ABSTRACT

At Stone City Bluff in southeast Texas, the contact between the Stone City Formation and the Cook Mountain Formation lies at the top of the Moseley Limestone. The contact is significant because it has been interpreted both as a regional disconformity marked by lithoclasts and alternatively as a conformable surface marked by burrow- fill structures protruding through the top of the limestone. The true nature of this contact is important because it may yield insight into the recognition of breaks in sedimentation within sections consisting of terrigenous marine sediments. The former interpretation is correct. Lithoclasts are of two types: rounded clasts of"glauconite" arenite and irregularly shaped clasts of dark limestone, both of which are similar to rock types found within the Moseley Limestone. Both types of clasts were exposed as lithified objects on the seafloor because they have epibionts and endolithic traces preserved within them. The clasts originated by early diagenetic cementation in the form of concretions and lithified burrow fillings, which were then exposed by seafloor erosion. During a subsequent interval of nondeposition, encrusting and boring biota colonized the clast surfaces. The Moseley Limestone was pervasively cemented after final burial, with the clasts cemented to the upper surface. These relationships provide a more thorough understanding of the depositional history of the Moseley Limestone and criteria useful in recognizing sedimentation breaks in terrigenous strata.

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