Manifestations of Weathering on Granitic Rocks in the Himalaya and Bundelkhand Regions: A Field-based Observation

Weathering is controlled by factors such as lithology, geological structures, topography climate, tectonics and biota. The present study aims to highlight the manifestations of weathering in two contrasting settings- the Himalaya and Bundelkhand. The study area in the Himalayan region is characterised by active tectonics, steep topography, rugged landscape, cold and semi-arid climate, and sparse vegetation cover. The Bundelkhand region, however, is characterised by stable, undulatory topography, warm and sub-humid climate, and tropical dry deciduous forest. This study mainly presents field observations made during field campaigns to Gemur and Jispa (Lahul Valley) and Rohtang in the Himalaya; Jhansi, Orchha and Lidhora in the Bundelkhand region. Contrasting features about weathering, erosion and sediment generation in the Himalaya and the Bundelkhand were observed. Weathering through physical heterogeneities are common in the Himalaya as water is lost through surface run off due to steep slopes. Presence of large fragmented materials weathered in the Himalaya is relatable to the erosion dominated regime corresponding to the tectonically active steep topography. On the other hand, gently sloping areas in the Bundelkhand, experience lower surface runoff and higher infiltration. Therefore, weathering in the Bundelkhand proceeds to a greater depth contributing to deep weathering profiles characterized by weathering layers such as sap rock, saprolite and soil. Series of events like the exposure of parent granite, development of physical openings along joints and fractures, erosional activities, transport of eroded materials, and chemical weathering due to longer residence time and longer interaction with water would have supported the development of deep weathering profiles in the Bundelkhand region.