--> Abstract: Fluvial Input to Continental Slope Sedimentation, Southwest Louisiana, by J. R. Suter; #91012 (1992).

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ABSTRACT: Fluvial Input to Continental Slope Sedimentation, Southwest Louisiana

SUTER, JOHN R., Exxon Production Research Company, Houston, TX

An extensive grid of high-resolution seismic profiles shows that the continental shelf offshore southwestern Louisiana is dissected by discrete sets of incised drainage networks that are continuous from the current shoreline to the shelf margin. Mapping of the channel patterns and seismic facies analysis of the channel fill, as well as lithologic and chronological data from platform borings, indicate that these features formed as fluvial systems cut during glacioeustatic falls and lowstands. Three sets of incised drainages of different ages, separated by major flooding surfaces, can be recognized on the profiles. Associated deltaic systems prograded across the shelf, culminating in the establishment of depocenters at the shelf margin, which became the principal sources for sediments o the continental slope.

Depocenter locations are controlled by several factors. On the continental shelf, deposits of previous cycles exert a subtle topographic effect. Major fluvial drainages do not stack vertically but are displaced laterally from one cycle to the next. On the outer shelf and shelf margin, diapirism and growth faulting created topographic relief that influenced fluvial drainages and controlled the positions of slope depocenters.

Sediments were carried across the shelf by fluvial processes but were transported into the slope basins by gravity-driven flow. Interdiapiric basins directly downdip of incised drainages and shelf-margin deltas are filled with sediments that onlap the basin margins and interfinger with or are downlapped by deltaic clinoforms. Sediment thicknesses attributed to the last glacioeustatic lowstand reach as much as 200 m. These interdiapiric basin fills are interpreted as mostly turbidite deposits. Shelf margin deposits are deformed by extensive growth faults and diapirs, resulting in numerous slumps and associated channels that further contributed to downslope sediment transport.

 

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