Abstract
The Barracuda Fault Zone lies between the Lesser Antilles and the Mid-Atlantic Ridge. This paper describes the part between 15°–18°N and 56°–59°W. The main bathymetric feature is the east-west Barracuda Ridge bounded on the north by the Barracuda Abyssal Plain and on the south by the Demerara Abyssal Plain. Sediments are Globigerina ooze above depths of 5000 m and brown lutite below, except on the abyssal plains which are built up of inter-layered lutities and turbidites. Sediment thickness exceeds 3500 m under the Barracuda Abyssal Plain and 2500 m south of the ridge. Elsewhere thickness is only a few hundred meters. The crustal layers are about 7 km thick. The top of the crust and mantle are both about 3 km shallower under the ridge than elsewhere. Gravity anomalies correlate well with bathymetry or basement relief and are accounted for by density differences in the upper 15 km below sea level. Magnetic anomalies show north-south lineations north of the ridge and an irregular pattern to the south. This pattern, which may result mainly from remanent magnetization, suggests east-west motion along the Barracuda Fault. The mean heat flow is 1.25 × 10 −6 cal/cm 2 sec; this is also the mean for the ocean basins of the world. The Barracuda Ridge probably formed by normal faulting. Subsequent events were formation of the Demerara Abyssal Plain, and then of the Barracuda Abyssal Plain, by turbidites from the Amazon. Recently erosion may have occured on the Barracuda Abyssal Plain.
Published Version
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