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AGU: Tectonics

 

Keywords

  • Shillong plateau
  • apatite thermochronology
  • climate-tectonics couplings

Index Terms

  • Tectonophysics: Tectonics and climatic interactions
  • Geochronology: Thermochronology
  • Tectonophysics: Tectonics and landscape evolution
  • Geographic Location: Asia
Abstract
Cited By (6)
 

Abstract

Exhumation and uplift of the Shillong plateau and its influence on the eastern Himalayas: New constraints from apatite and zircon (U-Th-[Sm])/He and apatite fission track analyses

Subrata Biswas

Department of Geological Sciences, Jahangirnagar University, Savar, Bangladesh

Isabelle Coutand

UMR-CNRS 8110, Processus et Bilans des Domaines Sédimentaires, Université des Sciences et Technologies de Lille 1, Villeneuve d'Ascq, France

Djordje Grujic

Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, Canada

Christian Hager

Department of Geology, University of Kansas, Lawrence, Kansas, USA

Daniel Stöckli

Department of Geology, University of Kansas, Lawrence, Kansas, USA

Bernhard Grasemann

Center for Earth Sciences, University of Vienna, Vienna, Austria

The Shillong plateau is the only raised topography in the foreland of the Himalayas. Located on the trajectory of the Indian Summer Monsoon (ISM), the plateau perturbs the regional distribution of precipitation. As such, the Shillong plateau-eastern Himalaya-ISM is a unique system to quantify the couplings between climate, tectonics, and erosion. A change in long-term erosion rates along-strike of the Bhutan Himalaya was recently attributed to a climatic modulation due to the uplift of the Shillong plateau. To test this interpretation, it is essential to constrain the timing and rate at which the plateau was uplifted and the amount of partitioning of the India-Asia convergence into the plateau. We used apatite and zircon (U-Th-[Sm])/He and apatite fission track analyses to unravel the thermal histories of 13 basement samples collected along a N-S transect across the central Shillong plateau. We find that (1) the exhumation of the plateau began at least 9–15 Ma ago, (2) its surface uplift was chronologically decoupled from its exhumation and started after ∼3–4 Ma at rates of 0.4–0.53 mm/a, (3) the long-term horizontal shortening rate accommodated by the plateau is 0.65–2.3 mm/a, which represents only 10–15% of the India-Asia convergence rate. The uplift of the Shillong plateau did not significantly modify the rock uplift rate in the Bhutan Himalaya, which is consistent with the hypothesis of climatic modulation of the Pliocene erosion, tectonic, and landscape evolution previously documented along this orogenic front.

Received 24 February 2007; accepted 11 September 2007; published 25 December 2007.

Citation: Biswas, S., I. Coutand, D. Grujic, C. Hager, D. Stöckli, and B. Grasemann (2007), Exhumation and uplift of the Shillong plateau and its influence on the eastern Himalayas: New constraints from apatite and zircon (U-Th-[Sm])/He and apatite fission track analyses, Tectonics, 26, TC6013, doi:10.1029/2007TC002125.

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