The effect of sediment type on the shape and stratification of some modern fluvial deposits

Abstract

The percent silt-clay in sediment appears to be indicative of some physical properties of that sediment. Silt-clay is defined as that material passing the 200 mesh sieve or smaller than 0.074 mm. The shape of a stream channel cross section is found to be inversely related to the weighted mean percent silt-clay in channel banks and floor. The shape of paleochannels and their included channel-fill deposits may be similarly related to sediment type. Observations along actively aggrading streams suggest that the stratification of channel fill deposits may also be related to the percent silt-clay in these deposits. Stratification planes may be concave in channel fills composed of predominant silt-clay, whereas, they may be horizontal where the silt-clay content of the alluvium is small, and even convex in those channel fills with negligible silt-clay.