Figure 5. Methane ¹³C values plotted against volume of CH4 (in mL) released during stepwise degassing of PCS cores at Site 995. Data for gas volumes are in Table 1. The scale of the vertical axes is the same in all panels. Error bars show analytical uncertainties of 2 standard deviations (±0.4). For each core, the average ¹³C value calculated by weighting the individual measurements by the volume of CH₄ released is shown by a horizontal line (±2s uncertainty shown as dashed line).