This work was undertaken to try to determine the age relationships between the various formations in the Moonabie Range, namely, the Moonabie Grit, the Moonabie Porphyry and the Corunna Conglomerate. The stratigraphic relationships that were observed to exist between the Moonabie Grit, the Moonabie Porphyry and the Corunna Conglomerate in the northern Eyre Peninsula have not in the past been clearly understood. Absolute age determinations currently being carried out at the Australian National University, in conjunction with the South Australian Department of Mines, are being used to assist in resolving the mapping problems presented by these rocks, but it was desired to now obtain as much independent geological evidence on the age relations of these rocks as possible, mainly by petrological study, in order to check the relative results obtained from the absolute age determinations, as the use of these techniques may not yet be fully reliable. The South Australian Department of Mines therefore asked that a petrologist at Amdel examine in detail a small area in which the Moonabie Grit, the Moonabie Porphyry and the Corunna Conglomerate all occur, namely, the Moonabie Range. The area studied is about one mile wide, from east to west, and extends southwards for about 1.5 miles from the Lincoln Highway where it crosses the range.