--> Abstract: Deep-Water Axial Channel Deposition in Foreland Basins, Cretaceous Magallanes Basin, Chile and Oligo-Miocene Molasse Basin, Austria, by Stephen M. Hubbard and Menno J. De Ruig; #90039 (2005)

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Deep-Water Axial Channel Deposition in Foreland Basins, Cretaceous Magallanes Basin, Chile and Oligo-Miocene Molasse Basin, Austria

Stephen M. Hubbard1 and Menno J. De Ruig2
1 Stanford University, Stanford, CA
2 Rohöl-Aufsuchungs A.G, Vienna, Austria

Deep-water sedimentation in elongate basins is often dominated by axial currents, with secondary influences from transverse flow that inputs material from lateral margins. Axial currents focused within the confines of broad channels promote the transport of coarse material over long distances. Two examples of foreland basins characterized by deep-water sedimentation in immense, axial channel belts are the focus of this study: (1) the Cretaceous Cerro Toro Formation of the Magallanes Basin in southern Chile, and (2) the Oligo-Miocene Puchkirchen Formation of the Molasse Basin in Upper Austria.

Coarse-grained deep-water deposits of the Cerro Toro Formation are present along an outcrop belt >100 km long. Sediment accumulated in a 4-5 km wide channel belt that occupied the axial foredeep of the basin. Deposits are characterized by fining and less amalgamation towards channel margins. Margin architecture is characterized by laterally offset coarse-grained packages 50-100 m thick interfingered with constructional out-of-channel deposits.

Deposits of the Cerro Toro Formation are an excellent architectural analog to gas-prone sediments of the Puchkirchen Formation. A 3-5 km wide by 10's of km long channel system has been imaged in an extensive 3-D seismic dataset, calibrated by 100's of wells. The channel is characterized by broad meander bends that migrated over time and resulted in margin asymmetry, and channel fill consisting of conglomerate, sandstone and slump/debris flow deposits. Gas is produced primarily from thick-bedded channel-fill sandstone and thin-bedded overbank sedimentary bodies. Comparison of the two datasets offers a unique perspective of deep-water sedimentation in foreland basins.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005