Blocks 90 B-E contain sediments from four superimposed basins, ranging from Cambrian to Recent in age (Fig 3). The Permian Pedirka Basin lies immediately to the west of Block 90B (Fig 2). Exploration activity in the area has concentrated on the Pedirka, Simpson and Eromanga Basin sequences. Ten petroleum exploration wells have been drilled in the area (Table 1), and fifteen seismic surveys conducted (Table 2) since 1964.