Geochemistry of surface sediments from the northwestern Gulf of Mexico : implications for provenance and heavy metal contamination

Thirty-five near-surface sediment samples were recovered from the continental shelf and upper slope regions of the north-western (NW) Gulf of Mexico. The geochemical data of the sediments recovered were examined to investigate the weathering intensity, provenance, palaeo-oxygenation condition, and level of heavy metal contamination. The sediments analysed showed a moderate to high intensity of chemical weathering. Major and trace element concentrations indicated a terrigenous origin, closely related to the weathering of rocks rich in aluminosilicates. The results of this study further revealed that major rivers, the Bravo and Soto La Marina, played an important role in delivering sediments to the study area. The concentration of transition trace elements such as Cr, Cu, Ni, and V revealed that the sediments were derived from intermediate rocks such as andesite. The V/Cr, Ni/Co, and Cu/Zn ratios in the sediments were <2, <5, and <1, respectively, suggesting a depositional process occurred under well-oxygenated conditions. Principle Component Analysis (PCA) did not show a significant difference in sediment texture between the continental shelf and slope areas. The enrichment factor (EF) and Geo-accumulation index (lgeo) values were <2 and <1, respectively, suggesting the absence of an anthropogenic input.