Granulometric and Morphological Characteristics of the Sands of Sandstone/Basalt Transition Soils in Floraí/PR

Abstract

This paper deals with the differences of the landforms and associated materials (rocks, soils and deposits) of the northwestern areas of the state of Paraná, Brazil. We present a detailed discussion of the geometry of a hillslope and the granulometric and morphologic characteristics of the sands of a soil formed on the sandstones of the Caiuá Formation (Bauru Group) against a soil profile evolved from the basalts of the Serra Geral Formation (São Bento Group), in the basin of the Gurupá. In order to accomplish that, a series of procedures were conducted in the office, field and laboratory, all relatedto techniques used in Pedology, Sedimentology and Geomorphology, in a multi-scalar approach, which allowed for the description and analysis of the landforms and materials. In conclusion, we point to the clear morphological differences between the sand grains of the different soil profiles and to the moresubtle differences regarding mineralogic and granulometric characteristics. The Argisols, formed from sandstone, present quartz grains which are preferably rugged, with a vitreous/matte shine and a subangular/subrounded shape, depending on the depth, while the Nitisols, connected to the basalts presents grains of quartz which are predominantly rugged, matte and subrounded. These results corroborate with the hypothesis that suggests that the Caiuá Formation has two stages of deposition, eolic and fluvial/lacustrine, contradicting the idea of an exclusively eolic depositional environment. Besides that, the characteristics seen in the superficial volume, common to both soils, do not show a continuity in depth within the Nitisol, which indicates an allochthonous genesis of these materials on the basalt.