The dataset contains information about oxygen and carbon isotope ratios of four species of planktonic foraminifera. Foraminifera were selected from the first 9 cm of a marine sediment core collected in Soledad Basin, in the continental platform of the Baja California Peninsula. All analyses were performed at the Stable Isotopes Laboratory at the Instituto de Investigaciones Oceanológicas-UABC using a GasBench II coupled to an IRMS Delta V Advantage. Multicore was collected in 2018 aboard the Roger Revelle. The timeframe this data covers is around the last 30 years. Samples were analyzed to estimate the apparent calcification depth of the planktonic foraminifera and to reconstruct the thermal structure of the upper water column over the last millennium.