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Paleodepth estimates by transfer equation of benthic foraminiferal range depth distribution: Examples from the Styrian Basin - Results from FWF project P 13743-Bio

SPEZZAFERRI, S.1, HOHENEGGER, J.1, RÖGL, F.2 & CORIC, S.1

1Paleontology Institute, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria, 2Natural History Museum, Burgring 7, 1014 Wien Vienna, Austria

Correct estimate of paleobathymetry is essential in paleoceanography and basin analysis to reconstruct uplift and subsidence story of basins and to construct sea-level curves. Therefore, demand for accurate pa-leobathymetrical techniques has largely increased in the past decades. However, this demand has by no means been satisfied. The most widely used techniques are currently of micropaleontological nature and are based on the depth dependency of benthic foraminifera (e.g. Plankton/Benthos Ratio). However, several problems based on correct inter-pretation of data and on the concern that these forms may not be isobathyal in time and space, prevented accurate reconstruction of paleobathymetry. Neverthless, individual benthic foraminiferal genera do have distinct broad depth ranges and these ranges can be used as a framework to reconstruct basins paleodepth.

We introduce here a simple method to estimate paleo-depths of sediments from deep-sea, continental mar-gins, enclosed basins based on a transfer equation using the geometric mean of the range distribution of benthic foraminifera. The method uses qualitative assemblages data, and therefore, is of immediate and easy application. Due to the log normal depth distri-bution of most genera and species, the geometric mean allows a better depth approximation. In ad-dition, this method allows identification of reworked and/or redeposited species based on heterogenetic structure.

As case study we have selected two outcropping sec-tions and a borehole from the Austian marine Miocene: Wagna and the Retznei Sections and Perbersdorf 1 drilling located in the Styrian Basin and spanning the transition from the Late Karpatian to the Early Badenian corrsponding to the Latest Burdigalian - Early Langhian. Our paleodepth estimates suggest that sediments at Wagna were deposited in a water depth between 150 to 210 m and at Retznei in a water depth between 160 and 190 m. A shallowing-upward trend is identified in both sections. Paleodepth at Perbesdorf fluctuates between 200 and 300 m at the base and top of the sedimentary sequence. A shallower interval with paleodepth between 180 m and 200 m is identified from 330 m and 425 m. This shallower interval corresponds to the Karpatian-Badenian transition.