Evidence from both terrestrial and marine environments indicates a cooling of Earth's climate across the Eocene/Oligocene boundary (EOB), with the likely development of continental scale glaciation. The most geographically widespread and persuasive line of evidence for the shift in Earth's climate comes from variation in stable isotopes measured from benthonic foraminiferal carbonate, with a geologically rapid and globally observed > 1 %o increase in δ¹⁸0. Increasing foraminiferal δ¹⁸0 reflects either a cooling in the deep ocean or an increase in the δ ¹⁸0 of seawater, which is related to removal of light oxygen isotopes through continental glaciation. However, despite the global recognition of an increase of > 1.0 %o in benthonic foraminiferal δ¹⁸0 and fundamental change in Earth's climate, the proportion of change, i.e. temperature decrease and/or ice volume development, is poorly constrained. Deconvolution of the foraminiferal  δ¹⁸0 requires and independent proxy to isolate the temperature or ice-volume change, one such proxy is foraminiferal Mg/Ca ratios. Foraminiferal Mg/Ca ratios are a palaeotemperature proxy, however, their application has lead to the observation of bottom-water warming and thus suggesting bipolar glaciation; a scenario inconsistent with a warmer Earth and unsupported by sedimentary evidence. The warming observed in bottom-water Mg/Ca
palaeotemperatures, however, was determined from a deep-ocean site that experienced significant deepening of the carbonate compensation depth (CCD) concomitant with Mg/Ca increase, leading to the hypothesis increasing carbonate ion saturation (Δ[CO₃^2-]) caused enhanced foraminiferal uptake of Mg and thus the observed temperature increase. This study aimed to deconvolute the foraminiferal δ¹⁸0 record using paired benthonic foraminiferal records from a site with minimal change in Δ[CO₃^2-] Paired benthonic and planktonic foraminiferal stable-isotope and Mg/Ca records have been developed from Site 1211,Shatsky Rise; Site 1211 hypothesised to have a much reduced increase in Δ[CO₃^2-]. Foraminiferal geochemical records were supplemented with CCD proxy records, i.e. %calcium carbonate, to allow relative constraint Δ[CO₃^2-] change. Foraminiferal stable-isotope records from Site 1211 exhibit a positive δ¹⁸0 shift and δ¹³C excursion similar to published records, which lag a deepening of CCD by several hundred thousand years. Mg/Ca palaeotemperatures display a high degree of scatter hindering clear identification of EOB change, although an average increase is suggested. The similarity of palaeotemperature evolution from a range of water depths and postulated Δ[CO₃^2-] histories has been interpreted to show that changing Δ[CO₃^2-] has minimal control on benthonic foraminifera Mg/Ca. Estimation of ice-volume suggests a maximum ice-volume equivalent to the last glacial maximum was sustained for several hundred thousand years, with ice volumes reducing to modem day levels during the Early Oligocene.