SADME Byilkaoora no. 1 was drilled on the northeastern margin of the Officer Basin, in the Mt Johns Range, with the principal objective of coring a complete stratigraphic section of the Observatory Hill Beds. Good hydrocarbon source-rock potential had been determined for this sequence in SADME Wilkinson no. 1, 300 km to the south of Byilkaoora. This objective was accomplished. Byilkaoora no. 1 penetrated an ?Early Cambrian sequence of Trainor Hill Sandstone, Mt Johns Conglomerate, Observatory Hill Beds and Davies Bore Beds, and the underlying Rodda Beds of Adelaidean age, to a total depth of 496.7 m. Significant hydrocarbon shows were discovered in the Observatory Hill Beds, where a range of oil types bled from calcite veins and vugs in a carbonaceous carbonate/siltstone sequence. Ubiquitous suIphides in this sequence include chalcopyrite and sphalerite. A thick accumulation of evaporite-related sediments contains calcite pseudomorphs after minerals including shortite and trona. As a consequence Of Byilkaoora no. 1, Cambrian sediments in the eastern Officer Basin have asuamed an increased significance in hydrocarbon evaporite and metallic mineral search.