--> Abstract: Carbonate Gravity-Flow Processes on the Lower Permian Slope, Northwest Delaware Basin, by R. G. Loucks, A. A. Brown, and C. W. Achauer; #91004 (1991)

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Carbonate Gravity-Flow Processes on the Lower Permian Slope, Northwest Delaware Basin

LOUCKS, ROBERT G., ALTON A. BROWN, and C. W. ACHAUER, ARCO Oil and Gas Company, Plano, TX

Wolfcampian carbonate gravity-flow deposits accumulated on a low-angle slope in front of a platform of relatively low relief (220 m). A 25 m core, located approximately 15 km basinward of the self margin, was examined to determine processes of carbonate deposition in the middle to distal slope environments. The majority of the deposits are cohesive debris-flows composed of clast-supported conglomerates with a calcareous siliciclastic mudstone matrix. Other deposits include high- and low-density turbidites of lime packstones (sand- to boulder-size range), lime grainstones, and siliciclastic muddy siltstones and suspension deposits of calcareous siliciclastic mudstones.

Cohesive debris flows are generally massive and structureless, although several flows show an inverse-graded zone at their base indicating dispersive pressure forces that developed in a traction carpet. Other flows display coarse-tail fining-upward sequences indicating deposition by suspension settling from liquefied flow.

At the base of each high-density, gravelly turbidite is one to several inversely graded zones of carbonate clasts indicating a traction carpet zone. These traction carpets are overlain by normal-graded units of shell and clast material. The upper units appear to be deposited directly out of suspension. The low-density turbidites are interpreted to be the residual products of more shelfward-deposited debris flows and high-density turbidity currents. The residual products consist of Tc (starved ripple), Td (faint grain-laminated), and Te (suspension mud) layers.

Many of the depositional features decribed here for carbonate gravity-flow deposits are identical to those in siliciclastic deposits, therefore the depositional processes controlling these features are probably similar.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)