--> Abstract: Subsidence Evolution of a Transpressional Foreland Basin: The Austrian Molasse Basin, by J. Genser and F. Neubauer; #90942 (1997).

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Abstract: Subsidence Evolution of a Transpressional Foreland Basin: the Austrian Molasse Basin

GENSER, JOHANN, and FRANZ NEUBAUER

The Molasse basin in front of the Eastern Alps developed in response to the thrusting of the Alpine nappe edifice onto the European continental margin. The basin shows striking lateral differences in basin width and basin depth, albeit of a straight orogenic front.

Subsidence analyses display marked lateral differences and a temporal shift between the highest tectonic subsidence rates and the highest sediment accumulation rates. In western parts of the Austrian Molasse basin, subsidence started in the Late Eocene with the highest tectonic subsidence rates in the Early Oligocene, whereas towards the east subsidence is delayed, starting in the Oligocene with maximum rates of tectonic subsidence in late Oligocene to Early Miocene. Sediment accumulation rates are rather constant from the Eocene to the Oligocene, but increased markedly in the Early Miocene. This peak in sediment accumulation rates, synchronous along the whole section, also led to maximum basement subsidence rates in the Early Miocene. With the Middle Miocene, sediment accumulation and basement subsidence almost ceased. These features of subsidence evolution are attributed to oblique collision.

In the Pliocene to Pleistocene the whole basin underwent tectonic uplift, with a general trend of increasing relative tectonic uplift towards the foreland and from west to east. The present tectonic subsidence ranges from half of the maximum amount reached to net tectonic uplift compared with the initial (Eocene) sate. This uplift must reflect changing geodynamic boundary conditions that are presently fundamentally different from those leading to basin formation.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria