How is topography maintained in the western Himalayan and where is plate convergence accommodated?

• Applicant: Privatdozent Dr. Rasmus C. Thiede
• Subject Area: Geology ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429470703

Sediment transport from high-relief and tectonically active areas is often thought to occur with limited transient sediment storage. Lag times and burial duration, such as within the Himalaya wedge, have been argued to be negligible. This implies that the period over which sediments are transported within the catchment to the outlet must be short compared to the time span at which denudation occurs. These conditions are not met where significant sediment storage occurs. For low-elevation and low-relief settings as well as for glaciated environments it has been shown that sediment burial during transport can be significant. In these settings, neither the assumption of the catchment’s erosional-steady state nor that of negligible sediment transport time can be met. Investigations of steady state, transient time, and potential storage of sediments can be constrained by measuring in-situ produced cosmogenic nuclides (CRN), such as 10Be and 26Al. The surface production ratio of 26Al/10Be is ∼6.61 and lower ratios indicate shielding sediments from cosmogenic production often associated with burial. The estimation of burial times by measuring paired 10Be/26Al concentrations has helped to better understand the landscape evolution and rates of previously glaciated areas. Detailed numerical studies and simulations allow us to better estimate detrital CRN concentrations and their downstream evolution. However, the analysis and measurement of burial duration in glaciated catchments from field data in rapidly exhuming orogens are rarely available and their context is not well understood. Our preliminary results and measurements suggest that the burial component in the western Himalayan orogen is not zero. We use two sources of cosmogenic nuclide samples: Modern river-sand samples and fluvial-terrace samples from depth profiles. The study site in the rapidly exhuming Dhauladhar Range allows us to test the impact of glaciation on sediment-lag times: where the northern flanks have been glaciated during the LGM and are still covered by ice. In contrast, the south-facing catchments with similar lithologies have not been glaciated. Our first set of 37 in-situ cosmogenic nuclide samples (10Be and 26Al) and 15 new luminescence data from fluvial terraces and depth profiles several dozen to hundred kilometers downstream of the northern glaciated area show a burial component for some samples. We plan to study erosion rates and sediment lag times from 20 additional and already collected field samples. We also seek to elucidate the impact of burial times on erosion rates.

• DFG Programme: Research Grants
• International Connection: India
• Cooperation Partners: Professor Dr. Saptarshi Dey; Professor Vikrant Jain, Ph.D.
• Co-Investigator: Professor Bodo Bookhagen, Ph.D.