CORRELATION OF LITHOFACIES AND DEPOSITIONAL ENVIRONMENTS IN SILURIAN ROCKWOOD FORMATION OUTCROPS NEAR CHATTANOOGA, TN

Exposures of the Silurian Rockwood Formation in the Chattanooga, TN area are measured for bed thickness, grain size and composition, type of cement, and fossil content. Four stratigraphic units are identified in the thickest measured section and other sections are correlated to it. Stratigraphic units are characterized on the basis of thickness and number of siliciclastic shale, siltstone, limestone beds; type of cement; presence of fossils –brachiopods, bryozoans, solitary rugose and colonial tabulate corals, trilobite and echinoderm fragments. The depositional environment of the Rockwood in this area is interpreted as foreland-basin deposition of sediment affected by storms. Evidence supporting this interpretation includes interbedded siliciclastic shale-siltstone beds, the presence of parallel-laminations and low-angle truncations in the siltstone/fine sandstone beds, and the reestablishment of brachiopod communities on upper bedding planes of coarser-grained beds. Some portion of section thickness in at least one locality may be attributed to repetition of strata due to Alleghenian thrust-faulting; large and small thrust faults are observed in the field.