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Oxygen and carbon isotope ratios (δ18O, δ13C) were measured on 10 to 12 shells of mixed-layer dwelling species Globigerinoides subquadratus from the 250 to 315 μm size fraction from 425 meters composite depth (mcd) until its extinction at 390 mcd. Analyses then continue with Globigerinoides spp. until 350 mcd. In a few samples, where foraminiferal density was low, only 5–7 specimens were analyzed. Analyses were made with a VG Optima mass spectrometer with multi prep device at the British Geological Survey, Keyworth, UK. When picking shells, care was taken to exclude individuals with broken or missing chambers, although preservation of specimens was generally excellent (Fox & Wade, 2013). The external reproducibility of our measurements is ±0.07‰ and ±0.05‰ for δ18O and δ13C respectively. To examine the reproducibility of the results, duplicate measurements were made on 35 samples (5%), which indicate mean reproducibility better than ±0.12‰ and ±0.14‰ for δ18O and δ13C, respectively. Oxygen isotope data are reported as per mil on the VPDB scale (Table S1) calibrated through laboratory and international standards. At ODP Site 1146, δ18O and δ13C were measured by Holbourn et al., (2010) on the mixed-layer dwelling planktonic foraminifera Globigerinoides obliquus or Gs. subquadratus, using 10 to 20 well-preserved tests from the size fraction 250-350 μm. Paired measurements in 51 samples indicate no significant offset in δ18O and δ13C between Gs. obliquus and Gs. subquadratus. Detailed methods are outlined in Holbourn et al., (2010). δ13C data are not used here. For Mg/Ca analyses, we selected 25–35 specimens of Trilobatus quadrilobatus (140–550 μg) from the 250 to 315 μm size fraction; the same size fraction as used for δ18O analysis, to minimize size-related intraspecific elemental variation (Elderfield et al., 2002). Analyses were performed on 86 samples over the studied interval. The tests were gently crushed and subsequently cleaned according to the protocol of Martin & Lea (2002) to remove clays. Cleaning included a reductive step with hydrazine to remove Mn-(hydr)oxides. Samples were measured on an ICP-AES device at Christian-Albrechts-Universität zu Kiel, Germany. Analytical precision is ~1.1%, based on measurements of an internal laboratory standard. Replicate Mg/Ca measurements revealed an average standard deviation of ~0.08 mmol/mol. Adequate cleaning is indicated by very low Fe/Ca, Al/Ca and Mn/Ca ratios.
The dataset worksheet contains a list of core samples taken during IODP Exp 350 and foraminifera-based data for selected samples. The work was started with the aim of reconstructing palaeoproductivity changes (namely surface-to-deep carbon isotope gradients and U/Ca measurements) over tephra layers in order to test the ‘ash fertilisation hypothesis’. However, the work has been temporarily halted given the on-board volcanologists ongoing concerns that the ash layers in the selected cores have been reworked and therefore are not primary. Because of the induration and silicification of the core samples at quite shallow depths in the core, the other aim of the project (to reconstruct palaeoceanographic changes from 16-0 Ma) was not possible. The spreadsheet contains a full list of samples and a list of samples that have been examined and analysed. The data worksheet contains the no. of Globigerinoides ruber (with weight), Oridorsalis umbonatus, Uvigerina spp. and Cibicidoides spp. specimens for specific samples. For selected samples, stable oxygen and carbon isotopes are given and a graph of the carbon isotopes vs depth in core is presented.
This dataset includes the (stable) oxygen and carbon isotopic composition of benthic foraminifer tests (n= 686) and the (radiogenic) isotopic composition of the terrigenous fraction of marine sediments (n= 75), all sampled from Eocene to Oligocene-aged sediments recovered at Ocean Drilling Program (ODP) Site 689 and 690 (Maud Rise, Southern Ocean)
Benthic stable isotope (carbon and oxygen) data from IODP Site U1445. Generated by Yasmin Bokhari-Friberg, supervisied by Kate Littler and Pallavi Anand.
Carbon and oxygen isotopic composition of benthic foraminifera spanning the early and middle Eocene succession recovered from borehole 16/28-Sb01. For description of this sedimentary sequence see Haughton et al. 2005. Petroleum Geology: North-West Europe and Global Perspectives, Proceedings of the 6th Petroleum Geology Conference, 1077–1094.