Stable Isotope (oxygen and carbon) offsets between Benthic Foraminifera and ambient bottom water at surface sediments from the Equatorial and Southeast Pacific

The stable isotopes (raw data) obtained for the different species of benthic foraminifera (BF) from surface sediment samples in the Southeast Pacific (SEP) are stored by PANGAEA Data Publisher for Earth & Environmental Science under the name SIBFS-ESEP: Stable Isotope in Benthic Foraminifera of Surface Marine Sediments from the Equatorial and Southeast Pacific data base (SIBFS-ESEP_v1).

In this Zenodo database channel, you will find metadata of the samples (cruise, site name event, location, gear/type used, year of collection), the raw stable isotope of benthic foraminifera (full details in PANGAEA channel), bottom water δ¹⁸O equilibrium with the calcite (estimated by BOT), bottom water δ¹³C dissolved inorganic carbon (estimated by BOT and in-situ), computation of stable isotope offsets between the BF and bottom water, BF information (e.g, size of sieve used during the picking, operator of analysis) and flags "Notes.DRM". 

To quantify the magnitude of any oxygen and carbon isotopic disequilibria or offset (i.e., the difference between measured BF stable isotope data and ambient bottom water data), we calculate the difference between δ¹⁸O of BF and δ¹⁸O equilibrium with the calcite (eqcal) [δ¹⁸OBF-δ¹⁸Oeqcal], and δ¹³C of BF and δ¹³C dissolved inorganic carbon (DIC) [δ¹³CBF-δ¹³CDIC].  

For the calculations of δ18Oeqcal, we use bottom water temperature and δ¹⁸Osw (sea water) data of Reyes-Macaya, D et al. (2022): Isotopic characterization of water masses in the Southeast Pacific region: Paleoceanography implications ranging from 1.2−12.3 °C and -0.24−0.32 ‰ respectively. We use δ¹⁸Oeqcal-temperature linear (developed for the epifaunal BF genera Lobatula/Cibicidoides/Cibicides/Planulina) and quadratic (designed for the shallow infaunal BF Uvigerina) equations by Marchitto et al., (2014) across seawater temperatures ranging between -0.6 and 19 ℃. 

Information about bottom water estimations of δ¹⁸Oeqcal and δ¹³CDIC can be found BOT, a code to calculate bottom water hydrological parameters: a case in the Southeast and East Equatorial Pacific. Where available, in-situ δ¹³CDIC measurements were prioritized overestimated values to compute the isotopic disequilibria or offset. 

We identified samples that did not meet our quality control criteria based on factors such as Rose Bengal staining, radiocarbon age, and δ¹⁸O values. Samples with extreme δ¹⁸O values (outliers compared to δ¹⁸Oeqcal) were flagged with the word "DNPQC," which means the sample did not pass quality control.