Search

This paper presents the results of a small number of dates from sand samples collected at building sites in the eastern suburbs of Sydney. OSL ages of well-sorted, quartz sand ranges from 31 to 24 ka from within well-developed podzol soil profiles within a metre of the surface. The source of this sand appears to be from the east off the inner continental shelf during a period just prior to the maximum of the Last Glacial Maximum (LGM, Marine Isotope Stage 2) when sea-level was approximately 70-90 m below present level. During a later phase of the LGM, there is evidence from other coastal sites in central NSW and Gippsland, Victoria, that the dominant wind was from the west consistent with evidence from arid and semiarid Australia. Dune orientations in northern NSW into Queensland and other evidence at this time appear to reflect winds from the southeast quadrant. This study highlights the existence of a potential pivot area in dominant wind direction during the LGM between sustained westerly flow in southern area including Victoria and northeast Tasmania and southeast flow of northern NSW into Queensland. In central NSW, the circulation switched from easterly in Stage 2 to westerly as the glacial stage intensified in the LGM sometime after ca 25 ka. [ABSTRACT FROM AUTHOR]

Mineral matter in coals has been found to host valuable elements including germanium, lithium and rare-earth elements (REE), but such content of Australian coals remains under-explored. The aim of this paper is to provide a proof-of-concept study that determines elemental concentrations in the mineral matter of the high-ash, Fort Cooper Coal Measures (FCCM), Bowen Basin, Queensland. Coal in the FCCM has good coking properties but has not been extensively explored owing to its high ash content. This study performs a preliminary assessment of the elements from the coal portion that would typically become waste after washing or combustion. Given that the needs for industrial extraction methods will change over time, cataloguing and documenting the elemental composition of coal may assist future development of multiple products for the benefit of both the coal and mineral industries. This preliminary study has revealed similar elevations of REE and higher-than-average crustal concentrations of lithium, bismuth and scandium in some of the samples. Further analyses will be required on a larger dataset to better understand elemental associations and explore spatial patterns of elemental content that may indicate localised enrichments. Understanding the potential of valuable elements in the FCCM may stimulate interest in multiple-product-coal (or elemental-coal) mining in this under-exploited resource and further encourage the reduction of waste from other Australian coals at the wash-plant stage. [ABSTRACT FROM AUTHOR]

This paper describes the purpose, design and implementation of a new regional-scale geodetic network that has been installed in the Surat Basin, Queensland, and completed in November 2014. The network incorporates 65 survey marks and 40 radar corner reflectors to enable the combination of Global Navigation Satellite System measurements with remotely sensed surface deformation maps derived using the Interferometric Synthetic Aperture Radar technique. The combination of these geodetic techniques in this region will bring an enhanced understanding of how resource extraction affects the ground surface. [ABSTRACT FROM PUBLISHER]

In irrigated areas of central and northern New South Wales secondary soil salinisation is of increasing concern. This is particularly the case for the Bourke Irrigation District (mid-Darling River valley) where incipient traces of point-source salinisation are evident. Much of this is attributed to significant changes in the water balance and in particular increased deep drainage and mobilisation of primary salts. In the first instance, near-surface prior-stream channels and subsurface paleochannels evident within Cenozoic alluvial deposits act as significant hydrological features. Owing to the porosity and connectivity of the Cenozoic sediments, deep draining water interacts with ancient and highly saline Cretaceous marine mudstones. Unfortunately, natural resource data on the spatial distribution of near-surface and subsurface stratigraphy are not readily available to understand these processes or determine best management. In this paper, we demonstrate how fuzzy k-means (FKM) analysis of EM34 signal data collected across the Bourke Irrigation District can be used to identify and map common near-surface and subsurface stratigraphic units. EM34 survey was carried out in the horizontal mode of operation with measurements made at coil spacing of 10, 20 and 40 m (i.e. EM34-10, -20 and -40, respectively). In all, 1236 sites were visited on a ∼0.5-1 km grid. The EM34 signal data were classified numerically using the FKM clustering algorithm. The iteration of fuzzy exponents (f) and various indices, including the fuzziness performance index (FPI) and normalised classification entropy (NCE) enabled the determination of f = 1.6 and k = 4 classes to be selected for further investigation. Using fuzzy canonical analysis we find that the EM34-10 and EM34-20 signal data best discriminate the classes. The resulting k = 4 classes (i.e. Class A, B, C and D) are then mapped using a method that ensures summation of class membership (m) values to unity and using local ordinary kriging. Class A represents saline and clay-rich sediments associated with outcrops of the Cretaceous marine mudstone. Class D represents interbedding of sand within the clay units indicative of the Cenozoic alluvial deposits that overly the Cretaceous mudstone. Similarly, Class B represents Cenozoic sediments with the presence of paleochannel(s). Class C characterises the eolian dune and alluvial floodplain physiographic units. The use of a confusion index (CI) highlights areas of uncertainty in the FKM classification mapping and indicates where the collection of additional information is appropriate. Validation of the FKM approach is confirmed by calculating near-surface (0-6 m) and subsurface (6-12 m) class average soil physical and chemical property (i.e. clay content, cation exchange capacity and salinity) variance (i.e. S2Z) and total within-class variance (i.e. S2T) of a FKM map. Overall, the average subsurface ECe data produces the greatest reduction in variance. This suggests the FKM classification of EM34 signal data is influenced by saline groundwater-tables in the Cenozoic sediments which lie above the Cretaceous marine mudstone. The FKM class memberships and CI along a short but detailed transect across the Bourke Irrigation District are interpreted with respect to the spatial distribution of near-surface and subsurface soil property data. We conclude the FKM analysis of EM34 provides a better understanding of the spatial distribution and horizontal layering of the various stratigraphic units which characterise the Bourke Irrigation District. The results help explain the broad hydrological processes driving point source secondary soil salinisation and provides a framework for the deployment of measuring and monitoring sites. [ABSTRACT FROM AUTHOR]

This paper focuses on a small back-barrier sand-island on the southeast coast of Queensland. The freshwater lens in the study area exhibits anomalously high short-range salinity gradients at shallow depths, which cannot be explained using a standard seawater intrusion model. The island groundwater system consists of two aquifers: a semiconfined aquifer hosting saline to hypersaline groundwater and an overlying unconfined freshwater aquifer. The deeper aquifer is semiconfined within an incised paleovalley, and groundwater flow is restricted to an east - west direction. Tidal response observations show that the tidal signal propagates far more rapidly and is of much higher magnitude in the semiconfined aquifer than the unconfined aquifer. The tidal wave-pulse amplitude is also subject to greater attenuation in the unconfined aquifer. A conceptual hydrogeological model illustrates how upwelling of hypersaline groundwater, induced by density-dependent flow and tidal pumping, has contaminated the shallow groundwater resource. Salinisation at shallow depths is restricted to an area proximal to the paleovalley aquifer. The spatial distribution of lithological heterogeneity is an initial limiting control on the movement of the upwelling saline plume. The extent of shallow groundwater contamination is also limited by the presence of a baroclinic field, resulting from lateral variations in fluid density. Hydrochemical signatures have been used to support the model hypothesis and link the salinisation of fresh groundwater with the semiconfined aquifer as opposed to the surrounding estuarine surface water. The geometry and thickness of the freshwater lens are further controlled by the presence of the largely impermeable bedrock paleosurface between 9 and 12 m depth. The combination of hypersaline groundwater and hydraulically restrictive lithology at shallow depths has produced excessive thinning of the freshwater lens, demonstrating that the application of a model such as the Dupuit - Ghyben - Herzberg relationship would grossly overestimate the available groundwater resource. [ABSTRACT FROM AUTHOR]

In this paper we assess two competing tectonic models for the development of the Isa Superbasin (ca 1725–1590 Ma) in the Western Fold Belt of the Mt Isa terrane. In the ‘episodic rift-sag’ tectonic model the basin architecture is envisaged as similar to that of a Basin and Range province characterised by widespread half-graben development. According to this model, the Isa Superbasin evolved during three stages of the Mt Isa Rift Event. Stage I involved intracontinental extension, half-graben development, the emergence of fault scarps and tilt-blocks, and bimodal volcanism. Stage II involved episodic rifting and sag during intervening periods of tectonic quiescence. Stage III was dominated by thermal relaxation of the lithosphere with transient episodes of extension. Sedimentation was controlled by the development of arrays of half-grabens bounded by intrabasinal transverse or transfer faults. The competing ‘strike-slip’ model was developed for the Gun Supersequence stratigraphic interval of the Isa Superbasin (during stage II and the beginning of stage III). According to this model, sinistral movements along north-northeast-orientated strike-slip faults took place, with oblique movements along northwest-orientated faults. This resulted in the deposition of southeast-thickening ramp sequences with local sub-basin depocentres forming to the west and north of north-northeast- and northwest-trending faults, respectively. It is proposed that dilation zones focused magmatism (e.g. Sybella Granite) and transfer of strike-slip movement resulted in transient uplift along the western margin of the Mt Gordon Arch. Our analysis supports the ‘episodic rift-sag’ model. We find that the inferred architecture for the strike-slip model correlates poorly with the observed structural elements. Interpretation is made difficult because there has been significant modification and reorientation of fault geometry during the Isan Orogeny a... [ABSTRACT FROM AUTHOR]

Northeast Queensland contains multiple slices of mafic–ultramafic units, strung out along regional faults that mark major tectonic boundaries. One such complex is the Cowley Ophiolite Complex, which is situated along the Russell-Mulgrave Fault. The Cowley Ophiolite Complex is a differentiated mafic–ultramafic complex composed of gabbro, chlorite schist, anthophyllite schist and serpentinite. We interpret that the alteration assemblages observed throughout the Cowley Ophiolite Complex reflect an amphibolite facies metasomatic overprint within a supra-subduction zone setting. This interpretation is consistent with geochemical discrimination of the gabbro, and chromite grains from the anthophyllite schist. The Cowley Ophiolite Complex records a higher metamorphic grade than the surrounding Hodgkinson Formation, and we interpret this to reflect the allochthonous structural setting of the complex, positioned along an ancient subduction margin. This subduction margin is represented today by the Russell-Mulgrave Fault. Metasomatism and emplacement of the complex probably pre-dated deposition of the Mossman Orogen's active margin successions. Our interpretation of an active subduction complex, which pre-dated the formation of the Mossman Orogen, suggests that the Russell-Mulgrave Fault is a Paleozoic, continental suture zone. The Cowley Ophiolite Complex presents little indication of economic mineralisation; however, much of the complex remains unexplored. The Cowley Ophiolite Complex is a differentiated, mafic–ultramafic complex formed within a supra-subduction zone setting. Emplacement of the Cowley Ophiolite Complex, along the Russell-Mulgrave Fault, pre-dated the formation of the Hodgkinson Province. The Russell-Mulgrave Fault represents an ancient subduction margin, and is interpreted as a Paleozoic, continental suture zone. [ABSTRACT FROM AUTHOR]

Detrital zircon U–Pb age patterns in sandstones from the Triassic–Cretaceous Clarence-Moreton Basin, eastern New South Wales and Queensland, unexpectedly reveal sediment sources overwhelmingly dominated (>70%) by Precambrian–Cambrian zircons, with virtually no input, as was anticipated, from the nearby Carboniferous, Permian or Triassic magmatic arcs and contemporary accretionary wedge associated with the New England Orogen. Some rare, youngest zircons (<5%) are mostly contemporaneous with the estimated depositional age. The older, reworked zircon populations can only be acquired by postulating either (1) an Australian provenance by long overland sediment pathways from the interior to the west, during one or more transport cycles, perhaps from within the Thomson Orogen, and then bypassing or crossing the New England Orogen without any local contribution from that sector or (2) a North Zealandia provenance with a shorter transport distance from a postulated basement block to the east, within the Northern Lord Howe Rise and Kenn Plateau. This would comprise late Mesoproterozoic (1200–1000 Ma) and late Neoproterozoic–Cambrian (700–500 Ma) igneous and metamorphic complexes, similar to that proposed in South Zealandia. Triassic to Jurassic Clarence-Moreton Basin sedimentary rocks have provenances unlike their hinterland time-correlates in New South Wales and Queensland. The latter better share similarities with those in Murihiku Terrane, North Island, New Zealand. The provenance of Clarence-Moreton sediments is similar to that of time-correlates in New Caledonia, and it is postulated that they share a source region on the northern Lord Howe Rise or Kenn Plateau. [ABSTRACT FROM AUTHOR]

The upper Paleozoic–lower Mesozoic strata in the northeastern Galilee Basin are important for their hydrocarbon and groundwater potential; however, despite numerous previous investigations, the nature of this stratigraphic interval remains enigmatic. This study integrates lithostratigraphy, palynology and U–Pb zircon geochronology of well-exposed Permian and Triassic sedimentary rocks and nearby stratigraphic cores from the Hughenden district to determine their maximum depositional ages and then revises the stratigraphy where necessary. The newly defined Galah Tuff Bed was discovered at the top of the Betts Creek beds in Porcupine Gorge and was dated at 251.9 ± 3 Ma. This provides an important age constraint for the Betts Creek beds and is a tie-point for correlations with coeval units in the adjacent Bowen Basin and the Sydney and Gunnedah basins to the southeast. The Galah Tuff Bed is interpreted to correlate with the Yarrabee Tuff in the Bowen Basin. Unconformably overlying the Betts Creek beds is a newly recognised stratigraphic unit, defined herein as the Porcupine Gorge Formation. Detrital zircon maximum depositional ages and palynology indicate a significant depositional hiatus of up to 20 million years between the Betts Creek beds and Porcupine Gorge Formation. The hiatus indicates that the lower part of the Porcupine Gorge Formation is at least upper Middle Triassic, whereas the upper part of the unit extends into the Late Triassic. This age also constrains the overlying Warang Sandstone, which is considerably younger locally than previously reported and is likely diachronous across the northeastern Galilee Basin. An integrated lithostratigraphy, palynology and U–Pb detrital zircon geochronology methodology is applied to the Permian–Triassic succession the northeastern Galilee Basin. Two new stratigraphic units were recognised: the upper Permian Galah Tuff Bed (251.9 ± 3 Ma) and the late Middle–Late Triassic Porcupine Gorge Formation (238.7 ± 3 Ma). The Galah Tuff Bed, correlative of the Yarrabee Tuff in the Bowen Basin, is evidence for widespread volcanism in the late Permian. The age of the Porcupine Gorge Formation indicates diachroneity of the Triassic succession in the Galilee Basin, warranting further examination. [ABSTRACT FROM AUTHOR]

This paper is concerned with an example of quantitative modelling of orebody formation as a guide to reducing the risk for future mineral exploration. Specifically, the paper presents a detailed 3-D numerical model for the formation of the Century zinc deposit in northern Queensland. The model couples fluid flow with deformation, thermal transport and chemical reactions. The emphasis of the study is a systems approach where the holistic mineralising system is considered rather than concentrating solely on the mineral deposit. In so doing the complete plumbing system for mineralisation is considered with a view to specifying the critical conditions responsible for the ore deposit occurring where it does and having the size and metal grades that are observed. The numerical model is based on detailed geological, tectonic, isotopic and mineralogical data collected over the past 20 years. The conclusions are that the Century zinc deposit is located where it is because of the following factors: (i) a thermal anomaly is associated with the Termite Range Fault due to advection of heat from depth by fluid flow up the Termite Range Fault; (ii) bedding-plane fissility in the shale rocks hosting the Century zinc deposit has controlled the wavelength and nature of D1 folding in the vicinity of the deposit and has also controlled increases in permeability due to hydrofracture of the shales; such hydrofracture is also associated with the production of hydrocarbons as these shales passed through the ‘oil-window’; (iii) Pb–Zn leached from crustal rocks in the stratigraphic column migrated up along faults normal to the Termite Range Fault driven by topographic relief associated with inversion at the end of the Isan Orogeny; these fluids mixed with H 2 S derived at depth moving up the Termite Range Fault to mix with the crustal fluids to precipitate Pb–Zn in a plume downstream from the point of mixing. Critical factors to be used... [ABSTRACT FROM AUTHOR]

The transition between the North Australian Craton and the Thomson Orogen in the area south of the Mount Isa terrane lies under cover and is a critical element in interpretation of the nature of the Tasmanides. The location of the boundary between these domains is controlled by potential field results; the gravity and magnetic signatures are most sensitive to shallow structure, and so there is little information on structure at depth. Full-crustal reflection profiling crosses the boundary in a few locations but does not provide areal coverage. A deployment of 79 passive seismic stations spanning from southern Queensland into the Mount Isa terrane (AQT experiment) is exploited to examine the variations in crustal thickness and the nature of crustal structure across an area with no prior sampling. The analysis exploits the autocorrelation of the seismic signals that extracts the reflection response from the transmitted signals recorded at the surface, which can be migrated to provide an image of structure at depth. The combination of the active and passive seismic results and other geophysical data indicates that the structure of the northern and central Thomson Orogen is relatively homogeneous with a highly reflective, and magnetic, lower crust suggesting a common substrate across the region. The crust thickens and changes character in the North Australian Craton with variations under cover that can be linked to the areas of exposure. There is a zone approximately 100 km wide that separates the characteristic seismic signatures of the two domains indicating reworking at the craton margin. A combination of passive and active seismic imaging sheds light on the transition from the Thomson Orogen to the North Australian Craton. The north central Thomson Orogen shows a consistent reflection character with a strong band of lower crustal reflectivity. The North Australian Craton shows seismic domains with varying character of reflectivity and crustal thickness. A transition zone about 100 km wide separates the distinctive styles of crustal architecture. [ABSTRACT FROM AUTHOR]

Earthquakes are relatively rare in Queensland. Nevertheless, since European settlement, most parts of the state's east coast have felt the impacts of several moderate to high-magnitude events. Knowledge of seismic activity in Queensland is limited owing to sparse historical seismograph coverage, and the relatively short period (ca 1825 onwards) for which records are available. Previously published compilations of observational records for several high-magnitude historical earthquakes and their effects on local communities are incomplete. The National Library of Australia Trove newspaper collection and newspaper microfilm records were used to document 12 moderate–high-magnitude earthquakes that impacted major population centres in Queensland between 1879 and 1958, before the establishment of effective seismic monitoring. The Trove newspaper collection facilitates access to details on the timing, duration and intensity of events, and the damage caused for many locations where these earthquakes were felt. Newspaper reports for the 12 earthquakes were used to define their regions of impact and a re-evaluation of felt radii, epicentre locations and magnitudes against previously published interpretations. The Trove records are consistent with existing interpretations for the Gayndah 1883, Atherton Tablelands 1928, Bundaberg 1918, Gayndah 1935 and Cairns 1958 events. In contrast, previously published interpretations for the Townsville 1879, Cairns 1896, Mundubbera 1910, Coalstoun Lakes/Kilcoy 1913, Ravenswood 1913, Daintree 1942 and Atherton 1950 earthquakes are not consistent with Trove records, which facilitate improved estimates of epicentre locations and magnitudes. This study has identified and documented three earthquakes in southern Queensland previously unrecognised in the seismological literature that impacted Degilbo in ca 1873, Nanango in 1876 and Toowoomba in 1877. Inconsistencies were found between data on an event that impacted Toowoomba in 1875 and Trove records. This review demonstrates the usefulness of the Trove archive to better identify and document the attributes and impacts of historical earthquakes. Newspapers in the Trove archive are a useful source of information on historical earthquakes. Information from the Trove archive can be used to re-evaluate interpretations of historical earthquakes and discover previously unidentified earthquake events. The nature of historical buildings influenced the effects and the amount of damage caused by historical earthquakes in Queensland. [ABSTRACT FROM AUTHOR]

The presence of granitoid clasts in Devonian sequences of the Mt Morgan area has been considered indicative of a Late Devonian age, with the clasts derived from the Middle Devonian (377 Ma) Mt Morgan Trondhjemite. However, a sequence of limestone and volcanolithic arenites and breccias containing Middle Devonian corals and conodonts, overlies a granitoid-bearing conglomerate in Station Creek. This sequence, previously mapped as Dee Volcanics, is now assigned to the Raspberry Creek Formation of the Capella Creek Group. Petrographic and geochemical similarities between the granitoid clasts and phases of the Mt Morgan Trondhjemite indicate formation in similar tectonic environments by similar magmatic processes. These clasts were derived from either an earlier phase of Mt Morgan Trondhjemite magmatism, or from a discrete earlier magmatic episode of similar type and inferred tectonic setting to the Mt Morgan intrusion. [ABSTRACT FROM AUTHOR]

This study presents two chemical abrasion-thermal ionisation mass spectrometry (CA-TIMS) U–Pb zircon ages from tuffs as well as palynostratigraphic results from the embracing sedimentary succession of the Orallo Formation, Surat Basin, Queensland. Samples were taken from two Geological Survey of Queensland (GSQ) stratigraphic holes, GSQ DRD 26 and GSQ Roma 2. Palynological results assign the upper part of the Orallo Formation to the lower part of the Ruffordiaspora australiensis Interval Zone rather than the upper part of this zone as previously indicated. A late Valanginian isotopic date of 134.38 ± 0.04 Ma from GSQ DRD 26 and an early Hauterivian date of ≤132.46 ± 0.36 Ma from GSQ Roma 2 give the Orallo Formation a Berriasian?/Valanginian–Hautevarian age, rather than the previously inferred Berriasian–Valanginian age determined without any geochronological control. Additionally, when combined with previously published geochronological dates from the Westbourne Formation, these ages suggest that, in the Surat Basin succession, the Jurassic–Cretaceous boundary most likely lies within the Gubberamunda Sandstone. Two U–Pb CA-TIMS ages of 134.38 ± 0.04 Ma and ≤132.46 ± 0.36 Ma have been found, based on zircons extracted Orallo Formation tuffs. Sediments surrounding the two tuffs the zircons were extracted from yielded palynofloras assignable to the lower part of the Ruffordiaspora australiensis Interval Zone. These dates, combined with earlier work, show the Orallo Formation to be of Berriasian?/Valanginian–Hautevarian age. [ABSTRACT FROM AUTHOR]

The article provides an overview of the articles discussed in the journal "Geological Society of Australia." The authors describes results from the 1994 deep seismic-reflection traverse, in particular the regional detachment surface and basement-cutting faults associated with Mesoproterozoic, east-west shortening in the inlier. The discussion of the structural evolution of the southern Mount Isa valley. The insights into the genesis and diversity of epigenetic mineralization in the Cloncurry District of the Mount Isa Inlier in northwest Queensland. The authors present a detailed metamorphic isograd map across the Mount Isa Inlier.

The Drummond Basin of central Queensland preserves a large-volume succession of little studied, predominantly fluviatile, coarse-grained sedimentary rocks of mid-Mississippian age. The stratigraphy of the basin has been subdivided into three sedimentary cycles. The Cycle 1/Cycle 2 boundary records a distinct, but poorly understood change in provenance from a volcanic-dominated succession related to initial basin rifting (Cycle 1) to a quartz-rich, craton-derived succession (Cycle 2). Cycle 3 has been thought to mark a resumption of intrabasinal volcanism and related sedimentation. The purpose of this study was to enhance the understanding of the basin-wide siliciclastic sedimentation of Cycles 2 and 3, and causes for the changes in sediment provenance. This objective was achieved by constraining large-scale spatial and temporal depositional trends and investigating sediment transport pathways into and through the basin. Petrographic, QFL, paleocurrent and conglomerate clast analyses were undertaken. The observations presented here have several implications relevant to understanding the stratigraphy of the Drummond Basin and regional tectonic events at this time. Cycle 3 is revised here primarily to be a continuation of Cycle 2-style basement-derived sedimentation, rather than recording a resumption of volcanism in the area, as per prevailing models. Quartz-rich sedimentation in the Drummond Basin was, therefore, more long-lived than previously envisaged, and once established, was not significantly disrupted by volcanism. Cycle 2 formation thicknesses appear highly variable across the basin. This is unlikely to be a result of pre-existing rift-related topography as suggested in previous models. The thickness variations are more likely related to sediment bypassing and post-depositional deformation in the area. The distinctive coarse-grained, relatively quartz-rich sedimentation of Cycles 2 and 3 is unusual in its volume and extent. The sediment was transported into the basin from its southern/southwestern margin, implying long-distance transport and extrabasinal sediment supply. While the specific source terrain(s) remain unknown, one plausible tectonic driver was far-field influence of the intraplate Alice Springs Orogeny. [ABSTRACT FROM AUTHOR]

The New England Orogen (NEO), the youngest of the orogens of the Tasmanides of eastern Australia, is defined by two main cycles of compression–extension. The compression component involves thrust tectonics and advance of the arc towards the continental plate, while extension is characterised by rifting, basin formation, thermal relaxation and retreat of the arc towards the oceanic plate. A compilation of 623 records of U–Pb zircon geochronology rock ages from Geoscience Australia, the geological surveys of Queensland and New South Wales and other published research throughout the orogen, has helped to clarify its complex tectonic history. This contribution focuses on the entire NEO and is aimed at those who are unfamiliar with the details of the orogen and who could benefit from a summary of current knowledge. It aims to fill a gap in recent literature between broad-scale overviews of the orogen incorporated as part of wider research on the Tasmanides and detailed studies usually specific to either the northern or southern parts of the orogen. Within the two main cycles of compression–extension, six accepted and distinct tectonic phases are defined and reviewed. Maps of geological processes active during each phase reveal the centres of activity during each tectonic phase, and the range in U–Pb zircon ages highlights the degree of diachronicity along the length of the NEO. In addition, remnants of the early Permian offshore arc formed during extensive slab rollback, are identified by the available geochronology. Estimates of the beginning of the Hunter-Bowen phase of compression, generally thought to commence around 265 Ma are complicated by the presence of extensional-type magmatism in eastern Queensland that occurred between 270 and 260 Ma. [ABSTRACT FROM AUTHOR]

The Toomba flow is the youngest flow of the Nulla volcanic province, located in north Queensland. This 120 km-long flow has yielded a published 40Ar/39Ar age of 21,000 ± 3000 years. In contrast, seven published conventional radiocarbon (14C) analyses of carbon-bearing material beneath the flow yielded radiocarbon ages of 16,000 to <2500 BP. These radiocarbon ages are younger than the 40Ar/39Ar age, potentially due to contamination of the charcoal by younger carbon that was not removed by the acid-base pre-treatment. We have re-examined the radiocarbon age of Toomba flow using newly sampled charcoal buried beneath the Toomba flow in combination with hydrogen pyrolysis pre-treatment and accelerated mass spectrometer (AMS) measurements. We determined a calibrated radiocarbon age of 20,815-19,726 cal BP (2r) for the material beneath the Toomba flow. Our radiocarbon age, therefore: (1) is older than previous radiocarbon ages for the Toomba flow, (2) provides the most precise age yet available for the Toomba flow, (3) is in agreement with the 40Ar/39Ar age, and (4) validates that hydrogen pyrolysis is a robust and effective pre-treatment method, for subtropical conditions where samples are susceptible to contamination by younger carbon. The Toomba flow erupted during the Last Glacial Maximum, but the preserved surface suggests that the rate of weathering and soil formation has been almost negligible in this region, despite being situated in a subtropical climate that experiences highly variable often intense rainfall. [ABSTRACT FROM AUTHOR]

The southwestern Pacific region consists of segmented and translated continental fragments of the Gondwanan margin. Tectonic reconstructions of this region are challenged by the fact that many fragmented continental blocks are submerged and/or concealed under younger sedimentary cover. The Queensland Plateau (offshore northeastern Australia) is one such submerged continental block. We present detrital zircon geochronological and morphological data, complemented by petrographic observations, from samples obtained from the only two drill cores that penetrated the Paleozoic metasedimentary strata of the Queensland Plateau (Ocean Drilling Program leg 133, sites 824 and 825). Results provide maximum age constraints of 319.4 ± 3.5 and 298.9 ± 2.5 Ma for the time of deposition, which in conjunction with evidence for deformation, indicate that the metasedimentary successions are most likely upper Carboniferous to lower Permian. A comparison of our results with a larger dataset of detrital zircon ages from the Tasmanides suggests that the Paleozoic successions of the Queensland Plateau formed in a backarc basin that was part of the northern continuation of the New England Orogen and/or the East Australian Rift System. However, unlike most of the New England Orogen, a distinctive component of the detrital zircon age spectra of the Mossman Orogen is also recognised, suggesting the existence of a late Paleozoic drainage system that crossed the northern Tasmanides en route from the North Australian Craton. A distinctive shift from abraded zircon grains to grains with well-preserved morphology at ca 305 Ma reflects a direct drainage of first-cycle sediments, most likely from an outboard arc and/or backarc magmatism. [ABSTRACT FROM AUTHOR]

The major stratigraphic units of the Fort Cooper Coal Measures (FCCM) have been reviewed, and an internal coal seam architecture using 500 wireline logs in the Bowen Basin, southeast Queensland has been developed. The subdivisions of the coal measures include the Burngrove Formation, Middle Main Seam and Fair Hill Formation in the northern Bowen Basin. To the south of the basin, the Middle Main Seam is interpreted as the stratigraphic equivalent of Black Alley Shale Formation. The Yarrabee Tuff forms the top boundary of the coal measures and is distributed basin-wide except over the southern Denison and southern Taroom troughs. Accessory tuffs beneath the Yarrabee Tuff aided seam level correlation. The geometries of coal seams have been analysed for each morphotectonic zone of the Bowen Basin using gravity data, which highlight high and low topographic sites. The Collinsville Shelf in northwest of the Bowen Basin comprises thick and merged Burngrove and Fair Hill formation coals that split towards northeast in the Nebo Synclinorium and southeast in Taroom Trough. Coal seams split into daughter seams from north to south and are named as first, second or third order, based on the number of splits that occurred. First- and second-order splitting occurs at the boundary of the Nebo Synclinorium and Collinsville Shelf, at the Narrows of Nebo Synclinorium and Comet Ridge. Further, third- and fourth-order splitting occurs at the boundary of the Comet Ridge and Taroom Trough. Splitting zones found at the junction of morphotectonic zones are related to a change in subsidence. In addition, the association of split seams with coarse grain-dominated interburden reflects increased accommodation in low-lying areas such as the Nebo Synclinorium and the troughs. Thick and coalesced coal seams are associated with shelves and ridges of the basin reflecting low accommodation sites. Hence, the variation in the coal seam architecture of FCCM responds to the subsidence associated with different morphotectonic zones of the basin. [ABSTRACT FROM AUTHOR]

The New England Orogen in eastern Australia is characterised by orogenic-scale curvatures (oroclines). The largest and most prominent curvature in this system is the Texas Orocline, but its subsurface geometry is still poorly constrained. A large component of the orocline is covered by post-oroclinal sedimentary rocks, which obscure deeper sections of the orocline and make it difficult to understand how the structure is connected to other segments of the New England Orogen. Here, we present geophysical data that elucidate the structure of the Texas Orocline below the sedimentary cover. Using 2D seismic, aeromagnetic TMI (total magnetic intensity) and Bouguer gravity datasets, in combination with outcrop and well data, we identified the depth to the New England ‘basement’ and significant faults intersecting it. We also traced the strongly contorted subsurface continuation of the Peel-Yarrol Fault System, which is characterised by local gravity and magnetic anomalies associated with isolated serpentinite outcrops. Constraints on the timing of oroclinal bending were obtained from the interpretation of seismic transects, which showed that early Permian sedimentary rocks of the Bowen Basin were deposited in a subtrough that deviates from the general north–south trend of the Bowen Basin. The subtrough is oriented approximately parallel to the western limb of the Texas Orocline, thus suggesting that the orocline formed during and/or after early Permian rifting. Our analysis indicates that initial bending occurred contemporaneously with the development of the early Permian rift basins, most likely in the backarc region of a retreating subduction zone. Subsequently, phases of strike-slip and contractional deformation have further tightened the pre-existing curvatures. [ABSTRACT FROM PUBLISHER]

The Middle Jurassic Walloon Subgroup is a prolific coal seam gas (CSG) resource in the Surat Basin, Queensland. Sedimentary framework models constrain stochastic reservoir models of the geological heterogeneity, but there is limited basin analysis information in the public domain. Here we present a regionally consistent stratigraphic framework model for the Walloon CSG play in the eastern Surat Basin. Lithostratigraphic correlation of open-file industry and government wireline logs supports the interpretation of six subunits in the eastern Surat Basin (oldest–youngest: Durabilla Formation; Taroom Coal Measures; Tangalooma Sandstone; and Juandah Coal Measures, informally divided into three members named the lower Juandah Coal Measures, Juandah sandstone and upper Juandah Coal Measures). Important findings are that subunits within the Walloon Subgroup do not correlate along the entire CSG play area; in many places, the overlying Springbok Sandstone (Upper Jurassic) has incised to the lower Juandah Coal Measures level, removing the upper coal seam groups. The Walloon Subgroup thins to the south through a combination of depositional thinning and truncation. Lithofacies analysis and isopach maps support deposition in a southerly prograding fluvial system or clastic wedge. This stratigraphic and depositional interpretation informs models for hydrogeological studies of the Walloon Subgroup and underpins a regional assessment of controls on microbial methane distribution. [ABSTRACT FROM AUTHOR]

Carbon dioxide injection into subsurface reservoirs appears to be a promising solution for decreasing atmospheric CO2concentrations. Results and recommendations of a preliminary investigation of sedimentary basins suitable for carbon geostorage in Queensland designated the Surat Basin as a target area for further investigation. As a result, a comprehensive gap analysis of the Surat Basin datasets was followed by regional desktop studies, hydrodynamic analysis using petroleum well and groundwater bore data and a program of mineralogical data collection and interpretation. Allavailable open-file data (petroleum wells, department stratigraphic wells, department of the environment and resource management and Geological Survey of Queensland groundwater bores and seismic data) were reassessed, reinterpreted and/or refined. Petroseis® and GOCAD® were used for regional geological modelling of seismic horizons and fault systems, respectively. PressureQC™ was the quality control platform used for assessing petroleum well pressure data and the Geochemist's Workbench software was used for preliminary geochemical simulations of carbon dioxide impacts on groundwater and host rocks. The precompetitive studies and datasets recently released by the Carbon Geostorage Initiative address some issues, which are geostorage-specific, such as defining the supercritical boundary (800 m depth), fault plane geometry, groundwater flow vectors and the potential impact of carbon dioxide injection on the groundwater system and its mineral framework. Theprimary conclusions derived from this work are that the applicability of a given dataset must be considered prior to implementation. This is of particular importance for geological modelling studies where quality assurance processes are needed to validate the various datasets that have been used. In addition to this, the modelling methodologies themselves have been assessed in an appropriate context for geostorage investigations. [ABSTRACT FROM PUBLISHER]

The relative timing of the sequence of events is problematic where deformation partitioning strongly separates zones dominated by folds that formed in different periods of orogeny. This is particularly the case where they form orthogonal to one another in plan view. A succession of foliation inflection/intersection axes (FIAs) preserved within porphyroblasts readily resolves the sequence. In situ monazite age dating of porphyroblasts preserving W–E and N–S-trending FIAs yielded ages of 1645 ± 7 and 1591 ± 10 Ma, respectively. Peaks in the distribution of the two FIA sets coincide with the trends of the axial planes of the regional folds. The succession of FIAs, as well as foliations in the matrix in the Soldiers Cap Group of the eastern Mount Isa Inlier, supported with geochronological data reveal W–E directed bulk horizontal shortening followed N–S bulk horizontal shortening. This is despite the apparent regional lack of curvature of the W–E-trending folds around those trending N–S. Furthermore, N–S and W–E-directed bulk shortening resulted in at least 2 cycles of subvertical and subhorizontal foliation development that define the W–E and N–S-trending FIAs. [ABSTRACT FROM PUBLISHER]

The Talundilly Structure, southwestern Queensland, Australia, is represented on 2D seismic reflection transects as a major seismic anomaly disrupting the consistent ‘C’ seismic–stratigraphic horizon above the early Cretaceous Bulldog Wallumbilla Formation throughout the Eromanga Basin. The seismic anomalous zone, estimated at 84 km in diameter from the maximum extent of horizon disruption, coincides with a prominent aeromagnetic (TMI) high which is centrally located within a near-circular seismic anomaly of the ‘C’ horizon. The structure consists of a raised central area, with radial faults extending from the central high, an annular synform with disrupted seismic elements dipping at low angles towards the central uplift, and an outer faulted rim. Cuttings from the Talundilly-1 well, drilled ∼30 km northwest from the central high, contain quartz grains with planar deformation features (PDF) indicative of shock metamorphism. The age of the structure, as determined from seismic correlation and sparse palynology, post-dates the ‘C’ seismic horizon and is determined as approximately 125 Ma, coinciding with a marine transgression. Correlation of seismic profiles suggest that the Talundilly impact structure is a possible twin of the Tookoonooka impact structure, dated as 125 ± 1 Ma and located 328 km to the south. [ABSTRACT FROM AUTHOR]

The most likely source for oxidised brines that produced the Mount Isa copper–cobalt deposits is the hematitic meta-sediments of the <1500 Ma South Nicholson Group or its lateral equivalents. Downwards movement of the brines into relatively impermeable basement rocks at about 1370 Ma is suggested to have been a product of reactivation of NNW–SSE faults (e.g. Transmitter fault) during post-Isan inversion. Evidence for the involvement of such structures includes spatial association with major orebodies and mica–dickite–hematite alteration indicative of the passage of hot, acidic and oxidised fluid. Copper depletion and K enrichment in metabasalt of the ca 1830 Ma Eastern Creek Volcanics along such structures has previously been documented. Anhydrite-rich rocks preserved at the northern end of the copper orebodies represent a zone of high fluid input, where the characteristics of the original fluid are best preserved. The most plausible chemical process generating economic Cu is reduction of oxidised brine during reaction with carbonaceous meta-sediments of the Urquhart Shale. Many lithologies in the region would have had the chemical capacity to extract Cu from hydrothermal solutions. The availability of suitable reductant rocks was therefore not a limiting factor on Cu deposition. Rather, the distribution of porosity and permeability would have controlled deposit location. The Urquhart Shale is a particularly favourable host unit on account of pervasive mechanical anisotropy produced by regular interlayering of ductile metapelite and brittle metasiltstone. Strain partitioning during post-Isan inversion resulted in pervasive permeability development in metasiltstone, particularly when steeply dipping. An implication of this research is that rocks of the South Nicholson Group and equivalents could be targetted for sediment-hosted stratiform copper (SSC) deposits. [ABSTRACT FROM PUBLISHER]

High-resolution mineral maps derived from hyperspectral imaging (4.5 m pixel) enable the recognition of various types of hydrothermal alteration and the identification of fluid pathways. Airborne hyperspectral images from the Eastern Fold Belt of the Mount Isa Inlier were tested as a new tool for the detection of Fe-oxide Cu–Au (IOCG) related alteration. Four different types of hydrothermal alteration were identified with the hyperspectral mineral maps: (1) Metasomatic 1: white mica mineral maps show the spatial distribution of regional sodic–calcic alteration in metasedimentary successions of the Soldiers Cap Group in the Snake Creek Anticline. (2) Metasomatic 2: alteration zonation is evident from albitised granites assigned to the Williams–Naraku Suite along the Cloncurry Fault. These show characteristic absorption features in the shortwave infrared range (SWIR) which are depicted on the white mica mineral maps (white mica composition, white mica content, white mica crystallinity index). Alteration zonation in gabbros of the Cloncurry District was detected by a combination of MgOH and Fe2+ mineral maps (MgOH content, MgOH composition, amphibole/chlorite and Fe2+ and MgOH) combined with white mica mineral maps (white mica composition and white mica content). (3) Fluid channels 1: major fault zones, such as the Mt Dore fault zone in the Selwyn Corridor, are interpreted as important fluid pathways, where gradual changes in the mineral chemistry are highlighted with mineral maps (e.g. white mica content, white mica composition, white mica crystallinity index). (4) Fluid channels 2: MgOH and Fe2+ mineral maps were used to map breccia pipes in the northern Cloncurry District north of the Saxby Granite (Suicide Ridge). The MgOH and Fe2+ mineral maps were also used to distinguish various mafic rocks from amphibolites, which are host rocks for some of the IOCG deposits in the Eastern Fold Belt (e.g. Mount Elliott), and calcsilicate breccias pipes (e.g. Suicide Ridge). [ABSTRACT FROM PUBLISHER]

New geochemical, U–Pb zircon and Nd–Hf isotope data for felsic and mafic components of the Kalkadoon–Leichardt Belt (KLB) in the Mount Isa Inlier of northwest Queensland confirm that the evolution and tectonic make-up of this belt prior to 1.8 Ga was closely aligned with that of the Western Fold Belt. Like pre-1.8 Ga magmatic rocks of the Western Fold Belt, those in the KLB are characterised by late Archean to Paleoproterozoic crustal residence ages (TDM ca 2.6–2.3 Ga) but the geochemical data suggest stronger within-plate affinities, implying that the KLB intrusions underwent a greater degree of crustal assimilation and/or were emplaced further inboard of the active subduction margin. A new SHRIMP U–Pb zircon age of ca 1.86 Ga from a felsic intrusion in the northern KLB confirms earlier age constraints for the main phase of the Kalkadoon Granite. Nd isotope patterns for intrusions in the Western Fold Belt and the KLB are distinct from those of ca 1.7–1.5 Ga intrusions in the Eastern Fold Belt. This isotopic discrepancy suggests the Eastern Fold Belt underwent a separate evolutionary history and was accreted to the WFB/KLB at some stage prior to, or during, the ca 1.86 Ga Barramundi Orogeny. The occurrence of widespread, isotopically homogeneous ca 1.72 Ga magmatism (Argylla Event) across the entire Mount Isa Inlier implies that amalgamation of the allochthonous Eastern Fold Belt with the North Australian Craton was completed by that time. The significantly elevated metallogenic potential of the Eastern Fold Belt for ca 1540–1500 Ma Fe-oxide–copper–gold, relatively low endowment of the Kalkadoon–Leichhardt Belt, and predominance of ca 1650–1550 Ma base metal occurrences in the Western Fold Belt, are all consequences of the tectonic interplay and lithospheric processes that controlled the evolution of the Mt Isa Inlier prior to ca 1.8 Ga. [ABSTRACT FROM PUBLISHER]

Chrysoprase from Gumigil, near Marlborough in central east Queensland, occurs in weathered ophiolite of the Marlborough Block, in veins up to 20 cm thick in the lower parts of an approximately 50 m-thick regolith profile. Serpentinised harzburgite saprolite hosting magnesite and chalcedony veins with rare chrysoprase grades upward to a plasmic zone of chalcedony, nontronite and chlorite, with a lateritised zone above consisting of nodular or vermiform ferruginous duricrust, boxwork chalcedony and kaolinite. Gem chrysoprase and the poorer quality so-called ‘wetstone’ are dominantly chalcedonic quartz, coloured by willemseite, which occurs as 30–100 nm-wide zones largely aligned on polycrystalline quartz grain boundaries. Individual willemseite flakes (possibly single crystals) range from 2 to 12 nm thick. The quartz grainsize in chrysoprase is finer than in wetstone, and the willemseite domains in chrysoprase are smaller and less abundant, amounting to about 5% in chrysoprase and 15% in wetstone. Willemseite composition varies slightly between samples, with an average formula (Ni2.7Mg0.3)Si4O10(OH)2. [ABSTRACT FROM AUTHOR]

The Darling Basin, located in the northern part of the Lachlan Orogen, is cut by the 1000 km long east-northeast-trending Darling Lineament (Fault) which intersects the Koonenberry Fault to the north and the Mt Wintlow High (fault) to the south. During the Lachlan Orogeny these faults formed the Darling Basin Conjugate Fault System (DBCFS) in which the four sectors (NW, NE, SE, SW) showed alternate compression/uplift, and tension/subsidence. The DBCFS underwent five phases of development. During orogenic Phase 5, the northeast sector was in compression, and thick distal braidplains, deposited during orogenic Phase 4, when the sector was in tension, and underlying the older strata, were deformed. The study area has a 4-10 km wide concave northeast-facing fault zone, largely comprising, dextral faults, which is consistent with some tectonic transport of the fault blocks of the zone, largely to the southwest. Faulting followed an earlier period of east-west and southeast-northwest folding. This structure overprints unexposed strata deposited during orogenic phases 1, 2 and 4 in the Lachlan Orogeny as well as pre-Late Ordovician structure (Delamerian Orogeny). [ABSTRACT FROM AUTHOR]

Paleozoic and older basement rocks in northwestern New South Wales and southern and central Queensland are largely obscured by sedimentary rocks of the Mesozoic Eromanga Basin and younger Cenozoic sediments. Interpretations of the basement geology for that area have been heavily reliant upon interpretations of the regional aeromagnetic and gravity data. Geophysically, northwestern New South Wales is characterised by an east-west-trending belt of magnetic features which trend northwest in the western part and northeast to east-northeast in the eastern part; and by an east-west-trending gravity ridge. These east-west-trending features have previously been interpreted to represent the southern part of the Thomson Orogen, a separate tectonic domain to the Lachlan Orogen to the south. However, apart from these east-west geophysical trends there is sufficient geophysical and lithological evidence to suggest continuity of the Lachlan Orogen into southern and central Queensland. A new model is herein proposed whereby the geophysical features are attributed to structures resulting from crustal thickening of a Cambro-Ordovician backarc package, west of a volcanic arc, which occurred during the Late Ordovician to Early Silurian Benambran Orogeny. While the principal stress direction was oriented east-northeast-west-southwest, the structures formed via a process of tectonic escape or extrusion due to differential strain caused by the shape of the Precambrian margin in western New South Wales. The model is consistent with field observations, geophysical imagery, borehole data and seismic data. Analogue models using sand and gelatine were constructed to illustrate the concept and demonstrate that it is feasible. The model permits the extension of the Delamerian and Lachlan Orogens into southern and central Queensland to join with similar rock packages in northern Queensland, consistent with some previous tectonic models for the Tasmanides. This brings into question the need to delineate a separate Thomson Orogen. [ABSTRACT FROM AUTHOR]

The floodplain of the Lower Balonne River is in the upper reaches of the Murray-Darling Basin. The region has been extensively developed for agriculture, in particular irrigated cotton, and is highly productive. Multidisciplinary investigations to inform land management generated extensive sets of remotely sensed data including Landsat TM, airborne gamma-ray radiometrics, aerial photography, ASTER imagery and digital elevation models. These datasets provided the basis for regolith and geomorphic mapping. The wealth of data has allowed characterisation of the Lower Balonne River system, which is typical of many of the dryland rivers of southern Queensland. The geomorphic map of the Lower Balonne floodplain has eight major units based on landform and geomorphic processes. Bedrock consists of the slightly deformed and extensively weathered marine Cretaceous Griman Creek Formation. Coincident with erosion and weathering, Paleogene quartz gravels were deposited and are now extensively cemented and preserved as remnants forming zones of inverted relief. Much of the present landscape consists of a series of juxtaposed depositional units that have infilled an incised valley system. The different depositional units show the paleo-Balonne River migrating to the west. This is interpreted to be a result of tectonic depression and tilting to the west, causing avulsion and anastomosing of the paleochannels. The modern Balonne River system consists of a number of easily recognised segments. In the north, the modern channel is incised as a single channel. To the south the channel opens out onto an anastomosing plain with branching and reconnecting small-scale channels. Source-bordering dunes, currently inactive, have also formed along the western and eastern sides of the modern river and are prominent in large dunes in the south along the present Moonie River. Their absence in older landscape elements points to increasing aridity over time in the river system. [ABSTRACT FROM AUTHOR]

The principles of non-marine sequence stratigraphy were applied to the Jurassic strata in the lower part of the Surat Basin, in order to better determine the depositional history of the basin and highlight potential reservoir and source rocks. The lithostratigraphic units in the Early-early Late Jurassic interval can be divided into three supersequences: J, K and L. Each supersequence consists of a basal sandstone-dominated unit generally exhibiting an unconformable, diachronous relationship with the underlying unit. This is the lowstand system tract, which potentially offers an extensive well-sorted sandstone reservoir with interconnected porosity. These amalgamated sandstone sheets are overlain by a fining-upward interval consisting of predominantly muddier carbonaceous lithologies including coal and lacustrine deposits. This upper sequence embraces the transgressive system tract and possibly the highstand system tract. Isolated meander-belt sandstone bodies may be preserved within these widespread finer deposits and provide reservoirs juxtaposed to source rocks. Vitrinite reflectance values indicate that these Jurassic units are immature to marginally mature and, hence, may only have limited hydrocarbon-generating prospects. [ABSTRACT FROM AUTHOR]

A regional seismic synthesis of the 10 km-thick continental and shallow-marine succession of the Bowen Basin has revealed the basin-filling episodes and nine depositional supersequences (A-I). An Early Permian extensional phase, characterised by thick volcanics and half-graben development in a number of separated troughs, allowed fluviolacustrine sediments, including coal, to accumulate (Supersequence A). In the subsequent thermal subsidence phase, four marine supersequences (B-E) were generated. The onsets of supersequences B and C appear to be primarily tectonically controlled, but there is no evidence of tectonism initiating D, E and F. Supersequences B, D and E start with marine-flooding events, and in the Denison Trough end with either non-marine progradation (B), or high-energy nearshore sands (D and E). The first evidence of the compressional deformation associated with the development of a foreland basin occurs at the base of deltaic to marine Supersequence C. The thrust-induced loading of the foreland caused rapid subsidence in the adjacent Taroom Trough. It took about 10 Ma for the effects of thrust loading to spread across the basin from east to west. The foreland loading first affected the entire basin at the time of Late Permian Supersequence F, and lasted until the end of Triassic deposition. Four supersequences (F-I) have been identified in this phase of basin evolution. The later part of Supersequence F is almost wholly non-marine coal measures. The tectonism and base-level fall that generated the sequence boundary between Supersequences F and G, and ended coal deposition, represents a significant hiatus, and in places is characterised by low-angle unconformity and erosion. The pattern of the remaining units of the foreland basin phase indicates episodic basin filling as accommodation space became available, related to pulses of thrust loading. The regional geometry of the units, and the overstepping of Supersequence G by H, and then by I, indicates continuing westward progradation of foreland loading and corresponding changes in accommodation. It is striking that although the late foreland-loading phase displays the greatest rate of subsidence affecting the basin since the initial rift phase, there is little evidence of widespread flooding by the sea. The reasons were probably that the Late Permian-Early Triassic was a time of global first-order lowstand, and that foreland loading was able to provide simultaneously high rates of subsidence in the basin and greatly increased sediment supply from erosion in the mountains thrust up to the east. [ABSTRACT FROM AUTHOR]

Sandstone-rich, 6 km-thick, Eifelian-Frasnian strata of the northeast sector of the Darling Basin Conjugate Fault System, lie north of the Darling River Lineament, east of the Koonenberry Fault, and south of the Olepeloko Fault. Fossils are very rare in the study area: exceptions are in the Skolithos-rich beds of the Paroo National Park, and the early Eifelian fish-fragment horizon near Mt Jack Station. Four marker horizons are known southeast of the Paroo National Park: (i) the Mt Jack fish-fragment horizon; (ii) a Skolithos-rich belt at Momba Station; (iii) the mid-Givetian Keginni Conglomerate Member; and (iv) a ∼20 m-thick vein quartz clast-rich unit that crops out near the base of the Frasnian strata. Four braidplains are mapped: (i) White Cliffs (largest); (ii) Mt Jack; (iii) Bullocky Bore; and (iv) the distal part of the Keginni Conglomerate Member. Sediment derivation was from west of the Koonenberry Fault (White Cliffs Braidplain) from the northwest (Mt Jack Braidplain), from the north (Bullocky Bore Braidplain) and from the southeast (Keginni Conglomerate Braidplain). The braided streams/rivers depositing the sheet braidplains were very shallow, and sheet-flood deposition on the braidplains was widespread. [ABSTRACT FROM AUTHOR]

A sedimentological and stratigraphic study of Low Isles Reef off northern Queensland, Australia was carried out to improve understanding of factors that have governed Late Holocene carbonate deposition and reef development on the inner to middle shelf of the northern Great Barrier Reef. Low Isles Reef is one of 46 low wooded island-reefs unique to the northern Great Barrier Reef, which are situated in areas that lie in reach of river flood plumes and where inter-reef sediments are dominated by terrigenous mud. Radiocarbon ages from surface and subsurface sediment samples indicate that Low Isles Reef began to form at ca 3000 y BP, several thousand years after the Holocene sea-level stillstand, and reached sea-level soon after (within ∼500 years). Maximum reef productivity, marked by the development of mature reef flats that contributed sediment to a central lagoon, was restricted to a narrow window of time, between 3000 and 2000 y BP. This interval corresponds to: (i) a fall in relative sea-level, from ∼1 m above present at ca 5500 y BP to the current datum between 3000 and 2000 y BP; and (ii) a regional climate transition from pluvial (wetter) to the more arid conditions of today. The most recent stage of development (ca 2000-0 y BP) is characterised by extremely low rates of carbonate production and a dominance of destructive reef processes, namely storm-driven remobilisation of reef-top sediments and transport of broken coral debris from the reef front and margins to the reef top. Results of the present study enhance existing models of reef development for the Great Barrier Reef that are based on regional variations in reef-surface morphology and highlight the role of climate in controlling the timing and regional distribution of carbonate production in this classic mixed carbonate-siliciclastic environment. [ABSTRACT FROM AUTHOR]

At Ducabrook property, central Queensland, the mid-Visean Ducabrook Formation has yielded a diverse vertebrate fauna (fish and one tetrapod taxon) from a thin unit among siltstone interbedded with sandstone, minor oolitic limestone and conglomerate. Five lithofacies can be distinguished: the Oolitic Facies, distinguished by oolitic limestone and straight parallel ripple crests; the Sandy Facies, composed of plane-laminated and current-rippled sandstones; the Conglomeratic Facies, represented by pebble conglomerate displaying planar cross-bedded megaripples; the Silty Facies of siltstone with abundant calcrete nodules or sand/silt/clay interlaminations; and the Lime-Flake Facies, characterised by abundant locally derived lime flakes. The last includes the fossiliferous tetrapod unit. The Oolitic Facies was deposited in the inner (proximal) and outer (distal) zones of an estuary, based on identification of tidal sedimentary structures (e.g. mud drapes) and estuarine oolitic fabrics; the Lime-Flake Facies and Silty Facies were deposited in the estuary and lower reaches of a river and its surrounds; and the Sandy and Conglomeratic Facies represent braid-river deposits. Overall, the sequence represents intermittent deposition throughout an estuary, both within the tidal channel and the surrounding tidal flats, with additional deposition from the feeder river. The tetrapod unit, from the Lime-Flake Facies, represents a twin-peaked storm-induced flood event onto the tidal channel floor. The vertebrate bones have a shared taphonomic history and have undergone only local transport. The tetrapod and fish were spatially and temporally concurrent, probably in a shallow tidally influenced proximal estuarine habitat experiencing monsoonal conditions. Estuarine adaptations of these vertebrate taxa can explain migration along shallow-water continental shelves between the supercontinents during the Late Devonian and Early Carboniferous. [ABSTRACT FROM AUTHOR]

Indurated sand in the Late Quaternary coastal plain succession of northern Moreton Bay was examined in sand-mine pits, drillcores and the eroded bank of an estuarine channel. Samples show that the cements usually coat grains and partially infill interstitial pores. Distinctive cement habits reflect different constituents that are dominantly kaolinite and amorphous organic-rich complexes. Trace-metal concentrations in the cements are lower than previously reported for soils and estuarine sediments in the study region. Optically stimulated luminescence and thermoluminescence ages of these deposits indicate that pedogenic induration occurs over long periods, up to approximately 90 000 years, with only incipient induration evident in deposits 16 000 - 2600 years old. However, the rate of induration is far higher in relatively coarse channel fill, in which mineral and amorphous organic-rich cements have precipitated from shallow groundwater that flowed laterally through the deposit. The degree of induration, therefore, is strongly influenced by the original depositional texture and morphology of deposits, with well-indurated gravely channel fill (76 700 ± 6500 y), at least 2 m thick, sitting adjacent to medium-grained sand probably of dune origin, which contains a 30 cm-thick induration horizon (98 000 ± 9900 y). [ABSTRACT FROM AUTHOR]

Southeast Queensland's geomorphology is characterised by northwest - southeast-trending trunk drainage channels and highlands that strongly correlate with the distribution of geological units and major faults. Other geomorphological trends strongly coincide with subsidiary faults and geological domains. Australia is presently under compressional stress. Seismicity over the past 130 years records 56 earthquakes of >2 magnitude indicating continuing small-scale earth movements in the Moreton region. Highlands in this region are dominated by Paleozoic to Triassic metamorphic and igneous rocks, and are generally 20 - 80 km from the coastline. Coastal lowlands are largely dominated by Mesozoic sedimentary basins and a veneer of surficial sediments. The eastern coast of Australia represents a passive margin; crustal sag along this margin could be expected to produce relatively short, high-energy, eastward-flowing drainage systems. We performed a geomorphological analysis to characterise the drainage patterns in southeast Queensland and identify associations with geological features. Anomalous channel, valley and escarpment features were identified, which failed to match the anticipated drainage model and also lacked obvious geological control. Despite their proximity to the coast (base level), these features include areas where drainage channels flow consistently away from, or parallel to, the coastline. Although many channels do coincide with geological structures, the drainage anomalies cannot be directly related to known structural discontinuities. Anomalous drainage patterns are suggested to indicate previously unidentified structural features and in some cases relatively young tectonic control on the landscape. Recent seismicity data have also been analysed to assess spatial correlations between earthquakes and geomorphological features. Our results show that structure largely controls drainage patterns in this region, and we suggest that a presently unmapped and potentially active, deep-seated structure may exist parallel to the coast in the northern coastal region. We propose that this structure has been associated with uplift in the coastal region of southeast Queensland since mid-Cenozoic times. [ABSTRACT FROM AUTHOR]

The Atherton Basalt Province is centred on the Atherton Tableland, ∼50 km southwest of Cairns in north Queensland. Forty-eight K - Ar age determinations and four U/Th analyses from these basalts provide information on the distribution of the volcanics over time. Volcanism commenced at 7.1 Ma and continued into the Early Holocene, with volumetric peaks in activity occurring 3.5 - 3 Ma and 2 - 1 Ma. The province shows a change with time from eruptions of voluminous lava flows that built relatively large shield volcanoes, to the production of less voluminous lavas and pyroclastics associated with cinder cones during the last million years. Phreatomagmatic, maar-forming eruptions are also preserved among the most recent eruptions. Previous radiocarbon dating of swamp sediments suggested that volcanic activity may have occurred within the past 10 000 years. No systematic change over time is apparent in the location of the volcanoes of the province. Rather, a source region ∼80 km in diameter for the province as a whole has evolved over time. Extensive partial melting in the upper mantle may have led to the ascent and adiabatic melting of lesser volumes of mantle material from deeper levels. Changes in lithospheric stresses in north Queensland, caused by the docking of the Ontong Java Plateau and subsequent development of northward subduction at the San Cristobal Trench, may have allowed the ascent of magma from this mantle region. [ABSTRACT FROM AUTHOR]

The southeastern Georgetown Inlier (Greenvale Province) consists of Early Palaeozoic metamorphic rocks in fault contact along the Lynd Mylonite Zone with the Palaeoproterozoic to Mesoproterozoic craton of northeastern Australia. It has a central assemblage of metamorphosed silicic volcanic and sedimentary rocks considered equivalent to the Late Cambrian to Early Ordovician Seventy Mile Range Group that developed in an extensional backarc in the Charters Towers Province to the southeast. In the western part of the Greenvale Province, the Oasis Metamorphics have a U - Pb zircon SHRIMP metamorphic age of 476 ± 5 Ma and are intruded by the granodioritic Lynwater Complex with U - Pb zircon ages of 486 ± 5 Ma and 477 ± 6 Ma. These ages are consistent with these rocks forming basement and intrusive equivalents to the extensional volcanic basin. Existing geochronological constraints on the Halls Reward domain, located at the eastern margin of the province, are consistent with it being basement to the extensional basin. Several domains are recognised in the Greenvale Province with either dominantly steep or low to moderate dips of the main foliation, and each experienced multiple deformation with locally up to four overprinting structural phases. Steepening of foliation in several of the domains is attributed to contractional deformation in the Early Silurian that is inferred to have overprinted low-angle foliation developed during extensional tectonics in the backarc setting. Contractional deformation related to the Early Silurian Benambran Orogeny is considered responsible for multiple deformation in the Greenvale Province and reactivation of domain-bounding faults. [ABSTRACT FROM AUTHOR]

This study reports on the source, evolution, reactions and environmental impacts of F-rich thermal water at Innot Hot Springs, north Queensland. Thermal water of the Innot Hot Springs has a surface temperature of 71°C, alkaline pH (8.1), low dissolved oxygen (0.61 mg/L) and low total dissolved solids (652 mg/L). The main chemical composition is Na - Cl, with F concentrations (16 mg/L) being comparatively high. Concentrations of alkali and alkali-earth metals (Cs, Li, Rb, Sr) are elevated, while those of other trace elements (Ag, Al, As, Ba, Be, Cr, Cu, Ga, Mn, Mo, U, Zn) are significantly less. Hydrochemical and stable isotope data of hot spring water show that the fluid is meteoric in origin and has undergone significant water - granite interaction. Common geothermometers suggest temperatures of water - rock interaction at depth in the 119 - 158°C range (corresponding to a depth of <3.9 - 5.2 km). Solubility modelling of the thermal fluid demonstrates that the evolution of F concentrations in spring waters at the discharge site can be accounted for by fluid - rock interaction of a H2O - NaCl solution with fluorite - calcite-bearing granite assemblages between 150 and 200°C and subsequent granite-buffered cooling. Modelling also indicates that the F concentration in the hydrothermal system is largely controlled by interactions with fluorite, with less evidence for the significant involvement of F-topaz. Speciation calculations demonstrate that F speciation in the fluid is dominated by F- (99.4%), followed by minor CaF+ (0.5%) and NaF(aq) (0.1%), and traces of other F complexes. Thus, the F-rich Innot Hot Springs result from meteoric water circulating through fluorite-bearing granitic rocks and are the surface expression of a low-temperature, non-volcanic geothermal system. Discharge of the hot spring water occurs into an ephemeral stream located in a seasonally wet - dry tropical climate. As a result, the F content of local surface waters is distinctly elevated (max. 18 mg/L) during the dry season, making them unsuitable for stock water supplies. [ABSTRACT FROM AUTHOR]

Results of coupled mechanical and fluid-flow modelling provide insights into some of the factors that controlled gold mineralisation and deformation in the Hodgkinson Province in northeastern Queensland. These results aid in resolving why the north – south-striking segment of the terrane-bounding Palmerville Fault is barren, while many north – south- to northwest – southeast-trending, second-order fault zones throughout the Hodgkinson Province are spatially associated with gold deposits. The simplified, regional-scale model geometry used in this study permitted variation of boundary conditions, material properties and stress regimes. This included variation of lithological properties, the absence of fault zones in some models, and the application of plane strain or transpression. The model outcomes illustrate the importance of a listric fault geometry for focusing deformation and fluid flow in zones of relatively high permeability and/or low rock strength. Also, the orientation of fault zones with respect to the dominant far-field compressive stress regime is shown to be a key factor controlling deformation and fluid flow. In addition, fault bends and terminations are shown to influence significantly the distribution of deformation and fluid flow in our models. The results provide an improved understanding of first-order factors that may have controlled localisation of deformation and fluid flow in the regional geological architecture of the Hodgkinson Province. Focused fluid flow arising from localised dilation and permeability increase plays an important role in the formation of ore deposits; hence the outputs of the modelling may be of significant value for future exploration in the Hodgkinson Province and analogous regions elsewhere. The study illustrates the usefulness of numerical modelling as a tool for testing multiple scenarios, leading to improved conceptual understanding of geological systems. [ABSTRACT FROM AUTHOR]

Laser 40Ar/39Ar analyses were undertaken on Oligocene bimodal intraplate volcanic rocks from five volcanic areas spanning 320 km along a north-northeast-trending belt in southeast Queensland. Sixty-one mineral grains and groundmass fragments from 21 samples were analysed by incremental heating, while 99 mineral grains from 10 samples were analysed by total fusion. Fourteen samples are from localities dated previously by the K – Ar method. The 40Ar/39Ar ages are reproducible among different aliquots from the same sample and different samples from the same location, and correlate with latitude, ranging from 30.6 ± 0.3 Ma on Fraser Island in the north (25°S) to 25.8 ± 0.2 Ma at Flinders Peak in the south (27.7°S). This age progression is not evident from K – Ar ages compiled for the same region. The decrease of 40Ar/39Ar ages with latitude is consistent with previous suggestions for a hotspot origin for east Australian central volcanoes and yields an Australian Plate velocity, relative to the postulated fixed hotspot reference frame, of 71 (+7, -4) mm/y at an azimuth of N10°E for the period of ca 31 – 26 Ma. This velocity agrees within error with the values of about 65 ± 3 mm/y obtained from previously reported K – Ar analyses of east Australian central volcano provinces active in the last 35 million years. These results demonstrate that the improved accuracy and precision of the 40Ar/39Ar method permit resolution of age versus latitude relationships for narrower time windows, which may potentially provide constraints on changing plate velocities with time. This improved temporal resolution may also contribute to resolving current debate over the existence and the stationary versus mutable position of postulated mantle plumes and hotspots. [ABSTRACT FROM AUTHOR]

Central Queensland lies on the passive margin of eastern Australia and owes its landscape to processes that began following rifting and opening of the Tasman Sea. The modern landscape is the result of long-term processes of landform development, and the landforms themselves are the evidence of these processes. Hence, interpreting their significance provides an understanding of long-term landscape evolution. Along the eastern Australian coast, numerous rivers drain into the sea but among these, there are two that stand out: the neighbouring Fitzroy and Burdekin Rivers in central Queensland. These two streams have by far the largest catchments of any rivers along the eastern seaboard of Australia. The Burdekin and Fitzroy catchments contain widespread remnants of Cenozoic deposits, which accumulated predominantly in fluvial and lacustrine environments established during the Palaeogene. Alluvial sediments were supplied by erosion of nearby uplands, and accumulated in depressions and basins on a prior land surface. Volcanic activity also resulted in large lava flows in central western areas. Water was the main agent of sediment transport, distributing unconsolidated deposits along the drainage networks of the time, some of which were directed inland. It is inferred that during the Palaeogene, the divide between coastward and inland draining streams was further to the east than it is at present. Several basins were located west of the former coastal divide, and were characterised by continental environments of deposition in a generally westward drainage system. With continued accumulation of sediments, individual basins overflowed and merged to form a widespread flat-lying Palaeogene landscape that concealed an earlier land surface on which bedrock was more extensive. In the Early Cenozoic, there was a change from the depositional phase that resulted in the continental sequence, to an erosional phase that developed the modern landforms. The change from deposition to erosion probably started during the Palaeogene. Erosion continued through to the present, re-exposing parts of the basal Palaeogene sequence and earlier Mesozoic land surface. The erosional phase that shaped the landforms of the modern Burdekin and Fitzroy catchments can be explained by slowly evolving drainage basins in the interior being captured by small coastal streams—the predecessors of the Burdekin and Fitzroy Rivers. The coastal streams were short and steep in comparison with those in the interior, allowing a more active erosional environment along the coast. As the coastal streams expanded, the drainage divide moved rapidly westwards. Stream capture began a phase of regional erosion, which transported large quantities of sediments to the coast. The sediments contributed to coastal and nearshore features similar to the Holocene high sea-level examples at the mouth of the Burdekin River in the north, and the Fitzroy Delta and the Keppel Coast in the south. Large volumes of sediments were also transported beyond the present coast during low sea-levels of the Cenozoic, forming similar coastal features and contributing to a major eastward bulge on the central Queensland continental shelf. The emptying of continental basins has paralleled the development of the continental shelf bulge from the coast to the Marion Plateau. [ABSTRACT FROM AUTHOR]

We report results of metallogenic, structural, petrological and fluid-inclusion studies that characterise the nature of gold mineralisation in the Northcote district of the Hodgkinson Goldfield, one of the major goldfields in the Palaeozoic Hodgkinson Province of northeastern Queensland, Australia. Gold – arsenic and gold – antimony – arsenic deposits in the Northcote district are spatially associated with distinctive northwest-trending faults and shear zones suggesting a strong structural control on their development during several phases of deformation in the Late Devonian to Carboniferous. Field evidence, as well as petrographic, scanning electron microscope and fluid-inclusion analysis of mineralised samples, indicates the occurrence of two stages of gold genesis. Gold associated with the earlier of the two mineralising episodes exists mainly in solid solution with acicular arsenopyrite. SEM analysis indicated that minor sphalerite, galena and tetrahedrite formed during this episode of mineralisation. Gold deposited during the second mineralising episode has a strong association with antimony. Fluid-inclusion studies of quartz vein samples record minimum homogenisation temperatures between 108 and 312°C, and salinities of up to 13 wt% NaCl equivalent. Little to no difference in the nature of the fluids is observed between samples related to the two gold-forming stages. The style of gold mineralisation in the Northcote district is compatible with orogenic-gold deposits that form primarily during compressional and transpressional deformation along convergent plate margins. [ABSTRACT FROM AUTHOR]

Parabolic dunes invade coastal strandplains and overlie prior blown dunes in southeast Queensland. These coastal dune landscapes were produced primarily by real changes in wind strength and frequency. Sand movement began in past glacial ages and in the most recent instance persisted into Holocene time. Four interglacial shores are identified with marine isotope stages 5, 7, 9 and 11, and allow estimation of the ages of the dune and beach sands, by correlation with the EPICA Dome C ice core, as follows: Triangle dune sand, n.d.; Garawongera dune sand, 65 ka; Woorim beach sand, 125 ka; Bribie beach sand, 245 ka; Bowarrady dune sand, 270 ka; Poyungan beach sand, 335 ka; Yankee Jack dune sand, 360 ka; Ungowa beach sand, 410 ka; Awinya dune sand, 430 – 486 ka; Cooloola dune sand, >486 ka. [ABSTRACT FROM AUTHOR]

Over 500 zircon grains separated from modern sediments in 10 drainages covering the Eastern Succession of the Mt Isa Inlier have been analysed for U – Pb ages, Hf isotopes, and trace elements, using in situ LAM-ICPMS techniques, to evaluate the efficacy of this approach in characterising large-scale crustal evolution. U – Pb age spectra are used to estimate the timing of terrane-scale events, primarily magmatic episodes; Hf isotopes provide information on the relative contributions of juvenile material and reworked older crust at each stage of crustal evolution; trace-element patterns of zircons are used to characterise original magma types. The integration of these data for individual zircon grains produces an event signature that provides more information than that gained from U – Pb dating alone. The data define four major stages of crustal evolution in the area: 2550 – 2330 Ma, 1950 – 1825 Ma, 1800 – 1600 Ma, and 1590 – 1420 Ma. Each stage, except the last, involved crustal extension, and ended with a period of crustal homogenisation, which is reflected in the isotopic composition of magmatic rocks generated by crustal reworking in the succeeding stage. Reworking of Neoarchaean crust contributed significantly to crustal magmatism throughout the Proterozoic history. A major input of juvenile mafic material around 1625 Ma (interpreted as the magmatic age of the Toole Creek Volcanics) is poorly represented in the database of conventional geochronology but is prominent in the detrital zircon record. The major late-stage granitic magmatism of the Williams and Naraku Batholiths (1520 – 1490 Ma) was generated almost entirely from older crust, with little juvenile input. The study demonstrates that sampling of carefully selected modern drainages and the analysis of statistically large numbers of detrital zircons can provide insights additional to those gained from conventional analysis of U – Pb and Sm – Nd systematics in selected rock samples. The integrated use of U – Pb age, Hf-isotope composition and trace-element patterns in detrital zircons is a powerful and relatively inexpensive tool for the analysis of terrane-scale crustal evolution, and for the correlation of terranes. [ABSTRACT FROM AUTHOR]

The Mt Isa deep seismic transect images a regional detachment surface and basement-cutting faults associated with Mesoproterozoic, east – west shortening in the Mt Isa Inlier, Queensland. New mapping along the trace of the transect is combined with interpretations of seismic-reflection data to derive a structural cross-section for the top 12 km of the crust. A regional detachment surface is imaged beneath the eastern half of the inlier leading to a fold and thrust belt interpretation for this region, where supracrustal units were decoupled from basement and translated west or northwest. The detachment is imaged across most of the Eastern Fold Belt in the reflection data, and it emerges as a series of thrust faults along the western margin of this belt. This detachment is cross-cut by reverse faults related to a regional, basement-involved style of deformation that involved the entire inlier. Shortening in the Western Fold Belt is dominantly east-vergent and was accommodated by a complex interplay of local thrusts, folds and reverse faults. [ABSTRACT FROM AUTHOR]