Alluvial sediments

Deposits encountered beneath the site are unconsolidated, stratified, laterally discontinuous, Quaternary age alluvial sediments consisting predominantly of fine-... 

Soils derived from marine alluvial sediments tend to be dominated by mont-morillonitic 2 1 clays whereas those from riverine sediments have vermiculitic 2 1 clays with mixtures of 1 1 clays and metal oxides, the sediment being developed under more strongly weathered conditions. 

Reductive dissolution of Fe oxyhydroxides holding sorbed As appears to explain the very large concentrations of As in water from wells drilled into alluvial sediments of the Brahmaputra and Ganges Rivers in Bangladesh and West Begal (Nickson et al 1998, 2000). Dissolved As has accumulated from the reduction of As-rich Fe oxyhydroxides formed upstream of the contaminated areas by weathering of As-rich base metal sulfides. The reduction is driven by sedimentary organic matter in the deposits. Release of As from oxidation of pyrite in shallow wells contributes little to the water contamination because any As(IV) released would be re-sorbed on Fe oxides formed in pyrite oxidation. 

Erosional transport of iron stones may have led to a mechanical concentration of these spherical bodies in alluvial sediments or in marine depressions and caused their breakdown Trummererze). These deposits may be recemented by Fe oxides, predominantly goethite, formed in situ in the interstices. 

Seaman, J.C., Physicochemical and Mineralogical Controls on Colloid Generation and Transport within the Highly Weathered Alluvial Sediments of the Upper Coastal Plain, Ph.D. thesis, University of Georgia, 1994. 

Breit G. N., Cozzarelli 1. M., Johnson R. D., and Norvell J. S. (1996) Interaction of alluvial sediments and a leachate plume from a landfill near Norman Oklahoma. Geol. Soc. Am. Abstr. Prog. 28(7), A258. 

Vietnam lOOO recognised >1 million 1-3100 Quaternary alluvial sediment... 

Kamber, B.S., Greig, A., and Collerson, K.D., 2005a. A new estimate for the composition of weathered, young, upper continental crust from alluvial sediments, Queensland, Australia. Geochim. Cosmochim. Acta, 69, 1041-58. 

Atkinson, C.D. (1986) Tectonic control on alluvial sedimentation as revealed by an ancient catena of the Capella Formation (Eocene) of Northern Spain. In Paleosols. Their Recognition and Interpretation (Wright, V.P.), pp. 139-179. Princeton University Press, Princeton, SfJ. 

River and Amazon River basins, the Isthmus of Panama, and the Island of Taiwan and for rock types representative of bedrock in these basins. Symbols , samples from rivers that drain mostly mountain belts developed on felsic continental crust T, samples from rivers that drain mostly island-arc mountain belts developed on mafic oceanic crust +, samples from rivers that originate in continental mountain belts, but that drain large areas of era ton x, rivers that drain alluvial and non-alluvial sedimentary rocks in foreland and intracratonic basins D, rivers that drain only alluvial sediments in foreland and intracratonic basins A, rivers that drain hilly to mountainous shield on felsic crust V, rivers that drain hilly to mountainous shield on mafic crust or deeply eroded island arc O, rivers that drain peneplaned shield. The dashed oval represents the range of analyses for common igneous rocks the dashed lines that extend away from the igneous rock field represent the composition field for common sedimentary rocks. Adapted from Stallard (1988) with the permission of Kluwer Academic Publishers. 

Rock-alluvial sediment-aquatic moss relations... 

This chapter is devoted to situations in which trace elements are found as natural contaminants, in concentrations which considerably exceed natural background values discussed above. Such situations are typical for areas rich in metal ore deposits. Their potential environmental impact depends on their location within a catchment. If they are situated in the upper part, a large area and many different environmental compartments will be affected (Fig. 13). Local contamination of soils, plants, sediments and water occurs almost in every case, the degree to which a whole catchment is affected by contaminated waters and glacial or alluvial sediments depends on the size of the ore deposit, the slope and the climate of a given area. 

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