Callabonna Uranium's successful PACE Year 6 drilling project proposal was designed to test a number of exploration models for sedimentary uranium in the greenfields setting of the northern Callabonna Sub-basin, beyond the restricted areas that conventional exploration approaches would drill within to find extensions to known secondary uranium mineralisation and to trace inferred fluvial palaeochannels. The proposal made was to drill several regional traverses that overlap, so as to obtain subsurface information that should give a basin-wide understanding of the target strata and of important regional redox conditions and structures that could control sedimentary uranium mineralisation. It was hoped that this work and other ongoing exploration of the subject licences which presently cover a total area of 3370 square km might lead to making large new uranium discoveries of the sandstone-hosted style in this part of the sub-basin, where to date there has been no effective uranium exploration. The project area also straddles the north-eastern margin of the Curnamona Craton, a region of basement potential so far neglected by uranium explorers. All of the known uranium deposits have been found either along the craton's southern margin near outcropping Precambrian source rocks (e.g. Honeymoon), or near its north-western margin in the Mount Painter area (e.g. Beverley). In detail, the proposed PACE-subsidised drilling traverses were intended to test the following alternative exploration models: 1. The channel versus strandline hypothesis, to explain the large linear sand bodies interpreted here. For example, in the Texas Gulf uranium province the uranium-mineralised sand bodies are strandlines running parallel to the shoreline. 2. Various regional redox conditions, which are regarded as important controls on the very large sandstone-hosted uranium deposits. For example, most of the deposits in the San Juan Basin lie on a regional redox boundary close to the Jurassic Morrison Formation. Here there are also spatial relationships with the Cretaceous boundary, coal deposits and oil and gas accumulations. The presence of the latter may bear on the ability to reduce mobile uranium in the basin, and this factor is also relevant in the Callabonna Sub-basin. 3. A structural model that could leak methane from the reduced Mezozoic Bulldog Shale via faults into the Tertiary Namba Formation, to fix uranium. The proposed PACE drilling was designed to cross structures inferred from magnetic and gravity basement interpretations. 4. The layer cake versus transgressive sequence model. For example, sand channels could persist (transgress) upward in the stratigraphy and grade laterally into more clay. This was the present interpretation held for the Callabonna Sub-basin. However, one interpretation of the Kazak Basin uranium occurrences is of layer cake stratigraphy hosting sinuous redox roll-fronts sandwiched between the strata. In plan view these appear as channel-like features. Callabonna Uranium's Phase 1 drilling programme, which included the PACE Year 6 drillholes, was primarily aimed at fluvial palaeochannel targets defined by the company's airborne EM survey flown in April 2008 across the entire Curnamona North Project area (total coverage 3684 line km). For the PACE-assisted drilling component, 72 vertical rotary mud or aircore drillholes with a total penetration of 9041 m were completed along 5 traverses in the central-northern Quinyambie region, in two campaigns undertaken during October-November 2009 and May-July 2010. Six of the drillholes had to be abandoned before reaching their targets, but overall the programme was executed satisfactorily. Gamma ray logged indications [through drill rods] of minor elevated uranium content (to 85 ppm eU3O8) were detected within several adjacent drillholes put in at one location where lower Eyre Formation sands and clays are overlain by a lignitic unit. However, the best recorded intercept of an average 43.4 ppm eU3O8, made over a 2.5 m thick interval in hole CUN034, was not considered to be economically significant. The focus of the company's future exploration activities will now be shifted to its Curnamona South Project licences, as well as to the western portion of the subject Curnamona North Project acreage, to be closer to the Beverley uranium mine and to interpreted palaeochannels which drain the highly radioactive Mount Painter Block.