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Project Summary
Personnel:
Byron Adams
Kip
Hodges (Ph.D.)
Arjun
Heimsath (Ph.D.)
The physiography of the Bhutan
Himalaya is
remarkably different from the better studied Nepal Himalaya. In central
Nepal, the Himalaya is characterized by a mountainous but relatively
low-relief Lesser Himalaya “foothills” some 80km wide that is bound on
the south by the MFT and MBT thrusts. To the north, there is an abrupt
“physiographic transition” to the very rugged and high-relief High
Himalaya. The transition occurs near the tectono-stratigraphic position
of the MCT. From this topographic break, elevations climb rapidly to
the
high peaks and crest of the range. By contrast, in Bhutan, there is no
physiographic Lesser Himalaya – rugged, high-relief topography starts
in the immediate hanging wall of the MFT/MBT thrusts. But the climb to
high elevations is interrupted first by a laterally (E-W) discontinuous
“bench” of a low relief landscape perched above deep river gorges at
~3000m, separated by the KT (out of sequence thrust) from a second,
higher, glaciated bench at ~4500m. The prominent lower bench preserves
what are interpreted as klippe of Tethyan meta-sedimentary rocks in the
hanging wall of the STDS. How did this odd topography evolve? What does
it tell us about the space-time evolution of Bhutan tectonics? We are
using a combination of structural mapping, DEM analysis,
low-temperature thermochronology (40/39 Ar/Ar and Apatite (U-Th)/He),
and cosmogenic radionuclides to unravel the answers to these questions.
Our efforts are complementary to neotectonic studies underway by Jose
Hurtado at UTEP, AFT and structural work by Djordje Grujic and
colleagues, and ongoing structural mapping by Nadine McQuarrie.
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