High Precision Absolute Age Determinations Within the Plio-Pleistocene in Gulf of Mexico: ABSTRACT

Abstract

Absolute ages can be determined from Plio-Pleistocene sequences in the Gulf Coast using an 18O/16O analytical approach. The technique is based on the fact that glacial/interglacial cycles possess uniquely shaped fingerprints. The character of the isotopic record in the Gulf of Mexico is exaggerated because the Gulf has periodically received extreme riverine discharges of meltwater products from the Laurentide ice sheet which covered large portions of North America during the Plio-Pleistocene. The 18O record thus allows age determinations with a precision of ±20,000 to ±50,000 years in the Plio-Pleistocene. Close sampling via sidewall cores is required for initial calibration in a given basin. Sections ranging from middle shelf o bathyal depths can be reliably zoned, independent of regional or local biostratigraphic and lithostratigraphic zonations. Once an absolute age framework is established, stratigraphic correlations, sedimentation rates, and structural effects on sediment distribution can be determined. The technique has been developed using holes drilled from the MV Eureka (part of an early Shell Oil offshore study in the Gulf) as well as strategically placed piston cores and DSDP sites. Both benthic and planktonic foraminiferal shell carbonate should be suitable for these age determinations. A similar Plio-Pleistocene zonation can be established worldwide based on analysis of DSDP material. Preliminary data suggest that a similar zonation may be established throughout the Tertiary and perhaps the Mesozo c. Effects of diagenesis are unknown. End_of_Article - Last_Page 540------------