O Karst das vizinhanças setentrionais de Belo Horizonte : Minas Gerais

Resumo

The Karst of the region North of Belo Horizonte can be characterized by the sporadic existence of calcareous mole like rocks or towers or slopes, in the middle of regular concave convex per filled hills. These calcareous surfaces are actually reduced by the only chemical and biochemical processes, which burilize them with lapiez and caneluras. The tree roots seem to play an important role in the alargement of the diaclases.

            The sporadic occurrence of calcareous rocks can be explained by a series of factors, the principal of which are:

            A differential erosion which charged more rapidly and more compactly the metamorphic formation than the calcareous soils. This calcar is partially metamorphosed in its base in an irregular manner. The nuclei of pure calcar were separated of the metamorphic formation which form calcareous mole like rocks. The rough contact have equally increased in value, forming and straight walls.

            The up and down of the paleoclimatic quaternary, which regulate this differential erosion. During humid periods the metamorphic rocks were greatly changed to moving lime-sandy products of easy evacuations During the drought period the torrents and slopes carried considerable quantities of alteration products, mainly on the sloppy side, which umburried some calcareous walls and cleaned out covered lapiez.

            This study shows a new type of karst of karst of partially metamorphic formations. It stresses the importance of the covered karst forms in a tropical region, whilst, up to now, it had been insisted on uncovered forms, especially the karsts with towers and hills of the Antilhas. It demonstrates the necessity of considering important climatic-Quaternary fluctuations in order to explain the morphogenesis of the relief of Brazil on about 20 degrees south latitude.