Grau de evolução pedogeoquímica da superfície geomorfológica de Xanxerê (SC) - Planalto das Araucárias

Abstract

The presented work aimed to verify the pedogeochemichal evolution degree of the geomorphologic surface of Xanxerê (SC), placed on the Araucaria plateau. For such the subsequent steps were followed: fieldwork, to characterize the representative profile's weathering of the geomorphologic surface of Xanxerê (SC) and gathering of the macromorphological characteristics of the materials which compose the superficial coverage. Afterwards, lab analysis were performed, as follows, particle size analysis, soil and particle density to determine the total porosity, routine chemical analysis, sulfuric attack, mineralogy in the sand, silt and clay fraction, the ratios Fed, Feo and Fet measurement, total chemistry, and lastly, micromorphology. The representative profile weathering of the surface covering from Xanxerê (SC) presents 10.50m of exposed material in cutting level and presents the following horizons Ap, AB, Bw and Bt, which corresponds to the solum, the horizons C1 and C2 which correspond to alloterite, and the horizons C3, C4, C5, C6 and C7 which correspond to isalterite. From the routine chemistry attributes, we notice that the profile's weathering shows acid pH, and base deficiency and CEC implying in kaolinite soil, pointing that the profile's weathering shows an advanced stage of weathering. Regarding weathering levels, by sulfuric attack, the Ki and Kr levels show that the profile's weathering materials are highly weathered, presenting progressed pedogenic evolution and characteristics matching LATOSSOLO BRUNO Distrófico nitossólico, alítico character. The sand, silt and clay fraction mineralogic analysis has shown, in general, primary and secondary minerals derived from volcanic rocks from the Serra Geral Formation and minerals newly formed by partial hydrolysis procedures, by mono and bissialisation procedures. It's also seen the presence of minerals formed in distinct conditions from the current ones, allowing a primal interpretation as polygenetic soil. The information gathered from the iron analysis point to the existence of well crystallized minerals and thus confirming the progressed stage of weathering. The total chemistry analysis shows an intense leaching of basic cations showing that the profiles weathering is chemically well developed. Lastly, the micromorphological analysis hasn't shown any sign of allochthonous aspects, suggesting that the superficial coverage has an autochthonous origin. Therefore, as of the chemical, physical and mineralogic attribute analysis of the representative superficial coverage of the geomorphologic surface of Xanxerê (SC), it's possible that this surface has evolved from the etchplanation process.