The Calcium Isotope Systematics of the Late Quaternary Dead Sea Basin Lakes

Bradbury, Harold J. and Torfstein, Adi and Wong, Kenneth and Turchyn, Alexandra V. (2018) The Calcium Isotope Systematics of the Late Quaternary Dead Sea Basin Lakes. Geochemistry, Geophysics, Geosystems, 19 (11). pp. 4260-4273. ISSN 1525-2027 DOI https://doi.org/10.1029/2018GC007898

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Official URL: https://doi.org/10.1029/2018GC007898

Abstract

We report the calcium isotopic composition (δ44Ca) of primary aragonite laminae, primary gypsum, and secondary gypsum in sediments deposited from Lake Lisan, the last glacial cycle of the Dead Sea (70–14.5 ka). The δ44Ca of primary gypsum varies between 0.17‰ and 0.71‰ versus bulk silicate earth, with an average of 0.29‰, whereas the aragonite δ44Ca varies between −0.68‰ and −0.16‰ with an average of −0.4‰. The secondary gypsum δ44Ca is close to the calcium isotope composition of the aragonite, averaging at −0.3‰. The aragonite δ44Ca shows small variations temporally in sync with lake level fluctuations, suggesting the aragonite δ44Ca reflects changes in the lake calcium balance, which in turn reflects changes in the local hydrological cycle. The secondary gypsum calcium isotope composition (−0.3‰) overlaps with that of coeval aragonite, suggesting the calcium for secondary gypsum was derived from the aragonite through quantitative, or near‐isotopic equilibrium, recrystallization of the aragonite to gypsum after the lake desiccation and exposure of sediments during the Holocene. A numerical box model is used to explore the effect of changing lake water levels on the calcium isotope composition of the aragonite and gypsum in the lake. The relatively low variability in the δ44Ca over the lake's history suggests that a high‐concentration calcium‐rich brine buffers the calcium cycle.

Item Type: Article
Uncontrolled Keywords: 2018AREP; IA74
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
06 - Part-III Projects
12 - PhD
08 - Green Open Access
Journal or Publication Title: Geochemistry, Geophysics, Geosystems
Volume: 19
Page Range: pp. 4260-4273
Identification Number: https://doi.org/10.1029/2018GC007898
Depositing User: Sarah Humbert
Date Deposited: 17 Jan 2019 12:47
Last Modified: 12 Sep 2019 09:41
URI: http://eprints.esc.cam.ac.uk/id/eprint/4393

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