An area located along the Marree - Alice Springs Railway in the region of Curdimurka was selected to be explored on the basis of its potential to contain deposits of bedded trona in closed basins, and to have sodium carbonate brines present in near surface aquifers. Alkaline artesian spring groundwaters rich in sodium carbonate, that are discharging along the southern rim of the Great Artesian Basin, were regarded as likely sources of soda. Subsequent field reconnaissance indicated some additional potential for identifying sodium bentonite clays, based on a small discovery made adjacent to a trona-rich spring at Reedy Springs. Field investigations and an auger drilling programe (22 holes for 110 m) carried out by Consolidated Gold Fields failed to locate any bedded trona deposit, but a sub-economic size sodium bentonite clay occurrence was discovered, developed in Marree Formation shales around the Davenport Springs. Besides this, minor surface occurrences of trona, nahcolite and sodium bentonite were identified around various other artesian mound springs in the general area bordering Lake Eyre South. Field examination suggested that the bentonitic clays had formed within restricted alteration haloes surrounding the drainage lines from active mound springs, in a process whereby the sodium carbonate - rich groundwater discharging through fault-brecciated montmorillonite shales had partially beneficiated these clayey rocks into bentonite via the cation exchange of sodium for calcium. In late 1978, a joint venture was set up with Comalco to conduct stratigraphic drilling through the Cretaceous cover sequence to try to find significant subsurface occurrences of sodium carbonate - enriched brines. However, a new-found appreciation of the presence in the licence area since late Tertiary times of a widespread gypsite surface was considered to be a serious inhibiting factor to the creation of bedded trona deposits. Comalco's examination of numerous shale outcrops in deeply incised gullies around the mound springs showed that, although the top metre or so of Marree Formation is deeply weathered and has the appearance of bentonitic shale, below the surface alteration the shale is fresh and did not exhibit any notable swelling behaviour during field tests. Away from the spring drainage lines the shales appeared fresh and highly gypsiferous. A study was made of past wellhead measurements of groundwater quality, for the distribution of alkalinity, which defined sodium carbonate water chemistry anomalies as high as 850 ppm Na2CO3; the best of these wase rotary mud drilled to basement (1 hole for 146 m) and geophysically logged during November 1978, to test for the number of contributory aquifers and the respective composition of their waters. Unexpectedly, this drilling proved that there are no shallow intermediate aquifers within the Cretaceous sequence, by encountering only one basal Cretaceous aquifer which was very thin (3 to 4 m), indicating rapid pinchout of the porous unit towards the rim of the basin. The other, easternmost two drillholes of this campaign, sited within the JV's adjoining EL 355 Marree, were plugged after penetrating hard grey Adelaidean 'basement' quartzite.