Figure 7. The ¹³C of carbonate minerals (calcite, dolomite, and siderite) are shown relative to the ¹³C of the DIC and CO_2(gas) pools from Sites 994, 995, and 997 (solid line and dashed line respectively). The ¹³C of the DIC pool reaches a minimum at the sulfate/methane interface (SMI) and then increases to values as high as 10 PDB with depth. Below 200 mbsf, ¹³C of DIC decreases to values as low as -5 PDB. Authigenic siderite throughout the sedimentary section exhibits ¹³C values consistent with the DIC pool immediately above and within the gas hydrate-bearing section (shaded) of the sediment column.