GRAVITY TRANSECTS ACROSS LITHOSPHERIC BOUNDARIES OF THE SUWANNEE TERRANE, SOUTHERN APPALACHAINS

The Gondwanan Suwannee terrane is covered by coastal plain sediments, and its boundary with Laurentia (Suwannee suture) is poorly constrained. We are developing gravity profiles across proposed terrane boundaries to shed more light on the composition of crustal blocks. Refining the location of the Suwannee suture, in particular, will help distinguish the relationship between the Gondwana and Laurentian terranes and their roles in the Alleghanian orogeny. Gravity surveys have been conducted from White Springs, FL to Clermont, FL (241 kilometers), and from Cedar Key, FL to Crescent Beach, FL (a 204 kilometer transect across the peninsula). In an attempt to constrain the extent of the lower Paleozoic sediments of the Suwannee basin, a north-south transect extends across the southern boundary of the Suwannee basin and into the South Florida Mesozoic volcanic field. Measurements were taken at gravity stations approximately every 8 kilometers along the transects and corrected for limited changes in elevation using GPS and DEM. There is a general trend of declining values in the uncorrected data from White Springs, FL to Clermont, FL, with a change of 138 mGals. The East-West profile shows very limited variation, with only a change of 16 mGals along the transect. The increase in gravity towards northern boundary of the Suwannee basin may be due to the voluminous basalt flows and sills in the South Georgia basin. Additional data will be collected from White Springs, FL to Macon, GA and from Clermont, FL to Port Saint Lucie, FL. The new data collected in north Florida and South Georgia will cross the Suwannee suture and Mesozoic basins to the north and the St. Lucie metamorphic complex and Osceola granite to the south. Any significant changes in gravity gradients will help define the contact between the Suwannee terrane and Laurentia and boundaries between the crustal blocks that comprise the Suwannee terrane.