Distribution and genesis of tills in central South Norway

Abstract

The morphogenesis of tills below the culmination zones of the Weichselian inland ice has been studied in an upland area with a relief of 1500 m. The thickness of the tills varies considerably, depending principally on geomorphology, ice-movement directions, and glaciofluvial drainage during the last deglaciation period. The thickest tills, found in valleys, accumulated in three ways. Glaciofluvial/lacustrine sediments of presumed Mid-Weichselian age have been discovered beneath the tills at more then 10 localities. The overlying tills are correlated with different phases of ice movement reconstructed on the basis of detailed studies of striae. The till stratigraphy of one locality, Stenseng, is described in detail. Based upon combined analyses of texture, structure, and fabric, four different basal tills are recognized, each corresponding to a particular ice direction. A characteristic boulder layer represents a change in the direction of glacial movement. Boulder layers in till are thought to be essential for the development of earth pillars.