Investiga??o da influ?ncia dos processos denudacionais na evolu??o do relevo da Serra do Espinha?o Meridional, Minas Gerais ? Brasil.

Este trabalho se prop?e ao estudo da evolu??o da Serra do Espinha?o Meridional (SdEM), por meio de um estudo comparativo das taxas de eros?o (denuda??o geoqu?mica e is?topos cosmog?nicos (10Be)) das bacias das bordas leste (bacias atl?nticas) e oeste (bacias interioranas); comparar ?reas preservadas com ?reas mineradas e da an?lise regional dos perfis de solo. Atrav?s das an?lises f?sico-qu?micas de ?guas superficiais foram determinadas as taxas de denuda??o qu?mica atual das bacias, cujos resultados correspondem na por??o sul, a 3,84 ton/km2/ano e 5,71 ton/km2/ano, nas bacias dos rios S?o Francisco e Doce, respectivamente; e na por??o norte, a 1,40 ton/km?/ano e 0,74 ton/km?/ano, nas bacias dos rios S?o Francisco e Jequitinhonha. As taxas de rebaixamento geoqu?mico mostraram que o relevo da SdEM evolui lentamente na bacia do rio S?o Francisco (sul:1,43 m/Ma; norte: 0,28 m/Ma), na bacia do rio Doce (2,13 m/Ma) e na bacia do rio Jequitinhonha (0,52 m/Ma). As taxas foram maiores na bacia do rio Doce, indicando provavelmente processo de denuda??o diferencial influenciado pela neotect?nica do m?dio vale do rio Doce. Por meio da quantifica??o da concentra??o de is?topos cosmog?nicos de 10Be em sedimentos aluviais constatou-se, nas bacias com baixa interfer?ncia antr?pica , uma evolu??o lenta do relevo nos ?ltimos 1,5Ma, com as respectivas taxas na por??o sul (Parque Nacional da Serra do Cip?), 4.91?1.01 m/Ma e 3.65?1.26 m/Ma para as bacias do Doce e do S?o Francisco, respectivamente. Estes resultados evidenciam o controle litol?gico e a resist?ncia dos quartzitos frente ?s demais rochas constituintes da SdEM. Considerando a atividade antr?pica nas bacias do Planalto Diamantina, foram encontradas as seguintes taxas de denuda??o de longo-termo: (i) 2,60?0,08 m/Ma a 5,56?0,16 m/Ma, nas bacias onde os sedimentos aluviais foram retrabalhados pelo garimpo de diamantes, que se assemelham ?s taxas de denuda??o das bacias com baixa interfer?ncia antr?pica da Serra do Cip? e; (ii) 22,83?1,52 m/Ma e 6,42?0,21 m/Ma, nas bacias com sobrecarga de sedimentos em virtude da prospec??o de diamantes a partir do desmonte hidr?ulico do saprolito. Esse estudo demonstrou a influ?ncia da atividade mineral nas taxas de eros?o das bacias afetadas pela sobrecarga de sedimentos provenientes da remo??o do saprolito pela explota??o de diamantes. As an?lises granulom?tricas, qu?micas, mineral?gicas e micromorfol?gicas dos perfis de solo em unidades lito-estratigr?ficas da SdEM, apontaram para um perfil representativo constitu?do por Neossolos e Cambissolos, eoc?nicos, caracterizados pela presen?a de uma camada pedregosa discordante, sobre os horizontes HB ou HC. As forma??es superficiais desse perfil de solo foram erodidas provavelmente no Plioceno, em condi??es ?ridas, o que permitiu a concentra??o desses cascalhos, dando origem a um paleo-pavimento no processo de evolu??o da paisagem. A an?lise integrada da pedog?nese e das taxas de eros?o permitiu a compreens?o da lenta evolu??o do relevo da Serra do Espinha?o Meridional.This work aims to study the evolution of the Southern Espinha?o Range (SER), through a comparative study of the denudation rates (geochemical denudation and in situ production of the cosmogenic 10Be in fluvial sediments) estimated from these measurements were compared with those that affect the western (S?o Francisco River) and eastern (Doce and Jequitinhonha Rivers) basins, which face the West San Francisco craton and the Atlantic; to compare preserved natural catchments to those catchments subjected to panning processes; and regional analysis of soil profiles. The rates of geochemical denudation of surface waters showed that the relief of SER evolves slowly for the S?o Francisco River (southern portion, 1.43 m My-?; northern portion, 0.28 m My-?), the Doce River (2.13 m My-?) and Jequitinhonha River (0.52 m My-?) basins. The rates were slightly higher in the Doce River Basin, indicating differential denudation process probably as a consequence of a Quaternary distensive tectonic at the Doce River?s middle valley. The long-term 10Be denudation rates measured in alluvial sediments, in catchments less disturbed by human activities, showed that the relief of SER evolves slowly in the last 1.5 Ma: (i) in the southern portion were founded 4.91 ? 1.1 m My-? and 3.65 ? 1.26 m My-? for the Doce and S?o Francisco river basins, respectively. The low values showed the control exerted by resistant quartzitic lithology compared to other lithologies of the SER. Considering the catchments which was subjected to diamond exploitation in the Diamantina Plateau, the long-term 10Be denudation rates obtained were: (i) 2.60 ? 0.08 m My-? to 5.56 ? 0.16 m My-? in catchments where sediments were reworked by alluvial diamond mining, were similar to denudation rates from the natural preserved catchments in the Serra do Cip? and; (ii) 22.83 ? 1.52 m My-? and 6.42 ? 0.21 m My-?, in overloaded catchments (alluvial sediments originating from panning processes on saprolites located upstream). This study demonstrated the influence of mining activity on denudation rates in overload catchments affected by diamond exploitation. The chemical, mineralogical and micromorphological analysis of soil profiles in the lithostratigraphic units of SER, showed representatives profiles (Eocene) consisting of Regosols and Cambisols, characterized by the presence of a stone line unconformity on the horizons HB or HC. The surface formations of soil profile were eroded probably in the Pliocene, in arid conditions, which allowed the concentration of these gravels, yielding a paleo-pavement in the process of landscape evolution. The integrated analysis of pedogenesis and erosion rates allowed to understanding the slow relief evolution of the Southern Espinha?o Range