Remote detection of hydrocarbon microseepage areas in the Serra do Tonã region, Tucano basin, Brazil

Abstract

Landsat thematic mapper (TM) images enhanced through principal components analysis allowed the detection of tonal anomalies possibly associated with surface manifestations of hydrocarbon microseepage. Target areas occur mainly surrounding the Serra do Tonã plateau, in accordance with a previous geological model that explains the distribution of the hydrocarbon microseepage in the region. The spatial association between the tonal anomalies and anomalous concentration of hydrocarbon in soil was quantitatively evaluated using weight of evidence (WofE) analysis. Results indicated that tonal anomalies are positive evidence for the occurrence of anomalous concentrations of soil gas data, suggesting a possible geologic origin to the target areas. Field study investigated the terrain characteristics in one of the soil gas anomalies. Ground truth data confirmed anomalous concentrations of gaseous hydrocarbons in soils, accompanied by an increase in the abundance of radioactive and magnetic minerals, a fact that denotes the action of a reducing environment responsible for the precipitation of this hydrocarbon-induced mineralogical assemblage. Results suggest that remote sensing techniques may be used as an auxiliary prospecting tool for similar target areas in the remaining Tucano basin, or even throughout the Recôncavo‐Tucano‐Jatobá rift, in northeastern Brazil.