SEDIMENTOLOGICAL AND FORAMINIFERAL EVIDENCE OF POTENTIAL PALEOSTORM ACTIVITY ON DOMINICA, LESSER ANTILLES

Examining the sediment record for storm deposits provides the opportunity to extend existing hurricane records further back in time. Beach berms may allow for high-energy, storm-transported sediments to become trapped and preserved in the stratigraphic record. Identification of foraminifera assemblages, preservation of the foraminifera tests, and foraminiferal abundance may indicate the environment at the time of deposition. By analyzing these data, depositional facies throughout the core may be distinguished.

A sediment core extending 1.7 meters down was taken just beyond the berm crest at Woodford Hill Beach, on the eastern shore of the Caribbean island of Dominica. The core was logged, and includes observations of sorting, grain size, layer contacts, color, and sedimentary structures. Fifteen samples were obtained at each significant sediment change throughout the core for further grain size and foraminiferal analysis. Grain size analysis results formed lithofacies, while the foraminiferal analysis created biofacies; combined together the analyses describe the depositional facies. These analyses resulted in identification of at least four distinct environments (depositional facies): higher-energy normal marine salinity, average-energy normal marine salinity, lower-energy normal marine salinity, and volcanic ash horizon.

Future work will investigate other locations on Dominica, including cores already collected from beaches extending across the eastern and northern shores. A currently-pending AMS radiocarbon age for an organic layer preceding a potential paleostorm deposit will help determine a more precise date for the paleostorm event. This would provide an opportunity to better understand the distribution of paleostorm deposits on the island. These records could prove valuable as communities plan to rebuild Dominica after Hurricane Maria, which devastated the island in September of 2017.