Textural characteristics of channel bed sediments and heavy minerals of the Cauvery River, Southern India: implications on depositional environments, provenance, tectonics and climate

A systematic study of river sediments on a basin scale might help to understand prevalent environmental, climatic, tectonic, and source rock dynamics. The study attempts documentation of textural properties of the channel bed sediments and heavy mineral distributions from the origin to the confluence of the Cauvery River, within a tropical region of southern India, along with the interpretations on environmental, tectonics, and climatic conditions, as well as affinity with source rock lithologies. Cauvery flows on various lithologies and landscapes that experience multitudes of structural and land-use characteristics and shows the dominance of Peninsular gneiss and Southern granulite. The grain size variations between very coarse sand and fine sand exhibited tripartite sediment size characteristics. The sorting character showed maximum-to-minimum values from the origin to the delta head, and a progression within the moderate-well-sorted nature from the delta head to the confluence. Similarly, the skewness varied from strongly fine to coarse skewed, and most of the samples exhibited platykurtic-to-leptokurtic distributions. An average of 9% of the grains were heavy minerals, with their abundance increasing from a mere 1.9-23.7% towards the downstream, albeit with sporadic very high proportions in some samples in the upper regions of the basin. The heavy mineral roundness also increased from origin to confluence, and its energy-dispersive X-ray analysis (EDAX) mapping revealed variations in elemental composition between the upper, middle, and lower parts of the river channel. Overprinting of natural and anthropogenic interventions might have led to a deviation of sediment characteristics from normal trends. Results from heavy mineral, grain size, textural, and provenance analysis offer valuable data for reconstructing past climates, tracing sediment pathways, and identifying tectonic activities, predicting changes in sediment distribution, and assess the impact of human activities on fluvial environments, making this work significant for global environmental studies and hazard mitigation.