Late Quaternary drainage reorganization of the Sutlej River system at the Himalaya mountain-foreland transition

The relative influence of tectonics and climate on the long-term evolution of Himalayan river systems remains debated. We investigated the Sutlej River, a major snow-fed tributary of the Indus River at its exit from the Himalayan Front. Using an integrated dataset of geomorphic mapping, subsurface stratigraphy, and Optically Stimulated Luminescence geochronology, we identify a previously misidentified uplifted surface (the Ropar Surface), abandoned paleovalleys and fluvial terraces. Our results show that the Sutlej River on long-timescales occupied multiple flow strands, including a west and a south-flowing strand. This drainage configuration was forced by tectonic uplift along a transverse structural zone linking segments of the Main Frontal Thrust. Notably, this drainage reorganization occurred through river bifurcation and avulsion between >60 and 15 ka—significantly predating the mid-Holocene collapse of the Harappan Civilization. These findings indicate that abandonment of the paleo-Sutlej was a prolonged tectonically controlled process rather than a short-lived climate-driven event, thereby querying existing models of Himalayan river network reorganization in the mountain to foreland transition zone that emphasised climate driven processes. Sutlej River occupied a west and a south-flowing strand with the drainage reorganization occurring through river bifurcation and avulsion between <60 and 15 ka through a tectonically controlled process, as shown using optically stimulated luminescence geochronology and sedimentary, structural and geomorphic analysis.