Quaternary deep sea temperature histories derived from benthic foraminiferal Mg/Ca

We hake generated benthic foraminiferal Mg/Ca records from eastern tropical Atlantic core M16772 (3.9 km) and eastern tropical Pacific core TR163-31P (3.2 km) to assess the potential for using benthic Mg-paleothermometry to reconstruct Quaternary bottom water temperature histories. Variations in Mg/Ca records from both the Atlantic and Pacific show a significant correlation with climatic oscillations of the last 330 kyr. Shell Mg/Ca peaks during interglacial episodes. with marine isotope stage (MIS) 5e Mg/Ca nearly matching Holocene values in both cores. Lower Mg/Ca values occur during glacial internals. To estimate temperatures from downcore Mg/Ca. we have augmented the Published Cibicidoides sp. Mg/Ca-temperature dataset [Rosenthal et al., Geochim, Cosmochim, Acta 61 (1997) 3633-3643] with new data to include the temperature range of deep waters. Applying the 10.9% change in Mg/Ca per degreesC defined by the expanded calibration to the deep Atlantic data implies glacial-interglacial shifts in deep water temperature of 2-4degreesC over the last 300 kyr. Temperature estimates are comparable to deep Atlantic temperature changes proposed by Labeyrie et al, [Nature 327 (1987) 477-482]. There is greater uncertainty in deriving temperatures from the tropical Pacific core due to a limited Uvigerina spp. core top calibration set: however, glacial-interglacial temperature oscillations appear to be on the order of 2-3degreesC. In addition. core TR163-31P records clear millennial-scale Mg/Ca and delta(18)O oscillations in MIS 3 corresponding to temperature fluctuations of >0.5degreesC. Additional calibration studies are needed to address potential secondary effects on Mg/Ca. (C) 2002 Elsevier Science B.V. All rights reserved.