Influence of the Amazon River on the Nd isotope composition of deepwater in the western equatorial Atlantic during the Oligocene-Miocenetransition

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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 Helmholtz Centre for Ocean Research Kiel, Wischhofstraße 1-3 D-24148 Kiel, Germany

d

School of Environment, Earth and Ecosystem Science, Walton Hall, The Open University, Milton Keynes, MK7 6AA, UK

*Corresponding author. Tel: +1 843 725 4833, Email: Joseph.Stewart@noaa.gov

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).

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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

ε

Nd

used by Vance and Burton, (1999).

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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).

Depth (mbsf)

Age (Ma)

No. Individuals Sample mass (mg)

Nd/Ca (?mol/mol)

Mn/Ca (?mol/mol)

926 B 46 4 W 71.5 - 73.5 428.02 21.62 33 1.16 1.56 563

926 B 46 5 W 146 - 148 430.26 21.69 31 1.26 1.74 673

926 B 47 1 W 65 - 67 433.05 21.80 31 1.08 1.53 735

926 B 47 3 W 104 - 106 436.44 21.91 40 1.44 1.38 661

926 B 47 5 W 25 - 27 438.65 21.98 31 1.09 1.92 684

926 B 48 1 W 86 - 88 442.96 22.13 36 1.25 1.95 682

926 B 48 3 W 122 - 124 446.32 22.24 37 1.38 2.30 635

926 B 48 6 W 132 - 134 450.92 22.39 33 1.34 1.94 542

926 B 49 2 W 12 - 14 453.32 22.48 32 1.18 1.38 682

926 B 49 3 W 83 - 85 455.53 22.56 50 1.97 1.26 860

926 B 49 5 W 35 - 37 458.05 22.65 59 2.42 1.20 737

926 B 49 5 W 117.5 - 119.5 458.88 22.68 31 1.31 1.16 821

926 B 49 6 W 55 - 57 459.75 22.72 40 1.65 1.50 764

926 B 50 1 W 21 - 24 461.61 22.80 41 1.57 2.00 825

926 B 50 1 W 71 - 75 462.11 22.81 45 1.88 1.48 807

926 B 50 1 W 103.5 - 107.5 462.44 22.82 38 1.48 1.81 854

926 B 50 1 W 103.5 - 107.5 462.44 22.82 28 1.04 1.82 847

926 B 50 1 W 131 - 134 462.71 22.83 34 1.33 2.37 783

926 B 50 2 W 11.5 - 14 463.02 22.84 35 1.36 1.68 829

926 B 50 2 W 38 - 42 463.28 22.86 32 1.12 1.86 680

926 B 50 2 W 65.5 - 69.5 463.56 22.87 42 1.54 2.01 648

926 B 50 2 W 96 - 99 463.86 22.88 35 1.40 1.98 829

926 B 50 2 W 122 - 124 464.12 22.89 35 1.26 1.54 864

926 B 50 3 W 0 - 4 464.40 22.90 40 1.37 2.38 759

926 B 50 3 W 27 - 29 464.67 22.91 41 1.58 2.71 767

926 B 50 3 W 57 - 59 464.97 22.93 37 1.35 1.28 945

926 B 50 3 W 81.5 - 84 465.22 22.94 37 1.27 1.71 962

926 B 50 3 W 112 - 114 465.52 22.95 36 1.38 1.95 923

926 B 50 3 W 138 - 141 465.78 22.96 35 1.27 1.84 712

926 B 50 4 W 18.5 - 21.5 466.09 22.97 38 1.37 1.56 794

926 B 50 4 W 47 - 49 466.37 22.98 16 0.58 2.23 856

926 B 50 4 W 76 - 78 466.66 22.99 36 1.39 2.86 808

926 B 50 4 W 102 - 105 466.92 23.00 22 0.88 1.87 857

926 B 50 4 W 102 - 105 466.92 23.00 36 1.31 1.77 800

926 B 50 4 W 131 - 134 467.21 23.01 39 1.34 2.42 747

926 B 50 5 W 5.5 - 7.5 467.46 23.02 26 0.92 2.24 874

926 B 50 5 W 46 - 49 467.86 23.03 40 1.54 2.63 800

926 B 50 5 W 68 - 70 468.08 23.04 37 1.48 1.75 900

926 B 50 5 W 91 - 95 468.31 23.05 36 1.38 2.26 891

926 B 50 5 W 111 - 114 468.51 23.06 44 1.64 2.12 835

926 B 50 5 W 134 - 137 468.74 23.07 33 1.15 1.98 669

926 B 50 6 W 7 - 9 468.97 23.07 53 2.04 2.55 826

926 B 50 6 W 28 - 30 469.18 23.08 44 1.57 2.64 678

926 B 50 6 W 50 - 53 469.40 23.09 34 1.30 1.88 706

926 B 50 6 W 72.5 - 74.5 469.63 23.10 39 1.52 1.66 685

926 B 50 6 W 93 - 96 469.83 23.11 39 1.47 2.40 782

926 B 50 6 W 115 - 119 470.05 23.12 33 1.25 2.28 621

926 B 51 1 W 21 - 23 471.21 23.16 31 1.14 2.45 694

926 B 51 1 W 41 - 43.5 471.41 23.17 33 1.27 1.47 756

926 B 51 1 W 63.5 - 67.5 471.64 23.18 38 1.46 1.69 637

926 B 51 1 W 109 - 111 472.09 23.19 26 1.03 2.04 671

926 B 51 2 W 1.5 - 3.5 472.52 23.21 35 1.36 1.83 690

926 B 51 2 W 46 - 49.5 472.96 23.22 36 1.34 1.83 674

926 B 51 2 W 112 - 114 473.62 23.25 32 1.38 1.57 796

926 B 51 3 W 72 - 74 474.72 23.29 43 1.91 1.55 650

926 B 51 4 W 111 - 113.5 476.61 23.36 40 1.57 1.89 753

926 B 51 6 W 79 - 81 479.29 23.52 33 1.40 1.72 737

926 B 52 1 W 141 - 143.5 481.91 23.64 33 1.39 3.10 659

926 B 52 4 W 49 - 51 485.49 23.78 20 0.79 2.28 698

926 B 52 6 W 11.5 - 13.5 488.12 23.89 33 1.28 1.39 729

926 B 53 1 W 99 - 101.5 491.19 24.00 22 1.00 1.66 699

ODP Sample Identification Site, Hole, Core, Section, Half, Int.

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References

Green, D.R.H., Cooper, M.J., German, C.R., Wilson, P.A., 2003. Optimization of an inductively coupled plasma-optical emission spectrometry method for the rapid determination of high-precision Mg/Ca and Sr/Ca in foraminiferal calcite.

Geochem. Geophys. Geosyst. 4, 8404.

Martínez-Botí, M.A., Vance, D., Mortyn, P.G., 2009. Nd/Ca ratios in plankton-towed and core top foraminifera:

Confirmation of the water column acquisition of Nd. Geochem. Geophys. Geosyst. 10, Q08018.

Pälike, H., Frazier, J., Zachos, J.C., 2006. Extended orbitally forced palaeoclimatic records from the equatorial Atlantic Ceara Rise. Quat. Sci. Rev. 25, 3138-3149.

Palmer, M.R., 1985. Rare earth elements in foraminifera tests. Earth and Planetary Science Letters 73, 285-298.

Rosenthal, Y., Field, M.P., Sherrell, R.M., 1999. Precise determination of element/calcium ratios in calcareous samples using sector field inductively coupled plasma mass spectrometry. Anal. Chem. 71, 3248-3253.

Influence of the Amazon River on the Nd isotope composition of deepwater in the western equatorial Atlantic during the Oligocene-Miocenetransition