『Abstract
Glaciers and rivers control the shape of the high relief topography
of mountain ranges However, their relative contribution in response
to climatic oscillations and tectonic forcing and whether landscapes
can reach equilibrium conditions during the Quaternary are still
unclear. Here we introduce a new thermochronometer of exceptionally
low closure temperature (ca. 30-35℃) based on Optically Stimulated
Luminescence (OSL) dating and illustrate how it may be used to
measure relief evolution and exhumation rates within the last
glacial cycle in the Southern Alps of New Zealand, one of the
most tectonically active orogens and an area that has experienced
rapid, high magnitude climate changes. We find that exhumation
rates have remained steady over the last glacial cycle and match
rates observed at a million year timescale. This suggests that,
despite an extreme exhumation rate of the order of 800 m in 100
ka, and the fact that in the last ca. 11-18 ka most hillslope
sides have changed from U to V-shape valleys and have been dissected
by debris-flows, landslides and rock avalanches, the mean exhumation
rates have remained nearly constant. This may imply that tectonics,
not climate, has a primary control on the rates of exhumation
in tectonically active and wet mountain belts. On the contrary,
tectonically active mountain ranges might not attain equilibrium
on similar timescales in weathering and/or transport limited landscapes
as, for example, in arid regions.
Keywords: OSL dating; thermochronology; glacial erosion; relief
change; stochastic inversion; thermal modeling』
1. Introduction
2. OSL-thermochronology
3. Geological setting and sample collection
4. OSL measurements
5. Inversion of the thermochronological data to infer exhumation
rates and the evolution of relief
6. Discussion
7. Conclusions
Acknowledgements
Appendix A. Supplementary data
References