The extinction of the dinosaurs Brusatte, Stephen L.; Butler, Richard J.; Barrett, Paul M. ...
Biological reviews of the Cambridge Philosophical Society,
20/May , Letnik:
90, Številka:
2
Journal Article
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ABSTRACT
Non‐avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and ...changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long‐term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long‐term decline across non‐avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large‐bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult.
Mass extinction at the Cretaceous–Paleogene (K-Pg) boundary coincides with the Chicxulub bolide impact and also falls within the broader time frame of Deccan trap emplacement. Critically, though, ...empirical evidence as to how either of these factors could have driven observed extinction patterns and carbon cycle perturbations is still lacking. Here, using boron isotopes in foraminifera, we document a geologically rapid surface-ocean pH drop following the Chicxulub impact, supporting impact-induced ocean acidification as amechanism for ecological collapse in the marine realm. Subsequently, surface water pH rebounded sharply with the extinction of marine calcifiers and the associated imbalance in the global carbon cycle. Our reconstructed water-column pH gradients, combined with Earth system modeling, indicate that a partial ∼50% reduction in global marine primary productivity is sufficient to explain observed marine carbon isotope patterns at the K-Pg, due to the underlying action of the solubility pump. While primary productivity recovered within a few tens of thousands of years, inefficiency in carbon export to the deep sea lasted much longer. This phased recovery scenario reconciles competing hypotheses previously put forward to explain the K-Pg carbon isotope records, and explains both spatially variable patterns of change in marine productivity across the event and a lack of extinction at the deep sea floor. In sum, we provide insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a postextinction world, and the way in which marine life imprints its isotopic signal onto the geological record.
The Albian-Santonian interval (∼113–83 Ma) is a key interval for Cretaceous climatic and environmental changes. This interval is associated to a rise in sea level until the Late Cenomanian (∼ 94 Ma) ...and to a progressive increase in oceanic temperatures, leading to consider the Late Cenomanian-Santonian interval (∼ 94–83 Ma) as the warmest period of the last 200 Myr. While the Albian-Santonian interval has been well studied in the Northern Hemisphere, the climatic and environmental variations and their consequences on weathering conditions are less documented of the Southern Hemisphere, especially in mid and high latitudes. To better understanding the evolution of weathering conditions, associated to continental climate and sea level changes during this key period, an integrated study, based on a coupled mineralogical and geochemical approach, was carried out on the clay-sized (< 2 μm) fraction from sediments of International Ocean Discovery Program Site U1513 (Mentelle Basin, South-western Australia) and Oceanic Drilling Program Site 763 (Carnarvon Basin, North-western Australia). To determinate variations in weathering conditions, the mineral assemblages of the clay fraction was determined by X-ray diffraction and observed for selected samples by electron microscopy. To identify sources of clay minerals, the concentrations of major and selected trace elements, including rare earth elements, together with strontium and neodymium isotopic measurements were performed on the clay-sized fraction. The X-ray diffraction analyses reveal that clay fraction is dominated by R0-type illite/smectite mixed-layers (smectites), followed by variable proportions of illites, kaolinites for both sites and only on Site 763 of palygorskites. These clay minerals are associated with opal and clinoptilolites. Electron microscopy observations have highlighted the dominance of detrital fleecy smectites but also the occurrence of recrystallized lathed smectites and volcanogenic folded smectites for Site U1513, and authigenesis of clay minerals, associated to palygorskites especially on Turonian to Santonian deposits for Site 763. This authigenesis, confirmed by negative cerium anomaly, is also carried by other minerals in the clay-sized fraction (e.g., clinoptilolites, barite). These different authigenic minerals record a seawater-derived isotopic signature. Therefore, isotopic compositions of the clay-sized fraction reflect a mix between a continental contribution, carried by detrital clay minerals and marine one, supported by authigenic minerals, which complicates the identification of sediment sources. However, despite this, our study demonstrates the major influence of sea level variations on mineralogical variations from Albian to Cenomanian in Western margin of Australia. The decrease in kaolinite proportions at Site U1513 from the Albian to the end of the Cenomanian, is probably related to the increase of sea level, which cause a decrease in detrital inputs in the Mentelle Basin associated with a decrease of weathering and drainage conditions. The progressive sea level rise has also enhanced the effect of the differential settling process of clay minerals by the deposition of coarse clays (e.g., kaolinites and illites) on the continental shelf. Kaolinite-bearing clay deposits, derived from the weathering of the Western Australian Craton during the Albian-Cenomanian times, have been progressively substituted from the Turonian by a carbonate sedimentation, for which the terrigenous component consists only of rare detrital and volcanogenic smectites. In Site 763, the occurrence in kaolinite content during the Coniacian would indicate a decrease of differential settling process related to the weathering of the north part of the Western Australia Craton.
•A 3D convolutional neural network is able to create a functional relationship between pore morphology and the steady state solution of the Navier-Stokes equation for laminar flow.•Four geometric ...features extracted from the binary image are needed to make the model robust.•A model trained only with spherepacks is able to perform accurately in different domains including non-consolidated samples, synthetic heterogeneous geometries, and sandstone and carbonate x-ray images.
We present the PoreFlow-Net, a 3D convolutional neural network architecture that provides fast and accurate fluid flow predictions for 3D digital rock images. We trained our network to extract spatial relationships between the porous medium morphology and the fluid velocity field. Our workflow computes simple geometrical information from 3D binary images to train a deep neural network (the PoreFlow-Net) optimized to generalize the problem of flow through porous materials. Our results show that the extracted information is sufficient to obtain accurate flow field predictions in less than a second, without performing expensive numerical simulations providing a speed-up of several orders of magnitude. We also demonstrate that our model, trained with simple synthetic geometries, is able to provide accurate results in real samples spanning granular rocks, carbonates, and slightly consolidated media from a variety of subsurface formations, which highlights the ability of the model to generalize the porous media flow problem. The workflow presented here shows the successful application of a disruptive technology (physics-based training of machine learning models) to the digital rock physics community.
ABSTRACT
Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic–Cretaceous transition. However, despite its potential importance in shaping ...animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic–Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic–Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic‐Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade‐specific factors may have been more important than overarching extrinsic drivers of faunal turnover during the Jurassic–Cretaceous boundary interval.
This paper presents new zircon and sphene U–Pb ages, biotite and hornblende 40Ar/39Ar ages, Hf isotopic data, and geochemical data for five Mesozoic plutons in the Erguna Massif of NE China. These ...data are used to constrain the late Mesozoic tectonic evolution of the Mongol–Okhotsk orogenic belt. This new dating, when combined with previously published ages, indicates that the Late Jurassic–Early Cretaceous (J3–K1) intrusive rocks can be subdivided into three stages that represent periods of magmatism during the Late Jurassic (~155Ma), early Early Cretaceous (~137Ma), and late Early Cretaceous (~123Ma). In addition, the rocks have undergone later deformation recorded by peak ages of ~137 and ~123Ma. The Late Jurassic and early Early Cretaceous intrusive rocks in the study area are dominantly syenogranites and are either A-type granites or are classified as alkaline series, suggesting that they formed in an extensional environment. The late Early Cretaceous intrusive rocks in this area are generally monzogranitic and were emplaced as dikes in an extensional environment, along with coeval bimodal volcanics. These data, combined with the presence of regional unconformities in the northern part of Hebei Province and western part of Liaoning Province, and the spatial distribution of coeval volcanic rocks in NE China, suggest the Late Jurassic and early Early Cretaceous magmatisms and the early Early Cretaceous deformation in this area occurred in an extensional environment related to the delamination of a thickened part of the crust after closure of the Mongol–Okhotsk Ocean. In comparison, the late Early Cretaceous deformation and magmatism occurred in an extensional environment related to either delamination of the previously thickened crust related to the Mongol–Okhotsk tectonic regime or the subduction of the Paleo-Pacific Plate, or the combined influence of these two tectonic regimes.
•J3–K1 magmatic events in the Erguna Massif can be subdivided into three stages.•J3–K1 intrusive rocks consist mainly of A-type granites and monzonites.•J3–K1 intrusive rocks underwent two stages of deformations.•J3–K1 magmatisms and deformations formed in an extensional environment.
The first day of the Cenozoic Gulick, Sean P. S.; Bralower, Timothy J.; Ormö, Jens ...
Proceedings of the National Academy of Sciences - PNAS,
09/2019, Letnik:
116, Številka:
39
Journal Article
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Highly expanded Cretaceous-Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)-International Continental Scientific Drilling ...Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to forma peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarsegrained suevite, including clasts possibly generated by melt-water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting.Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impactinduced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms.
A large body of evidence suggests that there were extensive coastal mountains along the East Asian margin during the Late Cretaceous. However, current knowledge of the paleo-mountains — the period, ...range, and elevation — is limited. Therefore, direct paleoaltimetry is needed to validate and evaluate the paleo-mountains in East Asia. Our study area is Jiaolai Basin, which is located at the East Asian continental margin. We estimate the paleoelevation of Jiaolai Basin during the Late Cretaceous using carbonate clumped isotope paleothermometry. After correcting for seasonal preference, latitudinal difference, and secular climate change, we conclude that the paleoelevation of Jiaolai Basin was almost certainly ≥2.0 km at ∼80 Ma. Combined with the evidence from stratigraphy, paleogeography, and paleoclimatology, our results suggest that the existence of coastal mountains along East Asia during the Late Cretaceous is likely and the model of Okhotomorsk–East Asia collision is preferred.
•There were coastal mountains along the East Asian margin during the Late Cretaceous.•We applied clumped isotope paleothermometry to paleosol carbonates in Jiaolai Basin.•We quantitatively estimate the paleoelevation of the coastal mountains.•The paleoelevation was almost certainly ≥2 km.•The model of Okhotomorsk–East Asia collision is preferred.
The vast eastern-Tethyan oceanic domain that throughout the Mesozoic extended between Gondwana and Eurasia was a puzzle of larger and smaller microcontinents separated by larger and smaller oceans, ...the paleogeographic reconstruction of which poses major challenging problems. This review article summarizes the available stratigraphic, sedimentological, petrological, geochronological, geochemical, tectonic, and paleomagnetic evidence on the Bangong-Nujiang suture zone and adjacent geological domains now at the heart of the Tibetan Plateau, with the final aim to reconstruct the history of the Bangong-Nujiang Ocean from its birth to its growth and final demise. The vivid debate on these highly controversial geological issues touches on several key problems in plate tectonics, including the birth of an ocean, the nature of microcontinents and seamounts, the initiation of oceanic subduction, the implications of subduction polarity, and the timing of continental collision. Rifting between South Qiangtang and the Lhasa blocks took place in the Early to Middle Permian. The Bangong-Nujiang Ocean was still narrow in the Late Permian. The Triassic saw the rapid northward drift of South Qiangtang and active sea-floor-spreading in the Bangong-Nujiang Ocean, which reached a maximum north–south width of ~4000 km in about 50 million years. In the Early Jurassic (~190–180 Ma), Bangong-Nujiang oceanic lithosphere began to subduct northward. After some 30–40 million years of oceanic subduction, documented by arc magmatism and high-pressure metamorphic rocks, the Bangong-Nujiang Ocean closed its northern branch (the Dongqiao-Amdo ocean) in the latest Middle Jurassic (166–163 Ma), when the Amdo and Dongkacuo microcontinents collided with South Qiangtang. The southern oceanic branch (the Beila-Nagqu ocean) closed in the latest Jurassic (150–145 Ma) at the onset of collision between the Lhasa and Qiangtang blocks. Early Cretaceous (140–120 Ma) syncollisional arc-type magmatism was widely distributed in the Lhasa-Qiangtang collisional zone. At earliest Late Cretaceous time, the complete demise of seaways and the transition to widespread deposition of continental red beds along the Bangong-Nujiang suture zone marked the onset of intracontinental convergence leading to initial uplift of the Tibetan Plateau.
•Critical review of geological data related to the Bangong-Nujiang Ocean from its birth to its growth and demise.•Bangong-Nujiang Ocean opened in the Early Permian and started to subduct northward -~190–180 Ma.•Dongqiao-Amdo and Beila-Nagqu oceans closed at 166–163 Ma and 150–145 Ma, respectively.
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