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Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from ^(40)Ar/^(39)Ar and (U-Th)/He thermochronology

Kirby, Eric and Reiners, Peter W. and Krol, Michael A. and Whipple, Kelin X. and Hodges, Kip V. and Farley, Kenneth A. and Tang, Wenqing and Chen, Zhiliang (2002) Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from ^(40)Ar/^(39)Ar and (U-Th)/He thermochronology. Tectonics, 21 (1). Art. No. 1001. ISSN 0278-7407.

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High topography in central Asia is perhaps the most fundamental expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperature-time paths inferred from ^(40)Ar/^(39)Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar ^(40)Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling (<1°C/m.y.) from Jurassic times until the late Miocene or early Pliocene. The regional extent and consistency of thermal histories during this time period suggest the presence of a stable thermal structure and imply that regional denudation rates were low (<0.1 mm/yr for nominal continental geotherms). Beginning in the late Miocene or early Pliocene, these samples experienced a pronounced cooling event (>30°–50°C/m.y.) coincident with exhumation from inferred depths of ∼8–10 km, at denudation rates of 1–2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period (∼3°C/m.y.), suggesting limited exhumation (1–2 km). However, these samples record a slight increase in cooling rate (from <1 to ∼3°C/m.y.) at some time during the middle Tertiary; the tectonic significance of this change remains uncertain. Regardless, late Cenozoic denudation in this region appears to have been markedly heterogeneous, with the highest rates of exhumation focused at the topographic front of the plateau margin. We infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable Sichuan Basin and thus marks the onset of deformation related to the development of the Tibetan Plateau in this region. The present margin of the plateau adjacent to and north of the Sichuan Basin is apparently no older than the late Miocene or early Pliocene (∼5–12 Ma).

Item Type:Article
Related URLs:
URLURL TypeDescription
Kirby, Eric0000-0002-5701-8688
Reiners, Peter W.0000-0001-7240-2373
Whipple, Kelin X.0000-0002-8430-6925
Hodges, Kip V.0000-0003-2805-8899
Farley, Kenneth A.0000-0002-7846-7546
Additional Information:© 2002 American Geophysical Union. Received 29 June 2000; revised 20 July 2001; accepted 20 August 2001; published 1 January 2002. Our work in eastern Tibet has been supported by the NSF Continental Dynamics program (EAR-9614970 and EAR-9725723). Reviews by Mihai Ducea, Dave Foster, Brad Hacker, and Brian Wernicke significantly improved the manuscript. We wish to acknowledge preliminary (U-Th)/He and fission track analyses by Martha House (Caltech) and Shari Kelly (NMT) which, although not included here, were instrumental in helping us design a sampling strategy. We also thank Clark Burchfiel, Marin Clark, and Wiki Royden for lively discussions.
Funding AgencyGrant Number
NSF Continental Dynamics ProgramEAR-9614970
NSF Continental Dynamics ProgramEAR-9725723
Subject Keywords:Tibetan Plateau; thermochronology; denudation; relief
Issue or Number:1
Record Number:CaltechAUTHORS:20130313-131557163
Persistent URL:
Official Citation:Kirby, E., P. W. Reiners, M. A. Krol, K. X. Whipple, K. V. Hodges, K. A. Farley, W. Tang, and Z. Chen, Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from 40Ar/39Ar and (U-TH)/He thermochronology, Tectonics, 21(1), doi:10.1029/2000TC001246, 2002.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37501
Deposited By: Jason Perez
Deposited On:13 Mar 2013 21:00
Last Modified:03 Oct 2019 04:48

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