ROLE OF TECTONICS AND CLIMATE ON SEDIMENTATION IN PARTS OF MOHAND AREA, DEHRADUN SUB-BASIN

Abstract

The role of tectonics and climate on sedimentation and their influence on erosion, deformation, grain size distribution, regional uplift, rainfall and litho logy is investigated in Middle and Upper Siwalik sedimentary successions in Parts of Mohand area, Dehradun Sub-basin by field work, grain size analysis and mineralogical analysis. After formation of Dehradun Sub-basin, Middle Siwalik sedimentation, characterized by sandstone-mudstone, sandstone and conglomerate-sandstone-mudstone facies in Mohand area, is dominantly governed by climate, though tectonic activities prevailed in the area. At 5.23 Ma, facies change to conglomerate-sandstone with thin mudstone units which grade into conglomerate facies in upper section. This change in sedimentation pattern in the area is identified with the revival of tectonic activity along Main Boundary Thrust (MBT). Therefore, it is found that deposition in tectonically formed Dehradun sub-basin in parts of Mohand area is most likely result of climate driven fluvial sedimentation, enhanced by tectonic uplift after 5.23 Ma. 09711008/Manas