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doi:10.2204/iodp.proc.307.202.2009 Data report: carbon and oxygen isotopes of bulk sediments from the off-mound site, Hole U1318B1Chizuru Takashima,2 Akihiro Kano,2 and Xianghui Li3AbstractThe first and only attempt to drill throughout a deepwater coral mound was carried out during Integrated Ocean Drilling Program Expedition 307. Along with Site U1317 at the summit of Challenger Mound, offshore Ireland, two reference sites were selected in order to construct the regional stratigraphic framework. Sediments from near-shelf Site U1318 are mainly composed of silty clay and sands of Miocene–Pleistocene age. We analyzed oxygen and carbon isotopic composition of the bulk sediments for the upper 90.5 m in order to understand the source of the carbonate fraction. δ13C values range from –3.15‰ to 1.20‰ (versus Vienna Peedee belemnite [VPDB]) and δ18O values range from –4.59‰ to 1.87‰ (versus VPDB). A distinct stratigraphic trend is that the Miocene sediments record higher δ18O values. In general, the carbonate fraction of Site U1318 sediments have much lower oxygen and higher carbon isotopic values than the mound sediments, and the oxygen values are similar to those of Cretaceous chalk. |