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ABSTRACT

Deep-sea sediments from the eastern equatorial Atlantic indicate that dissolution of carbonate was greater during the late Pleistocene glacial stages than at present or during the last interglacial stage. Surface (Holocene) carbonate distribution shows a correlation with the 1.9°C potential temperature isotherm which represents the top of Antarctic Bottom Water. A comparison of the surface versus glacial Pleistocene (18,000 YBP) carbonate distribution indicates that the effects of Antarctic Bottom Water were felt 200 to 700 meters shallower during glacial then interglacial conditions.

Records of carbonate composition for the past 200,000 years show increases in both carbonate dissolution and terrigenous noncarbonate dilution during glacial stages. Likewise, microscopic examination of the planktonic foraminiferal faunas indicates much greater test fragmentation and destruction and higher percentages of benthonic forams per total foram populations during glacial conditions. The available evidence suggests that Antarctic Bottom Water was the mechanism that produced the increased carbonate dissolution. Therefore, probably either an increase in the production and circulation of Antarctic Bottom Water during glacial stages or the production of a glacial North Atlantic Bottom Water occurred. Regardless of the model used to explain the observations, all of these data suggest that the eastern equatorial Atlantic experienced greater carbonate dissolution during late Pleistocene glacial stages.

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