--> Abstract: Simulation of the Evolution of a Lower Cretaceous Ramp to Rim Carbonate Margin in Texas and Louisiana, by G. Whittle, C. C. St. C. Kendall, R. W. Scott, P. Moore, R. L. Cannon, D. R. Hellmann, and K. Spainhour; #90987 (1993).

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WHITTLE, GREGORY, and * CHRISTOPHER C. G. ST.C. KENDALL, Department of Geological Sciences, Univ. of South Carolina, Columbia, SC; ROBERT W. SCOTT, Amoco Production Research, Tulsa, OK; PHILIP MOORE, Department of Geological Sciences, Univ. of South Carolina, Columbia, SC; ROBERT L. CANNON, DOUGLAS R.HELLMANN, and KEITH SPAINHOUR, Department of Computer Sciences, Univ. South Carolina, Columbia, SC

ABSTRACT: Simulation of the Evolution of a Lower Cretaceous Ramp to Rim Carbonate Margin in Texas and Louisiana

The depositional sequences of the Albian shelf margins of Texas and Louisiana display: 1) ramp to rim geometries created during times of aggradation and progradation at locations where the carbonate accumulation rate kept up with rises in relative sea level, and 2) drowned surfaces where carbonate production could not match rises in relative sea level.

The ramp systems tracts of the Comanche Shelf are aggrading wedges composed of downdip transgressive muds grading updip into coastal plain clastics; the rimmed margin systems tracts are prograding wedges of highstand shelf lagoon, shelf margin and forereef slope facies. These systems tracts were primarily influenced by the available accommodation created by the combined effects of sea level fluctuation and tectonic subsidence. The end members produced by significant changes in accommodation are inferred to be: 1) drowning uncomformities - where pelagic facies overlie shallow shelf facies; and 2) exposure unconformities - where terriginous facies overlie marine carbonate facies.

Successful simulation of the geometries of the Comanche Shelf depositional sequences, as observed in seismic cross section, was accomplished using SEDPAK. This 2-D computer modeling program allows models to be constrained with such input parameters as clastic and carbonate production, sea level curves, tectonic movement, initial basin surface, and angles of deposition. Experiments were made with the interrelationships between sea level, tectonics, and sediment accumulation to produce progradational, aggradational, and retrogradational geometries to gain insight into the relative importance of each in the overall shelf margin geometries.

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