HR: 14:25h
AN: H52D-04 INVITED     [PDF]
TI: Constraining Landscape Evolution from Age-Elevation Relationships: a Quantitative Approach
AU: * Braun, J
EM: Jean.Braun@anu.edu.au
AF: Australian National University, Research School of Earth Sciences, Canberra, ACT 0200 Australia
AU: Herman, F
EM: Frederic.Herman@anu.edu.au
AF: Australian National University, Research School of Earth Sciences, Canberra, ACT 0200 Australia
AU: Robert, X
EM: xrobert@ens-lyon.fr
AF: Ecole Normale Superieure de Lyon, Laboratoire de Sciences de la Terre, 46 Allee d'Italie, Lyon, 69364 France
AU: van der Beek, P
EM: pvdbeek@ujf-grenoble.fr
AF: Universite Joseph Fourier, Laboratoire de Geodynamique des Chaines Alpines, Grenoble, 38400 France
AB: Using a complex three-dimensional model of heat transport that incorporates the effects of heat conduction, advection and production, under a finite-amplitude, rapidly changing surface topography, we have recently demonstrated how the rate of landscape evolution can be constrained in a variety of tectonic settings by careful analysis of the relationship between rock cooling ages and elevation. This is because the perturbation to the temperature structure caused by surface topography is a strong function of the wavelength of the topography. To demonstrate this point, we show how the effects of the recent glaciations on the morphology of the Southern Alps in the South Island of New Zealand can be extracted from low-temperature thermochronological datasets and separated from the effects on the ages caused by the rapid exhumation along the Alpine Fault. Turning our attention to post-orogenic settings, we demonstrate that the relationship between age and elevation is also affected by the nature of isostatically-driven exhumation. This effect is strongly dependent on the mechanical strength of the underlying lithosphere that determines whether the isostatic response to erosion-driven exhumation is spatially correlated or not. A strong lithosphere behaves like a thick elastic beam characterized by a large flexural wavelength; a weak lithosphere is charcaterized by a small flexural wavelength. Consequently, we demonstrate that age-elevation relationships also contain information about the mechanical strength of the underlying lithopshere and we provide means of extracting it. Finally, by coupling a surface processes model to the three-dimensional heat transport model, we demonstrate how thermochronological datasets can provide important constraints on the evolution with time of major geomorphic features such as the Great Escarpment of Southeastern Australia.
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2003 Fall Meeting