Quaternary Tectonics & Sedimentation in Narmada Rift Valley, With Special Reference to Garudeshwar and Bharuch Section Gujarat State India

Manuscript History: The Narmada river originates at Amarkantak at an elevation of about 1057 m above m.s.l.it descends across the rugged and mountainous tract through deep and steep gorges in straight sinuous to meandering pattern over a distance of 1280 km across the middle of the Indian sub-continent to join the Gulf of Cambay in Arabian sea in Gujarat state. It negotiates in sinuous to meandering pattern, at places it has conspicuous straight segment controlled by E-W lineament. It is bound by Vindhyachal in the north and Satpura range to the south; the area in between these two upland linear trench is found to be ideal area for study of Quaternary sedimentation as witnessed by the presence of multicyclic sequence of Quaternary terraces in Jabalpur- Baruche section. These terraces represent the former levels of valley floors formed by cumulative erosional and depositional activities of the river system. In the area of study in lower Narmada between Grudeshwar and Baruche is occupied by thick Quaternary deposits of about 800 m which represent various domain of sedimentation. Based on sedimentlogical characters, depositional environments, erosional processes and their relation with depositional activity revealed that it comprised of four domains of sediments viz glacial, fluvio-glacial fluvial and tidal flats. The lower most unit (Boulder bed) is, of glacial origin, followed by the boulder conglomerate of glacio- fluvial and subsequently by fluvial of paleo- domain of Narmada and tidal flats. The top four formations Ankleshwar, Tilakwarda & Bharuch and Aliabat are designated as (NTo-NT3). Boulder conglomerate is assigned an independent formational status based on distinct lithology and fossil assemblage. The sequence of Quaternary events and the history of sedimentation of Narmada indicate that the upper 180 of the Narmada alluvium was deposited in two distinct aggradations episode with a distinct, well defined break in sedimentation in rift system. The dissection of the quaternary blanket resulted in to two terraces (NT3-NT2), after break in sedimentation. The sediments of this aggradations episode constitute three lithostratigraphy units viz Ankhleshwar, Tilakwarda and Bharuch formation. The sediments of the alluvial phase are underlain by a boulder bed of glacio- fluvial origin. Thus, the fossiliferous boulder conglomerate, the basal unit of alluvium marks a disconformity between the lower glacial-boulder layer and upper fluvial sediments. The fossiliferous basal boulder conglomerate is being of middle Pleistocene age.