Clay Mineral Distribution of Dharmsala Sediments in Northwest India

Clay mineral distribution in Dharmsala sediments over a region extending from Palampur to Mandi and Sarkaghat in northwest India was studied using standard X-ray diffractometer techniques. Lower Dharmsala sediments show uniform clay mineral distribution over the region and contain partially degraded illite and chlorite with minor amounts of kaolinite. Upper Dharmsala sediments seem to vary in clay mineralogy from one part of the region to another. They are characterized by the presence of illite, chlorite and vermiculite at Palampur-Baijnath. The clay minerals are mainly degraded illite, vermiculite and expandable mixed layers at Jogindernagar-Mandi and Rewalsar areas. Upper Dharmsala clays at Sarkaghat consist of montmorillonite, expandable mixed layers and minor amounts of highly degraded chlorite. Differences in clay mineral distribution over the region is explained here by variations in the characters of source rocks, weathering intensity, sediment transport, drainage and topography. The present findings are compatible with information obtained from paleocurrent investigalions.