Differentiating hurricane deposits in coastal sedimentary records: two storms, one layer, but different processes

Abstract

Hurricanes Gustav and Ike consecutively impacted coastal Louisiana in 2008. Two sediment cores taken from Bay Champagne, a coastal backbarrier lake near Port Fourchon, Louisiana, contain a depositional layer of clastic sediment up to 21 cm thick attributable to these two storms. X-ray fluorescence measurements and statistical analysis suggest the two storm events can be distinguished from one another based on contrasting geochemical profiles. The bottom portion of the layer, attributable to Gustav, contains high concentrations of marine-derived elements, suggesting a strong influence from storm surge. The top portion of the layer, attributed to Ike, contains higher concentrations of terrestrially-derived elements, indicative of contributions from fluvially-driven deposition. The elemental concentration profiles and corresponding environmental data suggest the storm deposits in each core were deposited through two distinct hydrological processes: a storm surge-driven marine intrusion event during Gustav, followed by a mixture of storm-surge and fluvial deposition resulting from Ike. Results show that hurricane-generated deposition in coastal environments is a bi-directional process in which the role of fluvial freshwater deposition cannot be ignored.