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Unravelling contamination signals in biogenic silica oxygen isotope composition: the role of major and trace element geochemistry

Brewer, TS; Leng, MJ; Mackay, AW; Lamb, AL; Tyler, JJ; Marsh, NG; (2008) Unravelling contamination signals in biogenic silica oxygen isotope composition: the role of major and trace element geochemistry. Journal of Quaternary Science , 23 (4) 321 - 330. 10.1002/jqs.1171. Green open access

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Abstract

The oxygen isotope composition of diatom silica (delta O-18(diatom)) provides valuable information for palaeoclimate studies where carbonate proxies are either rare or absent in many lakes and ocean sediments. Unfortunately, mineral and rock fragments found alongside diatoms in most sediments can be problematic as the method used will liberate oxygen from all components within the sediment, producing both high-frequency noise and low-frequency excursions that can resemble climate signals. Removal of mineral contamination to date has largely relied upon the combination of chemical leaching and physical separation techniques (e.g. sieving, density). This combination can be inefficient and often significant proportions of contaminants are present in the 'purified' diatom sample. Using electron optical imaging and whole-rock geochemistry on previously 'purified' diatom samples, a mass balance approach has been developed whereby the types and proportions of residual contaminants are identified. By integrating this information with measured oxygen isotope ratios of the contaminants, it is then possible to remove contamination effects from the delta O-18(diatom) record. Contamination effects relating to carbonates, tephra and silt are modelled for cores from Lake Tilo (Ethiopia) and Lake Baikal (Siberia). In both lakes the new modelled delta O-18(diatom) curves show less high-frequency noise, thus enabling better resolution of low-frequency climate signals. (c) Natural Environment Research Council (NERC) copyright 2008. Reproduced with the permission of NERC. Published by John Wiley & Sons Ltd.

Type: Article
Title: Unravelling contamination signals in biogenic silica oxygen isotope composition: the role of major and trace element geochemistry
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/jqs.1171
Publisher version: http://dx.doi.org/10.1002/jqs.1171
Language: English
Additional information: This is the pre-peer reviewed version of the following article: Brewer, TS and Leng, MJ and Mackay, AW and Lamb, AL and Tyler, JJ and Marsh, NG (2008) Unravelling contamination signals in biogenic silica oxygen isotope composition: the role of major and trace element geochemistry. Journal of Quaternary Science , 23 (4) 321 - 330, which has been published in final form at http://dx.doi.org/10.1002/jqs.1171
Keywords: biogenic silica, contamination, major elements, trace elements, oxygen isotopes, Lake Tilo, Lake Baikal, DIATOM SILICA, LAKE, SEPARATION, SEDIMENTS, RECORDS
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/140883
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