GEOMORPHOLOGIC INVESTIGATION OF A WASHOVER-FAN COMPLEX, SAN SALVADOR ISLAND, BAHAMAS

San Salvador, one of the easternmost Bahamian islands, faces the open Atlantic and is frequented by strong storm events, which leave distinguishable sedimentary signatures along the island’s coast. Overwash deposits are commonly found here extending into coastal water bodies and offer an opportunity to investigate their formation and evolution in response to repeated storm influence.

One of the prominent washover fans on the island is located on the southeastern side, separated from the shoreline by a ~3 m-high dune ridge. The sandy fan extends northward from the beach environment into a stagnant basin formerly connected to a tidal lagoon. Aerial photographs reveal that this feature has been in existence since at least the early 1940s; however, newer aerial photographs and satellite images suggest that this washover fan has considerably evolved in terms of its morphology. Research currently underway aims to reconstruct the internal architecture of this washover fan using GPR and core data in order to elucidate the nature of deposition and its control mechanisms.

Preliminary findings suggest that this fan was deposited over multiple storm events. This is most evident in cores collected from atop the feature, which show stacked sequences of fining upward, coarse- to medium-grained carbonate sands containing debris, interpreted as storm-washover layers. These are separated by organic-rich and finer-grained sand deposits, inferring more quiescent conditions and aeolian transport.

Additional work will expand upon these preliminary findings and likely facilitate a more process-oriented understanding of the nature of fan evolution in carbonate settings. GPR data collected from atop the subaerial fan structure may provide a means to quantify sediment volumes for each respective depositional package while additional cores from the more distal, subaqueous pond basin may provide information on the full spatial extent of overwash. A detailed understanding of this washover feature and its evolution is useful for better constraint of the dynamics of costal response to storm influence.