Pre-deccan trap topography in central India and crustal warping in relation to Narmada rift structure and volcanic activity

A study of the geology of the Dhar Forest, the Pachmarhi plateau and the area around Bari in Central India has led to the conclusion that the pre-Deccan Trap topography which was completely covered by the lava flows and is being exposed with spectacular clarity by the process of exhumation, had much the same relief as the present land surface. The geomorphological studies of the Vindhyan and Pachmarhi plateau suggest a characteristic rise and increasing separation of different planation surfaces towards the edges of the Narmada rift valley and indicate upwarping movements in several distinct stages. In considering the possible causes of the upwarping movements special significance is attached to epeirogenic movements probably representing the various stages of Himalayan orogeny. The succession of events in Peninsular India suggests that these upwarping movements were caused by rising magma which led to the fissure eruptions of the Deccan Trap lavas; which presumably took place during a period of tension in the upwarped area. The problem of the origin of the Narmada rift structure is discussed and evidence is adduced to show that the final sinking of the crest of the upwarped area has caused the out-pouring of the Deccan Trap lavas. The individual lava flow with their typical field and microscopic characteristics maintaining their interflow differences have been traced over long distances. These studies have led to the correlation of the flows between the measured sections. Further, as regards the cause of the higher elevation of the base of the basal flow in Katangi (1950), the possibility of a post-Deccan Trap upwarping movement is briefly considered.