Paleoenvironmental reconstruction and metal assessment in the Prodelta of a gulf in southern Caribbean through last millennium.

Estuarine sediments are major repositories for terrigenous materials and can record the changes of regional human activities as well as natural processes. This study seeks to evaluate correlations among the sedimentary content of silicon (Si), titanium (Ti), aluminum (Al), iron (Fe), manganese (Mn), magnesium (Mg), arsenic (As), cobalt (Co), chromium (Cr), nickel (Ni), lead (Pb), vanadium (V), and mercury (Hg) with changes in precipitation patterns, land use in tributary basins, chemical weathering, erosion, oxygenation, redox potential or oceanographic dynamics in a Caribbean gulf during the late Holocene. The geochemical analysis was performed on a sedimentary profile 210 cm long and 6.35 cm in diameter recovered in the northeastern sector of the prodelta in the Gulf of Urabá. The geochemistry used Si, Al, and Ti as normalizing elements. The temporal variation of the 13 metals in the profile extended ca. 1000 calendar years, based on C results. The sediments were mainly muddy with few interbedded sandy facies. The metal content ranged 45.12-50.48 % for Si; 0.73-0.78 % for Ti; 16.40-17.11 % for Al; 9.72-10.17 % for Fe; 0.20-0.30 % for Mn; 3.81-4.02 % for Mg; 15.00-23.00 mg/kg for As; 20.00-24.00 mg/kg for Co; 142.00-154.00 mg/kg for Cr; 54.00-64.00 mg/kg for Ni; 7.00-13.00 mg/kg for Pb; 229.00-252.00 mg/kg for V; and 70.15-113.55 μg/kg for Hg. The enrichment factor (EF) and geo-accumulation index (Igeo) revealed moderate but significant enrichment of polymetals, except for Pb. The Si, Ti, Al, Mn, Mg, Co, Ni, and Hg correlated with the granulometry and the organic matter, expressed as loss on ignition (LOI). The correlation between Al and Fe was high and significant. The granulometry of the sedimentary profile recovered in the Prodelta showed an increasing long-term trend, indicating a slight increase in the transport energy towards present. Decreased content of Al, Si, and Ti atop core indicated reduction in contemporary centennial precipitation rate. The increased transport energy might have not originated from river flow, but rather from positive feedback of sea level rise, increased surface temperature and sedimentation of tributary channels.