Continuous Seismic Profiles of the Continental Terrace off Southeast Florida

Six continuous seismic reflection profiles traverse the Florida continental terrace (shelf plus slope), and four additional profiles extend nearly across the Florida Straits between 26° N. lat. and 25° N. lat. The terrace at 26° N. comprises a shelf of high-reflectivity material with scarplike relief, probably limestone, and a dip slope of low-reflectivity sediment. At 25° N, the terrace is formed by a prograded tongue of low-reflectivity sediment of problematic origin. A replacement series exists between the two end members in which the sedimentary tongue progrades the limestone shelf, last tentatively identified beneath about 270 m of sediment (about 470 m below sea level). The mean shelf depth is maintained at 300 ± 75 m throughout the change in terrace composition and structure. The gradient along the limestone-shelf surface at about 2.5 m/km to the south appears fairly consistent with regional subsidence combined with local isostatic response to sediment load.