Structure of the Blake-Bahama Outer Ridge

Many of the recent high-resolution seismic reflection profile data substantiate the depositional nature of the Blake-Bahama outer ridge and show that its sedimentary structure is quite complex. The structure is revealed principally by the configuration of two prominent acoustic reflectors observed above horizon A, which are referred to as reflectors X and Y. Layer A-X is shown to have been deposited preferentially along the ridge axis; thus, the over-all shape of the ridge was established. Two major sedimentary regimes are distinguished above reflector X: a “northern” regime, which mantles the crest of the northern half of the ridge, and a younger “southern” regime, which laps onto the northern and creates sharp unconformable contacts in some localities. The most important of these contacts divides the regimes at latitude 30°15′N and suggests that the post reflector X depositional history of the ridge north and south of this latitude is different.