A comparative study of boron isotopes and trace elements of the marine foraminifers during the last glacial maximum and Holocene

Science China Earth Sciences - Tập 53 - Trang 91-100 - 2009
YunYan Ni1,2
1Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, China
2Bristol Isotope Group, Department of Earth Sciences, Bristol University, Bristol, UK

Tóm tắt

Boron isotopic compositions in marine planktonic foraminifers can record changes in seawater pH and hence provide a new tool to reconstruct the changes of paleo-atmospheric PCO2. Here a comparative study was done on boron isotopes and trace element abundances of planktonic foraminifers, Globigerinoides sacculifer and Globigerinoides ruber from three tropical ODP sites, Site 806B, Site 664C and Site 999A. It is demonstrated here that G. ruber is a better species to be used for downcore boron isotope analyses on glacial-interglacial scales, particularly since G. sacculifer is prone to dissolution causing unexpectedly light boron isotopes during glacial times. It has been shown that the trace elements composition of foraminifers (i.e., Mg/Ca, U/Ca, B/Ca, and Li/Ca) can reflect the variations of seawater temperature and/or [CO3 2−]. However, all of these systems are highly species de- pendent and affected by other vital effects, and it is therefore important to perform necessary calibrations when applying them to the downcore analyses.

Tài liệu tham khảo

Zeebe R E, Wolf-Gladrow D. CO2 in Seawater: Equilibrium, Kinetics, Isotopes. Amsterdam: Elsevier Science and Technology, 2001

Carbon Dioxide Survey Science Team (DOE). DOE Handbook of Methods. Oak Ridge, Tennessee: Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, 1994

Hönisch B, Hemming N G. Ground-truthing the boron isotopepaleo-pH proxy in planktonic foraminifera shells: Partial dissolution and shell size effects. Paleoceanography, 2004, 19: PA4010, doi: 10.1029/2004PA001026

Ni Y, Foster G, Bailey T, et al. A core top assessment of proxies for the ocean carbonate system in surface dwelling foraminifers. Paleoceanography, 2007, 22: PA3212, doi: 10.1029/2006PA001337

Zeebe R E, Wolf-Gladrow D A, Bijma J, et al. Vital effects in foraminifera do not compromise the use of δ11B as a paleo-pH indicator: Evidence from modeling. Paleoceanography, 2003, 18: 1043, doi: 10.1029/2003PA000881

Yu J, Elderfield H, Hönisch B. B/Ca in planktonic foraminifera as a proxy for surface seawater pH. Paleoceanography, 2007, 22: PA2202, doi: 10.1029/2006PA001347

Cléroux C, Cortijo E, Anand P, et al. Mg/Ca and Sr/Ca ratios in planktonic foraminifera: Proxies for upper column temperature reconstruction. Paleoceanography, 2008, 23: PA3214, doi: 10.1029/2007PA00150

Rosenthal Y, Lohmann G P, Lohmann K C, et al. Incorporation and preservation of Mg in Globigerinoides sacculifer: Implications for reconstructing the temperature and 18O/16O of seawater. Paleoceanography, 2000, 15: 135–145

Elderfield H, Vautravers M, Cooper M. The relationship between shell size and Mg/Ca, Sr/Ca, δ18O, and δ13C of species of planktonic foraminifera. Geochem Geophys Geosyst, 2002, 3, doi: 10.1029/2001GC000194

Sadekov A Y, Eggins S M, de Deckker P. Characterization of Mg/Ca distributions in planktonic foraminifera species by electron microprobe mapping. Geochem Geophys Geosyst, 2005, 6: Q12P06, doi: 10.1029/2005GC000973

Wara M W, Delaney M L, Bullen T D, et al. Possible roles of pH, temperature, and partial dissolution in determing boron concentration and isotopic composition in planktonic foraminifera. Paleoceanography, 2003, 18: 1100, doi: 10.1029/2002PA000797

Palmer M R, Pearson P N. A 23000-year record of surface water pH and PCO2 in the western equatorial Pacific Ocean. Science, 2003, 300: 480–482

Barker S, Elderfield H. Foraminiferal calcification response to glacial-interglacial changes in atmospheric CO2. Science, 2002, 297: 833–836

Broecker W S, Clark E. CaCO3 dissolution in the deap sea: Paced by insolation cycles. Geochem Geophys Geosyst, 2003, 4: 1059, doi: 10.1029/2002GC000450

Broecker W S, Clark E. Holocene atmospheric CO2 increase as viewed from the seafloor. Glob Biogeochem Cycles, 2003, 17: 1052, doi: 10.1029/2002GB001985

Key R M, Kozyr A, Sabine C, et al. A global ocean carbon climatology: Results from Global Data Analysis Project (GLODAP). Glob Biogeochem Cycles, 2004, 18: GB4031, doi: 10.1029/2004 GB002247

Schlitzer R. Ocean data view. http://www.awi-bremerhaven.de/GEO/ODV. 2000

Pelletier L C, Lewis E, Wallace D. A calculator for the CO2 system in seawater for Microsoft Excel/VBA. Washington State Department of Ecology, Olympia, WA, Brookhaven National Laboratory Upton, NY, 2005

Mehrbach C C, Culberson H, Hawley J E, et al. Measurement of the apparent dissociation constant of carbonic acid in seawater at atmospheric pressure. Limnol Oceanogr, 1973, 18: 897–907