This dataset lists the results of stable oxygen and carbon isotope measurements (in ‰ VPDB) from International Ocean Discovery Program (IODP) Site U1403 off Newfoundland (~40°N, 51°W; 4944 m water depth, Expedition 342, NW Atlantic Ocean). Stable isotope analysis were carried out on specimens of N. truempyi. Stable isotopes were analyzed using a ThermoFinnigan MAT253Plus gas source mass spectrometer equipped with a Thermo Fisher Scientific KIEL IV carbonate device. Values are reported relative to the VPDB through the analysis of an in-house standard (Solnhofen limestone) calibrated to IAEA-603.