ANALYSIS OF SEDIMENTARY DEPOSITS ON DICKMAN’S POINT BEACH, SOUTHWEST FLORIDA: NATURAL AND ANTHROPOGENIC INFLUENCES

Dickman’s Point Beach is located at the northern tip of the Ten Thousand Islands chain in Collier County, Southwest Florida. Unlike many coastal islands, it has been uninhabited and undeveloped since European settlement (circa 1600). It is possible that the sediments and Anthropocene growth of this island should represent natural, non-anthropogenically influenced barrier island development. This survey study examines these natural sedimentary processes and the potential impact of nearby human activity on the geomorphological development of Dickman’s Point.

Field collection included 5 surface grab samples, 14(61cm) sediment cores and GPS locations along multiple north-south and east-west transects. Sieve analysis of whole sediment samples range from cobble to clay size. Sediment composition averaged 63% quartz and other siliciclastics, 12% whole/comminuted carbonate shells and 25% organic and clay size particles. Grain size analysis and frequency distributions of sand were conducted to determine the origin of beach deposits. Ground Penetrating Radar (GPR) data were collected along the same transects to study profiles of subsurface structures and storm influence.

LiDAR datasets (courtesy of Florida Department of Environmental Protection) were analyzed for elevations along the perpendicular transects and used to construct a base map for this and future studies. Additionally, satellite (from 1995-2020) and aerial imagery (from 1926-2020) were evaluated to determine the presence of a north-south longshore current with a notable amount of sediment possibly being worked into the beach at Dickman’s Point.

Both sediment and GPR profiles indicate action on the beach by major storms and wave activity. The GPR profiles, and composition and size range of beach sediments may also have been influenced by anthropogenic detrital replenishment efforts from Marcos Island directly north of Dickman’s Point. Historical Marco Island renourishment volumes provided by CCCAC (Collier County Coastal Advisory Committee) report that 1.75 million yd³ of nearshore, offshore, and upland detrital materials have been added to Marco Island Beaches since 1991. Increasing sea level and storm intensity may be confluent factors in the sedimentological and geomorphological development of Dickman’s Point.