In this text, two of the world's leading experts in palynology and paleobotany provide a comprehensive account of the fate of land plants during the 'great extinction' about 65 million years ago. ...They describe how the time boundary between the Cretaceous and Paleogene Periods (the K–T boundary) is recognised in the geological record, and how fossil plants can be used to understand global events of that time. There are case studies from over 100 localities around the world, including North America, China, Russia and New Zealand. The book concludes with an evaluation of possible causes of the K–T boundary event and its effects on floras of the past and present. This book is written for researchers and students in paleontology, botany, geology and Earth history, and everyone who has been following the course of the extinction debate and the K–T boundary paradigm shift.
No consensus currently exists regarding the magnitude of Cretaceous short-term (less than 3Ma in duration) eustatic sea-level change. The lack of a consensus limits the ability to predict sedimentary ...facies and architecture and to assess the potential drivers of eustasy during a period of Earth history considered as significantly warmer than today. Consequently, this review documents, weighs, synthesises, and summarises records of short-term relative sea-level change and evaluates the observed trends in magnitude within the context of potential climatic drivers and their eustatic expression.
Although Cretaceous sea-level change is addressed in many publications, estimates of absolute values are relatively limited, often cover short time intervals, and use different methods. Based upon integrated geological and statistical analyses, four broad episodes of magnitude change have been identified. Three of these episodes reflect trends of increasing magnitudes of sea-level change from the Berriasian to early Hauterivian, late Hauterivian to Aptian, and Santonian to Maastrichtian. The fourth episode reflects a decreasing magnitude trend from the Albian to Coniacian. In addition, the maximum magnitude of sea-level change, at an approximate stage level, has been identified and categorised as slight (less than 10m), modest (10 to 40m), or significant (41 to 65m). Significant magnitudes are inferred for the Valanginian, Aptian, Albian, and Maastrichtian; exclusively slight magnitudes are restricted to the Berriasian. Such an assessment casts doubt on the repeated and stratigraphically widespread episodes of very large magnitudes (more than 75m) advocated by some workers, and instead defines distinct periods and magnitudes of sea-level change that should be globally reflected in sedimentary facies patterns. For example, intervals of sea-level fall of significant magnitude are commonly associated with the increased delivery of sediment into basinal settings, including the marked progradation of shallow-marine sediments, whilst up-systems tract there can be enhanced development of karst and erosional features.
Because climatically driven eustasy is the likely cause of short-term sea-level change, an assessment of the characteristic maximum magnitude limits of the principal climatic drivers (thermo-, aquifer-, and glacio-eustasy) has been made. Such a comparison argues for glacio-eustasy as the driver of significant short-term sea-level change. In addition, climate proxy data demonstrates that the Valanginian, Aptian, Albian, and Maastrichtian are intervals of cooling within the Cretaceous, thereby supporting the link between significant magnitudes and glacio-eustasy.
The Winton Formation provides an important snapshot of Australia's late Mesozoic terrestrial biota, boasting a vertebrate fauna that includes dinosaurs, crocodyliforms, aquatic squamates, turtles, ...lungfish and teleost fishes, and a flora that has previously been considered to include some of the world's earliest known flowering plants. Despite its significance, poor age control has thus far prevented precise regional and global correlations, limiting the depth of paleobiogeographic assessments. The goal of this study was to use U–Pb isotope dating of detrital zircons by laser ablation to refine the depositional age range of selected horizons within the Winton Formation. We applied this technique, with refined instrumental tuning protocols, to systematically investigate detrital zircon grain ages for five samples from different stratigraphic levels and vertebrate-bearing fossil locations throughout the Winton Formation. Seven different metrics for interpreting the maximum depositional age of each of the detrital zircon samples were compared and our results suggest that sedimentation of the Winton Formation commenced no earlier than latest Albian (~103.0–100.5Ma) and that deposition of the upper vertebrate fossil-rich portion of the section began roughly near or after the Cenomanian–Turonian boundary (93.9Ma), demonstrating that the formation and its important flora and fauna were deposited primarily during the Late Cretaceous. These results provide a significant advancement in understanding the age of the Winton Formation's flora and fauna, and will help to contextualize Australia's Late Cretaceous terrestrial biota within a broader Gondwanan framework.
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► Improved dating of continental fossil faunas via U–Pb detrital zircon geochronology ► Evaluation of maximum depositional age metrics in detrital zircon studies ► A revised Late Cretaceous for one of Australia's most important dinosaur faunas
Front cover: Cover image: See Y. Pochat‐Cotilloux et al., ‘The neuroanatomy and pneumaticity of Hamadasuchus (Crocodylomorpha, Peirosauridae) from the Cretaceous of Morocco and its paleoecological ...significance for altirostral forms’, this issue.
The Mesozoic Western Pacific subduction system significantly impacted the North China and South China blocks along the East Asian continental margin and influenced the tectonic, magmatic, ...metallogenic and geomorphic evolution of the region. However, the dynamics and impact on the zone along the East Asian ocean-continent connection zone remain debated. Here we provide a comprehensive synthesis of the state-of-the-art information from deformation analysis, magmatism, geochronology, tomography and other fields from this region. We evaluate first the pre-Yanshanian (pre-Jurassic) final assembly of blocks and the Late Triassic formation of the unified continental margin in East China. We then focus on the Jurassic and Cretaceous geological processes in the East Asian ocean-continent connection zone. The temporal and spatial evolution of structural propagation, sedimentary depocentre, age zonation and migration of magmatism, as well as the large-scale tectono-morphological inversion in the Earth surface system combined with deep processes, are probed. In the early Yanshannian Period (Early and Middle Jurassic, 200–160 Ma), the destruction of the North China Craton (NCC) was mainly affected by the westward early-stage layered rollback, and stepwise delamination and thinning of its continental lithosphere, resulting in the early Yanshanian westward migration of tectonism and magmatism. Coevally, the combined effect of the closure of the Mongal-Okhotsk Ocean to the north and the subduction of the Bangong-Co- Nujiang Ocean to the south imparted an overall compressional setting in the East Asian Ocean-Continent Connection Zone (EAOCCZ). The centres of asthenospheric upwelling and mantle extrusion at depth continued to migrate eastward, driving the eastward lithospheric thinning with periodic and alternating extension and compression. The South China Block experienced a westward flat subduction during the early Yanshanian Period, resulting in the westward propagation of deformation and magmatism, followed by late two-stage delamination to induce the eastward tectono-magmatism. The difference in tectono-magmatic styles between the North China and South China blocks is a result of the different mechanisms and syles of the deep delamination processes under the superconvergence regime of the East Asian and adjacent plates. Especially delamination under North China generated the northwestward layered and fractured subcontinental lithospheric mantle, whereas under the eastern South China Block, were the oceanic lithospheric mantle of the Paleo- Pacific Plate that underwent flat subduction, or continental garnet peridotite mantle. In the middle Yanshanian Period (Late Jurassic to early Early Cretaceous, 160–125 Ma), the EAOCCZ underwent escape tectonics to form some basins related to strike slip faulting. Generally the extensional basins in the tails of the triangular-shaped escape blocks are perpendicular to the extrusion direction. The transtensional or transpressional basins are controlled by the strike slip faults distributed on both sides of the triangular block, and the flexural basins occur in front. In the late Yanshanian Period (late Early Cretaceous-Late Cretaceous, 125–65 Ma), the Paleo-Pacific (Izanagi) Plate subducted NNW-ward beneath the Eurasian continent, and the subduction angles changed gradually following eastward mantle extrusion induced by the closure of the Okhotsk Ocean to the north and Bangong-Nujiang Ocean to the south, as well as the rollback and subduction retreat of the Paleo-Pacific Plate to the east. The EAOCCZ gradually experienced lithospheric collapse and the formation of metamorphic core complexes, as well as obvious landscape reversal. During 70–45 Ma, the Izanagi-Pacific Ridge subducted beneath the EAOCCZ to induce wide uplift resulting in the formation of the Cenozoic dextral transtension-related basins.
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