The western North Atlantic record of MIS 13 to 10: Changes in primary productivity, organic carbon accumulation and benthic foraminiferal assemblages in sediments from the Blake Outer Ridge (ODP Site 1058)

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Geography and Geology


We used multiple paleoceanographic proxies to examine sediments from the Blake Outer Ridge (ODP Site 1058, 2996 m water depth) that span the MIS 13-10 time interval. Benthic foraminiferal delta(13)C, organic delta(13)C, and total delta(15)N values are lower in MIS 12 and 10 than in MS 11, and indicate glacial-interglacial changes in both thermohaline circulation and ocean-wide biogeochemical processes that affect deep and surface waters. Three time intervals of higher productivity, as evidenced by higher organic carbon accumulation rates (1.6-4.5 g m(-2) yr(-1)), occur at the end of MIS 13 and during the early and late parts of MIS 11, in association with the transition from obliquity minima to obliquity maxima. Benthic faunas in these intervals show a distinct increase in opportunistic species that feed on phytodetritus (Epistominella exigua) or are adapted to elevated but intermittent organic carbon fluxes (Bulimina aculeata and Bulimina marginata) and that imply episodes of recurrent phytoplankton blooms at the surface and consequent export of labile organic matter to the seafloor. Late interglacial MIS 11.3 is a time of low organic carbon fluxes (<0.5 g m(-2) yr(-1)) and is characterized by higher abundances of epifaunal benthic foraminiferal taxa (Cibicidoides wuellerstorfi, Gyroidina spp., Gyroidinoides spp. and Nuttallides umbonifera) that are typical of modem oligotrophic environments. In contrast, during glacial MIS 12 and 10 higher organic carbon fluxes (>0.5 g m(-2) yr(-1)) and benthic assemblages dominated by infaunal taxa (Uvigerina spp. and Bulimina alazanensis) indicate sustained organic carbon delivery and diminished pore water oxygenation. (C) 2010 Elsevier B.V. All rights reserved.

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