Fertile Farmlands in Cauvery Delta: Evolution through LGM

The Cauvery delta encompasses legendary farmlands for at least over the last ~2300 years BP that had supported the growth of the famous Chola and Pandya kingdoms. The chrono-stratigraphic study from six sediment cores taken from the Cauvery basin indicates Holocene evolution of the present delta in response to the past sea-level changes. It is found that at the time of lower sea level during the Last Glacial Maximum, older sediments from the present delta plain, were removed and the extent of removal in different parts was observed to have been controlled by the variation in shelf morphology. Subsequent sealevel rise during the deglaciation after the Last Glacial Maximum, led to filling of the incised valleys with the younger sediments of the Holocene. Nilgiri- Kodaikanal-Palani-Biligirirangan hills granulites and Brahmagiri regions constitute the upper catchment. Geochemistry of the sediments indicates presence of plagioclase and dominance of 2:1 clay, suggesting weathering-limited provenance of southern granulitetype rocks, the source of which is perhaps the high relief and tectonically more active Nilgiri-Kodaikanal- Palani-Biligirirangan hills mountain region rather than the Brahmagiri region. A continuous deposition since the beginning of the Holocene has resulted in the formation of fertile farmlands in the Cauvery delta region.