Characteristics of three turbidites, Hispaniola-Caicos Basin

Abstract

The absence of analyses of complete sedimentary units resulting from single turbidity currents has been a major shortcoming of turbidite studies. Previous studies have extrapolated single-flow characteristics by averaging attributes of groups of flows. Distinctive source areas surrounding the 9500 km2, 4100 m deep Hispaniola-Caicos Basin allow long-distance correlation of beds and afford an unusual opportunity to study turbidites resulting from single-flow events. On the basis of data from closely spaced piston cores, 3 individual turbidites have been mapped in their entirety. Two of the flows contain abundant terrigenous material; they originated from Hispaniola or Cuba. The 3rd flow is almost exclusively bioclastic; it originated from Great Inagua Carbonate Bank. All of the flows traveled about 100 km across the flat basin floor. They range in total volume from 8.9 .times. 108 m3 to 30.8 .times. 108 m3. The flows cover areas ranging from 3500-5200 km2, indicating the importance of lateral spreading on the basin floor. Maximum thicknesses, including upper pelitic intervals, are well over 200 cm. The flow deposits generally thin away from their basin entry points but thicken by ponding in basin depressions. Marked horizontal sorting occurs on the basis of constituent particle density and size. In 2 flow deposits, Bouma interval structure units A through E are present everywhere. In the 3rd turbidite, the complete Bouma sequence is present only near the basin entry point, and the upper flow regime units (A and B) disappear within 30 km of the basin edge. Fossils found include foraminifera, pteropods, diatoms, green algae and red algae.