NDLI: The Triassic–Jurassic boundary in the shallow-water marine carbonates from the western Northern Calcareous Alps (Austria)

Content Provider	Springer Nature Link
Author	Felber, Roland Weissert, Helmut J. Furrer, Heinz Bontognali, Tomaso R. R.
Copyright Year	2015
Abstract	The Triassic–Jurassic (T–J) boundary coincides with one of the five biggest mass extinctions in the Phanerozoic. This event has been extensively studied in the eastern and central Northern Calcareous Alps (NCA), where the global stratotype section and point for the base of the Jurassic is outcropping. We present one of the first combined bio-, litho- and carbonate carbon isotope stratigraphic study across the T–J boundary from the western NCA, focusing on the shallow-water marine carbonate successions “Lorüns” and “Steinernes Meer”. An almost complete T–J succession with the Upper Triassic Kössen Formation, the T–J Schattwald beds and the Lower Jurassic Lorüns oolite is preserved in the Lorüns section, whereas a stratigraphic hiatus at the T–J boundary is observed in the Steinernes Meer section. The carbonate carbon isotope record of Lorüns shows the characteristic T–J carbon isotope evolution with a short initial negative carbon isotope excursion (CIE) in the lower Schattwald beds, which is separated from the following and longer main negative CIE in the Lorüns oolite by a positive excursion in the upper Schattwald beds. The synchroneity of the initial and main CIE with the last occurrence of Triassic fauna and the first appearance of Jurassic ammonites suggests placing the T–J boundary at the base of the Lorüns oolite. The Steinernes Meer section records only the main negative CIE in the Lorüns oolite due to emersion and/or no sedimentation between the Upper Triassic Kössen Formation and the Lower Jurassic Lorüns oolite, caused by regression and synsedimentary tectonics. This study provides new evidence in support the hypothesis that the latest Rhaetian decrease and the Hettangian recovery of the carbonate production coinciding with the initial and main CIE, respectively, can be interpreted as evidence of acidification of the Tethys ocean due to elevated atmospheric CO2 concentrations, probably caused by voluminous volcanic gas emissions.
Starting Page	213
Ending Page	224
Page Count	12
File Format	PDF
ISSN	16618726
Journal	Swiss Journal of Geosciences
Volume Number	108
Issue Number	2
e-ISSN	16618734
Language	English
Publisher	Springer Basel
Publisher Date	2015-07-30
Publisher Place	Basel
Access Restriction	Subscribed
Subject Keyword	Rhaetian–Hettangian Tethys Biocalcification crisis Emersion Isotope stratigraphy Geology
Content Type	Text
Resource Type	Article
Subject	Geology

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