Abstract
Brown Hill Soil and five terrace soil types (Shallow Red Brown Terrace Soil, Deep Red Brown Terrace Soil, Brown Mottled Terrace Soil, Shallow Grey Terrace Soil and Deep Grey Terrace Soil) were investigated to characterize their clay mineralogical compositions as a part of the systematic studies of General Soil Types of Bangladesh.
The clay of Brown Hill Soil was rich in mica and hydroxy-Al interlayered vermiculite with relatively low contents of smectite, vermiculite, kaolinite and chlorite (less than 10%). In contrast to hill soil, all five terrace soil clays examined were differentiated by the trace or very low presence of smectite and vermiculite, which were also different from the clays of previously studied calcareous and noncalcareous soils. The main characteristics of terrace soils were the presence of kaolinite/smectite along with the higher presence of mica and kaolinite. The interstratification of other types were very complex and could not be easily identified by means of XRD only. Mica seems to be weathered to kaolinite/smectite to kaolinite through some intermediates of hydroxy-Al interlayering and other irregular interstratifications.
