Climate-driven sediment aggradation and incision since the late Pleistocene in the NW Himalaya, India

New surface-exposure dating of six terrace levels with in-situ cosmogenic 10Be indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4±3.2 ka and 43.0±2.7 ka (1σ). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6±1.2 ka and 15.3±0.9 ka, while terraces sculpted into the upper Pleistocene-Holocene fan (AF2) provide ages of 9.3±0.4 ka (T3), 7.1±0.4 ka (T4), 5.2±0.4 ka (T5) and 3.6±0.2 ka (T6). Together with previously published OSL ages yielding the timing of aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision.