The stratified slope deposits of Tierra del Fogo (Argentina) as an annalogue for similar pleistocene deposits in Galicia (NW Spain)

Abstract

This paper focuses on slope dynamics in schist/slate materials in cold humid environments. It characterises the sedimentological features and controls involved in the for-mation of stratified slope deposits in two areas with similar topographical, lithological and cli-matic characteristics. In both areas, the slopes have dips >30º and the dominant rock types are schists and slates. In the case of Tierra del Fuego, the sedimentary deposits studied are modern; those in Galicia are Pleistocene in age. The slope processes operating in Tierra del Fuego, gen-erating modern stratified slope sedimentary deposits, throw light upon the interpretation of sim-ilar ancient sediments studied in Galicia. This comparative study reveals the fundamental role played by snow and freeze-thaw cycles in the creation of stratified slope deposits. Firstly, snow cover has a direct effect on the slope, compacting sediments, keeping ground temperature stable during winter, or moving clasts as they slip down the slope or act as a slide ramp. Indirectly, as the snow melts, it creates surface run-off and mud or gravel slides. Secondly, the activity gen-erated by numerous freeze-thaw cycles results in the vertical mobility of clasts. However, the continuous loading of sediments on the slope hinders the formation of coarse-grained pavement. Thirdly, the rock type and slope steepness play an important role in the creation of stratified slope deposits.