During the Mineral Systems Drilling Program (MSDP) in 2015, four diamond holes were drilled in the Six Mile Hill area, on the southeast margin of the Gawler Ranges. Three of these drillholes intersected a succession of mafic and felsic volcanics of the lower Gawler Range Volcanics in excess of 1,100 m thick that contrasts dramatically with that recorded at Roopena, only 25 km to the south, where they are significantly thinner (<250 m) and comprise mafic volcanics interlayered with volcaniclastic lacustrine sediments This article summarises the key features of MSDP01, which reached a depth of 1,116.8 m, and intersected the thickest sequence of volcanics. The interpreted depositional environment for the Gawler Range Volcanics at Six Mile Hill is a broadly low-relief depositional basin, which fluctuated between subaerial and subaqueous settings, the latter occurring after basalt lava flows blocked watercourses to form lakes of moderate depth and probably substantial size. The most likely basalt sources in a relatively large lava field are either fissures or shield volcanoes.