RECENT GEOLOGICAL AND GEOPHYSICAL RESULTS IN THE NORTHEASTERN CANNING BASIN

Abstract

The exploration programme conducted in Exploration Permits 58 and 59 in the northeastern Canning Basin during the past three years has clarified regional structural and stratigraphic relationships. Interpretation of the combined results of field geological, high sensitivity aeromagnetic and reflection seismic surveys has delineated five major structural elements, some previously unrecognised. These are, from north to south, the Billiluna Shelf, the Betty Terrace, the Fitzroy Trough, the Crossland Platform and the Helena Platform. Sedimentary rocks from Proterozoic to Mesozoic age occur in the permits. The Phanerozoic rocks range in thickness from in excess of 15000 m in the Fitzroy Trough to a veneer of probably less than 1000 m over the Billiluna Shelf. On the Crossland Platform and the Helena Platform, up to 4000 m of Lower and Middle Palaeozoic rocks overlain by up to 1500 m of Upper Palaeozoic sediments are interpreted to be present.

Whilst no wells have been drilled within the area, results of exploratory holes in adjoining permits have been used to refine the interpretations presented in this paper. The principal stratigraphic features of interest to petroleum exploration are a possible Devonian reef trend located on the junction of the Crossland and Helena Platforms and subdued structural features caused by halokinesis on the Helena Platform.

Two major geological conclusions were drawn from the exploration programme to date. One is that the age of the formation of the Fitzroy Trough, at least in this part of the Canning Basin, is younger than previously postulated. The other is the presence in the northeastern part of the Canning Basin of a Proterozoic infrabasin with depths to magnetic basement comparable with measured outcrop thicknesses on the southern flank of the Kimberley Block.

Future exploration plans for the region call for further seismic exploration and the drilling of medium depth wildcat tests to investigate the hydrocarbon potential of the region.