Received Date : 19-Jun-2014 Revised Date : 06-Jan-2015 Accepted Date : 16-Jan-2015 Article type : Original Article Sediment storage and release from Himalayan piggyback basins and implications for downstream river morphology and evolution Alexander L. Densmore1*, Rajiv Sinha2, Swati Sinha2, S.K. Tandon2, and Vikrant Jain3 1 Institute of Hazard, Risk and Resilience and Department of Geography, Durham University, Durham DH1 3LE, UK 2 Department of Earth Sciences, Indian Institute of Technology Kanpur, Kanpur 208016 (UP), India Article 3 Division of Earth Sciences, Indian Institute of Technology Gandhinagar, Ahmedabad 382424, Gujarat, India * Corresponding author: email
[email protected] Abstract Piggyback basins developed at the mountain fronts of collisional orogens can act as important, and transient, sediment stores along major river systems. It is not clear, however, how the storage and release of sediment in piggyback basins affects the sediment flux and evolution of downstream river reaches. Here we investigate the timing and volumes of sediment storage and release in the Dehra Dun, a piggyback basin developed along the Himalayan mountain front in northwestern India. Based on OSL dating, we show evidence for three major phases of aggradation in the dun, bracketed at ~41-33 ka, 34-21 ka, and 23-10 ka, each accompanied by progradation of sediment fans into the dun. Each of these phases was followed by backfilling and (apparently) rapid fan-head incision, leading to abandonment of the depositional unit and a basinward shift of the active depocentre. Excavation of This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may Accepted lead to differences between this version and the Version of Record.