Influence of the Amazon River on the Nd isotope composition of deep
water in the western equatorial Atlantic during the Oligocene-Miocene
transition
Joseph A. Stewart a,b*, Marcus Gutjahr c, Rachael H. James a, Pallavi Anand d, Paul A. Wilson a
a National
Oceanography Centre Southampton, University of Southampton, European Way, Southampton, SO14 3ZH, UK.
b National
Institute of Standards and Technology, Hollings Marine Laboratory, 331 Fort Johnson Rd, Charleston, SC, 29412, USA
c GEOMAR
d School
Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3 D-24148 Kiel, Germany
of Environment, Earth and Ecosystem Science, Walton Hall, The Open University, Milton Keynes, MK7 6AA, UK
*Corresponding author. Tel: +1 843 725 4833, Email: [email protected]
Supplementary information:
1.1
Trace element analysis
The Ca content of foraminiferal calcite solutions was first determined by inductively coupled plasma optical
emission spectroscopy (ICP-OES; Green et al., 2003) to ensure that the trace element standards were matrix
matched with the samples. Nd/Ca ratios were then determined by ICP mass spectrometry (ICP-MS; Perkin
Elmer Elan DRC II) following techniques described in Rosenthal et al., (1999). The external reproducibility of
the Nd/Ca measurements was ±3.4% (2σ) based on repeat analysis (n=23) of two in-house foraminiferal calcite
standards. Mn/Ca ratios (reproducibility ±6.9%; 2σ) were also determined by ICP-MS to assess the efficacy of
removal of Fe-Mn coatings.
Nd/Ca values measured in D. venezuelana range from 1 to 3 μmol/mol, and corresponding Mn/Ca values are
between 500 and 1000 μmol/mol (Supplemental Figure 1; data in Supplemental Information Table). There is no
correlation between Mn/Ca and Nd/Ca but absolute values are considerably higher (by up to 500 μmol/mol and
1 μmol/mol, respectively) than Mn/Ca and Nd/Ca values measured in recently buried (<1.8 Ma) and living
planktonic foraminifera (Supplemental Figure 1; Palmer, 1985; Vance and Burton, 1999; Martínez-Botí et al.,
2009).
Supplemental Figure 1: Relationship between Mn/Ca and Nd/Ca for cleaned planktonic foraminifera. D. venezuelana (this
study) are shown by the shaded blue symbols. Error bars represent the 2σ external reproducibility of the analyses. Also
shown are planktonic foraminifera data for the Labrador Sea (open black circles, 0 to 100 meters below seafloor; Vance
and Burton, 1999), and core top data from the Mediterranean Sea (open red circles; Martínez-Botí et al., 2009) and
equatorial Atlantic Ocean (open blue circles; Palmer, 1985). Black dashed line is the maximum cut-off point for accurate
reconstruction of surface water εNd used by Vance and Burton, (1999).
Supplemental Information Table: Nd/Ca and Mn/Ca of cleaned planktonic foraminifera D. venezuelana. Core depth shown
in metres below sea floor (mbsf). Sample ages are calculated using the age model of Pälike et al. (2006).
ODP Sample Identification
Site, Hole, Core, Section, Half, Int.
Depth
(mbsf)
Age
(Ma)
No. Individuals
Sample mass
(mg)
Nd/Ca
(?mol/mol)
Mn/Ca
(?mol/mol)
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
926 B
428.02
430.26
433.05
436.44
438.65
442.96
446.32
450.92
453.32
455.53
458.05
458.88
459.75
461.61
462.11
462.44
462.44
462.71
463.02
463.28
463.56
463.86
464.12
464.40
464.67
464.97
465.22
465.52
465.78
466.09
466.37
466.66
466.92
466.92
467.21
467.46
467.86
468.08
468.31
468.51
468.74
468.97
469.18
469.40
469.63
469.83
470.05
471.21
471.41
471.64
472.09
472.52
472.96
473.62
474.72
476.61
479.29
481.91
485.49
488.12
491.19
21.62
21.69
21.80
21.91
21.98
22.13
22.24
22.39
22.48
22.56
22.65
22.68
22.72
22.80
22.81
22.82
22.82
22.83
22.84
22.86
22.87
22.88
22.89
22.90
22.91
22.93
22.94
22.95
22.96
22.97
22.98
22.99
23.00
23.00
23.01
23.02
23.03
23.04
23.05
23.06
23.07
23.07
23.08
23.09
23.10
23.11
23.12
23.16
23.17
23.18
23.19
23.21
23.22
23.25
23.29
23.36
23.52
23.64
23.78
23.89
24.00
33
31
31
40
31
36
37
33
32
50
59
31
40
41
45
38
28
34
35
32
42
35
35
40
41
37
37
36
35
38
16
36
22
36
39
26
40
37
36
44
33
53
44
34
39
39
33
31
33
38
26
35
36
32
43
40
33
33
20
33
22
1.16
1.26
1.08
1.44
1.09
1.25
1.38
1.34
1.18
1.97
2.42
1.31
1.65
1.57
1.88
1.48
1.04
1.33
1.36
1.12
1.54
1.40
1.26
1.37
1.58
1.35
1.27
1.38
1.27
1.37
0.58
1.39
0.88
1.31
1.34
0.92
1.54
1.48
1.38
1.64
1.15
2.04
1.57
1.30
1.52
1.47
1.25
1.14
1.27
1.46
1.03
1.36
1.34
1.38
1.91
1.57
1.40
1.39
0.79
1.28
1.00
1.56
1.74
1.53
1.38
1.92
1.95
2.30
1.94
1.38
1.26
1.20
1.16
1.50
2.00
1.48
1.81
1.82
2.37
1.68
1.86
2.01
1.98
1.54
2.38
2.71
1.28
1.71
1.95
1.84
1.56
2.23
2.86
1.87
1.77
2.42
2.24
2.63
1.75
2.26
2.12
1.98
2.55
2.64
1.88
1.66
2.40
2.28
2.45
1.47
1.69
2.04
1.83
1.83
1.57
1.55
1.89
1.72
3.10
2.28
1.39
1.66
563
673
735
661
684
682
635
542
682
860
737
821
764
825
807
854
847
783
829
680
648
829
864
759
767
945
962
923
712
794
856
808
857
800
747
874
800
900
891
835
669
826
678
706
685
782
621
694
756
637
671
690
674
796
650
753
737
659
698
729
699
46
46
47
47
47
48
48
48
49
49
49
49
49
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
51
51
51
51
51
51
51
51
51
51
52
52
52
53
4W
5W
1W
3W
5W
1W
3W
6W
2W
3W
5W
5W
6W
1W
1W
1W
1W
1W
2W
2W
2W
2W
2W
3W
3W
3W
3W
3W
3W
4W
4W
4W
4W
4W
4W
5W
5W
5W
5W
5W
5W
6W
6W
6W
6W
6W
6W
1W
1W
1W
1W
2W
2W
2W
3W
4W
6W
1W
4W
6W
1W
71.5
146
65
104
25
86
122
132
12
83
35
117.5
55
21
71
103.5
103.5
131
11.5
38
65.5
96
122
0
27
57
81.5
112
138
18.5
47
76
102
102
131
5.5
46
68
91
111
134
7
28
50
72.5
93
115
21
41
63.5
109
1.5
46
112
72
111
79
141
49
11.5
99
-
73.5
148
67
106
27
88
124
134
14
85
37
119.5
57
24
75
107.5
107.5
134
14
42
69.5
99
124
4
29
59
84
114
141
21.5
49
78
105
105
134
7.5
49
70
95
114
137
9
30
53
74.5
96
119
23
43.5
67.5
111
3.5
49.5
114
74
113.5
81
143.5
51
13.5
101.5
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