Series of information sheets designed to provide landholders and local community with information regarding the activities being underatken as part of the Southern Thomson pre-competitive geoscience project, run in collaboration with the Queensland and New South Wales State Geological Surveys.

The Central Queensland Seismographic Network consisting of four short-period seismographs was established between May 1990 and March 1991 by the University of Central Queensland, the Bureau of Mineral Resources and the Queensland Department of Resource Industries. These stations have been located to provide coverage over approximately 70 000 km2 of central Queensland where the earthquake hazard and risk are above average for continental Australia. The network has enabled discriminants to be devised to distinguish local earthquakes from large blasts at the coal mines and quarries in the region; travel times from blasts are being used for studies of local crustal structure. Several small local and regional earthquakes have been detected in the short period of network operation; their relationship to the regions tectonic history is being assessed. The intensity in Rockhampton of the June 1918 Bundaberg earthquake, the largest known earthquake along the eastern seaboard of Australia, is re-evaluated. The area of strong shaking was larger than originally supposed and alluvial areas of downtown Rockhampton were subject to significant amplification of ground motion.

In Cape York Peninsula ferricrete is found in a wide variety of locations, including scarp edges, lower valley slopes, around surface depressions, on gently sloping interfluves and on recently eroded surfaces. Ferricretes are not associated with any particular geomorphic surfaces, but rather occur where conditions are suitable for iron accumulation and hardening. In general, these conditions are found in the mottled zones of deep weathering profiles, where the mottled zones cement after exposure at the surface, and in lower parts of the landscape, where iron moves laterally to the surface and cements whatever regolith materials may be present. There is no evidence for former extensive covers of ferricrete, nor is there any evidence for particular periods of ferricrete formation. Ferricrete continues to form at present. It is therefore unreliable for determining either relative ages of geomorphic surfaces, or correlating widespread bodies of regolith.

The Coolibah Formation outcropping around the Toko Syncline, southeastern Georgina Basin, was sampled for conodonts during a multidisciplinary study of Georgina Basin geology by the Australian Geological Survey organisation. Twenty-two species of conodonts belonging to 17 genera recovered from acid insoluble residues are described. Alcoorina and Tokoconus are new genera; Alcoorina nadala, Bergstroemognathus kirki and Tokoconus wheelamanensis are previously undescribed species. Four species remain in open nomenclature awaiting more material. The conodont faunas are grouped into three broad biostratigraphic associations, although few sections record all three. Faunas low in the Coolibah Formation are dominated by Drepanoistodus costatus (Abaimova) and Scolopodus multicostatus Barnes and Tuke, with Diaphorodus tortus (McTavish), Scandodus sp. nov. A and hyaline conical elements. The succeeding conodont association records first appearances of Ansella fengxiangensis (An and others). Aurilobodus? leptosomatus An. Paroistodus originalis (Sergeeva). Protoprioniodus nyinti Cooper. and Triangulodus larapintinensis (Crespin). Specimens of younger species are found in the uppermost Coolibah Formation. Examination of these associations within different sections indicates that both upper and lower contacts of the Coolibah Formation are probably diachronous. Recovered conodonts are closest in affinity to those of North China, and North and South Korea. They range in age from middle to late Arenig.

The Iverian Stage is proposed for the concept of a post-Idamean/pre-Payntonian, Late Cambrian, interval in the eastern Georgina Basin, western Queensland. Designation and definition of this stage completes the local stadial biochronological scheme for the Upper Cambrian platform sequences of Australia and conterminous regions. Lithostratigraphic and biostratigraphic material diagnostic of this stage in its type area is integrated and correlated within Australia and globally. In the interests of simplification and clarification, it is suggested that a generic zone concept be overlaid on the current assemblage-zone biostratigraphic scheme for the Iverian Stage.

Planktic and larger benthic foraminiferids have been studied in thin section from a suite of dredge samples of two sites on the Marion Plateau, offshore Queensland. The two sites gave different results. (1) The northern site sampled an Early to Middle Miocene carbonate platform, with shallow-water foraminiferal assemblages. This limestone has solution cavities (developed during periods of subaerial exposure) infilled with Late Miocene shallow-water planktic foraminiferid-bearing sediments. The rock is cross-cut by several generations of mud-filled borings. Some of the fill in these borings could be biostratigraphically dated, with ages ranging from Pliocene to Pleistocene. (2) At the southern site, a Late Miocene carbonate platform was sampled; the only sample recovered was a limestone slab consisting of a late Miocene rhodolith-bearing floatstone with a marine hardground overlain by a condensed section of phosphatic wackestone of Pliocene age. A series of mounds is present down the slope from the Late Miocene platform sampling site; these also were sampled and were found to be of probable Pliocene and probable Pleistocene age (Zones N.18 and N.22). Water depths for the deposition of the platform phase were shallow, probably less than 50 m, as testified by the presence at the northern site of large benthic foraminiferids, Halimeda , hermatypic corals, and nodular coralline algae. The cavity-fill sediments, probably typical of the overlying sediments, have good planktic foraminiferal faunas, but also include some shallow-water faunal components (Amphistegina) and reworked older faunas (Lepidocyclina). The infilled borings tend to be almost totally composed of planktic foraminiferids, as do some discrete samples. This faunal evidence indicates that for the northern platform no deposition took place during much of the Middle Miocene and early Late Miocene, probably due to a long period of subaerial exposure. During the Late Miocene, the northern platform slope was flooded and subsided to its present depth by the Pleistocene. The southern platform was built during the Late Miocene and subsided to its present depth in the Pliocene. Samples from the mounds contain shallow-water assemblages of two ages: one may be of similar Pliocene age as found on the platform sites, and another of probable Pleistocene age. The presence of hermatypic corals, Halimeda, and larger benthic foraminiferids suggest warm surface water temperatures since the Early Miocene.

The Queensland Trough is a 155°-trending bathymetric deep, located just seaward of the Great Barrier Reef of northeast Australia. The trough reaches a maximum depth of 2800 m, separating the continental shelf and the submerged Queensland Plateau. It is underlain by extended continental crust. This preliminary interpretation of the troughs deep structure uses 3700 km of 1970s vintage seismic data, supplemented by gravity and magnetic data from the same surveys. The main seismic profile grid has a spacing of approximately 50 km. However, another survey shot in a zigzag pattern provides line spacing locally as close as a few kilometers. Acoustic basement, characterized by a chaotic and indistinct seismic signature with rare, discontinuous steeply dipping reflections, is overlain by two main acousto-stratigraphic megasequences within the trough: (1) The post-rift section comprises flat-lying , continuous reflections and extends up to two seconds two-way travel time (TWT) below the water bottom. (2) The syn-rift section consists of moderately dipping semi-continuous reflections, separated by zones of chaotic reflections and diffractions. The reflection separating the syn- and post-rift packages is quite distinct, characterized by angular discordances and truncated reflections. No wells have penetrated the syn-rift package. Seismic profiles in all orientations reveal tilted basement fault blocks . Many bounding faults are clearly listric. Half-graben form a series of syn-rift depocenters with up to 5 km of syn-rift fill. Syn-rift depocenters appear to be elongate along the axis of the trough, suggesting rift-parallel bounding faults and orthogonal extension. However, no structures parallel or perpendicular to the trough axis have been recognized. Most of the syn-rift depocenters are composed of two or more smaller "deeps". Two rifting models provide alternative syn-rift structural interpretations: (1) Curvilinear faults, based on a model derived from the East African Rift where the tectonic transport direction has been shown to be oblique to the rift axis, define a series of half-graben. Accommodation zones and half-graben polarity switches are identified from profile and plan-view geometries. (2) Nearly rectilinear 110°_ and 020o -striking faults, based on orthogonal extension models, predominate. However, both of these trends are oblique to the rift axis contrary to predicted geometries. "Transfer faults" provide a structural basis for the apparent compartmentalization the syn-rift isopach cells into the "deeps". The data are insufficient to unequivocally support either model, although the orthogonal extension fault geometry better explains the distribution of the depocenters. Both interpretations, combined with limited basement dip information suggest that the structure underlying the Queensland Trough is the product of oblique rifting. Extension is aligned obliquely to the trough at 110°, rather than perpendicular to the rift elongation at 065°. The proposed kinematics suggest that formation of the trough pre-dates either the Coral or Tasman Sea taphrogenesis.

Seismic exploration throughout the Eromanga Basin has identified several regionally-extensive seismic reflection horizons. The C horizon, at the boundary of the Wallumbilla and Cadna-owie Formations, is one of the most significant. A difference in the petrophysical properties of these two formations is evident from sonic, density, gamma ray and resistivity well log data, and indicates that the amplitude of the C horizon reflection is related to a sequence of low-density (undercompacted) shales in the basal part of the Wallumbilla Formation. The properties of the shales appear to be a consequence of rapid subsidence (undercompaction) and burial. The empirical relationships between the C horizon reflection amplitude, formation density and reflection coefficient are discussed, and geological implications for petroleum prospectiveness of the Eromanga Basin are outlined.

Examination of new Late Cambrian samples from the upper part of the Chatsworth Limestone and lower part of the Ninmaroo Formation from Black Mountain, Georgina Basin, western Queensland (representing the pre-Payntonian, Payntonian and Datsonian Stages) has delineated five conodont assemblages in an interval that had previously not been subdivided using conodonts. Examination of the conodont fauna unambiguously confirms that the entire Payntonian Stage is of Cambrian age, as earlier indicated by the trilobite fauna, and provides three conodont assemblages that may subsequently form the basis for a conodont zonation. The Datsonian Stage, defined by the FAD of the Cordylodus proavus conodont assemblage and previously considered to equate with the Early Tremadoc (= Early Ordovician) of Europe, is now considered to represent the terminal Cambrian stage in northern Australia. The base of the Ordovician, equated with the base of Tremadoc correlatives, lies close to the Datsonian/Warendian boundary on the Black Mountain section. Two new conodont genera, Eodentatus and Hispidodontus, are established, along with four new species, E. bicuspatus, H. resimus, H. appressus and H. discretus. All are found in the Payntonian Stage in the upper part of the Chatsworth Limestone or the lower part of the Ninmaroo Formation.

The stratigraphic and spatial distributions of phosphatic and organic-matter rich Middle Cambrian sediments of the Georgina Basin are outlined in terms of sequence stratigraphic concepts. This approach has permitted an integrated analysis of Middle Cambrian depositional patterns and their time constraints. It has also provided insights into aspects of the basins structure, the timing of subsidence of its primary Components, and frequency of relative sea level fluctuations. Middle to early Late Cambrian sediments of the Georgina Basin are interpreted to occur in two stratigraphic sequences. In each sequence phosphorites, phosphatic limestones and organic-matter rich shales comprise a suite of repeating lithofacies restricted to retrogradational parasequence sets of the transgressive systems tract. The position of facies within each transgressive systems tract depends on relative sea level, palaeogeography and palaeotectonics. In sequence 1 (early Middle Cambrian), phosphogenesis is related to gradual transgression of a continent with irregular palaeotopography. Sequence 1a is interpreted to be of local significance, related to early subsidence of the Mt Isa Block during the late Ordian to early Templetonian. A rapid fall in relative sea level terminated sediment accumulation in sequence 1 and led to the development of a subaerial exposure surface. Sediments of the transgressive systems tract in stratigraphic sequence 2 are of lateTempletonian to early Undillan age. Deposition in sequence2 ceased in the Mindyallan. Rocks of the transgressive systemstract occur in three retrogradational parasequence sets. Recognition of sequence boundaries has helped clarify lateralbiofacies, leading to improved reconstructions of thepalaeogeographic distribution of the phosphorites and organic-matter rich shales.