Sedimentological Characteristics of Regional-Scale Washover Deposits Caused by Hurricane Ivan

Washover deposits induced by Hurricane Ivan are examined along a 260-km stretch of northern Florida coast. Initial response to the overwash event is dominated by dramatic nearshore, beach, and dune erosion. Eroded sediment is in-turn redistributed landward across the barrier-island profile. Distinct sedimentological characteristics of the washover deposits are recognized in different barrier-island sub-environments. Deposits on the beach are bound by a basal erosional surface, and exhibit planar seaward-dipping stratification. Over the barrier interior, preservation of fresh, in-place vegetation below the washover indicates that limited erosion occurred prior to washover deposition landward of the foredune. Washover deposits over the interior platform are characterized by horizontal to sub-horizontal stratification. Increased accommodation space landward within flooded interior wetlands and the back-bay yields substantially thicker washover deposits characterized by steeply inclined sigmoid and tabular foreset stratification. Back-bay deposition locally accounts for 120 m of landward bayside-shoreline migration.