Abstract

Side-looking airborne radar coverage acquired over central Sumatra provided valuable geological information for an area with limited accessibility. The use of side-looking radar data as a regional mapping tool, particularly synthetic aperture radar (SAR) images, has been effective in Indonesia and other areas. A significant amount of radar data has been acquired in heavily vegetated tropical regions, where favorable cloud-free conditions for air photo surveys are seldom present.

Geological interpretation of SAR images for the Mahato-Mandian Block required and evaluation of the expected energy-terrain interaction characteristics with regard to vegetation and physical environment. During the interpretation of the Sumatra data, anomalous features which are not related to geological or terrain parameters were identified.

Other sources of reconnaissance data for the Mahato-Mandian area, including aerial photos and Landsat images, were analyzed and provided additional information. Their impact on the structural interpretation and exploration program, however, was less than that of the radar data because (a) they did not provide up-to-date information about area accessibility, (b) cloud cover restricted use of available Landsat coverage, and (c) high-quality mosaics could not be prepared from aerial photos for regional geological studies.

Results of a preliminary interpretation of the SAR data show the presence of a strong NW-SE structural grain, which is well expressed in the south western side of the Mahato-Mandian Block. Less conspicuous structural grains have NNW-SSE, E-W, and NE-SW directions. Features with a NW-SE-trending direction are believed to have been formed as a result of the most recent tectonic events in the area.