Comparison of methods of size analysis for sands of the Amazon-Solimões Rivers, Brazil and Peru

Cumulative frequency curves and bivariate textural plots of sands collected and sieved from the medium-grained (1.94), well-sorted (0.46) Amazon-Solimões Rivers are not environmentally sensitive. Only 13 % of the samples plot as fluvial using cumulative frequency curves, and only one of the nine bivariate plots successfully identified the fluvial environment. Thus, identification of depositional environments of sands by size distribution based only on sieving is not a reliable technique—even when the results of diagenesis are not considered.