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doi:10.2204/iodp.proc.303306.207.2009

Results

Results of carbon stable isotope analyses of interstitial waters from Sites U1305, U1306, and U1307 are shown in Figure F2 and are reported in Table T1. Our results indicate a downhole decreasing trend in δ¹³C_DIC in the upper ~50–80 meters below seafloor (mbsf) at the three sites studied. The most depleted δ¹³C_DIC value of approximately –34.1‰ is recorded at 79.15 mbsf at Site U1307. At Sites U1305 and U1306, the δ¹³C_DIC minima occur at 51.4 and 85.8 mbsf, respectively. Below the depth of δ¹³C_DIC minima, the δ¹³C_DIC values generally increase to approximately –3‰ toward the bottom of the cored interval.

Also presented in Figure F2 are dissolved sulfate (SO₄^2–) and headspace methane (C₁) concentration profiles from shipboard measurements (see the “Site U1305,” “Site U1306,” and “Site U1307” chapters). The depth at which the most depleted δ¹³C_DIC value is recorded at each site typically coincides with the sulfate/methane interface inferred from the shipboard SO₄^2– and C₁ profiles (Fig. F2).

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