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Sedimentological Characteristics and Internal Architecture of Two Overwash Fans from Hurricanes Ivan and Jeanne

Mark Horwitz1 and Ping Wang2
1BCI Engineers and Scientists, Inc., Lakeland, Florida 33803
2Department of Geology, University of South Florida, Tampa, Florida 33620

Extensive overwash occurred along the Florida coast during the passage of four strong hurricanes in 2004, providing an excellent opportunity to study the spatial patterns and sedimentary architecture of washover deposits. Detailed 3D sedimentological characteristics of two of the over-wash fans were studied through coring, trenching, and ground penetration radar surveys. The first washover-fan complex, deposited by hurricanes Frances and Jeanne is located on the Atlantic facing Hutchinson Island in southeastern Florida. The second fan, deposited by hurricane Ivan is located on the Gulf-facing Santa Rosa Island in northwestern Florida. Subsurface imaging using a 250 MHz Ground penetrating radar profiling system correlated well with bedding features observed in cores and trenches; while the Ground penetrating radar profiling provided greater spatial coverage. The internal architecture of the overwash lobes is generally characterized by: (1) planar horizontal to sub-horizontal stratification resulting from sheet flow regime overwashing a subaerial surface, and (2) steeply landward dipping tabular foresets, formed during landward progradation and subaqueous deposition, likely into a washover pond or lagoon. Associated local features such as truncated inclined bedding, scour holes, and truncated dunes are also common to washover sediment deposits.


AAPG Search and Discovery Article #90080©2005 GCAGS 55th Annual Convention, New Orleans, Louisiana