GEOMORPHOLOGY OF A LATE HOLOCENE CARBONATE STRANDPLAIN ON SAN SALVADOR ISLAND, BAHAMAS

San Salvador Island exists as an isolated carbonate platform, whose southeastern extent sharply transitions from a shallow lagoon environment to the deep water of the open North Atlantic. The formation of a ~1.5 km²strandplain complex along this wave- and storm-dominated coastline is linked to the Hurricane Hyperactivity Period in the Caribbean, which lasted from 1000 – 3400 ybp. This strandplain has prograded ~ 1km eastward over the late Holocene, producing four distinct sets of strand lines that vary in orientation, area, ridge elevation and spacing.

The sets become progressively older with increasing distance landward. The oldest deposits occupy the highest elevation; whereas, the youngest deposits occupy lower elevations. Set one contains 10 ridges with an average spacing interval of 0.05 km and occupies an area of 0.56 km²; set two: 5 ridges, 0.04 km and 0.21 km²; set three: 4 ridges, 0.04 km and 0.17 km²; and set four: 11 ridges, 0.03 km and 0.61 km², respectively. As the strandplain progrades, the newer sets truncate the older ones. It appears that sediments deposited atop the seaward dipping bedrock explains part of this profile.

A study is currently underway to better characterize the morphology of this strandplain complex and its late Holocene evolution. GPR will provide insight into the depositional nature of this coastal region, while surveying the height of the individual strands may serve as an additional proxy of storm intensity and frequency. Sediment analyses of strand deposits will help reveal changes in the nature of sediment supply regimes. Mapping topography and subsurface architecture of this strandplain will provide insight into how sea level rise, sediment supply, and hurricane influence drive morphologic change.