Table 4. Overview of calcium and magnesium gradients.

Table 4. Overview of calcium and magnesium gradients.

Calcium minimum

Gradients at depth

Site name (latitude)

Site

Concentration (mM)

Depth (mbsf)

Comments on Ca and Mg gradients
and Ca vs. Mg regression

Ca
(mM/100 m)

Mg
(mM/100 m)

Ca/Mg*

r²

Gorda Transect (~40°N):

Eel River Basin 1019 0.97 41
Deepest 14 points, from where Mg increase ends +1.5 -5.9 -0.24 0.87

Delgada Slope 1022 4.1 31
Deepest 6 points, from Ca minimum +1.9 -8.8 -0.21 0.88

Eastern flank, Gorda Ridge 1020 5.1 50
Deepest 8 points, below Ca minimum +11.4 -11.8 -0.82 0.94

Outer Delgada Fan 1021 8.7 107
Deepest 8 points, from Ca minimum +1.9 -0.87 -2.1 0.78

Conception Transect (~35°N):

Santa Lucia Slope 1017 2.4 29-48
Deepest 8 points, from Ca minimum +2.3 -11.0 -0.16 0.82

Pelagic site, off Point Conception 1016 5.2 79
Deepest 8 points, from Ca minimum +4.1 -8.9 -0.80 0.92

Baja Transect (~30°N):

Animal Basin 1011 3.4 41
Mg increases deeper than minimum at 136 mbsf — — — —

Ocean crust, near Guadalupe Island 1010 — —
Ca decreasing throughout entire depth sampled (n = 13) +4.2 -3.3 -1.3 0.96

Coastal Transect (other sites):

Sediment drift, south of Guide Seamount (~37°N) 1018 3.6 28
Deepest 15 points, from Ca minimum +2.1 -7.6 -0.28 0.97

Tanner Basin (~33°N) 1014 2.8 36
Mg increases to a maximum at 137 mbsf — — — —

San Nicolas Basin (~33°N) 1013 3.5 38
No inverse relationship between Ca and Mg observed (shallow total sediment thickness) — — — —

East Cortes Basin (~32°N) 1012 2.2 47
Deepest 6 points, below Ca minimum +1.2 -10.2 -0.13 0.95

		Calcium minimum
Site name (latitude)	Site	Concentration (mM)	Depth (mbsf)	Comments on Ca and Mg gradients and Ca vs. Mg regression	Ca (mM/100 m)	Mg (mM/100 m)	Ca/Mg*	r²
Gorda Transect (~40°N):
Eel River Basin	1019	0.97	41	Deepest 14 points, from where Mg increase ends	+1.5	-5.9	-0.24	0.87
Delgada Slope	1022	4.1	31	Deepest 6 points, from Ca minimum	+1.9	-8.8	-0.21	0.88
Eastern flank, Gorda Ridge	1020	5.1	50	Deepest 8 points, below Ca minimum	+11.4	-11.8	-0.82	0.94
Outer Delgada Fan	1021	8.7	107	Deepest 8 points, from Ca minimum	+1.9	-0.87	-2.1	0.78
Conception Transect (~35°N):
Santa Lucia Slope	1017	2.4	29-48	Deepest 8 points, from Ca minimum	+2.3	-11.0	-0.16	0.82
Pelagic site, off Point Conception	1016	5.2	79	Deepest 8 points, from Ca minimum	+4.1	-8.9	-0.80	0.92
Baja Transect (~30°N):
Animal Basin	1011	3.4	41	Mg increases deeper than minimum at 136 mbsf	—	—	—	—
Ocean crust, near Guadalupe Island	1010	—	—	Ca decreasing throughout entire depth sampled (n = 13)	+4.2	-3.3	-1.3	0.96
Coastal Transect (other sites):
Sediment drift, south of Guide Seamount (~37°N)	1018	3.6	28	Deepest 15 points, from Ca minimum	+2.1	-7.6	-0.28	0.97
Tanner Basin (~33°N)	1014	2.8	36	Mg increases to a maximum at 137 mbsf	—	—	—	—
San Nicolas Basin (~33°N)	1013	3.5	38	No inverse relationship between Ca and Mg observed (shallow total sediment thickness)	—	—	—	—
East Cortes Basin (~32°N)	1012	2.2	47	Deepest 6 points, below Ca minimum	+1.2	-10.2	-0.13	0.95

Notes: Site numbers in bold in the onshore-offshore transects indicate sites that are also part of the north-south Coastal Transect. * = the correlation coefficients for the linear regressions of Ca vs. Mg are all significant at the 99% confidence level, except for regressions at Sites 1021 and 1017, where the correlation coefficient is significant at the 95% confidence level. — = not applicable.