Middle to Late Eocene paleoenvironmental changes in a marine transgressive sequence from the northern Tethyan margin (Adelholzen, Germany).
The northern Tethyan margin is a key region for determining environmental changes associated with the collision of continental and oceanic tectonic plates and Alpine orogeny. Herein we investigated Middle to Late Eocene neritic to bathyal sediments deposited during an interval of unstable climatic conditions. In order to quantify paleoenvironmental changes, we developed a detailed age model based on biozonations of planktic foraminifera, calcareous nannoplankton, and larger benthic foraminifera. The section at Adelholzen covers the almost complete Lutetian Stage (calcareous nannoplankton zones NP15a-16, planktic foraminifera zones E8-11, shallow benthic (foraminifera) zones SBZ13-15) and large parts of the Priabonian Stage (NP18-20, E14/15), while the intermediate Bartonian Stage (NP17) is completely missing. Foraminiferal, calcareous nannoplankton, and macrofossil assemblages were analyzed for changes in paleo-water depth, mixing and stratification, paleo-primary productivity (pPP), food supply, and bottom water oxygenation. Paleo-water depth estimates range from 50 m (middle neritic, early Lutetian) to nearly 500 m (upper bathyal, late Priabonian). The combination of assemblage composition, planktic and benthic foraminiferal accumulation rates, and derived parameters (carbon-flux to sea floor, pPP) enabled us to identify a series of distinct paleoceanographic events of at least regional significance. Such events are characterized by considerable changes in primary productivity or reduced bottom water ventilation. Calculated pPP-values indicate oligotrophic conditions throughout.
Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria.
Holger
H
Gebhardt
Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria.
Stjepan
S
Ćorić
Naturkundemuseum Siegsdorf, Auenstr. 2, D-83313 Siegsdorf, Germany.
Robert
R
Darga
Universität Wien, Institut für Paläontologie, Althanstraße 14, A-1090 Wien, Austria.
Antonino
A
Briguglio
Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria.
Bettina
B
Schenk
Bayerische Staatssammlung für Paläontologie und Geologie und GeoBioCenterLMU, Richard-Wagner-Str. 10, D-80333 München, Germany.
Winfried
W
Werner
Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, Christian-Albrechts-Universität Kiel, Max-Eyth-Str. 11, D-24118 Kiel, Germany.
Nils
N
Andersen
Geologische Bundesanstalt, Neulinggasse 38, A-1030 Wien, Austria ; Universität Wien, Institut für Paläontologie, Althanstraße 14, A-1090 Wien, Austria.
Benjamin
B
Sames
Eocene; calcareous nannoplankton; deepening upward sequence; northern Tethyan margin; paleo-primary productivity; paleo-water depth; planktic and benthic foraminifera