Terrain characteristics of a tonal anomaly remotely detected in an area of hydrocarbon microseepage, Tucano Basin, north-eastern Brazil

• Published in: International journal of remote sensing Vol. 23; no. 18; pp. 3893 - 3898
• Main Authors: Almeida-Filho, R., Miranda, F. P., Galvão, L. S., Freitas, C. C.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Group 20.09.2002; Taylor and Francis
• Subjects: Applied geophysics; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Hydrocarbons; Internal geophysics; Pollution, environment geology; Sedimentary rocks; Brazil; Tucano Basin; Bahia Brazil; South America; diagenesis; magnetic minerals; Thematic Mapper; pebbles; hydrocarbons; Landsat; boulders; remote sensing; concentration; seepage; anomalies; chemical analysis; clay; sedimentary rocks; enrichment; depth; imagery; silicification; magnetic susceptibility; soil gases; absorption spectra; clastic rocks; radioactivity
• ISSN: 0143-1161; 1366-5901
• DOI: 10.1080/01431160210137695

This study reports the geological characteristics of a tonal anomaly in an area of hydrocarbon microseepage, identified in Landsat-5 Thematic Mapper (TM) images. A diversified dataset was gathered, which included soil gas geochemistry determinations, soil radioactivity intensity and soil magnetic susceptibility measurements, as well as laboratory soil spectra. Data indicated that the tonal anomaly holds a higher concentration of gaseous hydrocarbons in soils than the surroundings, accompanied by enrichment in radioactive minerals. However, there is no definitive evidence of magnetic mineral enrichment inside the tonal anomaly compared with the surroundings. An intense silicification process, characterized by a cover of fine-grained silicified cobbles and boulders, seems to be responsible for inhibiting the development of diagenetic clay mineralization, as indicated by variations in the depth of the 2200 nm soil spectra absorption band.