Carretier Sébastien, Godderis Y., Delannoy T., Rouby D. (2014). Mean bedrock-to-saprolite conversion and erosion rates during mountain growth and decline. Geomorphology, 209, p. 39-52. ISSN 0169-555X.
Titre du document
Mean bedrock-to-saprolite conversion and erosion rates during mountain growth and decline
Carretier Sébastien, Godderis Y., Delannoy T., Rouby D.
Source
Geomorphology, 2014,
209, p. 39-52 ISSN 0169-555X
Weathering and associated atmospheric CO2 consumption are thought to increase during the erosion of uplifting mountain ranges, but the effect of enhanced erosion on weathering is still the subject of active debate. We explore the possibility that erosion heterogeneity in uplifting landscapes significantly impacts the temporal relationships among mean uplift, erosion and weathering using a 3D landscape evolution model applied to a synthetic surface with different uplift and climate scenarios. Although we do not strictly simulate the weathering outflux of the mountain, we analyze the weathering response through the evolution of the mountain-mean saprolite production rate and compare it to the mountain-mean erosion rate through time. The parametrical analysis shows that the temporal relationship between the mean erosion and saprolite production rates depends mainly on the ratio of the maximum saprolite production rate and the uplift rate w(m)/U. We explore two end-members. (I) When W-m/U> I, which corresponds to mountain ranges under a hot and humid climate, the mean erosion and saprolite production rates vary at the same rate during the uplift and after, once the uplift is stopped. When the uplift is stopped, the mean saprolite production increases and then decreases locally at different times. This heterogeneity induces an overall decrease in the mean saprolite production rate. (2) When w(m)/U < 1, which corresponds to most of the mountain ranges at mid-latitudes, the mean saprolite production rate peaks early and then remains constant, while erosion continues to increase and reaches a steady-state after a time corresponding to -3-5 times the time needed to reach the mean saprolite rate peak. When the uplift is stopped, both the erosion and saprolite production rates decrease, although at different rates with time lags of million years in model time. These results illustrate that a causal relationship between erosion and saprolite production can lead to asynchronous evolutions of their mean values at the mountain range scale. Furthermore, the model suggests that the weathering of large flat continental surfaces should be considered in the geological carbon budget as their size may compensate for their low weathering rate.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Géologie et formations superficielles [064]
