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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Earth Sci. | doi: 10.3389/feart.2019.00302

Selective recording of tectonic forcings in an Oligocene/Miocene submarine channel system: Insights from new age constraints and sediment volumes from the Austrian Northern Alpine Foreland Basin

 Julian Hülscher1*, Gero Fischer1, Patrick Grunert2,  Gerald Auer3 and  Anne Bernhardt1*
  • 1Freie Universität Berlin, Germany
  • 2Institute of Geology and Mineralogy, Faculty of Mathematics and Natural Sciences, University of Cologne, Germany
  • 3Japan Agency for Marine-Earth Science and Technology, Japan

Detailed characterization of variations in sediment architecture, flux, and transport processes in peri-orogenic basins offers insights into external climatic or tectonic forcings. We tested how four well-known tectonic/erosional events in the Oligocene/Miocene Alpine source area are recorded in the sediment-accumulation rates (SARs) of the deep marine sink in the Northern Alpine Foreland Basin (NAFB): exhumation of the Lepontine Dome (starting at 30 Ma) and the Tauern Window (23-21 Ma), erosion of the Augenstein Formation (~21 Ma), and the visco-elastic relaxation of the European Plate.
The Upper Austrian NAFB offers a unique opportunity to investigate external forcings on sedimentary infill due to the large amount of data on the Alpine source and Foreland. Deep-marine sedimentation, forming the Puchkirchen Group and the basal Hall Formation, was controlled by a basin-axial submarine channel (3-5 km wide, >100 km length). Two basin-wide unconformities were recognized in seismic-reflection data: the Northern Slope Unconformity (NSU) and the Base Hall Unconformity (BHU). We combine biostratigraphic and chemostratigraphic analyses of 316 drill-cutting samples from three wells with a large 3D-seismic-reflection data set (3300 km2, >5 km depth) to determine age and duration of the unconformities and to calculate spatially averaged SARs for the submarine channel and its overbanks, separately.
Deepening of the basin, recorded by the NSU, occurred between 28.1 and 26.9 Ma. The Puchkirchen Group (26.9–19.6 Ma) is characterized by constant SARs (within standard deviation) in the channel (432–623 (t/m2/Ma)) and on the overbanks (240–340 (t/m2/Ma)). The visco-elastic relaxation of the European Plate results in low SARs on the overbanks (186 (t/m2/Ma)), a decrease in sediment grain size in channel deposits and a decrease in sea level at the BHU (19.6–19.0 Ma). In the upper Hall Formation (19.0–18.1 Ma), clinoforms prograding from the south filled up the basin (1497 (t/m2/Ma)) within 1 Myrs. We conclude that only two of the tectonic signals are recorded in this part of the deep-marine sink, erosion of Augenstein Formation and visco-elastic relaxation of the European Plate; the exhumation of the Tauern Window and Lepontine Dome remain unrecorded.

Keywords: foraminiferal analysis, calcareous nannoplankton analysis, chemostratigraphy, Submarine channel, Molasse basin, environmental signal propagation, Turbidity currents, time-scale invariant sediment accumulation rates

Received: 04 Jul 2019; Accepted: 31 Oct 2019.

Copyright: © 2019 Hülscher, Fischer, Grunert, Auer and Bernhardt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Mx. Julian Hülscher, Freie Universität Berlin, Berlin, Germany, julian.huelscher@fu-berlin.de
Mx. Anne Bernhardt, Freie Universität Berlin, Berlin, Germany, anne.bernhardt@fu-berlin.de