Late Quaternary bedrock incision in the Narmada River at Dardi Falls

Abstract

Fluvial incision in bedrock is common in many rivers i the Indian Peninsula. We investigated a site in the gorg of the Narmada river at Dardi Falls that display geomorphic evidence of intense bedrock erosion. We report here a terrestrial cosmogenic radionuclide date from an eroded rock surface in Peninsular India. Terrestrial cosmogenic radionuclide dating of the rock surface adjacent to the inner gorge indicated that the minimum age of the gorge is 40 ka. We suggest that the present gorge has developed in two phases, separated by a period of large-scale aggradation that filled the gorge with alluvium. Gorge formation is most likely associated with tectonic activity in the Son Narmada-Tapi lineament zone. Erosion at this scale also requires large palaeodischarges with high unit stream power. This study illustrates the powers of combining newly developing geomorphic, DEM and geochronological methods to elucidate the dynamics and nature of landscape evolution.