Selwyn 3D Interactive Module

The Selwyn area is located approximately 140 km south-southeast of Mt Isa. Rocks here consist of Proterozoic rocks of the Mt Isa Inlier, Cambrian sediments of the Burke River Structural Belt and Mesozoic sediments of the Eromanga Basin. In many places these rocks have been highly weathered. Duricrusts, cemented by either silica (A) or iron (B), and highly weathered bedrock are common. Elsewhere landscapes with relatively high rates of erosion are exposed on slightly weathered basement rocks. The ternary gamma-ray image therefore reflects a mixed bedrock and regolith component (K in red, Th in green and U in blue).

Major features highlighted in the gamma-ray ternary image (turn on the Text in the 3D model to see these) are:

Two satellite images are also included in the 3D model. The first is Band 5 of Landsat TM highlighting major landform features and the second is a spectrally-enhanced Landsat TM image highlighting major regolith materials. The latter uses the second principle component of ratio bands 4/3 and 5/7 in red, ratio 5/4 in green and the addition of bands 7 and 1 in blue. The image shows saprolite materials in red, colluvial sediments in blue and ferruginous sediments and saprolite in yellow (Wilford 1997).

Figure captions (right):
Figure A:
Silicified mesas over granitic saprolite.
Figure B: Massive blocky ferruginous duricrust over granitic saprolite.
Figure C: Colluvial gravels over saprolite.
Figure D: Highly weathered ferruginous duricrust developed on Mesozoic sediments.