Scanning electron microscopy of feldspar and volcanic glass weathering and neoformation of clay minerals in a quaternary paleosol sequence, Mount Kenya, East Africa

Abstract

Volcanic glass, feldspar, magnetite, quartz, and trace amounts of other minerals (e.g. nepheline, biotite, amphibole) are the detrital components of the 63–250 μm sand fractions of the samples studied. Halloysite/metahalloysite, showing fibrous, tubular, platey and nodular shapes, and gibbsite (essentially nodular) occur as important weathering products. They formed essentially through weathering of volcanic glass reflecting the high precipitation and low evapotranspiration expected in a tropical bamboo forest as well as great amounts of time. Feldspar weathering occurs mainly as dissolution etching. The distribution of gibbsite and halloysite/metahalloysite are interpreted with regard to the paleoclimatic conditions under which the paleosols developed during pre-Teleki and Teleki/Liki interglacial periods.