Collected from the southwestern Gulf of Mexico (GoM), the marine piston Core RC10-265 was used to reconstruct surface water masses, circulation and paleotemperature shifts at orbital scales, over the last ~180 ka. The chronology was constructed based on radiocarbon ages, planktonic foraminifera biostratigraphy and stable oxygen isotopes (δ18O). The ocean surface conditions were reconstructed based on planktonic foraminifera assemblages and the sea surface temperatures (SST) based on Mg/Ca ratios, analysed through LA-ICP-MS. Applying a Q-mode Factor Analysis, two scenarios were characterised through seven species. (1) The subtropical assemblage (Globigerinoides ruber - Globoconella inflata (positive scores) and the Globorotalia menardii group - Pulleniatina obliquiloculata (negative scores)) suggests that during the end of MIS-6, and MIS-4 to MIS-2, the surface waters were colder (~22-25 °C), with less oligotrophic and a more profound mixed layer depth (MLD) relative to interglacials. (2) The tropical assemblage (Globigerinoides ruber - Neogloboquadrina dutertrei - Globorotalia truncatulinoides (positive scores) and Globoconella inflata - Globigerina falconensis (negative scores)) suggests that during the early MIS-6, MIS-5e to 5b and MIS-1, the surface waters were warm (~28-32 °C), oligotrophic, with a shallow MLD like average modern conditions. Despite evidence of early diagenesis by clay coatings, the reconstructed paleotemperatures are consistent with palaeothermometry studied in the Caribbean and northern Gulf. The studied information shows the relevance of the Loop Current (extended vs. contracted mode) and the associated variability in mesoscale eddies as a key control of the GoM paleoecology and paleotemperatures at orbital scales.
