<p>1 Table 1. Cast Latitude (°N) Longitude (°W) X Y  Number AT734V1 30 05.0000 42 08.0000 482 5542 - 2 AT734V3 30 07.4352 42 07.2063 610 10042 0.078 0 AT734V4 30 07.4340 42 07.2048 610 10039 0.002 0 AT734V5 30 05.0000 42 08.0000 482 5542 0.030 2 AT734V6 30 07.4346 42 07.2239 608 10030 0.004 0 AT734V7 30 07.4613 42 07.2259 607 10090 0.007 0 AT734V8 30 07.4346 42 07.2846 597 10040 0.055 0 AT734V9 30 07.4290 42 07.1557 618 10030 0.004 0 AT734V10 30 07.3590 42 07.4630 568 9900 0.004 5 AT734V11 30 07.3407 42 07.7541 552 9867 0.013 0 AT734V12 30 07.4289 42 07.2183 608 10030 1.438 0 AT734V13 30 07.4679 42 07.2118 609 10101 0.018 0 AT734V14 30 07.4501 42 07.1428 620 10069 0.048 0 2</p><p>1 3 Table 2. Cas 3He 3He depth dEh/dt 3He∆ H CH depth dEh/dt 3He∆ H CH t (fmol/kg) 2 4 C (fmol/kg) 2 4 (m) (mV/s) (fmol/kg) (nM) (nM) (m) (mV/s) (fmol/kg) (nM) (nM) ID a 1 2500 0 2.64 0.00 2 1 8 751 -44 2.64 0.03 2 1 1 2002 0 2.67 0.00 3 2 8 700 -197 2.62 0.05 1 2 1 1501 0 2.70 0.00 2 1 8 601 -22 2.54 0.04 1 2 1 1253 0 2.69 0.00 1 1 9 831 -1879 3.16 0.53 153 179 1 1002 -7 2.68 0.00 0 1 9 810 -120 2.76 0.14 26 29 1 750 -22 2.61 0.00 3 2 9 780 -64 2.67 0.05 28 10 1 501 0 2.43 0.00 1 3 9 731 -43 2.59 0.00 3 2 3 719 -21 2.60 0.01 0 4 9 650 -110 2.55 0.02 - - 3 701 -21 2.60 0.03 1 2 1 988 -12 2.65 -0.02 1 1 3 650 -91 2.55 0.01 0 2 10 950 -7 2.66 -0.01 0 1 3 601 -3 2.51 0.01 0 2 10 900 -13 - - 0 1 3 550 -4 2.50 0.03 0 2 10 751 -61 2.64 0.03 48 7 3 500 0 - - 1 3 10 701 0 2.55 -0.02 0 2 3 401 -9 2.41 - 0 2 10 1004 -3 2.66 -0.02 1 1 4 747 -145 2.69 0.08 80 33 1 950 0 2.66 0.00 1 1 4 734 -44 2.65 0.05 19 8 1 801 1 - - 5 3 4 651 -17 2.57 0.03 1 2 1 771 -21 - - 27 8 6 771 0 2.61 -0.01 14 2 12 750 -10 - - 3 2 6 750 -66 2.63 0.02 16 2 12 746 -6 - - 5 3 6 741 -1772 - - 59 21 12 726 0 - - 0 1 6 721 -1074 2.64 0.05 41 5 12 701 0 - - 0 1 6 700 -28 2.60 0.03 5 2 12 791 0 - - 9 8 6 649 0 2.57 0.03 3 2 13 776 -16 - - 1 2 6 601 0 2.53 0.03 3 2 13 741 -623 - - 156 54 6 500 0 2.43 0.00 1 3 13 736 -623 - - 77 28 7 794 -237 2.76 0.14 317 43 13 720 -2 - - 2 2 3</p><p>2 Cas 3He 3He depth dEh/dt 3He∆ H CH depth dEh/dt 3He∆ H CH t (fmol/kg) 2 4 C (fmol/kg) 2 4 (m) (mV/s) (fmol/kg) (nM) (nM) (m) (mV/s) (fmol/kg) (nM) (nM) ID a 7 781 -134 2.75 0.13 51 8 1 701 -9 - - 2 1 7 751 -54 2.63 0.02 349 53 13 813 -9 - - 30 6 7 701 -8 2.61 0.03 6 3 14 800 -91 - - 82 15 8 847 1 2.66 0.02 8 8 14 780 -29 - - 293 47 8 825 -148 2.70 0.07 28 18 14 700 -5 - - 0 2 8 800 -100 - - 51 14 4 4 5</p><p>3 6 Table 3. Vent Depth (m) of Marker Water CTD strongest Possible ID Depth (m) H2/CH4 cast ID signal H2/CH4 Source Mk 3 730 8.8 6 741 2.8 BH/2/6/C/7 13 741 2.9 BH/2/6/C/7 Mk BH 744 9.1 4 747 2.4 2/6/C/7 10 751 6.9 out of field 7upper 751 6.6 6/C Mk 2 764 3.1 12 771 3.4 6/C/7 Mk 6 778 9.3 14 780 6.2 C Mk C 780 10.1 7lower 794 7.4 Chaff Beach 8 800 3.6 7 Mk 7 801 4.2 Mk 8 802 2.3 9 831 0.9 H Mk H 850 0.93 7</p><p>4 8</p><p>9 10 Figure 1.</p><p>5 11</p><p>12 13 Figure 2.</p><p>6 14</p><p>15</p><p>16</p><p>7 17</p><p>18 19 Figure 3. 20</p><p>8 21</p><p>22</p><p>23 24 Figure 4. </p><p>9 25 26 Figure 5. 27</p><p>10 28 29 Figure 6. 30</p><p>11 31 32 Figure A1.</p><p>12</p>