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Isostatic Controls on Carbonate Platform Development

T. Aigner, M. Doyle, D. T. Lawrence

Although carbonate bodies represent a significant surface load on the lithosphere, isostatic effects have been little studied in carbonate systems. In addition to well-documented controls such as spatially varying growth potential, the isostatic response to carbonate platform loads can be an important control on a variety of large-scale patterns in carbonate platform evolution.

(1) The "bucket structure" as the basic anatomy of carbonate platforms can be explained isostatically by load-induced sagging of platform interiors and upbulging of platform margins. (2) Pulses of rapid sea level rises may transform isostatically sagged platform interiors into partly drowned "intra-platform basins" surrounded by elevated rims. (3) Differential drowning of isostatically sagged platforms may cause a wide-spread megabank to evolve into an archipelago of isolated platforms and intervening troughs. This may be an alternative mechanism for the origin of isolated platforms in the Bahamas. (4) Isolated pinnacle reefs within carbonate/evaporite provinces that occur close to the shelf margin may be initiated in flexural bulges developing beyond the edges of the load of the carb nate shelf during a cycle of sea level fall and rise.

Quantitative computer simulations of the isostatic control on carbonate platform development will be presented.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.