On the western side of Cape York Peninsula, north Queensland (Fig. 1), in the Weipa-Aurukum area, surface water supplies are seasonal, and mining and pastoral development relies on the availability of groundwater. Artesian water is obtainable from the Mesozoic sandstone units of the Carpentaria Basin throughout the area, but the water is slightly saline (1000 ppm total dissolved salts) and unacceptably high in fluorine (around 15 ppm). Domestic and stock water is taken almost entirely from shallow aquifers within the late Cretaceous or early Tertiary Bulimba Formation, which underlies most of the area and supplies all the domestic and some of the processing water at Weipa and the domestic and irrigation water at Aurukun Mission. Because of the variable permeability of the Bulimba Formation pattern drilling is expensive for groundwater investigations on a large scale; in the area studied drilling alone had a 1 in 35 success rate. There is a need for a cheap reconnaissance geophysical method to locate favourable areas for drilling. The purpose of this note is to describe a resistivity traversing technique, supported by drilling, which was developed in a detailed geophysical and geological study (Pettifer et al., 1976) of a test area between Weipa and Aurukum, and to outline some interesting aspects of the use of resistivity methods in this type of environment.

The Carlo Sandstone is part of the Toko Group of the Georgina Basin. This basin, which straddles the Northern Territory-Queensland border, comprises carbonate and clastic rocks of Cambrian and Early Ordovician age; the Toko Group forms the uppermost and dominantly clastic part of the sequence. The Carlo Sandstone, which is of possible Early Ordovician age (? latest Arenig), consists of very fine to fine quartzose sandstone containing siltstone and mudstone pellets. Minor siltstone and mudstone interbeds are present. The unit is conformable with the underlying Nora and overlying Mithaka Formations. Sedimentary structures present include: flute marks, current crescents, various other current lineations, ripple-marks, cross stratification, lamination and various biogenic sedimentary structures. The palaeocurrent measurements indicate uni-directional currents. Fossils are rare except in the uppermost part of the unit where gastropods, pelecypods, nautiloids, trilobites, brachiopods and fish are present. A study of geometry, lithology, sedimentary structures, palaeocurrents and fossils indicate subtidal to intertidal depositional conditions. Of various depositional models, a barrier model is favoured. The Nora Formation represents the offshore, below wave base sediments; the Carlo Sandstone the barrier, either dunes or bars; and the Mithaka Formation the lagoon-bay sediments. The sediments were deposited in an elongate epicontinental sea that also covered the Amadeus, Wiso and Canning Basins.

Five new Carboniferous to Permian palynological Oppel-zones have been identified through detailed analyses of core samples taken from the Joe Joe Group sediments of the Galilee Basin. In ascending stratigraphic order, and in relation to their host formations , the Oppel-zones are: the Verrucosisporites basiliscutis Oppel-zone (A), spanning the Lake Galilee Sandstone and the basal Jericho Formation; the Brevitriletes leptoacaina Oppel-zone (B), in the mid-Jericho Formation ; the Diatomozonotriletes birkheadensis Oppel-zone (C), in the upper Jericho Formation; the Asperispora reticulatispinosus Oppel-zone (D), encompassing much of the Jochmus Formation and the uppermost part of Jericho Formation (including the Oakleigh Siltstone Member); and the Microbaculispora tentula Oppel-zone (E), in the upper part of the Jochmus Formation. The three oldest Oppel-zones are grouped to form the Carboniferous (Namurian A-upper Westphalian D) Spelaeotriletes queenslandensis Superzone, which correlates with the Spelaeotriletes ybertii Assemblage of earlier workers. The overlying Asperispora reticulatispinosus Oppel-zone (D) (upper Westphalian D-Upper Autunian, or early Asselian) mostly correlates with the Potonieisporites Assemblage. The uppermost Microbaculispora tentula Oppel-zone (E), late Autunian (late Carboniferous) to early Tastubian (Early Permian), correlates with the Upper Stage 2. Application of the Oppel-zones has clarified relationships between outcrop sections of the earlier defined Joe Joe Formation of the Galilee Basin and lithological units subsequently identified in the sub-surface. Stratigraphic interpretation of the Oppel-zones with their lithostratigraphic equivalents suggests that late Palaeozoic glaciation began in the Westphalian D and continued until the late Asselian/earliest Tastubian, when climatic warming resulted in sea level rise associated with continental glacial melting. The palynological record shows the impact of this glacial episode, which caused significant global compositional changes in palynofloras in the Late Carboniferous/Early Permian. These changes may allow correlations between Gondwana and Laurasia. Eleven new species of miospore are described.

The North Australian Element (NAE) is one of the most richly endowed cratonic blocks in the world, containing major Zn-Pb, U, Cu-Au, diamond and Au deposits as well as smaller deposits with a range of other commodities. This richness results from a complex tectonic history extending from the Archean through to the Paleozoic. The NAE largely assembled before ~1840 Ma through accretion of the Kimberley and Pine Creek provinces from the northwest, the Numil-Kowanyama Province from the east and Aileron Province from the south onto a proto-NAE comprising the Tanami-Tennant and Isa provinces. The last major growth of the NAE occurred during accretion of the Warumpi Province from the south at ~1640 Ma. This overlapped development of the North Australian Basin System along the eastern flank between ~1800 Ma and 1540 Ma. Since then the NAE has been affected by 1540-1500 Ma A-type magmatism, Meso- to Neoproterzoic alkaline magmatic events, and the development of the intracratonic Neoproterozoic-Paleozoic Centralian superbasin, which was terminated by Paleozoic inversion associated with accretion in the Tasman Element to the east. The oldest significant mineral deposits - VHMS, orthomagmatic Ni-Cu-PGE and REE deposits - relate to convergence and docking of the Kimberley and Pine Creek provinces at 1865-1830 Ma. The ~1850-1845 Ma Tennant Creek IOCG event may relate to convergence of the Aileron Province. Small VHMS (1810-1765 Ma) deposits and, possibly, the Tanami and Pine Creek lode gold provinces (1810-1795 Ma) relate to north-dipping subduction along the southern margin of the NAE. Syn- to post-collisional magmatism associated with the Strangways event, which terminated subduction, produced widespread but relatively minor W-Mo and Sn deposits at 1740-1720 Ma. Development of the North Australian Basin System was accompanied by U (1740-1610 Ma) and Zn-Pb (1690-1575 Ma) events, many of which correspond in time to bends in the apparent polar wander path. The last Mesoproterozoic mineralising events in the NAE occurred at 1540-1500 Ma, involving IOCG, sediment-hosted Cu, and apatite-REE-U-Th vein deposits. Between ~1500 Ma and initiation of the Centralian Basin System at ~850 Ma, mineralisation was associated with alkaline magmatism, including one of the world's the world's largest diamondiferous diatreme at ~1180 Ma. The most recent period of mineralisation accompanied inversion of the Centralian superbasin and included ~360 Ma MVT and ~320 Ma lode gold deposits.