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Abstract: Four-Dimensional Analysis of Prograding Geologic Systems: Example of the Gulf of Mexico Province*

EVANS, ROBERT, P.O. Box 24, The Sea Ranch, CA 95497

Prograding sedimentary regimes, whether large or small, are four-dimensional systems, and in order to be understood, must be analyzed as such. Geologists can use two-dimensional space-time diagrams, in which one of the Cartesian spatial dimensions has been replaced by time, to elucidate the temporal and spatial interaction of various geological processes. On the diagrams, the existence of a process in space and time is shown as a field, and only where the fields of two such processes intersect can there be any interaction between them. The diagrams have been used effectively in the analysis of various areas of the Gulf of Mexico region where puzzling geologic relationships are extant: sulfur in cap-rock of some domes, but not in otherwise identical structures; abundant petroleum around salt-domes in some areas, but not around other domes in identical geological situations. The four-dimensional analysis explains these disparities: the geologic variability is the spatial effect of the temporal interaction of the various processes that lead to accumulation of oil and gas: generation; migration; structural growth; preservation of traps; erosion. The methodology of four-dimensional analysis is amenable to display in three-dimensional graphics, and can be applied to the sedimentary systems along any trailing continental margin, including areas of exploration interest: the offshore Gulf of Mexico; Angola; the Niger Delta; the North West Shelf of Australia.

* Published with permission of Mobil Exploration and Producing Technical Center, Dallas, TX.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah