STECKLER, MICHAEL S., and DAVID J. REYNOLDS, Lamont-Doherty Geological Observatory, Palisades, NY

ABSTRACT: Modeling Shoreline Position and Facies Distribution in a Sequence Stratigraphic Framework

We have developed a numerical stratigraphic model to attempt to predict facies distributions in siliciclastic sequences. Sequence stratigraphy at the seismic scale provides a methodology for identifying the geometry of genetic packages of strata. However, it is important to recognize that sequence geometries alone do not serve as proxies for facies distributions. Previously, the `Exxon' conceptual model of sequences equated the clinoform break-in-slope or `offlap break' with the shoreface position. However, the shoreline is commonly located further inland than the clinoform break-in-slope and is associated with an order of magnitude smaller (5-10 m) topographic break. No model of sequence formation has yet achieved satisfactory prediction of facies distributions from seismics in silic clastic systems. To evaluate possible models of shoreline migration within sequences we utilize a physically-based numerical model that includes the effects of sea level, sedimentation, tectonic subsidence, isostatic compensation, and compaction on sequence formation and systems tract geometry. We present results for three widely used models of shoreline response to sea level change: (1) The shoreline position is coincident with the clinoform break-in-slope; (2) A modified Bruun's rule in which the shoreline shift is linearly proportional to the relative sea level change; and (3) The shoreline is determined by the volume of sand in the sediment supply. Correctly identifying the position of the shoreface has major consequences for both reservoir location and measurement of sea level chang s.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.