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

Research output: Contribution to journalArticle

20 Scopus citations

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 (US)
Pages (from-to)294-319
Number of pages26
JournalJournal of Geophysical Research: Earth Surface
Volume121
Issue number2
DOIs
StatePublished - Feb 2016

Keywords

  • Bhutan Himalaya
  • cosmogenic radionuclides
  • erosion rates
  • fluvial geomorphology
  • landscape evolution models
  • tectonics

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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