Multichannel Measurements Over a Possible Gas-Bearing Structure Near Cay Sal, Bahamas: ABSTRACT

Abstract

Multichannel reflection measurements in water depths of 500 m reveal an asymmetric anticline 70 km southeast of Cay Sal Bank. This fold has an apparent width of 10 km. The northern flank has a maximum relief of 1 km, and the southern flank's maximum relief is 400 m. North of this structure, in Santaren Channel, coherent reflections occur throughout our 5-sec record. Depth at 5 sec is approximately 10 km. South of the anticline, reflections are discontinuous below 1 sec, and no coherent reflections can be seen below 2 sec. A strong reflection at 2.3 sec in Santaren Channel (approximately 3 km depth) probably marks a middle Cretaceous unconformity. Seismic units inferred to be youngest Cretaceous and Paleogene show maximum thinning over this fold. The Upper Cretaceous seque ce shows maximum structural relief here. Amplitude anomalies occur on the crest. Reflections from the uppermost Cretaceous to Paleogene section are dim above reflections from inferred Upper Cretaceous units that contain several bright spots. Some flat reflections on the structure may stem from gas-liquid contacts. Ten kilometers south of the asymmetric anticline, a tilted block that may be composed of platform carbonate rocks rises to within 0.3 sec of the sea floor. This block has an east-west dimension of more than 20 km and a maximum relief of 1.3 km. A Lower Cretaceous carbonate platform edge underlies 800 m of water and 1.5 km of sediment at the junction of Nicholas Channel and Florida Straits. In Florida Straits, a strong reflection correlates with the middle Cretaceous unconformity. End_of_Article - Last_Page 894------------