Exploring geochemical controls on weathering and erosion of convex hillslopes: beyond the empirical regolith production function
Article first published online: 26 APR 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Earth Surface Processes and Landforms
Volume 38, Issue 15, pages 1793–1807, December 2013
How to Cite
Lebedeva, M. I. and Brantley, S. L. (2013), Exploring geochemical controls on weathering and erosion of convex hillslopes: beyond the empirical regolith production function. Earth Surf. Process. Landforms, 38: 1793–1807. doi: 10.1002/esp.3424
- Issue published online: 3 DEC 2013
- Article first published online: 26 APR 2013
- Accepted manuscript online: 23 MAR 2013 10:33AM EST
- Manuscript Accepted: 18 MAR 2013
- Manuscript Revised: 14 MAR 2013
- Manuscript Received: 2 FEB 2011
- hillslope evolution;
- reactive transport modeling;
Landscape curvature evolves in response to physical, chemical, and biological influences that cannot yet be quantified in models. Nonetheless, the simplest models predict the existence of equilibrium hillslope profiles. Here, we develop a model describing steady-state regolith production caused by mineral dissolution on hillslopes which have attained an equilibrium parabolic profile. When the hillslope lowers at a constant rate, the rate of chemical weathering is highest at the ridgetop where curvature is highest and the ridge develops the thickest regolith. This result derives from inclusion of all the terms in the mathematical definition of curvature. Including these terms shows that the curvature of a parabolic hillslope profile varies with distance from the ridge. The hillslope model (meter-scale) is similar to models of weathering rind formation (centimeter-scale) where curvature-driven solute transport causes development of the thickest rinds at highly curved clast corners. At the clast scale, models fit observations.
Here, we similarly explore model predictions of the effect of curvature at the hillslope scale. The hillslope model shows that when erosion rates are small and vertical porefluid infiltration is moderate, the hill weathers at both ridge and valley in the erosive transport-limited regime. For this regime, the reacting mineral is weathered away before it reaches the land surface: in other words, the model predicts completely developed element-depth profiles at both ridge and valley. In contrast, when the erosion rate increases or porefluid velocity decreases, denudation occurs in the weathering-limited regime. In this regime, the reacting mineral does not weather away before it reaches the land surface and simulations predict incompletely developed profiles at both ridge and valley. These predictions are broadly consistent with observations of completely developed element-depth profiles along hillslopes denuding under erosive transport-limitation but incompletely developed profiles along hillslopes denuding under weathering limitation in some field settings. Copyright © 2013 John Wiley & Sons, Ltd.