This dataset includes chemical and isotopic measurements on shells of the planktic foraminifera Neogloboquadrina pachyderma sinistral collected in April 2006 and April 2007 from two sediment traps moored in the Irminger Sea (IRM-3, 59°14.86'N, 39°39.47'W and IRM-4, 59°14.85'N, 39°39.47'W, both moored at a water depth of about 2750 m). Individual shells were analyzed in situ for their magnesium/calcium (Mg/Ca) ratios by Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS), and for their stable oxygen isotope composition (d18O) by secondary ion mass spectrometry (SIMS). Hydrographic measurements reveal that the water column at sample location is isothermal and isohaline during the month prior to collection. The purpose of this project was to determine potential differences in the Mg/Ca or d18O composition of the lamellar calcite, formed and the upper water column, and the crust calcite, precipitated in deeper waters but at the same temperature and salinity than the lamellar calcite.