This paper is another chapter in the long series of papers presented to APEA Conferences since 1964 on the geology of the Cooper Basin. The Patchawarra area became of interest after Bridge Oil on behalf of its partners discovered oil in the area while drilling Tirrawarra No. 1 as part of their obligations to earn a 50 percent interest in the area. This paper deals with the central part of the Patchawarra Gravity Low first described by the Author in 1966. The Tirrawarra Formation was deposited in the Patchawarra trough during early Permian. The Gidgealpa Innamincka trend constitutes the eastern boundary of this trough while the western boundary of the Patchawarra Gravity Low coincides with the western boundary of the Cooper Basin. Sedimentation during the Permian in the Cooper Basin is controlled regionally by the major structural trends such as, the Gidgealpa Innamincka Trend, but hiatii and minor local unconformities also developed around individual structrues. The major unconformity recognised in the Patchawarra Low occurs between the Upper Permian Toolachee Formation and the Lower Permian Moomba Formation.