Project Summary
Personnel:
Jeni McDermott
Kip
Hodges (Ph.D.)
Recent research on the Himalayan-Tibetan
orogenic system has focused on the role of monsoon climate in its
development. In one controversial hypothesis, aggressive monsoon
precipitation currently attracts the southward flow of a channel of
middle crust from beneath the Tibetan Plateau to the Himalayan orogenic
front. In this project, an Arizona State University research team, in
collaboration with scientists from the Chinese Academy of Sciences, is
testing the prediction that a recently active detachment occurs along
the southern edge of the Tibetan Plateau at the approximate position of
the Miocene South Tibetan fault system in the Ama Drime Range of
southern Tibet. This transverse range has the overall form of a
metamorphic core complex and is bound on the east and west by normal
fault systems that strike directly into previously mapped strands of
the South Tibetan fault system. The team is mapping critical
intersections among these fault systems that are spectacularly exposed
in this high-elevation region within the Himalayan rain shadow. They
are also using the techniques of structural geology, tectonic
geomorphology, low-temperature thermochronology, and cosmogenic nuclide
dating to establish the late Cenozoic exhumation history of the Ama
Drime massif and compare it with the exhumation history of the South
Tibetan fault footwall east and west of the massif. These results will
be used to evaluate the case for Quaternary channel extrusion and
either falsify it or establish the structural and geomorphic
consequences of deformation related to the upper bounding structure of
the extruding channel.
The concept of channel flow is a new and
controversial idea in the field of tectonics. It suggests a strong
coupling between climate and tectonics. The original version of the
channel flow-extrusion hypothesis envisioned that Early-Middle Miocene
southward extrusion of the channel was accommodated by slip on two
north-dipping structures: the Main Central thrust and the South Tibetan
fault systems. This study explores that idea that monsoon-induced
channel flow continues today. The results of this work will be central
to the ongoing debate over the style of deformation and the degree of
erosion and tectonics coupling in the Himalaya.
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