Conodont Biostratigraphy of the upper Devonian reef complexes of the Canning Basin, Western Australia

No abstract available

Twenty-five species of the Middle Cambrian Nepeidae of northern Australia are described; of these 10 are presented in open nomenclature, and 14 are named new. Four genera are recognized: Nepea Whitehouse and three new-Penarosa, Loxonepea, and FoIliceps. Of these Loxonepea is reminiscent of some Menomoniidae. The stratigraphic distribution is uneven; Nepea dominates in the Zone of Ptychagnostus nathorsti and Penarosa in the earlier zones. It is, however, apparent that they represent concurrent stocks. The older form to appear belongs to the Nepea stock. The currently used Middle Cambrian scale is essentially the Scandinavian agnostid scale of zones; the name Hypagnostus parvifrons Zone is, however, replaced by the name ElIagnostlls opimlls Zone. Collecting sites are described in superpositional order of strata. It appears that the nepeids lived in swarms floating most of the time in the surface waters. as inferred from the mode of embedding, from the occurrence in all kinds of sediments, the thin test, and the frontal boss-presumably a device to facilitate floating.

The McArthur Basin contains mainly mid-Proterozoic sedimentary rocks that form a platform cover sequence near the eastern edge of the North Australian Craton. The rocks are gently folded and faulted, unmetamorphosed, and appear to have been deposited in mostly shallow environments in an intracratonic basin, which at times was dominated by a prominent north-trending half-graben-the Batten Trough. The sequence in the southern half of the basin, the subject of this Bulletin, is divided by regional unconformities into four stratigraphic groups. The oldest, the Tawallah Group (about 4500 m thick), unconformably overlies crystalline basement that is about 1800 Ma old. Most of the group consists of thick formations of resistant quartz sandstone alternating with much thinner formations of deeply weathered basic volcanics and fine-grained elastics. <p>The oldest rocks are arkosic and conglomeratic, and mainly of continental origin. They are succeeded by monotonous, probably marine and aeolian orthoquartzites. The basic volcanics are poorly known, but include subaerial flows, intrusions, and volcaniclastics accompanied by iron formations and other redbeds. Rare units of stromatolitic dolostone similar to those higher in the basin succession are also present. The uppermost units are potassium-rich felsic igneous rocks which host the copper-bearing breccia pipes at Redbank, in the southeast. The unconformably overlying McArthur and Nathan Groups (combined thickness about 5500 m), which are separated by an unconformity, are dominated by formations consisting of evaporitic and stromatolitic cherty dolostones interbedded with dolomitic fine-grained elastics. <p>The formations, which are of shallow water origin and contain evidence of exposure and desiccation, were deposited mainly in peritidal, lagoonal, lacustrine, and possibly fluvial environments. A wide variety of evaporite pseudomorphs, solution-collapse breccias, and desiccation features, suggest dominantly arid climates. Tuffs in about the middle of the McArthur Group have yielded a U-Pb age of 1690125 Ma. The Roper Group (up to 2000 m thick), unconformably overlying the Nathan Group, consists of alternating resistant quartz sandstone and recessive micaceous siltstone and shale at least 1400 Ma old. Previous studies have identified three coarsening-up megacycles, which may represent major prograding episodes. Thin Cambrian and Cretaceous rocks (parts of other basin sequences) form discontinuous outliers in the west and south. <p>The structure of the southern McArthur Basin is dominated by the Batten Fault Zone (the site of the earlier Batten Trough), an eastward-deepening half-graben now expressed as a horst containing up to perhaps 12 km of sedimentary rock; the shelves either side of it contain only about 4 km of rock. During part of its history the basin sediments were deposited in pull-apart style sub-basins related to major northwest trending right-lateral wrench-faulting. Although no mines are presently operating, the McArthur Basin shows promising base-metal potential. The large shale-hosted McArthur River Pb-Zn deposits are well known. <p>Other prospects include <p>1) both discordant-vein and disseminated deposits of Pb-Zn, Pb-Ba, and Cu associated with karstically weathered rocks beneath unconformities, <p>2.) Cu-bearing breccia pipes, <p>3) stratabound disseminated Cu, <p>4) pisolitic Fe, and <p>5) U. <p>More recently a promising hydrocarbon potential has been identified: organic-rich shales occur at several levels; gaseous and solid hydrocarbons have been encountered during drilling; appropriate maturation levels have been indicated; and suitable reservoirs may occur within vuggy carbonates or among the extensive quartz arenites.

Legacy product - no abstract available

The authors have been engaged for the past four years in studying in the minutest details the material obtained from various borings in both the Lakes Entrance and the Stradbroke-Glencoe areas. This work has been done under the authority of the Department of Home Affairs at the Commonwealth Palaeontologist's Office at the National Museum, Melbourne. We would here like to acknowledge the exceptional facilities afforded by the Director and Trustees of the National Museum in making available to us their invaluable reference collection of fossils. We are also under great obligations to the officers of the Geological Survey of Victoria for their valuable help in facilitating the examination of the cores from the various bores here dealt with. We have examined six bores in the Lakes Entrance area, eleven bores in the Stradbroke-Glencoe areas, and eight quarry sections and surface samples from two bores in the Stradbroke-Glencoe areas. The bores and quarries are fully listed in sections Il and Ill. From the immense amount of details derived from the bore cores and quarry samples it has been possible to piece together conclusive evidence in regard to the sequence and age of the beds in East Gippsland.

This study arose out of the regional geological mapping of the Cairns Hinterland which was begun in 1956 as a joint undertaking by the Bureau of Mineral Resources and the Geological Survey of Queensland. It is another unit in the series of dating surveys stemming from the co-operation between the Australian National University and the Bureau of Mineral Resources. One of us (D.A.W.), assisted by F. de Keyser, was responsible for the supervision of the field operations connected with this study; another (C.D.B.) was concerned with the general investigation of these acid igneous rocks; the others (J.R.R. and A.W.W.) were assisted by J. A. Cooper in the production of the K-Ar results. We are indebted to W. Compston and M. J. Vernon for permission to publish the Rb-Sr results on the Palaeozoic rocks, and for assistance with measurements on the Croydon Volcanics. Samples were chosen with the aim of defining more closely the time limits of the two periods of activity that were thought to have produced the granites and acid volcanic rocks now covering about half the area. Regional mapping evidence had already suggested that a Precambrian age for the older granites was a reasonable possibility, and that the second event took place in the late Palaeozoic. Fossils collected by the mapping parties suggested that these periods were pre-Upper Ordovician and late Devonian/Carboniferous to Permian/Triassic (White, 1961). The present set of age data offers a most gratifying confirmation of some of these conclusions and provides a basis for the selection of samples for further study.

A selection of early Upper Cambrian trilobites from Queensland is described to lay a basis for zoning of the sequence and to gain knowledge of forms which are, or may become, useful in palaeogeography and in interprovincial correlation. The taxonomy and organization of the same fossils are studied. The zones of the sequence are conveniently grouped in two stages-the Idamean (above) and the Mindyallan (below). The basal Idamean fauna with Olenus ogilviei, and the uppermost with Irvingella tropica, are presented exhaustively. Lesser attention is paid to the Mindyallan fauna, which is rather large and which is studied separately. The paper is written essentially for readers concerned with the stratigraphy, correlation, and palaeontology of the Upper Cambrian of Australia. Some items of a more general interest, however, are also included. These are a discussion of the concepts of zones and stages and their nomenclature, and some problems of organization and suprageneric classification of trilobites. The source of material is the Commonwealth Palaeontological Collection, Bureau of Mineral Resources, Canberra. The fossils from the Glenormiston area were collected by a party of Bureau geologists led by J. N. Casey, and the writer participated in this enterprise. The fossils from the Selwyn Range and Pomegranate Creek area were collected by the writer. The complete specimens of Erixanium illustrated on Plate 9 were collected by Mr R. B. Leslie and party, Frome-Broken Hill Co. Pty Ltd, and kindly released for description by the Management of that Company.

This Bulletin deals with the groundwater resources of the central and eastern parts of the Barkly Tableland from the Queensland border westward to Tarrabool Lake and Rockhampton Downs homestead. This region comprises the Wallhallow, Brunette Downs, Alroy, Mount Drummond, Ranken, and Avon Downs 1:250,000 Sheet areas; it is bounded in the north by the headwaters of the McArthur, Clyde, and Nicholson Rivers, and in the south by the semidesert area which extends from near Tennant Creek east-south-eastwards to within a few miles west of Lake Nash homestead (Fig. 1). The region is served by the townships of Camooweal, 8 miles to the east on the Barkly Highway, and Tennant Creek, 70 miles to the west on the Stuart Highway. The bitumen-sealed Barkly Highway connects Mount Isa to Tennant Creek via Camooweal, and provides access to numerous station tracks and stock routes.

A spherical harmonic analysis has been made of the quiet-day diurnal variation of the geogmagnetic field during the IGY, based on mean hourly values from 64 observatories. Each of the 18 months has been analysed separately, and the coefficients have been averaged over each of four seasons. Fourier coefficients were expressed as functions of latitude and longitude by the Gram-Schmidt method, and non-significant coefficients of the orthogonal functions were discarded. The dependence on longitude was restricted so that only smooth departures from the local time dependence were allowed. The potential was derived by averaging that found from the east and north components. External and internal potentials were derived from the surface potential and vertical component. Ratios of, and phase differences between, the external and internal potentials were derived for each harmonic. They were also computed as functions of latitude and longitude, but no significant geographical distribution was found. The ratios and phase differences generally agree fairly well with those derived from earlier analyses. The amplitudes of the harmonics are generally about twice as great as those derived by Chapman for the 1905 data. This is probably because 1957 and 1958 were years of very high sunspot number. Tables of coefficients and maps of the elements and current functions are given.