A Hurricane Frederic–Generated Storm-Surge Deposit Exposed along a Surf-Zone Foredune Scarp on Dauphin Island, Alabama, U.S.A.

Abstract

Dauphin Island, Alabama, is a 22.5 km-long microtidal barrier island/barrier spit in the northern Gulf of Mexico. As a result of the geomorphic and topographic differences across the island, tropical storms and hurricanes impact it in a variety of ways. Hurricane Frederic crossed the western end of Dauphin Island on 12 September 1979. Storm waves measuring up to 4.6 m above the mean high water level washed over much of the barrier spit portion of the island. On the eastern end of the island, one or more storm surges created a well-defined stratigraphic unit that was subsequently buried and preserved by migrating quartz-sand foredunes. The size of the storm-surge deposit was limited by several factors, including the wave run-up energy and the areal extent and elevation of the foredunes. The nature and types of invertebrate faunas found within the surge-wave deposit reflect a nearshore subtidal source (i.e., inner neritic—likely less than 10-m water depth). The storm deposit provides invaluable information regarding the strength and intensity of the storm not directly attainable through atmospheric and sea-wave records and is consistent with washover fan sedimentation from other areas in the Gulf of Mexico.