Uplift of the western margin of the Andean plateau revealed from canyon incision history, southern Peru
- 1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- 2School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, USA
- 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
- 4Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
Abstract
We explore canyon incision history of the western margin of the Andean (Altiplano-Puna) plateau in the central Andes as a proxy for surface uplift. (U-Th)/He apatite data show rapid cooling beginning at ca. 9 Ma and continuing to ca. 5.1 Ma in response to incision. A minimum of 1.0 km of incision took place during that interval. The youngest apatite date and a volcanic flow perched 125 m above the present valley floor dated at 2.261 ± 0.046 Ma (40Ar/39Ar) show that an additional ∼1.4 km of incision occurred between ca. 5.1 and 2.3 Ma. Thus, we infer that a total of at least 2.4 km, or 75% of the present canyon depth was incised after ca. 9 Ma. (U-Th)/He zircon data collected along the same transect imply that the western margin of the plateau was warped upward into its present monoclinal form, rather than uplift being accommodated on major surface-breaking faults.
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- Accepted 25 January 2007.
- Received 10 November 2006.
- Revision received 18 January 2007.
- Geological Society of America
