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1 Department of Physical Geography, Stockholm University, S-10691 Stockholm, Sweden
2 Department of Quaternary Geology, Tornavägen 13, S-22363 Lund, Sweden
3 Department of Physical Geography, Earth Science Centre, Göteborg University, S-41381 Göteborg, Sweden
Saprolite remnants from different palaeosurfaces in southern Sweden have been analysed by XRD and SEM analyses. They represent two clearly different types. The first is a clay- and silt-rich saprolite with a kaolinite-dominated clay mineral association representative of mature saprolites and with chemically altered quartz grains. This saprolite type is associated with sub-Cambrian, sub-Jurassic and sub-Cretaceous denudation surfaces. The second type is gravelly and in a youthful stage of alteration with mainly vermiculitic clay minerals in the fine fractions. Microtextures developed on quartz grains indicate a mainly mechanical breakdown. Compared to overlying till beds this saprolite is in a more advanced stage of chemical alteration. It is not associated with any specific denudation surface. Its characteristics and thickness indicate a Plio-Pleistocene age.
The saprolites represent deep weathering of the bedrock surface at different times. The weathering resulted in thin kaolinitc saprolites during the Late Proterozoic, thick kaolinitic saprolites from the latest Triassic through the Jurassic and Cretaceous, and medium thick immature saprolites from the Pliocene and onwards. The depth of the deep weathering has been decisive for the shape of the present relief and thus etch processes have been of fundamental importance in shaping the relief, even in a formerly glaciated area.
