Springs comprising the Barcaldine supergroup occur over a 330 x 100 km area. They are concentrated in two lines: a western line of predominantly discharge springs and an eastern line comprising outcrop springs. There are also non-GAB springs emanating from local Tertiary sandstone aquifers to the west, east and south of the supergroup.

The outcrop springs within the Barcaldine supergroup occur towards the eastern margin of the Eromanga Basin where the sediments comprising aquifer units are outcropping. The springs typically occur in relatively flat terrain where there is outcropping sandstone. Most of these springs have been excavated and for some the water level is below the rim of the excavated sandstone.

The discharge springs extend in a north-south line. In the middle section this line of springs is associated with the floodplains of the tributaries of Aramac Creek, and in the northern section by the floodplain of Thunderbolt Creek. These sections are intersected by a residual plateau. In the far south and a long way from other springs in the line are the Northampton Hotel springs to the east-south-east of Blackall.

These springs (with the exception of the Northhampton Hotel Springs) almost certainly emanate from the Ronlow Beds/Hooray Sandstone where erosion has thinned or bisected the overlying Wallumbilla Formation. The springs occur along the margin of where the potentiometric surface in the Hooray Sandstone becomes artesian.

Additional information

• Section 3 of the DSITI 2015, Lake Eyre Basin Springs Assessment Final Report, Queensland Government, Brisbane.

Stratigraphic sections bisecting this line of springs suggest that they occur where there is a coincidence of a relatively thin confining layer and artesian pressure. Further to the east of this line there is insufficient aquifer pressure to provide artesian flow, and west of this line the aquitard may be too thick for a flow path to form. Where the springs occur the Wallumbilla formation generally between 40 and 100m m deep, but it may be considerably reduced where current streams enhanced erosion. The Wallumbilla Formation may include permeable beds sufficient to transmit discharge from the underlying sandstone over such distances.

There is also evidence of fault structures in some locations, such as at Corinda and Coreena , that faulting may be allowing discharge through fractures in the aquitard.

Additional information

• Section 3 of the DSITI 2015, Lake Eyre Basin Springs Assessment Final Report, Queensland Government, Brisbane.