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

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. The Quaternary blanket of in lower Narmada valley provides evidences of significant changes in channel kinetics of Paleo domain and present day domain of Narmada related with eustatic & sea-level fluctuation. The Quaternary deposits contained in the western asymmetric trench consist of sediments of various domains viz glacial, fluvio-glacial, fluvial, lacustrine and tidal flats later influenced by incursion of marine transgression and regression on tectonically active platform. It is evidenced by bore hole data and subsurface statistical analysis of sediments, quartz grain morphology of sediments, pale sole geometry and configuration of quaternary deposits in western segments of Narmada rift valley and SONATA TECTONIC ZONE. The Quaternary deposits and river terraces (NT1to NT3) entrapped in tectonic zone with rock cut equivalence and scars are positive significant imprints of euestatic change / climatic changes in the during the sedimentation. The alluvial fan in between Tilakwarda and Rajpipla within the loop of Narmada Chamyal (2002) is mono illustration of morphogenetic process associated with neotectonic event. The disposition of Quaternary blanket, fan deposit and other quaternary land forms are controlled and restricted by SONATA LINEAMENT towards north. The fan deposits as claimed are not persistent in conformity of piedmont sedimentation, further it is devoid of torrential stream net work which firmly rules out to be endogenetic fan deposits. It appears to be older quaternary deposits of Narmada which has moved from basement and has been pasted along SONATA LINEAMENT.