SEDIMENTOLOGY AND PETROGRAPHY OF MARIANNA AND GLENDON LIMESTONES OF THE VICKSBURG GROUP IN SMITH COUNTY, MISSISSIPPI
The contact between the Marianna Limestone and the underlying Mint Spring Formation is not exposed in the Smith County Quarry. Here, the Marianna Limestone is only 5 meters thick. It consists of poorly lithified to unlithified, highly bioturbated, carbonate mud and fossil fragments. Petrographic observations show abundant fossils of bryozoans, mollusks, and forams. Highly weathered glauconite grains and detrital sand-sized quartz are also present. Marianna Limestone lacks any high-energy sedimentary structures suggesting deposition in deep water below wave base.
The overlying Glendon Limestone is also 5 meters thick at the Smith County quarry. It consists of five highly lithified, ledge-forming limestone layers which alternated with poorly lithified marly limestone beds. Each layer varies in thickness from 20 cm to 80 cm. The transition between the two layer types is gradational. Petrogrpahic studies indicate that both layers are highly fossiliferous. In addition, lithification occurred by precipitation micrite cement in ledge-forming layers. Traction current features are absent in the Glendon Limestone suggesting deposition below a wave-based environment.