The National Aeronautics and Space Administration (NASA) space shuttle mission in November 1981 acquired images of parts of the earth with a synthetic aperture radar system at a wavelength of 23.5 cm (9.3 in.) and spatial resolution of 38 m (125 ft). This report describes the geologic interpretation of 1:250,000-scale images of Irian Jaya and eastern Kalimantan, Indonesia, where the all-weather capability of radar penetrates the persistent cloud cover. The inclined look direction of radar enhances subtle topographic features that may be the expression of geologic structures. On the Indonesian images, the following terrain categories are recognizable for geologic mapping: carbonate, clastic, volcanic, alluvial and coastal, melange, and metamorphic, as well as undifferentia ed bedrock. Regional and local geologic structures are well expressed on the images.

In the Vogelkop region of Irian Jaya, the major tectonic elements (Tamrau Mountains, Sorong fault, Kemum block, Bintuni basin, and Lengguru foldbelt) are readily mapped. On the image of the Sorong fault, geomorphic features (offset drainage, shutterridges, aligned notches) provide clear evidence for left-lateral strike-slip displacement. Several lineaments on the image correlate with previously mapped faults. Other lineaments may be the expression of previously unrecognized faults.

On the image of the mainland of Irian Jaya, a belt of metamorphic and melange terrain marks the zone of collision between the Pacific plate and the Australian plate. The high Central Range of Irian Jaya is located south of the metamorphic and melange belt. The generally homoclinal structure of the Central Range is interrupted in the Paniai Lake region by a series of southward directed thrust plates indicated by belts of carbonate terrain (New Guinea Limestone Group) that alternate with belts of clastic terrain (Kembelangan Formation). In the image of eastern Kalimantan, several major foldbelts are clearly expressed.

These limited examples of space shuttle radar images demonstrate their value for geologic interpretation of Indonesia. It is recommended that future shuttle missions acquire complete radar coverage of the main islands of Indonesia for use in geologic mapping and energy exploration. Shuttle radar images would also be valuable for other cloud-covered forested regions.