Clay Mineralogy and Major Element Geochemistry of the Upper Siwalik Sequence of Punjab, Northwestern Himalaya

The X-Ray diffraction and major element analyses of the upper Siwalik rocks of Punjab were carried out to assess the clay mineral composition of the rocks. The clay mineral assemblages comprise illite, smectite, kaolinite, chlorite and mixed layer phyllosilicates. The SiO₂/Al₂O₃ and SiO₂/R₂O₃ molecular ratios of the clays range between 3.86 and 6.60, and 2.94 and 5.37 respectively, suggesting dominance of 2:1 type clay minerals in these rocks. Inheritence and transformation were recognized as the chief processes responsible for genesis of these clay minerals. The clay mineral assemblages suggest their formation under moderate chemical weathering conditions in cool to temperate climate.