Detailed geological mapping of the Wilkatana and Augusta 1-mile mapsheet areas was completed by Geosurveys during the first quarter of 1955. This work revealed flat-lying sandstones and shales (of uncertain age - Cambrian or Ordovician?) overlying folded older or younger Proterozoic strata, west of the [Lake] Torrens [outflow] Valley. Intrusive dolerites and flow basalts were found near the base of the Torrensian Series outcropping east of the Pirie-Torrens Basin. A newly available airborne scintillometer technique, which was trialled over the Wilkatana area, proved unsuccessful. Further samples of crude oil were recovered from the artesian water bore at Wilkatana. During the second quarter of 1955, Geosurveys personnel held discussions with the SADM Geological Survey regarding (1) the wedge of the Flinders Ranges in the vicinity of Wilkatana; (2) the Lincoln map unconformity; and (3) the Tent Hill Formation. Drilling at Wilkatana: - by the end of July, Santos' Wilkatana 1 test hole, which had spudded on 1/6/1955, had been percussion drilled to 430 feet depth, and was in Tertiary sands and silts. Artesian groundwater coming to the surface from below 230 feet depth containned appreciable traces of light, honey-coloured, paraffin-base crude oil. Some conjecture is currently held as to whether this oil originates in bituminous (?sapropelitic) Tertiary lignites, or whether it has migrated into the Tertiary aquifer from the Tent Hill Formation or older rocks. A geophysical reconnaissance was conducted in the Oodnadatta region. This ground-based survey was hampered by abnormal rains, and so its conduct was suspended. 270 gravity stations occupied, located on airphotos. Results presented as Bouguer contour map. Accuracy low due to uncertainty in latitudes and altitudes, and terrain effects. Whole area strongly negative, increasing from west to east. Magnetometer survey of area represented by contour plan appearing to indicate basement depth throughout the area. Interpretation- approximately coinciding of negative gravity anomaly and area of low magnetic intensity indicates relatively deep sedimentary basin. Gravity picture suggests about 2,000 feet of sediments probably Tent Hill Formation or older. Plan of gravity contours superimposed on magnetic contours.