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A study of the particle size and mineralogic characteristics of bottom and suspended sediment from Kwikluak Pass of the Yukon River revealed that iron oxide and organic material act as binding agents. The binding agents appear to be equally responsible for the presence of aggregate particles which constitute a minimum of 14% of the sediment weight. The mean and standard deviation of the sediment in the aggregate state was x = 8.2 phi and ^sgr = 2.0 phi as suspended material and x = 5.4 phi and ^sgr = 1.5 phi as bottom material. These distributions are coarser and less variable than those measured after removal of iron oxide and organic binding agents: x = 8.6 phi and ^sgr = 2.3 phi as suspended sediment and x = 6.4 phi and = 2.6 phi as the bottom sediment. The proportion f aggregates as a function of grain size increases from 10% at 4.0 phi to 50% at 12.0 phi. The size distribution of particles composing an aggregate grain is distinctly bimodal indicating the binding of fine particles to larger grains. However, aggregates also may be composed entirely of fine grains. There was no evidence of mineralogic selectivity within these aggregates. This supports a probabilistic mechanism of formation, whereby the mineralogy of the aggregates is controlled by the frequency of the mineral type in the discrete state. The similarity of aggregates in the bottom and suspended sediments supports the hypothesis that the aggregates were formed in the soil horizon within the Yukon River basin.
The presence of aggregate particles within river sediments can significantly alter conclusions concerning grain-size parameters and resulting mineral-transport characteristics unless proper analytical procedures are utilized.
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