Identification and composition of secondary meniscus calcite in fossil coral and the effect on predicted sea surface temperature

Dalbeck, P., Cusack, M. , Dobson, P. , Allison, N., Fallick, A.E. and Tudhope, A.W. (2011) Identification and composition of secondary meniscus calcite in fossil coral and the effect on predicted sea surface temperature. Chemical Geology, 280(3-4), pp. 314-322. (doi: 10.1016/j.chemgeo.2010.11.018)

Abstract

This study uses electron backscatter diffraction (EBSD) and atomic force microscopy (AFM) to identify secondary calcite in coral skeletons. Secondary calcite appears to have nucleated on the original aragonite dissepiments, producing horizontal structures that mimic the morphology of the original coral aragonite, forming dissepiment-like meniscus structures. The Sr/Ca and δ18O of the pristine aragonite and secondary calcite were analysed by secondary ion mass spectrometry (SIMS). The effect of calcite inclusion on the mean geochemistry of the coral carbonate and subsequent sea surface temperature (SST) calculations were determined for both Sr/Ca and δ18O. Inclusion of as little as 1% secondary calcite within the primary coral aragonite elevates the Sr/Ca-derived SST by 1.2 °C and could markedly offset estimates of past tropical climate. Conversely, inclusion of 10% secondary calcite has little effect on the SST estimated from δ18O (+ 0.6 °C) indicating that this proxy is relatively robust to even large amounts of calcite. The different extents to which the two proxies would be influenced by inadvertent inclusion of such meniscus calcite demonstrate the importance of a multi-proxy approach.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Cusack, Professor Maggie and Dobson, Dr Phil and Fallick, Professor Anthony and Dalbeck, Dr Paul
• Authors: Dalbeck, P., Cusack, M., Dobson, P., Allison, N., Fallick, A.E., and Tudhope, A.W.
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering; College of Science and Engineering > School of Geographical and Earth Sciences; College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Chemical Geology
• ISSN: 0009-2541
• Published Online: 29 November 2010