Mg/Ca ratios of two Globigerinoides ruber (white) morphotypes: Implications for reconstructing past tropical/ subtropical surface water conditions
| Type | Article | ||||||||
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| Date | 2005-11-15 | ||||||||
| Language | English | ||||||||
| Author(s) | Steinke S1, Chiu Hy2, Yu Ps3, Shen Cc2, Lowemark L2, Mii Hs4, Chen Mt3 | ||||||||
| Affiliation(s) | 1 : Univ Bremen, RCOM, DFG Forschungszentrum Ozeanrander, D-28334 Bremen, Germany. 2 : Natl Taiwan Univ, Dept Geosci, Taipei 106, Taiwan. 3 : Natl Taiwan Ocean Univ, Inst Appl Geosci, Chilung 20224, Taiwan. 4 : Natl Taiwan Normal Univ, Dept Earth Sci, Taipei 116, Taiwan. |
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| Source | Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2005-11-15 , Vol. 6 , N. 11 , P. 1-12 | ||||||||
| DOI | 10.1029/2005GC000926 | ||||||||
| WOS© Times Cited | 99 | ||||||||
| Keyword(s) | planktonic foraminifera, Globigerinoides ruber (white), morphotypes, Mg/Ca, stable isotopes, sea surface temperature | ||||||||
| Abstract | Tests of the planktonic foraminifer Globigerinoides ruber ( white; d'Orbigny) have become a standard tool for reconstructing past oceanic environments. Paleoceanographers often utilize the Mg/Ca ratios of the foraminiferal tests for reconstructing low-latitude ocean glacial-interglacial changes in sea surface temperatures (SST). We report herein a comparison of Mg/Ca measurements on sample pairs (n = 20) of two G. ruber (white) morphotypes (G. ruber sensu stricto (s. s.) and G. ruber sensu lato ( s. l.)) from surface and downcore samples of the western Pacific and Indian Oceans. G. ruber s. s. refers to specimens with spherical chambers sitting symmetrically over previous sutures with a wide, high arched aperture, whereas G. ruber s. l. refers to a more compact test with a diminutive final chamber and small aperture. The G. ruber s. s. specimens generally show significantly higher Mg/Ca ratios compared to G. ruber s. l. Our results from the Mg/Ca ratio analysis suggest that G. ruber s. l. specimens precipitated their shells in slightly colder surface waters than G. ruber s. s. specimens. This conclusion is supported by the differences in delta O-18 and delta C-13 values between the two morphotypes. Although it is still unclear if these two morphotypes represent phenotypic variants or sibling species, our findings seem to support the hypothesis of depth and/or seasonal allopatry within a single morphospecies. | ||||||||
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