MAPEAMENTO DE UNIDADES GEOLOGICAS E SOLOS COM O USO DE IMAGENS MULTIESPECTRAIS ASTER (TIR): O EXEMPLO DA FORMAÇÃO SANTA TECLA (RS)

The use of multispectral techniques for lithology recognition in subtropical regions presents various challenges and even skepticism regarding their effective application in mapping. This situation changes when analyzing the results obtained from multispectral images within a "Multi" working perspective, which is fundamental in remote sensing. The Santa Tecla Formation occurs in the southwest of Rio Grande do Sul and is characterized as a cover composed of sediments cemented by silica, forming a siliceous crust (silcrete). This unit offers favorable conditions for multispectral mapping, such as uniform mineralogical and chemical composition and extensive exposed areas. Band ratios were utilized for the detection of silica within the thermal infrared spectrum of the ASTER sensor, and the results allow us to conclude that the methodology successfully identified the Santa Tecla Formation and additionally demonstrated a good correlation with silica contents in the other geological units of the study area.