WEATHERING OF SOILS DEVELOPED IN EOLIAN MATERIAL OVERLYING GLACIAL DEPOSITS IN EASTERN NEPAL

We used the ratio between well crystallized Fe-oxides and total Fe (Fe d-o/Fe-t) and weathering indices to study eight soils developed in eol ian material overlying glacial deposits in Eastern Nepal with regard t o intensity of soil development. Together with selected radiocarbon an alyses and information on soil morphology, we tried to interpret the d ata in terms of relative and absolute age distinctions of the deposits ,The results suggest no clear relationship between weathering intensit y and morphostratigraphical development and the age of the geomorphic surface. We assume that this is attributable to different orographic c onditions for sedimentation of the eolian dust at the study sites and to different degrees of pre-weathering of the eolian covers. However, we can show that formation of organic matter and soil development, in general, started around 2500-2800 years B.P. in the eolian cover of mo st soils studied. This indicates deposition of the bulk eolian sedimen ts around 2800 years B.P. and earlier. Two soils have greater relative ages in the subsoil with respect to the weathering indices. In these soils, parts of the eolian sediments are of late glacial origin or eve n older. Distinct variation of soil development and weathering indices within a vertical distance of 200 m provided evidence of marginal ice .