ABSTRACT

Samples were taken from a range of sedimentary microenvironments in a surficial mantle on a pedimented hillside. Variations in sedimentary materials presented some difficulties in particle analysis and statistical treatment; these are briefly discussed. However, when these are met, consistent sedimentary properties and environments are evident in the data.

Consistent particle size differences occurred between sediments on talus and pediment slopes; the bed load deposits of an ephemeral stream channel on the lower part of the pediment represented a third sedimentary group on the hillside. Consideration of the particle size differences indicated that fluvial transportation was the dominant factor in the movement of sediment. On talus slopes a very wide range of particle sizes was moved with the <100µ fraction traveling more quickly than other fractions. Immediately on passing from talus to pediment slope segments the >5 mm fraction was depleted, presumably due to incompetence of the fluvial process, but all of the <5 mm fractions moved simultaneously and at the same rate. Within the stream channel on the lower pediment slop , almost all of the <100µ fraction was lost. There is a brief discussion of the mechanics involved in changes within the sediments on the hillside.

This study provides quantitative sedimentary data for pediment slopes. Though it is specifically relevant to the large areas of Triassic sandstone terrain in coastal New South Wales, it also provides some general principles of a sedimentary environment of particular interest to soil workers.