Tectonic evolution of the Himalayan thrust belt in western Nepal: Implications for channel flow models

Delores M. Robinson, Peter G Decelles, Peter Copeland

Research output: Contribution to journalArticle

190 Citations (Scopus)

Abstract

We present a new geologic map of western Nepal and three balanced regional cross sections in the Himalayan thrust belt. The minimum shortening between the South Tibetan detachment and the Main Frontal thrust is 485-743 km and suggests that total Himalayan shortening may exceed 900 km. All rocks involved in the thrust belt are of upper crustal affinity, implying that a comparable length of Indian lower crust and mantle lithosphere was subducted beneath Tibet. Major structural features are the Subhimalayan thrust system, Lesser Himalayan imbricate zone, Dadeldhura thrust sheet, Lesser Himalayan duplex, Ramgarh thrust sheet, Main Central thrust sheet, and a north-dipping normal-sense shear zone, possibly related to the South Tibetan detachment. These structures are continuous along the entire Nepalese portion of the Himalayan thrust belt. New 40Ar/39Ar ages from the Ramgarh thrust zone, Greater Himalayan rocks, and the lower part of the Tethyan sequence support a kinematic model in which major thrust systems in Nepal propagated southward from early Miocene time onward. The geometry and kinematic history of the thrust belt in western Nepal are not compatible with recent models for southward ductile extrusion of Greater Himalayan rocks in a mid-crustal channel. Instead, the thrust belt in western Nepal behaved like a typical forward propagating thrust system, involving unmetamorphosed, brittlely deformed rocks in its frontal part and ductilely deformed, higher-grade metamorphic rocks in its hinterland region. Although our results do not support published versions of the channel flow model, they provide additional geological and geochronological data that will assist future attempts to develop geodynamic models for the Himalayan-Tibetan orogenic system.

Original languageEnglish (US)
Pages (from-to)865-885
Number of pages21
JournalBulletin of the Geological Society of America
Volume118
Issue number7-8
DOIs
StatePublished - Jul 2006

Fingerprint

channel flow
tectonic evolution
thrust
rock
kinematics
duplex
lower mantle
extrusion
metamorphic rock
lower crust
geodynamics
shear zone
lithosphere
cross section
Miocene

Keywords

  • Geochronology
  • Himalaya
  • Nepal
  • Regional mapping
  • Thrust belt

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Tectonic evolution of the Himalayan thrust belt in western Nepal : Implications for channel flow models. / Robinson, Delores M.; Decelles, Peter G; Copeland, Peter.

In: Bulletin of the Geological Society of America, Vol. 118, No. 7-8, 07.2006, p. 865-885.

Research output: Contribution to journalArticle

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