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

FORAMINIFERAL PALEOECOLOGY AND BIOSTRATIGRAPHY OF THE GRUND FORMATION (MOLASSE BASIN, LOWER AUSTRIA)

Pages: 155 - 164

Authors: SILVIA SPEZZAFERRI

Abstract: This study was undertaken to solve the debate about the age of the sediments from the Grund Formation and to propose an environmental interpretation based on benthic and planktonic foraminiferal assemblages from the profiles excavated in 1998 and 1999 in the type locality of the Grund Formation (Lower Austria). In particular, quantitative data of foraminifers from Profile G were statistically treated to unravel the ecological gradients subtending the samples. Planktonic foraminiferal assemblages suggest a warm paleoclimate for this area. Benthic foraminiferal assemblages testify to strong re-deposition processes displacing shallow-water sediments from the inner shelf to outer shelf. Re-deposition may derive from storm events. Oxygenation of bottom waters is difficult to assess on the basis of benthic foraminifers. In particular, it is not possible to identify the dysoxic episodes suggested by the occurrence of chemosymbiotic bivalves living with anaerobic bacteria as in Zuschin et al. (2001). The studied sediments can be attributed to the Lower Lagenidae Zone in the Badenian (Langhian, Middle Miocene) on the basis of the presence of index fossils like Praeorbulina glomerosa circularis and Uvigerina macrocarinata.

Keywords: Badenian, Austria, Grund Formation, ecology, stratigraphy, molasse, foraminifers

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Volume 55 no. 2 / April 2004

Volume 55 no. 2