Variations in fluvial gravel imbrication

Abstract

Few investigators have made use of gravel imbrication as an indicator of paleocurrent flow direction. It has been shown that in fluvial pebbles the short axis generally dips downstream, or, the plane of maximum projection, described by the intermediate and long axes, dips upstream. Recent investigations in the fluvial deposits of the Santiam River, northwestern Oregon, has shown that directions of imbrication in a particular gravel bar deviate notably from the general channel orientation, and exhibit considerable variation within the gravel bar. Similar variation has been noted in the imbrication directions in other stream deposits of western Oregon. The variations are attributable to changing conditions in the stream in relation to climate.