Spatial and vertical distributions of elements in sediments of the Colorado River delta and Upper Gulf of California |
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| Authors: | Evgueni N Shumilin Jos D Carriquiry Víctor F Camacho-Ibar Dmitry Sapozhnikov Stepan Kalmykov Alberto Snchez Sergio Aguíiga-García Yuri A Sapozhnikov |
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| Institution: | Evgueni N. Shumilin, José D. Carriquiry, Víctor F. Camacho-Ibar, Dmitry Sapozhnikov, Stepan Kalmykov, Alberto Sánchez, Sergio Aguíñiga-García,Yuri A. Sapozhnikov |
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| Abstract: | The abundance of major components (Fe, Ca, K, and organic carbon) and trace elements was analyzed in surface sediments and core samples from the Colorado River delta (CRD) and the Upper Gulf of California (UGC) using instrumental neutron activation analysis.The spatial distribution patterns of the elements studied are consistent with the model of sedimentary dynamics proposed for this area Mar. Geol. 158 (1999) 125]: intense tidal resuspension of sediments in the delta with subsequent transport of suspended particulate matter in a southerly direction, followed by sedimentation of fine-grained material in a depocenter near the southwestern margin of the UGC. Concentrations of most of the elements are higher in the surface sediments of this depocenter. The gradual mixing of terrigenous and marine biogenic materials, normally expected for the estuarine sediments, was not detected in the CRD–UGC system because of homogenization of the sediments by tides and wind.Vertical profiles of element contents in samples of the sediment core collected in the depocenter area revealed (i) almost no anthropogenic contamination of the area by environmentally important trace elements such as Cr, Co, Sb, and As; (ii) a twofold decrease of Fe, Sc, Cr, and Co in upper core sediments; and (iii) the enrichment of the sediments at 60–62 cm depth in the core, in calcium carbonate, Ca, Sr, and the Eun/Smn shale-normalized ratio along with a depletion in this layer of Fe, Sc, Cr, Co, light rare-earth elements (REEs), and some other elements of terrigenous origin, presumably caused by the dilution of fluvial terrigenous material by biogenic carbonates, which were probably introduced at this level in the sediments by the action of a strong episodic winter storm, followed by the advective transport of shell fragments from the coastal clam banks or as a result of strong planktonic bloom. |
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| Keywords: | Major elements Trace elements Sediments Colorado River delta Upper Gulf of California |
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