δ18O measurements of benthic foraminifera from sediment core MD13-3473

Stable O isotopic ratios were analysed in core MD13-3473, collected from the Tore seamount on the Iberian margin, for δ18O. Bulk subsamples of approximately 30 grams each were wet-weighed, freeze-dried, and reweighed, then ultrasonicated in a water bath, washed, and sieved with tap and distilled water into two grain-size fractions (63-150 μm and >150 μm) at the Sedimentology and Micropaleontology Laboratory of IGME-CSIC, Spain. These fractions were dried on paper filters in an oven at 40 ºC and weighed. Then, foraminifera species – approx. 30 individuals of planktonic foraminifera (Globigerina bulloides, Globorotalia inflata, and Orbulina universa), and approx. 10 individuals of benthic foraminifera (Cibicides wuellerstorfi and Cibicides lobatulus) – were picked from the >150 μm fraction in core MD13-3473. In total, 580 samples of core MD13-3473 were measured on a ThermoFisher 253plus gas isotope ratio mass spectrometer connected to a Kiel IV automated carbonate preparation device at MARUM, University of Bremen, Germany. Data were reported in the usual delta-notation versus V-PDB. The instrument was calibrated against the house standard (ground Solnhofen limestone), which in turn was calibrated against the NBS 19 standard reference material. Over the measurement period, the standard deviation of the house standard (uncorrected data) was +/- 0.08‰ for δ18O. Adittionally, 74 samples of MD13-3473 were performed at the GLPR, University of Cambridge, UK. Samples were analysed using a Micromass Multicarb sample preparation system attached to a VG SIRA Mass Spectrometer. The results were reported with reference to the international standard V-PDB, and the precision was better than +/- 0.08‰ for δ18O. For samples with fewer than 5 individuals, the vials were loaded into a carousel and analysed using a Thermo Kiel device attached to a Thermo MAT253 Mass Spectrometer in dual inlet mode. Due to strong carbonate dissolution at -5,500 m water depth, there are insufficient benthic shells (no-foram no-data, NFND), but planktonic isotope data are available (no-benthics, NB), mainly coincident with cold (sub)stages.