites in the Pontides. Thus, although the Çağlayan Basin occupied a fore-arc position above the subduction zone, the arc was missing, probably due to flat subduction, and the basin was largely fed from the Ukrainian

  8. Marine vs. local control on seawater Nd-isotope ratios at the northwest coast of Africa during the late Cretaceous-early Eocene

    NASA Astrophysics Data System (ADS)

    Kocsis, L.; Gheerbrant, E.; Mouflih, M.; Cappetta, H.; Ulianov, A.; Chiaradia, M.

    2013-12-01

    At the northwest corner of Africa excellent conditions existed for phosphate formation (i.e., stable upwelling system) during the late Cretaceous-early Eocene. This is probably in relation to stable tectonic evolution of shallow epicontinental basins at a passive continental margin and to their paleogeographic situation between the Atlantic and Tethys marine realms. To better comprehend paleoceanic conditions in this area, radiogenic isotope ratios (87Sr/86Sr and 143Nd/144Nd) and trace element compositions of fossil biogenic apatite are investigated from Maastrichtian to Ypresian shallow marine phosphorite deposits in Morocco (Ouled Abdoun and Ganntour Basins). Rare earth elements (REE) distributions in the fossils are compatible with early diagenetic marine pore fluid represented by negative Ce-anomaly and heavy REE enrichment. An overall shift in Ce-anomaly is apparent with gradually lower values in younger fossils along three distinct assemblages that correspond to Maastrichtian, Danian-Thanetian and Ypresian periods. The temporal change can be interpreted as presence of gradually more oxygenated seawater in the basins. Strontium isotopic ratios of the fossils follow the global Sr-evolution curve. However, the latest Cretaceous and the oldest Paleocene fossils yielded slightly higher ratios than the global ocean, which could reflect minor diagenetic alteration. Neodymium isotopic ratios are quite even along the phosphate series with ɛNd(t) values ranges from -6.8 to -5.8. These values are higher than those reported for average North Atlantic deep water and Tethyan seawater (e.g., Stille et al., 1996; Thomas et al., 2003). For the origin of the stable, high 143Nd/144Nd we propose three main hypotheses: (1) contribution of continental Nd-source, (2) locally controlled deep water Nd-isotope ratios near the coast from where upwelling originated in the area and (3) possible surface marine water contribution from the Pacific across the Atlantic. Stille, P., Steinmann

  9. An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils

    PubMed Central

    Beerling, D. J.; Lomax, B. H.; Royer, D. L.; Upchurch, G. R.; Kump, L. R.

    2002-01-01

    The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining the relative importance of each event as a driver of environmental and biotic change across the Cretaceous-Tertiary boundary (KTB) crucially depends on constraining the mass of CO2 injected into the atmospheric carbon reservoir. Using the inverse relationship between atmospheric CO2 and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO2 concentration (pCO2) levels with special emphasis on providing a pCO2 estimate directly above the KTB. Our record shows stable Late Cretaceous/Early Tertiary background pCO2 levels of 350–500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB. Numerical simulations with a global biogeochemical carbon cycle model indicate that CO2 outgassing during the eruption of the Deccan Trap basalts fails to fully account for the inferred pCO2 increase. Instead, we calculate that the postboundary pCO2 rise is most consistent with the instantaneous transfer of ≈4,600 Gt C from the lithic to the atmospheric reservoir by a large extraterrestrial bolide impact. A resultant climatic forcing of +12 W⋅m−2 would have been sufficient to warm the Earth's surface by ≈7.5°C, in the absence of counter forcing by sulfate aerosols. This finding reinforces previous evidence for major climatic warming after the KTB impact and implies that severe and abrupt global warming during the earliest Paleocene was an important factor in biotic extinction at the KTB. PMID:12060729

  10. Geologic models and evaluation of undiscovered conventional and continuous oil and gas resources: Upper Cretaceous Austin Chalk

    USGS Publications Warehouse

    Pearson, Krystal

    2012-01-01

    The Upper Cretaceous Austin Chalk forms a low-permeability, onshore Gulf of Mexico reservoir that produces oil and gas from major fractures oriented parallel to the underlying Lower Cretaceous shelf edge. Horizontal drilling links these fracture systems to create an interconnected network that drains the reservoir. Field and well locations along the production trend are controlled by fracture networks. Highly fractured chalk is present along both regional and local fault zones. Fractures are also genetically linked to movement of the underlying Jurassic Louann Salt with tensile fractures forming downdip of salt-related structures creating the most effective reservoirs. Undiscovered accumulations should also be associated with structure-controlled fracture systems because much of the Austin that overlies the Lower Cretaceous shelf edge remains unexplored. The Upper Cretaceous Eagle Ford Shale is the primary source rock for Austin Chalk hydrocarbons. This transgressive marine shale varies in thickness and lithology across the study area and contains both oil- and gas-prone kerogen. The Eagle Ford began generating oil and gas in the early Miocene, and vertical migration through fractures was sufficient to charge the Austin reservoirs.

  11. Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago

    PubMed Central

    Csiki-Sava, Zoltán; Buffetaut, Eric; Ősi, Attila; Pereda-Suberbiola, Xabier; Brusatte, Stephen L.

    2015-01-01

    Abstract The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We review the terrestrial Late Cretaceous record from Europe and discuss its importance for understanding the paleogeography, ecology, evolution, and extinction of land-dwelling vertebrates. We review the major Late Cretaceous faunas from Austria, Hungary, France, Spain, Portugal, and Romania, as well as more fragmentary records from elsewhere in Europe. We discuss the paleogeographic background and history of assembly of these faunas, and argue that they are comprised of an endemic ‘core’ supplemented with various immigration waves. These faunas lived on an island archipelago, and we describe how this insular setting led to ecological peculiarities such as low diversity, a preponderance of primitive taxa, and marked changes in morphology (particularly body size dwarfing). We conclude by discussing the importance of the European record in understanding the end-Cretaceous extinction and show that there is no clear evidence that dinosaurs or other groups were undergoing long-term declines in Europe prior to the bolide impact. PMID:25610343

  12. Polychronous (Early Cretaceous to Palaeogene) emplacement of the Mundwara alkaline complex, Rajasthan, India: 40Ar/39Ar geochronology, petrochemistry and geodynamics

    NASA Astrophysics Data System (ADS)

    Pande, Kanchan; Cucciniello, Ciro; Sheth, Hetu; Vijayan, Anjali; Sharma, Kamal Kant; Purohit, Ritesh; Jagadeesan, K. C.; Shinde, Sapna

    2017-07-01

    The Mundwara alkaline plutonic complex (Rajasthan, north-western India) is considered a part of the Late Cretaceous-Palaeogene Deccan Traps flood basalt province, based on geochronological data (mainly 40Ar/39Ar, on whole rocks, biotite and hornblende). We have studied the petrology and mineral chemistry of some Mundwara mafic rocks containing mica and amphibole. Geothermobarometry indicates emplacement of the complex at middle to upper crustal levels. We have obtained new 40Ar/39Ar ages of 80-84 Ma on biotite separates from mafic rocks and 102-110 Ma on whole-rock nepheline syenites. There is no evidence for excess 40Ar. The combined results show that some of the constituent intrusions of the Mundwara complex are of Deccan age, but others are older and unrelated to the Deccan Traps. The Mundwara alkaline complex is thus polychronous and similar to many alkaline complexes around the world that show recurrent magmatism, sometimes over hundreds of millions of years. The primary biotite and amphibole in Mundwara mafic rocks indicate hydrous parental magmas, derived from hydrated mantle peridotite at relatively low temperatures, thus ruling out a mantle plume. This hydration and metasomatism of the Rajasthan lithospheric mantle may have occurred during Jurassic subduction under Gondwanaland, or Precambrian subduction events. Low-degree decompression melting of this old, enriched lithospheric mantle, due to periodic diffuse lithospheric extension, gradually built the Mundwara complex from the Early Cretaceous to Palaeogene time.

  13. Possible detachment zone in Precambrian rocks of Kanjamalai Hills, Cauvery Suture Zone, Southern India: Implications to accretionary tectonics

    NASA Astrophysics Data System (ADS)

    Mohanty, D. P.; Chetty, T. R. K.

    2014-07-01

    Existence of a possible detachment zone at Elampillai region, NW margin of Kanjamalai Hills, located in the northern part of Cauvery Suture Zone (CSZ), Southern India, is reported here for the first time. Detailed structural mapping provides anatomy of the zone, which are rarely preserved in Precambrian high grade terranes. The detachment surface separates two distinct rock units of contrasting lithological and structural characters: the upper and lower units. The detachment zone is characterized by a variety of fold styles with the predominance of tight isoclinal folds with varied plunge directions, limb rotations and the hinge line variations often leading to lift-off fold like geometries and deformed sheath folds. Presence of parasitic folding and associated penetrative strains seem to be controlled by differences in mechanical stratigraphy, relative thicknesses of the competent and incompetent units, and the structural relief of the underlying basement. Our present study in conjunction with other available geological, geochemical and geochronological data from the region indicates that the structures of the detachment zone are genetically related to thrust tectonics forming a part of subduction-accretion-collision tectonic history of the Neoproterozoic Gondwana suture.

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

    PubMed

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

    2015-01-27

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

  15. Major transgression during Late Cretaceous constrained by basin sediments in northern Africa: implication for global rise in sea level

    NASA Astrophysics Data System (ADS)

    An, Kaixuan; Chen, Hanlin; Lin, Xiubin; Wang, Fang; Yang, Shufeng; Wen, Zhixin; Wang, Zhaoming; Zhang, Guangya; Tong, Xiaoguang

    2017-12-01

    The global rise in sea level during the Late Cretaceous has been an issue under discussion by the international geological community. Despite the significance, its impact on the deposition of continental basins is not well known. This paper presents the systematic review on stratigraphy and sedimentary facies compiled from 22 continental basins in northern Africa. The results indicate that the region was dominated by sediments of continental facies during Early Cretaceous, which were replaced by deposits of marine facies in Late Cretaceous. The spatio-temporal distribution of sedimentary facies suggests marine facies deposition reached as far south as Taoudeni-Iullemmeden-Chad-Al Kufra-Upper Egypt basins during Turonian to Campanian. These results indicate that northern Africa underwent significant transgression during Late Cretaceous reaching its peak during Turonian to Coniacian. This significant transgression has been attributed to the global high sea-level during this time. Previous studies show that global rise in sea level in Late Cretaceous may have been driven by an increase in the volume of ocean water (attributed to high CO2 concentration and subsequently warm climate) and a decrease in the volume of the ocean basin (attributed to rapid production of oceanic crust and seamounts). Tectonic mechanism of rapid production of oceanic crust and seamounts could play a fundamental role in driving the global rise in sea level and subsequent transgression in northern Africa during Late Cretaceous.

  16. Glendonites as a paleoenvironmental tool: Implications for early Cretaceous high latitudinal climates in Australia

    NASA Astrophysics Data System (ADS)

    De Lurio, Jennifer L.; Frakes, L. A.

    1999-04-01

    Glendonites, calcite pseudomorphs after the metastable mineral ikaite (CaCO 3 · 6H 2O), occur in the Late Aptian interval of the Bulldog Shale in the Eromanga Basin, Australia and in other Early Cretaceous basins at high paleolatitudes. Ikaite precipitation in the marine environment requires near-freezing temperatures (not higher than 4°C), high alkalinity, increased levels of orthophosphate, and high P CO2. The rapid and complete transformation of ikaite to calcite at temperatures between 5 and 8°C provides an upper limit on the oxygen isotopic composition of the pore waters: -2.6 <δ w <-3.4‰SMOW. If it is assumed that these pore waters are representative of the shallow Eromanga Basin, the calculated δ w can be used to reassess belemnite fossil oxygen isotopic paleotemperatures - temperature recorded by fauna living in the basin at the time of ikaite precipitation. Data previously reported as 11 to 16°C (assuming δ w = 0.0‰SMOW) yield paleotemperatures ranging from -1 to 5°C, squarely in the range of ikaite stability. The low δ w indicates hyposaline conditions, most likely caused by mixing high latitude meteoric waters with seawater. The 18O depleted, low temperature waters suggest that the region was at least seasonally colder than previously accepted.

  17. A new basal titanosaur (Dinosauria, Sauropoda) from the Lower Cretaceous of Brazil

    NASA Astrophysics Data System (ADS)

    Carvalho, Ismar de Souza; Salgado, Leonardo; Lindoso, Rafael Matos; Araújo-Júnior, Hermínio Ismael de; Nogueira, Francisco Cézar Costa; Soares, José Agnelo

    2017-04-01

    Although dinosaurian ichnofaunas are common in the Northeastern Brazilian Interior Basins, osteological remains are poorly represented in these areas. One of the main challenges in vertebrate paleontology in the Lower Cretaceous of this region is to recognize body-fossils, which can unveil the anatomy, functional morphology and paleoecological aspects of the dinosaurian fauna recorded until now only by footprints and trackways. The discovery of a new dinosaur specimen in the Rio Piranhas Formation of the Triunfo Basin opens new perspectives into the comprehension of paleogeographical and temporal distribution of the titanosaur sauropods. Titanosaurs are common in Upper Cretaceous rocks of Brazil and Argentina. The age of the Rio Piranhas Formation is considered to range from Berriasian to early Hauterivian. Thus, the description of this new species opens new viewpoints concerning the paleobiogeographical aspects of these sauropod dinosaurs.

  18. Debris-carrying camouflage among diverse lineages of Cretaceous insects.

    PubMed

    Wang, Bo; Xia, Fangyuan; Engel, Michael S; Perrichot, Vincent; Shi, Gongle; Zhang, Haichun; Chen, Jun; Jarzembowski, Edmund A; Wappler, Torsten; Rust, Jes

    2016-06-01

    Insects have evolved diverse methods of camouflage that have played an important role in their evolutionary success. Debris-carrying, a behavior of actively harvesting and carrying exogenous materials, is among the most fascinating and complex behaviors because it requires not only an ability to recognize, collect, and carry materials but also evolutionary adaptations in related morphological characteristics. However, the fossil record of such behavior is extremely scarce, and only a single Mesozoic example from Spanish amber has been recorded; therefore, little is known about the early evolution of this complicated behavior and its underlying anatomy. We report a diverse insect assemblage of exceptionally preserved debris carriers from Cretaceous Burmese, French, and Lebanese ambers, including the earliest known chrysopoid larvae (green lacewings), myrmeleontoid larvae (split-footed lacewings and owlflies), and reduviids (assassin bugs). These ancient insects used a variety of debris material, including insect exoskeletons, sand grains, soil dust, leaf trichomes of gleicheniacean ferns, wood fibers, and other vegetal debris. They convergently evolved their debris-carrying behavior through multiple pathways, which expressed a high degree of evolutionary plasticity. We demonstrate that the behavioral repertoire, which is associated with considerable morphological adaptations, was already widespread among insects by at least the Mid-Cretaceous. Together with the previously known Spanish specimen, these fossils are the oldest direct evidence of camouflaging behavior in the fossil record. Our findings provide a novel insight into early evolution of camouflage in insects and ancient ecological associations among plants and insects.

  19. Hughmillerites vancouverensis sp. nov. and the Cretaceous diversification of Cupressaceae.

    PubMed

    Atkinson, Brian A; Rothwell, Gar W; Stockey, Ruth A

    2014-12-01

    • Two ovulate conifer cones, one of which is attached terminally to a short leafy shoot, reveal the presence of a new species of Hughmillerites in the Early Cretaceous Apple Bay flora of Vancouver Island, British Columbia, Canada. This ancient conifer expands the diversity of Cupressaceae in the Mesozoic and reveals details about the evolution of Subfamily: Cunninghamioideae.• Specimens were studied from anatomical sections prepared using the cellulose acetate peel technique.• Vegetative shoots have helically arranged leaves that are Cunninghamia-like. Seed cones have many helically arranged bract/scale complexes in which the bract is larger than the ovuliferous scale. Each ovuliferous scale has three free tips that separate from the bract immediately distal to an inverted seed. Several ovuliferous scales show interseminal ridges between seeds.• This study documents a new extinct species of cunninghamioid conifers, Hughmillerites vancouverensis, expanding the record of the genus from the Late Jurassic to the Early Cretaceous. This new extinct species emphasizes the important role that conifers from subfamily Cunninghamioideae played in the initial evolutionary radiation of Cupressaceae. In light of recent findings in conifer regulatory genetics, we use H. vancouverensis to hypothesize that variations of expression in certain gene homologues played an important role in the evolution of the cupressaceous ovuliferous scale. © 2014 Botanical Society of America, Inc.

  20. New petrofacies in upper Cretaceous section of southern California

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Colburn, I.P.; Oliver, D.

    1986-04-01

    A distinctive sandstone-conglomerate petrofacies is recognized throughout the Late Cretaceous (Maestrichtian-late Campanian) Chatsworth Formation in the Simi Hills. It is named the Woolsey Canyon petrofacies after the district where it was first recognized. The petrofacies is also recognized in the Late Cretaceous (late Campanian and possibly early Maestrichtian) Tuna Canyon Formation of the central Santa Monica Mountains. The conglomerates in the petrofacies are composed predominantly of angular pebble-size clasts of argillite, quartz-rich rocks (orthoquartzarenite, metaorthoquartzarenite, mice quartz schist) and leucocratic plutoniate (granite-granodiorite). The conglomerate texture and composition are mirrored in the sandstone. The uniformly angular character of the conglomerate clastsmore » and the survival of argillite clasts indicate that the detritus underwent no more than 5 mi of subaerial transport before it entered the deep marine realm. Foraminifers collected from mudstones interbedded with the conglomerates indicate upper bathyal water depth at the site of deposition. A source terrane of low to moderate relief is indicated by the absence of cobbles and boulders. Bed forms, sedimentary structures, and textural features indicate the detritus moved north from its source terrane to be deposited by turbidity currents, debris flows, and grain flows on the Chatsworth Submarine Fan. The detritus of the Woolsey Canyon petrofacies was derived from basement rocks, now largely buried beneath the Los Angeles basin, that were being eroded during the formation of the Cretaceous Los Angeles erosion surface. The detritus came from the Los Angeles arch of that surface.« less

  1. The mafic-ultramafic complex of Aniyapuram, Cauvery Suture Zone, southern India: Petrological and geochemical constraints for Neoarchean suprasubduction zone tectonics

    NASA Astrophysics Data System (ADS)

    Yellappa, T.; Venkatasivappa, V.; Koizumi, T.; Chetty, T. R. K.; Santosh, M.; Tsunogae, T.

    2014-12-01

    Several Precambrian mafic-ultramafic complexes occur along the Cauvery Suture Zone (CSZ) in Southern Granulite Terrain, India. Their origin, magmatic evolution and relationship with the associated high-grade rocks have not been resolved. The Aniyapuram Mafic-Ultramafic Complex (AMUC), the focus of the present study in southern part of the CSZ, is dominantly composed of peridotites, pyroxenites, gabbros, metagabbros/mafic granulites, hornblendites, amphibolites, plagiogranites, felsic granulites and ferruginous cherts. The rock types in the AMUC are structurally emplaced within hornblende gneiss (TTG) basement rocks and are highly deformed. The geochemical signature of the amphibolites indicates tholeiitic affinity for the protolith with magma generation in island arc-setting. N-MORB normalized pattern of the amphibolites show depletion in HFS-elements (P, Zr, Sm, Ti, and Y) and enrichment of LIL-elements (Rb, Ba, Th, Sr) with negative Nb anomalies suggesting involvement of subduction component in the depleted mantle source and formation in a supra-subduction zone tectonic setting. Our new results when correlated with the available age data suggest that the lithological association of AMUC represent the remnants of the Neoarchean oceanic lithosphere.

  2. The eastern Black Sea-Caucasus region during the Cretaceous: New evidence to constrain its tectonic evolution

    NASA Astrophysics Data System (ADS)

    Sosson, Marc; Stephenson, Randell; Sheremet, Yevgeniya; Rolland, Yann; Adamia, Shota; Melkonian, Rafael; Kangarli, Talat; Yegorova, Tamara; Avagyan, Ara; Galoyan, Ghazar; Danelian, Taniel; Hässig, Marc; Meijers, Maud; Müller, Carla; Sahakyan, Lilit; Sadradze, Nino; Alania, Victor; Enukidze, Onice; Mosar, Jon

    2016-01-01

    We report new observations in the eastern Black Sea-Caucasus region that allow reconstructing the evolution of the Neotethys in the Cretaceous. At that time, the Neotethys oceanic plate was subducting northward below the continental Eurasia plate. Based on the analysis of the obducted ophiolites that crop out throughout Lesser Caucasus and East Anatolides, we show that a spreading center (AESA basin) existed within the Neotethys, between Middle Jurassic and Early Cretaceous. Later, the spreading center was carried into the subduction with the Neotethys plate. We argue that the subduction of the spreading center opened a slab window that allowed asthenospheric material to move upward, in effect thermally and mechanically weakening the otherwise strong Eurasia upper plate. The local weakness zone favored the opening of the Black Sea back-arc basins. Later, in the Late Cretaceous, the AESA basin obducted onto the Taurides-Anatolides-South Armenia Microplate (TASAM), which then collided with Eurasia along a single suture zone (AESA suture).

  3. High geomagnetic intensity during the mid-Cretaceous from Thellier analyses of single plagioclase crystals.

    PubMed

    Tarduno, J A; Cottrell, R D; Smirnov, A V

    2001-03-02

    Recent numerical simulations have yielded the most efficient geodynamo, having the largest dipole intensity when reversal frequency is low. Reliable paleointensity data are limited but heretofore have suggested that reversal frequency and paleointensity are decoupled. We report data from 56 Thellier-Thellier experiments on plagioclase crystals separated from basalts of the Rajmahal Traps (113 to 116 million years old) of India that formed during the Cretaceous Normal Polarity Superchron. These data suggest a time-averaged paleomagnetic dipole moment of 12.5 +/- 1.4 x 10(22) amperes per square meter, three times greater than mean Cenozoic and Early Cretaceous-Late Jurassic dipole moments when geomagnetic reversals were frequent. This result supports a correlation between intervals of low reversal frequency and high geomagnetic field strength.

  4. Cretaceous Vertebrate Tracksites - Korean Cretaceous Dinosaur Coast World Heritage Nomination Site

    NASA Astrophysics Data System (ADS)

    Huh, M.; Woo, K. S.; Lim, J. D.; Paik, I. S.

    2009-04-01

    South Korea is one of the best known regions in the world for Cretaceous fossil footprints, which are also world-renowned. Korea has produced more scientifically named bird tracks (ichnotaxa) than any other region in the world. It has also produced the world's largest pterosaur tracks. Dinosaur tracksites also have the highest frequency of vertebrate track-bearing levels currently known in any stratigraphic sequence. Among the areas that have the best track records, and the greatest scientific significance with best documentation, Korea ranks very highly. Objective analysis of important individual tracksites and tracksite regions must be based on multiple criteria including: size of site, number of tracks, trackways and track bearing levels, number of valid named ichnotaxa including types, number of scientific publications, quality of preservation. The unique and distinctive dinosaur tracksites are known as one of the world's most important dinosaur track localities. In particular, the dinosaur track sites in southern coastal area of Korea are very unique. In the sites, we have excavated over 10,000 dinosaur tracks. The Hwasun sites show diverse gaits with unusual walking patterns and postures in some tracks. The pterosaur tracks are the most immense in the world. The longest pterosaur trackway yet known from any track sites suggests that pterosaurs were competent terrestrial locomotors. This ichnofauna contains the first pterosaur tracks reported from Asia. The Haenam Uhangri pterosaur assigns to a new genus Haenamichnus which accomodates the new ichnospecies, Haenamichnus uhangriensis. At least 12 track types have been reported from the Haman and Jindong Formations (probably late Lower Cretaceous). These include the types of bird tracks assigned to Koreanornis, Jindongornipes, Ignotornis and Goseongornipes. In addition the bird tracks Hwangsanipes, Uhangrichnus, the pterosaur track Haenamichnus and the dinosaur tracks, Brontopodus, Caririchnium, Minisauripus and

  5. Titanite-scale insights into multi-stage magma mixing in Early Cretaceous of NW Jiaodong terrane, North China Craton

    NASA Astrophysics Data System (ADS)

    Jiang, Peng; Yang, Kui-Feng; Fan, Hong-Rui; Liu, Xuan; Cai, Ya-Chun; Yang, Yue-Heng

    2016-08-01

    The Early Cretaceous Guojialing-type granodiorites in northwestern Jiaodong terrane carry significant records for strong mantle-crust interaction during the destruction of North China Craton (NCC); however, the definite petrogenetic mechanism and detailed magmatic process remain an enigma. Titanite in igneous rocks can serve as an effective petrogenetic indicator. Here, we present integrated geochronological and geochemical studies on titanites from Guojialing-type granodiorites and their dioritic enclaves to constrain their petrogenesis. Titanites from granodiorites (G-type) and plagioclase-rich dioritic enclaves (E-type-I) present an identical U-Pb age ( 130 Ma) and an indistinguishable wide range of Zr and total REEs contents, and Th/U ratios. However, these two types of titanites exhibit distinct micro-scale textures and geochemical compositions. G-type titanites are characterized by oscillatory zonings with two Light BSE zones (LBZ) and two or three dark BSE zones, whereas E-type-I titanites are marked by core-mantle-rim zonings. Drastic increase of LREEs, Zr, Hf, and Fe and decrease of Nb, Ta, Al, and F contents are observed in LBZ of G-type titanites, whereas remarkable reduction of LREEs, Zr, and Hf and elevation of F contents are observed from the cores to the mantles of E-type-I titanites. Based on Zr-in-titanite thermometry, G-type titanites are interpreted to have experienced twice notable temperature increase, while E-type-I titanites are inferred to have undergone a rapid cooling process. Furthermore, we suggest that the drastic chemical changes in G-type and E-type-I titanites are ascribed to early-stage magma mixing between a colder felsic magma and a Fe-, REE-rich hotter dioritic magma. Compared to G-type and E-type-I titanites, titanites from plagioclase-poor dioritic enclaves (E-type-II) are characterized by their occurrence in interstitial space and present a relatively younger U-Pb age ( 128 Ma) and much narrower and lower range of Zr, total

  6. Paleolatitudes of the Tibetan Himalaya from primary and secondary magnetizations of Jurassic to Lower Cretaceous sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Huang, Wentao; van Hinsbergen, Douwe J. J.; Dekkers, Mark J.; Garzanti, Eduardo; Dupont-Nivet, Guillaume; Lippert, Peter C.; Li, Xiaochun; Maffione, Marco; Langereis, Cor G.; Hu, Xiumian; Guo, Zhaojie; Kapp, Paul

    2015-01-01

    The Tibetan Himalaya represents the northernmost continental unit of the Indian plate that collided with Asia in the Cenozoic. Paleomagnetic studies on the Tibetan Himalaya can help constrain the dimension and paleogeography of "Greater India," the Indian plate lithosphere that subducted and underthrusted below Asia after initial collision. Here we present a paleomagnetic investigation of a Jurassic (limestones) and Lower Cretaceous (volcaniclastic sandstones) section of the Tibetan Himalaya. The limestones yielded positive fold test, showing a prefolding origin of the isolated remanent magnetizations. Detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic investigation reveal that the magnetic carrier of the Jurassic limestones is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic sandstones is detrital magnetite. Our observations lead us to conclude that the Jurassic limestones record a prefolding remagnetization, whereas the Lower Cretaceous volcaniclastic sandstones retain a primary remanence. The volcaniclastic sandstones yield an Early Cretaceous paleolatitude of 55.5°S [52.5°S, 58.6°S] for the Tibetan Himalaya, suggesting it was part of the Indian continent at that time. The size of "Greater India" during Jurassic time cannot be estimated from these limestones. Instead, a paleolatitude of the Tibetan Himalaya of 23.8°S [21.8°S, 26.1°S] during the remagnetization process is suggested. It is likely that the remagnetization, caused by the oxidation of early diagenetic pyrite to magnetite, was induced during 103-83 or 77-67 Ma. The inferred paleolatitudes at these two time intervals imply very different tectonic consequences for the Tibetan Himalaya.

  7. Chemical Remagnetization of Jurassic Carbonates and a Primary Paleolatitude of Lower Cretaceous Volcaniclastic Rocks of the Tibetan Himalaya

    NASA Astrophysics Data System (ADS)

    Huang, W.; Van Hinsbergen, D. J. J.; Dekkers, M. J.; Garzanti, E.; Dupont Nivet, G.; Lippert, P. C.; Li, X.; Maffione, M.; Langereis, C. G.; Hu, X.; Guo, Z.; Kapp, P. A.

    2014-12-01

    Paleolatitudes for the Tibetan Himalaya Zone based on paleomagnetic inclinations provide kinematic constraints of the passive northern Indian margin and the extent of 'Greater India' before the India-Asia collision. Here, we present a paleomagnetic investigation of the Jurassic (carbonates) to Lower Cretaceous (volcaniclastic rocks) Wölong section of the Tibetan Himalaya in the Everest region. The carbonates yield positive fold tests, suggesting that the remanent magnetizations have a pre-folding origin. However, detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic studies reveal that the magnetic carrier of the Jurassic carbonates is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic rocks is detrital magnetite. We conclude that the Jurassic carbonates were remagnetized, whereas the Lower Cretaceous volcaniclastics retain a primary remanence. We hypothesize that remagnetization of the Jurassic carbonates was probably caused by the oxidation of early diagenetic pyrite to magnetite within the time interval at ~86-84 Ma during the latest Cretaceous Normal Superchron and earliest deposition of Cretaceous oceanic red beds in the Tibetan Himalaya. The remagnetization of the limestones prevents determining the size of 'Greater India' during Jurassic time. Instead, a paleolatitude of the Tibetan Himalaya of 23.8±2.1° S at ~86-84 Ma is suggested. This value is lower than the expected paleolatitude of India from apparent polar wander path (APWP). The volcaniclastic rocks with the primary remanence, however, yielded a Lower Cretaceous paleolatitude of Tibetan Himalaya of 55.5±3° S, fitting well with the APWP of India.

  8. Climate change and carbon-cycling during the latest Cretaceous-Early Paleogene; a new 13.5 million year-long, orbital-resolution, stable isotope record from the South Atlantic

    NASA Astrophysics Data System (ADS)

    Barnet, J.; Littler, K.; Kroon, D.; Leng, M. J.; Westerhold, T.; Roehl, U.; Zachos, J. C.

    2017-12-01

    The "greenhouse" world of the latest Cretaceous-Early Paleogene ( 70-34 Ma) was characterised by multi-million year variability in climate and the carbon-cycle. Throughout this interval the pervasive imprint of orbital-cyclicity, particularly eccentricity and precession, is visible in elemental and stable isotope data obtained from multiple deep-sea sites. Periodic "hyperthermal" events, occurring largely in-step with these orbital cycles, have proved particularly enigmatic, and may be the closest, albeit imperfect, analogues for anthropogenic climate change. This project utilises CaCO3-rich marine sediments recovered from ODP Site 1262 at a paleo-depth of 3600 m on the Walvis Ridge, South Atlantic, of late Maastrichtian-mid Paleocene age ( 67-60 Ma). We have derived high-resolution (2.5-4 kyr) carbon and oxygen isotope data from the epifaunal benthic foraminifera species Nuttallides truempyi. Combining the new record with the existing Late Paleocene-Early Eocene record generated from the same site by Littler et al. (2014), yields a single-site reference curve detailing 13.5 million years of orbital cyclicity in paleoclimate and carbon cycle from the latest Cretaceous to near the peak warmth of the Early Paleogene greenhouse. Spectral analysis of this new combined dataset allows us to identify long (405-kyr) eccentricity, short (100-kyr) eccentricity, and precession (19-23-kyr) as the principle forcing mechanisms governing pacing of the background climate and carbon-cycle during this time period, with a comparatively weak obliquity (41-kyr) signal. Cross-spectral analysis suggests that changes in climate lead the carbon cycle throughout most of the record, emphasising the role of the release of temperature-sensitive carbon stores as a positive feedback to an initial warming induced by changes in orbital configuration. The expression of comparatively understudied Early Paleocene events, including the Dan-C2 Event, Latest Danian Event, and Danian/Selandian Transition

  9. Isolated teeth of Anhangueria  (Pterosauria: Pterodactyloidea) from the Lower Cretaceous of Lightning Ridge, New South Wales, Australia

    PubMed Central

    Smith, Elizabeth T.; Bell, Phil R.

    2017-01-01

    The fossil record of Australian pterosaurs is sparse, consisting of only a small number of isolated and fragmentary remains from the Cretaceous of Queensland, Western Australia and Victoria. Here, we describe two isolated pterosaur teeth from the Lower Cretaceous (middle Albian) Griman Creek Formation at Lightning Ridge (New South Wales) and identify them as indeterminate members of the pterodactyloid clade Anhangueria. This represents the first formal description of pterosaur material from New South Wales. The presence of one or more anhanguerian pterosaurs at Lightning Ridge correlates with the presence of ‘ornithocheirid’ and Anhanguera-like pterosaurs from the contemporaneous Toolebuc Formation of central Queensland and the global distribution attained by ornithocheiroids during the Early Cretaceous. The morphology of the teeth and their presence in the estuarine- and lacustrine-influenced Griman Creek Formation is likely indicative of similar life habits of the tooth bearer to other members of Anhangueria. PMID:28480142

  10. Structural implications of an offset Early Cretaceous shoreline in northern California

    USGS Publications Warehouse

    Jones, D.L.; Irwin, W.P.

    1971-01-01

    Recognition of a nonmarine to marine transition in sedimentary rocks at Glade Creek and Big Bar in the southern Klamath Mountains permits reconstruction of the approximate position of a north-trending Early Cretaceous (Valanginian) shoreline. At the southern end of the Klamath Mountains, the shoreline is displaced 60 mi or more to the east by a west-northwest-trending fault zone. South of this fault zone the shoreline is buried at a much lower level beneath late Cenozoic rocks in the Great Valley. This large displacement probably is the result of differential movement along a system of left-lateral tear faults in the upper plate of the Coast Range thrust. The westward bulge of the Klamath arc also may have resulted from this faulting, as the amount and direction of the bulge is comparable with the displacement of the Valanginian shoreline.Basal clastic strata at both Glade Creek and Big Bar contain abundant fresh-water or brackish-water clams, many of which consist of unabraded paired valves. These are conformably overlain by Valanginian marine strata containing Buchia crassicollis solida.The position of the Valanginian shoreline beneath the Great Valley cannot be directly observed because it is buried by thick late Cenozoic deposits. However, its approximate westernmost limit must lie between the outcrop belt of marine strata on the west side of the valley and drill holes to basement on the east side, in which equivalent strata are absent.Franciscan rocks containing Valanginian fossils occur 10 mi southwest of Glade Creek, but these are deep-water marine eugeosynclinal rocks that were deposited far to the west of the shoreline. The deformation responsible for the displacement of the Valanginian shoreline and juxtaposition of the Franciscan rocks and Klamath Mountain basement rocks involved eastward under-thrusting of the Franciscan beneath the Coast Range thrust contemporaneous with differential movement along tear faults within the upper plate.

  11. Isotope and elemental geochemistry of Cretaceous fossiliferous concretions (Santana Formation, Brazil)

    NASA Astrophysics Data System (ADS)

    Heimhofer, Ulrich; Meister, Patrick; Bernasconi, Stefano M.; Ariztegui, Daniel; Martill, David M.; Schwark, Lorenz

    2014-05-01

    Exceptional three-dimensional fossil preservation (incl. phosphatization of soft-tissues) within organic carbon-rich mudstones is often associated with the formation of a protective carbonate shell surrounding the fossil specimen. Examples for this type of preservation are the Early Cretaceous fishes, turtles and pterosaurs from the Brazilian Santana Formation. Numerous studies proposed different conceptual models for concretion formation. Having new state-of-the-art geochemical tools at hand we revisited these models for the Santana Formation as an exemplary case. Differential compaction clearly indicates early precipitation of micritic calcite surrounding a central cavity containing the still decomposing fossil. The presence of pyrite forming a circular rim around the fossil and carbonate with negative carbon isotope compositions suggest intense sulphate reduction whereby the production of ammonium from the decay of proteins led to an increased alkalinity, which induced early carbonate precipitation. By means of micro-XRF scanning we found that pyrite is absent from the interior part of the concretions and that total iron content is very low, which indicate absence of sulphate reduction at the center of the concretions and possibly local onset of methanogenesis. We postulate that the central cavity may even have been filled with methane gas that evolved from the decaying animal. Methane diffusing outward was anaerobically oxidized in the surrounding sulphate reduction zone. Carbonate clumped isotopes revealed that micritic calcite formed early, but that these early precipitates are overprinted by two different late diagenetic cements precipitated at elevated temperatures. The occurrence of an outermost "cone-in-cone" calcite rim can be associated with burial showing temperatures of up to 60°C. Strontium-isotope ratios of matrix calcite and cement phases show radiogenic values (0.710416 to 0.712465), which are significantly higher than typical marine Cretaceous

  12. Brazilian continental cretaceous

    NASA Astrophysics Data System (ADS)

    Petri, Setembrino; Campanha, Vilma A.

    1981-04-01

    Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

  13. Exhumation History Of Brasilian Highlands After Late Cretaceous Alcaline Magmatism

    NASA Astrophysics Data System (ADS)

    Doranti Tiritan, Carolina; Hackspacher, Peter Christian; Carina Siqueira Ribeiro, Marli; Glasmacher, Ulrich Anton; Françoso de Godoy, Daniel

    2017-04-01

    The southeast Brazilian margin recorded a long history of tectonic and magmatic events after the Gondwana continent break up. The drifting of the South American Platform over a thermal anomaly generated a series of alkaline intrusions that are distributed from the interior to the coast from west to east. Several exhumation events are recorded on the region and we are providing insights on the landscape evolution of the region since Late Cretaceous, comparing low temperature thermochronology results from two alkaline intrusions regions. Poços de Caldas Alkaline Massif (PCAM), is lied in the interior, 300km from the coastline, covering over 800km2 intruding the Precambrian basement around 83Ma, nepheline syenites, phonolites and tinguaites intruded in a continuous and rapid sequence lasting between 1 to 2 Ma. São Sebastião Island (SSI) on the other hand is located at the coast, 200 km southeast of São Paulo. It is characterized by an intrusion in Precambrian/Brazilian orogen and intruded by Early Cretaceous sub-alkaline basic and acid dykes, as well as by Late Cretaceous alkaline stocks (syenites) and dykes (basanite to phonolite). Will be presenting the apatite fission track (AFT) and (U-Th)/He results that shows the main difference between the areas is that PCAM region register older history then the coastal area of SSI, where thermal history starts register cooling event after the South Atlantic rifting process, while in the PCAM area register a previous history, since Carboniferous. The results are giving support to studies that indicate the development of the relief in Brazil being strongly influenced by the local and regional tectonic movements and the lithological and structural settings. The landscape at the Late Cretaceous was witness of heating process between 90 and 60Ma due the intense uplift of South American Platform. The elevation of the isotherms is associated with the mantellic plumes and the crustal thickness that caused thermal anomalies due

  14. Dinosaur morphological diversity and the end-Cretaceous extinction.

    PubMed

    Brusatte, Stephen L; Butler, Richard J; Prieto-Márquez, Albert; Norell, Mark A

    2012-05-01

    The extinction of non-avian dinosaurs 65 million years ago is a perpetual topic of fascination, and lasting debate has focused on whether dinosaur biodiversity was in decline before end-Cretaceous volcanism and bolide impact. Here we calculate the morphological disparity (anatomical variability) exhibited by seven major dinosaur subgroups during the latest Cretaceous, at both global and regional scales. Our results demonstrate both geographic and clade-specific heterogeneity. Large-bodied bulk-feeding herbivores (ceratopsids and hadrosauroids) and some North American taxa declined in disparity during the final two stages of the Cretaceous, whereas carnivorous dinosaurs, mid-sized herbivores, and some Asian taxa did not. Late Cretaceous dinosaur evolution, therefore, was complex: there was no universal biodiversity trend and the intensively studied North American record may reveal primarily local patterns. At least some dinosaur groups, however, did endure long-term declines in morphological variability before their extinction.

  15. Endocranial Morphology of the Primitive Nodosaurid Dinosaur Pawpawsaurus campbelli from the Early Cretaceous of North America

    PubMed Central

    Paulina-Carabajal, Ariana; Lee, Yuong-Nam; Jacobs, Louis L.

    2016-01-01

    Background Ankylosaurs are one of the least explored clades of dinosaurs regarding endocranial anatomy, with few available descriptions of braincase anatomy and even less information on brain and inner ear morphologies. The main goal of this study is to provide a detailed description of the braincase and internal structures of the Early Cretaceous nodosaurid Pawpawsaurus campbelli, based on recently made CT scans. Methodology/Principal Findings The skull of Pawpawsaurus was CT scanned at University of Texas at Austin (UTCT). Three-dimensional models were constructed using Mimics 18.0 (Materialise). The digital data and further processed 3D models revealed inaccessible anatomic structures, allowing a detailed description of the lateral wall of the braincase (obscured by other bones in the articulated skull), and endocranial structures such as the cranial endocast, the most complete inner ear morphology for a nodosaurid, and the interpretation of the airflow system within the nasal cavities. Conslusions/Significance The new information on the endocranial morphology of Pawpawsaurus adds anatomical data to the poorly understand ankylosaur paleoneurology. The new set of data has potential use not only in taxonomy and phylogeny, but also in paleobiological interpretations based on the relative development of sense organs, such as olfaction, hearing and balance. PMID:27007950

  16. Paleomagnetic results from the Early Cretaceous Lakang Formation lavas: Constraints on the paleolatitude of the Tethyan Himalaya and the India-Asia collision

    NASA Astrophysics Data System (ADS)

    Yang, Tianshui; Ma, Yiming; Bian, Weiwei; Jin, Jingjie; Zhang, Shihong; Wu, Huaichun; Li, Haiyan; Yang, Zhenyu; Ding, Jikai

    2015-10-01

    To better constrain the Early Cretaceous paleogeographic position of the Tethyan Himalaya and the India-Asia collision process, a paleomagnetic study was performed on the Lakang Formation lava flows in the Cuona area in the southeastern Tethyan Himalaya. Stepwise thermal and alternating field demagnetizations successfully isolated reliable characteristic remanent magnetization (ChRM) directions that include antipodal dual polarities and pass positive fold tests at the 99% confidence level and reversal tests at 95% confidence level, indicating prefolding primary magnetizations. The distribution patterns of ChRM directions from the Lakang Formation lava flows are consistent with young lava flows at similar latitudes, suggesting that secular variation has likely been averaged out. The tilt-corrected site-mean direction for 31 sites is D = 261.6 °, I = - 68.5 ° with α95 = 3.6 °, which provides a paleopole at 26.8°S, 315.2°E (A95 = 5.7 °), corresponding to a paleolatitude of 52.2 ° ± 5.7 °S for the study area. Comparison of the paleolatitude observed from the Lakang Formation lava flows with that expected from the apparent polar wander paths of India at 130 Ma show a paleolatitude difference of ∼2.1° (∼230 km), indicating that neither a great north-south continental crustal shortening occurred between the Indian craton and the Tethyan Himalaya after 130 Ma, nor that a wide ocean separated them at that time. Comparison with reliable Cretaceous-Paleocene paleomagnetic results observed from the Tethyan Himalaya and the Lhasa terrane indicates that the latitudinal width of the Neo-Tethyan Ocean could have been up to ∼7000 km at 134-130 Ma and an extension should have existed between the Indian craton and the Tethyan Himalaya during the Late Cretaceous and Paleocene. Furthermore, reliable paleomagnetic results suggest that the India-Asia collision was a dual-collision process, consisting of a first collision of the Tethyan Himalaya with the Lhasa terrane

  17. Ontong Java volcanism initiated long-term climate warming that caused substantial changes in terrestrial vegetation several tens of thousand years before the onset of OAE1a (Early Aptian, Cretaceous)

    NASA Astrophysics Data System (ADS)

    Keller, Christina E.; Hochuli, Peter A.; Giorgioni, Martino; Garcia, Therese I.; Bernasconi, Stefano M.; Weissert, Helmut

    2010-05-01

    During Cretaceous times, several intense volcanic episodes are proposed as trigger for episodic climate warming, for changes in marine circulation patterns and for elevated marine productivity, which resulted in the widespread black shale deposits of the Oceanic Anoxic Events (OAE). In the sediments underlying the early Aptian OAE1a black shales, a prominent negative carbon isotope excursion is recorded. Its origin had long been controversial (e.g. Arthur, 2000; Jahren et al., 2001) before recent studies attributed it to the Ontong Java volcanism (Méhay et al., 2009; Tejada et al., 2009). Volcanic outgassing results in an increased pCO2 and should lead to a rise in global temperatures. We therefore investigated if the volcanically-induced increase in pCO2 at the onset of OAE1a in the early Aptian led to a temperature rise that was sufficient to affect terrestrial vegetation assemblages. In order to analyse changes in terrestrial palynomorph assemblages, we examined 15 samples from 12 black shale horizons throughout the early Aptian negative C-isotope spike interval of the Pusiano section (Maiolica Formation; N-Italy). These sediments were deposited at the southern continental margin of the alpine Tethys Ocean and have been bio- and magnetostratigraphically dated by Channell et al. (1995). In order to obtain a continuous palynological record of the negative C-isotope spike interval and the base of OAE1a, we combined this pre-OAE1a interval of Pusiano with the OAE1a interval of the nearby Cismon section (Hochuli et al., 1999). The sporomorph assemblages at the base of this composite succession feature abundant bisaccate pollen, which reflects a warm-temperate climate. Rather arid conditions are inferred from low trilete spore percentages. Several tens of thousand years before the onset of OAE1a, C-isotope values started to decrease. Some thousand years later, bisaccate pollen began to decrease, whereas an increase of Classopollis spp. and Araucariacites spp

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  19. Parallel Extension Tectonics (PET): Early Cretaceous tectonic extension of the Eastern Eurasian continent

    NASA Astrophysics Data System (ADS)

    Liu, Junlai; Ji, Mo; Ni, Jinlong; Guan, Huimei; Shen, Liang

    2017-04-01

    The present study reports progress of our recent studies on the extensional structures in eastern North China craton and contiguous areas. We focus on characterizing and timing the formation/exhumation of the extensional structures, the Liaonan metamorphic core complex (mcc) and the Dayingzi basin from the Liaodong peninsula, the Queshan mcc, the Wulian mcc and the Zhucheng basin from the Jiaodong peninsula, and the Dashan magmatic dome within the Sulu orogenic belt. Magmatic rocks (either volcanic or plutonic) are ubiquitous in association with the tectonic extension (both syn- and post-kinematic). Evidence for crustal-mantle magma mixing are popular in many syn-kinematic intrusions. Geochemical analysis reveals that basaltic, andesitic to rhyolitic magmas were generated during the tectonic extension. Sr-Nd isotopes of the syn-kinematic magmatic rocks suggest that they were dominantly originated from ancient or juvenile crust partly with mantle signatures. Post-kinematic mafic intrusions with ages from ca. 121 Ma to Cenozoic, however, are of characteristic oceanic island basalts (OIB)-like trace element distribution patterns and relatively depleted radiogenic Sr-Nd isotope compositions. Integrated studies on the extensional structures, geochemical signatures of syn-kinematic magmatic rocks (mostly of granitic) and the tectono-magmatic relationships suggest that extension of the crust and the mantle lithosphere triggered the magmatisms from both the crust and the mantle. The Early Cretaceous tectono-magmatic evolution of the eastern Eurasian continent is governed by the PET in which the tectonic processes is subdivided into two stages, i.e. an early stage of tectonic extension, and a late stage of collapse of the extended lithosphere and transformation of lithospheric mantle. During the early stage, tectonic extension of the lithosphere led to detachment faulting in both the crust and mantle, resulted in the loss of some of the subcontinental roots, gave rise to

  20. Extending the fossil record of Polytrichaceae: Early Cretaceous Meantoinea alophosioides gen. et sp. nov., permineralized gametophytes with gemma cups from Vancouver Island.

    PubMed

    Bippus, Alexander C; Stockey, Ruth A; Rothwell, Gar W; Tomescu, Alexandru M F

    2017-04-01

    Diverse in modern ecosystems, mosses are dramatically underrepresented in the fossil record. Furthermore, most pre-Cenozoic mosses are known only from compression fossils, lacking detailed anatomical information. When preserved, anatomy vastly improves resolution in the systematic placement of fossils. Lower Cretaceous deposits at Apple Bay (Vancouver Island, British Columbia, Canada) contain a diverse anatomically preserved flora that includes numerous bryophytes, many of which have yet to be characterized. Among them is a polytrichaceous moss that is described here. Fossil moss gametophytes preserved in four carbonate concretions were studied in serial sections prepared using the cellulose acetate peel technique. We describe Meantoinea alophosioides gen. et sp. nov., a polytrichaceous moss with terminal gemma cups containing stalked, lenticular gemmae. Leaves with characteristic costal anatomy, differentiated into sheathing base and free lamina and bearing photosynthetic lamellae, along with a conducting strand in the stem, place Meantoinea in family Polytrichaceae. The bistratose leaf lamina with an adaxial layer of mamillose cells, short photosynthetic lamellae restricted to the costa, and presence of gemma cups indicate affinities with basal members of the Polytrichaceae, such as Lyellia , Bartramiopsis , and Alophosia . Meantoinea alophosioides enriches the documented moss diversity of an already-diverse Early Cretaceous plant fossil assemblage. This is the third moss described from the Apple Bay plant fossil assemblage and represents the first occurrence of gemma cups in a fossil moss. It is also the oldest unequivocal record of Polytrichaceae, providing a hard minimum age for the group of 136 million years. © 2017 Botanical Society of America.

  1. Distribution and tectonic implications of Cretaceous-Quaternary sedimentary facies in Solomon Islands

    NASA Astrophysics Data System (ADS)

    Turner, C. C.; Hughes, G. W.

    1982-08-01

    Sedimentary rocks of the Solomon Islands-Bougainville Arc are described in terms of nine widespread facies. Four facies associations are recognised by grouping facies which developed in broadly similar sedimentary environments. A marine pelagic association of Early Cretaceous to Miocene rocks comprises three facies. Facies Al: Early Cretaceous siliceous mudstone, found only on Malaita, is interpreted as deep marine siliceous ooze. Facies A2: Early Cretaceous to Eocene limestone with chert, overlies the siliceous mudstone facies, and is widespread in the central and eastern Solomons. It represents lithified calcareous ooze. Facies A3: Oligocene to Miocene calcisiltite with thin tuffaceous beds, overlies Facies A2 in most areas, and also occurs in the western Solomons. This represents similar, but less lithified calcareous ooze, and the deposits of periodic andesitic volcanism. An open marine detrital association of Oligocene to Recent age occurs throughout the Solomons. This comprises two facies. Facies B1 is variably calcareous siltstone, of hemipelagic origin; and Facies B2 consists of volcanogenic clastic deposits, laid down from submarine mass flows. A third association, of shallow marine carbonates, ranges in age from Late Oligocene to Recent. Facies C1 is biohermal limestone, and Facies C2 is biostromal calcarenite. The fourth association comprises areally restricted Pliocene to Recent paralic detrital deposits. Facies D1 includes nearshore clastic sediments, and Facies D2 comprises alluvial sands and gravels. Pre-Oligocene pelagic sediments were deposited contemporaneously with, and subsequent to, the extrusion of oceanic tholeiite. Island arc volcanism commenced along the length of the Solomons during the Oligocene, and greatly influenced sedimentation. Thick volcaniclastic sequences were deposited from submarine mass flows, and shallow marine carbonates accumulated locally. Fine grained graded tuffaceous beds within the marine pelagic association are

  2. Brachyceran Diptera (Insecta) in Cretaceous ambers, Part IV, Significant New Orthorrhaphous Taxa

    PubMed Central

    Grimaldi, David A.; Arillo, Antonio; Cumming, Jeffrey M.; Hauser, Martin

    2011-01-01

    Abstract Thirteen species of basal Brachycera (11 described as new) are reported, belonging to nine families and three infraorders. They are preserved in amber from the Early Cretaceous (Neocomian) of Lebanon, Albian of northern Spain, upper Albian to lower Cenomanian of northern Myanmar, and Late Cretaceous of New Jersey USA (Turonian) and Alberta, Canada (Campanian). Taxa are as follows, with significance as noted: In Stratiomyomorpha: Stratiomyidae (Cretaceogaster pygmaeus Teskey [2 new specimens in Canadian amber], Lysistrata emerita Grimaldi & Arillo, gen. et sp. n. [stem-group species of the family in Spanish amber]), and Xylomyidae (Cretoxyla azari Grimaldi & Cumming, gen. et sp. n. [in Lebanese amber], and an undescribed species from Spain). In Tabanomorpha: Tabanidae (Cratotabanus newjerseyensis Grimaldi, sp. n., in New Jersey amber). In Muscomorpha: Acroceridae (Schlingeromyia minuta Grimaldi & Hauser, gen. et sp. n. and Burmacyrtus rusmithi Grimaldi & Hauser gen. et sp. n., in Burmese amber, the only definitive species of the family from the Cretaceous); Mythicomyiidae (Microburmyia analvena Grimaldi & Cumming gen. et sp. n. and Microburmyia veanalvena Grimaldi & Cumming, sp. n., stem-group species of the family, both in Burmese amber); Apsilocephalidae or near (therevoid family-group) (Kumaromyia burmitica Grimaldi & Hauser, gen. et sp. n. [in Burmese amber]); Apystomyiidae (Hilarimorphites burmanica Grimaldi & Cumming, sp. n. [in Burmese amber], whose closest relatives are from the Late Jurassic of Kazachstan, the Late Cretaceous of New Jersey, and Recent of California). Lastly, two species belonging to families incertae sedis, both in Burmese amber: Tethepomyiidae (Tethepomyia zigrasi Grimaldi & Arillo sp. n., the aculeate oviscapt of which indicates this family was probably parasitoidal and related to Eremochaetidae); and unplaced to family is Myanmyia asteiformia Grimaldi, gen. et sp. n., a minute fly with highly reduced venation. These new taxa

  3. Brachyceran Diptera (Insecta) in Cretaceous ambers, Part IV, Significant New Orthorrhaphous Taxa.

    PubMed

    Grimaldi, David A; Arillo, Antonio; Cumming, Jeffrey M; Hauser, Martin

    2011-01-01

    Thirteen species of basal Brachycera (11 described as new) are reported, belonging to nine families and three infraorders. They are preserved in amber from the Early Cretaceous (Neocomian) of Lebanon, Albian of northern Spain, upper Albian to lower Cenomanian of northern Myanmar, and Late Cretaceous of New Jersey USA (Turonian) and Alberta, Canada (Campanian). Taxa are as follows, with significance as noted: In Stratiomyomorpha: Stratiomyidae (Cretaceogaster pygmaeus Teskey [2 new specimens in Canadian amber], Lysistrata emerita Grimaldi & Arillo, gen. et sp. n. [stem-group species of the family in Spanish amber]), and Xylomyidae (Cretoxyla azari Grimaldi & Cumming, gen. et sp. n. [in Lebanese amber], and an undescribed species from Spain). In Tabanomorpha: Tabanidae (Cratotabanus newjerseyensis Grimaldi, sp. n., in New Jersey amber). In Muscomorpha: Acroceridae (Schlingeromyia minuta Grimaldi & Hauser, gen. et sp. n. and Burmacyrtus rusmithi Grimaldi & Hauser gen. etsp. n., in Burmese amber, the only definitive species of the family from the Cretaceous); Mythicomyiidae (Microburmyia analvena Grimaldi & Cumming gen. et sp. n. and Microburmyia veanalvena Grimaldi & Cumming, sp. n., stem-group species of the family, both in Burmese amber); Apsilocephalidae or near (therevoid family-group) (Kumaromyia burmitica Grimaldi & Hauser, gen. et sp. n. [in Burmese amber]); Apystomyiidae (Hilarimorphites burmanica Grimaldi & Cumming, sp. n. [in Burmese amber], whose closest relatives are from the Late Jurassic of Kazachstan, the Late Cretaceous of New Jersey, and Recent of California). Lastly, two species belonging to families incertae sedis, both in Burmese amber: Tethepomyiidae (Tethepomyia zigrasi Grimaldi & Arillo sp. n., the aculeate oviscapt of which indicates this family was probably parasitoidal and related to Eremochaetidae); and unplaced to family is Myanmyia asteiformia Grimaldi, gen. et sp. n., a minute fly with highly reduced venation. These new taxa significantly

  4. A synthesis of Jurassic and Early Cretaceous crustal evolution along the southern margin of the Arctic Alaska–Chukotka microplate and implications for defining tectonic boundaries active during opening of Arctic Ocean basins

    USGS Publications Warehouse

    Till, Alison B.

    2016-01-01

    A synthesis of Late Jurassic and Early Cretaceous collision-related metamorphic events in the Arctic Alaska–Chukotka microplate clarifies its likely movement history during opening of the Amerasian and Canada basins. Comprehensive tectonic reconstructions of basin opening have been problematic, in part, because of the large size of the microplate, uncertainties in the location and kinematics of structures bounding the microplate, and lack of information on its internal deformation history. Many reconstructions have treated Arctic Alaska and Chukotka as a single crustal entity largely on the basis of similarities in their Mesozoic structural trends and similar late Proterozoic and early Paleozoic histories. Others have located Chukotka near Siberia during the Triassic and Jurassic, on the basis of detrital zircon age populations, and suggested that it was Arctic Alaska alone that rotated. The Mesozoic metamorphic histories of Arctic Alaska and Chukotka can be used to test the validity of these two approaches.A synthesis of the distribution, character, and timing of metamorphic events reveals substantial differences in the histories of the southern margin of the microplate in Chukotka in comparison to Arctic Alaska and places specific limitations on tectonic reconstructions. During the Late Jurassic and earliest Cretaceous, the Arctic Alaska margin was subducted to the south, while the Chukotka margin was the upper plate of a north-dipping subduction zone or a zone of transpression. An early Aptian blueschist- and greenschist-facies belt records the most profound crustal thickening event in the evolution of the orogen. It may have resulted in thicknesses of 50–60 km and was likely the cause of flexural subsidence in the foredeep of the Brooks Range. This event involved northern Alaska and northeasternmost Chukotka; it did not involve central and western Chukotka. Arctic Alaska and Chukotka evolved separately until the Aptian thickening event, which was likely a

  5. The age and diversification of terrestrial New World ecosystems through Cretaceous and Cenozoic time.

    PubMed

    Graham, Alan

    2011-03-01

    Eight ecosystems that were present in the Cretaceous about 100 Ma (million years ago) in the New World eventually developed into the 12 recognized for the modern Earth. Among the forcing mechanisms that drove biotic change during this interval was a decline in global temperatures toward the end of the Cretaceous, augmented by the asteroid impact at 65 Ma and drainage of seas from continental margins and interiors; separation of South America from Africa beginning in the south at ca. 120 Ma and progressing northward until completed 90-100 Ma; the possible emission of 1500 gigatons of methane and CO(2) attributed to explosive vents in the Norwegian Sea at ca. 55 Ma, resulting in a temperature rise of 5°-6°C in an already warm world; disruption of the North Atlantic land bridge at ca. 45 Ma at a time when temperatures were falling; rise of the Andes Mountains beginning at ca. 40 Ma; opening of the Drake Passage between South America and Antarctica at ca. 32 Ma with formation of the cold Humboldt at ca. 30 Ma; union of North and South America at ca. 3.5 Ma; and all within the overlay of evolutionary processes. These processes generated a sequence of elements (e.g., species growing in moist habitats within an overall dry environment; gallery forests), early versions (e.g., mangrove communities without Rhizophora until the middle Eocene), and essentially modern versions of present-day New World ecosystems. As a first approximation, the fossil record suggests that early versions of aquatic communities (in the sense of including a prominent angiosperm component) appeared early in the Middle to Late Cretaceous, the lowland neotropical rainforest at 64 Ma (well developed by 58-55 Ma), shrubland/chaparral-woodland-savanna and grasslands around the middle Miocene climatic optimum at ca. 15-13 Ma, deserts in the middle Miocene/early Pliocene at ca. 10 Ma, significant tundra at ca. 7-5 Ma, and alpine tundra (páramo) shortly thereafter when cooling temperatures were augmented

  6. Upper Cretaceous and Lower Jurassic strata in shallow cores on the Chukchi Shelf, Arctic Alaska: Chapter C in Studies by the U.S. Geological Survey in Alaska, vol. 15

    USGS Publications Warehouse

    Houseknecht, David W.; Craddock, William H.; Lease, Richard O.

    2016-02-12

    Shallow cores collected in the 1980s on the Chukchi Shelf of western Arctic Alaska sampled pre-Cenozoic strata whose presence, age, and character are poorly known across the region. Five cores from the Herald Arch foreland contain Cenomanian to Coniacian strata, as documented by biostratigraphy, geochronology, and thermochronology. Shallow seismic reflection data collected during the 1970s and 1980s show that these Upper Cretaceous strata are truncated near the seafloor by subtle angular unconformities, including the Paleogene mid-Brookian unconformity in one core and the Pliocene-Pleistocene unconformity in four cores. Sedimentary structures and lithofacies suggest that Upper Cretaceous strata were deposited in a low accommodation setting that ranged from low-lying coastal plain (nonmarine) to muddy, shallow-marine environments near shore. These observations, together with sparse evidence from the adjacent western North Slope, suggest that Upper Cretaceous strata likely were deposited across all of Arctic Alaska.A sixth core from the Herald Arch contains lower Toarcian marine strata, indicated by biostratigraphy, truncated by a Neogene or younger unconformity. These Lower Jurassic strata evidently were deposited south of the arch, buried structurally to high levels of thermal maturity during the Early Cretaceous, and uplifted on the Herald thrust-fault system during the mid to Late Cretaceous. These interpretations are based on regional stratigraphy and apatite fission-track data reported in a complementary report and are corroborated by the presence of recycled palynomorphs of Early Jurassic age and high thermal maturity found in Upper Cretaceous strata in two of the foreland cores. This dataset provides evidence that uplift and exhumation of the Herald thrust belt provided sediment to the foreland during the Late Cretaceous.

  7. Mass Wasting during the Cretaceous/Tertiary Transition in the North Atlantic: Relationship to the Chicxulub Impact?

    NASA Astrophysics Data System (ADS)

    Mateo, Paula; Keller, Gerta; Adatte, Thierry; Spangenberg, Jorge

    2015-04-01

    Deep-sea sections in the North Atlantic are claimed to contain the most complete sedimentary records and ultimate proof that the Chicxulub impact is Cretaceous-Tertiary boundary (KTB) in age and caused the mass extinction. A multi-disciplinary study of North Atlantic DSDP Sites 384, 386 and 398, based on high-resolution planktonic foraminiferal biostratigraphy, carbon and oxygen stable isotopes, clay and whole-rock mineralogy and granulometry, reveals the age, stratigraphic completeness and nature of sedimentary disturbances. Results show a major KTB hiatus at Site 384 with zones CF1, P0 and P1a missing, spanning at least ~540 ky, similar to other North Atlantic and Caribbean localities associated with tectonic activity and Gulf Stream erosion. At Sites 386 and 398, discrete intervals of disturbed sediments with mm-to-cm-thick spherule layers have previously been interpreted as KTB age impact-generated earthquakes destabilizing continental margins prior to settling of impact spherules. However, improved age control based on planktonic foraminifera indicates deposition in the early Danian zone P1a(2) (upper Parvularugoglobigerina eugubina zone) more than 100 ky after the KTB. At Site 386, two intervals of white chalk contain very small (<63 μm) early Danian zone P1a(2) (65%) and common reworked Cretaceous (35%) species, in contrast to the in situ red-brown and green abyssal clays that are devoid of carbonate. In addition, high calcite, mica and kaolinite and upward-fining are observed in the chalks, indicating downslope transport from shallow waters and sediment winnowing via distal turbidites. At Site 398, convoluted red to tan sediments with early Danian and reworked Cretaceous species represent slumping of shallow water sediments as suggested by dominance of mica and low smectite compared to in situ deposition. We conclude that mass wasting was likely the result of earthquakes associated with increased tectonic activity in the Caribbean and the Iberian Peninsula

  8. Definition of Greater Gulf Basin Lower Cretaceous and Upper Cretaceous Lower Cenomanian Shale Gas Assessment Unit, United States Gulf of Mexico Basin Onshore and State Waters

    USGS Publications Warehouse

    Dennen, Kristin O.; Hackley, Paul C.

    2012-01-01

    An assessment unit (AU) for undiscovered continuous “shale” gas in Lower Cretaceous (Aptian and Albian) and basal Upper Cretaceous (lower Cenomanian) rocks in the USA onshore Gulf of Mexico coastal plain recently was defined by the U.S. Geological Survey (USGS). The AU is part of the Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) of the Gulf of Mexico Basin. Definition of the AU was conducted as part of the 2010 USGS assessment of undiscovered hydrocarbon resources in Gulf Coast Mesozoic stratigraphic intervals. The purpose of defining the Greater Gulf Basin Lower Cretaceous Shale Gas AU was to propose a hypothetical AU in the Cretaceous part of the Gulf Coast TPS in which there might be continuous “shale” gas, but the AU was not quantitatively assessed by the USGS in 2010.

  9. Facies changes in the Cenomanian (Cretaceous) of the northwestern Elbe Valley near Dresden (Saxony, Germany)

    NASA Astrophysics Data System (ADS)

    Tröger, Karl-Armin

    2017-03-01

    The Upper Cretaceous of the Elbe Valley in Saxony and the erosion outliers west of it mark an Upper Cretaceous NW-SE-running strait between the Westsudetic Island in the NE and the Mid-European Island to the west. This street connected the NW-German-Polish Basin in the north and the Bohemian Cretaceous Basin (and adjacent regions of the Tethys) in the south. However, post-Cretaceous erosion north of Meißen removed any Upper Cretaceous deposits but erosion outliers at Siebenlehn and especially north of the Forest of Tharandt proof the presence of a marly through silty belt in this area. Three transgressions (base of uppermost Lower to Middle Cenomanian, base of Upper Cenomanian and base of the geslinianum Zone in the mid-Upper Cenomanian) have taken place. The sedimentation was influenced by the topography of the mentioned islands and by movements at structural lines in the Proterozoic and Palaeozoic basement. During the early Late Cenomanian, a marly-silty sedimentation (Mobschatz Formation) in the north existed besides sandy sedimentation in the south (Oberhäslich Formation). The transgression at the base of the geslinianum Zone caused the final submergence of island chains between Meißen, Dresden and Pirna, and a litho- and biofacies bound to cliffs and submarine swells formed. A silty-marly lithofacies, a mixed sandy-silty lithofacies (Dölzschen Formation) and a sandy lithofacies in the south (Sächsisches Elbsandsteingebirge) co-existed during the latest Cenomanian. The first mentioned biofacies yields a rich fauna mainly consisting of oysters, pectinids, rudists, and near-shore gastropods accompanied by echinids and, in some cliffs, teeth of sharks. The Pennrich fauna (Häntzschel 1933; Uhlig 1941) especially consists of the very common serpulids Pyrgopolon (P.) septemsulcata and Glomerula lombricus (formerly Hepteris septemsulcata and G. gordialis).

  10. Dental Disparity and Ecological Stability in Bird-like Dinosaurs prior to the End-Cretaceous Mass Extinction.

    PubMed

    Larson, Derek W; Brown, Caleb M; Evans, David C

    2016-05-23

    The causes, rate, and selectivity of the end-Cretaceous mass extinction continue to be highly debated [1-5]. Extinction patterns in small, feathered maniraptoran dinosaurs (including birds) are important for understanding extant biodiversity and present an enigma considering the survival of crown group birds (Neornithes) and the extinction of their close kin across the end-Cretaceous boundary [6]. Because of the patchy Cretaceous fossil record of small maniraptorans [7-12], this important transition has not been closely examined in this group. Here, we test the hypothesis that morphological disparity in bird-like dinosaurs was decreasing leading up to the end-Cretaceous mass extinction, as has been hypothesized in some dinosaurs [13, 14]. To test this, we examined tooth morphology, an ecological indicator in fossil reptiles [15-19], from over 3,100 maniraptoran teeth from four groups (Troodontidae, Dromaeosauridae, Richardoestesia, and cf. Aves) across the last 18 million years of the Cretaceous. We demonstrate that tooth disparity, a proxy for variation in feeding ecology, shows no significant decline leading up to the extinction event within any of the groups. Tooth morphospace occupation also remains static over this time interval except for increased size during the early Maastrichtian. Our data provide strong support that extinction within this group occurred suddenly after a prolonged period of ecological stability. To explain this sudden extinction of toothed maniraptorans and the survival of Neornithes, we propose that diet may have been an extinction filter and suggest that granivory associated with an edentulous beak was a key ecological trait in the survival of some lineages. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Geological and technological characterization of the Late Jurassic-Early Cretaceous clay deposits (Jebel Ammar, northeastern Tunisia) for ceramic industry

    NASA Astrophysics Data System (ADS)

    Ben M'barek-Jemaï, Moufida; Sdiri, Ali; Ben Salah, Imed; Ben Aissa, Lassaad; Bouaziz, Samir; Duplay, Joelle

    2017-05-01

    Late Jurassic-Lower Cretaceous clays of the Jebel Ammar study site were used as raw materials for potential applications in ceramic industry. Physico-chemical characterization of the collected samples was performed using atomic absorption spectroscopy, X-ray diffraction, thermogravimetry and dilatometry (Bugot's curve). Geotechnical study was also undertaken by the assessment of plasticity and liquidity limits. It was found that high concentrations of silica, alumina with SiO2/Al2O3 ratio characterized the studied clays; its high amounts of CaO and Fe2O3 in the Late Jurassic clays indicated their calcareous nature. In addition, technological tests indicated moderate to low plasticity values for the Late Jurassic and Lower Cretaceous clays, respectively. Clay fraction (<2 μm) reached 50% of the natural clay in some cases. Mineralogical analysis showed that Jurassic clays were dominated by smectite, illite and kaolinite, as clay mineral species; calcite was the main associated mineral. Lower Cretaceous clays were mainly composed of abundant illite accompanied by well-crystallized smectite and kaolinite. Kaolinite gradually increased upwards, reaching 70% of the total clay fraction (i.e. <2 μm). Quartz, calcite and feldspar were the main non-clay minerals. Based on these analyses, the clays meet technological requirements that would allow their use in the ceramic industry and for the manufacturing of ceramic tiles.

  12. A new hynobiid-like salamander (Amphibia, Urodela) from Inner Mongolia, China, provides a rare case study of developmental features in an Early Cretaceous fossil urodele

    PubMed Central

    Jia, Jia

    2016-01-01

    A new fossil salamander, Nuominerpeton aquilonaris (gen. et sp. nov.), is named and described based on specimens from the Lower Cretaceous Guanghua Formation of Inner Mongolia, China. The new discovery documents a far northern occurrence of Early Cretaceous salamanders in China, extending the geographic distribution for the Mesozoic fossil record of the group from the Jehol area (40th–45th parallel north) to near the 49th parallel north. The new salamander is characterized by having the orbitosphenoid semicircular in shape; coracoid plate of the scapulocoracoid greatly expanded with a convex ventral and posterior border; ossification of two centralia in carpus and tarsus; and first digit being about half the length of the second digit in both manus and pes. The new salamander appears to be closely related to hynobiids, although this inferred relationship awaits confirmation by research in progress by us on a morphological and molecular combined analysis of cryptobranchoid relationships. Comparison of adult with larval and postmetamorphic juvenile specimens provides insights into developmental patterns of cranial and postcranial skeletons in this fossil species, especially resorption of the palatine and anterior portions of the palatopterygoid in the palate and the coronoid in the mandible during metamorphosis, and postmetamorphic ossification of the mesopodium in both manus and pes. Thus, this study provides a rare case study of developmental features in a Mesozoic salamander. PMID:27761316

  13. Cretaceous origin and repeated tertiary diversification of the redefined butterflies.

    PubMed

    Heikkilä, Maria; Kaila, Lauri; Mutanen, Marko; Peña, Carlos; Wahlberg, Niklas

    2012-03-22

    Although the taxonomy of the ca 18 000 species of butterflies and skippers is well known, the family-level relationships are still debated. Here, we present, to our knowledge, the most comprehensive phylogenetic analysis of the superfamilies Papilionoidea, Hesperioidea and Hedyloidea to date based on morphological and molecular data. We reconstructed their phylogenetic relationships using parsimony and Bayesian approaches. We estimated times and rates of diversification along lineages in order to reconstruct their evolutionary history. Our results suggest that the butterflies, as traditionally understood, are paraphyletic, with Papilionidae being the sister-group to Hesperioidea, Hedyloidea and all other butterflies. Hence, the families in the current three superfamilies should be placed in a single superfamily Papilionoidea. In addition, we find that Hedylidae is sister to Hesperiidae, and this novel relationship is supported by two morphological characters. The families diverged in the Early Cretaceous but diversified after the Cretaceous-Palaeogene event. The diversification of butterflies is characterized by a slow speciation rate in the lineage leading to Baronia brevicornis, a period of stasis by the skippers after divergence and a burst of diversification in the lineages leading to Nymphalidae, Riodinidae and Lycaenidae.

  14. Cretaceous-Eocene provenance connections between the Palawan Continental Terrane and the northern South China Sea margin

    NASA Astrophysics Data System (ADS)

    Shao, Lei; Cao, Licheng; Qiao, Peijun; Zhang, Xiangtao; Li, Qianyu; van Hinsbergen, Douwe J. J.

    2017-11-01

    The plate kinematic history of the South China Sea opening is key to reconstructing how the Mesozoic configuration of Panthalassa and Tethyan subduction systems evolved into today's complex Southeast Asian tectonic collage. The South China Sea is currently flanked by the Palawan Continental Terrane in the south and South China in the north and the two blocks have long been assumed to be conjugate margins. However, the paleogeographic history of the Palawan Continental Terrane remains an issue of uncertainty and controversy, especially regarding the questions of where and when it was separated from South China. Here we employ detrital zircon U-Pb geochronology and heavy mineral analysis on Cretaceous and Eocene strata from the northern South China Sea and Palawan to constrain the Late Mesozoic-Early Cenozoic provenance and paleogeographic evolution of the region testing possible connection between the Palawan Continental Terrane and the northern South China Sea margin. In addition to a revision of the regional stratigraphic framework using the youngest zircon U-Pb ages, these analyses show that while the Upper Cretaceous strata from the Palawan Continental Terrane are characterized by a dominance of zircon with crystallization ages clustering around the Cretaceous, the Eocene strata feature a large range of zircon ages and a new mineral group of rutile, anatase, and monazite. On the one hand, this change of sediment compositions seems to exclude the possibility of a latest Cretaceous drift of the Palawan Continental Terrane in response to the Proto-South China Sea opening as previously inferred. On the other hand, the zircon age signatures of the Cretaceous-Eocene strata from the Palawan Continental Terrane are largely comparable to those of contemporary samples from the northeastern South China Sea region, suggesting a possible conjugate relationship between the Palawan Continental Terrane and the eastern Pearl River Mouth Basin. Thus, the Palawan Continental

  15. Syn-convergence extension in the southern Lhasa terrane: Evidence from late Cretaceous adakitic granodiorite and coeval gabbroic-dioritic dykes

    NASA Astrophysics Data System (ADS)

    Ma, Xuxuan; Xu, Zhiqin; Meert, Joseph G.

    2017-10-01

    Late Cretaceous (∼100-80 Ma) magmatism in the Gangdese magmatic belt plays a pivotal role in understanding the evolutionary history and tectonic regime of the southern Lhasa terrane. The geodynamic process for the formation of the early Late Cretaceous magmatism has long been an issue of hot debates. Here, petrology, geochronology and geochemistry of early Late Cretaceous granodiorite and coeval gabbroic-dioritic dykes in the Caina region, southern Lhasa, were investigated in an effort to ascertain their petrogenesis, age of intrusion, magma mixing and tectonic setting. Zircon U-Pb dating of granodiorite yields 206Pb/238U ages of 85.8 ± 1.7 and 86.4 ± 1.1 Ma, whilst that of the E-W trending dykes yields ages of 82.7 ± 2.6 and 83.5 ± 3.5 Ma. Within error, the crystallization ages of the dykes and the granodiorite are indistinguishable. Field observations and mineralogical microstructures are suggestive of a magma mixing process during the formation of the dykes and the granodiorite. The granodiorite exhibits geochemical features that are in agreement with those of subduction-related high-SiO2 adakites. The granodiorite and dykes have relatively constant εNd(t) values of +2.2 to +4.9 and initial 87Sr/86Sr ratios (0.7045-0.7047). These similar characteristics are herein interpreted as an evolutionary series from the dykes to granodiorite, consistent with magma mixing process. Ti-in-zircon thermometer and Al-in-hornblende barometer indicate that the granodiorite and the dioritic dyke crystallized at temperatures of ca. 750 and 800 °C, depths of ca. 6-10 and 5-9 km, respectively. Taking into account the synchronous magmatic rocks in the Gangdese Belt and the coeval rifted basin within the Lhasa terrane, the granodiorite and dykes reveal an early Late Cretaceous syn-convergence extensional regime in the southern Lhasa terrane, triggered by slab rollback of the Neotethyan oceanic lithosphere.

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

    NASA Astrophysics Data System (ADS)

    Gallois, Arnaud; Bosence, Dan; Burgess, Peter

    2015-04-01

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

  17. Magnetostratigraphy of displaced Upper Cretaceous strata in southern California

    NASA Astrophysics Data System (ADS)

    Fry, J. Gilbert; Bottjer, David J.; Lund, Steve P.

    1985-09-01

    A magnetostratigraphic study of Upper Cretaceous marine strata from the Santa Ana Mountains in southern California has identified a Campanian reversed magnetozone. This reversed interval, corresponding to marine magnetic anomaly 33 34 (Chron 33r) of Campanian age, can be correlated with a Campanian reversed magnetozone that has been reported from strata of the Great Valley Sequence in central California. The Late Cretaceous paleolatitude of the Santa Ana Mountains is estimated from this study to be 26.6°N. This is significantly different from the region's expected Cretaceous paleolatitude of 43.8°N as part of the North American stable craton, and indicates that this region (part of the Peninsular Ranges terrane) was 1900 km farther south in Cretaceous time relative to the stable craton. *Present address: Mobil Oil Corp., P.O. Box 900, Dallas, Texas 75221

  18. Gateways and Water Mass Mixing in the Late Cretaceous North Atlantic

    NASA Astrophysics Data System (ADS)

    Asgharian Rostami, M.; Martin, E. E.; MacLeod, K. G.; Poulsen, C. J.; Vande Guchte, A.; Haynes, S.

    2017-12-01

    Regions of intermediate/deep water formation and water-mass mixing in the North Atlantic are poorly defined for the Late Cretaceous, a time of gateway evolution and cooler conditions following the Mid Cretaceous greenhouse. Improved proxy data combined with modeling efforts are required to effectively evaluate the relationship between CO2, paleogeography, and circulation during this cooler interval. We analyzed and compiled latest Cretaceous (79 - 66 Ma) ɛNd and δ13C records from seven bathyal (paleodepths 0.2 - 2 km) and eight abyssal (paleodepths > 2 km) sites in the North Atlantic. Data suggest local downwelling of Northern Component Water (NCW; ɛNd -9.5 and δ13C 1.7 ‰) is the primary source of intermediate/deep water masses in the basin. As this water flows southward and ages, δ13C values decrease and ɛNd values increase; however, additional chemical changes at several sites require mixing with contributions from several additional water masses. Lower ɛNd ( -10) and higher δ13C ( 1.9 ‰) values in the deep NW part of the basin indicate proximal contributions from a region draining old continental crust, potentially representing deep convection following opening of the Labrador Sea. In the deep NE Iberian Basin, higher ɛNd ( -7) and lower δ13C ( 0.8 ‰) during the Campanian suggest mixing with a Tethyan source (ɛNd -7 and δ13C 0.1 ‰) whose importance decreased with restriction of that gateway in the Maastrichtian. Data from bathyal sites suggest additional mixing. In the SE Cape Verde region, observed ɛNd variations from -10 in the Campanian to -13 and -12 in the early and late Maastrichtian, respectively, may record variations in output rates of Tethyan and/or NCW sources and Demerara Bottom Water (ɛNd -16), a proposed warm saline intermediate water mass formed in shallow, equatorial seas. Pacific inflow through the Caribbean gateway impacts intermediate sites at Blake Nose (ɛNd values -8), particularly the shallowest site during the late

  19. Berriasian (Early Cretaceous) radiometric ages from the Grindstone Creek Section, Sacramento Valley, California

    USGS Publications Warehouse

    Bralower, T.J.; Ludwig, K. R.; Obradovich, J.D.

    1990-01-01

    The Grindstone Creek Section, Glenn County, Northern California is a sequence of hemipelagic mudstone, siltstone and sandstone interbedded with concretionary limestone and a few thin tuffs and bentonites. Two tuffs have been collected from a narrow interval of this sequence and subjected to mineralogical and isotopic analyses. UPb isotopic analyses of zircon fractions from these volcanic horizons indicate an age of 137.1 + 1.6/-0.6 Ma. A detailed investigation has been conducted on the calcareous nannofossil stratigraphy of this section based on numerous samples with moderately preserved assemblages. The nannoflora is largely of Tethyan affinity, and allows direct correlation with the Berriasian stratotype section, with sections with published magnetostratigraphies and with a DSDP site drilled between known magnetic anomalies. The dated tuffs lie in the lower part of the upper Berriasian Cretarhabdus angustiforatus Zone (Assipetra infracretacea Subzone) and within the narrow range of Rhagodiscus nebulosus. At three different sections, this subzone can be correlated with M-sequence Polarity Zones M16 and M16n. An independent magnetostratigraphic correlation is provided at DSDP Site 387, drilled between anomalies M15 and M16, where basal sediments contain R. nebulosus. Buchia collected within a meter of the lower tuff lie within the B. uncitoides Zone which is Berriasian in age. The upper tuff level, which occurs 65 m above the lower tuff, is situated within the overlying B. pacifica Zone. This zone had previously been correlated with the early Valanginian, but is clearly also partly of Berriasian age based on nannofossil stratigraphy. Our results allow an estimate of the age of the Berriasian-Valanginian and Jurassic-Cretaceous boundaries of 135.1 Ma and 141.1 Ma, respectively, and these fall within the range of, but differ significantiy from, several published time-scales. ?? 1990.

  20. Late Cretaceous stratigraphy, deformation and intrusion in the Madison Range of southwestern Montana ( USA).

    USGS Publications Warehouse

    Tysdal, R.G.; Marvin, R.F.; Dewitt, E.

    1986-01-01

    Dating of orogenic rock units in the central part of the Madison Range shows that Laramide deformation was virtually completed by the end of the Cretaceous. Early Campanian K-Ar dates of about 79 m.y. were obtained from welded tuffs in the basal part of the Livingston Formation, a volcanic and volcaniclastic assemblage that is conformable with underlying Cretaceous clastic rocks and with the overlying Sphinx Conglomerate. The Sphinx and the Livingston were deformed by the Hilgard fault system which extends along the western side of the southern two-thirds of the range. This north-trending fault system represents the culmination of Laramide shortening within the range. Dating of hornblende indicates an approximate date of 68-69 m.y. B.P. for emplacement of the igneous suite. The dacite postdates movement along faults of the Hilgard fault system, and postdates the synorogenic Sphinx Conglomerate. -from Authors

  1. Fossil Worm Burrows Reveal Very Early Terrestrial Animal Activity and Shed Light on Trophic Resources after the End-Cretaceous Mass Extinction

    PubMed Central

    Chin, Karen; Pearson, Dean; Ekdale, A. A.

    2013-01-01

    The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms. PMID:23951041

  2. Mineral chemistry of isotropic gabbros from the Manamedu Ophiolite Complex, Cauvery Suture Zone, southern India: Evidence for neoproterozoic suprasubduction zone tectonics

    NASA Astrophysics Data System (ADS)

    Yellappa, T.; Tsunogae, T.; Chetty, T. R. K.; Santosh, M.

    2016-11-01

    The dismembered units of the Neoproterozoic Manamedu Ophiolite Complex (MOC) in the Cauvery Suture Zone, southern India comprises a well preserved ophiolitic sequence of ultramafic cumulates of altered dunites, pyroxenites, mafic cumulates of gabbros, gabbro-norites and anorthosites in association with plagiogranites, isotropic gabbros, metadolerites, metabasalts/amphibolites and thin layers of ferruginous chert bands. The isotropic gabbros occur as intrusions in association with gabbroic anorthosites, plagiogranite and metabasalts/amphibolites. The gabbros are medium to fine grained with euhedral to subhedral orthopyroxenes, clinopyroxenes and subhedral plagioclase, together with rare amphiboles. Mineral chemistry of isotropic gabbros reveal that the clinopyroxenes are diopsidic to augitic in composition within the compositional ranges of En(42-59), Fs(5-12), Wo(31-50). They are Ca-rich and Na poor (Na2O < 0.77 wt%) characterized by high-Mg (Mg# 79-86) and low-Ti (TiO2 < 0.35 wt%) contents. The tectonic discrimination plots of clinopyroxene data indicate island arc signature of the source magma. Our study further confirms the suprasubduction zone origin of the Manamedu ophiolitic suite, associated with the subduction-collision history of the Neoproterozoic Mozambique ocean during the assembly of Gondwana supercontinent.

  3. Late Cretaceous and Paleogene sedimentation along east side of San Joaquin basin, California

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reid, S.A.

    1986-04-01

    Depositional systems of the Late Cretaceous contrast with those of the Paleogene in the subsurface along the east side of the San Joaquin basin between Bakersfield and Fresno, California. Upper Cretaceous deposits include thick fan-delta and submarine fan facies of the Moreno and Panoche Formations, whereas the paleogene contains extensive nearshore, shelf, slope, and submarine fan deposits of the Lodo, Domengine, and Kreyenhagen Formations. These sediments were deposited on a basement surface having several west-trending ridges and valleys. West-flowing streams draining an ancestral Sierra Nevada of moderate relief formed prograding fan deltas that filled the valleys with thick wedges ofmore » nonmarine channel deposits, creating a bajada along the shoreline. Detrital material moved rapidly from the shoreline through a narrow shelf, into a complex of submarine fans in the subduction trough. During the early Eocene, a low sea level stand plus an end of Sierra Nevada uplift resulted in the erosion of the range to a peneplain. Stream-fed fan deltas were replaced by a major river system, which flowed west on about the present course of the Kern River. Following a rapid sea level increase, sand from the river system was deposited on the now broad shelf along a wide belt roughly coincident with California Highway 99. The river was also the point source for sand in a submarine fan northwest of Bakersfield. Both Upper Cretaceous and Paleogene depositional systems probably continue north along the east edge of the Great Valley. This proposed scenario for the east side of the San Joaquin is analogous to forearc deposits in the San Diego area, including the Cretaceous Rosario fan-delta and submarine fan system and the Eocene La Jolla and Poway nearshore, shelf, and submarine fan systems.« less

  4. Carbonate sedimentation in an extensional active margin: Cretaceous history of the Haymana region, Pontides

    NASA Astrophysics Data System (ADS)

    Okay, Aral I.; Altiner, Demir

    2016-10-01

    The Haymana region in Central Anatolia is located in the southern part of the Pontides close to the İzmir-Ankara suture. During the Cretaceous, the region formed part of the south-facing active margin of the Eurasia. The area preserves a nearly complete record of the Cretaceous system. Shallow marine carbonates of earliest Cretaceous age are overlain by a 700-m-thick Cretaceous sequence, dominated by deep marine limestones. Three unconformity-bounded pelagic carbonate sequences of Berriasian, Albian-Cenomanian and Turonian-Santonian ages are recognized: Each depositional sequence is preceded by a period of tilting and submarine erosion during the Berriasian, early Albian and late Cenomanian, which corresponds to phases of local extension in the active continental margin. Carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units. The deep marine carbonate deposition ended in the late Santonian followed by tilting, erosion and folding during the Campanian. Deposition of thick siliciclastic turbidites started in the late Campanian and continued into the Tertiary. Unlike most forearc basins, the Haymana region was a site of deep marine carbonate deposition until the Campanian. This was because the Pontide arc was extensional and the volcanic detritus was trapped in the intra-arc basins and did not reach the forearc or the trench. The extensional nature of the arc is also shown by the opening of the Black Sea as a backarc basin in the Turonian-Santonian. The carbonate sedimentation in an active margin is characterized by synsedimentary vertical displacements, which results in submarine erosion, carbonate breccias and in the lateral discontinuity of the sequences, and differs from blanket like carbonate deposition in the passive margins.

  5. Are glendonites reliable indicators of cold conditions? Evidence from the Lower Cretaceous of Spitsbergen

    NASA Astrophysics Data System (ADS)

    Vickers, Madeleine; Price, Gregory; Watkinson, Matthew; Jerrett, Rhodri

    2017-04-01

    Glendonites are pseudomorphs after the mineral ikaite, and have been found in marine sediments throughout geological time. Ikaite is a metastable, hydrated form of calcium carbonate, which is only stable under specific conditions: between -2 and +5 °C, and with high alkalinity and phosphate concentrations. Glendonites are often associated with cold climates due to the strong temperature control on ikaite growth, and the coincidence in the geological record with episodes of global cooling. Glendonites are found in the Lower Cretaceous succession in Spitsbergen. During the Early Cretaceous, Spitsbergen was at a palaeolatitude of 60°N, and was part of a shallow epicontinental sea that formed during the Mesozoic as Atlantic rifting propagated northwards. Though the Early Cretaceous was generally characterised by greenhouse climate conditions, episodic cold snaps occurred during the Valanginian (the "Weissert Event") and during Aptian-Albian. Using high resolution carbon-isotope stratigraphy, we show that the first occurrences of glendonites are in the upper Lower Hauterivian and in the very upper Upper Hauterivian, stratigraphically higher than the Valanginian cooling event. Glendonites are also found in horizons in the Upper Aptian, coincident with the Aptian-Albian cold snap. Petrological analysis of the glendonite structure reveals differences between the Hauterivian and Aptian glendonites, with evidence for multiple diagenetic phases of growth in the Hauterivian glendonites, suggesting oscillating chemical conditions. This evidence suggests that local environmental conditions may have a stronger control on glendonite formation and preservation than global climate. We present a new model for ikaite growth and slow transformation to glendonite in marine sediments, which points to a more complex suite of diagenetic transformations than previously modelled. Furthermore, we critically assess whether such pseudomorphs after marine sedimentary ikaite may be indicators

  6. Estimating Latest Cretaceous and Tertiary Atmospheric PCO2 from Stomatal Indices

    NASA Astrophysics Data System (ADS)

    Royer, D. L.; Wing, S. L.; Beerling, D. J.

    2001-05-01

    Most modern C3 seed plants show an inverse relationship between PCO2 and stomatal index (SI), where SI is the proportion of epidermal cells that are stomatal packages. This plant-atmosphere response therefore provides a reliable approach for estimating paleo-CO2 levels. Since stomatal responses to CO2 are generally species-specific, one is limited in paleo-reconstructions to species that exist both in the fossil record and living today. Fossils morphologically similar to living Ginkgo biloba and Metasequoia glyptostroboides extend back to the early and late Cretaceous, respectively, indicating that the fossil and living forms are very closely related. Measurements of SI made on fossil Ginkgo and Metasequoia were calibrated with historical collections of G. biloba and M. glyptostroboides leaves from sites that developed during the anthropogenically-driven CO2 increases of the past 145 years (288-369 ppmv) and with saplings of G. biloba and M. glyptostroboides grown in CO2 controlled growth chambers (350-800 ppmv). Both nonlinear regressions are highly significant (Ginkgo: n = 40, r2 = 0.91; Metasequoia: n = 18; r2 = 0.85). Results from a sequence of 23 latest Cretaceous to early Eocene-aged Ginkgo-bearing sites indicate that CO2 remained between 300 and 450 ppmv with the exception of one high estimate ( ~800 ppmv) near the Paleocene/Eocene boundary, and results from 4 middle Miocene-aged Ginkgo- and Metasequoia-bearing sites indicate that CO2 was between 320 and 400 ppmv. If correct, the CO2 values estimated here are too low to explain via the CO2 greenhouse effect alone the higher global mean temperatures (e.g., 3-4 ° C for the early Eocene) inferred from models and geological data for these two intervals.

  7. An archaic crested plesiosaur in opal from the Lower Cretaceous high-latitude deposits of Australia

    PubMed Central

    Kear, Benjamin P; Schroeder, Natalie I; Lee, Michael S.Y

    2006-01-01

    Umoonasaurus demoscyllus gen. et sp. nov. is a new small-bodied (approx. 2.5 m) pliosauroid plesiosaur from the Lower Cretaceous (Aptian–Albian) of southern Australia. It is represented by several partial skeletons (one with a near complete skull is the most complete opalized vertebrate fossil yet known), and is unique in having large crests on the skull midline and above the orbits. Umoonasaurus is surprisingly archaic despite its relatively late age (approx. 115 Myr ago)—being simultaneously the most basal (primitive) and last surviving rhomaleosaurid. Notably, it lacks the ‘pliosauromorph’ features (large head, short neck, gigantism) typically characterizing many more derived Jurassic rhomaleosaurids; thus, reinforcing the suspected convergent evolution of the ‘pliosauromorph’ hypercarnivore body plan. Umoonasaurus inhabited an Early Cretaceous high-latitude (approx. 70° S) inland seaway subject to seasonally near-freezing climatic conditions. This extreme environment supported a diverse range of plesiosaur taxa, suggesting that these marine reptiles might have possessed adaptations (e.g. heightened metabolic levels) to cope with cold-water temperatures. Indeed, survival of ancient endemic lineages such as Umoonasaurus is a common phenomenon in Australian Cretaceous vertebrate assemblages and might have been facilitated by isolation in low-temperature high-latitude regions. PMID:17148303

  8. A review on the structural styles of deformation during Late Cretaceous and Paleocene tectonic phases in the southern North Sea area

    NASA Astrophysics Data System (ADS)

    Deckers, Jef; van der Voet, Eva

    2018-04-01

    The Mesozoic rifts in the southern North Sea area were affected by Late Cretaceous to Paleocene inversion. Two main inversion phases were traditionally identified in this interval: the Sub-Hercynian and the Laramide phases. The Sub-Hercynian phase started in the early Late Cretaceous, peaked during the Campanian and ended in the late Maastrichtian, while the Laramide phase started in the late Danian and ended in the Thanetian. The Late Cretaceous Sub-Hercynian phase was strong and occurred in several pulses. These pulses led to basin-scale uplift by large reverse movements along basin-bounding faults and resulted in large amounts of erosion (up to 2 km) of Mesozoic and older sediments. The middle Paleocene Laramide phase on the other hand resulted in mild, domal uplift of some Late Cretaceous inverted basins and subsidence (into depocenters) of others. The subsequent Cenozoic inversion phases displayed similar or lower amplitudes and wavelengths of vertical surface movements as the Laramide phase. The transition from the Sub-Hercynian to the Laramide phase in the southern North Sea area therefore coincides with the overall transition from fault-controlled inversion to broad domal vertical surface movements.

  9. Hydrogeology and preliminary assessment of regional flow in the upper Cretaceous and adjacent aquifers in the northern Mississippi embayment

    USGS Publications Warehouse

    Brahana, J.V.; Mesko, T.O.

    1988-01-01

    On a regional scale, the groundwater system of the northern Mississippi embayment is composed of a series of nonindurated clastic sediments that overlie a thick sequence of Paleozoic carbonate, sandstones, and shales. The units that comprise the geohydrologic framework of this study are the alluvium-lower Wilcox Aquifer the Midway confining unit, the Upper Cretaceous aquifer, the Cretaceous-Paleozoic confining unit, and the Ozark-St. Francois aquifer. The Upper Cretaceous aquifer of Late Cretaceous age is the primary focus of this investigation; the study is part of the Gulf Coast Regional Aquifer-System Analysis. A four layer finite-difference groundwater flow model enabled testing of alternative boundary concepts and provide a refined definition of the hydrologic budget of the deep aquifers. The alluvium-lower Wilcox aquifer, the Upper Cretaceous aquifer, and the Ozark-St. Francois aquifer form layers 2 through 4, respectively. Layer 1 is an inactive layer of constant heads representing shallow water levels, which are a major control on recharge to and discharge from the regional system. A matrix of leakance values simulates each confining unit, allowing vertical interchange of water between different aquifers. The model was calibrated to 1980 conditions by using the assumption that 1980 was near steady-state conditions; it was calibrated to simulate observed heads were found to be most sensitive to pumping, and least sensitive to the leakance. By using all available water quality and water level data, alternative boundary conditions were tested by comparing model simulated heads to observed heads. The results of the early modeling effort also contribute to a better understanding of the regional hydrologic budget, indicating that: upward leakage from the Ozark-St. Francois aquifer to the Upper Cretaceous aquifer is about 43 cu ft/sec; upward recharge of about 68 cu ft/sec occurs to the lower Wilcox-alluvium aquifer from the Upper Cretaceous aquifer; and the

  10. Radio-astrochronology of the Agrio Formation (Neuquén Basin, Argentina) to reduce the uncertainties of the geological time scale in Early Cretaceous times

    NASA Astrophysics Data System (ADS)

    Martinez, Mathieu; Beatriz, Aguirre-Urreta; Marina, Lescano; Julieta, Omarini; Maisa, Tunik; Thomas, Frederichs; Anna-Leah, Nickl; Heiko, Pälike

    2017-04-01

    the range of uncertainty mentioned by Martinez et al. (2015) (2.5 ± 0.4 myr), but being much longer than the duration of 1.21 myr proposed in the geological time scale 2016 (Ogg et al., 2016), suggesting the duration of the Hauterivian stage has to be increased by, at least, 0.9 myr for the next compilation. References: Aguirre-Urreta, B., et al., 2015. Filling the gap: new precise Early Cretaceous radioisotopic ages from the Andes. Geological Magazine 152, 557-564. Martinez, M., et al., 2015. Astrochronology of the Valanginian-Hauterivian stages (Early Cretaceous): chronological relationships between the Paraná-Etendeka large igneous province, the Weissert and the Faraoni events. Global and Planetary Change 131, 158-173. Ogg, J.G., et al., 2016. A Concise Geological Time Scale 2016. Elsevier B.V., 243 pp. Sagasti, G., 2005. Hemipelagic record of orbitally-induced dilution cycles in Lower Cretaceous sediments of the Neuquén Basin, in Veiga, G.D., Spaletti, L.A., Howell, J.A. and Schwarz E. (Eds.). The Neuquén Basin, Argentina: A Case Study in Sequence Stratigraphy and Basin Dynamics. Geological Society, London, Special Publications 252, 231-250.

  11. Environmental change during the Late Berriasian - Early Valanginian: a prelude to the late Early Valanginian carbon-isotope event?

    NASA Astrophysics Data System (ADS)

    Morales, Chloé; Schnyder, Johann; Spangenberg, Jorge; Adatte, Thierry; Westermann, Stephane; Föllmi, Karl

    2010-05-01

    European basins show that the climate became more humid during the Late Berriasian (Hallam et al., 1991, Schnyder et al., 2009). The aim of this project is to precisely characterize and date paleoenvironmental and paleoclimatic change during the latest Berriasian-Early Valanginian time interval in order to decipher if they can be viewed as precursor events, linked with the late Early Valanginian δ13C event. Three key sections have been studied: Capriolo (N Italy), Montclus (SE France) and Musfallen (E Switzerland) located in the Lombardian and Vocontian basins and on the Helvetic platform, respectively. Phosphorus and stable-isotope analyses have been performed, in addition to clay-mineralogy and facies determinations. The three sections show similar and comparable trends: The phosphorus content (in ppm) is higher in Late Berriasian sediments (compared to Early Berriasian and Valanginian deposits) and this period is also characterised by a decrease in δ13C values. This is interpreted as the result of enhanced continental weathering, which would be coeval with a change to a more humid climate during the Late Berriasian (Schnyder et al., 2009). References: Bornemann, A. and Mutterlose, J. (2008). "Calcareous nannofossil and d13C records from the Early Cretaceous of the Western Atlantic ocean: evidence of enhanced fertilization accross the Berriasian-Valanginian transition." palaios 23: 821-832. Duchamp-Alphonse, S., Gardin, S., Fiet, N., Bartolini, A., Blamart, D. and Pagel, M. (2007). "Fertilization of the northwestern Tethys (Vocontian basin, SE France) during the Valanginian carbon isotope perturbation: Evidence from calcareous nannofossils and trace element data." Palaeogeography, Palaeoclimatology, Palaeoecology 243(1-2): 132-151. Föllmi, K.B., Weissert, H., Bisping, M. & Funk, H. 1994: Phosphogenesis, carbon-isotope stratigraphy, and carbonate-platform evolution along the Lower Cretaceous northern tethyan margin. Geological Society of America, Bulletin 106, 729

  12. Sensitivity of the North Atlantic Basin to cyclic climatic forcing during the early Cretaceous

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.

    1999-01-01

    Striking cyclic interbeds of laminated dark-olive to black marlstone and bioturbated white to light-gray limestone of Neocomian (Early Cretaceous) age have been recovered at Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) sites in the North Atlantic. These Neocomian sequences are equivalent to the Maiolica Formation that outcrops in the Tethyan regions of the Mediterranean and to thick limestone sequences of the Vocontian Trough of France. This lithologic unit marks the widespread deposition of biogenic carbonate over much of the North Atlantic and Tethyan seafloor during a time of overall low sealevel and a deep carbonate compensation depth. The dark clay-rich interbeds typically are rich in organic carbon (OC) with up to 5.5% OC in sequences in the eastern North Atlantic. These eastern North Atlantic sequences off northwest Africa, contain more abundant and better preserved hydrogen-rich, algal organic matter (type II kerogen) relative to the western North Atlantic, probably in response to coastal upwelling induced by an eastern boundary current in the young North Atlantic Ocean. The more abundant algal organic matter in sequences in the eastern North Atlantic is also expressed in the isotopic composition of the carbon in that organic matter. In contrast, organic matter in Neocomian sequences in the western North Atlantic along the continental margin of North America has geochemical and optical characteristics of herbaceous, woody, hydrogen-poor, humic, type III kerogen. The inorganic geochemical characteristics of the dark clay-rich (80% CaCO3) interbeds in both the eastern and western basins of the North Atlantic suggest that they contain minor amounts of relatively unweathered eolian dust derived from northwest Africa during dry intervals.

  13. A paleolatitude reconstruction of the South Armenian Block (Lesser Caucasus) for the Late Cretaceous: Constraints on the Tethyan realm

    NASA Astrophysics Data System (ADS)

    Meijers, Maud J. M.; Smith, Brigitte; Kirscher, Uwe; Mensink, Marily; Sosson, Marc; Rolland, Yann; Grigoryan, Araik; Sahakyan, Lilit; Avagyan, Ara; Langereis, Cor; Müller, Carla

    2015-03-01

    The continental South Armenian Block - part of the Anatolide-Tauride South Armenian microplate - of Gondwana origin rifted from the African margin after the Triassic and collided with the Eurasian margin after the Late Cretaceous. During the Late Cretaceous, two northward dipping subduction zones were simultaneously active in the northern Neo-Tethys between the South Armenian Block in the south and the Eurasian margin in the north: oceanic subduction took place below the continental Eurasian margin and intra-oceanic subduction resulted in ophiolite obduction onto the South Armenian Block in the Late Cretaceous. The paleolatitude position of the South Armenian Block before its collision with Eurasia within paleogeographic reconstructions is poorly determined and limited to one study. This earlier study places the South Armenian Block at the African margin in the Early Jurassic. To reconstruct the paleolatitude history of the South Armenian Block, we sampled Upper Devonian-Permian and Cretaceous sedimentary rocks in Armenia. The sampled Paleozoic rocks have likely been remagnetized. Results from two out of three sites sampled in Upper Cretaceous strata pass fold tests and probably all three carry a primary paleomagnetic signal. The sampled sedimentary rocks were potentially affected by inclination shallowing. Therefore, two sites that consist of a large number of samples (> 100) were corrected for inclination shallowing using the elongation/inclination method. These are the first paleomagnetic data that quantify the South Armenian Block's position in the Tethys ocean between post-Triassic rifting from the African margin and post-Cretaceous collision with Eurasia. A locality sampled in Lower Campanian Eurasian margin sedimentary rocks and corrected for inclination shallowing, confirms that the corresponding paleolatitude falls on the Eurasian paleolatitude curve. The north-south distance between the South Armenian Block and the Eurasian margin just after Coniacian

  14. Evidence For Volcanic Initiation Of Cretaceous Ocean Anoxic Events (Invited)

    NASA Astrophysics Data System (ADS)

    Sageman, B. B.; Hurtgen, M. T.; McElwain, J.; Adams, D.; Barclay, R. S.; Joo, Y.

    2010-12-01

    Increasing evidence from studies of Cretaceous ocean anoxic events (OAE’s) has suggested that major changes in volcanic activity may have played a significant role in their genesis. Numerous specific mechanisms of have been proposed, including increases in atmospheric CO2 and surface temperature, leading to enhanced chemical weathering and terrestrial nutrient release, or increases in reduced trace metal fluxes, leading to oxygen depletion and possibly providing micronutrients for enhanced primary production. An additional pathway by which the byproducts of enhanced volcanic activity may have contributed to OAE genesis involves relationships between the biogeochemical cycles sulfur, iron, and phosphorus. Recent analysis of S-isotope data from carbonate-associated sulfate and pyrite collected across the Cenomanian-Turonian OAE2 in the Western Interior basin suggest that increases in sulfate to an initially sulfate-depleted ocean preceded onset of the event. Modern lake data support the idea that increases in sulfate concentration drive microbial sulfate reduction, leading to more efficient regeneration of P from sedimentary organic matter. If the early Cretaceous opening of the South Atlantic was accompanied by evaporite deposition sufficient to draw down global marine sulfate levels, and widespread anoxia leading to elevated pyrite burial helped maintain these low levels for the succeeding 30 myr, during which most Cretaceous OAE’s are found, perhaps pulses of volcanism that rapidly introduced large volumes of sulfate may have played a key role in OAE initiation. The eventually burial of S in the form of pyrite may have returned sulfate levels to a low background, thus providing a mechanism to terminate the anoxic events. This talk will review the evidence for volcanic initiation of OAE’s in the context of the sulfate-phosphorus regeneration model.

  15. Impact of the terminal Cretaceous event on plant–insect associations

    PubMed Central

    Labandeira, Conrad C.; Johnson, Kirk R.; Wilf, Peter

    2002-01-01

    Evidence for a major extinction of insect herbivores is provided by presence–absence data for 51 plant–insect associations on 13,441 fossil plant specimens, spanning the Cretaceous/Paleogene boundary in southwestern North Dakota. The most specialized associations, which were diverse and abundant during the latest Cretaceous, almost disappeared at the boundary and failed to recover in younger strata even while generalized associations regained their Cretaceous abundances. These results are consistent with a sudden ecological perturbation that precipitated a diversity bottleneck for insects and plants. PMID:11854501

  16. Potomacapnos apeleutheron gen. et sp. nov., a new Early Cretaceous angiosperm from the Potomac Group and its implications for the evolution of eudicot leaf architecture.

    PubMed

    Jud, Nathan A; Hickey, Leo J

    2013-12-01

    Eudicots diverged early in the evolution of flowering plants and now comprise more than 70% of angiosperm species. In spite of the importance of eudicots, our understanding of the early evolution of this clade is limited by a poor fossil record and uncertainty about the order of early phylogenetic branching. The study of Lower Cretaceous fossils can reveal much about the evolution, morphology, and ecology of the eudicots. Fossils described here were collected from Aptian sediments of the Potomac Group exposed at the Dutch Gap locality in Virginia, USA. Specimens were prepared by degaging, then described and compared with leaves of relevant extant and fossil plants. We conducted a phylogenetic analysis of morphological characters using parsimony while constraining the tree search with the topology found through molecular phylogenetic analyses. The new species is closely related to ranunculalean eudicots and has leaf architecture remarkably similar to some living Fumarioideae (Papaveraceae). These are the oldest eudicot megafossils from North America, and they show complex leaf architecture reflecting developmental pathways unique to extant eudicots. The morphology and small size of the fossils suggest that they were herbaceous plants, as is seen in other putative early eudicots. The absence of co-occurring tricolpate pollen at Dutch Gap either (1) reflects low preservation probability for pollen of entomophilous herbs or (2) indicates that some leaf features of extant eudicots appeared before the origin of tricolpate pollen.

  17. Foraminiferal biostratigraphy of Upper Cretaceous (Campanian - Maastrichtian) sequences in the Peri-Tethys basin; Moghan area, NW Iran

    NASA Astrophysics Data System (ADS)

    Omidvar, Mahboobeh; Safari, Amrollah; Vaziri-Moghaddam, Hossain; Ghalavand, Hormoz

    2018-04-01

    The Upper Cretaceous sediments in the Moghan area, NW Iran, contain diverse planktonic and benthic foraminifera, with a total of 33 genera and 53 species (17 genera and 38 species of planktonic foraminifera and 16 genera and 15 species from benthic foraminifera), which led to the identification of six biozones spanning the middle Campanian to late Maastrichtian. A detailed paleontological study and biostratigraphic zonation of these sequences has been carried out in four surface sections. This study shows that there are two different facies in the Moghan area, based on the faunal content. A deep open marine condition exists in the Molok, Selenchai and Nasirkandi sections. In these sections, Upper Cretaceous sequences have diverse planktonic foraminiferal species including the Globotruncana ventricosa (middle to late Campanian), Globotruncanella havanensis (late Campanian), Globotruncana aegyptiaca (latest Campanian), Gansserina gansseri (latest Campanian to early Maastrichtian), Contusotruncana contusa- Racemiguembelina fructicosa (early to late Maastrichtian) and Abathomphalus mayaroensis (late Maastrichtian) zones. This deep open marine setting grades laterally into shallower marine condition dominated by large benthic foraminifera such as Orbitoides media, Orbitoides gruenbachensis, Orbitoides cf. apiculata, Lepidorbitoides minor, Pseudosiderolites sp., Siderolites praecalcitrapoides, Siderolites aff. calcitrapoides and Siderolites calcitrapoides. This facies is mainly recorded in the Hovay section. A detailed biostratigraphic zonation scheme is presented for the studied sections and correlated with the results of other studies in the Tethyan realm. This is the first biozonation scheme for Upper Cretaceous sequences of the Moghan area that can be used as a basis for ongoing studies in this area and other parts of Tethys basin.

  18. Exceptional preservation of tiny embryos documents seed dormancy in early angiosperms.

    PubMed

    Friis, Else Marie; Crane, Peter R; Pedersen, Kaj Raunsgaard; Stampanoni, Marco; Marone, Federica

    2015-12-24

    The rapid diversification of angiosperms through the Early Cretaceous period, between about 130-100 million years ago, initiated fundamental changes in the composition of terrestrial vegetation and is increasingly well understood on the basis of a wealth of palaeobotanical discoveries over the past four decades and their integration with improved knowledge of living angiosperms. Prevailing hypotheses, based on evidence both from living and from fossil plants, emphasize that the earliest angiosperms were plants of small stature with rapid life cycles that exploited disturbed habitats in open, or perhaps understorey, conditions. However, direct palaeontogical data relevant to understanding the seed biology and germination ecology of Early Cretaceous angiosperms are sparse. Here we report the discovery of embryos and their associated nutrient storage tissues in exceptionally well-preserved angiosperm seeds from the Early Cretaceous. Synchrotron radiation X-ray tomographic microscopy of the fossil embryos from many taxa reveals that all were tiny at the time of dispersal. These results support hypotheses based on extant plants that tiny embryos and seed dormancy are basic for angiosperms as a whole. The minute size of the fossil embryos, and the modest nutrient storage tissues dictated by the overall small seed size, is also consistent with the interpretation that many early angiosperms were opportunistic, early successional colonizers of disturbance-prone habitats.

  19. The Mid-Cretaceous Frontier Formation near the Moxa Arch, southwestern Wyoming

    USGS Publications Warehouse

    Mereweather, E.A.; Blackmon, P.D.; Webb, J.C.

    1984-01-01

    The Frontier Formation in the Green River Basin of Wyoming, Utah, and Colorado, consists of sandstone, siltstone, and shale, and minor conglomerate, coal, and bentonite. These strata were deposited in several marine and nonmarine environments during early Late Cretaceous time. At north-trending outcrops along the eastern edge of the overthrust belt, the Frontier is of Cenomanian, Turonian, and early Coniacian age, and commonly is about 610 m (2,000 ft) thick. The formation in that area conformably overlies the Lower Cretaceous Aspen Shale and is divided into the following members, in ascending order: Chalk Creek, Coalville, Allen Hollow, Oyster Ridge Sandstone, and Dry Hollow. In west-trending outcrops on the northern flank of the Uinta Mountains in Utah, the Frontier is middle and late Turonian, and is about 60 m (200 ft) thick. These strata disconformably overlie the Lower Cretaceous Mowry Shale. In boreholes on the Moxa arch, the upper part of the Frontier is of middle Turonian to early Coniacian age and unconformably overlies the lower part of the formation, which is early Cenomanian at the south end and probably Cenomanian to early Turonian at the north end. The Frontier on the arch thickens northward from less than 100 m (328 ft) to more than 300 m (984 ft) and conformably overlies the Mowry. The marine and nonmarine Frontier near the Uinta Mountains, marine and mnmarine beds in the upper part of the formation on the Moxa arch and the largely nonmarine Dry Hollow Member at the top of the Frontier in the overthrust belt are similar in age. Older strata in the formation, which are represented by the disconformable basal contact of the Frontier near the Uinta Mountains, thicken northward along the Moxa arch and westward between the arch and the overthrust belt. The large changes in thickness of the Frontier in the Green River Basin were caused mainly by differential uplift and truncation of the lower part of the formation during the early to middle Turonian and

  20. Rebuilding Biodiversity of Patagonian Marine Molluscs after the End-Cretaceous Mass Extinction

    PubMed Central

    Aberhan, Martin; Kiessling, Wolfgang

    2014-01-01

    We analysed field-collected quantitative data of benthic marine molluscs across the Cretaceous–Palaeogene boundary in Patagonia to identify patterns and processes of biodiversity reconstruction after the end-Cretaceous mass extinction. We contrast diversity dynamics from nearshore environments with those from offshore environments. In both settings, Early Palaeogene (Danian) assemblages are strongly dominated by surviving lineages, many of which changed their relative abundance from being rare before the extinction event to becoming the new dominant forms. Only a few of the species in the Danian assemblages were newly evolved. In offshore environments, however, two newly evolved Danian bivalve species attained ecological dominance by replacing two ecologically equivalent species that disappeared at the end of the Cretaceous. In both settings, the total number of Danian genera at a locality remained below the total number of late Cretaceous (Maastrichtian) genera at that locality. We suggest that biotic interactions, in particular incumbency effects, suppressed post-extinction diversity and prevented the compensation of diversity loss by originating and invading taxa. Contrary to the total number of genera at localities, diversity at the level of individual fossiliferous horizons before and after the boundary is indistinguishable in offshore environments. This indicates an evolutionary rapid rebound to pre-extinction values within less than ca 0.5 million years. In nearshore environments, by contrast, diversity of fossiliferous horizons was reduced in the Danian, and this lowered diversity lasted for the entire studied post-extinction interval. In this heterogeneous environment, low connectivity among populations may have retarded the recolonisation of nearshore habitats by survivors. PMID:25028930

  1. Nannofossil carbonate fluxes during the Early Cretaceous: Phytoplankton response to nutrification episodes, atmospheric CO2, and anoxia

    NASA Astrophysics Data System (ADS)

    Erba, Elisabetta; Tremolada, Fabrizio

    2004-03-01

    Greenhouse episodes during the Valanginian and Aptian correlate with major perturbations in the C cycle and in marine ecosystems, carbonate crises, and widespread deposition of Corg-rich black shales. Quantitative analyses of nannofossil micrite were conducted on continuous pelagic sections from the Southern Alps (northern Italy), where high-resolution integrated stratigraphy allows precise dating of Early Cretaceous geological events. Rock-forming calcareous nannofloras were quantified in smear slides and thin sections to obtain relative and absolute abundances and paleofluxes that are interpreted as the response of calcareous phytoplankton to global changes in the ocean-atmosphere system. Increased rates of volcanism during the formation of Ontong Java and Manihiki Plateaus and the Paranà-Etendeka large igneous province (LIP) are proposed to have caused the geological responses associated with early Aptian oceanic anoxic event (OAE) 1a and the Valanginian event, respectively. Calcareous nannofloras reacted to the new conditions of higher pCO2 and fertility by drastically reducing calcification. The Valanginian event is marked by a 65% reduction in nannofossil paleofluxes that would correspond to a 2-3 times increase in pCO2 during formation of the Paranà-Endenteka LIP. A 90% reduction in nannofossil paleofluxes, which occurred in a 1.5 myr-long interval leading into OAE1a, is interpreted as the result of a 3-6 times increase in pCO2 produced by emplacement of the giant Ontong Java and Manihiki Plateaus. High pCO2 was balanced back by an accelerated biological pump during the Valanginian episode, but not during OAE1a, suggesting persisting high levels of pCO2 in the late Aptian and/or the inability of calcareous phytoplankton to absorb excess pCO2 above threshold values.

  2. Late Cretaceous vicariance in Gondwanan amphibians.

    PubMed

    Van Bocxlaer, Ines; Roelants, Kim; Biju, S D; Nagaraju, J; Bossuyt, Franky

    2006-12-20

    Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions.

  3. Cretaceous combined structure in eastern Sichuan Basin, China

    NASA Astrophysics Data System (ADS)

    Wang, P.; Liu, S.

    2009-12-01

    Eastern Sichuan Basin is confined by two thin-skinned fold-thrust belt, NW-trending Southern Daba Shan (Shan=Mountain) (SDB) in the northeast and NNE- or NE-trending Western XueFeng Shan (WXF) in the southeast, which constitute two convergent salients convex to the inner basin respectively. Although many factors can lead to the formation of fold-thrust belt salients, the eastern Sichuan salients would be attributed to the combined structure (firstly nominated by Chinese geologist, Li Siguang), which means the interaction of two structural belts in the same period. By field surveying and geological map interpreting, we found that WXF deformation began in Late Jurassic along the eastern side of structral belt, where the synclines cored by Upper-Middle Jurassic rock. The initial time of SDB deformation remains poorly determined, however our palaeocurrent data of Lower Cretaceous rock in adjecent foreland basin indicate the provenance from northeast or east. Hence we considered the two fold-thrust belt started interactive in Late Jurassic and mainly combined during Cretaceous. In Early Cretaceous, the front belt of WXF salient arrived near KaiXian where NEE-trending arc-shape folds converged with the NWW-trending arc-shape folds of SDB.The two salients shaped like an westward "open mouth", east of which EW-trending folds of two structural belts juxtaposed. Particularly in the middle belt of WXF (FengJie - WuFeng) the earlier NEE-trending folds were refolded by later NNE-trending folds. We interpret the NEE-trending folds as the front belt of earlier (maybe Late Jurassic) WXF salient. When the two combined fold belts propagated westward together, the original NNE-trending front belt of WXF constrained by the front belt of SDB and formed the curved fold trend lines convex to NNW. Then as WXF deformation continued but SDB gradually terminated, the consequent NNE-trending folds could not be curved and would superpose on the earlier NEE-trending folds.In Late Cretaceous

  4. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds.

    PubMed

    Zhang, Fucheng; Kearns, Stuart L; Orr, Patrick J; Benton, Michael J; Zhou, Zhonghe; Johnson, Diane; Xu, Xing; Wang, Xiaolin

    2010-02-25

    Spectacular fossils from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of dinosaurs and early birds, and contributed to our understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in integumentary filaments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres. Examples of both eumelanosomes and phaeomelanosomes have been identified, and they are often preserved in life position within the structure of partially degraded feathers and filaments. Furthermore, the data here provide empirical evidence for reconstructing the colours and colour patterning of these extinct birds and theropod dinosaurs: for example, the dark-coloured stripes on the tail of the theropod dinosaur Sinosauropteryx can reasonably be inferred to have exhibited chestnut to reddish-brown tones.

  5. Sedimentology and Reservoir Characteristics of Early Cretaceous Fluvio-Deltaic and Lacustrine Deposits, Upper Abu Gabra Formation, Sufyan Sub-basin, Muglad Rift Basin, Sudan

    NASA Astrophysics Data System (ADS)

    Yassin, Mohamed; Abdullatif, Osman; Hariri, Mustafa

    2017-04-01

    Sufyan Sub-basin is an East-West trending Sub-basin located in the northwestern part of the Muglad Basin (Sudan), in the eastern extension of the West and Central Africa Rift System (WCARS). The Early Cretaceous Abu Gabra Formation considered as the main source rock in the Muglad Basin. In Sufyan Sub-basin the Early Cretaceous Upper Abu Gabra Formation is the main oil-producing reservoir. It is dominated by sandstone and shales deposited in fluvio-deltaic and lacustrine environment during the first rift cycle in the basin. Depositional and post-depositional processes highly influenced the reservoir quality and architecture. This study investigates different scales of reservoir heterogeneities from macro to micro scale. Subsurface facies analysis was analyzed based on the description of six conventional cores from two wells. Approaches include well log analysis, thin sections and scanning electron microscope (SEM) investigations, grain-size, and X-ray diffraction (XRD) analysis of the Abu Gabra sandstone. The cores and well logs analyses revealed six lithofacies representing fluvio-deltaic and lacustrine depositional environment. The sandstone is medium to coarse-grained, poorly to moderately sorted and sub-angular to subrounded, Sub-feldspathic arenite to quartz arenite. On macro-scale, reservoir quality varies within Abu Gabra reservoir where it shows progressive coarsening upward tendencies with different degrees of connectivity. The upper part of the reservoir showed well connected and amalgamated sandstone bodies, the middle to lower parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenesis.The XRD and SEM analyses show that kaolinite and chlorite clay are the common clay minerals in the studied samples. Clay matrix and quartz overgrowth have significantly reduced the reservoir porosity and permeability, while the dissolution of feldspars

  6. The late early Miocene Sabine River

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Manning, E.

    Work on a new late early Miocene vertebrate fossil site, in a paleochannel deposit of the upper Carnahan Bayou Member of the lower Fleming Formation, has revealed unexpected data on the course and nature of the Sabine River of that time. Screen washing for smaller vertebrate remains at the site, just west of the Sabine River in Newton County, central eastern Texas, has resulted in the recovery of early Permian, Early Cretaceous, Late Cretaceous (Maestrichtian), Paleocene/Eocene, late Eocene, and Oligocene/Miocene fossils, in addition to the main early Miocene fauna. The reworked fossils, as well as distinctive mineral grains, show thatmore » the late early Miocene Sabine River was connected to the Texas/Oklahoma/Arkansas boundary section of the Red River, as well as to rivers draining the southern Ouachita Mountains. These rivers must have joined the Texas/Louisiana boundary section of the Sabine River somewhere in northwest Louisiana at that time. This suggests that the Louisiana section of the present Red River pirated the Texas/Oklahoma/Arkansas boundary section of the river some time after the early Miocene. The preservation of recognizable fossils transported hundreds of miles in a large river itself requires explanation. It is speculated here that the late early Miocene Sabine River incorporated a large amount of the then recently deposited volcanic ash from the Trans-Pecos Volcanic Field. Montmorillonite clay from the altered volcanic ash would have made the river very turbid, which could have allowed coarse sand-sized particles to be carried in the suspended load of the river, rather than in its bed load (where they would have been destroyed by the rolling chert gravel). Additional evidence for such long-distance fossil transport in the late early Miocene rivers of the western Gulf Coastal Plain comes from the abundant Cretaceous fossils of the upper Oakville Formation of southeast Texas and the Siphonina davisi zone of the southeast Texas subsurface.« less

  7. Early Cretaceous bimodal volcanism in the Duolong Cu mining district, western Tibet: Record of slab breakoff that triggered ca. 108-113 Ma magmatism in the western Qiangtang terrane

    NASA Astrophysics Data System (ADS)

    Wei, Shao-gang; Tang, Ju-xing; Song, Yang; Liu, Zhi-bo; Feng, Jun; Li, Yan-bo

    2017-05-01

    We report new zircon U-Pb ages and Hf isotope compositions, and whole-rock major and trace element and Sr-Nd isotope data for the Meiriqiecuo Formation (MF) bimodal volcanic rocks collected from the Duolong Cu mining district (DCMD) in the western Qiangtang terrane (QT), western Tibet. These data provide important constraints on the petrogenetic evolution and geodynamic setting of Early Cretaceous magmatism in the DCMD. The MF bimodal volcanic rocks are mainly basaltic andesite and andesite, with subordinate rhyolite. Four mafic samples yielded zircon U-Pb ages of ca. 108.2-113.0 Ma, and one silicic sample has an age of 109.3 ± 2.2 Ma, indicating that the mafic and silicic eruptions were contemporaneous. The MF bimodal volcanic rocks belong to the medium-K calc-alkaline to shoshonite series. The rocks show arc-type affinities characterized by significant enrichment in light rare earth (LaN/YbN = 7.74-12.60) and large-ion lithophile elements (Rb, Cs, K, and Pb), but depletions in the high-field-strength elements (Nb, Ta, and Ti), which geochemically resemble Andean arc basalts. Therefore, the MF bimodal volcanic rocks were likely emplaced at an Andean-type active continental margin and represent an Early Cretaceous magmatic arc that was located at the western QT margin. Moreover, the mafic volcanic rocks have high initial Sr isotopic ratios (0.705269-0.705413) and negative εNd(t) values of -1.5 to -0.6 compared with the silicic volcanic rocks ((87Sr/86Sr)i = 0.704770-0.704903; εNd(t) = +1.2 to +1.3). Zircons from silicic samples have significantly higher εHf(t) values (+11.6 to +15.5) and predominantly lower Paleoproterozoic Hf crustal model ages (TDMC = 180-428 Ma) than the mafic samples, which have variable εHf(t) values of +3.4 to +13.0 and TDMC ages of 346-952 Ma. These results indicate that the mafic and silicic end-members of the MF bimodal suite were generated from mantle and crustal sources, respectively. The basaltic andesite and andesite may have been

  8. New long-proboscid lacewings of the mid-Cretaceous provide insights into ancient plant-pollinator interactions.

    PubMed

    Lu, Xiu-Mei; Zhang, Wei-Wei; Liu, Xing-Yue

    2016-05-05

    Many insects with long-proboscid mouthparts are among the pollinators of seed plants. Several cases of the long-proboscid pollination mode are known between fossil insects (e.g., true flies, scorpionflies, and lacewings) and various extinct gymnosperm lineages, beginning in the Early Permian and increasing during the Middle Jurassic to Early Cretaceous. However, details on the morphology of lacewing proboscides and the relevant pollination habit are largely lacking. Here we report on three lacewing species that belong to two new genera and a described genus from mid-Cretaceous (Albian-Cenomanian) amber of Myanmar. All these species possess relatively long proboscides, which are considered to be modified from maxillary and labial elements, probably functioning as a temporary siphon for feeding on nectar. Remarkably, these proboscides range from 0.4-1.0 mm in length and are attributed to the most diminutive ones among the contemporary long-proboscid insect pollinators. Further, they clearly differ from other long-proboscid lacewings which have a much longer siphon. The phylogenetic analysis indicates that these Burmese long-proboscid lacewings belong to the superfamily Psychopsoidea but cannot be placed into any known family. The present findings represent the first description of the mouthparts of long-proboscid lacewings preserved in amber and highlight the evolutionary diversification of the ancient plant-pollinator interactions.

  9. Recycling of Amazonian detrital zircons in the Mixteco terrane, southern Mexico: Paleogeographic implications during Jurassic-Early Cretaceous and Paleogene times

    NASA Astrophysics Data System (ADS)

    Silva-Romo, Gilberto; Mendoza-Rosales, Claudia Cristina; Campos-Madrigal, Emiliano; Morales-Yáñez, Axél; de la Torre-González, Alam Israel; Nápoles-Valenzuela, Juan Ivan

    2018-04-01

    In the northeastern Mixteco terrane of southern Mexico, in the Ixcaquixtla-Atzumba region, the recycling of Amazonian detrital zircons records the paleogeography during the Mesozoic period in the context of the breakup of Pangea, a phenomenon that disarticulated the Sanozama-La Mora paleo-river. The clastic units of southern Mexico in the Ayuquila, Otlaltepec and Zapotitlán Mesozoic basins, as well as in the Atzumba Cenozoic basin, are characterized by detrital zircon contents with ages specific to the Amazonian craton, ranging between 3040 and 1278 Ma. The presence of zircons of Amazonian affinity suggests a provenance by recycling from carrier units such as the La Mora Formation or the Ayú Complex. In the area, the Ayú and Acatlán complexes form the Cosoltepec block, a paleogeographic element that during Early Cretaceous time acted as the divide between the slopes of the paleo-Gulf of Mexico and the paleo-Pacific Ocean. The sedimentological characteristics of the Jurassic-Cenozoic clastic successions in the Ixcaquixtla-Atzumba region denote relatively short transport in braided fluvial systems and alluvial fans. In this way, several basins are recognized around the Cosoltepec block. At the southeastern edge of the Cosoltepec block, the Ayuquila and Tecomazúchil formations accumulated in the Ayuquila continental basin on the paleo-Pacific Ocean slope. On the other hand, within the paleo-Gulf of Mexico slope, in the Otlaltepec continental basin, the Piedra Hueca and the Otlaltepec formations accumulated. The upper member of the Santa Lucía Formation accumulated in a transitional environment on the southwestern shoulder of the Zapotitlán basin, as well as on the paleo-Gulf of Mexico slope. In the Ayuquila basin, a marine transgression is recognized that advanced from south to north during the Late Jurassic. At the northeastern edge of the Cosoltepec block, we propose that the Santa Lucía formation attests to a transgression from the paleo-Gulf of Mexico

  10. Recurrent Early Cretaceous, Indo-Madagascar (89-86 Ma) and Deccan (66 Ma) alkaline magmatism in the Sarnu-Dandali complex, Rajasthan: 40Ar/39Ar age evidence and geodynamic significance

    NASA Astrophysics Data System (ADS)

    Sheth, Hetu; Pande, Kanchan; Vijayan, Anjali; Sharma, Kamal Kant; Cucciniello, Ciro

    2017-07-01

    The Sarnu-Dandali alkaline complex in Rajasthan, northwestern India, is considered to represent early, pre-flood basalt magmatism in the Deccan Traps province, based on a single 40Ar/39Ar age of 68.57 Ma. Rhyolites found in the complex are considered to be 750 Ma Malani basement. Our new 40Ar/39Ar ages of 88.9-86.8 Ma (for syenites, nephelinite, phonolite and rhyolite) and 66.3 ± 0.4 Ma (2σ, melanephelinite) provide clear evidence that whereas the complex has Deccan-age (66 Ma) components, it is dominantly an older (by 20 million years) alkaline complex, with rhyolites included. Basalt is also known to underlie the Early Cretaceous Sarnu Sandstone. Sarnu-Dandali is thus a periodically rejuvenated alkaline igneous centre, active twice in the Late Cretaceous and also earlier. Many such centres with recurrent continental alkaline magmatism (sometimes over hundreds of millions of years) are known worldwide. The 88.9-86.8 Ma 40Ar/39Ar ages for Sarnu-Dandali rocks fully overlap with those for the Indo-Madagascar flood basalt province formed during continental breakup between India (plus Seychelles) and Madagascar. Recent 40Ar/39Ar work on the Mundwara alkaline complex in Rajasthan, 120 km southeast of Sarnu-Dandali, has also shown polychronous emplacement (over ≥ 45 million years), and 84-80 Ma ages obtained from Mundwara also arguably represent post-breakup stages of the Indo-Madagascar flood basalt volcanism. Remnants of the Indo-Madagascar province are known from several localities in southern India but hitherto unknown from northwestern India 2000 km away. Additional equivalents buried under the vast Deccan Traps are highly likely.

  11. 15N/14N variations in Cretaceous Atlantic sedimentary sequences: implication for past changes in marine nitrogen biogeochemistry

    USGS Publications Warehouse

    Rau, G.H.; Arthur, M.A.; Dean, W.E.

    1987-01-01

    At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds ("black shales") were found to have significantly lower ??15N values (lower 15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in particular have ??15N values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools. In contrast, black, organic-carbon-rich beds at a third site (DSDP Site 603) contain predominantly terrestrial organic matter and have C- and N-isotopic compositions similar to organic matter of modern terrestrial origin. The recurring 15N depletion in the marine-derived Cretaceous sequences prove that the nitrogen they contain is the end result of an episodic and atypical biogeochemistry. Existing isotopic and other data indicate that the low 15N relative abundance is the consequence of pelagic rather than post-depositional processes. Reduced ocean circulation, increased denitrification, and, hence, reduced euphotic zone nitrate availability may have led to Cretaceous phytoplankton assemblages that were periodically dominated by N2-fixing blue-green algae, a possible source of this sediment 15N-depletion. Lack of parallel isotopic shifts in Cretaceous terrestrially-derived nitrogen (Site 603) argues that the above change in nitrogen cycling during this period did not extend beyond the marine environment. ?? 1987.

  12. Perinate and eggs of a giant caenagnathid dinosaur from the Late Cretaceous of central China

    PubMed Central

    Pu, Hanyong; Zelenitsky, Darla K.; Lü, Junchang; Currie, Philip J.; Carpenter, Kenneth; Xu, Li; Koppelhus, Eva B.; Jia, Songhai; Xiao, Le; Chuang, Huali; Li, Tianran; Kundrát, Martin; Shen, Caizhi

    2017-01-01

    The abundance of dinosaur eggs in Upper Cretaceous strata of Henan Province, China led to the collection and export of countless such fossils. One of these specimens, recently repatriated to China, is a partial clutch of large dinosaur eggs (Macroelongatoolithus) with a closely associated small theropod skeleton. Here we identify the specimen as an embryo and eggs of a new, large caenagnathid oviraptorosaur, Beibeilong sinensis. This specimen is the first known association between skeletal remains and eggs of caenagnathids. Caenagnathids and oviraptorids share similarities in their eggs and clutches, although the eggs of Beibeilong are significantly larger than those of oviraptorids and indicate an adult body size comparable to a gigantic caenagnathid. An abundance of Macroelongatoolithus eggs reported from Asia and North America contrasts with the dearth of giant caenagnathid skeletal remains. Regardless, the large caenagnathid-Macroelongatoolithus association revealed here suggests these dinosaurs were relatively common during the early Late Cretaceous. PMID:28486442

  13. Paleomagnetism of Jurassic and Cretaceous rocks in central Patagonia: a key to constrain the timing of rotations during the breakup of southwestern Gondwana?

    NASA Astrophysics Data System (ADS)

    Geuna, Silvana E.; Somoza, Rubén; Vizán, Haroldo; Figari, Eduardo G.; Rinaldi, Carlos A.

    2000-08-01

    A paleomagnetic study in Jurassic and Cretaceous rocks from the Cañadón Asfalto basin, central Patagonia, indicates the occurrence of about 25-30° clockwise rotation in Upper Jurassic-lowermost Cretaceous rocks, whereas the overlying mid-Cretaceous rocks do not show evidence of rotation. This constrains the tectonic rotation to be related to a major regional unconformity in Patagonia, which in turn seems to be close in time with the early opening of the South Atlantic Ocean. The sense and probably the timing of this rotation are similar to those of other paleomagnetically detected rotations in different areas of southwestern Gondwana, suggesting a possible relationship between these and major tectonic processes related with fragmentation of the supercontinent. On the other hand, the mid-Cretaceous rocks in the region yield a paleopole located at Lat. 87° South, Long. 159° East, A95=3.8°. This pole position is consistent with coeval high-quality paleopoles of other plates when transferred to South American coordinates, implying it is an accurate determination of the Aptian (circa 116 Ma) geomagnetic field in South America.

  14. The bivalve Anopaea (Inoceramidae) from the Upper Jurassic-lowermost Cretaceous of Mexico

    NASA Astrophysics Data System (ADS)

    Zell, Patrick; Crame, J. Alistair; Stinnesbeck, Wolfgang; Beckmann, Seija

    2015-07-01

    In Mexico, the Upper Jurassic to lowermost Cretaceous La Casita and coeval La Caja and La Pimienta formations are well-known for their abundant and well-preserved marine vertebrates and invertebrates. The latter include conspicuous inoceramid bivalves of the genus Anopaea not formally described previously from Mexico. Anopaea bassei (Lecolle de Cantú, 1967), Anopaea cf. stoliczkai (Holdhaus, 1913), Anopaea cf. callistoensis Crame and Kelly, 1995 and Anopaea sp. are rare constituents in distinctive Tithonian-lower Berriasian levels of the La Caja Formation and one Tithonian horizon of the La Pimienta Formation. Anopaea bassei was previously documented from the Tithonian of central Mexico and Cuba, while most other members of Anopaea described here are only known from southern high latitudes. The Mexican assemblage also includes taxa which closely resemble Anopaea stoliczkai from the Tithonian of India, Indonesia and the Antarctic Peninsula, and Anopaea callistoensis from the late Tithonian to ?early Berriasian of the Antarctic Peninsula. Our new data expand the palaeogeographical distribution of the high latitude Anopaea to the Gulf of Mexico region and substantiate faunal exchange, in the Late Jurassic-earliest Cretaceous, between Mexico and the Antarctic Realm.

  15. Paleomagnetism of Jurassic-Cretaceous basalts from the Franz Josef Land Archipelago: tectonic implications

    NASA Astrophysics Data System (ADS)

    Abashev, Victor; Mikhaltsov, Nikolay; Vernikovsky, Valery

    2015-04-01

    New paleomagnetic data were obtained from a total of 158 oriented samples collected from the Jurassic magmatic complexes exposed on the Franz Joseph Land Archipelago (FJL). The field work was conducted during 2011 field season. Present study was focused on the tholeiitic basaltic lava flows that crop out on the Hooker Island. The samples were subjected to a detailed step-wise thermal demagnetization in temperatures up to 600 deg C or alternating field demagnetization with maximum filed up to 140 mT. Natural remanent magnetization (NRM) was measured with a 2G cryogenic magnetometer or a JR-6A spin-magnetometer housed in a magnetically shielded room at the Institute of Petroleum Geology and Geophysics, Siberian Branch of Russian Academy of Sciences. The main NRM carriers in the FJL samples are titanomagnetites with varying Ti-content. Magnetic remanence was unblocked in temperatures of 350-400 deg C. Some samples are characterized by unblocking temperatures of 560 deg C. The new paleomagnetic data were combined with those previously obtained from the early Cretaceous volcanics exposed on the FJL. A new mean paleomagnetic direction for the Jurassic rocks was calculated as D=78.3 deg, I=74.7 deg, a95=3.1 deg, k=194.3, N=13. A corresponding paleomagnetic pole is now located at Plat=62.1 deg; Plon=136.5 deg, A95=5.5 deg, K=63.6. New results suggest that the JFL occupied a significantly different position from that of the present day. However, in early Cretaceous the JFL was already located close to its present day position. We propose a rifting event between the North Barentz terrane (FJL and possibly Svalbard) and the counterpart of European tectonic domain. The rifting occurred during Early-Middle Jurassic. This event was accompanied by a significant shift of the FJL to the north-east for approximately 500 km. New results are in good agreement with a hypothesis that the FJL was passing over the Icelandic-Siberian hot spot during the Jurassic-Cretaceous time

  16. Fossil evidence for the early ant evolution

    NASA Astrophysics Data System (ADS)

    Perrichot, Vincent; Lacau, Sébastien; Néraudeau, Didier; Nel, André

    2008-02-01

    Ants are one of the most studied insects in the world; and the literature devoted to their origin and evolution, systematics, ecology, or interactions with plants, fungi and other organisms is prolific. However, no consensus yet exists on the age estimate of the first Formicidae or on the origin of their eusociality. We review the fossil and biogeographical record of all known Cretaceous ants. We discuss the possible origin of the Formicidae with emphasis on the most primitive subfamily Sphecomyrminae according to its distribution and the Early Cretaceous palaeogeography. And we review the evidence of true castes and eusociality of the early ants regarding their morphological features and their manner of preservation in amber. The mid-Cretaceous amber forest from south-western France where some of the oldest known ants lived, corresponded to a moist tropical forest close to the shore with a dominance of gymnosperm trees but where angiosperms (flowering plants) were already diversified. This palaeoenvironmental reconstruction supports an initial radiation of ants in forest ground litter coincident with the rise of angiosperms, as recently proposed as an ecological explanation for their origin and successful evolution.

  17. Two-types of Early Cretaceous adakitic porphyries from the Luxi terrane, eastern North China Block: Melting of subducted Paleo-Pacific slab and delaminated newly underplated lower crust

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Xu, Zhaowen; Lu, Xiancai; Fu, Bin; Lu, Jianjun; Yang, Xiaonan; Zhao, Zengxia

    2016-01-01

    The origin and tectonic setting of Early Cretaceous adakitic rocks from the Luxi terrane in the eastern North China Block (NCB) remain debated. To resolve this issue, we determined whole-rock geochemistry, zircon U-Pb ages, and in situ Hf-O isotopes of the Mengyin and Liujing adakitic porphyries from the Luxi terrane. Zircon U-Pb dating results reveal that both the Mengyin and Liujing plutons were emplaced during the Early Cretaceous, with weighted mean 206Pb/238U ages of 130 ± 1 Ma (2σ) and 131 ± 2 Ma (2σ), respectively. In addition, abundant Neoarchean-Paleoproterozoic inherited zircon cores are identified in the Mengyin adakitic porphyry with 207Pb/206Pb ages ranging from 2.53 to 2.42 Ga. Rocks of both plutons are silicic (SiO2 = 65.4-70.2 wt.%), metaluminous, and alkaline in composition, comprising mainly quartz syenite porphyries. Samples from both plutons are enriched in large ion lithophile elements (LILEs) (e.g., Rb, Sr, and Ba), and light rare earth elements (LREEs), depleted in high field strength elements (HFSEs) (e.g., Nb, Ta, and Ti), and heavy rare earth elements (HREEs), and have either positive or no Eu anomalies. In addition, both adakitic porphyries have high Mg# values (51-64), high Sr and La contents, low Y and Yb contents, and high Sr/Y (Mengyin = 149-264; Liujing = 58-110) and (La/Yb)N (Mengyin = 32.4-45.3; Liujing = 43.8-53.1) ratios, similar to adakitic rocks worldwide. The Mengyin adakitic porphyry has higher whole-rock εNd(t) values (-5.8 to - 4.1), more radiogenic Pb [(206Pb/204Pb)i = 18.35-18.39, (207Pb/204Pb)i = 15.55-15.56, (208Pb/204Pb)i = 38.20-38.23], higher zircon rim εHf(t) values (+ 3.3 to + 8.8) and δ18O values (+ 6.5‰ to + 7.9‰), and lower (87Sr/86Sr)i ratios (0.7049-0.7050) than the Liujing adakitic porphyry [εNd(t) = - 12.4 to - 12.2, (206Pb/204Pb)i = 17.63-17.72, (207Pb/204Pb)i = 15.56-15.58, (208Pb/204Pb)i = 37.76-37.94, εHf(t) = - 14.8 to - 11.2, δ18O = + 5.9‰ to + 7.1‰, (87Sr/86Sr)i = 0.7090-0.7091]. The

  18. High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction

    PubMed Central

    Fischer, Valentin; Bardet, Nathalie; Guiomar, Myette; Godefroit, Pascal

    2014-01-01

    Background Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic–Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and ‘greensands’ deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation) offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early–Late Cretaceous boundary. Methodology/Principal Findings To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France); a revised taxonomic scheme is proposed. We recognize the following taxa in the ‘greensands’: the platypterygiines ‘Platypterygius’ sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa. Conclusion/Significance Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian–early

  19. Trace element and isotope geochemistry of Cretaceous-Tertiary boundary sediments: identification of extra-terrestrial and volcanic components

    NASA Technical Reports Server (NTRS)

    Margolis, S. V.; Doehne, E. F.

    1988-01-01

    Trace element and stable isotope analyses were performed on a series of sediment samples crossing the Cretaceous-Tertiary (K-T) boundary from critical sections at Aumaya and Sopelano, Spain. The aim is to possibly distinguish extraterrestrial vs. volcanic or authigenic concentration of platinum group and other elements in K-T boundary transitional sediments. These sediments also have been shown to contain evidence for step-wise extinction of several groups of marine invertebrates, associated with negative oxygen and carbon isotope excursions occurring during the last million years of the Cretaceous. These isotope excursions have been interpreted to indicate major changes in ocean thermal regime, circulation, and ecosystems that may be related to multiple events during latest Cretaceous time. Results to date on the petrographic and geochemical analyses of the Late Cretaceous and Early Paleocene sediments indicate that diagenesis has obviously affected the trace element geochemistry and stable isotope compositions at Zumaya. Mineralogical and geochemical analysis of K-T boundary sediments at Zumaya suggest that a substantial fraction of anomalous trace elements in the boundary marl are present in specific mineral phases. Platinum and nickel grains perhaps represent the first direct evidence of siderophile-rich minerals at the boundary. The presence of spinels and Ni-rich particles as inclusions in aluminosilicate spherules from Zumaya suggests an original, non-diagenetic origin for the spherules. Similar spherules from southern Spain (Caravaca), show a strong marine authigenic overprint. This research represents a new approach in trying to directly identify the sedimentary mineral components that are responsible for the trace element concentrations associated with the K-T boundary.

  20. First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition.

    PubMed

    Chure, Daniel; Britt, Brooks B; Whitlock, John A; Wilson, Jeffrey A

    2010-04-01

    Sauropod dinosaur bones are common in Mesozoic terrestrial sediments, but sauropod skulls are exceedingly rare--cranial materials are known for less than one third of sauropod genera and even fewer are known from complete skulls. Here we describe the first complete sauropod skull from the Cretaceous of the Americas, Abydosaurus mcintoshi, n. gen., n. sp., known from 104.46 +/- 0.95 Ma (megannum) sediments from Dinosaur National Monument, USA. Abydosaurus shares close ancestry with Brachiosaurus, which appeared in the fossil record ca. 45 million years earlier and had substantially broader teeth. A survey of tooth shape in sauropodomorphs demonstrates that sauropods evolved broad crowns during the Early Jurassic but did not evolve narrow crowns until the Late Jurassic, when they occupied their greatest range of crown breadths. During the Cretaceous, brachiosaurids and other lineages independently underwent a marked diminution in tooth breadth, and before the latest Cretaceous broad-crowned sauropods were extinct on all continental landmasses. Differential survival and diversification of narrow-crowned sauropods in the Late Cretaceous appears to be a directed trend that was not correlated with changes in plant diversity or abundance, but may signal a shift towards elevated tooth replacement rates and high-wear dentition. Sauropods lacked many of the complex herbivorous adaptations present within contemporaneous ornithischian herbivores, such as beaks, cheeks, kinesis, and heterodonty. The spartan design of sauropod skulls may be related to their remarkably small size--sauropod skulls account for only 1/200th of total body volume compared to 1/30th body volume in ornithopod dinosaurs.

  1. Early diagenetic dolomitization and dedolomitization of Late Jurassic and earliest Cretaceous platform carbonates: A case study from the Jura Mountains (NW Switzerland, E France)

    NASA Astrophysics Data System (ADS)

    Rameil, Niels

    2008-12-01

    Early diagenetic dolomitization is a common feature in cyclic shallow-water carbonates throughout the geologic record. After their generation, dolomites may be subject to dedolomitization (re-calcification of dolomites), e.g. by contact with meteoric water during emersion. These patterns of dolomitization and subsequent dedolomitization frequently play a key role in unravelling the development and history of a carbonate platform. On the basis of excellent outcrops, detailed logging and sampling and integrating sedimentological work, high-resolution sequence stratigraphic interpretations, and isotope analyses (O, C), conceptual models on early diagenetic dolomitization and dedolomitization and their underlying mechanisms were developed for the Upper Jurassic / Lower Cretaceous Jura platform in north-western Switzerland and eastern France. Three different types of early diagenetic dolomites and two types of dedolomites were observed. Each is defined by a distinct petrographic/isotopic signature and a distinct spatial distribution pattern. Different types of dolomites are interpreted to have been formed by different mechanisms, such as shallow seepage reflux, evaporation on tidal flats, and microbially mediated selective dolomitization of burrows. Depending on the type of dolomite, sea water with normal marine to slightly enhanced salinities is proposed as dolomitizing fluid. Based on the data obtained, the main volume of dolomite was precipitated by a reflux mechanism that was switched on and off by high-frequency sea-level changes. It appears, however, that more than one dolomitization mechanism was active (pene)contemporaneously or several processes alternated in time. During early diagenesis, percolating meteoric waters obviously played an important role in the dedolomitization of carbonate rocks that underlie exposure surfaces. Cyclostratigraphic interpretation of the sedimentary succession allows for estimates on the timing of early diagenetic (de

  2. Reinvestigating an enigmatic Late Cretaceous monocot: morphology, taxonomy, and biogeography of Viracarpon

    PubMed Central

    Manchester, Steven R.; Ramteke, Deepak; Villarraga-Gómez, Herminso

    2018-01-01

    Angiosperm-dominated floras of the Late Cretaceous are essential for understanding the evolutionary, ecological, and geographic radiation of flowering plants. The Late Cretaceous–early Paleogene Deccan Intertrappean Beds of India contain angiosperm-dominated plant fossil assemblages known from multiple localities in central India. Numerous monocots have been documented from these assemblages, providing a window into an important but poorly understood time in their diversification. One component of the Deccan monocot diversity is the genus Viracarpon, known from anatomically preserved infructescences. Viracarpon was first collected over a century ago and has been the subject of numerous studies. However, resolution of its three-dimensional (3D) morphology and anatomy, as well as its taxonomic affinities, has remained elusive. In this study we investigated the morphology and taxonomy of genus Viracarpon, combining traditional paleobotanical techniques and X-ray micro-computed tomography (μCT). Re-examination of type and figured specimens, 3D reconstructions of fruits, and characterization of structures in multiple planes of section using μCT data allowed us to resolve conflicting interpretations of fruit morphology and identify additional characters useful in refining potential taxonomic affinities. Among the four Viracarpon species previously recognized, we consider two to be valid (Viracarpon hexaspermum and Viracarpon elongatum), and the other two to be synonyms of these. Furthermore, we found that permineralized infructescences of Coahuilocarpon phytolaccoides from the late Campanian of Mexico correspond closely in morphology to V. hexaspermum. We argue that Viracarpon and Coahuilocarpon are congeneric and provide the new combination, Viracarpon phytolaccoides (Cevallos-Ferriz, Estrada-Ruiz & Perez-Hernandez) Matsunaga, S.Y. Smith, & Manchester comb. nov. The significant geographic disjunction between these two occurrences indicates that the genus Viracarpon

  3. Honeggeriella complexa gen. et sp. nov., a heteromerous lichen from the Lower Cretaceous of Vancouver Island (British Columbia, Canada).

    PubMed

    Matsunaga, Kelly K S; Stockey, Ruth A; Tomescu, Alexandru M F

    2013-02-01

    Colonists of even the most inhospitable environments, lichens are present in all terrestrial ecosystems. Because of their ecological versatility and ubiquity, they have been considered excellent candidates for early colonizers of terrestrial environments. Despite such predictions, good preservation potential, and the extant diversity of lichenized fungi, the fossil record of lichen associations is sparse. Unequivocal lichen fossils are rare due, in part, to difficulties in ascertaining the presence of both symbionts and in characterizing their interactions. This study describes an exceptionally well-preserved heteromerous lichen from the Lower Cretaceous of Vancouver Island. The fossil occurs in a marine carbonate concretion collected from the Apple Bay locality on Vancouver Island, British Columbia, and was prepared for light microscopy and SEM using the cellulose acetate peel technique. The lichen, Honeggeriella complexa gen. et sp. nov., is formed by an ascomycete mycobiont and a chlorophyte photobiont, and exhibits heteromerous thallus organization. This is paired with a mycobiont-photobiont interface characterized by intracellular haustoria, previously not documented in the fossil record. Honeggeriella adds a lichen component to one of the richest and best characterized Early Cretaceous floras and provides a significant addition to the sparse fossil record of lichens. As a heteromerous chlorolichen, it bridges the >350 million-year gap between previously documented Early Devonian and Eocene occurrences.

  4. A transitional snake from the Late Cretaceous period of North America.

    PubMed

    Longrich, Nicholas R; Bhullar, Bhart-Anjan S; Gauthier, Jacques A

    2012-08-09

    Snakes are the most diverse group of lizards, but their origins and early evolution remain poorly understood owing to a lack of transitional forms. Several major issues remain outstanding, such as whether snakes originated in a marine or terrestrial environment and how their unique feeding mechanism evolved. The Cretaceous Coniophis precedens was among the first Mesozoic snakes discovered, but until now only an isolated vertebra has been described and it has therefore been overlooked in discussions of snake evolution. Here we report on previously undescribed material from this ancient snake, including the maxilla, dentary and additional vertebrae. Coniophis is not an anilioid as previously thought a revised phylogenetic analysis of Ophidia shows that it instead represents the most primitive known snake. Accordingly, its morphology and ecology are critical to understanding snake evolution. Coniophis occurs in a continental floodplain environment, consistent with a terrestrial rather than a marine origin; furthermore, its small size and reduced neural spines indicate fossorial habits, suggesting that snakes evolved from burrowing lizards. The skull is intermediate between that of lizards and snakes. Hooked teeth and an intramandibular joint indicate that Coniophis fed on relatively large, soft-bodied prey. However, the maxilla is firmly united with the skull, indicating an akinetic rostrum. Coniophis therefore represents a transitional snake, combining a snake-like body and a lizard-like head. Subsequent to the evolution of a serpentine body and carnivory, snakes evolved a highly specialized, kinetic skull, which was followed by a major adaptive radiation in the Early Cretaceous period. This pattern suggests that the kinetic skull was a key innovation that permitted the diversification of snakes.

  5. A Triassic to Cretaceous Sundaland-Pacific subduction margin in West Sarawak, Borneo

    NASA Astrophysics Data System (ADS)

    Breitfeld, H. Tim; Hall, Robert; Galin, Thomson; Forster, Margaret A.; BouDagher-Fadel, Marcelle K.

    2017-01-01

    Metamorphic rocks in West Sarawak are poorly exposed and studied. They were previously assumed to be pre-Carboniferous basement but had never been dated. New 40Ar/39Ar ages from white mica in quartz-mica schists reveal metamorphism between c. 216 to 220 Ma. The metamorphic rocks are associated with Triassic acid and basic igneous rocks, which indicate widespread magmatism. New U-Pb dating of zircons from the Jagoi Granodiorite indicates Triassic magmatism at c. 208 Ma and c. 240 Ma. U-Pb dating of zircons from volcaniclastic sediments of the Sadong and Kuching Formations confirms contemporaneous volcanism. The magmatic activity is interpreted to represent a Triassic subduction margin in westernmost West Sarawak with sediments deposited in a forearc basin derived from the magmatic arc at the Sundaland-Pacific margin. West Sarawak and NW Kalimantan are underlain by continental crust that was already part of Sundaland or accreted to Sundaland in the Triassic. One metabasite sample, also previously assumed to be pre-Carboniferous basement, yielded Early Cretaceous 40Ar/39Ar ages. They are interpreted to indicate resumption of subduction which led to deposition of volcaniclastic sediments and widespread magmatism. U-Pb ages from detrital zircons in the Cretaceous Pedawan Formation are similar to those from the Schwaner granites of NW Kalimantan, and the Pedawan Formation is interpreted as part of a Cretaceous forearc basin containing material eroded from a magmatic arc that extended from Vietnam to west Borneo. The youngest U-Pb ages from zircons in a tuff layer from the uppermost part of the Pedawan Formation indicate that volcanic activity continued until c. 86 to 88 Ma when subduction terminated.

  6. Diversification of Rosaceae since the Late Cretaceous based on plastid phylogenomics.

    PubMed

    Zhang, Shu-Dong; Jin, Jian-Jun; Chen, Si-Yun; Chase, Mark W; Soltis, Douglas E; Li, Hong-Tao; Yang, Jun-Bo; Li, De-Zhu; Yi, Ting-Shuang

    2017-05-01

    Phylogenetic relationships in Rosaceae have long been problematic because of frequent hybridisation, apomixis and presumed rapid radiation, and their historical diversification has not been clarified. With 87 genera representing all subfamilies and tribes of Rosaceae and six of the other eight families of Rosales (outgroups), we analysed 130 newly sequenced plastomes together with 12 from GenBank in an attempt to reconstruct deep relationships and reveal temporal diversification of this family. Our results highlight the importance of improving sequence alignment and the use of appropriate substitution models in plastid phylogenomics. Three subfamilies and 16 tribes (as previously delimited) were strongly supported as monophyletic, and their relationships were fully resolved and strongly supported at most nodes. Rosaceae were estimated to have originated during the Late Cretaceous with evidence for rapid diversification events during several geological periods. The major lineages rapidly diversified in warm and wet habits during the Late Cretaceous, and the rapid diversification of genera from the early Oligocene onwards occurred in colder and drier environments. Plastid phylogenomics offers new and important insights into deep phylogenetic relationships and the diversification history of Rosaceae. The robust phylogenetic backbone and time estimates we provide establish a framework for future comparative studies on rosaceous evolution. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  7. Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation

    PubMed

    Sereno; Dutheil; Iarochene; Larsson; Lyon; Magwene; Sidor; Varricchio; Wilson

    1996-05-17

    Late Cretaceous (Cenomanian) fossils discovered in the Kem Kem region of Morocco include large predatory dinosaurs that inhabited Africa as it drifted into geographic isolation. One, represented by a skull approximately 1.6 meters in length, is an advanced allosauroid referable to the African genus Carcharodontosaurus. Another, represented by a partial skeleton with slender proportions, is a new basal coelurosaur closely resembling the Egyptian genus Bahariasaurus. Comparisons with Cretaceous theropods from other continents reveal a previously unrecognized global radiation of carcharodontosaurid predators. Substantial geographic differentiation of dinosaurian faunas in response to continental drift appears to have arisen abruptly at the beginning of the Late Cretaceous.

  8. A reappraisal of Polyptychodon (Plesiosauria) from the Cretaceous of England

    PubMed Central

    2016-01-01

    Pliosauridae is a globally distributed clade of aquatic predatory amniotes whose fossil record spans from the Lower Jurassic to the Upper Cretaceous. However, the knowledge of pliosaurid interrelationships remains limited. In part, this is a consequence of a few key taxa awaiting detailed reassessment. Among them, the taxon Polyptychodon is of special importance. It was established on isolated teeth from the mid-Cretaceous strata of East and South East England and subsequently associated with numerous finds of near-cosmopolitan distribution. Here the taxon is reassessed based on the original dental material from England, with special focus on a large collection of late Albian material from the Cambridge Greensand near Cambridge. The dental material is reviewed here from historical and stratigraphic perspective, described in detail, and discussed in terms of its diagnostic nature. The considerable morphological variability observed in the teeth attributed to Polyptychodon, together with a wide stratigraphic range of the ascribed material, possibly exceeding 35 Ma (early Aptian to ?middle Santonian), suggests that the taxon is based on a multispecies assemblage, possibly incorporating members of different plesiosaur clades. Due to the absence of any autapomorphic characters or unique character combinations in the original material, Polyptychodon interruptus, the type species of Polyptychodon, is considered nomen dubium. From a global perspective, Polyptychodon is viewed as a wastebasket taxon whose material originating from different localities should be reconsidered separately. PMID:27190712

  9. The mid-Cretaceous super plume, carbon dioxide, and global warming

    NASA Technical Reports Server (NTRS)

    Caldeira, Ken; Rampino, Michael R.

    1991-01-01

    Carbon-dioxide releases associated with a mid-Cretaceous super plume and the emplacement of the Ontong-Java Plateau have been suggested as a principal cause of the mid-Cretaceous global warming. A carbonate-silicate cycle model is developed to quantify the possible climatic effects of these CO2 releases, utilizing four different formulations for the rate of silicate-rock weathering as a function of atmospheric CO2. CO2 emissions resulting from super-plume tectonics could have produced atmospheric CO2 levels from 3.7 to 14.7 times the modern preindustrial value of 285 ppm. Based on the temperature sensitivity to CO2 increases used in the weathering-rate formulations, this would cause a global warming of from 2.8 to 7.7 C over today's glogal mean temperature. Altered continental positions and higher sea level may have been contributed about 4.8 C to mid-Cretaceous warming. Thus, the combined effects of paleogeographic changes and super-plume related CO2 emissions could be in the range of 7.6 to 12.5 C, within the 6 to 14 C range previously estimated for mid-Cretaceous warming. CO2 releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20 percent of the mid-Cretaceous increase in atmospheric CO2.

  10. The Cretaceous/Tertiary Extinction Controversy.

    ERIC Educational Resources Information Center

    McCartney, Kevin

    1984-01-01

    The cause of the Cretaceous/Tertiary extinction has become a major geologic controversy. Current evidence for the two opposing views is reviewed to provide an introduction to the controversy and to form the basis for a seminar of discussion topic. (Author/JN)

  11. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution.

    PubMed

    Lü, Junchang; Brusatte, Stephen L

    2015-07-16

    The famous 'feathered dinosaurs' from the Early Cretaceous of Liaoning Province, northeastern China, include several dromaeosaurids, which are among the closest relatives of birds. Most of these are small-bodied taxa with long arms and broad wings comprised of vaned feathers, but a single specimen (the holotype of Tianyuraptor) belongs to a much larger individual with reduced forelimbs, which unfortunately lacks any preserved integument. We describe a new specimen of large-bodied, short-armed Liaoning dromaeosaurid, which we designate as a new genus and species, Zhenyuanlong suni. The integument is well preserved and provides the first evidence of feather morphologies and distribution in a short-armed (and probably non-volant) dromaeosaurid, indicating that these rare and aberrant taxa had large wings consisting of pennaceous feathers on the arms and long pennaceous feathers on the tail very similar to their smaller and longer-armed relatives, but potentially lacked vaned feathers on the legs. Zhenyuanlong adds yet more diversity to the Liaoning dromaeosaurid fauna, helps further reveal a distinct short-armed bauplan among dromaeosaurids, and illuminates previously-unrecognized homoplasy that complicates dromaeosaurid phylogeny and suggests that the Liaoning taxa may not have formed their own clade.

  12. Seasonal Equability in Late Cretaceous Central-Eastern Iberia? Inferences from Isotopic Data on Vertebrates

    NASA Astrophysics Data System (ADS)

    Domingo, L.; Barroso-Barcenilla, F.; Cambra-Moo, O.

    2013-12-01

    After the mid-Cretaceous thermal maximum, the latest Cretaceous witnessed a long-term cooling trend (Santonian-Maastrichtian). It has been proposed that seasonal equability (low mean annual range of temperatures) accompanied the mid-Cretaceous greenhouse period, but was it also a climatic feature of the colder latest Cretaceous? Terrestrial proxies have proven useful in understanding past seasonality and in this vein, we performed oxygen isotope analyses of the phosphate (δ18OPO4) on the rich and exceptionally well preserved late Campanian-early Maastrichtian vertebrate assemblage of 'Lo Hueco' fossil site (Cuenca, Spain). We analysed theropod and crocodilian tooth enamel, turtle shell, and gar ganoine with the aim of evaluating paleoclimatic conditions existing in the western area of the Tethys realm. The 'Lo Hueco' locality was situated at a paleo-latitude of 31°N and sedimentological and paleontological studies point to a coastal environment with distributary channels and sporadic sabkhas. Samples were collected from two different levels: G1 (proximal muddy floodplain) and G2 (distal muddy floodplain), with G1 being older. δ18OH2O values were calculated from theropod, crocodilian and turtle δ18OPO4 values using established equations and in all cases they are in good agreement with precipitation water from subtropical latest Cretaceous and modern settings. Theropods recorded consistently slightly lower δ18OH2O values (G1: -4.1×1.4‰, G2: -3.5×0.5‰) than crocodilians (G1: -3.6×0.6‰, G2: -2.7×0.6‰) and turtles (G1: -3.8×0.6‰, G2: -2.9×0.5‰). This may be due to terrestrial endothermic taxa, such as theropods, recording ingested water year round, meanwhile semiaquatic ectothermic taxa, such as crocodilians and turtles, would record δ18OH2O values representing local meteoric waters over the warm season, when conditions are favorable for apatite synthesis. With these δ18OH2O values, we used gar ganoine δ18OPO4 values as an independent proxy to

  13. U-Pb Dating and Lu-Hf Isotopes of Detrital Zircons From the Southern Sikhote-Alin Orogenic Belt, Russian Far East: Tectonic Implications for the Early Cretaceous Evolution of the Northwest Pacific Margin

    NASA Astrophysics Data System (ADS)

    Liu, Kai; Zhang, Jinjiang; Wilde, Simon A.; Liu, Shiran; Guo, Feng; Kasatkin, Sergey A.; Golozoubov, Vladimir V.; Ge, Maohui; Wang, Meng; Wang, Jiamin

    2017-11-01

    The Sikhote-Alin orogenic belt in Russian Far East is comprised of several N-S trending belts, including the Late Jurassic to Early Cretaceous accretionary prisms and turbidite basin which are now separated by thrusts and strike-slip faults. The origin and collage of the belts have been studied for decades. However, the provenance of the belts remains unclear. Six sandstone samples were collected along a 200 km long east-west traverse across the major belts in the southern Sikhote-Alin for U-Pb dating and Lu-Hf isotope analysis to constrain the provenance and evaluate the evolution of the northwest Pacific margin at this time. The result reveals that the sediments from the main Samarka belt was mainly from the adjacent Bureya-Jiamusi-Khanka Block (BJKB); the eastern Samarka belt and the Zhuravlevka turbidite basin were supplied by detritus from both the North China Craton (NCC) and the BJKB; the Taukha belt was mainly fed by sediments from the NCC; whereas the data from the Sergeevka nappes are insufficient to resolve their provenance. In the Late Jurassic to Early Cretaceous, collision and subduction was important in the initial collage of most belts in Sikhote-Alin. However, merely E-W trending collage cannot explain the increasing importance of the NCC provenance from west to east. It is proposed that the main Samarka belt was located adjacent to the BJKB when deposited, whereas the other belts were farther south to accept the materials from the NCC. Sinistral strike-slip faulting transported the eastern belts northward after their initial collage by thrusting.

  14. Terrestrial biota and climate during Cretaceous greenhouse in NE China

    NASA Astrophysics Data System (ADS)

    Wan, X.

    2016-12-01

    Northeast China offers a unique opportunity to perceive Cretaceous stratigraphy and climate of terrestrial settings. The sediments contain variegated clastic and volcanic rocks, diverse terrestrial fossils, and important coal and oil resources. Four Cretaceous biotas of Jehol, Fuxin, Songhuajiang and Jiayin occurred in ascending order. For scientific purpose, a coring program (SK1 & 2) provides significant material for Cretaceous research. The SK1 present a continuous section of Upper Cretaceous non-marine fossil, magnetochron successions and chronostratigraphic events. These chronostratigraphic events are integrated with marine events by an X/Y graphic plot between the core data and a global database of GSSP and key reference sections. More precisely, age interpolation based on CA-ID-TIMS U-Pb zircon dates and the calibrated cyclostratigraphy places the end of the Cretaceous Normal Superchon at 83.07 ±0.15Ma. This date also serves as an estimate for the Santonian-Campanian stage boundary. It also places the K/Pg boundary within the upper part of the Mingshui Formation. The terrestrial and marine life and the analysis of elemental composition, δ13Corg, biomarkers show that lake water salinity changed along with a Coniacian-Santonian marine incursion. High lake-level coincides with the sea transgression during the time. High salinity resulted in the development of periodic anoxic environments of the basin. One of these times of deposition of organic-rich mud correlates with the mangnetochron of C34N/C33R and Coniacian-Santonian planktic foraminifera. This marine flooding correlates with OAE 3 and it is possible that the global oceanic anoxic event may have influenced organic carbon burial in the Songliao Basin for this brief period. The evolution of 4 biotas corresponds to the Cretaceous climate change. We tentatively interpret the terrestrial record to reflect the changes in both global climate and regional basin evolution.

  15. Cretaceous crust beneath SW Borneo: U-Pb dating of zircons from metamorphic and granitic rocks

    NASA Astrophysics Data System (ADS)

    Davies, L.; Hall, R.; Armstrong, R.

    2012-12-01

    and Phanerozoic zircons. The metamorphic rocks from SW Borneo are not an ancient core to the island as previously assumed. We propose that extensive arc volcanism produced fine grained volcanogenic sediments during the Early Cretaceous deposited on, or reworking, older crust. These sediments were subjected to low pressure 'Buchan-type' metamorphism soon after deposition. Magmatism continued into the Late Cretaceous, resulting in contact metamorphism.

  16. New long-proboscid lacewings of the mid-Cretaceous provide insights into ancient plant-pollinator interactions

    PubMed Central

    Lu, Xiu-Mei; Zhang, Wei-Wei; Liu, Xing-Yue

    2016-01-01

    Many insects with long-proboscid mouthparts are among the pollinators of seed plants. Several cases of the long-proboscid pollination mode are known between fossil insects (e.g., true flies, scorpionflies, and lacewings) and various extinct gymnosperm lineages, beginning in the Early Permian and increasing during the Middle Jurassic to Early Cretaceous. However, details on the morphology of lacewing proboscides and the relevant pollination habit are largely lacking. Here we report on three lacewing species that belong to two new genera and a described genus from mid-Cretaceous (Albian-Cenomanian) amber of Myanmar. All these species possess relatively long proboscides, which are considered to be modified from maxillary and labial elements, probably functioning as a temporary siphon for feeding on nectar. Remarkably, these proboscides range from 0.4–1.0 mm in length and are attributed to the most diminutive ones among the contemporary long-proboscid insect pollinators. Further, they clearly differ from other long-proboscid lacewings which have a much longer siphon. The phylogenetic analysis indicates that these Burmese long-proboscid lacewings belong to the superfamily Psychopsoidea but cannot be placed into any known family. The present findings represent the first description of the mouthparts of long-proboscid lacewings preserved in amber and highlight the evolutionary diversification of the ancient plant-pollinator interactions. PMID:27149436

  17. Evidence and dating of mid-Cretaceous tectonic activity in the San Rafael Swell, Emery County, Utah

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Eaton, J.G.; Kirkland, J.I.; Kauffman, E.G.

    1990-04-01

    Evidence of tectonic activity in the form of recycled conglomerates has been found in middle Cretaceous deposits on the western flank of the San Rafael Swell. These conglomerates, present in the upper part of the Dakota Formation and in the overlying basal Mancos Shale (Tununk Member), are separated by an earliest Turonian unconformity. The conglomerates appear to be derived from the Lower Cretaceous Buckhorn Conglomerate, or similar conglomerates, which were re-exposed by latest Cenomanian uplift. Coarse clastics provided to the nearshore facies of the Dakota Formation by coastal rivers are preserved as a coarsening upward sequence. Continued uplift eventually causedmore » a local marine regression by temporarily inhibiting the initial (latest Cenomanian) transgression of the Greenhorn Sea. In subaerially exposed environments pebbles and cobbles from the Buckhorn were distributed across the coastal floodplain by rivers. These clasts were reworked into a basal lag deposit when renewed transgression of the Greenhorn Sea occurred during the late early Turonian.« less

  18. Late Cretaceous seasonal ocean variability from the Arctic.

    PubMed

    Davies, Andrew; Kemp, Alan E S; Pike, Jennifer

    2009-07-09

    The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.

  19. Sedimentary environment and diagenesis of the Lower Cretaceous Chaswood Formation, southeastern Canada: The origin of kaolin-rich mudstones

    NASA Astrophysics Data System (ADS)

    Pe-Piper, Georgia; Dolansky, Lila; Piper, David J. W.

    2005-07-01

    The Lower Cretaceous fluvial sandstone-mudstone succession of the Chaswood Formation is the proximal equivalent of offshore deltaic rocks of the Scotian Basin that are reservoirs for producing gas fields. This study interprets the mineralogical consequences of Cretaceous weathering and early diagenesis in a 130-m core from the Chaswood Formation in order to better understand detrital and diagenetic minerals in equivalent rocks offshore. Mineralogy was determined by X-ray diffraction, electron microprobe analysis and scanning electron microscopy. The rocks can be divided into five facies associations: light gray mudstone, dark gray mudstone, silty mudstone and muddy sandstone, sorted sandstone and conglomerate, and paleosols. Facies transitions in coarser facies are related to deposition in and near fluvial channels. In the mudstones, they indicate an evolutionary progression from the dark gray mudstone facies association (swamps and floodplain soils) to mottled paleosols (well-drained oxisols and ultisols following syntectonic uplift). Facies transitions and regional distribution indicate that the light gray mudstone facies association formed from early diagenetic oxidation and alteration of the dark gray mudstone facies association, probably by meteoric water. Principal minerals in mudstones are illite/muscovite, kaolinite, vermiculite and quartz. Illite/muscovite is of detrital origin, but variations in abundance show that it has altered to kaolinite in the light gray mudstone facies association and in oxisols. Vermiculite developed from the weathering of biotite and is present in ultisols. The earliest phase of sandstone cementation in reducing conditions in swamps and ponds produced siderite nodules and framboidal pyrite, which were corroded and oxidized during subsequent development of paleosols. Kaolinite is an early cement, coating quartz grains and as well-crystallized, pore-filling booklets that was probably synchronous with the formation of the light gray

  20. Potential cretaceous play in the Rharb basin of northern Morocco

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jobidon, G.P.

    1993-09-01

    The autochthonous Cretaceous in the Rharb basin of northern Morocco is located underneath a cover of neogene sediments and of the Prerif nappe olistostrome, which was emplaced during the Tortonian 7 m.y. The presence of infranappe Cretaceous sediments is documented in a few onshore wells in the Rharb basin and in the adjacent Prerif Rides area, as well as in the Rif Mountains. Their presence in the deeper portion of the Rharb basin is difficult to detail because of poor seismic resolution data beneath dispersive prerif nappe. A recent study of offshore seismic data acquired by PCIAC in 1987 indicatesmore » that the infranappe interval can be more than 1500 m thick in some of the offshore Kenitra area. These sediments have seismic signatures that would correspond to Middle Cretaceous transgressions, culminating with a Turonian highstand. Their deposition systems were located on the northern and western flanks of the Meseta and were followed by a hiatus lasting until the Miocene. Regional studies of gravity and magnetic data provide and additional understanding of the Rif province, its evolution, and the possible presence of autochthonous Cretaceous sediments below the prerif nappe cover. The infranappe of Rharb basin has a good potential to develop into a major hydrocarbon play with the presence of middle Cretaceous reservoir rocks, Turonian-Cenomanian black shale source rocks, as well as the timely combination of trap formation, source rock maturation, and hydrocarbon migration.« less

  1. Cretaceous and Eocene Adakites in the Sikhote-Alin area (Russian Far East) and their correlation with adakitic rocks in the East Asia continental margin

    NASA Astrophysics Data System (ADS)

    Wu, T. J.; Jahn, B. M.

    2017-12-01

    Adakitic rocks of the Sikhote-Alin area were emplaced during two main periods: the Cretaceous (132-98 Ma) and Eocene (46-39 Ma). These rocks primarily occur in the Khanka Block and, less commonly, in the Sikhote-Alin Orogenic Belt. The adakitic rocks record the following chemical compositions: SiO2 = 57-74%, Al2O3 = 15-18%, Na2O = 3.5-6.1%, K2O = 0.7-3.2%, Na2O/K2O = 1.1-3.9, Sr/Y = 33-145, and (La/Yb)N = 11-53. The HREE and HFSE in these rocks are remarkably depleted. The Early Cretaceous adakites record ɛNd(T) = -1.0 to +3.2 and ISr = 0.7040-0.7090, and the Eocene adakitic rocks record Nd(T) = -2.0 to +2.2 and ISr = 0.7042-0.7058. Adakitic features suggest different modes of magma generation; a comparison of the Sr/Y and La/Yb ratios and geochemical data on Harker diagrams between the two periods of adakitic rocks reveals differences in their petrogenesis. The Cretaceous adakites may have been generated by the partial melting of meta-basic rocks in a subduction zone, accompanied by the emplacement of volcanic arc granitoids. Therefore, the subduction of the Paleo-Pacific Plate beneath the Sikhote-Alin was probably initiated during this time. The Eocene rocks, which record increasing adakitic features with increasing silica content, are most likely the product of andesite that underwent fractionation of mineral assemblage including clinopyoxene, orthopyroxene, garnet and amphibole. These rocks and associated basalts and rhyolite were formed after Cretaceous arc magmatism in the Sikhote-Alin area and were most likely generated by rollback of the subducting Pacific Plate after the Eocene. Abundant adakitic granitoids of Early Cretaceous and Eocene age occur in the Kitakami and Abukuma Mountains of NE Japan. Consequently, it is highly probable that a geological correlation existed between Sikhote-Alin and North Japan, particularly before the opening of the Japan Sea.

  2. Thermochronology of mid-Cretaceous dioritic granulites adjacent "Big Bend" in Australia-Pacific plate boundary, northern South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Sagar, M.; Seward, D.; Heizler, M. T.; Palin, J. M.; Toy, V. G.; Tulloch, A. J.

    2012-12-01

    The Western Fiordland Orthogneiss (WFO), situated south-east of the Australian-Pacific plate boundary (Alpine Fault), southern South Island, New Zealand is the largest suite of plutonic rocks intruded into the Pacific margin of Gondwana during the final stages of arc plutonism preceding break-up of the supercontinent in the Late Cretaceous. Dextral motion of c. 480 km along the Alpine Fault during the Cenozoic has offset originally contiguous Pacific Gondwana margin rocks in northern and southern South Island. The Glenroy Complex in northern South Island, west of the Alpine Fault is dominated by two-pyroxene+hornblende granulite facies monzodioritic gneisses. U-Pb zircon geochronological and geochemical data indicate the Glenroy Complex was emplaced between 128-122 Ma and is a correlative of the WFO. The Glenroy Complex forms the lower-most block bounded by an east-dipping set of imbricate thrusts that developed during the late Cenozoic to the west of the largest S-shaped restraining bend ("Big Bend") in the Alpine Fault. New 40Ar/39Ar and fission-track thermochronological data, combined with previous geological field-mapping, demonstrate that the Glenroy Complex cooled rapidly (c. 30° C/Ma) after emplacement and granulite facies metamorphism (c. 850°C) at c. 120 Ma, through c. 550 °C by c. 110-100 Ma. The average cooling rate during the Late Cretaceous-Cenozoic was relatively slow, and initial exposure in the late Early Miocene (c. 16 Ma) was followed by reburial to c. 3-4 km (c. 80-100 °C) before final exhumation post-Pliocene. This thermal history is similar to the WFO, which cooled rapidly through c. 350 °C during mid-Cretaceous continental extension, followed by slow cooling during the Late Cretaceous and Cenozoic until development of the Australian-Pacific boundary through New Zealand facilitated rapid, exhumation-related cooling from c. 240 °C at c. 20 Ma and final exhumation post-10 Ma (Davids, 1999). However, the Glenroy Complex cooled at a faster

  3. Tyrant dinosaur evolution tracks the rise and fall of Late Cretaceous oceans.

    PubMed

    Loewen, Mark A; Irmis, Randall B; Sertich, Joseph J W; Currie, Philip J; Sampson, Scott D

    2013-01-01

    The Late Cretaceous (∼95-66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah--including a new taxon which represents the geologically oldest member of the clade--to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.

  4. Rifting and reactivation of a Cretaceous structural belt at the northern margin of the South China Sea

    NASA Astrophysics Data System (ADS)

    Nanni, Ugo; Pubellier, Manuel; Chan, Lung Sang; Sewell, Roderick J.

    2017-04-01

    The Tiu Tang Lung Fault, Hong Kong Special Administrative Region - China, is located on the northern stretched continental margin of the South China Sea. Along this fault, Middle Jurassic volcanic rocks of the Tai Mo Shan Formation are tectonically juxtaposed on Lower Cretaceous sedimentary rocks of the Pat Sin Leng Formation. Both extensional detachments and compressional features are observed and various genetic strain configurations are proposed for the Tiu Tang Lung Fault with implications for understanding the dynamics of the pre-South China Sea rifting during the Cretaceous. We have identified tilted bedding planes in the continental deposits of the Pat Sin Leng Formation which can be related to Early Cretaceous syn-extensional deposition. A mid-Cretaceous penetrative top-to-the-south to top-to-the-west shear fabric is also observed and serves as an indicator of the strain pattern. This deformation is expressed by cleavages, schistosity, S/C fabrics, kink-folds, phacoids and stretched pebbles at both a macroscopic and microscopic scale. Cleavages and bedding are generally sub-parallel to the local shear orientation. The whole sedimentary pile is crosscut by Cenozoic N70 and N150 normal faults. These constraints, together with previous fission track, seismic and structural data, allow us to reinterpret the kinematics of this domain during syn-orogenic to syn-extensional periods. The observed top-to-the-south thrusting event is coeval with NE-SW strike-slip sinistral fault movement. Subsequent N-S extension can be correlated with South China Sea rifting from Eocene to Oligocene. These observations reveal a polyphase history associated with continental margin inversion which witnessed localized extension on previous compressional structures.

  5. Quantification of a greenhouse hydrologic cycle from equatorial to polar latitudes: The mid-Cretaceous water bearer revisited

    USGS Publications Warehouse

    Suarez, M.B.; Gonzalez, Luis A.; Ludvigson, Greg A.

    2011-01-01

    This study aims to investigate the global hydrologic cycle during the mid-Cretaceous greenhouse by utilizing the oxygen isotopic composition of pedogenic carbonates (calcite and siderite) as proxies for the oxygen isotopic composition of precipitation. The data set builds on the Aptian-Albian sphaerosiderite ??18O data set presented by Ufnar et al. (2002) by incorporating additional low latitude data including pedogenic and early meteoric diagenetic calcite ??18O. Ufnar et al. (2002) used the proxy data derived from the North American Cretaceous Western Interior Basin (KWIB) in a mass balance model to estimate precipitation-evaporation fluxes. We have revised this mass balance model to handle sphaerosiderite and calcite proxies, and to account for longitudinal travel by tropical air masses. We use empirical and general circulation model (GCM) temperature gradients for the mid-Cretaceous, and the empirically derived ??18O composition of groundwater as constraints in our mass balance model. Precipitation flux, evaporation flux, relative humidity, seawater composition, and continental feedback are adjusted to generate model calculated groundwater ??18O compositions (proxy for precipitation ??18O) that match the empirically-derived groundwater ??18O compositions to within ??0.5???. The model is calibrated against modern precipitation data sets.Four different Cretaceous temperature estimates were used: the leaf physiognomy estimates of Wolfe and Upchurch (1987) and Spicer and Corfield (1992), the coolest and warmest Cretaceous estimates compiled by Barron (1983) and model outputs from the GENESIS-MOM GCM by Zhou et al. (2008). Precipitation and evaporation fluxes for all the Cretaceous temperature gradients utilized in the model are greater than modern precipitation and evaporation fluxes. Balancing the model also requires relative humidity in the subtropical dry belt to be significantly reduced. As expected calculated precipitation rates are all greater than modern

  6. The toothless pterosaur Jidapterus edentus (Pterodactyloidea: Azhdarchoidea) from the Early Cretaceous Jehol Biota and its paleoecological implications

    PubMed Central

    Wu, Wen-Hao; Zhou, Chang-Fu; Andres, Brian

    2017-01-01

    Background In the Early Cretaceous Jehol Biota, the toothless pterosaurs flourished with the chaoyangopterids and tapejarids playing a key role in understanding the early diversity and evolution of the Azhdarchoidea. Unlike the more diverse tapejarids, the rarer chaoyangopterids are characterized by a long and low rostrum, supporting a close relationship with the huge azhdarchids. Unfortunately, our knowledge is still limited in the osteology, paleoecology, and taxonomy of the Chaoyangopteridae. As one of the best preserved skeletons, the type and only specimen of Jidapterus edentus provides an opportunity to understand the morphology and paleoecology of the chaoyangopterids. Results Our study of the osteology of Jidapterus edentus reveals valuable information about the morphology of the Chaoyangopteridae such as a rostrum with a curved dorsal profile, high Rostral Index (RI), larger angle between the dorsal and postorbital processes of the jugal, sequentially shorter fourth to seventh cervical vertebrae, sternum with a plate wider than long, contact of the metacarpal I with the distal syncarpal, pneumatic foramen on first wing phalanx, hatchet-like postacetabular process with unconstricted neck and small dorsal process, distinctly concave anterior margin of pubis, subrectangular pubic plate with nearly parallel anterior and posterior margins, longer proximal phalanges of pedal digits III and IV, as well as reduced and less curved pedal unguals. These features further support the validity of Jidapterus edentus as a distinct species and the close relationship of the chaoyangopterids with the azhdarchids. Paleoecologically, the chaoyangopterids are probably like the azhdarchids, more terrestrial than the contemporaneous and putatively arboreal tapejarids, which may have been limited to the forest-dominated ecosystem of the Jehol Biota. Discussion The osteology of Jidapterus edentus further supports the close relationship of the Chaoyangopteridae with the Azhdarchidae

  7. The Cretaceous/Tertiary Extinction Controversy Reconsidered.

    ERIC Educational Resources Information Center

    McCartney, Kevin; Nienstedt, Jeffrey

    1986-01-01

    Reviews varying positions taken in the Cretaceous/Tertiary (K/Y) extinction controversy. Analyzes and contests the meteoritic impact theory known as the Alvarez Model. Presents an alternative working hypothesis explaining the K/T transition. (ML)

  8. Upper Cretaceous sequences and sea-level history, New Jersey Coastal Plain

    USGS Publications Warehouse

    Miller, K.G.; Sugarman, P.J.; Browning, J.V.; Kominz, M.A.; Olsson, R.K.; Feigenson, M.D.; Hernandez, J.C.

    2004-01-01

    We developed a Late Cretaceous sealevel estimate from Upper Cretaceous sequences at Bass River and Ancora, New Jersey (ODP [Ocean Drilling Program] Leg 174AX). We dated 11-14 sequences by integrating Sr isotope and biostratigraphy (age resolution ??0.5 m.y.) and then estimated paleoenvironmental changes within the sequences from lithofacies and biofacies analyses. Sequences generally shallow upsection from middle-neritic to inner-neritic paleodepths, as shown by the transition from thin basal glauconite shelf sands (transgressive systems tracts [TST]), to medial-prodelta silty clays (highstand systems tracts [HST]), and finally to upper-delta-front quartz sands (HST). Sea-level estimates obtained by backstripping (accounting for paleodepth variations, sediment loading, compaction, and basin subsidence) indicate that large (>25 m) and rapid (???1 m.y.) sea-level variations occurred during the Late Cretaceous greenhouse world. The fact that the timing of Upper Cretaceous sequence boundaries in New Jersey is similar to the sea-level lowering records of Exxon Production Research Company (EPR), northwest European sections, and Russian platform outcrops points to a global cause. Because backstripping, seismicity, seismic stratigraphic data, and sediment-distribution patterns all indicate minimal tectonic effects on the New Jersey Coastal Plain, we interpret that we have isolated a eustatic signature. The only known mechanism that can explain such global changes-glacio-eustasy-is consistent with foraminiferal ??18O data. Either continental ice sheets paced sea-level changes during the Late Cretaceous, or our understanding of causal mechanisms for global sea-level change is fundamentally flawed. Comparison of our eustatic history with published ice-sheet models and Milankovitch predictions suggests that small (5-10 ?? 106 km3), ephemeral, and areally restricted Antarctic ice sheets paced the Late Cretaceous global sea-level change. New Jersey and Russian eustatic estimates

  9. Basin evolution during Cretaceous-Oligocene changes in sediment routing in the Eastern Precordillera, Argentina

    NASA Astrophysics Data System (ADS)

    Reat, Ellen J.; Fosdick, Julie C.

    2018-07-01

    The response of sedimentary basins to earliest onset of Andean contraction and lithospheric flexure in the southern Central Andes is debated and not well-resolved. The Upper Cretaceous to Oligocene strata of the Cuesta de Huaco anticline in the Argentine Precordillera record sedimentation, regional deformation, and climate patterns prior to the highly studied Oligocene-Miocene foreland basin phase. These deposits have recently been recognized as Cretaceous and Paleogene in age, prompting a re-evaluation of this depocenter as part of the early Andean system, prior to deposition of the aeolian foredeep sediments of the Oligocene Vallecito Formation. This work presents new data from the Argentine Precordillera fold-and-thrust belt at 30°S that sheds light on new reinterpretations of the timing of sedimentation for an important interval in Andean retroarc foreland basin history. We report the first Paleocene detrital radiometric ages from the Cuesta de Huaco 'red strata' of the pre-Oligocene Bermejo Basin. Detailed sedimentology and provenance data from the Cenomanian-Turonian Ciénaga del Río Huaco and Danian-Priabonian Puesto La Flecha formations reveal a Cenomanian-Turonian braided stream system that transitioned into a shallow freshwater lacustrine depocenter in Paleocene-Eocene time. During Late Cretaceous time, sediment in the braided river system was derived primarily from northeastern cratonic sources; during the Paleocene-Eocene, uplift and unroofing of the Andean arc and Frontal Cordillera resulted in an influx of western-derived sediment. We therefore suggest a revised timing of sedimentation for the transition to Andean retroarc foreland basin deposition.

  10. Cretaceous plate interaction during the formation of the Colombian plateau, Northandean margin

    NASA Astrophysics Data System (ADS)

    Kammer, Andreas; Piraquive, Alejandro; Díaz, Sebastián

    2015-04-01

    The Cretaceous subduction cycle at the Northandean margin ends with an accretionary event that welds the plateau rocks of the present Western Cordillera to the continental margin. A suture between plateau and rock associations of the continental margin is well exposed at the western border of the Central Cordillera, but overprinted by intense block tectonics. Analyzed in detail, its evolution tracks an increased coupling between lower and upper plate, as may be accounted for by the following stages: 1) The Cretaceous plateau suite records at its onset passive margin conditions, as it encroaches on the continental margin and accounts for an extensional event that triggered the emplacement of ultramafic and mafic igneous rock suites along major faults. 2) An early subduction stage of a still moderate plate coupling is documented by the formation of a magmatic arc in an extensional setting that may have been prompted by slab retreat. Convergence direction was oblique, as attested the transfer of strike-slip displacements to the forearc region. 3) A phase of strong plate interaction entailed the delamination of narrow crustal flakes and their entrainment to depths below the petrologic Moho, as evidenced by their present association to serpentinites in a setting that bears characteristics of a subduction channel. 4) During the final collisional stage deformation is transferred to the lower plate, where the stacking of imbricate sheets, combined with their erosional unloading, led to the formation of an antiformal bulge that fed a foreland basin. - The life time of this Cretaceous subduction cycle was strictly synchronous to the construction of the Colombian plateau. With the final collisional stage magmatic activity vanished. This coincidence incites to explore a relationship between plume activity and subduction.

  11. Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America.

    PubMed

    Mitchell, Jonathan S; Roopnarine, Peter D; Angielczyk, Kenneth D

    2012-11-13

    The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America.

  12. Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America

    PubMed Central

    Roopnarine, Peter D.; Angielczyk, Kenneth D.

    2012-01-01

    The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America. PMID:23112149

  13. Detrital zircon U-Pb geochronology and stratigraphy of the Cretaceous Sanjiang Basin in NE China: Provenance record of an abrupt tectonic switch in the mode and nature of the NE Asian continental margin evolution

    NASA Astrophysics Data System (ADS)

    Zhang, Feng-Qi; Chen, Han-Lin; Batt, Geoffrey E.; Dilek, Yildirim; A, Min-Na; Sun, Ming-Dao; Yang, Shu-Feng; Meng, Qi-An; Zhao, Xue-Qin

    2015-12-01

    The age spectra obtained from 505 spots of detrital zircon U-Pb ages of five representative sandstone samples from the Sanjiang Basin in NE China point to a significant change in its provenance during the Coniacian-Santonian. The predominant detrital source for the Sanjiang Basin during the early Cretaceous was the Zhangguangcai Range magmatic belt and Jiamusi Block along its western and southern periphery, whereas it changed in the late Cretaceous to its eastern periphery. The timing of these inferred changes in the detrital source regions and drainage patterns nearly coincide with the age of a regional unconformity in and across the basin. The time interval of non-deposition and unconformity development was coeval with a transitional period between an extensional tectonic regime in the early Cretaceous and a contractional deformation episode in the late Cretaceous. The Sanjiang Basin evolved during this time window from a backarc to a foreland basin. The migration of the coastal orogenic belt and the fold and thrust belt development farther inland during the late Cretaceous marked the onset of regional-scale shortening and surface uplift in the upper plate of a flat (or very shallow-dipping) subduction zone. The stratigraphic record, the detrital source and geochronology of the basinal strata, and the internal structure of the Sanjiang Basin present, therefore, an important record of a tectonic switch in the nature of continental margin evolution of Northeast Asia during the late Mesozoic.

  14. Sedimentology, stratigraphy, and extinctions during the Cretaceous-Paleogene transition at Bug Creek, Montana

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fastovsky, D.E.; Dott, R.H. Jr.

    1986-04-01

    Bug Creek Valley, the source of an unusual and controversial Cretaceous-Paleogene coincidence of mammals, dinosaurs, pollen, and iridium, exemplifies the importance of depositional process in the reconstruction of evolutionary events. Five sedimentary facies are recognized at Bug Creek: a cross-stratified sandstone, a green and purple siltstone, a lateral accretionary sandstone, a coal, and a variegated siltstone. Repeated fluvial channeling restricts the accuracy of lateral correlations, and the relationship of the fossil assemblage to the presumed Cretaceous-Paleogene boundary cannot be established. Sedimentologically, the Cretaceous-Paleogene transition is represented here by Cretaceous meandering channels that gave way initially to Paleogene swamp deposition. 13more » references, 4 figures.« less

  15. Tectonic setting of Cretaceous basins on the NE Tibetan Plateau: Insights from the Jungong basin

    USGS Publications Warehouse

    Craddock, W.H.; Kirby, E.; Dewen, Z.; Jianhui, L.

    2012-01-01

    Quantifying the Cenozoic growth of high topography in the Indo-Asian collision zone remains challenging, due in part to significant shortening that occurred within Eurasia before collision. A growing body of evidence suggests that regions far removed from the suture zone experienced deformation before and during the early phases of Himalayan orogenesis. In the present-day north-eastern Tibetan Plateau, widespread deposits of Cretaceous sediment attest to significant basin formation; however, the tectonic setting of these basins remains enigmatic. We present a study of a regionally extensive network of sedimentary basins that are spatially associated with a system of SE-vergent thrust faults and are now exposed in the high ranges of the north-eastern corner of the Tibetan Plateau. We focus on a particularly well-exposed basin, located ~20km north of the Kunlun fault in the Anyemaqen Shan. The basin is filled by ~900m of alluvial sediments that become finer-grained away from the basin-bounding fault. Additionally, beds in the proximal footwall of the basin-bounding fault exhibit progressive, up-section shallowing and several intraformational unconformities which can be traced into correlative conformities in the distal part of the basin. The observations show sediment accumulated in the basin during fault motion. Regional constraints on the timing of sediment deposition are provided by both fossil assemblages from the Early Cretaceous, and by K-Ar dating of volcanic rocks that floor and cross-cut sedimentary fill. We argue that during the Cretaceous, the interior NE Tibetan Plateau experienced NW-SE contractional deformation similar to that documented throughout the Qinling-Dabie orogen to the east. The Songpan-Ganzi terrane apparently marked the southern limit of this deformation, such that it may have been a relatively rigid block in the Tibetan lithosphere, separating regions experiencing deformation north of the convergent Tethyan margin from regions deforming

  16. Isotopic evaluation of ocean circulation in the Late Cretaceous North American seaway

    NASA Astrophysics Data System (ADS)

    Coulson, Alan B.; Kohn, Matthew J.; Barrick, Reese E.

    2011-12-01

    During the mid- and Late Cretaceous period, North America was split by the north-south oriented Western Interior Seaway. Its role in creating and maintaining Late Cretaceous global greenhouse conditions remains unclear. Different palaeoceanographic reconstructions portray diverse circulation patterns. The southward extent of relatively cool, low-salinity, low-δ18O surface waters critically distinguishes among these models, but past studies of invertebrates could not independently assess water temperature and isotopic compositions. Here we present oxygen isotopes in biophosphate from coeval marine turtle and fish fossils from western Kansas, representing the east central seaway, and from the Mississippi embayment, representing the marginal Tethys Ocean. Our analyses yield precise seawater isotopic values and geographic temperature differences during the main transition from the Coniacian to the early Campanian age (87-82 Myr), and indicate that the seaway oxygen isotope value and salinity were 2‰ and 3‰ lower, respectively, than in the marginal Tethys Ocean. We infer that the influence of northern freshwater probably reached as far south as Kansas. Our revised values imply relatively large temperature differences between the Mississippi embayment and central seaway, explain the documented regional latitudinal palaeobiogeographic zonation and support models with relatively little inflow of surface waters from the Tethys Ocean to the Western Interior Seaway.

  17. Geochronologic evidence for Late Cretaceous and Miocene tectonism in northern New England

    NASA Astrophysics Data System (ADS)

    Amidon, W. H.; Barr, M.; Walcott, C.; Kylander-Clark, A. R.

    2017-12-01

    The persistence of mountainous relief in the northeastern U.S. suggests post-rift tectonic rejuvenation has occurred, although specific mechanisms and timing have been difficult to identify. Here we present direct evidence for significant tectonism in New Hampshire and Vermont during the Late-Cretaceous ( 85-65 Ma) and Miocene periods ( 20-5 Ma). Low temperature thermochronology from a drill core in the White Mountains of New Hampshire suggests 2-3 km of accelerated exhumation during the Late Cretaceous. This exhumation is synchronous with compressional thrusting and rapid exhumation on many other Atlantic margins and also with a change in spreading direction in the Atlantic from 85-65 Ma. Recently obtained U-Pb ages of vein calcite from faults and fractures in the Champlain Valley of New York and Vermont suggest significant brittle fracturing occurred during the Late Cretaceous and also during the Miocene. Although many questions remain, this evidence points to tectonic rejuvenation by lateral tectonic stresses in the latest Cretaceous and possibly in the Miocene. The Late Cretaceous seems to have been a particularly significant tectonic episode in northern New England and elsewhere in the circum-Atlantic region.

  18. Selectivity of end-Cretaceous marine bivalve extinctions

    NASA Technical Reports Server (NTRS)

    Jablonski, D.; Raup, D. M.

    1995-01-01

    Analyses of the end-Cretaceous or Cretaceous-Tertiary mass extinction show no selectivity of marine bivalve genera by life position (burrowing versus exposed), body size, bathymetric position on the continental shelf, or relative breadth of bathymetric range. Deposit-feeders as a group have significantly lower extinction intensities than suspension-feeders, but this pattern is due entirely to low extinction in two groups (Nuculoida and Lucinoidea), which suggests that survivorship was not simply linked to feeding mode. Geographically widespread genera have significantly lower extinction intensities than narrowly distributed genera. These results corroborate earlier work suggesting that some biotic factors that enhance survivorship during times of lesser extinction intensities are ineffectual during mass extinctions.

  19. Depletion of 13C in Cretaceous marine organic matter: Source, diagenetic, or environmental sigal?

    USGS Publications Warehouse

    Dean, W.E.; Arthur, M.A.; Claypool, G.E.

    1986-01-01

    Geochemical studies of Cretaceous strata rich in organic carbon (OC) from Deep Sea Drilling Project (DSDP) sites and several land sections reveal several consistent relationships among amount of OC, hydrocarbon generating potential of kerogen (measured by pyrolysis as the hydrogen index, HI), and the isotopic composition of the OC. First, there is a positive correlation between HI and OC in strata that contain more than about 1% OC. Second, percent OC and HI often are negatively correlated with carbon isotopic composition (?? 13C) of kerogen. The relationship between HI and OC indicates that as the amount of organic matter increases, this organic matter tends to be more lipid rich reflecting the marine source of the organic matter. Cretaceous samples that contain predominantly marine organic matter tend to be isotopically lighter than those that contain predominantly terrestrial organic matter. Average ?? 13C values for organic matter from most Cretaceous sites are between -26 and -28???, and values heavier than about -25??? occur at very few sites. Most of the ?? 13C values of Miocene to Holocene OC-rich strata and modern marine plankton are between -16 to -23???. Values of ??13C of modern terrestrial organic matter are mostly between -23 and -33???. The depletion of terrestial OC in 13C relative to marine planktonic OC is the basis for numerous statements in the literature that isotopically light Cretaceous organic matter is of terrestrial origin, even though other organic geochemical and(or) optical indicators show that the organic matter is mainly of marine origin. A difference of about 5??? in ?? 13C between modern and Cretaceous OC-rich marine strata suggests either that Cretaceous marine planktonic organic matter had the same isotopic signature as modern marine plankton and that signature has been changed by diagenesis, or that OC derived from Cretaceous marine plankton was isotopically lighter by about 5??? relative to modern plankton OC. Diagenesis does

  20. Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans

    PubMed Central

    Loewen, Mark A.; Irmis, Randall B.; Sertich, Joseph J. W.; Currie, Philip J.; Sampson, Scott D.

    2013-01-01

    The Late Cretaceous (∼95–66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah—including a new taxon which represents the geologically oldest member of the clade—to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades. PMID:24223179

  1. Neovenatorid theropods are apex predators in the Late Cretaceous of North America.

    PubMed

    Zanno, Lindsay E; Makovicky, Peter J

    2013-01-01

    Allosauroid theropods were a diverse and widespread radiation of Jurassic-Cretaceous megapredators. Achieving some of the largest body sizes among theropod dinosaurs, these colossal hunters dominated terrestrial ecosystems until a faunal turnover redefined apex predator guild occupancy during the final 20 million years of the Cretaceous. Here we describe a giant new species of allosauroid--Siats meekerorum gen. et sp. nov.--providing the first evidence for the cosmopolitan clade Neovenatoridae in North America. Siats is the youngest allosauroid yet discovered from the continent and demonstrates that the clade endured there into the Late Cretaceous. The discovery provides new evidence for ecologic sympatry of large allosauroids and small-bodied tyrannosauroids. These data support the hypothesis that extinction of Allosauroidea in terrestrial ecosystems of North America permitted ecological release of tyrannosauroids, which went on to dominate end-Cretaceous food webs.

  2. Detrital Zircon Geochronology of Cretaceous and Paleogene Strata Across the South-Central Alaskan Convergent Margin

    USGS Publications Warehouse

    Bradley, Dwight; Haeussler, Peter J.; O'Sullivan, Paul; Friedman, Rich; Till, Alison; Bradley, Dan; Trop, Jeff

    2009-01-01

    Ages of detrital zircons are reported from ten samples of Lower Cretaceous to Paleogene metasandstones and sandstones from the Chugach Mountains, Talkeetna Mountains, and western Alaska Range of south-central Alaska. Zircon ages are also reported from three igneous clasts from two conglomerates. The results bear on the regional geology, stratigraphy, tectonics, and mineral resource potential of the southern Alaska convergent margin. Chugach Mountains - The first detrital zircon data are reported here from the two main components of the Chugach accretionary complex - the inboard McHugh Complex and the outboard Valdez Group. Detrital zircons from sandstone and two conglomerate clasts of diorite were dated from the McHugh Complex near Anchorage. This now stands as the youngest known part of the McHugh Complex, with an inferred Turonian (Late Cretaceous) depositional age no older than 91-93 Ma. The zircon population has probability density peaks at 93 and 104 Ma and a smattering of Early Cretaceous and Jurassic grains, with nothing older than 191 Ma. The two diorite clasts yielded Jurassic U-Pb zircon ages of 179 and 181 Ma. Together, these findings suggest a Mesozoic arc as primary zircon source, the closest and most likely candidate being the Wrangellia composite terrane. The detrital zircon sample from the Valdez Group contains zircons as young as 69 and 77 Ma, consistent with the previously assigned Maastrichtian to Campanian (Late Cretaceous) depositional age. The zircon population has peaks at 78, 91, 148, and 163 Ma, minor peaks at 129, 177, 330, and 352 Ma, and no concordant zircons older than Devonian. A granite clast from a Valdez Group conglomerate yielded a Triassic U-Pb zircon age of 221 Ma. Like the McHugh Complex, the Valdez Group appears to have been derived almost entirely from Mesozoic arc sources, but a few Precambrian zircons are also present. Talkeetna Mountains - Detrital zircons ages were obtained from southernmost metasedimentary rocks of the

  3. Late Cretaceous remagnetization of Proterozoic mafic dikes, southern Highland Mountains, southwestern Montana: A paleomagnetic and 40Ar/39Ar study

    USGS Publications Warehouse

    Harlan, S.S.; Geissman, J.W.; Snee, L.W.; Reynolds, R.L.

    1996-01-01

    Paleomagnetic results from Early Proterozoic metabasite sills and Middle Proterozoic diabase dikes from the southern Highland Mountains of southwestern Montana give well-defined, dual-polarity magnetizations that are statistically identical to those from a small Late Cretaceous pluton that cuts the dikes. The concordance of paleomagnetic directions from rocks of three widely separated ages indicates that the Proterozoic rocks were remagnetized, probably during Late Cretaceous time. Paleomagnetic, rock magnetic, and petrographic observations from the metabasite and diabase samples indicate that remanence is carried primarily by low-Ti magnetite. Combining virtual geomagnetic poles from metabasite sills, diabase dikes, and the Late Cretaceous pluton, we obtain a paleomagnetic pole at 85.5??N, 310.7??E (K = 19.9, A95 = 9.1??, N = 14 sites) that is similar to a reference pole from the 74 Ma Adel Mountain Volcanics of western Montana. Biotite and hornblende 40Ar/39Ar isotopic dates from host basement geneiss and a hornblende from a remagnetized metabasite sill yield ages of ca. 1800 Ma; these dates probably record cooling of the southern Highland Mountains following high-grade metamorphism at 1.9-1.8 Ga. The gneiss and metabasite age spectra show virtually no evidence of disturbance, indicating that the basement rocks were never heated to temperatures sufficient to cause even partial resetting of their argon systems. Thus, the overprint magnetization of the Highland Mountains rocks is not a thermoremanent magnetization acquired during conductive cooling of nearby Late Cretaceous plutons. Remagnetization of the metabasite sills and diabase dikes was probably caused by localized thermochemical and thermoviscous effects during circulation of Late Cretaceous hydrothermal fluids related to epithermal mineralization. The absence of significant disturbance to the 40Ar/39Ar age spectrum from the remagnetized metabasite hornblende indicates that some secondary magnetizations may

  4. Litho- and biofacies of Early Cretaceous rudist-bearing carbonate sediments in northeastern Japan

    NASA Astrophysics Data System (ADS)

    Sano, Shin-ichi

    1995-11-01

    Carbonate blocks of late Aptian (Lower Cretaceous) age occur in the Lower Yezo Group of central Hokkaido in northeast Japan. The shallow-water carbonates were emplaced by gravity sliding and rock fall into a deep-water flysch basin. Various lithofacies can be distinguished within the blocks including massive wackestone, bedded packstone and micro-oncoid grainstone, containing corals, rudists, an oyster, gastropods, calcareous algae and an orbitolinid foraminifer. Facies and palaeoecological analyses suggest deposition of low-energy biostromes and sand banks in open lagoonal and restricted environments with local higher-energy shoals and beaches. The presence of calcareous sandstones and abundant insoluble residues in limestones suggest deposition in an attached carbonate platform close to a supply of terrigenous material, rather than deposition upon seamounts within an oceanic setting. A narrow rimmed shelf in tropical-subtropical conditions would have been the depositional environment for these carbonates, which were subsequently deformed into blocks and transported into deep water as a result of the tectonic collapse of the platform.

  5. Impact of Sea Level Rise on Mangrove Ecosystem and its Dependent Fishing Communities in the Coastal Regions of Cauvery Delta: A Message for Policy Planners to Frame Suitable Antcipatory Adaptation Strategies

    NASA Astrophysics Data System (ADS)

    Amsad Ibrahim Khan, S. K.; Ramachandran, A.; Kandasamy, P.; Selvam, V.; Shanmugam, P.

    2014-12-01

    Coastal adaptation to sea-level rise (SLR) in the deltaic region is a multidimensional and complex process requiring informed decisions based on predicted impact and vulnerability assessment of SLR. Elevation plays a key role in determining the impact and vulnerability of coastal land areas to inundation from SLR. Highly accurate mapping of the elevation of the landscape is essential to identify low-lying coastal deltaic regions with valuable ecosystem like mangroves and its dependent human communities that are potentially at risk of inundation. It is difficult for policy planners and decision makers to identify suitable adaptation strategies without having information on the predicted impact and degree of vulnerability of coastal systems to SLR. Importantly, modeling and mapping will provide valuable input to climate change adaptation planning (NOAA 2010). Unfortunately, the comprehensive range of information that is typically required is seldom available and rarely in the possession of decision makers responsible for management of the deltaic and coastal zone (O'Regan, 1996). The present study seeks to provide insights on predicted impact of climate change induced SLR on mangrove ecosystem and its dependent human communities of Pichavaram mangroves, located at the Vellar-Coleroon estuarine region on the banks of Cauvery delta, Tamil Nadu, India. Based on real-time on-ground elevation measurement by DGPS (Differential Global Positioning System) survey and by using GIS portals, the study has identified about 597 ha of mangroves (one third of total mangrove regions) and about 9 fishing hamlets with 12,000 and more of human population that directly depends on this mangrove ecosystem for their livelihood are under threat of inundation to the predicted impact of 0.5m SLR. The present study is intended to showcase a method by providing reliable scientific information on predicted impact of SLR on mangroves and its dependent human communities to policy planner for

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

    NASA Astrophysics Data System (ADS)

    Bonev, N.; Stampfli, G.

    2003-04-01

    . Immobile trace element discrimination of both rock types constrains the volcanic (oceanic)-arc origin. They generally show low total REE concentrations (LREE>HREE) with enrichment of LIL elements relative to the HFS elements, and also very low Nb and relatively high Ce content consistent with an island-arc tectonic setting. We consider that the Meliata-Maliac ocean northern passive margin could be the source provenance for the Upper Permian clastics and Middle-Upper Triassic limestone blocks within the olistostromic melange-like unit, whereas turbidites and magmatic blocks may originate in an island arc-accretionary complex that relates to the southward subduction of the Maliac ocean under the supra-subduction back-arc Vardar ocean/island arc system. These new structural and petrologic data allow to precise the tectonic setting of the Mesozoic units and their geodynamic context in the frame of the Early Jurassic to Late Cretaceous evolution of the Vardar ocean.

  7. Controls on Albian-Cenomanian carbonate platform sedimentation in middle eastern region: Kesalon event, a middle Cretaceous sea level change in Israel and its correlation with global sea level changes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Braun, M.; Hirsch, F.

    1987-05-01

    After Neocomian regional denudation, Aptian Telemim (= Blanche) carbonates onlapped the Arabian subplate, followed by Yavne-Tammun regression and Albian transgression. Near the Levant coast, the Albian-early Coniacian Judea carbonate platform interfingers with the Talme Yaffe basin to the west. To the south and east, Judea-type carbonates gradually onlap the mainly continental Kurnub (Nubia type) clastics of the peri-Arabian belt. Detailed analysis of the cyclic sedimentation within the 700-m thick Judea Limestone reveals a regressive trend near the top of the Albian Yagur Formation in Galilee, the Hevyon Formation in the Negev, and the ledge of the Kesalon formation in centralmore » Israel Judean Hills, which represents the end of the Early Cretaceous sedimentary cycle. The early Cenomanian marly chalk of the En Yorqeam Formation starts the Cenomanian cycle, followed by bedded and massive dolomite and ammonoid-bearing limestone. Platform sedimentation before this Kesalon event is dominated by bank facies with some rudistid bioherms of presumable Albian age. After the Kesalon event, Cenomanian and Turonian platforms have fast-changing paleogeography on basinal chalks, shales, bioherms and backreef lagoons. Facies boundaries, running mainly east-west to southwest-northeast up to the Early Cretaceous, became close to north-south in the Late Cretaceous. Albian-Cenomanian regressive-transgressive cycles in Israel match fairly well with global sea level changes, in particular the Kesalon event, which corresponds to the Ka-Kb sea level change of Vail et al. Late Turonian-early Senonian thrusting of the peri-Arabian alpine belt and folding in the Syrian arc heavily affect the unraveling of global sea level changes on the Arabian subplate.« less

  8. Cretaceous rocks from southwestern Montana to southwestern Minnesota, northern Rocky Mountains, and Great Plains

    USGS Publications Warehouse

    Dyman, T.S.; Cobban, W.A.; Fox, J.E.; Hammond, R.H.; Nichols, D.J.; Perry, W.J.; Porter, K.W.; Rice, D.D.; Setterholm, D.R.; Shurr, G.W.; Tysdal, R.G.; Haley, J.C.; Campen, E.B.

    1994-01-01

    In Montana, Wyoming, North and South Dakota, and Minnesota, Cretaceous strata are preserved in the asymmetric Western Interior foreland basin. More than 5,200 m (17,000 ft) of Cretaceous strata are present in southwestern Montana, less than 300 m (1,000 ft) in eastern South Dakota. The asymmetry resulted from varying rates of subsidence due to tectonic and sediment loading. The strata consist primarily of sandstone, siltstone, mudstone, and shale. Conglomerate is locally abundant along the western margin, whereas carbonate is present in most areas of the eastern shelf. Sediment was deposited in both marine and nonmarine environments as the shoreline fluctuated during major tectonic and eustatic cycles.A discussion of Cretaceous strata from southwestern to east-central Montana, the Black Hills, eastern South Dakota, and southwestern Minnesota shows regional stratigraphy and facies relations, sequence, boundaries, and biostratigraphic and radiometric correlations. The thick Cretaceous strata in southwestern Montana typify nonmarine facies of the rapidly subsiding westernmost part of the basin. These strata include more than 3,000 m (10,000 ft) of synorogenic conglomerate of the Upper Cretaceous part of the Beaverhead Group. West of the Madison Range, sequence boundaries bracket the Kootenai (Aptian and Albian), the Blackleaf (Albian and Cenomanian), and the Frontier Formations (Cenomanian and Turonian); sequence boundaries are difficult to recognize because the rocks are dominantly non-marine. Cretaceous strata in east-central Montana (about 1,371 m; 4,500 ft thick) lie at the approximate depositional axis of the basin and are mostly marine terrigenous rocks. Chert-pebble zones in these rocks reflect stratigraphic breaks that may correlate with sequence boundaries to the east and west. Cretaceous rocks of the Black Hills region consist of a predominantly marine clastic sequence averaging approximately 1,524 m (5,000 ft) thick. The Cretaceous System in eastern South

  9. Long-Proboscid Flies as Pollinators of Cretaceous Gymnosperms.

    PubMed

    Peñalver, Enrique; Arillo, Antonio; Pérez-de la Fuente, Ricardo; Riccio, Mark L; Delclòs, Xavier; Barrón, Eduardo; Grimaldi, David A

    2015-07-20

    The great evolutionary success of angiosperms has traditionally been explained, in part, by the partnership of these plants with insect pollinators. The main approach to understanding the origins of this pervasive relationship has been study of the pollinators of living cycads, gnetaleans, and basal angiosperms. Among the most morphologically specialized living pollinators are diverse, long-proboscid flies. Early such flies include the brachyceran family Zhangsolvidae, previously known only as compression fossils from the Early Cretaceous of China and Brazil. It belongs to the infraorder Stratiomyomorpha, a group that includes the flower-visiting families Xylomyidae and Stratiomyidae. New zhangsolvid specimens in amber from Spain (ca. 105 mega-annum [Ma]) and Myanmar (100 Ma) reveal a detailed proboscis structure adapted to nectivory. Pollen clumped on a specimen from Spain is Exesipollenites, attributed to a Mesozoic gymnosperm, most likely the Bennettitales. Late Mesozoic scorpionflies with a long proboscis have been proposed as specialized pollinators of various extinct gymnosperms, but pollen has never been observed on or in their bodies. The new discovery is a very rare co-occurrence of pollen with its insect vector and provides substantiating evidence that other long-proboscid Mesozoic insects were gymnosperm pollinators. Evidence is thus now gathering that visitors and probable pollinators of early anthophytes, or seed plants, involved some insects with highly specialized morphological adaptations, which has consequences for interpreting the reproductive modes of Mesozoic gymnosperms and the significance of insect pollination in angiosperm success. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. The Zambezi sedimentary system (coastal plain - deep sea fan): a record of the vertical movements of the Mozambican margin since Cretaceous times.

    NASA Astrophysics Data System (ADS)

    Ponte, Jean Pierre; Robin, Cecile; Guillocheau, Francois; Baby, Guillaume; Dall'Asta, Massimo; Popescu, Speranta; Suc, Jean Pierre; Droz, Laurence; Rabineau, Marina; Moulin, Maryline

    2016-04-01

    The Mozambique margin is an oblique to transform margin which feeds one of the largest African turbiditic system, the Zambezi deep-sea fan (1800 km length and 400 km wide; Droz and Mougenot., AAPG Bull., 1987). The Zambezi sedimentary system is characterized by (1) a changing catchment area through time with evidences of river captures (Thomas and Shaw, J. Afr. Earth. Sci, 1988) and (2) a delta, storing more than 12 km of sediment, with no gravitary tectonics. The aim of this study is to carry out a source to sink study along the Zambezi sedimentary system and to analyse the margin evolution (vertical movements, climate change) since Early Cretaceous times. The used data are seismic lines (industrial and academic) and petroleum wells (with access to the cuttings). Our first objective was to perform a new biochronostratigraphic framework based on nannofossils, foraminifers, pollen and spores on the cuttings of three industrial wells. The second target was to recognize the different steps of the growth of the Zambezi sedimentary systems. Four main phases were identified: • Late Jurassic (?) - early Late Cretaceous: from Neocomian to Aptian times, the high of the clinoforms is getting higher, with the first occurrence of contouritic ridges during Aptian times. • Late Cretaceous - Early Paleocene: a major drop of relative sea-level occurred as a consequence of the South African Plateau uplift. The occurrence of two depocenters suggests siliciclastic supplies from the Bushveld and from the North Mozambique domain. • Early Paleocene - Eocene: growth of carbonate platforms and large contouritic ridges. • Oligocene - Present-day: birth of the modern Zambezi Delta, with quite low siliciclastic supply during Oligocene times, increasing during Miocene times. As previously expected (Droz and Mougenot) some sediments of the so-called Zambezi fans are coming from a feeder located east of the Davie Ridge. This study was founded by TOTAL and IFREMER in the frame of the

  11. Lower Cretaceous smarl turbidites of the Argo Abyssal Plain, Indian Ocean

    USGS Publications Warehouse

    Dumoulin, Julie A.; Stewart, Sondra K.; Kennett, Diana; Mazzullo, Elsa K.

    1992-01-01

    Sediments recovered during Ocean Drilling Program (ODP) Leg 123 from the Argo Abyssal Plain (AAP) consist largely of turbidites derived from the adjacent Australian continental margin. The oldest abundant turbidites are Valanginian-Aptian in age and have a mixed (smarl) composition; they contain subequal amounts of calcareous and siliceous biogenic components, as well as clay and lesser quartz. Most are thin-bedded, fine sand to mud-sized, and best described by Stow and Piper's model (1984) for fine-grained biogenic turbidites. Thicker (to 3 m), coarser-grained (medium-to-coarse sand-sized) turbidites fit Bouma's model (1962) for sandy turbidites; these generally are base-cut-out (BCDE, BDE) sequences, with B-division parallel lamination as the dominant structure. Parallel laminae most commonly concentrate quartz and/or calcispheres vs. lithic clasts or clay, but distinctive millimeter to centimeter-thick, radiolarian-rich laminae occur in both fine and coarse-grained Valanginian-Hauterivian turbidites.AAP turbidites were derived from relatively deep parts of the continental margin (outer shelf, slope, or rise) that lay below the photic zone, but above the calcite compensation depth (CCD). Biogenic components are largely pelagic (calcispheres, foraminifers, radiolarians, nannofossils); lesser benthic foraminifers are characteristic of deep-water (abyssal to bathyal) environments. Abundant nonbiogenic components are mostly clay and clay clasts; smectite is the dominant clay species, and indicates a volcanogenic provenance, most likely the Triassic-Jurassic volcanic suite exposed along the northern Exmouth Plateau.Lower Cretaceous smarl turbidites were generated during eustatic lowstands and may have reached the abyssal plain via Swan Canyon, a submarine canyon thought to have formed during the Late Jurassic. In contrast to younger AAP turbidites, however, Lower Cretaceous turbidites are relatively fine-grained and do not contain notably older reworked fossils. Early

  12. Sedimentary Provenance Constraints on the Middle Jurassic to Late Cretaceous Paleogeography of the Sichuan Basin, SW China

    NASA Astrophysics Data System (ADS)

    Li, Y.; He, D.; Li, D.; Lu, R.

    2017-12-01

    Sedimentary provenance of the Middle Jurassic to Late Cretaceous sediments in the Sichuan Basin is constrained by sandstone petrology and detrital zircon U-Pb geochronology, which provides critical insights into mid-late Mesozoic paleogeographic evolution of the Sichuan Basin. Petrographic analyses of 22 sandstone samples indicate moderate to high mature sediments and are primarily derived from cratonic or recycled sources. U-Pb age data for the Middle Jurassic to Late Cretaceous detrital zircons generally show populations at 130-200, 200-330, 400-490, 680-890, 1730-1960, and 2360-2600 Ma, with up-section variations. The Middle Jurassic sediments contain a relatively high density of 1.85 and 2.5 Ga zircons and a low density of the 800 Ma zircons, which are consistent with derivation mainly from the Songpan-Ganzi terrane and the South Qinling belt, and secondarily from the Western Jiangnan Orogen. The Late Jurassic and Early Cretaceous sedimentation with a scattered age distribution shared common multiple-source to sink systems that were predominantly draining towards the south and southeast, but increasingly drained southward, and were later disrupted by a synchronous northeastward drainage capture. Late Cretaceous sediments have a distinct reduction in <213 Ma zircons, suggesting that sedimentation involved southeastward and southwestward transport of sediments likely derived from the Songpan-Ganzi terrane, the south segment of the Longmenshan fault belt and western Yangtze Craton, and the uplifting areas of the N- and NE-Sichuan Basin. Changes in provenances during the mid-late Mesozoic period are coincident with temporal-spatial variations in depocenter migration and paleogeographic evolution of the Sichuan Basin, which are closely related to the multi-stage intracontinental subduction associated with clockwise rotation of the South China Block.

  13. Tectonostratigraphic reconstruction Cretaceous volcano-sedimentary in the northwestern Andes: from extensional tectonics to arc accretion.

    NASA Astrophysics Data System (ADS)

    Zapata, S.; Patino, A. M.; Cardona, A.; Mejia, D.; Leon, S.; Jaramillo, J. S.; Valencia, V.; Parra, M.; Hincapie, S.

    2014-12-01

    Active continental margins characterized by continuous convergence experienced overimposed tectonic configurations that allowed the formation of volcanic arcs, back arc basins, transtensional divergent tectonics or the accretion of exotic volcanic terranes. Such record, particularly the extensional phases, can be partially destroyed and obscure by multiple deformational events, the accretion of exotic terranes and strike slip fragmentation along the margin. The tectonic evolution of the northern Andes during the Mesozoic is the result of post Pangea extension followed by the installation of a long-lived Jurassic volcanic arc (209 - 136 ma) that apparently stops between 136 Ma and 110 Ma. The Quebradagrande Complex has been define as a single Lower Cretaceous volcano-sedimentary unit exposed in the western flank of the Central Cordillera of the Colombian Andes that growth after the Late Jurassic to Early Cretaceous magmatic hiatus. The origin of this unit have been related either to an oceanic volcanic arc or a marginal basin environment. The existence of such contrasting models reflect the regional perspective followed in published studies and the paucity of detail analysis of the volcano-sedimentary sequences.We integrate multiple approaches including structural mapping, stratigraphy, geochemistry, U-Pb provenance and geochronology to improve the understanding of this unit and track the earlier phases of accumulation that are mask on the overimposed tectonic history. Our preliminary results suggest the existence of different volcano-sedimentary units that accumulated between 100 Ma and 82 Ma.The older Lower Cretaceous sequences was deposited over Triassic metamorphic continental crust and include a upward basin deepening record characterized by thick fan delta conglomerates, followed by distal turbidites and a syn-sedimentary volcanic record at 100 ma. The other sequence include a 85 - 82 Ma fringing arc that was also formed close to the continental margin or

  14. The Changing Nature of the Hawaiian Hotspot in the Late Cretaceous-Early Tertiary: Evidence From Helium Isotopes and Melt Inclusion Compositions

    NASA Astrophysics Data System (ADS)

    Keller, R.; Graham, D.; Duncan, R.; Regelous, M.

    2002-12-01

    Ocean Drilling Program Leg 197 recovered basaltic basement from three of the Late Cretaceous-Paleogene Emperor seamounts: Detroit (Sites 1203 and 1204), Nintoku (Site 1205), and Koko (Site 1206) seamounts. The depths of penetration into basement achieved by this drilling (140-450 m), the range of rock types recovered (hawaiites, alkalic basalts, and tholeiitic basalts), and the age range (48-76 Ma) makes this one of the most comprehensive collections of the volcanic products of the Hawaiian hotspot available, and opens up new opportunities to study the temporal evolution of the Hawaiian hotspot during the Late Cretaceous and early Tertiary. Previous studies of the chemical evolution of the Hawaiian hotspot (Lanphere et al., 1980; Keller et al., 2000) found significant temporal variations. For example, Sr isotopic ratios of the tholeiitic basalts remain fairly constant along the Hawaiian Islands/Ridge between Kilauea volcano on Hawaii and the Hawaiian-Emperor bend, but then decrease steadily northward along the Emperor seamounts. Trace element compositions (especially the rare earth element patterns) also show limited variations along the Hawaiian Islands/Ridge, but change toward more depleted values northward along the Emperor seamounts. The trend to more MORB-like compositions back in time was attributed to a decrease in distance between the hotspot and the nearest spreading center, although a more comprehensive study suggests that variations in lithospheric thickness also caused changes in the composition of the plume melts (Regelous et al., 2002). We will complement these previous studies and the ongoing work of the other Leg 197 scientists by studying two aspects of the Emperor seamount basalts: helium isotopes and melt inclusion compositions. We will measure the helium isotopic ratios of selected olivine separates from three of the Leg 197 drill sites and from DSDP Site 433 on Suiko seamount (65 Ma) to determine if the composition of the Hawaiian "plume signal

  15. Facies analysis, palaeoenvironmental reconstruction and stratigraphic development of the Early Cretaceous sediments (Lower Bima Member) in the Yola Sub-basin, Northern Benue Trough, NE Nigeria

    NASA Astrophysics Data System (ADS)

    Sarki Yandoka, Babangida M.; Abubakar, M. B.; Abdullah, Wan Hasiah; Amir Hassan, M. H.; Adamu, Bappah U.; Jitong, John S.; Aliyu, Abdulkarim H.; Adegoke, Adebanji Kayode

    2014-08-01

    The Benue Trough of Nigeria is a major rift basin formed from the tension generated by the separation of African and South American plates in the Early Cretaceous. It is geographically sub-divided into Southern, Central and Northern Benue portions. The Northern Benue Trough comprises two sub-basins; the N-S trending Gongola Sub-basin and the E-W trending Yola Sub-basin. The Bima Formation is the oldest lithogenetic unit occupying the base of the Cretaceous successions in the Northern Benue Trough. It is differentiated into three members; the Lower Bima (B1), the Middle Bima (B2) and the Upper Bima (B3). Facies and their stratigraphical distribution analyses were conducted on the Lower Bima Member exposed mainly at the core of the NE-SW axially trending Lamurde Anticline in the Yola Sub-basin, with an objective to interpret the paleodepositional environments, and to reconstruct the depositional model and the stratigraphical architecture. Ten (10) lithofacies were identified on the basis of lithology, grain size, sedimentary structures and paleocurrent analysis. The facies constitute three (3) major facies associations; the gravelly dominated, the sandy dominated and the fine grain dominated. These facies and facies associations were interpreted and three facies successions were recognized; the alluvial-proximal braided river, the braided river and the lacustrine-marginal lacustrine. The stratigraphic architecture indicates a rifted (?pull-apart) origin as the facies distribution shows a progradational succession from a shallow lacustrine/marginal lacustrine (at the axial part of the basin) to alluvial fan (sediment gravity flow)-proximal braided river (gravel bed braided river) and braided river (channel and overbank) depositional systems. The facies stacking patterns depict sedimentation mainly controlled by allogenic factors of climate and tectonism.

  16. Small Theropod Teeth from the Late Cretaceous of the San Juan Basin, Northwestern New Mexico and Their Implications for Understanding Latest Cretaceous Dinosaur Evolution

    PubMed Central

    Williamson, Thomas E.; Brusatte, Stephen L.

    2014-01-01

    Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian – Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately co-eval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod diversity were lost

  17. Small theropod teeth from the Late Cretaceous of the San Juan Basin, northwestern New Mexico and their implications for understanding latest Cretaceous dinosaur evolution.

    PubMed

    Williamson, Thomas E; Brusatte, Stephen L

    2014-01-01

    Studying the evolution and biogeographic distribution of dinosaurs during the latest Cretaceous is critical for better understanding the end-Cretaceous extinction event that killed off all non-avian dinosaurs. Western North America contains among the best records of Late Cretaceous terrestrial vertebrates in the world, but is biased against small-bodied dinosaurs. Isolated teeth are the primary evidence for understanding the diversity and evolution of small-bodied theropod dinosaurs during the Late Cretaceous, but few such specimens have been well documented from outside of the northern Rockies, making it difficult to assess Late Cretaceous dinosaur diversity and biogeographic patterns. We describe small theropod teeth from the San Juan Basin of northwestern New Mexico. These specimens were collected from strata spanning Santonian - Maastrichtian. We grouped isolated theropod teeth into several morphotypes, which we assigned to higher-level theropod clades based on possession of phylogenetic synapomorphies. We then used principal components analysis and discriminant function analyses to gauge whether the San Juan Basin teeth overlap with, or are quantitatively distinct from, similar tooth morphotypes from other geographic areas. The San Juan Basin contains a diverse record of small theropods. Late Campanian assemblages differ from approximately coeval assemblages of the northern Rockies in being less diverse with only rare representatives of troodontids and a Dromaeosaurus-like taxon. We also provide evidence that erect and recurved morphs of a Richardoestesia-like taxon represent a single heterodont species. A late Maastrichtian assemblage is dominated by a distinct troodontid. The differences between northern and southern faunas based on isolated theropod teeth provide evidence for provinciality in the late Campanian and the late Maastrichtian of North America. However, there is no indication that major components of small-bodied theropod diversity were lost

  18. Current oil and gas production from North American Upper Cretaceous chalks

    USGS Publications Warehouse

    Scholle, Peter A.

    1977-01-01

    Production of oil and natural gas from North American chalks has increased significantly during the past five years, spurred by the prolific production from North Sea chalks, as well as by higher prices and improved production technology. Chalk reservoirs have been discovered in the Gulf Coast in the Austin Group, Saratoga and Annona Chalks, Ozan Formation, Selma Group, Monroe gas rock (an informal unit of Navarro age), and other Upper Cretaceous units. In the Western Interior, production has been obtained from the Cretaceous Niobrara and Greenhorn Formations. Significant, though subcommercial, discoveries of natural gas and gas condensate also have been made in the Upper Cretaceous Wyandot Formation on the Scotian Shelf of eastern Canada. All North American chalk units share a similar depositional and diagenetic history. The chalks consist primarily of whole and fragmented coccoliths with subordinate planktonic and benthonic Foraminifera, inoceramid prisms, oysters, and other skeletal grains. Most have between 10 and 35 percent HCl-insoluble residue, predominantly clay. Deposition was principally below wave base in tens to hundreds of meters of water. The diagenetic history of a chalk is critical in determining its reservoir potential. All chalk has a stable composition (low-Mg calcite) and very high primary porosity. With subsequent burial, mechanical and chemical (solution-transfer) compaction can reduce or completely eliminate pore space. The degree of loss of primary porosity in chalk sections is normally a direct function of the maximum depth to which it has been buried. Pore-water chemistry, pore-fluid pressures, and tectonic stresses also influence rates of cementation. Oil or gas reservoirs of North American chalk fall into three main groups: 1. Areas with thin overburden and significant primary porosity retention (for example, Niobrara Formation of Kansas and eastern Colorado). 2. Areas with thicker overburden but considerable fracturing. Here primary

  19. The early cretaceous evolution of carbonate platforms from northern Oman

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Masse, J.P.; Borgomano, J.; Maskiry, S.Al.

    1993-09-01

    In northern Oman (Jebel Akhdar and foothills) Hauterivian to early Aptian shallow carbonate platforms are widely extending and pass laterally to slope and basin environments in the Nakhl zone. Progradational geometries are identified in that zone where significant correlation between thickness and sediment types supports a prominent tectonic control. The platform records four main sedimentary breaks (drowning events). Early Barremian (lower Lekhwair Formation), Late Barremian (basal Kharaib Formation), lowermost early Aptian (upper Kharaib Formation) and middle Aptian (Shuaiba-Al Hassanat formations boundary). The late Aptian-early Albian hiatus (pre-Nahr Umr unconformity) is regarded as an early Albian tectonically driven erosion. In themore » Nakhl zone, coral-rudist limestones of late Aptian-early Albian (lower Al Hassanat Formation) document an east-west ribbon platform, the southward extension of which was obscured by the middle Albian erosions and rudist limestones of middle to late Albian (upper Al Hassanat Formation), a lateral equivalent of the Nahr Umr circa littoral shaly sediments, document an east-west-trending linear platform. The foregoing points out a northward progradation coeval with a southward transgressive major trend for the Hauterivian-early Aptian interval, a faulted margin corresponding with the Nakhl zone active during the Aptian-Albian, a late Aptian ribbon platform coeval with the Bab basin initiation southward, a regional uplifting and truncation during the early-Albian (Austrian phase), whereas shallow-water carbonates are still forming at the edge of the former platform, and an active linear platform at the northern edge of the Nahr Umr basin, the corresponding drowning contemporaneous with the onset of the Cenomanian platform eastward.« less

  20. Astronomically Forced Hydrology of the Late Cretaceous Sub-tropical Potosí Basin, Bolivia

    NASA Astrophysics Data System (ADS)

    Tasistro-Hart, A.; Maloof, A. C.; Schoene, B.; Eddy, M. P.

    2017-12-01

    Orbital forcings paced the ice ages of the Pleistocene, demonstrating that periodic variations in the latitudinal distribution of insolation amplified by ice-albedo feedbacks can guide global climate. How these forcings operate in the hot-houses that span most of the planet's history, however, is unknown. The lacustrine El Molino formation of the late Cretaceous-early Paleogene Potosí Basin in present-day Bolivia contains carbonate-mud parasequences that record fluctuating hydrological conditions from 73 to 63 Ma. This study presents the first cyclostratigraphic analysis using high-resolution drone-derived imagery and 3D elevation models, combined with conventional stratigraphic measurements and magnetic susceptibility data. The drone-derived data are integrated over the entire outcrop at two field areas using a novel application of stratigraphic potential field modeling that increases signal-to-noise ratios prior to spectral analysis. We demonstrate that these parasequences exhibit significant periodicities consistent with eccentricity (400 and 100 kyr), obliquity (50 kyr, 40 kyr, and 29 kyr), precession (17-23 kyr), and semi-precession (9-11 kyr). New U-Pb ID-TIMS zircon ages from intercalacted ash beds corroborate the interpreted sedimentation rates at two sites, indicating that the Potosí Basin contains evidence for hot-house astronomical forcing of sub-tropical lacustrine hydrology. Global climate simulations of late Cretaceous orbital end-member configurations demonstrate precessional-eccentricity and obliquity driven modulation of basin hydrology. In model simulations, the forcings drive long-term shifts in the location of the intertropical convergence zone, changing precipitation along the northern extent of the Potosí Basin's catchment area. This study is the first to demonstrate orbital forcing of a lacustrine system during the Maastrichtian and could ultimately contribute to a precise age for the Cretaceous-Paleogene boundary.

  1. Cretaceous biostratigraphy in the Wyoming thrust belt

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nichols, D.J.; Jacobson, S.R.

    Biostratigraphy is essential to exploration for oil and gas in the Wyoming thrust belt because fossils provide a temporal framework for interpretation of events of faulting, erosion, sedimentation, and the development of hydrocarbon traps and migration pathways. In the Cretaceous section, fossils are especially useful for dating and correlating repetitive facies of different ages in structurally complex terrain. The biostratigraphic zonation for the region is based on megafossils (chiefly ammonites), which permit accurate dating and correlation of outcrop sections, and which have been calibrated with the radiometric time scale for the Western Interior. Molluscan and vertebrate zone fossils are difficultmore » to obtain from the subsurface, however, and ammonities are restricted to rocks of margin origin. Palynomorphs (plant microfossils) have proven to be the most valuable fossils in investigations of stratigraphy and structures in the subsurface of the thrust belt because palynomorphs can be recovered from drill cuttings. Palynomorphs also are found in both marine and nonmarine rocks and can be used for correlation between facies. In this paper, stratigraphic ranges of selected Cretaceous marine and nonmarine palynomorphs in previously designated reference sections in Fossil Basin, Wyoming, are correlated with the occurrence of ammonities and other zone fossils in the same sections. These correlations can be related to known isotopic ages, and they contribute to the calibration of palynomorph ranges in the Cretaceous of the Western Interior.« less

  2. Plant microfossil record of the terminal Cretaceous event in the western United States and Canada

    NASA Technical Reports Server (NTRS)

    Nichols, D. J.; Fleming, R. F.

    1988-01-01

    Plant microfossils, principally pollen grains and spores produced by land plants, provide an excellent record of the terminal Cretaceous event in nonmarine environments. The record indicates regional devastation of the latest Cretaceous vegetation with the extinction of many groups, followed by a recolonization of the earliest Tertiary land surface, and development of a permanently changed land flora. The regional variations in depositional environments, plant communities, and paleoclimates provide insight into the nature and effects of the event, which were short-lived but profound. The plant microfossil data support the hypothesis that an abruptly initiated, major ecological crisis occurred at the end of the Cretaceous. Disruption of the Late Cretaceous flora ultimately contributred to the rise of modern vegetation. The plant microfossils together with geochemical and mineralogical data are consistent with an extraterrestrial impact having been the cause of the terminal Cretaceous event.

  3. A small azhdarchoid pterosaur from the latest Cretaceous, the age of flying giants.

    PubMed

    Martin-Silverstone, Elizabeth; Witton, Mark P; Arbour, Victoria M; Currie, Philip J

    2016-08-01

    Pterosaur fossils from the Campanian-Maastrichtian of North America have been reported from the continental interior, but few have been described from the west coast. The first pterosaur from the Campanian Northumberland Formation (Nanaimo Group) of Hornby Island, British Columbia, is represented here by a humerus, dorsal vertebrae (including three fused notarial vertebrae), and other fragments. The elements have features typical of Azhdarchoidea, an identification consistent with dominance of this group in the latest Cretaceous. The new material is significant for its size and ontogenetic stage: the humerus and vertebrae indicate a wingspan of ca 1.5 m, but histological sections and bone fusions indicate the individual was approaching maturity at time of death. Pterosaurs of this size are exceedingly rare in Upper Cretaceous strata, a phenomenon commonly attributed to smaller pterosaurs becoming extinct in the Late Cretaceous as part of a reduction in pterosaur diversity and disparity. The absence of small juveniles of large species-which must have existed-in the fossil record is evidence of a preservational bias against small pterosaurs in the Late Cretaceous, and caution should be applied to any interpretation of latest Cretaceous pterosaur diversity and success.

  4. The semi-aquatic pondweed bugs of a Cretaceous swamp.

    PubMed

    Sánchez-García, Alba; Nel, André; Arillo, Antonio; Solórzano Kraemer, Mónica M

    2017-01-01

    Pondweed bugs (Hemiptera: Mesoveliidae), considered a sister group to all other Gerromorpha, are exceedingly rare as fossils. Therefore, each new discovery of a fossil mesoveliid is of high interest, giving new insight into their early evolutionary history and diversity and enabling the testing of their proposed relationships. Here, we report the discovery of new mesoveliid material from Spanish Lower Cretaceous (Albian) amber, which is the first such find in Spanish amber. To date, fossil records of this family only include one species from French Kimmeridgian as compression fossils, two species in French amber (Albian-Cenomanian boundary), and one in Dominican amber (Miocene). The discovery of two males and one female described and figured as Glaesivelia pulcherrima Sánchez-García & Solórzano Kraemer gen. et sp. n., and a single female described and figured as Iberovelia quisquilia Sánchez-García & Nel, gen. et sp. n., reveals novel combinations of traits related to some genera currently in the subfamily Mesoveliinae. Brief comments about challenges facing the study of fossil mesoveliids are provided, showing the necessity for a revision of the existing phylogenetic hypotheses. Some of the specimens were studied using infrared microscopy, a promising alternative to the systematic study of organisms preserved in amber that cannot be clearly visualised. The new taxa significantly expand the fossil record of the family and shed new light on its palaeoecology. The fossils indicate that Mesoveliidae were certainly diverse by the Cretaceous and that numerous tiny cryptic species living in humid terrestrial to marginal aquatic habitats remain to be discovered. Furthermore, the finding of several specimens as syninclusions suggests aggregative behaviour, thereby representing the earliest documented evidence of such ethology.

  5. A New Pterosaur (Pterodactyloidea: Azhdarchidae) from the Upper Cretaceous of Morocco

    PubMed Central

    Ibrahim, Nizar; Unwin, David M.; Martill, David M.; Baidder, Lahssen; Zouhri, Samir

    2010-01-01

    The Kem Kem beds in South Eastern Morocco contain a rich early Upper (or possibly late Lower) Cretaceous vertebrate assemblage. Fragmentary remains, predominantly teeth and jaw tips, represent several kinds of pterosaur although only one species, the ornithocheirid Coloborhynchus moroccensis, has been named. Here, we describe a new azhdarchid pterosaur, Alanqa saharica nov. gen. nov. sp., based on an almost complete well preserved mandibular symphysis from Aferdou N'Chaft. We assign additional fragmentary jaw remains, some of which have been tentatively identified as azhdarchid and pteranodontid, to this new taxon which is distinguished from other azhdarchids by a remarkably straight, elongate, lance-shaped mandibular symphysis that bears a pronounced dorsal eminence near the posterior end of its dorsal (occlusal) surface. Most remains, including the holotype, represent individuals of approximately three to four meters in wingspan, but a fragment of a large cervical vertebra, that probably also belongs to A. saharica, suggests that wingspans of six meters were achieved in this species. The Kem Kem beds have yielded the most diverse pterosaur assemblage yet reported from Africa and provide the first clear evidence for the presence of azhdarchids in Gondwana at the start of the Late Cretaceous. This, the relatively large size achieved by Alanqa, and the additional evidence of variable jaw morphology in azhdarchids provided by this taxon, indicates a longer and more complex history for this clade than previously suspected. PMID:20520782

  6. Did southern Western Ghats of peninsular India serve as refugia for its endemic biota during the Cretaceous volcanism?

    PubMed Central

    Joshi, Jahnavi; Karanth, Praveen

    2013-01-01

    The Western Ghats (WG) of south India, a global biodiversity hotspot, has experienced complex geological history being part of Gondwana landmass and encountered extensive volcanic activity at the end of Cretaceous epoch. It also has a climatically and topographically heterogeneous landscape. Thus, the WG offer a unique setting to explore the influence of ecological and geological processes on the current diversity and distribution of its biota. To this end, three explicit biogeographical scenarios were hypothesized to evaluate the distribution and diversification of wet evergreen species of the WG – (1) southern WG was a refuge for the wet evergreen species during the Cretaceous volcanism, (2) phylogenetic breaks in the species phylogeny would correspond to geographic breaks (i.e., the Palghat gap) in the WG, and (3) species from each of the biogeographic subdivisions within the WG would form distinct clades. These hypotheses were tested on the centipede genus Digitipes from the WG which is known to be an ancient, endemic, and monophyletic group. The Digitipes molecular phylogeny was subjected to divergence date estimation using Bayesian approach, and ancestral areas were reconstructed using parsimony approach for each node in the phylogeny. Ancestral-area reconstruction suggested 13 independent dispersal events to explain the current distribution of the Digitipes species in the WG. Among these 13 dispersals, two dispersal events were at higher level in the Digitipes phylogeny and were from the southern WG to the central and northern WG independently in the Early Paleocene, after the Cretaceous Volcanism. The remaining 11 dispersal events explained the species’ range expansions of which nine dispersals were from the southern WG to other biogeographic subdivisions in the Eocene-Miocene in the post-volcanic periods where species-level diversifications occurred. Taken together, these results suggest that southern WG might have served as a refuge for Digitipes

  7. Paleomagnetism of the Cretaceous Galula Formation and implications for vertebrate evolution

    NASA Astrophysics Data System (ADS)

    Widlansky, Sarah J.; Clyde, William C.; O'Connor, Patrick M.; Roberts, Eric M.; Stevens, Nancy J.

    2018-03-01

    This study uses magnetostratigraphy to help constrain the age of the paleontologically important Galula Formation (Rukwa Rift Basin, southwestern Tanzania). The formation preserves a Cretaceous vertebrate fauna, including saurischian dinosaurs, a putative gondwanatherian mammal, and notosuchian crocodyliforms. With better dating, the Galula Formation and its fossils help fill a temporal gap in our understanding of vertebrate evolution in continental Africa, enabling better evaluation of competing paleobiogeographic hypotheses concerning faunal exchange throughout Gondwana during the Cretaceous. Paleomagnetic samples for this study were collected from the Namba (higher in section) and Mtuka (lower in section) members of the Galula Formation and underwent stepwise thermal demagnetization. All samples displayed a strong normal magnetic polarity overprint, and maximum unblocking temperatures at approximately 690 °C. Three short reversed intervals were identified in the Namba Member, whereas the Mtuka Member lacked any clear reversals. Given the relatively limited existing age constraints, one interpretation correlates the Namba Member to Chron C32. An alternative correlation assigns reversals in the Namba Member to recently proposed short reversals near the end of the Cretaceous Normal Superchron (Chron C34), a time that is traditionally interpreted as having stable normal polarity. The lack of reversals in the Mtuka Member supports deposition within Chron C34. These data suggest that the Namba Member is no older than Late Cretaceous (Cenomanian-Campanian), with the Mtuka Member less well constrained to the middle Cretaceous (Aptian-Cenomanian). The paleomagnetic results are supported by the application of fold and reversal tests for paleomagnetic stability, and paleomagnetic poles for the Namba (246.4°/77.9°, α95 5.9°) and Mtuka (217.1°/72.2°, α95 11.1°) members closely matching the apparent polar wander path for Africa during the Late Cretaceous. These

  8. Sedimentologic Expression of the Cretaceous OAEs in a Tropical Epicontinental Sea

    NASA Astrophysics Data System (ADS)

    Silva-Tamayo, J. C.; Eisenhauer, A.

    2015-12-01

    The acidification and deoxygention of modern oceans are major environmental concerns to the international community. The effects of ocean acidification and deoxigention in the biogeochemical cycles of modern tropical oceans are poorly constrained mainly due to the lack of empirical and quantitative data. The Cretaceous World witnessed several period of potential ocean acidification and deoxygenation, which resulted from the rapid additions of volcanic derived CO2 to the atmosphere. The effects of ocean acidification and deoxygenation on the Cretaceous biogeochemical cycles are evidenced mainly by major global C-isotope anomalies. These anomalies parallel the occurrence of organic rich black shales as well as major decreases in the deposition of shallow marine carbonates worldwide. Here we use detailed C- and Sr- chemostratigraphy as well as published bioestratigraphic information and volcanic zircon U-Pb ages to precisely constrain the geochemical and sedimentologic expression of the Cretaceous OAES along a tropical epicontinental sea, the La Luna Sea. Our multi-pronged approach allows identifying the occurrence of several of the Cretaceous Oceanic Anoxic Events (OAEs) in carbonate units paleogeographically located along the northern most part of the La Luna Sea, i.e. Weissert-OAE-(Palanz and Rosablanca Formations), Faraoni-(Rosablanca Formation), AOE1a-(Paja and Fomeque Formations, Cogollo Group), OAE1c-(Cogollo Group), OAE2-(Cogollo Group), OAE3-(La Luna Formation). These events are preserved in highly euxinic - organic rich "black shales" successions deposited along the deepest part of the seaway at the Middle Magdalena Valley and Cundinamarca Basin; Weiser-OAE-(Lutitas de Macanal Formation), OAE1a-(Paja Formation, Fomeque Formation), OAE1C-(San Gil Formation). Regional changes in depositional settings and sedimentary facies preserving the different Cretaceous OAEs were likely the result of the combined action of regional changes in paleogeography and tectonic

  9. An endoparasitoid Cretaceous fly and the evolution of parasitoidism.

    PubMed

    Zhang, Qingqing; Zhang, Junfeng; Feng, Yitao; Zhang, Haichun; Wang, Bo

    2016-02-01

    Parasitoidism is a key innovation in insect evolution, and parasitoid insects, nowadays, play a significant role in structuring ecological communities. Despite their diversity and ecological impact, little is known about the early evolution and ecology of parasitoid insects, especially parasitoid true flies (Diptera). Here, we describe a bizarre fly, Zhenia xiai gen. et sp. nov., from Late Cretaceous Burmese amber (about 99 million years old) that represents the latest occurrence of the family Eremochaetidae. Z. xiai is an endoparasitoid insect as evidenced by a highly developed, hypodermic-like ovipositor formed by abdominal tergites VIII + IX that was used for injecting eggs into hosts and enlarged tridactylous claws supposedly for clasping hosts. Our results suggest that eremochaetids are among the earliest definite records of parasitoid insects. Our findings reveal an unexpected morphological specialization of flies and broaden our understanding of the evolution and diversity of ancient parasitoid insects.

  10. An endoparasitoid Cretaceous fly and the evolution of parasitoidism

    NASA Astrophysics Data System (ADS)

    Zhang, Qingqing; Zhang, Junfeng; Feng, Yitao; Zhang, Haichun; Wang, Bo

    2016-02-01

    Parasitoidism is a key innovation in insect evolution, and parasitoid insects, nowadays, play a significant role in structuring ecological communities. Despite their diversity and ecological impact, little is known about the early evolution and ecology of parasitoid insects, especially parasitoid true flies (Diptera). Here, we describe a bizarre fly, Zhenia xiai gen. et sp. nov., from Late Cretaceous Burmese amber (about 99 million years old) that represents the latest occurrence of the family Eremochaetidae. Z. xiai is an endoparasitoid insect as evidenced by a highly developed, hypodermic-like ovipositor formed by abdominal tergites VIII + IX that was used for injecting eggs into hosts and enlarged tridactylous claws supposedly for clasping hosts. Our results suggest that eremochaetids are among the earliest definite records of parasitoid insects. Our findings reveal an unexpected morphological specialization of flies and broaden our understanding of the evolution and diversity of ancient parasitoid insects.

  11. High resolution carbon isotope stratigraphy and glendonite occurrences of the Christopher Formation, Sverdrup Basin (Axel Heiberg Island, Canada): implications for mid Cretaceous high latitude climate change

    NASA Astrophysics Data System (ADS)

    Herrle, Jens O.; Schröder-Adams, Claudia J.; Galloway, Jennifer M.; Pugh, Adam T.

    2013-04-01

    glendonites are concentrated in regular beds during the late Aptian to early Albian of the Christopher Formation supporting the idea of a cold snap (Kemper, 1987; Herrle & Mutterlose 2003; Mutterlose et al. 2009) within the mid-Cretaceous greenhouse period. References Herrle, J.O., Mutterlose, J., 2003. Calcareous nannofossils from the Aptian - early Albian of SE France: Paleoecological and biostratigraphic implications. Cretaceous Research 24, 1-22. Kemper, E., 1987. Das Klima der Kreide-Zeit. Geologisches Jahrbuch 96, 185 pp. Mutterlose, J., Bornemann, A., Herrle, J.O., 2009. The Aptian - Albian cold snap: Evidence for "mid" Cretaceous icehouse interludes. Neues Jahrbuch für Geologie und Palaeontologie, Abhandlungen 252, 217-225.

  12. Marine reptiles from the Late Cretaceous of northern Patagonia

    NASA Astrophysics Data System (ADS)

    Gasparini, Z.; Casadio, S.; Fernández, M.; Salgado, L.

    2001-04-01

    During the Campanian-Maastrichtian, Patagonia was flooded by the Atlantic and reduced to an archipelago. Several localities of northern Patagonia have yielded marine reptiles. Analysis of several assemblages suggests that the diversity and abundance of pelagic marine reptiles in northern Patagonia was higher by the end of the Cretaceous than previously thought. Several plesiosaurids, including Aristonectes parvidens and the polycotylid Sulcusuchus, and the first remains of mosasaurinae have been found. The Cretaceous marine reptile record from South America is scanty. Nevertheless, materials described here suggest that Tethyan and Weddelian forms converged in northern Patagonia, as seen with invertebrates.

  13. Late Cretaceous terrestrial vertebrate fauna, North Slope, Alaska

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Clemens, W.A.; Allison, C.W.

    1985-01-01

    Closely related terrestrial vertebrates in Cretaceous mid-latitude (30/sup 0/ to 50/sup 0/) faunas of North America and Asia as well as scattered occurrences of footprints and skin impressions suggested that in the Late Mesozoic the Alaskan North Slope supported a diverse fauna. In 1961 abundant skeletal elements of Cretaceous, Alaskan dinosaurs (hadrosaurids) were discovered by the late R.L. Liscomb. This material is being described by K.L. Davies. Additional fossils collected by E.M. Brouwers and her associates include skeletal elements of hadrosaurid and carnosaurian (.tyrannosaurid) dinosaurs and other vertebrates. The fossil locality on the North Slope is not at about 70/supmore » 0/N. In the Late Cretaceous the members of this fauna were subject to the daylight regime and environment at a paleolatitude closer to 80/sup 0/N. Current hypotheses attributing extinctions of dinosaurs and some other terrestrial vertebrates to impact of an extraterrestrial object cite periods of darkness, decreased temperature (possibly followed by extreme warming) and acid rain as the direct causes of their demise. Unless members of this North Slope fauna undertook long-distance migrations, their high latitude occurrence indicates groups of dinosaurs and other terrestrial vertebrates regularly tolerated months of darkness.« less

  14. Depositional facies, environments and sequence stratigraphic interpretation of the Middle Triassic-Lower Cretaceous (pre-Late Albian) succession in Arif El-Naga anticline, northeast Sinai, Egypt

    NASA Astrophysics Data System (ADS)

    El-Azabi, M. H.; El-Araby, A.

    2005-01-01

    The Middle Triassic-Lower Cretaceous (pre-Late Albian) succession of Arif El-Naga anticline comprises various distinctive facies and environments that are connected with eustatic relative sea-level changes, local/regional tectonism, variable sediment influx and base-level changes. It displays six unconformity-bounded depositional sequences. The Triassic deposits are divided into a lower clastic facies (early Middle Triassic sequence) and an upper carbonate unit (late Middle- and latest Middle/early Late Triassic sequences). The early Middle Triassic sequence consists of sandstone with shale/mudstone interbeds that formed under variable regimes, ranging from braided fluvial, lower shoreface to beach foreshore. The marine part of this sequence marks retrogradational and progradational parasequences of transgressive- and highstand systems tract deposits respectively. Deposition has taken place under warm semi-arid climate and a steady supply of clastics. The late Middle- and latest Middle/early Late Triassic sequences are carbonate facies developed on an extensive shallow marine shelf under dry-warm climate. The late Middle Triassic sequence includes retrogradational shallow subtidal oyster rudstone and progradational lower intertidal lime-mudstone parasequences that define the transgressive- and highstand systems tracts respectively. It terminates with upper intertidal oncolitic packstone with bored upper surface. The next latest Middle/early Late Triassic sequence is marked by lime-mudstone, packstone/grainstone and algal stromatolitic bindstone with minor shale/mudstone. These lower intertidal/shallow subtidal deposits of a transgressive-systems tract are followed upward by progradational highstand lower intertidal lime-mudstone deposits. The overlying Jurassic deposits encompass two different sequences. The Lower Jurassic sequence is made up of intercalating lower intertidal lime-mudstone and wave-dominated beach foreshore sandstone which formed during a short

  15. A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians

    PubMed Central

    Azuma, Yoichi; Xu, Xing; Shibata, Masateru; Kawabe, Soichiro; Miyata, Kazunori; Imai, Takuya

    2016-01-01

    Our understanding of coelurosaurian evolution, particularly of bird origins, has been greatly improved, mainly due to numerous recently discovered fossils worldwide. Nearly all these discoveries are referable to the previously known coelurosaurian subgroups. Here, we report a new theropod, Fukuivenator paradoxus, gen. et sp. nov., based on a nearly complete specimen from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs. Computed-tomography data indicate that Fukuivenator possesses inner ears whose morphology is intermediate between those of birds and non-avian dinosaurs. Our phylogenetic analysis recovers Fukuivenator as a basally branching maniraptoran theropod, yet is unable to refer it to any known coelurosaurian subgroups. The discovery of Fukuivenator considerably increases the morphological disparity of coelurosaurian dinosaurs and highlights the high levels of homoplasy in coelurosaurian evolution. PMID:26908367

  16. Impact of CO2 and continental configuration on Late Cretaceous ocean dynamics

    NASA Astrophysics Data System (ADS)

    Puceat, Emmanuelle; Donnadieu, Yannick; Moiroud, Mathieu; Guillocheau, François; Deconinck, Jean-François

    2014-05-01

    The Late Cretaceous period is characterized by a long-term climatic cooling (Huber et al., 1995; Pucéat et al., 2003; Friedrich et al., 2012) and by major changes in continental configuration with the widening of the Atlantic Ocean, the initiation of the Tethyan ocean closure, and the deepening of the Central Atlantic Gateway. The Late Cretaceous also marks the end of the occurrence of Oceanic Anoxic Events (OAEs), that are associated to enhanced organic carbon burial, to major crises of calcifying organisms, and to possible ocean acidification (Jenkyns, 2010). It has been suggested that the evolution in continental configuration and climate occurring during the Late Cretaceous could have induced a reorganization in the oceanic circulation, that may have impacted the oxygenation state of the oceanic basins and contributed to the disappearance of OAEs (Robinson et al., 2010; Robinson and Vance, 2012). Yet there is no consensus existing on the oceanic circulation modes and on their possible evolution during the Late Cretaceous, despite recent improvement of the spatial and temporal coverage of neodymium isotopic data (ɛNd), a proxy of oceanic circulation (MacLeod et al., 2008; Robinson et al., 2010; Murphy and Thomas, 2012; Robinson and Vance, 2012; Martin et al., 2012; Moiroud et al., 2012). Using the fully coupled ocean-atmosphere General Circulation Model FOAM, we explore in this work the impact on oceanic circulation of changes in continental configuration between the mid- and latest Cretaceous. Two paleogeography published by Sewall et al. (2007) were used, for the Cenomanian/Turonian boundary and for the Maastrichtian. For each paleogeography, 3 simulations have been realized, at 2x, 4x, and 8x the pre-industrial atmospheric CO2 level, in order to test the sensitivity of the modelled circulation to CO2. Our results show for both continental configurations a bipolar mode for the oceanic circulation displayed by FOAM. Using the Cenomanian/Turonian land-sea mask

  17. Discovery of fossil lamprey larva from the Lower Cretaceous reveals its three-phased life cycle

    PubMed Central

    Chang, Mee-mann; Wu, Feixiang; Miao, Desui; Zhang, Jiangyong

    2014-01-01

    Lampreys are one of the two surviving jawless vertebrate groups and one of a few vertebrate groups with the best exemplified metamorphosis during their life cycle, which consists of a long-lasting larval stage, a peculiar metamorphosis, and a relatively short adulthood with a markedly different anatomy. Although the fossil records have revealed that many general features of extant lamprey adults were already formed by the Late Devonian (ca. 360 Ma), little is known about the life cycle of the fossil lampreys because of the lack of fossilized lamprey larvae or transformers. Here we report the first to our knowledge discovery of exceptionally preserved premetamorphic and metamorphosing larvae of the fossil lamprey Mesomyzon mengae from the Lower Cretaceous of Inner Mongolia, China. These fossil ammocoetes look surprisingly modern in having an eel-like body with tiny eyes, oral hood and lower lip, anteriorly positioned branchial region, and a continuous dorsal skin fin fold and in sharing a similar feeding habit, as judged from the detritus left in the gut. In contrast, the larger metamorphosing individuals have slightly enlarged eyes relative to large otic capsules, thickened oral hood or pointed snout, and discernable radials but still anteriorly extended branchial area and lack a suctorial oral disk, which characterize the early stages of the metamorphosis of extant lampreys. Our discovery not only documents the larval conditions of fossil lampreys but also indicates the three-phased life cycle in lampreys emerged essentially in their present mode no later than the Early Cretaceous. PMID:25313060

  18. Paleomagnetic reconstruction of Late Cretaceous structures along the Midelt-Errachidia profile (Morocco). Tectonic implications.

    NASA Astrophysics Data System (ADS)

    Torres López, Sara; José Villalain, Juan; Casas, Antonio; El ouardi, Hmidou; Moussaid, Bennacer; Ruiz-Martínez, Vicente Carlos

    2017-04-01

    Remagnetization data are used in this work to obtain the palinspastic reconstruction at 100 (Ma) of one of the most studied profiles of the Central High Atlas: the Midelt-Errachidia cross-section (Morocco). Previous studies in the area on syn-rift sedimentary rocks of subsiding basins have revealed that the Mesozoic sediments of this region acquired a pervasive remagnetization at the end of the Early Cretaceous. Fifty-eight sites (470 samples) corresponding to black limestones, marly limestones and marls, Early to Middle Jurassic in age, have been studied. Sites are distributed along a 70 km transect cutting across the basin and perpendicular to the main structures. The magnetic properties of samples are very regular showing very high NRM. Thermal and AF demagnetization showed a single stable paleomagnetic component with unblocking temperatures and coercivities spectra of 300-475°C and 20-100 mT respectively. This characteristic remanent magnetization (ChRM) showed systematically normal polarity suggesting a widespread remagnetization. In spite of the good outcrops and the relatively well-constrained structure of the High Atlas, there are many tectonic problems still unsolved, as the controversial existence of intra-Mesozoic deformation episodes. The restoration of paleomagnetic vectors to the remagnetization acquisition stage (100 Ma) allows to determine the dip of the beds during this period and, thereby, to obtain a reconstruction of structures during that time. This reconstruction accounts for the relative contribution of Mesozoic transpressional/transtrenssional movements vs. Cenozoic compression to the present-day dip. The results obtained indicate that these structures have undergone different degrees of pre-late Cretaceous deformation and were re-activated during the Cenozoic compression to finally acquire their present-day geometry.

  19. Diatom microfossils from cretaceous and eocene sediments contain native silica precipitating long-chain polyamines.

    PubMed

    Bridoux, M C; Ingalls, A E

    2013-05-01

    Organic molecules from known biological sources (biomarkers) that are preserved over geological time are critical tools in the study of past conditions and events on earth. Polar molecules are typically recycled rapidly in marine environments and do not survive burial within aquatic sediments in unambiguously recognizable form. As such, geological biomarkers are formed almost exclusively from precursor biomolecules that have been altered, limiting their utility as paleoproxies. Here, we report that nitrogen-rich aliphatic long-chain polyamines (LCPAs), biosynthesized by diatoms in species-specific assemblages for the precipitation of nanopatterned siliceous cell walls (frustules), are preserved unaltered in the oldest available diatom fossils dating to the Lower Cretaceous (early Albian, 115-110 Ma). We further show that the cumulative LCPA pool accounts for 60% of the total C and 80% of the total N preserved in the Cretaceous age sediments. We suggest that silica glass formation by diatoms constitutes an important preservation mechanism for source-specific, polar biomolecules, protecting them indefinitely by encapsulation within the silicified frustule. LCPAs are a unique, source-specific carbon and nitrogen archive of diatom biomass, offering a promising tool for reconstruction of global cycles of carbon and nitrogen over geological timescales. © 2013 Blackwell Publishing Ltd.

  20. Ecophenotypic Variation and Developmental Instability in the Late Cretaceous Echinoid Micraster brevis (Irregularia; Spatangoida)

    PubMed Central

    Schlüter, Nils

    2016-01-01

    The Late Cretaceous echinoid genus Micraster (irregular echinoids, Spatangoida) is one of the most famous examples of a continuous evolutionary lineage in invertebrate palaeontology. The influence of the environment on the phenotype, however, was not tested so far. This study analyses differences in phenotypical variations within three populations of Micraster (Gibbaster) brevis from the early Coniacian, two from the Münsterland Cretaceous Basin (Germany) and one from the North Cantabrian Basin (Spain). The environments of the Spanish and the German sites differed by their sedimentary characteristics, which are generally a crucial factor for morphological adaptations in echinoids. Most of the major phenotypical variations (position of the ambitus, periproct and development of the subanal fasciole) among the populations can be linked to differences in their host sediments. These phenotypic variations are presumed to be an expression of phenotpic plasticiy, which has not been considered in Micraster in previous studies. Two populations (Erwitte area, Germany; Liencres area, Spain) were tested for stochastic variation (fluctuating asymmetry) due to developmental instability, which was present in all studied traits. However, differences in the amount of fluctuating asymmetry between both populations were recognised only in one trait (amount of pore pairs in the anterior paired petals). The results strengthen previous assumptions on ecophenotypic variations in Micraster. PMID:26849648

  1. Late Cretaceous paleomagnetism and clockwise rotation of the Silver Bell Mountains, south central Arizona

    USGS Publications Warehouse

    Hagstrum, J.T.; Sawyer, D.A.

    1989-01-01

    Late Cretaceous ash flow volcanism in the Silver Bell Mountains of southern Arizona (32.3??N, 248.5??E) was associated with caldera formation and porphyry copper mineralization. Oriented samples from 34 sites in volcanic, volcaniclastic, and intrusive units related to this episode of igneous activity (73-69 Ma) yield a mean paleomagnetic direction of (I = 61.2??, D = 24.0??, ??95 = 7.6??. Previously determined paleomagnetic data for southeastern Arizona suggest that this apparent clockwise rotation in the Silver Bell Mountains is a local phenomenon. Although preliminary, the average paleomagnetic direction for Oligocene and lower Miocene rocks in the Silver Bell area (I = 43.8??, D = 357.3??, ??95 = 16.5??) is similar to that calculated for stable North America (I = 50.2??, D = 352.2??, ??95 = 3.9??), implying that the observed rotation in the Silver Bell Mountains occurred before 26 Ma and was most likely associated with dextral strike-slip movement along the Ragged Top and related WNW trending faults bounding the Silver Bell Mountain block. These data, in conjunction with plate reconstructions and other paleomagnetic data from southwestern North America, imply that WNW trending strike-slip faults may have played an important role during Late Cretaceous to early Tertiary deformation in southern Arizona. -Authors

  2. Paleobiological implications of dinosaur egg-bearing deposits in the Cretaceous Gyeongsang Supergroup of Korea

    NASA Astrophysics Data System (ADS)

    Paik, In Sung; Kim, Hyun Joo; Huh, Min

    2010-05-01

    Dinosaur egg-bearing deposits in the Cretaceous Gyeongsang Basin in Korea is described in taphonomic aspect, their paleoenvironments are interpreted, and geobiological implications of dinosaur egg-bearing deposits in the world and Korea are analyzed in geographic occurrences, geological ages, paleoenvironments, and lithology. Dinosaur eggs with spheroolithids, faveoloolithid, and elongatoolithid structural types occur in several stratigraphic formations of the Cretaceous Gyeongsang Basin in South Korea, and most of the egg-bearing formations are the Late Cretaceous. The dinosaur eggs usually occur as clutches in purple sandy mudstone of floodplain deposits preserved as calcic paleosol with association of vertic paleosol features in places. Most of the eggs are top-broken and filled with surrounding sediments. The general depositional environment of dinosaur egg deposits in the Gyeongsang Supergroup are interpreted as a dried floodplain where volcanic activity occurred intermittently in the vicinity of the nesting sites. Their depositional settings on which floodplains developed are diverse from fluvial plain with meandering rivers to alluvial plain with episodic sheet flooding. The nesting areas in the Gyeongsang Basin are deemed to have been under semi-arid climate, which resulted in formation of calcic soils facilitating preservation of the dinosaur eggs. The geochronologic occurrences of dinosaur egg-bearing deposits are mostly restricted to the Late Cretaceous in the world as well as in Korea. If it has not been resulted from biased discoveries and reports of dinosaur eggs, biological rather than physical and chemical conditions for preservation of dinosaur eggs might be related with the restricted occurrences in the Late Cretaceous. Two hypotheses are suggested for probable biological causes to the geochronologically restricted occurrences of dinosaur egg-bearing deposits. One is related with the appearance of angiosperms in the Late Jurassic and the spreading

  3. Strongly foliated garnetiferous amphibolite clasts in ophiolitic melanges, Yarlung Zangbo Suture Zone, Tibet; Early Cretaceous disruption of a back-arc basin?

    NASA Astrophysics Data System (ADS)

    Guilmette, C.; Hebert, R.; Wang, C.; Indares, A. D.; Ullrich, T. D.; Dostal, J.; Bedard, E.

    2007-12-01

    Metre to decameter-size clasts of amphibolite are found embedded in ophiolitic melanges underlying the Yarlung Zangbo Suture Zone Ophiolites, South Tibet, China. These ophiolites and melanges occur at the limit between Indian and Tibetan-derived rocks and represent remnants of an Early Cretaceous intraoceanic supra-subduction zone domain, the Neo-Tethys. In the Saga-Dazuka segment (500 km along-strike), we discovered new occurrences of strongly foliated amphibolites found as clasts in the ophiolitic melange. In garnet-free samples, hornblende is green-blue magnesio-hornblende and cpx is low-Al diopside. In garnet- bearing samples, garnet is almandine with a strong pyrope component (up to 30 mol%) whereas coexisting hornblende is brown Ti-rich tschermakite and clinopyroxene is Al-diopside. Plagioclase composition was ubiquitously shifted to albite during a late metasomatic event. Geochemistry of these rocks indicates that their igneous protoliths crystallized from a slightly differentiated tholeiitic basaltic liquid that did not undergo major fractionation. Trace element patterns reveal geochemical characteristics identical to those of the overlying ophiolitic crust. These are 1) trace element abundances similar to that of N-MORBs or BABBs, 2) a slight depletion of LREE and 3) a moderate to strong Ta-Nb negative anomaly and a slight Ti anomaly. Such characteristics suggest genesis over a spreading center close to a subduction zone, possibly a back-arc basin. Step-heating Ar/Ar plateau ages were obtained from hornblende separates. All ages fall in the range of 123-128 Ma, overlapping the crystallization ages from the overlying ophiolite (126-131 Ma). Pseudosections were built with the THERMOCALC software in the system NCFMASH. Results indicate that the observed assemblage Hb+Pl+Gt+Cpx is stable over a wide range of P-T conditions, between 10-18 kbars and at more than 800°C. Measured mineral modes and solid solution compositions were successfully modeled, indicating

  4. The semi-aquatic pondweed bugs of a Cretaceous swamp

    PubMed Central

    Sánchez-García, Alba; Nel, André; Arillo, Antonio

    2017-01-01

    Pondweed bugs (Hemiptera: Mesoveliidae), considered a sister group to all other Gerromorpha, are exceedingly rare as fossils. Therefore, each new discovery of a fossil mesoveliid is of high interest, giving new insight into their early evolutionary history and diversity and enabling the testing of their proposed relationships. Here, we report the discovery of new mesoveliid material from Spanish Lower Cretaceous (Albian) amber, which is the first such find in Spanish amber. To date, fossil records of this family only include one species from French Kimmeridgian as compression fossils, two species in French amber (Albian-Cenomanian boundary), and one in Dominican amber (Miocene). The discovery of two males and one female described and figured as Glaesivelia pulcherrima Sánchez-García & Solórzano Kraemer gen. et sp. n., and a single female described and figured as Iberovelia quisquilia Sánchez-García & Nel, gen. et sp. n., reveals novel combinations of traits related to some genera currently in the subfamily Mesoveliinae. Brief comments about challenges facing the study of fossil mesoveliids are provided, showing the necessity for a revision of the existing phylogenetic hypotheses. Some of the specimens were studied using infrared microscopy, a promising alternative to the systematic study of organisms preserved in amber that cannot be clearly visualised. The new taxa significantly expand the fossil record of the family and shed new light on its palaeoecology. The fossils indicate that Mesoveliidae were certainly diverse by the Cretaceous and that numerous tiny cryptic species living in humid terrestrial to marginal aquatic habitats remain to be discovered. Furthermore, the finding of several specimens as syninclusions suggests aggregative behaviour, thereby representing the earliest documented evidence of such ethology. PMID:28890856

  5. parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages.

    PubMed

    Peñalver, Enrique; Arillo, Antonio; Delclòs, Xavier; Peris, David; Grimaldi, David A; Anderson, Scott R; Nascimbene, Paul C; Pérez-de la Fuente, Ricardo

    2017-12-12

    Ticks are currently among the most prevalent blood-feeding ectoparasites, but their feeding habits and hosts in deep time have long remained speculative. Here, we report direct and indirect evidence in 99 million-year-old Cretaceous amber showing that hard ticks and ticks of the extinct new family Deinocrotonidae fed on blood from feathered dinosaurs, non-avialan or avialan excluding crown-group birds. A †Cornupalpatum burmanicum hard tick is entangled in a pennaceous feather. Two deinocrotonids described as †Deinocroton draculi gen. et sp. nov. have specialised setae from dermestid beetle larvae (hastisetae) attached to their bodies, likely indicating cohabitation in a feathered dinosaur nest. A third conspecific specimen is blood-engorged, its anatomical features suggesting that deinocrotonids fed rapidly to engorgement and had multiple gonotrophic cycles. These findings provide insight into early tick evolution and ecology, and shed light on poorly known arthropod-vertebrate interactions and potential disease transmission during the Mesozoic.

  6. Distinguishing base-level change and climate signals in a Cretaceous alluvial sequence

    USGS Publications Warehouse

    White, T.; Witzke, B.; Ludvigson, G. A.; Brenner, R.

    2005-01-01

    We present the results of oxygen isotope and electron-microprobe analyses of sphaerosiderites obtained from Cretaceous paleosols in Iowa. The sphaerosiderite ??18O values record Cretaceous meteoric groundwater chemistry and an overall waning of brackish groundwater inundation during alluvial-plain aggradation and soil genesis. We focus on horizons that precipitated from freshwater, in which ??18O values ranging from -3.30??? to -6.8??? relative to the Peedee belemnite standard are interpreted to record variations in the Cretaceous atmospheric hydrologic cycle. During relative sea-level highstands, moisture was derived from the Cretaceous Western Interior Seaway, whereas during lowstands, when the seaway narrowed and occasionally withdrew from the Midcontinent, the dominance of hemispheric-scale atmospheric moisture transport initiated in the tropical Tethys Ocean led to decreased precipitation rates. These processes did not operate like a switch, but rather as a continuum of competing moisture sources and mechanisms of transport between the nearby epicontinental sea and the distant tropics. The sphaerosiderite data demonstrate (1) temporal variation in the intensity of hemispheric-scale atmospheric moisture transport and (2) long-term amplification of the global hydrologic cycle marked by extreme 18O depletion at the Albian-Cenomanian boundary. ?? 2005 Geological Society of America.

  7. Late Cretaceous tectonothermal evolution of the southern Lhasa terrane, South Tibet: Consequence of a Mesozoic Andean-type orogeny

    NASA Astrophysics Data System (ADS)

    Dong, Xin; Zhang, Ze-ming; Klemd, Reiner; He, Zhen-yu; Tian, Zuo-lin

    2018-04-01

    The Lhasa terrane of the southern Tibetan Plateau participated in a Mesozoic Andean-type orogeny caused by the northward subduction of the Neo-Tethyan oceanic lithosphere. However, metamorphic rocks, which can unravel details of the geodynamic evolution, are rare and only exposed in the south-eastern part of the Lhasa terrane. Therefore, we conducted a detailed petrological, geochemical and U-Pb zircon geochronological study of the late Cretaceous metamorphic rocks and associated gabbros from the Nyemo inlier of the southern Lhasa terrane. The Nyemo metamorphic rocks including gneisses, schists, marbles and calc-silicate rocks, experienced peak amphibolite-facies contact metamorphism under P-T conditions of 3.5-4.0 kbar and 642-657 °C with a very high geothermal gradient of 45-50 °C/km, revealing a distinct deflection from the steady-state geotherm during low-pressure metamorphism. Inherited magmatic zircon cores from the metamorphic rocks yielded protolith ages of 197-194 Ma, while overgrowth zircon rims yielded metamorphic ages of ca. 86 Ma. Whole-rock chemistry and zircon Hf isotopes suggest that the protoliths of the gneisses and schists are andesites and tuffs of the early Jurassic Sangri Group, which were derived from a depleted mantle source of a continental arc affinity. The coeval intimately-associated gabbro (ca. 86 Ma) crystallized under P-T conditions of 3.5-5.3 kbar and 914-970 °C, supplying the heat flux high enough to cause the contact metamorphism of the Sangri Group rock types. We propose that the intrusion of the gabbro and a simultaneous pressure increase of up to 4.0 kbar, which is related to crustal thickening due to crustal overthrusting and the intrusion of mafic material, resulted in the late Cretaceous metamorphism of the early Jurassic Sangri Group during an Andean-type orogeny. Furthermore the Nyemo metamorphic rocks, which have previously been considered to represent slivers of the Precambrian metamorphic basement of the Lhasa terrane

  8. Anatomically preserved fossil cornalean fruits from the Upper Cretaceous of Hokkaido: Eydeia hokkaidoensis gen. et sp. nov.

    PubMed

    Stockey, Ruth A; Nishida, Harufumi; Atkinson, Brian A

    2016-09-01

    The basal asterid clade Cornales radiated during the Late Cretaceous. However, our understanding of early evolutionary patterns and relationships remain obscure. New data from five permineralized fruits in calcareous concretions from the Upper Cretaceous (Coniacian-Santonian) Haborogawa Formation, Hokkaido, Japan provide anatomical details that aid our knowledge of the group. Specimens were studied from cellulose acetate peels, and three-dimensional reconstructions were rendered using AVIZO. Fruits are drupaceous, roughly pyriform, 2.9-4.3 mm in diameter, with a fleshy mesocarp, transition sclereids, and a stony endocarp of four to five locules, with the septa forming a cross or star-like pattern in transverse section, distinct germination valves, and one apically attached anatropous seed per locule. Vascular tissue occurs in zones between the mesocarp and exocarp, in two rows within the septa, and prominent seed bundles can be traced throughout the fruit sections. Seeds have a single integumentary layer of radially flattened square to rectangular cells and copious cellular endosperm. A fully formed, straight, cellular dicotyledonous embryo, with closely appressed, spathulate cotyledons, is present within each seed. The unique combination of characters shown by these fruits is found in Cornaceae, Curtisiaceae, and Davidiaceae and allows us to describe a new taxon of Cornales, Eydeia hokkaidoensis gen. et sp. nov., with many similarities to extant Davidia involucrata. These fossils underscore the phylogenetic diversification of Cornales that was underway during the Late Cretaceous and support the hypothesis that a Davidia-like fruit morphology is plesiomorphic within Cornales. © 2016 Botanical Society of America.

  9. Cretaceous to Tertiary paleogeographic reconstructions of the Alps-Pyrenees linking zone

    NASA Astrophysics Data System (ADS)

    Frasca, Gianluca; Dielforder, Armin; Ford, Mary; Vergés, Jaume

    2017-04-01

    The northwestern Mediterranean subduction systems underwent an important phase of reorganization between Late Cretaceous and Eocene. The mode and timing of this reorganization are still under debate. Great uncertainties mainly derive from the poorly preserved record of the early phases of orogenic evolution in both the Alps and Pyrenees and the distruction of the orogenic system between the Pyrenees and Alps by the Oligo-Miocene opening of the Gulf of Lion due to backarc rifting. Vestiges are nevertheless preserved in the Pyreneo-Provençal fold-and-thrust belt and associated basins in southern France and Corsica-Sardinia. In this work we first review published plate kinematic models for Iberia, Apulia and Europe from 83 Ma, focusing in particular on the restoration of the Corso-Sardinia block using the free software GPlates. Second, we characterize the Upper Cretaceous to Eocene depositional systems at the junction between the Alps, Pyrenees and Apennines, reviewing previous paleogeographic restorations for the Western Alpine and Eastern Pyrenean foreland basins. Last, we compare the kinematic models with reconstructed basin dynamics. We critically assess the implications of newly proposed paleogeographic reconstructions (at 83, 65, 50, 37 and 30 Ma) for the validity of various plate kinematic models. The information derived from the sedimentary basins help to define the mode and timing of the subduction reorganization that occurred between 83 and 30 Ma in the northwestern Mediterranean. This study is part of the Orogen research program funded by Total, the BRGM (Bureau de Recherches Géologiques et Minières), the CNRS (Centre National de la Recherche Scientifique).

  10. High-resolution leaf-fossil record spanning the Cretaceous/Tertiary boundary

    USGS Publications Warehouse

    Johnson, K.R.; Nichols, D.J.; Attrep, M.; Orth, C.J.

    1989-01-01

    THEORIES that explain the extinctions characterizing the Cretaceous/Tertiary (K/T) boundary1-3 need to be tested by analyses of thoroughly sampled biotas. Palynological studies are the primary means for stratigraphic placement of the terrestrial boundary and for estimates of plant extinction4-12, but have not been combined with quantitative analyses of fossil leaves (megaflora). Megafloral studies complement palynology by representing local floras with assemblages capable of high taxonomic resolution13, but have previously lacked the sample size and stratigraphic spacing needed to resolve latest Cretaceous floral history5,14-18. We have now combined megafloral data from a 100-m-thick composite K/T boundary section in North Dakota with detailed palynological analysis. Here the boundary is marked by a 30% palynofloral extinction coincident with iridium and shocked-mineral anomalies and lies ???2 m above the highest dinosaur remains. The megaflora undergoes a 79% turnover across the boundary, and smaller changes 17- and 25-m below it. This pattern is consistent with latest Cretaceous climatic warming preceding a bolide impact. ?? 1989 Nature Publishing Group.

  11. Anza palaeoichnological site. Late Cretaceous. Morocco. Part I. The first African pterosaur trackway (manus only)

    NASA Astrophysics Data System (ADS)

    Masrour, Moussa; Pascual-Arribas, Carlos; de Ducla, Marc; Hernández-Medrano, Nieves; Pérez-Lorente, Félix

    2017-10-01

    Cretaceous pterosaurs tracksites are very rare worldwide. Until now,only one African Cretaceous site withtracks of (Agadirichnus elegans and Pteraichnus) was known. This makes the discovery of a new outcrop in the Upper Cretaceous of Anza (Morocco) the third manifestation of this type of footprint in Africa, extending the existence of such traces from the Coniacian-Santonian to the Maastrichtian. The site contains only manus tracks, which can be explained as a result of erosion of pes prints. The lack of pes prints and the morphometric characteristics of the manus prints only allow us to relate these prints to Agadirichnus, Pteraichnus or maybe to a new ichnogenus. It is possible that the trackmakers are related to Ornithocheiroidea or Azhdarchoidea superfamilies whose fossil bones have been found from the Late Cretaceous in Morocco.

  12. Cretaceous flowers of Nymphaeaceae and implications for complex insect entrapment pollination mechanisms in early angiosperms.

    PubMed

    Gandolfo, M A; Nixon, K C; Crepet, W L

    2004-05-25

    Based on recent molecular systematics studies, the water lily lineage (Nymphaeales) provides an important key to understanding ancestral angiosperm morphology and is of considerable interest in the context of angiosperm origins. Therefore, the fossil record of Nymphaeales potentially provides evidence on both the timing and nature of diversification of one of the earliest clades of flowering plants. Recent fossil evidence of Turonian age (approximately 90 million years B.P.) includes fossil flowers with characters that, upon rigorous analysis, firmly place them within Nymphaeaceae. Unequivocally the oldest floral record of the Nymphaeales, these fossils are closely related to the modern Nymphaealean genera Victoria (the giant Amazon water lily) and Euryale. Although the fossils are much smaller than their modern relatives, the precise and dramatic correspondence between the fossil floral morphology and that of modern Victoria flowers suggests that beetle entrapment pollination was present in the earliest part of the Late Cretaceous.

  13. A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana.

    PubMed

    Simões, Tiago R; Wilner, Everton; Caldwell, Michael W; Weinschütz, Luiz C; Kellner, Alexander W A

    2015-08-26

    Iguanians are one of the most diverse groups of extant lizards (>1,700 species) with acrodontan iguanians dominating in the Old World, and non-acrodontans in the New World. A new lizard species presented herein is the first acrodontan from South America, indicating acrodontans radiated throughout Gondwana much earlier than previously thought, and that some of the first South American lizards were more closely related to their counterparts in Africa and Asia than to the modern fauna of South America. This suggests both groups of iguanians achieved a worldwide distribution before the final breakup of Pangaea. At some point, non-acrodontans replaced acrodontans and became the only iguanians in the Americas, contrary to what happened on most of the Old World. This discovery also expands the diversity of Cretaceous lizards in South America, which with recent findings, suggests sphenodontians were not the dominant lepidosaurs in that continent as previously hypothesized.

  14. Palynologically calibrated vertebrate record from North Dakota consistent with abrupt dinosaur extinction at the Cretaceous-Tertiary boundary

    USGS Publications Warehouse

    Pearson, D.A.; Schaefer, T.; Johnson, K.R.; Nichols, D.J.

    2001-01-01

    New data from 17 Cretaceous-Tertiary (K-T) boundary sections and 53 vertebrate sites in the Hell Creek and Fort Union Formations in southwestern North Dakota document a 1.76 m barren interval between the highest Cretaceous vertebrate fossils and the palynologically recognized K-T boundary. The boundary is above the formational contact at 15 localities and coincident with it at two, demonstrating that the formational contact is diachronous. Dinosaurs are common in the highest Cretaceous vertebrate samples and a partial dinosaur skeleton in the Fort Union Formation is the highest recorded Cretaceous vertebrate fossil in this area.

  15. Cretaceous anuran and dinosaur footprints from the Patuxent Formation of Virginia

    USGS Publications Warehouse

    Weems, R.E.; Bachman, J.M.

    1997-01-01

    Footprints of an anuran (gen. et sp. indet.), a theropod dinosaur (Megalosauropus sp.), and an ornithopod dinosaur (Amblydactylus sp.) have been recovered from the Lower Cretaceous Patuxent Formation in Stafford County, Virginia. These footprints are the first record of terrestrial vertebrates from Cretaceous strata in Virginia, and their discovery suggests that the scarcity of bones and teeth in the Patuxent probably is an artifact of preservation. The anuran trackway provides the oldest known direct evidence for hopping locomotion among these amphibians.

  16. Major wildfires at the Cretaceous-Tertiary boundary

    NASA Technical Reports Server (NTRS)

    Gilmour, Iain; Wolbach, Wendy S.; Anders, Edward

    1989-01-01

    K-T boundary (KTB) clays from five sites are enriched in soot and charcoal by factors of 100-1000 over Cretaceous levels, apparently due to a global fire. The soot profile nearly coincides with the Ir profile, implying that the fire was triggered by the impact. Much or all of the fuel was biomass, as indicated by the presence of retene and by the C isotopic composition. The amount of elemental C at the KTB (0.012 g/sq cm) is very large, and requires either that most of the Cretaceous biomass burned down or that the soot yield was higher than in small fires. At undisturbed sites, soot correlates tightly with Ir, As, Sb, and Zn. Apparently soot and Ir-bearing ejecta particles coagulated in the stratosphere and then scavenged additional chalcophiles from the hydrosphere. In view of this coagulation, the K-T fire would only slightly prolong the period of darkness and cold caused by impact ejecta.

  17. Petroleum geology of Cretaceous-Tertiary rift basins in Niger, Chad, and Central African Republic

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Genik, G.J.

    1993-08-01

    This overview of the petroleum geology of rift basins in Niger, Chad, and Central African Republic (CAR) is based on exploration work by Exxon and partners in the years 1969-1991. The work included 50,000 km of modern reflection seismic, 53 exploration wells, 1,000,000 km[sup 2] of aeromagnetic coverage, and about 10,500 km of gravity profiles. The results outline ten Cretaceous and Tertiary rift basins, which constitute a major part of the West and Central African rift system (WCARS). The rift basins derive from a multiphased geologic history dating from the Pan-African (approximately 750-550 Ma) to the Holocene. WCARS in themore » study area is divided into the West African rift subsystem (WAS) and the Central African rift subsystem (WAS) and the Central African rift subsystem (CAS). WAS basins in Niger and Chad are chiefly extensional, and are filled by up to 13,000 m of Lower Cretaceous to Holocene continental and marine clastics. The basins contain five oil (19-43[degrees]API) and two oil and gas accumulations in Upper Cretaceous and Eocene sandstone reservoirs. The hydrocarbons are sourced and sealed by Upper Cretaceous and Eocene marine and lacustrine shales. The most common structural styles and hydrocarbon traps usually are associated with normal fault blocks. CAS rift basins in Chad and CAR are extensional and transtensional, and are filled by up to 7500 m of chiefly Lower Cretaceous continental clastics. The basins contain eight oil (15-39[degrees]API) and one oil and gas discovery in Lower and Upper Cretaceous sandstone reservoirs. The hydrocarbons are sourced by Lower Cretaceous shales and sealed by interbedded lacustrine and flood-plain shales. Structural styles range from simple fault blocks through complex flower structures. The main hydrocarbon traps are in contractional anticlines. Geological conditions favor the discovery of potentially commercial volumes of oil in WCARS basins, of Niger, Chad and CAR. 108 refs., 24 figs., 4 tabs.« less

  18. Evolution of salt structures and Cretaceous uplift in westernmost Mississippi Salt basin, Madison Parish, Louisiana

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alam, A.H.M.S.; Pilger, R.H. Jr.

    1988-09-01

    Subsurface structures were interpreted from seismic images and well logs in the westernmost Mississippi Salt basin, Madison Parish, Louisiana. Structural and stratigraphic relations indicate that salt structures (Duckport, North Tallulah, South Coleman, Tallulah, and Walnut domes) have evolved through pillow, diapir, and postdiapir stages. Withdrawal synclines associated with each stage of growth occur adjacent to salt domes and are characterized by overthickening of sediments. Synclines associated with Walnut dome are particularly well recognized in the seismic data. Primary withdrawal synclines and present day turtle structure anticlines involve the deepest recorded reflections (possibly Jurassic carbonates) above seismically transparent Paleozoic basement andmore » overlying remnant salt. Similar early (Late Jurassic) salt mobility has recently been documented in North Louisiana and East Texas Salt basins. Secondary withdrawal synclines (Cotton Valley) are exceptionally overthickened and their axes are closer to the dome than the axes of primary synclines. Tertiary synclines are broad and appear to be active at present. North-south seismic sections that cross the approximate northwest boundary of the Mississippi Salt basin display post-middle Cretaceous upwarp (the Monroe Uplift) involving basement. Successively older Lower Cretaceous reflections are truncated to the north beneath an erosional surface. Upwarp apparently continued well into the Cenozoic.« less

  19. Mineralogy and diagenesis of low-permeability sandstones of Late Cretaceous age, Piceance Creek Basin, northwestern Colorado

    USGS Publications Warehouse

    Hansley, Paula L.; Johnson, Ronald C.

    1980-01-01

    This report presents preliminary results of a mineralogic and diagenetic study of some low-permeability sandstones from measured surface sections and cores obtained from drill holes in the Piceance Creek Basin of northwestern Colorado. A documentation of the mineralogy and diagenetic history will aid in the exploration for natural gas and in the development of recovery technology in these low-permability sandstones. These sandstones are in the nonmarine upper part of the Mesaverde Formation (or Group) of Late Cretaceous age and are separated from overlying lower Tertiary rocks by a major regional unconformity. Attention is focused on the sandstone units of the Ohio Creek Member, which directly underlies the unconformity; however, comparisons between the mineralogy of the Ohio Creek strata and that of the underlying sandstone units are made whenever possible. The Ohio Creek is a member of the Hunter Canyon Formation (Mesaverde Group) in the southwestern part of the basin, and the Mesaverde Formation in the southern and central parts of the basin. The detrital mineralogy is fairly constant throughout all of these nonrnarine Cretaceous sandstone units; however, in the southeastern part of the basin, there is an increase in percentage of feldspar, quartzite, and igneous rock fragments in sandstones of the Ohio Creek Member directly underlying the unconformity. In the southwestern part of the basin, sandstones of the Ohio Creek Member are very weathered and are almost-entirely comprised of quartz, chert, and kaolinite. A complex diagenetic history, partly related to the overlying unconformity, appears to be responsible for transforming these sandstones into potential gas reservoirs. The general diagenetic sequence for the entire Upper Cretaceous interval studied is interpreted to be (early to late): early(?) calcite cement, chlorite, quartz overgrowths, calcite cement, secondary porosity, analcime (surface only), kaolinite and illite, and late carbonate cements

  20. Extreme adaptations for probable visual courtship behaviour in a Cretaceous dancing damselfly.

    PubMed

    Zheng, Daran; Nel, André; Jarzembowski, Edmund A; Chang, Su-Chin; Zhang, Haichun; Xia, Fangyuan; Liu, Haoying; Wang, Bo

    2017-03-20

    Courtship behaviours, frequent among modern insects, have left extremely rare fossil traces. None are known previously for fossil odonatans. Fossil traces of such behaviours are better known among the vertebrates, e.g. the hypertelic antlers of the Pleistocene giant deer Megaloceros giganteus. Here we describe spectacular extremely expanded, pod-like tibiae in males of a platycnemidid damselfly from mid-Cretaceous Burmese amber. Such structures in modern damselflies, help to fend off other suitors as well as attract mating females, increasing the chances of successful mating. Modern Platycnemidinae and Chlorocyphidae convergently acquired similar but less developed structures. The new findings provide suggestive evidence of damselfly courtship behaviour as far back as the mid-Cretaceous. These data show an unexpected morphological disparity in dancing damselfly leg structure, and shed new light on mechanisms of sexual selection involving intra- and intersex reproductive competition during the Cretaceous.

  1. Masirah Graben, Oman: A hidden Cretaceous rift basin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beauchamp, W.H.; Ries, A.C.; Coward, M.P.

    1995-06-01

    Reflection seismic data, well data, geochemical data, and surface geology suggest that a Cretaceous rift basin exists beneath the thrusted allochthonous sedimentary sequence of the Masirah graben, Oman. The Masirah graben is located east of the Huqf uplift, parallel to the southern coast of Oman. The eastern side of the northeast-trending Huqf anticlinorium is bounded by an extensional fault system that is downthrown to the southeast, forming the western edge of the Masirah graben. This graben is limited to the east by a large wedge of sea floor sediments and oceanic crust, that is stacked as imbricate thrusts. These sediments/ophiolitesmore » were obducted onto the southern margin of the Arabian plate during the collision of the Indian/Afghan plates at the end of the Cretaceous. Most of the Masirah graben is covered by an allochthonous sedimentary sequence, which is complexly folded and deformed above a detachment. This complexly deformed sequence contrasts sharply with what is believed to be a rift sequence below the ophiolites. The sedimentary sequence in the Masirah graben was stable until further rifting of the Arabian Sea/Gulf of Aden in the late Tertiary, resulting in reactivation of earlier rift-associated faults. Wells drilled in the Masirah graben in the south penetrated reservoir quality rocks in the Lower Cretaceous Natih and Shuaiba carbonates. Analyses of oil extracted from Infracambrian sedimentary rocks penetrated by these wells suggest an origin from a Mesozoic source rock.« less

  2. Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co-evolution.

    PubMed

    Butler, R J; Barrett, P M; Kenrick, P; Penn, M G

    2009-03-01

    poor sampling in the Turonian-Santonian interval. Stegosauria shows a significant negative correlation with flowering plants and a significant positive correlation with the nonflowering cycadophytes (cycads, Bennettitales). This interesting pattern is worthy of further investigation, and it reflects the decline of both stegosaurs and cycadophytes during the Early Cretaceous.

  3. Chapter 4: The Cretaceous-Lower Tertiary Composite Total Petroleum System, Wind River Basin, Wyoming

    USGS Publications Warehouse

    Johnson, R.C.; Finn, Thomas M.; Kirschbaum, Mark A.; Roberts, Stephen B.; Roberts, Laura N.R.; Cook, Troy; Taylor, David J.

    2007-01-01

    The Cretaceous-Lower Tertiary Composite Total Petroleum System (TPS) of the Wind River Basin Province includes all strata from the base of the Lower Cretaceous Cloverly Formation to the base of the Waltman Shale Member of the Paleocene age Fort Union Formation and, where the Waltman is absent, includes strata as young as the Eocene Wind River Formation. Locally, Cretaceous-sourced gas migrated into strata as old as the Mississippian Madison Limestone, and in these areas the TPS extends stratigraphically downward to include these reservoirs. The extensive vertical migration of gases in highly fractured areas of the Wind River Basin led to the commingling of gases from several Upper Cretaceous and lower Tertiary sources, thus only two petroleum systems are recognized in these rocks, the Cretaceous-Lower Tertiary Composite TPS, the subject of this report, and the Waltman Shale TPS described by Roberts and others (Chapter 5, this CD-ROM). The Cretaceous-lower Tertiary Composite TPS was subdivided into (1) seven continuous gas assessment units (AU): (a) Frontier-Muddy Continuous Gas AU, (b) Cody Sandstone Continuous Gas AU, (c) Mesaverde--Meeteetse Sandstone Gas AU, (d) Lance-Fort Union Sandstone Gas AU, (e) Mesaverde Coalbed Gas AU, (f) Meeteetse Coalbed Gas AU, and (g) Fort Union Coalbed Gas AU; (2) one continuous oil assessement unit--- Cody Fractured Shale Continuous Oil AU; and (3) one conventional assessment Unit--- Cretaceous-Tertiary Conventional Oil and Gas AU. Estimates of undiscovered resources having the potential for additions to reserves were made for all but the Cody Fractured Shale Continuous Oil AU, which is considered hypothetical and was not quantitively assessed. The mean estimate of the total oil is 41.99 million barrels, mean estimate of gas is 2.39 trillion cubic feet, and mean estimate of natural gas liquids is 20.55 million barrels. For gas, 480.66 billion cubic feet (BCFG) is estimated for the Frontier-Muddy Continuous Gas AU, 115.34 BCFG for

  4. Geochemistry, 40Ar/39Ar geochronology, and geodynamic implications of Early Cretaceous basalts from the western Qinling orogenic belt, China

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Wang, Yuejun; Cawood, Peter A.; Dong, Yunpeng

    2018-01-01

    The Qinling-Dabie orogenic belt was formed by the collision of the North and South China Cratons during the Early Mesozoic and subsequently developed into an intracontinental tectonic process during late Mesozoic. Field investigations identified the presence of late Mesozoic basalts in the Duofutun and Hongqiang areas in the western Qinling orogenic belt. The petrogenesis of these basalts provides an important constraint on the late Mesozoic geodynamics of the orogen. The representative basaltic samples yield the 40Ar/39Ar plateau age of about 112 Ma. These samples belong to the alkaline series and have SiO2 ranging from 44.98 wt.% to 48.19 wt.%, Na2O + K2O from 3.44 wt% to 5.44 wt%, and MgO from 7.25 wt.% to 12.19 wt.%. They demonstrate the right-sloping chondrite-normalized REE patterns with negligible Eu anomalies (1.00-1.10) and PM-normalized patterns enriched in light rare earth element, large ion lithophile element and high field strength element, similar to those of OIB rocks. These samples additionally show an OIB-like Sr-Nd isotopic signature with εNd(t) values ranging from +6.13 to +10.15 and initial 87Sr/86Sr ratios from 0.7028 to 0.7039, respectively. These samples are geochemically subdivided into two groups. Group 1 is characterized by low Al2O3 and high TiO2 and P2O5 contents, as well as high La/Yb ratios (>20), being the product of the high-pressure garnet fractionation from the OIB-derived magma. Group 2 shows higher Al2O3 but lower P2O5 contents and La/Yb ratios (<20) than Group 1, originating from asthenospheric mantle with input of delaminated lithospheric component. In combination with available data, it is proposed for the petrogenetic model of the Early Cretaceous thickened lithospheric delamination in response to the asthenospheric upwelling along the western Qinling orogenic belt.

  5. Integrating palaeoenvironmental and climate cyclicities - Optimizing the stratigraphic framework in the non-marine Lower Cretaceous

    NASA Astrophysics Data System (ADS)

    Sames, Benjamin

    2015-04-01

    Studies on changing paleoenvironments and climate cycles in non-marine archives of the Cretaceous greenhouse earth are hitherto rare, primarily a result of the lack of high-resolution stratigraphy and correlations to the marine record. On the other hand, recent refinements of the geological time scale have made major advances for the Cretaceous to yield a resolution comparable to that of younger Earth history. In the Cretaceous marine record is now possible to correlate and date short-term sea-level records and their possible relation to climate and/or tectonic events with appropriate resolution. Correlation in the non-marine realm ('continental' aquatic) has long been fraught with considerable problems and limitations, especially on supraregional (i.e., inter-basinal) to global scales, thus often hampering serious attempts at dating and chronological linking of events documented by the respective deposits - let alone appropriate correlation to marine successions. A new interdisciplinary project and multi-proxy study funded by the Austrian Science Fund (FWF) uses the Lower Cretaceous European record (English Wealden) as a test site for the integration of ostracod biostratigraphy and assemblage changes, and cyclostratigraphy (orbitally/climate driven cycles). Ostracods (microcrustaceans with a calcified shell) are the most useful biostratigraphical and palaeoenvironmental tool in Lower Cretaceous non-marine sequences. During the past two decades, research progress in late Mesozoic non-marine ostracods led to their extended applicability, whereas their wide dispersal ability has become a key conside-ration in their supraregional (inter-basinal to global) biostratigraphical utility. The integrative methodology applied in this project, targets the correlation of the ostracod faunal composition change with the variation of geochemical and sedimentological parameters through time and inferences on controlling (palaeoenvironmental) factors and their regulating mechanisms

  6. Cretaceous origin of the unique prey-capture apparatus in mega-diverse genus: stem lineage of Steninae rove beetles discovered in Burmese amber

    PubMed Central

    Żyła, Dagmara; Yamamoto, Shûhei; Wolf-Schwenninger, Karin; Solodovnikov, Alexey

    2017-01-01

    Stenus is the largest genus of rove beetles and the second largest among animals. Its evolutionary success was associated with the adhesive labial prey-capture apparatus, a unique apomorphy of that genus. Definite Stenus with prey-capture apparatus are known from the Cenozoic fossils, while the age and early evolution of Steninae was hardly ever hypothesized. Our study of several Cretaceous Burmese amber inclusions revealed a stem lineage of Steninae that possibly possesses the Stenus-like prey-capture apparatus. Phylogenetic analysis of extinct and extant taxa of Steninae and putatively allied subfamilies of Staphylinidae with parsimony and Bayesian approaches resolved the Burmese amber lineage as a member of Steninae. It justified the description of a new extinct stenine genus Festenus with two new species, F. robustus and F. gracilis. The Late Cretaceous age of Festenus suggests an early origin of prey-capture apparatus in Steninae that, perhaps, drove the evolution towards the crown Stenus. Our analysis confirmed the well-established sister relationships between Steninae and Euaesthetinae and resolved Scydmaeninae as their next closest relative, the latter having no stable position in recent phylogenetic studies of rove beetles. Close affiliation of Megalopsidiinae, a subfamily often considered as a sister group to Euaesthetinae + Steninae clade, is rejected. PMID:28397786

  7. Organic Matter Production And Preservation During Transgression And Highstand Of The Niobrara Cyclothem, Cretaceous Western Interior Seaway

    NASA Astrophysics Data System (ADS)

    Salacup, J. M.; Petsch, S. T.; Leckie, R.

    2007-12-01

    The Upper Cretaceous Niobrara cyclothem (upper Turonian-lower Campanian) is a second-order transgressive- regressive cycle of the Cretaceous Western Interior Seaway reflecting interactions among eustatic sea level change, regional tectonic events, and sediment supply. These strata provide a unique window into Late Cretaceous sediment deposition and paleoceaonographic conditions in an epicontinental seaway. However, the response of organic matter production and burial to these forcings remains less than fully resolved. Geochemical analyses of the Montezuma Valley and Smoky Hill Members of the Mancos Shale at its principal reference section at Mesa Verde, Colorado, reveal potential relationships among organic matter abundance and composition, paleoceanographic conditions inferred from microfossils, and sea level change. These rock units represent transgression and early highstand of the Niobrara cyclothem. At Mesa Verde, the upper Smoky Hill coincides with the spatially-restricted but temporally-extended Oceanic Anoxic Event 3 of middle Coniacian to early Santonian age (~88.5-86.5 Ma). It is broadly characterized as dark-gray, foraminifer-rich calcareous shale, mudstone, and marlstone. Bulk geochemical properties, including %TOC, %CaCO3, and C/N, reflect changes in organic matter delivery and preservation, and are closely correlated to inferred water-depth and/or distance from shore. Proximity to the western paleo-shore appears to exercise a primary control over the composition of the identified biomarkers with secondary influence from redox-sensitive diagenetic processes and autochthonous microbial production, which in turn may reflect higher-order sea-level fluctuations. Changes in n-alkane, hopane, and sterane distributions are coincident with the second-order transgression of the seaway. Additionally, the presence in some samples of long-chain alkylcycloalkanes and alkylbenzenes may reflect the direct cyclization and aromatization of precursor algal and bacterial

  8. A mid-Cretaceous Eccrinales infesting a primitive wasp in Myanmar amber.

    PubMed

    Poinar, George

    2016-12-01

    A mid-Cretaceous Eccrinales in Myanmar amber is described as Paleocadus burmiticus gen. et sp. nov. in the family Eccrinaceae. The fossil is represented by two types of sporangiospores formed on different thalli protruding from the anus of a primitive wasp, with secondary infestation spores multinucleate and thin walled. Its presence establishes the Eccrinales in the mid-Cretaceous and shows that at that time, lineages of this group parasitized wasps, an association unknown with extant members of the Order. Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

  9. Compaction history of Upper Cretaceous shale (Al-Khod Formation) and its relationship to plate margin tectonics, Arabian Plate, Sultanate of Oman

    NASA Astrophysics Data System (ADS)

    AL-Sarmi, Musaab; Mattern, Frank; Scharf, Andreas; Pracejus, Bernhard; Al-Mamari, Amira; Al-Hinaai, Al-Shima

    2017-04-01

    Conglomerates of the late Cretaceous Al-Khod Formation have been intruded by older shale of the same formation along faults, which were opened/widened by extension, thus, resulting in shale dike formation. Following intrusion the shale was behaving plastically as its fissility follows the contact contours of the conglomeratic host rock and as stoped sandstone blocks are floating within the shale. Vertical calcite veins were ptygmatically folded with subhorizontal fold axial planes. All these aspects show that the shale contained a high water content in the beginning. The ptygmatically folded calcite veins display vertical shortening amounts of 40 % corresponding to 35 % to 45 % of water loss during compaction. Incalculable numbers of calcite veins of different orientations and thicknesses within the conglomerate along the shale contact indicate that the fluid was expelled from the shale into the conglomerate host rock under high pressure (overpressure?). Shale dyke formation took place after the late Cretaceous obduction of the Semail Ophiolite, before the deposition of early Tertiary carbonate rocks, and during the latest Cretaceous doming of the Saih Hatat area which was caused by deformation and slab breakoff, likely associated with gravitational collapse and elastic rebound. Shale intrusion was followed by deposition of 100 to 200 m thick sediments of the upper part of Al-Khod Formation, leading to compaction and water loss. The shale retained much of its water during the uppermost Cretaceous-late Paleocene stratigraphic hiatus as this interval is marked by erosion and a reduction of overburden, which was probably due to the elastic rebound. Folding of calcite veins together with a high amount of water loss was a consequence of compaction caused by the overburden of 1000 m thick shallow marine limestones which were deposited from the Eocene to Oligocene.

  10. Cellular preservation of musculoskeletal specializations in the Cretaceous bird Confuciusornis

    PubMed Central

    Jiang, Baoyu; Zhao, Tao; Regnault, Sophie; Edwards, Nicholas P.; Kohn, Simon C.; Li, Zhiheng; Wogelius, Roy A.; Benton, Michael J.; Hutchinson, John R.

    2017-01-01

    The hindlimb of theropod dinosaurs changed appreciably in the lineage leading to extant birds, becoming more ‘crouched' in association with changes to body shape and gait dynamics. This postural evolution included anatomical changes of the foot and ankle, altering the moment arms and control of the muscles that manipulated the tarsometatarsus and digits, but the timing of these changes is unknown. Here, we report cellular-level preservation of tendon- and cartilage-like tissues from the lower hindlimb of Early Cretaceous Confuciusornis. The digital flexor tendons passed through cartilages, cartilaginous cristae and ridges on the plantar side of the distal tibiotarsus and proximal tarsometatarsus, as in extant birds. In particular, fibrocartilaginous and cartilaginous structures on the plantar surface of the ankle joint of Confuciusornis may indicate a more crouched hindlimb posture. Recognition of these specialized soft tissues in Confuciusornis is enabled by our combination of imaging and chemical analyses applied to an exceptionally preserved fossil. PMID:28327586

  11. Upper Cretaceous and lower Eocene conglomerates of Western Transverse Ranges: evidence for tectonic rotation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reed, W.E.; Krause, R.G.F.

    1989-04-01

    Stratigraphic and paleomagnetic studies have suggested that the western Transverse Ranges (WTR) microplate is allochthonous, and may have experienced translational and rotational motions. Present paleocurrent directions from the Upper Cretaceous Jalama Formation of the Santa Ynez Mountains are north-directed; these forearc sediments (Great Valley sequence) contain magmatic arc-derived conglomerate clasts from the Peninsular Ranges in southern California. Paleocurrents in the lower Eocene Juncal and Cozy Dell Formations are south-directed. This juxtaposition is best explained by 90/degrees/ or more of clockwise rotation of the WTR microplate, so that Upper Cretaceous forearc sediments sourced from the Peninsular Ranges magmatic arc were depositedmore » by west-directed currents. Eocene sediments were derived from an uplifted portion of the western basin margin and deposited by east-directed currents. Franciscan olistoliths in the Upper Cretaceous sediments indicate deposition adjacent to an accretionary wedge; conglomeratic clasts recycled from the Upper Cretaceous sequence, and radiolarian cherts and ophiolitic boulders in the Eocene strata indicate derivation from an outer accretionary ridge.« less

  12. The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia

    NASA Astrophysics Data System (ADS)

    Godefroit, Pascal; Golovneva, Lina; Shchepetov, Sergei; Garcia, Géraldine; Alekseev, Pavel

    2009-04-01

    A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10°C), but the climate was apparently too cold for amphibians and ectothermic reptiles. The high diversity of Late Maastrichtian dinosaurs in high latitudes, where ectotherms are absent, strongly questions hypotheses according to which dinosaur extinction was a result of temperature decline, caused or not by the Chicxulub impact.

  13. Astrochronology of the Valanginian Stage (Early Cretaceous) : implications for the origin of the Weissert Event

    NASA Astrophysics Data System (ADS)

    Martinez, Mathieu; Deconinck, Jean-François; Pellenard, Pierre; Reboulet, Stéphane; Riquier, Laurent

    2013-04-01

    Due to the scarcity of available radioisotopic ages in the Lower Cretaceous, the Geologic Time Scale presents uncertainties that impact palaeoceanographic and palaeoclimatic reconstructions. Particularly, the chronological relationship between the Mid-Valanginian carbon-isotope excursion (namely the 'Weissert Event') and the activity of the Paraná-Etendeka Large Igneous Province is debated. To better constrain this relationship, an astrochronology of the Valanginian Stage is proposed based on high-resolution gamma-ray spectrometry measurements performed on five biostratigraphically well-constrained sections throughout the Vocontian Basin (SE France). The Valanginian sediments of the Vocontian Basin are composed of decimetric hemipelagic marl-limestone alternations. These lithologic cycles are attributed to orbital forcing because marls and limestones display significant differences within clay mineralogy, geochemistry and faunal assemblages and these marl-limestone alternations are correlated throughout the Western Tethys and the Atlantic Ocean. Among the analyzed sections, Vergol (GSSP candidate for the Berriasian-Valanginian boundary), La Charce (GSSP candidate for the Valanginian-Hauterivian boundary) and Angles (Valanginian Hypostratotype) are standard sections for the Valanginian Stage since all ammonite zones and subzones are precisely identified and bounded. Spectral analyses were performed using the multi-taper method and amplitude spectrograms on the gamma-ray signals. The comparison between sedimentary frequency ratios derived from the spectral analyses and orbital frequency ratios calculated from astronomical solutions allows the identification of a pervasive dominance of the precession and the 405 kyr-eccentricity cycles throughout the Valanginian Stage. A duration of 5.1 myr is proposed for the Valanginian Stage on the base of the recognition of the 405 kyr-eccentricity cycles. This duration is in agreement with the orbital calibration proposed from

  14. TEX 86 and stable δ 18O paleothermometry of early Cretaceous sediments: Implications for belemnite ecology and paleotemperature proxy application

    NASA Astrophysics Data System (ADS)

    Mutterlose, Jörg; Malkoc, Matthias; Schouten, Stefan; Sinninghe Damsté, Jaap S.; Forster, Astrid

    2010-10-01

    Recent studies have cast doubt on the unadjusted usage of Jurassic and Cretaceous δ 18O paleotemperature data derived from belemnites, since the latter data often reflect cooler paleotemperature estimates than would be expected. In this study we address this problem by analysing rocks of Barremian to early Aptian age from two outcrops in northern Germany using TEX 86 paleothermometry, along with 142 belemnite guards studied for their stable isotope (δ 13C, δ 18O) and trace element composition (magnesium, strontium, iron, and manganese). Both TEX 86 and δ 18O Bel indicate very warm water temperatures for a distinctive black shale sequence of late early Barremian age ("Hauptblätterton") with temperatures of up to 29 °C and 23 °C, respectively. We observe a constant offset of TEX 86 temperatures versus the 4 to 5 °C cooler δ 18O belemnite signal for this interval. The late Barremian sequence shows an increase of the δ 18O Bel values from - 1‰ to 0‰ reflecting temperatures around 16 to 12 °C, while the contemporaneous TEX 86 temperatures vary between 26 and 32 °C. The common occurrence of belemnites in the anoxic sediments of the early Barremian implies, however, clearly a nektonic way of life similar to that of recent teuthids, rather than a nektobenthic one like Sepia. This in turn suggests that the belemnites investigated here (genera Praeoxyteuthis, Aulacoteuthis, Oxyteuthis, and Neohibolites) were active swimmers, which inhabited a deeper habitat below the thermocline in an epicontinental sea of perhaps 100 to 250 m water depth. The offset of the TEX 86 and δ 18O Bel data is therefore interpreted to reflect temperature signals from two different depth habitats, i.e. the TEX 86 is selectively derived from warm sea-surface waters, and the belemnites likely occupied deeper and cooler waters with relative increasing salinities in the late Barremian. This study stresses the importance that the taxonomy, paleobiology and ecology of the belemnite taxa

  15. Sulu-Celebes-Banda basins: a trapped piece of Cretaceous to Eocene oceanic crust

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McCabe, R.J.; Hilde, T.W.; Cole, J.T.

    1986-07-01

    The Sulu-Celebes-Banda basin is composed of three poorly understood marginal basins located between northwest Australia and southeast Asia. Recent studies have proposed that these three basins are remnants of once-continuous ocean basin. The on-land geology of this region is complicated. However, numerous stratigraphic and paleomagnetic studies on pre-Oligocene rocks are consistent with the interpretation that older landmasses presently dissecting the basin were translated into their present position during the middle to late Tertiary. Paleomagnetic data from the Philippines suggest that the Philippine arc is a composite of Early Cretaceous to Holocene arcs that were translated clockwise and from the southeast.more » Paleomagnetic and stratigraphic data from Kalimantan and Sulawesi suggest that these landmasses share a common origin and that Sulawesi was rifted eastward off of Borneo during the late Tertiary. Stratigraphic studies from the Sula microcontinent, Buru, Ceram, and Timor show close correlation to the stratigraphy of northwest Australia or New Guinea. In addition, paleomagnetic studies from Timor suggest that a portion of the island was part of Australia since the early Mesozoic.« less

  16. The Rise of Flowering Plants and Land Surface Physics: The Cretaceous and Eocene Were Different

    NASA Astrophysics Data System (ADS)

    Upchurch, G. R.; Feild, T.

    2010-12-01

    The Cretaceous and Eocene have served as the poster children of past greenhouse climates. One difference between the two time periods is that angiosperms (flowering plants) underwent a major diversification and rise to dominance during the mid-Cretaceous to Paleocene. Flowering plants differ from all other living and fossil plants in having significantly higher rates of transpiration and photosynthesis, which in modern leaves correlate with the density of venation (Dv), a feature that can be measured directly from fossils. This increase in Dv, coupled with an increase in the abundance of angiosperms, is thought to have had major impact on the climate system. This is, in part, because transpiration plays an important role in determining the ratio of sensible to latent heat flux from the land surface and in determining precipitation rate in regions such as the equatorial rainforest. Analysis of Dv in fossil leaves indicates two phases of increase in transpiration rate for angiosperms during the Cretaceous-Paleocene. The oldest known angiosperms (Aptian-early Albian) have a low Dv characteristic of extant and fossil ferns and gymnosperms. At this time angiosperms are low-stature plants of minor importance in terms of relative abundance and diversity (<5%). The first phase of Dv increase occurs during the Late Albian to Cenomanian, where average Dv is 40% greater than that of conifers and ferns, and maximum Dv reaches levels characteristic of many trees from the temperate zone. This first phase coincides with the first local dominance of angiosperms, the first occurrence of moderate to large angiosperm trees (up to 1 m in diameter) , and the first common occurrence of angiosperms in the Arctic. The second phase of Dv increase occurs during the Maastrichtian to Paleocene, where average Dv reaches levels characteristic of modern tropical forests and maximum Dv reaches the level found in highly productive modern vegetation. This second phase coincides with the rise to

  17. Preliminary stratigraphy and facies analysis of the Upper Cretaceous Kaguyak Formation, including a brief summary of newly discovered oil stain, upper Alaska Peninsula

    USGS Publications Warehouse

    Wartes, Marwan A.; Decker, Paul L.; Stanley, Richard G.; Herriott, Trystan M.; Helmold, Kenneth P.; Gillis, Robert J.

    2013-01-01

    The Alaska Division of Geological and Geophysical Surveys has an ongoing program aimed at evaluating the Mesozoic forearc stratigraphy, structure, and petroleum systems of lower Cook Inlet. Most of our field studies have focused on the Jurassic component of the petroleum system (this report). However, in late July and early August of 2012, we initiated a study of the stratigraphy and reservoir potential of the Upper Cretaceous Kaguyak Formation. The Kaguyak Formation is locally well exposed on the upper Alaska Peninsula (fig. 25) and was named by Keller and Reiser (1959) for a sequence of interbedded siltstone and sandstone of upper Campanian to Maastrichtian age that they estimated to be 1,450 m thick.Subsequent work by Detterman and Miller (1985) examined 900 m of section and interpreted the unit as the record of a prograding submarine fan.This interpretation of deep-water deposition contrasts with other Upper Cretaceous rocks exposed along the Alaska Peninsula and lower Cook Inlet that are generally described as nonmarine to shallow marine (Detterman and others, 1996; LePain and others, 2012).Based on foraminifera and palynomorphs from the COST No. 1 well, Magoon (1986) concluded that the Upper Cretaceous rocks were deposited in a variety of water depths and environments ranging from upper bathyal to nonmarine. During our recent fieldwork west and south of Fourpeaked Mountain, we similarly encountered markedly varying lithofacies in the Kaguyak Formation (fig. 25), and we also found oil-stained rocks that are consistent with the existence of an active petroleum system in Upper Cretaceous rocks on the upper Alaska Peninsula and in lower Cook Inlet. These field observations are summarized below.

  18. Upper cretaceous microbial petroleum systems in north-central Montana

    USGS Publications Warehouse

    Lillis, Paul G.

    2007-01-01

    Methanogenesis began soon after the deposition (early-stage methanogenesis) of the Cenomanian to Campanian source sediments, and was either sustained or rejuvenated by episodic meteoric water influx until sometime in the Paleogene. Methanogenesis probably continued until CO2 and hydrogen were depleted or the pore size was compacted to below tolerance levels of the methanogens. The composition of the Montana and Colorado Group gases and coproduced formation water precludes a scenario of late-stage methanogenesis like the Antrim gas system in the Michigan basin. Some portion of the methane charge was originally dissolved in the pore waters, and subsequent reduction in hydrostatic pressure caused the methane to exsolve and migrate into local stratigraphic and structural traps. The critical moment of the microbial gas systems is this timing of exsolution rather than the time of generation (methanogenesis). Other studies suggest that the reduction in hydrostatic pressure may have been caused by multiple geologic events including the lowering of sea level in the Late Cretaceous, and subsequent uplift and erosion events, the youngest of which began about 5 Ma.

  19. Reconstructing a mid-Cretaceous landscape from paleosols in western Canada

    USGS Publications Warehouse

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.; Leckie, D.

    2005-01-01

    The Albian Stage of the mid-Cretaceous was a time of equable climate conditions with high sea levels and broad shallow epeiric seas that may have had a moderating affect on continental climates. A Late Albian landscape surface that developed during a regression and subsequent sea-level rise in the Western Canada Foreland Basin is reconstructed on the basis of correlation of paleosols penetrated by cores through the Paddy Member of the Peace River Formation. Reconstruction of this landscape refines chronostratigraphic relationships and will benefit future paleoclimatological studies milizing continental sphaerosiderite proxy records. The paleosols developed in estuarine sandstones and mudstones, and they exhibit evidence of a polygenetic history. Upon initial exposure and pedogenesis, the Paddy Member developed deeply weathered, well-drained cumulative soil profiles. Later stages of pedogenesis were characterized by hydromorphic soil conditions. The stages of soil development interpreted for the Paddy Member correlate with inferred stages of pedogenic development in time-equivalent formations located both basinward and downslope (upper Viking Formation), and landward and upslope (Boulder Creek Formation). On the basis of the genetic similarity among paleosols in these three correlative formations, the paleosols are interpreted as having formed along a single, continuous landscape surface. Results of this study indicate that the catena concept of pedogenesis along sloping landscapes is applicable to ancient successions. Sphaerosiderites in the Paddy Mem ber paleosols are used to provide proxy values for meteoric ??18O values at 52?? N paleolatitude in the Cretaceous Western Interior Basin. The meteoric ??18O values are used to refine existing interpretations about the mid-Cretaceous paleolatitudinal gradient in meteoric ?? 18O values, and the mid-Cretaceous hydrologic cycle. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).

  20. Depositional environment and distribution of Late Cretaceous [open quotes]source rocks[close quotes] from Costa Rica to West Africa

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Erlich, R.N.; Sofer, Z.; Pratt, L.M.

    1993-02-01

    Late Cretaceous [open quotes]source rocks[close quotes] from Costa Rica, western and eastern Venezuela, and Trinidad were studied using organic and inorganic geochemistry, biostratigraphy, and sedimentology in order to determine their depositional environments. Bulk mineralogy and major element geochemistry for 304 samples were combined with Rock Eval data and extract biomaker analysis to infer the types and distributions of the various Late Cretaceous productivity systems represented in the dataset. When data from this study are combined with published and proprietary data from offshore West Africa, Guyana/Suriname, and the central Caribbean, they show that these Late Cretaceous units can be correlated bymore » their biogeochemical characteristics to establish their temporal and spatial relationships. Paleogeographic maps constructed for the early to late Cenomanian, Turonian, Coniacian to middle Santonian, and late Santonian to latest Campanian show that upwelling and excessive fluvial runoff were probably the dominant sources of nutrient supply to the coastal productivity systems. The late Santonian to Maastrichtian rocks examined in this study indicate that organic material was poorly preserved after deposition, even though biologic productivity remained constant or changed only slightly. A rapid influx of oxygenated bottom water may have occurred following the opening of a deep water connection between the North and South Atlantic oceans, and/or separation of India from Africa and the establishment of an Antarctic oceanic connection. This study suggests that the most important factors that controlled source rock quality in northern South America were productivity, preservation, degree of clastic dilution, and subsurface diagenesis.« less

  1. Short Polarity Albian Events in the Cretaceous Normal Superchron - Magnetostratigraphy of the Morelos and Tlayua Formations (Mexico)

    NASA Astrophysics Data System (ADS)

    Benammi, M.; Urrutia-Fucugauchi, J.

    2007-12-01

    Interest in the long period of normal polarity in the Cretaceous has continued to increase since the early study of Helsley and Steiner (1969), who suspected that it corresponded to vast stretches of relatively low amplitude behaviour in the sea-floor magnetic anomaly profiles known informally as the "Cretaceous quiet zone". Since these first studies, paleomagnetists have continued to explore what is now known as the Cretaceous Normal Superchron, an interval of prolonged normal polarity from 118 to 84 Ma. Paleomagnetic data from sediment cores from the DSDP Holes 369, 386, and 364, were interpreted as brief reverse intervals (Keating and Helsley, 1978, 1979). Relatively fewer studies have been reported for land-based sections of pelagic and platform limestones; reports include studies in northern and central Italy (Vandenberg et al., 1978; Tarduno et al., 1992; Tarduno, 1990; Cronin et al., 2001) and Mexico (Urrutia-Fucugauchi, 1988; Benammi et al., 2006). We present here new magnetostratigraphic data for limestone sequences in central and southern Mexico from the Cretaceous Morelos and Tlayua Formations, which record short intervals of reversed polarity during the K normal superchron. The Morelos Formation has been revisited in Guerrero, southern Mexico, where the sequence of platform limestones with almost horizontal thick beds is well-exposed. The magnetostratigraphy shows dominant normal polarity for the sampled sections, with the occurrence of three short reverse polarity intervals corresponding to the Albian, which have been re-sampled and studied in additional detail for magnetic mineralogy and remanent acquisition. The Tlayua Formation is sampled in Tepeji de Rodriguez area, which is known for its rich and well-preserved fossil contents. Age control has mainly been provided from studies on ammonites, belemnites and benthic foraminifera (Cantu, 1987; Seibertz and Buitron, 1987; Kashiyama et al., 2003). Nine polarity intervals are documented in the Tlayua

  2. Cycles and trends in the δ18O and δ13C records over the Jurassic and Early Cretaceous

    NASA Astrophysics Data System (ADS)

    Martinez, Mathieu; Dera, Guillaume

    2015-04-01

    The million-year fluctuations of the Mesozoic climate are explored through spectral analyses performed on an exhaustive compilation of δ18O and δ13C data measured on belemnite rostra. The data include more than 3500 data points, all coming from Western Tethys and Euro-boreal domains, and covering a time interval spanning 76 Myr from the Sinemurian (~197 Ma; Early Jurassic) to the Aptian (~123 Ma; Early Cretaceous) with an average sample step of ~0.04 Myr. Spectral analyses are performed using the multi-taper method and the evolutive Fast Fourier Transform in order to get an accurate estimate of significant periods and their evolution during geological times. The age uncertainties of the Geological Time Scale 2012 are taken into account to assess the impact of these uncertainties on the identification of the significant periods. After implementing an error model that simulates the uncertainties of the Geological Time Scale, two periods remains significant: the δ13C displays a high-amplitude period at 9.1 Myr, while the δ18O displays a high-amplitude period at 16.4 Myr. The 16.4-Myr period is only expressed in the Early and Middle Jurassic, with maximum amplitudes reached during the 'Toarcian Plateau' (Dera et al., 2011). It is probably a consequence of the activity of the Karoo-Ferrar Large Igneous Province and is an event in the δ18O rather than a true cycle. The 9.1-Myr period displays a spectacular continuity from the Toarcian to the Aptian, and could be related to this intriguing 9.1-Myr cycle observed in the δ13C from the Cenozoic, related to a Myr-amplitude modulation of the eccentricity cycles (Boulila et al., 2012). The δ13C in the Western Tethys thus appears to have a very rhythmic behaviour, interpreted here as a long-term orbital modulation of moisture and heat transfer from equatorial to higher latitudes, modulating in return continental weathering, nutrient and detrital exports to basins, neritic vs. pelagic productivity and finally preservation

  3. Volcanic ash as a driver of enhanced organic carbon burial in the Cretaceous.

    PubMed

    Lee, Cin-Ty A; Jiang, Hehe; Ronay, Elli; Minisini, Daniel; Stiles, Jackson; Neal, Matthew

    2018-03-08

    On greater than million year timescales, carbon in the ocean-atmosphere-biosphere system is controlled by geologic inputs of CO 2 through volcanic and metamorphic degassing. High atmospheric CO 2 and warm climates in the Cretaceous have been attributed to enhanced volcanic emissions of CO 2 through more rapid spreading at mid-ocean ridges and, in particular, to a global flare-up in continental arc volcanism. Here, we show that global flare-ups in continental arc magmatism also enhance the global flux of nutrients into the ocean through production of windblown ash. We show that up to 75% of Si, Fe and P is leached from windblown ash during and shortly after deposition, with soluble Si, Fe and P inputs from ash alone in the Cretaceous being higher than the combined input of dust and rivers today. Ash-derived nutrient inputs may have increased the efficiency of biological productivity and organic carbon preservation in the Cretaceous, possibly explaining why the carbon isotopic signature of Cretaceous seawater was high. Variations in volcanic activity, particularly continental arcs, have the potential of profoundly altering carbon cycling at the Earth's surface by increasing inputs of CO 2 and ash-borne nutrients, which together enhance biological productivity and burial of organic carbon, generating an abundance of hydrocarbon source rocks.

  4. Evolution and palaeoenvironment of the Bauru Basin (Upper Cretaceous, Brazil)

    NASA Astrophysics Data System (ADS)

    Fernandes, Luiz Alberto; Magalhães Ribeiro, Claudia Maria

    2015-08-01

    The Bauru Basin was one of the great Cretaceous desert basins of the world, evolved in arid zone called Southern Hot Arid Belt. Its paleobiological record consists mainly of dinosaurs, crocodiles and turtles. The Bauru Basin is an extensive region of the South American continent that includes parts of the southeast and south of Brazil, covering an area of 370,000 km2. It is an interior continental basin that developed as a result of subsidence of the central-southern part of the South-American Platform during the Late Cretaceous (Coniacian-Maastrichtian). This sag basin is filled by a sandy siliciclastic sequence with a preserved maximum thickness of 480 m, deposited in semiarid to desert conditions. Its basement consists of volcanic rocks (mainly basalts) of the Lower Cretaceous (Hauterivian) Serra Geral basalt flows, of the Paraná-Etendeka Continental Flood Basalt Province. The sag basin was filled by an essentially siliciclastic psammitic sequence. In lithostratigraphic terms the sequence consists of the Caiuá and Bauru groups. The northern and northeastern edges of the basin provide a record of more proximal original deposits, such as associations of conglomeratic sand facies from alluvial fans, lakes, and intertwined distributary river systems. The progressive basin filling led to the burial of the basaltic substrate by extensive blanket sand sheets, associated with deposits of small dunes and small shallow lakes that retained mud (such as loess). Also in this intermediate context between the edges (more humid) and the interior (dry), wide sand sheet areas crossed by unconfined desert rivers (wadis) occurred. In the central axis of the elliptical basin a regional drainage system formed, flowing from northeast to southwest between the edges of the basin and the hot and dry inner periphery of the Caiuá desert (southwest). Life in the Bauru Basin flourished most in the areas with the greatest water availability, in which dinosaurs, crocodiles, turtles, fish

  5. Source rock potential of middle cretaceous rocks in Southwestern Montana

    USGS Publications Warehouse

    Dyman, T.S.; Palacas, J.G.; Tysdal, R.G.; Perry, W.J.; Pawlewicz, M.J.

    1996-01-01

    The middle Cretaceous in southwestern Montana is composed of a marine and nonmarine succession of predominantly clastic rocks that were deposited along the western margin of the Western Interior Seaway. In places, middle Cretaceous rocks contain appreciable total organic carbon (TOC), such as 5.59% for the Mowry Shale and 8.11% for the Frontier Formation in the Madison Range. Most samples, however, exhibit less than 1.0% TOC. The genetic or hydrocarbon potential (S1+S2) of all the samples analyzed, except one, yield less than 1 mg HC/g rock, strongly indicating poor potential for generating commercial amounts of hydrocarbons. Out of 51 samples analyzed, only one (a Thermopolis Shale sample from the Snowcrest Range) showed a moderate petroleum potential of 3.1 mg HC/g rock. Most of the middle Cretaceous samples are thermally immature to marginally mature, with vitrinite reflectance ranging from about 0.4 to 0.6% Ro. Maturity is high in the Pioneer Mountains, where vitrinite reflectance averages 3.4% Ro, and at Big Sky Montana, where vitrinite reflectance averages 2.5% Ro. At both localities, high Ro values are due to local heat sources, such as the Pioneer batholith in the Pioneer Mountains.

  6. Modeling the Impact of Forest and Peat Fires on Carbon-Isotopic Compositions of Cretaceous Atmosphere and Vegetation

    NASA Astrophysics Data System (ADS)

    Finkelstein, D. B.; Pratt, L. M.

    2004-12-01

    Prevalence of wildfires or peat fires associated with seasonally dry conditions in the Cretaceous is supported by recent studies documenting the widespread presence of pyrolytic polycyclic aromatic hydrocarbons and fusinite. Potential roles of CO2 emissions from fire have been overlooked in many discussions of Cretaceous carbon-isotope excursions (excluding K-P boundary discussions). Enhanced atmospheric CO2 levels could increase fire frequency through elevated lightning activity. When biomass or peat is combusted, emissions of CO2 are more negative than atmospheric CO2. Five reservoirs (atmosphere, vegetation, soil, and shallow and deep oceans), and five fluxes (productivity, respiration, litter fall, atmosphere-ocean exchange, and surface-deep ocean exchange) were modeled as a closed system. The size of the Cretaceous peat reservoir was estimated by compilation of published early Cretaceous coal resources. Initial pCO2 was assumed to be 2x pre-industrial atmospheric levels (P.A.L.). Critical variables in the model are burning efficiency and post-fire growth rates. Assuming 1% of standing terrestrial biomass is consumed by wildfires each year for ten years (without combustion of peat), an increase of atmospheric CO2 (from 2.0 to 2.2x P.A.L.) and a negative carbon isotope excursion (-1.2 ‰ ) are recorded by both atmosphere and new growth. Net primary productivity linked to the residence time of the vegetation and soil reservoirs results in a negative isotope shift followed by a broad positive isotope excursion. Decreasing the rate of re-growth dampens this trailing positive shift and increases the duration of the excursion. Post-fire pCO2 and new growth returned to initial values after 72 years. Both negative and positive isotope excursions are recorded in the model in surface ocean waters. Exchange of CO2 with the surface- and deep-ocean dampens the isotopic shift of the atmosphere. Excursions are first recorded in the atmosphere (and new growth), followed by

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  8. The Cretaceous - Paleogene paleogeography of Central Asia recorded in depositional environments of the Proto-Paratethys Sea in the Tarim Basin (Western China)

    NASA Astrophysics Data System (ADS)

    Yücel Kaya, Mustafa; Dupont-Nivet, Guillaume; Proust, Jean-Noel; Bougeois, Laurie; Meijer, Niels; Frieling, Joost; Fioroni, Chiara; Stoica, Marius; Roperch, Pierrick; Mamtimin, Mehmut; Aminov, Jovid

    2017-04-01

    The Proto-Paratethys, a shallow epicontinental sea, extended from Cretaceous to Paleogene times across Eurasia from the Mediterranean Tethys to the Tarim Basin in western China. Transgressive and regressive episodes of the Proto-Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained especially for the Cretaceous and early Paleogene. This hampers understanding of their driving mechanisms (geodynamic and/or eustatic) and paleoclimatic consequences on regional aridification and monsoons. As part of the ERC "MAGIC" project, we report an integrated sedimentologic and stratigraphic analysis of the Proto-Paratethys from its initial Cretaceous onset to the final Paleogene retreat from multiple investigated sections in the western border of Tarim Basin. Facies associations include field observations and microfacies analyses from carbonate samples. New bio- and magneto-stratigraphic results from key intervals are also provided to testify the previously constructed regional stratigraphic framework. The previously controversial number of marine incursions in the Tarim Basin is resolved to 6 (3 Cretaceous and 3 Paleogene) also recognized in the neighboring Tajik and Turan Basins to the west and the present-day Alai Valley. The eastward extent of these marine incursions varied through time with a maximum extent during late Paleocene - early Eocene. The first marine incursion is a Cenomanian transgression recorded in the marls and calcareous mudstones of the Kukebai Formation. The next two are Coniacian and Campanian transgressions recognized in the carbonate units of the Yigeziya Formation. The first Paleogene incursion is characterized by thick evaporites of the Paleocene Aertashi Formation overlain by the marine shales of the Lower Qimugen Formation. The latter represents the maximum extent and the deepest environments of the Proto-Paratethys. The marine Kalatar limestones and silty shales of the Wulagen

  9. Late cretaceous extensional tectonics and associated igneous activity on the northern margin of the Gulf of Mexico Basin

    NASA Technical Reports Server (NTRS)

    Bowen, R. L.; Sundeen, D. A.

    1985-01-01

    Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic activity involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern margin of the cratonic platform from Arkansas to Georgia.

  10. Characterizing Cretaceous Glaciation Events: K-Ar Ages of Southern Ocean Sediments

    NASA Astrophysics Data System (ADS)

    Wright, M. A.; Hemming, S. R.; Barbeau, D. L.; Torfstein, A.; Pierce, E. L.; Williams, T.; McManus, J. F.; Gombiner, J.

    2012-12-01

    Evidence from paleosols and carbonate weathering models suggest that the Late Cretaceous had a supergreenhouse climate due to atmospheric CO2 concentrations two to four times greater than modern levels, tropical sea surface temperatures exceeding 35°C, and high-latitude temperatures exceeding 20°C. Despite this warmth, the Late Cretaceous was apparently punctuated by large (>25 m) and rapid (<<1 million year) sea-level changes, as recorded by marginal marine stratigraphic architectures and pelagic stable isotope compositions. The magnitude and tempo of these changes suggest a glacio-eustatic control, presumably from the growth and decay of continental ice sheets on Antarctica. Because continental glaciation tends to increase the weathering of bedrock and production of sediment delivered to the oceans, circum-Antarctic marine sediment flux would be expected to increase during periods of glaciation. In order to identify a Late Cretaceous glaciation signal from such marine records, we must first constrain the compositional signal of continental detritus in marine sediments. Here we report the results of downcore K-Ar analysis of the terrigenous sediments of Quaternary Weddell Sea cores PS1170-1 and PS1388-3 in order to identify the compositional signature of continent-derived detritus deposited in the Weddell Sea during a known glacial period. Further, we use our K-Ar analyses of circum-Antarctic Quaternary sediment cores to pinpoint potential sediment source areas. Having constrained this glaciation signal, we also present preliminary K-Ar and Sm-Nd analysis of the Campanian-Maastrictian boundary event (69 Ma) at Ocean Drilling Project site 690C to assess the controversial hypothesis of Late Cretaceous glaciation of Antarctica.

  11. The Cretaceous glauconitic sandstones of Abu Tartur, Egypt

    NASA Astrophysics Data System (ADS)

    Pestitschek, Brigitte; Gier, Susanne; Essa, Mahmoud; Kurzweil, Johannes

    2010-05-01

    The Abu Tartur mine is located in the Western Desert of Egypt, 50 km west of El Kharga City. Geologically, the Abu Tartur plateau is built by a sequence of Upper Cretaceous (Campanian - Maastrichtian) phosphorites, black shales and glauconitic sandstones. The phosphate deposits are of great economic importance and have been mined since their discovery in 1967. Outcrop sections were measured, sampled, sedimentologically characterized and described. One specific glaucony layer was investigated mineralogically and chemically in detail and compared to a subsurface sample from the mine. Two depositional regimes can be interpreted based on sedimentary architecture and structures: 1) a deeper-water hemipelagic environment, where phosphorites and organic carbon-rich shales were deposited and 2) a shallower, prograding higher energy shelf environment with glauconies. From a sequence stratigraphic perspective 1) was deposited during the transgressive systems tract and the early highstand while 2) was deposited during the remaining highstand and a lowstand prograding wedge (Glenn & Arthur, 1990). Petrographic and SEM investigations show that the glaucony grains are of authochtonous origin. XRF, EMPA and thin-section analyses show that the glaucony grains from the outcrop differ significantly in their chemical composition, morphology and color from the grains of the mine sample. The fresh glauconies are enriched in Fe2O3 and K2O compared to the surface samples. XRD analyses of the clay fraction of the six outcrop samples and the mine sample show that the grains consist of illite(glauconite)/smectite mixed-layers, with more illite layers (80 %) in the mine sample. The charge distribution diagram muscovite-pyrophyllite-celadonite shows a clear trend from smectitic glaucony to illitic glaucony, the mine sample plots exactly in the field for glauconites. All these features indicate that the surface samples are strongly altered by weathering and that glauconite progressively

  12. Macrofossil evidence for a rapid and severe Cretaceous-Paleogene mass extinction in Antarctica.

    PubMed

    Witts, James D; Whittle, Rowan J; Wignall, Paul B; Crame, J Alistair; Francis, Jane E; Newton, Robert J; Bowman, Vanessa C

    2016-05-26

    Debate continues about the nature of the Cretaceous-Paleogene (K-Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K-Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous-Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.

  13. Macrofossil evidence for a rapid and severe Cretaceous-Paleogene mass extinction in Antarctica

    NASA Astrophysics Data System (ADS)

    Witts, James D.; Whittle, Rowan J.; Wignall, Paul B.; Crame, J. Alistair; Francis, Jane E.; Newton, Robert J.; Bowman, Vanessa C.

    2016-05-01

    Debate continues about the nature of the Cretaceous-Paleogene (K-Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K-Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous-Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.

  14. Stable Isotopes Reveal Rapid Enamel Elongation (Amelogenesis) Rates for the Early Cretaceous Iguanodontian Dinosaur Lanzhousaurus magnidens.

    PubMed

    Suarez, Celina A; You, Hai-Lu; Suarez, Marina B; Li, Da-Qing; Trieschmann, J B

    2017-11-10

    Lanzhousaurus magnidens, a large non-hadrosauriform iguanodontian dinosaur from the Lower Cretaceous Hekou Group of Gansu Province, China has the largest known herbivorous dinosaur teeth. Unlike its hadrosauriform relatives possessing tooth batteries of many small teeth, Lanzhousaurus utilized a small number (14) of very large teeth (~10 cm long) to create a large, continuous surface for mastication. Here we investigate the significance of Lanzhousaurus in the evolutionary history of iguanodontian-hadrosauriform transition by using a combination of stable isotope analysis and CT imagery. We infer that Lanzhousaurus had a rapid rate of tooth enamel elongation or amelogenesis at 0.24 mm/day with dental tissues common to other Iguanodontian dinosaurs. Among ornithopods, high rates of amelogenesis have been previously observed in hadrosaurids, where they have been associated with a sophisticated masticatory apparatus. These data suggest rapid amelogenesis evolved among non-hadrosauriform iguanodontians such as Lanzhousaurus, representing a crucial step that was exapted for the evolution of the hadrosaurian feeding mechanism.

  15. Sequence stratigraphy of the lower Upper Cretaceous Elbtal Group (Saxony, Germany): new data from Middle Cenomanian-Upper Turonian outcrops and boreholes

    NASA Astrophysics Data System (ADS)

    Richardt, Nadine; Wilmsen, Markus

    2013-04-01

    The formations of the Saxonian Cretaceous have been combined in the so-called Elbtal Group. Their sedimentation took place in a terrestrial to neritic environment palaeogeographically located between the Mid-European Island (MEI) in the SW and the Lusatian Massif in the NE. The through extended from the narrow marine strait of Saxony into the broad Bohemian Cretaceous Basin (Czech Republic) further to the SE. Deposition has been dominated by marine siliciclastics that accumulated on a graded shelf with basically three main facies zones: the coarse-grained nearshore zone ("Küstensandsteinzone"), the transitional zone ("Faziesübergangszone") and the fine-grained marly offshore facies zone ("Plänerfazies"). In general, transgression proceeded in late Early Cenomanian times from the N. Relictic remains of these marine bioclastic conglomerates (Meißen Formation) only occur in the northwesternmost area of the basin around Meißen and are related to the highstand of the depositional sequence Cenomanian 3 (DS Ce 3). After a short stratigraphic gap, onlap continued in the Middle Cenomanian with the following Niederschöna Formation consisting of coarse-grained braided river deposits at the base grading via carbonaceous point-bar cycles of a meandering river system into bioturbated, partly cross-bedded estuarine sediments toward the top. These sediments record DS Ce 4 and are capped by a paleosol. Sedimentation of DS Ce 5 started with a renewed transgressional pulse initiating the Late Cenomanian. The strata consist of bioturbated, cross-bedded predominantly fine- to medium-grained quartz sandstones with some shell-rich horizons corresponding to the Oberhäslich Formation. The unconformably overlying DS Tu 1 comprises the uppermost Cenomanian Dölzschen Formation and the Lower Turonian part of the Schmilka Formation. The onset of this depositional sequence is marked by a major transgression ("plenus Transgression) drowning the remaining pre-transgression topography

  16. Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J. J.; Lodolo, Emanuele

    2015-12-01

    The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known as the Patagonian Orocline (here renamed as Patagonian Arc), and the exhumation mechanism of an upper amphibolite facies metamorphic complex currently exposed in Cordillera Darwin. Here, we present results of anisotropy of magnetic susceptibility (AMS) from 22 sites in Upper Cretaceous to upper Eocene sedimentary rocks within the internal structural domain of the Magallanes fold-and-thrust belt in Tierra del Fuego (Argentina). AMS parameters from most sites reveal a weak tectonic overprint of the original magnetic fabric, which was likely acquired upon layer-parallel shortening soon after sedimentation. Magnetic lineation from 17 sites is interpreted to have formed during compressive tectonic phases associated to a continuous N-S contraction. Our data, combined with the existing AMS database from adjacent areas, show that the Early Cretaceous-late Oligocene tectonic phases in the Southern Andes yielded continuous contraction, variable from E-W in the Patagonian Andes to N-S in the Fuegian Andes, which defined a radial strain field. A direct implication is that the exhumation of the Cordillera Darwin metamorphic complex occurred under compressive, rather than extensional or strike-slip tectonics, as alternatively proposed. If we agree with recent works considering the curved Magallanes fold-and-thrust belt as a primary arc (i.e., no relative vertical-axis rotation of the limbs occurs during its formation), then other mechanisms different from oroclinal bending should be invoked to explain the documented radial strain field. We tentatively propose a kinematic model in which reactivation of variably oriented Jurassic faults at the South American continental margin controlled

  17. Accreted fragments of the Late Cretaceous Caribbean Colombian Plateau in Ecuador

    NASA Astrophysics Data System (ADS)

    Mamberti, Marc; Lapierre, Henriette; Bosch, Delphine; Jaillard, Etienne; Ethien, Raynald; Hernandez, Jean; Polvé, Mireille

    2003-02-01

    The eastern part of the Western Cordillera of Ecuador includes fragments of an Early Cretaceous (≈123 Ma) oceanic plateau accreted around 85-80 Ma (San Juan-unit). West of this unit and in fault contact with it, another oceanic plateau sequence (Guaranda unit) is marked by the occurrence of picrites, ankaramites, basalts, dolerites and shallow level gabbros. A comparable unit is also exposed in northwestern coastal Ecuador (Pedernales unit). Picrites have LREE-depleted patterns, high ɛNd i and very low Pb isotopic ratios, suggesting that they were derived from an extremely depleted source. In contrast, the ankaramites and Mg-rich basalts are LREE-enriched and have radiogenic Pb isotopic compositions similar to the Galápagos HIMU component; their ɛNd i are slightly lower than those of the picrites. Basalts, dolerites and gabbros differ from the picrites and ankaramites by flat rare earth element (REE) patterns and lower ɛNd; their Pb isotopic compositions are intermediate between those of the picrites and ankaramites. The ankaramites, Mg-rich basalts, and picrites differ from the lavas from the San Juan-Multitud Unit by higher Pb ratios and lower ɛNd i. The Ecuadorian and Gorgona 88-86 Ma picrites are geochemically similar. The Ecuadorian ankaramites and Mg-rich basalts share with the 92-86 Ma Mg-rich basalts of the Caribbean-Colombian Oceanic Plateau (CCOP) similar trace element and Nd and Pb isotopic chemistry. This suggests that the Pedernales and Guaranda units belong to the Late Cretaceous CCOP. The geochemical diversity of the Guaranda and Pedernales rocks illustrates the heterogeneity of the CCOP plume source and suggests a multi-stage model for the emplacement of these rocks. Stratigraphic and geological relations strongly suggest that the Guaranda unit was accreted in the late Maastrichtian (≈68-65 Ma).

  18. Neuquén Group (Upper Cretaceous): A case of underfilled-overfilled cycles in an Andean foreland basin, Neuquén basin, Argentina

    NASA Astrophysics Data System (ADS)

    Asurmendi, Estefanía; Sánchez, María Lidia; Fennell, Lucas

    2017-12-01

    The Nenquén Group was deposited during a period dominated by the Cretaceous Greenhouse and can be divided in three cycles correlated with large-scale changes in the evolution of the Andean foreland basin. The filling of the Neuquén Group is constituted by a complete cycle and two incomplete cycles of underfilled-overfilled, separated by first-order discontinuities assigned to the uplift of the Agrio fold-and-thrust belt during the Chasca/Catequil, Mid Ocean Ridge (CCMOR) collision, coinciding with first-order climatic changes within the Cretaceous greenhouse cycle. The Candeleros Formation in the base of this group was deposited in late underfilled conditions, showing prominent forebulge zones. It is demonstrated that during the Albian, with the cratonward migration of the uplifting forebulge zones, the axis of backbulge zones also migrated cratonwards and a wide uplifted forebulge zone was formed. On top, the Huincul Formation was deposited in an overfilled period without orogenic load, while the Cerro Lisandro Formation was deposited in early underfilled conditions with orogenic load. The Río Neuquén Subgroup started with a late underfilled period (Portezuelo Formation -second-order discontinuity), and after wards the Plottier Formation was deposited in an overfilled period without orogenic load. Finally, the Río Colorado Subgroup was deposited under late and early underfilled conditions (Bajo de la Carpa and Anacleto Formations respectively).

  19. Benthic foraminifera at the Cretaceous-Tertiary boundary around the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Alegret, Laia; Molina, Eustoquio; Thomas, Ellen

    2001-10-01

    Cretaceous-Tertiary (K-T) boundary sections in northeastern Mexico contain marly formations separated by a controversial clastic unit. Benthic foraminifera in seven sections indicate middle and lower bathyal depths of deposition for the marls, with the exception of the upper bathyal northernmost section. Mixed neritic-bathyal faunas were present in the clastic unit, indicating redeposition in the deep basin by mass-wasting processes resulting from the K-T bolide impact in the Gulf of Mexico. Benthic foraminifera in the Mexican sections, and at other deep-sea locations, were not subject to major extinction at the time of impact, but there were temporary changes in assemblage composition. Benthic faunas indicate well- oxygenated bottom waters and mesotrophic conditions during the late Maastrichtian and increased food supply during the latest Maastrichtian. The food supply decreased drastically just after the K-T boundary, possibly because of the collapse of surface productivity. Cretaceous and early Paleogene benthic foraminifera, however, did not exhibit the benthic-pelagic coupling of present-day faunas, as documented by the lack of significant extinction at the K-T collapse of surface productivity. Much of the food supplied to the benthic faunas along this continental margin might have been refractory material transported from land or shallow coastal regions. The decrease in food supply at the K-T boundary might be associated with the processes of mass wasting, which removed surface, food-rich sediment. Benthic faunas show a staggered pattern of faunal recovery in the lowermost Paleogene, consistent with a staged recovery of the vertical organic flux but also with a gradual buildup of organic matter in the sediment.

  20. The Cretaceous/Paleogene Transition on the East Tasman Plateau, Southwestern Pacific

    NASA Technical Reports Server (NTRS)

    Schellenberg, Stephen A.; Brinkhuis, Henk; Stickley, Catherine E.; Fuller, Michael; Kyte, Frank T.; Williams, Graham L.

    2004-01-01

    Ocean Drilling Program Leg 189 recovered a potentially complete shallow marine record of the Cretaceous-Paleogene boundary (KPB) at Site 1172 on the East Tasman Plateau. Here we present high-resolution (cm-scale) data from micropaleontology, geochemistry, sedimentology, and paleomagnetism that provide no evidence for a complete KPB, but instead suggest a boundary-spanning hiatus of at least 0.8 Ma. We interpret this hiatus to represent the sequence boundary between the uppermost Maastrichtian Tal.1 and lowermost Danian Ta1.2/ Da- 1 3rd-order sequence stratigraphic cycles. Microfloral assemblages indicate generally shallow paleodepths, restricted circulation, and eutrophic conditions through the section. Paleodepths progressively shallow through the late Maastrichtian, while more oceanic and warmer conditions dominate the early Danian. The Site 1172 KPB section is broadly comparable to other southern highlatitude sections in Antarctica and New Zealand, but appears to record a shallower and more restricted environment that permitted a eustatically-driven hiatus across the KPB mass extinction event.

  1. Sedimentology and sequence stratigraphy from outcrops of the Kribi-Campo sub-basin: Lower Mundeck Formation (Lower Cretaceous, southern Cameroon)

    NASA Astrophysics Data System (ADS)

    Ntamak-Nida, Marie Joseph; Bourquin, Sylvie; Makong, Jean-Claude; Baudin, François; Mpesse, Jean Engelbert; Ngouem, Christophe Itjoko; Komguem, Paul Bertrand; Abolo, Guy Martin

    2010-08-01

    The Kribi-Campo sub-basin is composed of an Early to Mid Cretaceous series from West Africa's Atlantic coast and is located in southern Cameroon in the Central African equatorial rain forest. It is the smallest coastal basin in Cameroon and forms the southern part of the Douala/Kribi-Campo basin known as Douala basin ( s.l.). Until now, no detailed sedimentological studies have been carried out on the outcrops of this basin located in the Campo area. The aim of this study was to characterise the depositional environments, vertical evolution and tectonic context of these Lower Cretaceous series in order to make a comparison with adjacent basins and replace them in the geodynamic context. Facies analysis of the Lower Mundeck Formation (Lower Cretaceous) indicates the presence of four major, interfigered facies associations, that are inferred to represent elements of an alluvial to lacustrine-fan delta system. The clast lithologies suggest proximity of relief supplying coarse-grained sediment during the deposition of the Lower Mundeck Formation at Campo. The general dip and direction of the bedding is approximately 10°-12°NW, which also corresponds to the orientation of the foliations in the underlying metamorphic basement. The main sedimentary succession is characterised by a major retrogradational/progradational cycle of Late Aptian age, evaluated at about 3 Ma, with a well-developed progradational trend characterised by fluctuations of the recognised depositional environments. Fluctuations in lake level and sediment supply were possibly controlled by active faults at the basin margin, although climatic changes may have also played a role. The consistently W-WNW palaeoflow of sediments suggests that the palaeorelief was located to the east and could be oriented in a NNE-SSW direction, downthrown to the west. Local outcrops dated as Albian, both north and south of the main outcrop, display some marine influence. These deposits are cut by 040-060 faults parallel to

  2. Comparative burial and thermal history of lower Upper Cretaceous strata, Powder River basin, Wyoming

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nuccio, V.F.

    1989-03-01

    Burial histories were reconstructed for three localities in the Powder River basin (PRB), Wyoming. Thermal maturity of lower Upper Cretaceous source rocks was determined by vitrinite reflectance (R/sub m/) and time-temperature index (TTI) modeling, producing independent estimates for timing of the oil window (0.55-1.35% R/sub m/). In the northwestern PRB, lower Upper Cretaceous rocks were buried to about 12,500 ft and achieved a thermal maturity of 0.50% to 0.56% at maximum burial, 10 Ma, based on measured R/sub m/. TTI modeling suggests a slightly higher thermal maturity, with an R/sub m/ equivalent of approximately 0.75%, placing the source rocks atmore » the beginning of the oil window 30 Ma. In the southwestern PRB, lower Upper Cretaceous rocks have been buried to about 15,000 ft and achieved thermal maturities between 0.66% and 0.75% about 10 Ma based on measured R/sub m/; therefore, petroleum generation may have begun slightly earlier. TTI modeling estimates an R/sub m/ equivalent of 1.10%, placing the beginning of the oil window at 45 Ma. In the northeastern PRB, lower Upper Cretaceous rocks have been buried only to approximately 5500 ft. Measured R/sub m/ and TTI modeling indicate a thermal maturity for lower Upper Cretaceous rocks between 0.45% and 0.50% R/sub m/, too low for petroleum generation. The higher R/sub m/ values determined by the TTI models may be due to overestimation of maximum burial depth and/or paleogeothermal gradients. The two independent maturity indicators do, however, constrain fairly narrowly the onset of petroleum generation.« less

  3. Leaf economic traits from fossils support a weedy habit for early angiosperms.

    PubMed

    Royer, Dana L; Miller, Ian M; Peppe, Daniel J; Hickey, Leo J

    2010-03-01

    Many key aspects of early angiosperms are poorly known, including their ecophysiology and associated habitats. Evidence for fast-growing, weedy angiosperms comes from the Early Cretaceous Potomac Group, where angiosperm fossils, some of them putative herbs, are found in riparian depositional settings. However, inferences of growth rate from sedimentology and growth habit are somewhat indirect; also, the geographic extent of a weedy habit in early angiosperms is poorly constrained. Using a power law between petiole width and leaf mass, we estimated the leaf mass per area (LMA) of species from three Albian (110-105 Ma) fossil floras from North America (Winthrop Formation, Patapsco Formation of the Potomac Group, and the Aspen Shale). All LMAs for angiosperm species are low (<125 g/m(2); mean = 76 g/m(2)) but are high for gymnosperm species (>240 g/m(2); mean = 291 g/m(2)). On the basis of extant relationships between LMA and other leaf economic traits such as photosynthetic rate and leaf lifespan, we conclude that these Early Cretaceous landscapes were populated with weedy angiosperms with short-lived leaves (<12 mo). The unrivalled capacity for fast growth observed today in many angiosperms was in place by no later than the Albian and likely played an important role in their subsequent ecological success.

  4. Explosive radiation of Malpighiales supports a mid-cretaceous origin of modern tropical rain forests.

    PubMed

    Davis, Charles C; Webb, Campbell O; Wurdack, Kenneth J; Jaramillo, Carlos A; Donoghue, Michael J

    2005-03-01

    Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, provide new tests of these hypotheses. We estimate that all 28 major lineages (i.e., traditionally recognized families) within this clade originated in tropical rain forest well before the Tertiary, mostly during the Albian and Cenomanian (112-94 Ma). Their rapid rise in the mid-Cretaceous may have resulted from the origin of adaptations to survive and reproduce under a closed forest canopy. This pattern may also be paralleled by other similarly diverse lineages and supports fossil indications that closed-canopy tropical rain forests existed well before the K/T boundary. This case illustrates that dated phylogenies can provide an important new source of evidence bearing on the timing of major environmental changes, which may be especially useful when fossil evidence is limited or controversial.

  5. Taxonomic Composition and Trophic Structure of the Continental Bony Fish Assemblage from the Early Late Cretaceous of Southeastern Morocco

    PubMed Central

    Cavin, Lionel; Boudad, Larbi; Tong, Haiyan; Läng, Emilie; Tabouelle, Jérôme; Vullo, Romain

    2015-01-01

    The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to ‘Stromerichthys’ from coeval deposits in Egypt. The ginglymodians were diversified with a large ‘Lepidotes’ plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa. PMID:26018561

  6. Taxonomic composition and trophic structure of the continental bony fish assemblage from the early late cretaceous of Southeastern Morocco.

    PubMed

    Cavin, Lionel; Boudad, Larbi; Tong, Haiyan; Läng, Emilie; Tabouelle, Jérôme; Vullo, Romain

    2015-01-01

    The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to 'Stromerichthys' from coeval deposits in Egypt. The ginglymodians were diversified with a large 'Lepidotes' plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

  7. The evolution of a Gondwanan collisional orogen: A structural and geochronological appraisal from the Southern Granulite Terrane, South India

    NASA Astrophysics Data System (ADS)

    Plavsa, Diana; Collins, Alan S.; Foden, John D.; Clark, Chris

    2015-05-01

    Gondwana amalgamated along a suite of Himalayan-scale collisional orogens, the roots of which lace the continents of Africa, South America, and Antarctica. The Southern Granulite Terrane of India is a generally well-exposed, exhumed, Gondwana-forming orogen that preserves a record of the tectonic evolution of the eastern margin of the East African Orogen during the Ediacaran-Cambrian (circa 600-500 Ma) as central Gondwana formed. The deformation associated with the closure of the Mozambique Ocean and collision of the Indian and East African/Madagascan cratonic domains is believed to have taken place along the southern margin of the Salem Block (the Palghat-Cauvery Shear System, PCSS) in the Southern Granulite Terrane. Investigation of the structural fabrics and the geochronology of the high-grade shear zones within the PCSS system shows that the Moyar-Salem-Attur shear zone to the north of the PCSS system is early Paleoproterozoic in age and associated with dextral strike-slip motion, while the Cauvery shear zone (CSZ) to the south of the PCSS system can be loosely constrained to circa 740-550 Ma and is associated with dip-slip dextral transpression and north side-up motion. To the south of the proposed suture zone (the Cauvery shear zone), the structural fabrics of the Northern Madurai Block suggest four deformational events (D1-D4), some of which are likely to be contemporaneous. The timing of high pressure-ultrahigh temperature metamorphism and deformation (D1-D3) in the Madurai Block (here interpreted as the southern extension of Azania) is constrained to circa 550-500 Ma and interpreted as representing collisional orogeny and subsequent orogenic collapse of the eastern margin of the East African Orogen. The disparity in the nature of the structural fabrics and the timing of the deformation in the Salem and the Madurai Blocks suggest that the two experienced distinct tectonothermal events prior to their amalgamation along the Cauvery shear zone during the

  8. Mummified precocial bird wings in mid-Cretaceous Burmese amber

    PubMed Central

    Xing, Lida; McKellar, Ryan C.; Wang, Min; Bai, Ming; O'Connor, Jingmai K.; Benton, Michael J.; Zhang, Jianping; Wang, Yan; Tseng, Kuowei; Lockley, Martin G.; Li, Gang; Zhang, Weiwei; Xu, Xing

    2016-01-01

    Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans. PMID:27352215

  9. Mummified precocial bird wings in mid-Cretaceous Burmese amber.

    PubMed

    Xing, Lida; McKellar, Ryan C; Wang, Min; Bai, Ming; O'Connor, Jingmai K; Benton, Michael J; Zhang, Jianping; Wang, Yan; Tseng, Kuowei; Lockley, Martin G; Li, Gang; Zhang, Weiwei; Xu, Xing

    2016-06-28

    Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans.

  10. Mid-Cretaceous transtension in the Canadian Cordillera: Evidence from the Rocky Ridge volcanics of the Skeena Group

    NASA Astrophysics Data System (ADS)

    Bassett, Kari N.; Kleinspehn, Karen L.

    1996-08-01

    The age relations, geochemistry, and sedimentology of the Rocky Ridge Formation of the Skeena Group are used to test competing tectonic reconstructions for the mid-Cretaceous Canadian Cordillera as well as the timing and location of the accretion of the Insular Superterrane. Pollen and macrofossil assemblages indicate that these intrabasinal basalts were erupted along the southern margin of the Bowser basin in the Early Albian to Early Cenomanian. Single-crystal fusion and step-heating 40Ar/39Ar dating of hornblendes in one basalt flow from the uppermost part of the formation yielded Middle Cenomanian ages of 94.3 ± 0.4, 95.6 ± 1.6, and 95.0 ± 1.6 Ma. Vesicular basalt flows interbedded with crystal-rich tuff breccias contain evidence for hot emplacement as pyroclastic flows. Individual eruptive centers are identified by their proximal facies, paleoflow indicators within the lava flows, paleoflow indicators within interbedded volcaniclastic fluvial deposits, geochemical differences, and geographic isolation of volcanic deposits. Major and trace-element geochemistry from 20 sampled lava flows indicates an alkali basalt composition for the volcanics. The basalts of the northern Rocky Ridge volcanic center show enrichment of light rare earth and large ion lithophile elements with strong negative Nb-Ta anomalies whereas the basalts of the southern Tahtsa Lake volcanic center show depletion to slight enrichment of light rare earth elements, slight enrichment of large ion lithophile elements with minimal negative Nb-Ta anomalies. The geochemistry combined with paleogeographic and regional tectonic reconstruction suggests a continental arc setting with intraarc extension. The presence of deeper marine facies to the west and the lack of a western sediment source in the Skeena Group indicate that the technically active Insular Superterrane was not west of the study area during mid-Cretaceous time. Thus we reconsider the Omineca Belt as the main axis of a mid-Cretaceous

  11. Dinosaur tracks from the Cedar Mountain Formation (Lower Cretaceous), Arches National Park, Utah

    USGS Publications Warehouse

    Lockley, Martin G.; White, Diane K.; Kirkland, James I.; Santucci, Vincent L.

    2004-01-01

    The seventh and largest known dinosaur tracksite from the Cedar Mountain Formation is reported from two important stratigraphic levels in the Ruby Ranch Member within the boundaries of Arches National Park. Previous reports of sites with a few isolated tracks are of limited utility in indicating the fauna represented by track makers. The Arches site reveals evidence of several theropod morphotypes, including a possible match for the coelurosaur Nedcolbertia and an apparently didactyl Utahraptor-like dromeosaurid. Sauropod tracks indicate a wide-gauge morphotype (cf. Brontopodus). Ornithischian tracks suggest the presence of an iguandontid-like ornithopod and a large ankylosaur. Dinosaur track diversity is high in comparison with other early Cretaceous vertebrate ichnofaunas, and it correlates well with faunal lists derived from skeletal remains, thus providing a convincing census of the known fauna.

  12. A Cretaceous eutriconodont and integument evolution in early mammals.

    PubMed

    Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D

    2015-10-15

    The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

  13. Genesis of late Early Cretaceous high-silica rhyolites in eastern Zhejiang Province, southeast China: A crystal mush origin with mantle input

    NASA Astrophysics Data System (ADS)

    Zhang, Ji-Heng; Yang, Jin-Hui; Chen, Jing-Yuan; Wu, Fu-Yuan; Wilde, Simon A.

    2018-01-01

    Voluminous Mesozoic felsic volcanic rocks and granites in southeastern China provide a unique opportunity for studying the role of crustal magmatism in the evolution and modification of the crust in the eastern Cathaysia Block. The high-silica rhyolites of the upper volcanic sequence in eastern Zhejiang Province were investigated, focusing on their genesis and their relationship with contemporaneous granites. Rhyolites in the Tiantai, Yongkang and Liucheng basins were dated as late Early Cretaceous (from 111 Ma to 106 Ma in age). These rocks contain a large proportion of inherited zircons of ca. 130 Ma, corresponding to the age of the lower volcanic sequence in the area. However, the zircons of different ages have similar ranges of oxygen and Hf isotopes, implying similarities in the magmas from which they were generated. The rhyolites of the upper sequence also resemble those of the lower sequence in terms of their geochemistry. It is concluded that the former were derived by reworking of magma mush formed during the earlier magmatic episode via fractionation of feldspars and accessory minerals, e.g., zircon. Fractionation took place within the magma crystal mush by extraction of interstitial melts and accumulation of residual mineral phases, aided by the emplacement of contemporaneous basaltic magmas at the base of the crust. Overall, the geochemical features of the volcanic rocks in southeastern China indicate that episodic magmatism and reworking of crystal mush were essential mechanisms that drove the evolution of the igneous rocks and the hence crustal architecture in this area.

  14. Nonexplosive and explosive magma/wet-sediment interaction during emplacement of Eocene intrusions into Cretaceous to Eocene strata, Trans-Pecos igneous province, West Texas

    USGS Publications Warehouse

    Befus, K.S.; Hanson, R.E.; Miggins, D.P.; Breyer, J.A.; Busbey, A.B.

    2009-01-01

    Eocene intrusion of alkaline basaltic to trachyandesitic magmas into unlithified, Upper Cretaceous (Maastrichtian) to Eocene fluvial strata in part of the Trans-Pecos igneous province in West Texas produced an array of features recording both nonexplosive and explosive magma/wet-sediment interaction. Intrusive complexes with 40Ar/39Ar dates of ~ 47-46??Ma consist of coherent basalt, peperite, and disrupted sediment. Two of the complexes cutting Cretaceous strata contain masses of conglomerate derived from Eocene fluvial deposits that, at the onset of intrusive activity, would have been > 400-500??m above the present level of exposure. These intrusive complexes are inferred to be remnants of diatremes that fed maar volcanoes during an early stage of magmatism in this part of the Trans-Pecos province. Disrupted Cretaceous strata along diatreme margins record collapse of conduit walls during and after subsurface phreatomagmatic explosions. Eocene conglomerate slumped downward from higher levels during vent excavation. Coherent to pillowed basaltic intrusions emplaced at the close of explosive activity formed peperite within the conglomerate, within disrupted Cretaceous strata in the conduit walls, and within inferred remnants of the phreatomagmatic slurry that filled the vents during explosive volcanism. A younger series of intrusions with 40Ar/39Ar dates of ~ 42??Ma underwent nonexplosive interaction with Upper Cretaceous to Paleocene mud and sand. Dikes and sills show fluidal, billowed, quenched margins against the host strata, recording development of surface instabilities between magma and groundwater-rich sediment. Accentuation of billowed margins resulted in propagation of intrusive pillows into the adjacent sediment. More intense disruption and mingling of quenched magma with sediment locally produced fluidal and blocky peperite, but sufficient volumes of pore fluid were not heated rapidly enough to generate phreatomagmatic explosions. This work suggests that

  15. Exhumation of the Cordillera de Domeyko: Implications for Andean retroarc evolution between the Late Cretaceous and the Oligocene

    NASA Astrophysics Data System (ADS)

    Henriquez, S.; Carrapa, B.; DeCelles, P. G.

    2017-12-01

    In Cordilleran-type orogens, exhumation of the thrust belt records the kinematic history of the orogenic system. In the Central Andes, the widest and thickest part of this orogen, several authors have documented the exhumation of the thrust belt in the modern forearc (Chile) and retroarc region (Bolivia and Argentina) showing an overall eastward propagation of deformation since the late Eocene. However, the exhumation of earlier Andean retroarc tectonic events remains poorly documented. In the forearc, the Cordillera de Domeyko and Salar de Atacama basin exhibit multiple pieces of evidence for earlier Andean orogenesis. The goal of this study is to document the thermal record of Late Cretaceous to Eocene retroarc deformation. To this end, this study investigates the cooling history of the easternmost basement uplift of the Cordillera de Domeyko. We couple this record with detrital thermochronology from cobbles in the Late Cretaceous to Miocene sedimentary units from the Salar de Atacama basin which records the unroofing history of this uplift. We employed a multi-dating approach combining apatite fission track (AFT) and apatite (U-Th-Sm)/He (AHe) thermochronology to constrain the timing and amount of exhumation in the early Andean retroarc region. Our results show episodic cooling ca. 90-80, 65-60 and 45-40 Ma. This new data provides a thermochronologic record of Late Cretaceous and Paleocene deformation in the retroarc region as well as of the widely recognized Eocene deformation event. The cooling signal is interpreted to reflect exhumation controlled by uplift and erosion in the retroarc region. These exhumation events reflect episodes of internal deformation, crustal thickening, and roughly similar amounts of local erosion. Exhumation in this region decreased by the late Oligocene; by this time the orogenic front was established to the east, in the Eastern Cordillera.

  16. Biostratigraphic data for the Cretaceous marine sediments in the USGS-St. George no. 1 core (DOR-211), Dorchester County, South Carolina

    USGS Publications Warehouse

    Self-Trail, Jean M.; Gohn, Gregory S.

    1997-01-01

    The USGS-St. George corehole was drilled for the U.S. Geological Survey (USGS) by a commercial drilling company during 1982. The corehole is located within the Coastal Plain Province in northern Dorchester County, South Carolina, about three miles southeast of the town of St. George near the village of Byrd (fig. 1). Coordinates for the corehole are 33o09'25'N latitude and 80o31'18'W longitude; ground elevation at the site is +78 feet (Reid and others, 1986). The St. George corehole is designated as USGS drill hole DOR-211. The St. George corehole was drilled to a total depth of 2,067 ft. The hole was cored continuously with generally good recovery from 300 ft to its total depth. Spot cores were taken at selected intervals between the top of the hole and a depth of 300 ft (50-55 ft, 100-110 ft, 150-165 ft, 200-205 ft, and 250-255 ft); however, recovery was poor in most of these intervals. The St. George core currently is stored at the USGS National Center, Reston, VA (March, 1997). The St. George corehole bottomed in basalt of probable early Mesozoic age beneath an Upper Cretaceous and Cenozoic sedi-mentary section. Reid and others (1986) placed the top of basalt saprolite at 1,962 ft in the hole. Our examination of the geophysical logs and original core descriptions suggests that the top of the saprolite is higher in the hole, at about 1,939 ft. The Cretaceous-Tertiary boundary was placed at or near 550 ft in the core by Reid and others (1986) and by Habib and Miller (1989). In this report, we provide paleontologic data for marine sediments in the upper part of the Upper Cretaceous section in the St. George core. Biostratigraphic and paleoenvironmental data and interpretations based on the study of calcareous nannofossils and ostracodes from the Cretaceous section are discussed.

  17. Evidence for global cooling in the Late Cretaceous

    PubMed Central

    Linnert, Christian; Robinson, Stuart A.; Lees, Jackie A.; Bown, Paul R.; Pérez-Rodríguez, Irene; Petrizzo, Maria Rose; Falzoni, Francesca; Littler, Kate; Arz, José Antonio; Russell, Ernest E.

    2014-01-01

    The Late Cretaceous ‘greenhouse’ world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the Campanian–Maastrichtian interval (~83–66 Ma) from hemipelagic sediments deposited on the western North Atlantic shelf. Our record reveals that the North Atlantic at 35 °N was relatively warm in the earliest Campanian, with maximum SSTs of ~35 °C, but experienced significant cooling (~7 °C) after this to <~28 °C during the Maastrichtian. The overall stratigraphic trend is remarkably similar to records of high-latitude SSTs and bottom-water temperatures, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by declining atmospheric pCO2 levels. PMID:24937202

  18. Cenozoic crustal shortening between the Pamir and Tien Shan and a reconstruction of the Pamir Tien Shan transition zone for the Cretaceous and Palaeogene

    NASA Astrophysics Data System (ADS)

    Burtman, V. S.

    2000-03-01

    The magnitude of the Late Cenozoic crustal shortening during convergence of the Pamir and Tien Shan was determined using a contemporary pattern consisting of facies zones, palaeomagnetic data (regarding the rotation of tectonic units) and data on the structure of the Tadjik Depression. By Late Cenozoic, Cretaceous and Palaeogene facies zones were cut by the Vakhsh-Trans-Alay overthrust and Darvaz strike-slip faults and a significant part of the Cretaceous-Palaeogene Tadjik Basin was overthrust by the Pamir massif. The sediments of easternmost part of the basin are preserved in the Tarim Depression. The facies zones of the southern slope of the Afghan-Tadjik Basin were deformed and moved northward. A pattern of facies zones indicates a convergence between the Pamir and Tien Shan over a distance of 300-400 km. A number of cross-sections through the Tadjik Depression were used to establish the structure before folding. A rotation of tectonic units, indicated by structural data, conforms to the angles of rotation as determined in palaeomagnetic studies. The data suggest 300 km of convergence between the Pamir and Tien Shan. Stratigraphic, lithological, structural and palaeomagnetic data formed the basis for the construction of the palinspastically-restored palaeogeographic and sedimentologic environments for the Tadjik shallow sea basin which was situated between the Pamir and Tien Shan before their convergence in the Late Cenozoic. The maps were constructed for the eight stratigraphic levels of the Cretaceous and Palaeogene. The Tadjik Sea was a bay in the enormous Turan Sea. In the Early Aptian this bay was located in what is now the Afghan-Tadjik Basin. In Late Cretaceous, the eastern shore of the bay lay 600-700 km further eastward and in the Eocene, marine environments extended even further eastward but after the Rupelian continental environments occupied all of this region.

  19. Stratigraphy and sedimentology of the Upper Cretaceous (Campanian) Anacacho Limestone, Texas, USA

    USGS Publications Warehouse

    Swezey, C.S.; Sullivan, E.C.

    2004-01-01

    The Upper Cretaceous Anacacho Limestone is exposed in outcrops between the cities of San Antonio and Del Rio, Texas. A detailed study of four outcrops (Blanco Creek section, Sabinal River section, Seco Creek section, Hondo Creek section) shows that the Anacacho Limestone rests on the Upson Clay (which contains fauna of early Campanian age) and is overlain by the Corsicana Marl (which contains fauna of early Maastrichtian age). An unconformity within the Anacacho Limestone is used herein to separate the limestone into a lower member and an upper member. The lower Anacacho member contains fauna of early Campanian age, whereas the upper Anacacho member contains fauna of middle Campanian age. The lower Anacacho member consists predominantly of wackestones to packstones, which are overlain by packstones to grainstones capped by the unconformity. This unconformity is interpreted as a marine flooding surface, delineating a transition from carbonate grainstones deposited in shallow water (<30 m depth) to a chalk deposited in deeper water. Above the unconformity, the upper Anacacho member is characterized by a chalk, overlain by wackestones and packstones. The uppermost section of the Anacacho Limestone consists of packstones and grainstones with abundant and diverse fossils. Most of the Anacacho Limestone developed in relatively shallow water (<50 m depth) leeward of a large carbonate build-up (possibly a rudistid reef) that now comprises the Anacacho Mountains. The environment, however, was open to marine water throughout deposition of the Anacacho Limestone. ?? 2004 Elsevier Ltd. All rights reserved.

  20. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs.

    PubMed

    Lockley, Martin G; McCrea, Richard T; Buckley, Lisa G; Lim, Jong Deock; Matthews, Neffra A; Breithaupt, Brent H; Houck, Karen J; Gierliński, Gerard D; Surmik, Dawid; Kim, Kyung Soo; Xing, Lida; Kong, Dal Yong; Cart, Ken; Martin, Jason; Hadden, Glade

    2016-01-07

    Relationships between non-avian theropod dinosaurs and extant and fossil birds are a major focus of current paleobiological research. Despite extensive phylogenetic and morphological support, behavioural evidence is mostly ambiguous and does not usually fossilize. Thus, inferences that dinosaurs, especially theropods displayed behaviour analogous to modern birds are intriguing but speculative. Here we present extensive and geographically widespread physical evidence of substrate scraping behavior by large theropods considered as compelling evidence of "display arenas" or leks, and consistent with "nest scrape display" behaviour among many extant ground-nesting birds. Large scrapes, up to 2 m in diameter, occur abundantly at several Cretaceous sites in Colorado. They constitute a previously unknown category of large dinosaurian trace fossil, inferred to fill gaps in our understanding of early phases in the breeding cycle of theropods. The trace makers were probably lekking species that were seasonally active at large display arena sites. Such scrapes indicate stereotypical avian behaviour hitherto unknown among Cretaceous theropods, and most likely associated with terrirorial activity in the breeding season. The scrapes most probably occur near nesting colonies, as yet unknown or no longer preserved in the immediate study areas. Thus, they provide clues to paleoenvironments where such nesting sites occurred.

  1. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs

    NASA Astrophysics Data System (ADS)

    Lockley, Martin G.; McCrea, Richard T.; Buckley, Lisa G.; Deock Lim, Jong; Matthews, Neffra A.; Breithaupt, Brent H.; Houck, Karen J.; Gierliński, Gerard D.; Surmik, Dawid; Soo Kim, Kyung; Xing, Lida; Yong Kong, Dal; Cart, Ken; Martin, Jason; Hadden, Glade

    2016-01-01

    Relationships between non-avian theropod dinosaurs and extant and fossil birds are a major focus of current paleobiological research. Despite extensive phylogenetic and morphological support, behavioural evidence is mostly ambiguous and does not usually fossilize. Thus, inferences that dinosaurs, especially theropods displayed behaviour analogous to modern birds are intriguing but speculative. Here we present extensive and geographically widespread physical evidence of substrate scraping behavior by large theropods considered as compelling evidence of “display arenas” or leks, and consistent with “nest scrape display” behaviour among many extant ground-nesting birds. Large scrapes, up to 2 m in diameter, occur abundantly at several Cretaceous sites in Colorado. They constitute a previously unknown category of large dinosaurian trace fossil, inferred to fill gaps in our understanding of early phases in the breeding cycle of theropods. The trace makers were probably lekking species that were seasonally active at large display arena sites. Such scrapes indicate stereotypical avian behaviour hitherto unknown among Cretaceous theropods, and most likely associated with terrirorial activity in the breeding season. The scrapes most probably occur near nesting colonies, as yet unknown or no longer preserved in the immediate study areas. Thus, they provide clues to paleoenvironments where such nesting sites occurred.

  2. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behaviour by Cretaceous dinosaurs

    PubMed Central

    Lockley, Martin G.; McCrea, Richard T.; Buckley, Lisa G.; Deock Lim, Jong; Matthews, Neffra A.; Breithaupt, Brent H.; Houck, Karen J.; Gierliński, Gerard D.; Surmik, Dawid; Soo Kim, Kyung; Xing, Lida; Yong Kong, Dal; Cart, Ken; Martin, Jason; Hadden, Glade

    2016-01-01

    Relationships between non-avian theropod dinosaurs and extant and fossil birds are a major focus of current paleobiological research. Despite extensive phylogenetic and morphological support, behavioural evidence is mostly ambiguous and does not usually fossilize. Thus, inferences that dinosaurs, especially theropods displayed behaviour analogous to modern birds are intriguing but speculative. Here we present extensive and geographically widespread physical evidence of substrate scraping behavior by large theropods considered as compelling evidence of “display arenas” or leks, and consistent with “nest scrape display” behaviour among many extant ground-nesting birds. Large scrapes, up to 2 m in diameter, occur abundantly at several Cretaceous sites in Colorado. They constitute a previously unknown category of large dinosaurian trace fossil, inferred to fill gaps in our understanding of early phases in the breeding cycle of theropods. The trace makers were probably lekking species that were seasonally active at large display arena sites. Such scrapes indicate stereotypical avian behaviour hitherto unknown among Cretaceous theropods, and most likely associated with terrirorial activity in the breeding season. The scrapes most probably occur near nesting colonies, as yet unknown or no longer preserved in the immediate study areas. Thus, they provide clues to paleoenvironments where such nesting sites occurred. PMID:26741567

  3. Global fire at the Cretaceous-Tertiary boundary

    NASA Technical Reports Server (NTRS)

    Wolbach, Wendy S.; Gilmour, Iain; Anders, Edward; Orth, Charles J.; Brooks, Robert R.

    1988-01-01

    Cretaceous-Tertiary boundary clays rich in iridium from five sites in Europe and New Zealand were investigated. The clays are found to be 100-10,000-fold-enriched in elemental carbon (mainly soot), which is isotopically uniform and apparently comes from a single global fire. The soot layer coincides with the iridium layer, suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled.

  4. Major wildfires at the Cretaceous-Tertiary boundary

    NASA Technical Reports Server (NTRS)

    Anders, Edward; Wolbach, Wendy S.; Gilmour, Iain

    1991-01-01

    The current status of the reconstruction of major biomass fire events at the Cretaceous-Tertiary boundary is discussed. Attention is given to the sources of charcoal and soot, the identification of biomass and fossil carbon, and such ignition-related problems as delated fires, high atmospheric O2 content, ignition mechanisms, and the greenhouse-effect consequences of fire on the scale envisioned. Consequences of these factors for species extinction patterns are noted.

  5. ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

    NASA Astrophysics Data System (ADS)

    Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.

    2014-12-01

    The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as

  6. The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle

    USGS Publications Warehouse

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

    2002-01-01

    A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining

  7. Press/Pulse: Explaining selective terrestrial extinctions at the Cretaceous/Palaeogene boundary

    NASA Astrophysics Data System (ADS)

    Arens, Nan Crystal

    2010-05-01

    Single-cause mass extinction scenarios require extreme conditions to generate sufficiently strong kill mechanisms. Such dire effects are commonly at odds with the taxonomic selectivity that characterizes most extinction events. In response, some researchers have proposed that the interaction of a variety of factors typify episodes of elevated extinction. Previous work (Arens & West 2008 Paleobiology 34:456-471) has shown that a combination of press and pulse disturbances increases the probability of elevated extinction. The press/pulse contrast is borrowed from community ecology, where researchers have long recognized that the ecological response to long-term stress differs from that of an instantaneous catastrophe. Scaled to the macroevolutionary level, press disturbances alter community composition by placing multigenerational stress on populations. Press disturbances do not necessarily cause mortality, but reduce population size by a variety of mechanisms such as curtailed reproduction. Pulse disturbances are sudden catastrophic events that cause extensive mortality. Either press or pulse disturbances of sufficient magnitude can cause extinction, however elevated extinction occurs more commonly during the coincidence of lower-magnitude press and pulse events. The Cretaceous/Palaeogene (K/P) extinction is one of the best examples of a press/pulse extinction. Deccan Trap volcanism, which straddled the K/P boundary, altered atmospheric composition and climate. This episodic volcanism likely contributed to the climate instability observed in terrestrial ecosystems and exerted press stress. Pulse disturbance was produced by bolide impact, which punctuated the end of the Cretaceous. The press/pulse mechanism also more effectively explains selectivity in terrestrial vertebrate and plant extinctions at the K/P boundary than do single-mechanisms scenarios. For example, why do environmentally sensitive vertebrates such as amphibians experience no extinction? And why do

  8. Interactions between tectonics, climate and vegetation during the Cretaceous. A context for the diversification of Angiosperms.

    NASA Astrophysics Data System (ADS)

    Sepulchre, Pierre; Chaboureau, Anne-Claire; Donnadieu, Yannick; Franc, Alain; Ladant, Jean-Baptiste

    2017-04-01

    It has long been thought that the Angiosperms diversification occurred within a context of warmer-than-present and equable climate during the Cretaceous. However, during the last decade, the view of a uniformely warm Cretaceous climate has been challenged both by paleoclimate proxies and numerical simulations. Among the processes likely affecting climate during this time, atmospheric pCO2 and tectonics appear to be pivotal to drive temperature and precipitation changes, while the feedbacks from vegetation cover changes on the hydrological cycles remain to be explored. Here we attempt to provide a review of the main studies exploring climate-vegetation interactions during the Cretaceous. Then we present climate simulations aiming at quantifying the impact of landmasses redistribution on climate and vegetation distribution from 225 Ma to 70 Ma. In our simulations, the Pangea breakup triggers the decrease of arid belts from the Triassic to the Cretaceous and a subsequent onset of humid conditions during the late Cretaceous. Positioning angiosperm-bearing fossil sites on our paleo-bioclimatic maps confirm that the rise of flowering plants occured within a context of changing climate. With additional simulations in which we modified physiological parameterizations of the vegetation, we explore the combined impact of paleogeography and shift to angiosperms-dominated land surfaces on climate at the regional and global scales. This gives us the opportunity to test earlier ideas that the angiosperms takeover could have benefited from a positive feedback induced by their particular transpiration capacities.

  9. A Gigantic Shark from the Lower Cretaceous Duck Creek Formation of Texas

    PubMed Central

    Frederickson, Joseph A.; Schaefer, Scott N.; Doucette-Frederickson, Janessa A.

    2015-01-01

    Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous. PMID:26039066

  10. Chronostratigraphic cross section of Cretaceous formations in western Montana, western Wyoming, eastern Utah, northeastern Arizona, and northwestern New Mexico, U.S.A.

    USGS Publications Warehouse

    Merewether, E. Allen; McKinney, Kevin C.

    2015-01-01

    In this transect for time-stratigraphic units of the Cretaceous, lateral changes in lithologies, regional differences in thicknesses, and the abundance of associated disconformities possibly reflect local and regional tectonic events. Examples of evidence of those events follow: (1) Disconformities and the absence of strata of lowest Cretaceous age in western Montana, western Wyoming, and northern Utah indicate significant tectonism and erosion probably during the Late Jurassic and earliest Cretaceous; ( 2) stages of Upper Cretaceous deposition in the transect display major lateral changes in thickness, which probably reflect regional and local tectonism.

  11. A new species of Allodaposuchus (Eusuchia, Crocodylia) from the Maastrichtian (Late Cretaceous) of Spain: phylogenetic and paleobiological implications

    PubMed Central

    Blanco, Alejandro; Fortuny, Josep; Vicente, Alba; Luján, Àngel H.; García-Marçà, Jordi Alexis

    2015-01-01

    Background. The Late Cretaceous is a keystone period to understand the origin and early radiation of Crocodylia, the group containing all extant lineages of crocodilians. Among the taxa described from the latest Cretaceous of Europe, the genus Allodaposuchus is one of the most common but also one of the most controversial. However, because of its fragmentary record, several issues regarding its phylogenetic emplacement and its ecology remain unsolved or unknown. The discovery of a single specimen attributed to Allodaposuchus, represented by both cranial and postcranial remains, from the Casa Fabà site (Tremp Basin, NE Spain) in the lower red unit of the Tremp Fm. (early Maastrichtian, Late Cretaceous) offers a unique opportunity to deepen in the phylogenetic relationships of the group and its ecological features. Methods. The specimen is described in detail, and CT scan of the skull is performed in order to study the endocranial morphology as well as paratympanic sinuses configuration. In addition, myological and phylogenetic analyses are also carried out on the specimen for to shed light in ecological and phylogenetic issues, respectively. Results. The specimen described herein represents a new species, Allodaposuchus hulki sp. nov., closely related to the Romanian A. precedens. The CT scan of the skull revealed an unexpected paratympanic sinuses configuration. Allosaposuchus hulki exhibits an “anterodorsal tympanic sinus” not observed in any other extant or extinct crocodilian. The caudal tympanic recesses are extremely enlarged, and the expanded quadratic sinus seems to be connected to the middle-ear channel. Phylogenetic analyses confirm the emplacement of the informal taxonomic group ‘Allodaposuchia’ at the base of Crocodylia, being considered the sister group of Borealosuchus and Planocraniidae. Discussion. Although this is a preliminary hypothesis, the unique paratympanic configuration displayed by A. hulki suggests that it could possess a high

  12. Global Ocean Circulation During Cretaceous Time

    NASA Astrophysics Data System (ADS)

    Haupt, B. J.; Seidov, D.

    2001-12-01

    Present--day global thermohaline ocean circulation (TOC) is usually associated with high--latitude deep-water formation due to surface cooling. In this understanding of the TOC driven by the deep--water production, the warm deep ocean during Mesozoic--Cenozoic time is a challenge. It may be questioned whether warm deep--ocean water, which is direct geologic evidence, does reflect warm polar surface--ocean regions. For the warm Cretaceous, it is difficult to maintain strong poleward heat transport in the case of reduced oceanic thermal contrasts. Usually, atmospheric feedbacks, in conjunction with the increase of atmospheric concentrations of greenhouse gases, are employed in order to explain the warm equable Cretaceous--Eocene climate. However, there is no feasible physical mechanism that could maintain warm subpolar surface oceans in both hemispheres, an assumption often used in atmospheric modeling. Our numerical experiments indicate that having a relatively cool but saltier high--latitude sea surface in at least one hemisphere is sufficient for driving a strong meridional overturning. Thus freshwater impacts in the high latitudes may be responsible for a vigorous conveyor capable of maintaining sufficient poleward oceanic heat transport needed to keep the polar oceans ice--free. These results imply that evaporation-precipitation patterns during warm climates are especially important climatic factors that can redistribute freshwater to create hemispheric asymmetry of sea surface conditions capable of generating a sufficiently strong TOC, otherwise impossible in warm climates.

  13. A new basal hadrosauroid dinosaur from the Late Cretaceous of Uzbekistan and the early radiation of duck-billed dinosaurs.

    PubMed

    Sues, Hans-Dieter; Averianov, Alexander

    2009-07-22

    Levnesovia transoxiana gen. et sp. nov., from the Late Cretaceous (Middle-Late Turonian) of Uzbekistan, is the oldest well-documented taxon referable to Hadrosauroidea sensu Godefroit et al. It differs from a somewhat younger and closely related Bactrosaurus from Inner Mongolia (China) by a tall sagittal crest on the parietals and the absence of club-shaped dorsal neural spines in adult specimens. Levnesovia, Bactrosaurus and possibly Gilmoreosaurus represent the earliest radiation of Hadrosauroidea, which took place during the Cenomanian-Turonian and possibly in North America. The second, Santonian-age radiation of Hadrosauroidea included Aralosaurus, Hadrosauridae and lineages leading to Tanius (Campanian) and Telmatosaurus (Maastrichtian). Hadrosauridae appears to be monophyletic, but Hadrosaurinae and Lambeosaurinae originated in North America and Asia, respectively.

  14. Text to accompany slides/photographs of Lower Cretaceous pollen and spores in sediments from the Muirkirk clay pit (Prince Georges County, MD)

    USGS Publications Warehouse

    Robbins, Eleanora I.

    1991-01-01

    The pollen and spores found in clay beds at the Muirkirk clay pit are those of ferns and lycopods, seed ferns, shrubby conifers, bald cypress-type conifers, and tree-sized conifers. Some of the ferns and conifers have modern representatives which help interpret the vegetation of this site that bears Early Cretaceous dinosaur fossils. The plants, as well as the presence of algae, fungi, and mineral remains of bacteria, show that the site was once a wetland that developed on the clay floor of a waning oxbow lake.

  15. New occurrences of fossilized feathers: systematics and taphonomy of the Santana Formation of the Araripe Basin (Cretaceous), NE, Brazil

    PubMed Central

    Anelli, Luiz Eduardo; Petri, Setembrino; Romero, Guilherme Raffaeli

    2016-01-01

    Here we describe three fossil feathers from the Early Cretaceous Santana Formation of the Araripe Basin, Brazil. Feathers are the most complex multiform vertebrate integuments; they perform different functions, occurring in both avian and non-avian dinosaurs. Despite their rarity, fossil feathers have been found across the world. Most of the Brazilian feather fossil record comes from the Santana Formation. This formation is composed of two members: Crato (lake) and Romualdo (lagoon); both of which are predominantly reduced deposits, precluding bottom dwelling organisms, resulting in exceptional preservation of the fossils. Despite arid and hot conditions during the Cretaceous, life teemed in the adjacency of this paleolake. Feathered non-avian dinosaurs have not yet been described from the Crato Member, even though there are suggestions of their presence in nearby basins. Our description of the three feathers from the Crato laminated limestone reveals that, despite the small sample size, they can be referred to coelurosaurian theropods. Moreover, based on comparisons with extant feather morphotypes they can be identified as one contour feather and two downy feathers. Despite their rareness and low taxonomic potential, fossilized feathers can offer insights about the paleobiology of its owners and the paleoecology of the Araripe Basin. PMID:27441102

  16. Late Cretaceous paleosols as paleoclimate proxies of high-latitude Southern Hemisphere: Mata Amarilla Formation, Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Varela, Augusto N.; Raigemborn, M. Sol; Richiano, Sebastián; White, Tim; Poiré, Daniel G.; Lizzoli, Sabrina

    2018-01-01

    Although there is general consensus that a global greenhouse climate characterized the mid-Cretaceous, details of the climate state of the mid-Cretaceous Southern Hemisphere are less clearly understood. In particular, continental paleoclimate reconstructions are scarce and exclusively derived from paleontological records. Using paleosol-derived climofunction studies of the mid- to Upper Cretaceous Mata Amarilla Formation, southern Patagonia, Argentina, we present a reconstruction of the mid-Cretaceous climate of southern South America. Our results indicate that at 60° south paleolatitude during the Cenomanian-Santonian stages, the climate was subtropical temperate-warm (12 °C ± 2.1 °C) and humid (1404 ± 108 mm/yr) with marked rainfall seasonality. These results are consistent with both previous estimations from the fossil floras of the Mata Amarilla Formation and other units of the Southern Hemisphere, and with the previous observations of the displacement of tropical and subtropical floras towards the poles in both hemispheres. The data presented here show a more marked seasonality and slightly lower mean annual precipitation and mean annual temperature values than those recorded at the same paleolatitudes in the Northern Hemisphere.

  17. Fossils of hydrothermal vent worms from Cretaceous sulfide ores of the Samail ophiolite, Oman

    USGS Publications Warehouse

    Haymon, R.M.; Koski, R.A.; Sinclair, C.

    1984-01-01

    Fossil worm tubes of Cretaceous age preserved in the Bayda massive sulfide deposit of the Samail ophiolite, Oman, are apparently the first documented examples of fossils embedded in massive sulfide deposits from the geologic record. The geologic setting of the Bayda deposit and the distinctive mineralogic and textural features of the fossiliferous samples suggest that the Bayda sulfide deposit and fossil fauna are remnants of a Cretaceous sea-floor hydrothermal vent similar to modern hot springs on the East Pacific Rise and the Juan de Fuca Ridge.

  18. Petrological and zircon evidence for the Early Cretaceous granulite-facies metamorphism in the Dabie orogen, China

    NASA Astrophysics Data System (ADS)

    Gao, Xiao-Ying; Zhang, Qiang-Qiang; Zheng, Yong-Fei; Chen, Yi-Xiang

    2017-07-01

    . The spatial and temporal distribution of Early Cretaceous granulite-facies metamorphic rocks in this region is associated with the bimodal magmatism within a short period of 120-130 Ma in the postcollisional stage. This provides a direct link in petrogenesis between the granulitic, migmatic and magmatic rocks in the collisional orogen to active continental rifting, whereby high heat flow was transferred from the asthenospheric mantle into the thinned orogenic lithosphere for partial melting.

  19. Balancing shortening and extension around the Adriatic Plate to constrain its independent motion and driving forces since Late Cretaceous time.

    NASA Astrophysics Data System (ADS)

    Le Breton, E.; Handy, M.; Ustaszewski, K. M.

    2015-12-01

    thought. This modified motion path for Adria raises the question of what forces drive the motion of Adria; so far, the most likely explanation invokes a combination of trench suction and slab pull along the northern borders of Adria in Late Cretaceous-Paleogene time, transitional to Africa push since Early Miocene time.

  20. Evaluating the use of amber in palaeoatmospheric reconstructions: The carbon-isotope variability of modern and Cretaceous conifer resins

    NASA Astrophysics Data System (ADS)

    Dal Corso, Jacopo; Schmidt, Alexander R.; Seyfullah, Leyla J.; Preto, Nereo; Ragazzi, Eugenio; Jenkyns, Hugh C.; Delclòs, Xavier; Néraudeau, Didier; Roghi, Guido

    2017-02-01

    Stable carbon-isotope geochemistry of fossilized tree resin (amber) potentially could be a very useful tool to infer the composition of past atmospheres. To test the reliability of amber as a proxy for the atmosphere, we studied the variability of modern resin δ13C at both local and global scales. An amber δ13C curve was then built for the Cretaceous, a period of abundant resin production, and interpreted in light of data from modern resins. Our data show that hardening changes the pristine δ13C value by causing a 13C-depletion in solid resin when compared to fresh liquid-viscous resin, probably due to the loss of 13C-enriched volatiles. Modern resin δ13C values vary as a function of physiological and environmental parameters in ways that are similar to those described for leaves and wood. Resin δ13C varies between plant species and localities, within the same tree and between different plant tissues by up to 6‰, and in general increases with increasing altitudes of the plant-growing site. We show that, as is the case with modern resin, Cretaceous amber δ13C has a high variability, generally higher than that of other fossil material. Despite the high natural variability, amber shows a negative 2.5-3‰ δ13C trend from the middle Early Cretaceous to the Maastrichtian that parallels published terrestrial δ13C records. This trend mirrors changes in the atmospheric δ13C calculated from the δ13C and δ18O of benthic foraminiferal tests, although the magnitude of the shift is larger in plant material than in the atmosphere. Increasing mean annual precipitation and pO2 could have enhanced plant carbon-isotope fractionation during the Late Cretaceous, whereas changing pCO2 levels seem to have had no effect on plant carbon-isotope fractionation. The results of this study suggest that amber is a powerful fossil plant material for palaeoenvironmental and palaeoclimatic reconstructions. Improvement of the resolution of the existing data coupled with more detailed