MICROMORPHOLOGICAL PROPERTIES OF COLLUVIUMS IN HILLSLOPE IN THE MIDDLE VALLEY OF MARRECAS RIVER (SOUTH-WEST OF PARANÁ STATE) - BASIS FOR DISTINCTION OFALLOCHTHONOUS AND AUTHOCHTHONOUS SURFACES FORMATIONS IN BASALTIC SUBSTRATUM

Abstract

This article presents the microscopic organization of colluviums located in the valley of Marrecas River (South-west of Paraná State), aiding to help in the genetic differentiation of allochthonous from the authochthonous surfaces formations in basaltic substratum. It has been procceded as it follows: i) survey of the sedimentological properties and the identification of lithofacies; and ii) micromorphological description of nine thin sections representatives of the colluvial units. The relative distributions of constituents and microstructures by processes were quantified in the thin sections, through image analysis. It has been identified matrix support massive gravelly mud and matrix support massive muddy gravel lithofacies. Microscopic properties of the colluvium deposits showed microstructures related to depositional processes, which were inherited from the source material and are resulted from post-depositional transformations. The microstrutures identified in the two situations can work as markers of allochthonous origin of surface formations rich in iron oxyhydroxides, assisting in its genetic differentiation.