SEQUENCE STRATIGRAPHY AND DEPOSITIONAL HISTORY OF MIDDLE-MISSISSIPPIAN CARBONATES OF THE SOUTHERN APPALACHIANS, TUSCUMBIA, AL

Mississippian low-latitude shallow-water carbonate deposits in the southeastern U.S. (Fort Payne Formation and Tuscumbia Limestone) currently lack a detailed depositional framework. The goal of this field-based research is to develop a sequence stratigraphic framework and detailed facies analysis as a basis for understanding depositional histories of well-exposed Mississippian carbonate systems in northwestern Alabama. This in turn, will be used to evaluate controls on deposition (e.g., nutrients, sea level, tectonics, paleogeography, and paleoceanographic conditions) and possible sources of the silica (chert) found within these units (e.g., continental runoff, upwelling). Field work will consist of measuring stratigraphic sections; physically tracing strata and surfaces; documenting sedimentary structures, facies, and diagenetic features indicative of sea-level positions; and collecting structural data (strike and dips, fault mapping) and way-up indicators to determine the amount of structural deformation overprinted on depositional profiles. Rock samples will be collected for petrographic thin-section analysis to further refine facies designations and estimate porosity. Field and lab data will be used to correlate strata and interpret depositional environments. Our results will be correlated with similar North American Mississippian carbonate systems (e.g., Kansas, Missouri, Georgia, Tennessee), which will allow for recognition of larger scale depositional patterns and controls on the systems. Additionally, preliminary results from this study indicate the presence of a heterozoan-dominated (minor photozoans) system that formed in a low-latitude shallow-water setting. The absence of photozoans in this setting suggests a perturbed depositional system. Ultimately, this project aims to evaluate the depositional controls (e.g., water depth, turbidity, nutrient levels, temperature) on the distribution of heterozoan versus photozoan facies. Understanding these systems aids in the development of predictive reservoir models and the study area will serve as an outcrop analog for subsurface producing Mississippian units (e.g., Black Warrior Basin).