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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Oxygen-isotope variations in planktonic Foraminifera (Orbulina universa, Globorotalia menardii, and Globigerinoides sacculifer) indicate that, in two Grenada Basin cores, paleontologic datum planes do not coincide with isotope boundaries. The time lag is greater when the boundaries are transitional from glacial to interglacial phases.
Recurrent-groups analysis of benthic foram assemblages led to the recognition of five groups. Only one of these, containing Osangularia culter, Bulimina buchiana, and Chilostomella oolina, appears to have any stratigraphic significance. The group shows its best development during interglacial times. In accordance with Weyl's paleo-oceanographic model, this group is associated with colder bottom waters and can be used to draw inferences about the influx of such waters. Periods of cold-water influx ranged from before 367,000 to 210,000 years B.P., from 139,000 to 81,000 years B.P., and from 22,000 to 8,600 years B.P. Cessation of influx 8,600 years B.P. is further substantiated by heat-flow calculations.
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