Ocean current intensification during the Cretaceous oceanic anoxic event 2 - evidence from the northern Tethys

Abstract

Mesozoic Oceanic Anoxic Events (OAEs) are expressions of major physical oceanographic changes at times of perturbation of the global carbon cycle. A northern Tethyan record of OAE2 is preserved in expanded Cenomanian-Turonian pelagic limestone sections (Seewen Formation) in Eastern Switzerland. The new carbonate carbon-isotope stratigraphy extracted from these limestones demonstrates that the OAE2 is condensed in all the studied successions and only the onset of the δ13C excursion (5.0‰) is present. The condensed interval is characterized by dissolution features, which are filled by a glauconite quartz sandstone. This bed is overlain by a well-sorted sandstone with intercalated limestone pebbles (Götzis Member), which can be compared with palimpsest sands forming today along current-swept shelves. The wide distribution of this thin sandstone layer within OAE2 indicates that an intense, erosive, east-west trending shelf current was active during the highest sea level and most extreme carbon-cycle perturbation of the OAE2.