--> ABSTRACT: Modeling Carbonate Progradation Geometry and Sediment Accumulation Rates: A Comparison of MARGIN Results with Outcrop Data, by Mark T. Harris; #91003 (1990).

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ABSTRACT: Modeling Carbonate Progradation Geometry and Sediment Accumulation Rates: A Comparison of MARGIN Results with Outcrop Data

Mark T. Harris

The relatively simple geometries of carbonate buildup margins are amenable to quantitative computer modeling. MARGIN allows comparison of how different margin geometries and sediment accumulation patterns influence progradation geometry.

MARGIN is a sediment accumulation model of a carbonate buildup written in Pascal for an IBM PC. The model uses a generalized three-dimensional buildup geometry with a circular or linear margin geometry, a foreslope with a constant dip, and a flat basin. The subsidence history, sediment production rate, and basinal sediment accumulation rate control the addition of sediment during a series of iterations. The simulation ends when the basin fills, the platform drowns, or a preselected platform thickness is reached. MARGIN calculates the buildup's geometric dimensions, relative rates of sediment accumulation, and outputs a scaled cross section.

Variations in sediment accumulation parameters or initial buildup geometry result in quite different progradation geometries. Enhanced progradation results from (1) low buildup relief, (2) steeper foreslope, (3) slow subsidence, (4) high sediment production, (5) linear margin geometry, and/or (6) high rates of basinal deposition.

For buildups several hundreds of meters thick, the extent of progradation depends upon the basin fill rate. Starved basins ultimately become too deep for foreslope infilling in all simulations. This geometric relation suggests that the thickness and timing of basinal sedimentation (commonly siliciclastics or evaporites) is a controlling factor on carbonate buildup progradation.

These results provide insights for interpretation of ancient buildup geometries (Triassic of the Dolomites, Permian of the Guadalupes). In these examples, the extent of buildup progradation appears dependent upon basinal deposition.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990