Table 3. Interstitial water chemical signatures of organic matter diagenesis.

Table 3. Interstitial water chemical signatures of organic matter diagenesis.

Site name (latitude) Site Water
depth*
(m) Distance
from shore
(km) Depth range of IW sampling (mbsf) Sulfate
"zero" depth^†
(mbsf) Alkalinity maximum

Phosphate maximum

Ammonium maximum

Concentration (mM)

Depth
(mbsf)

Concentration (mM)

Depth
(mbsf)

Concentration (mM)

Depth
(mbsf)

Gorda Transect (~40°N):

Eel River Basin^‡ 1019 989 59 242 13 95 78-147
>340 (to 400) 61-137
>13 165

Delgada Slope 1022 1927 87 161 or 326** 37 >15 37-161
>65 28-47
5.7 161 (still increasing)

Eastern flank, Gorda Ridge 1020 3050 167 260 107 20 31-136
55 12-50
>3 164-193

Outer Delgada Fan 1021 4215 364 305 — 9 136-165
>15 3-79
>0.5 79-189

Conception Transect (~35°N):

Santa Lucia Slope 1017 967 52 180 19 >40 19-48
>100 (to 161) 10-48 (at 19)
8.5 76-180

Pelagic site, off Point Conception 1016 3846 148 274 79 >17 40-50
57 31-40
2.3 79-274

Baja Transect (~30°N):

Animal Basin 1011 2033 [~1600] 85 247 41^†† >20 30-90
>40 10-60
>2.5 50-150

Ocean crust, near Guadalupe Island 1010 3465 209 170 — >4 50
Always <10 —
0.13 170

Coastal Transect (other sites):

Sediment drift, south of Guide Seamount (~37°N)
1018 2476 76 402 9 >50
19-76 >165 (to 182)
19-47(at 38) >6.5 to 7.5104-257

Tanner Basin (~33°N) 1014 1177 [1165] 155 444 17 >100 137-222
>150 (up to 200) 27-191 (108-137)
>35 347-444

San Nicolas Basin (~33°N) 1013 1575 [1106] 115 131 27 >50 46
>170 19
>13 Increasing throughout

East Cortes Basin (~32°N) 1012 1783 [1415] 105 267 19 67 162
100 7-38
>14 131

Site name (latitude)	Site	Water depth* (m)	Distance from shore (km)	Depth range of IW sampling (mbsf)	Sulfate "zero" depth^† (mbsf)	Alkalinity maximum			Ammonium maximum
Concentration (mM)	Depth (mbsf)		Concentration (mM)	Depth (mbsf)		Concentration (mM)	Depth (mbsf)
Gorda Transect (~40°N):
Eel River Basin^‡	1019	989	59	242	13	95	78-147	>340 (to 400)	61-137	>13	165
Delgada Slope	1022	1927	87	161 or 326**	37	>15	37-161	>65	28-47	5.7	161 (still increasing)
Eastern flank, Gorda Ridge	1020	3050	167	260	107	20	31-136	55	12-50	>3	164-193
Outer Delgada Fan	1021	4215	364	305	—	9	136-165	>15	3-79	>0.5	79-189
Conception Transect (~35°N):
Santa Lucia Slope	1017	967	52	180	19	>40	19-48	>100 (to 161)	10-48 (at 19)	8.5	76-180
Pelagic site, off Point Conception	1016	3846	148	274	79	>17	40-50	57	31-40	2.3	79-274
Baja Transect (~30°N):
Animal Basin	1011	2033 [~1600]	85	247	41^††	>20	30-90	>40	10-60	>2.5	50-150
Ocean crust, near Guadalupe Island	1010	3465	209	170	—	>4	50	Always <10	—	0.13	170
Coastal Transect (other sites):
Sediment drift, south of Guide Seamount (~37°N)		1018	2476	76	402	9	>50	19-76	>165 (to 182)	19-47(at 38)	>6.5 to 7.5104-257
Tanner Basin (~33°N)	1014	1177 [1165]	155	444	17	>100	137-222	>150 (up to 200)	27-191 (108-137)	>35	347-444
San Nicolas Basin (~33°N)	1013	1575 [1106]	115	131	27	>50	46	>170	19	>13	Increasing throughout
East Cortes Basin (~32°N)	1012	1783 [1415]	105	267	19	67	162	100	7-38	>14	131

Notes: Site numbers in bold in the onshore-offshore transects indicate sites that are also part of the north-south Coastal Transect. * = numbers in brackets indicate basin sill depth. IW = interstitial waters. † = depth of the shallowest sample with nondetectable sulfate concentrations (generally <1 mM). ‡ = this site has major decreases in chlorinity, salinity, and sodium in its interstitial water (IW) profiles; see site chapters in Lyle, Koizumi, Richter, et al. (1997). ** = samples from below 161 mbsf for Site 1022 were analyzed shipboard only for alkalinity, pH, and salinity, because of time limitations imposed by the end of the cruise. †† = sulfate increases again at depth at this site.