Abstract

The NASA Space Shuttle mission in November 1981 acquired images of portions of the earth with a synthetic aperture radar system at a wavelength of 23.5 cm and spatial resolution of 38 m. This report describes the geologic interpretation of representative 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 terrain, clastic terrain, volcanic terrain, alluvial and coastal terrain, melange terrain, metamorphic terrain, and undifferentiated 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 fold belt) are readily mapped. On the image of the Sorong fault, geomorphic features (offset drainage, shutter ridges, aligned notches) provide clear evidence for left-lateral strike-slip displacement. A number of 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 occurs 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 that are indicated by belts of carbonate terrain (New Guinea Limestone Group) than alternate with belts of clastic terrain (Kembelangan Formation). In the image of eastern Kalimantan, several major fold belts are clearly expressed.

These limited examples of Space Shuttle radar images demonstrate their value for geologic interpretation of Indonesia. It is recommended that future Space Shuttle missions acquire additional radar coverage of Indonesia for geologic mapping and energy exploration.