Wilga Basin coal deposits, Wilga, Boyup Brook Shire, Western Australia, Australiai

Regional Level Types
Wilga Basin coal deposits	Group of Deposits
Wilga	- not defined -
Boyup Brook Shire	Shire
Western Australia	State
Australia	Country

Coal bearing sediments. The remains of a formerly extensive sedimentary sequence is preserved in fault bounded grabens of the Yilgarn Craton.

The Wilga Basin is 39 square kilometres, 14 kilometres south of the coal bearing Collie Basin. The deposits were discovered by Michael O'Grady in 1918, from one of a series of exploration shafts which intersected a coal seam.

Western Aluminium NL in 1960 resolved the extent of the basin from gravity surveys. It was later explored by Geotechnics and CRA Exploration from 1984 to 1985.

Wilga is similar to the Collie Basin, forming a north-west to south-east axis. It is wedged shaped, tapering to the east. The basin is sub-divided into three parts by narrow upthrown basement rocks.

Wilga formed a succession of Permian basement units, overlain by Cretaceous sediments, and Tertiary laterites. At West Wilga the basement is granite, while East Wilga it is dark green basic intrusives and white/black mottled granite.

The Permian sediments are similar to the Collie Basin, preserved within fault bounded graben like structures up to 300 metres deep. From the base at Wilga is sandstone, siltstone, carbonaceous shale then coal. In the base unit are sub-ordinate conglomerates and irregular distributed diamictite, with a number of coal seams in the sediments. The sediments are poorly consolidated and are friable.

The coal seams range from a few centimetres to 3 metres thick, and eleven of them have been found so far, grouped into three zones.

Fossils

This region is too big or complex to display the fossil list, try looking at smaller subregions.

References