This report presents the results of a study jointly conducted by the Geological Survey of South Australia and CSIRO Mineral Resources which aimed to enhance the expression of geological structure in geophysical images and to derive depth to magnetic source estimates over Region 9A of the Gawler Craton Airborne Survey; viz. all of the TARCOOLA 1:250k map sheet area, plus the northern half of the CHILDARA 1:250k map sheet area. The study was based on magnetic field data, acquired during the period 5 November 2017 to 2 May 2018 by this airborne magnetic and radiometric survey commissioned by the Geological Survey of South Australia, that have been combined with ground gravity data from the South Australian state gravity database. The (now) 2017-2019 duration PACE Copper Gawler Craton Airborne Survey (GCAS) provides both higher resolution and more consistent mapping of the magnetic field than are available from previous coverage by multiple geophysical surveys of lesser extent. Advantages of the new survey data are quite evident upon inspection of the primary total magnetic intensity (TMI) data, but it is through the enhancement of that TMI data to assist in recovery of geological information that the advantages are most clearly expressed. Many of the enhancements presented in this report are necessarily of limited application to the TMI data previously obtained across the Gawler Craton area, mainly because of known numerous insufficiencies and imperfections in those data, and they would be hampered by the unavoidable effects of abrupt signal strength contrast that appear on passing between survey datasets acquired on different line spacings, flying heights or flight-line orientations. The GCAS data acquisition consistency and close line spacing therefore support higher resolution and more confident source depth mapping from the magnetic field data. Local magnetic field variations arise exclusively from ferromagnetic minerals which may only constitute of the order of 2% or less of the rock (even for what are considered strongly magnetised rocks), while lateral variations in geology which have no associated variation in magnetisation have no direct expression in the magnetic field imagery. In contrast, gravity data respond to variations in density, to which all components of the rock contribute. Gravity field variations therefore provide a complementary mapping of geology. Suitable combinations and contrasts of gravity and magnetic fields provide more diagnostic information about the subsurface than does the sum of the two fields processed and imaged independently. The output of this study is a collection of images and digital data products, downloadable herein, which have been generated to facilitate geological interpretation. The products are not themselves interpretive, but provide more direct access to interpretation than do directly measured datasets treated alone. These products, and in particular the magnetic source depth estimates, are designed to provide the genesis of a ‘live’ resource which can be progressively upgraded rather than simply being replaced when further studies are undertaken in the area, the depth solution database is added to, or when new drillhole information is reported. Within the Region 9A survey area, the SA state borehole database currently has 2835 entries for boreholes that were reported to have penetrated basement. This is a much higher number of holes than occur in many of the other GCAS survey areas, undoubtedly due substantially to the shallower level of basement which makes exploration by pattern drilling more viable. In the northern half of the survey area, where most of the holes are located, the application of magnetic studies to mapping basement depth at a regional scale is not required because of the density of the direct basement mapping done by each hole. Furthermore, the reduced basement depth substantially increases the percentage error in estimating depth from the magnetic field data, because those depth estimates have errors proportional to depth below sensor, which includes flying height. The major objective of geophysically estimating magnetic source depth is to augment true basement depths known from drilling data. This is generally achieved by suitable integration of the two depth sets, using the magnetic depths in those areas without or with insufficient boreholes. However, in Region 9A this is not feasible because of the substantial differences between the borehole and magnetic depth values, with each apparently mapping a different surface. Of the 2835 basement-penetrating boreholes on record, 1603 struck basement at a depth of 10 m or less, and 2090 at 20 m or less. These very shallow basement depths are not suited to depth mapping from magnetic field data acquired at 60 m above surface. Only 182 of the borehole top-of-basement depths (6.4% of the total) are 50 m or more, at which depths magnetic source depth mapping provides a more effective contribution in constraining basement depth. Two main factors are believed to be responsible for the said basement depth discrepancies: firstly, a deep weathering which forces the top of magnetisation (top of fresh rock) below the top of basement, with in some places a very considerable depth of weathering or palaeo-weathering. The second factor is that some reported borehole basement depths are suspiciously shallow, and may be based on the hardness of layers within cover that have been mistaken for the top-of-basement surface.