International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Probing the underground at the Badenian type locality: geology and sedimentology of the Baden-Sooss section (Middle Miocene, Vienna Basin, Austria)

Pages: 375 - 394

Authors: MICHAEL WAGREICH, PETER PERVESLER, MAKSUDA KHATUN, INGE WIMMER-FREY, ROBERT SCHOLGER

Abstract: A 102 m long core of fine-grained sediments of the Vienna Basin (Baden Group, “Badener Tegel”) was drilled at the Badenian type locality outcrop in Baden-Sooss. An Early Badenian age (regional Upper Lagenidae Foraminiferal Zone) is indicated by biostratigraphy. The core comprises mainly bioturbated, medium to dark grey marls and shales with a slightly higher degree of tectonic deformation in the upper part of the core. XRD indicates mainly quartz, muscovite/illite, chlorite, feldspar, calcite and minor dolomite as constituents. Carbonate contents vary between 10 % and 35 % and organic carbon between 0.32 % and 0.78 %. Rare intercalations include sand layers with shell debris, a conglomerate and a smectitic tuff layer. Mean grain size ranges from 4 to 8 μm. Cyclic sedimentation was identified by rhythmic variations in carbonate and organic carbon contents and magnetic susceptibility. Rock Eval pyrolysis indicates mainly type III kerogen from terrestrial higher plant material and minor marine input. The depositional environment can be characterized as offshore, below the fair-weather wave base but within the storm-wave base. The sediments are hemipelagites, transported by pelagic suspension, that is a mixture of pelagic biogenic carbonate, mainly calcareous nannofossils and foraminiferal tests, and terrigenous clay and silt. The positive correlation of carbonate to organic carbon indicates a dilution controlled siliciclastic deposition with varying siliciclastic input. Except for minor primary laminated intervals, oxygenated bottom water conditions are reconstructed from the presence of various trace fossils and ichnofabrics from the Zoophycos ichnofacies in the deeper part with a transition to the distal Cruziana ichnofacies towards the top of the core.

Keywords: Miocene, Badenian, Vienna Basin, sedimentology, geochemistry, clay mineralogy, hemipelagite

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