A triász végi kihalás és környezetváltozások oknyomozó vizsgálata = The end-Triassic mass extinction, coeval environmental change, and their driving forces

A triasz vegi kihalas es kornyezetvaltozasok esemenyeit, azok lefolyasat es okait kutatva sokoldalu vizsgalatokat vegeztunk hazai es kulfoldi triasz/jura (T/J) hatarszelvenyekben. Magyarorszagon harom kulonboző kornyezetben, sekelytengeri platform, melyebb medence, valamint szarazfoldi retegsorokban is fontos valtozasokat mutattunk ki. Csővaron tenger alatti lejtő- es medenceuledekekben a T/J hatar biosztratigrafiai megvonasat ammonitesz, radiolaria, foraminifera, konodonta es palinologiai vizsgalatokkal tamasztottuk ala. A hatar kozvetlen kozeleben a szenizotop osszetetelben eles es rovid ideig tarto negativ anomaliat mutattunk ki. A kihalas es a szenkorforgas zavaranak egybeeseset ugy ertelmeztuk, mint a Kozep-Atlanti Magmas Provincia (KAMP) vulkanizmusa altal előidezett uveghaz-felmelegedes nyoman a tengeraljzaton eltemetett gaz-hidrat disszociaciojabol szarmazo metan felszabadulasanak kovetkezmenyet. A T/J hatar kozeleből vett mintak U-Pb kormeghatarozasaval igazoltuk a KAMP es a T/J hataresemenyek egyidejűseget. A nedvesebbe valo eghajlatra egyarant utalnak a novenyvilag valtozasai es geokemiai bizonyitekok. A kora jura elejen meg magas volt a legkor CO2 tartalma, de az elővilag talpraallasa 1 millio even belul megindult. Ebből az időszakbol Kanada, Tibet es Erdely lelőhelyeiről gazdag ammonitesz egyutteseket irtunk le. | The events, processes and causes of the end-Triassic extinction and coeval environmental changes have been studied by multidisciplinary analyses of Triassic-Jurassic (T-J) boundary sections both in Hungary and other areas. Significant changes occur in three contrasting facies (shallow marine platform, deeper basin, and terrestrial environments) in Hungary. The biostratigraphy of the T-J boundary is documented in the submarine slope and basinal sediments at Csővar using ammonoids, radiolarians, foraminifera, conodonts and palynomorphs. Immediately at the boundary a sharp and short-lived negative carbon isotope excursion occurs. Coeval extinctions and perturbation of the carbon cycle are interpreted to record massive methane release from submarine gas-hydrate dissociation driven by greenhouse warming, likely related to volcanism of the Central Atlantic Magmatic Province (CAMP). U-Pb dating of samples from near the T-J boundary provide evidence for synchrony of the T-J boundary events and CAMP volcanism. An increasingly humid climate is suggested by vegetation changes and geochemical proxy records. The earliest Jurassic is characterized by high paleoatmospheric CO2 concentration. Biotic recovery was well underway within one million year. Rich ammonoid assemblages have been described from this interval in Canada, Tibet, and Transylvania.