ABSTRACT

Several 1- to 3-foot (0.3 to 1 m) thick, calcareous, indurated beds and concretionary zones occupy seemingly consistent stratigraphic positions along the outcrop of the otherwise unconsolidated Aquia and Brightseat Formations (Paleocene) in the Coastal Plain of Prince Georges County, Maryland. Although these key beds have been recognized and used for many years, neither their validity as rock-stratigraphic correlation tools nor the method of their formation have ever been investigated. A very simple and straightforward petrographic analysis of these indurated layers demonstrates their lateral continuity and thereby their usefulness in local lithostratigraphic correlations. The petrographic results and the presence of features similar to those resulting from demonstrably modern cementa ion of shallow sea floors suggests that these indurated beds were formed by syndepositional lithification.