VON LUNEN, ERIC, MALCOLM LIGHT, and
PAUL R. KNOX
Bureau of Economic Geology, The University of Texas at Austin, Austin TX
The evolution of the Vienna Basin involves a continuum of tectonic activity from foreland imbrication through Miocene extrusionary wedge or pull-apart phases closely associated with depositional sediment influxes. Detailed examination of a 3-D seismic in the Matzen field and recent research (supported by OMV) suggested that a variety of fault styles typical of pull-apart bas n tectonics are interwoven into a complex pattern. The principal fault patterns expected are built upon a sinistral strike-slip tectonic framework. An extensional trailing imbricate fault fan is observed in the Bockfliess area. The Matzen field area exhibits at various reservoir levels a divergent strike-slip EW fault trend cross-cut repetitively by NNE duplex fault geometry. The sinistral strikeslip pattern exhibits anastomosing fault traces at the 16th Tortonian (Badenian), which evolves vertically into a classic "negative flower structure" at the 7th Tortonian reservoir level. The Schonkirchen field area is underlain by a sinistral strike-slip fault exhibiting a restraining bend geometry at the deeper Badenian intervals with a minor horst fault block evolving at shallower reservoir intervals, e.g., 9th and 8th Tortonian, into a "positive flower structure." Both the Prottes and Schonkirchen areas are dissected by strike-slip duplexes, interconnecting the major sinistral fault trends. Duplex faults in the area exhibit a mature deformation, which is believed to be NNE to N Riedal shears rotated into intermediate-angle S-shaped fault patterns and flexures. The duplex shears fail again along the dominate Riedal shear axis. The duplex fault pattern is apparently repetitive in ~3-km intervals through the region, as predicted by other authors. These complex fault patterns subdivide the various Badenian reservoir levels into a series of rhomblike compartments in which both juxtaposition and clay smearing within fault planes may play a critical role in trap seals.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas