Emprego de técnicas de realce em imagens Landsat/ETM+ para o detalhamento geológico da borda Leste da Bacia do Parnaíba

The Geological Survey of Brazil-CPRM has studied the groundwater at the Eastern border of Parnaíba Sedimentary Basin, with the goal to increase water availability for cities at the plateau of the Serra Grande Aquifer, along the border between Ceará and Piauí States, Northeast Brazil. Images from Landsat 7 ETM + sensor were processed with the combination of two techniques that enhances multispectral information and proves suitable to highlight geological and structural features at Crateús/Ceará and Buriti dos Montes/Piauí regions. The RGB composite originated by the band ratio of the principal components PC4/PC5 (R-Red), PC2/PC1 (G-green) and PC3/PC4 (B-blue) distinguished the medium-to-fine grained sandstones of Tianguá Formation, the coarse-grained sandstones of Jaicós Formation and enhanced the Itaim Formation (base of Canindé Group), with fine-grained sandstones interbedded with shales. The color composite RGB 457 supports this discrimination, besides enhances the arboreal vegetation from open shrubby at the top of the plateau border. The combined PDI techniques allow the improvement of geological map and the mapping of geologic units which were not distinguishable on semi-detail scale before. Structural lineaments were interpreted after the fusion of the Landsat products with SRTM elevation data. The generation of slope orientation and gradient maps were integrated with the structural information to help understand localized groundwater flow to the east, contrary to westerly regional flow.Pages: 3664-367