AIM: The Colona Drilling Project aimed to test concealed basement in the vicinity of two ground magentic profiles that have been run across the most south-western, teardrop - shaped aeromagnetic anomaly of the Fowler Suture Zone. METHODS: 45 vertical RC holes were drilled for a total penetration of 3732 m. Five of the holes were abandoned within Cainozoic cover sediments, but the remainder successfully reached crystalline basement. Ten of the holes have bottomhole core. RESULTS: The Colona Drilling Project has provided significant new stratigraphic, structural, petrological and geochemical information for the southern Fowler Suture Zone. The granulite facies metamorphism seen in metabasalts and gabbros at Nundroo, 30 km to the south-southeast, was not detected in the Colona drillholes. The Colona diorites and gabbros show calcalkaline affinities whereas the basement mafic rocks encountered by earlier SADME drilling at Nundroo show disturbed tholeiitic and calcalkaline characteristics. Clearly the geological history of these two magnetically elongate domains is different. Their separation by major fault zones may indicate tectonic juxtaposition of very different terrains.