Late quaternary evolution of lower Kaveri and adjoining river basins in Tamil Nadu, Southern India: A combined approach using remote sensing and optical dating of fluvial records

Abstract

A drainage system responds swiftly on a regional or local scale to reveal the signature of neotectonic activities or any changes in climate. A few works in southern India have shown tectonic movements in terms of river and drainage response. The Gingee and the Vellar river basins (adjacent to the lower Kaveri Basin in Tamil Nadu) have been chosen for the present study. The morphometric analysis of the Gingee and the Vellar river basins and OSL dating of the sediments collected from the rivers' palaeochannels were carried out to achieve the proposed objectives. The study helped understand the role of climatic and tectonic elements in the evolution of the basins. The analysis indicates a regional scale-down warping shown by the southward tilting of the Gingee drainage systems and northward tilting of the Vellar drainage systems, strong asymmetry in some reaches (VRSB-II; III) and pronounced elongation of certain tributaries (GRSB-III; IV and VRSB-V). The Gingee River migrated clockwise (towards south) to its current position since the mid-Holocene period ∼3.5 ka, whereas the Vellar River shifted in an anti-clockwise (towards north) direction since 1.28 ka. This was the time when the study area experienced high precipitations. Also, these rivers are very coarse-grained bed load rivers found very shallow and thus, during heavy precipitation and discharges, prone to fill the channel quickly and shift the course. Luminescence ages of the paleochannels also suggest that both the rivers are migrating towards the central part with the same rate of ∼4.5 km/ka.