Geochemical characteristics of surface sediments from the marine-coastal region north and south of the paria peninsula, Venezuela

Abstract

[eng] Environmental characteristics of the Northern Platform of the Paria Peninsula (PP) and the Paria Gulf (GP)are caused by water flow and sediment of the Orinoco river, the ocean currents that move along the eastern coast of SouthAmerica transporting a large quantity of sediment from the Amazon river, the tidal action, waves and the current regime ofthe continental shelf including coastal upwelling induced by trade winds. All these factors affect biogeochemical processes insediments that have different sources and conditions of transport, sedimentation and preservation. Accordingly, it raises asfundamental objective of this paper to describe some environmental parameters of bottom water and some geochemicalcharacteristics such as texture, mineralogy and organic carbon content (Corg), sulfur (S), total phosphorus (TP) and totalnitrogen (TN) from surface sediments of the study region. The texture was performed according to the modified pipettemethod and mineralogy by X-ray diffraction. The Corg was determined by dry combustion technique after acid attack, S byEA-ICP, while the PT and NT by the method of VALDERRAMA (1981). Iso-concentration maps for the distribution of theseparameters on the continental shelf north of the Peninsula (PP) and Gulf of Paria (GP) were prepared. In general, thesediment has a texture or grain size of sandy-loam and sandy-silty type, mineralogical composition consists of quartz,muscovite, kaolinite, calcite for some PP stations and zircon for GP, making mineral distinctive environments sedimentationand sediment source. The average concentrations were Corg 1.53%, S 0.23%, PT 0.04% and NT 0.03%. Ocean currents andcoastal upwelling patterns may influence the spatial distribution of these variables. There is an effect on the production,distribution and sedimentation of OM in the study area, caused by the discharge of the Orinoco and Amazon River through theflow of Guyana, which directly impacts surface waters and sediments of the Paria Gulf. These results allow distinguishing twoenvironments of sedimentation with suspended matter inputs from different sources. The PP surface sediments with typicalcharacteristics of coastal marine sediment with input from autochthonous organic matter, resulting from primary productivitythat are influenced by the phenomenon of coastal upwelling. There is greater variability in the GP, indicating different sourcesof sediment that result in a mixture, confirming the contributions of the Orinoco and Amazon River. The GP provides marineenvironments, transitional and continental. In the other hand, the PP only provides marine environments that lead todifferentiation in composition, texture, mineralogy and distribution between the two regions. Sea currents and the source ofthe sediment may be the most important factors controlling the spatial distribution of sediments and the elements consideredin the region.