Environmental changes during the Permian-Triassic mass extinction – A palynological study of sediments from Spitsbergen
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Keywords:
Permian–Triassic extinction event
Extinction (optical mineralogy)
Early Triassic
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Carbon fibers
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Eight samples of brachiopod shell material have been analyzed for their strontium isotope composition in order to more accurately date Lower to Upper Permian siliceous biogenic strata of Spitsbergen (Kapp Starostin Formation) and the southern Barents Sea (Røye Formation). The results are interpreted as showing a mid‐Artinskian age for the basal Vøringen Member of the Kapp Starostin Formation and a range of late Artinskian to Roadian for the overlying part of this unit. The upper part of the Røye Formation yields ages in the range Roadian to Wuchiapingian. These results are consistent with available biostratigraphic data and confirm the potential of strontium isotope stratigraphy for developing a more accurate chronology of the widespread spiculite deposits that characterize the northern margin of Pangea in late‐Early Permian to Late Permian time and which constitute a potential target for petroleum exploration.
Outcrop
Isotopes of strontium
Radiometric dating
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Orbitally controlled, sedimentary cycles of the Newark Supergroup permit palyniferous Late Triassic sections to be calibrated in time. Carnian palynofloras from the Richmond basin exhibit 2-m.y. fluctuations in the spore/pollen ratio, but taxonomic composition remains stable. Diversity of Norian and Rhaetian palynofloras increases prior to a 60% reduction at the Triassic/Jurassic boundary. The extinction of Late Triassic palynomorph species is coincident with a spike in the spore/pollen ratio and approximately synchronous with the last appearances of tetrapod taxa and ichnofossil genera. This geologically brief episode of biotic turnover is consistent with bolide impact hypotheses.
Early Triassic
Tetrapod (structure)
Supergroup
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Extinction (optical mineralogy)
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We present a palynological study of a terrestrial Triassic–Jurassic (Tr–J; c . 200 Ma) boundary section at Astartekloft, East Greenland. We have generated a new palynostratigraphic scheme and vegetation history for this locality, and have integrated these with existing carbon isotope records. Samples for palynological analysis were collected from precisely the same stratigraphic horizons as plant macrofossils and samples used for geochemical analyses. Our results highlight four local sporomorph assemblage zones that are compositionally distinct from each other at Astartekloft. The extremely low abundance of Classopollis pollen in all samples, and the pronounced decline of Ricciisporites tuberculatus during the Late Rhaetian are notable features of the sporomorph record of Tr–J vegetation at Astartekloft. Correlation of Astartekloft and a marine Tr–J boundary section at St Audrie’s Bay, UK, provides no support for the idea that extinction and diversity loss in terrestrial ecosystems preceded biotic change in marine ecosystems at the Tr–J. Instead, the available data support suggestions that the onset of the Tr–J biotic crisis was synchronous in terrestrial and marine environments. Peak extinction among plants at Astartekloft occurred relatively late in the sequence of events across the Tr–J, and may represent a response to long-term cumulative effects of volcanism at this time. Supplementary material Plates of selected sporomorphs recovered from Astartekloft and a full pollen diagram are available at www.geolsoc.org.uk/SUP18553.
Macrofossil
Extinction (optical mineralogy)
Terrestrial plant
Palynofacies
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Sedimentological, palynological, clay mineralogical and carbon isotope studies were carried out on the Triassic/Jurassic (T/J) boundary interval in the Nw Tethyan realm. The analyses are based on two sections in the Slovakian Tatra Mountains (western Carpathians): the Siroký Žľab section in the Meďodoly Valley and the furkaska section above the Juraňova Valley. Clay mineralogical analysis suggests an increasing intensity of chemical weathering in the hinterland due to increasing humidity. The palynological data do not allow the inference of a major T/J boundary mass extinction event. The observed striking increase in spores points instead to sudden climatic change, interpreted as a result of distant volcanic activity associated with the onset of rifting of Pangea. The δ 13 C org excursion across the T/J boundary follows the globally documented perturbation of the carbon cycle during this period. it may be used for a more precise regional and global correlation.
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Paleosol
Acritarch
Biozone
Chemostratigraphy
Chronostratigraphy
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The Albian-Cenomanian strata of the Koppeh-Dagh Basin were investigated for their marine palynomorphs and palynofacies contents and used for palaeoclimatic, palaeoenvironmental and sequence stratigraphical purposes. Various palynofacies criteria such as Palynological Marine Index (PMI), chorate/proximate, proximochorate and cavate ratio (C/PPC) and outer neritic/inner neritic index (ON/IN) were applied as alternative indicators to monitor the proximal-distal trends. Higher values of the former proxies versus low continental/marine ratio (CONT/MAR) were documented during periods of relative rise of sea-level. Increasing values of the marine palynological proxies such as the PMI, C/PPC and ON/IN were consistent with maximum flooding surfaces (MFS). A relatively diverse dinoflagellate cyst assemblage was reported at MFS, whereas, during the periods of relative sea-level fall, the dinocyst diversity decreased and coincided with those above-mentioned marine palynological ratios that reinforced terrestrial conditions. Palaeovegetation reconstruction showed the predominance of the pteridophyte spores. This palynoflora indicates a humid and warm climate during the Albian-Cenomanian time. Three deducted depositional sequences correspond with those suggested in previous studies based on surface and subsurface geological data. Sea-level changes correspond well with those reported from other parts of the Tethys.
Palynofacies
Dinocyst
Cenomanian
Dinoflagellate
Acritarch
Sequence Stratigraphy
Marine transgression
Sequence (biology)
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Ammonite
Acritarch
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