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

• 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 fl ood 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 thepalynofloral 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 diversifi ed tetrapod ichnofauna in the earliest Jurassic strata indicates a rapid recovery and refi ll of ecological niches by dinosaurs.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

extinction

Triassic

Jurassic

end-Triassic biotic crisis

Earth Science with specialization in Historical Geology and Palaeontology

Geovetenskap med inriktning mot historisk geologi och paleontologi

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)