Foraminiferal assemblages, C-14 ages, and compositional variations in two sediment cores in the western Gulf of Mexico

Foraminifera species distribution, C-14 ages, and geochemistry data of sediment cores GM33 and GM34 recovered from the southwestern Gulf of Mexico were investigated to infer the age, sedimentation rate, provenance, heavy metal contamination, and depositional environment. Core GM34 (490 cm interval) reached an age of 34,346 +/- 280 cal Yrs. BP and the average sedimentation rate was calculated as 0.014 cm/yr. The weathering indices like Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA) revealed a moderate intensity of weathering in the source area. The trace elemental ratios and rare earth element (REE) patterns indicated the derivation of sediments from intermediate rocks like andesite. The trace element based bivariate (La/Sc and Co/Th) and ternary (Ni-Th-V) diagrams revealed that the sediments were derived mostly from andesite located along the Gulf of Mexico coastal areas. The enrichment factor and geo-accumulation index suggested the absence of heavy metal contamination in sediment cores. The redox proxy trace elemental ratios like V/Cr, Ni/Co, Cu/Zn, and (Cu + Mo)Zn suggested an oxic depositional condition. The benthic foraminiferal assemblages, Mn and Mo concentrations indicated that the late Pleistocene abyssal waters in the Gulf of Mexico were more oxygenated than the present. An absence of significant compositional variations between the core sediments revealed that the depositional condition in the southwestern Gulf of Mexico was probably similar for the last 34,346 cal Yrs. BP.