Logging of sludge samples taken from 18 water bores drilled in an area of previously unknown stratigraphy located between Watson and Maralinga has established a sequence of about 1000 feet of Marinoan shales and sandstones resting on diorite. These are overlain by a thin series of kaolinised grits, of either Permian fluvio-glacial origin or of Mesozoic age, with reworked Permian glacigenes. These are followed also by thin paralic Eocene silts and limestones, with a thick cover of Tertiary to Recent terrestrial sands. Extension of the Eucla Basin to the north is disproved, though there has been over-deepening of the Marinoan in the Tietkins Plains area, probably as the result of Permian glaciation.