Late Pleistocene-Holocene variability in the southern Gulf of Mexico surface waters based on planktonic foraminiferal assemblages

- Planktonic assemblages show sub to millennial scale variations in the S Gulf of Mexico.
- G. ruber represents the average conditions in the Gulf on a glacial-interglacial scale.
- Assemblages related to salinity decreases are linked to warm and humid periods.
- Assemblages related to salinity increases are linked to cold or dry periods.
- Changes in ITCZ, tropical Atlantic & paleo-ENSO act as main climate controls.

Planktonic foraminiferal assemblages are used as proxies of surface ocean variations, as documented in five marine sediment cores from the Bay of Campeche (BoC), Gulf of Mexico (GoM), spanning the last 34,000 cal yrs BP. This paper seeks to better understand the regional history by studying cores taken in the poorly studied Southern GoM. Multivariate factor analyses calculated five assemblages at millennial to glacial-interglacial scales. During the last glacial period, including the Last Glacial Maximum (LGM), the assemblage contained G. inflata, and T. sacculifer which suggests the presence of colder and less saline waters than younger times; although during the LGM, saltier waters and weaker ocean circulation may have occurred. During the deglaciation, the deep-dweller G. crassaformis suggest a reorganization of deep-thermocline waters and the establishment of transitional conditions, where mild to warm waters entered the Gulf. During the early to mid-Holocene, the tolerant tropical species G. ruber pink suggests salinity variations and warmer conditions than the previous interval. During the late-Holocene, only warm species comprise the assemblage, where the group G. menardii and G. truncatulinoindes suggest warm and stratified conditions, with an oxygen decrease in the thermocline, and rather high salinity levels linked to reduced moisture exported from the Pacific due to the progressively more influential ENSO-like conditions. Prominently, all the assemblages include the species G. ruber white chromotype, suggesting that the environmental conditions are continuously favorable to this abundant species. These scenarios show agreement to previous reconstructions in northern and western GoM, the Caribbean, as well as paleoclimate on land, which are mostly regulated by the position of the ITCZ, changes in the expansion of the Atlantic Warm Pool, the tropical circulation, and teleconnections with nearby regions.