IDENTIFYING HURRICANE OVERWASH IN SEDIMENT CORES FROM THE GREAT SOUTH BAY, NEW YORK

Aerial photographs taken immediately after several historical hurricanes made landfall on the south shore of Long Island show overwash - tongues of beach sediment redeposited by storm waves in the bayside marshes. Combining these photos with modern satellite imagery indicates where overwash sediment should exist in sediment cores. Several sediment cores collected from the barrier beach marshes in the Tiana Beach, NY area contain layers of coarser material that correspond to the overwash deposits identified from historical photos. One of these cores was collected from an area which aerial photography suggested should contain overwash from the 1938 “Long Island Express” hurricane. An unabraided fragment of glass bottle was recovered from immediately below a coarse sediment layer in the top 55 cm of the core. The fragment, a portion of the bottom of a bottle, includes enough of the manufacturers mark imprinted by the Owens-Illinois Company to indicate that it was manufactured in 1937. This find is consistent with the hypothesis that the coarse sediment layer was deposited by the 1938 hurricane. Similar layers of course sediment were found in several nearby cores where predicted by aerial imagery, however the lower sections of all cores contained much more homogenous sandy sediment with no obvious overwash deposits from earlier storms. In contrast, a suite of closely spaced cores collected from Gilgo Beach marsh, farther west along the barrier island, exhibit significantly different stratigraphy from core to core. The Gilgo Beach cores include possible overwash layers but are difficult to correlate and this complicates the reconstruction of a consistent record of overwash events. Pb, Cu, and Zn concentrations and pollen counts collected throughout several of the cores provide some constraint on sediment age, but are difficult to interpret in the absence of confident lithostratigraphic correlations. These results point to the importance of collecting replicate cores at small spatial scales in paleotempostological studies and the critical influence of coastal geomorphology in creating such records.