1.1.3 Geology


The principal geological province in the Galilee subregion is the crescent-shaped, intracratonic geological Galilee Basin, which covers about 248,000 km2 of central Queensland. Other geological features of interest for this bioregional assessment subregion include the younger sedimentary sequences of the Eromanga Basin, and the overlying Cenozoic river and lake deposits which have formed over the last 60 million years. These three distinctive packages of sedimentary deposition cover an important period of Australia’s geological history, including the major episodes of coal formation in the Permian to Triassic and Jurassic to Cretaceous.

The Galilee Basin is infilled with a mixed assemblage of clastic sedimentary rocks dominated by thick successions of sandstone, mudstone and coal. These rocks were deposited in terrestrial (rivers, lakes and swamps) and marginal marine (deltas and shallow continental slopes) environments from the Late Carboniferous to the Middle Triassic, approximately 323 to 238 million years ago. The maximum stratigraphic thickness in the Galilee Basin is about 2800 metres. The thickest rock sequences occur in structurally controlled depositional centres, such as the Koburra Trough and Lovelle Depression in the northern Galilee Basin and the Powell Depression in the southern Galilee Basin. Underlying the Galilee Basin are several older Paleozoic basins (the Drummond, Belyando and Adavale basins) as well as the basement crystalline rock terranes of the Thompson Orogen and the Mount Isa Inlier.

Surface exposures of Galilee Basin rocks occur only along the eastern margin of the basin, forming an elongated band about 600 km long and up to 80 km wide. West of this outcrop zone the Galilee Basin strata are buried under geologically younger sedimentary deposits such as the Mesozoic rocks of the Eromanga Basin, and the widespread but relatively thin veneer of terrestrial Cenozoic sediments. Deposition within the Eromanga Basin occurred from the Middle Jurassic to the Late Cretaceous, around 175 to 95 million years ago. The Eromanga Basin contains thick sequences of sandstone, mudstone and shale which formed in various depositional settings, such as rivers, lakes, swamps and shallow marine environments.

Multiple stratigraphic units in the Galilee Basin contain significant black coal resources, particularly the Early Permian Aramac Coal Measures and the Late Permian assemblage comprising of the Betts Creek beds, Bandanna Formation and Colinlea Sandstone. Although there are currently no mines in production, existing development plans are proposed for six mines. Some coal resources have also been defined in parts of the upper sequence of the Eromanga Basin (Winton Formation).

The Galilee Basin also has potential for future development of coal seam gas resources. To date, significant greenfield exploration programs have been undertaken in parts of the northern Galilee Basin, with two pilot well fields established in the Aramac Trough.

This geological overview of the Galilee subregion has synthesised the existing geoscientific knowledge of the Galilee Basin and the overlying sedimentary deposits formed in the Mesozoic (Eromanga Basin) and the more recent Cenozoic Era. New outputs herein include an updated stratigraphic column that integrates (for the first time) the stratigraphic framework for the Galilee and Eromanga basins, as well as the overlying Cenozoic deposits. Additionally, several new maps have been compiled to illustrate key components of the regional surface geology and structural architecture of the Galilee subregion.

Last updated:
5 January 2018