Carbon isotope data from coccolith calcite and coccolith-associated polysaccharides from sediments.

The data presented here are from: McClelland et al., 2024, Stable carbon isotope ratios of pristine carbohydrates preserved within nannofossil calcite. Geochim. Cosmochim. Acta, VOL, PP, DOI.

The data include carbon isotope values of coccolith calcite and coccolith-associated polysaccharides from sediment samples, from ODP Site 1123 (Expedition 181), which is located on Chatham rise, east of New Zealand in the southernmost Pacific, from the period approx. 190ka to 105ka. All carbon isotope values are reported as delta values, relative to the VPDB calcite standard. U^k₃₇′ and TEX₈₆ values from contemporaneous sediments are generated and interpreted using established techniques.

In the isotopes file, data are provided for two different size fractions of coccolith, which were separated into two near monospecific fractions, 2-3um and 8-12um.

Carbon isotopic compositions of the calcite were measured using a VG Isogas Prism II mass spectrometer with an on-line VG Isocarb common acid bath preparation system in the Department of Earth Sciences, University of Oxford, UK. Samples were dosed with acetone and dried at 60^oC for at least 30 minutes. In the instrument they were reacted with purified phosphoric acid at 90^oC. Calibration to PDB standard was via the international standard NBS-19 using the Oxford in-house (NOCZ) Carrara marble standard.

The purified CAP samples were measured on a Thermo Delta Plus Advantage stable isotope mass spectrometer, with Spooling Wire Microcombustion (SWiM) interface at Harvard University. The SWiM interface allows measurement of ng scale samples. A detailed description of the equipment and protocol is given in Sessions, et al. (2005; doi:10.1021/ac051251z). Organic carbon measurements made in Harvard were calibrated for consistency with measurements made in Oxford, using an apple pectin standard in a dilution series. For the isotopic analysis of CAP samples, a mass-balance correction was applied to account for the size and isotopic composition of the background. (See McClelland et al., 2024 for details of calculation and description of blanks).