Mineralogical Composition of Quaternary Swedish Clays

Abstract

THE general opinion was that the quaternary, that is, glacial and postglacial, clays of Sweden consist mainly of physical weathering products from the ice age. During this age, the moving glaciers attacked the top of the rocks (mainly granite, gneiss and similar materials) and ground them into particles of various size: boulders, stones, gravel, sand, silt and clay. As a result of transportation by ice and glacial rivers and subsequent deposition, the different quaternary formations were formed, the clays being deposited in the sea. It was therefore logical to regard the clay fraction as rock ‘flour’, built up of primary minerals, typical for the original rocks but more or less chemically weathered. The micas were assumed to be responsible for the high plasticity of the clays. However, doubts arose later as to the correctness of the opinion that the clays are built essentially from primary minerals.