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doi:10.2204/iodp.proc.323.203.2016

Introduction

Oxygen isotope stratigraphy has been widely used in paleoceanographic studies to determine relative ages of sediments by comparison of benthic foraminiferal oxygen isotope (δ¹⁸O) data to the composite LR04 global stack curve (Lisiecki and Raymo, 2005). In general, the subarctic Pacific and its marginal seas are known to have poor CaCO₃ preservation in sediments. During Integrated Ocean Drilling Program (IODP) Expedition 323, seven sites (U1339–U1345) were drilled in the Bering Sea along a depth transect ranging from ~800 to 3200 meters below seafloor (mbsf) and covering three different regions of the marginal sea: the Umnak Plateau, the Bowers Ridge, and the Bering lower slope region (see the “Expedition 323 summary”chapter [Expedition 323 Scientists, 2011a]). Of these, we targeted Site U1344 for this study because a continuous record of benthic foraminifers was documented during onboard biostratigraphic work (see the “Expedition 323 summary” chapter [Expedition 323 Scientists, 2011a). At ~3200 m water depth, Site U1344 is the deepest site drilled during Expedition 323. It is located along the small summit of a submarine-canyon interfluvial proximal to the Beringian continental slope north of the Aleutian Basin (59°03′N, 179°12′W). The site presently lies below the oxygen minimum zone (OMZ) and is both the coldest in temperature and the highest in dissolved oxygen among the sites cored during Expedition 323 (see the “Site U1344” chapter [Expedition 323 Scientists, 2011b]; see the “Expedition 323 summary” chapter [Expedition 323 Scientists, 2011a). Furthermore, Site U1344 lies under an area of high biological sea-surface productivity near the maximum extent of present-day seasonal sea-ice cover. These parameters play an important role in supplying nutrients to the seafloor and to benthic organisms (see the “Site U1344” chapter [Expedition 323 Scientists, 2011b]; Alvarez Zarikian, in press). Carbon isotopes (δ¹³C) of benthic foraminiferal shells reflect the carbon isotopic composition of dissolved inorganic carbon in deep/pore water, in which the shell calcified (McCorckle et al., 1990; Ravelo and Hillaire-Marcel, 2007), recording their microhabitat.

For this data report, carbon and oxygen (δ¹³C and δ¹⁸O) stable isotopes were measured in the shells of benthic foraminifers to establish an oxygen isotope stratigraphy for Site U1344. The established record consists of a high-resolution portion extending from the seafloor to 64 m core composite depth below seafloor (CCSF-A) (equivalent to the past ~140 ky) and a low-resolution portion from this depth to the bottom of the Site U1344 record (~750 mbsf in Hole U1344A). The complete stratigraphic section recovered at Site U1344 spans the past ~1.9 My (see the “Site U1344” chapter [Expedition 323 Scientists, 2011b]).

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