This report describes the results of a MESA consultant's second generation regional geological mapping and drillhole data interpretation work for the Roopena and Uno 1:100 000 sheets on PORT AUGUSTA, performed during 1993 and 1994 as part of the SAEI program, and designed to incorporate an interpretation of recently acquired SAEI detailed aeromagnetic data (part of the B4 survey). The project's aim was to produce a reliable and comprehensive compilation of information on economically significant mineralisation aspects of each mapsheet area, which could be used by future explorers in assessing local exploration potential. Salient elements of this database, which is available from MESA in digital CD-ROM or hardcopy format, consist of a summary geological report, detailed maps of outcrop geology, interpreted maps of pre-Tertiary geology, aeromagnetic TMI images in colour, maps of drillhole and drill traverse locations, a drillhole data spreadsheet which includes stratigraphy and geochemistry plus notes about mineral occurrence and rock alteration fabrics, and macrolithological descriptions of outcrop rock chip samples. A list of selected references pertinent to understanding the geological and tectonic setting of the areas studied in a regional context within the Gawler Craton also forms part of the summary report. Because of time constraints imposed on this project, the following limitations were found necessary to the conduct of a full remapping exercise: - new stratigraphic names were not applied to those rock units which show only a tenuous correlation with the existing stratigraphy; - mapping concentrated on pre-Pandurra Formation rock units, so the northeastern portion of Roopena sheet was not mapped beyond the outcrop of these rocks; - the Gawler Range Volcanics were not remapped; - the Tertiary and Quaternary sediments were not remapped; - only cursory attention was given to structural details; - only very limited petrology was carried out; - no geochemistry or isotope dating was carried out.