ABSTRACT: Dynamic Response of Carbonate Systems Tracts to Relative Sea Level Changes and the Development of Carbonate Depositional Sequences in Platforms and Ramps

C. Robertson Handford, Robert G. Loucks

Some carbonate facies models are extremely useful for interpreting the paleoenvironments of most cratonic and shelf-margin carbonates, but these models do not address how environments and their depositional products respond to relative changes in sea level. Recently developed depositional sequence models, however, are answering those concerns. Although eustasy, tectonic subsidence, and sedimentation rates control relative sea level changes and are the most important factors controlling the development of carbonate depositional sequences, other important controls also need addressing: initial morphology (ramp or rimmed shelf), continental linkage (attached or detached), marine setting (oceanic vs. cratonic sea, open vs. closed seaway), latitude (tropical or temperate), mag itude of shelf (wide or narrow), climatic factors (orientation to wind and humidity), sediment type (carbonate, carbonate/clastic, carbonate/evaporite, and carbonate/evaporite/clastic), and age (Paleozoic with no calcareous pelagic oozes, post-Paleozoic with calcareous pelagic oozes). When combined with the widely acknowledged fact that siliciclastic and carbonate depositional principles are profoundly different, these factors mandate the need for developing a variety of carbonate depositional sequence models for rimmed shelves and ramps that demonstrate the autogenesis of carbonate sediments, the unique ability of carbonate environments to develop pronounced sea-floor topography, and the tendency of carbonate terrains to develop karst topography. Carbonate depositional sequence and syst ms tract models presented here are geologic based in that they were synthesized from modern and ancient carbonate systems. They represent idealized and expected responses to relative sea level changes and assume total representation and preservation of products.

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