--> Simulation of Facies Development and Depositional Geometries in Carbonate Ramp Environments: Examples from the Jurassic Smackover and Permian San Andres Formations, by P. A. Levine, C. G. St. C. Kendall, P. D. Moore, and R. Cannon; #90986 (1994).

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Abstract: Simulation of Facies Development and Depositional Geometries in Carbonate Ramp Environments: Examples from the Jurassic Smackover and Permian San Andres Formations

Phillip A. Levine, Christopher G. St. C. Kendall, Phillip D. Moore, Robert Cannon

Carbonate ramp depositional sequences provide a sensitive record of the interaction between carbonate production and accumulation rates, eustatic sea level fluctuations, and subsidence. Variations in the sedimentation character and facies relationships that develop within this carbonate environment directly result from the interplay between these controlling factors. In an effort to extend our understanding of the development of shallow carbonate shelf facies and their resulting geometries, two carbonate ramp settings are simulated.

The first example is the Upper Jurassic Smackover Formation of the Gulf of Mexico. This formation consists of two carbonate sequences deposited in a ramp setting during a marine transgression/stillstand. The lower sequence consists of low-energy, shallow subtidal mudstones, whereas the upper sequence consists primarily of high-energy, shallow subtidal to intertidal, upward-shoaling grainstones and packstones. The contact between the two sequences is gradational.

The second example is the Upper Permian San Andres Formation of west Texas and New Mexico, which was deposited as a shallow carbonate ramp and can be subdivided into three depositional sequences. The lower San Andres consists of a low-energy transgressive sequence of dolomitized wackestones and packstones. The middle unit is separated from the lower unit by a drowning surface and consists of shallow subtidal mudstones which pass upwards into packstones and grainstones. This unit represents a shallowing upward sequence deposited during a high-energy highstand. The uppermost unit consists of oolitic grainstones, which are interpreted to represent an abrupt lowering of sea level.

Simulation of both the Smackover and San Andres formations illustrates the complex depositional facies geometries resulting from carbonate ramp deposition. The facies are modeled as a function of lateral position across the ramp, position with respect to adjacent facies, and water depth. Our results include a generalized conceptual model for predicting the distribution of these facies geometries.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994