INVESTIGATING DEPRESSIONAL FEATURES ASSOCIATED WITH SINKHOLES IN DEEP-SEATED INTERSTRATAL KARST USING NEAR-SURFACE SEISMIC REFLECTION TECHNIQUES IN CENTRAL FLORIDA.

Sinkholes are one of the major geohazards in karst areas, causing significant economic damage and even occasional loss of life. Sinkhole formation mechanisms vary depending on geological conditions but are initiated by dissolution of bedrock (generally carbonates or evaporites) below the ground resulting in ground surface deformation and eventual collapse. The process may be accelerated by natural events like storms or heavy rains and droughts, or human activities like water pumping or loading of the land surface. In Florida, limestone dissolution leading to sinkhole development often results in the formation of surface depressions that are often water-filled and develop into depressional wetlands.
Previous studies using near-surface geophysical imaging techniques (including seismic refraction) in Central Florida have shown the correspondence between depressional wetlands and sinkholes originated in deep-seated interstratal karst with a variable overburden. However, these geophysical techniques are often unable to reach the karst interface which may typically be positioned at depths exceeding < 50-60 m. This research investigates the use of ground-based seismic reflection techniques to image deep paleokarst relief and better understand sinkhole development and extent below the overburden. This approach follows earlier studies by others using seismic reflection methods to identify sinkholes under lakes in Central Florida. While these previous studies deployed the method over water, the approach here investigates how land-based near-surface seismic reflection surveys may provide similar results below depressional wetlands. A total of three different locations with depressional wetlands under similar geological conditions (but somewhat variable depth to the karst interface) are investigated, including the Disney Wilderness Preserve near Poinciana (FL), the Allapattah Flats Wildlife Management Area near Palm City (FL); and the J.W. Corbett Wildlife Management Area in Palm Beach County (FL).