Table 11. Composition of free gas collected in syringes from sediments at Site 994. "Core, section" Depth (mbsf) O2 (ppmv) N2 (ppmv) C1 (ppmv) CO2 (ppmv) C2 (ppmv) H2S (ppmv) C3 (ppmv) i-C4 (ppmv) n-C4 (ppmv) i-C5 (ppmv) n-C5 (ppmv) i-C6 (ppmv) n-C6 (ppmv) C1/C2 C1/C2+ 164-994C- 4H-7 32.8 137000 58000 237100 5500 4 1 5 0 1 2 19000 4H-2 25.7 183000 774000 1600 800 5H-6 41.2 191000 70000 63000 2400 6 4 2 2 0 0 1 1 11500 3800 6H-6 50.4 76000 240000 630300 1200 28 17 4 1 1 0 1 2 22500 11800 6H-2 44.4 138000 575000 244000 4200 28 4 1 2 1 4 8710 6070 7H-2 54.2 14000 76000 880700 16600 33 18 3 26700 16300 8H-7 71.2 99000 371000 484900 8100 23 11 2 21100 13500 10H-2 74.2 26000 114000 829400 22700 28 18 4 29600 16600 10H-3 75.7 31000 138000 845300 24400 26 19 4 2 32500 16600 10H-4 77.2 30000 105000 842400 12500 30 19 4 28100 15900 11H-1 82.2 39000 132000 786600 14500 28 18 4 28100 15700 11H-2 83.7 41000 101000 822400 17400 32 21 5 1 1 25700 13700 12H-2 93.2 159000 650000 151800 5900 12H-1 91.7 150000 614000 203600 7000 3 67900 12H-2 93.2 107000 442000 394600 12300 14 8 2 28200 16400 13H-1 101.2 101000 458000 344500 11400 8 43100 14H-1 110.7 28000 89000 859900 14700 30 20 6 1 28700 15100 14H-6 118.2 4000 679000 112000 3900 16H-6 137.2 58000 245000 648100 22000 22 15 5 2 29500 14700 16H-5 135.7 1000 4000 937400 34300 35 26 9 5 26800 12500 17H-3 142.2 1000 6000 753500 17200 32 24 9 5 23500 10800 20X-4 163.7 74000 299000 14900 200 21X-1 165.6 18000 72000 765300 100600 48 49 24 4 21 15900 5240 22X-6 181.7 3000 118000 726600 63300 64 20 9 11 11400 6990 23X-3 187.8 25000 102000 767800 94200 62 27 16 3 23 12400 5860 24X-3 197.4 17000 71000 819500 77400 133 18 8 2 16 6160 4630 26X-1 213.7 25000 105000 780300 73000 87 22 9 2 14 1 8970 5780 30X-2 244 179000 735000 21800 3400 31X-3 255.1 13000 NA 835900 72800 114 13 3 1 3 1 7330 6210 33X-2 272.69 118000 480000 56800 400 114 13 3 3 498 427 41X-2 340.2 182000 747000 25300 3900 5 5050 5050 43X-3 360.48 66000 164000 649300 65600 166 17 5 3 4 1 1 1 3910 3280 44X-3 370.08 18000 NA 831000 60400 133 19 7 11 6250 4890 51X-2 417.1 NA NA 570900 NA 11 3 4 1 1 1 27200 52X-4 429.7 42000 166000 682100 NA 373 29 6 3 8 1 1830 1630 54X-3 438.9 28000 108000 818600 NA 205 34 4 2 8 1 4000 3210 59X-3 485.38 24000 91000 790100 89300 415 44 6 4 7 3 3 4 1900 1630 64X-3 524.5 41000 163000 669300 115800 391 28 2 1710 1590 68X-4 554.1 1000 946000 38400 518 45 3 2 3 1 0 1 1830 1650 69X-4 564.51 18000 67000 843500 115800 673 53 4 4 4 1 1250 1140 71X-4 575.1 2000 2000 918200 86300 614 18 3 3 2 1 1 0 1500 1430 72X-2 580.8 15000 55000 796800 8000 614 72 7 7 6 2 1300 1130 73X-6 595.27 93000 314000 475900 62300 396 34 4 3 3 1 1 1 1200 1080 74X-5 603.02 60000 238000 568200 45400 473 27 4 3 3 1 0 1 1200 1110 75X-4 612.5 1000 900500 72700 766 54 5 5 4 1 0 1 1180 1080 76X-4 622.3 149000 633000 85100 21900 27 2 2 0 2 2 0 0 3120 2390 77X-5 632.39 59000 23000 597700 62100 568 36 5 4 3 1 0 0 1050 968 78X-3 640 46000 181000 607500 99400 628 37 4 4 3 1 0 0 967 897 79X-4 650.68 3000 7000 921600 71900 687 44 5 4 4 1 1340 1240 80X-5 661.21 20000 77000 992800 42600 785 53 7 5 5 2 1 1 1270 1160 81X-5 670.64 6000 21000 857900 56900 676 45 5 4 4 1 1 1 1270 1160 83X-2 685.98 14000 52000 741400 38000 520 38 3 3 3 1 1 1 1430 1300 84X-3 697.6 17000 50000 813800 87100 886 54 6 4 5 1 1 1 918 850 "Notes: Oxygen (O2) and nitrogen (N2) concentrations are included as a guide to the amount of air contamination in each sample. C1 through C7 = the alkanes: methane, ethane, propane, butane, pentane, hexane, and heptane." "Iso- and normal configurations of butane, pentane, and hexane are designated with i- and n- prefixes. C1/C2 = the methane/ethane ratio, and C1/C2+ = the ratio methane/the sum of (C2 through C6). NA = not analyzed."