SADME Nanyah 1 (hole synonym M154), a Murray Basin hydrogeological observation bore, was extended beneath the sedimentary cover to reach basement in order to investigate the source of a prominent aeromagnetic anomaly. A 3-metre bottomhole core of mafic igneous rock was cut over the hole interval below 412 m depth. The upper 1.6 metres of core is basalt, separated from an underlying coarse-grained dolerite by a sharp contact dipping at 45 degrees. Textural relationships suggest that the dolerite is the older. Although these rocks' major and trace element geochemistry does not closely match that of other known igneous suites in South Australia, rock geochemical data plots suggest an affinity with the early Palaeozoic Kulyong Volcanics.