Proc. IODP, 303/306, Data report: oxygen isotopes and foraminifer abundance record for the last glacial–interglacial cycle and marine isotope Stage 6 at IODP Site U1313

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Chapter contents Abstract Introduction Methods Results and discussion Conclusions Acknowledgments References Figures F1. δ¹⁸O and relative abundance. F2. Abundance and IRD/g vs. depth. F3. Abundance and IRD/g vs. age. Tables T1. δ¹⁸O and N. pachyderma (s). T2. IRD/g and relative abundance. PDF file			Previous \| Next doi:10.2204/iodp.proc.303306.216.2013 Introduction Data from planktonic foraminiferal assemblages have often been used to decipher past changes in sea-surface to near–sea surface conditions of the North Atlantic (Berggren, 1984; Weaver, 1987; Chapman et al., 2000). For example, the presence of polar surface water mass living species Neogloboquadrina pachyderma (sinistral), which dwells in subsurface water at present (Jonkers et al., 2010), at Integrated Ocean Drilling Program (IODP) Site U1313 suggests the presence of cold surface water conditions during the glacial period (Fairbanks et al., 1980; Raymo et al., 1989). In contrast, the presence of mixed-layer living Globigerina bulloides indicates subpolar to temperate conditions and has been implicated to the North Atlantic Current (NAC) (Ottens, 1991; van Kreveld, 1996). Neogloboquadrina incompta indicates subpolar conditions and is also associated with the NAC (van Kreveld, 1996). The transitional species Globorotalia inflata is assumed to thrive at the base of the thermocline and is associated with the NAC and the Gulf Stream (Kennett and Srinivasan, 1983; Ottens, 1991). Some of these species, however, also migrate and show preferential depth habitat that depends on temperature, salinity, and availability of food. As a result, the mere presence of these species cannot solely be correlated to surface climate conditions. In general, it is accepted that these foraminiferal assemblages can be used to infer changes in the surface to near-surface water conditions at Site U1313 (Raymo et al., 1989; Chapman et al., 2000). In this study, a quantitative abundance analysis of N. pachyderma (s) and G. bulloides oxygen isotope ratios (δ¹⁸O) for marine isotope Stages (MISs) 1–6 were performed using sediment from Site U1313 (see the “Site U1313” chapter [Expedition 306 Scientists, 2006]). We also detailed quantitative abundances of four planktonic foraminifers to assess changes in the surface to near-surface water conditions during the penultimate deglaciation (130–140 ka) as well as MIS 6 (140–180 ka). Ice-rafted debris (IRD) data were used to infer sea-surface freshening, as meltwater perturbs sea-surface salinity. Top of page \| Previous \| Next

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