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Climatic reversals related to the Central Atlantic magmatic province caused the end-Triassic biotic crisis—Evidence from continental strata in Poland

By
Grzegorz Pieńkowski
Grzegorz Pieńkowski
Polish Geological Institute–National Research Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland
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Grzegorz Niedźwiedzki
Grzegorz Niedźwiedzki
Subdepartment of Evolution and Development, Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden
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Paweł Brański
Paweł Brański
Polish Geological Institute–National Research Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland
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Published:
September 01, 2014

Eight climatic events can be distinguished in the Triassic–Jurassic (ca. 201 Ma) continental strata of Poland. These events are distinguished by kaolinite/illite ratio, chemical index of alteration (CIA), color of sediments, and palynomorphs. The first transition to wetter climate, evidenced by a shift from smectite- to kaolinite-dominated mudrocks, coincides with the earlier (“precursor”) Rhaetian negative δ13Corg excursion, which means that the beginning of climate perturbations predates the oldest known Central Atlantic magmatic province flood basalts by some 100–200 k.y. The later global, late Rhaetian “initial” negative δ13Corg excursion is divided into two subpeaks, each corresponding to hot and humid events, separated by a cooler and drier event. The upper subpeak is also associated with perturbation of the osmium isotope system (attributed to volcanic fallout), and darkened miospores, pointing to acid rains. Between the “initial” excursion and the Triassic-Jurassic boundary interval, five climatic fluctuations are inferred from the changing kaolinite/illite ratio, the last two of which are also associated with an Os isotope perturbation, polycyclic aromatic hydrocarbon (PAH) occurrences, a “spore peak,” and darkened miospores. A series of periodic atmospheric loading events by CO2, CH4, or alternatively by SO2, sulfate aerosols, and toxic compounds, is inferred to have caused this series of rapid climatic reversals and resulting extinction of many less-adapted forms. Just above the palynofloral extinction level, appearance of new forms commenced Jurassic palynofloral recovery. Tetrapod evolution events in the end-Triassic–earliest Jurassic were related to the extinction of the Pseudosuchia, Dicynodontia, Capitosauroidea, Plagiosaroidea, and Rhynchosauria, while appearance of highly diversified tetrapod ichnofauna in the earliest Jurassic strata indicates a rapid recovery and refill of ecological niches by dinosaurs.

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GSA Special Papers

Volcanism, Impacts, and Mass Extinctions: Causes and Effects

Gerta Keller
Gerta Keller
Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA
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Andrew C. Kerr
Andrew C. Kerr
School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, Wales, UK
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Geological Society of America
Volume
505
ISBN print:
9780813725055
Publication date:
September 01, 2014

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