MSDP03 is one of four diamond drillholes drilled during 2015 in the Six Mile Hill area as part of the Mineral Systems Drilling Program (MSDP). The hole was drilled vertically to 262.6 m depth over the period 25/9/2015-2/10/2015, and intersected two units from the lower part of the Mesoproterozoic Gawler Range Volcanics, comprising a ‘felsic volcanic unit’ (10.3-102.2 m), and a ‘mafic volcanic unit’ (102.2-262.6 m). This report includes a graphic log, description and interpretation of the main geological features of the lower GRV units in MSDP03, based on detailed logging of both the physical drill core and high resolution core images, as well as thin section petrological observations. The ‘felsic volcanic unit’ is a massive, homogeneous, relatively crystal-rich (25-39 modal %) dacite, which contains phenocrysts of mainly plagioclase and subordinate replaced ferromagnesian minerals, alkali feldspar and rare quartz, set in an originally glassy groundmass. A weak flow foliation occurs near the base of the unit, which is also finely amygdaloidal and weakly brecciated. The dacite is regarded as a coherent body emplaced as a single unit, but, in the absence here of its upper contact, could be interpreted as either a lava flow or a high level sill. The ‘mafic volcanic unit’ comprises 6 mainly aphyric basalt flow units, ranging in thickness from 17-31 m. Many of these flow units have oxidised tops marked by patchy development of abundant small amygdales, which have been interpreted as probable flow-top breccia. The sequence also includes a 16 m thick interval which consists of lengths of coherent basalt to 1 m, which are separated by intervals (to >1 m) of dark, fine monomictic breccia. The boundaries between the basalt and breccia are smoothly curved and dark. This interval has been interpreted as a mixed breccia composed of small pillows or pillow fragments with a hyaloclastite matrix. The base of the mafic volcanic sequence is marked by normally graded pebbly to fine-grained volcaniclastic sandstone, which in thin section, contains a significant amount of felsic volcanic grains.