Characterization of Mg/Ca distributions in planktonic foraminifera species by electron microprobe mapping

American Geophysical Union (AGU) - Tập 6 Số 12 - 2005
Aleksey Sadekov1, Stephen M. Eggins1, Patrick De Deckker2
1Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
2Department of Earth and Marine Sciences, The Australian National University, Canberra, ACT 0200, Australia

Tóm tắt

The distribution of Mg/Ca within the tests of eight modern planktonic foraminifer species has been characterized using electron microprobe mapping. Species include several that are commonly used for estimation of past seawater temperatures (Globigerinoides ruber, G. sacculifer, Neogloboquadrina incompta (synonym of N. pachyderma dex.), N. dutertrei, and G. truncatulinoides). Each of the investigated species displays large variations in Mg/Ca composition within individual tests. However, the pattern of Mg/Ca variation is notably different between symbiont‐bearing and symbiont‐free species. In symbiotic species, cyclic Mg/Ca compositional banding occurs that is characterized by narrow (<1–3 μm), high‐Mg/Ca (typically 8–11 mmol/mol) bands, intercalated between broader low Mg/Ca (typically 1–5 mmol/mol) bands. This factor of 2–3 difference equates to an apparent calcification temperature change of 10°C or more. Such temperature changes are considered highly improbable and suggest vital effects significantly modify the incorporation of Mg/Ca into the tests of symbiont‐bearing species. These vital effects remain poorly understood and demand further careful evaluation as they may need to be accounted for when making reliable reconstructions of past oceanic temperatures. Symbiont‐free species typically have fewer and broader compositional bands that may reflect more closely changes in calcification temperature as these species migrate within a water column.

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Tài liệu tham khảo

10.1029/2002GC000430

10.1029/2002PA000846

10.1029/2003GC000559

10.1016/j.quascirev.2004.07.016

10.1016/0377-8398(80)90014-6

Bé A. W. H., 1970, Calcification in a living planktonic foraminifer, Globigerinoides sacculifer (Brady), Neues Jahrb. Geol. Paläontol., 134, 221

10.1126/science.145.3634.823

Bé A. W. H., 1966, Shell microstructure of a planktonic foraminifer, Globorotalia menardii (d'Orbigny), Eclogae Geol. Helv., 59, 885

10.1016/0377-8398(85)90002-7

10.1029/2002GC000312

10.1016/0967-0637(94)90092-2

10.2113/gsjfr.20.2.95

10.1016/0012-821X(81)90022-4

10.1029/96PA01491

10.1016/0377-8398(90)90031-G

10.1029/2001GC000200

10.2113/gsjfr.17.1.14

10.2113/gsjfr.7.4.304

10.1016/S0012-821X(03)00283-8

10.1016/j.epsl.2004.06.019

10.1038/35013033

10.1016/0012-821X(96)00105-7

10.1029/2001GC000194

Erez J.(2003) The source of ions for biomineralization in foraminifera and their implications for paleoceanographic proxies inBiomineralization edited byM.Dove Patricia J.De Yoreo James andS.Weiner Rev. Mineral. Geochem. 54 115–149.

10.1016/0031-0182(81)90035-3

10.1029/90PA02731

10.1038/298841a0

10.1029/2003PA000970

Fleisher R. L., 1969, Secondary calcification in Globorotalia menardii (Foraminiferida), Am. Assoc. Pet. Geol. Bull., 53, 466

10.1029/2004GC000822

10.1016/j.margeo.2004.09.001

10.1029/97PA03147

10.1029/2003GC000539

10.2113/gsjfr.7.1.1

10.2113/gsjfr.15.4.254

10.1029/2004PA001026

Jha P., 2000, Variation of Mg/Ca and Sr/Ca in planktonic and benthic foraminifera from single test chemistry, Eos Trans. AGU, 81

10.4319/lo.1985.30.6.1253

10.1029/2004PA001050

10.1016/S0016-7037(99)00197-0

10.1126/science.289.5485.1719

10.1029/95PA00059

Lohmann G. P., 1993, Effects of secondary calcification and dissolution on the F, Mg, Sr, δ13C and δ18O chemistry of the planktonic foraminifer Globigerinoides sacculifer, Eos Trans. AGU, 74, F367

10.1029/PA005i001p00055

10.1029/2001GC000280

10.1016/S0377-8398(97)00045-5

10.1029/2000PA000604

10.1016/0016-7037(95)00446-7

10.1126/science.157.3796.1554

Ottens J. J.(1992) Planktic foraminifera as indicators of ocean environments in the northeast Atlantic Ph.D. thesis 189 pp. Vrije Univ. Amsterdam.

10.1029/2004GC000760

Peeters F.(2000) The distribution and stable isotope composition of living planktic foraminifera in relation to seasonal changes in the Arabian Sea Ph.D. thesis 184 pp. Vrije Univ. Amsterdam.

10.1029/2005GC000930

10.1016/0009-2541(94)90163-5

10.2307/1484251

10.1007/s002270050350

10.1029/2001PA000749

10.1016/S0016-7037(97)00181-6

10.1029/1999PA000415

10.1016/j.gca.2004.03.013

10.2113/33.3.192

10.1016/S0304-4203(98)00074-7

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American Geophysical Union (AGU)

Tập 6 Số 12

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