The Geomorphology of Eastern Brazil: As Interpreted by Lester C. King

Abstract

T I 'HE landscape of eastern Brazil carries the record of several successive cycles of erosion. These steplike erosion surfaces have been known for a long time; and for a long time it has seemed that these Brazilian landforms in certain ways fail to conform to the concept of the ideal cycle of erosion as formulated by William Morris Davis. In a paper published in 1933 the present writer described (with maps) the surface features of southeastern Brazil and called attention to certain scarps the origin of which was not clear.' The paper included a map (Fig. ii) of the relations between the three crystalline plateaus near Palmira (now Santos Dumont), in southeastern Minas Gerais: a lower one, in the valley of the Rio Pomba (a tributary to the Parafba), standing about 500 meters above sea level; an intermediate one, about 8oo meters; and a higher plateau, between iooo and 1ioo meters. A sharply marked scarp separates the lower and intermediate plateaus, and the article offered some speculations concerning the origin of this scarp. In spite of the long period during which these landforms have been known to exist, no proper field study of them had ever been made. In part this was due to the difficulties of travel away from the few roads and railroads, in part to the lack of reliable topographic maps. The maps on scales of 1: 200,000 and smaller proved too highly generalized to be useful for an analysis of the landforms. These difficulties have now been surmounted by the South African geomorphologist Lester C. King.2 Supported by a grant from the Conselho Nacional de Pesquisas, and supplied with a jeep and driver by the Instituto Tecnologico de Belo Horizonte, King traveled some 21,000 kilometers in two months and a half, crisscrossing the area south and east of the Rio Sao Francisco and southwestward beyond its headwaters into Sao Paulo state. Equipped with an aneroid barometer, which he checked frequently against measured elevations, King identified the positions of the several levels clearly visible in the landscape. But perhaps more important than either jeep or barometer, King brought with him a lifelong familiarity with the very similar landscape features of South Africa and a new theoretical concept of landform development, which departs in important ways from that formulated by Davis.