Top down and bottom up: Testing the fidelity of two paleoproductivity proxies in the context of the late Miocene to early Pliocene “biogenic bloom”

I propose to compare two paleoproductivity indicators recording “opposite” aspects of primary productivity, organic carbon production at the sea surface (coccolith Sr/Ca ratios) and its consumption on the sea floor (benthic foraminiferal accumulation rates, BFAR). Calcification and growth rates of coccolithophores can be linked to particulate organic matter production in the photic zone (Balch and Kilpatrick, 1996). Benthic foraminifera feed on particulate organic matter and thus respond to the flux of organic carbon reaching the deep ocean (Berger and Wefer, 1990). If coccolith calcification rates are indicative of surface ocean productivity as recorded in coccolith Sr/Ca, and a significant amount of the particulate organic matter makes it to the sea floor as recorded by BFAR, then a relationship should exist between coccolith Sr/Ca ratios and benthic foraminiferal accumulation rates. I will construct down-core coccolith Sr/Ca records to parallel down-core BFAR during the late Miocene to early Pliocene “biogenic bloom” interval. I have chosen this interval because there is benthic foraminiferal evidence for an increase in paleoproductivity; hence there is a signal. Each proxy has its own set of biological and biogeochemical controls, and consequently uncertainties. This study will test the applicability of the two proxies to paleoproductivity reconstructions on longer time scales in the face of these uncertainties. Results of this study are important to the Petroleum Research Fund because an improved understanding of these paleoproductivity proxies will be valuable to the reconstructions of primary marine productivity, the ultimate determinant of potential hydrocarbon resources.