Tal land soils of Bihar. II: Mineral assemblage

Genetically, the clay minerals in the Tal land soils representing Rasaibigha, Khanpur and Aurahi series developed on alluvium derived from rocks like granite-gneiss, mica-schist, quartzite, etc. seem to be geogenic and also pedogenic. The formation of smectite appears to be under basic environment, impeded drainage and waterlogged condition for a limited period. Mica is found to be derived from the micaceous parent material and feldspar. A major portion of kaolinite has been inherited from the parent materials. Some of the orthoclase feldspars appear to have weathered to kaolinite.