Denudation rates of the Southern Espinhaço Range, Minas Gerais, Brazil, determined by in situ-produced cosmogenic beryllium-10 Helen N. Barreto a, b, ⁎, César A.C. Varajão a , Régis Braucher b , Didier L. Bourlès b , André A.R. Salgado c , Angélica F.D.C. Varajão a a Department of Geology, Universidade Federal de Ouro Preto, Campus do Morro do Cruzeiro, CEP: 35.400-000 Ouro Preto/MG, Brazil b CEREGE, UMR 6635 CNRS/Université Aix-Marseille, BP 80, 13545 Aix-en-Provence Cedex 4, France c Department of Geography, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6.627 Pampulha, CEP 31270-901 Belo Horizonte/MG, Brazil abstract article info Article history: Received 7 November 2011 Received in revised form 20 January 2013 Accepted 25 January 2013 Available online 19 February 2013 Keywords: The Southern Espinhaço Range Beryllium-10 Cosmogenic nuclide Denudation rates Brazil To investigate denudation rates in the southern part of the Espinhaço Range (central-eastern Brazil) and to understand how this important resistant and residual relief has evolved in the past 1.38 My, cosmogenic 10 Be concentrations produced in situ were measured in alluvial sediments from the three main regional ba- sins, whose substratum is composed primarily of quartzites. The long-term denudation rates (up to 1.38 My) estimated from these measurements were compared with those that affect the western (São Francisco River) and eastern (Doce and Jequitinhonha Rivers) basins, which face the West San Francisco craton and the Atlantic, respectively. Denudation rates were measured in 27 samples collected in catchments of different sizes (6–970 km 2 ) and were compared with geomorphic parameters. The mean denudation rates determined in the northern part are low and similar to those determined in the southern part, despite slightly different geomorphic parameter values (catchment relief and mean slope). For the southern catchments, the values are 4.91±1.01 mMy -1 and 3.65 ± 1.26 m My -1 for the Doce and São Francisco River basins, respectively; for the northern catchments, they are 4.40±1.06 mMy -1 and 3.96±0.91 mMy -1 for the Jequitinhonha and São Francisco River basins, respectively. These low values of denudation rates suggest no direct correlation if plotted against geomorphic parameters such as the catchment area, maximum elevation, catchment relief, average relief and mean slope gradients. These values show that the regional landscape evolves slowly and is strongly controlled by resistant lithology, with similar erosional rates in the three studied basins. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Geomorphology studies landscape evolution through the under- standing and quantification of the temporal evolution of the underlying processes. Denudation is among the most important of all the processes that affect the morphological evolution of relief (Summerfield, 1998). The term “denudation” refers to all chemical weathering and physical erosion processes that contribute to the lowering of the land surface (Caine, 2004). Until recently, the quantification of denudation over timescales of thousands of years has remained a difficult problem. This difficulty has been overcome with the use of cosmogenic nuclides pro- duced in situ. Accumulating within minerals in the uppermost few me- ters of the Earth's surface as secondary particles produced by cosmic rays, in situ-produced cosmogenic nuclides can be quantified in terms of not only their exposure duration at or near the surface but also the rates of the processes bringing them to the surface and removing them from the surface (Brown et al., 1995; Riebe et al., 2000; Granger et al., 2001; Granger and Riebe, 2007). Measurements of cosmogenic nuclide concentrations in rapidly mixed river sediments can be used to deter- mine an average denudation at the scale of the studied river basin (Bierman and Steig, 1996; Granger et al., 1996; Shaller et al., 2001; Von Blanckenburg, 2006; Wittmann and von Blanckenburg, 2009). In this article, denudation rates given by 10 Be were utilized to eval- uate the evolution of an impressive Brazilian water divide, the Espinhaço Range (ER — Von Eschwege, 1832a,b), whose name means “big backbone”. The ER is a 1000-km-long north–south range. It extends across approximately one-fourth of the length of Brazil (Fig. 1). The ER is composed primarily of quartzitic rocks of the Paleo-Mesoproterozoic Espinhaço Supergroup, which exist side-by-side with Neoproterozoic rocks of the São Francisco Supergroup: (i) carbonatic and pelitic rocks of the Bambuí Group and (ii) iron formations and diamictites of the Macaúbas Group (Dussin and Dussin, 1995; Uhlein et al., 1999). The geological substratum is formed by a basement of Archean– Paleoproterozoic gneisses. Geomorphologically, the ER is a resistant quartzitic wall flanked by less resistant rocks. It is a residual landscape that has evolved since the early Proterozoic. The ER has become an im- portant natural water divide for the three largest rivers in SE–NE Brazil, Geomorphology 191 (2013) 1–13 ⁎ Corresponding author at: Department of Geology, Universidade Federal de Ouro Preto, Campus do Morro do Cruzeiro, CEP: 35.400-000 Ouro Preto/MG, Brazil. Tel.: +55 98 32337164. E-mail address: helennebias@yahoo.com.br (H.N. Barreto). 0169-555X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.geomorph.2013.01.021 Contents lists available at SciVerse ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph