Ground‐truthing the boron isotope‐paleo‐pH proxy in planktonic foraminifera shells: Partial dissolution and shell size effects

Paleoceanography - Tập 19 Số 4 - 2004
Bärbel Hönisch1, N. G. Hemming1
1School of Earth and Environmental Sciences Queens College Flushing New York USA

Tóm tắt

Sediment samples from the Ontong‐Java Plateau in the Pacific and the 90° east ridge in the Indian Ocean were used to investigate whether shell size and early diagenesis affect δ11B of the symbiont‐bearing planktonic foraminifer Globigerinoides sacculifer. In pristine shells from both study locations we found a systematic increase of δ11B and Mg/Ca with shell size. Shells in the sieve size class 515–865 μm revealed δ11B values +2.1 to +2.3‰ higher than shells in the 250–380 μm class. This pattern is most likely due to differences in symbiont photosynthetic activity and its integrated effect on the pH of the foraminiferal microenvironment. We therefore suggest smaller individuals must live at approximately 50–100 m water depth where ambient light levels are lower. Using the empirical calibration curve for δ11B in G. sacculifer, only shells larger than 425 μm reflect surface seawater pH. Partial dissolution of shells derived from deeper sediment cores was determined by shell weight analyses and investigation of the shell surface microstructure by scanning electron microscopy. The δ11B in partially dissolved shells is up to 2‰ lower relative to pristine shells of the same size class. In agreement with a relatively higher weight loss in smaller shells, samples from the Ontong‐Java Plateau show a more pronounced dissolution effect than larger shells. On the basis of the primary size effect and potential postdepositional dissolution effects, we recommend the use of shells that are visually pristine and, in the case of G. sacculifer, larger than 500 μm for paleoreconstructions.

Từ khóa


Tài liệu tham khảo

10.1016/0377-8398(80)90014-6

10.4319/lo.1972.17.2.0275

Berger W. H., 1982, Foraminifera on the deep‐sea floor: Lysocline and dissolution rate, Oceanol. Acta, 5, 249

10.1016/0967-0637(94)90092-2

10.2113/gsjfr.20.2.95

10.1016/0012-821X(85)90154-2

10.1029/1998PA900009

10.1029/96PA01491

10.1029/2001GC000200

Department of Energy (DOE)(1994) Handbook of methods for the analysis of the various parameters of the carbon dioxide system in seawater Washington D. C.

10.1016/0021-9614(90)90074-Z

10.1016/0198-0149(87)90021-5

10.1029/2001GC000194

10.1016/S0921-8181(02)00058-9

10.1007/978-3-642-78737-9_7

10.1016/0016-7037(92)90151-8

10.1016/0009-2541(94)90048-5

10.1016/0016-7037(95)00288-B

Hönisch B.(2002) Stable isotope and trace element composition of foraminiferal calcite—From incorporation to dissolution Ph.D. thesis Univ. of Bremen Bremen.

10.1016/S0377-8398(03)00030-6

10.1016/j.gca.2004.03.002

10.4319/lo.1985.30.6.1253

10.1246/bcsj.50.158

Levitus S., 1994, World Ocean Atlas

Lewis E. andD. W. R.Wallace(1998) Program developed for CO2system calculations Rep. ORNL/CDIAC‐105 Carbon Dioxide Inf. Anal. Cent. Oak Ridge Natl. Lab. U.S. Dep. of Energy Oak Ridge Tenn.

10.1029/95PA00059

Lorens R. B., 1977, The early nonstructural diagenesis of foraminiferal calcite, J. Sediment. Petrol., 47, 1602

10.4319/lo.1973.18.6.0897

10.1029/PA004i004p00333

10.1126/science.282.5393.1468

10.1038/35021000

10.1016/0025-3227(85)90108-2

10.1111/j.1469-8137.2007.02357.x

10.1007/s00338‐004‐0399‐5

10.1007/s002270050350

10.1029/1999PA000415

10.1029/1999PA900036

10.1038/373234a0

10.1029/96PA01858

10.1029/97GB00223

10.1016/S0016-7037(99)00437-8

10.1029/2000PA000547

10.1130/0016-7606(1973)84<2327:SIAMGO>2.0.CO;2

10.1029/1998PA900025

10.1016/S0277-3791(03)00172-0

10.1016/0377-8398(93)90045-Y

10.2113/gsjfr.15.4.273

10.1016/S0025-3227(02)00333-X

10.1016/S0304-4203(98)00074-7

Zeebe R. E., 2001, CO2in Seawater: Equilibrium, Kinetics, Isotopes

10.1029/2003PA000881

Thông tin
Thông tin xuất bản

Paleoceanography

Tập 19 Số 4

Thông tin tác giả