In this new study I am examining the degree sediment storage in the Himalaya plays in controlling the flux of sediment to the Indian Ocean. I particularly focus on those regions north of the Greater Himalaya in order to look at a region with drier, less monsoonal climate than those worked on by previous studies, especially along the Sutlej Valley. A provisional sediment budget for the entire river basin suggests that almost the entire delivery of sediment to the Indian Ocean since the Last Glacial Maximum could be accounted for simply by the re-working of sediment from fluvial terraces, and that 80% of this flux comes from mountain terraces with just 20% from the lowland flood plains. However, presently the budget is very poorly constrained and cannot be considered completely reliable largely because both the volumes of terraces and their ages are only known in outline.

LSU graduate and University of Queensland researcher Tara Jonell is now working with me to constrain the degree of sediment buffering in the Zanskar Basin in the Indian Himalaya. We are trying to estimate the volumes of sediment stored in the terraces, as well as the volumes that have been eroded. This involves field mapping of the terraces together with their analysis using satellite and aerial imagery. Sampling of the terraces in the summer of 2012 now allows us to place a chronology on the formation of the terraces and the timing of their re-working through the use of OSL dating methods.

The upper figure on the right shows the method that we use to estimate how much material has been removed from along the valleys. The Zanskar Basin is considered an appropriate region of study because it covers a large area, approximately 10,000 km², but is reasonably accessible for investigation/for field work. A diversity of bedrock sources within the basin will allow us to reconstruct how erosion patterns have changed as the monsoon has waxed and waned in the recent geological past, as they are preserved in the detrital mineral record of the modern and paleo-river sediments.

Sediment storage in the Himalayas