Conditions of formation of stratified screes, Slims River Valley, Yukon Territory: a possible analogue with some deposits from Belgium

Abstract

Stratified scree is forming today on 34–45° north-facing slopes in gullies in the Kluane Lake area of the St. Elias Range of the Yukon Territory. Low winter snowfall leaves the slopes snow-free in the dry spring weather, so that dry grain flows are extremely active. The coarsest material moves to the bottom of the slope, while the finer material is left behind. Summer rains mobilize the matrix-rich material upslope and cause it to flow down and cover the clast-supported deposits from the dry grain flows. The matrix-supported debris flow material dries and hardens, stabilizing the clast-supported material. This occurs in a region of discontinuous permafrost, but permafrost is not involved in the processes. A remarkably similar Pleistocene deposit occurs at Noiseux in Belgium. Detailed examination of the deposits from the Yukon and Noiseux shows that they have essentially similar characteristics, suggesting that the main deposit at Noiseux formed in the same way from frost-shattered Famenne siltstone with small quantities of loess. The deposit remaining today represents the sediments at the toe of this scree. Thus climatic conditions at Noiseux during part of the Late Pleistocene were similar to those found today at Kluane Lake. Copyright © 2000 John Wiley & Sons, Ltd.