COMPARISON OF KARSTIFICATION METHODS AND ISOSTATIC REBOUND IN THE SUWANNEE RIVER BASIN, FLORIDA

Plio-Pleistocene beach ridges in northern Florida are nearly 50 m above current sea level, but sea level during that time is not known to have been more than 25 m above current sea level. The height of beach ridges in northern Florida therefore create a conundrum because Florida is located on a passive margin in what is considered a tectonically stable environment. A series of recent studies have suggested that uplift on the Florida peninsula may be the result of the removal of subsurface crustal mass. Karstification of Florida’s carbonate matrix may provide a mechanism for subsurface crustal mass removal and regional isostatic uplift. The ability of karstification to drive uplift was assessed using a calcium mass balance study of the Suwannee River Basin, in north Central Florida. Limestone dissolution in the entire basin was determined though statistical relationships between Ca2+, which is the dominant cation in surface and groundwater and a primary component of calcite, and SpC and discharge. Because some water discharging from the Suwannee River Basin is also undersaturated with respect to calcite, maximum karstification potential for the basin was also calculated by assuming chemostatic conditions. Similar to past studies, isostatic uplift was calculated by assuming all dissolution occurred in the subsurface. Results from the application predicted anywhere from 77 to 6.7 mm k.y.-1 of uplift, with three of the six methods between 24 to 29 mm k.y.-1. Based on the results, karstification may be able to partially explain isostatic uplift of the northern Florida peninsula