COASTAL PROCESSES AND ANTHROPOGENIC FACTORS INFLUENCING THE GEOMORPHIC EVOLUTION OF WEEDON ISLAND, FLORIDA

Weedon Island, a peninsula located on the western inner shoreline of Tampa Bay, Florida, is the location of a collaborative geological and archaeological project that aims to relate the present day geomorphology to natural processes and human occupational activity during the middle to late Holocene. The area is known for its extensive archaeological sites, which were originally investigated in the 1920s, but have received relatively little scientific attention during most of the last century. We hypothesize that activities associated with pre-historic human occupation of Weedon Island at various times during the last ca. 5,000 years influenced the geomorphic evolution of the shoreline and the development of the upland landscape across the peninsula. An interdisciplinary approach, including geomorphic mapping, sediment-coring, and archaeological survey and excavation is being used to test our hypothesis and is expected to reveal the extent to which natural processes and human activities interacted to shape the present-day configuration of the peninsula.

To date 37 vibra-cores have been recovered in a transect from Riviera Bay, an inland body of water connected by tidal channel to Tampa Bay, across multiple dune ridges, depressions, freshwater wetlands, and forested uplands, to the pre-development shoreline position. Coring has revealed multiple paleosol horizons and buried archaeological midden deposits, which allow us to reconstruct the vertical aggradation of coastal and inland sediments. Initial radiocarbon dating on charcoal provides an age estimate of 1450 ± 40 ¹⁴C yr B.P. for the upper midden horizon. Wood fragments from a sand layer at the base of the core give a pre-occupation age of 3370 ± 50 ¹⁴C yr B.P. Additional dating and sediment analysis are expected to reveal paleoenvironmental shifts associated with mid to late Holocene sea-level rise and pre-historic human activity. More recent human impacts on the peninsula may impede our efforts in some areas. During the twentieth century, dredging, mosquito ditching, and road construction, have disturbed the surface and portions of the upper sediment record in many locations. Sediments below obvious disturbances or in unimpacted areas of the peninsula, along with current and planned radiocarbon dating will help reconstruct the mid to late Holocene paleoenvironments and paleolandscape of Weedon Island.