On a sorting-versus-grain-size (phi) plot, fluvial (river) deposits are typically moderately-to-poorly sorted and coarser, while aeolian (wind-blown) deposits are characteristically very well sorted, reflecting the more uniform, size-selective transport by wind.
Point A (poor sorting, coarser/negative phi) is consistent with a fluvial deposit, since river transport produces a wider range of grain sizes and only moderate...
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