Paleobathymetry and Paleotopography in the Gulf of Mexico: Comparison of Results from Cross-Section Restoration and Biostratigraphic Analysis

Mark G. Rowan, Tomas Villamil, Paul Weimer, Peter B. Flemings

A key factor in modeling the evolution of extensional basins is the progressive change in sea-floor topography and water depth through time. In computer-aided restoration of cross sections, the sea floor template has traditionally been constructed somewhat arbitrarily with a reasonable slope and estimated water depths. Faunal assemblages from well data can be used to constrain the solution, but these data are often unavailable or imprecise.

A systematic method has been developed for sequential backstripping and restoration of cross sections in areas of gravitational extension and salt tectonics (e.g., Gulf of Mexico). In addition to incorporating standard decompaction and structural restoration, the technique calculates the isostatic effects of sedimentary loading and salt movement; the result is that the paleobathymetry can be determined at selected points along a section for each restoration stage. These points are connected to construct sea-floor paleotopographic profiles, which are then used as templates for the structural restoration. Furthermore, restored salt geometries can be used to adjust the constructed sea floor based on topographic features observed over currently active salt diapirs.

The method has been tested along a regional N-S profile through western Eugene Island (offshore Louisiana). The results are compatible with water depths derived from biostratigraphic analyses and interpretation of depositional environments from nearby wells, and they show the gradual southward progradation of the shelf edge over the last 5 million years. The predicted water depths are more precise than the paleobathymetric environment ranges, but they are not necessarily more accurate. This method, if applied to analogous areas throughout the world where well data are less common, can be used to predict sedimentation patterns, depositional environments, and potential reservoir development.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995