Lower Proterozoic sedimentary, metamorphic, and igneous rocks of the Pine Creek Geosyncline and Nimbuwah Complex form the basement rocks of the Bathurst Terrace. To the west of the Bathurst Terrace, along the eastern edge of the adjoining Bonaparte Gulf Basin, Phanerozoic sedimentation commenced in the Early Permian and led to the accumulation of a conformable sequence comprising the Kulshill, Hyland Bay, and Mount Goodwin Formations, and an unnamed Middle to Upper Triassic formation. It was not until the Late Jurassic that the sea transgressed onto the Bathurst Terrace to deposit the Petrel Formation, followed by the Bathurst Island Formation in the Cretaceous, and the Van Diemen Sandstone in the Early Tertiary. In the Late Cretaceous and Tertiary, chemical weathering produced an extensive cover of laterite. Mineral sands containing ilmenite, zircon, and rutile occur along the northern and western coasts of Bathurst and Melville Islands. Uneconomical deposits of bauxite crop out on the northern headlands of Cobourg Peninsula and Croker Island. In addition, uneconomical deposits of uranium, manganese, phosphate, limestone, clay, and hydrocarbons have been found in the area. Subartesian water is available on Bathurst and Melville Islands from aquifers in the Van Diemen Sandstone, and artesian water was discovered in the Marligur Member of the Bathurst Island Formation in the southern Cobourg Peninsula Sheet area.