--> Abstract: Stratigraphic Interpretation of an Upper Pleistocene Sequence in a Salt-Bounded, Intra-Slope Basin, Offshore Louisiana, by T. D. J. England; #91012 (1992).

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ABSTRACT: Stratigraphic Interpretation of an Upper Pleistocene Sequence in a Salt-Bounded, Intra-Slope Basin, Offshore Louisiana

ENGLAND, TIMOTHY D. J., BP Exploration, Houston, TX

Pleistocene sedimentation on the upper slope of the Gulf of Mexico, offshore Louisiana, was extremely rapid, resulting in thick, undercompacted, bathyal deposits concentrated in salt-bounded subbasins. In northwestern Green Canyon, these subbasins had developed in the Pliocene by local withdrawal of a thick, Miocene canopy of allochthonous Jurassic salt. Although sedimentation was rapid, it was episodic, peaking several times during the Pleistocene, and much reduced during intervening times. This episodicity is evident in cycles of high amplitude continuous reflectors alternating with relatively acoustically transparent zones on seismic profiles of the succession. Well data confirm that many of the high amplitude, continuous reflectors are sand-poor, condensed intervals, deposited dur ng times of reduced sediment influx to the subbasins.

In one subbasin, which contains about 6000 m of Pleistocene sediment, a particularly thick (1200 m) and seismically distinct sequence is examined. Stratigraphic interpretation of this sequence relies on seismic facies analysis and data from one well. The sequence is partitioned into several units, which are from oldest to youngest: (1) a basin-floor fan deposit, (2) a channelized unit, (3) a nonchannelized unit, (3) a basin-edge fan deposit, (4) a prograding complex, and (5) a draping, passive-infill unit. The complex sedimentation in this basin was greatly influenced by local salt movement, which modified the basin topography by at least 1000 m during the 0.25 m.y. interval of sedimentation of the sequence.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)