A survey of the topography, sediments, and faunas in the northeastern Gulf of Mexico has demonstrated the presence of a belt of calcareous, reef-like features near the edge of the continental shelf between 40-55 fathoms. The zone of prominences is approximately one mile wide and discontinuous with 10-20-mile gaps. The average relief of the pinnacles is 30 feet.

A detailed study has been made of a 5-square-mile section of this feature at the edge of the shelf south of Mobile, Alabama. The sedimentary and faunal characteristics of the deposits form natural groupings that can be correlated with submarine topography, past and present ecological conditions, and history of the region.

This reef is intermediate in stage between active growth and fossilization and possesses some characteristics of both stages. Past and present processes have tended to distribute and modify the sediments and faunas so as to present a complex pattern of indigenous, relict, and reworked sedimentological characteristics in the area today.

The reef flourished under previous environmental conditions of shallower, possibly warmer waters. It has not survived a rise in sea-level and is now undergoing slow modification by aftergrowth and self-burial. The probability is high that this feature will be preserved in the geologic column. In some characteristics, it resembles known ancient reefs.