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Detailed study of the Oceanic Formation on Barbados has revealed a record of pelagic sedimentation from earliest middle Eocene through latest Oligocene (20-50 m.y. ago). A succession of diverse lithologies and lateral facies changes within contemporaneous sediments is recognized. The succession consists of foraminiferal, radiolarian, and nannoplanktonic clays and marls, radiolarites, spiculites, diatomites, cherts, brown clays, and volcanic ash beds. All are eupelagic, deep-sea sediments. Of particular interest are (1) radiolarites and cherts which correlate with middle Eocene cherts shown by Deep Sea Drilling Projects to be widespread in both the Atlantic and Pacific; and (2) regular, periodic fluctuations of carbonate sedimentation rates and Foraminifera-nannoplankton r tios, in the upper Oligocene foraminiferal marls, which are similar to those frequently observed in Pleistocene foraminiferal oozes and attributed to climatic periodicities.
No evidence for progressive shallowing of the Barbados Ridge is apparent until after deposition of both the Oceanic Formation and the overlying Conset Marl. No in situ shallow-water sediments on Barbados are older than 10-15 m.y. This is consistent with the predicted arrival of the Caribbean plate into the present eastern Caribbean.
Middle and late Eocene sediments exhibit lateral facies changes. These are characterized by both a decrease and an increase in absolute sedimentation rates of carbonate and terrigeneous clay, respectively, from north to south. The paleoslope determined from sedimentary structures deepens from north to south and suggests that the observed facies change may be attributed to increasing carbonate dissolution with depth. However, the accompanying increase in absolute sedimentation rate of terrigenous clays indicates that dissolution along is an inadequate explanation. Either dilution by terrigenous clays from the south, or local sediment redistribution by currents and slumping, must have occurred.
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