The MARREE mapsheet area lies in arid country about 400 miles north of Adelaide, South Australia. It includes the town of Marree, on the Alice Springs railway line, and part of the Birdsville and Strzelecki tracks. The area is covered mainly by flat lying Mesozoic and younger rocks of the Great Australian Artesian Basin. In the south-east is a small segment of the northern Flinders Ranges containing a granitic core, the Mount Painter Complex, flanked by folded and faulted upper Precambrian tillite, dolomite, siltstone and quartzite of the Umberatana and Willpena Groups of the Adelaide System. The edge of the Willouran Ranges occurs in the south-west and features a diapir composed of the Callanna Beds of the Adelaide System intruding the overlying Burra and Umberatana Groups. Near Marree the marginal Artesian Basin unit is an Aptian boulder-bearing bed termed the Wilpoorinna Breccia Member of the Marree Formation. In the south-east the lowermost marginal unit is the sandy Village Well Formation, overlain by a bouldery unit, the Pelican Well Formation. These last two formations are probably equivalent to the upper part of the Blythesdale Group of Queensland, and are overlain by the Trinity Well Sandstone Member of the Marree Formation. The Marree Formation is composed of grey Aptian and Albian shales, claystones, minor siltstone, sandstone and concretionary limestone and ironstone. It is broadly equivalent to the Cretaceous Roma and Tambo Formations of Queensland and is overlain by the predominantly sandy Blanchewater Formation which contains Albian fossils in its lower part. The lower Tertiary is represented by the sandy Murnpeowie Formation, the upper part of which is usually silicified to form a duricrust. The Etadunna Formation occurs in the north-west, near Lake Eyre, as low cliffs of dolomite and green clay. The main Quaternary deposits are higher level outwash gravels, gypsum sheets and longitudinal sand ridge systems. Cretaceous and Tertiary beds are gently folded, probably in response to basement folding; the main structure is the Cooryanna dome, which is elongated in a north-south direction. Near Blanchewater there are local steep monoclines. Peachawarinna bore, the deepest artesian bore in the area, lies in the north-west and taps the Blythesdale aquifer at a depth of nearly 2,484 feet. High grade talc is obtained from the Mount Fitton deposits in the south-east.