--> Abstract: Lowstand System Tract Deposition of the Western Malvinas Basin, by M. Toland, D. Kokogian, and W. Abbott; #90987 (1993).

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TOLAND, MICHAEL, DANIEL KOKOGIAN, and WARD ABBOTT, Occidental Petroleum, Bakersfield, CA

ABSTRACT: Lowstand System Tract Deposition of the Western Malvinas Basin

The western Malvinas basin, located approximately 150-200 km offshore of the coast of Tierra del Fuego in southern Argentina, offers excellent examples in the Tertiary section of lowstand system tract deposition. Deposited on the basin floor and passive margin shelf the prominent features are, respectively, an extensive basin floor fan covering the base Tertiary unconformity and slope fan turbidite mounds or prograding wedges advancing west to east across the basin.

The basin floor fan turbidite dominates the base Tertiary in the area of study; it is noticeable for the upper/mid/lower turbidite segments that can be defined from seismic. Major channeling, characteristic of upper fan deposition, can be interpreted. Also, increasingly parallel continuous reflectors of the mid to lower fan can be mapped as sediment is transported further from the source and energy. The overall geometry of this giant "wedge" can be followed seismically tens of kilometers even to the most distal depositional point on the basin floor fan.

The prograding wedges prograde across this passive margin and are dominated by shales or thin-bedded turbidites which correspond to the final stage of the turbidite system. Wells penetrating the features have encountered this type of lithology.

Due to its geotectonic location, the Malvinas basin also provides an excellent opportunity to compare the different stratigraphic framework developed either in a passive margin (north and east flank of the basin) or in an active margin (south flank).

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.