Exploring the potential of clumped isotope thermometry on coccolith-rich sediments as a sea surface temperature proxy

DOI

Understanding past changes in sea surface temperatures (SSTs) is crucial; however, existing proxies for reconstructing past SSTs are hindered by unknown ancient seawater composition (foraminiferal Mg/Ca and d18O), or reflect subsurface temperatures (TEX86) or have a limited applicable temperature range (Uk'37). We examine clumped isotope (D47) thermometry to fossil coccolith-rich material as an SST proxy, as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant. The D47-derived temperatures from <63, <20, 63 µm fraction removes most non-mixed layer components; however, the D47-derived temperatures display an unexpected slight decreasing trend with decreasing size fraction. This unexpected trend could partly arise because larger coccoliths (5-12 µm) are removed during the size fraction separation process. The c1 and <63 µm c2 D47-derived temperatures are comparable to concurrent Uk'37 SSTs. The <20, <10 and 2-5 µm c2 D47-derived temperatures are consistently cooler than expected. The D47-Uk'37 temperature offset is probably caused by abiotic/diagenetic calcite present in the c2 2-5 µm fraction (~53% by area), which potentially precipitated at bottom water temperatures of ~6 {degree sign}C . Our results indicate that clumped isotopes on coccolith-rich sediment fractions have potential as an SST proxy, particularly in tropical regions, providing that careful investigation of the appropriate size fraction for the region and timescale is undertaken.

Supplement to: Drury, Anna Joy; John, Cédric M (2016): Exploring the potential of clumped isotope thermometry on coccolith-rich sediments as a sea surface temperature proxy. Geochemistry, Geophysics, Geosystems, 17(10), 4092-4104

Identifier
DOI https://doi.org/10.1594/PANGAEA.865019
Related Identifier https://doi.org/10.1002/2016GC006459
Related Identifier https://store.pangaea.de/Publications/Drury_John_2016/Figure_2a-3d.zip
Related Identifier https://store.pangaea.de/Publications/Drury_John_2016/Supplementary_Table_S3.pdf
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.865019
Provenance
Creator Drury, Anna Joy ORCID logo; John, Cédric M ORCID logo
Publisher PANGAEA
Publication Year 2016
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Language English
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 2 datasets
Discipline Earth System Research
Spatial Coverage (-117.970 LON, 2.508 LAT)