Sedimentology, Stratigraphy and Geophysics of An Inner Shelf Shoal off Choctawhatchee Bay, Florida, USA

Though tectonically stable, the northeast Gulf of Mexico (GOM) is a storm dominated coast, receiving impacts from both tropical cyclones and cold fronts. However, the extent of the effect of these storms on the geomorphology and stratigraphic structure of the sediments on the inner shelf/nearshore region is not well understood. This study focuses on a smaller area of the northeastern GOM than previous studies, specifically a northeast-southwest trending shoal on the inner shelf and the adjacent nearshore region off the western Florida Panhandle, USA, in order to assess the stratigraphic and sedimentological evolution at a finer scale. This region is of particular interest given the increase in tourism and development in the past decade, as well as the increase in tropical storms in recent years. In addition, the shoal and nearshore regions have been designated as potential borrow sites of high quality sands for beach re-nourishment. In this study, sub-bottom (seismic) profiles and 277 vibracores, their stratigraphic logs and granulometry were analyzed. Preliminary results indicate that the shoal and nearshore region are characterized by a regionally transgressive sand sheet, the Mississippi-Alabama-Florida (MAFLA) sheet sand; this is a medium-to-fine grained deposit, underlain and sometimes interbedded by clay and organic material. The nature of this material does not conform to published data, indicating that previous concepts of material reworked offshore during storm events, may not be valid for this region. Modern indications of suspended sediments are evident in satellite imagery of MODIS true color images post-hurricanes. Further research is being conducted via radiocarbon dating of the organic material and geophysical interpretations, with the primary objective of more accurately describing the geological and physical forcing mechanisms affecting this region and the complexity of its structure.