ABSTRACT: Modeling Stratigraphic Sequences in Clastic Sedimentary Basins

Peter B. Flemings, Teresa E. Jordan

Sequence stratigraphy is used routinely for stratigraphic correlation and for predicting lithofacies in undrilled areas. We have developed a forward, process-based, stratigraphic model for clastic depositional systems in passive margin and foreland basins. The model predicts basin fill in two dimensions, including depositional sequences, in response to user-defined histories of subsidence, sea level, and sediment transport. Conceptual models of a basin's history over durations of 10⁵ to 10⁸ yr can be tested.

We illustrate the strengths and limitations of such a deterministic model by testing the premise that key features of depositional sequences in passive margin basins correlate to particular phases of a eustatic sea level cycle. As is consistent with empirical studies of passive margins, the computer model predicts that sediment passes into the marine zone during sea level fall and is trapped in the nonmarine zone during sea level rise. An input sinusoidal sea level history generates depositional sequences bounded by unconformities that are cut during sea level fall. The model goes beyond conceptual approaches by revealing that the ages of unconformities are dependent on the period of the sea level cycle. For long cycles (>30 m.y.), sequence-bounding unconformities are coincident wi h the time of maximum rate of sea level fall. However, for short cycles, the sequence boundary ages approach lowstand ages, but the exact age of the sequence boundary depends on the amplitude of the sea level curve, subsidence rate, and rate at which sediment is supplied to the basin.

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