STRUCTURAL AND TECTONIC EVOLUTION OF THE EASTERN CAYMAN TROUGH (CARIBBEAN SEA) FROM SEISMIC-REFLECTION DATA

The eastern Cayman Trough preserves a record of the Late Cretaceous to Paleogene Caribbean history that is largely affected by Neogene strik e-slip tectonics of the current plate boundary. We conducted an analys is of seismic data within the eastern Cayman Trough, based upon single and multichannel seismic reflection profiles collected during the Sea carib II cruise in 1987 and the Casis cruise in 1992. These data show that the basement of the eastern Cayman Trough can be divided into fou r domains from east to west, with distinct morphologic and sedimentary character and inferred older to younger ages: (1) a province of rifte d Mesozoic continental crust exhibiting seven parallel horst blocks st riking northeast-southwest; (2) a continent-ocean transition between p rovinces 1 and 3 that exhibits seamounts, small hills, and sedimentary basins; (3) an Eocene oceanic crust with rough basement but smoother relief than the rifted crust; basement trends are roughly north-south and oblique to the northwest trend in domain 1, and (4) the northern J amaica slope, which forms an east-west-trending slope, with northward- dipping strata that flank the three deeper water domains of the Cayman Trough. The domains are interpreted to be the product of the Eocene e ast-west opening of the Cayman Trough as a pull-apart basin in a left- lateral strike-slip setting. Closure of the 1100 km of Eocene and youn ger oceanic crust of the Cayman Trough places the fault-block province adjacent to the Belize margin of Central America. Restoration of norm al faults in the fault-block province places an additional 190 km of l eft-lateral offset along the Cayman Trough. A Neogene phase of transpr ession has reactivated structures in the four domains, along with on-l and structures described by previous authors in Jamaica. The proximity of the eastern margin of the Cayman Trough to petroliferous, continen tal rocks in Central America suggests an improved possibility of hydro carbon potential. Unfortunately, sediment thicknesses of less than 1 k m probably are not conducive to hydrocarbon formation.