Geochemistry of Cayman Trench Sediments: ABSTRACT

Abstract

The petrology of deep-sea sediments north of Jamaica and in the central Cayman Trench may be interpreted in terms of 2 basic sediment components, namely, the carbonate and terrigenous fractions. On the basis of trace-metal concentrations, the carbonate fraction shows considerable variability both laterally and vertically. Evidence suggests that the carbonates were derived from shallow-water, benthic environments as well as pelagic organisms. Both geochemical and sedimentologic characteristics indicate that the carbonate fraction has undergone resedimentation. Foraminifera make up a significant percentage of many of the graded, turbidite sand layers. The terrigenous component of the central Cayman Trench shows higher concentrations of cobalt, copper, chromium, lithium, manganese, nickel, and rubidium than those in the trench north of Jamaica. Lead concentrations, however, are higher in the terrigenous component of the latter area. This suggests that at least 2 sources of terrigenous sediment of distinctly different trace element chemistry supply the Cayman Trench in these different regions. The overall chemistry is indicative of variable sources for both the carbonate and terrigenous fractions. This is supported by the general petrology and sedimentologic evidence of mixing and resedimentation. End_of_Article - Last_Page 369------------