Testing the utility of paleonutrient proxies Cd/Ca and Zn/Ca in benthic foraminifera from thermocline waters

American Geophysical Union (AGU) - Tập 11 Số 1 - 2010
S. P. Bryan1, Thomas M. Marchitto1
1Department of Geological Sciences and Institute of Arctic and Alpine Research University of Colorado at Boulder Campus Box 450, Boulder Colorado 80309‐0450 USA

Tóm tắt

Reconstruction of oceanic nutrient concentrations in the past provides information about nutrient cycling and physical circulation and the role these processes have played in past climate changes. The Cd/Ca and Zn/Ca of benthic foraminifera have been used successfully to reconstruct past deep ocean nutrient concentrations. In this study we test the ability of benthic foraminiferal Cd/Ca and Zn/Ca to detect changes in thermocline nutrient concentrations using a set of 31 multicores collected in the Florida Straits. Multicore sites span depths of 173–751 m, estimated seawater Cd concentrations of 0.02–0.42 nmol kg−1, and estimated seawater Zn concentrations of 0.3–3.1 nmol kg−1. Cd/Ca in several taxa of benthic foraminifera captures the regional differences and general shape of the nutricline on either side of the Florida Straits, indicating that it is capable of resolving small changes in upper ocean nutrient concentrations in the past. We estimate that the upper ocean partition coefficient for calcitic Cd/Ca may be slightly higher than the established value. Low seawater Zn concentrations combined with low partition coefficients and slight laboratory contamination severely complicated the evaluation of benthic foraminiferal Zn/Ca. However, at least one species, C. pachyderma, incorporates Zn with a relatively high partition coefficient (∼22), minimizing these complications. C. pachyderma Zn/Ca reflects the regional differences and general shape of the nutricline on either side of the Florida Straits and demonstrates potential for thermocline paleoceanography.

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Tài liệu tham khảo

10.1029/2003GC000559

10.1029/94PA03058

10.1029/94PA03353

10.1016/0016‐7037(83)90029‐7

10.1029/PA003i004p00471

10.1146/annurev.ea.20.050192.001333

10.2113/gsjfr.25.1.4

10.1126/science.218.4574.784

10.1016/0012‐821X(85)90154‐2

10.1007/978-3-642-80353-6_23

10.1038/263042a0

10.1016/0012‐821X(84)90075‐X

10.1029/95PA01625

10.1007/978-1-4757-6864-0_23

10.1038/271741a0

10.1029/2007PA001553

10.1029/2007PA001450

10.1038/35012507

10.1016/S0304‐4203(99)00085‐7

10.1038/298260a0

10.1029/93GB01536

10.1038/338751a0

Lund D. C.(2005) Gulf Stream temperature salinity and transport during the last millennium Ph.D. thesis 256 pp. Mass. Inst. of Technol. Cambridge Mass.

10.1029/2004PA001008

10.1029/2005PA001218

10.1038/nature05277

10.1175/1520‐0485(1983)013<0292:TVT>2.0.CO;2

10.1038/45204

10.1029/2004GC000753

10.1029/2005GC001018

10.1029/2006GC001323

10.1038/31197

10.1029/1999PA000420

10.1029/2000PA000598

10.1016/j.epsl.2004.12.024

10.1016/0967‐0645(93)90009‐C

10.1029/95PA01427

McNaught A. D., 1997, IUPAC Compendium of Chemical Terminology

10.1016/S0016‐7037(99)00317‐8

10.1029/97PA02508

10.1016/S0016‐7037(97)00181‐6

10.1021/ac981410x

10.1029/00EO00028

10.1029/95PA01166

10.1016/S0012‐821X(02)00796‐3

10.1029/96PA01860

10.1029/1999PA000467

10.1016/S0012‐821X(02)00613‐1

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American Geophysical Union (AGU)

Tập 11 Số 1

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