CGRG Bibliography of Canadian Geomorphology
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Author : Chaumont, D.; and Roy, A.G.
Date : 1994
Title : Mineralogical tracing of the origin of sediments at river channel confluences
Publication : Geographie physique et Quaternaire
Issue : 48(2):
Page(s) : 195-206
Abstract
Mineralogical tracing of the origin of sediments at river channel confluences. Sedimentary dynamics of river channel confluences may be studied through the use of natural tracers. The information supplied by tracers is of crucial interest to understand the mixing processes of bea material from the confluent channels and of potential zones of accumulation of contaminated sediments. We examined the bed material of a confluence where the mineralogy of the sediments of the tributary watershed differs from that of the main channel. The potential of two tracers (K feldspars and micas) and the heavy mineral concentrations is assessed. Due to its shape and density, K feldspars is the most efficient tracer to reveal the mixing between the sediment loads coming from the upstream channels. The spatial distribution of the tracer suggests a very rapid mixing of the loads : at a distance equivalent to 2.1 channel width, mixing is nearly completed. Micas and heavy mineral concentrations are less reliable indicators of the sedimentary dynamics. The technique was also applied at a confluence along.the St. Lawrence River. In this case, clear mineralogical differences between the sediments of the watersheds are absent. The spatial pattern of heavy mineral concentrations is controlled by the main morphological feature of the confluence, that is, the avalanche face at the edge of a tributary mouth bar prograding within the St. Lawrence. Low heavy mineral concentrations are located on the avalanche face itself while higher concentrationms are found at the foot and top of the face This pattern reflects variations in sorting regime rather than origin of particles.
Bibliography of Canadian Geomorphology