During 1977-78, 32 fossiliferous Lower Devonian quartzite boulders were discovered entrained within Mesozoic sediments along the south-western margin of the Great Australian Basin. Previously only 2 specimens of such rocks had been discovered in South Australia, although similar occurrences in New South Wales had been known about since 1898. The boulders contain several fossils of types not previously recorded in South Australia, including the fish, Wuttagoonaspis; the brachiopods Howellella jaqueti and Sphaerirhynchia sp.; the bivalves Leptodesma inflatum, Sanguinolites sp. and Praectenodonta sp.; the gastropod Straparollus culleni; and abundant tentaculitids. Similar fossiliferous Devonian rocks are not known to occur in situ anywhere in South Australia. The probable source area for the boulders is in New South Wales, at outcrops of the fossiliferous Amphitheatre and Mulga Downs Groups near Cobar. It is suggested that the boulders were transported to South Australia during the Permian glaciation, and were then reworked into Cretaceous bouldery shales and sands. All but two of the boulders have been found within conglomeratic sediments at the base of the Bulldog Shale. Theories on transport processes during the Cretaceous are discussed; it is concluded that conglomeratic sediments at the base of the Bulldog Shale are reworked debris-flow deposits.