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Rapid exhumation of the eastern Himalayan syntaxis since the late Miocene

Karl A. Lang, Katharine W. Huntington, Russ F. Burmester and Bernard Housen
Rapid exhumation of the eastern Himalayan syntaxis since the late Miocene
Geological Society of America Bulletin (April 2016) 128 (9-10): 1403-1422

Abstract

The Himalayan syntaxes are exceptionally dynamic landscapes characterized by high-relief topography and some of the most rapid and focused crustal exhumation on Earth. In the eastern Himalayan syntaxis, it has been hypothesized that thermo-mechanical feedbacks between erosion by the Yarlung River and growth of a crustal-scale antiform may have locally sustained exhumation rates exceeding 5 km/m.y. during the late Pliocene and Pleistocene. However, young (younger than 3 Ma) cooling histories from syntaxial bedrock samples restrict interpretations of the timing and mechanism initiating feedback development. To extend this record of landscape evolution, we reconstructed an exhumation history since the late Miocene from analysis of detrital minerals in Himalayan foreland basin deposits. We combined magnetostratigraphy, detrital white mica (super 40) Ar/ (super 39) Ar thermochronology, and coupled zircon U-Pb and fission-track geothermochronology from a 4.6-km-thick stratigraphic section proximal to the eastern syntaxis. We used a simple thermal model to interpret the combined provenance and lag-time data set, concluding that rock exhumation rates in the core of the syntaxis increased by a factor of 5-10 in the late Miocene and have sustained extremely rapid exhumation rates (>5 km/m.y.) since 5 Ma. This onset significantly postdates the first appearance of Tibetan detritus in the Himalayan foreland, suggesting that thermo-mechanical feedbacks sustaining rapid exhumation are unrelated to river integration. Instead, such feedbacks may develop where large, antecedent rivers sustain elevated erosion rates across a region of enhanced rock uplift. Compilation of similar data sets across the Himalaya demonstrates extraordinary syntaxial exhumation histories, potentially resulting from peculiar geodynamics at these orogenic margins.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 128
Serial Issue: 9-10
Title: Rapid exhumation of the eastern Himalayan syntaxis since the late Miocene
Affiliation: University of Washington, Department of Earth and Space Sciences, Seattle, WA, United States
Pages: 1403-1422
Published: 20160427
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 174
Accession Number: 2016-054088
Categories: Structural geologyStratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2016103
Illustration Description: illus. incl. geol. sketch maps
N27°00'00" - N30°00'00", E94°00'00" - E96°00'00"
Secondary Affiliation: Western Washington University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201626
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