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In recent years, the nature of the complex interactions between the solid earth and the overlying atmosphere has been the subject of much debate (England and Molnar 1990; Whipple et al. 1999; Braun et al. 1999). Does erosion play an important role in the dynamics of mountain building? Is there a strong feedback into the balance of forces at the crustal scale from mass transport by erosional and depositional processes at the Earth’s surface? Or does erosion passively react to changes in the Earth’s surface topography to shape mountains with tectonic forces, originating in the underlying convecting mantle, dominating the dynamics of plate interactions and crustal deformation at convergent plate margins?
The answers to these fundamental questions lie in our ability to determine the rate at which surface processes can react to tectonic forcing (Whipple et al. 1999). Where erosion is efficient, the coupling will be strong as the rate of change of surface loading by mass transport will be similar to the rate of creation of topography by crustal deformation. This may lead to a concentration of deformation and thus exhumation in regions of intense erosion (Koons 1990; Willett et al. 1993; Beaumont et al. 2001; Koons et al. 2002, 2003; Braun and Pauselli 2004). Where erosion is relatively inefficient, mountain building is the result of a balance between internal driving forces and those originating from the deflection of an upper free surface; there is no feedback from erosional processes.
Low-temperature thermochronology, such as (U-Th)/He (He) or fission track (FT) dating in apatite and zircon, provides information on the rate at which rocks cool as they are exhumed towards the “cold” Earth surface (Duddy et al. 1988; Warnock et al. 1997; Farley 2000; Reiners and Farley 1999). Because the …