2.3.2 Summary of key system components, processes and interactions


The Cooper Basin is an Upper Carboniferous – Middle Triassic geological basin in north-eastern SA and south-western Queensland. The Cooper Basin is up to 2500 m thick, at subsurface depths of between 1000 and 4400 m. The southern Cooper Basin is marked by a series of troughs (e.g. Weena and Tenappera troughs) separated by ridges against which Permian sedimentary rocks thin or pinch out. The Cooper Basin unconformably overlies the Warburton Basin. Several granite bodies intrude the Warburton Basin and underlie the Cooper Basin. A thick alteration profile (clay-rich blanket) exists on the basal unconformity of the Cooper Basin.

The focus of the development of causal pathways is the Weena Trough and the southern Cooper subregion. This is due to the absence of any coal seam gas (CSG)-only developments identified in the rest of the subregion. There is the potential for CSG resources from interbedded shale and coal in other parts of the basin, such as the western flank, but such composite unconventional hydrocarbon resources are outside the scope of bioregional assessments (BAs). Rocks in the Weena Trough are interbedded fluvial sandstone, coal and shale. Cooper Basin strata above the Patchawarra Formation are not encountered. The Patchawarra Formation is therefore the uppermost unit of the Cooper Basin, directly underlying rocks of the Eromanga Basin. The Eromanga Basin is up to 1500 m thick. The geological Lake Eyre Basin is up to 400 m thick over the southern Cooper Basin. The Lake Eyre Basin sequence, comprising the basal Eyre Formation, the Namba Formation and Quaternary sediments, unconformably overlies the Winton Formation of the Eromanga Basin.

The watertable is hosted in the Namba Formation and Quaternary sediments, with regional flow south-westwards towards Lake Blanche. Groundwater within the Cadna-owie – Hooray Aquifer of the Great Artesian Basin flows south towards and beyond Lake Frome. Regional groundwater flow in the Cooper Basin is mainly towards the south-west.

The Rolling Downs Group aquitard is greater than 370 m thick. There is also a thick weathering overprint on the Winton Formation of about 100 m thickness which reduces the effective hydraulic conductivity of the Winton Formation.

There is limited recharge via diffuse infiltration of sporadic rain water, flood waters or streamflow to the groundwater system. The most significant source of groundwater recharge to the Eromanga Basin sequence in the Cooper subregion is inflow from outside the subregion. Recharge to the Cooper Basin occurs by vertical leakage or cross-formation flow.

The southern Cooper subregion is part of the Cooper Creek – Bulloo river basin. Cooper Creek is characterised by complex channel networks and numerous permanent and ephemeral wetlands. Water is derived from runoff from headwater catchments. Streamflow in Cooper Creek and its tributaries varies greatly between years from almost no flow to significant flooding.

Natural discharge to surface takes place at springs, as well as in lakes. The Lake Blanche springs are sourced from the Coorikiana Sandstone and Cenozoic aquifers via a fracture zone or fault pathway.

Last updated:
31 October 2018