In situ development of high-elevation, low-relief landscapes via duplex deformation in the Eastern Himalayan hinterland, Bhutan

BA Adams, KX Whipple, KV Hodges, AM Heimsath

Research output: Contribution to journalArticle (Academic Journal)peer-review

49 Citations (Scopus)
620 Downloads (Pure)

Abstract

Prior studies have proposed tectonic and climatic mechanisms to explain surface uplift throughout the Bhutan Himalaya. While the resulting enigmatic, low-relief landscapes, elevated above deeply incised canyons, are a popular setting to test ideas of interacting tectonic and climatic forces, when and why these landscapes formed is still debated. We test the idea that these landscapes were created by a spatially variable and recent increase in rock uplift rate associated with the formation of structural duplexes at depth. We utilize a new suite of erosion rates derived from detrital cosmogenic nuclide techniques, geomorphic observations, and a landscape evolution model to demonstrate the viability of this hypothesis. Low-relief landscapes in Bhutan are eroding at a rate of ~70 m/Ma, while basins from surrounding steep landscapes yield erosion rates of ~950 m/Ma, demonstrating that this portion of the range is in a transient period of increasing relief. Applying insights from our erosion rates, we explore the influence of an active duplex on overlying topography using a landscape evolution model by imposing a high rock uplift rate in the middle of a mountain range. Our simulations show that low-relief landscapes with thick alluvial fills form upstream of convex knickpoints as rivers adjust to higher uplift rates downstream, a pattern consistent with geologic, geomorphic, and thermochronometric data from Bhutan. With our new erosion rates, reconstructed paleo-river profiles, and landscape evolution simulations, we show that the low-relief landscapes were formed in situ as they were uplifted ~800 m in the past ~0.8–1 Ma.
Original languageEnglish
Pages (from-to)294-319
JournalJournal of Geophysical Research: Earth Surface
Volume121
Issue number2
Early online date5 Jan 2016
DOIs
Publication statusPublished - 14 Mar 2016

Keywords

  • cosmogenic radionuclides
  • landscape evolution models
  • erosion rates
  • fluvial geomorphology
  • Bhutan himalaya
  • Tectonics

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