Influence of topography and human activity on apparent in situ 10Be-derived erosion rates in Yunnan, SW China

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Schmidt, Amanda H. ; Neilson, Thomas B. ; Bierman, Paul R. ; Rood, Dylan H. ; Ouimet, William B. ; Sosa Gonzalez, Veronica (2016)

In order to understand better if and where erosion rates calculated using in situ <sup>10</sup>Be are affected by contemporary changes in land use and attendant deep regolith erosion, we calculated erosion rates using measurements of in situ <sup>10</sup>Be in quartz from 52 samples of river sediment collected from three tributaries of the Mekong River (median basin area = 46.5 km<sup>2</sup>). Erosion rates range from 12 to 209 mm kyr<sup>−1</sup> with an area-weighted mean of 117 ± 49 mm kyr<sup>−1</sup> (1 standard deviation) and median of 74 mm kyr<sup>−1</sup>. We observed a decrease in the relative influence of human activity from our steepest and least altered watershed in the north to the most heavily altered landscapes in the south. In the areas of the landscape least disturbed by humans, erosion rates correlate best with measures of topographic steepness. In the most heavily altered landscapes, measures of modern land use correlate with <sup>10</sup>Be-estimated erosion rates but topographic steepness parameters cease to correlate with erosion rates. We conclude that, in some small watersheds with high rates and intensity of agricultural land use that we sampled, tillage and resultant erosion has excavated deeply enough into the regolith to deliver subsurface sediment to streams and thus raise apparent in situ <sup>10</sup>Be-derived erosion rates by as much as 2.5 times over background rates had the watersheds not been disturbed.
  • References (60)
    60 references, page 1 of 6

    Andermann, C., Bonnet, S., and Gloaguen, R.: Evaluation of precipitation data sets along the Himalayan front, Geochem. Geophy. Geosy., 12, Q07023, doi:10.1029/2011GC003513, 2011.

    Balco, G., Stone, J. O., Lifton, N. A., and Dunai, T. J.: A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements, Quat. Geochronol., 3, 174-195, doi:10.1016/j.quageo.2007.12.001, 2008.

    Bierman, P. R. and Caffee, M.: Slow rates of rock surface erosion and sediment production across the Namib Desert and escarpment, southern Africa, Am. J. Sci., 301, 326-358, 2001.

    Bierman, P. R. and Caffee, M.: Cosmogenic exposure and erosion history of Australian bedrock landforms, Geol. Soc. Am. Bull., 114, 787-803, 2002.

    Bierman, P. R. and Steig, E.: Estimating rates of denudation and sediment transport using cosmogenic isotope abundances in sediment, Earth Surf. Proc. Land., 21, 125-139, 1996.

    Binnie, S. A., Phillips, W. M., Summerfield, M. A., and Fifield, L. K.: Tectonic uplift, threshold hillslopes, and denudation rates in a developing mountain range, Geology, 35, 743-746, 2007.

    Braucher, R., Bourlès, D., Brown, E., Colin, F., Muller, J.-P., Braun, J.-J., Delaune, M., Minko, A. E., Lescouet, C., and Raisbeck, G.: Application of in situ-produced cosmogenic 10 Be and 26 Al to the study of lateritic soil development in tropical forest: theory and examples from Cameroon and Gabon, Chem. Geol., 170, 95- 111, 2000.

    Brown, E. T., Stallard, R. F., Larsen, M. C., Raisbeck, G. M., and Yiou, F.: Denudation rates determined from the accumulation of in situ-produced 10Be in the Luquillo experimental forest, Puerto Rico, Earth Planet. Sc. Lett., 129, 193-202, 1995.

    Brown, E. T., Stallard, R. F., Larsen, M. C., Bourles, D. L., Raisbeck, G. M., and Yiou, F.: Determination of predevelopment denudation rates of an agricultural watershed (Cayaguas River, Puerto Rico) using in-situ-produced 10Be in river-borne quartz, Earth Planet. Sc. Lett., 160, 723-728, 1998.

    Burchfiel, B. C. and Chen, Z.: Tectonics of the southeastern Tibetan Plateau and its adjacent foreland, Geol. Soc. Am. Mem., 210, 2012.

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