Carbon isotope offsets between benthic foraminifer species of the genus Cibicides (Cibicidoides) in the glacial sub-Antarctic Atlantic
Type | Article | ||||||||||||
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Date | 2016-12 | ||||||||||||
Language | English | ||||||||||||
Author(s) | Gottschalk Julia1, 2, 3, Riveiros Natalia Vazquez1, 4, Waelbroeck Claire4, Skinner Luke C.1, Michel Elisabeth4, Duplessy Jean-Claude4, Hodell David1, Mackensen Andreas5 | ||||||||||||
Affiliation(s) | 1 : Univ Cambridge, Dept Earth Sci, Godwin Lab Palaeoclimate Res, Cambridge, England. 2 : Univ Bern, Inst Geol Sci, Bern, Switzerland. 3 : Univ Bern, Oeschger Ctr Climate Change Res, Bern, Switzerland. 4 : Univ Paris Saclay, CNRS CEA UVSQ, Lab Sci Climat & Environm, LSCE IPSL, Gif Sur Yvette, France. 5 : Alfred Wegener Inst Polar & Marine Res, Bremerhaven, Germany. |
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Source | Paleoceanography (0883-8305) (Amer Geophysical Union), 2016-12 , Vol. 31 , N. 12 , P. 1583-1602 | ||||||||||||
DOI | 10.1002/2016PA003029 | ||||||||||||
WOS© Times Cited | 35 | ||||||||||||
Abstract | Epibenthic foraminifer delta C-13 measurements are valuable for reconstructing past bottom water dissolved inorganic carbon d13C (delta C-13(DIC)), which are used to infer global ocean circulation patterns. Epibenthic delta C-13, however, may also reflect the influence of C-13-depleted phytodetritus, microhabitat changes, and/or variations in carbonate ion concentrations. Here we compare the delta C-13 of two benthic foraminifer species, Cibicides kullenbergi and Cibicides wuellerstorfi, and their morphotypes, in three sub-Antarctic Atlantic sediment cores over several glacial-interglacial transitions. These species are commonly assumed to be epibenthic, living above or directly below the sediment-water interface. While this might be consistent with the small delta C-13 offset that we observe between these species during late Pleistocene interglacial periods (Delta delta C-13=-0.19 +/- 0.31%, N=63), it is more difficult to reconcile with the significant delta C-13 offset that is found between these species during glacial periods (Delta delta C-13=-0.76 +/- 0.44%, N=44). We test possible scenarios by analyzing Uvigerina spp delta C-13 and benthic foraminifer abundances: (1) C. kullenbergi delta C-13 is biased to light values either due to microhabitat shifts or phytodetritus effects and (2) C. wuellerstorfi delta C-13 is biased to heavy values, relative to long-term average conditions, for instance by recording the sporadic occurrence of less depleted deepwater delta C-13(DIC). Neither of these scenarios can be ruled out unequivocally. However, our findings emphasize that supposedly epibenthic foraminifer delta C-13 in the sub-Antarctic Atlantic may reflect several factors rather than being solely a function of bottom water delta C-13(DIC). This could have a direct bearing on the interpretation of extremely light South Atlantic delta C-13 values at the Last Glacial Maximum. |
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