Table 9. Composition of free gas collected in syringes from sediments at Site 996.																	

"Core, section"	Depth (mbsf)	O2 (ppmv)	N2 (ppmv)	CO2 (ppmv)	H2S (ppmv)	C1 (ppmv)	C2 (ppmv)	C3 (ppmv)	i-C4 (ppmv)	n-C4 (ppmv)	i-C5 (ppmv)	n-C5 (ppmv)	i-C6 (ppmv)	n-C6 (ppmv)	n-C7 (ppmv)	C1/C2	C1/C2+

164-996A-																	
1H-1	0.51	27000	110000	10900	19600	861400	753	24.7	8.5	2.4	9.7	1.4		 		1140	1080
1H-5	3.3	2000	1000	12500	21900	989000	937	18	7		9			 		1060	1020
3X-1	10.01	7000	54000	20800	53200	915400	569	17.1	2.1	0.6	0.3			0.3		1610	1550
8H-3	50.34	9000	31000	8400		992600	629	28.2	11.1	2.5	7.5	1.2	0.6	0.4		1580	1460
8H-5	52.44	3000	5000			997700	697	19.5	4.5	1	3.2	0.6	0.2	0.1		1430	1370
9H-5	62.45	3000	2000	10900		1076000	733	24.7	8.6	2.1	7.2	1	0.4	0.2		1470	1390

164-996D-																	
4H-5	26.87	2000	5000	13600	15500	918400	671	6.1	1.7	0.6	2.5	1	0.1	0.2		1370	1340
6H-4	45	1000	1000	9700		977200	766	22	5.5	1.9	8	1.2	1	0.7		1280	1210

164-996E-																	
4H-5	28.21	2000	2000	9300		989300	714	11	1.1	0.5	1.6	0.3	0.2	0.2		1390	1360
5H-5	37.56	2000	5000	6200		985000	583	10	2.4	0.8	2.4	0.5	0.2	0.2	0.8	1690	1640
7X-5	48.51	1000	1000	18600	 	974000	633	20.3	6.2	1.6	5.9	0.6	0.8			1540	1460

"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)."