Triassic–Jurassic boundary events inferred from integrated stratigraphy of the Csővár section, Hungary

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• 作者：Jó ; zsef P&#xe1 ; lfy ; Attila Dem&#xe9 ; ny ; J&#xe1 ; nos Haas ; Elizabeth S. Carter ; Á ; gnes Gö ; rö ; g ; Dó ; ra Hal&#xe1 ; sz ; Anna Oravecz-Scheffer ; Magdolna Het&#xe9 ; nyi ; Emő ; M&#xe1 ; rton
• 关键词：Triassic– ; Jurassic boundary ; Integrated stratigraphy ; Extinction ; Carbon isotope ; Sea-level change
• 刊名：Palaeogeography ; Palaeoclimatology ; Palaeoecology
• 出版年：2007
• 期刊代码：68_00310182
• 类别：ear
• 出版时间：9 February 2007
• 卷：244
• 期：1-4
• 页码：11-33
• 文件大小：2458 K

摘要

Processes and causes of biotic and environmental change at the Triassic–Jurassic transition remain controversial, partly because of a scarcity of Triassic–Jurassic boundary sections studied in detail. Continuous marine strata spanning the boundary are exposed at Csővár, Hungary, where new integrated stratigraphic data were obtained from multidisciplinary investigations to help reconstruct the end-Triassic and Early Jurassic events. Boundary strata are predominantly slope to basinal carbonates deposited in a periplatform basin. The position of the system boundary is constrained by radiolarian, foraminiferan, conodont and ammonoid biostratigraphy. Pronounced radiolarian turnover is observed between assemblages assigned to the Late Rhaetian Globolaxtorum tozeri zone and the Early Hettangian Canoptum merum zone. Benthic foraminifera suffered lesser extinction. Successive conodont faunas of the latest Rhaetian Misikella posthersteini and Misikella ultima zones record a marked drop in diversity and abundance but sporadic survivors persist into the earliest Hettangian. The extinction is also recorded in a reduction of biogenic components in carbonates. Decline of benthic and planktic biota is followed by a negative δ¹³C_carb excursion of up to − 6‰ that is composed of short-term fluctuations revealed by dense sampling. Carbon and oxygen isotope ratios are positively correlated in the lower part of the section and appear to reflect primary variations. Drivers of the stable isotope trends are interpreted as warming in excess of + 10 °C and concomitant episodic, short-term perturbations of the global carbon cycle, possibly due to methane release from gas–hydrate dissociation induced by rapid climatic events. The main biotic and isotopic events occurred within a single sedimentary cycle but sea-level does not appear to have exerted a critical influence on these changes. The Triassic–Jurassic boundary crisis appears a short but not instantaneous event.