ALBERT

Description: Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding theimpacts of climate change on landscape evolution and depositional systems. In the Sub-Himalaya, late Pleistoceneto Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacityon timescale of 103to 105years, most likely related to past climatic fluctuations. To evaluate the climatic controlon sediment supply and transport capacity, we analyze remnant alluvial fans and terraces in the Kangra Basin ofthe northwestern Sub-Himalaya.Based on field observations and OSL and CRN-dating, we recognized two sedimentary cycles with ma-jor sediment aggradation and subsequent re-incision phases. The large one developed over the entire last glacialperiod with∼200 m high alluvial fan (AF1) and the second one during the latest Pleistocene/Holocene with∼50m alluvial fan (AF2) and its re-incision . Surface-exposure dating of six terrace levels with in-situ cosmogenic nu-clides (10Be) indicates the onset of channel abandonment and ensuing incision phases. Two terrace surfaces fromthe highest level (T1) sculpted into the oldest-preserved AF1 dates back to 48.9±4.1 ka and 42.1±2.7 ka (2σerror). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 16.8±2 ka and 14.1±0.9 ka, whileterraces sculpted into the late Pleistocene- Holocene fan (AF2) provide ages of 8.4±0.8 ka, 6.6±0.7 ka, 4.9±0.4 ka and 3.1±0.3 ka. Together with previously-published ages on the timing of aggradation, we find a correla-tion between variations in sediment transport with oxygen-isotope records from regions affected by Indian SummerMonsoon. During stronger monsoon phases and post-LGM glacial retreat manifested by increased sediment de-livery (moraines and hillslope-derived) to the trunk streams, causing aggradation in the basin; whereas, weakenedmonsoon phases characterized by reduced sediment-delivery from the hillslope or moraines resulted into inci-sion of the transiently-stored sediments. Sediment cycles in the Kangra Basin are largely synchronous with thosedocumented from other NW Himalayan valleys.