(1) University of Alabama, Tuscaloosa, AL
ABSTRACT: Lower Cretaceous Rudist Outcrop Analog for Washita Reefs in the Northeastern Gulf of Mexico
Lower Cretaceous (Upper Albian to Lower Cenomanian) caprinid reef facies have been recognized and studied in core from the OCS Main Pass Field located along the Lower Cretaceous shelf margin trend in the northeastern Gulf of Mexico. Rudists, which constitute the reef framework, are interpreted as being in growth position (semi-recumbent). The buildup represents a reef of more than 20 meters in thickness, or represents a succession of smaller patch reefs. Because these carbonates have been highly dolomitized and are not exposed in outcrop in the eastern Gulf Coastal Plain, it is difficult to determine their geometries and extent for accurate petroleum reservoir characterization and modeling.
A Lower Cretaceous (Aptian) caprinid reef of about 3 meters in thickness exposed in the Southern Alps, Italy, has been analyzed for comparative study. The rudists, which constitute the reef framework, are well preserved and are in growth position(semi-recumbent to semi-erect). These reef caprinds are tightly packed, and no other macrofossils appear to contribute to the buildup. Previous workers have interpreted the buildup as a patch reef that developed in a platform environment on a substrate that was faulted and subsequently exposed.
By using the Lower Cretaceous rudist outcrop in Italy to assist in the characterizing and modeling of Washita reefs in the northeastern Gulf of Mexico, geoscientists and engineers can develop improved reservoir models for hydrocarbon development of Washita rudist reef carbonates.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado