Table T2. Hydrogen, helium, and methane gas concentrations in PCS gas samples.
Core
Sample
Volume (mL)
Depth
(mbsf)
H2
(ppm)
Average
H2 (ppm)
He
(ppm)
CH4
(%)
Start
Stop
204-1244E-
11P G14 134 110 72.6 595.00 595.00 5.80 99.94
15P G6 125 195 103.1 1035.52 1035.52 38.20 99.89
15P G8 120 90 103.0 794.82 915.17 14.13 99.92
204-1249F-
4P G12 140 105 13.5 173.40
2.51 99.98
4P G18 130 100 13.5 64.93
2.37 99.99
4P G20 140 103 13.5 62.48
2.15 99.99
4P G24 140 103 13.5 67.26
2.12 99.99
4P G26 138 110 13.5 105.07
2.13 99.99
4P G38 130 95 13.5 105.64 96.46 2.24 99.99
204-1249C-
6P G3 140 105 33.5 16.45
2.30 100.00
6P G5 140 105 33.5 20.27
2.34 100.00
6P G8 140 115 33.5 18.04 18.39 2.35 100.00
204-1249F-
6P G10 140 103 33.5 18.81 18.81 2.23 100.00
14P G5 135 105 72.4 74.56
5.36 99.99
14P G5 135 105 72.4 85.41 79.98 ND 99.99
204-1250D-
5P G3 134 100 35.0 250.40
17.17 99.97
5P G8 135 100 35.0 317.95 284.17 7.90 99.97
204-1250C-
9P G2 152 115 71.0 66.11
9.02 99.99
9P G5 110 85 71.0 108.52
31.63 99.99
9P G6 140 110 71.0 139.38 122.69 19.55 99.98
204-1250D-
13P G6 130 100 103.5 120.15
21.77 99.99
13P G7 125 105 103.5 119.65
8.21 99.99
13P G7 125 105 103.5 133.68 126.66 53.63 99.98
204-1251D-
6P G2 135 100 45.9 490.36
ND 99.95
6P G3 125 90 45.9 282.65
8.91 99.97
6P G5 138 100 45.9 154.26
9.49 99.98
GP G6 135
45.9 215.80
2.56 99.98
SP G10 120 90 45.9 176.53 263.92 7.77 99.98
204-1251B-
12P G4 140 105 104.1 128.75 128.75 29.09 99.98
18P G6 145 100 153.4 379.92
29.29 99.96
18P G7 130 99 153.4 379.10 379.51 23.45 99.96
204-1251D-
21P G2 140 103 173.4 215.28
58.08 99.97
21P G5 135 100 173.4 227.48 221.38 ND 99.98
204-1251B-
35P G2 135 100 290.6 209.13
7.24 99.98
35P G9 137 105 290.6 339.06 274.10 21.80 99.96

Notes: Hydrogen concentrations varied widely between gas samples taken from the same core over time. There is some systematic variation with time such that the later samples tend to have higher concentrations that likely reflect the high solubility of hydrogen. Because gas from the core must travel through water to be sampled, earlier samples reflect residual hydrogen. Later, when the water is more saturated with hydrogen content, gaseous concentration should increase. Average hydrogen concentrations are given and plotted in Figures F3, F4, F5, F6, F7, and F8, in order to compensate for this sampling artifact. Sample start and stop volumes note the amount of gas sampled (e.g., 145–100 equates to 45 mL gas in the sample). ND = none detected.