Abstract
Abstract. Worldwide erosion rates seem to have increased strongly since the beginning of the Quaternary, but there is still discussion about the role of glaciation as a potential driver and even whether the increase is real at all or an artifact due to losses in the long-term sedimentary record. In this study we derive estimates of average erosion rates on the timescale of some tens of millions of years from the terrestrial impact crater inventory. This approach is completely independent from all other methods to infer erosion rates such as river loads, preserved sediments, cosmogenic nuclides, and thermochronometry. Our approach yields average erosion rates as a function of present-day topography and climate. The results confirm that topography accounts for the main part of the huge variation in erosion on Earth, but also identifies a significant systematic dependence on climate in contrast to several previous studies. We found a 5-fold increase in erosional efficacy from the cold regimes to the tropical zone and that temperate and arid climates are very similar in this context. Combining our results into a worldwide mean erosion rate, we found that erosion rates on the timescale of some tens of millions of years are at least as high as present-day rates and suggest that glaciation has a rather regional effect with a limited impact at the continental scale.
Highlights
Potential systematic errors in thermochronometry have been discussed in previous years (Valla et al, 2010; Willenbring and Jerolmack, 2015), and the worldwide increase found by Herman et al (2013) has recently been questioned by Schildgen et al (2018)
Our study yields long-term mean erosion rates as a function of topography expressed in terms of the 10 km relief and climate represented by the primary Köppen–Geiger classes
While the huge variation in topography on Earth forms the biggest contribution to the worldwide variability in erosion rates, our results reveal a significant systematic dependence on climate in contrast to the results of several previous studies
Summary
The origin of the apparently huge increase in worldwide erosion in the late Cenozoic Era is one of the major puzzles in the younger geologic history of our planet (Molnar and England, 1990; Zhang et al, 2001; Molnar, 2004; Willenbring and von Blanckenburg, 2010; Herman et al, 2013; Wang et al, 2014; Marshall et al, 2015; Willenbring and Jerolmack, 2015). The theoretical arguments were supported by beryllium isotope ratios revealing no systematic variation in weathering rates during the last 12 Myr. On the other hand, a recent study on thermochronometric data that do not depend on the long-term sedimentary record has revealed a strong increase, at least in some mountainous regions, with high erosion rates during the last 10 Myr (Herman et al, 2013). In a study on organic carbon fluxes, Ludwig and Probst (1996) estimated sediment fluxes into the oceans and found a strong correlation with climate. The presumably most comprehensive compilation of millennial-scale erosion rates (Portenga and Bierman, 2011) involving cosmogenic nuclide data from almost 1600 drainage basins and outcrops even yielded an unsystematic dependence on climate, presumably because the dominant effect of topography shadows all other influences. Recent studies (Moon et al, 2011; Ferrier et al, 2013) have at least confirmed the correlation between precipitation and erosion rates that is implicitly assumed in all models of fluvial erosion within regions with high contrasts in precipitation
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