Contrasting Facies Architecture of Wave- and Tide-Dominated Coastal Sand Bodies

Richard A. Davis, Jr.

Coastal sand bodies are widespread in the stratigraphic record and have become objects of extensive exploration for petroleum. Most of these sand bodies are products of barrier island complexes and therefore reflect a combination of wave- and tide-dominated conditions. Recognizing the dominant process from the stratigraphic sequence permits the development of the appropriate facies architecture, which can greatly increase the efficiency of exploration.

Wave-dominated coastal sand bodies represent two major environments: beach/nearshore zone and washover fans. The beach/nearshore sequence includes textural trends, predictable physical and biogenic structures, and paleocurrent indicators that permit detailed reconstruction of the environment. Both transgressive and progradational sequences of these linear, shore-parallel sediment bodies are preserved and have a relatively simplistic architecture compared to other coastal sand bodies. The washover facies also has its own characteristic sequence, but it appears similar both under transgressive and progradational conditions. These thin and tabular sand bodies tend to be individually local but can coalesce into extensive systems.

Tide-dominated sand bodies are restricted in their extent in the barrier island complex and may represent three basic components of tidal inlets, each having markedly different architecture and preservation potential. These are ebb-tidal delta, flood-tidal delta, and the spit platform which fills the migrating inlet. The ebb-tidal delta is rarely preserved and shows a combination of both wave- and tide-generated features in its sequence and architecture. The inlet fill sequence is dominated by tidal features with minor wave influence. The flood-tidal delta consists of tide-generated features. Both of the latter have high preservation potentials and distinctive architecture.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.